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1.
Effect of Silicon Substitution on the Sintering and Microstructure of Hydroxyapatite 总被引:3,自引:0,他引:3
Iain R. Gibson Serena M. Best William Bonfield 《Journal of the American Ceramic Society》2002,85(11):2771-2777
The substitution of between 0 and 1.6 wt% silicon (Si-HA) in hydroxyapatite (HA) inhibited densification at low temperatures (1000°–1150°C), with these effects being more significant as the level of silicon substitution was increased. For higher sintering temperatures (1200°–1300°C), the sintered densities of HA and Si-HA compositions were comparable. Examination of the ceramic microstructures by scanning electron microscopy (SEM) showed that silicon substitution also inhibited grain growth at higher sintering temperatures (1200°–1300°C). The negative effect of silicon substitution on the sintering of HA at low temperatures (1000°–1150°C) was reflected in the hardness values of the ceramics. However, for higher sintering temperatures, e.g., 1300°C, where sintered densities were comparable, the hardness values of Si-HA compositions were equal to or greater than that of HA, reflecting the smaller grain sizes observed for the former. 相似文献
2.
Hongquan ZhangMing Zhang 《Ceramics International》2011,37(1):279-286
Two kinds of hydroxyapatite (HA) whiskers, prepared using urea and acetamide, were investigated to determine their thermal stability in air at 800-1200 °C. The thermal decomposition behavior and the phase stability of the whiskers upon heating were found to depend on the synthesis method, crystallinity and constitution of the whiskers. The phase transformation of the whiskers prepared using urea took place at a temperature below 800 °C due to low crystallinity and more carbonate and HPO4 ions substitutions. Long rod-like particles appeared in the products treated at 1000-1200 °C. However, the whiskers prepared using acetamide were morphologically and structurally stable at 1200 °C due to their high crystallinity and low ions substitution, but with minor TCP caused by the decomposition of HPO4 in the structure. Such whiskers would be useful and promising reinforcement for fabricating highly reliable HA ceramics or composites either in dense or porous form. 相似文献
3.
Sintering behavior and electromagnetic properties of Ni0.5Zn0.5Fe2−xO4−3/2x ferrite (x = 0, 0.4, 0.8) by the sol–gel method are investigated. Fe deficiency in the composition enhances sintering and retards grain growth. The near fully dense Fe-deficient samples could be obtained at a sintering temperature as low as 1120 °C and the highest relative density appears in the x = 0.8 sample sintered at 1150 °C. Second phase zincite ZnO resulting from Fe deficiency plays an important role in spinel NiZn ferrites by acting as a grain growth inhibitor and the grain growth of NiZn ferrite is effectively suppressed. When the sintering temperature is above 1200 °C, extensive grain growth occurs due to the probability of serious volatilization of zinc at high temperatures. The ratio of Ni to Zn of NiZn ferrites increases with increasing Fe deficiency due to the separation of zinc from spinel lattice, which results in the decrease in initial permeability and the increase in Curie temperature and resonant frequency. 相似文献
4.
Xiao-Fei Zhang Qing XuYu-Heng Huang Han-Xing LiuDuan-Ping Huang Feng Zhang 《Ceramics International》2010
Ba0.6Sr0.4TiO3 powder was synthesized by a citrate method. The phase development was examined with respect to calcining temperature and heating rate during the calcining process. The results reveal a crucial role of the heating rate to the formation of a pure perovskite phase at low calcining temperatures. It was found that keeping relatively low heating rates ≤0.7 °C/min during the calcining process after 300 °C was favorable to a sufficient decomposition of (Ba,Sr)2Ti2O5·CO3 intermediate phase at low temperatures and consequently led to the formation of a pure perovskite phase at 550 °C. Ba0.6Sr0.4TiO3 powder calcined at the temperature under the heating rate of 0.7 °C/min showed a superfine and uniform particle morphology and high sintering reactivity. As a result, the ceramic specimens prepared from the powder attained reasonable relative densities (94–95%) at sintering temperatures of 1250–1270 °C. 相似文献
5.
Pure hydroxyapatite (HA), HA and partially stabilized zirconia composites (PSZ) with YF3 and HA–PSZ composite containing 5 wt% PSZ without YF3 were sintered in air at 900 °C, 1100 °C and 1300 °C for 1 h. The reactions and transformation of the phases in the composites were determined by X-ray diffraction. All the composites with or without YF3 showed desirable thermal stability below 1300 °C and besides various amounts of CaZrO3, any amount of tri-calcium phosphate (TCP) was not observed. Above 1100 °C, composites with YF3 showed higher thermal stability than the composites without YF3. On the other hand, pure HA started to decompose and TCP was observed at 1300 °C. Composites with YF3 showed improved thermal stability than the composite containing 5 wt% PSZ without YF3 and pure HA at lower sintering temperatures such as 900 °C and 1100 °C. However, it was observed that the increasing amount of YF3 addition caused negative effect on the thermal stability of the composites. 5ZHA composites with YF3 showed the highest relative density among all of the composites with or without YF3. 相似文献
6.
Alieh Aminian Mehran Solati-HashjinAli Samadikuchaksaraei Farhad BakhshiFazel Gorjipour Arghavan FarzadiFattolah Moztarzadeh Martin Schmücker 《Ceramics International》2011,37(4):1219-1229
Silicon-substituted hydroxyapatite (Si-HA) with up to 1.8 wt% Si content was prepared successfully by a hydrothermal method, using Ca(NO3)2, (NH4)3PO4 or (NH4)2HPO4 and Si(OCH2CH3)4 (TEOS) as starting materials. Silicon has been incorporated in hydroxyapatite (HA) lattice by partially replacing phosphate (PO43−) groups with silicate (SiO44−) groups resulting in Si-HA described as Ca10(PO4)6−x(SiO4)x(OH)2−x. X-ray diffraction (XRD), Fourier transform IR spectroscopy (FTIR), inductively coupled plasma AES (ICP-AES) and scanning electron microscopy (SEM) techniques reveal that the substitution of phosphate groups by silicate groups causes some OH− loss to maintain the charge balance and changes the lattice parameters of HA. The crystal shape of Si-HA has not altered compared to silicon-free reference hydroxyapatite but Si-incorporation reduces the size of Si-HA crystallites. Based on in vitro tests, soaking the specimens in simulated body fluid (SBF), and MTT assays by human osteoblast-like cells, Si-substituted hydroxyapatite is more bioactive than pure hydroxyapatite. 相似文献
7.
S. Ramesh C.Y. TanW.H. Yeo R. ToloueiM. Amiriyan I. SopyanW.D. Teng 《Ceramics International》2011,37(2):599-606
The sinterability of Bi2O3-doped hydroxyapatite (HA) has been studied and compared with the undoped HA. Varying amounts of Bi2O3 ranging from 0.05 wt% to 1.0 wt% were mixed with the HA. The study revealed that most sintered samples composed of the HA phase except for compacts containing 0.3, 0.5 and 1.0 wt% Bi2O3 and when sintered above 1100 °C, 1000 °C and 950 °C, respectively. In general, the addition of 0.5 wt% Bi2O3 was identified as the optimum amount to promote densification as well as to improve the mechanical properties of sintered HA at low temperature of 1000 °C. Throughout the sintering regime, the highest value of relative bulk density of 98.7% was obtained for 0.5 wt% Bi2O3-doped HA when sintered at 1000 °C. A maximum Young's modulus of 119.2 GPa was measured for 0.1 wt% Bi2O3-doped HA when sintered at 1150 °C. Additionally, the ceramic was able to achieve highest hardness of 6.08 GPa and fracture toughness of 1.21 MPa m1/2 at sintering temperature of 1000 °C. 相似文献
8.
I. Mobasherpour M. Solati Hashjin S.S. Razavi Toosi R. Darvishi Kamachali 《Ceramics International》2009
Nanocrystalline hydroxyapatite powder has been synthesized from a Ca(NO3)2·4H2O and (NH4)2HPO4 solution by the precipitation method. In the next step we prepared ZrO2–Al2O3 powder. After preparation, the powder was dried at 80 °C and calcined at 1200 °C for 1 h. Various amounts (HAP–15 wt% ZA, HAP–30 wt% ZA) of powder were mixed with the hydroxyapatite by ball milling. The powder mixtures were pressed and sintered at 1000 °C, 1100 °C and 1200 °C for 1 h. In order to study the structural evolution, X-ray diffraction (XRD) was used. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to estimate the particle size of the powder and observe fracture surfaces. Results show that the bending strength of pressed nanocrystalline HAP was improved significantly by the addition 15 wt% of ZrO2–Al2O3 powders at 1200 °C, but the fracture toughness was not changed, however when 30 wt% of ZA powders were added to nanocrystalline HAP, the bending strength and fracture toughness of the specimens decreased at all sintering temperature. 相似文献
9.
One-step mechanochemical process followed by thermal treatment has been used to produce calcium phosphate-based composite nanopowders. Effects of milling and subsequent heat treatment on the phase transition as well as structural features were investigated. The products were characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) techniques. The results revealed that the dominant phases after mechanical activation were hydroxyapatite, anatase (TiO2), and periclase (MgO), while after thermal annealing process at 700 °C hydroxyapatite along with geikielite (MgTiO3) and periclase (MgO) were the major phases. In addition, decomposition of hydroxyapatite to tricalcium phosphate (β-TCP) occurred after heat treatment in the range 900–1100 °C which resulted in the formation of tricalcium phosphate-based composite nanopowders. Evaluation of structural features of the samples calculated by X-ray diffraction profiles analysis indicated that the average crystallite size of hydroxyapatite after 10 h of milling and subsequent heat treatment at 700 °C were about 21 and 34 nm, respectively. TEM and SEM studies exhibited that the considerable morphological changes at temperatures ≥900 °C had to be ascribed not only to grain growth, but also for the transformation of hydroxyapatite to β-TCP. 相似文献
10.
Spherical shape borate-based bioactive glass powders with fine size were directly prepared by high temperature spray pyrolysis. The powders prepared at temperatures between 1200 and 1400 °C had mixed phase with small amounts of fine crystal and an amorphous rich phase. Glass powders with amorphous phase were prepared at a temperature of 1500 °C. The mean size of the glass powders prepared by spray pyrolysis was 0.76 μm. The glass powders prepared at a temperature of 1200 °C had two distinct exothermic peaks (Tc1 and Tc2) at temperatures of 588 and 695 °C indicating crystallization. The glass transition temperature (Tg) of the powders prepared at a temperature of 1200 °C was 480 °C. Phase-separated crystalline phases with spherical shape were observed from the surface of the pellet sintered at a temperature of 550 °C. Crystallization of the pellet was completely occurred at temperatures of 750 and 800 °C. The pellets sintered at temperatures below 700 °C had single crystalline phase of CaNa3B5O10. The pellet sintered at a temperature of 800 °C had two crystalline phases of CaNa3B5O10 and CaB2O4. 相似文献
11.
Wei-Gang YangBo-Ping Zhang Nan MaLei Zhao 《Journal of the European Ceramic Society》2012,32(4):899-904
BaTiO3-xLiF ceramics were prepared by a conventional sintering method using BaTiO3 powder about 100 nm in diameter. The effects of LiF content (x) and sintering temperature on density, crystalline structure and electrical properties were investigated. A phase transition from tetragonal to orthorhombic symmetry appeared as sintering temperatures were raised from 1100 °C to 1200 °C or as LiF was added from 0 mol% to 3 mol%. BaTiO3-6 mol% LiF ceramic sintered at 1000 °C exhibited a high relative density of 95.5%, which was comparable to that for pure BaTiO3 sintered at 1250 °C. BaTiO3-4 mol% LiF ceramic sintered at 1100 °C exhibited excellent properties with a piezoelectric constant d33 = 270 pC/N and a planar electromechanical coupling coefficient kp = 45%, because it is close to the phase transition point in addition to high density. 相似文献
12.
Joining of carbon fiber reinforced carbon matrix composite to a carbon fiber reinforced C-SiC dual matrix composite has been realized through a reaction joining process using boron-modified phenolic resin with micro-size B4C and nano-size SiO2 powder additives. The effect of the heat-treatment temperature on the retained strength of the joints, calculated by dividing the strength of the heat-treated joints by the strength of the joints before heat-treatment, was studied. The maximum retained strength of the joints is 91.9% after heat-treatment at 1200 °C for 30 min in vacuum, indicating good heat-resistance of the joints. The interlayer with a thickness of about 25 μm is uniform and densified. There are no obvious cracks or pores at the interfaces. The interlayer is composed of B4C, SiO2, glassy carbon, B2O3 and borosilicate glass. Si diffuses from the interlayer into the substrates and reacts with carbon to form SiC. Both B and O migrate from the interlayer into the substrates, contributing to the interfacial bonding. The B4C and the SiO2 powder additives contribute to the densification of the interlayer, the bonding at the interfaces and the heat-resistance of the joints. 相似文献
13.
Nickel oxide films were synthesized by electrochemical precipitation of Ni(OH)2 followed by heat-treatment in air at various temperatures (200-600 °C). Their structure and electrochemical properties were studied by cyclic voltammetry, X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). XRD results showed that the nickel oxide obtained at 250 °C or above has a crystalline NiO structure. The specific capacitance of the oxide depends on the heat-treatment temperature, showing a maximum value at 300 °C. XAS results revealed that the non-stoichiometric nickel oxide (Ni1−xO) approached the stoichiometric NiO structure with increasing heat-treatment temperature due to the defect healing effect. The defective nature of the nickel oxide could be utilized to improve its specific capacitance for supercapacitor application. 相似文献
14.
Micro- and mesoporous carbide-derived carbon (CDC) was synthesised from molybdenum carbide (Mo2C) powder by gas phase chlorination in the temperature range from 400 to 1200 °C. Analysis of XRD results show that C(Mo2C), chlorinated at 1200 °C, consist mainly on graphitic crystallites of mean size, La = 9 nm and Lc = 7.5 nm. The first-order Raman spectra showed the graphite-like absorption peak at ∼1587 cm−1 and the disorder-induced (D) peak at ∼1348 cm−1. The low-temperature N2 adsorption experiments were performed and a specific surface area up to 1855 m2 g−1 and total pore volume up to 1.399 cm3 g−1 were obtained. Sorption measurements showed the presence of both micro- and mesopores after chlorination at 400-900 °C and only mesopores after chlorination at 1000°-1200 °C. Stepwise formation of micro- and mesopores was achieved and the peak pore size can be shifted from 0.8 nm up to 4 nm by increasing the chlorination temperature. 相似文献
15.
Ce0.8Gd0.2O1.9 (CGO) and Ce0.8Sm0.2O1.9 (CSO) have been prepared as polycrystalline materials using a freeze-dried precursor. This method yields amorphous nanometric powders. Crystallization of the fluorite phase occurred on heating at 600 °C or higher temperatures. The grain size of freeze-dried powders increases to about 100 nm after calcination at 800 °C, or about 200 nm after firing at 1000 °C. Freeze-dried powders were used to prepare dense ceramic disks by sintering at 1400 °C. Some disks were sintered at 1000 °C by adding small amounts of cobalt nitrate solution to assist the densification. The electrical conductivity results obtained for these gadolinia-doped ceria and samaria-doped ceria ceramics are similar to those obtained for CGO pellets obtained from commercial nanopowders (Rhodia). Though the bulk conductivity of CSO is probably higher than that of CGO, its grain boundary conductivity is inferior, and tends to control the overall behaviour, at least at relatively low temperatures. 相似文献
16.
Sintering compacts of carbonated hydroxyapatite (CHA) nanoparticles (3.4 wt% CO32−) in a CO2 flow (4 mL/min) proceeded at a temperature which was more than 200 °C lower than that for hydroxyapatite in air (1150 °C). During heating from RT to 1200 °C (5 K/min) the rate of shrinkage of the CHA compacts showed a maximum thrice as high as that in air at about 929 °C. The shrinkage correlates with a mass loss caused by the release of CO2 due to the thermal decomposition of CO32− ions that substitute PO43− ions in the CHA lattice. Firing the compacts in the CO2 flow at 800 and 900 °C for 2 h resulted in an additional carbonatation on the B-sites and a further decrease in the sintering temperature to 890 °C. The compacts fired in the 900-1000 °C range became almost complete ceramics with high densities and mechanical properties close to those of medical implants. Firing at temperatures above 1000 °C resulted in an additional carbonatation on the A-sites. However, this led to a material with low densities and poor mechanical properties. A supposition has been proposed that the effect of CO2 gas-activated sintering is a result of the intensification of the diffusion in the nanoparticles caused by CO2 molecules entering the bulk from the CO2 atmosphere and (or) releasing from the bulk due to the decomposition of carbonates on the B-sites in the lattice. 相似文献
17.
Jung Sang Cho Jeong-Cheol Lee Shin Hye Chung Jeong Kon Seo Sang-Hoon Rhee 《Ceramics International》2014
The effect of grain size and density of hydroxyapatite particles, which were prepared by different spray-pyrolysis temperatures, on the sinterability of hydroxyapatite disk was investigated. Calcium phosphate solution (Ca/P ratio of 1.67 and 0.1 M concentration) was prepared by reacting calcium nitrate tetrahydrate and diammonium hydrogen phosphate solutions, and adding nitric acid. Spray-pyrolysis was carried out at 900 °C, 1200 °C, and 1500 °C at a carrier gas flowing rate of 10 L/min. The particles synthesized at 900 °C were large, hollow spheres with a hole at the outer surface, a broad size distribution, but had small grain sizes. Conversely, the particles synthesized at 1500 °C were small, solid spheres with a narrow size distribution, but had large grain sizes. The particles synthesized at 1200 °C had intermediate properties. A sinterability test conducted at 1100 °C for 1 h demonstrated that small and dense particles with large grain sizes showed a higher relative sintered density compared with large and hollow particles with small grain sizes. The results were explained in terms of the grain size and density of a particle, which were inversely and proportionally affected to sinterability. The practical implication of these results is that highly sinterable hydroxyapatite powders can be synthesized through spray-pyrolysis at a high temperature under a fixed initial concentration of calcium phosphate solution and flow rate of carrier gas. 相似文献
18.
Liquid polycarbosilane (LPCS) derived hard coatings of silicon carbide (SiC) were deposited on Inconel alloy at three different moderately high temperatures by chemical vapour deposition. The deposited films were characterized by X-ray diffractometry and Field emission scanning electron microscopy. Liquid PCS yielded a mixture of α-SiC and β-SiC during decomposition having uniform round-shaped particles of dimension around 200–300 nm without extensive cracking and few discrete shaped particles were also found to form at higher temperature (i.e. 1100 °C and 1200 °C) deposited films. The coated samples showed substantial increment in hardness and fracture toughness as compared to the uncoated sample. The fracture toughness (KIC) values of the deposited films were in the range of 6.7–10.7 MPa(m)1/2. The tribological properties and hardness of the films were also found to vary with deposition temperature. The scratch tracks of the films revealed that brittle failures occurred in all SiC coated substrates. 相似文献
19.
This paper studies the preparation of UO2/TiO2 composite ceramic fuel through sol gel-press forming. The research shows that at 1200–1300 °C, UO2/TiO2 composite ceramic grains are small, uniform and compact. Among them, UO2–0.5 wt%TiO2 has the highest density and good mechanical strength at 1250 °C. 相似文献
20.
The suspensions of hydroxyapatite (HA) nanoparticles were prepared in different alcohols. The zeta potential of HA nanoparticles was the highest in butanolic suspension (65.65 mV) due to the higher adsorption of RCH2OH2+ species via hydrogen bonding with surface P3OH group of HA. Electrophoretic deposition was performed at 20 and 60 V/cm for different times. Deposition rate was faster in low molecular weight alcohols due to the higher electrophoretic mobility of HA nanoparticles in them. The coating deposited from butanolic suspension had the highest adhesion strength and corrosion resistance in SBF solution at 37.5 °C. The surface of this coating was covered by apatite after immersion in SBF solution for 1 week. 相似文献