Study of physical and mechanical applications on ceramics of the lateritic and alluvial clayey mixtures of the Yaoundé region (Cameroon)

International audienceCeramic products were prepared by mixing lateritic and alluvial clayey materials of Yaoundé (Cameroon) in the humid tropical region, with 20, 50 and 80 wt.% of alluvial clay respectively in lateritic clay. Samples were grounded and sieved and powders obtained were shaped by uniaxial pressing of wet granules and fired under low temperatures between 350 and 1050 °C. Open porosity, bulk density and flexural strength were the principal properties characterised. Results indicates that a maximum of 80 wt.% of alluvial clayey material must be added to lateritic clays of Yaoundé, to obtain weakly porous ceramics and to attain the bulk density ranging from 1.56 to 1.97 g/m3 and a flexural strength of 6–19.85 MPa would be equivalent alluvial clay ceramics. But ceramics with lesser amount of alluvial clayey materials also have interesting flexural strengths in the range of 5–16 MPa, thus higher than porous lateritic clay ceramics

Effect of the use of a fruit waste (Musa paradisiaca) onto the microstructure and the densification of a kaolino-illitic clay from Central African Republic

International audienc

Preliminary analysis of physical and chemical phenomena occurring in droplet at solution precursor plasma spraying of zirconia coatings

International audienc

Caractérisation de quelques variétés d’argiles de Centrafrique : valorisation dans le domaine de la céramique

International audienc

Microestrutura e distribuição de Weibull da resistência à ruptura de cerâmicas de argila-talco

International audienceThe mechanical properties of clay-talc ceramics containing 0 to 10 wt% of talc fired at 1100 °C were obtained by flexural measurements. With the average value of flexural strength of 23.1 MPa, the sample with 5 wt% of talc (G5) was the strongest and it had the lowest value of interconnected pore (64%). The scattering of strength values was described with the Weibull distribution model. For all samples, Weibull plots showed either a typical linear behavior or a multi-stage response and the Weibull modulus varied in a large range of 3 to 14, depending on the ceramic type and on the applied load. Interconnections between pores formed a network of possible failures under the stress field, resulting in a change of Weibull plots. Reducing the grain size range and the pore interconnectivity led to a reduced strength distribution. The flaw size range had a unimodal distribution for sample G5 with homogeneous microstructure and correspondingly a Weibull modulus m=9.79. © 2019 Associacao Brasileira de Ceramica. All rights reserved.As propriedades mecânicas das cerâmicas de argila-talco contendo 0 a 10% em massa de talco sinterizadas a 1100 °C foram obtidas por medidas de flexão. Com o valor médio de resistência à flexão de 23,1 MPa, a amostra com 5% de talco (G5) foi a mais forte e apresentou o menor valor de poro interconectado (64%). A dispersão dos valores de resistência foi descrita com o modelo de distribuição de Weibull. Para todas as amostras, os gráficos de Weibull mostraram um comportamento típico linear ou uma resposta de múltiplos estágios e o módulo de Weibull variou em uma ampla faixa de 3 a 14, dependendo do tipo de cerâmica e da carga aplicada. Interconexões entre poros formaram uma rede de possíveis falhas sob o campo de tensão, resultando em uma mudança nos gráficos de Weibull. Reduções da faixa de tamanho dos grãos e da interconectividade dos poros levaram a uma redução na distribuição da resistência. A faixa de tamanho de defeito apresentou uma distribuição unimodal para a amostra G5 com microestrutura homogênea e correspondentemente um módulo de Weibull m=9,79

Contribution à la caractérisation et à la valorisation des argiles de Centrafrique dans le domaine de la céramique par incorporation d’un déchet vert

National audienc

Microstructure and Weibull distribution of rupture strength of clay-talc ceramics

International audienceThe mechanical properties of clay-talc ceramics containing 0 to 10 wt% of talc fired at 1100 °C were obtained by flexural measurements. With the average value of flexural strength of 23.1 MPa, the sample with 5 wt% of talc (G5) was the strongest and it had the lowest value of interconnected pore (64%). The scattering of strength values was described with the Weibull distribution model. For all samples, Weibull plots showed either a typical linear behavior or a multi-stage response and the Weibull modulus varied in a large range of 3 to 14, depending on the ceramic type and on the applied load. Interconnections between pores formed a network of possible failures under the stress field, resulting in a change of Weibull plots. Reducing the grain size range and the pore interconnectivity led to a reduced strength distribution. The flaw size range had a unimodal distribution for sample G5 with homogeneous microstructure and correspondingly a Weibull modulus m=9.79. © 2019 Associacao Brasileira de Ceramica. All rights reserved.As propriedades mecânicas das cerâmicas de argila-talco contendo 0 a 10% em massa de talco sinterizadas a 1100 °C foram obtidas por medidas de flexão. Com o valor médio de resistência à flexão de 23,1 MPa, a amostra com 5% de talco (G5) foi a mais forte e apresentou o menor valor de poro interconectado (64%). A dispersão dos valores de resistência foi descrita com o modelo de distribuição de Weibull. Para todas as amostras, os gráficos de Weibull mostraram um comportamento típico linear ou uma resposta de múltiplos estágios e o módulo de Weibull variou em uma ampla faixa de 3 a 14, dependendo do tipo de cerâmica e da carga aplicada. Interconexões entre poros formaram uma rede de possíveis falhas sob o campo de tensão, resultando em uma mudança nos gráficos de Weibull. Reduções da faixa de tamanho dos grãos e da interconectividade dos poros levaram a uma redução na distribuição da resistência. A faixa de tamanho de defeito apresentou uma distribuição unimodal para a amostra G5 com microestrutura homogênea e correspondentemente um módulo de Weibull m=9,79

Cocoa Cortex Ashes as Fluxing Additive for Vitrified Ceramic Making from Alluvial Clay

International audienc

Contribution à la caractérisation et à la valorisation des argiles de Centrafrique (RCA) dans le domaine de la céramique

International audienc

Thermal behaviour and microstructural evolution of metakaolin and meta-halloysite-based geopolymer binders: a comparative study

Two calcined clays (halloysite and kaolinite clays at 700 °C) were used as solid precursors for geopolymer synthesis. This study compares the physicochemical properties of the both resulting geopolymer series heated at 200, 400, 600 and 800 °C. The end specimens were characterized using Optical Dilatometer, XRD, FTIR, MIP and SEM analyses. Results revealed that the flexural strengths were 18.10 and 21.74 MPa for meta-halloysite- and metakaolin-based geopolymers, respectively. After subjected to high temperatures, the flexural strength drastically decreased from 18.10 ± 1.06 to 6.7 ± 0.23 MPa and 21.74 ± 1.20 to 4.63 ± 0.24 MPa, respectively. The maximum shrinkage recorded on metakaolin and meta-halloysite-based geopolymers was 14 and 16% around 950 °C, respectively. The thermal conductivities decreased with increase in heating temperature from 0.78 to 0.19 Wm−1 K−1 and 0.96 to 0.26 Wm−1 K−1, respectively. This reduction is linked to the additional voids and microcracks that occurred within the geopolymer network. The cumulative intrusion in both geopolymers increased with increase in heating temperature up to 600 °C, leading to the degradation of geopolymer network that affected the mechanical strength evolution. Both synthesized geopolymer series are potential candidates for insulation materials or refractory applications