• Journal of Navigation and Port Research
• /
• v.35 no.7
• /
• pp.569-573
• /
• 2011

In this paper, we developed a Smart Heat Radiating Sheet(SHRS) having the absorption ability of more than 15 dB, and thermal conduction rate more than 20 W/mk for port logistics RFID(Radio Frequency IDentification) system by using AMP(Amorphous Metal Powder) and shielding sheet. Firstly, the EM(Electro_Magnetic) wave absorber samples were fabricated by using AMP and CPE (Chlorinated Polyethylene) with different composition ratios of 80 : 20 wt.% and 85 : 15 wt.%, respectively. Secondly, we fabricated the Smart Heat Radiating Sheet using the shielding sheet to attach EM Wave Absorber. As a result, the Smart Heat Radiating Sheet with absorption ability of 16 dB at 433 MHz and thermal conduction rate is 24 W/mk has been developed with the composition ratio of Amorphous Metal Powder : CPE = 85 : 15 wt.% and thickness of 5.5 mm.

• Journal of Powder Materials
• /
• v.13 no.5 s.58
• /
• pp.305-312
• /
• 2006

Amorphous carbon nanotubes were synthesized by a reaction of benzene, ferrocene and Na mixture in a small autoclave at temperatures as low as $400^{\circ}C$. The resulting carbon nanotubes were short and straight, but their inner hole was filled with residual products. The addition of quartz to the reacting mixture considerably promoted the formation of carbon nanotubes. A careful examination of powder structure suggested that the nanotubes in this process were mainly formed by surface diffusion of carbon atoms at the surface of solid catalytic particles, not by VLS(vapor-liquid-solid) mechanism.

• Journal of Powder Materials
• /
• v.6 no.4
• /
• pp.270-276
• /
• 1999

Ti-Ni-Cu alloy powders were fabricated by ball milling, and the properties of these powders were characterized. Mixed 50Ti-(50-x)Ni-xCu powders of 5 to 10at.%Cu composition were milled for 100 hours using SUS 1/4" balls in argon atmosphere. Ball to powder ratio was 20:1 and rotating speed was 100 rpm. Tensile strength, microstructure and phase transformation of ball milled Ti-(50-x)Ni-xCu powders were studied. After 100 hours milling, Ti, Ni and Cu elements were alloyed completely and an amorphous phase was formed. Amorphous phase was crystallized to martensite(B 19') and austenite(B2) after heat treatment for 1 hour at $850^{\circ}C$. As the Cu contents were increased, tensile strength of extruded 6061Al/TiNiCu was decreased, and B19'martensite phases In the TiNi particles were the causes of high tensile stress of extruded 6061Al/TiNiCu.NiCu.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07b
• /
• pp.670-673
• /
• 2002

Powder synthesis using the alkoxy precursor technique exhibits processing flexibility not available in traditional high temperature solid-state reaction. With proper process control, impurities can be reduced to very low levels. The major distinction of the present work lies in the method of accomplishing the hydrolysis reaction. In the present case, water is not added to the system. Instead the metal alkoxide/alcohol solution is heated to a temperature at which water is formed through dehydration of the alcohol solvent, causing precipitation of the corresponding metal oxide (hydroxide). The present method provides a means of producing amorphous alumina.

• Journal of Powder Materials
• /
• v.14 no.6
• /
• pp.405-409
• /
• 2007

The Cu-based bulk metallic glass (BMG) composites containing Zr-based metallic glass phase have been consolidated by spark plasma sintering using the mixture of Cu-based and Zr-based metallic glass powders in their overlapped supercooled liquid region. The Zr-based metallic glass phases are well distributed homogeneously in the Cu-based metallic glass matrix after consolidation process. The successful consolidation of BMG composites with dual amorphous phases was corresponding to the sound viscous flow of the two kinds of metallic glass powders in their overlapped supercooled liquid region.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.950-951
• /
• 2006

[ $Mg_{55}Y_{15}Cu_{30}$ ] metallic glass powders were prepared by the mechanical alloying of pure Mg, Y, and Cu after 10 h of milling. The thermal stability of these $Mg_{55}Y_{15}Cu_{30}$ amorphous powders was investigated using the differential scanning calorimeter (DSC). $T_g$, $T_x$, and ${\Delta}T_x$ are 442 K, 478 K, and 36 K, respectively. The as-milled $Mg_{55}Y_{15}Cu_{30}$ powders were then consolidated by vacuum hot pressing into disk compacts with a diameter and thickness of 10 mm and 1 mm, respectively. This yielded bulk $Mg_{55}Y_{15}Cu_{30}$ metallic glass with nanocrystalline precipitates homogeneously embedded in a highly dense glassy matrix. The pressure applied during consolidation can enhance thermal stability and prolong the existence of amorphous phase within $Mg_{55}Y_{15}Cu_{30}$ powders.

• Journal of the Korean Ceramic Society
• /
• v.28 no.5
• /
• pp.390-398
• /
• 1991

$\beta$-Sialon powder was prepared from Wando pyrophyllite by the carbothermic reduction and nitridation at 135$0^{\circ}C$ for 10 h nitrogen atmosphere. Amorphous silica prepared from Si(OC2H5)4 was added to Wando pyrophyllite powder in order to control the final Z value. Two different methods were applied for synthesis of $\beta$-sialon powders. In Process A, the amorphous silica prepared from Si(OC2H5)4 was admixed to Wando pyrophyllite powder. Process B was started from the mixture of Wando Y2O3 was added to the synthesized $\beta$-Sialon powders as a sintering aid, and the mixed powders were hot pressed at 175$0^{\circ}C$ for 120 min in nitrogen atmosphere under 30 MPa. Their mechanical properties were compared. The maximum values of M.O.R., hardness and KIC were 667 MPa, 16 GPa and 6.3 MN/m3/2, respectively, and they are the values obtained form $\beta$-Sialon ceramics prepared by process A of Z=0.5.

• Journal of Powder Materials
• /
• v.16 no.5
• /
• pp.363-369
• /
• 2009

The amorphization process and the thermal properties of amorphous Ti$_{40}$Cu$_{40}$Ni$_{10}$Al$_{10}$ powder during milling by mechanical alloying were examined by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The chemical composition of the samples was examined by an energy dispersive X-ray spectrometry (EDX) facility attached to the scanning electron microscope (SEM). The as-milled powders showed a broad peak (2$\theta$ = 42.4$^{\circ}$) with crystalline size of about 5.0 nm in the XRD patterns. The entire milling process could be divided into three different stages: agglomeration (0 < t$_m$ $\leq$ 3 h), disintegration (3 h < t$_m$ $\leq$ 20 h), and homogenization (20 h < t$_m$ $\leq$ 40 h) (t$_m$: milling time). In the DSC experiment, the peak temperature T$_p$ and crystallization temperature T$_x$ were 466.9$^{\circ}C$ and 444.3$^{\circ}C$, respectively, and the values of T$_p$, and T$_x$ increased with a heating rate (HR). The activation energies of crystallization for the as-milled powder was 291.5 kJ/mol for T$_p$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.6
• /
• pp.562-569
• /
• 2009

Recently, Hi-pass system(non-stop electric toll collection) using DSRC is working. However, it has various problems such as system errors by EM wave interference or multi-path reflection. The EM wave absorber is able to solve these problems. In this paper, we designed and fabricated EM wave absorber using amorphous substance. As a result EM wave absorber with composition of amorphous metal powder:CPE=45:55 wt.% has the thickness of 2.65 mm and absorption ability was higher than 40 dB at 5.8 GHz.

• Journal of Powder Materials
• /
• v.17 no.1
• /
• pp.36-43
• /
• 2010

In present work, amorphous TiCuNi powders were fabricated by mechanical alloying process. Amorphization and crystallization behaviors of the TiCuNi powders during high-energy ball milling and subsequent microstructure changes were studied by X-ray diffraction and transmission electron microscope. TEM samples were prepared by the focused ion beam technique. The morphology of powders prepared with different milling times was observed by field-emission scanning electron microscope and optical microscope. The powders developed a fine, layered, homogeneous structure with milling times. The crystallization behavior showed that glass transition, $T_g$, onset crystallization, $T_x$, and super cooled liquid range ${\Delta}T=T_x-T_g$ were 628, 755 and 127K, respectively. The as-prepared amorphous TiCuNi powders were consolidated by spark plasma sintering process. Full densified TiCuNi samples were successfully produced by the spark plasma sintering process. Crystallization of the MA powders happened during sintering at 733K.