• Journal of Powder Materials
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• v.15 no.6
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• pp.471-476
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• 2008

Sintered Nd-Fe-B magnets have been widely used due to their excellent magnetic properties, especially for driving motors of hybrid and electric vehicles. The microstructure of Nd-Fe-B magnets strongly affects their magnetic properties, in particular the coercivity. Therefore, a post-sintering process like heat-treatment is required for improving the magnetic properties of Nd-Fe-B sintered magnets. In this study, cyclic heat treatment was performed at temperatures between $350^{\circ}C$ and $450^{\circ}C$ up to 16 cycles in order to control microstructures such as size and shape of the Nd-rich phase without grain growth of the $Nd_{2}Fe_{14}B$ phase. The 2 cycles specimen at this temperature range showed more homogeneous microstructure which leads to higher coercivity of 35 kOe than as-sintered one.

• Journal of Magnetics
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• v.15 no.4
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• pp.155-158
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• 2010

The HDDR (hydrogenation, disproportionation, desorption, and recombination) process can be used as an effective way of converting a no coercivity Nd-Fe-B ingot material, with a coarse $Nd_2Fe_{14}B$ grain structure, to a highly coercive one with a fine grain structure. Careful control of the HDDR process can lead to an anisotropic powder with good $Nd_2Fe_{14}B$ grain texture; the most critical step for inducing texture is disproportionation. The critical conditions (hydrogen pressure and temperature) for the disproportionation reaction of fully hydrogenated $Nd_{12.5}Fe_{81.1-(x+y)}B_{6.4}Ga_xNb_y$ (x = 0 or 0.3, y = 0 or 0.2) alloys, in different atmospheres of pure hydrogen and a mixed gas of hydrogen and argon, was investigated with TPA (thermopiezic analyser). From this, the hydrogen pressure-temperature diagram showing the critical conditions was established. The critical disproportionation temperature of the fully hydrogenated $Nd_{12.5}Fe_{81.1-(x+y)}B_{6.4}Ga_xNb_y$ alloys was slightly increased as the hydrogen pressure decreased in both pure hydrogen and mixed gas. The critical disproportionation temperature of the hydrogenated alloys was higher in the mixed gas than in pure hydrogen. Addition of Ga and Nb increased the critical disproportionation temperature of the fully hydrogenated Nd-Fe-B alloys.

• Korean Journal of Veterinary Research
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• v.39 no.6
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• pp.1218-1223
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• 1999

The purposes of this study are to examine seroprevalence of Mycoplasma hyopneumoniae infection in pigs of different age groups, and retrospectively determine if nursery depopulation (ND) could influence the seroprevalence of M hyopneumoniae infection in nurseries. Sera of 4, 8, 12, 16, and 20 weeks old pigs from 7 farms were first selected from a serum bank to examine serologic profiles for M hyopneumoniae infections. Availability of representative sera in the serum bank was a major criterion for farm selection. The sera were tested for M hyopneumoniae antibodies by an enzyme linked immunosorbent assay (ELISA) using Tween-20 extracted antigen. Serum samples were also selected from 15 of 34 swine farms that previously participated in a ND study. In order to evaluate M hyopneumoniae infection following ND, ELISA was performed with sera of 8~10 weeks old nursery pigs collected prior to and after ND for up to 12 months from the 15 farms. Serological profiles showed positive ELISA titers for 2 of 7 farms at 8 weeks, 4 of 7 farms at 12 weeks, 6 of 7 farms at 16 weeks, 6 of 6 farms at 20 weeks of age. Prior to ND, 11 of the 15 farms had positive titers in sera of 8~10 weeks old pigs. Sera of 8~10 weeks old pigs collected from 7 of the 11 farms (63.6%) were ELISA antibody negative for up to 12 months following ND. In conclusion, seroconversion to M hyopneumoniae was detected commonly between 10~16 weeks of age, indicating the occurrence of natural infection during the nursery age. The ND appeared to be an effective method to prevent M hyopneumoniae infection within the nursery pig in some farms.

• Journal of Powder Materials
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• v.26 no.6
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• pp.477-480
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• 2019

Magnetic 0-D Nd₂Fe₁₄B powders are successfully fabricated using 1-D Nd₂Fe₁₄B nanowire formed by an efficient and facile electrospinning process approach. The synthesized Nd-Fe-B fibers and powders are investigated for their microstructural, crystallographic, and magnetic properties according to a series of subsequent heat treatments. Each heat-treatment process leads to the removal of organic impurities and the formation of the respective oxides/composites of Nd, Fe, and B, resulting in the formation of Nd₂Fe₁₄B powders. Nd-Fe-B fibers exhibit the following magnetic properties: The coercivity (H_ci) of 3260 Oe, a maximum magnetization at 3T of 109.44 emu/g, and a magnetization remanence (M_r) of 44.11 emu/g. This process easily mass produces hard magnetic Nd₂Fe₁₄B powders using a 1-D synthesis process and can be extended to the experimental design of other magnetic materials.

• Journal of the Korean Magnetics Society
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• v.22 no.6
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• pp.221-227
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• 2012

High performance permanent magnets have become the subject of considerable attention because of the potential applications in the traction motors of hybrid and electric vehicles and wind generators. Nd-Fe-B magnets have attracted considerable interest due to a large maximum energy product. However, Nd-Fe-B magnet cannot be used in high temperature (${\sim}200^{\circ}C$) applications due to the thermal degradation of coercivity. Therefore, the development of high coercivity Nd-Fe-B permanent magnet is a challenging issue. In case of high coercivity Nd-Fe-B permanent magnet, an increment in the intrinsic coercivity can be easily achieved by substituting Nd atoms with Dy or Tb atoms. However, these heavy rare-earth elements are known to cause a decrease in remanence due to the antiferromagnetic coupling between Dy and Fe atoms. In addition, Dy is relatively expensive and being limited in quantity. Hence, a new technology that can increase the coercivity of Nd-Fe-B sintered magnet using only a small amount, or even, no amount of heavy rare-earth elements is being investigated. This article describes the research trend in reducing the heavy rare-earth elements in Nd-Fe-B magnets.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.226-227
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• 2001

CsLiB$_{6}$O$_{10}$(CLBO) 단결정은 넓은 광투과 영역, 극자외선 영역에서의 광투과성, 비교적 큰 비선형 광학계수, 높은 레이저 광손상 문턱값 등의 우수한 특성으로 인해 극자외선 영역에서의 파장변환과 고출력 레이저의 파장변환에 매우 활발한 응용이 시도되고 있다. 본 연구에서는 CLBO 단결정을 이용하여 Nd：YAG 레이저의 1064 nm 파장을 4차 조화파인 266 nm 파장으로 변환시키고 광변환 특성을 조사하였다. (중략)

• Korean Journal of Poultry Science
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• v.11 no.1
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• pp.49-64
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• 1984

During the 1978-79 Newcastle disease (ND) epizootic period, a detailed survey was conducted on the five representative farms which had been following one of the recommended vaccination programs. When the disease broke out during laying period, clinical symptoms were mild to moderate respiratory distress and greenish diarrhea. Affected flocks experienced weekly mortality from less than 1% to 17%. Egg production returned to normal 18 to 36 days after the initial signs appeared although some flocks never returned to normal. On postmortem examination,, most affected chickens showed severe hemorrhagic lesions in the duodenum, hematoma on ova, and heavy fat accmulation on various visceral organs. Most of the NO affected flocks had geometric mean hemagglutination inhibition antibody(HIA) titers of 7 log$_2$ or higher two to three weeks after the appearance of clinical signs. These HIA titers were at least 16-fold higher than those before infection. Flock mean HIA titers before infection were usually lower than 3 log$_2$. Severity of clinical signs and anamnestic antibody response were maximum in the flocks whose vaccination immunity was insufficient or waned considerably. Observations showed that even young birds, if properly vaccinated, could get effective protection from field ND exposure.

• Transactions on Electrical and Electronic Materials
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• v.6 no.6
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• pp.284-288
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• 2005

We have systematically studied the superconducting properties and flux pinning enhancement of $(Y_{0.33}Sm_{0.33}Nd_{0.33})\;Ba_2Cu_3O_y$ [(YSN)-123] composite oxides by melt growth process in air. A sample prepared by this method showed well-textured microstructure, and $(Y_{0.33}Sm_{0.33}Nd_{0.33})\;BaCuO_5$ [(YSN)211] nonsuperconducting particles were uniformly dispersed in large (YSN) 123 superconducting matrix. The sample showed a sharp superconducting transition at 91 K. The magnetization measurements of the (YSN)-123 sample exhibited the enhanced flux pinning, compared with $YBa_2Cu_3O_y$ (Y-123) sample without Sm and Nd. Critical current densities of (YSN)-123 sample was $2.5{\times}10^4 A/cm^2$ at 2 T and 77 K.

• Analytical Science and Technology
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• v.27 no.5
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• pp.254-260
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• 2014

In this study, heavy metals, PCDD/PCDFs, PAHs in wastes generated from thermal processes were analyzed. Waste from lead thermal metalurgy (EWC 10 04) inorganic metal substances in the regulation were detected in the highest concentrations of Pb. EWC 10 04 seems to be a result of the dust. Waste from zinc thermal metalurgy (EWC 10 05) inorganic metal substances in the regulation were detected in high concentration of Zn. EWC 10 05 seems to be a result of the dust. Waste from copper thermal metalurgy (EWC 10 06) Cu in the 651,77 mg/kg to 651 times higher than regulation standard appeared in the copper thermal metallurgy process seems to be a result of dust. The concentrations of PCDD/PCDFs ranged from 0.0005~11.748 ng-TEQ/g in dust, 0.0027 ng-TEQ/g in fly ash. PCDD/PCDFs content was not detected in excessive value in regulation standard. PAHs concentration was in the range of ND~118.9 mg/kg in Naphthalene, ND~9.6 mg/kg in Phenanthrene, ND~48.4 mg/kg in Benzo[b]fluoranthene, ND~62.6 mg/kg in Benzo[a]pyrene, ND~10.7 mg/kg in Fluoranthene, ND~11.5 mg/kg in Benzo[a]anthracene.

• Proceedings of the KWS Conference
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• 2003.05a
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• pp.90-92
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• 2003