• International Journal of Korean Welding Society
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• v.3 no.2
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• pp.40-45
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• 2003

A series of experiments has been carried out to investigate the effect of titanium, boron and nitrogen on the microstructure and toughness of simulated heat affected zone (HAZ) in quenched and tempered (QT) type 490MPa yield strength steels. For acquiring the same strength level, the carbon content and carbon equivalent could be lowered remarkably with a small titanium and boron addition due to the hardenability effect of boron during quenching process. Following the thermal cycle of large heat input, the coarsened grain HAZ (CGHAZ) of conventional quenched and tempered (QT) type 490MPa yield strength steels exhibited a coarse bainitic or ferrite side plate structure with large prior austenite grains. While, titanium and boron bearing QT type 490MPa yield strength steels were characterized by the microstructure in the CGHAZ, consisting mainly of the fine intragranular ferrite microstructure. Toughness of the simulated HAZ was mainly controlled by the proper Ceq level, and the ratio of Ti/N rather than titanium and nitrogen contents themselves. In the titanium­boron added QT steels, the optimum Ti/N ratio for excellent HAZ toughness was around 2.0, which was much lower than the known Ti/N stoichiometric ratio, 3.4. With reducing Ti/N ratio from the stoichiometric ratio, austenite grain size in the coarse grained HAZ became finer, indicating that the effective fine precipitates could be sufficiently obtained even with lower Ti/N level by adding boron simultaneously. Along with typical titanium carbo­nitrides, various forms of complex titanium­ and boron­based precipitates, like TiN­MnS­BN, were often observed in the simulated CGHAZ, which may act as stable nuclei for ferrite during cooling of weld thermal cycles

• Polymer(Korea)
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• v.36 no.5
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• pp.549-554
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• 2012

It was known that triphenyl phosphate wasn't homogeneously dispersed in HDPE/EPDM/boron carbide blends, which caused the decrease in mechanical properties. HDPE, EPDM, boron carbide, and triphenyl phosphate were blended with PE-g-MAH(polyethylene-graft-maleic anhydride) as a compatiblizer for improving the miscibility of triphenyl phosphate. Tensile strength of HDPE/EPDM/boron carbide blends decreased with increasing the contents of triphenyl phosphate for flammability. However, the mechanical properties of HDPE/EPDM/boron carbide/triphenyl phosphate blends increased by the addition of compatiblizer because triphenyl phosphate was homogeneously mixed in the blend system. The homogeneous dispersibility of triphenyl phosphate was confirmed by using scanning electron microscopy (SEM). Increased thermal stability and flammability derived from high miscibility of triphenyl phosphate were confirmed by the results of thermogravimetric analysis (TGA) and limiting oxygen index (LOI). A self-extinguishing HDPE/EPDM/boron carbide/triphenyl phosphate blend was successfully fabricated with more than 21% LOI.

• Journal of Photoscience
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• v.3 no.1
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• pp.39-42
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• 1996

The photochemical reaction of phenyl(tribromomethyl)mercury with nido-decaborane gives a new boron cluster expanded compound. The two borons at the 6- and 9- positions in decaborane behave as electrophilic centers for the reaction with dibromocarbene. The first step in this reaction is the addition of two molar equivalents of dibromocarbene which is produced from phenyl(tribromomethyl)mercury to nido-decaborane. In the second step the unstable intermediate generates the product, 1,2-$Br_2C_2B_{10}H_{10}$ through loss of H$_2$.

• Journal of the Korean Chemical Society
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• v.15 no.4
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• pp.171-175
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• 1971

Significant structure theory has been applied to the viscosities of supercooled liquids with success. In the supercooled region, the effect of free volume decrease is so significant that the thermal effects on the solid-like volume must be considered properly. In addition, the two state theories proposed by Jhon and Eyring for water and Litovitz et al. for boron trioxide have been successfully applied to the structure change in the liquid state. Considered liquids are benzene, carbon tetrachloride, p-xylene, water and boron trioxide.

• Journal of Korea Foundry Society
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• v.36 no.5
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• pp.147-152
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• 2016

Aluminum has been used as an alternative material for copper, due to its good electrical and thermal conductivities. However, small quantities of transition elements such as Ti and V affect the conductivities of aluminum. Therefore, in this study, the influence of B addition to reduce the effects of Ti and V on the conductivities of aluminum was investigated. Both the electrical and thermal conductivities of aluminum were improved with addition of B up to 0.05 wt%, while the conductivities were gradually reduced with an excess amount of B. SEM-EDS and XRD results exhibited that B reacted with Ti and V element to form diborides, such as $TiB_2$ and $VB_2$ phase, and those diborides tended to settle down to the bottom of the crucible because their densities were higher than that of aluminum melt. As a result, B reduced the deleterious effects of Ti and V, and the electrical and thermal conductivities of aluminum were improved.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.1
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• pp.25-32
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• 2020

Generally, high-temperature, high-pressure, high-priced sintering equipment is used for diamond sintering, and conductivity is a problem for improving the surface modification of the sintered body. In this study, to improve the efficiency of diamond sintering, we identified a new process and material that can be sintered at low temperature, and attempted to develop a composite thin film that can be discharged by doping boron gas to improve the surface modification of the sintered body. Sintered bodies were sintered by mixing Si and two diamonds in different particle sizes based on CIP molding and HIP molding. In CVD deposition, CVD was performed using WC-Co cemented carbide using CH₄ and H₂ gas, and the specimen was made conductive using boron gas. According to the experimental results of the sintered body, as the Si content is increased, the Vickers hardness decreases drastically, and the values of tensile strength, Young's modulus and fracture toughness greatly increase. Conductive CVD deposited diamond was boron deposited and discharged. As the amount of boron added increased, the strength of diamond peaks decreased and crystallinity improved. In addition, considering the release processability, tool life and adhesion of the deposition surface according to the amount of boron added, the appropriate amount of boron can be confirmed. Therefore, by solving the method of low temperature sintering and conductivity problem, the possibility of solving the existing sintering and deposition problem is presented.

• Journal of Powder Materials
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• v.25 no.2
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• pp.120-125
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• 2018

Boron nitride nanotubes (BNNTs) are receiving great attention because of their unusual material properties, such as high thermal conductivity, mechanical strength, and electrical resistance. However, high-throughput and high-efficiency synthesis of BNNTs has been hindered due to the high boiling point of boron (${\sim}4000^{\circ}C$) and weak interaction between boron and nitrogen. Although, hydrogen-catalyzed plasma synthesis has shown potential for scalable synthesis of BNNTs, the direct use of $H_2$ gas as a precursor material is not strongly recommended, as it is extremely flammable. In the present study, BNNTs have been synthesized using radio-frequency inductively coupled thermal plasma (RF-ITP) catalyzed by solid-state ammonium chloride ($NH_4Cl$), a safe catalyst materials for BNNT synthesis. Similar to BNNTs synthesized from h-BN (hexagonal boron nitride) + $H_2$, successful fabrication of BNNTs synthesized from $h-BN+NH_4Cl$ is confirmed by their sheet-like properties, FE-SEM images, and XRD analysis. In addition, improved dispersion properties in aqueous solution are found in BNNTs synthesized from $h-BN+NH_4Cl$.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.06a
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• pp.207-209
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• 1997

Influences of boron addition on the oxygen solubiligy in silicon melt and the amount of evaporation loss from the melt surface were investigated. It has been found the oxygen concentration increases from 2${\times}$1018 to 4${\times}$1018 atoms/㎤. The amount of evaporation loss was found to vary widely depending on the melt temperature. The amount of SiO evaporating form boron doped (∼102121 atoms/㎤) silicon melt at 1550$^{\circ}C$ is about twice as much as the value of non-doped melt.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.205-209
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• 2009

Wetting properties between silver-copper-titanium braze alloys with different titanium contents up to 2.8 mass% and hexagonal boron nitride ceramics were investigated using sessile drop method at 1123K in Argon. The final contact angle is less than $30^{\circ}$ when the Ti content was over 0.41 mass%. Meanwhile, the contact angle curves show different behavior. In case of using braze alloy containing 2.8 mass% of titanium, the initial contact angle is acute angle just after the melting of braze. In case of brazes containing titanium less than 2.26 mass%, the contact angle is larger than $90^{\circ}$ at the beginning and slowly decreases to acute angle. The reaction layer of titanium nitride is observed at the interface. In addition, the reaction of Ti in the braze and N in the bulk h-BN seemed to show diffusion limited spreading.

• Current Photovoltaic Research
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• v.6 no.4
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• pp.94-101
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• 2018

Light elevated temperature induced degradation (LeTID) was noted as an issue in multi-crystalline silicon solar cells (MSSC) by Ram speck in 2012. In contrast to light induced degradation (LID), which has been researched in silicon solar cells for a long time, research about both LeTID and the mechanism of LeTID has been limited. In addition, research about LeTID in single-crystalline silicon solar cells (SSSC) is even more limited. In order to improve understanding of LeTID in SSSC with a passivated emitter rear contact (PERC) structure, we fabricated four group samples with boron and oxygen factors and evaluated the solar cell characteristics, such as the cell efficiency, $V_{oc}$, $I_{sc}$, fill factor (FF), LID, and LeTID. The trends of LID of the four group samples were similar to the trend of LeTID as a function of boron and oxygen.