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Showing 1 to 20 of 100 for “"Crystallite size"”.
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PEG-coated Fe3O4 for li-Ion battery anodes: Effects of crystallite size and surface chemistry
… examines the effects of surface chemistry and crystallite size (10 nm vs. 20 nm) on battery performance. Variations in surface chemistry are due to the synthesis methods used for Fe3O4, which use ammonium hydroxide or triethylamine as a base. XRD and TEM initially characterized the active …
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Determination of Phase Fraction, Lattice Parameters and Crystallite Size in Mechanically Alloyed Fe-Ni Powders
… and to determine the lattice parameters and crystallite size. The main objective of this project is to study how the milling at low temperatures affects the region of two phase co-existence, phase structure and crystallite size. It was found that the composition ranges of the bcc and fcc …
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The effect of temperature and crystallite size on the growth and morphology of carbon nanotubes
The aim of the study was to synthesise iron oxide crystallites with different crystallite sizes supported on y-A120 3 using the reverse micelle technique. It was hypothesised that changing the crystallite size of the synthesised iron oxide crystallites could lead to the control of the external …
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The Effect of Zr-Doping and Crystallite Size on the Mechanical Properties of TiO2 Rutile and Anatase
… TiO2 and Ti0.9Zr0.1O2 starting materials with crystallite size in the micro- and also nanometer range. Quenched samples of rutile, anatase and high pressure polymorphs synthesized at up to 10 GPa adopt 10 mol% ZrO2, Zr-doped TiO2 starting materials therefore have the composition Ti0.9Zr0.1O2. …
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The influence of metal crystallite size of the cobalt Fischer-Tropsch catalyst on the re-oxidation of cobalt with water
… In the present study the role of the cobalt crystallite size on the re-oxidation of a 5%(wt) Co/SiO2 catalyst has been investigated with TPR, TPO, H2 chemisorption, TEM and Fischer-Tropsch synthesis. The supported catalysts used in this study were prepared by impregnating a silica support …
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Effects of Crystallite size and water partial pressure on the activity and selectivity of low temperature iron-based fischer-tropsch catalysts
… Therefore it is expected that the smaller the crystallite size of the metal, the more active the catalyst will be under test conditions. This work investigates the influence of iron crystallite size and water co-feed on the activity and selectivity of low temperature Fischer-Tropsch synthesis. …
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Nanosized iron crystallites for Fischer-Tropsch synthesis
… weight specific catalytic activity, the metal crystallites should possess large specific surface areas and that is only achievable with small metal crystallites. However, a minimum crystallite size might exist below which catalyst activity drops. Consequently, in order to investigate the role of …
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Preparation of model cobalt catalysts for Fischer-Tropsch synthesis using ultrasound preparation techniques
… to study the oxidation behaviour of small cobalt crystallites during Fischer-Tropsch synthesis, it is necessary to prepare model catalysts with cobalt crystallites of which the size distributions can be adjusted. Here ultrasonication was used to decomposed a tricarbonyl precursor in n-decane to …
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Preferential oxidation of carbon monoxide in hydrogen-rich gases over supported cobalt oxide catalysts
… the absence of hydrogen has been reported to be crystallite size-dependent when using Co₃O₄ as the catalyst. However, studies looking at the effect of crystallite size during the CO-PROX reaction are very few. Metal-support interactions also play a significant role on the catalyst's performance. …
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Grain Boundary Pinning Approach for Manufacturing High-Strength Nanocrystalline Aluminum Alloys
… particle morphology, elemental composition, and crystallite size. The results showed changes in the morphology of powders and a reduction in crystallite size with the increase in cryomilling duration. Thereafter, the bulk samples using cryomilled powders were manufactured using two different …
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Preparation of nano and Angstrom sized cobalt ensembles and their performance in the Fischer-Tropsch synthesis
… on an inert carrier. Recent studies on nano sized iron, cobalt, ruthenium and rhodium crystallites indicate that below a certain crystallite size they display a decrease in surface specific activity. This work aims to study the crystallite size effect of cobalt, supported on an industrially …
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Structural characterisation of apatite-like materials
… studied. Emphasis was given to changes in the crystallite size and crystallinity of apatite samples produced by three different methods: chemical precipitation method, hydrothermal method, and bacterial biosynthesis. A general observation was that all samples contained a certain amount of …
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Grain size effect on structure and properties for chemically-prepared barium titanate
… when prepared as a powder with small particle size $({<}1\mu$m) or as a polycrystalline ceramic with small grain size, displays dramatic deviations in crystal structure and electrical properties, compared with forms involving larger crystallite sizes. Specifically, ceramists have been concerned …
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Iron modification of rhodium nano-crystallites for CO hydrogenation
… of iron on alumina-supported well defined nano-sized rhodium crystallites on the activity and selectivity for CO hydrogenation. The objective was to prepare model catalysts with similar average crystallite size and narrow size distribution.
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Development of nanocrystalline Fe80Cr20 alloy using combination technique of ball milling and ultrasonic treatment for fuel cell interconnector
… ultrasonic treatment (UT) in obtaining smaller crystallite size, finer surface morphology, higher thermal stability and more homogenous nanocrystalline Fe80Cr20 alloys. This condition was motivated by the previous research that some of the grain growth was observed in a high temperature. At …
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Preparation and Water-Gas Shift Performance of Zinc Oxide Supported Dispersed Gold Catalysts
… Decreasing post-calcination (120°C} gold crystallite size with increasing ageing pH [as reported by Haruta (1997)] was also observed (figure 11.2) - but it is not clear whether this resulted from pH dependent crystallization dynamics, from crystallite size being simply determined by the …
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Optimization of titanium dioxide (TiO2) thin film using dip coating technique for oxygen gas sensor
… film is even and uniform in manner with grain size of 13.3 nm. The crystallite size obtained from HIGHSCORE software is 69.02 nm and calculated crystallite size using Scherrer’s equation is 55.7 nm. The electrical studies showed that the film resistivity is 1.64 x 10 -3 Ω.cm. The gas sensor …
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Investigating mechanical properties of ordinary portland cement. Investigating improvements to the mechanical properties of Ordinary Portland Cement (OPC) bodies by utilizing the phase transformation properties of a ceramic (Zirconia).
… Cement were observed during which the effect of crystallite size pH on the preparation solution, precursor salt, and the presence of co-precipitates, Fe(OH)3, SnO2 and SiO2 on the crystallization temperature, enthalpy and crystal structure, immediately following the crystallization exothermic …
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Optical properties of size selected nanocrystallites in porous silicon
… on processing and diagnosing porous silicon nanocrystallites that have novel chemical, structural and photoluminescent properties. FTIR and Auger electron spectroscopy showed that while conventional porous films have incomplete hydrogen passivation and tend to be plagued with defects that compete …
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Characterization of gold catalysts for methanol synthesis
… is significantly affected by the average crystallite size of the gold crystallites in the catalyst. Supported gold catalysts are most commonly characterized for particle size using TEM and XRD. Both of these methods can have a large degree of inaccuracy associated with them at low metal …
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