Refractory Clay Research Articles

Development of fireclay aluminosilicate refractory from lithomargic clay deposits

Lithomargic clay until now has not been utilised to produce refractory bodies due to its low plasticity. In this work, the development and evaluation of fireclay refractory material produced from lithomargic clay deposit has been studied by addition of clay binder. Three formulations were prepared by mixing, semi-dry moulding, drying and firing at temperatures ranging from 1200 to 1400°C. The fired samples were investigated to determine their physical properties such as bulk density, apparent porosity, linear firing shrinkage, and cold crushing strength. The chemical and mineralogical compositions were also determined. The results show that the linear firing shrinkage values were within limits acceptable for refractory clays. The cold crushing strength increases as temperature increased to 1400°C. Cold crushing strength increased with increasing binder content. The increase of the highly refractory phases (cristobalite and mullite) and the densification of the bricks due to the presence of fluxing agents were responsible for the high cold crushing strength values. The investigated properties indicate that lithomargic clay underlying bauxite deposits could be used to produce fire clay aluminosilicate refractories.

Mechanism of solid-phase transformations accompanying firing of light-tone ceramic brick: thermodynamic substantiation

The results of thermodynamic modeling of the solid-phase processes accompanying the firing of light-tone volume-colored ceramic brick based on refractory clay and an artificial fluxing agent are presented. X-ray diffraction studies of ceramic samples confirm the results of the thermodynamic calculations. Consistent patterns in phase formation occurring in ceramic brick prepared with an artificial fluxing agent are presented.

Production of interior facing tiles using local raw materials

Mix compositions for interior facing tile have been developed using local raw materials: low-melting polymineral clay from the Gaidukovka deposit, dolomite from the Ruba deposit, granitoid dust from the Mikashevich deposit and sand from the quartz Gomel’ Mining-Enrichment Works as well as DNPK refractory clay and KS-1 kaolin, both imported from Ukraine. The ceramic tiles have high physical-chemical properties.

Caracterização tecnológica da argila plástica de Pântano Grande, RS

A região de Pântano Grande, RS, é conhecida pela qualidade de seus caulins. Nesta região, incluindo-se as cercanias das cidades de Gravataí e Viamão, encontra-se uma argila plástica de cor de queima clara, mas com característica refratária. Ressalva-se a importância desta argila, pela dificuldade de se obter argilas plásticas a distâncias convenientes para indústria cerâmica. Neste trabalho, foi realizada a caracterização tecnológica desta argila. As propriedades de queima foram avaliadas para a faixa de temperatura de 1200 ºC a 1400 ºC, incluindo-se uma mistura com uma argila refratária e queima a 1300 ºC. Após, investigou-se o comportamento de gresificação por meio de misturas com fundentes sódicos, potássicos e cálcicos, analisando-se também a resistência mecânica à flexão. Deste modo, obteve-se a completa caracterização da referida argila, destacando-se o potencial de aplicação da mesma.

Post-treated incinerator bottom ash as alternative raw material for ceramic manufacturing

Abstract New ceramics based on 60 wt% of alternative raw material derived from post-treated municipal solid waste incinerator bottom ashes and 40 wt% of refractory clay were studied. The chemical analysis of the compositions was evaluated by ICP. The thermal and densification behavior of the ceramic batches were evaluated by DTA-TG and dilatometry techniques, respectively. After that, the degree of sintering at different temperatures and soaking times was evaluated in detail, measuring open and closed porosities, linear shrinkage and water absorption. The crystallinity at different temperatures (during heating and after cooling) and microstructure of the obtained samples were evaluated by high-temperature X-ray diffraction (HTXRD) and scanning electron microscopy (SEM), respectively. For these new ceramics, the experimental results highlighted sintering range between 1190–1240 °C. In addition, the specimens demonstrated low water absorption and high crystallinity (with anorthite as main crystalline phase), leading to mechanical characteristics comparable to those of commercial ceramic products (bending strength > 40 MPa).

Experimental study of the thermo-mechanical behaviour of alumina-silicate refractory materials based on a mixture of Algerian kaolinitic clays

In the framework of a general study carried out on the thermo-mechanical behaviour of refractory products made from Algerian refractory clays, silica–alumina bricks based on a mixture of halloysite from Djebel Debbagh and kaolin from Tamazert were studied. The material's initial chemical composition and physical properties are reported. Uniaxial compression and three-point bending tests were performed under temperature conditions from room temperature to 1200 °C on representative specimens cut from the bricks. The evolution of the material's resistance in tension and compression as of its modulus of elasticity with testing temperature is reported. The thermal expansion of the material was investigated as were optical and SEM micrographs at various temperatures. The evolution of the material rheological behaviour from quasi-brittle, between room and 900 °C, to viscous at higher temperatures was shown by both bending and compression tests. The general behaviour of the material with increasing temperature was analysed through the various microstructure investigations and the presence of micro-cracking induced by the differential expansions of the multiple phases in presence.

Physicochemical methods for studying the mineral composition and pore structure for the argillaceous part zircon-ilmenite ore gravitation tailings

It is established that the argillaceous part zircon-ilmenite ore gravitation tailings (ZIG) is a refractory clay, but it has a complex mineral composition, including in contrast to traditional refractory clays more than ten minerals and an increased amount of Fe2O3 (>5%). The main clay mineral of ZIG is kaolinite, which is poorly crystallized. An increase in ZIG ceramic specimen firing temperature to 1300°C promotes pore size uniformity.

A thermogravimetric study of refractory clays chlorination

The chlorine effect on different samples of refractory clays has been studied within a wide temperature interval. The isothermal and non isothermal calcination assays were carried out in currents of N 2 and a mixture of Cl 2/N 2 (1:1), using a thermogravimetric system designed in our laboratory and masses of approximately 300 mg. Isothermal assays were also performed with masses of 2 g, using a fixed bed reactor with horizontal dynamic flow. The initial samples of refractory clays and the residues resulting from thermal treatments were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA), specific surface area analysis (BET) and CIELAB colorimetry. The thermograms in N 2 and Cl 2/N 2 showed two mass losses, between room temperature and 650 °C, due to the elimination of the mineral hydration water and the transformation of kaolinite into metakaolinite. A third mass loss was observed over 750 °C in Cl 2/N 2 due to the chlorination and elimination of the iron contained in the samples. The X-ray diffractograms of the residues from the different thermal treatments showed that the calcination produced the total transformation of kaolinite and other phases contained in the mineral. The XRF analysis of the residues resulting from the isothermal assays in Cl 2/N 2 permitted to determine that the iron contained in the samples might be completely removed by chlorination at 900 °C for 2 h. The colorimetric analysis of the chlorination residues indicated that the discoloration and bleaching of samples were caused by the deferrification of the mineral. The results of the characterizations using SEM and EPMA supported the previous observations.

Firing transformations of Chilean clays for the manufacture of ceramic tile bodies

This contribution is focused on the study of the mineralogical changes occurring in the ceramic body after heating ceramic clays. Chile has an important local ceramic industry. Five deposits of clays with industrial applications were studied. The clays came from San Vicente de Tagua-Tagua (SVTT), Litueche (L), Las Compañías-Río Elqui (LC), La Herradura-Coquimbo (LH) and Monte Patria-Coquimbo (MP). The samples were heated to 830, 975, 1080 and 1160°C keeping at the maximum temperature for 35min. The bending strength of each ceramic body was determined at 1100°C. Mineralogical analysis of the fired samples was carried out by X-ray diffraction. The SVTT contained quartz, spinel, cristobalite, microcline, albite, anorthite, hematite and enstatite; the LC clays quartz, mullite, spinel, microcline, albite, anorthite, hematite, diopside, enstatite, illite/muscovite and talc; the LH clays quartz, cristobalite, microcline, albite, anorthite, hematite, diopside, illite and augite; the MP clays quartz, cristobalite, microcline, albite, anorthite, hematite, diopside, gehlenite, enstatite and wollastonite and the L clays quartz, microcline and mullite. The persistence of illite at at least 900°C was observed for LC and LH. SVTT and LH showed the required specifications for earthenware. The L clays were refractory clays with very low bending strength.

Effect of nanodisperse particles of silicon and aluminum oxide hydrosols on structure formation of clay minerals in aqueous medium

The effect of nanodisperse particles of Al and Si oxide hydrosols on structure formation of minerals in aqueous suspensions of bentonite and refractory clays was examined. The following were determined during formation of the structure of the ceramic material: pH and structure of clay suspensions, slip fluidity, shrinkage and compressive strength of samples poured from slips made of dried and thermally activated (350°C) clays.

PAUL‐LOUIS CYFFLÉ'S (1724–1806) TERRE DE LORRAINE: A TECHNOLOGICAL STUDY

Fragments of four Terre de Lorraine biscuit figurines were subjected to porosity analysis, X‐ray fluorescence analysis, X‐ray diffraction analysis, backscattered‐electron image analysis—coupled with energy dispersive spectrometry—and electron backscatter diffraction analysis to determine the porosity, bulk, major, minor and trace element compositions, and the composition and the proportion of their constituent phases. Cyfflé's Terre de Lorraine wares embrace two distinct types of paste, a calcareous and an aluminous–siliceous one. Both are porous (9–25% water adsorption). The former consists of a mixture of different proportions of ground quartz or calcined flint, ground Pb‐bearing glass and calcium carbonate with a refractory clay. The firing temperature was between 950 and 1050°C. For the latter, Cyfflé mixed ground pure amorphous SiO2, ground quartz or calcined flint, ground porcelain, ground Na–Ca‐glass and coarse‐grained kaolinite with a fine‐grained kaolinitic clay. The figurines were fired below 1000°C. The result was a porous, hard paste porcelain‐like material. Cyfflé's recipes for both pastes can be calculated from the chemical and the modal analyses.

Production of facing tiles from low-quality clay initial materials

It is shown that ceramic facing tiles with satisfactory characteristics can be obtained from low-quality polymineral clays by semi-dry pressing. The following special methods must be used to improve the quality of the clay initial materials: process the initial material in electro-mass-classifier, mix clays with activated water, and introduce technological additives (mechanically activated quartz-glauconitic sands, refractory clay) into the initial material. Lime clays and zeolite-bearing siliceous rock can be used to expand the raw materials base for tile production.

Optimal mix for building ceramics

It is determined on the basis of experimental data and calculations that frost-resistant ceramics can be obtained from a mixture of low-melting illite-bearing clays without other, more expensive, refractory clays. Techniques for planning “property–property” experiments were used to formulate the molding mixes. For the optimal content of the molding mixes, a sintered ceramic material with frost-resistance of more than 250 cycles with omni-directional freezing and from 75 to 125 cycles with uni-directional freezing was obtained.

Ferrous Iron Oxidation by Immobilized on Refractory Clay Tiles

Refractory clay tiles are composed of kaolin, which is the commercial name of clay, and this consists mainly of kaolinite mineral. Two such tiles and caowool packed in glass columns were used for the immobilization of Acidithiobacillus ferrooxidans cells in a ferrous iron medium, which was percolated through the supports. Colonization was carried out by several media replacements with no further inoculation until maximum ferric iron productivity was reached. One of the tiles was discarded due to the high iron precipitation during bacterial growth. The columns with the other supports were used for ferrous iron oxidation in batch and continuous flow modes of operation and these appeared to be promising supports for A. ferrooxidans. A ferrous iron oxidation rate of 14.5 mmol.l-1.h-1 was reached in one of the columns in the continuous culture. After being used for several cultures, pieces of tiles with immobilized cells were stored at 4 ºC. Samples at different times were incubated in ferrous medium and these showed high cell activity even after 6 months.

Survey of Russian Federation inventions on refractories

Mullite-corundum refractory prepared from mixes, including corundum, clay, orthophosphoric acid and an additive distinguished by the fact that the addition to the mix contains a barium oxide concentrate with a barium sulphate content of not less that 85 wt.% with the following ratio of components, wt.%: barium oxide concentrate 6 – 10; refractory clay 1 – 4, corundum 79 – 88, orthophosphoric 5 – 7.

Working Properties of Some Selected Refractory Clay Deposits in South Western Nigeria

Working properties of some clay deposits in Ekiti State, Nigeria were investigated with a view to determine their suitability for use as refractory bricks. The samples were collected from three different commercial pottery clay centers in Ekiti State; they are Ara, Awo and Isan. Two varieties were collected from both Ara and Isan, which are named Ara 1, Ara 2, and Isan 1, Isan 2 respectively while only one type was collected from Awo. The clay samples were crushed, pulverized, sieved and their chemical compositions were determined. The clay samples were treated separately as well as blended together in different proportions and moulded into bricks. The bricks were dried and fired to 1050 o C. Tests for refractoriness, thermal shock resistance, shrinkage, thermal expansion; bulk density, porosity, and compressive strength were carried out on each batch specimen. The results showed that Ara 2 and Ara 1, 2 combined in equal proportions displayed the highest thermo chemical stability. They also possess comparatively high cold crushing strength, and high thermal shock resistance, but definitely not the highest. The apparent porosity of all the batch specimens was found to be high as well as the bulk densities, while the shrinkage of all the specimens were low. It was concluded that 100% Ara 2, and a blend of Ara 1 and 2 in equal proportions, are most suitable for production of crucibles, and furnace lining for non ferrous metals processing, such as Aluminium, Lead and Bronze.

Characterization and origin of late Devonian illitic clay deposits southwestern Iran

Illitic clay deposits of Esteghlal Mine that represent the largest refractory clay deposit in Iran were subjected to petrographical, mineralogical and geochemical investigations to examine their origin. Geological investigation showed that the illitic clay deposits of Esteghlal Mine intercalated with limestone beds rich in marine conodonts range in age from early to middle Famennian indicating the deposition of these illite deposits in marine environment during the early to middle Famennian. The deposits are composed mainly of illite with traces of kaolinite. Non-clay minerals are mainly very fine quartz and altered feldspars phenocrysts disseminated the very fine illite matrix. Scanning electron microscope revealed the occurrence of illite as crumbled plates with undefined outlines of sizes around 2 μm. Kaolinite occurs as flakes of deformed morphology and unclear outlines or as curved and bent flakes. These morphologies along with the abundance of detrital quartz and altered feldspars and low crystallinity of illite suggest a detrital origin of these clays. Nb/Y–Zr/TiO 2 discrimination diagram indicated that the studied illitic clay deposits were derived from trachy–andesite source. The relative enrichment of light REE over heavy REE with negative Eu anomalies supports this interpretation. Absence of smectite and illite/smectite mixed layers and detrital nature of illite and kaolinite suggest that illite was formed as a result of hydrothermal alteration of acidic to intermediate igneous rocks then transported to the depositional basin rather than its formation as a result of diagenesis of precursor clays.

Sintering of clay-chamotte ceramic composites for refractory bricks

Clay-chamotte composites were realized for manufacturing refractory bricks. We used two kaolinitic refractory clays mined in Cameroon and two calcined clays (chamottes) with a large grain size (0.1–4 mm). Clay-chamotte composites containing various quantities of chamotte (0–50 wt%) were shaped and sintered at 1200–1350 °C. The structural characteristics of composites indicated the presence of quartz from the initial clay, cristobalite and mullite. SEM observations revealed very heterogeneous microstructures where porosity is weakly distributed and large pores are entrapped at the vicinity of large chamotte and quartz grains. In general, the global porosity increases with the chamotte content. A specific interpretation of the matrix role on the global sintering behaviour reveals that only a part of the matrix acts effectively. Since the most part of the global porosity is within the matrix, it is distributed in matrix zones, which participate effectively to sintering and in inert matrix zones where larger pores occur. The global mechanical strength is controlled by the matrix behaviour, but the high porosity of this phase is unfavourable to high strength values. Besides, the occurrence of larges pores and local cracks at large grain interfaces from thermal stresses are critical flaws, which reduce the mechanical strength.

Argilas especiais: o que são, caracterização e propriedades

Special clays are a group of clays different from the large volume of clay mineral products named Industrial Clays: kaolins, ball clays, refractory clays, bentonites, fuller's earths, common clays. Two groups of special clays exist: rare, as in the case of hectorite and sepiolite and restricted areas, as in the case of white bentonite, halloysite and palygorskite (attapulgite). A review is given of the most important producers of the special clays and their properties in the Western World, as well as a discussion of the occurrence of these types of clays in Brazil.

Evaluation of aluminum dross waste as raw material for refractories

An aluminum dross waste from plasma processing for Al metal reclamation was tested as a replacement raw material in refractories. The main phases of the starting Al dross waste material were MgAl 2O 4 and AlN. The waste was tested to replace calcined alumina in castables and refractory clay in a molded refractory at levels below 6.5%. The results of physical and mechanical tests indicated that the waste may be applied directly, without prior calcination, as a substitute for fine structural components in refractories. The waste and water contents used in processing, however, must be optimized to avoid the formation of crack-like defects in the microstructure. The origin of these defects is related to the generation of gas from the waste at high temperatures. It is not known if these crack defects impact physical properties. The waste was also tested as a replacement for anti-oxidant elements (Al and Si powders) in a resin-bonded refractory. Oxidation tests, however, indicated a negative effect on oxidation resistance.