• Journal of Technologic Dentistry
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• v.31 no.4
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• pp.25-30
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• 2009

Zirconia($ZrO_2$) has attracted much attention in science and technology because of its high refractive index, high melting temperature, hardness, low thermal conductivity and corrosion barrier properties. And it is widely used as the dental restoration material because of its esthetic appearance. In this research, we analyzed the particle size and composition of the imported dental porcelain for zirconia. And the glass frit was produced. To decrease the glass transition temperature and softening temperature of the glass frit, $Li_2O$ was added into it and the effect of $Li_2O$ on the firing temperature was researched. Then the glass which contains leucite crystal with a high coefficient of thermal expansion(CTE) was manufactured and it was mixed with the glass frit to control the CTE. The phase composition were analyzed using the X-ray diffraction. The morphologies of the samples were observed by the scanning electron microscope. The 4wt% $Li_2O$-added glass frit has the optimal glass transition temperature and softening temperature. And 6 wt% leucite crystal was mixed with the glass frit to control the CTE. From the experimental results of crystallization, the crystal phase was found only leucite crystal.

• Asian-Australasian Journal of Animal Sciences
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• v.23 no.7
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• pp.937-945
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• 2010

This study aimed to investigate the effects of dietary zinc (Zn), environmental temperatures and Zn${\times}$temperature interaction on growth, feathering score and mineral composition of broilers. A total of 256 d-old Avian male broiler chicks were randomly allocated to a $4{\times}2$ factorial arrangement with four corn-soybean meal basal diets (containing 44 mg Zn/kg) supplemented with 0, 40, 60 mg/kg Zn (Diets 1, 2 and 3, respectively; 0.8% Ca for these three diets) and non-Zn supplementation, 1.6% Ca (Diet 4) and two temperature conditions (low: 26, 24, $22^{\circ}C$ vs. high: 30, 28, $26^{\circ}C$). All birds were given feathering coverage scores for back, breast, wing, under-wing and tail. The wing and tail were further evaluated for the occurrence and severity of defect feathers. Feathers were then pooled for mineral composition analysis. The results showed that in high temperature conditions, broilers fed Zn-unsupplemented, 0.8% Ca ration (Diet 1) had significantly (p<0.05) lower ADFI and ADG (wk 1-6) than birds under low temperature conditions. However, when the birds were fed 40 and 60 mg/kg Zn supplementation (Diets 2 and 3), the ADFI and ADG in both temperature conditions were not significantly different. In low temperature conditions, the ADFI, ADG (p<0.05), all feather coverage (p<0.01) and tail defect scores (p<0.001) of birds fed Diet 4 (excess Ca) were significantly poorer than those fed Diet 1. More Ca (p<0.05) was retained in the feathers of broilers fed Diet 4 under high temperature conditions. Broilers fed the Zn-unsupplemented ration (Diet 1) had significantly higher feather phosphorus (p<0.01) and potassium (p<0.05) concentrations than those fed the 60 mg/kg Zn-supplemented ration (Diet 3). A reduction of feather phosphorus (p<0.01) and potassium (p<0.05) and higher manganese (p<0.05) concentrations were observed in Diet 4 broilers as compared to those fed Diet 1. Under high temperature conditions, broilers had lower iron (p<0.05) and higher manganese (p<0.05) concentrations in feathers. Broilers kept in high temperature conditions had a higher Zn requirement and 40 mg/kg Zn supplementation was sufficient for the birds to achieve optimum growth. Supplemental Zn ameliorated the adverse effect of high temperature on growth and occurrence of tail feather defects. Excess Ca disrupted Zn metabolism to exert a detrimental effect on growth performance and normal feathering and this was elucidated in the birds kept in low temperature conditions.

• Journal of the Korean Ceramic Society
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• v.19 no.2
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• pp.101-108
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• 1982

As raw materials wollastonite, kaolin and pyrophyllite were used to synthesize mullite, anorthite and pseudowoll-astonite which were known as low thermal expansion substance. Increasing the amount of wollastonite in the composition resulted in a linear thermal expansion behavior. However, the increases of pyrophyllite indicated the relatively unstable themmal expansion behavior, because the phase transition occured in quartz of the pyrophyllite compositon. To lowering sintering temperature feldspar (Kebook and Anyang) were added in the composition that showed the linear thermal expantion behavior, and over 50'C were lowered.

• Journal of the Korean institute of surface engineering
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• v.42 no.3
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• pp.116-121
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• 2009

The 2-step low temperature plasma processes (the combined carburizing and post-nitriding) offer the increase of both surface hardness and thickness of hardened layer and corrosion resistance than the individually processed low temperature nitriding and low temperature carburizing techniques. The 2-step low temperature plasma processes were carried out for improving both the surface hardness and corrosion resistance of AISI 316L stainless steel. The influence of gas compositions on the surface properties during nitriding step were investigated. The expanded austenite (${\gamma}_N$) was formed on all of the treated surface. The thickness of ${\gamma}_N$ and concentration of N on the surface increased with increasing both nitrogen gas and Ar gas levels in the atmosphere. The thickness of ${\gamma}_N$ increased up to about $20{\mu}m$ and the thickness of entire hardened layer was determined to be about $40{\mu}m$. The surface hardness was independent of nitrogen and Ar gas contents and reached up to about 1200 $HV_{0.1}$ which is about 5 times higher than that of untreated sample (250 $HV_{0.1}$). The corrosion resistance in 2-step low temperature plasma processed austenitic stainless steels was also much enhanced than that in the untreated austenitic stainless steels due to a high concentration of N on the surface.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.1
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• pp.1-4
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• 1991

The applicability of $LiNbO_{3}$ as a substrate for fabrication of Ti-indiffused waveguide electro-optic devices is limited. Ti diffuses comparatively in congruently melting $LiNbO_{3}$; the Curie temperature of this material is too low to permit diffusion temperatures much above $1100^{\circ}C$ without the necessity of re-poling the crystal. Both of hese difficulties could be eliminated by incorporating certain dopants in $LiNbO_{3}$. Crystals of $LiNbO_{3}$ doped with Ti and Mg were grown and evaluated. The electroptic coefficients and birefringence of $LiNbO_{3}$ doped crystals were measured at ${\lambda}=.6328$ and $1.32\;$\mu{m}$. Curie temperatures were measured. The Curie temperature of both undoped and Ti-doped $LiNbO_{3}$ was $1130^{\circ}C$; that for Mg-doped $LiNbO_{3}$ was $30^{\circ}$ higher. From these data, a composition for the crystals was estimated. Thermogravimetric data confirmed this estimate and showed that the composition of Mg : $LiNbO_{3}$ was $49.3{\pm}0.2mole%\;Li_{2}O$ ; the composition of the undoped and Ti : $LiNbO_{3}$ samples was $48.6{\pm}0.2mole%$. Diffusion of Ti into both Mg-doped and Ti-doped $LiNbO_{3}$ crystals was studied as a function of $Li/NbO_{3}$ ratio and temperature.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.32.1-32.1
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• 2018

Novel soft magnetic materials can be achieved by altering material properties such as morphology, composition, crystallinity, and grain size of soft magnetic alloys. Especially, magnetic properties (i.e., saturation magnetization, coarcivity) of soft magnetics are significantly affected by grain boundaries which act as a control of magnetic domain wall movement. Thus, we herein develop a two-step electroless plating method to control morphology and grain size of FeCo films for excellent magnetic properties. Accordingly, the chemical composition to control the degree of polarization of FeCo alloys was altered by electroless deposition parameters; for example, electrolyte concentration and temperature. The grain size and crystallinity of FeCo alloys was dramatically affected by the reaction temperature because the grain growth mechanism dominantly occurs at $90^{\circ}C$ where as the neucleation only happens at $50^{\circ}C$. By simply controlling the temperature, the micron-sized FeCo grains embedded FeCo film was synthesized where the large grains allow high magnetization originated from larger magnetic domain with low corecivity and the nano-sized grains allow excellent soft magnetic properties due to the magnetic correlation length.

• International Journal of Industrial Entomology and Biomaterials
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• v.39 no.1
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• pp.39-44
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• 2019

The effect of heat treatment on the sterilization and fatty acid compositions of silkworm powder was carried out under the guidance of Ministry of Food and Drug Safety. Food borne pathogens or microorganisms including E. coli, Salmonella spp., Listeria monocytogenes, Staphylococus aureus, Clostridium perfringens and aflatoxin, were not detected. The fatty acid composition was hardly changed after the silkworm powder was treated to a high temperature of $121^{\circ}C$. The low temperature sterilization of silkworm powder at $63^{\circ}C$ decreased the concentration of E. coli while high temperature sterilization at $121^{\circ}C$ has found no traces of microorganism.

• Journal of the Korean Society of Clothing and Textiles
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• v.11 no.1
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• pp.79-85
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• 1987

The purpose of this study was to help the consumer about the care of nonwoven fabrics by investigation of the properties such as launderability. shrinkage, color fastness and strenth. Materials used were two types, soft and stiff, of commercial nonwoven fabrics. Deter-gents used were neutral detergents, synthetic detergents and dry cleaning solutions(perch-toro-ethylene) The results of this study were summerized as follows; 1. Laundering of nonwoven fabrics in low temperature is more ideal as morphological changes by laundering in high temperature were more prominent than that in low temperature. 2. Ironing of nonwoven fabrics wants more attention on environmental temperature as the rate of shrinkage in high temperature was higher than that in low temperature. Neutral detergents are more desirable as the rate of shrinkage of nonwoven fabrics by laundering with synthetic detergents was more prominent than that with neutral deter-gents. The rate of shringkage of nonwoven fabrics was not affected by dry cleanining. 3. Special care is wanted in order to prevent color transfer from non woven fabrics to polyester or wool during dry cleaning or laundering as the color fastness test show that color changes of nonwoven fabrics were not affected, but that color stain was increased on polyester or wool. 4. The strength was affected by composition of fibers and types of nonwoven fabrics, soft or stiff.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.214-216
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• 2006

In this study, in order to develop the composition ceramics for low loss and low temperature sintering multilayer piezoelectric actuator, PMN-PZN-PZT ceramics were fabricated using two stage calcination method and $Li_2CO_3$, $Bi_2O_3$ and CuO as sintering aids and their piezoelectric characteristics were investigated according to the 2nd calcination and sintering temperature. At the calcination temperature of $750^{\circ}C$ and sintering temperature of $930^{\circ}C$, density, electromechanical coupling factor ($k_p$), mechanical quality factor ($Q_m$), Dielectric constant (${\varepsilon}_r$) and piezoelectric constant ($d_{33}$) of specimen showed the optimum value of $7.94g/cm^2$ 0.581, 1554, 1555 and 356pC/N, respectively for multilayer piezoelectric actuator application.

• Journal of the Korean Ceramic Society
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• v.21 no.2
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• pp.135-142
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• 1984

The electrical conductivity of compositions in the system $CaO-ZrO_2$ has been measured by 2-probe tech-nique in the temperature range 350~75$0^{\circ}C$. The composition of maximum conductivity in this system is within the cubic solid-solution region close to low-calcia cubic solid-solution phase boundary. The results are as follows : 1) The maximum conductivity was found 13mol CaO in zirconia. 2) As the CaO content was increased from 13 to 21 mol% the electrical conductivity decreased for any given temperature and the activation energy increased. 3) As the firing temperature and soaking time was increased the electrical conductivity increased and activation energy decreased.