• The Journal of Advanced Prosthodontics
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• v.5 no.2
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• pp.75-83
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• 2013

PURPOSE. Maxillofacial silicone elastomer is usually colored intrinsically with color pigments to match skin colors. The purpose of this study was to investigate the color stability of a maxillofacial silicone elastomer, colored with a thermochromic, color changing pigment. MATERIALS AND METHODS. Disc-shaped maxillofacial silicone specimens were prepared and divided into 3 groups: a conventionally colored control group, one group additionally colored with 0.2 wt% thermochromic pigment, and one group with 0.6 wt% thermochromic pigment. Half of the surface of each specimen was covered with an aluminium foil. All of the specimens were exposed to UV radiation in 6 hour cycles over 46 days. In between the UV exposures, half of the specimens were stored in darkness, at room temperature, and the other half was stored in an incubator, at a humidity of 97% and a temperature of $+37^{\circ}C$. Color measurements were made with a spectrophotometer and registered according to the CIELAB $L^*a^*b^*$ color model system. The changes in $L^*$, $a^*$ and $b^*$ values during artificial aging were statistically analyzed by using paired samples t-test and repeated measures ANOVA. P-values <.05 were considered as statistically significant. RESULTS. The UV exposure resulted in visually noticeable and statistically significant color changes in the $L^*$, $a^*$ and $b^*$ values in both of the test groups containing thermochromic pigment. Storage in the incubator lead to statistically significant color changes in the $a^*$ and $b^*$ values of the specimens containing thermochromic pigment, compared to those stored at room temperature. CONCLUSION. The specimens containing thermochromic pigment were very sensitive to UV radiation, and the thermochromic pigment is not suitable, as such, to be used in maxillofacial prostheses.

• Korean Journal of Materials Research
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• v.30 no.6
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• pp.279-284
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• 2020

In this work, a carbon-doped carbon nitride photocatalyst is successfully synthesized through a simple centrifugal spinning method after heat treatment. The morphology and properties of the prepared photo catalyst are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis spectrophotometer (UV-vis), and specific surface area. The results show that the band gap of the prepared sample, g-CN-10 is 2.1 eV, is significantly lower than that of pure carbon nitride, 2.7 eV. As the amount of cotton candy increased, the absorption capacity of the prepared catalyst for visible light is significantly enhanced. In addition, the degradation efficiency of Rhodamine B (RhB) by sample g-CN-10 is 98.8 % over 2 h, which is twice that value of pure carbon nitride. The enhancement of photocatalytic ability is attributed to the increase of specific surface area after the carbon doping modifies carbon nitride. A possible photocatalytic degradation mechanism of carbon-doped carbon nitride is also suggested.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.374.2-374.2
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• 2016

Volatile organic compounds (VOCs) in the atmosphere are harmful materials which influence indoor air environment and human health. Titanium dioxide ($TiO_2$) is photocatalyst extensively used in degradation of organic compound. To improve the photocatalytic activity in the visible light region, doping with non-metals element or loading noble metals on the surface of $TiO_2$ is generally proposed. In this study, N- doped $TiO_2$ having photocatalytic activity in visible light region was attached noble metal such as Pt, Ag, Pd, Au by coupling method. Catalytic activities of Noble metal coupled $N-TiO_2$ powders were evaluated by the improvement of their photocatalytic activities and the degradation of VOC gas. A UV-Vis spectrophotometer was used to measure the diffuse reflectance spectra of coupled $N-TiO_2$ sample. The photocatlytic activities of as prepared samples were characterized by the decoloration of aqueous MB solution under Xenon light source (UV and visible light). To measure of decomposition VOCs, ethylbenzene was selected for target VOC material and the concentration was monitored under UVLED irradiation in a closed chamber system. Adjusting the initial concentration of 10~12 ppm, to evaluate the removal characteristics by using the coupled $N-TiO_2$.

• Fashion & Textile Research Journal
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• v.8 no.4
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• pp.465-470
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• 2006

Walnut hull is a by-product from the Walnut tree, used as natural dyestuff from ancient times. This study was done to examine the effects of extractive conditions on the properties of walnut hull extracts for making efficient use of the walnut hull as a natural colorant. Aqueous extracts of walnut hull were prepared at various extractive concentration, temperature and time. Then they were characterized using UV-Vis. Spectrophotometer, FT-IR Spectrometer, Prep Liquid Chromatography, and Energy dispersive X-ray spectrometer. The aqueous extracts have two absorbency peaks of UV-Vis. Spectrum, shoulder type peak in the range of 270-280 nm and broad type band around 420 nm. Intensity of absorbency is increased with increase of extraction concentration and time. However, Boiling temperature extraction method showed the most efficiency of all. Intensity of absorbency is also affected by extraction pH. The Prep LC examined two kinds of isolated colorant with different molecular weight. FT-IR spectra of hull extracts showed an absorption band around $3400cm^{-1}$, the peaks at $1700-1600cm^{-1}$, which are characteristic of aromatic compounds with unsaturated ketone and benzene ring. It showed that the extraction contained some mineral ions, such as K, Ca, Si, Mg.

• Journal of Korean Ophthalmic Optics Society
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• v.12 no.1
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• pp.17-22
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• 2007

Metal-doped $TiO_2$ thin films were prepared on soda-lime-silica glass substrates by using a spin coating-pyrolysis process. As-deposited films were prefired at $500^{\circ}C$ or 10 min in air. Five-coated films were finally annealed at $600^{\circ}C$ for 30 min in air. High resolution X-ray diffraction, field emission scanning electron microscope and UV spectrophotometer were used to analyze film's property. The largest red shift in optical energy gap is obtained in the Fe-doped $TiO_2$ film.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.5 no.2
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• pp.103-108
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• 2007

The absorption spectra of Pu in stock solution were measured using a UV-Vis-NIR spectrophotometer after dissolving $PuO_2\;with\;HNO_3$, HF and $HClO_4$. The spectroscopic characteristics of Pu (III, IV, VI) in acidic, neutral and alkali media were investigated. Also, the intensities and position of major peaks for Pu(VI) were observed with increasing acidic and alkali concentration. The variation of oxidation states of Pu(VI) with an adding reducing reactant was investigated in HCl and NaOH medium.

• Journal of the Korean Chemical Society
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• v.41 no.6
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• pp.299-303
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• 1997

The rate constants($k_{OH}$) for the alkaline hydrolysis of the 4-substituted phenyl ethyl benzylphosphonates were determined in various buffer solutions by UV(Vis spectrophotometer. The activation entropies of the title reactions show negative values and this result is not consistent with a dissociative mechanism (EA) for which a positive or slightly negative value of the entropy of activation should be expected. An associative mechanism(AE) is favorable because the negligible negative charge is generated on the leaving group in the rate determining step from a good Hammett relationship(ρ=1.89). By the results of a kinetic study, we conclude that a dissociative mechanism is not proceeded in the title reactions.

• Clean Technology
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• v.12 no.3
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• pp.145-150
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• 2006

Electrolysis of aqueous solution produces hydroxide ions and proton ions for the hydrolysis of reactive organic compounds, and oxidizing agent such as hypochlorite ions for the oxidative decomposition of organic chemicals. Electrolytic decomposition of dying chemicals was tested with our custom made system, and analyzed by HPLC and UV-VIS spectrophotometer. The electrolytic system could decompose dying chemicals with very high reactivity and low cost. Disposal of byproduct and refill of reactant during electrolysis was not necessary. Decomposition time of dying chemicals is compared under similar conditions, and application to water purification is discussed.

• Journal of Adhesion and Interface
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• v.9 no.2
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• pp.1-7
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• 2008

Using biodegradable polycaprolactone, the microcapsules were prepared by solvent evaporation method. Retinol was selected as a core material, which was used as an important ingredient material in cosmetic fields. Poly(vinyl alcohol) was used as a stabilizer. The shape and property of the microcapsules were characterized by scanning electron microscope and differential scanning calorimeter, and the release rate of the microcapsule was measured by UV spectrophotometer. The microcapsules were prepared, changing the concentration of wall material, the stirring rate, and the concentration of stabilizer. Under the optimum condition, the microcapsules were formed, which showd 5~6 um in diameter and got the homogeneous sphere shape.

• Elastomers and Composites
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• v.51 no.3
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• pp.240-249
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• 2016

$BiVO_4$ nanomaterial was synthesized from bismuth (III) nitrate pentahydrate [$Bi(NO_3)_3{\cdot}5H_2O$] and ammonium vanadate (V) [$NH_4VO_3$]. The $BiVO_4$-graphene nanocomposite was fabricated by calcining the $BiVO_4$ nanomaterial and graphene under an oxygen-free atmosphere at $700^{\circ}C$. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to characterize structural and morphological properties of samples. The catalytic activity of the $BiVO_4$-graphene nanocomposite was studied for the reduction of 4-nitrophenol, 3-nitrophenol and 2-nitrophenol by sodium borohydride [$NaBH_4$]. The photocatalytic activity of the $BiVO_4$-graphene nanocomposite was demonstrated by the degradation of organic dyes like BG, MB, MO and RhB under irradiation at 365 nm. The catalytic and photocatalytic activity were studied by UV-vis spectrophotometry.