Thermal expansion of hydroxyapatite between − 100 °C and 50 °C

Hydroxy apatite (HAp) ceramic was synthesized using traditional sintering. Dilatometric and lattice thermal expansion properties of a HAp ceramic were evaluated at temperatures of ? 100–50 °C. In that temperature range, the dilatometric thermal expansion coefficient and the lattice thermal expansion coefficient of the HAp ceramic were, respectively, 10.6 × 10^? 6/°C and 9.9 × 10^? 6/°C. Furthermore, thermal expansion properties of a human tooth were measured. The thermal expansion coefficient of the horizontal direction perpendicular to the growing direction of a tooth was 15.5 × 10^? 6/°C; that of the vertical direction along with the direction of tooth growth was 18.9 × 10^? 6/°C at the temperature range described above.     

Accelerated transformation of brushite to octacalcium phosphate in new biomineralization media between 36.5 °C and 80 °C

This study investigated the hydrothermal transformation of brushite (dicalcium phosphate dihydrate, DCPD, CaHPO₄·2H₂O) into octacalcium phosphate (OCP, Ca₈(HPO₄)₂(PO₄)₄·5H₂O) in seven different newly developed biomineralization media, all inspired from the commercial DMEM solutions, over the temperature range of 36.5 °C to 90 °C with aging times varying between 1 h and 6 days. DCPD powders used in this study were synthesized in our laboratory by using a wet-chemical technique. DCPD was found to transform into OCP in the Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^?, Cl^? and H₂PO₄^? containing aqueous biomineralization media in less than 72 h at 36.5 °C, without stirring. The same medium was able to convert DCPD into OCP in about 2 h at 75–80 °C, again without a need for stirring. Samples were characterized by using powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM).     

Synergistic effects of acetic acid and nitric acid in water-based sol–gel synthesis of crystalline TiO2 nanoparticles at 25 °C

Journal of Materials Science - Organic and inorganic acid catalysts enable control over the sol–gel synthesis of crystalline TiO2 nanoparticles. While the mechanism of organic acids (e.g.,...     

Tribological behavior of Ni3Al matrix self-lubricating composites containing WS2, Ag and hBN tested from room temperature to 800 °C

Ni₃Al matrix self-lubricating composites (NMSC) containing varied amounts of WS₂, Ag and hBN (WAh) with weight ratio of 1:1:1 were fabricated by in situ technique using spark plasma sintering. The friction and wear properties of NMSC against the commercial Si₃N₄ ceramic ball at the load of 10 N and sliding speed of 0.234 m/s for 80 min from room temperature to 800 °C were investigated. The results showed that the tribological properties of NMSC strongly depended on the addition content of WAh. Moreover, NMSC with 15 wt.% WAh and 5 wt.% TiC exhibited the relatively lower friction coefficients and the less wear rates from RT to 800 °C. The excellent tribological behavior of NMSC with 15 wt.% WAh and 5 wt.% TiC was attributed to the synergetic action of composite lubricants of WAh and reinforced phase of TiC.     

Tribological performance of TiAl matrix self-lubricating composites containing Ag,Ti3SiC2 and BaF2/CaF2 tested from room temperature to 600 °C

Dry sliding tribological behaviors of TiAl matrix self-lubricating composites (TMSC) containing varying amounts of Ag, Ti₃SiC₂ and BaF₂/CaF₂ eutectic (BaF₂–38 wt.%CaF₂) (ATBC) with weight ratio of 1:1:1 against Si₃N₄ from room temperature (RT) to 600 °C at the condition of 10 N–0.234 m/s were experimentally studied. The results implied that the ATBC could improve friction-reducing and anti-wear ability of TMSC over an extreme range of operating temperatures, which was attributed to the synergetic effect of Ag, Ti₃SiC₂ and BaF₂/CaF₂ lubricants. In addition, TMSC containing 9 wt.% ATBC exhibited the best tribological properties over the wide temperature range from RT to 600 °C.     

Composition ranges of Ln<Subscript>2 − <Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>3 ± δ</Subscript> (Ln = Y,Ho, Er) solid solutions between 900 and 1400°C in air

The metal stoichiometry ranges of the Ln_{2 − x} Mn _x O_{3 ± δ} (Ln = Y, Ho, Er) manganites have been determined using X-ray diffraction analysis of ceramic samples prepared by reacting oxide mixtures in air at temperatures from 900 to 1400°C. The results are represented as partial phase diagrams of the Ln-Mn-O systems in air. Comparison of the phase diagrams demonstrates that the phase boundaries of the manganites are determined not only by the effective cation radius of the rare-earth metal. The solubilities of the binary oxides Y₂O₃, Ho₂O₃, and Mn₃O₄ in yttrium and holmium manganites increase with temperature, with significant quantitative distinctions. The Er₂O₃ and Mn₃O₄ solubilities in erbium manganite remain unchanged over the entire temperature range studied. The LnMn₂O₅ solubility in LnMnO_{3 ± δ} is an intricate function of temperature. We analyze the possible causes of the Ln₂O₃, Mn₃O₄, and LnMn₂O₅ solubility in the LnMnO_{3 ± δ} (Ln = Y, Ho, Er) manganites.