Abstract: Chromium oxynitride (Cr(N,O)) thin film have been successfully prepared by using pulsed laser deposition. The composition of the thin film was determined to be Cr0.50N0.23O0.28 by Ruthreford backscattering spectroscopy (RBS). The structural analysis was carried out by using X-ray diffraction (XRD), and out-of-plane and in-plane measurements were used to clarify the axial ratio (c/a) of the Cr(N,O) phase. The lattice constants of a and c axes in the Cr(N,O) phase were found to be 0.414 and 0.419 nm, respectively. From these results, the cubic to tetragonal phase change by substitution of the oxygen atoms for nitrogen atoms was confirmed for the crystal Cr(N,O) compounds.
Abstract: Copper nanosized powders were prepared by pulsed wire discharge (PWD) in N2 gas at low pressure (130 Pa) with high-speed gas puff. The pressure around one of the electrodes was changed to investigate the effect of electrical discharge prevention by gas puff. The peak pressure was changed from 22 kPa to 10 kPa in the gas puff apparatus by changing the distance from an acrylic resin tube and a bottom plate. The energy deposition in the copper wire at 22, 15 and 10 kPa was about 40, 37 and 33 J, respectively. The energy deposition in the wire increased with the increase in pressure around the electrode.
Abstract: The effects of hBN content on microstructure, mechanical properties, and machinability of the pressureless-sintered Si3N4 ceramics were investigated. Flexural strength, Young’s modulus, and hardness decreased with increasing h-BN content. The mechanical properties are decreased mainly because of increased porosity of composite, and the much lower Young's modulus of BN
compared to that of Si3N4. Pressureless-sintered Si3N4/hBN composites exhibit strong texture of BN grains oriented with the c-axis parallel to the cold-pressing direction. Cutting resistance of Si3N4 ceramic composites with more than 10 vol% hBN decreased with increasing hBN content, demonstrating a good machinability of the composites. The residual pores can be attributed to improved machinability of pessureless-sintered Si3N4-BN composite.
Abstract: In this study, powder blasting techniques are applied for micro groove forming on the
developed AlN/hBN composites. First, material properties of the composites are evaluated according to the variation of h-BN contents. And, a series of required experimental works are performed to determine optimum powder blasting conditions for micro groove forming. The experiments are performed for the prepared samples with masked patterns. As the results, it can be observed that the machiniability of the developed AlN/hBN composites increases as h-BN contents in the composites. Also, from the experimental results, it is possible to determine the optimum
blasting conditions for micro groove forming on the developed AlN/hBN composites.
Abstract: Sub-micron and nano-sized β-SiC powders were sintered with AlN and Y2O3 as sintering additives by spark plasma sintering (SPS). The sintered densities reached >95% of theoretical with a different molar ratio of AlN to Y2O3 at total amount of 10vol% and temperature of 1900oC for 10min in N2 atmosphere under a pressure of 30MPa. With increasing amount of the AlN additive, the size of SiC grains decreased and the shape changed from globular to columnar. The fully
densified SiC at AlN:Y2O3=95:5mol% had an average grain size of 0.5-1µm and 50-100nm in diameter by using sub-micron and nano-sized SiC starting powders, respectively. Flexural strength of the specimen having grain size of 0.5-1µm was approximately 1200MPa at room temperature.
Abstract: The effect of the impurity ions Al3+, Fe3+ and Mg2+ on the formation yield and crystal
properties of precipitated calcium carbonate(PCC) produced by the carbonation process was investigated in Ca(OH)2-H2O-CO2 system. The effect of the impurity ions Al3+, Fe3+ and Mg2+ on the formation yield using particle size distribution and morphology of PCC were discussed. The particle size distribution of PCC was increased with increase of impurity ions. The morphology was
transformed in order of spheroidal, scalenohedral, rhombohedral calcite for Al3+, Fe3+ and rhombospheroidal, spherical, scalenohedral for Mg2+ with increase of impurity ions.
Abstract: This paper reports fabrication of high temperature stable, chemically inert SiC and SiCN monolithic porous microchannels by micromolding in capillaries (MIMIC) method. These types of high surface area materials hold tremendous untapped potential in micro-total analysis systems, micro-reaction technology and clean energy systems. Owing to their excellent durability under harsh conditions, SiC and SiCN micro-components are imperative in fields like fuel cells, for hydrogen
generation and as environmental sensors. The report also describes the use of template particles of different size and type with diameter of ranging from 0.5 to 1.5 µm to prepare porous, high temperature stable ceramic microchannels. In the present work, ceramic porous channels have been fabricated via polymer to ceramic conversion route by using commercially available polymer precursors.
Abstract: Barium strontium titanate (Ba0.66Sr0.34TiO3) thin films and seed-layers were deposited on the Pt/Ti/SiO2/Si substrate by R.F. magnetron sputtering method. Effects of the substrate temperature on electrical properties of BST thin films were studied. The effect of seed-layer was also studied. From the XRD results, we could confirm that the seeding layer of BST thin film plays a key role in lowering
the crystallization temperature of BST thin films. When seed-layer was inserted between BST and Pt, the crystallization of the BST thin films was considerably improved and the processing temperature was lowered. Compared to the pure BST thin films, dielectric constant, dielectric loss, and leakage current of BST thin films deposited on the seed-layer were considerably improved. It could be
revealed that electrical properties are influenced by the substrate temperatures of BST thin films and are enhanced by the seed-layer.
Abstract: The PZT thin film was deposited by R.F. Magnetron sputtering with Pb 1.1Zr0.53Ti0.47O3 target. When interlayers were inserted at the between PZT and Pt, The grain growth of the PZT thin films was considerably improved by various interlayers (PbO, TiO2, TiO2/PbO) and had low-processing temperature. Compared to the pure PZT thin films, pyroelectric properties of the PZT thin films inserted by interlayers were relatively measured high value. In particular, PZT thin film deposited on interlayer(PbO) was appeared the best pyroelectric properties (P=189.4μ C/㎠K, FD=12.7×10-6Pa-1/2, FV=0.018㎡/C) respectively. As a result of XPS depth profile analysis, both PZT thin film and interlayers were confirmed as independently existing layer respectively.