4 results
Search Results
Now showing 1 - 4 of 4
Article Citation - WoS: 11Citation - Scopus: 10Synthesis and Characterization of Hydrothermally Grown Potassium Titanate Nanowires(Korean Assoc Crystal Growth, inc, 2015) Kapusuz, Derya; Kalay, Y. Eren; Park, Jongee; Ozturk, Abdullah; Metallurgical and Materials EngineeringPotassium titanate (KT) nanowires were synthesized by a one-step hydrothermal reaction between TiO2 and aqueous KOH solution. The effects of KOH concentration and reaction time on hydrothermal formation and KT nanowire growth were investigated. The nanowire growth mechanism was elucidated using a combined study of powder X-ray diffraction, and scanning and transmission electron microscopy. The results revealed that hydrothermal growth was initiated by the formation of amorphous-like Ti-O-K sheets in anatase. Increasing hydrothermal reaction time caused the transformation of anatase to Ti-O-K sheets, from which potassium hexa-titanate (K2Ti6O13) nuclei formed and grew to establish one-dimensional morphology through preferential growth along the b-axis. It was revealed that the hydrothermal reactions followed a quite different mechanism than the well-known calcination route. Potassium tetra-titanate (K2Ti4O9) crystals formed in the amorphous region using the hexa-titanate phase as a nucleation site for heterogeneous crystallization. Increasing the KOH concentration in the solution accelerated the hydrothermal reaction rate.Article Citation - WoS: 4Citation - Scopus: 2Mechanical Properties and Electrical Resistivity of Sic-Tic Composites With Nitrate Sintering Additives(Korean Assoc Crystal Growth, inc, 2020) So, Sung Min; Hwang, Hee Woong; Yi, Sam Heang; Park, Joo Seok; Kim, Kyoung Hun; Lee, Kwang Ho; Lee, Sung GapWe fabricated SiC-TiC composites by hot-press sintering with aluminum and yttrium nitrate additive and evaluated crystal phase, relative density, microstructure, electrical resistivity and mechanical properties of the sintered body. And the effect of nitrate additive on the densification of SiC-TiC composites was compared with that of Al2O3 and Y2O3 additives. Because nitrate additives were uniformly dispersed in SiC and TiC mixture, it inhibited the growth of crystal grain between each other and formed fine and uniform microstructure, thereby improving mechanical properties and electrical resistivity. The electrical resistivity and flexural strength of the SiC-TiC composite with aluminum and yttrium nitrate additive were 2.3 Omega.cm and 652.3 MPa respectively.Article Citation - WoS: 3Citation - Scopus: 3Effect of Ionic Substitution on the Structural, Dielectric and Electrical Properties of Bismuth Zinc Niobate Ceramics(Korean Assoc Crystal Growth, inc, 2012) Qasrawi, A. F.; Abu Je'ib, Hussein A.; Mergen, A.; Department of Electrical & Electronics EngineeringThe effects of tin substitution on the structural, dielectric and electrical properties of the Bi1.5Zn0.92Nb1.5O6.92 pyrochlore ceramics have been investigated. Tin atoms was substituted in the A (Bi1.5Zn0.46)-site instead of zinc and in the B ((Zn0.46Nb1.5)-site instead of niobium in accordance to the chemical formulae Bi1.5Zn0.92Nb1.5-xO6.92-x/2 and (Bi1.5-x/3Zn0.46-3x/2Snx)(Nb1.5Zn0.46)O-6.92, for 0.00 <= x <= 0.40 and 0.00 <= x <= 0.60, respectively. A relative single phase formation of the structures was possible for x values less than 0.25 and less than 0.10. Pronounced tunability in the dielectric constant values associated with very low dielectric loss are obtainable by Sn substitution. Furthermore, a frequency invariant but linearly varying temperature dependent dielectric constant is observed. The electrical conductivity decreased by two and one order of magnitude for the A and B-site substitutions, respectively. The temperature-dependent conductivity analysis in the temperature region of 300-500 K, reflected the existence of shallow and deep impurity energy levels being created by the doping process.Article Citation - WoS: 8Citation - Scopus: 6Preparation and Photocatalytic Activity of Apatite-Precipitated Tio2(Korean Assoc Crystal Growth, inc, 2011) Soysal, K.; Park, J.; You, S. H.; Shin, D. W.; Bae, W. T.; Ozturk, A.; Metallurgical and Materials Engineering; English Translation and InterpretationApatite was precipitated on the surface of titanium dioxide (TiO2) powder by a biomimetic process. The precipitation was accomplished by immersing TiO2 powder in simulated body fluid (SBF) for 1, 3, 6, 12 and 24 h. Photocatalytic activity of the apatite-precipitated TiO2 (HAp-TiO2) powders was investigated to assess the decomposition of methylene blue (MB) in aqueous solution and the removal of acetaldehyde gas under UV irradiation. Hydroxyapatite precipitation enhanced the photocatalytic activity of the TiO2 powder. The time required for the complete degradation of MB decreased from 3.5 to 2 h with the immersion of TiO2 powders in SBF for 3 h. In terms of acetaldehyde gas decomposition, less than 1 h was sufficient to achieve complete removal for HAp-TiO2 powder but at least 2 h were required for the bare TiO2 powder. HAp-TiO2 powders could therefore be a promising candidate photocatalyst for environmental purification.
