• Transactions of the Korean hydrogen and new energy society
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• v.21 no.5
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• pp.398-404
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• 2010

Process conditions for MEA fabrications have significant effects on properties and performance of the MEAs for PEMFCs. In this study, effects of additives on the surface properties of the MEA was investigated to improve homogeneity of the coated catalyst layer. Another parameter that affects on characteristics of the MEAs is hot-pressing condition. Hot pressing condition was optimized by using DOE (design of experiment) method.

• Journal of Mechanical Science and Technology
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• v.20 no.7
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• pp.1002-1011
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• 2006

In this study, we describe the conventional hot pressing (CHP) of layered $Al-B_4C$ composites and their characterization. The matrix alloy Al-5 wt.%Cu was prepared from elemental powder mixtures. The metal and B4C powders were mixed to produce either $Al-Cu-10vol.%B_4C$ or $Al-Cu-30vol.%B_4C$ combinations. Then, these powder mixtures were stacked as layers in the hot pressing die to form a two-layered composite. Hot pressing was carried out under nitrogen atmosphere to produce $30\times40\times5mm$ specimens. Microstructural features and age hardening characteristics of composites were determined by specimens cut longitudinally. The flexural strength of both layered composites and their monolithic counterparts were investigated via three point bending tests. In the case of layered specimens of both $10vol.%B_4C$ and $30vol.%B_4C$ containing layers were loaded for three-point test. The results show that a homogeneous distribution of $B_4C$ particles in the matrix alloy which is free of pores, can be obtained by CHP method. The ageing behavior of the composites was found to be influenced by the reinforced materials, i.e. higher hardness values were reached in 8 hrs for the composites than that for the matrix alloy. Flexural strength test showed that two-layered composites exhibited improved damage tolerance depending on layer arrangement. Microstructural investigation of the fracture surfaces of the bending specimens was performed by means of scanning electron microscope (SEM). While layer with lower reinforcement content exhibited large plastic deformation under loading, the other with higher reinforcement content exhibited less plastic deformation.

• Journal of Powder Materials
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• v.3 no.4
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• pp.253-259
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• 1996

The efficiency of thermoelectric devices for different applications is known to depend on the thermoelectric effectiveness of the material which tends to grow with the increase of its chemical homogeneity. Thus an important goal for thermal devices is to obtain chemically homogeneous solid solutions. In this work, the new process with rapid solidification (melt spinning method) followed by hot pressing was investigated to produce homogeneous material. Characteristics of the material were examined with HRD, SEM, EPMA-line scan and bending test. Property variations of the materials were investigated as a function of variables, such as dopant ${CdCl}_{2}$ quantity and hot pressing temperature. Quenched ribbons are very brittle and consist of homogeneous $Bi_2Te_3$, ${Bi}_{2}{Se}_{3}$ solid solutions. When the process parameters were optimized, the maximum figure of merit was 2.038$\times$$10^{-3}K^{-4}. The bending strength of the material hot pressed at 50$0^{\circ}C$ was 8.2 kgf/${mm}^2$.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.2
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• pp.125-131
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• 1991

Electrolyte matrix fabrication process can be classifed as hot pressing, tape casting, callendering, electrophoretic deposition. however, these have limits in practice. Hot pressing is cumbersome method, because of careful heating and cooling. Furthermore, the perfected tile is so fragile that it is difficult to fit in a cell. Therefore this method is not adequate for mass production of the electrolyte matrix. Using electrophoretic deposition method, a very thin matrix can be made, but many attempts of the electrolyte embeding were found to be failure. Tape casting and callendering methods are employed in most of the matrix fabrication for the present. But these methods require lots of water as a solvent, so that coating of the LiAlO sub(2) with electrolyte is difficult. Recently, hot roll milling method has been developed and the perfected matrix was proved to be free from crack. The method, however, needs a roller to make a matrix and a perfected matrix is carefully striped off from the cooled roller. Therefore, this method requires a long time due to the cooling process. The author proposes a cold rolling process. On this method, heated slurry of the LiAlO sub(2) mixed with binder, is rolled with a cold roller. The heated slurry dose not adhere to the roller, since contacted hot slurry is rapidly solidified. Therefore fabrication speed is increased, without getting rid of merits of the hot rolling process.

• Journal of the Korean Wood Science and Technology
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• v.25 no.4
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• pp.29-38
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• 1997

The effect and control of wood property of reconstituted composite panels for improved board properties by wood-waste materials and development of combination method for heterogeneous materials have been of interest to the wood science researchers. The purpose of this study is to consider the properties in relation to hot pressing conditions and to develope the optimum hot pressing condition with waste wood and waste tire for the manufacturing of composite boards. The study of composite boards for recycling of wood and waste tire is nothing up to the present. Physical and mechanical properties such as specific gravity, moisture content, swelling coefficient, modulus of rupture and modulus of elasticity in bending test were studied. The condition of 3-stage press time for the lowest moisture content of composite board was $4{\rightarrow}3{\rightarrow}3$ minutes. Specific gravity of composite panels was affected mainly by the amount of rubber chip. Because of the low rigidity and high elasticity in rubber chip, it is considered the composite panel was adequate material in the place of compression load, but not bending load. Therefore, it was concluded that a use of rubber-based wood composite panel is proper to the interior materials such as floor a room than exterior materials. From the test results, the most optimum hot pressing conditions were $4{\rightarrow}3{\rightarrow}3$ minutes for 3-stage press time and $45{\rightarrow}20{\rightarrow}5kg/cm^2$ for 3-stage press pressure. The rubber-based wood composite panel was very excellent in elasticity by combination of rubber chip in comparison with existing other wood-based materials. Therefore, it was considered that rubber-based wood composites can be applicable to every interior materials such as floor a room and will be expected to effective reuse and recycle of waste tires and wood-waste materials, and will be contribute to protection of environment pollution in earth.

• Journal of the Korean Ceramic Society
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• v.24 no.6
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• pp.602-604
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• 1987

The high TcY1Ba2Cu3Ox superconductor has recently gained widespread interest in the scientific community. The principal problems at the present time are how to densify this material and how to raise the critical current density. To date the majority of samples have had densities of 90%(of theoretical) or less. In this study we report that we obtained density of 96% by Hot-Pressing method.

• Journal of the Korean Electrochemical Society
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• v.2 no.4
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• pp.190-194
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• 1999

Etched Nafion membrane and electrode assemblies were fabricated and those performances were observed in PEMFC. Adhesion of membrane to electrode increased with abrasion of membrane surface. Membrane surface ething results in reduction of hot pressing temperature, as a consequence, in improving of cell performance. It was found that Nafion etching was effective in painting method. The optimum content of electrode catalyst should be selected according to etching intensity.

• Journal of the Korean Wood Science and Technology
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• v.32 no.2
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• pp.65-72
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• 2004

A melamine-urea-formaldehyde (MUF) resin, based on 5 percent melamine addition of the resin solids weight, was synthesized in the laboratory for particleboard (PB) manufacture. Laboratory PBs were made with the MUF resin at three press times (3, 4, 5 min) and two resin application rates (6, 8 percent). Enclosed caul system was used for collecting the exhaust gases materials generated during the hot-pressing of PBs. Exhaust gases materials generated inside the enclosed caul during the hot-pressing of PBs were collected in a controlled air stream. Formaldehyde from the exhaust gases collected was determined per a chromotropic method of the National Institute of Occupational Safety and Health Method 3500. The measurement results showed that formaldehyde emissions during the hot-pressing of PB significantly increased with increasing press time, and MUF resin application rates. PB' performance test results showed that internal bond (IB) of PB made with 3-minute press time exceeded the minimum requirement for KS F 3104 PB type 8.0.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.485-490
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• 2010

In our previous studies, continuous SiC fiber-reinforced SiC-matrix composites ($SiC_f$/SiC) had been fabricated by two different slurry infiltration methods: vacuum infiltration and electrophoretic deposition (EPD). 12 wt% of $Al_2O_3-Y_2O_3$-MgO with respect to SiC powder was used as additives for liquid-phase assisted sintering. After hot pressing at $1750^{\circ}C$ under 20 MPa for 2 h in Ar atmosphere, a high composite density could be achieved for both cases, whereas the problems such as large grain size and non-uniform distribution of liquid phase were observed, which was resulted in the relatively poor mechanical properties of composites. Therefore, efforts have been made to reduce the grain growth during the sintering, including the optimization for hot pressing condition and utilization of spark plasma sintering using a SiC monolith. Based on the results, spark plasma sintering was found to be effective method in decreasing the amount of sintering additive, time and grain growth, which will be explained in comparison to the results of hot pressing in this paper.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.2
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• pp.146-153
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• 1993

Thd specimens were melited in high frequency induction furnace. The samples for measurements were prepared by machining cylinder of 9.5mm diameter and 15mm height. These samples were then hot-pressed according to strain rate ( .epsilon. ). These samples were decanned and cut out, and subsequently heat treated at 1000 .deg. C for 4hours. These were investigated for the change of microstructure, domain pattern, X-ray diffraction and magnetic properties. The stress distributions in the specimens during compressing process were calculated by a finite element method program(SPID). The calculated stresses were effective stress( .sigma. $_{eff}$), compressive direction stress( .sigma. $_{z}$), and shear stress( .tau. $_{rz}$ ). These stresses were compared with the experimental data.a.a.