SG increased the initial fluidity of UHPC without decreasing within 1 h. When the SG dosage was ≥0.06%, the slumps at 30 min and 60 min increased slightly. (2) In the setting hardening stage, the addition of SG inhibited the formation of calcium hydroxide (CH), which significantly extended the setting time of UHPC. When the dosage of SG was 0.15%, the initial and final setting times were 5.0 times and 4.5 times that of the blank group, respectively. SG had no obvious effect on the hydration rate of cement in the accelerated period, but the peak hydration temperature of UHPC was increased when the SG dosage was 0.03~0.12%. (3) In the strength development stage, the 1 d and 3 d strength of UHPC decreased significantly with the increase in the SG dosage. However, SG could promote the formation of AFt at the pores and aggregate interface in the later stage, reduce the porosity of cementite, and improve the compressive strength of UHPC in 28 d, 60 d, and 90 d. When the SG dosage was 0.12%, the 90d strength increased by 13%.The properties of concrete can be significantly affected by sodium gluconate (SG) at very small dosages. In this paper, the effects of SG on the fluidity, setting time, heat of hydration, and strength of ultra-high-performance concrete (UHPC) were studied. The results show that (1) in the plastic stage, SG inhibited the formation of early ettringite (AFt) and delayed the hydration of tricalcium silicate (C Ultra-high-performance concrete (UHPC) is a new cementitious composite material with ultra-high strength, ultra-high durability, and high toughness . The matA high-performance superplasticizer is an indispensable component for preparing UHPC ,6. In re3S), that is, gluconate can inhibit the hydration of C3S by adsorbing on the dissolution site on the silicate phase surface [2+ inhibits the formation of ettringite (AFt) [4·2H2O, and SG delays the formation of AFt by preventing the dissolution of CaSO4·2H2O [3S [3A), and thus the mechanism of SG retardation at low dosages is mainly hindering the nucleation of hydrated calcium silicate and the growth of hydration products [3S, and the hydrolysis increases the concentration of Na+ and gluconic acid. The remaining gluconic acid prevents the dissolution of CaSO4·2H2O and is adsorbed on the surface of C3A after binding to Ca2+, hindering the hydration of C3A and the formation of AFt. That is, when the SG dosage is high, it not only delays the hydration of C3S but also retards the formation of AFt by preventing the dissolution of CaSO4·2H2O. Therefore, excessive addition of SG can severely delay the setting time due to the excessive inhibition of hydration. In addition, some scholars [Sodium gluconate (SG) is an organic electrolyte with good solubility in water; it belongs to sugars and has a retarding effect when mixed with cement ,10,11. H surface ,13,14, rte (AFt) . (3) Regscholars  believe 2+ and also increase the zeta potential on the surfaces of cement particles, thereby improving the dispersion effect of the SPs. In addition, there is also a competitive adsorption effect between SG and SPs, and the adsorption capacity of an SP will be reduced after adding SG. Previous studies have shown that a small amount of SG can enhance the steric hindrance effect of SPs [Except for its setting retarding effect, SG also has an obvious “auxiliary plasticizing effect”. That is, the water reduction rate of SG itself is very small, but when used together with a superplasticizer (SP), it can significantly increase the water reduction rate of the SP or significantly increase the fluidity of concrete and reduce slump loss . This ist of SPs , but exct of SPs ,25. Accot of SPs ,26,27, tt of SPs ,25,26. Lt of SPs  demonstrt of SPs  showed tt of SPs  showed tt of SPs ,21.A trace amount of SG also had a significant enhancement effect on the strength of concrete, which gradually increased with the increase in SG from 0.03% to 0.08% at the same water–cement ratio . The latUHPC is a system with an ultra-low water-to-binder ratio, large amounts of cementitious materials, and large amounts of nano-powder. Currently, the mechanism of how SG affects the various properties of UHPC in this system, the extent of its influence, the optimal dosage, and how it affects the hydration leading to a significant increase in strength has been little studied. In addition, existing studies have mostly focused on the influence of SG on one or two stages of concrete plastic, setting hardening, and strength development, while the developments of the three stages of concrete have been shown to be closely linked and interact with each other. Therefore, the systematic analysis of these three stages can comprehensively explain the impact of SG on the cement hydration process. However, a systematic analysis of the entire process of these three stages has not been reported.In this paper, the effects of SG on the fluidity, setting time, and compressive strength of UHPC are discussed in three sections, and the mechanism of action is analyzed according to the compositions and morphologies of the hydration products, and finally, the mechanism of the effect of SG on UHPC throughout the process from the beginning of water addition to 90 days is discussed, and the research steps are shown in Trace amounts of SG can significantly affect the fluidity, setting time, and strength growth of concrete, which has only attracted the attention of a few researchers, and its application in UHPC has not been reported. With a high cementitious material dosage and an ultra-low water-to-binder ratio, the role of SG in UHPC may be more significant. The purpose of this study is to observe the effect of SG on the whole process of the UHPC plasticity stage, setting hardening stage, and strength development stage.2/kg, the chemical composition is shown in The cement used in this experiment was Ordinary Portland cement ‘P·O 52.5R’, according to Chinese National Standards GB 175-2007. The specific surface area was 411 mThe particle size of quartz sand was 0.045~1.7 mm, and the chemical composition is shown in The base mix proportion of UHPC is shown in The fluidity of the UHPC mixture, including slump, expansion, and expansion loss over time, was determined in accordance with the relevant provisions of GB/T 50080. The initial and final setting times of UHPC were determined using the penetration resistance method according to the method of T/CECS 864-2021.The heat of hydration of UHPC was measured according to the direct method in GB/T 12959-2008 by using the proportion and mixing time of the base proportion after removing the coarse aggregate to prepare the samples. According to the calorimeter in a constant temperature environment, the temperature change of the specimen in the calorimeter was determined directly, and the heat of hydration of the cement within 7 d was obtained by calculating the sum of the accumulated and dissipated heat with the calorimeter. The temperature was always maintained at 20 °C during the test, and the temperature change data were recorded continuously for 7 d.The compressive strength of UHPC was determined according to the relevant provisions of GB/T 50081, using 100 mm × 100 mm × 100 mm cubic specimens.The hydration products of UHPC containing different doses of SG at different ages were analyzed using XRD. The microstructure of UHPC containing different doses of SG was observed via SEM using a ZEISS Sigma300 , including the morphologies of the hydration products at different ages and the morphologies of the interface areas between the aggregates, steel fibers, and matrix.The paste was made of SG containing different dosages in the same conditions as the reference mix ratio and mixing time. The prepared samples were poured into plastic cups, and bottles were sealed and stored in a standard curing chamber at a temperature of 20 ± 1 °C and relative humidity of 95 ± 4%. Before performing XRD and SEM, small pieces were soaked in absolute ethanol, and hydration was terminated after 1 d, 3 d, 7 d, and 28 d. The small pieces were then dried to a constant weight in a vacuum drying oven at 45 °C and stored in sealed bags. For XRD analysis, the dried samples were further ground to pass through a 200-mesh sieve. Before SEM testing, the samples were gold-plated at 20 mA for 2 min. XRD analysis was performed with the Bruker D8 Advance model from Germany using CuK radiation in the range of 5–70° with a scanning speed of 10°/min.Fluidity is an important performance indicator that affects UHPC pouring, which is generally evaluated according to slump and expansion. The initial 30 min and 60 min slumps and expansions of UHPC mixed with SG are shown in UHPC cementitious materials contain a large number of nanoscale particles while using an ultra-low water-to-binder ratio, so there are more SPs. In such a system, the addition of an appropriate amount of SG plays a significant role in the auxiliary plasticizing effect, that is, it significantly improves the initial fluidity while making almost no loss or even a slight increase in the 1h fluidity. There are two reasons for this: one is the retarding effect; the second is competitive adsorption ,25,33,343S and dicalcium silicate (C2S), indicating that SG inhibited the hydration of the initial C3S and C2S. It can also be seen in In 2+ in the solution to form calcium gluconate with low solubility, which reduces the concentration of Ca2+ in the solution and promotes the dissolution of gypsum due to the homogenic effect. On the other hand, undissolved gypsum in an aqueous solution is positively charged, and SG is an anionic polymer, which adsorbs on the surface of gypsum and hinders the contact between the water and gypsum when the adsorption amount is large, thereby inhibiting the dissolution of gypsum. However, the ion reaction rate in the solution was faster than that of surface adsorption; thus, at 15 min, a small amount of SG mainly promoted the dissolution of gypsum through complexation and solubilization, while at 30 min, the surface adsorption mainly inhibited dissolution, so the solubility of gypsum decreased with the increase in the SG dosage. The gypsum diffraction peak of the SG-doped sample was significantly enhanced at 30 min compared with 15 min, which may be due to the initial AFt formation being inhibited by the composite use of PCE and SG, and the initial dissolved SO42− was not converted to AFt [42− concentration increased, and the solubility of CaSO4·2H2O was lower, so CaSO4·2H2O crystals were re-formed [There are obvious differences in the gypsum diffraction peaks in d to AFt . As the e-formed .2+ in the solution forms an electric double layer with the negatively charged mineral surface, and the concentration of Ca2+ is an important factor affecting the zeta potential of the diffusion electric double layer [2+ to form water-insoluble calcium gluconate, it reduced the concentration in the solution bilayer, thus increasing the zeta potential of the diffusion electric double layer, which is conducive to improving the electrostatic repulsion between particles and thus increasing the fluidity of the paste , it not only adsorbed on the surface of C3A but also heavily adsorbed on the surface of positively charged AFt. The growth of AFt crystals in the encapsulation layer formed during the induction period of cement, which leads to the rupture of the encapsulation layer, was an important factor affecting the hydration rate of cement during the acceleration period. Therefore, the excess SG significantly affected the hydration rate of cement during the acceleration period and significantly reduced the hydration exothermic temperature and early accumulated hydration heat release [The important reason for cement hydration to enter the accelerated period after the induction period is that the CaS-H gels . SG is af cement ,31,36. W release ,31,36.The speed of concrete setting and hardening significantly affects the early strength of concrete, but it generally has little effect on the later strength. Porosity and pore structure are important factors affecting the strength of concrete. The porosity and pore distribution of UHPC with different SG dosages at 90 days were tested using the mercury pressure method, and the results are shown in The XRD patterns of UHPC with different SG doping at 3 d, 7 d, 28 d, and 90 d are shown in As can be seen in The reason for the ability of SG to significantly increase the strength of UHPC can be observed in the SEM images of the hydration products at different ages. + ions in water with a negatively charged carboxylic acid at one end, SG was able to absorb with positively charged adsorption vacancy on the surfaces of cement particles. The alkyl backbone of SG contains five hydroxyl groups, which can form a solvated water film layer via hydrogen bonding with water molecules. In addition, SG is easily soluble in water, while the solubility of calcium gluconate is very low at room temperature but increases significantly at high temperatures. Therefore, adding SG to cement has the adsorption coverage function of inhibiting hydration, competitive adsorption, and complexation to stabilize Ca2+ [The previous experimental results show that SG has a significant effect on the fluidity, hydration, setting and hardening, and mechanical properties of cement. Carbohydrates are mostly high-efficiency retarders but are unlike glucose and sucrose, whose molecular structures are mostly cyclic structures. SG is a ring-opening structure, as shown in ize Ca2+ ,26,33,343S and C2S and the formation of AFt due to adsorption coverage, while the competitive adsorption effect of SG resulted in the presence of more PCE in the solution. These aspects resulted in a significant increase in the initial fluidity of the UHPC paste doped with SG and a reduction in the fluidity loss [During the plastic stage of the UHPC paste, SG inhibited the hydration of initial City loss ,26,33,342+ effect of SG complexation and the continuation of the previous adsorption covering effect significantly prolonged the time for Ca2+ to reach saturation, thereby greatly extending the initial setting time of UHPC. However, due to the increase in the hydration temperature of UHPC during the accelerated period, the solubility of calcium gluconate increased and Ca2+ was re-released. Therefore, there was no significant effect of SG on the hydration rate during the acceleration period.During the setting and hardening stage of UHPC, the stabilizing CaDuring the strength development stage of UHPC mixed with SG, due to the slower hydration in the early stage, the hydration products generated in the early stage were more uniformly distributed. More AFt with finer grains and staggered symbiotics were generated in the pores and interfaces, which improved the pore structure of the UHPC matrix, thus improving the compressive strength of UHPC.With the increase in the SG dosage, the initial fluidity and fluidity retention continued to increase, and the initial and final setting times continued to increase. However, the early strength (1 d and 3 d) gradually decreased with the increase in the SG dosage, while the later strength  increased with the increase in the SG dosage. The greater the SG dosage, the longer the enhancement effect takes to appear. Considering the influence of fluidity, setting time, and strength, the amount of SG in UHPC should be 0.03~0.09%, and too much SG leads to severe retardation and increased cost.The amount of SG added to UHPC was very small, but it had a significant effect on its fluidity, setting time, and strength. The effects of SG on the composition, morphology, hydration heat, and pore structure of hydration products were studied in this paper. However, due to the complex composition of UHPC and the small amount of SG, many differences cannot be well characterized with existing research methods, especially since the existence of admixtures in hardened concrete has not been reported. In subsequent studies, new means can be used to study the existence of forms of admixtures in the hardened matrix.SG is an organic electrolyte that exists in the form of ions in cement solutions. When cement is mixed with various electrolytes , it significantly affects the ion concentration in the solution and affect the effectiveness of SG, and this effect needs to be further studied. In addition, UHPC has the characteristics of high toughness and ultra-high durability, and the effect of SG on the toughness, shrinkage performance, and durability of UHPC should be researched in the future.(1)The fluidity loss of UHPC without SG was significant within 30 min, at approximately 10%. It was further reduced at 60 min, with a loss of approximately 4% at 60 min. When the initial fluidity of UHPC was 0.15%, the initial slump and expansion of UHPC increased by 15.6% and 55.1%, respectively, and the fluidity did not decrease or increased slightly within 1 h.(2)2+ to generate insoluble calcium gluconate, inhibit the hydration of C3S and C2S, prolong the time for Ca2+ to reach saturation, prolong the induction period, and thus delay the setting time of UHPC.The addition of SG significantly prolonged the initial and final setting times of UHPC but had little effect on the interval between the initial and the final setting times. SG inhibited the dissolution of gypsum in cement and delayed the formation of AFt in the early stage of hydration. SG can also complex with Ca(3)SG significantly affected the hydration kinetics of UHPC but had no obvious effect on the hydration rate of cement during the acceleration period. The addition of 0.06~0.12% SG reduced the peak hydration temperature and the heat of hydration of UHPC.(4)When the SG dosage exceeded 0.09%, the 1 d and 3 d strengths of UHPC decreased significantly, but the strength from 7 d to the later stage was not affected and could significantly exceed that of the blank sample. When the SG dosage reached 0.12%, the compressive strength at 90 d increased by 13.0% compared with the blank group. SG causes more AFt to form in the pores in the later stage, reduces the porosity of UHPC, improves the pore structure, and thus effectively enhances the strength of UHPC.In this paper, the influences of SG on the fluidity, setting times, hydration heat, and compressive strength of UHPC were studied, and the mechanism of SG was preliminary analyzed through XRD, SEM, and mercury pressure, and the main conclusions are as follows:


This study demonstrated the effectiveness of this method in improving the durability and functionality of metal pipes and its potential for various industrial applications.An innovative brush plating process for preparing coatings on the inner wall of metal pipes is proposed, which aims to solve the limitations of current electroplating technology and improve the performance of the inner walls of metal pipes. While optimizing the process, the effect of working voltage on the microhardness, thickness, surface morphology, corrosion resistance, and elastoplasticity of the Ni coating on the inner wall of the tube was studied under the new process. The results indicate this technique can produce high-quality coatings on the inner wall of pipes in a simple and efficient manner. As the working voltage increases, the surface quality and comprehensive performance of the coating show an increasing trend followed by a decreasing trend. At 12 V, the coating exhibits the highest surface density and uniformity, the lowest surface roughness, the best corrosion resistance, and the maximum microhardness of 575.8 HV, with a corrosion current density of 1.040 × 10 As the global economic infrastructure develops rapidly, pipes, as essential tools for storing and transporting drinking water, oil and gas, and chemicals over long distances, have been extended annually . HoweverNumerous domestic and international scholars have conducted extensive research to solve the problem of pipe wall protection and repair ,10. ExisIn this study, an innovative process was proposed for preparing coatings on the inner walls of metal pipes, combining the technique of electro-brush plating. While optimizing the process, a Ni coating was prepared on the inner surface of the metal pipe by using a self-built in-pipe deposition platform, and the effect of the working voltage on the surface morphology and mechanical properties of the coatings was investigated. The results demonstrate the effectiveness of this method in enhancing the durability and functionality of metal pipes, and provide a new innovative processing method and technical foundation for the preparation of environmentally friendly, energy-efficient protective coatings on the inner walls of pipes ,35,36.A Ni coating was prepared on the inner wall of a pipe using a self-built experimental apparatus for in-pipe deposition. The apparatus comprises a control system, a pipe walking and driving device, an electrolyte supply system, a graphite brush head rotation device, and an electroplating power supply. The structure of the graphite brush head is designed as a semi-arc graphite block, and the brush head is wrapped with felt to facilitate filling with plating solution while adhering closely to the inner wall of the pipe, as depicted in Commercially available Q235 low-carbon steel pipe with an inner diameter of 80 mm and an outer diameter of 87 mm was used as the experimental substrate. Q235 low-carbon steel sheet with a size of 40 mm × 20 mm × 2 mm was used as the substrate for the optimization experiment of the pre-treatment process. The main process of the pre-treatment optimization test is as follows: grinding sample piece, pre-treatment, brush plating deposit, performance comparison. The process of pipe inner wall coating is as follows: lye degreasing, deionized water rinse, 5% HCl impurity removal activation, deionized water rinse, coating deposition, deionized water rinse, cut sample, deionized water rinse, drying, coating quality inspection.In the pretreatment process optimization experiment, the configuration of the plating solution used for the 1st pre-treatment and 2rd pre-treatment is shown in The plating solution configuration shown in The experiment was carried out at room temperature (25 °C), and the power supply was a MESTEK DP2050 DC power supply. The pre-treatment process optimization experiment was carried out on a flat electric brush plating platform, and the process parameters were as follows: working voltage 8 V, plating solution supply speed 16 mL/min, brush head moving speed 10 m/min; The process parameters remain unchanged, and the test plating experiments are carried out on the inner wall of the pipeline at 100 r/min, 180 r/min, and 260 r/min to verify the feasibility of the optimized process.The preparation process parameters of the Ni deposition layer on the inner wall of the pipeline under different working voltages are as follows: plating solution supply speed 16 mL/min, brush head speed 180 r/min. Working voltages of 6 V (Label P-1), 8 V (Label P-2), 10 V (Label P-3), 12 V (Label P-4), 14 V (Label P-5), and 16 V (Label P-6) were used. The effect of working voltage on the surface morphology and properties of the coatings was investigated by varying the working voltage. Samples were taken from commercially available galvanized steel pipes of the same material and size (Label P) to participate in the tests and were compared. The enhancement effect of the electro-brush plating deposition process on the coatings on the inner walls of pipes was studied.(1)The surface morphology of the coating was analyzed using a Quanta 200 scanning electron microscope  at a magnification of 2000 times.(2)The hardness of the deposited layer was characterized using a microhardness tester . A load of 25 gf was applied at 5 different positions for 15 s, and the average value of the obtained data were recorded.(3)The cross-section of the coating was observed using a Leica DMi8 M metallographic microscope at a magnification of 500 times .(4)Electrochemical experiments were performed using an electrochemical workstation  in a 3.5 wt% NaCl corrosion medium at room temperature. The three-electrode system had a saturated calomel electrode (SCE) as the reference electrode, a platinum electrode as the working electrode, and a potential range of 1500 mV to 1000 mV with a scan rate of 1 mV/s.(5)The deformation resistance of the coating was analyzed using a G200 nanoindenter . A load of 100 mN was applied to 5 different points on the surface of the coating, with a Poisson’s ratio of 0.25 set based on the material properties.Traditional brush plating requires step-by-step electroplating and multiple pre-treatment processes, any of which are related to the final quality of the coating ,38. ThisQ235 steel plates with a size of 40 mm × 20 mm × 2 mm were selected as the substrate. Using identical process parameters and the bath configuration in To solve this problem, enhancing the bonding strength of the coating is a prerequisite, such as replacing a more effective substrate activation method and a plating solution configuration with a better deposition effect. HCl can effectively remove the oxide film on the surface of the substrate, slightly etch the surface of the substrate to expose the metal crystal structure and better combine the metal ions with the surface of the substrate. Adding an appropriate amount of surfactant into the bath can reduce the surface tension of the bath and promote ion transfer, and it can provide better deposition conditions for coating deposition. Proven by experiment, pretreatment with 5% HCl can effectively activate the substrate. Using the plating solution configuration in The above work has optimized the plating process, and the Ni coating has been trial-produced on the inner wall of the pipeline, the feasibility of the process has been verified. In the subsequent study, the effect of the working voltage on the surface morphology and properties of the coating on the inner wall of the pipeline was studied by using this process.The surface morphology of the Ni coatings prepared on the inner wall of the pipe using the optimized process at different working voltages is shown in From the surface quality of the coatings, it can be observed that with the increase in the working voltage, the surface quality of the coating shows a trend of improvement first and then deterioration. When the working voltage is 12V, the coating surface shows most dense performance overall. With the gradual increase in the working voltage, the coating quality deteriorates. In Because the surface topography of the nickel plating layer on the inner wall of the electro-brush plating pipe is greatly influenced by the working voltage, as demonstrated in Compared with 3 corrosion.The cross-sectional morphology and deposition rate of the Ni coatings prepared on the inner wall of the pipe using the optimized new process at different working voltages are shown in This phenomenon can be explained as follows: As the working voltage increases, the unit area current increases, resulting in a higher deposition rate, which is directly proportional to the product of the current passing through the unit area and the duration of the electrolysis process. When the duration is fixed, a higher current passing through the unit area leads to a faster deposition rate. However, excessively high working voltage can cause concentration polarization and hydrogen evolution, which results in poor surface quality of the coating. The aggregation of a large number of crystal cells and grains also leads to a porous and loose coating, while some loosely bound grains may be removed by the motion of the brush head. This leads to the growth rate of deposition rate slows down and the deterioration of the cross-sectional quality of the coating after a working voltage of 12 V .The results indicate that using an appropriate working voltage during the electro-brushing deposition process on the inner wall of the pipe can ensure that the coating exhibits good surface, cross-sectional morphology and is well-adhered to the substrate while still achieving a high deposition rate.The hardness values corresponding to different samples are shown in It can be observed that the microhardness of the coating increases first and then decreases with the increase in working voltage. When the working voltage is 12 V (P-4), the hardness value reaches the maximum value of 575.8 HV. According to the surface morphology and cross-sectional morphology results shown in σS represents the yield strength, and σ0 and K are constants, while d is the average grain diameter in a polycrystalline material. It is evident that the surface of the coating becomes denser with a smaller grain size, leading to an increase in the microhardness of the coating. Consequently, the hardness value of the coating is closely related to its surface quality. A coating with a uniform and dense surface, obtained at an optimal working voltage, exhibits a higher hardness value.According to the Hall–Petch formula :σS = σ0 The results show that the Ni coating on the inner wall of the pipe prepared by brush plating at a suitable working voltage has high microhardness. Additionally, its hardness is obviously better than the inner wall coating of commercially available galvanized steel pipes.The corrosion resistance of the coatings prepared under different voltages was evaluated. −5 A·cm−2, respectively. The corresponding corrosion rate is 0.1220 mm·a−1, indicating the minimum corrosion tendency of the coating. A further increase in the working voltage leads to a decrease in the corrosion potential and an increase in the corrosion current, which ultimately reduces the corrosion resistance of the coating.From the results presented in This is because the corrosion resistance of the coating is closely related to the surface quality of the coating. At lower working voltages, the coating surface displays noticeable protrusions and pores , indentation tests were carried out on the Ni coating of the P-4 sample. Among them, the measured displacement–load curve of sample P-4 is shown in max), residual depth (hr), and elastic recovery depth (he) in the indentation experiments. Each sample corresponds to the elastic recovery depth (he), residual depth (hr), and maximum indentation depth (hmax), as well as the elastic recovery rate curve, as shown in Under the same load (100 mN), indentation tests were carried out on five different parts of each sample, and reliable experimental data were selected. Additionally, the displacement–load curves obtained from the tests are presented in max) declines and then rises. Meanwhile, the elastic recovery rate increases initially, and then decreases. The coating’s toughness increases as the elastic recovery rate grows, and its plasticity is directly proportional to the ratio of elastic recovery depth (he) to maximum indentation depth (hmax). At a working voltage of 12 V (Label P-4), the curve reaches the far left, with hmax reaching a minimum of 760 nm, he reaching a maximum of 271 nm, and the elastic recovery ratio he/hmax reaching a maximum of 0.36. At this point, the coating exhibits its best elastic-plastic performance.The displacement–load curves for all samples are depicted in The reason for this is that, as the operating voltage gradually increases, the current density per unit area increases, causing the distribution of metal ion charges to become more uniform and the grain size to decrease. The movement of the brush head relative to the cathode facilitates the removal of air bubbles from the coating surface, and at the same time, it can polish the raised unit cells to refine the grains. This dynamic process results in a more compact and uniform surface, and an enhancement in its resistance to deformation.3/E2) for each sample are illustrated in 3/E2) can also be utilized to evaluate the coating’s fracture toughness. The greater the ratio, the stronger the resistance to deformation. It can be observed from 3/E2 initially increases and then decreases as the working voltage increases, which is consistent with the elastic recovery rate trend. The ratio of H3/E2 reaches its highest value of 0.049 at a working voltage of 12 V, indicating the best resistance to plastic deformation [The trends in microhardness (H), Young’s modulus (E), and the ratio Through the optimization of the pre-treatment process and plating solution formula, nine steps in the electro-brush plating process have been simplified to five steps. Moreover, Ni coatings with dense and uniform surface and good performance can be prepared conveniently and efficiently on the inner wall of metal pipes.(2)As the working voltage gradually increases, the surface and cross-sectional morphology of the pipe inner wall coating exhibit a trend of improvement followed by deterioration. The deposition rate shows a trend of acceleration followed by deceleration. By using an appropriate working voltage (12 V), a coating with superior surface and cross-sectional morphology, as well as good adhesion to the substrate, can be obtained while maintaining a high deposition rate (169.2 μm/h).(3)−5 A·cm−2, a corrosion rate of 0.122 mm·a−1, and an elastic recovery ratio (he/hmax) of 0.36. The results indicate that the coating prepared at 12 V has the best microhardness, corrosion resistance, and deformation resistance.The microhardness, corrosion resistance, and elastic-plasticity of the Ni coating prepared on the inner wall of the pipe show a trend of initially increasing and then decreasing as the working voltage gradually increases. The coating exhibits the best surface quality, the fewest defects, and the most significant grain refinement effect when the working voltage is 12V. At this voltage, the coating has a hardness of 575.8 HV, a corrosion current density of 1.040 × 10(4)Ni coating on the inner wall of a metal pipe via an optimized electro-brush plating deposition process. Compared with the coating on the inner wall of commercially available galvanized steel pipes, the resultant Ni coating exhibited significant enhancements in surface morphology, coating hardness, corrosion resistance, and elastoplasticity. Moreover, the proposed method features several advantages including simple and convenient equipment, uniform and dense surface morphology, high deposition rate, and simplified plating solution and process.


Flood-controlled ancient dikes play a significant role in flood control and have received widespread attention as historical and cultural symbols. Flood-controlled ancient dikes often undergo disasters, and research on their repair is receiving increasing attention from experts and scholars. This article studies the control of seepage and bank slope instability in flood-controlled ancient dikes. Starting from the repair of ancient dike materials, three types of work are carried out: a test of soil’s mechanical properties, finite element numerical simulation, and repair technology research. The research results show that the soil of the ancient dike site has hardened after being contaminated with waste oil from catering. The strength index of the ancient dike soil decreases and shows brittleness when the water content is 15% and the oil content exceeds 6%. The strength index and permeability coefficient of oil-contaminated soil improved using modified lime mortar (MLM), which was achieved using the method of MLM to repair oil contaminated soil. When the MLM content was 10% and the oil content was 6%, the friction angle of the soil sample reached its maximum value. When the MLM content was the same, the higher the density of the soil sample, the greater the friction angle and cohesion and the smaller the permeability coefficient. Establishing a finite element numerical model, through comparative analysis, it was found that after MLM remediation of oil-contaminated soil, the extreme hydraulic gradient of the ancient dike decreased by 31.3%, and the extreme safety factor of the bank slope stability increased by 31.2%. MLM pressure grouting technology was used to improve the soil during the remediation of contaminated soil at the ancient dike site. Through on-site drilling inspection, the effective diffusion radius of MLM grouting was obtained, and the plane layout and grouting depth of MLM pressure grouting were determined. The on-site water injection permeability test showed that using MLM pressure grouting technology can effectively repair oil-contaminated soil in the ancient dike while reducing the permeability coefficient by 8–15%. The urbanization process in China has had a significant impact on the urban water system structure, and urban construction planning optimization based on flood control safety and historical water engineering protection is gradually becoming a research hotspot ,2,3,4,5.The mineral oil of common contaminated soil includes oil, gasoline, diesel, and gasoline, and the contaminated soil includes cohesive soil, fine sand, silty clay, etc. Oil-contaminated soil samples were prepared by mixing the residual soil and oil and were tested in the laboratory. The results showed that oil pollution led to the deterioration of the geotechnical properties of the soil samples. Compared with raw soil, its maximum dry density, optimum water content, permeability, and shear strength decreased ,7,8. TheDue to the special historical and cultural value of ancient dikes to be preserved during repair, the repair materials should be compatible with the raw materials, and lime should be the main material ,25,26,27Many scholars have studied the effects of physical and mechanical properties of soil on the seepage and bank-slope stability of flood control dikes. Based on the change in the microstructural arrangement of soil particles, the microscopic change in the permeability coefficient of soil is studied experimentally ,46,47. TThere are many flood-controlled ancient dikes in China. These ancient dikes still play a role in flood control, and at the same time, they are often protected cultural relics and landmark buildings in towns. Representative flood-controlled ancient dikes in southern China are all distributed in densely populated towns along rivers in a. Take tAncient dikes have suffered various forms of damage. The bank slope of Lanxi Ancient Dike is mainly filled with artificial soil, Through experiments, the physical and mechanical parameters of soil were obtained, and changes in soil, oil content, and modified lime mortar (MLM) content on mechanical indicators were compared and analyzed. Then, the stability of flood-controlled ancient dike was studied using the finite element numerical analysis approach to take into account the intrinsic variability of the soil parameters. The research provides theoretical guidance for the study of ancient dike seepage, slope stability, and reinforcement measures, as shown in 1 and I2 and sand gravel-filled layer II. The thickness of soil layers I1 and I2 is 2.5~4.5 m, the thickness of sand gravel layer II is 6.1~11.5 m, and the layer below layer II is the argillaceous silty sand layer. The soil of layer I1 is newly artificially filled soil, mainly composed of silty cohesive soil with mixed rubble and a small number of broken bricks in the middle. In some embankment sections, there are still brick wall structures of previous houses left. This layer of soil has poor uniformity, complex material composition, unstable properties, and poor impermeability. The filling soil of layer I2 is mainly composed of silty clay with sand gravel. Compared to layer I1, this layer has a relatively long filling history. The structure of this layer is moderately dense, with general uniformity. This layer of soil has medium water permeability. Layer II is composed of sandy gravel pebbles, mixed with silty clay, and is moderately dense with medium water permeability. The impact range of waste oil leakage from catering is mostly in layer I1 and layer I2, and the impact range of seepage deformation is in layer I1, layer I2, and layer II. The soil used in this test is taken from this range, and after drying and screening, the soil with a particle size of less than 2 mm is taken for the remolded soil test.The soil for the test was taken from a typical section of the Lanxi Ancient Dike. The ancient dike is adjacent to residential buildings and municipal facilities, and the bank slope often collapses suddenly, as shown in 1, I2, and II were measured with the drying method, the specific gravity with the pycnometer method, and the liquid plastic limit and plastic limit of Ⅰ1 and Ⅰ2 soil samples with the combined liquid plastic limit method according to the Standard for Soil Test Methods (GB/T50123-2019), as shown in The dry density and moisture content of soil samples of soil layers IAfter the soil sample was fully air-dried, it was fully rolled with a rubber rod and sieved through a 2 mm sieve, and the sieve residue was stored in a sealed bag for standing by. In order to analyze the composition and distribution of soil particles, a 0.075 mm sieve was used to divide the soil samples into two groups: coarse particles with a diameter of 0.075~2 mm and fine particles with a diameter of less than 0.075 mm. The soil samples were put into a self-sealing bag for standby, as shown in The particle grading curves of three soil samples were obtained, as shown in Through environmental field investigation and geological survey, according to the composition analysis of soil samples, it is found that the leakage of waste cooking oil causes soil contamination. With the change in waste oil content, soil properties change. The mechanism of the influence of waste cooking oil infiltration on soil properties is still unclear, and there are few relevant studies. This paper carried out an experimental study on this topic. Since the main component of waste cooking oil is edible oil, light and low-viscosity vegetable oil was selected as the test oil. See The test is divided into two groups, namely, a consolidated undrained test and a saturated seepage test. The effect of oil content on the mechanical properties of soil was studied by measuring the stress–strain relationship of soil samples through a consolidated undrained triaxial test. The saturated seepage test was used to study the influence of reducing the fine particle content in soil samples on the permeability coefficient and to explore the change in the permeability coefficient in the process of seepage deformation.3, 1.68 g/cm3, and 1.79 g/cm3 and a grain size of 0.075~2 mm were each taken for preparing samples for the consolidated undrained test. The masses of soil, water, and oil were calculated according to Equations (1)–(3). The reconstituted soil samples were configured with a water content of 15%; an oil content of 0%, 3%, 6%, 9%, and 12%; a diameter of 3.8 cm; and a height of 7.6 cm. GDS triaxial apparatus (DYNTTS) was used for he consolidated undrained compression test.3; and 3.Soil samples with a dry density of 1.53 g/cm−5 mbar, and then one moves to the sample stage using the relevant buttons and finds the best observation position, changes the magnification and focus, and adjusts the astigmatism until a satisfactory image is obtained. The voltage is 12~15 kV, and photos are taken at 1000 times magnification; then, satisfactory images are saved and printed.The soil sample was mixed with vegetable oil and left to stand for 24 h. The microstructure and main components of the soil sample were analyzed using scanning electronic microscopy (SEM)  and energy-dispersive spectroscopy (EDS). Due to the poor conductivity of soil, it is necessary to perform sputtering with gold in advance, about 15 min before SEM scanning. After the sample stage is sent to the corresponding position of the instrument, the sample needs to be automatically evacuated for 20 min to avoid interference with the radiation signal of the scanned sample. A vacuum is maintained at 7.0 × 10The microscopic analysis adopts ZEIZZ-EVO15  scanning electron microscope for phase analysis, LaB6 electron gun, acceleration voltage EHT of 12~15 KV, probe current I probe of 20 pA, X-ray composition analysis current of 300~600 pA, and working distance WD of 8~15 mm. The EDS is used to determine the elemental composition of the sample by the back-scattered detector image. X-ray diffraction (XRD) was used to study the crystalline and amorphous phases of the original soil samples and the soil samples contaminated by vegetable oil.Standard for geotechnical testing method (GB/T50123-2019), after evenly mixing with water, the soil surface is covered with film and left to stand at room temperature, 20 °C, for 24 h, and then the oil and soil are mixed with an oil content of 3%, 6%, 9%, and 12% and left to stand for 7 d. Oil content soil samples are prepared densities of 1.53, 1.68, and 1.79 g/cm3. After saturation in a vacuum in pure water in a vacuum cylinder for 8 h, the consolidated undrained test is carried out on the GDS triaxial tester. The test process is shown in According to 2, and the mineral powder is S95-grade ground granulated blast furnace slag. The modified lime mortar (MLM) is prepared according to a ratio of hydrated lime to mineral powder of 2:3, the water–cement ratio is 0.43, and additives such as viscosity additives are added. The modified lime mortar is mixed evenly with 5%, 10%, and 15% content and 6% oil-content-contaminated soil after 24 h of static and cured at 20 °C and 90% relative humidity for 7 days for standby.The MLM is then prepared. The main component of hydrated lime is Ca (OH)See The test flow of two soil samples is shown in The test was divided into two groups. For the first group, the results of microstructure and strength properties of oil-contaminated soil with 0%, 3%, 6%, and 9% oil content were analyzed, and for the second group, the changes in strength and permeability properties of MLM were analyzed to improve oil-contaminated soil.The microstructure and main constituent elements of soil samples were analyzed using scanning electron microscopy, and the microstructure of crystalline and amorphous materials of original soil samples and soil samples contaminated with vegetable oil were studied using phase analysis.According to the image of the change in the SEM microstructure in 2), microcline (KAlSi3O4), muscovite (K0.77Al1.93(Al0.5SiO3.5)(OH)2), Albite (AlSi3O4) and chlorite-serpentine 44O10(OH)4). Among these, quartz accounted for 48%, microcline accounted for 24%, muscovite accounted for 17%, albite accounted for 8%, and chlorite-seripentine accounted for 1%.XRD diffraction analysis showed that there was no obvious change before versus after the crystal composition of the soil were contaminated by oil. It can be judged that there was no chemical reaction between vegetable oil and the soil, and no new substances were produced. 3, the water content was 15%, and the oil contents of the different samples were 0%, 3%, 6%, and 9%. The soil volume, water volume, and oil volume were measured according to Equations (1)–(3). The soil particles were weighted, and the water and oil were fully mixed and then covered with film for storage and left to stand at room temperature for 24 h. After the soil, water, and oil were evenly mixed, the soil was taken for sample preparation. After the sample was saturated in a vacuum for 7 h in the saturator, the GDS triaxial apparatus was used for a consolidated undrained compression test. The system shall set the confining pressure and back pressure by levels, and the confining pressure and back pressure differences of the different groups were 30 kPa, 60 kPa, 90 kPa, and 120 kPa. The pressure difference was kept between the confining pressure and, the backpressure was kept as a constant in each test. After each stage of confining pressure and backpressure pressurization, a pore pressure coefficient B value test was conducted. The pore pressure coefficient B was the pore-pressure coefficient under the condition of equal isotropic stress, which is the increment of pore pressure caused by the unit increment of confining pressure when the soil is in the state of isotropic compressive stress. If the B value is greater than or equal to 0.95, the sample can be considered saturated. Under special circumstances, the B value of individual samples remains unchanged for a long time, which is also considered saturation. After consolidation, the next undrained shear test can be conducted. When the bias stress reaches its peak value, 3~5% of the axial strain is then sheared. If the stress reading does not decrease significantly, it is sheared until the axial strain reaches 15~20%, and the whole test is complete. The peak value of deviatoric stress is taken. If there is no obvious peak value, the deviatoric stress corresponding to the axial strain of 15% is taken as the peak value.When preparing soil samples, the dry density was 1.68 g/cmFive parallel tests on each group of samples were carried out. Due to the influence of uncertain factors in the test, the data with large deviations were removed, the average values of 3–4 parallel test data were taken as the result; the deviatoric stress axial strain curves are drawn in 3 are taken to draw stress circle strength envelope lines with oil contents of 0%, 3%, 6%, and 9%, as shown in It can be seen from 3, the change in the strength index of oil-contaminated soil after treatment with MLM content was tested. The MLM accounted for 0%, 5%, 10%, and 15%, respectively, and the soil samples with 6% oil content were prepared. The consolidated undrained test was completed after 7 days of curing under standard conditions. Five parallel tests were carried out on each group of samples, the average value of 3–4 parallel test data were taken as the result, and the molar stress circle and strength envelope were drawn; see 3 and an oil content of 6%, the friction angle gradually increased with the increase in the lime content. When the MLM content was 10%, the friction angle reached a maximum value of 30.07°, which is 1.26 times the friction angle of the non-lime-content-contaminated soil, and the maximum value of cohesion was 32.47 kPa, which was 1.32 times that of the non-lime content contaminated soil.In view of the large strength index of soil samples with an oil content of 6% and a density of 1.79 g/cm3, 1.68 g/cm3, and 1.79 g/cm3 were prepared. After the soil samples were cured under standard conditions for 7 days, five parallel tests and consolidated undrained shear tests were conducted on each group of samples, and the average value of 3–4 parallel test data was taken as the result. The peak value of the average principal stress deviation at each oil content is shown in According to 10% of MLM content, soil samples with densities of 1.53 g/cm3, 1.68 g/cm3, and 1.79 g/cm3 at each oil content is shown in The peak value of the principal stress deviation of soil samples with densities of 1.53 g/cm(1) Influence of oil content on permeability2; L is seepage path, L = 4 cm; A is the cross-sectional area of the soil sample, A = 30 cm2; The permeability characteristics of soil samples with different oil content and 10% MLM content were studied. After the soil sample was saturated in a vacuum for 12 h, the permeability coefficient of the soil sample was measured using the variable-head permeability test. According to Darcy’s law, the seepage flow through the soil sample at the same time was equal to the flow through the water head gauge. The seepage coefficient can be expressed as3. The permeability coefficient of the soil samples with an oil content of 9% was 2.18 −5 cm/s, which is 2.4 times the permeability coefficient of the 1.79 g/cm3 soil sample. The soil sample used in this test was silty clay mixed with MLM. After vegetable oil pollution, a film is formed on the surface of soil particles, which shortens the seepage path of water between soil particles and increases the permeability coefficient.The relationship between the permeability coefficient of the three densities of soil samples and the oil content is shown in (2) Influence of MLM content on permeability3 and an MLM content of 15% was 9.86 −7 cm/s, which is 24% of the permeability coefficient of soil samples with an MLM content of 0%, namely 4.03 −6 cm/s.The permeability coefficient of the three densities o soil samples decreases gradually when the MLM content increases, and the relationship between the MLM content and the permeability coefficient is shown in 3 and MLM content of 15% was 9.86 −7 cm/s and that of the soil sample with MLM content of 0% was 4.03 −6 cm/s; the former is 24% of the latter.The permeability coefficient of the three densities of soil samples decreased gradually with the increase in lime content, and the relationship between MLM content and permeability coefficient is shown in 1 is located 2.10 m above the foundation behind the ancient dike, that is, at 26.90 m elevation. See After the soil of the Lanxi ancient dike was contaminated with oil, the permeability coefficient and strength index of the soil changed, affecting the permeability deformation and stability of the bank slope. When using the finite element method to establish a numerical model , several1 on the back of the wall. The results of finite computing show that the hydraulic gradient of the ancient dike soil changes with the rise and fall of the flood peak of the Lanjiang River. At the maximum rate of water pressure change, the hydraulic gradient of the soil reaches its maximum value. The distribution of gradient values corresponding to a 6% oil content in the soil is shown in 1 rapidly increases. When the water level is 26.58 m, the water level change rate reaches its maximum value, and the hydraulic gradient at point A1 reaches its maximum value of 0.64. When the water level change rate decreases, the hydraulic gradient begins to decrease. As the growth rate of the Lanjiang River water level slows down, the hydraulic gradient at point A1 gradually decreases. When the flood peak rapidly decreases, the hydraulic gradient decreases rapidly. When the water level changes slow down, the hydraulic gradient changes gradually stabilize. In the case of a sudden drop in water level in the Lanjiang River, when the rate of change reaches the stagnation point, the minimum stability safety coefficient of the ancient dike is 1.004. The typical calculated sliding surface is shown in 1 decreases to 0.44, which is 31.3% lower than the hydraulic gradient value of oil contaminated soil. The minimum stability coefficient of the bank slope is 1.317, which is 31.2% higher than the stability safety coefficient of oil contaminated soil. As shown in The numerical analysis results indicate that the seepage and slope stability of the ancient dike after being contaminated with oil are shown in The MLM pressure grouting measures were adopted to repair the oil-contaminated soil in the ancient dike. A modified lime grouting test was conducted on the ancient dike slope, and ZK1 grouting holes were set up with a diameter of 10 cm. The MLM shall be grouted in six steps. The MLM shall be prepared according to the proportion, and then the soil surface shall be treated, the position of the grouting nozzle shall be calibrated, and then the hole shall be drilled. After the grouting nozzle is installed, the pressure grouting shall be carried out, and the static curing shall be more than 24 h. After the joint is sealed, the secondary grouting shall be carried out, and the pressure shall be controlled at 0.1~0.5 MPa, so as to ensure that the slurry is full without leakage and dense without bubbles. Seventy-two hours after the completion of ZK1 grouting, inspection boreholes were set up at positions ZK2, ZK3, and ZK4 with a hole spacing of 40 cm, as shown in The layout of MLM pressure grouting is shown in After using MLM pressure grouting for ancient dikes, the pore water pressure and seepage ratio decreased significantly compared to the original structure section with good permeability. The results indicate that setting MLM pressure grouting can effectively reduce the permeability of the foundation soil, improve the cohesion of soil particles, and suppress the occurrence of piping in flood-controlled ancient dikes and repair engineering without changing the cultural relics. The compactness of the soil was improved inside the city wall, defects were treated, and leakage channels were blocked.In order to verify the anti-seepage effect of MLM pressure grouting, on-site water injection permeability tests were conducted, with two inspection holes arranged as shown in The physical properties, strength index, and permeability coefficients of oil-contaminated silty clay have changed, leading to the susceptibility of flood-controlled ancient dikes to disasters such as leakage and bank-slope instability. Through dynamic triaxial tests and variable head permeability tests, the strength index and permeability coefficient changes in oil-contaminated soil and MLM-improved soil were obtained. By using the finite element numerical simulation method for comparative analysis, the effect of MLM improvement on oil-contaminated soil on improving the leakage of flood-controlled ancient dikes and bank slope stability was obtained. Subsequently, MLM pressure grouting technology was used to repair the ruins of flood-controlled ancient dikes. The following conclusions were drawn from the above series of studies.(1) After the silty clay was contaminated with oil, the relationship between the principal stress deviation and strain of the soil sample changed with the change in oil content, leading to stress hardening. When the oil content increased, the strength index also changed. When the oil content was 6%, the friction angle reached its maximum value, but as the oil content continued to increase, the friction angle decreased. When MLM was used to repair oil-contaminated soil, as the MLM content increased, the friction angle and cohesion of the soil sample also increased. When the MLM content was 10% and the oil content was 6%, the friction angle of the soil sample reached its maximum value. At the same MLM content, the higher the density of the soil sample, the greater the friction angle and cohesion, and the smaller the permeability coefficient.(2) The finite element numerical simulation analysis shows that after the soil of the flood-controlled ancient dike was contaminated with oil, when the water level was at its maximum rate of change, and the water level was 26.58 m, the extreme hydraulic gradient of the ancient dike soil reached 0.64, and the extreme safety coefficient of bank slope stability was 1.004. When MLM was used to repair oil-contaminated soil, when the MLM content was 10%, the extreme hydraulic gradient of the ancient dike was 0.44, a decrease of 31.3%, and the extreme safety factor of bank slope stability was 1.317, an increase of 31.2%.(3) MLM pressure-grouting technology was used to repair flood-controlled ancient dikes. The effective diffusion radius of MLM was detected through grouting tests, and then the distance, arrangement, and depth of MLM pressure grouting holes were determined. After the MLM grouting repair of oil-contaminated soil on the slope of the ancient dike was completed, on-site water injection permeability tests showed that the permeability coefficient of the ancient dike soil decreased by 8–12%.Notably, this study can provide research methods and technical measures for the repair of similar flood-controlled ancient dikes.


Cyberlindnera jadinii yeast in media prepared from potato wastewater and glycerol (after biodiesel production), supplemented with magnesium salt. The research was carried out in two stages. In the first, the ability to binding magnesium by yeast in media supplemented with various doses of this element was tested. In the second stage, after selecting the appropriate dose of magnesium, the culture was carried out in a bioreactor. The composition of the yeast biomass was also analysed in terms of lipids and protein content and amino acid composition. Studies have shown that this type of medium can be used as a culture medium for the growth of C. jadinii yeast. In the first stage of the study, the most magnesium (8.97 mg/gd.m.) was bound by yeast cells after 48 h of cultivation in a medium supplemented with the addition of magnesium at a dose of 2 g/L. In the second stage of the research, the highest magnesium content in the biomass (7.9 mg/gd.m.) was noted after 24 h of cultivation in the same medium. The lipid and protein contents in the biomass obtained after 24 h of cultivation in the bioreactor were 6.35 and 43.73%, respectively. The main fatty acids present in the yeast lipids were oleic acid (59.4%) and linoleic acid (8.6%). Analysis of the amino acid profile of the proteins showed the highest proportions were glutamic acid (13.7%) and aspartic acid (11%).The aim of this study was to determine the magnesium-binding capacity of  Magnesium is called the element of life. It plays an important role in the biochemical processes that take place in living organisms. It improves the functioning of metabolic processes and activates over 300 enzymes, which are responsible, among others, for the stabilisation of nucleic acids and ribosomes . MagnesiCyberlindnera jadinii yeast has the ability to bioaccumulate various elements, including magnesium and selenium in amounts significantly exceeding the natural needs of the cells ..44].C. jadinii yeast depends on the composition of the culture medium, and, above all, on the type of nitrogen source, which is described, among others, by Somda et al. [C. utilis FMJ12 yeast in a medium prepared using mango waste supplemented with various nitrogen sources. Very large differences in the content of amino acids were found depending on the nitrogen source used. For example, C. utilis FMJ12 yeast did not synthesise methionine in the peptone medium, while in the other three variants of the medium its content was 1.67 g/100 g protein (yeast extract), 0.48 g/100 g protein (ammonium sulphate) and 0.03 g/100 g protein (ammonium nitrate). For C. jadinii ATCC 9950 yeast grown in a medium with potato wastewater, glycerol and magnesium, the dominant amino acid was glutamic acid, the highest content of which was 16.57 g/100 g of protein, which the authors found after cultivation in a medium with yeast extract [The comparison of the amino acid composition showed a higher content of histidine, valine, isoleucine, leucine, lysine, phenylalanine + tyrosine and threonine in the yeast protein of the tested strain than in the FAO/WHO standard. Due to the absence of methionine, the sum of the sulphur-containing amino acids was lower than in the standard protein profile. The profile of the amino acids synthesised by a et al. . The aut extract .C. jadinii ATCC 9950 yeast. By supplementing the culture media with Mg2+ cations, valorisation of the cell biomass of the tested yeast strain was achieved, which can be successfully used as a potential source of well-absorbed magnesium bioplexes to treat a deficiency of this element in the diet of animals and humans. The cell biomass of C. jadinii yeast obtained with a 3.5 L-scale bioreactor with a medium of potato wastewater and glycerol enriched with the addition of magnesium at a dose of 2 g Mg2+/L was characterised by a high content of magnesium, a valuable profile of fatty acids  and a high content of proteins with a favourable amino acid composition due to the significant proportion of some exogenous amino acids .The conducted research showed the possibility of using potato wastewater and waste glycerol from the production of biodiesel as cheap components of the culture medium for producing the cell biomass of


The quantification of the single or combined variation of the process parameters specific to a thermochemical treatment is the key to a full factorial experiment and a first step in the development of computer-aided process engineering. Powdery solid media are frequently used in the practice of thermochemical treatments when the number of processed products is reduced, additional investments are not justified, or when there are no technological alternatives. The control of the process carried out in such powdery solid media involves both the control of the thermal and temporal parameters of the process on the layer growth kinetics and its phase composition, as well as the ratio of the powdery solid mixture mass percentage . In this paper, using the specific full factorial experiment ), the full model of the regression equation of the interactions between the specific process parameters of the silicide layer formation in a powdery solid media, applied to the low alloy P265GH steel grade and used in the petrochemical industry, were evaluated. Fe-ARMCO was chosen as the reference in the experimental research carried out. Silicon cementation in powdery solid media represents, in many situations, a particularly attractive thermochemical processing alternative. The silicon saturation of the silicide layer formation allows a substantial increase in corrosion resistance, refractoriness, hardness, and wear resistance, or, frequently, a combination of these properties imposed by the operating demands of various categories of alloys and parts ,2,3,4. IThe carbon affinity of alloying elements, such as molybdenum and tungsten, increases the thickness of the silicon alloyed ferrite layer.1 phase  [A particular problem associated with superficial silicon saturation is the appearance of diffusion porosity, which is most commonly related to the difference in partial intrinsic diffusivities of the components, known as the "Kirkendall–Frenkel effect". There is a multitude of solutions to reduce the consequences of the Kirkendall–Frenkel effect’s manifestation , but theSilicon cementation can also be applied to landmarks made of alloys with a different base than that of iron, for example, aluminum–bronze alloys, providing them with a substantial reduction in the coefficient of friction simultaneously with an increase in wear resistance  or alloyThe use of experimental programming methods, and the statistical processing of the data actually obtained by carrying out the imposed cycle of experiments, allows the obtaining of mathematical models of the interactions between the processing parameters  and the growth kinetics of the compound layer ,9,10,17.The purpose of the experimental research was to quantify the variation of the technological parameters’ effects of the silicon cementation process in a powdery solid media, with ferrosilicon (FeSi75C) as the active component, on the growth kinetics of the total silicized layer and to determine the mathematical models of the interactions between them.The metallic materials used in the experimental research to highlight the aspects studied were high-purity iron (Fe-ARMCO) and low-alloy grade steel, SR EN ISO 10028-2:2017/P265GH , mainly The chemical compositions for the two metallic materials are presented in The characteristics of the components of powdered solid mixtures used in the research are as follows:Ferrosilicon powder  produced by the Norwegian company, FINNFJORD ; particles with an average equivalent diameter of 40–50 mm were subsequently ground into ball mills to an average the equivalent diameter of 3–4 mm.2O3 > 98.5%) were produced at Alum S.A. , fraction >150 µm max. 10%; fraction < 45 µm max. 12%.Alumina powders (Al4Cl) of analytical purity was produced by SilverChemicals .Ammonium chloride .The samples, with dimensions of 15 × 15 × 10 mm, were packed in solid powder mixtures and positioned in refractory steel containers. After that, the containers were sealed with clay, placed in the furnace at 200 °C, and heated with the furnace up to the holding temperature. After the holding time imposed by the experimental program, the containers were taken out and cooled freely in the air; the extraction of samples was realized when the temperature of the containers was below 300 °C.4Cl) was 3, 6, and 9%.The technological parameters of the silicon cemented process in a powdery solid media were: holding temperature at 950, 1050, and 1150 °C; holding time at mentioned temperatures about 1, 3, and 5 h; the proportion of the active component (FeSi75C) of the powdery mixture was 40, 50, and 60%; and the proportion of the ammonium chloride  by means of the Vickers hardness test.Microhardness analysis was carried out using a Neophot 21 microscope N1096 series  with Hanneman’s indenter under load of 50 gf (HVLight Microscopy (LM) was carried out using a Zeiss Z1m Observer microscope—Axio Vision 4.8/038-12837 .XRF analyses were performed on the SPECTRO xSORT device no. 143714 , used to verify %Si along the coating thickness layer.Energy dispersive spectrometry (EDS Sapphire type dispersive energy spectrometer with a resolution of 128 kV) was carried out using a Phenom ProX SEM .The achieving the requirements imposed by the full factorial experiment is represented by the explanation of the mathematical models of the interactions between the independent parameters of the studied process and, respectively, the dependent ones ,9,10,17.i identified are:In the analyzed situation, silicon cementation in a powdery solid media of Fe-ARMCO and low-alloy P265GH grade steel, the independent parameters (inputs factors) XX1—silicon cementation temperature.X2—siliconizing process holding time.X3—the proportion of the active component in the mixture—FeSi75C .X4—the proportion of the activator in the mixture—NH4Cl.2O3, and its proportion was calculated according to the formula [2O3 = 100 − Σ (%FeSi + %NH4Cl).The neutral component, with the role of blocking the sintering tendency of the powdery solid media, was Al formula ,17,19,202 as an active component, the presence of pure aluminum powder is also necessary to initiate and maintain the aluminothermic reduction reaction of SiO2 and the release of silicon in the active state.As active components, suppliers of silicon, in the practice of silicon cementation, ferrosilicon powders, silicon, silicon carbide, Si-Ca, or their mixtures are most frequently used in order. As mentioned by Celebi Efe and others , when usY, the total thickness of the silicide layer obtained for each of the technological variants imposed by the adopted research program was chosen.As a dependent parameter, Starting from the information given by Lahtin and Arzamasov , regardiX1…X4) and the dependent ones (Y) in the form of the full model of the regression equation of the type:Following this, we explained the correlations between the independent parameters taken into the analysis .ix; jx—the coded values of the factors .Y—the real value of the dependent parameter—total thickness of the silicon cemented layer.The actual experimental conditions for explaining the regression Equation (1), related to the two situations taken into the analysis (active component FeSi75C) and the results obtained, are presented in ib; ijb; ijkb…) involves the determination of the experimental S02 reproducibility , the dispersion in the determination of the biS2 coefficients, and the confidence interval Δib with which coefficients were calculated; see The calculation algorithm and statistical verification of the coeficients of the first-order CFE , as shown in The graphical expressions of the regression Equations (2) and (3) made for a series of restrictive packages of variables  and (3) in relation to the experimental ones see  are reflThus, it is found that, from 1050 °C see , the inc4Cl), at the upper limit of the range of values adopted in the active experimental program  and associated with temperatures at the lower limit of the same program (950 °C), apparently generate some deviations from the expected mode of variation of the total thickness of the silicide layer, depending on the proportion of the active component in the mixture (%FeSi75C powder) and, respectively, the holding time, as shown in High proportions of the component with the role of activator (NHAlloying the iron matrix with Mn (1.05% for P265GH grade steel) and increasing the carbon content (0.1% compared to 0.02% for Fe-ARMCO), causes a decrease in the value of the silicon diffusion coefficient in the metal matrix which affects the speed of growth and the formation of the layer, as shown in Thus, under the same thermochemical processing conditions, the P265GH low-alloy grade steel registers a slower growth kinetics layer than in the case of Fe-ARMCO.The explanation of such behavior can be found starting from the analysis of probable reactions from a thermodynamic point of view  that can2) in the sequence of reactions, that lead to the formation of silicon in the active state and its proportion, can have undesirable consequences on the kinetics of the cemented layer growth if the proportion of halide in the powdery mixture is not carefully correlated with the processing temperature, respectively, with the proportion of the active component of the mixture.The appearance of ferrous chloride (FeClmelt = 677 °C) and at 1023 °C it starts to vaporize. An excess of it at the media–metal matrix interface, determined by the high proportions of the component with the role of activating the reactions in the media (NH4Cl), causes a decrease in the layer formation kinetics due to the blocking of silicon adsorption , the increase in the proportion of FeSi75C in the powdered solid mixture, in the presence of a high proportion of reaction activator, has an accelerating effect on the kinetics, over time, the accumulation of the ferrous chloride melt makes its effect felt.4Cl) in the powdered solid mixture when used at low processing temperatures , can generate major disturbances in the layer growth kinetics, caused by a significant increase in chlorine concentration in the superficial areas of the layer.Incorrect dosing (overdosing) of the proportion of halide (NH4Cl), highlight the existence of some concentrations’ high levels of chlorine in the superficial areas of the silicide layer along the coating thickness, as shown in X-ray fluorescence investigations carried out on the samples of the two metallic materials silicon cemented at the lower limit of the temperature range, i.e., at 950 °C and at, respectively, high proportions of halide in the powdery solid media  and by the pressure exerted by it; changing its state of aggregation upon cooling, it will be found in its crystallized form at room temperature.The presence of chlorine in these areas is determined by the accumulation of ferrous chloride at the interface . In these new processing conditions, a particular intensification of the growth kinetics of the compound layer is recorded. The mass concentration of nitrogen varies between 1.43% and 1.77%, and of chlorine between 0.00% and 0.06%.With an increase in the thermochemical processing temperature and the proportion of the active component in the powdery solid mixture, and simultaneous decrease in the proportion of the component with the role of activating the reactions between the components of the environment , a decrease in the chlorine concentration at the interface by more than an order of magnitude is recorded see , as well3Si compound (located outwards), as is shown in The metallographic analysis performed on samples from the two metallic materials (Fe-ARMCO and P265GH steel grade), with silicon cemented in powdery solid media containing high proportions of FeSi75C and low halides, highlights an area with a columnar aspect specific to the presence of α solid solutions of silicon in iron, and a second one α′, the solid solution based on the FeAs a particularity, in the case of low-alloy P265GH grade steel, an increase in the proportion of carbon generated by silicon diffusion can be observed in the substrate, which has the effect of a considerable increase in the proportion of pearlite (the structure of these areas corresponds to a hypereutectoid steel).Another peculiarity of the obtained layers is related to the presence of diffusion porosity, the consequence of the Kirkendall–Frenkel effect.0.05, regardless of the processing regime, reaching up to about 600 μHV0.05 at about 600 μm from the surface. The values represent the average of 10 indentations.The microhardness tests carried out on P265GH grade steel samples, thermochemically processed under the mentioned conditions, highlighted the fact that the value in the layer, at about 20 μm of the surface, falls within the range of 150 ÷ 200 μHV-They allow anticipation by calculation of the silicon cemented thickness layer under strictly specified conditions.-They allow the determination/quantification of the way in which the level of a certain independent parameter can be compensated at a given time by modifying the other influencing factors.-They allow the automatic management of the process.-They allow the construction of graphic representations, as shown in The regression Equations (2) and (3), obtained through the statistical processing of the experimental data, ensure the possibility of more rigorous control of the silicon saturation process:Powdery FeSi75C represents a potent active component of powdery solid mixtures used in the silicon saturation process of metal products.The most intense layer growth kinetics is observed with a powdered solid mixture with high values of the active component correlated with low values of the one with the role of activation.The mechanism of silicon adsorption during thermochemical processing has both an atomic and an ionic character.The calculated regression equations of the interactions between the independent parameters of the thermochemical processing and, respectively, the dependent ones , ensure a multitude of facilities: (i) the optimization of the process; (ii) the estimation of the total thickness of the silicized layer under strictly specified conditions; (iii) the determination of how the deficit or excess of a certain independent parameter can be compensated (if it can be compensated) by changing the others.


The study reveals the half-metallic nature of the currently studied materials. For the mechanical stability of RbVX3 compounds, all three independent elastic coefficients (Cij) were determined, from which it was concluded that these materials are mechanically stable. Moreover, from the Poison and Pugh's ratios, it was found that the RbVCl3 and RbVBr3 materials have ductile nature, while RbVI3 has brittle nature upon the applied stress.The non-toxic nature of lead-free materials with cubic perovskite structure has attracted the researcher's attention, and huge work is ongoing for the search of such materials. Furthermore, due to demand for their utilization in diverse applications, such as photovoltaic and optoelectronics, these inorganic-halide materials have become more enchanting for engineers. In the present work, all the key properties, including structural, electronic, optical, and mechanical, of rubidium based RbVX The non-toxic nature of lead-free materials with cubic perovskite structure has attracted the researcher's attention, and huge work is ongoing for the search of such materials. Many types of materials have been studied and utilized in different types of applications. Among these varieties of materials, ABX3 materials for various types of devices display various combinations of properties depending on the treatment process by the material scientists in the laboratory during their synthesis. There are some ABX3 materials exhibiting perovskite structures but their unique nature of behaving like semiconductors in one spin while metallic in the opposite spin makes them ideal for applications such as piezo-electricity, superconductors at high temperature, colossal magneto-resistivity, photo-luminescence, vehicle energy devices, lenses applications, and photovoltaics.9–17 In 2002, a research group also investigated computationally such types of materials having dual nature in their spins. The authors reported that both the MTiF3 (where M stands for Rb and Cs) materials have metallic nature in their spin-up, while in the spin-down configuration, they showed semiconducting behavior. The authors claimed that both the aforesaid materials are elastically stable and have attractive optical properties.18 A lot of other materials have been studied by different research groups using DFT calculations in order to help experimentalists with producing cost effective, easy, and more suitable materials than the existing materials for practical applications.19,20These ABX3 materials have been studied in detail via the DFT approach.Our research study was also focused on the above-discussed aim, and for that purpose, the structural, electronic, optical, and mechanical properties of the new RbVX21 All the important properties, such as structural, electronic, optical and elastic, were studied in the present work. For the aforementioned properties, the k-points chosen were 2000. From the optimized energy vs. unit cell volume, the basic lattice parameter for the structures was calculated using the well-known Birch–Murnaghan equation of state.22 The WIEN2K interface package IRelast was used for calculating the elastic properties of the studied material.23 For the optical properties of the presently studied materials, the essential parameters, such as dielectric function, absorption coefficient, optical conductivity, and refractive index, were determined. Some other well-known software like Origin, Xcrysden, and Xmgrace were also used for the plotting purpose in this study. In order to avoid the charge outflow from the atomic spheres, the energy gap between the core and valence electrons was selected as −6 Ry, and also a value of 7 was selected for the RMT × Kmax, which is needed for the phenomena of convergence.In the recent research study, the potentials of TB-mBJ along with the combination of GGA were adopted for various calculations. These potentials are applied in the WIEN2K code and installed with the DFT.3  material had a cubic crystal structure and is included in the space group of Fm3̄m (no. 221). Moreover, from this study, it became clear that a total 5 atoms take part in the unit cell of the investigated RbVX3 materials, as presented in From the structural study, it was concluded that the RbVX3 materials structure and thermodynamic endurance , and these values of the phonon dispersion for the investigated materials authenticate the dynamical stability of phonon of all the materials. The same result was also seen for BaAgCl3 and BaCuCl3 materials in a computational study.28The phonon study of any material is essential because phonons are known as the main factor of the thermal characteristics of any material and their dynamic behavior.3  materials were mainly analyzed using the Brillouin zone with high symmetry directions. Using the PBE functional while adopting the Tb-mBJ approximation, the band structures and the respective density of states (DOS) profiles of the RbVX3  materials were calculated. 3  compounds with the Fermi energy at zero point and the energy band ranges between 8 eV to 6 eV. From the results of the band structures shown in 3  compounds were entirely different from the spin-up calculations since none of the band structure curves of the materials cross the Fermi level. The spin-down configuration results of all the presently studied RbVX3  compounds authenticate their semiconducting nature due to having large band gaps between their valence and conduction bands, as shown in 3 compounds overlap the zero level for spin-up calculations; however, none of the TDOS and PDOS cross or overlap the zero level for the spin-down configuration. Furthermore, the total and partial density of state outcome strengthens the results of the band structure of the studied materials.The first step to knowing about any material is to study its electronic properties since all the properties of any material are a function of the electronic state and its behavior. In this study, the electronic properties of the studied RbVX3  materials were calculated. These three  elastic constants were evaluated for the RbVX3  compounds and their respective calculated values are listed in 3  compounds have positive values of elastic constants and authenticate the conditions of stability that are needed for the perovskite structures as suggested by Spinodal shear and Born criteria .29 Moreover, the Cauchy pressure values were also calculated for the RbVX3  compounds while using the elastic constant C12 and C44. The values of Cauchy pressure enable us to know about the ductility and brittleness of the materials.30 It is clear from 3  compounds are all positive, hence confirming the ductile nature of all the studied materials. With the utilization of single-crystal elastic constants, the two important moduli, shear modulus G and bulk modulus B, of the poly-crystalline materials were calculated adopting the Hill approximations. Moreover, for the calculation of Pugh's ratio (B/G), anisotropy factor, and Young's modulus, the following formulas were employed.31All three independent elastic constants, which comprise all the data regarding the dynamical, thermodynamic, and mechanical activity that also assure the structural stability under strain of all the three RbVX3  compounds were in the range of 26 to 42 GPa, which confirms the soften and non-rigid nature of all the studied materials. Moreover, it is clear from the table that the bulk modulus value of the material having a non-metallic atom with smaller ionic radii at the X position is greater than the other materials having a larger ionic radii non-metallic atom at the X position; the value of bulk modulus moves towards smaller value as the chlorine is replaced by another X atom having comparatively larger ionic radii. Finally, on the basis of the bulk modulus, these materials are best to be utilized in bendable devices because of their softness and flexible nature. Furthermore, the anisotropy factor (A) for investigated compounds was calculated and is listed in 3  materials. The shear modulus G values were calculated and found to be the lowest at 0.6 for the RbVBr3 material while highest for the RbVI3 material. Thus, the RbVI3 is more resistive to transverse deformation than the RbVCl3 & RbVBr3.The bulk modulus values calculated for all the three RbVX3 and RbVBr3 have a greater value of Poisson ratio than 0.33 and confirms their ductile nature, while the RbVI3 was found to have brittle nature rather than ductile because it has a Poisson ratio value of 0.004.32 The ratio of B/G as suggested by Pugh's was also calculated and is represented in B/G ratio values of RbVCl3 and RbVBr3 are found to be greater than 1.75, while the RbVI3 had a lower value of 0.67. So, the Pugh's ratio values of the studied materials also confirm the brittle nature of RbVI3 material and ductile nature of the remaining two (RbVCl3 and RbVBr3) materials.33Among the three studied materials, RbVCli.e., real ε1(ω) and imaginary ε2(ω) part) of the recently studied RbVX3  compounds are presented in For any material to be implemented in optoelectronic applications, it is necessary to study the optical response of that material in the numerous electromagnetic energy ranges. The dielectric function that is composed of two main parts (ε1(ω) parts of the dielectric functions for the recently investigated RbVX3 materials in the energy range of 0–40 eV of photons are plotted in 3 materials were found as 73 for RbVI3, 24 for RbVBr3, and 17 for RbVCl3, and these curves showed a sudden decline in their values with a very little increment in the photon energy. However, for the further increment in the photon energy than 1.5 eV, the ε1(ω) curves of all the materials showed nearly the same manner of variation, and finally, the RbVI3 first achieved the negative value at about 8 eV, which confirms that this material reflects all the incident photons of having energies in this range and behaved like metal.34 For the energies of photons greater than 20 eV, all the investigated materials showed no countable variation. The optical band gap and absorption information of any material can be gathered from the imaginary part of the dielectric function. The static value of RbVI3 was found to be much higher than the other two studied materials; however, the RbVCl3 and RbVBr3 had almost similar static values, as shown in ε2(ω), which means that these materials have less absorption ability in the higher energies of incident photons.The 3  materials are presented in ε1(0) = n2(0).35 From the figure, it is clear that the n(ω) showed greater variation in its values for the photons having energies in the range of 2–25 eV but almost negligible variation for the photons having energies greater than 25 eV.The refractive index patterns against the energy values of photons in the range of 0–40 eV of the studied RbVX3  materials in the energy range of 0–40 eV. It is clear from the figure that the curves of both the optical conductivity and absorption coefficient had the same way of improvement and decline in their values with the photon energy variation. For lower values of photon energy, the absorption curves showed small peaks, and as a result, the optical conductivity values were also smaller at these lower ranges of photon energy. However, as the photon energy crosses the limit of 5 eV, the absorption ability of all the materials is enhanced, and as a result, the optical conductivity of the materials is also increased. It was concluded from the patterns of absorption coefficient that the investigated materials had excellent ability of absorption of the incident photons in the energy range of 16–20 eV, and as a result, all the materials showed excess of photo-electrons in these UV energy ranges of incident photons. Moreover, the RbVCl3 material showed good ability of the incident photon absorption as well as the emission of photo-electrons in the studied energy range of photons. From the peaks of the absorption coefficient and optical conductivity of the investigated RbVX3  materials, it can be concluded that the non-metal having smaller ionic radii at the X position can cause a greater value of absorption coefficient and optical conductivity than the non-metal having greater ionic radii for the same range of incident photons. The highest values of optical conductivity were noted as 7000 unit, 6500 unit, and 5800 unit for the RbVCl3, RbVBr3, and RbVI3, respectively, for the incident UV photon energy range of 5–20 eV. All three materials showed a decline in their values of absorption coefficient and optical conductivity for higher values of incident photon energy, which makes these materials as a reflector for these range of incident photons. The greater values of the optical conductivities and large energy range of absorption of the studied halide materials make them suitable for their use in numerous practical opto-electronic devices.3  materials, the reflectivity phenomena against the incident photon energy were also determined in order to know about the surface characteristics of the materials. From For the presently investigated RbVX3, RbVBr3, and RbVI3 by density functional theory using WIEN2K software. These compounds were found stable in a cubic structure. The electronic properties of these compounds indicate that these materials possess dual nature in their spin-up and spin-down configurations. The mechanical properties show that these compounds are mechanically stable. Furthermore, Poisson ratio values deduced from the elastic constants indicate that the compounds RbVCl3 and RbVBr3 are ductile, while RbVI3 is brittle. The greater values of the optical conductivities and large energy range of absorption of the studied halide materials make them suitable for their use in numerous practical opto-electronic devices.We reported theoretical results on the structural, electronic, optical as well as elastic properties of RbVClThe authors declare no competing interests.