• Journal of the Korean Ceramic Society
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• v.44 no.2 s.297
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• pp.84-88
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• 2007

CdSe hollow spheres with the diameter of about 30-50 nm were synthesized after ultrasonic irradiation in the presence of $Cd(NO_3)_2,\;Na_2SeSO_3$, and polyvinylalcohol(PVA). The characteristics of CdSe hollow spheres were analyzed using X-ray diffraction(XRD), transmission electron microscopy(TEM), UV-vis measurement and PL spectrometer. The characteristics of solvent as water and water-1-propanol mixture in the system played important roles on the controlled synthesis of hollow sphere. Based on the observation of morphological difference of CdSe, the possible mechanism of CdSe hollow sphere formation will be discussed.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.11
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• pp.992-998
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• 2009

We investigated the influence of organic solvents on the droplet properties of 6,13-bis (triisopropylsilylethynyl) pentacene (TIPS-pentacene), which was used for semiconductor of organic thin film transistors (OTFTs) and deposited by ink jet printing. From the result of the investigation, the conditions of a suitable solvent is that boiling point should be above $200^{\circ}C$ to reduce coffee stain and the surface tension above 32 dyn/cm to decrease the droplet size. Consequently, we selected tetralin which have a high boiling point ($207^{\circ}C$) and high surface tension (34.3 dyn/cm) as the solvent for TIPS-pentacene, and applied it to OTFTs. In fabrication process the conventional bank process employing photolithography and etching process was replaced by ink jet printed bank process, resulting in simplifying the process. Especially, polyvinylphenol was used for the bank, and the high hydrophobicity could improve the confinement of TIPS molecules inside the bank, enhancing the performance over the conventional hydrophilic polyvinylalcohol bank. The mobility was $0.18\;cm^2/Vs$, current on/off ratio $2.09{\times}10^5$, subthreshold slope 0.42 V/dec, and off state current $0.049\;pA/{\mu}m$.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1291-1293
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• 2005

Hybrid insulator pentacene thin film transistors (TFTs) were fabricated with thermally grown oxide and cross-linked polyvinylalcohol (PVA) including surface treatment by dilute ploymethylmethacrylate (PMMA) layers on $n^+$ doped silicon wafer. Through the optimization of $SiO_2$ layer thickness in hybrid insulator structure, carrier mobility was increased to above 35 times than that of the TFT only with the gate insulator of $SiO_2$ at the same transverse electric field. The carrier mobility of 1.80 $cm^2$/V-s, subthreshold swing of 1.81 V/decade, and $I_{on}$/ $I_{off}$ current ratio > 1.10 × $10^5$ were obtained at low bias (less than -30 V) condition. The result is one of the best reported performances of pentacne TFTs with hybrid insulator including cross-linked PVA material at low voltage operation.

• Journal of the Korean Society of Clothing and Textiles
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• v.13 no.4
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• pp.427-436
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• 1989

Poly (vinyl alcohol) films, which .were annealed at various different annealing conditions, were carried out by uniaxial stretching them with free width in water and were investigated drawing behaviours and rupture phenomena. l) After dipping the specimen into the water, it took about 15 min. for the specimen's swelling to approach to equilibrium. 2) When the film annealed at $180^{\circ}C$ for 10 min. was drawn at $20^{\circ}C$. it was shown very toughness. 3) By means of birefringence measurements, the total molecular orientation of the annealed films increased until the draw ratio of 4, but drawing them above the draw ratio of 5, that of untreated films increased. 4) In the case of the mechanical properties of the drawn films. the annealed films tended to good trend for the draw ratios between 1 and 4. but drawing them above the draw ratio of 5. the untreated films tended to good trend for them.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.318-321
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• 2007

CdSe nanoparticles were prepared by chemical solution methods using $CdCl_2{\cdot}4H_2O$ (or $Cd(NO_3)_ 2{\cdot}4H_2O$) and $Na_2SeSO_3$. The characteristics of CdSe nanoparticles were controlled by the react ion time, reaction temperature and reaction method as well as the surfactants. Cetyltrimethyl ammonium bromide(CTAB) was used as a capping agent to control the chemical reactions in aqueous solution. Polyvinylalcohol(PVA) was used as a templet in sono-chemical method. CdSe nanoparticles synthesized in aqueous solution showed homogeneous size distribution with relatively stable surface. CdSe nanoparticles synthesized in non-aqueous solution containing diethanolamine(DEA) showed the structure transformation from cubic to hexagonal as the reduction temperature increased from 80 to $160^{\circ}C$. Core shell CdSe was synthesized by sono-chemical method. Characteristics of CdSe nanoparticles were analyzed using transmission electron microscopy(TEM), x-ray photoelectron spectroscopy(XPS), x-ray diffraction(XRD), UV-Vis absorption spectra, fourier transform infrared spectroscopy(FT-IR) and photoluminescence spectra spectroscopy(PL). This paper presents simple routes to prepare CdSe nanoparticles for solar cell applications.

• International Journal of Oral Biology
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• v.30 no.4
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• pp.131-134
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• 2005

In the present study, performances of several in vitro maturation (IVM) systems for porcine follicular oocytes were evaluated, and an efficient chemically defined IVM system for porcine oocytes was proposed. The proposed one-step culture system supplemented with polyvinylalcohol (PVA) gave competitive efficiencies in terms of oocyte maturation and blastocyst development after parthenogenetic activation and in vitro culture, compared with the conventional two-step culture system by a supplementation of porcine follicular fluid (pFF). Additionally, it is identified that the proposed chemically defined one-step culture system yielded the comparable level of blastocyst production to the conventional maturation system in porcine somatic cell nuclear transfer (SCNT). Therefore, one can eliminate un-expected effects accompanied by supplementation of pFF. No medium replacement during whole maturation period is an additional benefit by applying this new system. Thus, these data support that the developed PVA supplemented chemically defined one-step IVM system for porcine follicular oocyte might be used in porcine SCNT program.

• Electrical & Electronic Materials
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• v.9 no.10
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• pp.1053-1059
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• 1996

The pulse-echo response of the piezoceramics PZT-polymer 3-3 type composite transducers with various PVA additions were investigated. The PZT powder was prepared by the molten salt synthesis method. The porous PZT specimens will be used as a filler to make 3-3 type comosite were prepared from a mixture of PZT and polyvinylalcohol(PVA) sphere by utilizing BURPS(Bumout Plastic Sphere) technique. It was shown that the transmitting and receiving sensitivity of 3-3 type piezoelectric composite transducers could be improved than that of solid PZT transducers. The reason is that 3-3 type piezoelectric composite have low dielectric constant, density and acoustic impedance. The distance between transducer and reflector was in good agreement with the distance calculated from the longitudinal velocity of the specimens and receiving time observed pulse-echo responses on the ultrasonic transducer analyzer.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.45 no.4
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• pp.558-561
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• 1996

PZT powders were prepared by the molten salt synthesis method. The porous PZT ceramics were made from a mixture of PZT and polyvinylalcohol(PVA) by BURPS(Burnout Plastic Sphere) technique. The porous PZT bodies were fabricated from the green compacts with various amounts of PVA spheres. The piezoelectric coefficient d$_{33}$ (334~350*10$^{-12}$ C/N)of porous PZT ceramics(364*10$^{-12}$ C/N). The figure of merit(d$_{h}$g$_{h}$) of porous PZT specimens evaluating the sensitivity for ultrasonic transducer applications was improved significantly(11~70times) in comparison with that of single phase PZT ceramics(100*10$^{-15}$ m$^{2}$/N). The thickness mode coupling factor k$_{t}$(0.5~0.6) of porous specimens was comparable with that of single phase PZT ceramics(k$_{t}$=0.7). The mechanical quality factor of porous PZT specimens was smaller than 10, and thus these porous PZT ceramics would be believed as a good candidate for broad band hydrophone applications. (author). 10 refs., 7 figs.igs.igs.

• Membrane Journal
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• v.14 no.3
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• pp.240-249
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• 2004

Crosslinked PVA membranes were achieved by esterification between the hydroxyl groups of PVA and carboxyl group of sulfosuccinic acid (SSA). SSA containing sulfonic group was used as a chemical crosslinking agent as well as a donor of fixed anionic group ($-SO_3$H). The crosslinking density of membranes was controlled by SSA content and calculated using polar and non-polar solvent. The crosslinking density measured by using non-polar solvent such as xylene and benzene increases with SSA content. However, using the polar solvent such as water and methanol, the crosslinking density increases up to SSA content of 20 wt% and above the content decrease due to sulfonic acid groups. The crosslinked PVA membranes were studied in relation with water diffusion coefficient and mechanical property as well as proton conductivity and methanol permeability as a function of crosslinking density. These properties were all dependent on the effect of SSA content.

• Membrane Journal
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• v.16 no.1
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• pp.9-15
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• 2006

PVA/SSA/HPA composite membranes were prepared by the addition of SSA as a crosslinking agent and HPA such as PWA or SiWA. The water uptake decreased and the IEC increased as the HPA contents increased in PVA/SSA/HPA composite membranes. XRD results showed that HPA distributed well into the composite membranes as the HPA concentration increased, and SiWA dispersed better than PWA in the composite membranes. TGA results showed that PVA/SSA composite membranes were more heat-resistant than PVA due to the crosslinking of PVA, and the heat stability of the composite membranes improved much more as the concentration of HPA increased. The methanol barrier property of PVA/SSA/HPA composite membranes was superior to Nafion, and the methanol permeability of the composite membranes decreased as the concentration of HPA increased.