• International Journal of Korean Welding Society
• /
• v.2 no.2
• /
• pp.14-18
• /
• 2002

Titanium and titanium alloy are excellent in corrosion resistance and specific intensity, and also in the biocompatibility. On the other hand, the brazing is bonding method of which productivity and reliability are high, when the complicated and precise structure of the thin plate is constructed. However, though conventional titanium-based brazing filler metal was excellent in bond strength and corrosion resistance, it was disadvantageous that metal structure and mechanical property of the base metal deteriorated, since the brazing temperature ( about $1000^{\circ}C$ ) is considerably high. Authors developed new brazing filler metal which added Zr to Ti-Cu (-Ni) alloy which can be brazed at $900^{\circ}C$ or less about 15 years ago. In this paper, the development of more low-melting-point brazing filler metal was tried by the addition of the fourth elements such as Ni, Co, Cr for the Ti-Zr-Cu alloy. As a method for finding the low-melting-point composition, eutectic composition exploration method was used in order to reduce the experiment point. As the result, several kinds of new brazing filler metal such as 37.5Ti-37.5-Zr-25Cu alloy (melting point: $825^{\circ}C$) and 30Ti-43Zr-25Cu-2Cr alloy (melting point: $825^{\circ}C$) was developed. Then, the brazing joint showed the characteristics which were almost equal to the base metal from the result of obtaining metallic structure and strength of joint of brazing joint. However, the brazing filler metal composition of the melting point of $820^{\circ}C$ or less could not be found. Consequentially, it was clarified that the brazing filler metal developed in this study could be practically sufficiently used from results such as metal structure of brazing joint and tensile test of the joint.

• Journal of Korean Ophthalmic Optics Society
• /
• v.3 no.1
• /
• pp.21-25
• /
• 1998

We investigated the optical properties of lead zirconate($PbZrO_3$, PZ) thin films. The PZ films for the measurement of optical properties were prepared on ITO glass by sol-gel method. By post annealing, with annealing temperature $T=700^{\circ}C$, the pyrochlore phase of as-deposited specimen was transformed into the perovskite phase. The surface of films were plat, transmittance were from 60 to 80% at 480~2000nm, and refractive index were from 2.1 to 1.9 at 480~1000nm.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09b
• /
• pp.1023-1024
• /
• 2006

Al-8Fe-2Mo-2V-1Zr alloys were prepared by the gas atomization/hot extrusion and the melt spinning/hot extrusion. For the gas atomized and extruded alloy, equiaxed grains with the average size of 400 nm and finely distributed dispersoids with their particle sizes ranging from 50nm to 200nm were observed. For the melt spun and hot extrusion processed alloy, refined microstructural feature consisting of equiaxed grains with the average size of 200nm and fine dispersoids with their particle sizes under 50nm appeared to exhibit a difference in microstructure. Strength of the latter alloy was higher than that for the former alloy up to elevated temperatures.

• Bulletin of the Korean Chemical Society
• /
• v.30 no.8
• /
• pp.1715-1718
• /
• 2009

A series of sitting-atop (SAT) complexes, [(ZrO)$H_2t(X)pp(NO_3)_2$], have been prepared via the reactions of free base meso-tetraarylporphyrins, $H_2$t(X)pp, with zirconyl nitrate hydrate, ZrO(N$O_3)_2{\cdot}xH_2$O. The products have been characterized by a variety of methods including $^1H\;NMR,\;^{13}C$ NMR, IR and UV-Vis spectroscopies, elemental analysis and conductance measurements. The data indicate that the meso-tetraarylporphyrins coordinate with two pyrrolenine nitrogen atoms to the zirconyl cation located above the distorted porphyrin plane and two protons remain on the pyrrole nitrogens. Such half sandwich-type sitting-atop complexes may be considered as models for the initial steps of the metallation of the macrocycles.

• Journal of the Korean Ceramic Society
• /
• v.51 no.6
• /
• pp.623-628
• /
• 2014

Orthorhombic $Ba(Ti_{0.94}Zr_{0.06})O_3$ single crystals are fabricated using the cost-effective solid-state single crystal growth (SSCG) method; their dielectric and piezoelectric properties are also characterized. Measurements show that (001) $Ba(Ti_{0.94}Zr_{0.06})O_3$ single crystals have an electromechanical coupling factor ($k_{33}$) higher than 0.83, piezoelectric charge constant ($d_{33}$) of about 400 [pC/N], and piezoelectric voltage constant ($g_{33}$) higher than 50 [${\times}10^{-3}Vm/N$]. The transition temperature ($T_{OT}$) of the (001) $Ba(Ti_{0.94}Zr_{0.06})O_3$ single crystals between orthorhombic and tetragonal phases is also observed to be about $61^{\circ}C$. Because their electromechanical coupling factor ($k_{33}$) and piezoelectric voltage constant ($g_{33}$) are higher than those of soft PZT ceramics, it is expected that (001) $Ba(Ti_{0.94}Zr_{0.06})O_3$ single crystals can be used as "lead-free" piezoelectric materials in many piezoelectric applications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.28 no.6
• /
• pp.375-378
• /
• 2015

In this study, in order to develop the composition ceramics with the excellent electrocaloric properties, $(Pb_{0.88}La_{0.08})(Zr_{0.65}Ti_{0.35})O_3$ ceramics were fabricated by the conventional solid-state method. Electrocaloric effects of $(Pb_{0.88}La_{0.08})(Zr_{0.65}Ti_{0.35})O_3$ ferroelectric ceramics were investigated and discussed using the characteristics of P-E hysteresis loops at wide temperature range from room temperature to $220^{\circ}C$. The temperature change ${\Delta}T$ due to the electrocaloric effect was calculated by Maxwell's relations, and reached the maximum of ~0.19 at $190^{\circ}C$ under applied electric field of 30 kV/cm.

• Journal of Korean Ophthalmic Optics Society
• /
• v.3 no.1
• /
• pp.15-19
• /
• 1998

The purpose of this study, when one prepared lead zirconate thin films by sol-gel method, was to find the preferred direction of crystal growth and dielectric characteristics for ratio of Pb and Zr. We used the Pt/Ti/$SiO_2$/Si substrate, and annealing condition was $800^{\circ}C$ for lminute. When Pb was deficient, preferred direction was <221>. And when it was stoichiometric ratio, they were grown <200> and <221> direction. But they have antiferroelectric properties, they don't appear distinct domain switching.

• Journal of the Korean Society for Heat Treatment
• /
• v.18 no.5
• /
• pp.312-317
• /
• 2005

The precipitation process in Cu-0.2 wt.%Cr-0.05 wt.%Zr alloys has been studied by electrical electrical resistivity measurements. The kinetics of precipitation could be well described by Johnson-Mehl-Avrami equation, $f(t)=1-\exp(-kt^n)$. The values of n were found to be in the range of 0.36~0.42 at first stage and 1.3~1.6 at second stage. The activation energy was determined by cross-cut method and was 80~89 kJ/mol. The value is similar to the energy for the migration of either a vacancy or a vacancy-solute complex through the lattice.

• Environmental Engineering Research
• /
• v.25 no.2
• /
• pp.186-196
• /
• 2020

Pillared clays with Zr and Fe/Cu/Zr polycations have been prepared from natural clays found in large deposits of Kazakhstan and assessed as catalysts for the catalytic wet peroxide oxidation (CWPO), using 4-nitrophenol (4-NP) as model compound. The performance of the catalysts was followed by measuring the concentration of 4-NP, H₂O₂ and the total organic carbon (TOC), considering C_4-NP = 5 g L^-1, $C_{H_2O_2}$ = 17.8 g L^-1, C_cat = 2.5 g L^-1, initial pH = 3.0 and T = 50℃. At those selected conditions, the pillared clays showed higher activity than natural clays in the CWPO of 4-NP. The conversion of the model pollutant was complete when Fe/Cu/Zr-PILCs were used, with the TOC removal reaching 78.4% after 24 h with the best Fe/Cu/Zr-PILC. The H₂O₂, 4-NP and TOC time-evolution was well described by a kinetic model based on TOC lumps in three blocks, considering the initial TOC (corresponding to 4-NP), the production of oxidizable intermediates and the formation of refractory products.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.29A no.10
• /
• pp.17-23
• /
• 1992

A ($Pb_{1-x}Ca_{x})ZrO_{3}$ system which has a high dielectric constant, low dielectric loss and temperature coefficient was investigated. For sintering temperatures above 1350$^{\circ}C$ the microstructures of sintered bodies were unchanged regardless of the amount of CaO. The dielectric constant and dielectric loss decreased and the temperature coefficient varied from positive to negative with the increasing amount of CaO. For the CaO content of 0.37, i.e. ($Pb_{0.63}Ca_{0.37})ZrO_{3}$, the ceramic showed very good dielectric properties such as ${\varepsilon}_1$=100, Q > 1200 at 3GHz, and T$_f$=$\pm$3ppm/$^{\circ}C$.