PURPOSE: To assess the reproducibility and validity of a single-item, self-administered questionnaire on walking used in two population-based prospective cohort studies in northern Japan, using pedometer counts as the reference standard.METHODS: Fifty-one men and 55 women participating in the main cohort studies (mean age: 61.7 years) responded to a question on the average duration of walking per day five times at 3-month intervals. The subjects also provided 3 consecutive days of pedometer counts four times along with the first four questionnaire surveys.RESULTS: For the first and the fifth questionnaires administered one year apart, 55% of the subjects chose concordant categories among three options (=<30 min / between 30 and 60 min / >= 60 min), and 13% chose the highest category in one questionnaire and the lowest in the other questionnaire. The sex- and age-adjusted mean daily numbers of walking steps counted by the pedometer were 5,857, 7,047, and 7,621 for the three categories of walking duration in the fifth questionnaire, and it showed significant linear associations with all of the five questionnaire measurements.CONCLUSON: The single-item questionnaire on walking is reasonably reproducible and valid, and useful in studying the health effects of walking among the Japanese population. The self-reports of walking and other forms of physical activity have been validated against physical activity recalls and records,12,13 In this study, we assess the reproducibility and validity of a single-item, self-administered questionnaire on walking used in two population-based prospective cohort studies in northern Japan, using pedometer measurements as the reference standard.Pedometer directly counts the number of steps walked, and the measurement is independent of errors associated with subjects’ recall or recording of walking. Although pedometer counts may be useful as the reference standard in assessing the validity of questionnaires on walking, only the limited number of studies have been reported.14 and in 1994.15 The subjects were participants in one or two of the cohort studies who lived in two rural towns. We selected 59 men and 60 women on the voluntary basis. Written informed consent was obtained from all the subjects.This study was conducted as part of an investigation to assess the reproducibility and validity of a self-administered food frequency questionnaire used in two population-based prospective cohort studies in Miyagi Prefecture in the northern Japan that were started in 1990We conducted five surveys with 3-month intervals from November 1997 through November 1998. During each of the first four surveys, pedometer measurement was conducted for three consecutive days , and the self-administered questionnaire including a single-item question on the average duration of walking per day was surveyed on the first day. Only the questionnaire was administered for the fifth survey.The question on walking was worded as “How long do you walk a day on average?” and the subjects were asked to choose one out of three options; 30 minutes or less, between 30 minutes and one hour, and one hour or more.16 We asked subjects to record any problems or incompleteness during the survey  to subsequently exclude inadequate measurements.The subjects were instructed to wear the electronic pedometer  from the moment they got up until they went to bed. The pedometer was firmly attached to the clothes at the waist with the aid of a clip. The number of steps counted by the pedometer was read and recorded at the end of each day by the participants. They were instructed to reset the instrument to zero at the end of each day. The reproducibility and validity of the pedometer in counting walking steps were fully evaluated.We excluded 7 subjects providing less than 10 days of adequate pedometer data and 6 subjects who did not responded to all the questionnaires. We used 106 remaining subjects (51 men and 55 women) for this analysis. There were 84, 15, and 7 subjects providing pedometer counts for 12, 11, and 10 days, respectively, with a total of 1,243 person-days of observations.As a measure of the reproducibility of the questionnaire, we computed the proportions of subjects responding to the concordant categories or the extremely discordant categories (the highest in one questionnaire and the lowest in the other questionnaire) for all combinations of the five questionnaires (10 pairs).17 We computed two-sided p-values for linear trend by treating the categories of walking question as an ordinal variable.As the reference standard in assessing the validity of the questionnaire, we used the number of walking steps measured by the pedometer that was averaged for each subject over the number of days in which the pedometer counts were available (10-12 days). We compared the geometric mean levels according to the three categories of walking question. The mean values were adjusted for sex and age in years by analysis of covariance using the SAS GLM procedure.The mean age  of the subjects was 61.7 (8.6) years. Most of the men were engaged in farming or manual labor, and most of the women did farming and/or housekeeping. The mean (SD) levels of body mass index, weight (kg) divided by the square of height (m), were 24.2 (2.9) for men, and 24.9 (3.4) for women.The mean daily number of walking steps, measured by the pedometer, showed a skewed frequency distribution . The num18 This question asked about the average duration of walking outside and inside per day, using four categories. The adjusted geometric mean numbers of walking steps per day for those choosing “hardly walk (n = 4)”, “about 30 minutes (n = 7)” or “30 minutes to 1 hour (n = 11)”, and “1 hour or more (n = 84)” were 6,646, 5,902, and 7,394, respectively (trend p = 0.040).On the same day as the fourth questionnaire was administered, we administered another single-item walking questionnaire used in the national collaborative prospective study of cancer.In this study of a subsample of participants in two population-based prospective cohort studies in northern Japan, a single item question on walking was reasonably reproducible and valid in classifying the subjects according to the actual number of walking steps measured by the pedometer.This study had several potential limitations. The self-administered questionnaire used in our prospective studies included only two items on physical activities . Furthermore, the questionnaire did not ask various ways of walking  in separate questions. This is because we did not originally intend to calculate total energy expenditure, or quantify the levels of walking according to different ways of walking, based on these questions. Despite the limitation in the original design of our questionnaire, however, it is of notice that even a single question with only three categories of walking is reasonably valid in classifying the subjects according to the relative levels of walking that are measured with pedometer covering all types of walking.We did not sample the subjects randomly from the participants of main prospective studies but selected them on the voluntary basis. It is probably unlikely, however, that the voluntary nature of the subjects substantially distorted the association between self-reports and pedometer counts of walking.19 conducted in 1998 using a nationally representative sample reported that the mean daily numbers of walking steps measured by pedometer among subjects who were 60-69 years old were 7,352 for men (n = 830) and 6,907 for women (n = 931). Corresponding values in our subjects of the same age group were 7,519 for men (n = 23) and 6,498 for women (n = 22). Thus, the levels of walking are generally comparable between our subjects and the Japanese general population. Although the majority of our subjects were engaged in farming, many of them did it on the part time basis, so that their levels of walking were not necessarily higher than those of the Japanese general population.We recruited the subjects from rural communities in northern Japan. The Japanese National Nutrition Survey12 questionnaire measurement of daily walking distance was moderately correlated with the average of pedometer measurement collected over 7 consecutive days , but the subjects underestimated their daily walking distance on the questionnaire, compared with the pedometer values. In a study of 493 men and women aged 25-74 years in Switzerland,13 self-report of walking and gardening during leisure time was a significant predictor of the average daily number of steps recorded by the pedometer for 7 consecutive days. In a study of 30 elderly men and women aged 63-80 years in the Netherlands,20 questionnaire scores of total physical activity were highly correlated with pedometer scores averaged over 3 consecutive days (Spearman r=0.72). However, this study did not report specifically the correlation for walking measured by the questionnaire and the pedometer.Only a limited number of studies have used pedometer as the reference standard in examining the validity of questionnaires on walking. In a U.S. study of 96 men and women aged 25-70 years examining the validity of the College Alumnus questionnaire,21 the 2,000 steps would correspond to 17.7 minutes of walking for men and 16.4 minutes for women. Therefore the questionnaire may overestimate the actual group differences in walking duration. Nevertheless, it should discriminate subjects according to the meaningful contrast of walking, since walking 15-20 min longer per day has been associated with decreased risk of various health outcomes in previous prospective studies.6-9In our study, there should theoretically be at least 30 minutes of difference in time spent for walking per day between subjects choosing the lowest (30 minutes or less) and the highest (one hour or more) categories of the walking question. We actually found approximately 2,000 steps of difference between the two categories . Conside22 Although only about a half of subjects (55%) chose the concordant categories for the first and the fifth questionnaires administered with one-year interval, most of the remaining subjects (32%) chose the adjacent categories, and very few subjects (13%) selected the extremely discordant categories. These results indicate that the questionnaire has a modest, but reasonable, degree of reproducibility over one-year interval.The reproducibility of our questionnaire decreased over time . Both raIn conclusion, this single-item, self-administered questionnaire on walking used for population-based prospective studies in northern Japan is reasonably reproducible and valid, and useful in studying the health effects of walking among the Japanese population.


The utilization of solid waste for filling mining presents substantial economic and environmental advantages, making it the primary focus of current filling mining technology development. To enhance the mechanical properties of superfine tailings cemented paste backfill (SCPB), this study conducted response surface methodology experiments to investigate the impact of various factors on the strength of SCPB, including the composite cementitious material, consisting of cement and slag powder, and the tailings’ grain size. Additionally, various microanalysis techniques were used to investigate the microstructure of SCPB and the development mechanisms of its hydration products. Furthermore, machine learning was utilized to predict the strength of SCPB under multi-factor effects. The findings reveal that the combined effect of slag powder dosage and slurry mass fraction has the most significant influence on strength, while the coupling effect of slurry mass fraction and underflow productivity has the lowest impact on strength. Moreover, SCPB with 20% slag powder has the highest amount of hydration products and the most complete structure. When compared to other commonly used prediction models, the long-short term memory neural network (LSTM) constructed in this study had the highest prediction accuracy for SCPB strength under multi-factor conditions, with root mean square error (RMSE), correlation coefficient (R), and variance account for (VAF) reaching 0.1396, 0.9131, and 81.8747, respectively. By optimizing the LSTM using the sparrow search algorithm (SSA), the RMSE, R, and VAF improved by 88.6%, 9.4%, and 21.9%, respectively. The research results can provide guidance for the efficient filling of superfine tailings. Tailings are one of the largest contributors to bulk solid waste, yet they have a notably low comprehensive utilization rate ,2,3. TakAlthough there have been multiple studies on tailings cemented filling technology, superfine-tailings cemented paste backfill (SCPB) still has problems including low utilization, low filling efficiency, high filling cost, and unstable filling quality ,12. To oThe development of artificial intelligence has shown potential for application in engineering, including filling mining ,20,21,22In this study, response surface methodology (RSM) was applied to optimize the experimental design to investigate the mechanism and effect of slag powder dosage, slurry mass fraction, and underflow productivity (characterizing the grain size of tailings) on the UCS of SCPB. At the same time, microstructure and hydration product characteristics of SCPB were analyzed with the assistance of various microscopic testing methods. Then, the UCS prediction model of SCPB under multiple factors was constructed using long-short term memory neural network (LSTM). Finally, the LSTM was optimized based on various optimization algorithms to achieve high accuracy prediction of the UCS of SCPB.The objective of this study is to investigate experimentally the impact patterns and mechanisms of different factors on superfine SCPB, and to achieve high-precision prediction of SCPB strength under the influence of multiple factors using intelligent algorithms. The results of the research have important implications for improving the utilization and filling effectiveness of superfine tailings and for developing efficient applications of machine learning in filling mining.3 and 1.58 g/cm3, respectively. The main chemical composition of the tailings is shown in 50) of the unclassified tailings (underflow productivity is 100%) from this gold mine is 12.53 μm, and particles less than 75 μm account for more than 90%, which indicates that the tailings are superfine and the UCS of the SCPB is low.In this research, tailings from a gold mine in Guizhou Province, China, were used as filling aggregates. The density and bulk density of the tailings were 2.65 g/cmP is the underflow productivity (%); ic is the inlet mass fraction (%); c0 is the overflow mass fraction (%); and dc is the underflow mass fraction (%).The gradation of the tailings is an important factor in determining the mix proportion of the SCPB, which has a significant effect on the UCS of the SCPB. To investigate the effect of tailings with different grain sizes on the UCS of SCPB, graded tailings with underflow productivity of 55%, 65%, and 75%, respectively, were prepared by cyclones at Haiwang company . From In this research, the cement and slag powder were selected to form a composite cementitious system. The parameters and properties of the materials are listed below.(1)3S, C2S, and C4AF, indicating that the cement possesses strong hydrolytic capabilities.This study employed cement as the binder, sourced from the same mine as the tailings to ensure experimental materials are in line with field conditions, thereby enhancing the applicability of the research. According to (2)2/kg and a density of 2.9 g/cm3. As shown in 0 = 1.17 > 1; the quality coefficient K = 2.27 > 1.8; the activity coefficient Ma = 1.57 > 1 [Slag powder was used as the supplementary cementitious and active material. It has a specific surface area of 440 m1.57 > 1 . This inSeveral testing methodologies were employed to study the mechanical properties and formation mechanisms of SCPB. The testing procedures are illustrated in (1)Uniaxial compressive strength test (UCS test): When the specimen was cured for a specific time, the UCS was tested using a WDW-2000 automatic pressure testing machine. To ensure the accuracy of the experimental results, three samples were prepared for each group of tests, and their UCS values were measured separately. The average value of the three samples was taken as the UCS of the corresponding mix proportion for that group.(2)X-ray diffraction test (XRD test): SCPB specimens were ground into powder and analyzed for their mineral phases using an X-ray diffractometer to determine the fractions of hydration products under different affecting factors. The equipment model used for XRD was a Bruker D8 Focus Bragg-Brentano diffractometer. The XRD test was conducted within the 2θ range of 5~70°, with a data collection rate of 7 s/step and a step size of 0.03°.(3)Fourier transform infrared spectroscopy test (FT-IR test): When a beam of infrared rays of different wavelengths is irradiated onto the molecules of a substance, an infrared absorption spectrum is formed because different substances absorb infrared rays of specific wavelengths ,36. Base(4)Thermogravimetry and differential thermogravimetry test (TG-DTG test): The TG curve reflects the mass change of a substance with temperature, and the DTG curve represents the rate of change of the mass of a substance as a function of time and temperature ,38. When(5)Scanning electron microscopy test (SEM test): SEM is a widely used method for observing microscopic structures. In this study, this method was employed to observe the distribution of pores in the microstructure of SCPB under different mix proportions. Additionally, Image J software was utilized to conduct grayscale analysis of the microstructure, in order to compare the compactness of different SCPB samples. Furthermore, SEM was utilized to observe the hydration products in SCPB, which aided in analyzing the degree of hydration reactions in different samples ,40.The relationship between the mix proportion and the UCS of SCPB is highly complex and uncertain, exhibiting non-linear behavior. To investigate the impact of various factors on the UCS of SCPB, this study employed response surface methodology (RSM) for experimental design ,42.X1, X2, and X3, respectively), and the UCS of SCPB at 7d, 14d, and 28d as the response values . The experimental scheme and results are shown in According to previous extensive exploratory experiments, the UCS of SCPB can be achieved according to the requirements of the construction site when the cement dosage is 15% of the solid material. The RSM experiments take the slag powder dosage (mass proportion of slag powder to cement), slurry mass fraction, and underflow productivity as the independent variables . As the cement hydrates, the continuous generation of CH causes the pH of the slurry to gradually increase and starts to stimulate the activity of the slag powder. The OH− in the alkaline environment then decomposes the glassy structure of the slag powder, which in turn produces hydration products such as C-S-H and AFt.XRD was applied to analyze the mineral phases of hydration products in SCPB with 10%, 20%, and 30% of slag powder dosage, respectively, and the results are shown in 3S and C3A, which are highly reactive in cement, were not detected in any of the three sets of results shown in 2S indicates that some amount of this substance still existed in the SCPB. This is due to the low activity of C2S, which requires a higher alkaline environment for the hydration reaction to happen. Overall, the highest C2S diffraction peaks and the lowest AFt diffraction peaks were observed in the SCPB with 30% slag powder dosage. This was due to the relatively lower cement dosage caused by the high slag powder dosage, which in turn led to an alkaline environment, provided by cement hydration, that cannot fully react with C2S. The lowest diffraction peak of C2S and the highest diffraction peak of AFt were observed in the SCPB with 20% slag powder dosage. This is due to the disaggregation of the glassy structure of the slag powder, along with the release of AlO45− and Ca2+ by the CH generated by the hydration of the cement. These ions fully react with gypsum to form AFt, which decreases the C2S content and increases the AFt content in SCPB. The above analysis shows that the appropriate slag powder dosage can promote the hydration reaction of cement in the cement–slag composite cementitious system, while the cement hydration products in turn promote the decomposition of slag powder. This is the reason why the SCPB containing 20% slag powder had the highest UCS.The mineral phases of C− in the hydration products, and its characteristic peaks are mainly those of stretching vibrations in the range from 3000 cm−1 to 3750 cm−1 and the characteristic peaks of bending vibrations located near 1600 cm−1. The characteristic peaks of the stretching vibrations of the O-H bond in this study were located at 3627 cm−1 and 3420 cm−1, and the characteristic peaks of the bending vibrations were located at 1650 cm−1. From the characteristic peaks of the O-H bond, it can be seen that the infrared transmission rate of SCPB with 20% slag powder dosage was lower than that of the other two slag powder dosages of SCPB, indicating that more hydration products such as AFt and C-S-H were generated after the 20% slag powder dosage was added to the cement, which in turn reduced the transmission rate of the peak position. This result is in agreement with the XRD analysis. The characteristic peaks at 1410 cm−1 and 870 cm−1 are those of the stretching vibration and bending vibration of C-O bonds in CO32−, mainly from dolomite and carbonation products in the raw material.FT-IR was used to analyze the molecular structures of hydration products in SCPB with slag powder dosages of 10%, 20%, and 30%, respectively, and the results are shown in −1 is from the bending vibration of the S-O bond of SO42− in gypsum. The characteristic peak is extremely small, which indicates that the gypsum in the cement is almost completely involved in the hydration reaction. The characteristic peaks near 990 cm−1 and 695 cm−1 are the vibrational systolic peaks of silicon–oxygen tetrahedra (SiO4); the characteristic peaks near 528 cm−1 are the vibrational systolic peaks of aluminum–oxygen tetrahedra (AlO4). Both SiO4 and AlO4 are derived from the depolymerization of glassy structures in slag powder. The OH− generated by the hydration of cement breaks the Si-O and Al-O bonds in the glassy structure of slag powder to form SiO4 and AlO4, and then the glassy structure is continuously depolymerized so that the SiO4 and AlO4 in the liquid phase gradually increase. These two substances further react with gypsum in cement to form hydration products such as C-S-H and C-A-S-H gels and AFt crystals. Overall, the SCPB with 20% slag powder dosage had the lowest transmittance of SiO4 and AlO4, which indicates that the depolymerization of slag powder in SCPB at this proportion was the most complete and generated the most hydration products. This is in agreement with the XRD results and further explains why the UCS of SCPB at this proportion was the highest. In the cement–slag composite cementitious system, when the cement and slag powder reach optimal proportions, it can promote the complete hydration of cement and fully activate the activity of slag powder, which gives the composite cementitious system optimal cementitious ability.The characteristic peak at 1160 cm2 from the carbonate product.The results of TG-DTG analysis for SCPB with slag powder dosages of 10%, 20%, and 30% are shown in The mass loss was more pronounced around 108 °C for the SCPB specimens. This loss peak corresponds to the evaporation of crystal water in C-S-H gels, C-A-S-H gels, and AFt crystals. Comparing the DTG curves of SCPB with different slag powder dosages, it was found that the SCPB with slag powder dosage of 20% had the largest loss peak, indicating that the SCPB with this slag powder dosage had the highest rate of mass loss and the largest mass loss at about 108 °C. This demonstrates that the SCPB with slag powder dosage of 20% had the greatest quantity of hydration products. A less pronounced loss peak was observed around 165 °C, which was due to mass loss from the decomposition and water loss of gypsum. This indicates the existence of a tiny amount of incompletely reacted gypsum in the SCPB. The mass loss around 420 °C was due to the decomposition of CH. The mass loss of SCPB with slag powder dosage of 10% or 30% was more significant, but there was almost no mass loss of SCPB with slag powder dosage of 20%, which indicates that the SCPB with slag powder dosage of 20% contained almost no CH. The slag powder can participate in the hydration reaction only after the disaggregation of the glass structure. The disaggregation of the glass structure requires the consumption of CH, and a lower content of CH indicates that the disaggregation of the glass structure of slag powder is more complete. The disaggregation of glass structure produces hydration products such as AFt and C-S-H, which is the main reason for the mass loss of SCPB with slag powder dosage of 20% at about 108 °C. These results corroborate those of the XRD and FT-IR analysis.The microstructure images of SCPB were obtained using SEM. The grayscale and UCS analysis of different microstructures are shown in Comparing A long short-term memory neural network (LSTM) is a commonly used deep learning algorithm for modeling sequential data, which can solve the problem of vanishing gradients encountered in conventional RNN algorithms. Typically, LSTM consists of input gates, forget gates, and output gates, each composed of a sigmoid neural network and an element-wise multiplication operation. In addition, LSTM uses a structure called “cell state” to store and transmit information. The cell state can be regarded as the “memory” of LSTM, as it can retain previous information and pass it on to subsequent time steps. During the training phase, LSTM updates the parameters in the model using the backpropagation algorithm to minimize the error between predicted values and actual values. During the prediction phase, LSTM takes the current input and the state of the previous time step as inputs, and outputs the predicted value for the current time step ,47,48. TDifferent model parameters lead to different prediction effects for models, and the prediction effects of different models are also different. To evaluate the prediction effects of the different models, the following common performance metrics were applied to compare their prediction performance:In this research, a back propagation neural network (BPNN), extreme learning machine (ELM), and radial basis function neural network (RBFNN) were used for comparison with LSTM to determine the optimal model that can map the relationship between the four variables and UCS. Due to limitations of space, the formulas and derivation process of the above three neural networks are not discussed in this section; interested readers can refer to the references ,50,51.m is the number of inputs, n is the number of outputs, and l is the adjustable constant on the interval .To ensure the fairness of the comparison and to avoid overfitting, above all, neural networks are networks with a single hidden layer. The initial learning rate, target error, and max iterations were set to 0.005, 0.001, and 100, according to references ,25,31, wThe 51 UCS samples obtained from the experiments in The 11 sets of samples from the validation set were substituted into the neural network already trained in Performance metrics of different models are shown in Previous studies have shown that the number of hidden layer nodes and the learning rate have a significant effect on the performance of LSTM ,60,61,62The optimal parameters were obtained after using LSTM improved by GWO (GWO-LSTM): the learning rate was 0.0162 and the number of hidden layer nodes was 26. The prediction results of GWO-LSTM for the UCS of the training set and validation set are shown in The optimal parameters were obtained after using LSTM improved by PSO (PSO-LSTM): the learning rate was 0.0381 and the number of hidden layer nodes was 37. The prediction results of PSO-LSTM for the UCS of the training set and validation set are shown in The optimal parameters were obtained after using LSTM improved by SSA (SSA-LSTM): the learning rate was 0.0146 and the number of hidden layer nodes was 19. The prediction results of SSA-LSTM for the UCS of the training set and validation set are shown in The training process of the above three optimized LSTMs was tracked by using the half mean square error as the loss function, as shown in The predictive performance of the different models can be seen in (1)The strength of SCPB exhibited an initial increase followed by a decrease with an increase in slag powder dosage. It showed an increase with the rise in slurry mass fraction and a decrease with the increase in underflow productivity. The combined influence of slag powder dosage and slurry mass fraction had the most pronounced effect on UCS, whereas the coupling effect of slurry mass fraction and underflow productivity had the least impact on UCS.(2)45− and Ca2+. These ions fully reacted with gypsum in the cement to produce a large quantity of hydration products, and the consumption of CH by slag powder further promotes the hydration of the cement.The generation of hydration products of SCPB with slag powder dosage of 20% was the highest, for the following reasons. The CH generated by the hydration of cement caused complete depolymerization of the glass bodies of slag powder, and released AlO(3)The LSTM model developed in this study demonstrates the highest prediction accuracy for the strength of SCPB under multi-factor conditions. The model achieved R, RMSE, and VAF values of 0.9131, 0.1396, and 81.8747, respectively. Through optimization using the SSA algorithm, the LSTM model’s performance was further enhanced, resulting in an improvement of 9.4% in R, 88.6% in RMSE, and 21.9% in VAF.To improve the utilization of ultrafine tailings and optimize the mechanical properties of SCPB, a series of experiments and tests were conducted to analyze the effects of different factors on the strength of SCPB. Furthermore, prediction of SCPB strength under multiple factors was carried out by combining machine learning. The main conclusions are as follows:


The strength-formation mechanism for industrial-construction residue cement stabilization of crushed aggregate (IRCSCA) is not clear. To expand the application range for recycled micro-powders in road engineering, the dosages of eco-friendly hybrid recycled powders (HRPs) with different proportions of RBP and RCP affecting the strengths of cement-fly ash mortar at different ages, and the strength-formation mechanism, were studied with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the early strength of the mortar was 2.62 times higher than that of the reference specimen when a 3/2 mass ratio of brick powder and concrete powder was mixed to form the HRP and replace some of the cement. With increasing HRP content substituted for fly ash, the strength of the cement mortar first increased and then decreased. When the HRP content was 35%, the compressive strength of the mortar was 1.56 times higher than that of the reference specimen, and the flexural strength was 1.51 times higher; XRD and SEM studies of the hydrated cement mixed with HRP showed that the amount of CH in the cement paste was reduced by the pozzolanic reaction of HRP at later hydration ages, and it was very useful in improving the compactness of the mortar. The XRD spectrum of the cement paste made with HRP indicated that the CH crystal plane orientation index R, with a diffraction angle peak of approximately 34.0, was consistent with the cement slurry strength evolution law, and this research provides a reference for the application of HRP to produce IRCSCA. In cement production, the greenhouse gases produced account for 8% of global greenhouse gas emissions . The aca3/km of recycled aggregate can be utilized for the production of cement-stabilized materials (CSCA) 2, Al2O3,concrete  and otheTherefore, the pozzolanic characteristics of the RBP and RCP show that the HRP can be used as a cement supplement. Based on this, more and more interest has been attracted to exploring the use of the HRP. Furthermore, it is worth noting that fly ash exhibits potential applications as a concrete admixture and auxiliary cementing material in the context of cement stabilization of crushed aggregate (CSCA) for road engineering purposes. However, there are few reports on the interaction between solid waste materials and cement. However, there is a limited number of studies available that explore the impact of RBP, RCP, and fly ash on the strength of cement mortar as well as the underlying mechanisms of hydration. To respond to this need, in the presence of fly ash, it is of great theoretical significance to explore the comprehensive effect of RBP and RCP and its influence on the strength-formation mechanism of cement mortar, which is the basis for the evaluation of the corresponding mechanical properties and durability of the CSCA in road engineering, especially for the future development of HRP as concrete mineral admixture and auxiliary cementitious material.The C&BW utilized in the production of RBP and RCP was sourced from the demolition of a factory district that had been in existence for 50 years. The factory district was situated in Er-qi town, located in Zhengzhou, Henan Province. This waste consisted of clay bricks, concrete, ceramics and so on. Ordinary Portland cement 42.5, in compliance with the Chinese standard JTG/T F20-2015 , was preThe production of HRP involved a three-stage process subsequent to the initial processing of the waste clay bricks and concrete. During the initial stage, a crusher was employed to reduce the size of the waste bricks and concrete particles to achieve a fine particle size below 10 mm. Subsequently, the particles were sorted into various particle sizes through the utilization of a vibrating screen; these were categorized as recycled coarse aggregate. In the second stage, the material obtained from the first stage was introduced into a ball-grinding mill featuring a circular cavity. This process aimed to produce fine aggregates with a maximum size of 2.36 mm, thereby classifying them as recycled fine aggregate. Subsequently, the output obtained from the second stage was subjected to an electromagnetic sample pulverizer to produce fine powders with maximum sizes of 45 μm, which were classified as HRP. The preparation process for HRP through comprehensive processing of the C&BW is depicted in 2 and Al2O3, which contribute to the enhanced pozzolanic activity. Consequently, it is anticipated that appropriately sized RBP and RCP particles can serve as SCM in concrete. Upon extensive grinding, both RBP and RCP exhibit a notably heightened reactivity. Consequently, these materials are harnessed as SCM during the process of concrete formulation. Moreover, scholars worldwide have conducted extensive research on the micro-performance, mechanical characteristics, and long-term durability of concrete incorporating RBP and RC. Under the same alternative mass fraction, as the curing period progresses, the strength of recycled composite micronized cement sand gradually increased in the presence of fly ash, and when the regenerated composite powder completely replaced fly ash, the strength of the mortar with HRP increased at 3 d and 7 d, and the strength decreased by 28 d, which indicated that the regenerated composite micro-powder mainly played a microaggregate filling effect in the early strength formation of the specimen, and with the gradual extension of the age, the later strength decrease was not significant because the active ingredient could react with cement hydration products. The plastic properties of mortar with HRP are improved.In order to examine the progression patterns of these recycled materials and comprehend the mechanical and hydration mechanisms of cement-fly ash mortars incorporating HRP, the proportions of RBP and RCP were chosen as variables, while maintaining a constant water/binder (w/b) ratio of 0.45 and a constant binder/sand (b/s) ratio of 0.3. The composition of RBP and RCP exhibits similarities to that of fly ash, characterized by elevated levels of SiOBased on the results of Xiao , Tang 33, Zhu 3, Li 49]49], KaneThe mortars were cast into prismatic molds measuring 40 mm × 40 mm × 160 mm for casting and demolded after 24 h. The mortar specimen color changed with the changes in the RBP replacement rate, as shown in To analyze the effect of the HRP on the strengths of cement-fly ash mortars with cement paste (CP) as the benchmark, cement-fly ash paste (CFP), cement-fly ash recycled brick powder paste (CFBP), cement-fly ash recycled concrete paste (CFCP), and cement-fly ash recycled brick powder concrete paste (CFBCP) were used as research objects. The paste specimens were prepared with an NJ-160B mixer and then modelled in rectangular molds measuring 40 mm × 40 mm × 160 mm. The curing conditions employed for the paste were analogous to those employed for the mortar specimens. The relative compressive strength of the composite micronized concrete was evaluated at 3, 7, and 28 days, considering various substitution rates.The particle size distributions of both RBP and RCP were determined using a laser diffraction particle size analyzer. The chemical compositions and mineralogical compositions of both RBP and RCP were analyzed using X-ray fluorescence spectrometry (XRF) and X-ray diffraction (XRD) techniques. The flexural strength and unconfined compressive strength of the investigated cement-mortar samples were determined in accordance with the specifications outlined in GB/T17671-2021. The respective strengths were measured to evaluate the mechanical performance of the samples. The specimens were subjected to flexural strength and uniaxial compressive loads, with loading rates of 50 N/s and 2500 N/s, respectively, until failure occurred. Scanning electron microscopy (SEM) was used to study the micromorphology of the HRP, and the cement-fly ash mortars contained HRP. The SEM sample preparation and observation procedures were conducted as described below: After conducting the 28-day compressive strength test on the cement-fly ash mortar samples containing HRP and the cement-fly ash mortar samples without HRP, three cubes measuring 1 cm × 1 cm × 1 cm were carefully extracted from the central region of each specimen. The extracted cubes were immersed in anhydrous ethanol to halt the hydration process, followed by drying in an electric heating blast-drying oven maintained at 60 °C. Once cooled, the samples underwent gold coating before being subjected to SEM imaging. The mineralogical compositions of the respective pastes were determined with XRD analysis, employing a scan rate of 0.02°/min.The particle size distributions of RBP and RCP reflect their gradations. The laser particle size analyses of the cement, recycled coarse aggregate (RCP), recycled fine aggregate (RBP), and fly ash are depicted in 2 content of the RBP closely resembled that of the fly ash. Additionally, the CaO, Al2O3, and Fe2O3 contents of RBP were found to lie between those of the cement and fly ash. This observation suggests that RBP exhibited a favorable distribution of oxides. Based on the diffraction peaks shown in 2 crystals, which can be combined with the Ca(OH)2 generated by cement hydration to generate C-S-H and C-A-S-H, calcium sulfoaluminate hydrate [2 increased the compactness and strength of a mortar sample. 2, and Ca(OH)2 improves the activity of the RBP. Moreover, both the RBP and RCP contained SiO2 and Al2O3. Hence, both powdered materials exhibited pozzolanic activity, which effectively improved the late strengths of the mortars. In addition, there was a small amount of albite in the recycled concrete powder, which may have arisen from mixing of fine aggregate stone chips; additionally, the recycled brick powder contained a large amount of albite, and albite was one of the main components of the clay bricks. The presence of CaCO3 in RCP has the potential to reduce the induction period of C3S and actively participate in the hydration reaction, leading to the formation of carboaluminates. This, in turn, contributes to the refinement of pore structures in cement pastes [ hydrate ,58,59. Lt pastes . NonetheThe hydration behavior of cementitious materials is intricately linked to their macroscopic and microscopic characteristics. Good hydration leads to higher concrete strength. Enhanced fineness of the recycled powders led to an increase in the concentration of amorphous oxides within the cementitious materials, thus improving their hydration reactivities ,54,61 FiIn the presence of fly ash, RBP (B) and RCP (C) were compounded with mass ratios of 3/2 and 4/1 to replace some of the cement cementitious materials or fly ash, and the samples were denoted HRP-I and HRP-II.The effects of the RBP and RCP contents on the flexural strengths of the cement-fly ash mortar at different ages are shown in 2 and Al2O3 in the recycled micro-powder with the Ca(OH)2 generated by hydration of the cement clinker to produce the pozzolanic effect and generate hydraulic C-S-H and C-A-S-H [ C-A-S-H ,45,54,58The paramount mechanical property parameter, compression strength, assumes a position of utmost significance. In the context of hardened mortar, this parameter assumes a pivotal role primarily attributed to its capacity for bonding and facilitating load transfer. The outcomes depicted in 2, which then reacted with SiO2 and Al2O3 in the RBP to generate hydraulic C-S-H3745 and C-A-H [The 3 d compressive strength of the mortar exhibited the most pronounced increase, as evident from the findings presented in nd C-A-H ,58; this2. This activation process further facilitated the pozzolanic effect of RBP, consequently enhancing the strength of the cement-fly ash mortar.Compared with the JZ specimen, when the HRP-I replacement ratio was 15%, the compressive strength of the mortar at 3 d and 7 d after casting were measured to be 7.64 MPa and 16.8 MPa, respectively, and the 28 d compressive strength was 23.90 MPa, a maximum increase of 11.68%. These results indicated that HRP-I prepared with a mass ratio of 3/2 effectively improved the early strength, which was consistent with the microstructure of the HRP shown in 2 and Al2O3 in the fly ash with the cement hydration product Ca(OH)2, which is consistent with the conclusions of Du [2O3 and Ca(OH)2 in fly ash. A comparison of 2, which promoted a secondary hydration reaction between the active component of the RBP and the cement hydration product. The combined effects of RBP and RCP increased the hydration products formed in the mortar with HRP, and the thicknesses of white flocculated substances attached around the fly ash particles in ns of Du , Hardjitns of Du , and Narns of Du . Needle-3), ettringite (AFt), calcium hydroxide (CH), SiO2, C-S-H, and C-A-H. SiO2 came from the fly ash, CaCO3 came from the HRP, and calcium hydroxide (CH) was derived from the cement hydration products. The hydration process was similar to that described in the literature [2 and Al2O3 in the CFBCP were reduced because of the reactions occurring between the SiO2 and Al2O3 in the HRP with the cement hydration product CH to form the C-S-H gel and C-A-H gel. R for the calcium hydroxide (CH). When the R value was larger, the orientation of the CH was more substantial, and the compressive strength was lower. In this paper, the CH crystal plane with a diffraction angle of 18.1° (001) was selected as the reference plane, and the crystal plane orientation index R with a diffraction angle of 34.0° (101) was:terature ,60 and m2 was 0.979 when an exponential function was used to fit a plot of the orientation index R versus the compressive strength of the mortar. With a linear function, the correlation coefficient R2 was 0.925. This observation signifies that the compressive strength of the paste is influenced by a multitude of factors. The orientation index R served as an indicator to gauge the impact of HRP on the compressive strength within the cement-fly ash system. In addition, in the presence of fly ash, the R values of the HRP pastes were lower than the R values for the RBP or the RCP, and the R value for RBP was greater than that for RCP. This occurred because the SiO2 in the RBP and fly ash accelerated the hydration processes in the early stages of cement hydration, which resulted in decreased intensities for some of the diffraction peaks. This was consistent with the change law for the CH diffraction peak eigenvalues at diffraction angles of 18.1° (001) and 34.0° (101). Therefore, the orientation index R indicated the effect of the HRP on the compressive strength of the cement-fly ash system. The orientation index R of CH can be used to reveal the strength evolution law for the HRP-cement-fly ash system.The utilization of construction solid waste is an effective aspect of green and sustainable economic development. The comprehensive experimental study described herein indicates the viability of green recycling and using HRP to replace Portland cement and fly ash. The mechanical and hydration mechanisms of the cement-fly ash mortar were investigated by varying the proportions of RBP and RCP in HRP, and the replacement ratio of HRP. Based on the outcomes derived from this study, the subsequent conclusions can be drawn.(1)HRP has specific activities and can be used as auxiliary cementitious material to replace some cement. In the presence of fly ash with increasing HRP content, the strength of the cement mortar first increased and then decreased, and the early strengths of the cement-mortar specimens with single RBP were better than those of the cement-mortar specimens with RCP. When the single content was lower than 15%, the maximum increase in 3 d compressive strength was 19.08%, and the maximum decrease in 28 d compressive strength was 2.39%.(2)HRP can be used as a mineral admixture to replace some of the fly ash. They were mixed with a mass ratio of 3/2 to form the HRP, which effectively improved the strength of the mortar specimen. When the RBP, RCP, and fly ash were mixed with the mass ratio 21/14/65, the flexural strength of the mortar was 1.51 times higher than that of the cement-fly ash specimen, and the compressive strength was 1.56 times higher at 28 d.(3)In the presence of fly ash, the HRP mainly exerted the microaggregate effect and promoted the cement hydration reaction, which significantly improved the microstructural compactness of the mortar and the thickness of the C-S-H on the surfaces of the fly ash particles.(4)The pozzolanic effect operating on the HRP in the later stages reduced the intensities of the CH diffraction peaks. The crystal plane orientation index R with a diffraction angle of 34.0° (101) was consistent with the evolution law for compressive strength.


There is interest in this type of ceramics on account of their prospects for application in tritium production in thermonuclear power engineering, as well as several other applications related to alternative energy sources. During the investigations undertaken, it was found that variation in the MgO dopant concentration above 0.10–0.15 mol resulted in the formation of impurity inclusions in the ceramic structure in the form of a MgLi2ZrO4 phase, the presence of which resulted in a rise in the density of the ceramics, along with elevation in resistance to external influences. Moreover, during experimental work on the study of the thermal stability of the ceramics to external influences, it was found that the formation of two-phase ceramics resulted in growth in the preservation of stable strength properties during high-temperature cyclic tests. The decrease in strength characteristics was observed to be less than 1%.The article considers the effect of doping with magnesium oxide (MgO) on changes in the properties of lithium-containing ceramics based on lithium metazirconate (Li The rapid development of industry and the increase in resource and energy consumption poses great risks for humanity in the near future in terms of shortage of energy resources and the consequences of their use ,2,3. HowOne of the most important problems in thermonuclear energy is the problem of the production of tritium, which is an integral part of the fuel cycle of thermonuclear plants since it is used as the main nuclear fuel ,8,9. Thi2ZrO3 ceramics, which have great potential as blanket materials for tritium propagation. The most pronounced advantages of Li2ZrO3 ceramics include high compatibility with structural materials and reflector materials, in particular with beryllium, high mechanical and corrosion resistance, and excellent tritium release and accumulation during irradiation [The main hypothesis of this study concerns the assessment of the prospects of using a magnesium oxide (MgO) dopant ,20, whicadiation ,22,23,244 × 3H2O, ZrO2, and MgO in given stoichiometric ratios were used as the initial components for synthesis; the chemical purity was 99.95%. The MgO dopant concentration for the experiments ranged from 0.05 to 0.25 mol. Mixing was carried out using a planetary mill PULVERISETTE 6 classic line  at a grinding speed of 400 rpm for 30 min. After grinding, the resulting mixtures were subjected to thermal sintering in a muffle furnace at a temperature of 1300 °C for 8 h, followed by cooling for 24 h. Annealing was conducted in a RUS-universal muffle furnace ; the heating rate was 10 °C/min, the temperature was controlled using thermocouples, SiC heating elements were used as heating elements. The formulas of the chemical reactions expected during the synthesis after thermal annealing are shown below:The ceramics were synthesized by mixing the initial components in a planetary mill in order to achieve a homogeneous powder, which was subsequently subjected to thermal annealing. Under the selected grinding conditions, the processes of mechanochemical phase formation cannot be initiated. In this case, grinding was necessary to create homogeneously mixed powders of the initial components, which were subsequently annealed at a temperature of 1300 °C, at which the process of phase transformations took place. Powders of LiClOG) was calculated for both reactions that occur during the thermal annealing of the ground components. Values of ∆G = −15.6 kJ/mol for chemical reaction (1) and ∆G = −7.3 kJ/mol for reaction (2) were obtained. The negative value of ∆G for both reactions indicates that the formation of both Li2ZrO3 and MgLi2ZrO4 phases under the chosen temperature annealing conditions can occur freely.Using a priori data on the initial components used to obtain the ceramics, the Gibbs free energy . The phase composition was refined using the DiffracEVA v.4.2 program code. Determination of the phase composition and the phase ratio was performed using card values from the PDF-2 (2016) database. Refinement of the crystal lattice parameters and the structural ordering degree was conducted using the method of comparative estimation of the deviation of the position of diffraction peaks from the reference values, followed by calculation of the experimentally acquired values of the parameters. The structural ordering degree was estimated from the change in the ratio of the crystalline phase contributions, characterized by the areas of the reflections, and the amorphous inclusions, which were described by approximating the area in the diffraction patterns characteristic of the background radiation.V0 is the unit cell volume, Z is the number of atoms in a crystal cell, and A is the atomic weight of the atoms. Moreover, in the case of variation in the phase composition attributable to a change in the content of the phases, the density is calculated considering the contribution of each phase to the composition of the sample, and, as a result, the average density value calculated, taking into account the contribution factors of each phase, is used in further analyses.The determination of porosity via the X-ray diffraction method was based on the following assumptions: One of the important parameters affecting the change in the density of materials is the crystal lattice volume, the alteration of which results in changes in the material density. Formula (3) was used to estimate the density :(3)p=1.6dilP) is calculated using Formula (4) [p0 is the density of the reference sample; as a rule, this value is taken from the PDF-2 database, which is typical for the given phase.The classical approach to determining the value of the porosity using X-ray diffraction methods is presented in the work of J.I. Goldstein , which dmula (4) ,30:(4)PdImpedance spectroscopy was conducted on a HIOKU IM3533-01 RLC-meter  in the frequency range 2–200,000 Hz. The ceramic powders were pressed into tablets using polyvinyl alcohol as a binder. Silver paste was applied to both sides of the tablets to create electrical contacts.The morphological features of the synthesized lithium-containing ceramics were studied by scanning electron microscopy using a Hitachi TM3030 scanning electron microscope .Measurement of the strength properties of the lithium-containing ceramics doped with magnesium oxide depending on the dopant concentration was performed using the microindentation method using a LECO LM700 microhardness tester .When MgO was added to the initial mixture at concentrations of 0.05–0.10 mol, the formation of a fraction of larger particles having an oval or rhomboid shape was observed, and these particles were larger than the volume of the ceramics  ceramics, the size was 50–100 nm; at dopant concentrations of 0.05–0.10 mol, the average size was no more than 130–150 nm, and the degree of homogeneity was more than 90%. In the case of dopant concentration above 0.15 mol, the average particle size was 200–250 nm, and change in the particle shape was observed. It should also be noted that, at dopant concentrations of 0.20–0.25 mol, a small quantity of fine grains was observed, the size of which was less than 30–50 nm.2ZrO3-(1-x)MgO ceramics depending on the concentration of the dopant, along with related phase transformations and processes of formation of the impurity phases, was conducted using the method of X-ray diffraction analysis. 2ZrO3 structure with a monoclinic type of crystal lattice ) and crystal lattice parameters a = 5.4021 Å, b = 9.0079 Å, c = 5.4110 Å, β = 112.31° . The differences in the parameters of the crystal lattice of the experimental sample from the reference values are associated with deformation processes caused by the grinding processes in a planetary mill, accompanied by strong deformation of the structure, substitution processes, and subsequent thermal annealing and relaxation of the deformation distortions. The degree of structural ordering of the undoped sample was 87.1%, which is typical for highly structurally ordered materials.Determination of structural changes in xLiWith respect to MgO dopant addition to the ceramic composition at a concentration of 0.05 mol, the creation of impurity inclusions or new phases was not identified, which points to the absence of phase formation or phase transformation processes at a given dopant concentration. The main changes observed for this sample were linked to an alteration in the parameters of the crystal lattice and elevation in the structural ordering degree to 88.5%, which indicated a decline in the defective fraction in the ceramic composition.2ZrO4 (PDF-01-078-0198) tetragonal phase, the appearance of which was because of the processes of phase transformation and the formation of substitutional or interstitial solid solution phases related to them. Moreover, elevation in the MgO dopant concentration resulted in a rise in the contribution of the new phase in the composition of the ceramics, and, at a dopant concentration of 0.25 mol, resulted in insignificant dominance of MgLi2ZrO4 in the composition of the ceramics (more than 50%).At MgO dopant concentrations of 0.10 mol and higher, the presented X-ray diffraction patterns had the appearance of diffraction reflections characteristic of the MgLi2ZrO3-(1-x)MgO ceramics depending on MgO dopant concentration, it was found that a rise in the dopant concentration above 0.10 mol resulted in phase transformations of the Li2ZrO3 → Li2ZrO3/MgLi2ZrO4 type, followed by formation of two-phase ceramics with an equal content of the two phases.According to evaluation of the phase composition of the xLi2ZrO4 tetragonal phase, increase in which was most pronounced at a MgO concentration of 0.20–0.25 mol. Based on the acquired data from the X-ray phase analysis, the crystal density was calculated; the results were then compared with the data acquired from the analysis of the density of the ceramics pressed into tablets using the gravimetric method (Archimedes method). The results of a comparative analysis of the change in the density of the ceramics depending on the MgO dopant concentration are shown in As can be seen from the data presented in 2ZrO3-(1-x) MgO ceramics depending on the MgO dopant concentration showed a pronounced maximum at concentrations of 0.10–0.15 mol, followed by a decline in density to 4.01–3.95 g/cm3 for dopant concentrations of 0.20–0.25 mol, respectively. The decrease in density for samples acquired at a dopant concentration of 0.20–0.25 mol was because of effects linked to the crystal lattice volume elevation.As can be seen from the presented data, the change in the density of the xLi2ZrO3-(1-x)MgO ceramics depending on the MgO dopant concentration.2ZrO3 monoclinic phase (PDF-00-033-0843) and the MgLi2ZrO4 tetragonal phase (PDF-01-078-0198).An analysis of the frequency dependencies demonstrates that, in different parts of the frequency range, the values of ε’, tan δ can differ significantly depending on the molar fraction of the MgO dopant. It is known that the value of the permittivity depends on the polarizability of the dipoles and the magnitude of the dipole moment, which, in crystals with ionic bonding, depends on the crystal structure. On the other hand, the permittivity is a structurally sensitive physical parameter. For this reason, the dielectric properties of ceramics are determined by two factors: the microstructure and the crystalline properties. In addition, at low frequencies, the permittivity value is strongly affected by through conduction caused by ion transport. 2ZrO3/MgLi2ZrO4 solid solution, Li+ cations can be replaced by Mg2+ cations, as a result of which the charge ratio between the crystal lattice sites can change. When Li+ is replaced by an ion with a higher oxidation state, Zr4+ → Zr3+ is oxidized to compensate for the charge ratio. In this case, an acceptor impurity can be created in the crystal grains, which generates an increased concentration of holes, which, in turn, increases the electrical conductivity [2ZrO4 phase increases, which means that the effective conductivity of the ceramic increases. The more pronounced dielectric properties of the ceramics  at MgO fractions of 0.05 and 0.15 are related to the porosity, which can be detected in the SEM images. The volatilization of lithium upon annealing can also contribute to elevation in the permittivity in the high-frequency region because of the formation of charged defects that interact with the electric field. In general, the dielectric constant value of an undoped sample and samples with substitution have similar values in studies of the dielectric and structural properties of Li2ZrO3-MgO ceramics [The increased electrical conductivity in samples with MgO 0.20 and 0.25 can be explained by the large grain size and the concomitant low defectiveness of the grain structure, which results in higher mobility of the charge carriers ,34. On tuctivity . As the ceramics ,37.2ZrO4 phase formation on the resistance to external influences. The results of indentation are presented in Analysis of the influence of changes in the strength properties of the synthesized ceramics depending on the MgO concentration was conducted by determining the indentation. A Vickers pyramid was used as an indenter; the load on the indenter was 100 N. The microhardness was determined by serial tests (25–30 indentations) from different parts of the ceramics, along with subsequent determination of the standard deviation and measurement error. Indentation in the form of serial tests was conducted to establish the isotropy of the strength properties of the ceramics, and to evaluate the influence of MgLi2ZrO3 (4.16–4.21 g/cm3) phase.The overall appearance of the dependence of the change in the hardness of ceramics reflects the effect of hardening with a rise in the MgO dopant concentration at concentrations of 0.05–0.15 mol and a slight decrease in hardness compared to the maximum value at concentrations of the MgO dopant of 0.20–0.25 mol. The alteration in the hardness of the ceramics depending on the MgO dopant concentration was because of the effect of structural hardening and a rise in density as a result of a decline in the concentration of defective inclusions and a decline in the crystal lattice porosity. Moreover, analyzing the data on the changes in density and hardening presented in The hardening value was calculated based on a comparative analysis of changes in the hardness of the doped samples at different dopant concentrations with the original, undoped samples. The maximum increase in hardening was 10.3% for a sample with a dopant concentration of 0.15 mol compared to an undoped sample. In this case, hardening may be due not only to phase formation effects, but also to change in the porosity of the ceramics in the case of their compaction and change in density.A further increase in concentration resulted in a decline in hardness by 1.0–2.0% in comparison with the maximum value, and, in comparison with the undoped sample, the hardening value exceeded 7–10%. Such an alteration in the strength properties, in addition to an alteration in the density and, as a consequence, the porosity of the crystal structure, can be explained by the formation of a two-phase structure of the ceramics at dopant concentrations above 0.10 mol.One of the key criteria for the applicability of ceramic materials as structural materials used under extreme conditions, including thermal heating, corrosion, and mechanical pressure, is the retention of their strength properties under prolonged external influences. Determination of resistance to high-temperature degradation and stress resistance during heating was conducted by conducting cyclic tests of samples when heated to 1000 °C, held at this temperature for 1 h and rapidly cooled, with the procedure repeated for several cycles. The maximum number of test cycles was 10 cycles. After 1, 3, 5, 7, and 10 cycles, the hardness values of the ceramic samples with different concentrations of the MgO dopant were measured. The results are presented in As can be seen from the data presented, the general appearance of the observed changes indicates high-temperature degradation of the strength properties of the studied samples depending on the cyclic tests in the case of elevation in the number of cycles. Moreover, it should be noted that the trends in the change in the values of hardness, indicating strength disordering, are different in nature depending on the MgO dopant concentration in the composition of the ceramics. In the case of an undoped sample of ceramics, the decrease in hardness during the cyclic tests occurred already after three successive cycles, and the nature of the decrease in strength with a rise in the number of cycles of stress tests had a clear appearance of softening growth. Such behavior of specimens during endurance tests for stability may be because of the effects of high-temperature structural degradation during rapid heating and cooling of the specimens, which results in the appearance of a gradient of temperature jumps in the specimens related to alteration in the magnitudes of the thermal fluctuations. This results in destructive disordering of the crystal structure, which has a negative effect on the strength properties of the ceramics. With alteration in the structural ordering degree in the case of the addition of low concentrations of the MgO dopant, which results in densification of the ceramics, with a decline in hardness because of high-temperature degradation during the stress tests, a similar trend towards a decline in hardness is observed; however, the magnitude of the changes is slightly different in nature in comparison to the undoped ceramic samples.2ZrO4 phase in the composition of the ceramics resulted in a rise in the resistance to thermal degradation in the case of the stress tests, which was expressed in the fact that the most noticeable decrease in hardness values was observed after 7–10 cyclic tests. This stability behavior indicates elevated resistance of the ceramics to thermally induced structural degradation. Moreover, it should be noted that the ceramics with a MgO dopant concentration of 0.15 mol had the highest stability, with the highest strength and low porosity observed. In the case of the doped ceramics, not only was a general increase in resistance to a destructive decrease in strength observed, but also a destruction rate decrease, which was expressed in the fact that the decline in hardness occurred after 5–7 cycles, while for the undoped ceramics, a similar decrease was already observed after 3 successive test cycles.According to the data acquired from the cyclic tests, formation of the MgLiAn analysis of the acquired data on changes in the stability of the strength properties of the ceramics in the case of the thermal tests made it possible to estimate the strength degradation degree after the cyclic tests. The results of the degradation assessment are shown in 2ZrO4 phase was observed, because of a rise in the concentration of MgO in the composition of the ceramics, had the highest stability. In this case, hardening was primarily because of the formation of interfacial boundaries, the appearance of which resulted in alteration in the dislocation density, along with the density of the boundary effects. With respect to the single-phase Li2ZrO3 ceramics with a monoclinic type of crystal lattice, after 10 cycles of thermal tests, the decrease in hardness values was more than 15%, which indicates significant destruction of the near-surface layer, along with a decline in the crack resistance of the ceramics. The degradation in the strength properties as a result of the heat resistance tests was primarily because of the appearance of structurally distorted areas caused by alteration in the thermal vibrations of the crystal lattice, leading to destructive thermal expansion of the crystal structure of the ceramics and possible penetration of oxygen into the near-surface layer of the ceramics, with subsequent penetration into the nodes and interstices of the crystal lattice. In this case, the introduction of oxygen into the interstices can also lead to a partial expansion of the crystal lattice and growth in its volume, which results in a destructive change in the strength properties of the ceramics. Also, in the case of the undoped ceramics, the decrease in resistance to the thermal tests was because of the effects of high porosity and low density, which, in turn, resulted in a high probability of oxygen penetration into the ceramic composition, with possible subsequent introduction into the composition.As can be seen from the presented data on the change in the value of the stability of the strength properties of the ceramics after 10 successive cycles of testing for thermal stability, the ceramics in which the presence of inclusions in the form of the MgLi2ZrO4 phase, along with subsequent increase in its contribution, resulted in the appearance of additional boundary effects and interfacial boundaries, which created additional obstacles to the introduction of oxygen, along with thermal expansion of the crystal lattice. Thus, the formation of the two-phase ceramics resulted in a rise not only in strength properties, but also in elevation in their resistance to the thermal tests and structural degradation under temperature differences. The overall change in strength properties for the two-phase ceramics after 10 successive cyclic tests was less than 1%.The addition of MgO to the composition of ceramics, which resulted in the formation of an MgLi2ZrO3-MgLi2ZrO4 ceramics with a high degree of structural order were obtained. Moreover, during the studies, it was found that the formation of the MgLi2ZrO4 impurity phase in the composition of the ceramics resulted in elevation in the hardness of the ceramics by 3–7%, which indicates a positive effect of the dopant related to hardening. Also, during the studies, it was found that the appearance of the MgLi2ZrO4 phase was accompanied by a rise in the density of the ceramics; however, at a high concentration of this phase, a slight decrease in density was observed. During tests for resistance to high-temperature heating, it was found that the formation of the MgLi2ZrO4 impurity phase resulted in the preservation of the stability of the strength characteristics, along with their resistance to destruction.In this paper, single- and two-phase Li


It was demonstrated that the size and shape of the nanoparticles in the resulting nanocomposites does not depend on the ratio of the initial reagents. Spherical particles with a mean diameter 2–3 nm of were obtained in different reaction mixtures with a mass fraction of cerium from 6.4 to 14.1%. The scheme of the dual stabilization of CeO2 nanoparticles with carboxylate and hydroxyl groups of CMC was proposed. These findings demonstrate that the suggested easily reproducible technique is promising for the large-scale development of nanoceria-containing materials.An elegant method of one-pot reaction at room temperature for the synthesis of nanocomposites consisting of cerium containing nanoparticles stabilized by carboxymethyl cellulose (CMC) macromolecules was introduced. The characterization of the nanocomposites was carried out with a combination of microscopy, XRD, and IR spectroscopy analysis. The type of crystal structure of inorganic nanoparticles corresponding to CeO Salvia macrosiphon Boiss seeds [Cerium oxide nanoparticles (nanoceria) are of interest in a wide range of applications, especially in the field of biomedicine. Many chemical methods for the synthesis of nanoceria are reported in the literature. Precipitation methods such as co-precipitation, chemical precipitation, microwave, sonochemical, hydrothermal, reverse-co-precipitation, and microwave–hydrothermal methods are basic procedures of synthesis ,12,13,14ss seeds . HoweverA high degree of biocompatibility, low toxicity, and catalytic activity of nanodispersed cerium dioxide make it possible to consider it as a promising material for biomedical applications as antioxidant, anticancer, and antibacterial agents ,18,19. T3+ and Ce4+, which distinguishes them from most other rare earth metals, which exist predominantly in the trivalent state [3+ ions on the surface of nanoparticles. In addition, the size and state of the surface of CeO2 particles determine the possibility of inactivation of superoxide free radicals, preventing oxidative stress in cells [The influence of nanocrystalline cerium dioxide in the protection of living cells from oxidative stress is of particular interest. The uniqueness of cerium dioxide nanoparticles is due to the fact that they can exist in different oxidation states, Cent state ,21. The nt state . In thisin cells . The mosin cells ,24.Along with the complicated preparation procedures of cerium-containing nanoparticles, there exists the important problem of their stabilization against aggregation (agglomeration). Different approaches to the stabilization of nanoparticles, such as gold, silver, and iron oxides as well as cerium oxide, are widely discussed in the literature. For example, various stabilizers have been found to be effective in preventing the agglomeration of nanosized particles, including thiols, carboxylic acids, surfactants, and polymers ,28,29,302) nanoparticles, sodium salt of carboxymethyl cellulose was used. CMC is water soluble and commonly used in the food industry [In this work, for the preparation of stable cerium oxide 2Ce(NO3)6 , and sodium borohydride .The following reagents were used in this work: sodium salt of CMC with molecular mass 90.000 Da DS 0.7 , ammonium cerium nitrate, (NH4)2Ce(NO3)6 was added dropwise under vigorous stirring. The masses of (NH4)2Ce(NO3)6 in solutions were varied from 6.3 to 17.6 mg. Then, 0.5 mL solution containing 3 mg to 5 mg of NaBH4, respectively, was added to the reaction mixture under intensive stirring. The resulting volume of the reaction mixture was 8 mL. The obtained solution was stirred for 12 h. Then, purification from low-molecular-weight components was carried out using dialysis  against water for 24 h. The resulting products were lyophilized.The synthesis of composite materials based on the sodium salt of carboxymethyl cellulose and cerium oxide nanoparticles was carried out according to the following procedure. To 2.5 mL of a 2 wt.% solution of CMC, 5 mL of the solution of . Absorption spectra of the solutions containing cerium ions of various concentrations and a calibration curve are presented in The determination of the cerium content in the composites was carried out using the UV spectroscopy method. The measurements were carried out on a Specord M40 device from Carl Zeiss  in the spectral range from 280 to 500 nm ,35. SampStructural studies were carried out with transmission (tunneling) electron microscopy (TEM) on a JEM-100B setup (JEML) equipped with an attachment for X-ray phase analysis . The samX-ray studies were carried out on a Rigaku D/Max2500 diffractometer with a rotating anode (Japan). The survey was carried out in reflection mode (Bragg–Brentano geometry) using CuKα1 radiation (cf. wavelength λ = 1.54183 Å). The generator operation parameters were: accelerating voltage 40 kV, tube current 200 mA. The survey was carried out in quartz cuvettes without averaging rotation. Solvents were not used to fix the powder samples. The recording parameters were: angle interval 2θ = 2°–60°, step (in 2θ) 0.02°, spectrum recording rate 5°/min . SiliconQualitative analysis of the obtained radiographs was performed using the WinXPOW software package (version 1.06) using the ICDDPDF-2 database.The nature of the interaction between the samples was studied using IR spectroscopy on a Specord M80 instrument . Studies were carried out in the absorption mode by preparing tablets from KBr (matrix) .The microstructure of the samples was studied using a scanning electron microscope with a LEO SUPRA 50VP field emission source . For the study, the samples were glued on a metal table using a conductive carbon adhesive tape and a layer of carbon or chromium was deposited on them (sputtering unit Quorum 150T—(UK), voltage 1000–1200 V, current strength 5–10 mA, deposition time 5–10 min ). The ac2 nanocomposites. The CMC–CeO2 nanocomposites were obtained by treating CMC with solutions of (NH4)2Ce(NO3)6 and a reducing agent (NaBH4) at room temperature. A feature of the proposed approach is the formation of cerium oxide in an aqueous medium simultaneously in the presence of a strong reducing agent and atmospheric oxygen. The need to use a reducing agent is due to the chemical specificity of this process, which, apparently, includes the following stages [An original technique was used for the first time to obtain CMC–CeOg stages ,37:Ce4+ During the synthesis, the concentration of CMC was kept constant, while the concentration of the cerium salt, the source of cerium (IV) ions, changed six-fold  from the dissolved (NH4)2Ce(NO3)6 undergoes reduction to cerium (III) in the form of cerium hydroxide, which undergoes oxidation by air oxygen dissolved in water. The growth of the nanoparticles is restricted by a stabilizing agent—CMC. Using different CMC-to-cerium molar ratios, a series of nanocomposites was obtained. The morphology and the size of the inorganic nanoparticles stabilized with CMC was studied using TEM. For the all studied compositions of the reaction mixtures the resulting nanoparticles had a spherical shape and a mean diameter of 2–3 nm. Thus, CMC restricts the growth of nanoparticles, providing effective stabilization of the inorganic surface with carboxylate and hydroxyl functional groups. It should be stressed that not only electrostatic but coordination contacts as well provide the stabilization of the nanoparticles. The SEM experiments demonstrated a violation of the continuous film structure of the CMC after the formation of the nanocomposites. In the initial CMC film the intra- and intermolecular hydrogen bonds of the polymer supply the smooth, non-porous structure. The formation of the nanoparticles and their incorporation in the polymer matrix result in destruction of the internal structure of the polymer film due to a change in the function of coordination bonds from stabilization of the film to stabilization of the nanoparticles.A one-pot synthesis of fine dispersed CeO2. For the CeO2 powder the characteristic peaks should be observed at angles 2θ = 28.4°, 34.38°, 47.6°, and 57°. The obtained values of 2θ correspond to the following parameters of the CeO2 crystalline lattice: 110; 004; 220; 214; 311. With the increase in the inorganic phase share in the nanocomposites, the reflections corresponding to the crystalline lattice of CeO2 become more intensive. No additional peaks arise with the increase in the Ce(IV)-to-CMC ratio in the nanocomposite, confirming that the structure of inorganic nanoparticles does not depend on ratio of the components in the reaction mixture.The nature and the structural type of the nanoparticles formed were determined using XRD and TEM analyses. Dark field TEM images of the nanocomposites allows one to estimate the crystalline nature of the inorganic phase. Diffractograms of these particles confirm the crystalline structure of the nanoparticles. However, due to the small size of inorganic particles no detailed information about the structure could be obtained with diffractometer-integrated TEM. The XRD analysis confirmed that the nanoparticles represent themselves as crystals of CeO2 nanoparticles with groups of CMC, IR spectroscopy was applied. The initial spectrum of the CMC contains characteristic peaks at 1740 cm−1, 1688 cm−1, 1420 cm−1, and 1220 cm−1 reflecting carboxyl, carboxylate, and hydroxyl groups. The formation of nanocomposites results in the vanishing of the 1740 cm−1 peak, which reflects the formation of intra- and intermolecular hydrogen bonds. At the same time, the intensive peaks reflecting carboxylate groups were retained in the spectra of the nanocomposites. Hence, the stabilization of the nanoparticles is supplied by electrostatic interactions. Transformation of the 1220 cm−1 peak from a wide to a sharp shape with the increase in the cerium content reflects the incorporation of the hydroxyl groups of CMC in interactions with the surface of the inorganic particles.To support the proposed nature of the stabilization of CeOWe suggest that geometrically surrounded nanoparticles of cerium oxide are stabilized with both carboxylate and hydroxyl groups of CMC. The first one ensures electrostatic stabilization while the second one is responsible for the coordination contacts. The dual action of these groups results in effective stabilization of the nanoparticles with a relatively small size.2 nanoparticles stabilized by carboxymethyl cellulose macromolecules were obtained. In the resulting nanocomposites, the content of the inorganic component was determined with UV spectrophotometry. The nanocomposites were also characterized by TEM, SEM, XRD, and IR spectroscopy. It has been found that varying the ratio of the components of the reaction mixture in the course of synthesis makes it possible to obtain nanocomposites with different contents of the inorganic phase while the size and morphology of the nanoparticles did not depend on the reaction mixture composition. The nanoparticles had a spherical shape with an average diameter of 2–3 nm. It was demonstrated that the type of crystal lattice of the nanoparticles corresponds to the structure of CeO2.The type of crystal structure did not depend on the ratio of the components in the reaction mixture as well. With the use of a combination of SEM and IR spectroscopy, it has been demonstrated that the stabilization of the nanoparticles is attributed to both electrostatic and coordination contacts of the inorganic surface with the macromolecules. These findings could be useful for the further development and application of cerium oxide nanoparticles.Nanocomposites consisting of CeO