• 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.

• Journal of the Korean Society for Heat Treatment
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• v.17 no.4
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• pp.223-229
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• 2004

The effects of the cooling and annealing conditions on the microstructures and corrosion properties were investigated for the Cu-contained Zr-Nb alloy (Zr-1.1Nb-0.07Cu). After annealing at $1050^{\circ}C$ for 15 min, the specimens were cooled by three methods of water quenching, air cooling, and furnace cooling. Widmanstatten structures were developed in both air- and furnace-cooled specimens, and the Widmanstatten plate width of the furnace-cooled specimens was wider than that of the air-cooled ones. The weight gain in the furnace-cooling case was higher than that in the air-cooling case. This could be the reason why the diffusion time was more enough during the furnace cooling than the air cooling. The oxide of the furnace-cooled specimen was nonunformly formed just beneath the Widmanstatten plate boundaries, where ${\beta}_{Zr}$ phases were exised concentrately. Compared with the $640^{\circ}C$ annealing after the water quenching, the $570^{\circ}C$ annealing could make the ${\beta}_{Nb}$ phases and a concomitant reduction of the Nb in the matrix, and then it could improve the corrosion resistance with the increase of the annealing time. It would be concluded that the corrosion resistance of the Zr-1.1Nb-0.07Cu was good when the Nb concentration in the matrix was reached at an equilibrium level and then the ${\beta}_{Nb}$ phase was formed.

• Journal of the Korean Ceramic Society
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• v.47 no.1
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• pp.82-85
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• 2010

Recently, thin film processes for oxides and metal deposition, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), have been widely adapted to fabricate solid oxide fuel cells (SOFCs). In this paper, we presented two research area of the use of such techniques. Gadolinium doped ceria (GDC) showed high ionic conductivity and could guarantee operation at low temperature. But the electron conductivity at low oxygen partial pressure and the weak mechanical property have been significant problems. To solve these issues, we coated GDC electrolyte with a nano scale yittria-doped stabilized zirconium (YSZ) layer via atomic layer deposition (ALD). We expected that the thin YSZ layer could have functions of electron blocking and preventing ceria from the reduction atmosphere. Yittria-doped barium zirconium (BYZ) has several orders higher proton conductivity than oxide ion conductor as YSZ and also has relatively high chemical stability. The fabrication processes of BYZ is very sophisticated, especially the synthesis of thin-film BYZ. We discussed the detailed fabrication processes of BYZ as well as the deposition of electrode. This paper discusses possible cell structure and process flow to accommodate such films.

• Journal of the Korean Chemical Society
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• v.57 no.5
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• pp.547-553
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• 2013

Zirconium oxide ($ZrO_2$) nano porous membranes were fabricated by electrochemical two-step anodization with an electropolished zirconium substrate in inorganic water-based and organic electrolyte systems containing small amounts of fluoride. Using two-step anodization and organic electrolytes, highly regular and ordered nanotubular $ZrO_2$ oxide layers can be compared with aqueous electrolytes. The morphology and size of the nano porous layers were characterized by FE-SEM (field emission scanning electron microscopy), XRD (X-ray diffraction), and EDS (energy dispersive spectroscopy). Luminescence properties were investigated by photoluminescence measurements.

• Nuclear Engineering and Technology
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• v.49 no.1
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• pp.178-188
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• 2017

To study the effects of zirconium (Zr) addition on the microstructure, hardness and the tensile properties of oxide dispersion strengthened (ODS) ferritic-martensitic steels, two kinds of 9Cr-ODS ferritic-martensitic steels with nominal compositions (wt.%) of $Fe-9Cr-2W-0.3Y_2O_3$ and $Fe-9Cr-2W-0.3Zr-0.3Y_2O_3$ were fabricated by the mechanical alloying (MA) of premixed powders and then consolidated by hot isostatic pressing (HIP) techniques. The experimental results showed that the average grain size decreases with Zr addition. The trigonal ${\delta}$-phase $Y_4Zr_3O_{12}$ oxides and body-centered cubic $Y_2O_3$ oxides are formed in the 9Cr-Zr-ODS steel and 9Cr non-Zr ODS steel, respectively, and the average size of $Y_4Zr_3O_{12}$ particles is much smaller than that of $Y_2O_3$. The dispersion morphology of the oxide particles in 9Cr-Zr-ODS steel is significantly improved and the number density is $1.1{\times}10^{23}/m^3$ with Zr addition. The 9Cr-Zr-ODS steel shows much higher tensile ductility, ultimate tensile strength and Vickers hardness at the same time.

• Composites Research
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• v.35 no.4
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• pp.288-297
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• 2022

This study investigated the effect of addition of zirconia(zirconium oxide) powder on the curing behavior of phenolic resins. The heating rate controlled curing and isothermal curing behaviors of the phenol resin according to the content of the zirconia powder were analyzed. The viscosity and thermal decomposition characteristics of the phenolic resin with the zirconia content were also examind. From the DSC analysis, the degree of cure and the rate of cure were obtained. Finally, the activation energy for the cure reaction were calculated from the DSC data of the zirconia added phenolic resin. As a found, the higher the zirconia content, the longer the curing was delayed and the greater the activation energy required for curing. Additionally, the TGA result that as the content of zirconia increased, less weight loss was observed. The surface tackiness of the Carbon/Phenol prepreg was partially changed according to the zirconia content, but had no significant effect.

• Electrical & Electronic Materials
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• v.16 no.9
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• pp.61.1-61
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• 2003

Stoichiometric, uniform, amorphous ZrO$_2$ films with an equivalent oxide thickness of ∼1.5nm and a dielectric constant of ∼18 were deposited by an atomic layer controlled deposition process on silicon for potential application in meta-oxide-semiconductor(MOS) devices. The conduction mechanism is identified as Schottky emission at low electric fields and as Poole-Frenkel emission at high electric fields. the MOS devices showed low leakage current, small hysteresis(〈50mV), and low interface state density(∼2*10e11/cm2eV). Microdiffraction and high-resolution transmission electron microscopy showed a localized monoclinic phase of ${\alpha}$-ZrO$_2$ and an amorphous interfacial ZrSi$\_$x/O$\_$y/ layer which has a correspondign dielectric constant of 11

• Journal of the Korean Ceramic Society
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• v.48 no.2
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• pp.195-199
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• 2011

The effect of copper oxide on migration and interaction of protons in barium zirconate was investigated using density functional theory. One copper atom was substituted for a zirconium atom site, and a proton was added to a $3{\times}3{\times}3$ barium zirconate superstructure. An energy barrier of 0.89 eV for proton migration was the highest among several energy barriers. To investigate the interaction between multiple protons and a copper atom, two protons were added to the superstructure. Various proton positions were determined by the interaction between the two protons and the copper atom.

• Journal of the Korean institute of surface engineering
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• v.31 no.5
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• pp.278-285
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• 1998

Alloys of Ti-15Mo-5Zr-3Al(wt%) were oxidized in air between 700 and $900^{\circ}C$. It was found that the oxidation resistance is much better than that of either commercially available pure Ti-6Al-4V(wt%) alloys. The oxide scales were primarily composed of thick Ti-ox-ides which were formed by the inward diffusion of oxygen from the atmosphere. At higher temperatures a thin $\alpha$-$Al_2O_3$ layer was formed on Ti-oxides owing to the outward diffusion of Al from the base alloys. Molybdenum, the noblest metal among the alloy components, was predominantly present behind the oxide-substrate interface. Zirconium, an oxygen active metal, was present at both the oxide layer and the substrate.

• Resources Recycling
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• v.21 no.5
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• pp.18-30
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• 2012

Zirconium is one of the most important material used as cladding of fuel rods in nuclear reactors because of its high dimensional stability, good corrosion resistance and especially low neutron-absorbing cross section. However, Hf free nuclear grade Zr sponge is commercially produced by only three countries including USA, France and Russia. So, Zr has been thoroughly managed as a national strategic material in Korea. Most of the zirconium is used for Korean nuclear industry as nuclear fuel cladding materials manufactured from Hf free Zr alloy raw material. Also, there are some other applications such as alloying element and detonator. In this review, zirconium production and recycling technologies have been reviewed and current industrial status was also analyzed. And recent achievements in innovative reduction technologies such as electrolytic reduction process and molten oxide electrolysis were also introduced.