The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Ferdi Schuth - One of the best experts on this subject based on the ideXlab platform.
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influence of Crystallite Size on the properties of zirconia
Chemistry of Materials, 1998Co-Authors: Wolfram Stichert, Ferdi SchuthAbstract:Systematic studies on the properties of zirconia for catalytic applications revealed that the concentration of the stock solution, from which precipitation is carried out, strongly influence the Crystallite Size of the resulting zirconia. The Crystallite Size influences the BET surface area, the crystallization temperature, and the phase transition temperature. The findings of this study clarify the parameters governing the formation of specific phase with desired surface areas.
Zulkifly Abbas - One of the best experts on this subject based on the ideXlab platform.
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x ray diffraction studies on Crystallite Size evolution of cofe2o4 nanoparticles prepared using mechanical alloying and sintering
Applied Surface Science, 2010Co-Authors: Samaila Bawa Waje, Mansor Hashim, Wan Mohamad Daud Wan Yusoff, Zulkifly AbbasAbstract:NanoSized cobalt ferrite spinel particles have been prepared by using mechanically alloyed nanoparticles. The effects of various preparation parameters on the Crystallite Size of cobalt ferrite which includes milling time; ball-to powder weight ratio (BPR) and sintering temperature, were studied using X-ray diffractometer (XRD). Scherrer's equation was used to study the Crystallite Size evolution of the as-prepared materials. The results of the as-milled sample revealed that both milling time and BPR plays a role in determining the Crystallite Size of the milled powder. However, where sintering is involved, the sintering temperature results in grain growth, and thus plays a dominant role in determining the final Crystallite Size of the samples sintered at higher temperature (above 900 °C). From the vibrating-sample magnetometer (VSM) measurement it was observed that the coercivity of the as-milled samples without sintering is almost negligible, which is a type characteristic of superparamagnetic material. However, for the sintered samples, the saturation increases while coercivity decreases with increases sintering temperature.
Ana Terleckibaricevic - One of the best experts on this subject based on the ideXlab platform.
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kinetics of deep oxidation of n hexane and toluene over pt al2o3 catalysts platinum Crystallite Size effect
Applied Catalysis B-environmental, 2004Co-Authors: Nenad Radic, Bosko Grbic, Ana TerleckibaricevicAbstract:Abstract The kinetics of n-hexane and toluene complete oxidation has been studied over 0.12% Pt/Al2O3 catalysts. Measurements were performed in an external recycle reactor. Reaction rates were measured as a function of temperature and reactants concentrations for two platinum Crystallite Sizes, 1.0 and 15.5 nm. The turnover frequency (TOF) for the oxidation of both hydrocarbons is about 10 times higher for the 15.5 nm than for the 1.0 nm Pt Crystallite Size. The reaction constants are calculated according to Mars van Krevelen (MVK) mechanism. The oxygen chemisorption rate constant (kO) is the same during the n-hexane and the toluene oxidation for each Sizes of platinum Crystallite. For both hydrocarbons the oxygen chemisorption rate constant and the surface reaction rate constant (ki) are higher for 15.5 nm than for 1.0 nm Crystallite Size. The activation energy for kO decreases with the increase of the Pt Crystallite Size. The activation energy for ki is independent on the Pt Crystallite Size for both hydrocarbons. The values of kinetic constants reveal that the increase of the reaction rate for large Pt Crystallites could be related to the lower activation energy for kO. This implies that on large Pt Crystallites oxygen is held on Pt atoms with a lower bond strength that on small Pt Crystallites, which explains the structure sensitivity found for n-hexane and toluene oxidation.
Kyeong Youl Jung - One of the best experts on this subject based on the ideXlab platform.
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effect of surface area and Crystallite Size on luminescent intensity of y2o3 eu phosphor prepared by spray pyrolysis
Materials Letters, 2005Co-Authors: Kyeong Youl Jung, Yun Chan KangAbstract:Abstract The luminescent intensity of Y 2 O 3 :Eu phosphor prepared by spray pyrolysis was monitored as a function of the surface area and Crystallite Size. In order to control the surface area or the Crystallite Size, some organic additives and flux materials were introduced in the spray solution. The reduction of surface area, which was achieved by only controlling the quantity of the organic additive, was found to be helpful for the improvement of luminescent intensity of Y 2 O 3 :Eu particles. The addition of Li 2 CO 3 flux to the spray solution with the organic additive of 0.3 M enlarged the surface area of Y 2 O 3 :Eu particles as a consequence of the reduction of particle Size. Then, the increase of surface area did not lower the luminescent intensity of Y 2 O 3 :Eu phosphor particles since the added Li 2 CO 3 flux increased the crystallinity, simultaneously. It was found that the Y 2 O 3 particles with larger Crystallite Size had higher photoluminescence regardless of the surface area. Therefore, we concluded that the crystallinity is more important factor than the surface area and increasing the Crystallite Size is essentially needed to enhance the luminescent intensity of Y 2 O 3 phosphor prepared by spray pyrolysis.
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linear relationship between the Crystallite Size and the photoactivity of non porous titania ranging from nanometer to micrometer Size
Applied Catalysis A-general, 2002Co-Authors: Kyeong Youl Jung, Seung Bin ParkAbstract:The dependency of the photoactivity on the Crystallite Size of anatase titania for the decomposition of trichloroethylene (TCE) was investigated. The Crystallite Size of anatase-phase was controlled at a fixed surface area and particle Size by the spray pyrolysis. The surface area was also changed by the gas-phase decomposition of titanium-tetra-iso-propoxide (TTIP) by keeping the Crystallite Size in a similar range. The photoactivity of titania particles of the same surface area and particle Size increased linearly with increasing the Crystallite Size of anatase-phase as long as no significant rutile phase was formed. It was proved that the photoactivity of titania is supposed to be enhanced by increasing the surface area while keeping a similar Crystallite Size. The lab-made titania particles of nanometer Size and pure anatase-phase had higher photoactivity than that of Degussa P25 due to the larger crystallinity, although their surface area was smaller than that of Degussa P25. For all titania samples, the photoactivity normalized by the surface area was linearly increased with increasing the Crystallite Size of anatase-phase, regardless of the preparation method; the particle Size ranging from nanometer to micrometer.
Ruth Marlene Campomanes Santana - One of the best experts on this subject based on the ideXlab platform.
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thermal decomposition of wood influence of wood components and cellulose Crystallite Size
Bioresource Technology, 2012Co-Authors: Matheus Poletto, Ademir Jose Zattera, Maria Madalena De Camargo Forte, Ruth Marlene Campomanes SantanaAbstract:The influence of wood components and cellulose crystallinity on the thermal degradation behavior of different wood species has been investigated using thermogravimetry, chemical analysis and X-ray diffraction. Four wood samples, Pinus elliottii (PIE), Eucalyptus grandis (EUG), Mezilaurus itauba (ITA) and Dipteryx odorata (DIP) were used in this study. The results showed that higher extractives contents associated with lower crystallinity and lower cellulose Crystallite Size can accelerate the degradation process and reduce the wood thermal stability. On the other hand, the thermal decomposition of wood shifted to higher temperatures with increasing wood cellulose crystallinity and Crystallite Size. These results indicated that the cellulose Crystallite Size affects the thermal degradation temperature of wood species.