• Transactions of Materials Processing
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• v.26 no.4
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• pp.216-221
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• 2017

Recently, interest in multifunctional energetic structural materials (MESMs) has grown due to their multifunctional potential, especially in military applications. However, there are few studies about extrinsic factors that govern the reactivity of MESMs. In this paper, a shock compaction process was performed on the nano Ni/Al-mixed powder to investigate the effect of particle size on the shock reaction condition. Additionally, heating the statically compacted specimen was also performed to compare the mechanical properties and microstructure between reacted and unreacted material. The results show that the agglomerated structure of nanopowders interrupts the reaction by reducing the elemental boundary. X-ray diffraction analysis shows that the NiAl and $Ni_3Al$ intermetallics are formed on the reacted specimen. The microhardness results show that the $Ni_3Al$ phase has a higher hardness than NiAl, but the portion of $Ni_3Al$ in the reacted specimen is minor. In conclusion, using Ni/Al composites as a reactive material should focus on energetic use.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.219-219
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• 2003

HVOF(High Velocity Oxygen Fuel)법을 사용한 MCrAlY(M=Ni, Co, Fe)계 열차폐 코팅(thermal barrier coating)은 열기관 내부의 극심한 환경 부하에 대해 구조물 표면에 열적, 화학적 장벽을 형성함으로써 구조물의 내구성을 향상시킨다 이와 동시에 열차폐 효과는 구조물의 온도상승 없이 내부 가동 온도를 높일 수 있게 함으로써 열효율을 상승시키고 연료 효율을 높여 가동비용 절감을 이룰 수 있는 동시에 고 연소를 통한 오염원의 배출을 감소시킬 수 있다. 본 연구에서는 $H_2O$$_2$=5:1 분위기 하에서 HVOF법을 사용하여 Hastelloy-X 기판위에 125$\mu\textrm{m}$의 두께로 다음 5종류의 (Ni, Co, Cr)계 MCrAlY 코팅을 용사시켰다. 준비된 (Ni, Co)-Cr-Al-(Y, Ta, Re), (Ni, Co)-Cr-Al-(Y, Re), (Ni, Co)-Cr-Al-(Y, Ta), (Ni, Co)-Cr-Al-Y, (Ni,Co)-Cr-Al-Ir 코팅시편에 대한 산화성질을 조사하기 위해 대기 중 1000, 1100, 120$0^{\circ}C$에서 50, 100, 150, 200시간 등온실험(Isothermal oxidation)을 실시하였고, XRD, SEM/EDS, EPMA를 이용하여 생성된 산화막과 코팅 시편의 조직 변화를 조사하였다. 산화온도와 산화시간이 증가할수록 산화막의 박리가 많이 발생하였으며, 분석 결과 미세하게 분포된 a-Al$_2$O$_3$ 입자, NiCr$_2$O$_4$스피넬 상, 미세한 Cr$_2$O$_3$가 관찰되었고, 코팅 조성 변화에 따라 형성되는 이들 산화물의 존재비가 달라졌으며, 산화온도가 높아질수록 산화속도가 가속화되었다.

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.87-92
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• 2006

The steam reforming of methane over Ru-promoted $Ni/Al_2O_3$ was carried out. Compared with $Ni/Al_2O_3$, which needs pre-reduction by $H_2$, $Ru/Ni/Al_2O_3$ catalysts exhibited relatively higher activity than conventional $Ni/Al_2O_3$. According to $H_2-TPR$ of reduced or used catalysts and $CH_4-TPR$, it was revealed that the reduction of $RuO_x$ by $CH_4$ decomposition begins at a lower temperature ($220^{\circ}C$) and the reduced Ru facilitates the reduction of NiO, and leads to self-activation. To improve metal dispersion, the catalyst was soaked in 7 M aqueous $NH_4OH$ for 2 h at $45^{\circ}C$ while stirring. As a result, $Ru/Ni/Al_2O_3$ catalysts with aqueous $NH_4OH$ treatment have higher activity, larger metal surface area (by $H_2$-chemisorption), and small particle size (by XRD and XPS). It is noted that the amount of noble metal could be reduced by aqueous $NH_4OH$ treatment.

• Journal of the Korean institute of surface engineering
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• v.34 no.3
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• pp.206-214
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• 2001

The purpose of this study is to determine the effects of Ni on precipitate formation in a Ni added galvanizing bath, which has various Ni content from 0.03wt.% to 0.5wt.%. The addition of hi in the Ni containing galvanizing bath resulted in the formation of Al-Ni intermetallic compounds such as $Al_3$$Ni_2$ and $Al_2$Ni, which make up most of the top precipitates. At 0.07wt.%Ni, Al-Ni intermetallic compound formed sensitively with small amount of Al addition. By analysing the reaction thickness of galvanized steel, it was found that Ni addition in a Zn-0.18w1.%Al bath tended to suppress the formation of Fe-Zn intermetallic compounds but the formation of these compounds increased with increasing Ni concentration above 0.1wt.%.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1316-1317
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• 2006

The paper investigates the possibility to avoid extrinsic embrittlement of $Ni_3Al$, also increasing the high temperature strength, by alloying with both Fe - of a high strengthening effect and Cr - able to remove a part of diffused oxygen along the grain boundaries. As Cr homogenization in $Ni_3Al$ is difficult because of its low diffusion coefficient, for its improving a mechanical alloying (MA) step before the compound synthesis by Self-propagating High-temperature Synthesis (SHS) was adopted. The obtained better homogenization resulted in higher mechanical resistance and deformability than of the unalloyed $Ni_3A/Ni_3Al$ alloys of the same composition obtained without MA step.

• Journal of the Korean Institute of Gas
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• v.11 no.2 s.35
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• pp.25-30
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• 2007

The catalysts for decomposition reaction of acetaldehyde were investigated. The catalysts were prepared with transition metal Ni, Mo, Al on ${\gamma}-Al_2O_3$ support by impregnation method. Physio-chemical properties of catalysts were characterized by SEM-EDS, XRD, XPS, BET and TPR techniques. The conversion efficiency of catalysts for acetaldehyde was measured in the temperature range of $150{\sim}500^{\circ}C$ by GC through the micro reactor system. The 8 wt% $Ni/{\gamma}-Al_2O_3$ was found to be the most active catalyst of mono-metal catalysts tested, and the 1-3 wt% $Ni-Al/{\gamma}-Al_2O_3$ showed higher conversion efficiency than other bimetallic catalysts.

• Journal of Powder Materials
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• v.5 no.4
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• pp.334-339
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• 1998

In purpose of introducing the inverse magnetostrictive properties into the structural ceramics, $Al_2O_3$ based nanocomposites dispersed with nano-sized Ni-Co particles were studied. The composites were fabricated by the hydrogen reduction and hot-pressing of $Al_2O_3$ and NiO-CoO mixed powders. The mixtures were prepared by using Ni- and Co-nitrate $(Ni(NO_3)_2\;{\cdot}\;6H_2O\;and\;Co(NO_3)_2\;{\cdot}\6H_2O)$ as source materials for the Ni-Co particles. Microstructural observations revealed that nano-sized Ni-Co particles were dispersed homogeneously at $Al_2O_3$ grain boundaries. High strength above 1 GPa was obtained for the $Al_2O_3/10$ wt% Ni-Co nanocomposite fabricated by a controlled powder preparation process. The inverse magnetostrictive response to applied stress was obtained due to the presence of dispersed Ni-Co particles, which indicates a possibility to incorporate new functions into the structural ceramics without loosing the mechanical properties.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.3
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• pp.306-310
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• 2016

In Na-base Battery for ESS, ${\alpha}-Al_2O_3$ and metal bonding was used to prevent direct reaction between electrolyte and electrode. The hard metal was metalized at $1600^{\circ}C$ in a flowing hydrogen gas for high bonding strength. In this study, instead of hard metal metalizing, Ni was plated on ${\alpha}-Al_2O_3$ by electroless Ni plating technique and then bonded with metal. To enhance the bonding strength, surface of ${\alpha}-Al_2O_3$ was treated with $H_3PO_4$. The effects of strength and leakage of joining as a function of acid treatment time on ${\alpha}-Al_2O_3$ are described.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.61-61
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• 2003

다결정 실리콘 박막은 박막 트랜지스터와 실리콘 태양전지등에 응용되며, 비정질 실리콘을 재결정화 하여 얻어지는 다결정 실리콘 박막이 주로 이용되고 있다. 비정질 실리콘 박막을 금속 원소와 접촉시킨 상태에서 열처리할 경우 결정화 온도가 낮아지고 결정화에 필요한 열처리 시간이 짧아지게 된다. 금속을 실리콘 박막 표면에 가하는 방법은 진공증착법등으로 비정질 실리콘 박막 위에 금속원소 층을 형성하는 방법이 주로 이용되었다. 본 연구에서는 AlCl$_3$와 NiCl$_2$ 금속화합물 분위기에서 LPCVD 비정질 실리콘 박막을 열처리하여 결정화 거동을 관찰하였다. 금속화합물과 결정화할 비정질 실리콘 박막을 각각 다른 온도로 가열해 줄 수 있는 노를 이용하여 열처리를 시행하였다. AlCl$_3$와 NiCl$_2$ 분말을 혼합하여 소스로 이용한 경우 48$0^{\circ}C$ 5시간 열처리로 결정화가 완료되었으며, 박막 전체에 걸친 균일도와 재현성이 우수하였다. AlCl$_3$와 NiCl$_2$를 이용한 결정화 초기 상태에는 박막 전면에 걸쳐 등근 형태의 결정립이 균일한 핵 생성으로 나타났다. 이와 같은 결과는 Al과 Ni이 고상결정화에 동시에 작용하면서 나타난 것으로, Al이 가해진 비정질 실리콘으로 인해 결정화 속도가 빨라지고 결함이 작은 결정립을 얻을 수 있었으며, Ni로 인해 결정화의 균일성과 재현성을 높일 수 있었다.

• Journal of the Korean Ceramic Society
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• v.33 no.5
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• pp.536-546
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• 1996

The TiC-Ni/Al reaction-bonding composites were prepared by the infiltration of Ni/Al melt into the TiC preforms. The microstructure the reaction composition crystalline phase and the mechanical properties of the composites were investigated. During the reaction-bonding Ni/Al mixture had a good wettability and per-meability with TiC preform and pore-free and fully dense sintered bodies were produced. In the case of the Ni/Al atomic ratio of 0.3 and 0.5 TiC raw particle shape was changed to irregular particles because of the decomposition in the liquid matrix and its phenomena was more distinguished in the Al-rich liquid matrix. With increasing more than 1 of the Ni/Al atomic ratio the sample of TiC grain shape was changed from spherical to palatelet particles. Also with increasing the atomic ratio of Ni/Al bending strength and fracture spherical to palatelet particles. Also with increasing the atomic ratio of Ni/Al bending strength and fracture toughness were increased and its maximum value was 1073 MPa and 11 MPa.m1/2 respectively.