• Analytical Science and Technology
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• v.18 no.1
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• pp.1-4
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• 2005

The stable $Ti(OPr^i)_2(OAc)_2$ sol which reacts with a solution of prehydrolysed $Si(OEt)_4$ was made by addition of acetic acid. The structure evolution of the reaction mixture was monitered by $^1H$, $^{29}Si$ NMR and FT-IR spectroscopy.

• Journal of the Korean Ceramic Society
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• v.40 no.8
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• pp.751-757
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• 2003

Rapid densification of a SiC-30 wt% TiC powder with additive 10 wt% A1$_2$O$_3$-Y$_2$O$_3$-CaO was conducted by Spark Plasma Sintering(SPS). The fully-densified materials can be obtain through the SPS process with very fast heating rate and short holding time. In the present work, the heating rate and applied pressure were kept to be $100^{\circ}C$/min and 40 MPa, while sintering temperature varied from $1600^{\circ}C$ to $1800^{\circ}C$ for 10 min. The full densification of SiC-30 wt% TiC composites with the addition of $Al_2$O$_3$, $Y_2$O$_3$ and CaO was achieved at the temperature above $1700^{\circ}C$ by spark plasma sintering. The XRD found that 3C-SiC and TiC were maintained the entire SPS process temperature, without phase transformation of SiC and formation of YAG phase to $1800^{\circ}C$. The microstructures of the rapidly densified SiC-30 wt% TiC composites consisted of smaller equiaxed SiC grains and larger TiC grains. The biaxial strength of 635.2 MPa and fracture toughness of 6.12 MPaㆍ$m^{1/2}$ were found for the specimen prepared at $1750^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.1
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• pp.22-26
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• 2013

PTCR ceramics of $(Ba_{0.998}Sm_{0.002})TiO_3+0.001MnCO_3+xSiO_2$ (x=1, 2, 3, 4, 5, 6 mol%) were fabricated by solid state method. Disk samples of diameter 5 mm and thickness about 1mm were sintered at $1,290^{\circ}C$ for 2 h in reduced atmosphere of $5%H_2-95%N_2$ followed by re-oxidation at $600^{\circ}C$ for 30 min. in $20%O_2-80%N_2$.and their microstructures and electrical properties were investigated with SEM and Multimeter. The color of sintered samples was strongly dependent on $SiO_2$ content showing that the color of samples with $SiO_2$ of 1~2 mol% was gray but that of samples with $SiO_2$ of 4~6 mol% was changed from gray to blue, which seems to be related with the reduction of samples due to the oxygen vacancies created during the sintering in reduced atmosphere. $SiO_2$ content had a great influence on the microstructure and the electrical properties. With increasing $SiO_2$ content, the grain size of samples increased and the resistivity as well as the resistivity jump ($R_{285}/R_{min}$) decreased, which is considered to be attributed to the resistivity change at grain interior and grain boundary due to the fast mass transfer through $SiO_2$ liquide phase during the sintering. Samples with 2 mol% $SiO_2$ has the resistivity of $202{\Omega}cm$ and the resistivity jump of 3.28. It is expected that $SiO_2$ doped $BaTiO_3$ based PTC ceramics can be used for multilayered PTC thermistor due to the resistance to the sintering in reduced atmosphere.

• Journal of the Korean Ceramic Society
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• v.31 no.6
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• pp.623-628
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• 1994

TiO2-SiO2 homogeneous sol was prepared by means of complexing titanium iso-propoxide with acetylacetone. Crack-free, monolithic binary TiO2-SiO2 aerogels were obtained by evacuating the solvent under the pressure of 2,200 psi at 28$0^{\circ}C$, which was determined as a supercritical condition. The microstructure of the binary aerogels was observed to be finer and more homogeneous as the Ti content decreased. The microstructure was related to the optical transition of aerogels from opaque to transluscent.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.12
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• pp.1017-1024
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• 2000

Effect of the microwave dielectric properties and the microstructure on a mole fraction(x=0.1~0.9) of (1-x)Mg$_2$SiO$_4$-xZnAl$_2$O$_4$ ceramics was investigated. When (1-x)Mg$_2$SiO$_4$-xZnAl$_2$O$_4$(x=0.1~0.9) ceramics were sintered at 130$0^{\circ}C$, 135$0^{\circ}C$ and 140$0^{\circ}C$ for 2hr, the microwave dielectric properties were obtained $\varepsilon$r=6.8~8.3, Q.f$_{0}$=36000~77600. On the other hand, the temperature coefficients of resonant frequency($\tau$$_{f}$) were obtained in the properties of -62ppm/$^{\circ}C$ to -49ppm/$^{\circ}C$. In order to adjust the temperature coefficient of resonant frequency($\tau$$_{f}$), CaTiO$_3$was added in (1-x)Mg$_2$SiO$_4$-xZnAl$_2$O$_4$ceramics. 0.7Mg$_2$SiO$_4$-0.2ZnAl$_2$O$_4$-0.1CaTiO$_3$ceramics sintered at 135$0^{\circ}C$ for 2hr showed the excellent microwave dielectric properties of $\varepsilon$r=7.7, Q.f$_{0}$=32000, and $\tau$$_{f}$=-7.9 ppm/$^{\circ}C$.EX>.>.EX>.

• Bulletin of the Korean Chemical Society
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• v.22 no.12
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• pp.1366-1370
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• 2001

Thin films of the SiO2-TiO2-PDMS composite material have been prepared by the sol-gel dip coating method. Acid catalyzed solutions of tetraethoxy silane (TEOS) and polydimethyl siloxane (PDMS) mixed with titanium isopropoxide Ti(OiPr) were used as precursors. The optical and structural properties of the organically modified 70SiO2-30TiO2 composite films have been investigated with Fourier Transform Infrared Spectroscopy (FT-IR), UV-Visible Spectroscopy (UV-Vis), Differential Thermal Analysis (DTA) and prism coupling technique. The films coated on the soda-lime-silicate glass exhibit 450-750 nm thickness, 1.56-1.68 refractive index and 88-94% transmittance depending on the experimental parameters such as amount of PDMS, thermal treatment and heating rate. The optical loss of prepared composite film was measured to be about 0.34 dB/cm.

• Journal of the Korean Ceramic Society
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• v.40 no.7
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• pp.637-643
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• 2003

In order to improve the photoluminescent properties and crystallinity, Zn$_2$SiO$_4$:Mn, M(M=Cr, Ti) phosphors were synthesized by the sol-gel method. The willemite single phase was obtained at 110$0^{\circ}C$, which is lower temperature than that of the conventional solid-state reaction (130$0^{\circ}C$). The characteristics of fired samples were obtained by a 147 nm excitation source under VUV (Vacuum Ultraviolet). To investigation the effect of co-dopant, the content of Mn and the ratio of $H_2O$ to TEOS was fixed as 2 ㏖% and 36. 1, respectively. The highest emission intensity was obtained when the concentration of Cr and Ti was 0.1 ㏖% relative to Zn$_2$SiO$_4$:Mn. While the emission intensity decrease continuously the decay time improved as increased the Cr concentration. In the case of Ti added samples, however, the emission intensity increase up to 2 ㏖％ concentration.

• Transactions of Materials Processing
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• v.15 no.8 s.89
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• pp.615-620
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• 2006

The reduction behavior of $TiO_{2}$ in Al and Al/CaSi containing self-reducing $TiO_{2}$ briquettes(SRTB) was investigated. The maximum yield of Ti was expected with the slag composition of 45-55%CaO in the $CaO-Al_{2}O_{3}$ system. When $CaCO_{3}$ was used as a flux, the oxidation loss of reducing agent by $CO_{2}$ should be compensated, and therefore it leads to excessive requirement of the reducing agent. By using Al and CaSi mixture as a reducing agent of $TiO_{2}$, the reaction products both oxide and metal could be liquefied, and separated effectively with each other. As a result, the yield of Ti increases remarkably. The optimum mixing ratio of CaSi to Al is 78%CaSi-22%Al.

• Journal of the Korean Ceramic Society
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• v.39 no.8
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• pp.742-749
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• 2002

The PZT thin films werre deposited on Pt/Ti/$SiO_2$/Si substrate by R. F. magnetron sputtering with $Pb_{1.1}Zr_{0.53}Ti_{0.47}O_3$ target. When interlayers(PbO, $TiO_2$, PbO/$TiO_2$) were inserted between PZT and Pt, the crystallization of the PZT thin films was considerably improved and the processing temperature was lowered. Compared to the pure PZT thin films, dielectric constant, dielectric loss and polarization properties of PZT thin films with interlayers were considerably improved. From XPS depth profile analysis, it was confirmed that PZT thin films and interlayers existed independently. In particular, PZT thin films deposited on interlayer(PbO/$TiO_2$) showed the best dielectric property (${\varepsilon}_r$=414.94, tan${\delta}$=0.0241, Pr=22${\mu}C/cm^2$).

• Journal of the Korean Vacuum Society
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• v.19 no.2
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• pp.91-95
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• 2010

A UV-enhanced atomic layer deposition (UV-ALD) process was developed to deposit $TiO_2$ thin films on Si substrates using titanium isopropoxide(TIP) and $H_2O$ as precursors with UV light. In the UV-ALD process, the surface reactions were found to be self-limiting and complementary enough to yield a uniform, conformal, pure $TiO_2$ thin film on Si substrates at room temperature. The UV light was very effective to obtain the high-quality $TiO_2$ thin films with good adhesive strength on Si substrates. The UV-ALD process was applied to produce uniform and conformal $TiO_2$ coats into deep trenches with high aspect ratio.