Eco-Materials Processing & Design VII

Volumes 510-511

doi: 10.4028/

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Authors: Tae Yeoung Lim, Y.M. Park, Jong Hee Hwang, Chang Yeoul Kim, Cheol Y. Kim
Abstract: The porous ceramic panel using glass powder as a main raw material can be applied for the thermal insulator in architecture and industry since it is noncombustible and chemically stable as well as eco-friendly unlike the organic thermal insulators. For the study of fabrication and characterization of this material, we used grinded glass powder with grain size smaller than 150, and Calcium carbonate(CaCO3) and Calcium phosphate(Ca3(PO4)2, CaHPO4·2H2O) as foaming agent. The shape and size of pore cell in porous glass structure with the change of additives and sintering temperature were studied. The physical properties as like density, thermal conductivity and compressive strength of materials are also studied. It was possible to make a porous ceramic panel with multi-layered which has the form of sandwich with layer of low density and high density in one body by adjusting the foaming characteristics.
Authors: Jong Gwan Ahn, Dong Jin Kim, Hai Hoang, Jae Ryeong Lee, Hun Saeng Chung
Abstract: Ultra-fine copper powders with an average size of 150 nm were synthesized from Cu(OH)2 .H2O slurry with hydrazine monohydrate as a reduction agent by using the wet reduction method. Parameters such as temperature, reduction agent feeding rate, stirring rate, stirring speed, Cu(OH)2 concentration, and surfactants were investigated. It was found that the feeding rate of hydrazine monohydrate and the use of surfactants mainly affect the morphology and size of the copper powders along with their dispersion. XRD, PSA, and SEM were used to characterize the prepared particles.
Authors: Bum Rae Cho, Han Young Lee
Abstract: Mullite reinforced composites were produced by the injection molding technique to develop environmentally friendly friction materials for automotive applications. In order to examine the effect of mullite content on the friction and wear properties, two different specimens containing 10wt% and 30wt% of mullite were respectively fabricated and wear-tested by using the plate-on-disc type sliding friction and wear test machine. The sliding friction and wear test demonstrated that both specimens show similar tendencies at different sliding speeds under a low load of 2.9N. In comparison with common glass fiber reinforced composites, both of the mullite reinforced composites exhibited a lower wear rate at room temperature.
Authors: Hyoun Woo Kim, Ju Hyun Myung, S.H. Shim
Abstract: We have synthesized gallium oxide (Ga2O3) nanomaterials at two different growth temperatures on iridium (Ir)-coated substrates by thermal evaporation of GaN powders. The products consist mainly of nanobelts, with some additional nanosheets. The nanobelts were of a single-crystalline monoclinic Ga2O3 structure. The broad emission photoluminescence band of 900°C-products had a different peak position from that of the 970°C-products.
Authors: Hyoun Woo Kim, S.H. Shim, Ju Hyun Myung
Abstract: One-dimensional structures of tin oxide (SnO2) on TiN-coated substrates were obtained by simple heating of Sn powders. X-ray diffraction, high-resolution transmission electron microscopy, and the selected area electron diffraction showed that 1D structures are composed of SnO2 with rutile structure. The photoluminescence of the structures in the visible region suggests possible applications in nanoscaled optoelectronic devices.
Authors: Jae Ryeong Lee, Ikkyu Lee, Hun Saeng Chung, Jong Gwan Ahn, Dong Jin Kim, Byoung Gyu Kim
Abstract: As the result of combustion reaction in Al-Al2O3-N2 system, AlON phase can be synthesized in the range of initial nitrogen pressure, from 1 to 5 MPa. On the occasion of rm = 0.3, the unreacted Al was detected in the case of 1 MPa of PN2. Its intensity decreases with an increase of nitrogen pressure. Ultimately, no peak of Al was observed in the product at nitrogen pressure of 5 MPa. In addition, the peak intensity of AlON in the products increases proportionally with the nitrogen pressure, while the intensities of AlN and Al2O3 decrease slightly with an increase of nitrogen pressure. The formation of AlON may be induced by successive two reactions. The former is the formation of AlN, and the latter is the reaction between AlN and Al2O3 in the after-burning period sustaining high temperature.
Authors: Joong Kee Lee, Bup Ju Jeon, Sang Wha Lee
Abstract: Cu/C:H films were prepared on the PET (polyethylene terephthalate) substrate under room temperature by ECR (electron-cyclotron-resonance) chemical vapor deposition coupled with a (-)DC bias system. Hydrogen contents in the plasma strongly affected the crystallographic structures, sheet resistivity, and the composition of deposited films. Cu (111) peaks by XRD analysis were clearly observed with the increase of hydrogen contents. The surface morphology also indicated that copper grains of very fine crystallites were incorporated in the metal-organic composite films by the introduction of hydrogen gas to the plasma. Cu/C:H composite films exhibited a good adhesion force due to the generation of sp3-CH2 bonding. These observations imply that hydrogen induced the formation of stable volatile organic compounds and the reduction of copper, consequently leading to a significant alteration of the crystallographic structure and composition of deposited films. Finally, the EMI shielding efficiency was increased by the addition of hydrogen gas to the plasma, probably due to the increase of copper contents in the film.
Authors: Chong Mu Lee, Yeon Kyu Park, Anna Park, Choong Mo Kim
Abstract: This paper investigated the effects of annealing atmosphere on the carrier concentration, carrier mobility, electrical resistivity, and PL characteristics as well as the crystallinity of ZnO films deposited on sapphire substrates by atomic layer deposition (ALD). X-ray diffraction (XRD) and photoluminescence (PL) analyses, and Hall measurement were performed to investigate the crystallinity, optical properties and electrical properties of the ZnO thin films, respectively. According to the XRD analysis results, the crystallinity of the ZnO film annealed in an oxygen atmosphere is better than that of the ZnO film annealed in a nitrogen atmosphere. It was found that annealing undoped ZnO films grown by ALD at a high temperature above 600°C improves the crystallinity and enhances UV emission.
Authors: Chong Mu Lee, Kyung Ha Kim, Jong Min Lim
Abstract: Since the hexavalent chromium used in chromium electroplating was found to cause cancer in human body, alternative deposition techniques have been widely investigated. Sputter deposition of chromium (Cr) as a deposition technique for replacing electroplating was studied. Effects of RF-power, substrate temperature on the deposition rate, corrosion-resistance, hardness and adhesion strength were investigated. X-ray diffraction (XRD) analysis was performed to determine the structure and the compositions of the films. The hardnesses of the films were measured by using a nanoindenter. The microstructures of the films were observed using scanning electron microscopy. The deposition rate and hardness of the sputter-deposited Cr film tend to increase with the increasing RF-power and substrate temperature of the sputtering process. Both the hardness and adhesion strength of the sputter-deposited chromium film was found to be higher than those of the electroplated chromium film.
Authors: Seung Uk Paik
Abstract: Microcapsules containing agrochemical pesticides used to control insects have attracted considerable interest for the last three decades in the search for reducing intrinsic toxicities, overconsumption, and ecological problems that have been caused generally by conventional pesticides. Biodegradable polyurea microcapsules containing pesticides such as ethyl parathion, benlate, and daconyl were prepared by the interfacial polymerization of polyisocyanate monomers with polyamines. In the process of microencapsulation with various emulsifying agents under the condition of high to medium concentration, polysulfonated emulsifiers such as lignosulfonate and styrenesulfonate sometimes failed to produce microcapsules because of random solidification of the aqueous mass leaving a serious problem of reproducibility. A protective colloid, polyvinylalcohol (PVA), was examined to prepare the stable high-concentrated emulsion under various conditions. Capsule slurry with 33% active ingredient was successfully obtained by the use of ca. 1% PVA as a protective colloid. In the case of the capsule with 42% active ingredient, the wall-forming reaction produced microcapsules, which turned out to be considerably coagulated or sometimes resulted in the failure of producing microcapsules. However, it was found that the mixed emulsifier of 10% of PVA and 90% of poly (sodium4-styrenesulfonate (PSS) produced stable emulsion and successfully led to microcapsules in high concentration under various conditions without any problems of reproducibility. The particle size distribution of the microcapsules was not much influenced by surfactants, and the size and distribution of the obtained microcapsules were directly affected by the agitation speed of emulsion.

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