• Bulletin of the Korean Chemical Society
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• v.22 no.12
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• pp.1309-1315
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• 2001

Zirconium sulfate supported on zirconia catalysts were prepared by impregnation of powdered $Zr(OH)_4$ with zirconium sulfate aqueous solution followed by calcining in air at high temperature. The characterization of prepared catalysts was performed using Fourier transform infrared (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and by the measurement of surface area. The addition of zirconium sulfate to zirconia increased the phase transition temperature of $ZrO_2$ from amorphous to tetragonal due to the interaction between zirconium sulfate and zirconia, and the specific surface area and acidity of catalysts increased in proportion to the zirconium sulfate content up to 10 wt% of $Zr(SO_4)_2$. Infrared spectra of ammonia adsorbed on $Zr(SO_4)2}ZrO_2$ showed the presence of Bronsted and Lewis acid sites on the surface. $10-Zr(SO_4)_2}ZrO_2$ calcined at $600^{\circ}C$ exhibited maximum catalytic activities for 2-propanol dehydration and cumene dealkylation. The catalytic activities for both reactions were correlated with the acidity of catalysts measured by ammonia chemisorption method.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.5
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• pp.288-296
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• 2005

The corrosion behaviors of Zr-based alloys were very sensitive to their microstructures which were determined by manufacturing process. The specimens of Zr-based alloy named as HANA-4 for nuclear fuel cladding were investigated in order to get the optimized manufacturing process such as the intermediate annealing temperature and cold working steps after the ${\beta}$ quenching. From the microstructural analysis, cold worked microstructure of the samples was changed to the recrystallized microstructure by performed process. The corrosion behaviors of HANA-4 alloy were affected by the different manufacturing process. The ${\beta}$-Zr phase was formed in the matrix and the Nb concentration in the ${\beta}$-Zr phase was increased as progressing the manufacturing process. So, it was found that the corrosion rate of HANA-4 alloy was affected by the Nb concentration in the matrix.

• Journal of the Korean Ceramic Society
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• v.28 no.4
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• pp.315-323
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• 1991

The preparation of zirconium carbide powders by the halogenide process of ZrCl4-C-Mg system (1:1:2, molar ratio) was studied between 300。 and 120$0^{\circ}C$ under Ar gas flow (200 mι/min). The formation mechanism and kinetics of zirconium carbide and characteristics of the synthesized powder were examined by TG-DTA, XRD, SEM and PSA. 1) The formation mechanism of zirconium carbide were as follows, above 30$0^{\circ}C$ ZrCl4(S)+Mg(s)longrightarrowZrCl2(s)+MgCl2(s) above 40$0^{\circ}C$ ZrCl2(S)+Mg(s)longrightarrowZr(s)+MgCl2(s) above 50$0^{\circ}C$ Zr(s)+C(s)longrightarrowZrC(s) 2) The apparent activation energy of the reduction-carbonization at temperature of 800$^{\circ}$to 100$0^{\circ}C$ was 11.9 kcal/mol. 3) The lattice parameter and the crystallite size of ZrC which was produced from the mixture powder of ZrCl4, C and Mg (1:1:2, molar ratio) at 100$0^{\circ}C$ for 1 h were 4.700A and 180A, respectively. 4) The powders obtained from the mixture powder of ZrCl4, C and Mg(1:1:2, molar ratio) at 100$0^{\circ}C$ for 1 h were agglomerate with the average size of about 13${\mu}{\textrm}{m}$ in SEM micrograph.

• Journal of the Korean Chemical Society
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• v.63 no.1
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• pp.37-44
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• 2019

N,N'-bis(ethyldihydrogen phosphate)-1,4,5,8-naphthalene bis(dicarboximide) (EPNI) and N,N'-bis(ethyldihydrogen phosphate)-3,4,9,10-perylene bis(dicarboximide) (EPPI) and their zirconium bisphosphate multilayers (Zr-EPNI and Zr-EPPI), that had been briefly reported by us, were further investigated in terms of their electrochemical properties. EPNI in aqueous solution showed typical two reversible reductions at ITO electrode but the reductions were strongly dependent on solution pH while EPPI showed only an irreversible reduction. The single and mixed multilayers of Zr-EPNI and Zr-EPPI were well constructed on ITO electrode by the alternate adsorptions of zirconium ion and the bisimides. While Zr-EPNI multilayer on ITO electrode showed single broad reversible reduction with $E_{1/2}=-0.68V$, Zr-EPPI gave two separated reductions at $E_{1/2}=-0.54$ and -0.81 V vs SCE, quite differently from the solution properties. The average layer densities of the multilayers were estimated as $1.5{\times}10^{-10}$ and $2.3{\times}10^{-10}mol/cm^2$ for Zr-EPNI and Zr-EPPI, respectively. Both the monolayers of Zr-EPNI and Zr-EPPI could not completely block the electron transfer between $Fe(CN){_6}^{3-}$ in solution and ITO electrode but 3-5 layers of Zr-EPNI and Zr-EPPI could block it completely and mediated the one-way electron transfer at the potential shifted to their reduction potentials. When the monolayer of zirconium 1,10-decanediylbisphosphonate (Zr-DBP) was used as a sublayer of Zr-EPNI and Zr-EPPI layers, the mediated electron transfer became prominent without any direct electron transfer.

• Korean Journal of Materials Research
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• v.31 no.12
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• pp.690-696
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• 2021

The purpose of this study is to develop a zirconium-based alloy with low modulus and magnetic susceptibility to prevent the stress-shielding effect and the generation of artifacts. Zr-7Cu-xSn (x = 1, 5, 10, 15 mass%) alloys are prepared by an arc melting process. Microstructure characterization is performed by microscopy and X-ray diffraction. Mechanical properties are evaluated using micro Vickers hardness and compression test. The magnetic susceptibility is evaluated using a SQUID-VSM. The average magnetic susceptibility value of the Zr-7Cu-xSn alloy is 1.176 × 10^-8 cm³g^-1. Corrosion tests of zirconium-based alloys are conducted through polarization test. The average Icorr value of the Zr-7Cu-xSn alloy is 0.1912 ㎂/cm². The elastic modulus value of 14 ~ 18 GPa of the zirconium-based alloy is very similar to the elastic modulus value of 15 ~ 30 GPa of the human bone. Consequently, the Sn added zirconium alloy, Zr-7Cu-xSn, is very interesting and attractive as a biomaterial that reduces the stress-shielding effect caused by differences of elastic modulus between human bone and metallic implants. In addition, this material has the potential to be used in metallic dental implants to effectively eliminate artifacts in MRI images due to low magnetic susceptibility.

• Korean Chemical Engineering Research
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• v.45 no.4
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• pp.378-383
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• 2007

A novel fabrication method for the multi-component metal oxides such as zirconium titanate($Zr_xTi_{1-x}O_2$) has been suggested, which would yield the uniform film characteristics and control the film composition at relatively low process temperature. The method has the basic concept that firstly layer-by-layer structure is constructed with the primitive oxide layers, which are components of the desired multi-component oxides, and secondly the film is annealed at appropriate thermal conditions for the transformation to a single-phase multi-component oxides. In this study, PRTMOCVD(pulsed rapid thermal metalorganic chemical vapor deposition) possessing the superior thickness controllability was introduced to prepare $ZrO_2$ and $TiO_2$ thin film for zirconium titanate. Single-phase zirconium titanate thin films have been prepared successfully by the interdiffusion of oxide multilayers having several alternating layers of $ZrO_2$ and $TiO_2$. The Zr/Ti ratio of zirconium titanate could be controlled easily by altering the thickness of $ZrO_2$ and $TiO_2$ thin film.

• Resources Recycling
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• v.21 no.6
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• pp.32-38
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• 2012

In this study, direct reduction of $ZrO_2$ using liquid calcium was investigated. The influence of molar ratio of Ca and $ZrO_2$, reaction time and temperature on the reduction behavior of $ZrO_2$ was studied. Experiments were conducted in a closed stainless steel chamber under Ar atmosphere during 5 to 60 minutes. Most of the $ZrO_2$ was reduced to Zr in 5 minutes at 1223 K and 3 Ca/$ZrO_2$ molar ratio. The minimum oxygen content in reduced metal Zr was obtained about 0.66 wt% at 1373 K after 30 minutes and 4 Ca/$ZrO_2$ molar ratio. The morphology of zirconium powder obtained was highly affected by the reaction temperature and reaction time.

• The Journal of Advanced Prosthodontics
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• v.6 no.6
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• pp.512-520
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• 2014

PURPOSE. The purpose of this study was to assess the surface characteristics and the biocompatibility of zirconium (Zr) coating on Ti-6Al-4V alloy surface by radio frequency (RF) magnetron sputtering method. MATERIALS AND METHODS. The zirconium films were developed on Ti-6Al-4V discs using RF magnetron sputtering method. Surface profile, surface composition, surface roughness and surface energy were evaluated. Electrochemical test was performed to evaluate the corrosion behavior. Cell proliferation, alkaline phosphatase (ALP) activity and gene expression of mineralized matrix markers were measured. RESULTS. SEM and EDS analysis showed that zirconium deposition was performed successfully on Ti-6Al-4V alloy substrate. Ti-6Al-4V group and Zr-coating group showed no significant difference in surface roughness (P>.05). Surface energy was significantly higher in Zr-coating group than in Ti-6Al-4V group (P<.05). No difference in cell morphology was observed between Ti-6Al-4V group and Zr-coating group. Cell proliferation was higher in Zr-coating group than Ti-6Al-4V group at 1, 3 and 5 days (P<.05). Zr-coating group showed higher ALP activity level than Ti-6Al-4V group (P<.05). The mRNA expressions of bone sialoprotein (BSP) and osteocalcin (OCN) on Zr-coating group increased approximately 1.2-fold and 2.1-fold respectively, compared to that of Ti-6Al-4V group. CONCLUSION. These results suggest that zirconium coating on Ti-6Al-4V alloy could enhance the early osteoblast responses. This property could make non-toxic metal coatings on Ti-6Al-4V alloy suitable for orthopedic and dental implants.

• Journal of the Korean Ceramic Society
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• v.53 no.1
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• pp.50-55
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• 2016

In order to make a highly ordered three-dimensionally macro-porous structure of zirconia ceramics, porogen precursors PMMA beads were prepared by emulsion polymerization using acrylic monomer. The monodisperse PMMA latex beads were closely packed by centrifugation as a porogen template for the infiltration of zirconium acetate solution. The mixed compound of PMMA and zirconium acetate was dried. According to the firing schedule, dry compacts of PMMA and zirconium acetate were calcined at $475^{\circ}C$ to obtain micro-, macro-, and meso- structures of polycrystalline zirconia with monodispersed porosity. Inorganic frameworks composed of $ZrO_2$ were formed and showed a three Dimensionally Ordered Microstructure [3DOM] of $ZrO_2$ ceramics. The obtained $ZrO_2$ skeleton was calcined at $710^{\circ}C$. The 3DOM $ZrO_2$ skeleton showed color tuning in solutions such as deionized [DI] $H_2O$ and/or methanol. The monodispersed crystalline micro-structure with micro/meso porosity was observed by FE-SEM.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.4
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• pp.165-170
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• 2021

Zirconium has excellent mechanical strength and high heat resistance and excellent corrosion resistance, and it is very important to study zirconium's dissimilar welding properties since it can be used in various applications under harsh environments. Similar welding of pure zirconium and dissimilar metal welding of pure zirconium and pure titanium were performed by TIG welding, and the welding properties were studied in association with microstructural and mechanical properties. In the Zr/Zr welded specimen, sound FZ and HAZ regions showed a basketweave microstructure composed of plate α phase. FZ region of Zr/Ti dissimilar welded specimen exhibited a maximum hardness value of 354.8 Hv, which is about three times higher than that of Ti base metal, due to the precipitation of very fine metastable ω and α phases in the beta matrix. In addition, due to the microstructural continuity in the FZ and HAZ regions, excellent elongation property of 21% was exhibited.