Composition and Technological Properties of Clays for Structural Ceramics in Limpopo (South Africa)

This study evaluated the potential of raw clays from the Mukondeni region for structural ceramics and pottery based on traditional firing techniques. Physical properties were identified by particle size distribution, consistency limits, and clay activity. Mineralogical and chemical properties were investigated by X-ray diffraction (XRD) and X-ray fluorescence (XRF). Extruded clay bodies were fired at 900 °C. Technological characteristics were measured by weight loss (WL), bulk density (BD), dry linear shrinkage (DLS), fired linear shrinkage (FLS), water absorption (WA), and flexural strength (FS). The clays were low in <2 µm fractions (≤19%) and of medium to high plasticity with a clayey silt texture. Smectite was the dominant clay mineral while quartz and feldspar were major non clay minerals. The most abundant oxides were SiO2 (63.57–68.73%), Al2O3 (13.9–15.61%), and Fe2O3 (4.86–6.18%), whereas K2O, CaO, MgO, Na2O, TiO2, and P2O5 were depleted. Characterization based on the clay workability chart, Winkler’s diagram, and compositional ternary diagrams revealed acceptable extrusion properties and suitability for structural ceramics and earthenware. The clays showed acceptable WL, BD, LS, and WA, but unsatisfactory FS (≤1.08 MPa). Low mechanical strength was attributed to presence of smectites and inert nature of feldspar at 900 °C. Beneficiation through mixing with carbonate-rich raw materials is recommended.

Middle Bronze Age Pottery Kilns at Şaraga Höyük

As a result of archeological research conducted on prehistoric and protohistoric periods in Anatolia a limited number of ceramic kilns were found. Therefore, two kilns, which have been found during the 2003 excavation season in Saraga Hoyuk and which belong to MBA II, are of great importance because they provide information regarding the ceramic production technology in the 2nd millennium B.C. One of these kilns is of big (Kiln 1) and the other is of small (Kiln 2) size. The both kilns show the similar work systems but both of them show same different features as the typologically. The kilns consist two chambers, in which the combustion and firing chambers. The kilns have heat transmission duct for the transfering of heat between combustion and firing chambers. Kiln 1 was used for firing of big size vessels and Kiln 2 for small size vessels. A few Middle Bronze Age pottery kiln were found in Southeast Anatolia and culturally related neighboring regions. Although, when we look Bronze and before age pottery kilns, we can say no radical shift has been empirically observed in the pottery firing techniques in the region. Kilns of Saraga Hoyuk proved that grooved rim ceramic group found along the Euphrates Valley has been produced locally at Saraga Hoyuk. The Middle Bronze Age level of Şaraga Höyük yielded material evidence for all stages of ceramic production at the site, including rotary stone, lumps of unbaked clay, pottery kilns of small and large sizes, scatters of ceramic wasters concentrated around the kilns, as well as intact ceramic vessels found in situ in the kilns.

Mechanical Strength and Interface Adhesion of a Solid Oxide Fuel Cell with Doped Ceria Electrolyte

An SOFC must have sufficient mechanical strength and interface adhesion to ensure it can be handled without breakage during fabrication and assembly, and has desired performance and reliability. Methods for measuring mechanical properties and interface adhesion of an SOFC have been developed and measurements made on a cermet-supported SOFC with a SDC electrolyte. The SOFC evaluated had a porous NiO-YSZ substrate, a porous NiO-SDC anode and a dense SDC electrolyte fabricated using tape-casting, screen-printing and co-firing techniques. The flexural strength and interface adhesion of the substrate, the anode and the electrolyte, along with their Young’s modulus, hardness and residual stress, were quantitatively measured. The results of the measurements indicate that the NiO-YSZ supported, SDC electrolyte SOFC has adequate mechanical strength and sufficient interface adhesion.

Surface treatment of Neolithic vessels from Macedonia and Thrace

This article examines the methods of surface treatment of the Neolithic vessels from northern Greece. The work is based on the study of a large sample of ceramics, covering the whole span of the Neolithic, from Macedonia and Thrace. Macroscopic study of the material was complemented by microscopic examination (SEM and petrographic analysis) and retiring tests. The results are compared with data from other technological analyses of Neolithic vessels from northern Greece. Apart from identifying, in some cases for the first time, methods of surface treatment and materials used by the potters of these regions, the present study considers the changes in surface treatment and firing techniques through time.