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1.
Kassoum Barry Gisèle Laure Lecomte-Nana Mohamed Seynou Michael Faucher Philippe Blanchart Claire Peyratout 《International Journal of Applied Ceramic Technology》2022,19(6):3084-3098
Silicate ceramics were shaped using tape casting (TC) and freeze tape casting (FTC) processes from three clays labeled HCR, KORS, and KCR. These clays exhibited mass content of 77% halloysite–10 Å, 29% kaolinite, and 98% kaolinite minerals, respectively. After casting the slurries, the dried tapes were sintered at 1200°C. The microstructure changes were characterized before and after sintering using scanning electron microscopy. The apparent porosity of TC samples was lower (36–47 vol.%) compared to values obtained with FTC samples (67–79 vol.%). The latter samples exhibited a highly textured porosity, with micron-sized pores aligned perpendicular to the tape surfaces. Upon sintering, the porosity of TC samples tended to decrease conversely to the case of FTC samples. Such behavior seemed related to the simultaneous effect of organic additives and ice templating. Consequently, the FTC samples showed a relatively low mechanical strength of 3–7 MPa and thermal conductivity of .14– .22 W m−1 K−1. After sintering, the mullite crystallization contributed to strengthen the bulk materials, helping to compensate for the detrimental effect of porosity on the stress to rupture and on thermal conductivity values. 相似文献
2.
Gisèle Boiteux Pascal Dublineau Michel Feve Christophe Mathieu Gérard Seytre Jacek Ulanski 《Polymer Bulletin》1993,30(4):441-447
Summary The curing of different epoxy-amine model systems which present only gelification and/or vitrification processes has been followed with the evolution of their viscoelastic and electrical behaviours during the network formation. Some attempts are performed to correlate the significant evolution of the mechanical and electrical parameters with the physico-chemical changes of these well defined chemical systems during their hardening and complete curing. 相似文献
3.
Gisèle Laure Lecomte Jean Pierre Bonnet Philippe Blanchart 《Journal of Materials Science》2007,42(20):8745-8752
Global thermal transformation of kaolinite–muscovite mixtures containing at most 25 mass % of muscovite was studied up to
1,100 °C. Quantitative and qualitative DTA analysis reveals a great intereaction between the two phylosilicates above 900 °C,
which is characterized by an enhancement of spinodal demixion contribution during the structural reorganization of metakaolinite.
The corresponding enthalpy variation are respectively −32 ± 1 kJ/mol and −15 ± 1 kJ/mol of kaolinite for pure kaolinite and
for the mixture containing 15 mass % of muscovite. This interaction is mainly correlated with the diffusion of potassium ions
from muscovite platelets into metakaolinite structure. The resulting consequence is an enhancement of mullite crystallization
and grain growth at 1,050 °C (earlier than in the case of pure kaolinite mineral). 相似文献
4.
Adriane S. Gruber Gisèle Boiteux Roberto F. de Souza Michèle O. de Souza 《Polymer Bulletin》2002,47(6):529-537
Summary
Phenylacetylene (PhA) is polymerized by the dicationic nickel complex Ni(MeCN)6(BF4)2 associated with AlEt2Cl as co-catalyst. The production of 200g of polymer per gram of nickel per hour represents a typical activity of this system.
Under our experimental conditions, the polymer displays an exclusive trans structure. The molecular weight distribution of the polymer is polymodal (5000 g.mol−1 and 200 g.mol−1). The highest average molecular weight fraction (5000 g. mol−1) represents the highest published value for polyphenylacetylene (PPA) where a nickel catalyst is employed. The electrical
conductivities vary between 10−7 and 10−16 S.cm−1, and are characteristic of a semi-conductor polymer. Equivalent values are cited in the literature only in the case of doped
PPA. Experimental observations enabled us to propose a mechanism for the formation of the active species through the reaction
of Ni(MeCN)6(BF4)2 with AlEt2Cl.
Received: 13 September 2001/Revised version: 10 January 2002/ Accepted: 11 January 2002 相似文献
5.
Mohammad Jouni David Djurado Valérie Massardier Gisèle Boiteux 《Polymer International》2017,66(9):1237-1251
In this review we present the results of our literature investigation into the electrical and thermal properties of carbon nanotube polymer composites. A short selection of data relating to conductive polymer composites with various fillers is provided for comparison. The effects of filler properties such as type and size, the use of hybrid fillers, fabrication methods for polymer composites and the importance of the modeling of the electronic and thermal transport mechanisms are discussed, as are more general factors influencing the properties of these composites. This review represents a comprehensive survey and constructive study and should serve as a useful reference tool for industrial and academic researchers working in this field. © 2017 Society of Chemical Industry 相似文献
6.
Rosellyne Serewane Deramne Gisèle Laure Lecomte-Nana Claire Peyratout Benoit Naït-Ali Gado Tchangbedji 《International Journal of Applied Ceramic Technology》2020,17(6):2638-2648
The present study aimed at using plant waste (Musa Paradisiaca) for manufacturing clay-based ceramics in order to promote lower sintering temperature while preserving the properties of use. Two kaolinic-illitic clays (NZ1 and KO) from Central African Republic were used mixed with 1 to 10 mass% of the plant waste (MP). The clays and the waste exhibited accessory phases: quartz and iron oxides, and K2O respectively. MP was collected, dried and sieved (<100 μm) previously to its mixture with clays. According to the sintering behavior of KO and NZ1 derived from thermodilatometry, the densification was obtained after firing at 1200°C. Results showed that open porosity decreased from 35% to 17% with increasing temperature in the range 900 to 1200°C for KO and NZ1. This porosity remained in the range 30%-40% while increasing the MP content (firing at 1000°C for 1h.). The optimized MP content was 3 and 5 mass% for KO and NZ1 clay materials respectively. The compressive strength and thermal conductivities were improved compared to clay samples without MP fired at 1200°C. Moreover a significant decrease in the sintering temperature was achieved, leading to energy saving in line with sustainability issues. 相似文献
7.
Gisèle Lecomte-Nana Amina Mokrani Nicolas Tessier-Doyen Kévin Boussois Hervé Goure-Doubi 《Ceramics International》2013,39(8):9047-9053
The present work aimed to investigate the processing of textural clay based materials using tape casting together with freezing. Two model raw materials were used, namely: BIP kaolin from France and ABM montmorillonite from Mediterranean region. The mixtures of both clays were studied, whereby, the amount of montmorillonite was 0, 5, 10, 20 or 50 mass%. After tape casting, the as-obtained green bands were frozen into liquid nitrogen, lyophilized and then fired at 1050 °C or 1200 °C.The amount of montmorillonite appeared as a critical parameter that controls the cohesion of the dry products. For montmorillonite content ≥20 mass%, the products exhibited multiple cracks after lyophilisation. With lower montmorillonite content, the cohesion of the dry products was satisfactorily and a macroscopic cross-linked surface texturation was observed. After calcination at 1050 °C or 1200 °C, the texturation appeared well defined. Moreover, calcination at 1200 °C increased the densification of products and the occurrence of a glassy phase was noted.The combination of both tape casting and freezing (freeze tape casting) is a promising way to develop various clay-based and composites materials exhibiting unique microstructure organization and characteristics with potential application in the field sustainable and environmentally friendly filtration, adsorption or catalysis. 相似文献
8.
9.
Aghiles Hammas Gisèle Lecomte-Nana Imane Daou Fatima Zibouche 《International Journal of Applied Ceramic Technology》2020,17(5):2265-2276
The present work aims at studying the effect of the sintering temperature and magnesite addition on the structure and final properties of silicate ceramics tapes. A kaolinitic clay from Algeria was selected and mixed with different magnesite contents (≤12 mass%). Tape casting process was used to produce the green tapes in an aqueous system with optimized amount of surfactants. The green tapes were fired from 1000°C to 1200°C using a dwelling time of 30 minutes. The effect of the dwelling time was investigated for a firing temperature of 1200°C namely: 30 minutes, 1 hour 30 minutes and 3 hours for samples with 6 and 12 mass% of magnesite. Regarding firing conditions, crystalline phases, thermal conductivity, porosity, and flexural strength were analyzed. The results showed that increasing the sintering temperature to 1200°C tended to significantly decrease the total porosity of samples, which led to the improvement of the stress to rupture values. Specimens with 6 and 12 mass% sintered during 3 hours exhibited highest stress to rupture values (≈117 MPa) and lowest thermal conductivity (<0.2 W.m−1.K−1) and moderate open porosity (27%). The as-obtained ceramics appeared promising for further utilization in refractory industry, thanks to the presence of both cordierite and mullite phases. 相似文献
10.
Maple sap processing and microbial contamination are significant aspects that affect maple syrup quality. In this study, two sample sets from 2005 and 2008 were used to assess the maple syrup quality variation and its relationship to microbial populations, with respect to processing, production site and harvesting period. The abundance of maple sap predominant bacteria (Pseudomonas fluorescens group and two subgroups, Rahnella spp., Janthinobacterium spp., Leuconostoc mesenteroides) and yeast (Mrakia spp., Mrakiella spp.,Guehomyces pullulans) was assessed by quantitative PCR. Maple syrup properties were analyzed by physicochemical and sensorial methods. Results indicate that P. fluorescens, Mrakia spp., Mrakiella spp. G. pullulans and Rahnella spp. are stable contaminants of maple sap, as they were found for every production site throughout the flow period. Multiple factor analysis reports a link between the relative abundance of P. fluorescens group and Mrakia spp. in maple sap with maple and vanilla odor as well as flavor of maple syrup. This evidence supports the contribution of these microorganisms or a consortium of predominant microbial contaminants to the characteristic properties of maple syrup. 相似文献