• Journal of the Korean Crystal Growth and Crystal Technology
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• v.16 no.2
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• pp.59-65
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• 2006

Al-doped and F-doped ZnO (ZnO : Al & ZnO : F) thin films were coated onto glass substrate by sol-gel method. These films showed c-axis orientation in common, but different I(002)/[I(002) + I(101)] and FWHM (full width at half-maximum). In particular, the grain size of the ZnO : Al films decreased with the increase in the Al-doping concentration, while for the ZnO : F films the grain siae increased up to F 3 at% and then decreased. For the electrical properties, Hall effect measurement was used. The resistivity of the ZnO : Al films and the ZnO : F films were, respectively, $2.9{\times}10^{-2}{\Omega}cm$ at Al 1 at% and $3.3{\times}10^{-1}{\Omega}cm$ at F 3 at%. Moreover compared with ZnO:Al films, ZnO:F films have lower carrier concentration (ZnO : Al $4.8{\times}10^{18}cm^{-3}$, ZnO : F $3.9{\times}10^{16}cm^{-3}$) and higher mobility (ZnO : Al $45cm^2/Vs$, ZnO : F $495cm^2/Vs$). For average optical transmittances, ZnO : Al thin films have $86{\sim}90%$ and ZnO : F films have $77{\sim}85%$ comparatively low.

• Journal of the Korean Ceramic Society
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• v.39 no.3
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• pp.315-320
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• 2002

Treatment effects of dilute hydrofluoric acid (6 wt% HF) on the surface properties of $Al(OH)_3$ were investigated at the molar ratio of F/Al(fluoride/aluminum)=0.15. Temperature and pH variations in the reaction system were recorded to analyze reaction mechanism between $Al(OH)_3$ and aqueous Hf. The reaction of HF to the surface of $Al(OH)_3$ accompanied with a quantity of heat evolution, resulting in increasing temperature of a reactionsystem. And also the reaction was proceeded as transitional state which metastable ${\alpha}-form\;AlF_3{\cdot}3H_2O$ was transferred to insoluble ${\beta}$-form. The resulting ${\beta}-form\;AlF_3{\cdot}3H_2O$ formed by a surface treatment was identified by FT-IR and X-ray diffractormetry. The formation of ${\beta}$-form aluminum fluoride hydrates with diameter less than $1{\mu}m$ on the surface of $Al(OH)_3$ could be visulaized by SEM imgae, making up a coating layer as precipitate-like. The surface whiteness of $Al(OH)_3$ treated with aqueous HF was furthermore increased approximately 6.6% due to the formation of surface hydrates.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.7
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• pp.665-668
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• 2008

Multi-layered thin films of $Fe_2O_3/Na_3AlF_6/Fe_2O_3/Cu$, Cr, Al were deposited on glass substrate by evaporation process. As high and low refractive index material, $Fe_2O_3$ and $Na_3AlF_6$ were selected and additionally Cu, Al and Cr were chosen as mid reflective layer respectively. Optical properties including reflectance were systematically studied depending on optical thickness of $Na_3AlF_6$ especially $0.25{\lambda}$ and $0.5{\lambda}$. In order to expect the experimental result, the simulation program, the Essential Macleod Program(EMP) was adopted and compared with the experimental data. Based on the results taken by spectrophotometer at viewing angle $45^{\circ}C$, the $Fe_2O_3/Na_3AlF_6/Fe_2O_3/Cu$ show the colour rage between red and orange in $0.25{\lambda}$ and green and pupple in $0.5{\lambda}$ respectively. When the Al was used as mid reflective layers in $Fe_2O_3/Na_3AlF_6/Fe_2O_3$ system, typical yellow colour and mixed colour between green and pupple were appeared in $0.25{\lambda}$ and $0.5{\lambda}$ of $Na_3AlF_6$ respectively. As compared the experimental result to simulation data, it was found out that the experimental data is relatively well matched with the EMP simulation data.

• Journal of the Korean Ceramic Society
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• v.43 no.10 s.293
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• pp.595-600
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• 2006

The preparation of $\beta$-SiAlON powder by SHS in the system of $Si-Al-SiO_2-NH_4F(\beta-Si_3N_4)$ was investigated in this study. In the preparation of SiAlON powder, the effect of gas pressure, compositions such as Si, $NH_4F$, \beta-Si_3N_4$ and additive in mixture on the reactivity were investigated. At 50 atm of the initial inert gas pressure in reactor, the optimum composition for the preparation of pure $\beta$-SiAlON was $3Si+Al+2SiO_2+NH_4F$. The $\beta$-SiAlON powder synthesized in this condition was a single phase $\beta$-SiAlON with a rod like morphology.

• Journal of the Korean Ceramic Society
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• v.28 no.8
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• pp.647-653
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• 1991

In order to synthesize fine AlN powder by the direct nitridation of Aluminum metal power added LiF and BaF2 as additives was heated at 150$0^{\circ}C$ for 3 hrs. in nitrogen gas with flow rate of 20 mι/sec. Additives are promoted the nitridation by prevented the aggromerate of powders when 3% LiF and 2% BaF2 were added to Al metal powder. Rate of nitridation was about 100% and average size of AlN powders were very fine such as 0.3 ${\mu}{\textrm}{m}$. Specific surface area of synthesized AlN powder was 3.95$m^2$/g and also O2 and N2 contents were 2.595% and 33.25%, respectively.

• Korean Journal of Materials Research
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• v.9 no.6
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• pp.630-634
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• 1999

Porous mullites were fabricated using $Al(OH)_3$ and amorphous $SiO_2$ as starting materials by reaction sintering method. The molar ratios of alumina and silica varied from stoichiometric mullite composition to silica-rich and alumina-rich compositions. $AlF_3$ of 0, 1, 5, 10 wt% wad added to each composition, and the effects of composition and the additive for the formation of mullite were examined. The temperature of mullite formation decreased as the amount of $AlF_3$ increased, and themullite phase was formed in the stoichiometric composition in addition of 5 wt% $AlF_3$ at $1250^{\circ}C$ and porous whiskered mullite were synthesized in the sample sintered at $1300^{\circ}C$ and higher temperature. The effect of temperature on the mullite formation was not observed for the sample with 5 wt% or higher content of $AlF_3$, and the body showed little contraction after sintering.

• Applied Chemistry for Engineering
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• v.9 no.3
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• pp.372-376
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• 1998

Supported Pd($Pd/AlF_3$, $Pd/{\gamma}-Al_2O_3$) catalysts and solid-acid catalysts(${\gamma}-Al_2O_3$, ${\alpha}-Al_2O_3$, $AlF_3$) were used to perform dechlorination of HCFC-142b(1-chloro-1,1-difluoroethane) in the presence of excess hydrogen. In the reactions the effects of reaction temperature, the mole ratio(r) of $H_2$ to HCFC-142b and the amount of supported Pd on dechlorination of HCFC-142b into HFC-143a(1,1,1-trifluoroethane) or HFC-152a(1,1-difluoroethane) were investigated. The experimental results showed that the conversion of HCFC-142b to product gases were 60% and 92%, respectively, and the selectivity to HFC-143a in the product gases were 58% and 64% for $Pd/AlF_3$ and $Pd/{\gamma}-Al_2O_3$ catalysts, respectively. On these catalysts an optimum reaction condition was found at $200^{\circ}C$ with the space time of reactant gases as 1.05 second and the mole ratio of $H_2$ to HCFC-142b as 3. Solid-acid catalysts were also tested at the same reaction condition. The results showed that the conversions of HCFC-142b to product gases were 12%, 8% and 7%, and the selectivities to HFC-152a were 94%, 92% and 90% for ${\gamma}-Al_2O_3$, ${\alpha}-Al_2O_3$ and $AlF_3$ catalysts, respectively.

• Korean Journal of Materials Research
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• v.21 no.12
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• pp.644-649
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• 2011

[ $A_{3-2x/3}Al_{1-z}In_{z}O_4F:Eu_x^{3+}$ ](A = Ca, Sr, Ba, x = -0.15, z = 0, 0.1) oxyfluoride phosphors were simply prepared by the solid-state method at $1050^{\circ}C$ in air. The phosphors had the bright red photoluminescence (PL) spectra of an $A_{3-2x/3}Al_{1-z}In_{z}O_4F$ for $Eu^{3+}$ activator. X-ray diffraction (XRD) patterns of the obtained red phosphors were exhibited for indexing peak positions and calculating unit-cell parameters. Dynamic excitation and emission spectra of $Eu^{3+}$ activated red oxyfluoride phosphors were clearly monitored. Red and blue shifts gradually occurred in the emission spectra of $Eu^{3+}$ activated $A_3AlO_4F$ oxyfluoride phosphors when $Sr^{2+}$ by $Ca^{2+}$ and $Ba^{2+}$ ions were substituted, respectively. The concentration quenching as a function of $Eu^{3+}$ contents in $A_{3-2x/3}AlO_4F:Eu^{3+}$ (A = Ca, Sr, Ba) was measured. The interesting behaviors of defect-induced $A_{3-2x/3}Al_{1-z}In_{z}O_{4-{\alpha}}F_{1-{\delta}}$ phosphors with $Eu^{3+}$ activator are discussed based on PL spectra and CIE coordinates. Substituting $In^{3+}$ into the $Al^{3+}$ position in the $A_{3-2x/3}AlO_4F:Eu^{3+}$ oxyfluorides resulted in the relative intensity of the red emitted phosphors noticeably increasing by seven times.

• Toxicological Research
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• v.14 no.2
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• pp.163-169
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• 1998

Fluoride (F), over a narrow concentration range, increases bone formation. Aluminum (Ai) too is biphasic in its action on bone, being mitogenic at very low levels and inhibitory at higher levels. Both F and Al are present in finished drinking water where the chemical interaction of these two agents is well characterized. F and AI, given individually, accumulate preferentially in bone. In addition. in vivo studies have shown that F causes the co-accumulation of Al in bone. Thus, it was necessary to determine the interactive effect of these two agents on bone mitogenesis. Calvaria were obtained from neonatal CD-1 mice and cultured with various concentrations of F (0.05~19 ppm) as NaF, Al (2 ppb~2 ppm) as $AlCl_3$ , or F and Al for 3 days at $37^{\circ}C$ on a rotating roller drum. Alkaline phosphatase activity in calvaria and $\beta$-glucuronidase activity in culture medium were determined as a measures of bone turnover. Alkaline phosphatase activity in calvaria was significantly increased by F (0.05~2 ppm) treatment and $\beta$-glucuronidase activity was slightly increased in the culture medium of calvaria treated with 0.3 ppm Al. The combination of 19 ppm F and 0.3 ppm Al increased alkaline phosphatase activity in calvaria, but did not affect $\beta$-glucuronidase activity, suggesting the interactive effect of fluoride and aluminum on bone turnover.

• Korean Journal of Materials Research
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• v.21 no.11
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• pp.604-610
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• 2011

The effect of $BaF_2$ flux in $Y_3Al_5O_{12}:Ce^{3+}$(YAG:Ce) formation was investigated. Phase transformation of $Y_3Al_5O_{12}$(YAG) was characterized by using XRD, SEM, and TEM-EDS, and it was revealed that the sequential formation of the $Y_4Al_2O_9$(YAM), $YAlO_3$(YAP) and $Y_3Al_5O_{12}$(YAG) in the temperature range of 1000-1500$^{\circ}C$. Single phase of YAG was revealed from 1300$^{\circ}C$. In order to find out the effect of $BaF_2$ flux, three modeling experiments between starting materials (1.5$Al_2O_3$-2.5$Y_2O_3$, $Y_2O_3$-$BaF_2$, and $Al_2O_3$-$BaF_2$) were done. These modeling experiments showed that the nucleation process occurs via the dissolution-precipitation mechanism, whereas the grain growth process is controlled via the liquid-phase diffusion route. YAG:Ce phosphor particles prepared using a proposed technique exhibit a spherical shape, high crystallinity, and an emission intensity. According to the experimental results conducted in this investigation, 5% of $BaF_2$ was the best concentration for physical, chemical and optical properties of $Y_3Al_5O_{12}:Ce^{3+}$(YAG:Ce) that is approximately 10-15% greater than that of commercial phosphor powder.