Abstract: Porous refractory ceramics combine the high thermomechanical and chemical resistances of oxide-based compounds with the low thermal conductivity and specific heat of porous materials. This two-part study is devoted to understanding and critically reviewing their outstanding behavior as thermal insulators for high-temperature industrial processes (200-2000 °C). The first part (Interceram, v. 70, n. 03, 2021, p. 38-45, "The Science Behind Energy Saving") provided a compilation of updated information on thermal energy consumption per area of human activity and examples of industrial processes that occur in each temperature range. This second part presents classification criteria for insulators established according to their thermomechanical properties, installation method, microstructure, and temperature at use, analyses of some important grades of porous insulators, and the most common causes of premature failure.
Abstract: The aim of the project was to develop a variothermal tool technology using innovative SiC ceramics in order to optimize the production of thermoplastic fiber composites. The development focused on a new, innovative tool design, the production of the ceramics with integrated cooling channels and intrinsic heating by means of ceramic heating elements, as well as the use of the tools for processing fiber composites. By the end of the project, it should be possible to produce thermoplastically reinforced fiber composite components that cannot be manufactured more cost-effectively using any other process because of their complex structure and geometry.
Interceram: Could you give us some background on the CERANEA project? Csaba Balázsi: The project is a cooperative venture concerning the development of multi-layer ceramics, which could be high temperature ceramics or bioceramics, and we are concentrating on having different types of what we call “functionally graded materials (FGMs)”. These are sandwich structures made of several functional layers. This involves a broad group of researchers in Hungary, Germany and Slovakia in this ERA funded project, under the main working title “Multi-Functional Ceramic Graphene Coatings for New Emerging Applications”. I lead the project but we initiated this program with partners. The Eötvös Loránd Research Network at the Centre for Energy Research (ELKH-CER) here in Budapest functions as the main preparatory laboratory. Our colleagues at Fraunhofer IKTS and the Slovakian Academy of Science are principally involved in the characterization role. We are dealing with different aspects such as manufacturing processes, how these ceramics can be made by various preparation techniques and then different sintering techniques. We address options that are the most convenient and most affordable for research and also for the industry.
Abstract: In the field of additive manufacturing, ceramic materials have become increasingly popular in recent years. One of the most important applications is the individualized production of molds for investment casting, which enables the economic production of geometrically complex cast components even for low quantities. A ceramic-filled resin for the stereolithographic production of investment casting molds was developed from commercially available materials and established for the extended process chain of investment casting. This, in combination with commercially available stereolithography technology in the low-price segment, forms a promising approach to the cost-effective production of individualized ceramic molds for investment casting.
Abstract: By using Glatt's powder synthesis technology and the associated spray drying and calcination processes, new opportunities in raw material production have been explored. In this article, the inherent potential of barium strontium cobalt iron oxide (BSCF), doped and coated zirconium dioxide is described.
Abstract: In this article, the manufacturing of Al2O3ceramics by 3D printing through different methods of material extrusion is investigated in terms of porosity, density and flexural strength. The methods of cold plastic material extrusion with pastes and thermoplastic material extrusion with filament and with granules are compared. It can be shown that significant differences result with regard to the physical properties investigated, which can be attributed to the processes used, to the specific machines and the starting materials.
Abstract: Reduction of the carbon footprint in human activities is an urgent concern, and the use of thermal insulators for preventing undesirable heat exchange and saving energy is a growing trend in industrial processes. Refractory porous ceramics offer a useful combination of high thermo-mechanical and chemical resistances of oxide-based compounds with the low thermal conductivity of porous materials. This three-part study is devoted to understanding and critically reviewing their outstanding behavior as high-temperature thermal insulators (200-2000 °C), from conventional and well-known materials to state-of-art developments. This third part highlights novel compositions, microstructures, and processes (fully developed or at the initial research stage) for high-and-ultra-high-temperature insulation, focusing on microporous refractory ceramics (µPRC).
Abstract: This study focuses on the influences of the fine particle fraction and the minimum particle size on the density, the shrinkage, the Young's modulus E, and the anisotropies of shrinkage and E. A lower minimum particle size and a higher fines content improved the particle packing, lubrication and sintering densification resulting in higher densities and E. Presumably due to a lower-density neutral zone after pressing, the anisotropic shrinkage was higher in the pressing direction, improving the density homogeneity. For the Young's modulus, the extent of the anisotropy increased mainly with a higher sintering capability (high fines content). Especially the core as a part of the neutral zone had a lower E. Exemplary density and open porosity distributions revealed that flaws formed in the core, which led to the lower E. The pressure distribution during uniaxial pressing leads to a density distribution and, finally, to a flaw density or flaw size distribution after sintering.
Abstract: Regarding corrosion-resistant crucibles and shell molds for titanium investment casting, recent research focused on suitable materials based on calcium zirconate (CaZrO3) and novel technologies, such as spray coating. Complex cast parts of Ti6Al4V without a hard and brittle alpha-case layer were successfully produced. This overview also shows current trends, for example shell mold recycling and advanced technologies for microstructure functionalization such as flame spraying and electrospinning.
Abstract: Silica bricks with cemented silica and crystalline silica as raw materials show different properties. In this paper, the phase and structural characteristics of different kinds of silica raw materials and silica bricks after heat treatment at different temperatures are explored by the means of XRD, SEM and CT, and the formation mechanism of tridymite in the silica bricks is clarified. Results show that the liquid phase formed by impurities in both crystalline silica and cemented silica raw material cannot promote the transformation of quartz to tridymite at high temperatures. The phase composition of both cemented silica and crystalline silica after heat treatment at 1460 and 1550 °C is cristobalite.
Abstract: Ceramics for tableware and sanitaryware are shaped by slip casting. The proliferation of bacterial and fungal microorganisms occurs during the storage of the slips and disturbs their properties, which leads to defects in the final products. This work aims to characterize the microbiological efficiency of several biocides and to evaluate their impact on the rheology and the quality of the final products. The results of the study highlight the microbiological efficiency and the potential rheological disturbance on slips and glaze compositions. The study seeks a better understanding of the interaction mechanisms between biocides and ceramics, as well as a more efficient and adapted use of those substances.
Abstract: In Germany, more and more electricity is being generated from renewable energy sources, resulting in an ever greater need for reliable power storage devices. The focus is shifting increasingly towards green hydrogen, which is now a key element of energy policy. The layout of the hydrogen economy is triggering a cascade of developments. Energy-intensive industrial processes are changing, but every innovative technology can only ever be as good as the ceramic materials used in it.
Abstract: Clays are irreplaceable raw materials for ceramic processing. The availability of clay deposits of suitable quality and quantity is an important competitive factor and a key issue for the economic sustainability of ceramic production. The identification of adequate sources of clay materials is an important issue that requires an appropriate methodological approach. In the form of simple guidelines, this articles reports on how to conduct clay prospecting and evaluate the technological properties of raw materials. The first part described the deposits of different types of ceramic clays, illustrating their origin, composition and geological criteria in the prospection. This second part introduces the technological evaluation of clay materials and describes the four steps to follow in clay prospecting in detail.
