• Journal of the Korean Magnetics Society
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• v.18 no.1
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• pp.39-42
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• 2008

[ $AB_2X_4$ ](A, B=Transition Metal, X=O, S, Se) are cubic spinel normal ferrimagnets, in which M ions occupy the tetrahedral sites and Cr ions occupy the octahedral sites. Recently, they have been investigated for behaviour of B site ions and A-B interaction. Polycrystalline $[Co_{0.9}Zn_{0.1}]_A[Cr_{1.98}{^{57}Fe_{0.02}}]_BO_4$ compound was prepared by wet-chemical process. The ferrimagnetic transition was observed around 90K. $M\"{o}ssbauer$ absorption spectra at 4.2K show that the well-developed two sextets are superposed with small difference in hyperfine fields($H_{hf}$). The hyperfine fields of $CoCr_{1.98}{^{57}Fe_{0.02}}O_4$ and $Co_{0.9}Zn_{0.1}Cr_{1.98}{^{57}Fe_{0.02}}O_4$ were determined to be 488, 478 kOe and 486, 468 kOe, respectively. We notice that the one of the magnetic hyperfine field values changes with Zn ion substitution. These results suggest the incommensurate states and spin-reorientation temperature($T_S=18K$) changes with Zn ions substitution below spin-reorientation temperature($T_S=28K$) of $CoCr_{1.98}{^{57}Fe_{0.02}}O_4$

• Journal of the Korean Ceramic Society
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• v.39 no.8
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• pp.728-734
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• 2002

Stabilization behavior of Cr, Cd, Cu, Pb, Fe and Zn heavy metals in the EAF dust was investigated by adding EAF dust to clay or white clay, respectively, up to 50 wt% with 10 wt% intervals and sintering at temperatures between 200 and $1200^{\circ}C$ with $200^{\circ}C$ intervals with an aid of ICP-AES followed by TCLP test to evaluate heavy metal cation exchange capacity of the clay or the white clay. The clay or the white clay had a better Cr ion exchange capacity than that of zeolite. The TCLP leaching test for the sintered specimens showed that Cr and Fe were rarely detected for all the specimens and the concentration of Cd and Zn decreased with increasing sintering temperature and decreasing EAF dust contents respectively. When the clay or the white clay were mixed with EAF dust, cation exchange may occur between the clay and the EAF dust so that the first stabilization of the mixtures containing semistabilized heavy metals may happen. Stabilization of heavy metals in the ceramic bodies was further completed probably due to the eutectic reaction caused by the sintering of semi-stabilized mixtures. It was conceivable that the white clay rather than the clay may be a better stabilizer for the EAF dust containing heavy metals.

• Composites Research
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• v.36 no.6
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• pp.441-447
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• 2023

Recently, as demand for high-strength, lightweight materials has increased, there has been great interest in joining with metals. In the case of mechanical bonding, such as bolting and riveting, chemical bonding using adhesives is attracting attention as stress concentration, cracks, and peeling occur. In this paper, surface treatment was performed to improve the adhesive strength, and the change in adhesive strength was analyzed. For the adhesive strength test were conducted with Carbon Fiber Reinforced Plastic(CFRP), CR340(Steel), and Al6061(Aluminum), and laser and plasma surface treatment were used. After plasma surface treatment, the adhesive strength improved by 7.3% and 39.2% in CFRP-CR340 and CFRP-Al6061, respectively. CR340-Al6061 was improved by 56.2% in laser surface treatment. Surface free energy(SFE) was measured by contact angle after plasma treatment, and it is thought that the adhesion strength was improved by minimizing damage through a chemical reaction mechanism. For laser surface treatment, it is thought that creates a rough bonding surface and improves adhesive strength due to the mechanical interlocking effect. Therefore, surface treatment is effect to improve adhesive strength, and based on this paper, the long-term fatigue test will be conducted to prevent fatigue failure, which is a representative cause of actual structural damage.

• Journal of Dental Rehabilitation and Applied Science
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• v.33 no.2
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• pp.71-79
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• 2017

Purpose: Ni-Cr alloy does not contain Beryllium, causing the metal compound to form oxides in the furnace but by using Titanium as a chemical catalyst the forming of the oxides can be controlled, and by controlling the impurities formed on the metal surface, the possibility of the Ni-Cr alloy bond strength being increased can be analysed. Materials and Methods: Titanium was used as a chemical catalyst in the porcelain for the oxidation of beryllium-free metal (Ni-Cr) alloy. The T1 group, which does not use Titanium power as a chemical catalyst is a reference model for comparison. The T2 group and T3 group used 10 g and 20 g of Titanium power, respectively. They are fabricated to observe the shear bond strength and surface properties. There was no significance when One-way ANOVA analysis/Tukey Honestly Significant Difference Test was conducted for statistical analysis among groups (P > 0.05). Results: Results of measuring the three-point flexural bond strength of the Ni-Cr alloy and thickness of the oxide film. Experiment T3 using 20 g Titanium chemical catalyst: $39.22{\pm}3.41MPa$ and $6.66{\mu}m$, having the highest bond strength and thinness of oxide film. Experiment T2 using 10 g Titanium chemical catalyst: $34.65{\pm}1.39MPa$ and $13.22{\mu}m$. Experiment T1 using no Titanium chemical catalyst: $32.37{\pm}1.91MPa$ and $22.22{\mu}m$. Conclusion: The T2 and T3 experiments using Titanium chemical catalyst showed higher bond strength for the Ni-Cr alloy and lower thickness of oxide film than experiment T1, and the titanium catalyst being able to increase bond strength was observed.

• Korean Journal of Materials Research
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• v.21 no.9
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• pp.515-519
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• 2011

The purpose of this study was to determine the optimal firing condition and composition for $Al_2TiO_5$ crystal, which is suitable for stable coloration in glazes at high temperatures, using $Cr_2O_3$ as chromophore for the synthesis of $Al_2TiO_5$ system pigments. $Al_2TiO_5$ has a high refractive index and good solubility of chromophore in the $Al_2TiO_5$ lattice, making this structure a good candidate for the development of new ceramic pigments. Pigments were synthesized by using $Al_2O_3$ and $TiO_2$ mainly. Various amounts of $Cr_2O_3$ such as 0.01, 0.02, 0.03, 0.04 and 0.05 mole were also added. Each compound was synthesized at $1300^{\circ}C$, $1400^{\circ}C$, and $1500^{\circ}C$ for 2 hours and cooled naturally. The crystal structure, solubility limit, and color of the synthesized pigments were analyzed by XRD, SEM, Raman spectroscopy, UV and UV-vis. The changes in color as the result of applying 6 wt% of the synthesized pigments to lime barium glaze were expressed as CIE-L*a*b* values. A $Cr_2O_3$ 0.03 mole doped $Al_2TiO_5$ brown pigment was successfully synthesize at $1400^{\circ}C$, and the values of CIE-L*a*b* parameters were L* = 44.62, a* = 3.10, and b* = 17.25. In the case of the pigment synthesized at $1500^{\circ}C$, the brown color was obtained at 0.01 mole and 0.02 mole $Cr_2O_3$, and the CIE-L*a*b* values were 55.34, 1.73, 28.64, and 49.39, 0.51, 21.33, respectively. At $1500^{\circ}C$, the maximum limit of solid solution was 0.03 mole $Cr_2O_3$. The glazed sample showed green color, and the values of the CIEL* a*b* parameters were L* = 45.69, a* = -0.98, and b* = 20.38.

• Korean Journal of Animal Reproduction
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• v.18 no.3
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• pp.207-216
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• 1994

본 연구는 돼지 난포란으로부터 생산된 수정란의 체외발달에 미치는 아미노산, 우태아혈청 (FBS)과 Leukemia Inhibitry Factor의 영향을 조사하였다. 돼지난포란은 도살된 돼지의 난소로부터 회수하여 39$^{\circ}C$, 5% CO2 배양조건하에서 1$\mu\textrm{g}$/ml FSH-p, 1$\mu\textrm{g}$/ml Estradiol-17$\beta$와 10%FBS가 첨가된 TCM-199 배양액내에서 42시간동안 성숙시켰다. 사출된 정자의 수정능 획득은 45와 90% Percoll density gradient법을 통한 원심분리에 의해 얻었으며, 이들 수정능획득된 정자를 성숙된 난포란이 함유된 배양액에 3$\times$105/ml의 농도로 주입하여 10$\pm$1시간동안 배양함으로서 체외수정을 유도하였다. 수정된 난포란은 ; 1) 10% FBS가 함유된 TCM-199, DMEM, mKRB 또는 CR1aa 배양액, 2) 아미노산 또는 10% FBS가 첨가된 CR1 배양액, 3) STO 세포 또는 mLIF (1,000 unit/ml) 첨가된 CR1aa(10%FBS) 배양액, 4) mLIF (1,000 unit/ml)를 수정 직후 또는 8-세포기 이후에 첨가된 CR1aa(10%FBS)의 네가지 배양조건에서 각각 분리 배양하였다. 그결과 체외수정란의 배반포까지 발달율은 아미노산과 10%FBS가 포함된 CR1 배양액에서 다른 배양액에서보다 양호하였고, 특히 8-세포기 이후에 mouse LIF를 첨가한 CR1aa(10% FBS) 배양액에서는 다른 배양조건보다 현저히 높은 결과를 보였으며, 부화 배반포까지도 배발달을 유도할 수 있었다. 따라서 돼지수정란의 발달에 있어서 배양액내에 아미노산과 FBS 및 mouse LIF의 첨가는 효과가 있으며, 특히 8-세포기 이후에 있어서 mouse LIF의 첨가는 돼지의 수정란을 배반포 이후의 단계에까지 발달시킬 수 있었다.

• Journal of Magnetics
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• v.21 no.1
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• pp.35-39
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• 2016

$Cr_{100-x}Ti_x$ amorphous texture-inducing layers (TIL) were investigated to realize highly (002) oriented $L1_0$ FePt-C granular films through hetero-epitaxial growth on the (002) textured bcc-$Cr_{80}Mn_{20}$ seed layer (bcc-SL). As-deposited TILs showed the amorphous phase in Ti content of $30{\leq}x(at%){\leq}75$. Particularly, films with $40{\leq}x{\leq}60$ kept the amorphous phase against the heat treatment over $600^{\circ}C$. It was found that preference of the crystallographic texture for bcc-SLs is directly affected by the structural phase of TILs. (002) crystallographic texture was realized in bcc-SLs deposited on the amorphous TILs ($40{\leq}x{\leq}70$), whereas (110) texture was formed in bcc-SLs overlying on crystalline TILs (x < 30 and x > 70). Correlation between the angular distribution of (002) crystal orientation of bcc-SL evaluated by full width at half maximum of (002) diffraction (FWHM) and a grain diameter of bcc-SL indicated that while the development of the lateral growth for bcc-SL grain reduces FWHM, crystallization of amorphous TILs hinders FWHM. $L1_0$ FePt-C granular films were fabricated under the substrate heating process over $600^{\circ}C$ with having different FWHM of bcc-SL. Hysteresis loops showed that squareness ($M_r/M_s$) of the films increased from 0.87 to 0.95 when FWHM of bcc-SL decreased from $13.7^{\circ}$ to $3.8^{\circ}$. It is suggested that the reduction of (002) FWHM affects to the overlying MgO film as well as FePt-C granular film by means of the hetero-epitaxial growth.

• Korean Journal of Environmental Agriculture
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• v.27 no.4
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• pp.382-388
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• 2008

This study was initiated to elucidate the relation between the toxicity of $Cr^{6+}$, $Zn^{2+}$, and $Cd^{2+}$ and sludge age (Solids retention time, SRT). The effect of SRT on the toxicity of $Cr^{6+}$, $Zn^{2+}$, and $Cd^{2+}$ in activated sludge system was investigated with INT-dehydrogenase assay. Experimental results showed that the inhibitory effects of $Cr^{6+}$, $Zn^{2+}$, and $Cd^{2+}$ were reduced as the sludge age increased from SRT 5 d to SRT 25 d. It is noteworthy that the experimental results enabled to determine the relative toxicity of the tested metals depending on the sludge age. At the SRT of 5 and 9 days, the order of toxicity of the three metals to the activated sludge was $Cr^{6+}$ > $Zn^{2+}$ > $Cd^{2+}$ (the $IC_{50}$ value of $Cr^{6+}$, $Zn^{2+}$, and $Cd^{2+}$ was 16.15, 25.90, and 32.49 mg/L, respectively) and $Zn^{2+}$ > $Cr^{6+}$ > $Cd^{2+}$ (the $IC_{50}$ value of $Cr^{6+}$, $Zn^{2+}$, and $Cd^{2+}$ was 39.12, 27.93, and 42.31 mg/L, respectively), respectively. However, the toxicity of three metals was almost same at the SRT of 14 and 25 days (the range of $IC_{50}$ in SRT 14 and 25 days was from 49.80 mg/ L to 53.44 mg/L among three heavy metals). This results would be explained by that the quantity of biopolymer formed in short SRT was small, whereas that in long SRT was large. Consequently, it is recommended that sludge age be maintained at long SRT in order to avoid the toxicity inhibition of heavy metals such as $Cr^{6+}$, $Zn^{2+}$, and $Cd^{2+}$.

• 한국해양학회지
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• v.18 no.1
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• pp.29-42
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• 1983

This stidy was intended to investigate the heavy metal contents in the bottom sediments of the continental shelt around the Jeju Island and ot the southern coastal area of the Korean Peninsula. For this study 39 bottom sedinent samples were taken from the study area using Phleger gramity corer and Snapper. The average contents of heavy metals were 59.1 ppm Zn, 362.6 ppm Mn, 63.8 ppm Cr, 15.7 ppm Pb, 10.0 ppm Co, 28.9 ppm Ni, 10.5 ppm Cu, and 2.7% Fe in the surficial sediments around the Jejr Island; and 79.ppm Zn, 384 ppm Mn, 8.6 ppm Pb, 17.8 ppm Ni, 23.2 ppm Cu, and 1.59 % fe in those of nearsgore of the southern coastal area respectively. The heavy metal contents were higher in the northwestern part around the Jeju Island compared to those in other region. However, these tendencies were not the result of pollution, but of the differences of grain size of the sedimenrs. In the nearshore of the southern coast, the heavy metal contents did not show any geographical tendency. However, those of Masan and Jinhae Bays wew higher than those of the other region. These seemed to be caused by waste disposal from the industrial compsex located at the adjacent land. Nevertheless these values of heavy metal content except for Zn and Cu in Masan Bay and inner bay of Jinhae are lower than the average values of the each world-wide data of the nearshore sedimentl. The pair correlations of the cach heavy metal elements were calculated by regressino analysis using VAX 780 computer. the following pair elements, such as Zn-Cu, Ni-Cu, Fe-cu, Cr-Cu, Co-Zn, Ni-Zn, Cr-Zn, Ni-Co, Fe-Co, Cr-Co, Fe-Ni, Cr-Ni and Cr-Fe show closely posetive linear correlations in the sediments around the Jeju Island. In general, the heavy metal content increases in proportion to the increase of the mean values of the grain size of the sediments around the Jeju Island. In the southern coastal area, in gineral, thepair correlations of each heavy metal elements did not southern coastal area, in general, the pair correlatttttions of rach heavy metal elements did not show any positive correlation except for the positive linear correlations of Cu-Zn, Cu-ni and Ni-Mn. It is interpreted as a result of the differences of the physecochemical environment of the sampling sites and also of the influences of the ondustrial wastes from the manufacturing factores located at the coastal zone of the study area.

• 대한방사선방어학회:학술대회논문집
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• 2010.04a
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• pp.182-183
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• 2010