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1.
Submicrometer-sized, pure calcium hydroxyapatite (HA, (Ca10 (PO4 )6 (OH)2 )) and β-tricalcium phosphate (β-TCP, Ca3 (PO4 )2 ) bioceramic powders, that have been synthesized via chemical precipitation techniques, were used in the preparation of aqueous slurries that contained methyl cellulose to manufacture porous (70%–95% porosity) HA or β-TCP ceramics. The pore sizes in HA bioceramics of this study were 200–400 μm, whereas those of β-TCP bioceramics were 100–300 μm. The pore morphology and total porosity of the HA and β-TCP samples were investigated via scanning electron microscopy, water absorption, and computerized tomography. 相似文献
2.
Eun Jin Kim Sung-Woo Choi Seong-Hyeon Hong 《Journal of the American Ceramic Society》2007,90(9):2795-2798
Eu3+ -doped (1–12 mol%) calcium hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) powders were synthesized by a precipitation method and their photoluminescence (PL) properties were investigated. Eu has a limited solubility in HA and Eu2 O3 was detected by X-ray diffraction above 3% doping, whereas a nearly single β-phase was obtained up to 6% doping in TCP but EuPO4 appeared in the 12% Eu-doped specimen. Electron spin resonance measurement confirmed that europium ions exist as Eu3+ in both samples. Eu3+ -doped HA exhibited a strong emission at 575 nm with several minor peaks at 610–640 nm and Eu3+ -doped TCP had an intense emission at 613 nm with secondary peaks at 590–600 nm, which were consistent with the earlier reports determined at low temperatures. In Eu-doped TCP, the PL intensity increased with increasing calcination temperature without phase transformation. The more the Eu added, the higher the PL intensity obtained in both cases. 相似文献
3.
Nallusamy Venkatachalam Yu Saito Kohei Soga 《Journal of the American Ceramic Society》2009,92(5):1006-1010
The synthesis and characterization of yttrium hydroxyl carbonate (Y(OH)CO3 2− ) and yttrium nitrate hydroxide hydrate (Y(OH)NO3 H2 O) precursor materials as well as Y2 O3 nanoparticles are reported. The resultant precursor particle size is about 10–12 nm with a narrow size distribution by the enzymatic decomposition method, whereas the particle size was smaller than those acquired by the homogeneous and alkali precipitation methods. The formation of Y(OH)CO3 2− and Y(OH)NO3 H2 O species was also evident from the fourier-transform infrared spectrometry (FT-IR) analysis. Precipitated Y(OH)CO3 2− precursors have an amorphous nature whereas Y(OH)NO3 H2 O precursors have a crystalline nature, which was manifested from the XRD analysis. Moreover, precipitated Y(OH)NO3 H2 O precursors were found in the agglomerated form and Y(OH)CO3 2− was established in the monodispersed form, as determined from the FE-SEM, TEM and DLS measurements. It was demonstrated that calcination of precursor materials at 900°C eventually removed the inorganic anions from the precursors and consequently produced crystalline Y2 O3 nanoparticles, which was evident from the XRD and FT-IR analysis. The EDS analysis confirms Er3+ doping in the Y2 O3 nanoparticles. The morphology and the size of the Y2 O3 nanoparticles are almost unchanged before and after the calcination. 相似文献
4.
Juliana Marchi Peter Greil José Carlos Bressiani Ana Bressiani Frank Müller 《International Journal of Applied Ceramic Technology》2009,6(1):60-71
Mixtures of hydroxyapatite (HAp) and tricalcium phosphate (TCP) powders with different Ca/P ratios were prepared by a wet chemical precipitation synthesis of calcium-deficient hydroxy apatite (CDHA) and subsequent calcination. The influence of precipitation method and calcination temperature on the chemical and physical properties of the resulting powders were evaluated. Different ratios between HAp and TCP were obtained by variation of the velocity of orthophosphoric acid addition into calcium hydroxide suspension. Slow addition (1 mL/min, S-powder) of H3 PO4 into Ca(OH)2 suspension lead to a higher amount of CO3 groups substituting PO4 in the apatite lattice compared to powders synthesized by fast addition (200 mL/min, F-powder). Consequently, the Ca/P molar ratio of S-powder (1.55) was higher than that of F-powder (1.52), leading to a higher amount of HAp in the resulting calcinated powders. Both powders show significant differences in their calcinations behavior. Whereas for F-powders a temperature of 750°C was adequate for a complete transformation of CDHA to TCP and HAp, 950°C were required for S-powders. 相似文献
5.
Francesca Licci Giuseppe Turilli Patrizia Ferro Antonio Ciccarone 《Journal of the American Ceramic Society》2003,86(3):413-419
LaMn1− y 3+ Mn y 4+ O3±d and La0.67 R0.33 Mn1− y 3+ Mn y 4+ O3±d (R = Ca, Sr, Ba) phases were synthesized at 350°C by using very reactive, amorphous precursors obtained from the stoichiometric citrate solutions. The chemical process was optimized with respect to the solution concentration, pH, and additives. The precursor reactions were investigated as a function of the cation stoichiometry and the additive by simultaneous thermal and thermogravimetric analysis and X-ray diffraction. The reaction pathway was found to be independent of the cation stoichiometry, but related to the acid or base additive. The annealing temperature was systematically increased in the 350–1200°C interval and the La0.67 Sr0.33 MnO3±d properties (i.e., crystal sizes, Mn average valence, Curie temperature, magnetization, magnetic susceptibility) were measured and found to vary consistently as a function of it. 相似文献
6.
MICHAEL GREBIEN FLORIAN HABEREY KURT SAHL 《Journal of the American Ceramic Society》1984,67(10):195-C
The pseudobinary system Ga2 O3 -Bi2- x 3+ Bi x 5+ O3+ x 2- was studied in view of its importance for growth of SrGa12 O19 crystals from a bismuth oxide flux. A subsolidus transition of γ*-Bi2 O3 to a β'-phase and a strictly stoichiometric 1:2 phase with 33.3 mol% bismuth oxide were found. The single-crystal data for the compound indicated space group P21 21 2, with lattice constants a=0.79180±0.0003 nm, b =0.8288±0.0003 nm, and c =0.5889±0.0003 nm; the measured density was 7.1±0.3 g/cm3 and the cell content (Z) 2. 相似文献
7.
K2 O activity in K+ -(α+β)-alumina was determined from emf data of the galvanic cell Pt,O2 ,(α+β)-alumina/K+ -β-alumina/K2 SO4 ,SO2 +SO3 +O2 ,Pt. K2 O activity in the K+ -(α+β)-alumina was expressed by the equation log ak2o (±0.038)=(−18295±120)(K/T)+(0.998±0.110), where 961 K+ -β-alumina are discussed: the standard Gibbs energy of formation of K2 O·11Al2 O3 from K2 O and α-Al2 O3 and from K, O, and Al; the thermodynamic stabilities of K+ -β-alumina in the atmospheres of SOx (x=2, 3) and CO2 ; the equilibrium vapor pressure of potassium over K+ -β-alumina under a constant O2 pressure; and the stability of K+ -β-alumina in the molten Na-K alloy. 相似文献
8.
Jungho Ryu Byung-Dong Hahn Jong-Jin Choi Woon-Ha Yoon Byoung-Kuk Lee Joon Hwan Choi Dong-Soo Park 《Journal of the American Ceramic Society》2010,93(1):55-58
Porous photocatalytic TiO2 thin films were fabricated by the leaching technique, followed by aerosol deposition. Mixed powders of TiO2 and β-tricalcium phosphate (TCP) were aerosol deposited at room temperature for the initial fabrication of composite films. After the β-TCP phases were leached out from the composite films in a diluted HCl aqueous solution for 24 h, porous TiO2 films remained on the substrate. To fabricate these porous films, the β-TCP content was varied from 10 to 45 wt% and submicrometer-sized pores were formed after leaching. The porous TiO2 films showed strong initial photocatalytic activities due to the adsorption effect of the pores and the enlarged surface area. 相似文献
9.
Masatomo Yashima Yoichi Kawaike Masahiko Tanaka 《Journal of the American Ceramic Society》2007,90(1):272-274
Unit-cell parameters of the α-tricalcium phosphate [TCP; Ca3 (PO4 )2 ] were investigated using high-resolution synchrotron powder diffraction and the Rietveld method. The diffraction experiment was conducted at 29°C at the BL-15XU experimental station of SPring-8, Japan. Precise unit-cell parameters of the α-TCP were obtained; a =12.87271 (9), b =27.28034(8), c =15.21275(12) Å, α=γ=90°, and β=126.2078(4)°. The calculated density of α-TCP (2.8677 g/cm3 ) is smaller than that of β-TCP, indicating the "looser" structure of α-TCP. 相似文献
10.
Gaoxiang Chen Wanwan Li Bingxia Zhao Kang Sun 《Journal of the American Ceramic Society》2009,92(4):945-948
Calcium polyphosphate (CPP) was added to hydroxyapatite (HA) to develop a novel biphasic calcium phosphate (BCP). The effects of varying CPP dosage on the sintering property, the mechanical strength, and the phase compositions of HA were investigated. Results showed that CPP reacted with HA and produced β-calcium phosphate (β-TCP) and H2 O and that an excessive dosage of CPP (>10 wt%) obtained a novel BCP of β-TCP/amorphous-CPP, while a lesser dosage of CPP (<10 wt%) obtained a traditional BCP (HA/β-TCP). The porous β-TCP/amorphous-CPP scaffolds (porosity of 66.7%, pore diameter of 150–450 μm, and compressive strength of 6.70±1.5 MPa) were fabricated and their in vitro degradation results showed a significant improvement of degradation with the addition of CPP. 相似文献
11.
Hilde Lea Lein Kjell Wiik Mari-ann Einarsrud Tor Grande Edgar Lara-curzio 《Journal of the American Ceramic Society》2006,89(9):2895-2898
Steady-state compressive creep rate of La0.5 Sr0.5 Fe0.5 Co0.5 O3−δ (LSFC) and La0.5 Sr0.5 CoO3−δ (LSC) is reported in the temperature region 900°–1050°C and stress range 5–28 MPa. The stress exponents for the two materials were 1.71±0.18 and 1.24±0.15, respectively. The activation energy for creep was considerably higher for LSC (619±56 kJ/mol) than for LSFC (392±28 kJ/mol). The grain size exponent for LSC was 1.28±0.14. Considerably higher creep rates were observed for both materials in N2 compared with air. Relaxation by creep of chemical-induced stresses in oxygen-permeable membranes is addressed, especially at low partial pressure of oxygen. 相似文献
12.
Subsolidus phase relationships in the Ga2 O3 –Al2 O3 –TiO2 system at 1400°C were studied using X-ray diffraction. Phases present in the pseudoternary system include TiO2 (rutile), Ga2−2 x Al2 x O3 ( x ≤0.78 β-gallia structure), Al2−2 y Ga2 y O3 ( y ≤0.12 corundum structure), Ga2−2 x Al2 x TiO5 (0≤ x ≤1 pseudobrookite structure), and several β-gallia rutile intergrowths that can be expressed as Ga4−4 x Al4 x Ti n −4 O2 n −2 ( x ≤0.3, 15≤ n ≤33). This study showed no evidence to confirm that aluminum substitution of gallium stabilizes the n =7 β-gallia–rutile intergrowth as has been mentioned in previous work. 相似文献
13.
The parameters affecting strength development in compacted cylinders of 3CaO- SiO2 and β-2CaO- SiO2 mortars exposed to CO2 were investigated. Strength increased with time up to 81 min, the duration of the longest detailed study. The β-2CaO- SiO2 develops strength more slowly initially, but both silicates achieved compressive strengths of 7,000 to 10,000 psi. The rate of increase in strength depends on both the amount of water used in molding the compact and the amount of water present in the CO2 . Increasing CO2 pressures from 1 to 2 atm increased the rate of reaction, but a further increase to 4 atm had little additional effect. Carbonation occurs mainly in the outer portions of the cylindrical compacts. The initial reaction on exposure to CO2 appears to be accelerated hydration of the silicates to a CaO-SiO2 -H2 O-like gel and calcite. The gel has a stoichiometry similar to that found in conventional hydration. Further reaction results in progressive carbonation of the gel, which decreases its lime content. The reaction products appear to be intimately dispersed in the microstructure. 相似文献
14.
Jianren Zeng Yoshinari Miyamoto Osamu Yamada 《Journal of the American Ceramic Society》1991,74(9):2197-2200
Fine Si3 N4 -SiC composite powders were synthesized in various SiC compositions to 46 vol% by nitriding combustion of silicon and carbon. The powders were composed of α-Si3 N4 , β-Si3 N4 , and β-SiC. The reaction analysis suggested that the SiC formation is assisted by the high reaction heat of Si nitridation. The sintered bodies consisted of uniformly dispersed grains of β-Si3 N4 , β-SiC, and a few Si2 N2 O. 相似文献
15.
Oliver Renoult Jean-Pierre Boilot Marcel Boncoeur 《Journal of the American Ceramic Society》1994,77(1):249-253
An alkoxide-hydroxide route has been developed to prepare Li4 + x Al4 − 3 x Si2 x O8 (0 ≤ x ≤ 0.25) powders by taking into account fundamental aspects of the sol-gel process. This technique allows one to prepare powders which exhibit the β-LiAlO2 type of structure after drying at 150°C. The β→γ-LiAlO2 topotactic transformation spreads over a large temperature range (746–839°C for x = 0.125) with no significant dilatometric and enthalpic change. Stoichiometric γ-LiAlO2 -based ceramics with a large variety of uniform microstructures are fabricated by a direct sintering of β-LiAlO2 powders in the temperature range of 900–1100°C. 相似文献
16.
Sintering, crystallization, microstructure, and thermal expansion of Li2 O·Al2 O3 ·4SiO2 glass-ceramics doped with B2 O3 , P2 O5 , or (B2 O3 + P2 O5 ) have been investigated. On heating the glass powder compacts, the glassy phase first crystallized into high-quartz s.s., which transformed into β-spodumene after the crystallization process was essentially complete. The effects of dopants on the crystallization of glass to high-quartz s.s. and the subsequent transformation of high-quartz s.s. to β-spodumene were discussed. The major densification occurred only in the early stage of sintering time due to the rapid crystallization. All dopants were found to promote the densification of the glass powders. The effect of doping on the densification can fairly well be explained by the crystallization tendency. All samples heated to 950°C exhibited a negative coefficient of thermal expansion ranging from about −4.7 × 10-6 to −0.1 × 10-6 K-1 . Codoping of B2 O3 and P2 O5 resulted in the highest densification and an extremely low coefficient of thermal expansion. 相似文献
17.
Koji Tsukuma 《Journal of the American Ceramic Society》2000,83(12):3219-3221
Composites of β-Ce2 O3 ·11Al2 O3 and tetragonal ZrO2 were fabricated by a reductive atmosphere sintering of mixed powders of CeO2 , ZrO2 (2 mol% Y2 O3 ), and Al2 O3 . The composites had microstructures composed of elongated grains of β-Ce2 O3 ·11Al2 O3 in a Y-TZP matrix. The β-Ce2 O3 ·11Al2 O3 decomposed to α-Al2 O3 and CeO2 by annealing at 1500°C for 1 h in oxygen. The elongated single grain of β-Ce2 O3 ·11Al2 O3 divided into several grains of α-Al2 O3 and ZrO2 doped with Y2 O3 and CeO2 . High-temperature bending strength of the oxygen-annealed α-Al2 O3 composite was comparable to the β-Ce2 O3 ·11Al2 O3 composite before annealing. 相似文献
18.
Hideki Taguchi Katsuyuki Nakade Masashi Yosinaga Masaki Kato Ken Hirota 《Journal of the American Ceramic Society》2008,91(1):308-310
X-ray photoelectron spectroscopy was performed to elucidate the catalytic activity of CH4 oxidation on perovskite-type Ca(Mn1− x Ti x )O3−δ synthesized at 1173 K in a flow of oxygen from a gel with citric acid and ethylene glycol. The Mn ion content decreases and the ratio of the Mn3+ ion in the Mn ion increases with increases in x . Ca(Mn1− x Ti x )O3−δ has a high catalytic activity of CH4 oxidation at x =0.4. These results indicate that the catalytic activity strongly depends on the Mn3+ ion content of the surface. 相似文献
19.
Anita Fossdal Mari-Ann Einarsrud Tor Grande 《Journal of the American Ceramic Society》2005,88(7):1988-1991
The phase relations in the pseudo-ternary system La2 O3 –SrO–Fe2 O3 have been investigated in air. Isothermal sections at 1100° and 1300°C are presented based on X-ray diffraction and thermal analysis of annealed samples. Extended solid solubility was observed for the compounds Sr n +1− v La v Fe n O3 n +1−δ ( n =1, 2, 3, and ∞) and Sr1− x La x Fe12 O19 , while only limited solubility of La in Sr4− z La z Fe6 O13±δ was observed. At high Fe2 O3 content, a liquid with low La2 O3 content was stable at 1300°C. 相似文献
20.
Ba6−3 x Nd8+2 x Ti18 O54 ceramic powders were synthesized by the modified Pechini method using ethylenediaminetetraacetic acid (EDTA) as a chelating agent. A purplish red, molecular-level, homogeneously mixed gel was prepared, and transferred into a porous resin intermediate through charring. Single-phase and well-crystallized Ba6−3 x Nd8+2 x Ti18 O54 powders were obtained from pulverized resin at a temperature of 900°C for 3 h, without formation of any intermediate phases. Meanwhile, the molar ratio of EDTA to total metal cation concentration had a significant influence on the crystallization behavior of Ba6−3 x Nd8+2 x Ti18 O54 . The Ba6−3 x Nd8+2 x Ti18 O54 ( x = 2/3) ceramics prepared via EDTA precursor have excellent microwave dielectric characteristics: ɛ= 87, Qf = 8710 GHz. 相似文献