Production Of Ceramic Materials Research Articles

Technology of Composites Based on Kul’-Yurt-Tau Pyrophyllites

The basic technical characteristics of composites based on pyrophyllite and raw rocks from the Kul’-Yurt-Tau deposit and using phosphate binders are determined. While these materials have satisfactory strength their thermal expansion and thermal conductivity are low while the frost resistance and thermal stability are high. Such materials can be recommended as refractories and building materials for use at temperatures to 1250 – 1350°C depending on the composition of the initial batch. The technology for obtaining these materials is described. Parts and refractory mixes have found applications at certain enterprises. An analysis of published data and research [1 – 3] has shown that in a number of cases it is best to use pyrophyllite rock as an initial material in the production of ceramic materials for fabricating parts for different applications. In the process, the possibilities of rocks from the Kul’-Yurt-Tau (Bashkortostan) and Ovruchskoe (Ukraine) deposits were compared. The general technology for obtaining parts included the following operations: preparation of the initial material, preparing batch and batching, preparation of molding mix, parts molding, drying and heat-treatment of parts and sorting and warehousing finished products. The objective of the present work was to optimize the technology for obtaining composites based on pyrophyllite raw material and phosphate binders as well as to determine the basic technical characteristics of the materials obtained with respect to their applications in actual production. Preparation of initial materials. Portions of samples were obtained from deposits of quartz-pyrophyllite rocks from the Kul’-Yurt-Tau deposit (QPPS) without the bulk component from different sections distributed over height and areas, taking account of pieces with the required size and color. The rock delivered in the form of rubble was crushed in two stages: primary crushing to about 50 mm size in a SM-166 jaw crusher from the Vyksunskii plant followed by secondary crushing in a jaw crusher (Modis NOT, JSC, in Rybinsk); this gave 0.5 – 3.0 mm particles.

Utilização do resíduo da extração de esmeraldas em uma formulação de massa de revestimento cerâmico

Empresas envolvidas na mineração de esmeralda e beneficiamento representam uma importante área de desenvolvimento industrial no Brasil, com significativa contribuição para a produção mundial desse minério. Como resultado, grandes volumes de resíduos de esmeralda são constantemente gerados e abandonados no ambiente, contribuindo negativamente para a sua preservação. Por outro lado o interesse no uso do resíduo de mineração como aditivo na produção de material cerâmico tem crescido entre os pesquisadores nos últimos anos. A indústria cerâmica está constantemente buscando a ampliação do mercado para o setor e tentando aperfeiçoar a qualidade dos produtos e aumentar a variedade de aplicações. A tecnologia de obtenção de cerâmica de revestimento que usa resíduos de mineração é um mercado ainda pouco explorado. Neste cenário, o objetivo do presente estudo foi caracterizar o resíduo gerado a partir de mineração de esmeralda, bem como para avaliar seu potencial uso como matéria-prima fundente para a produção de revestimentos cerâmicos. Misturas cerâmicas foram preparadas a partir de matérias-primas caracterizadas por fluorescência de raios X e difração de raios X. Cinco composições foram preparadas utilizando índices de resíduos de esmeraldas de 0%, 10%, 20%, 30% e 40%. As amostras foram preparadas por prensagem, sinterizadas em 1000, 1100 e 1200 ºC e caracterizadas visando estabelecer sua composição mineralógica, absorção de água, retração linear e módulo de ruptura à flexão. Os resultados mostraram que o resíduo de esmeraldas estudado pode ser incorporado na massa de revestimento cerâmico até 20% em substituição ao feldspato sem comprometimento das propriedades do produto final.

Wet-chemistry processing of powdery raw material for high-tech ceramics

The purpose of this study was to develop wet-chemistry approaches for the synthesis of ultradispersed and mesoporous metal oxide powders and powdery composites intended for usage in the production of ceramic materials with desired properties. The focus is on the development of template synthesis of mesoporous metal silicates as well as obtaining nano- and subnanopowders by a modified sol-gel technique and template methods. Families of mesoporous (2 to 300 nm) metal silicates and nano-oxides and subnanopowders (4 to 300 nm) were synthesized by the template method and modified sol-gel technique, respectively. Texture and morphology of the obtained objects have been studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller analysis, and N2 adsorption-desorption. It was found that morphological parameters of the metal oxide obtained by the modified sol-gel technique depend nonlinearly on the initial molar ratio value of the sol stabilizer and metal in the reaction medium as well as the nature of the stabilizer. It has been shown that the nature of structure-directing components determines the morphology of the silicate obtained by the template method: dispersion and shape of its particles. The developed laboratory technology corresponds to the conception of soft chemistry and may be adapted to the manufacture of ultradispersed materials for catalysis, solar cells, fuel cells, semiconductors, sensors, low-sized electronic devices of new generation, etc.

Plasma Processed Nanosized-Powders of Refractory Compounds for Obtaining Fine-Grained Advanced Ceramics

One of the ways for the production of ceramic materials with a fine-grained structure is the use of nanopowders. Different methods are used for the production of nanopowders. One of them is the method of plasmachemical synthesis. Different nanopowders of refractory materials can be obtained by this method. The preparation of nanosized powders of nitrides and oxides and their composites by the method of plasmachemical synthesis, the possibilities to receive nanopowders with different particle size and the potential advantages of nanopowders were investigated.

Production of ceramic materials by the sintering of ground basalt

The process of the heating of ground basalt was studied. Based on the obtained results, samples of basalt ceramics without a binding agent were fabricated by sintering. The physicochemical properties of the obtained samples were investigated.

FABRICATION OF MICROPOROUS SILICA CERAMICS WITH VARIED POLYMORPHIC FORMS AND INVESTIGATION OF THEIR THERMAL SHOCK BEHAVIOUR

In this study; the SiO2 micro-porous ceramics in the phase α-quartz, α-cristobalite and β-cristobalite were produced and thermal shock resistance of products were compared. In the production of ceramic materials; α-quartz obtained from natural quartz powder, α-cristobalite from pure silica powder which prepared by Stober technique and β-cristobalite from sol-gel approach. The β-composition was designed as 1 x x x / 2 2 Si Al Ca O - where x = 0.05 and obtained gel was calcined at 850°C. Before shaping, α-quartz powder and calcined β-cristobalite powder were grind in the planetary mill and the powder produced by Stober technique was shaped directly without any milling process. The prepared powders were shaped by uniaxally press at 50 bars. The samples produced from α-quartz and β-cristobalite powders were sintered at 1150 °C and α-cristobalite obtained by Stober technique was sintered at 1400 °C. In the defined polymorphic structure, micro-porous materials with pore size ~0.1-5 μm were produced and thermal shock tests were applied. Irrespective of β-cristobalite material, the samples were cracked and the tests could only repeat on the samples with β-cristobalite material. In the result, the β-cristobalite sample is believed to be great potential to use as a membrane filters for harsh thermal environments.

Study of nanoconfigurations in Zircon-Mullite composites using perturbed angular correlations

It has been already published that, at nanoscopic level, zircon exhibits wide regions of aperiodic material not detected by the ordinary techniques used to analyse the obtained product in the production of ceramic materials. In this paper it is reported how the Perturbed Angular Correlations (PAC) technique has assisted the interpretation of a mismatch between experiment and theoretical estimation of a mechanical property in some zircon-mullite composites. In fact, it has been proved that the difference observed between the calculated and the experimental value of the elastic modulus in composites of the form (1−x) ZrSiO4 − x 3Al2O3.2SiO2 (with x = 15, 25, 35 and 45 wt.%) behaves very similarly as the relative amount of aperiodic zircon determined by PAC. This result allows to re-interpret the mullite role during the materials preparation.

Thermal analysis of Romanian ancient ceramics

The present work is focused on thermoanalyt- ical investigations as thermogravimetric analysis (TG) and derivative thermal analysis (DTG), applied for the char- acterization of some samples collected from archaeological sites (Brasov and Trofeum Traiani) located in different regions of Romania. New informations derived about ceramic technologies concerning raw materials and binding materials (mineralogical components) have been obtained. All these experimental results have been correlated with related techniques as X-ray diffraction (XRD), energy- dispersive X-ray fluorescence (EDXRF) and inductively coupled plasma—atomic emission spectrometry (ICP- AES). By progressive heating in static air atmosphere and in the temperature range of 20-800 � C, all investigated materials exhibit three main successive processes, associ- ated with the dehydration and thermo-oxidative degrada- tions. The rate of the first thermooxidative process, temperatures corresponding to the maximum rate of the second thermooxidative process and shrinkage temperature were associated with the damage of the investigated materials due to environmental impact. Heating also affects the contact between the fine-sized clay matrix and mineral clast fragments, appearing in reaction rims, sometimes showing newly formed phases. The temperature at which ancient ceramics and pottery were fired varies over a wide range (600-800 � C) depending on the type of clay used, although firing temperatures not above 30-400 � C have also been suggested. Clay minerals, as the main material for production of ceramics and pottery, show some char- acteristic reactions (dehydroxylation, decomposition, transformation) in the course of firing (heating effects) and several thermoanalytical criteria can be used for recon- struction of former production conditions.

Lightening of red-buring clays in the production of ceramic materials

A light ceramic, based on red-burning clay, with good decorative and technical properties has been obtained by introducing into the ceramic mix CaCO 3 in the form of finely dispersed waste products from sugar production.

Synthesis of nanocrystalline calcium hydroxyapatite from calcium saccharates and ammonium hydrogen phosphate

The synthetic hydroxyapatite Ca 10 (PO 4 ) 6 (OH) 2 (HAP) is a mineral component of the bone tissue of mammals. HAP is biocompatible with the human body, capable of biointegration with the bone tissue, has no negative influence on the immune system, is nontoxic, and shows osteoconductive behavior. Therefore, HAP is used to design ceramic materials for bone implants [1]. The activity of powders toward sintering in the production of ceramic materials increases with a decrease in the particle size of the powder [2, 3]. For bioceramics, an important feature is the absence of acute cytotoxicity, which is determined by the chemical purity of the initial powder. To prepare HAP containing no toxic or associated products difficult to remove, the reaction of calcium hydroxide with ammonium phosphate is used. In this case, one component, Ca(OH) 2 , is taken as a suspension [4]. An obvious drawback of the synthesis of calcium phosphates from a poorly soluble compound is that dissolution of Ca(OH) 2 is the rate-limiting step, and this increases the duration of synthesis. The formation of calcium phosphates may also occur on the surface of Ca(OH) 2 particles, which shifts the reaction to a region of slower diffusion through a solid calcium phosphate bed and gives rise to an inhomogeneous target product. The use of soluble calcium compounds for preparing highly dispersed powders is preferred, because this implements the known bottom-up approach to the creation of a dispersion system (from small to large) [5]. In the presence of saccharose, the solubility of calcium hydroxide increases due to formation of soluble calcium saccharates [6]. Organic compounds being adsorbed on the surface of the inorganic crystals formed prevent their growth and thus ensure the formation of a finely crystalline powder [7]. The purpose of the present work was to prepare nanocrystalline HAP containing a biocompatible associated product, saccharose, from ammonium hydrogen phosphate and calcium saccharates. The study was carried out with solutions of calcium saccharates Ca n C 12 H 22 – 2 n O 11 at different n ( n is the Ca : C 12 H 22 O 11 molar ratio in the saccharate synthesis) and HAP samples synthesized from different calcium saccharates and ammonium hydrogen phosphate.

Effect of an Iron Catalyst and Process Parameters on Si-Based Ceramic Materials Synthesized From Rice Husks

Silica and carbon are naturally occurring in rice husks (RH) and these were used for the production of ceramic materials made of Si, C, N and O as the main constituents. The various “silicon-based” ceramics were produced from the thermal decomposition of rice husks and posterior heat treatment at temperatures varying from 1200–1450 °C under a pure nitrogen atmosphere. FeSO4 in various concentrations was introduced to the decomposed rice husk prior to the heat treatment. The formation of various Si/C/N/O ceramics in general and silicon nitride in particular, were studied with respect to the concentration of FeSO4 (4–10%) as well as temperature (1200–1450 °C). The formation of different phases were confirmed by XRD and FT-IR analysis. Morphology and surface properties of the products have been studied using SEM. The maximization of whiskers of the ceramic products was also studied through microstructural analysis. Elemental analysis of the whiskers product was analyzed through EDX. The chemical analysis of raw rice husk was also carried out.

Aplicação de rejeito argiloso de uma mineração de areia industrial como matéria-prima na indústria cerâmica

O reaproveitamento de rejeitos argilosos provenientes da mineração de areia industrial da Formação Pirambóia representa uma opção na diminuição dos impactos ambientais gerados pela sua disposição em tanques de decantação. O presente trabalho teve por objetivo testar a aplicação destes rejeitos na confecção de produtos cerâmicos. Com este intuito, foi feita a caracterização química e mineralógica, bem como ensaios cerâmicos, de amostras provenientes dos espessadores e dos tanques de decantação de uma mineração de areia da região de Analândia (SP). As amostras dos espessadores apresentam características homogêneas, alta plasticidade e presença dominante do argilomineral caulinita. Já as amostras do tanque de decantação são mais heterogêneas, silicosas e menos plásticas. Para a produção de blocos, as argilas dos espessadores mostraram-se mais adequadas por apresentarem características homogêneas, facilitando a extrusão e reduzindo os defeitos dimensionais das peças, proporcionando assim um produto final de qualidade.

Desempenho mecânico de misturas asfálticas confeccionadas com agregados sintéticos de argila calcinada

Expressivo número de municípios amazonenses se encontra localizado em áreas carentes em agregados pétreos, o que leva os construtores de pavimentos a adotarem alternativas que, em retrospecto histórico, propiciam pavimentos de deficiente resistência mecânica. Conquanto mais eficaz e apropriado do ponto de vista técnico, o concreto betuminoso usinado à quente é normalmente evitado por conta da indicada carência estadual em agregados pétreos. Em face do peculiar contexto amazonense, revela-se recomendável à circunstância em testilha a adoção de agregados sintéticos de argila calcinada (ASAC), com matéria-prima abundante (argila) no Amazonas. Trabalhos anteriores, realizados pelo Grupo de Geotecnia da Universidade Federal do Amazonas, demonstram que solos argilosos, costumeiramente empregados para produção de material cerâmico, podem produzir agregados sintéticos com adequadas propriedades mecânicas. Nesta pesquisa, amostras com características similares às desses solos foram encontradas na rodovia BR-319, que liga Manaus (AM) a Porto Velho (RO). Trata-se de estrutura, em geral, a ostentar péssimas condições de tráfego, incluída, de maneira justificável, como um dos alvos da política pública de recuperação de rodovias, conduzida pelo Ministério dos Transportes. Neste estudo, dosaram-se misturas asfálticas com agregado sintético e com seixo rolado oriundo do leito dos rios amazonenses, a fim de se comparar o desempenho mecânico de tais misturas por meio da determinação do módulo resiliente (MR). Os resultados, em regra, denotam que as misturas asfálticas confeccionadas com agregado sintético de argila calcinada, quando confrontadas com aquelas confeccionadas com o material natural (seixo), apresentaram: (a) maiores resistências à tração e aos módulos resiliente; (b) baixa tendência à deformação, assim como uma recuperação elástica considerável e (c) menor susceptibilidade às deformações permanentes.

Characterisation of raw materials for production of ceramics

The aim of this paper is to characterize some raw materials used for ceramics material production. Five samples of clay have been analyzed. It has been carried out a patterned sampling in a quarry in Rosarno (South Italy).

Caracterização de argilas encontradas em solos de Terras Indígenas do RS com o auxílio da espectroscopia Mössbauer de 57Fe

As argilas encontradas em amostras de solos, provenientes de Terras Indígenas do planalto médio do Rio Grande do Sul, foram caracterizadas com o intuito de fornecer dados e parâmetros técnicos para seu uso como matéria prima de produtos cerâmicos. O estudo mineralógico efetuado nas amostras utilizando a técnica de difração de raios X demonstrou que o argilomineral predominante é a caulinita. Outros minerais, como quartzo e rutilo, encontram-se presentes em menor quantidade. As análises químicas demonstram que as quantidades de óxido de Mg, Mn, K, Na, Ca, Cu e Zn são baixas (a soma das porcentagens é menor que 0,97 %). As amostras foram analisadas por espectroscopia Mössbauer de 57Fe. Os espectros Mössbauer obtidos na temperatura ambiente confirmam a presença do mineral caulinita. Os espectros a 77 K revelam a existência dos minerais goetita e hematita, na forma de partículas magnéticas ultrafinas (nanopartículas) em estado superparamagnético. Os testes físicos efetuados nas amostras indicam que os solos são finos e apresentam características granulométricas e de plasticidade, que podem ser aproveitadas para a produção de materiais cerâmicos para construção ou objetos ornamentais.

Sol – Gel Modelling Associated with the Rheology of Polymeric Precursors of Ceramic Materials

Abstract A general constitutive relation describing the change of viscoelastic behavior during the liquid - solid (sol - gel) transition which takes place in preceramic polymers is derived on the basis of Jeffrey’s 3-constants model with time dependent viscosities and elasticity. It is postulated that the sol - gel - transition can be analyzed analogous to the solutions of the Avrami equation used for modeling crystallization processes. Two different polymer systems used as precursor for the production of ceramic materials are investigated here: i) a mixture based on polysiloxane, alumatrane and isopropanol; ii) a non-oxidic carbodiimide gel based on the reaction of chlorosi-lanes with bis(trimethylsilyl)carbodiimide. Continuous measurements of the dynamic moduli versus reaction time, as well as creep tests at constant shear stress, evidenced both qualitative similarities and quantitative differences associated with the sol - gel transition of the two polymer systems. The shear rate and viscosity dependence of reaction time in creep tests, respectively the evolution of Lissajous figures associated with oscillatory experiments, are found to be consistent with the numerical simulations of the proposed constitutive relation.

Caracterização de cinza de casca de arroz para uso como matéria-prima na fabricação de refratários de sílica

The characterization of rice husk ash, a deriving by-product of the burning of the rice husk during the rice processing is the object of this study. This by-product, for being rich in silica, can be an important raw material for the production of siliceous ceramics, such as thermal insulators and refractory. A combination of surface analysis, thermal analysis and microscopy analysis techniques was used for the characterization. The characterized by-product presented as main component the silica, under amorphous form, with a maximum content of alkalis around 1%, features that become it potentially interesting for the production of ceramic materials.

The Production of Ceramic Materials in Roman Pavia: An Archaeometric NAA Investigation of Clay Sources and Archaeological Artifacts

Part of a research program on cultural heritage aimed to elucidate the production of ceramic artifacts in Roman Pavia is devoted to the localization of the possible sources of raw materials (claypits) as well as to the technological production processes. Clay samples were collected in two different areas nearby Pavia, Lomellina and Oltrepo. Some of these samples were also fired at 950 °C. Archaeological ceramic samples, mostly bricks and tiles of Roman age, were obtained from excavations of Roman settlings close to Pavia. All samples were submitted to instrumental neutron activation analysis for the determination of Ca, Fe and a number of trace elements. Results indicate (1) fired and raw clay samples keep the same elemental fingerprint so that only raw samples data can be used in archaeometric studies; (2) some parameters based on rare earth elements are useful to discriminate the clay samples from the two investigated areas; (3) clay discrimination is confirmed also by discriminant analysis; and (4) the insertion of the elemental composition data of the ceramic artifacts in the statistical treatment allows one to assign the artifacts to one of the investigated areas and confirms that, at Roman times, the production of ceramic building materials was mostly based on the use of local prime matter.

99/02199 Raw-materials mixtures from waste of the coal industry for production of ceramic materials: Galpern, E. I. and Paschenko, L. V. DGMK Tagungsber., 1998, 9802, 253–259

99/02199 Raw-materials mixtures from waste of the coal industry for production of ceramic materials: Galpern, E. I. and Paschenko, L. V. DGMK Tagungsber., 1998, 9802, 253–259

Comprehensive study of base rocks as raw material for ceramic production

Phase transformations proceeding in base rocks (metadiabases, metagabbro) upon heat treatment are considered. It is found that metadiabases can be used as fluxes in ceramic mixtures intended for high-temperature firing and in raw and fritted glazes as well.