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Volume Percent (volume + percent)

Distribution by Scientific Domains

Polymers and Materials Science	60%

Selected Abstracts

Properties of Porous Si3N4/BN Composites Fabricated by RBSN Technique

INTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 4 2010
Ji-Xuan Liu
Reaction bonding of silicon nitride (RBSN) technique combined with slip-casting shaping process was used to fabricate porous Si3N4/BN ceramic composites. Si/BN slurry with chemical stability, good dispersibility, and viscosity was prepared using glycerol trioleate (GTO) covering on Si surface and poly(acrylic acid) (PAA) as dispersant. The hydrolysis of Si was strongly prevented by GTO coating. The dispersibility of covered Si and BN suspensions were improved by PAA dispersant. Twenty volume percent covered Si/BN slurries with low viscosity were successfully casted. The cast bodies were dried at room temperature, debindered at 750°C and nitrided below 1450°C. The nitrided samples mainly consist of ,-Si3N4, ,-Si3N4, and h-BN. The composites exhibit homogeneous microstructure consisting of faceted particles, ,-Si3N4 nanowires and a large amount of pores. The porosity is 52.64% and the pore size is in the range of 60,300 nm. The composites show compressive strength of 16.6±1.5 MPa. The dielectric constant of the composite is about 3.1 and the dielectric loss is below 0.5% under different frequencies. [source]

Disequilibrium partial melting experiments on the Leedey L6 chondrite: Textural controls on melting processes

METEORITICS & PLANETARY SCIENCE, Issue 11 2001
S. N. Feldstein
Chips of the L6 chondrite, Leedey, were heated at 1200 °C and log ,O2 = IW-1 for durations of 1 h to 21 days. We observed a progression of kinetically-controlled textural changes in melt and restite minerals and changes in the liquidus mineralogy in response to factors such as volatile loss. During the course of the experiments, both olivine and orthopyroxene recrystallized at different times. Rare relic chondrules could still be identified after 21 days. The silicate melts that form are very heterogeneous, in terms of both major and trace element chemistry, reflecting heterogeneity of the localized mineral assemblage, particularly with respect to phosphates and clinopyroxene. Metal-sulfide melts formed in short-duration runs are also heterogeneous. The experimental data are relevant to aspects of the genesis of primitive achondrites such as the acapulcoites. The observed textures are consistent with a model for acapulcoite petrogenesis in which silicate melting was limited to only a few volume percent of the chondritic source rock. The experiments are also relevant to the behavior of chondritic material that has been partially melted in an impact environment. [source]

Micromechanics for fiber volume percent with a photocure vinyl ester composite

POLYMER COMPOSITES, Issue 3 2007
Richard C. Petersen
Micromechanics for fiber volume percent (Vf) from 0.0Vf to 54.0 Vf were conducted using (3 mm long × 9 ,m diameter) high-purity quartz fibers in a visible-light vinyl ester particulate-filled photocure resin. MTS fully articulated four-point bend fixtures were used with a 40 mm test span and 50 × 2 × 2 mm3 sample dimensions. Specimens were tested following the combined modified ASTM standards for advanced ceramics ASTM-C-1161,94 and polymers ASTM-D-6272,00 for modulus, flexural strength, and yield strength. Experimental data provided reliable statistical support for the dominant fiber contribution expressed through the rule-of-mixtures theory as a valid representation of micromechanical physics. The rule-of-mixtures micromechanics described by Vf could explain 92, 85, and 78% of the variability related to modulus, flexural strength, and yield strength respectively. Statistically significant improvements with fiber addition began at 10.3Vf for modulus, 5.4Vf for flexural strength, and 10.3Vf for yield strength, p < 0.05. In addition, correlation matrix analysis was performed for all mechanical test data. An increase in Vf correlated significantly with increases in modulus, flexural strength, and yield strength as measured by the four-point bending test, p < 10,10. All mechanical properties in turn correlated highly significantly with one another, p < 10,9. POLYM. COMPOS., 28:294,310, 2007. © 2007 Society of Plastics Engineers [source]

Using Acetylene for Selective Catalytic Reduction of NO in Excess Oxygen

CHINESE JOURNAL OF CHEMISTRY, Issue 5 2006
Shan-Shan Yu
Abstract Acetylene as a reducing agent for selective catalytic reduction of NO (C2H2 -SCR) was investigated over a series of metal exchanged HY catalysts, in the reaction system of 0.16% NO, 0.08% C2H2, and 9.95% O2 (volume percent) in He. 75% of NO conversion to N2 with hydrocarbon efficiency about 1.5 was achieved over a Ce-HY catalyst around 300 °C. The NO removal level was comparable with that of selective catalytic reduction of NOx by C3H6 reported in literatures, although only one third of the reducing agent in carbon moles was used in the C2H2 -SCR of NO. The protons in zeolite were crucial to the C2H2 -SCR of NO, and the performance of HY in the reaction was significantly promoted by cerium incorporation into the zeolite. NO2 was proposed to be the intermediate of NO reduction to N2, and the oxidation of NO to NO2 was rate-determining step of the C2H2 -SCR of NO over Ce-HY. The suggestion was well supported by the results of the NO oxidation with O2, and the C2H2 consumption under the conditions in the presence or absence of NO. [source]