Home About us Contact
|
Home About us Contact | ||
|
|
||
Mechanical Mixing (mechanical + mixing)
Selected AbstractsInfluence of Wet Mechanical Mixing on Microstructure and Vickers Hardness of Nanocrystalline Ceramic,Metal CompositesINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 5 2008Tatsuo Kumagai Nanocrystalline (nc) ceramic,metal composite bulk samples have been fabricated by consolidation of mixture of attrition-milled (AM) amorphous base ceramic ((ZrO2,3 mol% Y2O3),20 mol% Al2O3) and AM amorphous base metallic (Ti,48 mol% Al) powders using a pulse-current pressure sintering system. Microstructural observations revealed that the ceramic and metallic colonies appear blocky in morphology in the composite bulk samples, and both the ceramic and the metallic colonies consist of a large number of equiaxed fine grains with the sizes of 78,82 and 81,86 nm, respectively. Mechanical mixing treatments by wet ball milling in ethanol before consolidation process are effective for refinement of the ceramic and metallic colonies. In all the obtained composite bulk samples, the ceramic colonies consist of the dominant phase of tetragonal (t) ZrO2 solid solution (ss) together with the minor phases of monoclinic (m) ZrO2ss and ,-Al2O3. On the other hand, the dominant phase in the metallic colonies changes from Ti3Al (,2) to Tiss (,) with an increase in the t -ZrO2ss volume fraction by abrasion of 3 mol% yttria-stabilized tetragonal polycrystalline zirconia balls during wet mechanical mixing treatments. Such a phase transformation from ,2 to , is considered to be due to the decrease in the aluminum content in the metallic colonies by combination of aluminum with oxygen (i.e., the formation of ,-Al2O3), which is probably taken from ethanol (C2H5OH) into the powders during wet mechanical mixing treatments. The obtained nc composite bulk samples show good Vickers hardness values, which are considerably higher than those estimated from the rule of mixture. [source] Curing behavior and mechanical properties of hollow glass microsphere/bisphenol a dicyanate ester compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010Jinhe Wang Abstract Hollow glass microsphere (HGS)/bisphenol A dicyanate ester (BADCy) composites have been prepared by mechanical mixing, followed by a stepped curing process. The effect of HGS on the curing behavior of BADCy was studied using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The mechanical properties of the composites were examined by mechanical tests, and the improvements of the mechanical properties were investigated by scanning electron microscopy (SEM) and dynamic mechanical analysis (DMA). The results show that HGS is catalytic for the polycyclomerization of the BADCy, which is advantageous to reduce the maximal processing temperature. The impact strength, flexural strength, flexural modulus and storage modulus of BADCy are improved. The improvements of the mechanical properties without sacrificing thermal properties, the ability of lowing processing temperature and the low cost make HGS good filler for cyanate ester resin. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Contrasting textural record of two distinct metamorphic events of similar P,T conditions and different durationsJOURNAL OF METAMORPHIC GEOLOGY, Issue 8 2005O. LEXA Abstract A structural, metamorphic and geochronological study of the Staré M,sto belt implies the existence of two distinct metamorphic events of similar peak P,T conditions (700,800 °C, 8,10 kbar) during the Cambro-Ordovician and the Carboniferous tectonometamorphic events. The hypothesis of two distinct periods of metamorphism was suggested on the basis of structural discordance between an undoubtedly Carboniferous granodiorite sill intrusion and earlier Cambro-Ordovician fabrics of a banded amphibolite complex. The analysis of crystal size distribution (CSD) shows high nucleation density (N0) and low average growth rate (Gt) for Carboniferous mylonitic metagabbros and mylonitic granodiorites. The parameter N0 decreases whereas the quantity Gt increases towards higher temperatures progressively approaching the values obtained from the Cambro-Ordovician banded amphibolite complex. The spatial distribution of amphibole and plagioclase shows intense mechanical mixing for lower-temperature mylonitic metagabbros. In high-temperature mylonites a strong aggregate distribution is developed. Cambro-Ordovician amphibolites unaffected by Carboniferous deformation show a regular to anticlustered spatial distribution resulting from heterogeneous nucleation of individual phases. This pattern, together with CSD, was subsequently modified by the grain growth and textural equilibration controlled by diffusive mass transfer during Carboniferous metamorphism. The differences between the observed textures of the amphibolites are interpreted to be a consequence of the different durations of the Carboniferous and Cambro-Ordovician thermal events. [source] Effect of characteristics of compounds on maintenance of an amorphous state in solid dispersion with crospovidoneJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2007Yusuke Shibata Abstract Solid dispersion (SD) of indomethacin with crospovidone (CrosPVP) shows useful characteristics for preparation of dosage forms. This study aimed to determine the types of drugs that could adopt a stable amorphous form in SD. Twenty compounds with various melting points (70,218°C), molecular weights (135,504) and functional groups (amide, amino, carbonyl, hydroxyl, ketone etc.) were prepared in SD with CrosPVP. The CrosPVP SDs were prepared using a mechanical mixing and heating method. Melting point and molecular weight were found to have no influence on the ability of a compound to maintain an amorphous state in SD. All compounds containing hydrogen-bond-donor functional groups existed in an amorphous state in SD for at least 6 months. Infrared spectra suggested an interaction between the functional groups of these compounds and amide carbonyl group of CrosPVP. Compounds without hydrogen-bond-donor groups could not maintain an amorphous state and underwent recrystallization within 1 month. It was suggested that the presence of a hydrogen-bond-donor functional group in a compound is an important factor affecting the stable formation of SD with CrosPVP, which contains a hydrogen-bond acceptor. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96:1537,1547, 2007 [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] Processability studies of silica-thermoset polymer matrix nanocompositesPOLYMER ENGINEERING & SCIENCE, Issue 2 2008C. Lekakou The aim of this study is to investigate the processability of silica-thermoset polymer matrix nanocomposites in terms of dispersion of silica nanoparticles and their effect on curing. Two thermosetting resins were considered, an epoxy and a polyester resin, with 5% silica, although 1% silica was also used in preliminary studies in the polyester system. Various combinations of mechanical mixing and sonication were investigated for the dispersion of silica nanoparticles under different processing conditions and times in solvent-free and solvent-containing systems. It was found that the best dispersion route involved a solvent-aided dispersion technique. Consequently, different procedures for the solvent removal were investigated. Optical microscopy and SEM were used to characterize the resulting nanocomposites. DSC and rheological DMTA tests demonstrated that the silica nanoparticles shorten the gel time and promote curing in these thermosetting systems. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers [source] Nanocomposite systems based on unsaturated polyester and organo-clayPOLYMER ENGINEERING & SCIENCE, Issue 2 2005I. Mironi-Harpaz Unsaturated polyester (UP) systems give rise to numerous possible approaches in synthesizing nanocomposites. A simultaneous mixing method was used to synthesize UP-resin/organo-clay nanocomposites. The effects of various mixing processes, using several organically-modified clay types, were investigated. The incorporation of these organo-clays resulted in an intercalated structure, the extent of which depended mainly on the type of the clay organic treatment. Organo-clays that exhibited the highest intercalation levels were further studied using a sequential mixing method. The UP-alkyd (without styrene) was mixed with different organo-clays. Processing parameters such as mixing modes, applied shearing levels, clay contents, and mixing-temperatures were investigated. Prolonged high shear levels promoted the intercalation and exfoliation of the silicate layers, resulting in a better dispersion of clay particles. The high shear levels effects were achieved by vigorous mechanical mixing and were intensified by using large amounts of clay and optimized matrix viscosity. Rheological studies of the nanocomposites were found complementary and in correlation with morphological and thermal characterization. This methodological approach provides a basis for understanding the structuring processes involving the formation of the UP/clay nanocomposites and establishing materials-processing-structure interrelations. Polym. Eng. Sci. 45:174,186, 2005. © 2005 Society of Plastics Engineers. [source] Role of nocturnal turbulence and advection in the formation of shallow cumulus over landTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 628 2007Jordi Vilà-Guerau de Arellano Abstract Shallow cumuli over land are normally studied from a diurnal perspective. However, the thermodynamic vertical profiles of the morning transition may play an important role in setting up favourable conditions for the formation of shallow cumuli. In turn, these profiles are highly dependent on the evolution of the nocturnal boundary characteristics and of their layer aloft. By analysing thermodynamic profiles measured by radiosondes launched every three hours at four different stations, we are able to determine how horizontal advection and turbulent mixing modify the atmospheric stability and the differences in potential temperature and specific humidity at the interface between the atmospheric boundary layer and the layer above it. Two consecutive nights are studied. They show very similar boundary-layer development; but variations in the layer aloft by a low-level-jet advection event during the second night, and intense turbulent mechanical mixing, lead to the development of two diurnal boundary layers with very different characteristics: the first one clear, the second cloudy. To complete the observational study, we perform a sensitivity analysis using a mixed-layer model to examine the role of the morning initial conditions in the formation of shallow cumuli over land. The complexity and subtlety of the observed situation,namely, the interaction of a strongly-mixed nocturnal boundary layer and horizontal advection,make this case suitable for testing the capacity of mesoscale models to reproduce cloudy boundary layers that are largely dependent on conditions during the previous night. Copyright © 2007 Royal Meteorological Society [source] | |||||||||||||