• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2007년도 추계학술대회 논문집
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• pp.118-119
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• 2007

Phase stability and morphological investigation on the $Si/SiO_2/HfO_2$ and $Si/SiO_2/ZrO_2$ stack are presented. Thermal stability of $HfO_2$ and $ZrO_2$ determines the quality of interface and subsequently the performance of device. The stacks have been fabricated and annealed at $1000^{\circ}C$ for various time. In evolution of crystalline phase and morphology (electrical and geometrical) of high-k materials, annealing time and process are observed to be crucial factors. The crystallization of some phase has been observed in the case of $Si/SiO_2/HfO_2$. The chemical environment around Zr and Hf in respective samples is observed to be different.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.633-636
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• 1999

In this study, we have fabricated amorphous FeZrBAg thin films with low core losses by using DC magnetron sputtering method. After deposition, rotational field annealing (RFA) method was performed in the dc field of 1.5 kOe. The amorphous FeZrBAg thin films produced by annealing at 35$0^{\circ}C$ was founded to have high permeability of 8680 at 100 MHz, 0.2 mOe, low coercivity of 0.86 Oe high magnetization of 1.5 T and very low core loss of 1.3 W/cc at 1 MHz, 0.IT respectively. Excellent soft magnetic properties in a amorphous FeZrBAg thin films in the present study are presumably the homogeneous formation of very fine bcc $\alpha$-Fe crystalline with the 8.2 nm in an amorphous FeZrBAg thin film matrix.

• 열처리공학회지
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• 제29권1호
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• pp.1-7
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• 2016

Titanium and its alloys can be usually joined with brazing method. And the alloys should be brazed at low temperature to keep their original microstructure. In this study, the mechanical strength and microstructure of the CP-Ti joint-brazed with $Zr_{54}Ti_{22}Ni_{16}Cu_8$ filler metal having melting temperature of $774{\sim}783^{\circ}C$ were investigated. The tensile strengths of the joint-brazed at $800^{\circ}C$ with $100^{\circ}C/min$ of cooling rate showed more than 400 MPa which was as high as base metal. The $Widmanst{\ddot{a}}tten$ structure consisting of Ti and $Ti_2Ni$ phase was observed in the joint area. However, the tensile strengths of the joint-brazed at $800^{\circ}C$ with $15^{\circ}C/min$ of cooling rate were decreased and the Ti, $(Ti,Zr)_2Ni$ and $Ti_2Ni$ phases were observed at the joint area. It is believed that the $(Ti,Zr)_2Ni$ laves phases could decrease the mechanical strength of the joint and the cooling rate should be controled to get high strength of the titanium joint.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.149-152
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• 2001

A great deal of attention has been focused on the application of miniaturized piezoelectric transformers to the low power source for the microsystem. The dielectric and piezoelectric properties of Pb(Mn,W,Sb,Nb)O$_3$-Pb(Zr,Ti)O$_3$ ceramics have been investigated on different calcination(750$^{\circ}C$∼950$^{\circ}C$) and sintering(1100$^{\circ}C$∼1300$^{\circ}C$) temperatures. The perovskitic phase was formed by the solid phase reaction of the oxides. Anisotropic (k$\sub$t/k$\sub$p/) properties of electromechanical coupling coefficient and piezoelectric coefficient have been proven to be depending on processing temperatures. The value of electromechanical coupling factor of K$\sub$p/>0.51 and a mechanical quality factor of Q$\sub$m/>2000 were obtained. The piezoelectric transformer was prepared using this ceramics with the composition of Pb(Mn,W,Sb,Nb)O$_3$-Pb(Zr,Ti)O$_3$ We studied the influence of different processing temperature on the microstructure and piezoelectric properties of complex PZT-based ceramics. and the characteristic of piezoelectric transformer.

• 한국태양에너지학회 논문집
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• 제37권2호
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• pp.13-22
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• 2017

Two-step water splitting thermochemical cycle with $CeO_2/ZrO_2$ foam device was investigated by using a solar simulator composed of 2.5 kW Xe-Arc lamp and mirror reflector. The hydrogen production of $CeO_2/ZrO_2$ foam device depending on heat recovery of Thermal-Reduction step and Water-Decomposition step was analyzed, and the hydrogen production of $CeO_2/ZrO_2$ and $NiFe_2O_4/ZrO_2$ foam devices was compared. Resultantly, the quantity of hydrogen generation increased by 52.02% when the carrier gas of Thermal-Reduction step is preheated to $200^{\circ}C$ and, when the $N_2/steam$ is preheated to $200^{\circ}C$ in the Water-Decomposition step, the quantity of hydrogen generation increased by 35.85%. Therefore, it is important to retrieve the heat from the highly heated gases discharged from each of the reaction spaces in order to increase the reaction temperature of each of the stages and thereby increasing the quantity of hydrogen generated through this.

• 한국수소및신에너지학회논문집
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• 제17권1호
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• pp.31-38
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• 2006

There are two types of metal hydride electrodes as a negative electrode in a Ni-MH battery, $AB_2$ Zr-based Laves phases and $AB_5$ LM(La-rich mischmetal)-based alloys. The $AB_5$ alloy electrodes have characteristic properties such as a large discharge capacity per volume, easiness in activation, long cycle life and a low cost of alloy. However they have a relatively small discharge capacity per weight. The $AB_2$alloy electrodes have a much higher discharge capacity per weight than $AB_5$ alloy electrodes, however they have some disadvantages of poor activation behavior and cycle life. Therefore, in order to improve the discharge capacity of the $AB_5$ alloy electrode the Zr, Ti and V which are the alloying elements of the $AB_2$ alloys were added to the $LaNi_{3.6}Ai_{0.4}Co_{0.7}Mn_{0.3}$ alloy which was chosen as a $AB_5$ alloy with a high capacity. The addition of Zr, Ti and V to $LaNi_{3.6}Ai_{0.4}Co_{0.7}Mn_{0.3}$ alloy improved the activation to be completed in two cycles. The discharge capacities of Zr 0.02, Ti 0.02 and V 0.1 alloys in $LaNi_{3.6}Ai_{0.4}Co_{0.7}Mn_{0.3}M_y$ (M = Zr, Ti, V) were respectively 346, 348 and 366 mAh/g alloy. The alloy electrodes, Zr 0.02, Ti 0.05 and V 0.1 in $LaNi_{3.6}Ai_{0.4}Co_{0.7}Mn_{0.3}M_y$ (M = Zr, Ti, V), have shown good cycle property after 200 cycles. The rate capability of the $LaNi_{3.6}Ai_{0.4}Co_{0.7}Mn_{0.3}M_y$ (M = Zr, Ti, V) alloy electrodes were very good until 0.6 C rate and the alloys, Zr 0.02, Ti 0.05 and V 0.1, have shown the best result as 92 % at 2.4 C rate. The charge retention property of the $LaNi_{3.6}Ai_{0.4}Co_{0.7}Mn_{0.3}M_y$ (M = Zr, Ti, V) alloys was not good and the alloys with M content from 0.02 to 0.05 showed better charge retention properties.

• 한국전기전자재료학회논문지
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• 제19권5호
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• pp.417-421
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• 2006

In this study, in order to develop low temperature sintering piezoelectric ceramics for LTCC (Low-Temperature Cofired Ceramic) multilayer piezoelectric actuator, PMW-PMN-PZT ceramics using $0.2wt%\; Li_2CO_3$ and $0.25wt%\;CaCO_3$ as sintering aids were investigated according to the varation of PMW substution. Composition ceramics could be sintered at $900^{\circ}C$ by adding sintering aids. As the amount of PMW substitution increased, the crystal structure of PMW-PMN-PZT ceramics moved from tetragonal phase to rhombohedral phase gradually, and MPB(Morphotrophic Phase Boundary) region appeared at 2 mol% PMW substitution. At the sintering temperature of $900^{\circ}C$, the density, electromechanical coupling factor(kp), mechanical quality factor(Qm), dielectric constant(${\epsilon}r$), piezoelectric constant(d33) and Curie temperature(Tc) of 2 mol% PMW substituted PMW-PMN-PZT ceramics showed the optimal values of $7.88g/cm^3$, 0.58, 1002, 1264, 352 pC/N and $336^{\circ}C$, respectively, for LTCC multilayer piezoelectric actuator application.

• Journal of Magnetics
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• 제4권2호
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• pp.46-51
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• 1999

A solid-HDDR characteristics of the Nd-Fe-B-type alloys magnetic properties of the solid-HDDR treated materials have been investigated using three types of alloys; $Nd_{15}Fe_{77}B_8 (alloy A), Nd_{16}Fe_{75.9}B_8Zr_{0.1}(alloy B), and Nd_{12.6}Fe_{68.7}Co_{11.6}B_8Ga_{1.0}Zr_{0.1} $(alloy C). It has been found that the four-components alloy B and six-components alloy C have showed higher hydrogenation temperatures than the ternary alloy A. The alloys A and B appeared to absorb more hydrogen gas more rapidly as well compared to the alloy C. The disproportionation temperature of hydrogenated materials was exhibited no significant difference among the alloys. The thermal stability of the hydrided materials of the three types of alloys was found to become more stable in order of number of components. The disproportionation and the recombination kinetics were significantly sluggish in the solid-HDDR manner with respect to the conventional manner. Some degree of anisotropic nature was found to exist in the ingot and this anisotropic nature was retained even after the solid-HDDR treatment. It was suggested the solid-HDDR treatment may possibly be used for a preparation of an isotropic or anisotropic Nd-Fe-B-type cast magnets.

• 센서학회지
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• 제17권6호
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• pp.418-424
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• 2008

The PZT based piezoelectric thick films prepared by screen printing method have been mainly used as a functional material for MEMS applications due to their compatibility of MEMS process. However the screen printed thick films generally reveal poor electrical and mechanical properties because of their porous microstructure. To improve microstructure we mixed attrition milled powder with ball milled powder of 0.01Pb$(Mg_{1/2}W_{1/2})O_3$-0.41Pb$(Ni_{1/3}Nb_{2/3})O_3$-$0.35PbTiO_3$-$0.23PbZrO_3$+0.1 wt% ${Y_2}{O_3}$+1.5 wt% ZnO composition. By mixing 25 % of attrition milled powder and 75 % of ball milled powder, the broadest particle size distribution was obtained, leading to a dense thick film with crack-free microstructure and improved dielectric properties. The X-ray diffraction analysis revealed that the film was in wellcrystallized perovskite phase. The remanent polarization was increased from $13.7{\mu}C/cm^2$ to $23.3{\mu}C/cm^2$ at the addition of 25 % attrition milled powder.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1993년도 추계학술대회 논문집
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• pp.10-13
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• 1993

ln this study, x PSN - y PT - z PZ ceramics doped with w MnO$_2$were fabricated by the mixed oxide method at 1250[$^{\circ}C$] for 2[hr] and then the dielectric and pyroelectric properties were investigated. In the 0.05 PSN - 0.4 PT - 0.55 PZ specimen with 0.5[wt.%] MnO$_2$, the pyroelectric coefficient was 6.6${\times}$10$\^$-8/[C/cm$^2$$.$$^{\circ}C$], respectibly.