Abstract Cement mortar is typically formulated by blending fine aggregate and water, yielding a matrix characterized by heterogeneity and porosity. However, these inherent characteristics can exacerbate structural leakage, allowing water infiltration in buildings. Bentonite is a promising waterproofing additive for various mortar types, owing to its remarkable water swelling properties and recognized attributes of being non-toxic and cost-effective. Hence, this study examined calcium or sodium-activated bentonites as cost-effective waterproofing additives in polymer-modified cement mortars. A commercial mortar with varying amounts (0-2wt.%) of these bentonites was prepared. The research focused on characterizing the additives and assessing mortar performance regarding fluidity, water absorption, mechanical strength, resistance to water penetration under negative and positive pressure, and microstructural features. Results showed sodium bentonite had a smaller particle size, higher reactivity, and swelled three times more than calcium bentonite. These additives altered the fresh mortars rheological properties due to flocculation. Incorporating 2 wt.% of sodium bentonite into the mortar did not significantly change the water absorption or crushing strength of samples cured at room temperature for 28 days. However, it led to an 18.6% reduction in water penetration under positive pressure and prevented liquid percolation to the upper surface of the samples during tests under negative pressure. porosity However leakage buildings types nontoxic non toxic costeffective. costeffective cost effective. effective Hence sodiumactivated activated polymermodified polymer modified 02wt.% 02wt wt 0 2wt.% 2wt (0-2wt.% prepared fluidity features size reactivity flocculation wt. days 186 18 6 18.6 02wt. 2wt. (0-2wt. 1 18. (0-2wt

Abstract The utilization of waste or by-products in geopolymers is an effective strategy that contributes to the development of more sustainable ceramics. The present study aimed to evaluate the physico-mechanical properties of compositions prepared by partially replacing aluminosilicate precursors (metakaolin or calcined diatomite) with solid wastes (granite, roof tile chamotte, or glass powder) at contents of 10, 20, and 40 wt%. Geopolymers were synthesized by blending the solid raw materials (precursor+wastes) with an alkaline activating solution comprising NaOH and colloidal silica suspension. The samples were cured at 40 °C for 24 h, and the following analyses were conducted: elastic modulus, compressive strength, porosity, density, X-ray diffraction, and Fourier-transform infrared spectroscopy measurements. The results demonstrated that the formulation containing 10 wt% of chamotte exhibited the best performance, showing a remarkable mechanical strength of 31.7 MPa after one day of curing. Therefore, by incorporating waste materials into geopolymers, not only can the environmental impact be minimized, but it also presents an opportunity to utilize resources that would otherwise go to waste. byproducts products ceramics physicomechanical physico metakaolin diatomite granite, granite (granite powder 20 4 wt precursor+wastes precursorwastes precursor (precursor+wastes suspension C 2 h conducted modulus porosity density Xray X ray diffraction Fouriertransform Fourier transform measurements 1 performance 317 31 7 31. curing Therefore minimized 3

Abstract The composition-processing-structure-properties relationship of Na2O-Al2O3-SiO2-based geopolymers containing calcium sources is critical for the design of enhanced ceramic binders. This work evaluated the addition of 1-6 wt% of calcium hydroxide (CH) to a metakaolin-based geopolymer (prepared with NaOH 12 M and colloidal silica suspension) and how it affected the performance of the prepared samples after thermal treatments up to 1000 °C. The setting time, mechanical strength, porosity, density, permanent linear change, and phase and bond type evolution of the specimens with temperature were analyzed. The incorporation of 3 or 6 wt% of CH into the designed composition led to a fast hardening of the mixtures (1.7 h), resulting in geopolymers with high green mechanical strength (18.9 to 23.9 MPa). Nepheline and albite generation in the samples containing 6 wt% of CH resulted in a ceramic with improved cold crushing strength (45.2 MPa) and lower linear shrinkage (-10.5%) when compared to the calcium-free composition. compositionprocessingstructureproperties processing structure properties Na2OAl2O3SiO2based NaOAlOSiObased Na2O Al2O3 SiO2 based Na O Al SiO binders 16 1 1- wt (CH metakaolinbased metakaolin suspension 100 C °C time porosity density change analyzed 1.7 17 7 (1. h, h , h) 18.9 189 18 9 (18. 239 23 23. MPa. MPa . 45.2 452 45 2 (45. 10.5% 105 10 5 (-10.5% calciumfree free OAl NaO AlO Al2O 1. (1 18. (18 45. 4 (45 10.5 (-10.5 ( (4 10. (-10. (-10 (-1 (-

Abstract The possibility of recycling solid wastes in the production of geopolymers and advanced ceramic products has received special attention recently. This work investigated the feasibility of replacing a high amount (70-90 wt%) of metakaolin with roof tile waste (CW) in the production of Na-geopolymer composites. Additionally, the influence of this alternative material, in the phase transformations and properties evolution (elastic modulus, compressive strength, porosity, density, and linear shrinkage) of the prepared compositions after distinct thermal treatments (40-1000 °C) was evaluated. The results showed that the incorporation of CW powder into the geopolymeric compositions enhanced their thermal and mechanical properties up to 1000 °C. The best performance was reached when using 80 wt% of the selected waste, which led to ceramic specimens with high crystallinity (presenting quartz, hematite, and albite phases), compressive strength (39.6 MPa), suitable linear shrinkage (-7.4%), and improved thermal stability (without visual cracks) after firing at 1000 °C. recently 7090 70 90 (70-9 wt (CW Nageopolymer Na geopolymer composites Additionally material elastic modulus porosity density 401000 40 (40-100 °C C evaluated 100 8 presenting quartz hematite phases, phases , phases) 39.6 396 39 6 (39. MPa, MPa MPa) 7.4%, 74 7.4% 7 4 (-7.4%) without cracks 709 9 (70- 40100 (40-10 10 39. 3 (39 7.4 (-7.4% (70 4010 (40-1 1 (3 7. (-7.4 (7 401 (40- ( (-7. (40 (-7 (4 (-

Abstract Fused alumina is a material used in the manufacturing of abrasive tools, due to its high fusion point, great hardness, and mechanical toughness. In this context, this study addressed the influence of niobium addition on the properties of fused alumina for abrasive applications. A comparison was also made between this oxide and the brown fused alumina and the white fused alumina traditionally applied in this market, using different characterization techniques, such as particle size characterization, scanning electron microscopy, real and bulk density, chemical analysis, fracture resistance, and abrasiveness indexes. Among the main findings of this study, it was possible to observe that the addition of niobium to fused alumina significantly increased the fracture resistance and abrasiveness indexes compared to the brown and white fused alumina.

Abstract Thin film solar cell materials such as 3D metal halide perovskites are cheaper alternatives to silicon. Presently, the conversion efficiency of 3D lead halide perovskites is 25.5% (2021), which represents an increase of more than 550% since their discovery in 2009 (3.8%). Despite this remarkable progress, concerns about the toxicity of lead have sparked the quest for possible substitutes, in particular, 3D tin halide perovskites. This review covers the general properties of tin halide perovskites, synthesis and stability. It also identifies possible gaps and application beyond solar cells.

Resumo O presente estudo avaliou a viabilidade da utilização do pó de retífica (PR), resíduo gerado na produção de revestimentos de discos de embreagem, como aditivo retardador em matrizes cimentícias. Para isso, o PR foi adicionado nos teores de 5%, 10% e 15%, em relação à massa de cimento, e avaliou-se o efeito desta adição no tempo de pega, pelo método de Vicat. Além destes ensaios, foi analisada a influência deste material na reologia (flow table, squeeze-flow e reometria rotacional) e nas propriedades físico-mecânicas das matrizes endurecidas. Os resultados indicaram um retardo de pega crescente em função de um maior teor de PR adicionado e uma redução na fluidez das matrizes cimentícias, sendo que os melhores resultados para as propriedades no estado endurecido foram verificados para as matrizes cimentícias contendo 5% de adição. Assim, observou-se que o PR é eficaz no retardo da pega, apresentando grande potencial de utilização na construção civil, sem prejudicar as suas propriedades.

Abstract The present study evaluated the feasibility of the use of grinding dust (GD), a waste generated in the clutch disc finishing process, as a retardant additive in cementitious matrices. For this, the waste was added in contents of 5%, 10% and 15%, relative to the cement weight, and the setting time was determined by the Vicat method. In addition, the influence of this material on rheology (flow table, squeeze-flow and rotational rheometry) and on the physical-mechanical properties of the hardened matrices was analyzed. The results indicated an increase in setting time and a reduction in the fluidity of the mortars as a function of the addition of GD and the best results for the hardened state properties were verified for the cementitious matrices containing a 5% addition. Therefore, it was observed that GD is effective in retarding the setting time, presenting great potential for use in civil construction, without impairing its properties.

Resumo O desenvolvimento de perovskitas ferroelétricas capazes de absorver a luz visível, particularmente KBNNO - [KNbO3]0,9[BaNi0,5Nb0,5O3-δ]0,1 (band-gap Eg= 1,39 eV), tem encorajado a aplicação desses materiais na camada ativa de células solares. Em dispositivos fotovoltaicos, esses materiais podem permitir a obtenção de voltagens superiores à magnitude de seus band-gaps e contribuir para uma separação de portadores de cargas mais eficiente. A obtenção de KBNNO na forma de pó de elevada área superficial pode ser uma estratégia para posterior incorporação do óxido em células compostas de materiais processados a baixas temperaturas. Neste trabalho, reporta-se pela primeira vez o uso da rota de combustão em solução como uma alternativa para a síntese de KBNNO. As amostras foram caracterizadas por DRX, MEV, EDS, TG/DSC e espectroscopia UV-vis. As propriedades ópticas confirmaram a contribuição na absorção da luz visível e um band-gap próximo do valor ideal para aplicações fotovoltaicas.

Abstract The development of visible-light-absorbing ferroelectric perovskite materials, particularly KBNNO - [KNbO3]0.9[BaNi0.5Nb0.5O3-δ]0.1 (band-gap Eg= 1.39 eV), has provided encouragement for the use of such materials in photoactive layers. When applied in photovoltaic devices, these materials might generate above-bandgap photovoltages and a more efficient separation of charge carriers. The synthesis of this oxide as a powder with high surface area might be a strategy to further incorporation in solar cells composed of low-temperature processing materials. This work reports for the first time the application of the solution combustion as an alternative route for the synthesis of KBNNO. Characterization by XRD, SEM, EDS, TG/DSC and diffuse reflectance UV-vis spectroscopy confirmed the success of the synthesis. The optical properties showed the visible-light absorption contribution and band-gap close to the ideal magnitude for solar applications.

Resumo Arcabouços de óxido de titânio (TiO2) com Biosilicato® incorporado foram produzidos e avaliados com relação à porosidade e microestrutura. Arcabouços para regeneração óssea devem apresentar porosidade que favoreça o crescimento de tecidos ósseos através do material. O TiO2 é um material cerâmico altamente biocompatível com boas propriedades mecânicas e osseocondutoras, permitindo a migração do tecido ósseo sobre a interface do material, mas sem estimular a atividade das células osteogênicas que geram o tecido ósseo. Com o intuito de induzir a formação de tecido ósseo o Biosilicato®, um material com elevada bioatividade, foi incorporado à matriz cerâmica de TiO2. Para a obtenção dos macroporos foi utilizado o método de eliminação por queima, no qual partículas orgânicas são empregadas na matriz cerâmica como agentes formadores de poros, que possui a vantagem de adaptar as características dos poros do componente cerâmico final por meio da escolha apropriada do agente formador de poros. Neste trabalho foi feita uma mistura homogênea de TiO2 com serragem de cambará e posteriormente adicionou-se o Biosilicato®. Após a queima as amostras foram avaliadas pelo método de Arquimedes, para a determinação da porosidade aparente, e por microscopia eletrônica de varredura (MEV) para a visualização da morfologia dos grãos e distribuição e tamanho de poros. A etapa de queima garantiu a eliminação completa dos agentes formadores de poros e a completa sinterização do TiO2. O Biosilicato® facilitou a sinterização do TiO2 e a consolidação da matriz cerâmica. Foram obtidos arcabouços com porosidade aparente de 63% e poros com tamanhos maiores que 200 µm. Por meio da análise de MEV, observou-se a distribuição homogênea dos poros e suas interligações. Além disso, foi possível observar a distribuição do Biosilicato® entre as partículas de TiO2, sendo um caminho para o crescimento e regeneração do tecido ósseo.

Abstract Titanium dioxide (TiO2)-Biosilicate® scaffolds were produced and evaluated for porosity and microstructure. Scaffolds for bone regeneration must provide adequate porosity to promote bone tissue growth through the material. TiO2 is a highly biocompatible ceramic material with high reliable mechanical and good osteoconductive properties to allow bone tissue migrates on material interface, but without stimulating the activity of osteogenic cells that produce bone tissue. In order to induce bone tissue formation a material with high bioactivity named Biosilicate® was incorporated into the ceramic matrix of TiO2. To obtain macropores, organic particles in the ceramic matrix as pore forming agents were employed, using the sacrificial template method which has the advantage to adapt the final ceramic pores characteristics by appropriate choice of pore former agent. In this work, a homogeneous mixture of TiO2 with sawdust was prepared and later the Biosilicate® was added. After firing, the samples were evaluated by Archimedes method for determining porosity and by scanning electron microscopy (SEM) for imaging grain morphology, and pore size and distribution. The firing stage ensured complete elimination of pore forming agents and complete sintering of TiO2. The Biosilicate® facilitated sintering of TiO2 and consolidation of ceramic matrix. Scaffolds were obtained with 63% apparent porosity and pore size higher than 200 µm., Homogeneous pores distribution and their interconnections were observed by SEM analysis. Moreover, it was possible to observe Biosilicate® distribution among TiO2 particles being a path for bone tissue growth and regeneration.

Resumo Coatings de alta emissividade têm sido utilizados em aplicações industriais há mais de 40 anos com o objetivo de reduzir as perdas térmicas em processos de aquecimento. Com a aplicação de um coating de alta emissividade na superfície dos revestimentos internos de um forno industrial é possível aumentar a eficiência nas trocas térmicas entre a atmosfera e as paredes do revestimento, reduzindo a perda de calor e também o consumo de combustíveis. Em geral são utilizados compostos cerâmicos como óxido de cério, carbeto de boro, boreto de silício, siliceto de molibidênio ou óxido de cromo como agentes de emissividade para se obter as propriedades termo-ópticas desejadas nos coatings. Entretanto tais compostos muitas vezes inviabilizam sua aplicação, devido ao seu elevado valor comercial ou ainda sua escassez. Neste contexto, o presente trabalho buscou avaliar os efeitos da cromita de ferro, um óxido mineral abundante e de valor comercial acessível, em sua utilização como agente de emissividade em coatings refratários de alta emissividade. Por meio de um método indireto de medição de emissividade, foram avaliadas de maneira comparativa composições com e sem a presença da cromita de ferro visando sua aplicação como cobertura de revestimentos isolantes e refratários de fornos de aquecimento industrial. Com adições de 7,5% de cromita de ferro, observaram-se aumentos na emissividade dos coatings da ordem de 8%, sugerindo seu potencial para essa aplicação.

Abstract High emissivity coatings have been used in industrial applications over 40 years with the goal of reducing the thermal losses in heating processes. By applying a high emissivity coating on the internal surface of a kiln lining, it is possible to increase the efficiency in heat exchange between the atmosphere and the walls, reducing the heat loss and also the fuel consumption. In general ceramic compounds such as cerium oxide, boron carbide, silicon boride, molybdenum silicide or chromium oxide are used as emissivity agents to obtain the desired thermo-optical properties in coatings. However, such compounds often prevent their application due to its high commercial value or its scarcity. In this context, this study aimed to evaluate the effects of iron chromite, an abundant mineral oxide and affordable commercial value in its use as emissivity agent in high emissivity refractory coatings. Through an indirect method of measuring emissivity, different coatings compositions with and without the addition of iron chromite were evaluated, in a comparative manner, aiming its application as coatings for refractory and insulation linings of industrial heating furnaces. With iron chromite additions of 7.5%, there was almost 8% increase in the emissivity of the coatings, suggesting their potential for this application.

ResumoPorcelanas aluminosas contendo diferentes concentrações de Fe2O3 foram sinterizadas em atmosfera oxidante e redutora. A microestrutura e fases formadas foram investigadas com o auxílio de difração de raios X e microscopia eletrônica de varredura. Espectroscopia de impedância foi utilizada para estudar as propriedades elétricas. Os resultados indicaram que todas as amostras apresentaram mulita e coríndon como fases majoritárias e pequenas frações de quartzo. A adição de Fe2O3 provocou o surgimento de hematita nas amostras sinterizadas em atmosfera oxidante e, ferro metálico nas amostras contendo > 3%p sinterizadas em atmosfera redutora. Os espectros de impedância indicam que as características da fase vítrea e interface entre fase vítrea /fases cristalinas regem o comportamento elétrico global das amostras. Não obstante, diferentes atmosferas de queima provocam efeitos opostos na resistividade elétrica das porcelanas contendo Fe2O3. A presença de hematita foi considerada a responsável pela diminuição da resistividade elétrica nas amostras sinterizadas em atmosfera oxidante, enquanto que o aumento na resistividade elétrica das amostras sinterizadas em atmosfera redutora foi atribuído à elevada quantidade de fase vítrea e porosidade. Estes resultados indicam que atmosfera redutora durante a queima pode favorecer o uso de matérias-primas com maiores concentrações de Fe2O3, desde que todo óxido de ferro tenha se dissolvido na fase liquida durante a queima.

AbstractAluminous porcelain containing different Fe2O3 concentrations were sintered in oxidizing and reducing atmosphere. The microstructure and crystalline phase formation were investigated by scanning electron microscopy and X-ray diffraction. Electrical properties were investigated by Impedance spectroscopy. The results indicated that all samples showed mullite and corundum as major phases and small fractions of quartz. The addition of Fe2O3 caused the appearance of hematite in samples sintered in oxidizing atmosphere and metallic iron for the samples containing > 3%wt. and sintered in reducing atmosphere. The impedance spectrum indicates that the glass phase and crystal/glassy phase interface govern the overall electrical behavior of the samples. However, different firing atmospheres cause opposite effect on the electrical resistivity of the porcelain containing Fe2O3. The presence of hematite was considered to be responsible for the decrease in resistivity for samples sintered in oxidizing atmosphere, whereas the increase in the resistivity of the sample sintered in a reducing atmosphere was attributed to the high amount of glassy phase and porosity. These results indicate that reducing atmosphere during firing may favor the use of raw materials with higher concentrations of Fe2O3, since all iron oxide have been dissolved into the melting phase during the sintering of porcelain bodies.

O cromito de lantânio (LaCrO3) é um material cerâmico sintético, que apresenta como principais características boa condutividade elétrica em altas temperaturas (> 800 °C), estabilidade química e física em atmosferas oxidantes e redutoras e, significativa atividade catalítica quando na forma de pós. Estas características o tornam atrativo para diversas aplicações de interesse tecnológico, como catalisadores, resistências para fornos de alta temperatura e geração de energia elétrica, sendo que nesse campo é potencialmente o material mais adequado para utilização como interconector em células a combustível de óxido sólido (Solid Oxide Fuel Cell - SOFC). As características intrínsecas, propriedades e técnicas de processamento do cromito de lantânio são consideradas neste trabalho por meio de uma revisão dos principais estudos relatados ao longo dos últimos 40 anos.

The lanthanum chromite (LaCrO3) is a synthetic ceramic material, which has as main characteristics of good electrical conductivity at high temperatures (> 800 °C), physical and chemical stability in oxidizing and reducing atmospheres, and a significant catalytic activity when used as powder. These features make it attractive for various technological applications such as catalysts, resistance to high temperature furnaces and electric power generation, and this field is potentially the most appropriate material for use as interconnector in Solid Oxide Fuel Cells (SOFC). The intrinsic characteristics, properties and processing of lanthanum chromite are detailed in this paper through a review of major studies reported over the past 40 years.

Este trabalho teve como objetivo sintetizar e caracterizar pós de alumina-boretos, por moagem reativa, visando a obtenção de compósitos de misturas de fases de alta dureza. Os experimentos envolveram reações de aluminotermia ativadas por moagem de alta energia, tendo como precursores WO3, TiO2 ou Ti, B2O3 ou B e Al. O alumínio metálico atua como agente redutor para obter misturas de alumina com boretos de titânio e de tungstênio. As reações obtidas foram do tipo auto-propagante, com tempos curtos de moagem até a ignição (2 a 15 min). O tempo de ignição das reações foi monitorado por infravermelho e os produtos das reações foram mantidos sob moagem para obter partículas nanométricas. Os pós obtidos foram caracterizados por difração de raios X e determinação da densidade real e prensados para obter corpos de prova em forma de discos após sinterização a 1700 °C sob alto vácuo. Esses foram caracterizados por densidade aparente, difração de raios X e microscopia eletrônica de varredura. Os pós resultantes da moagem de alta energia mostraram completa transformação dos reagentes, formando pós com composições do sistema Al2O3 - (WB/W2B/WB2/W2B5) - TiB2. Dependendo da reação de síntese, os pós obtidos apresentaram diferentes comportamentos durante a sinterização: pós que densificaram até porosidade aparente próxima de zero e pós que não densificaram, resultando em porosidade aparente em torno de 30%.

This study aimed to synthesize and characterize alumina-boride powders by reactive milling to obtain composite of mixtures of high hardness phases. The experiment involved aluminothermic reactions activated by high energy milling of WO3 , TiO2 , or Ti , B2O3 or B and aluminum powder, as precursors. Aluminum is the reducing agent to obtain a mixing of alumina with titanium and tungsten borides. The reactions were of the self - propagating type, with short milling times until the ignition (between 2-15 min). The ignition time of the reactions was monitored by infrared and the reaction products were kept under additional milling time to obtain nanometric particles. The powders were characterized by X-ray diffraction and measurement of density. Specimens pressed in form of discs and sintered at 1700 °C under high vacuum were characterized by apparent density, X-ray diffraction and scanning electron microscopy. The results showed complete conversion of the reactants forming multiphase powders of the system Al2O3 - (WB/W2B/WB2/W2B5) - TiB2. Depending on the synthesis reaction, the powder presented different behavior during sintering: powders that densify to approximately zero porosity and powders that do not densify, with final apparent porosity of about 30%.

The acid-base cements are materials developed by means of reactions between an acid component and another basic one. This type cement belongs to the family of the so called "chemically bonded phosphate ceramics" (CBPCs), new types of inorganic materials that have special physico-chemical properties and that, in contrast to most advanced ceramics, are made by processing the material at ambient temperature. In the present work, cylindrical specimens were molded (30 mm × 50 mm) with magnesium phosphate cement and grinding dust (waste from an automobile industry) which was added to ceramic matrices in varied contents (0% to 40% in mass). The influence of this addition with regard to phase formation and to mechanic resistance (axial compression and traction by diametrical compression) of the compositions (3, 7 and 28 days after the molding) was evaluated using a universal test machine. The samples of magnesium phosphate cement mortars containing grinding dust were then analyzed after being subjected to an accelerated aging test for a period of 1200 hours (50 days), equivalent to one year of natural aging. The results obtained showed a decrease in the compressive strength of the mortar between 28 days and 1 year of age but this loss in performance is not associated with the presence of grinding dust and the CBPCs proved highly satisfactory for the encapsulation of hazardous wastes.

O desenvolvimento de substratos cerâmicos porosos de fina espessura (< 1 mm) apresenta grande interesse tecnológico, podendo ter aplicações em diversas áreas, dentre as quais se destacam as eletrônicas e catalíticas. O processo viscoplástico tem se destacado como método de conformação cerâmica por minimizar a quantidade de líquido adicionado e a aglomeração de partículas durante o processamento, a partir de intenso cisalhamento da massa. Este processo permite a conformação de corpos cerâmicos de modo mais simples e sem aditivos tóxicos como na colagem de fita, método normalmente utilizado. Neste trabalho os substratos foram conformados por rolos a frio com espessura entre 400 e 700 µm, e velocidade dos rolos laminadores de 15 rpm. Estes foram secos antes de ser submetidos a queima a 1600 ºC por 1 h. Como agente porogênico foi estudada a grafite em pó que foi adicionada a massa plástica de alumina em duas concentrações diferentes, 9% e 18% em peso, a qual resultou numa porosidade aparente de 21% e 52% respectivamente.

The development of porous ceramic substrates with thickness less than 1 mm presents a great technology interesting for electro-electronic or catalytic applications. Among all the techniques of ceramic conformation, the viscoplastic processing shows great advantages decreasing the amount of liquids and the particles agglomeration from an intensive shearing of the ceramic paste. This process allows the conformation of ceramic samples in a simple way and without toxic additives, the opposite of tape casting, which is the method often applied. The substrates were conformed by cold roll pressing in a thickness between 400 and 700 µm, and with the rotation of rollers of 15 rpm. Theses were dried before the firing at 1600 ºC for 1 h. As a pore-forming agent it was studied the graphite powder which was added to the alumina plastic paste in two different concentrations, 9 and 18 wt%, which results in an apparent porosity of 21 and 52%, respectively.