• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.1104-1105
• /
• 2006

Several boride sintered bodies such as $TiB_2$, $ZrB_2$, and $SiB_6$ were previously reported. In the present study, the sinterability and physical properties of chromium boride $(CrB_2)$ containing chromium carbide $(Cr_3C_2)$ sintered bodies were investigated in order to determine its new advanced material. The samples were sintered at desired temperature for 1 hour in vacuum under a pressure by hot pressing. The relative density of sintered bodies was measured by Archimedes' method. The relative densities of $CrB_2$ addition of 0, 5, 10, 15 and 20 mass% $Cr_3C_2$ composites were 92 to 95%. The Vickers hardness of the $CrB_2$ with 10 and 15 mass% $Cr_3C_2$ composites were about 14 and 15 GPa at room temperature, respectively. The Vickers hardness at high temperature of the $CrB_2$ addition of 10 mass% $Cr_3C_2$ composite decreased with increasing measurement temperature. The Vickers hardness at 1273 K of the sample was 6 GPa. The Vickers hardness of $CrB_2$ addition of $Cr_3C_2$ composites was higher than monolithic $CrB_2$ sintered body. The powder X-ray diffraction analysis detected CrB and $B_4C$ phases in $CrB_2$ containing $Cr_3C_2$ composites.

• Journal of the Korean institute of surface engineering
• /
• v.34 no.4
• /
• pp.321-326
• /
• 2001

The TiCrN Coatings haying three kinds of Compositions of $Ti_{36}$ $Cr_{26}$ $N_{38}$ , $Ti_{31}$ $Cr_{35}$ $N_{34}$ / and $Ti_{14}$ $Cr_{52}$ $N_{34}$ were deposited on STD 61 steel substrate by arc ion plating and were oxidized between 700 and 100$0^{\circ}C$ to identify the oxide scales formed on the coatings. The oxide scales were then analyzed using EPMA, XRD and GAXRD. During oxidation, the coatings consisting of TiN and CrN phases were reduced to TiO2 and $Cr_2$$O_3$, respectively. Titania tended to form at the outer oxide layer, whereas chromia tended to form at the inner oxide layer, owing to the different oxygen affinity. The substrate elements as well as coating elements diffused outwardly toward the oxide layer due to the concentration gradient. The growth of oxide from the TiCrN coatings was schematically expressed on the basis of thickness measurement of the reacted and unreacted coatings. The Cr element showed its stronger role to keep the TiCrN coatings from oxidation, when compared with Ni.

• Journal of Power System Engineering
• /
• v.9 no.1
• /
• pp.76-81
• /
• 2005

The effect of micro-pulse plasma nitriding temperature and time on the case thickness, hardness and nitride formation in the surface of Fe-12Cr-22Mn-X alloy with 3% Co and 1% Ti alloys elements investigated. External compound layer and internal diffusion layer was constituted in plasma nitride case of Fe-12Cr-22Mn-X alloys and formed nitride phase such as ${\gamma}'-Fe4N\;and\;{\varepsilon}-Fe2-3N$. Case depth increased with increasing the plasma nitriding temperature and time. Surface hardness of nitrided Fe-12Cr-22Mn-X alloys obtained the above value of Hv 1,600 and case depth obtained the above value of $45{\mu}m$ in Fe-12Cr-22Mn-3Co alloy and $60{\mu}m$ in Fe-12Cr-22Mn-1Ti alloy. Wear-resistance increased with increasing plasma nitriding time and showing the higher value in Fe-12Cr-22Mn-1Ti alloy than Fe-12Cr-22Mn-3Co alloy.

• Journal of the Korean institute of surface engineering
• /
• v.46 no.5
• /
• pp.216-222
• /
• 2013

In order to improve the performance of electrodeposited diamond-nickel composite, surface modification of diamond particles was carried out using powder immersion reaction assisted coating (PIRAC). Titanium and chromium were selected as coating elements, which are known as carbide former. With respect to the powder elements, various phases were formed on diamond; metallic Ti and TiC for Ti powder, $Cr_3C_2$ for Cr powder, and TiC and $Cr_3C_2$ for Ti-Cr mixed powder. Surface modified diamond particle showed higher specific surface area, especially Ti coating induced considerable increase of specific surface area. The increase of specific surface area suggests increase of surface roughness, and that was confirmed by surface observation using FE-SEM. In addition, wear properties of diamond-nickel composite including surface modified diamonds were improved, and Ti coated diamond showed the highest performance. The wear property of diamond-nickel composite is dependent on adhesion strength between diamond particle and nickel layer. Therefore, surface modification of diamond particle by PIRAC increasing surface roughness is effective to improve the properties of diamond-nickel composite.

• Journal of Korea Foundry Society
• /
• v.21 no.1
• /
• pp.15-23
• /
• 2001

The changes in the microstructures and $D0_3{\leftrightarrow}B2$ transition temperature were investigated for Fe-30at.%AI-5at.%Cr alloy with the ordered $D0_3$, structure when Ti, Hf and Zr were added respectively. The addition of Cr has no effect on the microstructure. However, as the amount of Ti addition increased, the grain size became smaller. Addition of Ti+Hf, Ti+Zr and Ti+Hf+Zr also showed the similar effect. When 20at.% of Ti was added, the second phase precipitates on the substrate. The addition of Cr, Hf and Zr alone has no effect on $D0_3{\leftrightarrow}B2$ transition temperature. However, as the amount of Ti addition increased by 5, 10, 15 and 20at.%, the transition temperatures showed 929, 930, 960 and $930^{\circ}C$ respectively.

• Journal of the Korean Electrochemical Society
• /
• v.18 no.1
• /
• pp.17-23
• /
• 2015

$Li_4Ti_5O_{12}$ (LTO) have attracted much attention of researchers in the field of energy storage, because of their excellent stability for electric vehicle application. A main drawback of LTO is however their insulating nature due to the wide bandgap, which should be addressed to enhance the battery performance. In this study, we investigated the effect of water solubility of dopant precursor on the electrochemical characteristics of conducting LTO prepared by doping with $Cr^{3+}$ ions with the well-known wet-mixing method. The solubility of dopant precursor directly affected the morphology and the phase of doped LTO, and therefore their battery performance. In the case of employing the most soluble dopant precursor, $Cr(NO_3)_2$, the doped LTO demonstrated a markedly enhanced discharge capacity at high C-rate (130mAh/g @ 10C), which is about 2 times higher value than that of bare LTO.

• Journal of the Korean institute of surface engineering
• /
• v.44 no.5
• /
• pp.196-200
• /
• 2011

The Ni-based superalloy, Inconel 713, was oxidized at $800{\sim}1100^{\circ}C$ for 50 and 100 hours in air. It displayed excellent oxidation resistance, forming a few micrometer-thick scales. The major scale was ${\alpha}-Al_2O_3$. Other scales formed were $TiO_2$, $NiAl_2O_4$ and $Cr_2O_3$. Generally, uniform oxidation occurred over the alloy surface, resulting in the formation of ${\alpha}-Al_2O_3$ with and without $Cr_2O_3$. Other oxides such as $TiO_2$ and $NiAl_2O_4$ sometimes also formed. Locally, nodular oxidation occurred at the nodules that consisted of diverse alloying elements. The scales were adherent at $800^{\circ}C$. However, they spalled a little at $900{\sim}1100^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1991.10a
• /
• pp.68-72
• /
• 1991

In this study, to improve temperature stability 0.05 Pb(Sn$\_$$\frac{1}{2}$/Sb$\_$$\frac{1}{2}$/O$_3$ - 0.35PbTiO$_3$ - 0.60PbZrO$_3$ + 0.4[wt%]MnO$_2$ piezoelctric oeramics of low dielectric constant and large mechanical quality factor were manufactured with the addition of Cr$_2$O$_3$by Hot Press method. And the SAW delay line was fabricated and the propagation characteristics of SAW was investigated, and the SAW filter was fabricated on C4 added by 0.2[wt%] Cr$_2$O$_3$and its frequency characteristics was investigated. The specimen, whose propagation characteristics of surface acoustic wave were the best, was C4 added by 0.2[wt%] Cr$_2$O$_3$, and its electromechanical coupling factor(ks$^2$) was 3.11[%] and its temperature coefficient of the center frequency (C$\_$fo/) was -21.27[ppm/$^{\circ}C$]. The 31[MHz] SAW IF filter of C4 scarcely had diffraction phenomena and its group delay time was 1.4673 ${\pm}$40[ns] in the pass band, and the insertion loss was -24.419[dB] on no impedance matching.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.41 no.5
• /
• pp.502-507
• /
• 1992

To improve temperature stability, 0.05Pb(SnS11/2TSbS11/2T)OS13T-0.35PbTiOS13T-0.60PbZrOS13T+0.4[wt%]MnO S12T piezoelectic ceramics were manufactured with the addition of CrS12TOS13T by Hot Press method. And the SAW delay line was fabricated and effects of CrS12TOS13T to the propagation characteristics of SAW was investigated, and the SAW filter was fabricated on C4 specimen added by 0.2[wt%] CrS12TOS13T whose propagation characteriatics of surface acoustic wave were the bast and its frequency characteristics was investigated. Electromechancal coupling factor(kS1sTS02T) was 3.11[%] and its temperature coefficient of the center frequency(CS1foT)was -21.27[ppm/$^{\circ}C$] in C4. The 31[MHz]]SAW IF filter of C4 scarcely had diffraction phenomena and therefore it was proper.

• Journal of the Korean institute of surface engineering
• /
• v.39 no.6
• /
• pp.263-267
• /
• 2006

As technology advances, there is a demand for development of hard solid lubricant coating. (Ti, Cr, Zr)N-$MoS_2$ films were deposited on AISI H13 tool steel substrate by co-deposition of $MoS_2$ with (Ti, Cr, Zr)N using a D.C. magnetron sputtering process. The influence of the $N_2Ar$ gas ratio, the amount of $MoS_2$ in the films and the bias voltage on the mechanical and structural properties of the films were investigated. The highest hardness level was observed at the $N_2/Ar$ gas ratio of 0.3. Hardness of the films did not change much with the increase of the $MoS_2$ content in the films. As the substrate bias potential was increased, hardness level of the film reached maximum at -150 V. Surface morphology of these films indicated that high hardness was attributed to the fine dome structure.