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Abstract  

New 40 vol%[(Cu)–Ni]–YSZ cermet materials processed by mechanical alloying (MA) of the row powders are prepared. The powder compacts are sintered in air, hydrogen and inert (argon) atmospheres at a dilatometer and tubular furnace up to 1,350 °C. Sintering by activated surface concept (SAS) can anticipate and enhance the densification in such powders. Stepwise isothermal dilatometry (SID) sintering kinetics study is performed allowing determining kinetic parameters for Ni–YSZ and Ni–Cu–YSZ pellets. Two-steps sintering processes is indicated while Cu-bearing material features the smallest activation energy for sintering. The allied MA–SAS method is a promising route to prepare SOFC fuel cell anode materials.

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Abstract  

Thermal analysis was done to determine the temperatures of thermal reactions, phase transformations or melting reaction during continuous heating. These reactions are a direct response to the steel composition and to the sintering atmosphere. Simultaneous thermal analysis TG-DTA (STA) shows up the sintering behaviour of sintered low prealloyed chromium steels and their peculiarities. Given the high oxygen affinity of chromium, graphite additions can modify their thermal reactions, and hence the sintering behaviour of the steel. Evidence is given of the effect of carbon on the sintering process and the nature of the oxides.

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Abstract  

A novel thermo-optical measuring system (TOM) is described, which is able to monitor simultaneously and in situ thermal and optical properties of materials during the process of sintering. These are thermal diffusivity, heat capacity, thermal conductivity, transfer of heat radiation and scattering of light. Additionally, the geometric shrinkage is recorded by a non-contact optical dilatometer. The system has been designed for an efficient optimization of time-temperature-atmosphere cycles in sintering processes. Therefore, in the construction of the TOM system transferability of process parameters to other sintering furnaces is an important requirement. Due to this, compromises have been necessary in the layout of the measuring methods. Nevertheless, a high resolution was achieved for the distinction of different sintering states. Besides dilatometry, thermal diffusivity measurement by a laser-flash technique is a promising tool for the in situ monitoring of changes in microstructure during sintering.

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Abstract  

The present investigation has been revealed that homogeneous silver-tungsten (Ag–W) composite powders doped with cobalt as sinter aid can be produced by the two-stage reduction of co-precipitated tungstate. The sintering of the powders has been studied using dilatometry and the results showed that the critical level for activated sintering is of the order of 0.3 mass percent cobalt with respect to the tungsten content of the compact powder. This critical level is equivalent to approximately six to seven atomic layer coverage of the tungsten particles by cobalt. The levels of cobalt addition above the critical amount leads to the formation of cobalt tungsten (CoW3) intermetallic compound precipitates, which become trapped within the silver phase in the sintered composite material. Microstructural evaluation of sintered specimens has been carried out using optical and electron microscopy. Transmission electron microscopy results revealed the neck formation between adjacent tungsten particles along with the presence of silver around the tungsten particles. Energy dispersive X-ray (EDX) analysis also confirmed that amounts of cobalt was 0.3 mass percent, in the region containing the silver at the tungsten particle interface which agreed with the level of activated sintering.

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Abstract  

An optical pyrometer is used to measure and, in conjunction with temperature programmer and controller, control the temperature of the NETSZSCH Dilatometer DIL 402 E/7 up to 2400°C. This instrument is thus suitable to investigate sintering of technical ceramic materials such as SSiC and ZrO2. Measurements carried out on these materials containing organic additives show that the sintering range of SSiC starts at 1800°C—although its final density is not reached at 2400°C at a heating rate of 20 deg·min−1—and that the densification of ZrO2 occurs between 1000° and 1800°C. Using rate controlled sintering (RCS) the sintering process can be extended on a time scale, but the same densities are obtained at the same temperatures when comparing the measurements with and without RCS.

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Abstract  

Sintering processes in the Y2O3–Al2O3–B2 O3 system and its subsystems (Y2O3–B2O3 and Al2 O3–B2O3) have been investigated by using combined DTA and XRD measurements to get a better understanding of solid state chemical changes resulting in the formation of yttrium aluminum borate (YAl3(BO3)4, YAB) phase and to study the possible role and contribution of various simple borates formed also in the former processes. Two new exothermic heat effects of YBO3 formation have been detected by DTA in the Y2O3–B2O3 system between 720 and 980C. In the Al2O3–B2O3 system a new experimental XRD profile of Al4B2O9 was observed. Formation of these borates seems to promote the nucleation of double borate YAB below 1000C. Conversion of Al4B2O9 to Al18B4 O33 was observed after a long term (10 h) sintering at 1050C. Similarly, an increased formation of YAB has been observed as a product of the sintering reaction between YBO3 and Al18B4O33 at 1150C. The two latter single borates are found to be identical with the high temperature decomposition products of YAB.

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After much improvement of a new type of RP-18 sintered plate, mobile phase could be successfully used in planar electrochromatography (PEC) without addition of buffer salts. It is very convenient to use such a mobile phase, because in so doing we save much human energy and derive new operating skills. In addition, high potential could be used with lower Joule heating. Our preliminary work revealed that a suitable degree of bonding of C18 was from 0.03 to 0.06, and good end-capping was achieved by placing the bonded sintered plate in a solution of dimethyldichlorosilane in toluene (ratio 1:100 to 1:1000) at room temperature for 20 min. If the degree of bonding was too high, the sintered plate would not work in the mobile phase without addition of buffer salts or would give bad separation results. New skills, for example high-speed wetting of the thin-layer plate and multi-electrodevelopment, are also introduced, incidentally, in this paper.

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Abstract  

Ceramic blocks with high porosity and low heat conductivity are effective tools to improve the indoor comfort level and also to reduce energy consumption. The main objective of this study was focused on the development of the porous ceramic blocks processing with different pore forming agents by adapting a German technology to the Brazilian environmental conditions. In this process, the clay mixtures are homogenized before sampling as the sintering of porous ceramic materials was about 900–1100°C. TG/DTG, DSC and coupled MS experiments were carried. The formed products have low apparent density, high porosity and reasonable mechanical strength with a good heat and acoustic insulation properties.

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Abstract  

Sintering of barium titanate by microwave heating with barium borate as a liquid-phase forming material was examined as a means of saving energy. A liquid phase was generated faster and over a wider temperature range by intermittent heating at constant power than by constant heating with variable power. When sufficient amount of the liquid-phase forming material were present, the samples were densified at temperatures below those at which the liquid-phase is normally formed. A sample containing 10 mol% of the liquid-phase forming material was densified efficiently. When too much liquid-phase forming material was present, densification of the sample was obstructed.

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Abstract  

A study of three Spanish and one Bulgarian basaltic rock demonstrated that, after thermal treatment at temperatures higher than 800C, crystallization of pyroxenes, anorthite and magnetic occurred. Following sintering of the original basalts and powdered original glasses, the same crystalline phases were nucleated and grown in the resulting glass-ceramics. Chemical and DTA/TG analyses suggested similar behaviour for the synthesized Canarian basalt glasses, which are located in the tephrite-basanite field, and different behaviour for the trachy-andesite Canarian and the basaltic-andesite Bulgarian basalt glass. In consequence of the high sensitivity of the specific heat to phase transformations, Cp(T) and TMA experiments allowed a distinction between the tephrite-basanite and trachy-andesite Canarian glasses on the basis of their different thermal behaviour.

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