1,721,030 research outputs found
POWDER PREPARATION AND SINTERING BEHAVIOR OF ZRO2-20MOL-PERCENT-CEO2 SOLID-SOLUTIONS PREPARED BY VARIOUS METHODS
No full textTHERMAL-SHOCK RESISTANCE OF CORDIERITIC FILTER FOR DIESEL-ENGINES
No full textCordierite porous ceramics are attractive materials for diesel particulate traps, but are sensitive to the thermal shocks provoked by the ignition of accumulated soot. The present paper reports an investigation on a commercial porous cordierite to be used as a substrate for catalysts in exhaust pipes. Samples have been subjected to thermal shock tests to study the response of these ceramics to the repetitive thermal shock that occurs within automotive systems during the regeneration processes. In particular the effect of thermal treatment on microstructure and mechanical propel ties has been examined and explained
Mechanical properties and microstructure of fast fired tiles made with blends of kaolin and olivine powders
No full textThe paper reports on some experimental results obtained from the production of ceramic tiles containing olivine and kaolin powders mixed in different proportions. Blending of components was done by attrition milling. Pressed powders were fast fired (55 min cold to cold) in air up to
1250 1C. Fired products were characterized by shrinkage, water absorption, density, strength, hardness, toughness, crystal phases and
microstructure. It has been demonstrated that all the samples prepared have properties in line with the industrial production of some ceramic
materials, but those containing 60 wt% of olivine and 40 wt% of kaolin displayed the best overall behaviour and therefore the blend is a possible candidate of an eventual industrial production of tile
THERMAL-SHOCK RESISTANCE OF MATERIALS BASED ON CEO2-STABILIZED TETRAGONAL ZIRCONIA POLYCRYSTALS
No full textMaterials based on tetragonal zirconia polycrystals fully stabilized with CeO2 have been prepared starting from commercial powders. The mechanical properties of samples with different compositions were measured at room temperature and after quench tests. The effects of thermal treatments on the microstructure and crystal phases and their detrimental influence on strength, toughness and hardness were evaluated. Experiments demonstrated that residual porosity and higher amounts of ceria favourably influence the retention of material properties after thermal treatment
Microstructural development and mechanical properties of alumina-hexaluminate composites As-sintered and after aging in aqueous and physiological solution
No full textAddition of calcium, strontium or barium nitrates to alumina powders promotes the crystallization "in situ" of calcium, strontium and barium hexaluminates during the sintering of green compacts. Calcium and strontium hexaluminates develop platelike structures randomly dispersed in the alumina matrix whereas barium hexaluminate does not. The strength and toughness of as-fired samples containing calcium or strontium hexaluminates are greater than those of the matrix. Materials containing barium hexaluminate have lower values. These composites maintain the same properties after aging for 30 d at 35 degrees C in aqueous or physiological solution and no chemical reaction between the ageing media and the hexaluminates was observed on examination by scanning electron microscope
Mechanical properties and microstructure of (CeO2)-stabilised ZrO2/Al2O3 composites
No full textIn this investigation a series of Al2O3-ZrO2 composites materials were prepared using unstabilised ZrO2 or different amount of either Y2O3 or CeO2 for stabilising the ZrO2 in its metastable tetragonal form. The mechanical properties (hardness, bend strength and toughness) were measured and the influence of the different micro structure obtained as well as the role of phase transformation and micro cracks has been assessed
Effects of milling on coprecipitated 3Y-PSZ powders
No full textThe present research compares properties and behaviour of co-precipitated 3Y-PSZ powders submitted, after co-precipitation, to different milling
treatments. The characteristics of the different products were evaluated by measurement of particle size distribution, thermogravimetric analysis,
X-ray diffraction, specific surface area and scanning electron microscopy analysis. It has been demonstrated that 1 h of attrition milling enables the
production of powders containing soft agglomerates of nanometric particles: the dispersing liquid used on milling has little influence. Crystallisation
into a cryptocrystalline structure of the amorphous powder is achieved after 1 h of high energetic milling, avoiding thermal treatments
Recycling Glass Cullet from Waste CRTs for the Production of High Strength Mortars
Full text linkhe present paper reports on the results of some experiments dealing with the recycling of mixed cathode ray tube (CRT) glass waste in the production of high-strength mortars. Waste CRT glass cullet was previously milled, and sieved, and the only fine fraction was added to the fresh mortar in order to replace part of the natural aggregate. The addition of superplasticizer was alsoinvestigated. All hydrated materials displayed high compressive strength after curing. Samples containing CRT mixed glass showed a more rapid increase of strength with respect to the reference compositions, and materials with a superplasticizer content of 1% showed the best overall performance due to the favourable influence of the small glass particles which increase the amount of silicate
hydrated produced. The induced coupled plasma (ICP) analysis made on the solutions, obtained from the leaching tests, confirmed the low elution of hazardous elements from the monolithic materials produced and consequently their possible environmental compatibility
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