Zinc oxide(ZnO) micro/nanocrystals are grown via thermal evaporation of ZnO powder mixed with Mn powder, which is used as a reducing agent. The ZnO/Mn powder mixture produces ZnO micro/nanocrystals with diverse morphologies such as rods, wires, belts, and spherical shapes. Rod-shaped ZnO micro/nanocrystals, which have an average diameter of 360 nm and an average length of about 12 μm, are fabricated at a temperature as low as 800 °C due to the reducibility of Mn. Wireand belt-like ZnO micro/nanocrystals with length of 3 μm are formed at 900 °C and 1,000 °C. When the growth temperature is 1,100 °C, spherical shaped ZnO crystals having a diameter of 150 nm are synthesized. X-ray diffraction patterns reveal that ZnO had hexagonal wurtzite crystal structure. A strong ultraviolet emission peak and a weak visible emission band are observed in the cathodoluminescence spectra of the rod- and wire-shaped ZnO crystals, while visible emission is detected for the spherical shaped ZnO crystals.

In this study, a relatively effective process is used to sterilize Escherichia coli on the surface of micro-sized calcium citrate powder using nitrogen and argon as process gases in a low-temperature vacuum plasma treatment. The purpose of this study is to confirm and to introduce the effectiveness of homogeneous surface treatment for the sterilization of fine inorganic powder by the rotatable low-temperature RF plasma system designed by ourselves. The results of the test using 3M petrifilm showed that there were no remarkable spots in the case of the surface of plasma treated powder, whereas the untreated powder showed many blue spots, which indicating that the E. coli was alive. After 5 days, in the same samples, the blue spots were seen to be larger and darker than before, while the plasma-treated powder showed no changes. The results from FE-SEM analysis showed that the E. coli was damaged and/or destroyed by reactive species generated in the plasma space, resulting in the E. coli being sterilized. Furthermore, the sterilization effects according to the selected parameters (N2 and Ar; flow rate 30 and 50 sccm) adapted in this study were mutually similar, regardless of such different process parameters, and this indicates that homogeneous treatment of powder surfaces could be more effective than conventional methods. Therefore, the plasma apparatus used in this study may be a practical method to use in a powerful sterilization process in powder-type food.

An optimum route to fabricate a hybrid-structured W powder composed of nano and micro size powders was investigated. The mixture of nano and micro W powders was prepared by a ball milling and hydrogen reduction process for WO3 and W powders. Microstructural observation for the ball-milled powder mixtures revealed that the nano-sized WO3 particles were homogeneously distributed on the surface of large W powders. The reduction behavior of WO3 powder was analyzed by a temperature programmed reduction method with different heating rates in Ar-10% H2 atmosphere. The activation energies for the reduction of WO3, estimated by the slope of the Kissinger plot from the amount of reaction peak shift with heating rates, were measured as 117.4 kJ/mol and 94.6 kJ/mol depending on reduction steps from WO3 to WO2 and from WO2 to W, respectively. SEM and XRD analysis for the hydrogen-reduced powder mixture showed that the nano-sized W particles were well distributed on the surface of the micro-sized W powders.

The effect of the mixing method on the characteristics of hybrid-structure W powder with nano and micro sizes is investigated. Fine WO3 powders with sizes of ~0.6 μm, prepared by ball milling for 10 h, are mixed with pure W powder with sizes of 12 μm by various mixing process. In the case of simple mixing with ball-milled WO3 and micro sized W powders, WO3 particles are locally present in the form of agglomerates in the surface of large W powders, but in the case of ball milling, a relatively uniform distribution of WO3 particles is exhibited. The microstructural observation reveals that the ball milled WO3 powder, heat-treated at 750oC for 1 h in a hydrogen atmosphere, is fine W particles of ~200 nm or less. The powder mixture prepared by simple mixing and hydrogen reduction exhibits the formation of coarse W particles with agglomeration of the micro sized W powder on the surface. Conversely, in the powder mixture fabricated by ball milling and hydrogen reduction, a uniform distribution of fine W particles forming nano-micro sized hybrid structure is observed.

Novel polymer mold process for fabrication of microcomponents using metal nanopowders was developed and experimentally optimized. Polymer mold for forming green components was produced by using a hard master mold and polydimethylsiloxane (PDMS). In the preparation of metallic powder premix for the green components without any defect, 90 wt.% 17-4PH statinless steel nanopowders and 10 wt.% organic binder were mixed by a ball milling process. The green components with very clear gear shape were formed by filling the powder premix into the PDMS soft mold in surrounding at about . Cold isostatic pressing (CIP) was very potent process to decrease a porosity in the sintered microcomponent. The microgear fabricated by the improved process showed a good dimension tolerance of about 1.2%.

Micro-porous nickel (Ni) with an open cell structure was fabricated by powder metallurgy. The pore size of the micro-porous Ni approximated and . For comparison, porous Ni with a macro-porous structure were also prepared by both powder metallurgy (pore size ) and the traditional chemical vapour deposition method (pore size ). The mechanical properties of the micro-and macro-porous Ni samples were evaluated using compressive tests. Results indicate that the micro-porous Ni samples exhibited significantly enhanced mechanical properties, compared to those of the macro-porous Ni samples.

New powder compaction process, in which a Bingham semi-solid/fluid mold is utilized, is developed to fabricate micro parts. In the present process, a powder material is filled as slurry in a solid wax mold, dried and compressed. The wax is heated during compaction and becomes semi-solid state, which can acts as a pressurized medium for isostatic compaction. Since the compacted micro parts are very fragile, the mold's temperature is controlled to higher than its melting point during unloading, to avoid breakage of the compacts. To demonstrate effectiveness of this process, some micro compacts of alumina are shown as examples.

A novel production method for porous metal components has been developed by applying powder space holder (PSH) method to metal powder injection molding (MIM) process. The PSH-MIM method has an industrial competitive advantage that is capable of net-shape manufacturing the micro-sized porous metal products with complicated shapes and controlled porosity and pore size. In this study, the small impeller with homogeneous micro-porous structure was manufactured by the PSH-MIM method. The effects of combinations in size and fraction of PMMA particle on dimensional tolerance and variation of sintered porous specimens were investigated. It was concluded that the PSH-MIM method could manufacture commercially microporous metal components with high dimensional accuracy.

In recent years, micro powder injection molding is being explored as an economical fabrication method for microcomponents in microsystems technology (MST). Technical and economic comparison was performed for processes. Molding experiment and simulation during the filling process were performed to evaluate several different geometries and processing conditions. The influence of material parameters and process conditions on mold filling were examined as a function of features size using microchannels as an example. It was found that the heat conductivity and viscosity of feedstock, geometry and mold temperature were the most critical parameters for complete filling of micro features.

Small powder size is very useful in achieving detailed structures. STS 316 nanopowders with an average diameter of 100 nm and were utilized to produce feedstock. The mixing behavior of the feedstock indicated that the nanoparticle feedstock produced the highest mixing torque at various powder loading compared to the micropowder feedstock. The nanoparticles feedstocks showed that elastic properties are dominant in flow behavior and high viscosity. Conversely the micropowders feedstocks, viscous properties are dominant in flow behavior and less viscosity, nanopowders feedstock perform lower flow activation energy than feedstock with bigger particles.

통상적인 금속분말의 성형은 분말야금 공정으로 이루어지기 때문에 복잡한 형상의 부품을 구현하는 데는 제약이 있다. 하지만, 1970년대 후반 이래 새로운 금속분말의 성형기술로 크게 각광을 받으며 연구되고 있는 금속분말사출성형(Metal Powder Injection Molding, MIM) 기술을 이용하면 다양한 형태의 부품을 성형할 수 있다 최근에는 이러한 MIM 기술을 이용하여 다양한 산업분야에 응용될 수 있는 마이크로 부품을 제조하고자 하는 연구개발

The production of micro components is one of the leading technologies in the fields of information and communiation, medical and biotechnology, and micro sensor and micro actuator system. Microfabrication (micromachining) techniques such as X-ray lithography, electroforming, micromolding and excimer laser ablation are used for the production of micro components out of silicon, polymer and a limited number of pure metals or binary alloys. However, since the first development of microfabrication technologies there have been demands for the cost-effective replication in large scale series as well as the extended range of available material. One such promising process is micro powder injection molding (PIM), which inherits the advantages of the conventional PIM technology, such as low production cost, shape complexity, applicability to many materials, applicability to many materials, and good tolerance. This paper reports on a fundamental investigation of the application of W-Cu powder to micro metal injection molding (MIM), especially in view of achieving a good filling and a safe removal of a micro mold conducted in the experiment. It is absolutely legitimate and meaningful, at the present state of the technique, to continue developing the micro MIM towards production processes for micro components.

When the reinforced concrete structure is in a high salinity environment, chlorine ions penetrate from the surroundings, resulting in corrosion of the reinforcing bars, resulting in low durability. Therefore, studies on the immobilization of chlorine ions are underway, and anion exchange resin, one of them, was used in this study. In this study, chloride ion fixing ability was confirmed by replacing OPC, conventional bead anion exchange resin, and powder anion exchange resin with mortar and then using an electron probe X-ray micro-analyzer. The bead anion exchange resin replaced 3% of the fine aggregate volume and the powder anion exchange resin 5% of the cement volume. The fabricated specimens were cured for 28 days, immersed in NaCl solution for 28 days, and confirmed by electron probe X-ray micro-analyzer.