• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.411.1-411.1
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• 2016

In this study, we examined the effects of boron doping on the dielectric reliability of solution processed aluminum oxide ($Al_2O_3$). When boron is doped in aluminum oxide, the hysteresis reliability is improved from 0.5 to 0.4 V in comparison with the undoped aluminum oxide. And the accumulation capacitance is increased when boron was doped, which implying the reduction of the thickness of dielectric film. The improved dielectric reliability of boron-doped aluminum oxide is originated from the small ionic radius of boron ion and the stronger bonding strength between boron and oxygen ions than that of between aluminum and oxygen ions. Strong boron-oxygen ion bonding in aluminum oxide results dielectric film denser and thinner. The leakage current of aluminum oxide also reduced when boron was doped in aluminum oxide.

• Carbon letters
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• v.1 no.2
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• pp.64-68
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• 2000

This paper describes the mechanical properties and oxidation resistance of carbon fibers with and without additions of boron oxide additives, and describes the changes in the properties resulting from increased heat treatment temperature (HTT) of the fibers. Carbon fibers in this experiment were heat treated up to $2800^{\circ}C$ each with and without boron oxide treated on the surface of fibers. In the case of boron oxide added carbon fibers, they do not show the improvement of tensile strength and modulus compared to those of no treated carbon fibers below $2200^{\circ}C$ since they are doped substitutionally with boron above $2600^{\circ}C$, which accelerate the graphitization of carbon fibers. Boron oxide implanted carbon fibers showed high resistance to oxidation, however, when carbon fibers were heat treated below $2200^{\circ}C$, they showed almost the same trend of air oxidation.

• Korean Journal of Materials Research
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• v.28 no.5
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• pp.279-285
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• 2018

Graphene is an interesting material because it has remarkable properties, such as high intrinsic carrier mobility, good thermal conductivity, large specific surface area, high transparency, and high Young's modulus values. It is produced by mechanical and chemical exfoliation, chemical vapor deposition (CVD), and epitaxial growth. In particular, large-area and uniform single- and few-layer growth of graphene is possible using transition metals via a thermal CVD process. In this study, we utilize polystyrene and boron oxide, which are a carbon precursor and a doping source, respectively, for synthesis of pristine graphene and boron doped graphene. We confirm the graphene grown by the polystyrene and the boron oxide by the optical microscope and the Raman spectra. Raman spectra of boron doped graphene is shifted to the right compared with pristine graphene and the crystal quality of boron doped graphene is recovered when the synthesis time is 15 min. Sheet resistance decreases from approximately $2000{\Omega}/sq$ to $300{\Omega}/sq$ with an increasing synthesis time for the boron doped graphene.

• Journal of the Korean Ceramic Society
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• v.41 no.11
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• pp.812-818
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• 2004

This study has been undertaken with objective of studying the mechanism and condition of formation of hexagonal boron nitride from reduction of boric okide in the presence of carbon under nitrogen atmosphere. It was found that the formation of hexagonal boron nitride was started at 1400$^{\circ}C$ and almost completed its conversion at 1550$^{\circ}C$. The morphology of boron nitride synthesized in this study was very fine and platelet. It was considered as reaction pathway of hexagonal boron nitride that boron oxide was reduced to born and evaporated by activated carbon, and then it was reacted with nitrogen.

• Journal of the Korean Ceramic Society
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• v.27 no.7
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• pp.869-876
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• 1990

Hexagonal boron nitride was synthesized from boron oxide and sodium amide in ammonia gas stream. The reaction mechanisms and characteristics of as synthesized boron nitride was investigated by means of TG, DTA, IR, XRD, SEM and PSA. The results are ; 1) hexagonal boron nitride was synthesized from reactions at temperatures above 40$0^{\circ}C$ 2) Sodium metaborate was present as by-product after reaction so that the reaction mechanism is reduced as follows : 2B2O3＋3NaNH2longrightarrowBN＋3NaBO2＋2NH3. 3) boron nitride obtained at the reaction temperature below 40$0^{\circ}C$ is found to have random layer strudcture but the structure transits to ordered layer structure rapidly with increasing reaction temperature, showing separation of (101) differaction line from (10)band in XRD pattern of the reaction product at 50$0^{\circ}C$.

• 연구논문집
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• s.29
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• pp.141-149
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• 1999

Brazing of Fe-Cr-Al alloy was carried out at $1200^{\circ}C$ in vacuum furnace using nickel-based filler metals : BNi-5 powder(Ni-Cr-Si-Fe base alloy} and MBF-50 foil (Ni-Cr-Si-B). The effect of boron content on the stability of oxide scale on the brazed joint was investigated by means of cyclic oxidation test performed at $1050^{\circ}C$ and $1200^{\circ}C$. Apparently, the joints brazed with MBF-50 containing boron showed relatively stable oxidation rates compared to boron-free BNi-5 at both temperatures. However, it was considered that the slower weight loss of MBF-50 brazed specimen wasn’t resulted from the low oxidation rate but from the spallation of oxide layer. The oxide layer consisted of thick spinel oxide on the surface and $Al_2 O_3$ internal oxide layer along the interface between mother alloy and braze, the mother alloy was also eroded seriously by the formation of spinel oxides such as $FeCr_2 O_4$ and $NiCr_2 O_4$ on the surface, likely to be induced by the change of oxide forming mechanism due to diffusion of boron from the braze. On the contrary, the joint brazed with BNi-5 showed the good oxidation resistance during the cyclic oxidation test. It seems that the oxidation can be retarded by the formation of stable $Al_2 O_3$ layer at the surface.

• Carbon letters
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• v.5 no.3
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• pp.127-132
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• 2004

Chop molding composites and 2D carbon/carbon composites were manufactured by hot press molding method. Phenol resin of novolac type was used for matrix precursor and PAN-based carbon, PAN-based graphite and pitch-based carbon fiber were used for reinforcement and boron oxide was used for oxidation retardant. All of the composites were treated by $2000^{\circ}C$ and $2400^{\circ}C$ graphitization process, respectively. After graphitization process, amount of a boron residue in carbon/carbon composites is much according to irregularity of used raw materials. Under the presence of boron in carbon/carbon composites, catalytic effect of boron was a little at $2000^{\circ}C$ graphitization temperature. However, it was quite at $2400^{\circ}C$ graphitization.

• Journal of the Korean Applied Science and Technology
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• v.31 no.4
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• pp.731-739
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• 2014

Aluminum and boron co-doped zinc-oxide(AZOB) powders as transparent conducting oxide(TCO) were prepared by spray pyrolysis at $900^{\circ}C$. The micron-sized AZOB particles were prepared by spray pyrolysis from aqueous precursor solutions for aluminium, boron, and zinc. The micron-sized AZOB particle after the spray pyrloysis underwent post-heat treatment at $700^{\circ}C$ for 2 hours and it was changed fully to nano-sized AZOB particle by ball milling for 24 hours. The size of primary AZOB particle by Debye-Scherrer Equation and surface resistance of AZOB pellet were measured.

• Korean Journal of Materials Research
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• v.28 no.9
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• pp.495-498
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• 2018

Intermetallic compound matrix composites have been expected to be established as high temperature structural components. $Ni_3Al$ is a representative intermetallic alloy, which has excellent ductility even at room temperature by adding certain alloying elements. $Ni_3Al$ matrix composites with aluminum oxide particles, which are formed by the in-situ reaction between the alloy and aluminum borate whiskers, are fabricated by a powder metallurgical method. The addition of aluminum borate whiskers disperses the synthetic aluminum oxide particles during sintering and dramatically increases the strength of the composite. The uniform dispersion of reaction synthesized aluminum oxide particles and the uniform solution of boron in the matrix seem to play an important role in the improvement in strength. There is a dramatic increase in strength with the addition of the whisker, and the maximum value is obtained at a 10 vol% addition of whisker. The $Ni_3Al$ composite with 10 vol% aluminum oxide particles $0.3{\mu}m$ in size and with 0.1 wt% boron powder fabricated by the conventional powder metallurgical process does not have such high strength because of inhomogeneous distribution of aluminum oxide particles and of boron. The tensile strength of the $Ni_3Al$ with a 10 vol% aluminum borate whisker reaches more than twice the value, 930 MPa, of the parent alloy. No third phase is observed between the aluminum oxide and the matrix.

• Transactions of Materials Processing
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• v.31 no.1
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• pp.17-22
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• 2022

Hot stamping is widely used to manufacture structural parts to satisfy requirements of eco-friendly vehicles. Recently, hot forming technology using uncoated steel sheet is being studied to reduce cost and solve patent problems. In particular, research is focused on process technology capable of suppressing the generation of an oxide layer. To evaluate the oxide layer in the hot stamping process, Gleeble testing machine can be used to evaluate the oxide layer by controlling the temperature history and the atmosphere condition. At this time, since cooling by gas injection is impossible to protect the oxide layer on the surface of a specimen, research on a method for securing a quenching speed through natural cooling is required. This paper proposes a specimen shape design method to secure a target quenching speed through natural cooling when evaluating the oxide layer of an un-coated boron steel sheet by Gleeble test. For the evaluation of the oxide layer of the un-coated steel sheet through the Gleeble test, dog-bone and rectangular type specimens were used. In consideration of the hot stamping process, the temperature control conditions for the Gleeble test were set and the quenching speed according to the specimen shape design was measured. Finally, the quenching speed sensitivity according to shape parameter was analyzed through regression analysis. A quenching speed prediction equation was then constructed according to the shape of the specimen. The constructed quenching speed prediction equation can be used as a specimen design guideline to secure a target quenching speed when evaluating the oxide layer of an un-coated boron steel sheet by the Gleeble test.