Home About us Contact
|
Home About us Contact | ||
|
|
||
Ball Milling (ball + milling)
Kinds of Ball Milling Selected AbstractsBismuth,Ceramic Nanocomposites with Unusual Thermal Stability via High-Energy Ball Milling,ADVANCED FUNCTIONAL MATERIALS, Issue 10 2003M.A. Meitl Abstract Electrically conducting nanocomposites of bismuth metal and insulating ceramic phases of SiO2 and MgO were generated via high-energy ball milling for 24 h using zirconia milling media. The resulting nanocomposites contain Bi nanoparticles with sizes down to 5 nm in diameter. The morphology is a strong function of the oxide phase: specifically, the Bi appears to wet MgO while it forms spherical nanoparticles on the SiO2. X-ray diffraction measurements indicate a nominal bismuth grain size of 50 nm, and peak fitting to a simple bidisperse model yields a mixture of approximately 57,% bulk bismuth and 43,% 27 nm diameter crystallites. Nanoparticles as small as 5 nm are observed in transmission electron microscopy (TEM), but may not constitute a significant volume fraction of the sample. Differential scanning calorimetry reveals dramatic broadening in the temperatures over which melting and freezing occur and a surprising persistence of nanostructure after thermal cycling above the melting point of the Bi phase. [source] Combustion-type hydrogenation of nanostructured Mg-based composites for hydrogen storageINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2009M. V. Lototsky Abstract In this study Reactive Ball Milling in hydrogen gas was used to synthesize nanostructured hydrogenated composites of Mg and V-based alloy. After hydrogen desorption, the nanocomposites exhibited a dramatic facilitation of the rate of H absorption by Mg and reduction of the temperature of onset of hydrogenation. These favourable changes were caused by a synergy of catalytic effect of the V-based alloy on hydrogen absorption by Mg and heat release caused by exothermic hydrogen absorption by the V-based alloy. When the initial interaction temperature exceeded a threshold, rather low, value of 20,125°C, depending on the H2 pressure, composition of the sample and its total amount, a combustion-type hydrogenation took place. With optimal interaction parameters applied, H absorption was completed in just 5,70,s and was accompanied by a significant heat release. The observed features can be utilized to reach fast recharge of the Mg-based H stores and to develop efficient heat management systems. Copyright © 2009 John Wiley & Sons, Ltd. [source] ChemInform Abstract: Mechanically Activated Synthesis of 1,3,5-Triaryl-2-pyrazolines by High Speed Ball Milling.CHEMINFORM, Issue 28 2009Xingyi Zhu Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [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] Tailoring Hydrogen Storage Materials Towards ApplicationADVANCED ENGINEERING MATERIALS, Issue 5 2006M. Dornheim Abstract A breakthrough in hydrogen storage technology was achieved by preparing nanocrystalline hydrides using high-energy ball milling and the use of suitable catalysts/additives. These new materials show fast or in case of Mg-based hydrides very fast absorption and desorption kinetics within minutes, thus qualifying lightweight Mg- or Al-based hydrides for storage applications. This article summarizes our current understanding of the kinetics of Mg-based light metal hydrides, describes an approach for a cost-effective processing technology and highlights some promising new developments in lightweight metal hydride research. [source] High-Performance Carbon-LiMnPO4 Nanocomposite Cathode for Lithium BatteriesADVANCED FUNCTIONAL MATERIALS, Issue 19 2010Seung-Min Oh Abstract A cathode material of an electrically conducting carbon-LiMnPO4 nanocomposite is synthesized by ultrasonic spray pyrolysis followed by ball milling. The effect of the carbon content on the physicochemical and electrochemical properties of this material is extensively studied. A LiMnPO4 electrode with 30 wt% acetylene black (AB) carbon exhibits an excellent rate capability and good cycle life in cell tests at 55 and 25 °C. This electrode delivers a discharge capacity of 158 mAh g,1 at 1/20 C, 126 mAh g,1 at 1 C, and 107 mAh g,1 at 2 C rate, which are the highest capacities reported so far for this type of electrode. Transmission electron microscopy and Mn dissolution results confirm that the carbon particles surrounding the LiMnPO4 protect the electrode from HF attack, and thus lead to a reduction of the Mn dissolution that usually occurs with this electrode. The improved electrochemical properties of the C-LiMnPO4 electrode are also verified by electrochemical impedance spectroscopy. [source] Enhancement of Thermoelectric Figure-of-Merit by a Bulk Nanostructuring ApproachADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Yucheng Lan Abstract Recently a significant figure-of-merit (ZT) improvement in the most-studied existing thermoelectric materials has been achieved by creating nanograins and nanostructures in the grains using the combination of high-energy ball milling and a direct-current-induced hot-press process. Thermoelectric transport measurements, coupled with microstructure studies and theoretical modeling, show that the ZT improvement is the result of low lattice thermal conductivity due to the increased phonon scattering by grain boundaries and structural defects. In this article, the synthesis process and the relationship between the microstructures and the thermoelectric properties of the nanostructured thermoelectric bulk materials with an enhanced ZT value are reviewed. It is expected that the nanostructured materials described here will be useful for a variety of applications such as waste heat recovery, solar energy conversion, and environmentally friendly refrigeration. [source] Water-Based Method for Processing Aluminum Oxynitride (AlON)INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2008Lior Miller A water-based method for producing aluminum oxynitride (AlON) green bodies with a relatively high density is described. While alcohol is usually the medium for ball milling, this approach utilizes water to form a rigid network of aluminum hydroxide in Al2O3,AlN preforms. Al2O3,AlN preforms were prepared by four different routes based either on alcohol or water-based slips, and underwent identical sintering procedures. Samples prepared using the water-based method and pressure filtration reached a green density of 67%, compared with 52% and 47% for samples prepared from alcohol-based slips and formed using pressure filtration and dry pressing, respectively. [source] Mechanochemical Synthesis of Blue Luminescent Alkyl/Alkenyl-Passivated Silicon NanoparticlesADVANCED MATERIALS, Issue 22 2007S. Heintz A mechanochemical method for the simultaneous one-step production and functionalization of silicon nanoparticles is presented. Fresh surface created through mechanical attrition of the silicon during high energy ball milling (HEBM) allows for direct reaction between the silicon and the reactive alkene or alkyne media, resulting in a covalent linkage. The resulting nanoparticles exhibit strong blue luminescence, indicative of small nanoparticle sizes and a functionalized surface. [source] Preparation 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] Dispersion of nanoscale BaTiO3 suspensions by a combination of chemical and mechanical grinding/mixing processesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Kuo-Liang Ying Abstract The colloidal stability of aqueous nanometer- and micrometer-scale barium titanate (BaTiO3) utilizing poly (methacrylic acid) (PMAA-Na) and polyacrylamide/(,- N,N -dimethyl- N -acryloyloxyethyl)ammonium ethanate (PDAAE) was investigated. In addition to chemical dispersants, the effects of mechanical milling using either conventional ball milling or nanogrinding/-mixing on the dispersion of BaTiO3 suspensions were also studied. Characterization of the particle size distribution (d50), viscosity, and morphology of BaTiO3 particles in the suspensions revealed that a sole chemical dispersant or mechanical milling was insufficient to achieve nanometer-scale dispersion. The best dispersion results were obtained with a combination of PMAA-Na dispersant and nanogrinding/-mixing, which could provide sufficient electronic repulsive force and shear force to disperse the 80-nm BaTiO3 powders uniformly in the aqueous suspension. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [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] Brittle-Ductile Transitions in Sucrose and the Influence of Lateral Stresses During CompactionJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 2 2000R. J. ROBERTS Sucrose, in a range of particle sizes, has been compacted to investigate both the effect of brittle-ductile transition and the effect of lateral stresses on the deformation stress as measured using Heckel plots. All particles with a diameter greater than 30 ,m exhibited cracking in line with both theoretical predictions and literature data from hammer and ball milling. In addition, crack lengths in compressed particles examined microscopically were very similar to those predicted from the deformation stress, confirming the applicability of the model. [source] Fe3+ Ions Acting as Probes and Agents in Aggregation Processes and Solid-State Reactions in AlO(OH)/Al2O3 MatricesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2010Reinhard Stößer The fate of doped iron species during various mechanically and thermally initiated redox reactions and aggregation processes in crystalline and amorphous AlO(OH) or Al2O3 matrices was investigated. The amorphization of the matrix was performed by chemical (i.e., via sol,gel processes) or mechanochemical treatment (high-energy ball milling). Thermal analysis, coupled with mass spectrometry (TA-MS), Mössbauer spectroscopy, and electron spin resonance (ESR), was used. The TA under various gas atmospheres allowed preparing samples under a controlled temperature regime, together with a controlled gas influence. Both the effect of mechanical activation and the influence of the iron doping could be followed macroscopically via the down-shift of the peak temperature of the corundum formation. The ESR data characterize the Fe3+ ions and their interaction with the magnetic surrounding based on the fine structure parameters. The Mössbauer data allowed the characterization of the Fe(0), Fe2+, and Fe3+ species, together with providing information about their coordinative surrounding. Both methods provided general complementary spectroscopical information. Unexpectedly, (FeOx)n and (FexAl1,x)2O3 aggregates could also be detected in the range of low Fe concentrations. It was demonstrated that even in the low-level doped systems [(FexAl1,x)2O3 with x,0.01], all the essential spectroscopic phenomena occur. At higher Fe concentrations, they were discovered to be caused by magnetic and spin exchange interactions as well as by solid-state reactions during and after the mechanical activation. [source] Sintering Behavior and Dielectric Properties of Bi3NbO7 Ceramics Prepared by Mixed Oxides and High-Energy Ball-Milling MethodsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2007Di Zhou The sintering behavior and dielectric properties of Bi3NbO7 ceramics prepared by the high-energy ball milling (HEM) method and conventional mixed oxides method with V2O5 addition were investigated. All the samples were sintered between 840° and 960°C. For the ceramics prepared by the mixed oxides method, the pure tetragonal Bi3NbO7 phase formed without any cubic phase. With changing sintering temperature, the dielectric constant ,r lies between 79 and 92, while the Q×f values are between 300 and 640 GHz. The samples sintered at 870°C have the best microwave dielectric properties with ,r=79, Q×f=640 GHz, and the temperature coefficients of resonant frequency ,f between 0 and ,20 ppm/°C. For the ceramics prepared by the HEM, a pure cubic phase was obtained. The ,r changes between 78 and 80 and Q×f were between 200 and 290 GHz. [source] Spark-Plasma Sintering of Silicon Carbide Whiskers (SiCw) Reinforced Nanocrystalline AluminaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2004Guo-Dong Zhan The combined effect of rapid sintering by spark-plasma-sintering (SPS) technique and mechanical milling of ,-Al2O3 nanopowder via high-energy ball milling (HEBM) on the microstructural development and mechanical properties of nanocrystalline alumina matrix composites toughened by 20 vol% silicon carbide whiskers was investigated. SiCw/,-Al2O3 nanopowders processed by HEBM can be successfully consolidated to full density by SPS at a temperature as low as 1125°C and still retain a near-nanocrystalline matrix grain size (,118 nm). However, to densify the same nanopowder mixture to full density without the benefit of HEBM procedure, the required temperature for sintering was higher than 1200°C, where one encountered excessive grain growth. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results indicated that HEBM did not lead to the transformation of ,-Al2O3 to ,-Al2O3 of the starting powder but rather induced possible residual stress that enhances the densification at lower temperatures. The SiCw/HEBM,-Al2O3 nanocomposite with grain size of 118 nm has attractive mechanical properties, i.e., Vickers hardness of 26.1 GPa and fracture toughness of 6.2 MPa·m1/2. [source] Synthesis of Dense TiB2 -TiN Nanocrystalline Composites through Mechanical and Field ActivationJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2001Jae Won Lee The synthesis of dense nanometric composites of TiN-TiB2 by mechanical and field activation was investigated. Powder mixtures of Ti, BN, and B were mechanically activated through ball milling. Some powders were milled to reduce crystallite size but to avoid initiating a reaction. In other cases powders were milled and allowed to partially react. All these were subsequently reacted in a spark plasma synthesis (SPS) apparatus. The products were composites with equimolar nitride and boride components with relative densities ranging from 90.1% to 97.2%. Crystallite size analyses using the XRD treatments of Williamson-Hall and Halder-Wagner gave crystallite sizes for the TiN and TiB2 components in the range 38.5,62.5 and 31.2,58.8 nm, respectively. Vickers microhardness measurements (at 2 N force) on the dense samples gave values ranging from 14.8 to 21.8 GPa and fracture toughness determinations (at 20 N) resulted in values ranging from 3.32 to 6.50 MPa·m1/2. [source] Untersuchungen zur Herstellung siliziumkarbid-partikelverstärkter Aluminiumpulver durch Hochenergiekugelmahlen.MATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 6 2010Fabrication of silicon carbide reinforced aluminium powders by high-energy ball-milling High-energy ball milling; Aluminium matrix composite; AA2017; SiC particle reinforcement; Microstructure Abstract Die Herstellung von Siliziumkarbid-Aluminium-Verbundpulver stellt die erste Stufe der pulvermetallurgischen Herstellungsroute für partikelverstärkte Aluminiumwerkstoffe dar. Der Prozess der Verbundpulverausbildung beim Mahlen in einer Hochenergiekugelmühle und der Einfluss von Prozessparametern werden anhand der Al-Legierung EN AW-2017 mit 10 und 15 Vol.-% Siliziumkarbidteilchen der Kornfraktion <2 ,m untersucht. Die Gefügeentwicklung des Pulvers wird materialografisch charakterisiert. Bestimmte Prozessparameter beeinflussen den Verbundpulverzustand zum Teil gegenläufig, so dass der erreichte Optimierungsstand als Kompromiss anzusehen ist. Lösungsvarianten für eine weitere Verbesserung werden aufgezeigt. The fabrication of aluminium silicon-carbide composite powder is the first step of the powder metallurgical production of particle-reinforced aluminium material. This paper deals with the production of silicon-carbide reinforced aluminium matrix (AA2017) composite powder through an high energy ball milling process by using simoloyer- and planetary high energy mills. The Stages of composite powder formation during the high-energy ball milling process will be shown by means of materialographic studies and by micro hardness. Major factors of influence as well as typical problems are discussed. [source] Synthesis and thermoelectric properties of YbSb2Te4PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 6 2007Amado S. Guloy Abstract The study of the ternary phase diagram Yb,Sb,Te has led to the synthesis of YbSb2Te4 as a pure phase by way of high energy ball milling followed by annealing, whereas typical high temperature powder metallurgy leads to multiphase sample with impurities of the very stable YbTe. The Hall mobility, Seebeck coefficient, electrical resistivity and thermal conductivity of the layered compound YbSb2Te4 were measured in the range of 20,550 °C. The thermoelectric figure of merit peaks at 525 K and reaches 0.5. Of particular interest is the very low lattice thermal conductivity (as low as a glass) which makes YbSb2Te4 and related compounds promising thermoelectric materials. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cu/Ti base multicomponent amorphous Cu47Ti33Zr11Ni8Si1 and nanocrystalline silver compositesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2010Jan Dutkiewicz Abstract An easy glass-forming alloy based on Cu,Ti of composition Cu47Ti33Zr11Ni8Si1 was ball milled for 40,h to obtain amorphous powder. X-ray diffraction and differential scanning calorimetry (DSC) measurements confirmed the dominant presence of the amorphous phase after ball milling. However, transmission electron microscopy from powders allowed identification of Si particles and intermetallic phases a few nanometre in diameter, often of CuNi2Ti or Cu,Ti structures. The powder was then hot pressed in vacuum at temperature of 460,°C between the glass transition and the crystallization point to form bulk amorphous samples. Composites were prepared in the same way from mixed milled amorphous powders and nanocrystalline silver powder prepared by ball milling. Various ratios of amorphous to silver powder were applied with a maximum of 60% of nanocrystalline silver The microhardness of the amorphous phase component was near 1100,HV, much higher than the 90,HV of silver. Composites containing 20% of nanosilver have shown a much higher compression strength of 850,MPa, as compared to the 450,MPa of the composite containing 60% of silver, however, the latter has better ductility, near 5%, before fracture. [source] Thermal conductivity reduction in fullerene-enriched p-type bismuth telluride compositesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2010N. Gothard Abstract We present a systematic study of the effects of fullerene nanoinclusions upon a p-type bismuth,antimony,telluride matrix, where the ultimate goal is maximizing the figure of merit by reducing the thermal conductivity (TC). Nanocomposites consisting of a bismuth,telluride matrix with fullerene inclusions have been prepared both by mechanical mixing and ball milling, with the final consolidation in each case achieved by uniaxial hot pressing. A series of samples was produced with fullerene concentrations ranging from fractional levels to several molar percent, and the effects of the fullerene additions upon the resulting microstructure have been considered. Thermal and electrical transport properties have been measured from 10 to 300,K, and the data are discussed in light of the underlying physical mechanisms. [source] Polymer,nanofiller prepared by high-energy ball milling and high velocity cold compactionPOLYMER COMPOSITES, Issue 3 2008Bruska Azhdar High-energy ball milling using comilling in a solid state by low-temperature mechanical alloying to prepare nickel-ferrite (NiFe2O4) nanopowders and ultrafine poly(methyl methacrylate) (PMMA), dispersing nanoparticles in a polymer matrix, and a uniaxial high-velocity cold compaction process using a cylindrical, hardened steel die and a new technique with relaxation assists have been studied. The focus has been on the particle size distributions of the nanocomposite powder during the milling and on the surface morphology of the nanocomposite-compacted materials after compaction with and without relaxation assists. Experimental results for different milling systems are presented showing the effects of milling time and material ratio. It was found that a longer mixing time give a higher degree of dispersion of the nanopowder on the PMMA particle surfaces. Furthermore, with increasing content of NiFe2O4 nanopowder, the reduction of the particle size was more effective. Different postcompacting profiles, i.e. different energy distributions between the upper and lower parts of the compacted powder bed, lead to different movements of the various particles and particle layers. Uniformity, homogeneity, and densification on the surfaces in the compacted powder are influenced by the postcompacting magnitude and direction. It was found that the relaxation assist device leads to an improvement in the polymer powder compaction process by reducing the expansion of the compacted volume and by reducing the different opposite velocities, giving the compacted composite bed a more homogeneous opposite velocity during the decompacting stage and reducing the delay time between the successive pressure waves. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers [source] Silicon nanoparticles with chemically tailored surfacesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 2010Andrew S. Heintz Abstract Silicon nanoparticles are useful materials for optoelectronic devices, solar cells and biological markers. The synthesis of air-stable nanoparticles with tunable optoelectronic properties is highly desirable. The mechanochemical synthesis of silicon nanoparticles via high-energy ball milling produces a variety of covalently bonded surfaces depending on the nature of the organic liquid used in the milling process. The use of the C8 reactants including octanoic acid, 1-octanol, 1-octaldehyde and 1-octene results in passivated surfaces characterized by strong SiC bonds or strong SiO bonds. The surfaces of the nanoparticles were characterized by infrared spectroscopy and nuclear magnetic resonance spectroscopy. The nanoparticles were soluble in common organic solvents and remarkably stable against agglomeration and air oxidation. The luminescence and optical properties of the nanoparticles were very sensitive to the nature of their passivating surface. Copyright © 2009 John Wiley & Sons, Ltd. [source] Effects of ultrasound in coating nano-precipitated CaCO3 with stearic acidASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009K. W. Kow Abstract Nano-Precipitated CaCO3 (NPCC) are coated with stearic acid to improve its dispersion in polymer as well as to reduce agglomeration. In this work, coating was done by wet method using ethanol. Ultrasonication was applied to NPCC to de-agglomerate micron size NPCC into smaller size. Effects of amplitude, temperature and energy input of ultrasonication was investigated. The amplitude was varied from 60% to 100% whereas temperature was varied from 5°C to 45°C. The energy input was stressed up from 3.6 kJ to 180 kJ. Mean diameter of NPCC were observed by using Particle Size Analyzer and Transmission Electron Microscopy (TEM). It was found that mean diameter of NPCC do not vary significantly with temperature. Mean diameter of NPCC, however, decreases exponentially with the energy input. Comparisons were done on NPCC coated with others methods such as dry ball milling and aqueous coating. TEM images show that coating NPCC with ultrasonication is more uniform than other methods. In addition, first derivative mass loss with temperature (DTG) reveals that NPCC coated with ultrasonication do not contain excessive free acid as exhibited by those coated in aqueous and dry ball milling. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] A Highly Efficient Asymmetric Organocatalytic Aldol Reaction in a Ball MillCHEMISTRY - A EUROPEAN JOURNAL, Issue 17 2007Belén Rodríguez Dr. Abstract Anti -aldol products with up to >99,% enantiomeric excess (ee) have been obtained by proline catalysis in excellent yields under experimentally simple solvent-free conditions. Efficient mixing of all the components is accomplished by applying a mechanochemical technique (ball milling). The catalysis is air and moisture tolerant and can be performed with non-purified starting materials. Even mixtures of solely solid compounds react, giving (mostly solid) products through a partially homogeneous (honey-like) intermediate melt. Since the reactant ratio is almost 1:1 (avoiding the common excess of ketone), the product isolation is easy leading to high aldol product yields. [source] | |||||||||||||||||||||||||||||||