共查询到20条相似文献,搜索用时 15 毫秒
1.
Morphology and composition of nanograde calcium phosphate needle-like crystals formed by simple hydrothermal treatment 总被引:5,自引:0,他引:5
Li Yubao K. De Groot J. De Wijn C. P. A. T. Klein S. V. D. Meer 《Journal of materials science. Materials in medicine》1994,5(6-7):326-331
Nanograde calcium phosphate needle-like crystals are prepared from wet synthesized Ca–P precipitates by simple hydrothermal treatment at 140°C and 0.3 MPa for 2 h. The morphology of these crystals is observed by transmission electron microscopy (TEM). The phase composition is tested through X-ray diffractometer (XRD) and infrared spectroscopy (IR). It is found that the morphology of these crystals is related to the activity or fresh degree of the starting Ca–P precipitates and the added fluorine ions, but is not greatly influenced by the Ca/P ratio of the precipitates. These crystals with a Ca/P ratio between 1.67 and 1.5 show a poorly crystallized apatite structure at room temperature and a biphasic (HA+–TCP) structure at 1100°C, corresponding to their Ca/P ratio. It is demonstrated that these nonstoichiometric apatite crystals contain lattice-bound water which could play an important role in the formation of bone apatite. The similarity in morphology and composition between these needle-like crystals and the apatite crystals in bone provides a possibility to make a bone-like implant consisting of these needle-like crystals and collagen, etc. 相似文献
2.
3.
4.
L. P. Kozeeva M. Yu. Kameneva N. V. Podberezskaya A. I. Smolentsev V. E. Fedorov 《Inorganic Materials》2011,47(1):68-74
We have studied conditions for bismuth ferrite, BiFeO3, crystallization from off-stoichiometric Bi2O3-Fe2O3 melts, obtained crystals of different morphological types (dendritic and faceted pseudocubic) up to 3 mm in size, and characterized them by a variety of techniques (X-ray diffraction, IR spectroscopy, differential thermal analysis, X-ray structure analysis, and X-ray microanalysis). 相似文献
5.
Preparation and characterization of some single,mixed and doped crystals and instrumentation aspects
R Krishnaswamy 《Bulletin of Materials Science》1981,3(3):281-293
The preparation and characterization (salient ones) of KAl (SO4)2. 12H2O, KCr (SO4)2·12H2O, mixed crystals of both with 10 to 90% of each component, mixed crystals of CsCl with CuCl2, doped crystals of KBr with K3FeCN6, mixed crystals (NH4)2SO4 with CuSO4 or NiSO4, NaCl with growth improver Pb+2, Mn+2, metallic crystals of Zn, Bi, ionic crystals of alkali halides with Pb+2, or Cd+2, etc. are presented. Instrumentation aspects of a rotary crystallizer, a homogeniser, an ingot release mechanism and a zone
refiner are shown. 相似文献
6.
7.
Qiaofeng Han 《Materials Letters》2008,62(14):2050-2052
Orthorhombic Sb2Se3 belts are synthesized via a hydrothermal treatment at 200 °C and pH = 9-10 for 16 h. Transmission electron microscopic (TEM) images show that as-obtained Sb2Se3 belts are with a typical width in the range of 200-400 nm and length up to 20 μm. High-resolution transmission electron microscopic (HRTEM) studies reveal that the Sb2Se3 are oriented in the [001] growth direction. The influences of poly vinyl alcohol (PVA) and the reaction conditions on the formation of belt-like Sb2Se3 microstructures are discussed. 相似文献
8.
9.
The hydrothermal synthesis of large port mordenite crystals and experimental observations are reported. Unit cell parameters
are estimated asa = 18·142,b = 20·328 andc = 7·508 ?. Prismatic and prismatic pyramidal mordenite crystals are illustrated. The average particle size computed was 8–20μ. Adsorption capacities of synthesized mordenite crystals are 13·4% for water, 9·9% for methanol and 5·8% for benzene by weight. 相似文献
10.
N.B. Singh R.H. Hopkins W.E. Gaida Donald H. Lemmon J.D. Feichtner R. Mazelsky 《Materials Letters》1985,4(1):21-26
Good quality single crystals of silver thallium selenide (AgT1Se) up to the size of 15 mm diameter and 15.0 cm length were grown from the melt by the Bridgman-Stockbarger technique. The purification of the source materials minimized the surface voids and compositional inhomogeneities, and enhanced the optical quality of the crystals. The effect of annealing on the optical transmittance was studied for a crystal of 6 mm thickness. Lattice parameters were also determined. The values are in good agreement with literature values for crystals with orthorhombic symmetry. 相似文献
11.
12.
Flux growth and characterization of TiC crystals 总被引:1,自引:0,他引:1
Shiro Shimada Jun Watanabe Kohei Kodaira Toru Matsushita 《Journal of Materials Science》1989,24(7):2513-2515
Single crystals of TiC were grown using nickel and cobalt metal as a flux at soaking temperatures of 1500 to 1800° C and at compositions of 12.5 to 30 mol% TiC. The use of cobalt flux produced crystal sizes less than 0.5 mm under all conditions. With a nickel flux, a maximum crystal size of 1.5 mm was obtained at 1700 and 1800°C and at 20 and 25 mol% TiC composition, using a cooling rate of 3° C min–1. A slower cooling rate of 0.2° C min–1 also gave crystals of 1.5 mm at 1600° C. The crystals were cubic and metallic-lustre silver grey in colour. The lattice parameter of the crystal was measured to bea
0 = 0.432 75 ± 0.000 05 nm, with nearly stoichiometric composition. The grown faces were of the {1 0 0} family with a dislocation density around 107 cm-2. The Vickers' microhardness on these faces was in the range 2600 to 2800 kg mm–2. The nickel impurity and free carbon contents in the crystals were 700 to 1000 p.p.m. and 0.8 to 4 wt%, respectively. 相似文献
13.
Studies on hydrothermal synthesis of zeolite crystals, in Na2O-Al2O3-SiO2-H2O system, are reported. Experimental procedure and growth parameters are briefly described. Cube-like and rod-like crystals (called VSZ-1 and VSZ-2) are illustrated. It is established that VSZ-1 crystals are metastable, while VSZ-2 crystals are stable. Crystallanity of these two samples is established. Observations and results of characterization of these two varieties by TEM, SEM, electron microprobe and infrared methods are described, illustrated and interpreted. The role of Si/Al ratio is explained. 相似文献
14.
R. M. Frazier B. N. Feigelson M. E. Twigg M. Murthy J. A. Freitas 《Journal of Materials Science: Materials in Electronics》2008,19(8-9):845-848
Hexagonal BN crystals were grown from solution by application of a thermal gradient. The solvent used to dissolve the source was optimized by changing the ratio of components to have the lowest melting point. The investigation of adding a third component demonstrated further reduction of the melting point with BN as an additive. A solution was created with enhanced properties allowing the growth of BN. BN was grown on a PBN seed at T g = 900 °C and P = 0.2 MPa for approximately 65 h. The BN crystals were found to be embedded in a solvent matrix, as determined by EDS. In addition, GaN crystals were grown in a modified solution at T g = 800 °C and P = 0.2 MPa. Raman spectroscopy verified wurtzite GaN structure with good crystallinity. The successful growth of BN and GaN from solution suggests this to be a method of choice for growth of the III-Ns, and may prove to be a viable alternative to current costly wafer production techniques. 相似文献
15.
《Materials Letters》2001,47(4-5):314-318
Nickel tungstate (NiWO4) catalyst has been synthesized by reacting ammonium metatungstate and nickel nitrate as a function of temperature from 673 to 1073 K and of 1-h reaction time. It was found that NiWO4 is formed from 823 to 1073 K. The yield of 99% was obtained from 903 K to higher temperatures. The average crystal sizes have been determined by the Scherrer analysis and the surface area was measured by the Brunauer–Emmett–Teller (BET) method. The former increase from 55 to 112 nm, while the second decrease from 16 to 3 m2 g−1 in both cases, as the reaction temperature increases from 823 to 1073 K. Elemental composition and morphological structure were studied by energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The structural characterization has been performed using X-ray diffraction (XRD). 相似文献
16.
Naru Shiraishi Takahisa Anada Yoshitomo Honda Taisuke Masuda Keiichi Sasaki Osamu Suzuki 《Journal of materials science. Materials in medicine》2010,21(3):907-914
The present study was designed to investigate whether the amount of octacalcium phosphate (OCP) affects the characteristics of alginate (Alg)/OCP scaffolds regarding the pore formation and its distribution, and the thermodynamic stability from OCP to hydroxyapatite (HA) in an in vitro physiological environment. Alg/OCP composites with weight ratios of 100/0, 75/25, 50/50, and 25/75 were prepared through mixing the ground synthesized OCP crystals with an Alg solution and applying lyophilization. Analysis of X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and mercury intrusion porosimetry verified that the crystalline phase of OCP and the porosities were retained regardless of the OCP amount. On the other hand, the elastic modulus, determined by mechanical testing, and, interestingly, the pore size increased with increasing the OCP amount. The immersion of the composites in a simulated body fluid up to 14 days revealed that OCP in Alg matrices tends to convert to HA with enhancing the calcium consumption depending on the OCP amount. The results indicated that the inclusion of OCP crystals in the Alg matrix by the mixing process controls the character of the pore distribution in Alg/OCP composites while maintaining the transitory nature of OCP. 相似文献
17.
Single crystals of tetraethylammonium tetrachlorocobaltate were grown by solution method and characterized through single crystal X-ray diffraction, thermogravimetric analysis (TGA), differential scanning calorimetric studies (DSC) and infrared spectroscopic technique (IR). The crystals were bright, transparent and blue coloured. The unit cell parameters were found to bea =b = 90363 Å andc = 14.9879 Å and α = β = γ = 90°, showing tetragonal lattice from the XRD data. Thermogravimetric analysis showed a loss of weight at 683 K from which the decomposition reaction was formulated. Thermal anomalies were found for this crystal at temperatures 200 K, 220 K in the cooling cycle and at temperatures 200 K, 240 K in the heating cycle, respectively which showed that this crystal was associated with first order phase transition. All the vibrational frequencies corresponding to (TEA)+ ions and CoCl 4 2? ions were assigned from the IR spectral data of this crystal. 相似文献
18.
Homogeneous crystals of Cd.95Mn.05Se of high optical quality have been grown by a modified Bridgman method. Magnetic susceptibility measurements verify the uniform distribution of Mn(II) obtained after annealing at 600°C.Crystals grown in the presence of 5 atomic percent excess selenium showed high resistivity; the addition of 1 mg iodine to a 10 g charge resulted in n-type conductivity and a room-temperature carrier concentration of 2.9 × 1016 cm?3. The Hall mobility of these crystals was approximately 290 cm2 V?1 sec?1. 相似文献
19.
Characterization of the gel-grown barium hydrogen phosphate (BHP) crystals was performed by utilizing the techniques of chemical
analysis, X-ray diffraction, infrared and thermal behaviour. The results show that BHP crystals had chemical composition BaHPO4 at room temperature. TG and DTA studies revealed the BHP crystals to be anhydrous at room temperature and decomposed at temperatures
above 370°C and the decomposition was an endothermic process. Magnetic susceptibility measurements indicate the material to
be diamagnetic. 相似文献
20.
Potassium titanyl phosphate (KTP) is a relatively new nonlinear optical material with excellent combination of physical properties.
This paper presents the combined etching and X-ray topographic studies carried out on KTP crystals with a view to characterizing
their defects. KTP crystals employed in this investigation were grown from flux. Optical microscopic study of habit faces
revealed growth layers and growth hillocks on (100) and (011) faces respectively. Etching of (011) habit faces proved that
growth hillocks corresponded to the emergence point of dislocation out crops on these faces. The suitability of the new etchant
to reveal dislocation was confirmed by etching the matched pairs obtained by cleaving. The defects present in the crystal
were also studied by X-ray topography. The defect configuration in these crystals is characteristic of crystals grown from
solution. The dislocations arc predominantly linear with their origin either at the nucleation centre or inclusions. In general,
grown crystals were found to have low dislocation density and often large volumes of crystals free from dislocation could
be obtained. 相似文献