• Journal of Welding and Joining
• /
• v.23 no.2
• /
• pp.75-80
• /
• 2005

The effect of chemical constituents of $(Cr,\;Fe)_7C_3$ carbide phase on its hardness in the chromium-carbide type Cr white iron hardfacing weld deposits has been investigated. In order to examine $(Cr,\;Fe)_7C_3$ carbide phase, a series of filler metals with varying chromium contents was used. The alloys were deposited once or twice on a mild steel plate using the self?shielding flux cored arc welding process. The hardness of $(Cr,\;Fe)_7C_3$ carbide phase was measured by the micro-Vickers hardness test. It was shown that hardness of $(Cr,\;Fe)_7C_3$ carbide phase increased with increasing Cr content in $(Cr,\;Fe)_7C_3$ carbide phase. This behavior of the hardness of $(Cr,\;Fe)_7C_3$ carbide phase was explained by the types of chemical bonds that hold atoms together in $(Cr,\;Fe)_7C_3$ carbide phase.

• Korean Journal of Materials Research
• /
• v.10 no.7
• /
• pp.489-492
• /
• 2000

Three different white cast irons alloyed with Cr and Si were prepared in order to study their distribution be-havior in matrices and carbides. The specimens were produced using a 15kg-capacity high frequency induction fur-nace. Melts were super-heated to $1600^{\circ}C$, and poured at $1550^{\circ}C$ into a pepset mold. Three combinations of the alloys were selected so as to observe the distribution behavior of Cr and Si : 0.5%C-25.0%Cr-1.0%Si(alloy No. 1), 0.5%C-5.0%Cr-1.0%Si(alloy No. 2) and 2.0%C-5.0%Cr-1.0%Si(alloy No. 3). Cellular $M_7C_3$ carbides-$\delta$ferrite eutectic were developed at $\delta$ferrite liquid interfaces in the alloy No. 1 while only traces of $M_7C_3$ carbides-$\delta$ferrite eutectic were precipitated in the alloy No. 2. With the addition of 2.0% C and 5.0% Cr, ledeburitic $M_3C$ carbides instead of cellular $M_7C_3$ carbides were precipitated in the alloy No. 3. Cr was distributed preferentially to the $M_7C_3$ carbides rather than to the matrix structure while more Si was partitioned in the matrix structure rather than the $M_7C_3$ carbides. $K^m$ for Cr was ranged from 0.56 to 0.68 while that for Si was from 1.12 to 1.28. $K^m$ for Cr had a lower value with increased carbon contents. The mass percent of Cr was higher in the $M_7C_3$ carbides with increased Cr contents.

• Journal of the Korean Magnetics Society
• /
• v.16 no.2
• /
• pp.111-114
• /
• 2006

We investigated the magnetism and electronic structures for the layered structures consisting of (110) layers of zinc-blende CrAs and MnAs. We calculated the electronic structures for $(CrAs)_3(MnAs)_3(110)$ superlattice consisted of alternating three layers of CrAs(110) and MnAs(110) by the full-potential linearized augmented plane wave (FLAPW) method. The calculated magnetic moment of Cr in interface layer ($3.07\;\mu_B$) was slightly larger than that of Cr atom in center layer ($3.06\;\mu_B$), while that of interface Mn atom ($3.74\;\mu_B$) was slightly smaller than the value of Mn atom in center layer ($3.76\;\mu_B$). The electronic structure and half-metallicity in this superlattice were discussed using the calculated density of states.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
• /
• 2009.11a
• /
• pp.258-260
• /
• 2009

광촉매능을 갖는 $TiO_2$는 국내외적으로 많은 연구가 진행되고 있으며, 빛의 조사로 발생하는 다양한 물리 화학적 촉매특성이 환경정화뿐만 아니라 및 에너지 흡수차단 기능도 갖고 있어 최근 주목을 받고 있다. 본 연구에서는 친수성을 가지는 친환경 창호소재용 및 초친수성을 가지는 자동차의 사이드미러 개발을 위해 유리표면에 이종밴드갭을 갖는 복합구조 $TiO_2/Cr_2O_3/Cr$ 박막을 스퍼터링법으로 증착하여 중간층인 $Cr_2O_3$의 역할을 고찰하였다. Cr, 결정질 $Cr_2O_3$ 기판의 경우 Anatase상과 Rutile상이 공존하는 미세조직이 관찰 되었으며 비정질 $Cr_2O_3$ 기판의 경우는 균일한 결정질 anatase-$TiO_2$상이 나타났다.

• Korean Journal of Materials Research
• /
• v.12 no.11
• /
• pp.845-849
• /
• 2002

Alloys of $Fe_3$Al, $Fe_3$Al-6Cr, $Fe_3$Al-4Cr-1Mo, $Ni_3$Al, and $Ni_3$Al-2.8Cr were oxidized at $1000^{\circ}C$ in air, and the oxide scales formed were studied using XRD. SEM, EPMA, and TEM. The oxide scales that formed on $Fe_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$ containing a small amount of dissolved Fe and Cr ions, whereas those that formed on $Ni_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$, together with a small amount of $NiAl_2$$O_4$, NiO and dissolved Cr ions. For the entire alloys tested, nonadherent oxide scales formed, and voids were inevitably existed at the scale-matrix interface.

• Journal of Magnetics
• /
• v.20 no.3
• /
• pp.211-214
• /
• 2015

$Cr_2O_3$ nanoparticles were prepared via one-step reactive laser ablation of Cr in oxygen. The metastable $CrO_2$ phase was obtained through the subsequent oxidation of $Cr_2O_3$ nanoparticles under $O_2$ with gas pressures of up to 40 MPa. The as-prepared $Cr_2O_3$ nanoparticles are spherical or rectangular in shape with sizes ranging from 20 nm to 50 nm. High oxygen pressure annealing is effective in producing meta-stable $CrO_2$ from as-dried $Cr_2O_3$ nanoparticles, and the $Cr_2O_3$ nanoparticles exhibit a weak ferromagnetic behavior with an exchange bias of up to 11 mT that can be ascribed to the interfacial exchange coupling between uncompensated surface spins and the antiferromagnetic core. The $Cr_2O_3/CrO_2$ nanoparticles exhibit an enhanced saturation magnetization and a reduced exchange bias with an increasing faction of $CrO_2$ due to the elimination of uncompensated surface spins over the $Cr_2O_3$ nanoparticles when exposed to a high pressure of $O_2$ and/or possible phase segregation that results in a smaller grain size for both $Cr_2O_3$ and $CrO_2$.

• Journal of the Korean Chemical Society
• /
• v.43 no.4
• /
• pp.418-422
• /
• 1999

A method is described for the selective determination of Cr(III) and Cr(VI) in aqueous solutios by flame atomic absorption spectrometry. Selective extraction of $Cr_2O_7^{2-}$ was performed by Aliquat 336/NIBK from the mixtures of $Cr^{3+}$ and $Cr_2O_7^{2-}$, and the extraction of $Cr^{3+}$ was followed after complex formation with citrate by using the same extractant. The concentraction of each analyte in the extract was determined by $N_2O-C_2H_2$ flame atomic absorption spectrometry. The recoveries of $Cr^{3+}$ and $Cr_2O_7^{2-}$ from 50mL of aqueous solution ranging 0.1~1.0 ${\mu}g/mL$ as Cr respectively by single extractions with 5 mL of 1%(V/V) Aliquat 336/MIBK were resulted as 98.8∼101.7%.

• Journal of radiological science and technology
• /
• v.29 no.4
• /
• pp.241-247
• /
• 2006

Recently, interests and utilization on Computed Radiography(CR) and Digital Radiography(DR) tends to increase owing to an introduction of Picture Archiving and Communication System(PACS) and an accuracy control of special medical equipment for a breast imaging examination. This study was intended to compare and analyze a detector's imaging quality by each system to be used for the breast imaging examination by using ACR Phantom used at the accuracy control. As an evaluation method, a significance and reliability of image's value using the ACR Phantom was analyzed by using SPSS program. The results are followed. 1. For the fiber, there was 3.9 score in Screen-Film, 4.2 score in CR($50{\mu}m$), 3.2 score in CR($100{\mu}m$), and 4.2 score in DR. There was the high score in the order of CR($50{\mu}m$), DR, Screen-Film, and CR($100{\mu}m$)(P<0.05). 2. For the calcification, there was 2.7 score in Screen-Film, 2.5 score in CR($50{\mu}m$), 2.0 score in CR($100{\mu}m$), and 2.9 score in DR. There was the high score in the order of DR, Screen-Film, CR($50{\mu}m$), and CR($100{\mu}m$).(0.025(P<0.05). 3. For Mass, there was 3.8 score in Screen-Film, 3.8 score in CR($50{\mu}m$), 3.6 score in CR($100{\mu}m$), and 4.5 score in DR. There was the high score in the order of DR, CR($50{\mu}m$), Screen-Film, and CR($100{\mu}m$) (P<0.1). 4. As the total score, there was 10.4 score in Screen-Film, 10.6 score in CR($50{\mu}m$), 8.7 score in CR($100{\mu}m$), and 11.3 score in DR. There was the high score in the order of DR, $CR(50{\mu}m$), Screen-Film, and $CR(100{\mu}m$). As shown in the above results, it can be known that DR and Screen-Film System has higher image quality than CR. But, DR has unstability caused by element, and Screen-Film has the low image quality caused by artifact as disadvantages. When Dual-Side CR($50{\mu}m$) was used among CR systems which had the problem of low image quality, it was indicated that there was no difference with Screen-Film System. Because the radiation imaging examination tends to become digitalized, each system for the breast imaging examination will need to be developed and supplemented.

• Korean Journal of Materials Research
• /
• v.10 no.6
• /
• pp.398-402
• /
• 2000

Three kinds of $Al_3Ti-Cr$ alloys, namely, $Al_{67}Ti_{25}Cr_8,\;Al_{66}Ti_{24}Cr_{10}\;and\;Al_{59}Ti_{26}Cr_{15}$, were prepared by induction melting followed by the thermomechanical treatment. The corrosion behavior in 3.5% NaCl solution and the high-temperature oxidation behavior at 1000, 1100 and $1200^{\circ}C$ for the prepared alloys were investigated. Electrochemical results indicated increased resistance to localized corrosion with increasing Cr content. Cr additions were found to prevent passive film from undergoing brittle fracture. XPS results revealed the passive films of $Al_3Ti-Cr$ alloys were composed mainly of $Al_2O_3$ that coexisted with $TiO_2$ and $Cr_2O_3$. The overall oxidation resistance of the prepared alloys were excellent. Specifically, the oxidation resistance increased in the order of $Al_{59}Ti_{26}Cr_{15},\;Al_{66}Ti_{24}Cr_{10}\;and\;Al_{67}Ti_{25}Cr_8$. As the Al content in the base alloys increased, the $Al_2O_3$ formation was facilitated leading to the increased oxidation resistance.

• Journal of the Korean Magnetics Society
• /
• v.21 no.4
• /
• pp.127-131
• /
• 2011

In this paper, we study the electronic and magnetic properties of Cr substituted SiTe in the rock-salt structure compound using the full potential linearized augmented plane wave method within the generalized gradient approximation to the exchange correlation potential. Two stoichiometries are studied: $CrSi_3Te_4$ with 25 %, and $CrSiTe_2$ with 50 % Cr substitution. We found, from the total energy calculations, that the equilibrium lattice constant for cubic $CrSi_3Te_4$ is 11.64 a.u. and a = 7.89 a.u. and c = 11.13 a.u. for tetragonal $CrSiTe_2$. The integer value of the calculated magnetic moment per unit cell, $4{\mu}_B$ for $CrSiTe_2$ suggests that this compound is halfmetallic. The magnetic moment per unit cell for $CrSi_3Te_4$ is slightly larger than $4{\mu}_B$. The magnetic moment on Cr atoms are 3.61 and $3.62{\mu}_B$ in the $CrSi_3Te_4$ and $CrSiTe_2$, respectively. The presence of Cr atoms causes that the other atoms become slightly magnetized in both compounds. The electronic properties and the magnetism are discussed with the calculated spin-polarized density of states.