Calcium Oxide Content Research Articles

Predictive control research for cement burning system using two-cycle coupling optimization

A stable, high quality cement burning system producing clinker with low energy consumption is important for cement company. However, in the actual operation of the combustion system, there are contradictory indicators such as electricity consumption, coal consumption and clinker quality that are difficult to be jointly optimized, as well as dynamic and complex working conditions that are difficult to be artificially adjusted to the optimal state. In order to solve the above problems, a multi-objective optimal predictive control model is proposed in this paper. The prediction part of the model consists of a prediction model of cement burning system based on convolutional neural network. The optimization part, on the other hand, combines electricity and coal consumption into one energy target and uses cement clinker quality as a constraint to find the optimal production state. This modeling approach simplifies the problem and avoids the need to solve for the Pareto optimal solution. The control part is then based on the above-mentioned model with a double-cycle coupled cycle optimization to obtain set values of controlled variables that satisfy the changing operating conditions and finally control target to track the dynamic operating conditions. Experimental results show that the method described in this paper reduces the content of free calcium oxide after cement combustion, thus improving the quality of cement clinker, while reducing the fluctuations of the control variables in each production process and improving the stability of the combustion system. There is also a significant reduction in production energy consumption.

Antibacterial, remineralising and matrix metalloproteinase inhibiting scandium-doped phosphate glasses for treatment of dental caries

ObjectivesAntibiotic resistance is increasingly a growing global threat. This study aimed to investigate the potential use of newly developed scandium-doped phosphate-based glasses (Sc-PBGs) as an antibacterial and anticariogenic agent through controlled release of Sc3+ ions. MethodsSc-PBGs with various calcium and sodium oxide contents were produced and characterised using thermal and spectroscopic analysis. Degradation behaviour, ion release, antibacterial action against Streptococcus mutans, anti-matrix metalloproteinase-2 (MMP-2) activity, remineralisation potential and in vivo biocompatibility were also investigated. ResultsThe developed glass system showed linear Sc3+ ions release over time. The released Sc3+ shows statistically significant inhibition of S. mutans biofilm (1.2 log10 CFU reduction at 6 h) and matrix metalloproteinase-2 (MMP-2) activity, compared with Sc-free glass and positive control. When Sc-PBGs were mounted alongside enamel sections, subjected to acidic challenges, alternating hyper- and hypomineralisation layers consistent with periods of re- and demineralisation were observed demonstrating their potential remineralising action. Furthermore, Sc-PBGs produced a non-toxic response when implanted subcutaneously for 2 weeks in Sprague Dawley rats. SignificanceSince Sc3+ ions might act on various enzymes essential to the biological mechanisms underlying caries, Sc-PBGs could be a promising therapeutic agent against cariogenic bacteria.

Prediction of f-CaO content in cement clinker: A novel prediction method based on LightGBM and Bayesian optimization

The content of free calcium oxide(f-CaO) in cement clinker is an important index affecting the quality of cement clinker. Because f-CaO content in cement clinker cannot be measured directly, it is of great significance to accurately and quickly predict its content. However, it is difficult to establish an accurate prediction model of f-CaO due to the problems of time-varying delay, coupling between variables and uncertainty in the cement calcination production process. To solve these problems, we proposed a Bayesian Optimization Light Gradient Boosting Machine (BO-LightGBM) cement clinker f-CaO prediction model based on time series input window. Firstly, a time series input window containing time-varying delay information is designed according to the production process to form a high-dimensional time series data matrix. Then LightGBM histogram algorithm is used to extract time-varying delay features from high-dimensional time series matrices. Finally, the Bayesian optimization algorithm is used to perform global hyperparametes tuning for the characteristics of LightGBM with multiple hyperparameters. The experimental results show that compared with support vector regression (SVR), back propagation (BP), gradient boosting decision tree (GBDT), eXtreme gradient boosting (XGBoost), and LightGBM, our method BO-LightGBM has better prediction accuracy, robustness and generalization ability.

Influence of CaO Content on the Fly Ash–Lime System Hydrothermal Synthesis Reaction Under Autoclave Curing

As a substitute for traditional Portland cement, the development and research of “low-temperature-synthesized fly ash cement” has been receiving extensive attention. This study explores the effects of calcium oxide content on the fly ash–lime system hydrothermal synthesis reaction under autoclave curing, focusing on the effects of CaO content on the strength of the cement paste. The changes in phase composition, microstructure, and morphology were characterized using X-ray diffraction and scanning electron microscopy (SEM) analysis. The results show that with an increase in the CaO content, the amounts of β-C2S and C12A7 in the gelling material also increase. However, when the CaO content is very high, the amounts of β-C2S and C12A7 in the gelling material no longer increase, and the strength is lost.

Property improvement of biodegradable citric acid-crosslinked rice starch films by calcium oxide

Due to several important limitations for packaging applications of starch film such as strength and hydrophilicity, rice starch (Oryza sativa) film was crosslinked with citric acid and modified by different contents of calcium oxide. FTIR spectra showed the evidence of crosslinking by citric acid and the presence of calcium oxide in the modified rice starch films. After the crosslinking, the decrease of degree of crystallinity and swelling including the increase of film smoothness and strain at maximum load were observed. The application of both citric acid and calcium oxide caused greater decrease of swelling, moisture uptake as well as higher stiffness and antibacterial activity than those of the use of only the citric acid. The highest stiffness and antibacterial activity were found for the crosslinked film added by 5 wt% calcium oxide. Moreover, the effect of calcium oxide contents on morphological, thermal and biodegradable properties of the crosslinked films was also investigated.

Flexural Behaviour, Microstructure and Cost-Benefit Analysis of Ternary Binder Foamed Concrete

Foamed concrete is a controlled low-density concrete, and due to its excellent thermal insulating and acoustic absorption properties, its application has been on a steady rise. Palm Oil Fuel Ash (POFA), an agricultural waste generated by the Palm Oil industry and Eggshells, causes many environmental problems. The pozzolanic nature of POFA and the high calcium oxide content in Eggshell Powder (ESP) are the components that contribute to their suitability as a partial cement replacement in concrete. This experimental work studied the flexural behavior, as well as the compressive strength of lightweight ternary binder foamed concrete incorporating 20% - 25% POFA and 5% - 10% ESP by weight of the total binder, as partial cement replacement. The test results were analyzed and compared with conventional foamed concrete without POFA and ESP. It was observed that POFA is a class C pozzolanic material. The combined utilization of POFA and ESP increased the compressive and flexural compared with control concrete. Furthermore, most of the cracks of the prisms were nearer to the middle of the samples and between two locations of loads applied due to the same load value applied at both locations. It was also observed the air voids were blocked due to increased pozzolanic activity and development of C-S-H gels and thus increase in strength. The utilization of POFA and ESP in concrete can be beneficial in reducing the overall cost. The cost to produce 1 m3 of concrete incorporating POFA and ESP was reduced ranging from was reduced by 12.59% (with 20% POFA and 5% ESP) to 17.53% (with 25% POFA and 10% ESP). It can be concluded that the M4 concrete mix is the optimum and cost-effective, as the maximum cement content is replaced (35%), as well as the compressive and flexural strengths are significantly higher than the control concrete M0.

Performance evaluation of regenerated clinker from completely recyclable mortar

This study aims to characterize the performance of recycled clinker prepared from more sustainable concrete that can preserve natural resources. A completely recyclable mortar (CRM) was designed with a composition similar to that of the raw cement materials. Then, recycled cement generated from CRM was used to prepare another CRM and further recycled. The XRD patterns, free calcium oxide content, and mechanical strength of the recycled clinker after each cycle were studied. The results showed that as the number of cycles increased, the strength and hydration activity of the recycled cement clinker gradually decreased. Mineralogical composition analysis showed the weakening of the C3S diffraction peak and decrease in C3S content as well as strengthening of the C2S diffraction peak and increase in C2S content with an increase in cycle number. The degradation of the recycled clinker performance may be attributed to the presence of unhydrated cement particles in the heat-cured mortar. Although the hydration activity of the recycled cement clinker decreased, its carbonization strength increased significantly, which could be attributed to its high C2S content.

Carbon dioxide uptake by pure Portland and blended cement pastes

Carbon dioxide sequestration by cement-based materials is a chemical process known as carbonation. Carbon dioxide absorption by cement consists of its reaction with calcium hydroxide, among other Portland cement components. This phenomenon should be taken into account in the calculation of the net contribution of cement production to greenhouse gas emissions. Therefore, carbon dioxide uptake should be considered into future life-cycle assessment protocols.This paper presents the carbon dioxide absorption results recorded in paste specimens during almost four years by 15 different types of Portland composite cements made of siliceous coal fly ash, natural pozzolan, ground granulated blast-furnace slag and limestone. Prismatic (10 ​× ​10 ​× ​60 mm) Portland cement pastes made of several types of cement (5% and 35% by weight) and with two cement/water ratios (0.45 and 0.60) were manufactured. The specimens were cured at 95% relative humidity for 24+ ​48 ​h and afterwards they were kept under laboratory room conditions for 25 more days. After this period, a set of the specimens remained in the lab, whereas other were moved outdoors for being kept sheltered or exposed from rain.Thermogravimetric measurements were performed along the time to determine the carbon dioxide absorption by the Portland cement pastes. The results were fitted to an exponential function. The maximum carbon dioxide absorption and the absorption rate depends on the exposure conditions, the water/cement ratio, the cement type (calcium oxide contents, type and percentage of the additions in the cement paste and compressive strength) and portlandite formed at 28-days. The results of this paper show that the absorption amounts were 13% and 30% in weight. of ignited cement.

Hunting colours: origin and reuse of glass tesserae from the Wierum terp

Mosaic glass tesserae were imported to Dutch sites during the Early Medieval period, probably to address the demand for coloured glass needed in ornamental bead manufacture. Although challenging, because of the uncertainty of the material’s context, the Wierum Early Medieval collection represents an extraordinary opportunity, being the most significant find of glass tesserae in the Netherlands to date. The combined use of electron microprobe analysis (EMPA) and hand-held X-ray fluorescence spectrometry (HH XRF) allowed us to examine glass tesserae and other vitreous samples from the site. Low levels for magnesium and potassium oxides (<1.5 wt%) and the chemical components linked with the silica source, fluxes, opacifiers and chromophores are compatible with an older Roman soda-lime-silica glass production. Alumina and calcium oxide contents together with the adoption of antimony-based opacifiers are compatible with mosaic tesserae of a first to third century AD Roman tradition. We assume that these tesserae were collected during the spoliation of a lavish building and reused for glass objects produced locally. The hypothesis seems to be confirmed by the presence in the collection of tesserae still embedded in mortar, stone tesserae fragments and a rounded fragment of Egyptian blue.

Effect of direct carbonation routes of basic oxygen furnace slag (BOFS) on strength and hydration of blended cement paste

Mineral carbonation of alkali solid wastes is envisaged to be an effective method to sequester CO2 and turn the wastes into more valuable end products. Steel slag generated from the steel-making industry contains a high content of calcium oxide, which is a potential medium to sequestrate CO2 via the carbonation process. In this paper, the influence of reaction parameters including solid to liquid ratio, CO2 flow rate, temperature, volume of water and carbonation time on aqueous carbonation of basic oxygen furnace slag (BOFS) in maximizing CO2 sequestration was determined. The structural and mineralogical changes of carbonated BOFS were also analyzed using thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy. Using an optimized aqueous carbonation condition, about 16.35% of CO2 can be sequestered, which was obviously higher compared with dry carbonation (about 4.91%) at ambient conditions. Subsequently, the effect of replacing cement with carbonated BOFS (either by aqueous or dry route) on the micro-mechanical properties and hydration characteristics of blended cement paste was studied. The results demonstrated that as a small ratio of aqueous carbonated BOFS (10%-20%) blended in the cement paste they can accelerate the rate of early heat evolution during the first 24 h. On the contrary, as the carbonated BOFS ratio increased, the overall heat of hydration and mechanical strength were decreased. In comparison, BOFS carbonated by aqueous method is found to perform better in blended cement paste than its counterpart carbonated by dry method at the same replacement ratio due to the presence of a greater calcite content (acting as nucleation sites) in the aqueous carbonated BOFS.

Effects of maize straw treated with various levels of CaO and moisture on composition, structure, and digestion by in vitro gas production.

ObjectiveThe objective of this study was to explore the effects of maize straw treated with calcium oxide (CaO) and various moisture, on the composition and molecular structure of the fiber, and gas production by fermentation in an in vitro rumen environment.MethodsThe experiment used 4×3 Factorial treatment. Maize straws were treated with 4 concentrations of CaO (0%, 3%, 5%, and 7% of dry straw weight) and 3 moisture contents (40%, 50%, and 60%). Scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray fluorescence spectroscopy were employed to measure the surface texture, secondary molecular structure of carbohydrate, and calcium (Ca) content of the maize straw, respectively. The correlation of secondary molecular structures and fiber components of maize straw were analyzed by CORR procedure of SAS 9.2. In vitro rumen fermentation was performed for 6, 12, 24, 48, and 72 h to measure gas production.ResultsOverall, the moisture factor had no obvious effect on the experimental results. Neutral detergent fiber (NDF), acid detergent fiber, acid detergent lignin, hemicellulose and cellulose contents decreased (p<0.05) with increasing concentrations of CaO treatment. Surface and secondary molecular structure of maize straw were affected by various CaO and moisture treatments. NDF had positive correlation (p<0.01) with Cell-H (H, height), Cell-A (A, area), CHO-2-H. Hemicellulose had positive correlation (p<0.01) with Lignin-H, Lignin-A, Cell-H, Cell-A. Ca content of maize straw increased as the concentration of CaO was increased (p<0.01). Gas production was highest in the group treated with 7% CaO.ConclusionCaO can adhere to the surface of the maize straw, and then improve the digestibility of the maize straw in ruminants by modifying the structure of lignocellulose and facilitating the maize straw for microbial degradation.

Use of Lebedinsky Mining and Processing Works Overburden Chalkstone for Iron-Ore Pellet Fluxing

Mine rocks generated abundantly in the course of iron-ore deposit development and containing high quality overburden chalkstone are mainly stored in dump pits. This relates to the Lebedinsky Mining and Processing Works as well. This results in certain environmental issues. Therefore the work provides the investigation results in some measure allowing the defined problem solution through complete replacement of limestone used for iron-ore pellet fluxing by the overburden chalkstone. This required a whole set of experiments. Derivatographic investigation was carried out on the overburden chalkstone samples of the Lebedisky Mining and Processing Works and allowed defining of the studied sample temperature and heating time impact on production of chalkstone with varying decarbonization process extent. Activity of the lime produced from the chalkstone was evaluated through determination of the total content of active calcium and magnesium oxides in it. In the course of the experiments the temperature and time impact on the liming process was defined. To justify the potential of the overburden chalkstone use as an additive for iron-ore pellet fluxing and their production with sufficiently high strength properties ensured, as well as of the complete replacement of the limestone used for these purposes, the experiments with the briquettes were carried out. At that the briquette composition complied with that of the fluxed iron-ore pellets. The briquette strength properties with chalkstone additives versus the firing temperature and degree were studies, as well as physicochemical processes occurring in the samples at their heat treatment. As a result of the investigation it was determined that the chalkstone additive use in the pellet fluxing contributes to their significant strength increase. The obtained results are of certain interest for the specialists dealing with iron ore material preparation for metallurgical conversion and allow development of pellet heat treatment conditions ensuring their high metallurgical performance.

Multi-objective collaborative optimization in cement calcination process: A time domain rolling optimization method based on Jaya algorithm

Coal consumption and free calcium oxide (f-CaO) content are two important production indicators in the cement calcination process, and its collaborative optimization is of great significance to improve the production performance. However, due to the multiple dynamic interferences and multiple conflicts between coal consumption and f-CaO, product quality is unstable and coal consumption becomes high. To address the problems, this paper proposes a multi-objective collaborative optimization method for cement calcination process. This method takes the coal consumption and f-CaO content as the optimization objectives to establish a multi-objective optimization model. In addition, to solve the problem that static single-step optimization is difficult to track the continuous change of working conditions, we propose a time domain rolling multi-objective Jaya algorithm (TDRM-Jaya) to optimize the model. The algorithm, involving a population update strategy, a selection strategy and a time domain rolling strategy, realizes the dynamic rolling optimization for the cement calcination process. The test comparison with several common intelligent optimization algorithms demonstrates the advantages of using TDRM-Jaya. Besides, practical industrial data validates the effectiveness of the proposed optimization method.

Palm Oil Fuel Ash and Mussel Shell Powder as Supplementary Cementitious Materials in Non-Load Concrete Brick

The pozzolanic properties of the industrial by-product palm oil fuel ash (POFA) has given this material a unique characteristic that can be used as a cement substitute. Meanwhile, the abundance of waste seashells which contain an enormous amount of calcium oxide (CaO) available around the world has led this material to be another potential waste material as substitutes for conventional materials in concrete. The percentage amount of POFA used as a replacement was constant at 20% from the amount of cement. On the other hand, mussel shell powder (MSP) was replaced by 2%, 4%, 6% and 8% with the decrement of 2% of OPC used for each of the design. The physical and chemical properties of the materials and the mechanical properties of concrete brick were identified for 7, 14 dan 28 days. The inclusion of POFA and MSP in the concrete brick mix in this study reduced the compressive strength of the concrete in the early days and enhanced at the late stages. Apart from that, the compressive strength of the concrete brick mixtures decreased along with the increasing percentage of MSP as the increment content of CaO from MSP reduced the hydration process. The optimum percentage of MSP replacement in this study is 4% with 20% replacement of POFA and 76% OPC. The application of these materials as supplementary cementitious materials in the construction industry, particularly in producing non-load concrete brick will simultaneously encourage reducing potential pollutions and promote sustainability.

Influence of Ground Calcium Carbonate Waste on the Properties of Green Self-Consolidating Concrete Prepared by Low-Quality Bagasse Ash and Rice Husk Ash.

Bagasse ash (BA) and rice husk ash (RHA) are by-products from electricity power plants. Ground calcium carbonate waste (GCW) is the by-product of the mining of calcium carbonate (CaCO3) in the color pigment manufacturing industry. Both BA and RHA are classified as low-quality pozzolanic materials, differing from GCW, which contains a high calcium oxide (CaO) content that leads to products equivalent to the hydration reaction. Therefore, GCW is likely able to improve the properties of self-consolidating concrete (SCC) incorporating BA and RHA. This paper discusses the production of green self-consolidating concrete (gSCC) and identifies the benefit of using GCW in gSCC prepared by triple combined GCW (10 and 20 wt%), BA (10, 20, and 30 wt%), and RHA (20 wt%). The results indicate that the majority of the gSCC retain acceptable flowability. The differences in the levels of gSCC substitution and the V-funnel flow results show general correlations with the increase in GCW. The gSCC prepared by 10 wt% GCW associated with 10 wt% BA and 20 wt% RHA was improved significantly. The filling and passing abilities of the gSCC were improved by using GCW. In addition, gSCC achieved mechanical property development and was able to minimize the consumption of OPC by up to 40%.

Utilization of alkali-activated construction demolition waste for sandy soil improvement with large-scale laboratory experiments

Using alkali-activated materials to treat waste materials is becoming more prevalent in geotechnical engineering. Adding these materials into soil particles as a cementitious material can improve the geotechnical properties of problematic soils, and minimize environmental pollution. The present study focused on the feasibility of using alkali-activated construction demolition waste (CDW) as a stabilizer for large-scale soil improvement applications. The CDW was used as a source of aluminosilicate; sodium hydroxide (NaOH), potassium hydroxide (KOH), and calcium oxide (CaO) (at concentrations of 2 M, 6 M, 10 M, and 14 M) were used as the alkaline media. CDW (16%) was selected as the source of alkali-activated material. The optimal concentrations of NaOH, KOH, and CaO were found to be 10 M, 10 M, and 6 M, respectively. Moreover, 21 days and 39 °C yielded the best results at the bearing capacity values. Thus, the use of CDW as an alkali activator is a better remedy for soil engineering properties, and contributes to soil improvement.

Effects of CaO on the Clonal Growth and Root Adaptability of Cypress in Acidic Soils

Cypress (Cupressus funebris Endl.) is a major tree species planted for forestland restoration in low-fertility soil and in areas where rocky desertification has occurred. Calcium (Ca) fertilizer can adjust the pH of soil and has an important effect on the growth of cypress. Soil and water losses are serious in Southern China, and soil acidification is increasing, which results in high calcium loss. However, the adaptability of cypress clones to different concentrations of calcium in acidic soils has not been studied. In this investigation, a potted-plant experiment was set up with three concentrations of calcium oxide (CaO) fertilizer (0, 3, and 6 g·kg−1) added under local soil conditions with 0 and 3 g·kg−1 nitrogen (N), phosphorus (P), and potassium (K) fertilizer. The effects of CaO on the growth, root development, and nutrient uptake and utilization efficiency of cypress clones were analyzed. The growth, root development, and nutrient absorption and utilization of cypress differed when calcium fertilizer was applied to acidic soils with different degrees of fertility. In the soil with 0 g·kg−1 NPK fertilizer, the 3 and 6 g·kg−1 CaO treatments significantly increased the clonal growth of cypress seedling height, basal diameter, and dry-matter weight. In addition, the length, surface area, and volume of the roots less than 2.0 mm of root diameter also significantly increased, indicating that the fine cypress roots were somewhat able to adapt to differing Ca levels under lower fertility conditions. Moreover, the efficiency of N, P, and Ca accumulation was highest in the 3 g·kg−1 CaO treatment. After adding 3 g·kg−1 CaO fertilizer to the soil with 3 g·kg−1 NPK fertilizer, only the root dry-matter weight increased significantly, indicating that root development (including root length, surface area, and volume) in the D1–D3 diameter classes (≤1.5 mm in diameter) was significantly elevated. When CaO application reached 6 g·kg−1, the seedling height, basal diameter, and dry-matter weight of each organ decreased, as did the length, surface area, and volume of the roots in the all diameter classes, indicating that the addition of excessive CaO to fertile soil could inhibit the growth and root development of cypress. In Ca-deficient low-quality acidic soils, adding CaO fertilizer can promote the development of fine roots and the uptake and utilization of N, P, and Ca. The results of this study provide a basis for determining the optimal fertilization strategy when growing cypress in acidic soils in Southern China.

Screening for key material parameters affecting early-age and mechanical properties of blended cementitious binders with mine tailings

Considering the vast amounts and wide variability of tailings available worldwide, means to assess the potential of tailings for cement clinker replacement based on their physical, chemical and mineralogical characteristics would be useful. This work studied the early-age properties and mechanical performance of mortar of Portland limestone cement (CEM II/A-LL) clinker in a ternary blend with partial clinker substitution by 13 metal and mineral mine tailings. The properties studied included workability, setting time, porosity and compressive strength. The effects of replacement level and mine tailing characteristics on the performance of mortar were assessed by chemometrics.The results showed that most mine tailings reduced the workability of mortar (3–19 %) and that an increased replacement level reduced the workability further. For most mine tailings, the initial setting time was identical to the reference, while they reached the final setting faster. Tailings had a variable impact on the porosity at low replacement, while porosity generally increased at a higher replacement. The compressive strength decreased with increasing replacement in most cases, and a clear negative correlation was found between compressive strength and porosity. However, five mine tailings developed up to 10 % higher strength after 28 days with 20 % supplementary composite material compared to the reference.Chemometric analyses showed that tailings with high specific surface area and silicon dioxide content influenced the mechanical properties of the mortar most positively. Conversely, larger grain sizes, high loss on ignition, calcium oxide and calcium carbonate content impacted compressive strength negatively.The analyzed characteristics do, however, not fully explain the resulting early-age and mechanical properties, thus additional investigations are needed to understand the performance in detail.

PHASE EQUILIBRIA IN THE NaCl–CaCl2–CaO SYSTEM

The phase equilibria of the ternary system CaCl2 – NaCl – CaO in the area which enriched of calcium and sodium chloride were investigated by the methods of differential-thermal analysis and powder X-ray phase analysis. In the systems were determined the equilibrium concentration of calcium oxide and the composition of the phases, which at the same time exist in an equilibrium state at different temperatures. The surfaces of liquidus and solidus were established, the compositions of the sections of the ternary system CaCl2–NaCl–CaO were defined, which recommended for electrochemical reduction of refractory metal oxides (titanium, zirconium and other), which allow electrolysis in the temperature range from 550 to 1000 °С. Five polythermal sections of the NaCl – CaCl2 – CaO ternary system were studied. For each polythermal section the regions of existence of the liquid and solid phases were established. For each polythermal section state diagrams were constructed. Used X-Ray phase analyses it was established the compositions of liquid and solid phases for each polythermal sections. The phases of which the system consists were determined. At a constant ratio of components [NaCl]:[CaCl2] = 1.06 (mol.) in the melts of the ternary system CaCl2 – NaCl – CaO, the equilibrium content of calcium oxide reaches 12.0 mol.%, while their crystallization temperature does not exceed 550 °C. This allows us to recommend mixtures of this composition for electrochemical reduction of refractory metal oxides in a wide range of temperatures (from 550 to 1000 °C) with a high content of both calcium and sodium chlorides (not less than 40 mol.%) and oxide. calcium (up to 12.0 mol.%). The eutectic of this ternary system has a melting point of 480 ° C and corresponds to he composition (mol.%): CaCl2 (45.8) – NaCl (47.0) – CaO (7.2).

Study on ancient lime glazes and lime alkali glazes-limitations of surface analysis

Traditional lime glazes and alkali glazes from past dynasties were studied based on petrographic and optical coherence tomography (OCT) analysis. Calcium feldspar crystals were formed on glaze in Yue kilns based on experimental archaeology to prove that the calcium oxide content of the glazes decreased significantly due to the formation of calcium feldspar crystals between glazes of ancient ceramic bodies with a high aluminum matrix. This is the limitation of fluorescence analysis as a surface analysis technique, and it has an effect on judging the kinds of lime glaze and lime alkali glaze as well as the glaze making process. The lithofacies structure has a significant difference between the lime glaze and lime alkali glaze. Petrographic analysis shows that the characteristics of bubbles and crystallizations can help judge the types of lime glaze and lime alkali glaze. This structural feature can be used as the identification standard for nondestructive OCT analysis.