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Kaolinite-Magnesite Or Kaolinite–Talc-Based Ceramics. Part II: Microstructure and the Final Properties Related Sintered Tapes

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Kaolinite-Magnesite Or Kaolinite–Talc-Based Ceramics. Part II: Microstructure and the Final Properties Related Sintered Tapes minerals Article Kaolinite-Magnesite or Kaolinite–Talc-Based Ceramics. Part II: Microstructure and the Final Properties Related Sintered Tapes Aghiles Hammas 1 , Gisèle Lecomte-Nana 2,* , Imane Daou 2, Nicolas Tessier-Doyen 2, Claire Peyratout 2 and Fatima Zibouche 1 1 Laboratoire de Traitement et Mise en Forme des Polymères Fibreux, Faculté des Sciences, Université M’Hamed Bougara Boumerdes, Boumerdes 35000, Algeria; [email protected] (A.H.); [email protected] (F.Z.) 2 Institut de Recherche sur les Céramiques (IRCER, UMRCNRS 7315), ENSIL-ENSCI, Université de Limoges, CEC, 12 rue Atlantis, CEDEX, 87068 Limoges, France; [email protected] (I.D.); [email protected] (N.T.-D.); [email protected] (C.P.) * Correspondence: [email protected] Received: 28 October 2020; Accepted: 27 November 2020; Published: 1 December 2020 Abstract: In recent decades, talc and kaolinite have been widely used as raw materials for the ceramic industry. In this study, the final characteristics of kaolinitic clay mixed with 6 mass% of magnesite obtained in our previous work were compared with those obtained with mixtures of kaolin (kaolin BIP) and talc (as the source of magnesium oxide). However, different amounts of talc in the kaolin powder were studied, namely 10, 30, and 50 mass% of added talc (with respect to kaolin + talc). The tape casting process was used during this work in order to manufacture the green tapes in an aqueous system with 0.2 mass% of dispersant. Subsequently, the green tapes were heated to 1000 and 1100 ◦C with a dwelling time of 12 min. The green and sintering tapes were characterized using the following techniques: DTA/TG, X-ray diffraction, porosity, and flexural strength analyses. The results obtained from our previous work indicate that the specimen with 6 mass% of MgCO3 sintered at 1200 ◦C for 3 h exhibited the best performances, with high flexural strength and weak porosity value—117 MPa and 27%—respectively. As results from this study, the optimal mechanical and thermal properties of sintering tapes were obtained for the specimen with 10 mass% of added talc sintered at 1100 ◦C. Indeed, this specimen exhibited 50 MPa and 43% of stress to rupture and apparent porosity, respectively. Keywords: kaolinite; talc; magnesite; tape casting; biaxial flexural strength 1. Introduction Many traditional and advanced ceramic materials are made from clay (or clay mixed with other materials) [1–4]. Indeed, the mixture of two or more clays of different composition and texture to form a paste is performed to improve the workability and firing behavior in comparison to the behavior of each single clay. Additionally, the blending of sediments with different proportions of clay and non-clay particles and/or different clay minerals is commonly used to enhance the final properties of some ceramics [5,6]. However, kaolinite and talc are both phyllosilicate minerals which present considerable interest to produce several types of ceramic materials (traditional and advances ceramics) for having certain valuable properties [7–11]. The addition of talc has positive effects on ceramic—for example, it increases the mechanical and optical properties of the ceramic material and glazes [12–14]. Kaolinite has a 1:1 sheet structure with chemical formulae Al2Si2O5(OH)4 (39.8 mass% Al2O3, 46.38 mass% SiO2, and 13.9 mass% H2O). It is a layered clay mineral consisting of the pilling up of two Minerals 2020, 10, 1080; doi:10.3390/min10121080 www.mdpi.com/journal/minerals Minerals 2020, 10, x FOR PEER REVIEW 2 of 12 Minerals 2020, 10, x FOR PEER REVIEW 2 of 12 MineralsKaolinite2020, 10, 1080has a 1:1 sheet structure with chemical formulae Al2Si2O5(OH)4 (39.8 mass% Al2 of2O 123, Kaolinite has a 1:1 sheet structure with chemical formulae Al2Si2O5(OH)4 (39.8 mass% Al2O3, 46.38 mass% SiO2, and 13.9 mass% H2O). It is a layered clay mineral consisting of the pilling up of 46.38 mass% SiO2, and 13.9 mass% H2O). It is a layered clay mineral consisting of the pilling up of two sheets—one tetrahedral sheet of silica (SiO4) joined to one octahedral sheet of alumina (AlO6) two sheets—one tetrahedral sheet of silica (SiO4) joined to one octahedral sheet of alumina (AlO6) sheets—one tetrahedral sheet of silica (SiO4) joined to one octahedral sheet of alumina (AlO6)[15–18]. [15–18].[15–18]. Indeed,Indeed, thethe morphologymorphology ofof kaolinitekaolinite mineralmineral isis plate-like.plate-like. ItsIts crystalcrystal systemsystem isis triclinictriclinic withwith aa Indeed,C1-based the space morphology group. According of kaolinite to mineral literature is plate-like.[19], the unit Its crystalcell structure system of is kaolinite triclinic with is illustrated a C1-based in C1-basedspace group. space According group. According to literature to literature [19], the unit [19], cell the structure unit cell ofstructure kaolinite of iskaolinite illustrated is illustrated in Figure1 in. FigureFigure 1.1. FigureFigure 1. 1. StructureStructure ofof kaolinitekaolinite primitiveprimitive cellcell (white,(white, hydrogen;hydrogen; redred oxygen;oxygen; pink,pink, aluminum;aluminum; yellow,yellow, yellow, silicon)silicon) [19]. [[19].19]. On thethe other other hand, hand, talc is atalc magnesium is a magnesium hydrosilicate hydrosilicate with the theoretical with formulathe theoretical 3MgO 4SiO formulaH O, On the other hand, talc is a magnesium hydrosilicate with the theoretical· formula2· 2 corresponding3MgO·4SiO2·H2 toO, 63.35corresponding mass% SiO 2to, 31.9063.35 mass% mass% MgO, SiO2 and, 31.90 4.75 mass% mass% MgO, of chemically and 4.75 bound mass% water of 3MgO·4SiO2·H2O, corresponding to 63.35 mass% SiO2, 31.90 mass% MgO, and 4.75 mass% of (hydroxide) [20]. In contrast, other minerals can be associated with talc, such as, chlorites, mica, chemicallychemically boundbound waterwater (hydroxide)(hydroxide) [20].[20]. InIn contracontrast,st, otherother mineralsminerals cancan bebe associatedassociated withwith talc,talc, actinolite, feldspars, rutile, pyrrhotite, carbonates, pyrite, magnetite, and hematite [12]. The crystalline suchsuch as,as, chlorites,chlorites, mica,mica, actinolite,actinolite, feldspars,feldspars, rutile,rutile, pyrrhotite,pyrrhotite, carbonates,carbonates, pyrite,pyrite, magnetite,magnetite, andand structure of talc has a 2:1 or TOT layer type with one octahedral (O) magnesium layer sandwiched hematitehematite [12].[12]. TheThe crystallinecrystalline structurestructure ofof talctalc hahass aa 2:12:1 oror TOTTOT layerlayer typetype withwith oneone octahedraloctahedral (O)(O) between two tetrahedral silica layers (Figure2)[21]. magnesiummagnesium layerlayer sandwichedsandwiched betweenbetween twotwo tetetrahedraltrahedral silicasilica layerslayers (Figure(Figure 2)2) [21].[21]. Figure 2. Schematic representation of the talc structures. FigureFigure 2.2. SchematicSchematic representationrepresentation ofof thethe talctalc structures.structures. In our previous work [1,17], the effect of magnesite amount on the different properties of kaolinitic InIn ourour previousprevious workwork [1,17],[1,17], thethe effecteffect ofof mamagnesitegnesite amountamount onon thethe didifferentfferent propertiesproperties ofof clay ceramics was studied. However, in this study, we aimed to compare the final characteristics of the kaolinitickaolinitic clayclay ceramicsceramics waswas studied.studied. However,However, inin thisthis study,study, wewe aimedaimed toto comparecompare thethe finalfinal kaolinitic clay from Algeria (KT2) mixed with 6 mass% of magnesite, with those resulting from the use characteristicscharacteristics ofof thethe kaolinitickaolinitic clayclay fromfrom AlgeriaAlgeria (KT2)(KT2) mixedmixed withwith 66 mass%mass% ofof magnesite,magnesite, withwith thosethose of a commercial kaolin (kaolin BIP) mixed with talc (as the source of magnesium oxide). Several mass resultingresulting fromfrom thethe useuse ofof aa commercialcommercial kaolinkaolin (kaolin(kaolin BIP)BIP) mixedmixed withwith talctalc (as(as thethe sourcesource ofof contents of talc in the kaolin powder were investigated—10, 20, 30, 40, and 50 mass% of added talc. magnesiummagnesium oxide).oxide). SeveralSeveral massmass contentscontents ofof talctalc inin thethe kaolinkaolin powderpowder werewere investigated—10,investigated—10, 20,20, 30,30, In a former paper, we suggested a firing temperature of up to 1200 C, but the use of talc (melting of 40,40, andand 5050 mass%mass% ofof addedadded talc.talc. InIn aa formerformer paper,paper, wewe suggestedsuggested aa◦ firingfiring temperaturetemperature ofof upup toto 12001200 samples) did not allow performing heat treatments above 1100 C. The structural changes (XRD, SEM), °C,°C, butbut thethe useuse ofof talctalc (melting(melting ofof samples)samples) diddid notnot allowallow performingperforming◦ heatheat treatmentstreatments aboveabove 11001100 °C.°C. the mechanical, and thermal properties of the manufactured samples using tape casting were analyzed before and after sintering at 1000 and 1100 ◦C. Minerals 2020, 10, 1080 3 of 12 2. Materials and Methods 2.1. Raw Materials In the present study, two kaolins were used: kaolinitic clay KT2 from Algeria (Tamazert, El Milia, Jijel, Algeria) and a commercial kaolin noted kaolin BIP the kaolin (Kaolin de Beauvoir, Imerys Limoges, France). The magnesite and the talc were provided by x and y, respectively. The chemical compositions of these raw materials are shown in Table1. In this study, the kaolin KT2 was mixed with magnesite (KxMy), and kaolin BIP was mixed with talc (KxTy);
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