• 대한치과보철학회지
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• 제33권4호
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• pp.645-661
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• 1995

As the mechanical property of composite resin improved, composite resin has been widely used esthetic dentistry. In the field of esthetic dentistry, the color of prosthetic material is very important. The purpose of this study was to evaluate the color difference of specimens, by the types of alloys and gold electrodeposit. Experimental groups were as follows : Group Prec : Au-Pt alloy with no gold coating and no resin veneer. Group Semi : Pd-Ag alloy with no gold coating and no resin veneer. Group BAse : Ni-Cr alloy with no gold coating and no resin veneer. Group Gsem : Pd-Ag alloy with no gold coating and no resin veneer. Group Gbas : Ni-Cr alloy with no gold coating and no resin veneer. Group PreR : Resin veneer on the Pd-Ag alloy without gold coating. Group SemR : Resin veneer on the Pd-Ag alloy without gold coating. Group GbsR : Resin veneer on the Ni-Cr alloy with gold coating Group BasR : Resin veneer on the Ni-Cr alloy without gold coating. In this study, colors of metal surfaces and veneered resins were evaluated by the CIE $L^{*}a^{*}b$ system. The results obtained were as follows : 1. different alloy types and gold coating make the $L^{*}a^{*}b$ system. 2. The ${\Delta}E^*$ab value between groups semi and Base was less than 1.5 and there was no $a^*$ and $b^*$ value difference between groups Gsem and Gbas 3. The values of $L^*$ and $a^*$ ain groups GsemR and GbasR were so similar that the ${\Delta}E^*$ab value was as small as 0.58. 4. In resin specimens with gold coated semiprecious or base alloys showed yellower and redder deviation than the resin specimens with precious alloy. 5. The ${\Delta}E^*$ab values between goups PreR-GsemR and groups PreR-GbasR were as small as 2.68 and 2.22 respectively.

• 한국재료학회지
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• 제10권6호
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• pp.403-408
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• 2000

본 연구에서는 고온용 고강도 Al 합금을 제조하기 위해 Al-Cr-Zr 복합금속분말을 attritor에서 300rpm의 회전속도로 20시간 동안 기계적 합금화방법으로 제조한 후 진공 고온 압축성형하였다. Al-Cr-Zr 합금의 미세구조 및 조직관찰은 XRD, TEM 등을 사용하여 분석하였고, 열적 안정성은 열적 노출시간에 따른 미소경도측정을 통하여 조사하였다. 진공 열간 압축성형 되었을 때 MA Al-Cr-Zr 합금의 이론 밀도의 97%에 이르는 조밀화르 f보였으며, $300^{\circ}C$에서 100시간 열처리 한 경우에는 경도변화가 거의 없었고, $500^{\circ}C$에서 100시간 열처리한 경우에도 감소가 6% 이내로 우수한 열적 안정성을 나타내었다. 이와 같은 MA Al-Cr-Zr 합금의 우수한 열적 안정성은 기계적 합금화에 의해 Al 기지 내에 미세하고 균일하게 분산된 Cr과 Zr이 고온 성형과 열처리 과정에 의해 $Al_3Zr,\;Al_{13}Cr_2$의 금속간 화합물들의 형성되었으며, 열처리 후의 이 합금의 최종 결정립 크기는 150mm 크기 이하이었다.

• 한국수소및신에너지학회논문집
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• 제9권4호
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• pp.161-167
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• 1998

Ni/MH 2차전지의 음극용 금속간화합물전극의 부식특성에 미치는 합금원소와 결합제의 영향을 조사하였다. 전극의 재료는 $(LM)Ni_{4.49}Co_{0.1}Mn_{0.205}Al_{0.205}$와 $(LM)Ni_{3.6}Co_{0.7}Mn_{0.3}Al_{0.4}$의 $AB_5$ type합금을 모재로 하였다. 여기에 Si sealant 또는 PTFE를 결합제로 첨가한 것과 원재료 분말에 구리를 20% 무전해도금한 것을 냉간 압착하여 전극을 제조하였다. 부식특성을 조사하기위해 탈공기된 6M의 KOH 용액에서 동전위법과 순환전위법을 이용하여 부식전류와 전류밀도를 측정하였다. 모재에 Co가 많이 함유되면 전극의 내식성을 향상시키고 Ni이 많이 함유되면 충전과 방전을 반복하는 동안에 전극의 안정성을 저하시켰다. 부식전류밀도는 Si sealant를 결합제로 사용한 전극의 경우가 PTFE를 사용한 전극의 경우보다 낮았고 Cu가 도금된 전극은 내식성에서 가장 우수하게 나타났다.

• 한국수소및신에너지학회논문집
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• 제8권2호
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• pp.79-90
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• 1997

Extensive work has been done on investigating the inner cell pressure characteristics of sealed type Ni-MH battery in which Zr-Ti-Mn-V-Ni alloy is used as anode. The inner cell pressure of this type Ni-MH battery much more increases with the charge/discharge cycling than that of the other type Ni-MH battery where commercialized $AB_5$ type alloy is used as anode. The increase of inner cell pressure in the sealed type Ni/MH battery using Zr-Ti-Mn-V-Ni alloy system is mainly due to the accumulation of oxygen gas during charge/discharge cycling. The accumulation of oxygen gas arises mainly due to the low rate of oxygen recombination on the MH electrode surface during charge/discharge cycling. The difference of oxygen recombination rate between $AB_5$ type electrode and Zr-Ti-Mn-V-Ni electrode is caused by the difference of electrode reaction surface area resulting from different particle size after their activation and the difference of surface catalytic activity for oxygen recombination reaction, respectively. After EIS analysis, it is identified that the surface catalytic activity affects much more dominantly on the oxygen recombination reaction than the reaction surface area does. In order to suppress the inner cell pressure of Ni-MH battery where Zr-Ti-Mn-V-Ni is used as anode, it is suggested that the surface catalytic activity for oxygen recombination should be improved.

• 한국수소및신에너지학회논문집
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• 제12권3호
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• pp.177-189
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• 2001

T hydrogen absorption-desorption behavior induced by thermal or hydrogen pressure cycling in a closed system was observed in hydrogen storage alloys, $(La-R-Mm)Ni_{4.5}Fe_{0.5}$, $MmNi_4Fe_{0.85}Cu_{0.15}$ and $(Ce-F-Mm)Ni_{4.7}Al_{0.2}Fe_{0.1}$. Thereby (La-R-Mm), Mm and (Ce-F-Mm) refer to La-rich mischmetal, mischmetal and Ce-free mischmetal respectively. As the results, it is found that the alloy stabilities during thermal cycling varies with alloy composition change. The highest stability occurs in $MmNi_4Fe_{0.85}Cu_{0.15}$ and the lowest stability in $(La-R-Mm)Ni_{4.5}Fe_{0.5}$. Comparing hydrogen pressure cycling with thermal cycling, pressure cycling causes severer degradation of the alloy $(Ce-F-Mm)Ni_{4.7}Al_{0.2}Fe_{0.1}$ than thermal cycling. When the 1500 times-cycled alloy is annealed at $400^{\circ}C$ for 3hrs under 1 atm of hydrogen pressure the hydrogen storage capacity is recovered only partially but not completely to the initial capacity. The amount of capacity loss after annealing is larger in the hydrogen pressure cycled samples than in the thermal cycled, suggesting an incoming of impure gas during hydrogen pressure cycling.

• 한국수소및신에너지학회논문집
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• 제8권4호
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• pp.161-171
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• 1997

$AB_2$ type Zr-based Laves phase alloys have been studied for potential application as negative electrode in Ni/MH batteries. However, They have a serious disadvantage of poor activation behavior in KOH solution. In this work, a new method of alloy design method was tried for improving Zr-based alloy activation. this method has focused on phase controlling to make multi-phase microstructure. In the case of multi-phase Zr-V-Mn-Ni shows good performance in activation, but activation mechanism has not been known. So, we were in search of elucidating this mechanism, Using morphological and electrochemical analysis, we could find that surface morphology and electocatalytic activity of the alloy change during immersion in KOH solution. V-rich second phases are selectively corroded and dissolved and then become Ni-rich phases. Resulting from these surface reaction in KOH solution, self-hydrogen charging occurs through Ni-rich phase. However, the alloy has poor cyclic durability because of such a corrosion mechanism. Therefore, finally we developed durable alloys by substitution of other alloying element.

• 한국수소및신에너지학회논문집
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• 제13권3호
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• pp.181-189
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• 2002

A series of multicomponent $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{1-x}Fe_{x}$ (x=0.00, 0.08, 0.15, 0.22, and 0.30) alloys are prepared and their oystal structure and P-C-T curves are examined. The electrochemical properties of these allqys such as activation conditions, discharge capacity, cycling performance are also investigated. $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{1-x}Fe_{x}$ (x=0.00, 0.08, 0.15, 0.22 and 0.30) have the C14 Laves phase hexagonal structure. The electrode was activated by the hot-charging treatment. The best activation conditions were the current density 120 mA/g and the hot-charging time 12h at $80^{\circ}C$ in the case of the alloy with x=0.00. The discharge capacity increased rapidly until the fourth cycle and then decreased. The discharge capacity increased again from the 13th cycle, arriving at 234 mAh/g at the 50th cycle. The discharge capacily just after activation decreases with the increase in the amount of the substituted Fe but the cycling performance is improved. The discharge capacity after activation of the alloy with x=0.00 is 157 mAh/g at the current density 120 mA/g. $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}Fe_{0.15}$ is a good composition with a medium quantity of discharge capacities and a good cycling performance. The ICP analysis of the electrolyte for these electrodes after 50 charge-discharge cycles shows that the concentrations of V and Zr are relatively high. Another series of multicomponent $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}M_{0.15}$ (M = Fe, Co, Cu, Mo and Al) alloys are prepared. They also have the C14 Laves phase hexagonal structure. The alloys with M = Co and Fe have relatively larger hydrogen storage capacities. The discharge capacities just after activation are relatively large in the case of the alloys with M = Al and Cu. They are 212 and 170 mAh/g, respectivety, at the current density 120mA/g. The $Zr_{0.8}Ti_{0.2}Mn_{0.4}V_{0.6}Ni_{0.85}Co_{0.15}$ alloy is the best one with a relatively large discharge capacity and a good cycling performance.

• 한국수소및신에너지학회논문집
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• 제9권4호
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• pp.169-176
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• 1998

Ni/MH 2차전지의 음극용 금속간화합물전극의 부식특성에 미치는 합금원소와 결합제의 영향을 조사하였다. 전극의 재료는 $(LM)Ni_{4.49}Co_{0.1}Mn_{0.205}Al_{0.205}$와 $(LM)Ni_{3.6}Co_{0.7}Mn_{0.3}Al_{0.4}$의 $AB_5$ type합금을 모재로 하였다. 여기에 Si sealant 또는 PTFE를 결합제로 첨가한 것과 원재료 분말에 구리를 20% 무전해도금한 것을 냉간 압착하여 전극을 제조하였다. 부식특성을 조사하기위해 탈공기된 6M의 KOH 용액에서 동전위법과 순환전위법을 이용하여 부식전류와 전류밀도를 측정하였다. 모재에 Co가 많이 함유되면 전극의 내식성을 향상시키고 Ni이 많이 함유되면 충전과 방전을 반복하는 동안에 전극의 안정성을 저하시켰다. 부식전류밀도는 Si sealant를 결합제로 사용한 전극의 경우가 PTFE를 사용한 전극의 경우보다 낮았고 Cu가 도금된 전극은 내식성에서 가장 우수하게 나타났다.

• 한국재료학회지
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• 제12권8호
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• pp.624-633
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• 2002

In order to improve the hydrogen storage capacity and the activation properties of the hydrogen storage alloys, the rare-earth metal alloy series, MmN $i_{4.5}$M $n_{0.5}$Z $r_{x}$(x=0, 0.025, 0.05, 0.1), are prepared by adding excess Zr in MmN $i_{4.5}$M $n_{0.5}$ alloy. The various parts in hydrogen storage vessel consisted of copper pipes reached the setting temperature within 4~5 minutes after heat addition, which indicated that storage vessel had a good heat conductivity required in application. The performance test on storage vessel filled with rare-earth metal alloys of 1000 gr was also conducted after hydrogen charging for 10 min at $18^{\circ}C$ under 10 atm. It showed that the average capacity of discharged hydrogen volume was found to be for $MmNi_{4.5}$ $Mn_{0.5}$ and $MmNi_{4.5}$ $Mn_{x}$ 0.5/$Zr_{samples}$ indicated that the released amount of hydrogen for this $AB_{5}$ type alloys was more than 92 % of theoretic value, and also it was found that the optimum discharging temperature for obtaining an appropriate pressure of 3 atm was determined to be $V^{\circ}C$ for $MmNi_{4.5}$ $Mn_{0.5}$$Zr_{x}$(x=0, 0.025, 0.05, 0.1) hydrogen storage alloys. The released amount of these hydrogen storage samples was 125 $\ell$ , 122.4 $\ell$ and 108.15 $\ell$/kg for $MmNi_{4.5}$ $Mn_{0.5}$ $Zr_{0.025}$ $MmNi_{4.5}$M $n_{0.5}$Z $r_{0.05}$, and MmN $i_{4.5}$ Mn_0.5$Zr_{0}$, at $70^{\circ}C$ respectively. Amount of the 2nd phases increase with increase on Zr contents in $MmNi_{4.5}$$Mn_{0.5}$ $Zr_{ 0.1}$/ alloy. This phenomenon indicates that$ ZrNi_3$ in $MmNi_{4.5}$ $Mn_{0.5}$ $Zr_{x}$ / phase, which shows the maximum storage capacity and the strong resistance to intrinsic degradation, is considered as a proper alloy for hydrogen storage. As the Zr contents increase, the activation time and the plateau pressure decreases and sloping of the plateau pressure increases.creases.eases.s.