• 한국공작기계학회논문집
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• 제16권4호
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• pp.119-126
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• 2007

Generally, the machinability of materials that have a good mechanical properties is poor. The material having a high strength, high toughness in high temperature and wear resistance, it is difficult to remove a chip from workpiece. STD11 and NAK80 are kinds of these materials and these materials can be used in many industrial fields. But it is limited in use because of high cost and poor machinability. In this experimental study, the cutting of STD11 and NAK80 were used to decide the machinability and the tool shape of CBN ball end mill. From the results, the CBN ball end mill is verified that the estimated cutting edge shape of rake angle 30 degree has consistent effect on the tool wear and cutting force.

• International Journal of Precision Engineering and Manufacturing
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• 제3권1호
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• pp.76-82
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• 2002

This paper presents an experimental study of the effect of cutting tool materials on surface quality when turning hardened steels. Machining tests on a lathe are performed using polycrystalline cubic boron nitride (PCBN) and ceramic tools at various cutting conditions without coolant. From the experiments, it is observed that the radial force is the largest force component regardless the type of tool used. The specific cutting energy for the hard turning is estimated to be considerably smaller than the specific grinding energy. It is also found that cutting force and surface roughness with the PCBN tools are higher and better than those with the ceramic tools under the same cutting condition. It is due that the PCBN tools transfer the generated heat more effectively than the ceramic tools due to their higher thermal conductivity. The optimal cutting conditions for the best surface quality are selected by using an orthogonal array concept.

• 한국응용과학기술학회지
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• 제24권4호
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• pp.369-376
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• 2007

우리는 마이카, boron nitride, bismuthoxychloride와 같은 판상 분체에 ZnO 나노입자를 코팅한 고 기능성 무기 분체를 합성하였다. 본 실험에서 우리는 수열침전법을 이용하여 합성 분체를 합성하였다. 출발물질은 $ZnCl_2$를 사용하였고 침전제로는 hexamethylenetetramine(HMT)와 urea를 사용하였다. 본 실험의 반응변수로는 출발물질의 농도, 침전제 및 반응온도를 변화시켜 실험하였다. 합성물의 형태, 결정성 및 UV-차단능은FE-SEM, XRD, FT-IR, TGA-DTA, in vitro SPF 테스트를 활용해 분석하였다. 본 실험의 결과, 나토입자 크기를 갖는 ZnO는 동일한 최적의 합성조건하에서 다양한 판상 분체의 종류에 관계없이 균일하게 코팅되었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.900-902
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• 1999

This paper deals with the interrupting characteristics of fuses element in different media of arc extinguisher. Aluminum hydro-oxide, boron nitride, silica and there size have been investigated here for their prospects as filling media in heavy current, high breaking capacity fuses. The result of these study are compared with those on silica sand at high current. This study demonstrates that silica sand is far superior filler in fuses for heavy current interrupting then the compound tested.

• 한국정밀공학회지
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• 제34권4호
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• pp.253-258
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• 2017

This paper presents a numerical study on the thermal characteristics of a milling process of titanium alloy with nanofluid minimum-quantity lubrication (MQL). The computational fluid dynamics (CFD) approach is introduced for establishing the numerical model for the nanofluid MQL milling process, and estimated temperatures for pure MQL and for nanofluid MQL using both hexagonal boron nitride (hBN) and nanodiamond particles are compared with the temperatures measured by thermocouples in the titanium alloy workpiece. The estimated workpiece temperatures are similar to experimental ones, and the model is validated.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.20-25
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• 1996

The needs to machine hardened steels with high productivity and good surface integrity have been increased in the dies ＆ molds industry. This paper presents some experimental results on the CBN ball endmilling for hardened tool steel. This investigation concerns on the effects of cutting speed and cutting fluids on the cutting performance such as cutting forces, tool wear, and surface finish. The wear of CBN ball endmill for each cutting conditions were also examined through the microscopic observation. It has been found out that the higher cutting speeds with cutting fluids result in better cutting performance.

• 한국생산제조학회지
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• 제7권5호
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• pp.29-37
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• 1998

In recent years, grinding techniques for precision machining of stainless steel used in shaft, screw parts and clear value have been improved by using the superabrasive wheel and precision grinding machine. The completion of optimum dressing of superabrasive wheel makes possible the effective precision grinding of stainless steel. However, the present dressing system cannot have control of optimum dressing of the superabrasive wheel. In this study, a new system and the grinding mechanism of optimum in-process dressing of superabrasive wheel. Therefore, the optimum in-process electrolytic dressing is a good method to obtain the efficiency and mirror-like grinding of stainless steel (STS304)

• 한국분말재료학회지
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• 제8권3호
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• pp.174-178
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• 2001

The microstructure and mechanical properties of $Si_3N_4/BN $nanocomposites synthesized by chemical processing were investigated. The nanocomposites containing 15 vol% hexagonal BN (h-BN) were fabricated by hot-pressing $\alpha-Si_3N_4$powders covered with turbostratic BN (t-BN). The t-BN coating on $\alpha-Si_3N_4$particles was prepared by heating $\alpha-Si_3N_4$ particles covered with a mixture of boric acid and urea in hydrogen gas. TEM observations of this nanocomposite revealed that nano-sized h-BN particles were homogeneously dispersed within $Si_3N_4$grains as well as at grain boundaries. The strength and thermal shock resistance were significantly improved in comparison with the $Si_3N_4/BN$ microcomposites.

• EDISON SW 활용 경진대회 논문집
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• 제4회(2015년)
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• pp.388-391
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• 2015

본 연구에서는 탄소로 이루어진 그래핀과 붕소와 질소의 합성물인 h-BN을 적절하게 섞어, 밴드갭(band gap)의 변화를 범밀도함수이론(DFT)을 통하여 설계하려고 한다. 본 연구에서 태양전지의 가장 높은 효율을 가지기 위한 밴드갭 1.2eV 가지는 모델을 설계하려고 한다. Armchair 방향으로 B와 N을 도핑을 하여 width에 따른 Nanorribbons 형태를 만들어 밴드갭(band gap)의 변화를 살펴 볼 것이다. 그래핀과 h-BN을 각각 고정시키며 다른 한쪽의 width를 늘리면서 밴드갭(band gap)의 변화도 살펴 볼 것이다. 그래핀와 h-BN의 비가 5:3일 때 1.14eV로 가장 1.2eV에 비슷하게 나왔고 3:5일 때 1.12eV로 그 다음으로 가장 가까운 결과를 얻을 수 있엇다. 또한 비슷한 밴드갭을 가지더라도 그러한 원자 구조가 얼마나 안정적인지를 알기 위해 cohesive 에너지를 계산 할 것이다. 이러한 결과로 인해 태양에너지 연구에 큰 이바지를 할 수 있다.

• 한국결정학회:학술대회논문집
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• 한국결정학회 2003년도 춘계학술연구발표회
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• pp.6-6
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• 2003

Highly crystalline 5H-polytypic form of sp3-bonded boron nitride (BN) was grown by pulsed-laser-vaporization of BN, where synchronous reactive-plasma packets assisted the crystal growth in the vapor phase. The structure of the product crystallites (˙5 micrometers) was confirmed by using transmission electron diffraction and electron energy loss spectroscopy. This material proved to have a sharp and dominant band at 225 nm by cathode luminescence at room temperatures and corresponding monochromatic images revealed that they uniformly emitted the ultraviolet light. Considering that cubic BN has already been doped as p- and n- type semiconductors, this material may be applied to the light-emitting devices working at almost the deepest limit of the UV region that is functional without vacuum.