• Bulletin of the Korean Chemical Society
• /
• v.34 no.1
• /
• pp.143-148
• /
• 2013

Novel titanium containing solid core mesoporous shell silica has been synthesized by using octadecyltrichloro silane and triethylamine. The synthesized material was characterized by various physicochemical techniques. The mesoporous character of the material has been revealed from PXRD studies. The presence of octadecyltrichloro silane and triethylamine in the sample has been confirmed from EDAX studies. TG/DTA analysis reveals the thermal characteristics of the synthesized material. The presence of titanium in the frame work and its coordination state has been studies by UV-vis DR studies and XPS analysis. Chemical environment of Si in the framework of the material has been studied by $^{29}SiMASNMR$ studies. The surface area of the material is found to be around $550\;m^2g^{-1}$ and pore radius is of nano range from BET analysis. The spherical morphology and particle size of the core as well as shell has been found to be 300 nm and 50 nm respectively from TEM analysis. The catalytic application of this material towards the synthesis of caprolactam from cyclohexanone in presence of hydrogen peroxide through ammoxidation reaction has been investigated. The optimum conditions for the reaction have been established. The plausible mechanism for the formation of core silica and conversion of cyclohexanone has been proposed.

• Journal of the Korean Academy of Esthetic Dentistry
• /
• v.3 no.1
• /
• pp.32-43
• /
• 1995

Ni-Ti alloy has excellent corrosion resistance, biocompatibility, shape memory effect and superelasticity, so it has been used widely in biomedical fields. But it has difficulty in casting due to its high melting temperature and oxygen affinity at high temperature. Recently it has been attempted to cast Ni-Ti alloy using new casting machine and investment. The purpose of this study was to examine the superelastic behavior of cast shape memory Ni-Ti alloy and to compare the mechanical properties of the cast shape memory alloy with those of commercial alloys for removable partial denture framework. Ni-Ti alloy(Ni 50.25%, Ti 49.75% : atomic ratio) was cast with dental argon-arc pressure casting machine and Type IV gold alloy, Co-Cr alloy, Ni-Cr alloy, pure titanium were cast as reference. Experimental cast Ni-Ti alloy was treated with heat($500{\pm}2^{\circ}C$) in muffle furnace for 1 hour. Transformation temperature range of cast Ni-Ti alloy was measured with differential scanning calorimetry. The superelastic behavior and mechanical properties of cat Ni-Ti alloy were observed and evaluated by three point bending test, ultimate tensile test, Vickers microhardness test and scanning electron microscope. The results were as follows : 1. Cast Ni-Ti alloy(Ni 50.25%, Ti 49.75% : atomic ratio) was found to have superelastic behavior. 2. Stiffness of cast Ni-Ti alloy was considerably lesser than that of commercial alloys for removable partial denture. 3. Permanent deformation was observed in commercial alloys for removable partial denture framework at three point bending test over proportional limit(1.5mm deflection), but was not nearly observed in cast Ni-Ti alloy. 4. On the mechanical properties of ultimate tensile strength, elongation and Vickers microhardness number, cast Ni-Ti alloy was similiar to Type IV gold alloy, Co-Cr alloy, Ni-Cr alloy and pure titanium. With these results, cast Ni-Ti alloy had superelastic behavior and low stiffness. Therefore, it is suggested that cast Ni-Ti alloy may be applicated to base metal alloy for removable partial denture framework.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.8
• /
• pp.1214-1218
• /
• 2005

Ti-HMS samples in which titanium species exist in various forms of isolated tetrahedral state, finely dispersed $TiO_2$ cluster, and some in extra-framework anatase phase were prepared via a direct synthesis route using dodecylamine (DDS) as a structure directing agent by systematically varying the titanium loadings between 2 and 50 mol% Ti/(Ti+Si) in substrate composition. Physicochemical properties of the materials were evaluated using XRD, SEM/TEM, N2 adsorption, UV-vis and XANES spectroscopies. Catalytic properties of Ti-HMS in cyclohexene and 2,6-di-tert-butyl phenol (2,6-DTBP) oxidation using aqueous $H_2O_2$, and vapor phase photocatalytic degradation of acetaldehyde were evaluated. High $H_2O_2$ selectivity was obtained in cyclohexene oxidation, and cyclohexene conversion was found primarily dependent on the amount of tetrahedrally coordinated Ti sites. For bulky 2,6-DTBP oxidation and photocatalytic oxidation of acetaldehyde, on the other hand, conversions were found dependent on the total amount of Ti sites and maintaining an uniform mesoporous structure in the catalysts was not critical for efficient catalysis.

• The Journal of Advanced Prosthodontics
• /
• v.14 no.6
• /
• pp.346-359
• /
• 2022

PURPOSE. Four and six implant-supported fixed full-arch prostheses with various framework materials were assessed under different loading conditions. MATERIALS AND METHODS. In the edentulous maxilla, the implants were positioned in a configuration of four to six implant modalities. CoCr, Ti, ZrO₂, and PEEK materials were used to produce the prosthetic structure. Using finite element stress analysis, the first molar was subjected to a 200 N axial and 45° oblique force. Stresses were measured on the bone, implants, abutment screw, abutment, and prosthetic screw. The Von Mises, maximum, and minimum principal stress values were calculated and compared. RESULTS. The maximum and minimum principal stresses in bone were determined as CoCr < ZrO₂ < Ti < PEEK. The Von Mises stresses on the implant, implant screw, abutment, and prosthetic screws were determined as CoCr < ZrO₂ < Ti < PEEK. The highest Von Mises stress was 9584.4 Mpa in PEEK material on the prosthetic screw under 4 implant-oblique loading. The highest maximum principal stress value in bone was found to be 120.89 Mpa, for PEEK in 4 implant-oblique loading. CONCLUSION. For four and six implant-supported structures, and depending on the loading condition, the system accumulated different stresses. The distribution of stress was reduced in materials with a high elastic modulus. When choosing materials for implant-supported fixed prostheses, it is essential to consider both the number of implants and the mechanical and physical attributes of the framework material.

• Korean Journal of Crystallography
• /
• v.7 no.1
• /
• pp.57-63
• /
• 1996

The compound titanium (III) pyrophosphate, KTiP2O7 has been prepared and the crystal structure of the compound has been determined by the X-ray diffraction techniques. It crytallizes in the space group P21/a of the monoclinic system with four formula units in a cell of dimensions a=8.210(3), b=10.292(2), c=7.434(1)Å and β=106.71(2)°. The structure consists of the framework possessing corner-sharing octahedral TiO6 and pyrophosphate groups. As a result, a tunnel structure has been constructed and the K+ cations reside inside the tunnel. KTiP2O7 is isostructural with other trivalent metal pyrophosphates such as KAlP2O7 and RbTiP2O7 but the size difference of the alkali metals causes the variation in the structure. The classical charge balance of the compound can be described as [K+][Ti3+][P24O74-].

• KIEE International Transactions on Electrophysics and Applications
• /
• v.5C no.3
• /
• pp.119-123
• /
• 2005

Lithium titanium oxide as anode material for energy storage prepared by novel synthesis method. Li$_{4}$Ti$_{5}$O$_{12}$ based spinel-framework structures are of great interest material for lithium-ion batteries. We describe here Li$_{4}$Ti$_{5}$O$_{12}$ a zero-strain insertion material was prepared by novel sol-gel method and by high energy ball milling (HEBM) of precursor to from nanocrystalline phases. According to the X-ray diffraction and scanning electron microscopy analysis, uniformly distributed Li$_{4}$ Ti$_{5}$O$_{12}$ particles with grain sizes of 100nm were synthesized. Lithium cells, consisting of Li$_{4}$ Ti$_{5}$O$_{12}$ anode and lithium cathode showed the 173 mAh/g in the range of 1.0 $\~$ 3.0 V. Furthermore, the crystalline structure of Li$_{4}$ Ti$_{5}$O$_{12}$ didn't transform during the lithium intercalation and deintercalation process.

• Transactions of Materials Processing
• /
• v.14 no.8 s.80
• /
• pp.681-688
• /
• 2005

The high-temperature deformation mechanisms of a ${\alpha}+{\beta}$ titanium alloy (Ti-6Al-4V), near-a titanium alloy (Ti-6.85Al-1.6V) and a single-phase a titanium alloy (Ti-7.0Al-1.5V) were deduced within the framework of inelastic-deformation theory. For this purpose, load relaxation tests were conducted on three alloys at temperatures ranging from 750 to $950^{\circ}C$. The stress-versus-strain rate curves of both alloys were well fitted with inelastic-deformation equations based on grain matrix deformation and grain-boundary sliding. The constitutive analysis revealed that the grain-boundary sliding resistance is higher in the near-${\alpha}$ alloy than in the two-phase ${\alpha}+{\beta}$ alloy due to the difficulties in relaxing stress concentrations at the triple-junction region in the near-${\alpha}$ alloy. In addition, the internal-strength parameter (${\sigma}^*$) of the near-${\alpha}$ alloy was much higher than that of the ${\alpha}+{\beta}$ alloy, thus implying that dislocation emission/ slip transfer at ${\alpha}/{\alpha}$ boundaries is more difficult than at ${\alpha}/{\beta}$ boundaries.

• Applied Chemistry for Engineering
• /
• v.5 no.4
• /
• pp.714-721
• /
• 1994

Titanium and zirconium-containing MFI type zeolites have been prepared hydrothermally. Incorporation of titanium or zirconium into the framework of zeolite has been demonstrated by XRD, FT-IR, $^{29}Si$ MAS NMR analysis, and the catalytic benzene hydroxylation or n-hexane oxidation was used for checking the properties of catalysts. Pure titania and zirconia powder showed no catalytic activity at all for these reactions but Ti and Zr modified zeolite had the high activities in both reactions. The catalytic activity strongly depended on the kind of solvents, and the conversion of benzene or n-hexane increased with the increasing content of Ti and Zr in zeolites.

• Applied Chemistry for Engineering
• /
• v.9 no.5
• /
• pp.639-647
• /
• 1998

Al-containing titanium silicalite-1 ([Al]-TS-1) catalyst was prepared hydrothermally, and the effects of synthesis parameters such as silica/alumina sources, $SiO_2/TiO_2$ ratio, and aging treatment were investigated. The structure, crystal size, and shape were examined by XRD and SEM, and the extent of titanium incorporation into the zeolite framework was examined using UV-vis DRS spectroscopy. For [Al]-TS-1 catalyst preparation, aging of ca. 24h was essential, and the faster crystallization rates were achieved with Cab-O-Sil than with Ludox or TEOS as a silica source. In addition, the higher crystallinity and faster crystallization rate were obtained using sodium aluminate as an aluminum source. 2-butanol oxidation using $H_2O_2$ as an oxidant was carried out to confirm the redox property of the [Al]-TS-1. Acid sites catalyzed toluene alkylation study indicated that lattice titanium species in [Al]-TS-1 weakened the acid strength, and the para-ethyltoluene selectivity was enhanced as a results.

• Korean Journal of Crystallography
• /
• v.10 no.1
• /
• pp.51-55
• /
• 1999

Cesium titanium(III) pyrophosphate 화합물인 CsTiP2O7을 합성하고 X절 회절법을 이용하여 그 결정구조를 해석하였다. 이물질은 단사정계의 P21/a 공간군으로 결정화되었고 a=8.369(2) , b=10.208(2) , c=7.752(1) , β=104.77(2)o, V=640.4(2) 3, and Z=4이다. 이 물질의 구조는 모서리를 공유하고 있는 TiO6 팔면체와 P2O7 pyrophosphate group들로 구성된 framework로 구성되어 있으며 그 결과로 형성된 tunnel 안에는 Cs+이온이 존재한다. CsTiP2O7은 ATiP2O7(A=K, Rb)와 KAIP2O7 그리고 AMoP2O7(A=K, Rb, Cs)등 다른 +3금속 pyrophosphate들로 유사한 구조를 가지고 있다. 이 물질은 [Cs+][Ti3+][P2O74-]의 식으로 표현할 수 있다.