High Porous Alumina Bodies: Production and Properties via Gel-Casting Technique | اضافه به علاقه مندیها
Abstract Porous ceramic materials have found widespread technological and industrial applications from filtration, absorption, catalysts and catalyst supports to lightweight structural components. In the present work, processing is based on the generation of foam from an aqueous suspension of ceramic powder and the subsequent stabilization of the structure by in-situ polymerization of organic monomers. The process offers a number of advantages from other processes. It is shown here, the in-situ polymerization of organic monomers led to a fast solidification and strong, porous bodies. SEM results showed, that the ceramic foams had highly interconnected network of spherical cells with low densities. The cell size distribution was dependent on the density of the samples as well as the polymerization onset time. Good correlations were found between the green microstructure, rheology of the suspensions and the particle interaction forces.
An investigation on the properties and microstructure of mullite-bonded cordierite ceramics | اضافه به علاقه مندیها
The fabrication of a mullite-bonded cordierite body suitable for use as kiln furniture has been investigated in this article. First of all cordierite powder was synthesized by mixing talc, kaolin and alumina as starting materials, pressing and firing up to 1325oC. The amount of cordierite phase was estimated by an X-ray diffraction technique. The synthesized cordierite was then mixed with certain amounts of kaolin and alumina as the starting materials for mullite formation and the mixture was shaped by a pressing method, following by firing at different temperatures. The changes of density, porosity and cold crushing strength of the samples were measured as a function of heat treatment temperature. The results showed that these properties improve by a rise in temperature. The mullite formation within the samples was confirmed by an XRD method. The thermal expansion coefficient of the samples fired at 1350oC was determined by a dilatometer having an average value of 3.18×10−6 (1/K), which indicates an excellent thermal shock resistant for the samples. The microstructure of the fired samples was studied using scanning electron microscopy (SEM), which showed interesting results.
Response Surface Optimization of dispersing conditions for aqueous alumina nanopowders slip casting | اضافه به علاقه مندیها
Abstract: In the present work, the optimum dispersing conditions for aqueous alumina nanopowder slips using response surface methodology (RSM) were determined. Rheological behavior is evaluated with changing of pH and amount of dispersant sedimentation height and zeta potential of the slips. Finally, mathematical models were presented to predict the sedimentation height and zeta potential.
EFFECT OF FINE ANDALUSITE ON THE PROPERTIES AND MICROSTRUCTURE OF LOW-CEMENT CORDIERITE-MULLITE CASTABLES | اضافه به علاقه مندیها
Results are presented from the development and study of cordierite-mullite panels which are based on low-cement refractory castables (LCC) and can be used as kiln furniture. Cordierite powder was synthesized from talc, kaolin, and alumina. Synthetic cordierite aggregate was used as the main component in addition to andalusite, Kerphalite, cement Secar 71, calcined alumina, and microsilica. It was established that samples of the cordierite-based material with a mullite binder had a satisfactorily low CLTE (3.72 10–6 1/K), which is indicative of their excellent thermal shock resistance.
PRODUCTION OF LIGHTWEIGHT REFRACTORY INSULATION PANELS ON THE BASIS OF PERLITE | اضافه به علاقه مندیها
For saving energy in industrial furnaces, various forms of insulation are used such as bricks, blocks, castable and fibers. Lightweight refractory insulation panels on the basis of Perlite (~30 wt.%) with chemical bonding (H3PO4) were successfully prepared by Extruding technique after sintering at 900-1100 °C. Properties such as density, sintering shrinkage percent, permanent linear change (PLC) and cold crushing strength are measured. The particle morphology was directly imaged by using scanning electron microscopy (SEM) and mineral phases present in the samples were determined at room temperature by using X-Ray diffraction patterns. According to results, samples with 30 wt.% Perlite with Phosphate bond in the range of 950-1000 °C to have the desired properties such as strength~ 30-35 Kgf/cm2, density~ 0.42-0.45 g/cm3 and application temperature at ~ 1100 °C.
THE EFFECT OF TiO2 ON SINTERABILITY AND THE FORMATION OF SPINELS PHASES ON MgO-Al2O3-TiO2 SYSTEMS | اضافه به علاقه مندیها
MgO-Al2O3-TiO2 composite refractories were prepared by using magnesium-aluminate spinel and titanium dioxide as main starting materials and being sintered at high temperature. But, In this research, the influences of titanium dioxide addition on sinterability, the formation of in-situ magnesium-aluminate spinel and their complex compounds formation at 1400 ºC were investigated. Microstructural analysis and phase identification were done by scanning electron microscopy with energy dispersive X-ray analyzer (SEM/EDS), also mineral phases present in the samples were determined at room temperature by using X-Ray diffraction patterns. The results revealed with increasing TiO2 content, the densification of the composites first increased and then decreased. This indicated appropriate amount of TiO2 could contribute to the sintering of the composites due to the solid solution of TiO2 in the in-situ magnesium-aluminate spinel and in general, the simultaneous formation of the complex solid solution(MgO.TiO2 – MgO.Al2O3) spinel.
Removal of dyes which are toxic in nature from industrial wastewaters is currently of great interest. For this purpose, the use of Bentonite for the removal of methyl violet dye from aqueous solutions at different contact times, pH and temperature was investigated. Bentonite has a high potential to adsorb reactive dyes from aqueous solutions according to TEM image. The extent of dye removal increased with increasing adsorbent concentration, contact time, pH and temperature. Increasing the temperature shows increasing the rate of diffusion of the adsorbate molecules across the external boundary layer and in the internal pores of the adsorbent particle. The kinetics of the adsorption process was tested for the pseudo-first order and pseudo-second order reaction models. The rate constant of adsorption was obtained for the pseudo-second order kinetic model. The adsorption capacity of the Bentonite is comparable to the other available adsorbents, and it is quite cheaper.
Poly(lactic-co-glycolic) /Nanostructured Merwinite Porous composites For Bone Tissue Engineering. I. Preparation and Morphology | اضافه به علاقه مندیها
A novel merwinite/ Poly(lactic-co-glycolic) nanocomposite was synthesized by a solvent casting/salt leaching technique with varying merwinite contents from 10 to 30% (w/w). Poly(lacticco- glycolic) /merwinite foams with a co-continuous structure of interconnected pores were formed. The microstructure of the pores and the walls was controlled by varying the merwinite content. The pore structure becomes more and more irregular with increasing merwinite content. Pore sizes ranging from several microns to a few hundred microns were obtained. The degradation assessment of the scaffolds is performed in phosphate-buffered saline (PBS) solution at 37°C. Weight loss during storage at 37°C in PBS (pH 7.4) was determined for the scaffolds. Weight loss increased from pure to high content during incubation time. The prepared merwinite/ (Polylactic-co-glycolic) nanocomposite with uniform microstructure may be used in bone tissue engineering applications.
Microwave-assisted sol–gelsynthesisofalphaaluminananopowder and studyoftherheologicalbehavior | اضافه به علاقه مندیها
In the present work,, alpha alumina nano powder was synthesized via a sol-gel route. After preparation of bohemite (AlOOH) sol carbon black was added and the resultant sol was dried and calcined in micro wave furnace for 10 min. XRD results showed that alpha alumina was the only crystalline phase with specific surface area, mean diameter and crystallite size of 51m2 g1, 100 and 25 nm, respectively. Rheological measurements revealed that the optimal content of T iron at pH=10 is 1 and 0.1 g per 100 g nano - and micron - alumina (1.5 m2 g1), respectively. Furthermore ,the optimum solid conten tof the slips was determined as 35 - 45 and 70 wt.% for nano-and micron-alumina,respectively.