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Milling Time (milling + time)
Selected AbstractsPreparation and microstructure characterization of ball-milled ZrO2 powder by the Rietveld method: monoclinic to cubic phase transformation without any additiveJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2002S. Bid The phase transformation kinetics of high-energy ball-milled monoclinic ZrO2 have been studied in detail by Rietveld powder structure refinement analysis. In the present study, no stabilizing compound was required to obtain the cubic phase. The fine-grain powder was milled in a planetary ball mill for up to several hours at different BPMRs (ball to powder mass ratios): 10:1, 20:1, 35:1 and 40:1. During the process of ball milling, the monoclinic phase is gradually transformed to the cubic phase. The relative phase abundances of the respective phases, the particle sizes, the r.m.s. strains, the lattice parameter changes, etc., have been estimated from Rietveld analysis of X-ray powder diffraction data. It has been found that a higher BPMR exerts more influence on rapid phase transformation. In the m - to c -ZrO2 phase transformation, no formation of an intermediate tetragonal ZrO2 phase has been found. The small change in the lattice volume of m -ZrO2, which is very close to the lattice volume of c -ZrO2, caused by ball milling may be attributed to this phase change. The formation of the c phase is noticed, in general, after just 1,h of ball milling, and the particle size of the m phase is reduced to a large extent at the first stage of milling and remains almost unchanged with increasing milling time. However, the particle size of the c phase increases with increasing milling time for the samples milled with higher BPMRs (35:1 and 40:1), suggesting that quenching caused by a high impact energy followed by an annealing effect may play a vital role, which is further manifested in the agglomeration of small particles. [source] Simultaneous wet ball milling and mild acid hydrolysis of rice hullJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 1 2010Jinxiang Zhou Abstract BACKGROUND: Rice hull, an abundant residue but a big issue for the rice processing industry, has the potential to serve as a feedstock for production of ethanol because of its lignocellulosic composition. Simultaneous wet ball milling and mild acid hydrolysis of rice hull was studied in this work. RESULTS: Ball milling with 150 small stainless steel beads and rotation speed of 600 rpm in citrate solvent of pH 4 was the optimal condition for hydrolysis, and the yield of sugar increased with increased milling time. Corresponding structure transformations before and after milling analyzed by X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM) and transmission fourier transform infrared spectroscopy (FT-IR) clearly indicate that this hydrolysis could be attributed to the crystalline and chemical structure changes of cellulose in rice hull during ball milling in mild acid solvent. CONCLUSION: This combined treatment of ball milling and citrate solvent greatly changed the crystalline and chemical structure and continuously generated sites accessible to citrate solvent, thus enabling hydrolysis of the rice hull. Copyright © 2009 Society of Chemical Industry [source] Corrosion of ZrB2 Powder During Wet Processing , Analysis and ControlJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2008Sea-Hoon Lee Corrosion behavior of ZrB2 powder during wet processing in water or ethyl alcohol was studied both with and without an organic additive. Incorporation of oxygen and pH change did not intensively occur during static aging of aqueous slurries, but corrosion was enhanced when stirring the slurries. The oxygen content of the powder increased rather rapidly with milling time in ethyl alcohol. The molecular weight of polyethylenimine effected the pH change and oxygen content of ZrB2 powder, after corrosion in water for 18 months. X-ray photoelectron spectroscopy analysis informed that the surface of both the pristine and corroded powders was mainly covered with ZrOH, but a certain amount of Zr,B bonding remained at the powder surface after the wet processing. [source] New Route for the Extraction of Crude Zirconia from ZirconJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2002Nicholas J. Welham A commercial grade of zircon (ZrSiO4) concentrate was mechanically milled with MgO for up to 100 h in a laboratory-scale mill. The resultant powders were subjected to thermal processing, chemical leaching, and X-ray diffraction (XRD). There was no direct evidence of reaction during the milling step, with no new phases evident from XRD. Leaching of the powder showed that a reaction had occurred, and increased solubility with milling time was attributed to the formation of a nanostructured Mg-Zr-Si oxide, which dissolved congruently. Heating the powders resulted in a number of thermal events, including the formation/crystallization of ZrO2 and Mg2SiO4. Thermal treatment of the milled powders allowed selective chemical leaching of the magnesium and silicon, leaving a powder containing ,90% ZrO2. [source] Mechano-Chemical Changes of Nano Sized ,-Al2O3 During Wet Dispersion in Stirred Ball MillsPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 1 2004Frank Stenger Abstract The mechano-chemical changes in synthetic ,-Al2O3 during wet dispersion in a stirred ball mill, are studied. It is shown that a second phase is generated which can be identified as an aluminum hydroxide (Bayerite) by use of dynamic scanning calorimetry (DSC), X-ray diffraction (XRD), thermogravimetry (TG), Fourier transformed infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). The amount of the Bayerite phase produced increases with milling time. A comparison of the evaluated amounts from TG- and DSC-measurements are in reasonable agreement. Furthermore, the measured BET surface area shows a strong dependence on the temperature of sample preparation. Depending on the temperature, the bayerite phase is seen to convert to the ,-phase again and also forms meso- and possibly micro-pores, leading to a high BET surface area. In this paper, we highlight the necessity for using different methods to characterize the dispersion process, and for a correct interpretation of the measurement results. [source] Thermomagnetic monitoring of nanocomposite formation in mechanically alloyed Nd,Fe,B alloysPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2004H. W. Kwon Abstract A mechanical alloying technique was applied to NdxFe94,xB6 (x = 5.5,11.0) alloys for preparing an exchange-coupled nanocomposite. The structural development during the nanocomposite formation was monitored by thermomagnetic means. The mechanically alloyed NdxFe94,xB6 alloys in the as-milled condition consisted of an amorphous Nd,Fe,B phase and ,-Fe nanocrystallites. The crystallisation temperature of the amorphous phase was independent of the milling time. The amorphous phase in the as-milled NdxFe94,xB6 alloys with higher Nd content had a lower crystallisation temperature. The NdxFe94,xB6 (x = 8.5) alloy milled for longer than 30 h consisted of a two-phase structure containing ,-Fe and Nd2Fe14B phases after being isothermally annealed at 600 °C for 20 min. This annealed powder showed a smooth demagnetisation curve, indicating an intergranular exchange coupling between the hard Nd2Fe14B and soft magnetic ,-Fe grains. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Composition influence on positron annihilation parameters in ZnO-based nanocrystal semiconductor powdersPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 10 2007L. C. Damonte Abstract Zn1,xMgxO powders at various compositions were obtained by mechanical milling from the binary oxides. The progressive incorporation of Mg atoms into the ZnO lattice was monitored by X-ray diffraction (XRD). The evolution of annihilation parameters with milling time and composition were analyzed and related to the possible types of mechanical and substitutional induced defect present. It was concluded that the average lifetime constitute a useful parameter to sense the complete cation substitution in the wurtzite structure. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Mechanochemical Activation-Assisted Low-Temperature Synthesis of CaZrO3JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2007Guotian Ye Calcium zirconate (CaZrO3, CZ) was prepared using a solid-state reaction with mechanochemical activation through vibro-milling, aiming at completing the reaction CaO+ZrO2=CaZrO3 at relatively low calcination temperatures. Changes in the crystallite size and homogeneity of the mixed components CaO and ZrO2 in the starting mixtures were observed with different milling times. The influence of milling on the incipient temperature of CZ formation and completion of CZ formation was investigated. It is concluded that milling of the reactants for 20 h lowered the incipient temperature of CZ formation from 800° to 600°C, and the temperature of complete CZ formation from above 1100° to 800°C. [source] Ni Catalyst Coating on Fecralloy® Microchanneled Foils and Testing for Methane Steam ReformingCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2010N. de Miguel Abstract The procedure following the washcoating of three different Ni catalyst systems (MgO, Al2O3, and CeO2/Al2O3 supported) on pretreated Fecralloy® microchanneled foils under controlled milling times and viscosities of the slurries is described. The activity of the prepared coatings is also presented. Four different series of coated foils were prepared: one per each catalyst system, keeping constant the average particle size on 5 ,m, and one extra series to study the effect of reducing the average particle size of the MgO-supported catalyst system to 3 ,m. For each coating, scanning electron microscopy pictures were taken and specific surface areas and average densities of the catalyst layers were estimated. Finally, each series of coated foils was stacked and tested in a microreactor for the methane steam reforming (MSR) reaction under different conditions. [source] | ||||||||||||||||