Solid State Phenomena Vols. 124-126

Abstract: The electrospinning is a novel and efficient tool for fabrication of carbon nanotube (CNTs) -polymer composites. We have fabricated polymer/CNTs composite by doping multi-walled carbon nanotubes (MWNTs) in nylon fibers using electrospinning technique. The solution, containing MWNTs/nylon, was ejected from the spinneret to form fibers. Spun fibers were collected on the water surface in the water bath and transfer to the winding drum. We observed that, the unwoven fibers were transformed into aligned bundles. The fiber alignment is discussed. The electrical properties of the aligned fibers were analyzed.

Abstract: The organic-inorganic hybrid nanocomposites were successfully obtained by the sol-gel process with tetraethylorthosilicate (TEOS) as an inorganic networking precursor and 2-hydroxyethylmethacrylate (HEMA) as the nonsurfactant template in the presence of benzil initiator. The characteristics of the obtained hybrid were examined by means of TGA, FTIR, SEM, and TEM. The synthesized HEMA/SiO2 hybrid was nearly transparent, monolithic, and monodispersed with the average size of 25 nm. It was found that the hybrid structure could be defined by intertwining organic and inorganic polymeric networks.

Abstract: Poly(ε-caprolactone)/multiwalled carbon nanotube (PCL/MWCNT) composites with different MWCNT contents were successfully prepared by in situ bulk polymerization, which could make them good competitors for commodity materials such as general purpose plastics, while allowing them to completely retain their biodegradability. The mechanical properties of the PCL/MWCNT composites were effectively increased due to the incorporation of the MWCNTs. The composites were characterized using scanning electron microscopy, in order to obtain information on the dispersion of the MWCNTs in the polymeric matrix. In the case where 0.5 wt% of MWCNTs were dispersed in the matrix, the strength and modulus of the composite increased by 23% and 71%, respectively. In addition, the dispersion of the MWCNTs in the PCL matrix resulted in a substantial decrease in the electrical resistivity of the composites being observed as the MWCNTs loading was increased from 0 wt% to 0.5 wt%.

Abstract: Compressive behavior of 7xxx series Al metal matrix composite (MMC) powders with different ceramic contents and different particle size were investigated. As a starting powder of the experiments, ceramic contents of each starting powder were 5 and 10 wt.% and ceramic particle size of starting powder were 20 and 100 ㎛, respectively. And 7xxx Al blended powder was used for comparison. The powders were uniaxially cold-compacted using cylindrical die with a compacting pressure 250 MPa and sintered at 620oC in a dry N2 atmosphere for 60 min with heating rate of 20oC/min. In case of heat treatment condition, sintered parts were solution treated at 475oC and aged at 175oC. To reveal the effect of Al2O3 particle content and particle size on the mechanical properties of composites, compression test were conducted with constant strain rate of 1×10-3/s using sub-size cylindrical samples of 9 mm diameter. Compression test was performed 5 times and its average value was used. Then fractography analysis was conducted using scanning electron microscope.

Abstract: The effect of a microwave-enhanced wet chemical etching process of SiC particles on the electroless copper plating and on the Al/Cu-coated SiC composites was investigated. The microwave-enhanced wet etching process increased the concentration of surface oxides on SiC. The BET surface area of SiC increased, reached its maximum value at 30 s, and then decreased during an etching process. The enhanced chemical adhesion strength between the coated copper and SiC was observed after an etching process. Furthermore, the sintering density and transverse rupture strength (TRS) of Al/Cu-coated SiC composites were improved when SiC particles were etched. This result indicated that the microwave-enhanced etching of SiC particles also improved chemical and mechanical adhesion of Al/Cu-coated SiC composites.

Abstract: Dense nanostructured ZrSi2-SiC composite was synthesized by high frequency induction heated combustion synthesis (HFIHCS) method within 1 minute in one step from powders of ZrC and 3Si. Simultaneous combustion synthesis and densification were accomplished under the combined effects of an induced current and mechanical pressure. Highly dense ZrSi2-SiC with relative density of up to 98% were produced under simultaneous application of a 60MPa pressure and the induced current. The average grain size and mechanical properties (hardness and fracture toughness) of the composite were investigated.

Abstract: Two methods, High-Frequency Induction-Heated Sintering (HFIHS) and Pulsed Current Activated Sintering (PCAS), were utilized to consolidate WC-8wt.%Ni hard materials. The demonstrated advantages of these processes are rapid densification to near theoretical density in a relatively short time and with insignificant change in grain size. The hardness, fracture toughness, and the relative density of the dense WC–8Ni composites produced by HFIHS and PCAS were investigated. And the effect of variation in particle size of WC powder on the sintering behavior and mechanical properties were investigated.

Abstract: The unprecedented technology advancements in miniaturizing integrated circuits, and the resulting plethora of sophisticated, low cost electronic devices demonstrate the impact that micro/nano scale engineering can have when applied only to the area of electrical and computer engineering. Current research efforts in micro/nano fabrication technology for implementing integrated devices hope to yield similar revolutions in life science fields. The integrated life chip technology requires the integration of multiple materials, phenomena, technologies, and functions at micro/nano scales. By cross linking the individual engineering fields through micro/nano technology, various miniaturized life chips will have future impacts in the application markets such as medicine and healthcare.