Advanced Materials Research Vols. 581-582

Abstract: An experimental study was carried out to study the low-velocity impact characteristics and the influence of impact energy on the damage of plain woven carbon fiber reinforced silicon carbide composite. Visual, ultrasonic scanning, X-ray, industrial CT and infrared thermal imaging were then utilized respectively for Nondestructive Testing of the test specimens after impact test. The results show that the material damage area increase significantly with the increase of the impact energy. But as the specimen is run through, when the impact energy comes to12J, the damage area decrease. Compare the changing curves of the damage areas obtained by different detection methods, we can find that the changing trends of the damage areas obtained by ultrasonic C-scan and infrared thermal imaging are the same with the impact energies, indicating that the damage of the specimen are more credible by the two methods.

Abstract: Natural graphite and carbonaceous materials are the most promising materials as the anode for lithium ion batteries. Carbon coating on natural graphite can inhibit the insertion of lithium complex into graphite and reduce its irreversibility. This study verifies that furan resin can be used as a carbon-coating material to enhance the electrochemistry of the charging and discharging cycles. Furan resin changes into amorphous carbon after heat treatment at 1100°C. It is determined that the 40 wt.% furan resin/natural graphite combination material clearly improves the electrochemical properties by electrical cycling tests. The surface properties have been investigated by Raman spectroscopy profiles and the bulk analyzed by X-ray diffraction (XRD) measurements.

Abstract: The effects of heat treatment on microstructure and corrosion resistance of Ni-Cr-Mo-Fe nickel-based alloys were investigated by X-ray diffraction (XRD), metallographic microscope (MM), scanning electron microscopy (SEM) and electrochemical analysis, respectively. Experimental results indicated that the samples which were prepared via electric arc melting shielded by argon were pure solid solutions with homogeneous microstructure. Segregation of chromium element and slightly smaller grain size were found after heat treatment. Better corrosion resistance of samples was achieved after heat treatment, due to improvement of microstructure, morphology and distribution of elements.

Abstract: The effect of hydrogenation on structure and properties of TC21 alloy by die forming and sintering using hydrogenated powder was researched by means of the room-temperature die forming and sintering in protection air to produce titanium alloy. The results show that the structure of TC21 titanium sintered body using hydrogenated powder with hydrogen content of 0.39 wt% by die forming and sintering is thinner and the density is higher than the others. The compression strength and compressive yield strength of TC21 sintered body with hydrogen content of 0.39 wt% are well. With hydrogen content increasing, the structure of TC21 production using hydrogenated powder by die forming and sintering gets well and the grain size becomes smaller. After annealing, the structure of TC21 titanium production gets more uniformity and refinement obviously, and the hydrogen content of TC21 alloy safety state is achieved. In the end, the density and mechanical property of TC21 titanium alloy sintered body with hydrogen content of 0.39wt % is the best.

Abstract: The mullite whiskers were synthesized from commercial raw materials by sintering in air. Three factors influencing the aspect ratio of whiskers, including sintering temperature, holding time and addition amount of V₂O₅, were analyzed based on single factor design and response surface methodology respectively. The optimum conditions for the synthesis of mullite whiskers with highest aspect ratio was obtained, i.e. sintering temperature was 1316.87°C, addition amount of V₂O₅ was 4.09wt.% and holding time was 1.96h. The experiment at the optimum condition was conducted and the real experimental value agrees to the predicted value based on response surface methodology.

Abstract: The magnetorheological fluid is a new smart material. its mechanical properties has been widely known .Under the influence of a magnetic field ,the apparent viscosity of magnetorheological fluid will increase by two orders of magnitude . To verify magnetorheological fluid would have a similar change in the electrical and thermal conductivity, some testing have been done and concludes that under the different magnetic field the conductivity of magnetorheological is variational . At some extend, the stronger the magnetic field the better the electrical and thermal conductivity of magnetorheological fluid. A theoretical explanation for this phenomenon has been given.

Abstract: Several chelating agents in silicon polishing slurries were studied about their effects on copper adhesion to the surface of silicon wafer. The copper contamination level on the Si wafer surface was measured with GFAAS. The results indicate that PAA and HEDP for acid slurries can reduce 80% copper contamination with respect to the situation of without chelating agent. EDTA, the most common chelating agent for alkaline slurries, has no predominant compared with FA/O and AEEA. The copper contamination on Si wafer surface can reduce nearly 50% by adding EDTA while the addition of FA/O or AEEA in the same concentration for alkaline slurries can reach more than 70% reduction of copper contamination level.

Abstract: The effect of suspension casting on the properties of fly-ash particle reinforced aluminum matrix composites is studied in this paper. The result shows that adding suspending agent with the same composition of aluminum matrix ,can improve the microstructure of aluminum matrix composites contain 5vol% fly-ash particle when addition temperature is 800°Cand addition quantity of suspending agent is 3%. The hardness and wear-resistance of fly-ash particle reinforced aluminum matrix composites can be increased by 13.10% and 20.10%.

Abstract: The thermodynamic properties of YCu intermetallics with B2 structure are investigated with molecular dynamics. The thermodynamic properties at various temperatures, such as lattice parameter, cohesive energy, enthalpy of formation, elastic constants, heat capacity, vibrational entropy and vibrational free energy are computed. The present calculated results show good agreements with available experimental and previous calculated data. The calculated elastic constants suggested that YCu compound has a mostly ductile behavior. This prediction match well with experimental findings. At high temperature, the heat capacity tends to a constant with obeys the classical equipartition law. At 300K, the heat capacity of YCu is 23.80J mol-1 K-1. The calculated coefficient of thermal volume expansion α increases sharply at T<20K. When T<300K α gradually approaches a linear increase with enhanced temperature and the propensity of increment becomes moderate. At T=300K, the value of α is 5.88×10-5K-1. And those data enrich thermodynamic data-base for YCu compound.

Abstract: In this paper, LS-DYNA software was used to simulate the penetration of metal-ceramic functionally graded material armor made of Aluminum alloy reinforced by ceramic particle. The ceramic particle volume fraction varies from layer to layer along the armor thickness. The armor’s geometry of the calculation model considered was a four-sides-fixed supported square plate whose side length was far out weight its thickness. The penetrator considered was a long rod projectile, and it impacted the plate with three different speeds along the centre line of the plate. Three different armors with the same areal density were investigated. The results show that at relative low impact velocity, the ballistic resistance has very close relation with the gradient distribution of the armor. At relative high impact velocity, the ballistic resistance of functionally graded armors is not sensitive to the ceramic particle distribution. For the same areal density, the ballistic resistance of ceramic particle reinforced functionally graded armors is better than homogeneous aluminum alloy armor at any velocity situation.