International Journal of Ceramic Engineering & Science最新文献

Li-ion solid-state batteries have the potential for high energy densities and improved safety. Oxidic all solid-state batteries require co-sintering of the Li-ion conductive solid electrolyte, the active electrode material, and an electronic conductive additive to give a composite electrode. A first step for the realization of this complex system is the study of the sintering behavior of the active material itself as a single-phase component and to investigate the electrochemical activity as well as the electronic properties after heat treatment. In this study monolithic NCM622 cathodes with a thickness of about 90 μm were sintered at temperatures up to 900°C by using a low-melting glass as sintering additive. For these ceramic cathodes sintered at T = 800°C, an electronic conductivity of 3.0 × 10^–3 S cm^–1 and six orders of magnitude lower Li-ion conductivity of about 10^–9 S cm^–1 were determined by DC conductivity measurement. To investigate the electrochemical performance of the sintered cathode material, the porous microstructure was infiltrated with liquid electrolyte and a charging capacity of 140 mAh g^–1 (92% of the theoretical capacity) was measured with C/50 cycling rate. In comparison, the electrochemical performance without infiltration of a Li-ion conductive liquid was tested with polyethylene oxide as polymeric separator. With these measurements the ability of the sintered cathode to charge/discharge as well as to provide sufficient high electronic conductivity has been demonstrated.

This document summarizes key research directions as they emerged during the proceedings of the Inaugural Orton Workshop that aimed to define scientific areas of current interest to the ceramics community around the theme of: “High Temperature Ceramics and Composites for Extreme Environments.” The topic was selected due to the timely interest in such materials to meet the needs of hypersonic aviation and space exploration and habitation. Experts from funding agencies supporting ceramics research, thought-leaders from academia with expertise spanning materials processing, characterization, and modeling, as well as research and development leaders from key (aviation-related) industries, gathered to evaluate the state-of-the-art in this field and to address key questions with the intent of accelerating research and development efforts on all fronts. Highlights of the work presented and of the discussion and brainstorming sessions are provided here. It was the purpose of the organizers (The Orton Ceramic Foundation and the Orton Chair in Ceramic Engineering at OSU) to establish this event as a service to the Ceramics community in the spirit the founder of the field of Ceramic Engineering, Dr. Edward Orton Jr.

Geopolymer refers to a large group of nanoporous, nanoparticulate materials that are synthesized by dissolution and polycondensation of aluminosilicates in basic solutions and can be made from a variety of starting materials, such as industrial waste ash, volcanic rock, or calcined clay. Geopolymers are X-ray amorphous, corrosion resistant, refractory, and made at ambient temperature and pressure similar to cements. In this study, potassium metakaolin-based geopolymer (KGP) composites containing alumina platelets and glass frit were fabricated, and the impact of heating temperature, dwell time, and heating/cooling rate on the microstructure was studied. The composites, heat treated up to 900°C for up to 20 h using heating/cooling rates of up to 1°C/min, showed that the addition of alumina platelets prevented major microcracking and was also able to reduce linear shrinkage. Glass frit has been shown to heal microcracks formed during KGP dehydration and crystallization. The resulting material had an open porosity of less than 1% and a uniform surface glaze of 250 μm thickness, while Oswald ripening of round closed pores occurred due to the migration of molten glass in the system.

Three crystalline SiC fibers were studied: Tyranno, Hi-Nicalon, and Sylramic. Thermodynamic stability of the SiC fibers was determined by high temperature oxide melt solution calorimetry. Results shed light on the thermodynamic penalty or benefit associated with microstructural modification of the ceramic fibers, and how energetics correlate to mechanical properties. Enthalpies of formation from components (SiC, SiO₂, Si₃N₄, and C, ∆H°_f,comp) for Tyranno, Hi-Nicalon, and Sylramic are −12.05 ± 8.71, −58.75 ± 6.93, and −71.10 ± 8.71 kJ/mol Si, respectively. The microstructure in Sylramic offers the greatest stabilizing effect, thus resulting in its much more exothermic enthalpy of formation relative to elements and crystalline components. In contrast, the microstructure in Tyranno offers the least stabilization. The thermodynamic stability of the fibers increases with increasing mixed bonding (Si bonded to both C and O). From mechanical testing, Young's moduli of Tyranno, Hi-Nicalon, and Sylramic are 112, 205, and 215 GPa, respectively. Greater thermodynamic stability is correlated with a higher Young's modulus.

Shogo Hayashi, Tomoki Kobayashi, Shota Sakai, Noritaka Saito, Kunihiko Nakashima. Effects of temperature and humidity on adhesion of water scale to glass substrates. International Journal of Ceramic Engineering & Science, 3(5), 204–210. https://doi.org/10.1002/ces2.10099

Note that this is a change in the unit of the vertical axis of the graph and does not affect the general shape of the graph. Thus, it is not expected to affect the main discussion in the paper.

Preferred orientation in polycrystalline materials is one of the most challenging problems for structural analysis. Significant preferred orientation can severely affect the structure-property analysis of the systems having substantial crystallographic anisotropy. Here, an extremely high degree of preferred orientation has been demonstrated in R-block hollandite hexagonal PbFe_xV_6−xO₁₁ compounds, which has recently been shown to exhibit an unusual colossal electroresistance response that has a strong dependence on structural modifications. The present results warn against possible errors in understanding the evolution of the crystal structure of these hollandites, which might adversely affect the estimation of the influence of the same on their spectacular physical properties.

High-tech ceramics are typically engineered by controlling point defects and interfaces while one-dimensional dislocations have found much less attention so far. Nevertheless, their impact on almost any functional property and the sudden ease to fabricate them with novel synthesis methods, such as rapid densification, brings spotlight attention to dislocations as design dimension. Although the typical brittleness of ceramics insinuates the irrelevance of dislocations for mechanical behavior, abundant literature is spread over materials, decades, and disciplines, however, often unconnected. Here, a conceptual framework for dislocation mechanics in ceramics separated into five logical aspects, (1) fundamental mobility, (2) obstacles to motion, (3) limitation by necessity of nucleation, (4) motion complexity, and (5) avoidance of competing mechanisms, brings oversight into the complex behavior. In consequence, quicker identification of the limiting step allows to estimate the potential involved more precisely and to identify open research questions with greater ease. An introduction to dislocations and the functionality involved, a look back over the last six decades, and highlights of open question are dedicated to provide a framework and bridge the gap between the attached research fields.

Fused cast alumina (FCA) has been and continues to be used as a refractory material in energy intensive industries such as glass melting and chemical processing. In-service degradation due to high temperature exposure in harsh environment affects the designed furnace thermal profiles and energy consumption. Phase transformation may occur at the refractory hot face during glass melting altering the properties. Three FCA blocks recovered from industrial furnaces were investigated in this study. The as-received FCA consists primarily of a mixture of alpha (α) and beta (β) alumina that has a thermal conductivity value of 5–6 W/mK. The Hot Disk method was used to obtain thermal conductivity directly on the refractory blocks. At the hot face, a transformation from β to α alumina occurred and was confirmed by an X-ray diffraction study. Thermal conductivity measurements as a function of position also showed a clear transition from β to α alumina at both ends of a complete block with no voids. Thermal conductivity of the α alumina tripled compared to β alumina. This study provides important information of heat transfer and thermal conductivity evolution to refractory manufacturers and users.

In long run, the ceramic industry's environmental footprint is a serious issue for its survival. This study focused on the substitution of clay (kaolin) by incinerated bottom ash, which is generated from reppi waste to energy power plants for ceramic wall tile production. Dry pressed ceramic wall tile samples were prepared by adding bottom ash from 0 to 60 wt% with clay (kaolin). The sample was analyzed after sintered at 1110°C for the residence time of 45 min by testing water absorption, breaking strength, and flexural strength. The water absorption is greater than 10%, and higher flexural strength of 24.83 MPa was obtained for the clay with 30 wt% incinerated bottom ash addition. Encouraging test result has been obtained on using up to 30% of incineration bottom ash in the manufacturing of dry pressed ceramic wall tile to substitute clay (kaolin).

A computational simulation for sintering based on the Monte Carlo (MC) method implemented with a virtual spring was developed to predict the shrinkage and deformation of compacts. Conventional MC models do not sufficiently consider the local strain of the cells. The proposed model considered the local strain using a virtual spring in each cell. The model linked with the finite element method enables direct calculation of the deformation of the powder compacts. The results indicate that the distortion tendency of the simulations agreed with the experimental results of the sintering of Al₂O₃ powder compacts. Furthermore, the results indicate the potential of the model to predict the stress distribution in a microstructure during sintering.