Refractory Industry Research Articles

Mineralogical, chemical and physico-mechanical properties of fired bricks for refractory industry applications

This study aims to characterize soils for their use in the refractory industry applications. Two types of hydromorphous soil were sampled in the locality of Minkoameyos in the neighbouring city of Yaoundé-Cameroon: multicolored soil clay (A001) and grey soil clay (A002). Mineralogical, chemical and physico-mechanical properties were investigated. Bricks made from these soils were heated at 900 °C, 1100 °C and 1200 °C temperatures. Physico-chemical properties showed that these soils are light (A002), silty (A001), inorganic and acidic, with pH values of 5.45 and 4.47 for A001 and A002, respectively. Chemical analysis revealed that these soils are essentially composed of silica (40 and 46%), alumina (35.9 and 32.5%) and coloring oxides (8.5 and 6.3%) for A001 and A002 samples, respectively. Mineralogical analyses of these soils revealed the presence of quartz, kaolinite, illite and muscovite. Bricks heated at 900 °C, 1100 °C and 1200 °C showed a variation in color from orange to reddish brown for A001 sample; from light orange yellow to dull orange for A002 sample and a sound ranging from dull to slightly metallic. Residual mechanical performance showed a slight drop in strength at the heating temperature of 900 °C (8.8 and 8.3 MPa for multicolored soil clay A001 and grey soil clay A002, respectively). This temperature seems sufficient for this type of floor. Above 900 °C, the impact of carbon is significant. These results showed that Minkoameyos hydromorphous soils clay have remarkable properties and can produce refractory materials.

A perspective to efficient synthesis of zirconium carbide via novel pyro-vacuum method: lower temperatures and enhanced purity

The use of ultra-high temperature ceramics (UHTCs) as a novel additive in the refractory industry is becoming increasingly popular. However, the synthesis of such materials is associated with some commercial obstacles, mainly high-temperature synthesis methods. In the present study, the pyro-vacuum method is presented as a new method to decrease the final product's synthesis temperature and oxygen content. Some thermodynamic aspects and phase evolution of the materials during the synthesis procedure are described for the synthesis of non-oxide material. Conclusively, it seems that by applying vacuum conditions, the final UHTC phases can be synthesized at significantly lower temperatures (>400 °C lower, for ZrC), if adequate powder mixtures are considered. Also due to phase analysis, it was found that the oxygen content of the final phase is lower than the conventional routes and other references. The process provides promising prospects for the economic synthesis of UHTCs.

Utilizing nano-computed tomography to characterize the structural nature of industrial minerals

Abstract X-ray computed tomography (XRT) is a nondestructive and thus reproducible examination method allowing the three-dimensional (3D) investigation of the internal and external structures of objects regardless of their material and geometry. In the present study, XRT was used to investigate the influence of hydrochloric acid leaching on the composition and constitution of iron-rich bauxite grains. Reducing the iron content in raw bauxites by acid leaching is a promising method for the beneficiation of iron-rich bauxites for subsequent use in the refractory industry. Not only the effect of the leaching process on the chemical composition of the bauxites, but also aspects such as the acid’s influence on the mineralogical composition and the resulting porosity of the individual grains have hardly been taken into account so far. To address these issues, various bauxites were examined before and after acid leaching using XRT analysis and specifically characterized with regard to their constitution.

Tailoring microstructure and properties of porous mullite-based ceramics via sol-gel impregnation

Nanotechnology has been introduced into the refractory industry decades ago. However, there are still some peculiarities that hinder its routine application. Poor mechanical strength is one of them. Here we present the fabrication technique for mullite porous ceramics using a calcium-free colloidal binder system followed by secondary sol-gel impregnation intended for fabrication of large up-scaled monoliths. The primary foam was prepared via direct foaming of slurry containing colloidal silica, gelling agents, surfactant, silica fume, and different types of alumina. The foam mixture was cast, de-molded and dried using a cascade drying procedure. The investigation of mullitization that occurred during the high-temperature treatment was studied by XRD and TG-DTA analysis. The optimized sintering curve was then applied to obtain the highest mechanical properties. The resulting foam (with open porosity, volume density about 900 kg/m3 and mechanical strength about 10 MPa) was further processed by the impregnation step. The applied silica or combined silica/aluminum sol and unreacted alumina underwent secondary mullitization during following high-temperature treatment, which significantly enhanced the mechanical strength (up to 18 MPa). The secondary mullitization process was also investigated by HT-XRD and TG-DTA analysis. Foam microstructure was observed by an electron scanning microscope. Thermal conductivity of as-prepared ceramics foams varied from 0.3 to 0.4 W/m·K. The foam wall porosity evolution was studied by mercury intrusion porosimeter and estimated from image analysis.

Chemical Interaction between the Sr4Al6O12SO4 Ceramic Substrate and Al–Si Alloys

Samples of Sr4Al6O12SO4 are obtained through a solid-state reaction of Al2O3, SrSO4, and SrCO3. The samples are then made into 1 and 4 cm pellets by compacting them at 100MPa and sintering them at 1400 °C for 4 h. The compound is analyzed using X-ray diffraction. Static immersion and wettability tests are carried out to evaluate corrosion resistance in contact with Al–Si. Corrosion tests are conducted by immersing the samples at 800, 900, and 1000 °C for 24, 50, and 100 h, while wettability is studied at 900, 1000, and 1100 °C for 2 h. Afterwards, the samples are subject to metallographic preparation. The samples are then analyzed using optical microscopy, scanning electron microscopy, and image analysis. In general, reaction products consisting of alumina, spinel, oxides, and sulfates are found. The contact angles obtained are between 124° and 135°. It is concluded that the Sr4Al6O12SO4 ceramic substrate is resistant to corrosion by the Al–Si alloy because of the slight thickness of the reaction products found in the samples (73 μm), considering the severe conditions of the experiment: 1000 °C and 100 h of isothermal temperature. Furthermore, Sr4Al6O12SO4 is not wettable by Al–Si alloys. These results suggest that the ceramic substrate could be used in the refractory industry, possibly as an additive to commercial refractory ceramics. For future work, it is recommended to carry out the same study with the aluminum–magnesium alloy and as an additive in commercial refractory ceramics.

Analysis of comorbidities in workers of aluminum and refractory industries

Recent findings in occupational medicine have demonstrated that common pathology is one of the main factors determining poor health of workers in hazardous industries. Non-occupational pathology also has a significant effect on timing of occupational disease onset. Our objective was to conduct a comparative analysis of comorbidities in patients with different occupational diseases. The study was conducted retrospectively. We created a database of medical records of aluminum and refractory workers and analyzed all diagnoses and systemic disorders identified during the clinical examination of these patients using SPSS Statistics 23. The comorbidity index was used to determine the degree of somatic burden of the subjects. We assessed transnosological and transsystemic multimorbidity, as well as the relationship between multimorbidity and the diagnosed occupational disease. The hypothesis for normality of the indicators under study was tested by carrying out calculations using the Kolmogorov–Smirnov test, which allowed the use of parametric sample estimates, Student's t-test and one-way analysis of variance for data analysis. We established comorbidities that were significantly more frequent among the patients suffering from fluorosis or silicosis. Exposure to occupational hazards in different industries affects the profile of comorbidity. We observed a pronounced polysystemic nature of lesions in aluminum production workers and the predominance of comorbid diseases of the respiratory system in refractory workers. The level of multimorbidity among the workers of the refractory industry was significantly lower than that in the aluminum production, which allows a conclusion on a more pronounced negative impact of a combination of hazards in the latter on workers’ health.

К оценке вероятности развития коморбидных нарушений разного профиля у работников алюминиевого и огнеупорного производств

Recent findings in occupational medicine have demonstrated that common pathology is one of the main factors determining poor health of workers in hazardous industries. Non-occupational pathology also has a significant effect on timing of occupational disease onset. Our objective was to conduct a comparative analysis of comorbidities in patients with different occupational diseases. The study was conducted retrospectively. We created a database of medical records of aluminum and refractory workers and analyzed all diagnoses and systemic disorders identified during the clinical examination of these patients using SPSS Statistics 23. The comorbidity index was used to determine the degree of somatic burden of the subjects. We assessed transnosological and transsystemic multimorbidity, as well as the relationship between multimorbidity and the diagnosed occupational disease. The hypothesis for normality of the indicators under study was tested by carrying out calculations using the Kolmogorov–Smirnov test, which allowed the use of parametric sample estimates, Student's t-test and one-way analysis of variance for data analysis. We established comorbidities that were significantly more frequent among the patients suffering from fluorosis or silicosis. Exposure to occupational hazards in different industries affects the profile of comorbidity. We observed a pronounced polysystemic nature of lesions in aluminum production workers and the predominance of comorbid diseases of the respiratory system in refractory workers. The level of multimorbidity among the workers of the refractory industry was significantly lower than that in the aluminum production, which allows a conclusion on a more pronounced negative impact of a combination of hazards in the latter on workers’ health.

Analysis of the Current Situation and Problems of Technical Personnel in Material Production Enterprises

With the rapid development of high- temperature industry, our country has become the largest country in the world in the production, consumption and export of refractory products. However, the technical quality of front-line employees in refractory enterprises is generally low. Especially with the continuous upgrading of refractory production equipment, process and quality control, the problem of lack of technical and skilled personnel is becoming more and more serious. From the perspective of human resources, and in-depth investigation on the development of refractory industry and its personnel status, the current situation and problems of refractory enterprise technical personnel are analyzed. It is found that leading large enterprises are still in short supply of high-tech application-oriented technical personnel and operational personnel even though the structure of senior technical personnel is relatively reasonable, and small and medium-sized Enterprises gradually enter into a vicious circle of low wages, low technology, low labor productivity because they only focus on production, not research. In addition, vocational students working in different refractory enterprises often face a dilemma, some feeling lack of relatively complete theoretical knowledge, some wanting to improve the ability to operate and deal with faults.

Vocational Core Competence in Higher Vocational Education

From the perspective of talent training objectives, material engineering technology major cultivates highly skilled talents with comprehensive production process knowledge and management knowledge of material engineering technology and strong practical ability, who are oriented to the first line needs of production, construction, management and service. Refractory industry at present, the whole foundation is relatively weak, refractory resource utilization level is low, the quality of the refractory grade is not high, excess production capacity, the ordinary products some high quality high technology content of key products can production, but the quality is not stable, service life and refractory consumption compared with foreign advanced level, there is a considerable gap. the fundamental reason is the lack of high-level talents. To better meet the iron and steel, machinery, chemical industry, power and other industries to the needs of the refractory material, must be to the professional production and technical management personnel's quality and ability are put forward new requirement, not only can be competent the job requirements of the current position, and should have the ability of learning new technology, to adapt to the new job, it is particularly important in today's high-tech.

Dolomite industrial by-products as active material for CO2 adsorption and catalyst for the acetone condensation

The feasibility of using dolomite powders, by-product from the refractory industry, as a CO2 adsorbent and as a catalyst for the acetone liquid-phase self-condensation is demonstrated in this article. The performance of this material can be largely improved by combining physical pretreatments (hydrothermal ageing, sonication) and thermal activation at different temperatures (500–800 °C). The highest CO2 adsorption capacity was observed for the sample after sonication and activated at 500 °C (46 mg·g−1). As to the acetone condensation, the best results were obtained also with the sonicated dolomites, mainly after activation at 800 °C (17.4% of conversion after 5 h at 120 °C). The kinetic model reveals that this material optimizes the equilibrium between catalytic activity (proportional to the total basicity) and deactivation by water (specific adsorption process). These results demonstrate that the valorisation of dolomite fines is feasible, proposing attractive pretreatments for obtaining activated materials with promising results as adsorbents and basic catalysts.

A refractory engineering program for the 21 st century

The Federation for International Refractory Research and Education (FIRE) has been conceptualized twenty years ago. At the time, its purpose was to maintain the training of graduated engineers to enroll and to adapt to the new business plans in the refractory industry. It was the blooming of the Information Age, of the knowledge workers.This paper is about the need to adjust to a new era, knowing that the benefit of education prime value is its long-term value. To have an outer and an inner vision about innovation, the first part of the paper is concerned about how do we learn and how our brain rules. In the second part we try to anticipate the customers’ needs trying to surf with them on the Ecology wave, including the Environment, Energy, Economy, and Ethics other waves.Accepting that this is already brewing at an accelerated rate, the conclusion is that FIRE and the other educators need to continue mimicking the CDIO (Conceive Design Implement Operate) approach which has inspired us for the last 20 years, for another 20 years, to adjust to the Conceptual Age in order to educate the creators and the empathizers who will direct the flow, in the refractory industry.

Formation of mullite in fused cast AZS refractories

Fused cast refractories, based on the system Al2O3-ZrO2-SiO2 (AZS), are used in industrial glass tanks and are in direct contact with the glass melt and/or the furnace atmosphere (combustion gases, evaporation products, and dusts) at temperatures up to 1600 °C. Three samples of AZS materials were studied, (i) the original AZS refractory as delivered from the refractory industry, (ii) AZS refractory thermally treated similar to furnace heat up over days and ending for 10 h at 1580 °C and (iii) AZS refractory thermally cycled 600 times between 1530 and 1580 °C after furnace heat up simulation.The samples were studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) including Energy Dispersive X-ray analysis (EDX) and Electron Backscatter Diffraction (EBSD). In the untreated AZS, monoclinic ZrO2 (m-ZrO2) and Al2O3 were detected, while in AZS thermally treated at 1580 °C, mullite also occurred. Thermal cycling led to further increase in the mullite concentration and to a small concentration of tetragonal ZrO2 (t-ZrO2). The Al2O3 crystals as well as some of the ZrO2 had a blocky morphology. Surprisingly also formed mullite crystals were block and not needle-like. In the mullite as well as in the Al2O3 crystals tiny m-ZrO2 crystals were embedded which were formed during cooling in the production process from t-ZrO2 and were heavily twinned.

China's refractory industry. Reforms, problems and prospects

The stages of development of the refractory industry in China are considered. Currently, China is a world leader in the production of refractories. As a result of the reforms carried out in the country, the domestic market was completely saturated with refractories and penetration into the market of Europe and other countries began. In recent years, there has been a tendency to deepen partnership relations with Russia.

The problem of import substitution in metallurgy and refractory industry

The problem of import substitution in metallurgy and refractory industry is considered. The state does not classify metallurgy as an industry that is heavily dependent on imports. Despite this, enterprises have problems in acquiring spare parts for operating equipment. In the refractory industry, due to Western sanctions, problems arose in obtaining raw materials for modern refractories for critical purposes. This problem can be solved by using parallel imports from China and friendly countries. Ref. 8.

Collection and preparation of raw materials for the refractory industry

The characteristic of sand, which is the raw material of silicate and clay bricks, glass and mineral fibers, is given. Sand is a part of ceramic products used for the production of refractory products. A number of vehicles for collecting dust-forming materials are proposed. A trowel unit has been developed for collecting sand in a quarry. A fluidized bed drying unit for drying wet sand with a detailed description of its operation is proposed. Ill. 2. Ref. 11.

Characterization of Nigerian Zircon Sand and Its Suitability for Different Industrial Applications

This paper describes the potential industrial use of zircon from Nigeria (Plateau, Nasarawa, Kano, Kaduna, Bauchi, and Adamawa states). Different techniques, equipment, and indices such as scanning electron microscope, energy dispersive X-ray fluorescence, X-ray diffraction, Fourier transform infrared spectroscopy, specific gravity, refractive index, pH, and hardness were used to examine the samples. The X-ray diffraction showed predominantly quartz, zirconium oxide, and other heavy minerals. All twelve samples showed the presence of Zr-O, SiO42−, Zr-OH, and OH, with pH values ranging from 7.3 to 7.8. Six of the zircon samples had a refractive index between 1.4 and 12.5. The hardness values ranged from 0.0021 to 0.0703 GPa, while the elastic moduli were between 0.00558 and 0.9593 GPa. Four of the twelve untreated zircon samples with specific gravities above 4.2 g/cm3, which is the United States Geological Survey minimum recommended standard for zircon sand, needed to be upgraded to increase the ZrO2 weight percentages and purity toward improving their suitability for zircon-reinforced composites applications in aerospace and also for ceramic, foundry, building and construction, and refractory industries. The study’s findings can be incorporated by the industries into their businesses for the development of novel industrial materials as well as the processing methods and procedures for beneficiation of the mineral for value-addition.

A New Look at Silicon Carbide

Silicon Carbide, SiC is one of the most widely used materials that plays a critical role in industries such as: aerospace, electronics, industrial furnaces and wear-resistant mechanical parts among others. Although SiC is widely used in electronics and other high technology applications, the metallurgical, abrasive, and refractory industries are dominate by volume. It is only in the last five or six years that SiC has gained a new and important role in the semiconductor industry. SiC has become a key material in the drive towards electrification. It’s unique physical properties, wide band gap, especially, high temperature performance and “ease of manufacturability makes it a key material going forward. The physical properties that make SiC so unique also represent some serious problems to large scale manufacturing of SiC diodes, transistors and modules. SiC is a very tough material, it has a Mohs hardness rating of 9.5 approaching that of diamond. Just as the semiconductor industry needed high quality defect free silicon wafers to move forward, so did the SiC industry. High quality defect free wafers have just come into the market. They are 4 and six wafers that will allow SiC. These boules can be “sliced” in wafers and run on a standard CMOS fabrication process. Next comes the dicing of the wafers into devices. A diamond saw has to be run at a very slow rate to a material almost as hard as the diamond itself. Die attach brings an interesting problem the devices are generally rate at 200+ deg C and voltages >1000W. Standard epoxy and even Au/Si eutectic die attach has issues has issues at these extreme operating conditions. Lastly, the epoxy molding compound has to be capable of withstanding the harsh conditions and not breakdown. These are all challenges that are being met today. This is a continuing story of how the semiconductor industry adapts to ever changing requirements

Finite element modelling and analysis of brass coated steel fibre reinforced concrete beams

The study's objective was to use brass-coated micro steel fibre to improve the strength and flexibility of beams. Steel fibres with a brass coating are resistant to corrosion and improve the fracture resistance and tensile strength of the concrete, making them appropriate for use in the building and construction industry, refractory industry, rocket launch pads, airport runways and highway pavements etc. In this work analytical research on the flexural behaviour of RC beams with brass-coated steel fibre reinforcements is presented. The beams were modelled and analysed using the Abaqus FEA software. Five beams total with various fibre volume percentages (Vf = 0, 0.5, 1, 1.5, 2) were examined for this purpose. The beam cross sections were 1000 mm in length, 100 mm broad, and 150 mm deep. The analytical results show that addition of 2.0% volume of fibres exhibited better performance. When compared to the reference beam, the increase in maximum load and deflection was found to be 36.3% and 61.84%, respectively. The load–deflection and fracture patterns of different beams were compared with the experimental and analytical responses. Amongst the two approaches, it demonstrates good agreement across the whole range of loading. Thus, the deflections obtained from both the methods are ‘very close to each other’ and within ‘generally acceptable limits (say10%)’. Modeling and evaluating the structural parts can be done much more quickly and affordably using the Finite Element Analysis (FEA).

Collection and Preparation of Raw Materials for the Refractory Industry

Collection and Preparation of Raw Materials for the Refractory Industry

Refractory materials for construction based on quartzite

Information about the presence and characteristics of existing deposits of high silica and refractory clay raw materials of the Republic of Uzbekistan is given. It is shown that the main raw materials for the production of silica refractories are veined quartz, quartzites, quartz sands containing not less than 92 wt.% 8i02, and also for packing masses kaolin clays are used, which are promising raw materials. It is established that the studied quartzite rocks are of great interest and are a promising raw material base for the refractory industry of the Republic of Uzbekistan.