• Transactions of Materials Processing
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• v.10 no.7
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• pp.565-572
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• 2001

It is well known that a multicomponent $Zr_{4l.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ bulk metallic glass alloy shows good bulk glass forming ability due to its high resistance to crystallization in the undercooled liquid state. DSC and XRD have been performed to confirm the amorphous structure of the master alloy. To investigate the mechanical properties and deformation behavior of the bulk metallic $Zr_{4l.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ alloy, a series of compression tests has been carried out at the temperatures ranging from $351^{\circ}C$ to $461^{\circ}C$at the various initial strain rates from $2{\times}10^4s^1$ to $2{\times}10^2s^1$. Three types of nominal stress-strain curves have been identified such as linear stress-strain relationship meaning fracture at maximum stress, plastic deformation including stress overshoot and steady-state flow, plastic deformation without stress overshoot depending on the strain rate and test temperature. Also DSC analysis for the compressed specimens was carried out to investigate the change of structure, thermal stability and crystallization behavior for the various test conditions.

• Journal of the Korean Society for Heat Treatment
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• v.5 no.3
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• pp.149-156
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• 1992

Transformation behavior and reversible shape memory effct of Ti-Ni-Cu alloys with various Cu content has been investigated by means of electrical resistivity measurement, differential scanning calorimetry. X-ray diffraction and strain gage sensor. The transformation sequence in Ti-Ni-Cu alloys substituted by Cu for Ni up to 5at.% occurs to $B2{\leftrightarrow}B19^{\prime}$ and it proceeds in two stages by addition of 10 at.%Cu. i.e. $B2{\leftrightarrow}B19{\leftrightarrow}B19^{\prime}$. But the content of Cu increases up to 20at.%, it has been transformed in one stage ; $B2{\leftrightarrow}B19$. The shape change of Ti-40Ni-10Cu alloy which was constrain aged in circular form bended in $B2{\leftrightarrow}B19$ transformation but it spreaded out in $B19{\leftrightarrow}B19^{\prime}$ transformation. The amount of reversible shape change (${\Delta}{\varepsilon}$) of Ti-47Ni-3Cu alloy constrain aged at $400^{\circ}C$ after solution treatment has a maximum value of about $5.6{\times}10^{-3}$, but that of cold rolled and constrain aged specimens exhibits a little value independent of Cu concentrations.

• Korean Journal of Materials Research
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• v.11 no.3
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• pp.171-177
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• 2001

The thermal and mechanical properties of amorphous Z $r_{62-x}$N $i_{10}$C $u_{20}$A $l_{8}$ $Ti_{x}$ (x=3, 6, 9at%) alloys were investigated. The crystallization process was confirmed as amorphous longrightarrow amorphous + Z $r_2$A $l_3$+ Zr + (Ni,Ti) longrightarrow Z $r_2$Cu + Al + (Ni,Ti) for 3at%Ti, amorphous longrightarrow amorphous + Al longrightarrow $Al_2$Ti + NiZr + CuTi for 6at%Ti and amorphous longrightarrow amorphous + Zr + Al longrightarrow Zr + $Al_2$Zr + Al $Ti_3$+ CuTi for 9at%Ti. lickers hardness ( $H_{v}$ ) increased with increasing volume fraction( $V_{f}$ ) of pricipitates for all concerned compositions. Tensile fracture strength ($\sigma_{f}$ ) showed a maximum value 1219MPa at $V_{f}$ = 38% for 3at%Ti, 1203MPa at $V_{f}$ = 2% for 6at%Ti and 1350MPa at $V_{f}$ = 5% for 9at%Ti. The $\sigma_{f}$ was rapidly decreased after showing the maximum value. The $V_{f}$ corresponding to rapidly decreased $\sigma_{f}$ coincided with the $V_{f}$ transited from ductile to brittle fracture surface.ace.

• Journal of Environmental Science International
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• v.28 no.1
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• pp.65-73
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• 2019

The catalytic activity of Ni-0.2%YSZ (Yttria-Stabilized Zirconia) with different promoters was evaluated for $CO_2$ methanation. The catalysts were weighed for mixing and they were dried at $110^{\circ}C$ for molding into disks. The concentration of $CO_2$ and $CH_4$ for conducting of $CO_2$ methanation were analyzed by gas chromatography and the physical characteristics of the disk-type catalyst formed were analyzed by X-ray diffraction, scanning electron microscope and energy dispersive x-ray spectrometer. The addition of $CeO_2$ as a promoter for Ni-0.2%YSZ (denoted as Ni-5%Ce-0.2%YSZ) resulted in the highest $CO_2$ methanation. It also showed catalytic activity at a low temperature($200^{\circ}C$). Following this, $ZrO_2$, $SiO_2$, $Al_2O_3$ and $TiO_2$ were added to Ni-5%Ce-0.2%YSZ to compare the $CO_2$ methanation, and the highest efficiency was found for. Ni-1%Ti-5%Ce-0.2%YSZ Then, the concentration of Ti was increased to 10% and the catalytic activity was estimated using seven different types of commercial $TiO_2$. In conclusion, ST-01 $TiO_2$ showed the highest efficiency for $CO_2$ methanation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.3
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• pp.624-634
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• 1998

The photoelastic model material with shape memory effect and the molding processes for the material are developed in this research. The matrix and fiber of the photoelastic model material developed in this research are epoxy resin (Araldite to hardner 10 to 3 (weight ratio)) and wire of $Ti_50-Ni_50$ shape memory alloy, respectively. It is called Ti50-Ni50 Shape Memory Alloy Fiber Epoxy Composite $(Ti_50-Ni_50SMA-FEC).$ Ti50-Ni50 SMA-FEC is satisfied with the requirements of the photoelastic model material and can be used as a photoelastic model material. The maximum recovering strain of $Ti_50-Ni_50$SMA-FEC is occurred at $80^{\circ}C$ in any prestrain of $Ti_50-Ni_50$ shape memory alloy fiber and in any fiber volume ratio. Recovering strain(force) is increased with the increment of the prestrain and the fiber volume ratio. The best prestrain of $Ti_50-Ni_50$SMA-FEC is 5% for the recovering force among 1%, 3%, 5%.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.4
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• pp.65-69
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• 2012

Composite coating can be manufactured during the electroplating with the bath containing a suspension of particles: ceramic, polymer, nanopowders. Improvement of hardness, wear resistance, corrosion resistance and lubrication properties are well-known advantage of composite coating. In this study, nano $TiO_2$ powder dispersed Ni composite plating was investigated. The improvement of surface hardness and photo decomposition effects can be expected in this coating. Zeta potential was measured with pH. The effect of ultrasonication time and types of ultrasonicator were studied to minimize the agglomeration of $TiO_2$ nanopowders in the electrolyte. Optimum conditions for nano $TiO_2$ dispersed Ni composite coating were $40mA/cm^2$ of current density, pH 3.5, and $50^{\circ}C$. At these conditions, $TiO_2$ nanoparticles contents in the Ni deposit was 15-20 at.%.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.644-645
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• 2006

TiC-and Ti(C,N)-based cermets are excellent in semi-and final finishing of work piece during cutting operations. Typical microstructure of the cermets is a core/rim structure. The undissolved Ti(C,N) cores contribute to their high hardness while the rim phases, (Ti,M1,M2)(C,N)-type solid solutions, play great roles in enhancing the toughness. In this paper, various ultrafine pre-mixed MeC-Ni powders were synthesized and the powders were sintered or hot pressed after mixing in order to control the size and volume fractions of core and rim phases in the system. This paper will present the factors determining the microstructure along with mechanical properties.

• Journal of the Korean Chemical Society
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• v.25 no.4
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• pp.236-245
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• 1981

The electrical conductivities of oxidized pure and Ni-doped $SrTiO_3$ single crystals were measured as a function of the oxygen partial pressure($Po_2$) at temperature from 700 to $1200^{\circ}C$ and $Po_2$ of $10^{-8}$ to $10^{-1}$ atm. Plots of log ${\sigma}$ vs. 1/T at constant $Po_2$ were found to be linear, and the activation energies obtained from the slopes of these plots have an average value of 1.34 eV for oxidized pure and 1.06 eV for oxidized Ni-doped $SrTiO_3$ single crystals at $Po_2$'s between $10^{-8}$ to $10^{-1}$ atm. The log ${\sigma}$ vs. log $Po_2$ curves at constant temperature were found to be linear with an average slope of ${\frac{-1}{5.6}}\;{\sim}\;{\frac{-1}{6.2}}$ in the $Po_2$ ranges. From the agreement between experimental and theoretically predicted values for the electrical conductivity dependences on $Po_2$, an oxygen vacancy defect model was found applicable to oxidized pure and Ni-doped $SrTiO_3$ single crystals over the temperature range, 700~$1200^{\circ}C$. Conduction mechanisms were proposed to explain the dependences of electrical conductivity on temperature and $Po_2$.

• Journal of the Korean Ceramic Society
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• v.46 no.1
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• pp.116-121
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• 2009

The constituent phases in Ti($C_{0.7}N_{0.3}$)-xWC-20Ni (wt%, x=5, 15, 25) cermets were characterized using nanoindentation in conjunction with observation of microstructure. The microstructure of cermet is composed of hard phase and binder phase, which gave rise to a wide range of hardness distribution when nanoindentation was carried out on the polished surface of cermets. Because of the inhomogeneous nature of cermet microstructure, observation of indented surface was indispensable in order to separate the hardness of each constituent phase. The measured values of hardness using nanoindentation were ${\sim}14\;GPa$ for the binder phase and ${\sim}24$ to 28 GPa for the hard phase, of which nanoindentation hardness was decreased with the addition of WC into Ti($C_{0.7}N_{0.3}$)-Ni system. In addition, the nanoindentation hardness of Ni binder phase was much higher than reported Vickers hardness, which could result from confined deformation of binder phase due to the surrounding hard phase particles.

• Journal of Korea Foundry Society
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• v.27 no.3
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• pp.120-125
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• 2007

The microstructure, mechanical properties and melting range of Ni-Cr-Mo based alloys were investigated to develop Be-free Ni-Cr-Mo base dental alloys for Porcelain-Fused-to-Metal Firing(PFM). All as-cast alloys showed dendritic structure. Rockwell hardness of 20Cr7Mo was increased with addition of Si and Ti. On the contrary, it was decreased with addition of Co. The duplex alloying elemental addition such as 3Co + xTi, 2Si + xCo and 2Si + xTi to 20Cr7Mo resulted in much increase of hardness. Rockwell hardness and compressive strength for 20Cr3CoSiTi or 17Cr6CoSiTi alloy that add Si-Ti had similar values compared to the commercial alloys. Melting range for 20Cr3CoSiTi and 17Cr6CoSiTi alloy that add Si-Ti showed similar or lower than commercial alloys. In conclusion, 20Cr3CoSiTi and 17Cr6CoSiTi alloys can be applied for commercial use.