Refractory Clay Research Articles

Influence of variable valence metal oxides on physico-chemical and antibacterial properties of semi-coated glazes

The paper presents the results of studies on the production of semi-coated glazes with antibacterial activity by introducing variable valence oxides CeO2, WO3, Bi2O3, Fe2O3, MnO2 and MoO3 into their composition. The raw polycomponent compositions were comprised of aluminosilicate multi-calcium glass frit, dolomite powder, feldspar, alumina, quartz sand, wet-enriched kaolin and refractory clay. The coatings were obtained by single firing on a ceramic-based porcelain stoneware at a temperature of 1 200 ± 5 °C in a high-speed mode for 60 ± 2 minutes. The study focused on the processes of glaze formation of coatings and the influence of the components of glaze charges on decorative and aesthetic characteristics of coatings (color, texture, gloss and whiteness). Parameters of physical and chemical properties were determined in accordance with the existing specification for the products, i. e. temperature coefficient of linear expansion, heat resistance, chemical resistance, microhardness, frost resistance, wear resistance, etc. Antibacterial activity of the coatings towards Escherichia coli ATCC 8739 and Staphylococcus aureus ATCC 6538 test strains was studied.

Injection 3D Printing of Doubly Curved Ceramic Shells in Non-Synthetic Particle Suspensions.

This paper examines the application of non-synthetic particle suspensions as a support medium for the additive manufacturing of complex doubly curved ceramic shells with overhangs between 0° and 90° using clay paste. In this method, the build-up material is injected within a constant volume of air-permeable particle suspension. As the used clay paste does not solidify right after injection, the suspension operates like a support medium and enables various print path strategies. Different non-synthetic suspension mixtures, including solid and flexible components such as quartz sand, refractory clay, various types of wood shavings, and cotton flocks, were evaluated for their ability to securely hold the injected material while allowing drying of the water-based clay body and its shrinkage. The balance between grain composition, added water, and the compressibility of the mixture during printing and drying played a pivotal role in the particle suspension design and assessment. Furthermore, the moisture absorption of the particle suspension and the structural integrity of the layer bond of the fired ceramics were also assessed. The examined additive manufacturing process not only enables the production of meso-scale doubly curved ceramic shells with average overhang of 56° but also introduces a new practice for designing specialized surfaces and constructions.

Red mud in high-strength ceramics production

The work is devoted to the creation of high-strength ceramic materials with technogenic waste fillers.Purpose: Investigation of the ceramic and composite production based on chemical and metallurgical wastes to create new types of high quality constructional ceramics.Methodology/approach: The use of refractory clay with the addition of high-iron bauxite sludge as the main raw material. Bauxite sludge functions in compositions with aluminosilicate raw materials at burning at 1100 to 1200 °С, reduce to sintering due to its melting at 1150 °С.Research findings: Refractory clay compositions with red mud in the amount of 20 to 50 % at the burning temperature of 1050 °С, provide the ceramic formation possessing the compressive strength 1.3 to 1.5 times higher than that of clay samples without additives, i.e., 91 and 122–132 MPa, respectively.Value: The obtained ceramic compositions based on red mud determine a production of high-strength anorthite and anorthite-helenite ceramics using dry pressing.

Getting a Face Brick of Light Shades Based on Marl

The article reflects the topic of the shortage of raw materials for the production of face bricks of light colors. This problem has particularly affected producers in the European part of Russia due to the cessation of clay supplies from the territory of Donbass. Therefore, one of the relevant directions is the search for alternative sources of raw materials. The accumulated experience and laboratory tests have shown the possibility of producing light bricks using marl. As components of the ceramic mass, clays from the Vladimirovsky deposit in the Rostov region of the East Kazakhstan region, charge and marl KO-2 were also accepted from deposits in the Rostov region. By changing the percentage of marl and refractory clay and the firing temperature, it is possible to adjust the color of the fired products, as well as water absorption, average density, strength of products and their shrinkage. Industrial tests conducted on the basis of two brick factories in Rostov-on-Don and the region showed positive results. The use of marl ranged from 40 to 70% of the total weight. Clay from the East Kazakhstan region Vladimirovskoye deposit in the amount of 30 to 60%, respectively, acted as a plastic component. The brick turned out to be light beige to light yellow in color. One of the factories launched the “Svetly” brick into mass production. The material fully meets the requirements of GOST 530–2012. Thus, the problem of the shortage of light clays can be solved by using alternative raw materials – marl. The introduction of 50 to 70% of the mass into the composition is particularly effective. Preliminary calculations show the profitability of the technology by saving raw materials up to 20–25%, while increasing the aesthetic characteristics of the front brick.

Use of technogenic raw materials in ceramic technology

Studies have shown that burnt rocks and ash-and-slag materials, as corrective additives, improve the properties of poor-quality clay raw materials. The possibility of using this technogenic raw material in ceramics technology for the manufacture of ceramic products for various purposes is shown. The use of burnt rocks and ash-and-slag materials improves the sintering of the shards, intensifies the crystallization of mullite-like compounds, which has a positive effect on the physical and mechanical properties of ceramic products: strength and frost resistance increase, shrinkage deformations and water absorption decrease. The use of burnt rocks and ash-and-slag materials makes it possible to obtain refractory products on loam instead of refractory clays. The results of laboratory studies are confirmed by tests of pilot batches of ceramic bricks and tiles, thin-walled ceramic products (roof tiles and artistic ceramics).

Evaluation of Ceramic Properties of Bauxitic Materials from SE of Iberian Range

The use of aluminum-rich clays and bauxites as refractory materials is common. Upon firing, these materials form mullite crystals in the shape of needles embedded in a siliceous and vitreous matrix, with mullite being responsible for the refractory properties. In this study, bauxite samples for use in refractory applications have been characterized. Chemical analysis revealed that the alumina content varied between 34 and 40%, with silica values generally being high (around 40%), except for one sample (26%). Two samples were found to be the most suitable for use as “refractory clay” refractories. However, high silica or Fe oxide contents can affect mineralogical transformations at high temperatures. Mineralogical analysis confirmed the presence of several minerals in the bauxite materials, including kaolinite, halloysite, anatase, rutile, gibbsite and boehmite. Differential thermal analysis (DTA) showed the decomposition of gibbsite and its partial transformation to boehmite and alumina, and the dehydroxylation of kaolinite, with primary mullite crystallization observed at a high temperature. These findings provide valuable information for the selection and optimization of bauxite materials for refractory applications, considering their chemical composition and mineralogical characteristics.

ВИСОКОПЕРСПЕКТИВНІ ОБ'ЄКТИ МІНЕРАЛЬНО-СИРОВИННОЇ БАЗИ УКРАЇНИ. ЧАСТИНА 2. НЕМЕТАЛІЧНІ КОРИСНІ КОПАЛИНИ

A brief description of highly prospective objects of the mineral-raw material base of non-metallic minerals of Ukraine is given. Based on an expert assessment of their investment attractiveness, the following types of raw materials were selected as the most prospective: kaolin (Zhezhelivske, Glukhovetske, Turbivske, Velikogadomynetske deposits); facing stones (Slipchytske and Golovinske deposits of labradorite; Omelyanivske, Tokivske, Kapustianske, Lyznitske and Kornynske deposits of granite); refractory clays (Chasiv-Yarske, Novoraiske, Volodymyrivske, Pologivske); graphite (Zavallivske, Burtynske (Khmelivska section) deposits); granate (Slobidske, Ivanivske); quartz raw materials (Husarivske, Velikohlibovitske); piezoquartz (Volynske); phosphorites (Zhvanske); limestones for the sugar industry (Zamok, Lysohirka); bentonite (Cherkaske deposit). Among the non-metallic minerals of Ukraine, these deposits have the highest level of investment attractiveness, the lowest investment risks, and can be recommended as priority objects for investment in their study and industrial development. To determine the investment prospects of concrete objects, a preliminary geological and economic assessment of the feasibility and profitability of their industrial development is necessary.

Plasma Coatings Based on Self-Fluxing NiCrBSi Alloy with Improved Wear Resistance Properties

The structure and properties of plasma coatings sprayed with a composite material based on a self-fluxing NiCrBSi alloy (PG-10N-01 alloy) modified with a composite material obtained by self-propagating high-temperature synthesis were studied. Titanium powders, carbon black, aluminum, iron oxide, PT-NA-01 thermosetting powder and PGOSA-0 refractory clay were used as the initial components of modified with a composite material. Mixing and mechanical activation of the initial powders was carried out in a BM-1 ball mill for 15 minutes at 130 rpm in a ratio of 1 to 40 of the mass of the charge to the mass of the falling bodies (steel balls with a diameter of 6 mm). Initiation of the self-propagating high-temperature synthesis was carried out using a special device by introducing a heated nichrome spiral. The process of coatings spraying was performed on the MPN-004 microplasma spraying unit at a current of 45 A, a voltage of 30 V with a distance of 100 mm on samples made of 65G steel with a thickness of 3 mm. Argon was used as a plasma-forming and shielding gas. In order to substantiate the feasibility of the self-propagating high-temperature synthesis, a part of the samples was sprayed with a self-fluxing alloy PG-10N-01 with the addition of a mechanical mixture of starting powders. It was established that as a result of plasma spraying of the PG-10N-01 alloy and the composite material of the modified with a composite material + PG-10N-01 composition, coatings with a dense and multiphase structure are formed. The microstructure of the PG-10N-01 alloy coating consists of a solid solution based on nickel (γ-Ni) with inclusions of nickel borides Ni3B and chromium carbides Cr3C2. When adding modified with a composite material in a nickel-based solid solution, in addition to the phases indicated above, borides of titanium TiB2, carbides of titanium TiC and silicon SiC were detected. Their presence leads to an increase in the microhardness of such coatings and their greater wear resistance under conditions of abrasive wear in comparison with the spraying coating of the PG-10H-01 alloy.

Archaeological science, globalisation, and local agency: gold in Great Zimbabwe

Great Zimbabwe (CE1000–1600) is world famous for outstanding cultural innovations and localised and globalised entanglement with trans-Africa and trans-Indian Ocean exchange. New excavations yielded fragments of over a hundred gold processing vessels comprising reused pottery and purpose-made crucibles from stratified contexts in the Eastern Ridge Ruins and adjacent areas. Selected samples were studied using archaeological, microscopic, and compositional (SEM–EDS) techniques. All ceramics were made of alumina-rich clays and contain minerals common to granite-derived lithologies typical of the area, although it is possible that particularly refractory clays were selected to make crucibles locally. These technical ceramics were used for refining and collecting gold at high temperature, most likely producing not only relatively standardised ingots but also finished objects. The composition of the gold prills set in crucible slag is consistent with that of natural, unalloyed gold, while the variability in silver levels and minor impurities point to heterogeneous sources of the gold. Considering these finds in their multiple site and regional contexts, and together with complementary threads of information from early reports of antiquarians and looters, we argue that local agency and gold consumption were much more significant than generally assumed. The conclusion to the paper is that Great Zimbabwe’s famous participation in local and global exchanges was backed by internally driven but improvisation laden production and consumption occurring in homesteads located throughout its various settlements. We end by raising a word of caution about oversimplified narratives of globalisation and their archaeological expressions (see Supplementary Material S0 for the abstract in Shona).

Designing engobe coatings for ceramic bricks

This paper reports research into the development of compositions of engobe coatings for ceramic bricks and investigating the influence of technological production factors on their physical and mechanical properties. The results of this work make it possible to solve the task of expanding the range and improving the operational properties of building ceramics. The data obtained have made it possible to establish physicochemical processes occurring during the formation of the phase composition and structure of engobe coatings. This has revealed the possibilities for designing engobe for various types of ceramic bricks, which differ in technological parameters of production and operational properties. The charge compositions were designed in a three-component system "refractory clay – quartz sand – cullet", taking into account the possibility of their practical implementation in large-tonnage production. It has been established that the most important condition for obtaining high-quality products is the correlation of shrinkage and temperature coefficients of linear expansion of the ceramic shard and engobe coating. To prevent various defects, these indicators should vary by no more than 10 %. The crystal-phase composition of engobe is represented by b-quartz and a small amount of devitrite, which are evenly distributed in a vitreous dense layer of coating on the surface of the ceramic shard. Distinctive features of the results relate to the fact that a solution to the problem of designing engobe coatings for ceramic bricks has been proposed and the physicochemical bases of production have been highlighted. This paper also suggests ways to achieve coordination of finely dispersed coatings with coarse-grained ceramic masses by shrinkage and thermal processes. The results reported here could be applied in typical production of face, clinker, and in some cases – ordinary brick or ceramic stone with firing temperatures of 950–1150 °C

ASSESSMENT OF THE REFRACTORY AND PLASTIC PROPERTIES OF CLAY MINERAL DEPOSITS IN UHONMORA, OWAN WEST LOCAL GOVERNMENT AREA IN EDO STATE , NIGERIA

In order to assess the plastic and thermal behaviour of the clay mineral deposits at Uhonmora, Edo State, Nigeria, the chemical, mineralogical and physical properties were evaluated. The results of the study showed that the deposits consisted of phyllosilicate minerals such as kaolinite, illite and clinochlore; other mineral present were quartz, sanidine high, geonalite, diaspore and and lepidocrocite. The clay minerals exhibited moderate swelling characteristics and medium plasticity; the linear shrinkage and apparent porosity were within the accepted values for refractory clays. It is reddish-brown colour on account of the presence of coloured iron mineral lepidocrocite. The clay minerals also exhibited good thermal shock resistance and refractoriness above 1200oC. The properties of the clay mineral deposits were reflection of the combined effects of the properties of the clay minerals and other non-clay mineral constituents. The study revealed that the clay mineral deposits studied had good refractory characteristics and can be used at operating temperature conditions above 1200oC.

Sintering Characteristics and Thermal Properties of Porous Ceramic Based on Hydrophlogopite and Refractory Clays

Sintering Characteristics and Thermal Properties of Porous Ceramic Based on Hydrophlogopite and Refractory Clays

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.

Late Cretaceous–Paleogene terrestrial sequence in the northern Kitakami Mountains, Northeast Japan: Depositional ages, clay mineral contents, and vitrinite reflectance

AbstractForearc basin deposits on continental margins contain important information that can be used to reconstruct the tectonic setting, volcanism, and climate at the time of their deposition. Coal‐bearing terrestrial to shallow marine strata in Northeast Japan were deposited in a forearc basin along the Eurasian continental margin during the Cretaceous–Paleogene. The rocks exposed in the Kado district, Iwate Prefecture, in the northern Kitakami Mountains include the Upper Cretaceous Yokomichi Formation and the Paleogene Kogawa Group; the latter is known for high‐quality refractory clay (kaolin clay). However, their stratigraphy and sedimentological characteristics are not yet fully understood. To reconstruct the formation and filling of the basin, we investigated field observations, U–Pb dating of tuff samples, XRD analysis of tuff and mudstone samples, and vitrinite reflectance of coal samples in this sequence. The U–Pb ages of the Yokomichi Formation and the Kogawa Group are ∼86 Ma and 58–52 Ma, respectively. The U–Pb age of the kaolin‐dominated tuffaceous rock (“red rocks”) is 56.1 ± 0.2 Ma. The mean random vitrinite reflectance (VRr) ranges from 0.37% to 0.53% through the sequence. We propose the following sequence for the formation and filling of the basin. (1) The basin initially formed during the Coniacian–Santonian (Late Cretaceous) and was filled by fluvial–lacustrine sediment. (2) These sediments kept the shallow burial depths during a ∼28 Myr and made a hiatus (86–58 Ma). (3) The basin was reactivated and covered by tuffs during the Thanetian, and the tuffs were altered to kaolin clay during the Paleocene–Eocene Thermal Maximum. (4) The basin was filled rapidly by alluvial fan deposits and subsided <2300 m (assuming a geothermal gradient of >30 K/km). (5) The basin was uplifted and exhumed at a rate of >50 m/Myr faster than the mean exhumation rate of the Kitakami Mountains since the Paleogene.

ЖАРОСТОЙКИЙ ФОСФАТНЫЙ ГАЗОБЕТОН НА СВЯЗУЮЩЕМ ИЗ ТЕХНОГЕННОГО АЛЮМОСИЛИКАТНОГО СЫРЬЯ

A modified aluminophosphate binder has been technogenically developed using aluminosilicate. Waste – a by-product of production firing of refractory clays from the Nizhne-Uvelskoye deposit – was used for obtaining the raw materials for the binder. Нeat-resistant phosphate aerated concrete was developed based on the modified aluminophosphate binder. Its density was 600–800 kg/m3 and the temperature of application about 1400–1450 °C. The main heat-resistant properties of aerated concrete were investigated and aerated concrete using a modified aluminophosphate binder is not inferior to cellular materials based on known aluminophosphate binders.

A Chemical Study of Archaeometallurgical Ceramics from Southwestern Tanzania

Archaeometallurgical ceramics, including furnaces, tuyères, and potteries, were required for successful pre-industrial iron smelting and refining. However, there are limited chemical studies on archaeometallurgical ceramics in Tanzania. This paper examined the nature of clay source in terms of refractoriness, determined whether there were multiple clay sources, and verified the refractoriness of the archaeometallurgical ceramics. An x-ray fluorescence (XRF) analytical technique and experimental re-firing of the archaeometallurgical ceramics were employed. The chemical data clustered in the mullite region on the Al2O3-SiO2-FeO ternary system indicate that iron smelters and refiners chose refractory clay sources for making archaeometallurgical ceramics. Small range and standard deviation suggest that the furnaces and tuyères were made from similar refractory clay source, while the relatively slight difference in range and standard deviation of the potteries indicate that they were made from another different clay source. The archaeometallurgical ceramics re-fired in the furnace lab did not bloat at 1300 oC, it verifies that they were indeed refractory.

Raw kaolinitic–illitic clays as high-mechanical-performance hydraulically pressed refractories

The usage possibility of 19 composites of raw refractory clays from Serbia containing approximately 53.29% of SiO2 and 26.73% of Al2O3 is presented. The sum of fluxing oxides was 57.74%, while these materials contained 32% of quartz, 29% of kaolinite and 26% of illite–mica. Dilatometry tests revealed a sudden shrinkage with the peak at approximately 1115 °C, owing to the formation of mullite. The refractoriness was in the range of 1581–1718 °C, which classifies the composites from low- to high-duty refractories. Based on correlation analysis, the refractoriness mostly depended on the content of alumina. The lightness of the fired test pieces was lower after firing when compared to the dry samples, and it decreased with the firing temperature from reddish to grayish. The study presents a novel attempt to define all the necessary properties of raw refractory clays and products fired at the 1100–1300 °C range on a laboratory level. Most of these clays can be used as natural refractory materials for ceramic and glass furnace lining. The organic matter in some of the samples influences negatively the fast-firing process.Graphical Abstract

Study of refractory raw materials of the Republic of Kazakhstan

Important aspects of increasing the competitiveness of domestic metallurgy and mechanical engineering are increasing the durability of thermal units and involving non-traditional, cheaper energy resources in production. One of these resources is carbon waste from the aluminum industry - electrode scrap and waste from the carbon lining of electrolyzers. The problem of their use as substitutes for solid fuels (coke coal) in the metallurgical, engineering and energy industries is fluorine- and alkali-containing salts that impregnate them, destroying the traditional lining of thermal units. The development of effective refractories resistant to fluorine- and alkali-containing corrodants (melts and gases) makes it possible to increase the competitiveness and efficiency of thermal units both through the use of cheaper energy carriers and by increasing the duration of their campaign. An important aspect is the simultaneous disposal of hazardous industrial waste and the reduction of the environmental burden on the ecosphere of the Republic of Kazakhstan. The basis for the development of new refractory materials resistant to fluorine- and alkali-containing corrodants is the analysis of the existing raw material base of the Republic of Kazakhstan and the choice of materials that make it possible to obtain aluminosilicate refractories with increased chemical resistance. In the work, the phase and chemical composition of refractory clays and kaolins of the Republic of Kazakhstan were studied, their rheological and thermophysical properties were investigated. Selected raw materials for the development of technology for the production of dense aluminosilicate refractory products.

Analysis of clay types and their binary systems

The objects of study were the Mali Budyshcha and Opishnia clays of two deposits in the Poltava region (Ukraine), binary systems of these clays, and ceramics based on them. It is noted that the efficiency of the practical use of these clays can be increased taking into account the peculiarities of their mineralogical composition. The features of the qualitative mineralogical composition of clays were studied by the methods of chemical, X-ray phase and thermal analysis. The amount of rock-forming minerals was determined using the new computer program «Mineral». It has been established that with an increased content of quartz in both samples, the Mali Budyshcha clay is characterized by a combination of clayey rock-forming minerals – 18.8 % montmorillonite, 12.1 % kaolinite, 17.9 % feldspar and 7 % calcite. According to the intensity of characteristic diffraction peaks and the plane of the endothermic effect with a maximum at 550–575 °C, Opishnia clay is marked by a significantly higher content of kaolinite – 48.1 %. Large values of the quantitative ratio of oxides SiO2:Al2O3 and the content of alkaline earth and alkaline oxides of the RO+R2O type determine the ratio of Mali Budyshcha clay to the group of low-melting clays with a fire resistance of 1230 °C, in contrast to refractory clay (1620 °C). It has been established that in the range of maximum firing temperatures of 950–1100 °C, samples of Mali Budyshcha clay differ from Opishnia clay in changes in average density from 1.90 to 2.28 g/cm3 versus 2.00–2.09 g/cm3, a decrease in water absorption from 15.3 to 5.0 wt % versus 12.0–9.1 wt %. It is shown that the use of binary systems of the studied clays has a significant effect on the chemical and mineralogical composition, the degree of sintering, and the physical and mechanical properties of ceramics. When varying the quantitative ratio of clays from 4:1 to 1:1, the content of kaolinite changes the most – from 19.3 to 30.1 %. An increase in the content of kaolinite in binary systems leads to a gradual expansion of the possible temperature range of firing. At the same time, in comparison with Mali Budyshcha clay, Opishnia clay achieves a decrease in water absorption, an increase in density and strength.

Microbial features of mature and abandoned soils in refractory clay deposits

Processes of soil restoration in anthropogenically disturbed soils is an urgent topic in modern ecology and nature management. Being mediator between mineral soil composition and plant vegetation, soil microbial community is important factor of soil restoration processes. Analysis of main soil nutrition components followed by 16S amplicon sequencing are sufficient methods for primary analysis of novel locations. Here is the primary analysis in a novel location in Northwest Europe (Russia). Main nutrition parameters (pH, P, Na and NH4+) and 16S rDNA Illumina amplicons were explored in abandoned soils from sandy pit quarry (2 sites) and refractory clay mining dumps (4 sites).Microbial communities of mature soils and dumps are variable and different in terms both nutritional and microbial components. pH, N and TOC are strong predictors for microbial composition. Dumps of refractory clays pQ_2 are non-developed soils, highly acidic and form specific microbial community. Differences between dumps and mature soils in both pre-quaternary and quaternary soils are connected with specific bacterial taxa. Those taxa are connected more with plant composition, not the soil properties themselves. The exact changes in microbial community are unique for different soils and areas.Graphical