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1.
Hydroxylapatite (HA) composites with pure zirconia (ZrO2), and 3 and 8% Y2O3 doped ZrO2 were pressure-less sintered in air and hot isostatically pressed (under 120 MPa gas pressure) at 1100 °C for 2 h. The reactions and phase transformations were monitored by X-ray diffraction, thermal analysis, and Raman spectroscopy. HA/pure ZrO2 composites were not thermally stable in air sintering; HA dissociated into α and β tricalcium phosphate while monoclinic ZrO2 was transformed into tetragonal and cubic phases. No decomposition in HA or phase transformation in ZrO2 were observed in hydroxylapatite/3% Y2O3 doped ZrO2 or HA/8% Y2O3 doped ZrO2 composites. On the other hand, HA and ZrO2 phases in hot isostatically pressed composites remained stable. The highest densification was found in a composite initially containing 10% monoclinic ZrO2 among the composites sintered in air. The densification of the composites decreased at lower sintering temperatures and higher ZrO2 contents upon air-sintering. The HIPped composites were densified to about 99.5% of theoretical densities in all mixing ratios. The reactivity between ZrO2 and HA was dependent on the amount of air in the sintering environment. Hot isostatic pressing with very limited retained air was proved to be a very convenient method to insure both phase stability and full densification during the production of hydroxylapatite zirconia composites.  相似文献   

2.
(1 − x)SiO2-(x)ZrO2 (x = 0.1, 0.2) composite fiber mats were prepared by electrospinning their sol-gel precursors of zirconium acetate and tetraethyl orthosilicate (TEOS) without using a polymer binder. The electrospun composite fibers were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR) and mercury porosimetry. The composite fibers having a tetragonal crystalline ZrO2 were obtained by calcining the electrospun composite fibers at high temperatures. The results show that the structure and crystallization of ZrO2 in the composite fibers can be controlled by sintering temperature, while the porosity and morphology of the fiber mats did not depend on the sintering temperature.  相似文献   

3.
Effects of zirconium oxide (ZrO2) nanoparticles additive on the microstructure and physical properties of hydroxyapatite (HA) were investigated. The HA powder was derived from natural bovine bone by a sequence of thermal processes. The composites containing nanoparticles of ZrO2 (0.2–1.0 vol%) were fabricated by a solid-state reaction mixed oxide method. All samples showed traces of HA, beta-tricalcium phosphate (β-TCP) and alpha-tricalcium phosphate (α-TCP) phases while the x≥0.1 samples also showed ZrO2 phase. Amount of β-TCP and α-TCP phases tend to decrease with ZrO2. The additive inhibited grain growth as a result of a decrease in grain size. However, the x=0.2 sample exhibited higher hardness value which is consistent with the density data. In addition, bioactivity test suggested that the additive promoted an apatite forming with the values of Ca/P close to the value obtained from HA.  相似文献   

4.
《Ceramics International》2023,49(5):7466-7475
This study examined the mechanical properties, wettability, and tribology of hydroxyapatite (HA)–zirconia (ZrO2)–carbon nanotube (CNTs) ceramic nanocomposites (with various CNT ratios (x): 1, 5, and 10 wt%). HA–ZrO2–CNT-x powders were hydrothermally synthesized. Hot isostatic pressing (HIP) and cold isostatic pressing were used to manufacture solid and dense tablets; consolidation was performed by sintering the nanocomposites under Ar gas at 1150 °C during HIP. The microstructure and morphology of the nanocomposites were characterized via transmission electron microscopy, energy-dispersive X-ray spectroscopy, powder X-ray diffractometry, Fourier transform infrared (FTIR), and scanning electron microscopy. The effects of ZrO2 and CNTs on the mechanical characteristics of the nanocomposites were examined via nanoindentation, reciprocating wear, and Vickers hardness tests. The microhardness of HA–ZrO2–CNT-1% and HA–ZrO2–CNT-5% increased by 36.8% and 66.67%, respectively, compared with that of pure HA. The nanohardness of the HA–ZrO2–CNT-1%, HA–ZrO2–CNT-5%, and HA–ZrO2–CNT-10% samples was 8.3, 9.65, and 8.02 Gpa, and the corresponding elastic modulus was 83.72, 114.34, and 89.27 GPa, respectively. Both of these parameters were higher than those of pure HA. However, in the nanocomposite reinforced with 10% CNT, as opposed to those with lower CNT ratios, their values were lower. Additionally, HA–ZrO2–CNT-10% was the most hydrophilic nanocomposite synthesized in this study with a contact angle of 48.8°.  相似文献   

5.
《Ceramics International》2017,43(8):6221-6231
In the present work, an investigation of the mechanosynthesis of calcium hydroxyapatite (HA, Ca10(PO4)6(OH)2) from a mixture of calcium oxide (СаО) and ammonium hydrophosphate ((NH4)2HPO4) and mechanotreatment of HA in a planetary mill with the use of steel drums and milling body has been performed. The obtained results have shown that the mechanosynthesis of crystalline nanodisperse HA proceeds through the stage of formation of an amorphous material. The temperature treatment of HA powders at 1000 °C has enabled us to establish the influence of the treatment time on the phase composition of the powders and establish the following sequence of phase transformations: Ca10(PO4)6(OH)2→β-Ca3(PO4)2 (tmilling~2 h), β-Ca3(PO4)2→α-Ca3(PO4)2 (tmilling~5 h), β-,α-Ca3(PO4)2→Ca10(PO4)6(OH)2 (tmilling~7 h).The mechanosynthesis and mechanotreatment of hydroxyapatite in steel drums with steel balls is accompanied by the contamination of hydroxyapatite by their wear debris (iron + manganese). A large part of oxidized iron forms superparamagnetic inclusions distributed in HA powder. A small part of Fe3+ and Mn2+ ions from the steel wear debris enters into the hydroxyapatite lattice, substituting Ca2+ ions. As a result, a nanocomposite powder consisting of hydroxyapatite, alloyed by Fe3+ and Mn2+ ions and ferrite inclusions forms. The phase composition of HA powders, the degree of their alloying by Fe3+ and Mn2+ ions, and the content of ferrite inclusions can be controlled by changing the time of mechanotreatment.  相似文献   

6.
β-CaSiO3/ZrO2 (3Y) nanocomposites were successfully fabricated by spark plasma sintering (SPS) technique. The addition of nanocrystalline ZrO2 could inhibit the phase transition of micrometer sized CaSiO3 and increase its phase transitional temperature. The relative densities of the dense β-CaSiO3/ZrO2 nanocomposites were above 98%. Nanocrystalline ZrO2 has formed a network structure in the nanocomposites, which could improve the mechanical properties of nanocomposites. The fracture strength and fracture toughness of the nanocomposites were as high as 395 MPa and 4.08 MPa m1/2, respectively. The nanocomposites showed good in vitro bioactivity with hydroxyapatite (HA) layer formation on the ZrO2 network of the nanocomposites in simulated body fluid. The spark plasma sintered β-CaSiO3/ZrO2 (3Y) nanocomposite may provide a new bone graft for load bearing applications.  相似文献   

7.
Yuzhan Li 《Electrochimica acta》2007,52(15):4922-4926
Li3V2(PO4)3/carbon composite material was synthesized by a promising sol-gel route based on citric acid using V2O5 powder as a vanadium source. Citric acid acts not only as a chelating reagent but also as a carbon source, which enhance the conductivity of the composite material and hinder the growth of Li3V2(PO4)3 particles. The structure and morphology of the sample were characterized by TG, XRD and TEM measurements. XRD results reveal that Li3V2(PO4)3/carbon was successfully synthesized and has a monoclinic structure with space group P21/n. TEM images show Li3V2(PO4)3 particles are about 45 nm in diameter embeded in carbon networks. Galvanostatic charge/discharge and cyclic voltammetry measurements were used to study its electrochemical behaviors which indicate the reversibility of the lithium extraction/insertion processes. Li3V2(PO4)3/carbon performed in a voltage window (3.0-4.8 V) exhibits higher discharge capacity, better cycling stability and its discharge capacity maintains about 167.6 mAh/g at a current density of 28 mA/g after 50 cycles.  相似文献   

8.
Microstructural features and improvements on the mechanical properties and thermal shock behaviours of MgO-spinel composite refractories with ZrO2 addition were examined. ZrO2 incorporation into MgO-spinel led to improvements around ∼1.5-fold ratios on mechanical properties, Rst values and thermal shock results. The basic parameters improving mechanical properties and thermal shock resistance of MgO-spinel-ZrO2 composite refractories were determined as follows: (i) propagation of microcracks for a short distance by interlinking each other, (ii) stopping or deviation of microcracks when reaching pores or ZrO2 particles, (iii) concurrent occurrence of mostly intergranular and some transgranular cracks on fracture surfaces, and with the addition of ZrO2 (iv) the increase in bulk density, and (v) a significant decrease in MgO grain size. The improvements observed in thermo-mechanical properties confirmed that MgO-spinel-ZrO2 refractories showed a low strength loss and high thermal shock damage resistance at high temperatures, leading to longer service lives for using industrial applications.  相似文献   

9.
The aim of this research was to evaluate the mechanical properties, biocompatibility, and degradation behavior of scaffolds made of pure hydroxyapatite (HA) and HA-modified by MnO2 for bone tissue engineering applications. HA and MnO2 were developed using sol-gel and precipitation methods, respectively. The scaffolds properties were characterized using X-ray diffraction (XRD), Fourier transform spectroscopy (FTIR), scanning electron microcopy (SEM), energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM). The interaction of scaffold with cells was assessed using in vitro cell proliferation and alkaline phosphatase (ALP) assays. The obtained results indicate that the HA/MnO2 scaffolds possess higher compressive strength, toughness, hardness, and density when compared to the pure HA scaffolds. After immersing the scaffold in the SBF solution, more deposited apatite appeared on the HA/MnO2, which results in the rougher surface on this scaffold compared to the pure HA scaffold. Finally, the in vitro biological analysis using human osteoblast cells reveals that scaffolds are biocompatible with adequate ALP activity.  相似文献   

10.
Al2O3/ZrO2 one-dimensional nanocomposite structures were synthesised by chemical vapour deposition using Al2O3 nanowires and a ZrCl4 powder source at a temperature of 800?°C and a pressure of 130?Pa. The samples were characterised using X-ray diffraction, the scanning electron microscopy, the transmission electron microscopy, and N2 adsorption–desorption. The results revealed that Al2O3/ZrO2 composite nanowires coated with surface-embedded ZrO2 nanocrystals were formed and that the ZrO2 macroporous and mesoporous structures changed as the ZrO2 deposition time increased. The pore structure and surface area were also elucidated from the N2 adsorption–desorption measurements.  相似文献   

11.
Mullite-based multilayered structures have been suggested as promising environmental barrier coatings for Si3N4 and SiC ceramics. Mullite has been used as bottom layer because its thermal expansion coefficient closely matches those of the Si-based substrates, whereas Y–ZrO2 has been tried as top layer due to its stability in combustion environments. In addition, mullite/ZrO2 compositions may work as middle layers to reduce the thermal expansion coefficient mismatch between the ZrO2 and mullite layers. Present work studies the thermal behaviour of a flame sprayed mullite/ZrO2 (75/25, v/v) composite coating. The changes in crystallinity, microstructure and thermal conductivity of free-standing coatings heat treated at two different temperatures (1000 and 1300 °C) are comparatively discussed. The as-sprayed and 1000 °C treated coatings showed an almost constant thermal conductivity (K) of 1.5 W m−1 K−1. The K of the 1300 °C treated specimen increased up to twice due to the extensive mullite crystallization without any cracking.  相似文献   

12.
Ultra-fine ZnAl2O4 spinel hydrogel precursor synthesized from mixed salt solutions of Zn2+ and Al3+ ions using ammonium hydroxide–hexamethylenetetramine as basic media for co-precipitation was used as bonding material and sintering aid for pure alumina system. The hydrogel powder exhibited some well-defined ZnAl2O4 spinel phases at 800 °C. Alumina compacts were fabricated by incorporating small proportions of the precursor in alumina powder and firing at different temperatures (1350–1500 °C). The degree of densification was studied by measurement of fired shrinkage, apparent porosity, bulk density and cold crushing strength. Phase compositions and microstructural features of sintered samples were evaluated by XRD and SEM respectively. Addition of 0.2% hydrogel powder to alumina exhibited remarkable influence on development of high mechanical strength. The in situ formed ZnAl2O4 spinel dopant acted as a grain growth inhibitor in the alumina system.  相似文献   

13.
A series of MoO3–ZrO2 composite oxide catalysts were prepared by coprecipitation and impregnation methods and characterized by XRD, Raman, UV–Vis, TEM and sorptometric techniques. Characterization studies indicated the presence of tetragonal zirconia phase and well dispersed MoO3 species as isolated and polymolybdate clusters in the composite oxide. The MoO3(20 mol%)–ZrO2 material was used as efficient catalyst for synthesis of amidoalkyl naphthols under solvent free conditions using conventional as well as microwave heating. The results obtained clearly showed that the composite oxide catalyst was recyclable and highly efficient for the reaction giving good yield and purity of the products.  相似文献   

14.
Impedance spectroscopy was used to study the electrochemical performance of pure and ion-impregnated La0.7Sr0.3MnO3 (LSM) cathodes on YSZ (Y2O3-stabilized ZrO2) electrolytes in single chamber fuel cell conditions, i.e. a mixture gas with oxygen as oxidant, methane as fuel and nitrogen as dilute gas. Measurements were taken at the furnace temperature range of 550-750 °C and the CH4/O2 ratios from 1 to 2. Polarization resistances (Rp) for pure and impregnated LSM cathodes increased obviously as the CH4/O2 ratio increased at 650-750 °C. Polarization resistances of Sm0.2Ce0.8O1.9 (SDC) impregnated LSM cathode were much smaller than the ones of pure LSM cathode under the same conditions. Overtemperatures were occurred at both cathodes due to the partial oxidation of methane.  相似文献   

15.
Spark plasma sintering was used to fabricate Cu/TiO2−x composites by adding Cu powder to nonstoichiometric titanium dioxide, TiO2−x. The composition and crystal forms of the composites were examined. The thermoelectric properties of the composites were measured and the effects of composite formation on these properties were discussed. The rule of mixture (ROM) of composite and general effective medium theory (GEM) were used to investigate the composite effects of the Cu/TiO2−x composites. The results revealed that the electrical resistivities of the composites was much lower than that of TiO2−x. As the added amount of Cu powder increased, the electrical properties of the composites shifted from semiconductor behavior to metallic behavior. The thermoelectric performances of the composites improved as a result of composition formation. The thermoelectric performance can be improved by adjusting the balance among electrical resistivity, thermal conductivity and the Seebeck coefficient, based on the composite effects.  相似文献   

16.
Solubility and diffusivity of supercritical CO2 in poly(l-lactide)-hydroxyapatite (PLLA-HA) and poly(d,l-lactide-co-glycolide)-hydroxyapatite (PLGA-HA) composite materials were measured using a magnetic suspension balance at a temperature of 313 K and a pressures range of 10-30 MPa. The effect of the HA concentration on the solubility and diffusivity was investigated by varying filler content in the range of 0-50 wt%. For the PLLA-HA composites the solubility decreases with the increase of filler concentration. Diffusivity of the gas in the substrate is also lower as the HA content increases. In the case of PLGA-HA composites, small filler content favors the solubility and diffusivity of CO2 due to incomplete wetting of the solid particles by the polymer. As the amount of HA increases solubility decreases. The results suggest that dense CO2 could be used as a ‘green’ processing agent for composite biomaterials when organic solvents or high temperatures should be avoided.  相似文献   

17.
Two Al2O3–ZrO2 mixture preparation routes: classical powder mixing and addition of a Zr (IV) precursor solution to a well dispersed Al2O3 suspension, were used to produce alumina (Al2O3)–zirconia (ZrO2) slip cast composites. For the conventional powder mixing route, two commercial 3 mol% yttria-partially stabilized zirconia powders, 0.3 wt% Al2O3-doped (Al-doped Y-PSZ) and without Al2O3 (Y-PSZ), were employed. The influence of the zirconia content and the solid loading on the rheological properties of concentrated aqueous Al2O3–ZrO2 slips were investigated. The density of green samples was studied and related to the degree of slip dispersion. In addition, the influence of the processing conditions on the density and microstructure development of sintered samples were investigated. By using the Zr (IV) precursor route, nano-sized ZrO2 (ZN) particles homogeneously distributed on the Al2O3 particle surfaces were obtained; however, it let to aggregates of some Al2O3 particles with very fine ZrO2 uniformly distributed. The viscosity and yield stress values of Al2O3–ZN suspensions were markedly higher than those of Al2O3–Al-doped Y-PSZ and Al2O3–Y-PSZ ones, for all the compositions and solid loading studied and resulted in a less dense packing of cast samples. However, for the composite with 10.5 vol% ZN a high sintered density and a smaller ZrO2 grain size distribution compared with the conventional powder mixing route could be obtained.  相似文献   

18.
High burnup is a goal for further development of advanced nuclear power in the future. However, along with the increase of burnup, it becomes more diffidult to control reactor reactivity, which affects the operation safety of the nuclear reactor. Al2O3/B4C burnable poison materials widely used in pressurized water reactor currently will not meet the requirements of burnable poison materials in high burnup nuclear power. Because of the better performance of ZrO2/Gd2O3 burnable poison materials than that of Al2O3/B4C, this paper studies the preparation of ZrO2/Gd2O3 composite ceramic materials by the coprecipitation method. The experimental results show that at the sintering temperature of 1500–1650 °C, ZrO2/Gd2O3 composite ceramic grains are small, compact and uniform with the generation of homogeneous solid solution. At 1600 °C, ZrO2–10%Gd2O3 has the highest density and mechanical strength.  相似文献   

19.
A novel VO2(B)-multiwall carbon nanotube (MWCNT) composite with a sheet-like morphology was synthesized by a simple in situ hydrothermal process. The morphology and structural properties of the samples were investigated by X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). FE-SEM observations demonstrated that the nanosheets are frequently grown together in the form of bundles composed of numerous nanosheets, each with a smooth surface and a typical length of 300-500 nm, width of 50-150 nm, and thickness of 10-50 nm. Electrochemical measurements were carried out using different discharge cut-off voltages. Electrochemical tests show that the VO2(B)-MWCNT composite cathode features long-term cycling stability and high discharge capacity (177 mAh g−1) in the voltage range of 2.0-3.25 V at 1 C with a capacity retention of 92% after 100 cycles. The electrochemical impedance spectra (EIS) indicate that the VO2(B)-MWCNT composite electrode has very low charge-transfer resistance compared with pure VO2(B), indicating the enhanced ionic conductivity of the VO2(B)-MWCNT composite. The enhanced cycling stability is attributed to the fact that the VO2(B)-MWCNT composite can prevent the aggregation of active materials, accommodate the large volume variation, and maintain good electronic contact. We strongly believe that the VO2(B)-MWCNT composite can be considered as a potential cathode material for lithium-ion batteries.  相似文献   

20.
Homogeneous composite nanopowders of hydroxyapatite/30 wt% yttria-stabilized zirconia (HA–YSZ) containing 0, 3, 5, and 8 mol% Y2O3 (namely; HA–0YSZ, HA–3YSZ, HA–5YSZ, and HA–8YSZ) were successfully synthesized using the sol–gel method. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Fourier transformed infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques were utilized to characterize the prepared nanopowders. Analyses of HA–YSZ composite nanopowders showed the successful formation of desirable phases. HA unit cell volume in the composites increased as a result of ion exchange of calcium and zirconium between HA and zirconia. Results revealed the formation of HA particles with irregular morphology (40–80 nm) and spherical yttria-stabilized zirconia particles (20–30 nm). Segregation of yttrium ions at the grain boundaries of ZrO2 particles retarded the grain growth of zirconia particles and the presence of ZrO2 nanoparticles among the hydroxyapatite particles resulted in grain growth inhibition of HA particles. This process can be used to synthesize HA–YSZ composite nanopowders with improved properties, which are much needed for hard tissue repair and biomedical applications.  相似文献   

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