زینترینگ سرامیک های Nd:YAG شفاف تحت اتمسفر اکسیژن

Sintering of transparent Nd:YAG ceramics in oxygen atmosphere 

زینترینگ سرامیک های Nd:YAG شفاف تحت اتمسفر اکسیژن

ABSTRACT

Yttrium aluminum garnet (YAG) transparent ceramics were fabricated by sintering at oxygen atmosphere. Tetraethyl orthosilicate (TEOS) was added as the sintering additive to control the grain growth and densification. Pores were eliminated clearly at temperature lower than 1700 °C, while grain size was around 3 μm. The in-line transmittance was 80% at 1064 nm when samples were sintered at 1710 °C. The effect of TEOS was studied in oxygen atmosphere sintering for Nd:YAG transparent ceramics. At higher temperature like 1710 °C, the grain growth mechanism was solute drag, while at 1630 and 1550 °C the grain growth was controlled by liquid phase sintering mechanism. And 0.5 wt.% TEOS was the best adding content for Nd:YAG sintered in oxygen atmosphere.

 

رفتار زینترینگ و مقاومت هیدروژنی دولومیت واکنشی

Sintering, consolidation, reaction and crystal growth by

the spark plasma system (SPS)

رفتار زینترینگ و مقاومت هیدروژنی دولومیت واکنشی

ABSTRACT

Sintering of raw dolomite and hydroxides derived from dolomite was carried out in the temperature range 1350–1650 °C. The hydroxide derived from dolomite was developed through pre-calcination of dolomite followed by its hydration. For hydroxide development, after precalcination one sample was air-quenched and the other powder was furnace cooled before hydration. The air quenched samples showed better densification than that of the furnace cooling process at the same temperature. Fe2O3 addition enhances sintering by liquid formation at higher temperature. The grain size of doloma with Fe2O3 addition is bigger than that without additive. Hydration resistance was related to densification and grain size of sintered dolomite.

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فرایند زینترینگ انفعالی و خواص ترموالکتریک کاربیدهای غنی از بور

Reactive sintering process and thermoelectric properties of

boron rich boron carbides

فرایند زینترینگ انفعالی و خواص ترموالکتریک کاربیدهای غنی از بور

ABSTRACT

Dense boron rich boron carbides were reactive sintered by hot pressing at 2050 °C using elementary boronsingle bondcarbon compositions with carbon contents of 9.1, 11.1, 13.3 and 18.8 at.%. The following material characteristics are presented: relative density, SEM images, EDX, X-ray diffraction and corresponding lattice parameters, Seebeck coefficient, electrical conductivity and thermoelectric power factor. Significant grain growth has been obtained with increasing boron content. A deeper understanding of the boron and carbon reaction and the overall sintering process is gained by thermal and chemical analysis in combination with X-ray diffraction. Additionally a thermal experiment with boron and carbon layers illustrates the solid state diffusion behaviour. The found results of boron carbide properties of this paper correspond with results by other authors. The aim is to correlate technological aspects of sintering procedure with material properties. This should help to improve the thermoelectric efficiency of boron carbide based materials.

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تولید زیرکنیای تثبت شده با ایتریا به کمک تفجوشی مایکروویو

Microwave synthesis of yttria stabilized zirconia

تولید زیرکنیای تثبت شده با ایتریا به کمک تفجوشی مایکروویو

 

ABSTRACT

Yttria stabilised zirconia (YSZ) nanocrystals, with a mean size between 5 and 10 nm, were prepared by microwave flash synthesis. Flash synthesis was performed in alcoholic solutions of yttrium, zirconium chloride and sodium ethoxide (EtONa) using a microwave autoclave (RAMO system) specially designed by authors. Energydispersive X-ray analysis (EDX), X-ray powder diffraction (XRD), BET adsorption technique, photon correlation spectroscopy (PCS) transmission and scanning electron microscopy (TEM and SEM) are used to characterized these nanoparticles. Compared with conventional synthesis, nanopowders can be produced in a short period (e.g. 10 s), both high purity and stoechiometric control are obtained. Nevertheless, this mean of production is more cheaper and much faster than the ones commonly used to produce yttria stabilized zirconia (YSZ) by conventional sol–gel techniques.