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1.
In this study, abrasive wear behaviour of bio-active glass ceramic materials produced with two different processes is studied.
Hot pressing process and conventional casting and controlled crystallization process were used to produce bio-active ceramics.
Fracture toughness of studied material was calculated by fracture toughness equations using experimental hardness results
of the bio-active glass ceramic material. Two fracture toughness equations in the literature were used to identify the wear
behaviour of studied ceramics. Wear resistance results that identified with both of the equations were similar. The results
showed that the abrasive wear resistance of the bio-active glass ceramics produced with hot pressing process was found to
be higher than that of the ceramics produced by conventional casting and controlled crystallization process. 相似文献
2.
M. P. Mahabole R. C. Aiyer C. V. Ramakrishna B. Sreedhar R. S. Khairnar 《Bulletin of Materials Science》2005,28(6):535-545
Hydroxyapatite (HAp) biomaterial ceramic was synthesized by three different processing routes viz. wet chemical process, microwave
irradiation process, and hydrothermal technique. The synthesized ceramic powders were characterized by SEM, XRD, FTIR and
XPS techniques. The dielectric measurements were carried out as a function of frequency at room temperature and the preliminary
study on CO gas sensing property of hydroxyapatite was investigated. The XRD pattern of the hydroxyapatite biomaterial revealed
that hydroxyapatite ceramic has hexagonal structure. The average crystallite size was found to be in the range 31–54 nm. Absorption
bands corresponding to phosphate and hydroxyl functional groups, which are characteristic of hydroxyapatite, were confirmed
by FTIR. The dielectric constant was found to vary in the range 9–13 at room temperature. Hydroxyapatite can be used as CO
gas sensor at an optimum temperature near 125°C. X-ray photoelectron spectroscopic studies showed the Ca/P ratio of 1.63 for
the HAp sample prepared by chemical process. The microwave irradiation technique yielded calcium rich HAp whereas calcium
deficient HAp was obtained by hydrothermal method. 相似文献
3.
P. K. Thiruvikraman 《Bulletin of Materials Science》2006,29(4):371-374
We propose a microscopic, phenomenological model for the decrease in the viscosity observed at glass transition. Our model
is primarily applicable to chalcogenide glasses. According to this model, the decrease in the viscosity at glass transition
is mainly due to the breaking of the Van der Waals bonds in the chalcogenides. Using this model, we derive a relationship
between the glass transition temperature,T
g
,and the molar volume
V
m.The validity of this relation is checked using experimental data available in the literature for two binary systems (Ge-Se
and As-S) and a pseudo-binary system (As
40
Se
x
Te
60-x
. 相似文献
4.
A series of calcium substituted polycrystalline ferrite ceramics with magnetoplumbite structures were synthesized using perfect
stoichiometric mixtures of oxides with chemical composition, CaAlxCoxFe12−2xO19 (x = 2−5), by standard ceramic technique. The variation in the values ofH
candM
s,which depends on the additive content and the temperature, was studied by means of a vibration magnetometer. The strong variation
observed in coercivity, saturation magnetization and Curie temperature with chemical composition give rise to the possibility
of controlling these properties and hence applying these compounds in the millimeter— microwave range. 相似文献
5.
S. R. Murthy 《Bulletin of Materials Science》2001,24(6):611-616
Polycrystalline NiZn ferrites with different grain sizes (1.2 (Am to 10.2 (Am) were prepared by the usual ceramic method.
The magnetic properties were measured at room temperature. The ultrasonic velocity and attenuation were measured on Ni-Zn
ferrite by using the pulse transmission method at 1 MHz, in the temperature range 300–600 K. The velocity was found to be
slightly sample dependent at room temperature and decreased with increasing temperature, except near the Curie temperature,
T
c
,where a small anomaly was observed. The longitudinal attenuation (α
1
)at room temperature was found to be more sample dependent. The temperature variation of ultrasonic longitudinal attenuation
exhibited a broad maximum around 400 K and a sharp maximum just below Curie temperature (
T
c
).The above observations were carried out in the demagnetized state. The application of a 380 mT magnetic field allowed us to
reach the saturated state of the sample at all the measuring temperatures. The anomaly observed in the thermal variation of
velocities (longitudinal and transverse) and attenuation has been qualitatively explained with the help of the temperature
variation of the magneto-crystalline anisotropy constant. 相似文献
6.
T. Kokubo H. Kushitani C. Ohtsuki S. Sakka T. Yamamuro 《Journal of materials science. Materials in medicine》1992,3(2):79-83
Glass-ceramic A-W containing crystalline apatite and wollastonite in an MgO-CaO-SiO2 glassy matrix bonds to living bone through an apatite layer which is formed on its surface in the body. The parent glass G of glass-ceramic A-W and glass-ceramic A, which has the same composition as glass-ceramic A-W but contains only the apatite, also bond to living bone through the surface apatite layer, whereas glass-ceramic A-W(Al), which contains the apatite and wollastonite in an MgO-CaO-SiO2-Al2O3 glassy matrix, neither forms the surface apatite layer nor bonds to living bone. In the present study, in order to reveal the mechanism of formation of the surface apatite layer, changes in ion concentrations of a simulated body fluid with immersion of these four kinds of glass and glass-ceramics were investigated. Bioactive glass G and glass-ceramics A and A-W all showed appreciable increases in Ca and Si concentrations, accompanied by an appreciable decrease in P concentration, whereas non-bioactive glass-ceramic A-W(Al) hardly showed any element concentration change. It was speculated from these results that dissolution of the Ca(II) and Si(IV) ions from bioactive glass and glass-ceramics plays an important role in forming the apatite layer on their surfaces in the body. 相似文献
7.
The metallic glass samples of Fe
67Co18B14Si1 (2605CO), prepared by the melt spinning technique were procured from the Allied Corporation. The kinetics of crystallization
of this multicomponent glassy alloy is studied using differential scanning calorimetry (DSC). The crystallization data have
been examined in terms of modified Kissinger and Matusita equations for the nonisothermal crystallization. The results show
enhanced bulk nucleation in general. At high heating rates added to it is surface induced abnormal grain growth resulting
in fractal dimensionality.
5th IUMRS ICA98, October 1998, Bangalore. 相似文献
8.
Le Nihouannen D Duval L Lecomte A Julien M Guicheux J Daculsi G Layrolle P 《Journal of materials science. Materials in medicine》2007,18(10):1983-1990
The biological properties of synthetic calcium phosphate bioceramics have made them the third choice of material for bone
reconstructive surgery, after autologous bone and allografts. Nevertheless, bioceramics lack the osteogenic properties that
would allow them to repair large bone defects. One strategy in bone tissue engineering consists of associating a synthetic
scaffold with osteogenic cells. Mesenchymal stem cells (MSC) are usually isolated from bone marrow cultured for several weeks
and seeded on to a small quantity of bioceramic. We have studied the association of total bone marrow cells, harvested from
femurs of rats, with increasing amounts of calcium phosphate ceramic granules (50–250 mg). A cell viability test indicated
that a little quantity of bioceramics granules (50 mg) was less detrimental for culturing 1 million nucleated cells from the
whole bone marrow population. Cell morphology, viability, adhesion and differentiation were studied after different culture
periods. Among the heterogeneous population of bone marrow cells, only a limited amount of cells attached and differentiated
on the bioceramics. To explain the influence of the amount of synthetic scaffold on cell viability, media calcium concentrations
were measured. Low cell viability could be explained by calcium phosphate precipitation leading to a decrease in calcium concentrations
observed with relatively large amounts of scaffold. This study showed that the chemical stability of the ceramic plays a critical
role in the viability of bone marrow cells. 相似文献
9.
Powder XRD investigations were made on mixtures of title compounds and strength of monoclinic, orthorhombic and super-lattice
phases were evaluated. Interpretations were made in terms of the influence of tunnel-like defects (TLIDs) and a linear relationship
was noticed between the strength of orthorhombic phase and <lTLID>. 相似文献
10.
Porous bioceramics with high porosity for bone tissue engineering were fabricated by the foam impregnation technique, but
their mechanical strength was poor, only a mean compressive strength of 1.04 ± 0.15 MPa and an mean elastic modulus of 0.1 GPa.
In order to reinforce porous ceramics, the ceramic samples were immerged in 5% gelatin solution and gelatin coatings were
formed on the inter-surface of their pores. It was found that the mean compressive strength value and the mean elastic modulus
value of porous samples coated with gelatin were improved to 5.17 ± 0.17 MPa and 0.3 GPa respectively without sacrificing
their porosity greatly. Moreover composite samples were not as fragile as sintered ceramics. The results indicated that the
gelatin coatings on the inter-surface of pores reinforced porous bioceramics effectively. 相似文献
11.
Four different varieties of class F fly ashes, collected from different sources from the state of West Bengal (India) were
mixed with lime in 9 : 1 wt ratio, followed by compaction of the mixes. The compacts were subjected to steam curing to develop
an optimum strength by the reaction between fly ash and lime. The steam cured compacts were heated at different elevated temperatures
and free lime content, compressive strength, bulk density and water absorption tendency of these compacts were measured and
FTIR spectral changes were studied as a function of the heating temperatures. Kinetics of thermal dehydration of the compacts
was also studied from thermogravimetric measurements under non-isothermal condition to ascertain the order of dehydration
process and the associated activation energy. 相似文献
12.
Electron-beam (e-beam) induced polymerization of epoxy resins proceeds via cationic mechanism in presence of suitable photoinitiator.
Despite good thermal properties and significant processing advantages, epoxy-based composites manufactured using e-beam curing
suffer from low compressive strength, poor interlaminar shear strength, and low fracture toughness. A detailed understanding
of the reaction mechanism involving e-beam induced polymerization is required to properly address the shortcomings associated
with e-beam curable resin systems. This work investigated the effect of hydroxyl containing materials on the reaction mechanism
of e-beam induced cationic polymerization of phenyl glycidyl ether (PGE). The alcohols were found to play important roles
in polymerization. Compared to hydroxyl group of aliphatic alcohol, phenolic hydroxyl group is significantly less reactive
with the oxonium active centre, generated during e-beam induced polymerization of epoxy resin system. 相似文献
13.
External stimuli response on a novel chitosan hydrogel crosslinked with formaldehyde 总被引:1,自引:0,他引:1
Keeping in mind the significance of hydrogels as an external stimuli sensitive super absorbing material, some transparent
covalent hydrogels of chitosan were prepared by crosslinking with varying amounts of formaldehyde solution used as crosslinking
agent. The characteristics of hydrogels were investigated by Fourier transform infrared (FT-IR) spectroscopy and swelling
experiments. The effect of crosslinking agent on water absorbency has been investigated. The hydrogels exhibited a relatively
higher swelling ratio in the range of 2066–3306% and equilibrium water content (EWC) in the range of 95-38–97 06% at pH 7
and 35°C temperature. The influence of external stimuli such as pH, temperature, and ionic strength of the swelling media
on equilibrium swelling properties has been observed. Hydrogels showed a typical pH and temperature responsive behaviour such
as low pH and high temperature has maximum swelling while high pH and low temperature show minimum swelling. An increase in
the ionic strength of swelling media caused a continuous decrease in the swelling of hydrogels at both acidic and basic pH. 相似文献
14.
Indium tin oxide (ITO) films containing different In : Sn atomic ratios, viz. 90 :10, 70 :30, 50 : 50, 30 :70, were deposited
on two types of glass substrates by sol-gel spinning technique. XPS analysis of the films was done under as-received and after-sputtering
conditions. The narrow spectra obtained for the Na1s, In3d, Sn3d and O1s have been discussed. Oxygen was found to exist in
three chemical environments in as-received samples due to the existence of (i) environmental hydroxyl (-OH) group, (ii) crystalline
ITO and (iii) amorphous ITO; but it was in two chemical environments, (ii) and (iii), after surface cleaning by sputtering.
The presence of both tin metal and tin oxides was confirmed by the peak analysis of Sn3d. The In : Sn atomic ratio taken in
the precursor sols did not change considerably in the case of developed films of low Sn content, but considerable change was
observed in the films having high Sn content. 相似文献
15.
具有良好贯通性的颗粒造孔支架的制备及表征 总被引:1,自引:0,他引:1
支架孔隙贯通性的研究一直是多孔生物陶瓷的研究重点之一.采用石蜡球作为造孔剂, 在常规的颗粒造孔法制备多孔陶瓷支架的基础上,通过二甲苯处理以便在石蜡球间形成桥联结构, 以扩大颗粒间的接触面积,从而提高多孔陶瓷支架的孔隙贯通性. 借助扫描电镜(SEM)观察陶瓷支架的多孔结构,评价二甲苯处理石蜡球对陶瓷支架孔隙贯通性的改善效果; 采用密度法测定了陶瓷支架的孔隙率并计算其收缩率,并用成骨细胞评价陶瓷支架的细胞相容性. 结果表明,通过二甲苯的处理, 不仅改善了陶瓷支架孔隙的贯通性,而且提高了其孔隙率, 但孔隙率对陶瓷支架的收缩率无明显影响.细胞培养实验显示成骨细胞可进入多孔陶瓷支架内部, 并在材料表面正常生长,贯通性好的多孔陶瓷支架可为成骨细胞生长提供更充分的空间. 相似文献
16.
Vaibhav Kulshrestha K. Awasthi N. K. Acharya M. Singh Y. K. Vijay 《Bulletin of Materials Science》2005,28(7):643-646
In the present study the polyethersulphone (PES) membranes of thickness (35 ±2) μm were prepared by solution cast method.
The permeability of these membranes was calculated by varying the temperature and by irradiation of α ions. For the variation
of temperature, the gas permeation cell was dipped in a constant temperature water bath in the temperature range from 303–373
K, which is well below the glass transition temperature (498 K). The permeability of H2 and CO2 increased with increasing temperature. The PES membrane was exposed by a-source (95Am241) of strength (1 μ Ci) in vacuum of the order of 10−6 torr, with fluence 2.7 × 107 ions/cm2. The permeability of H2 and CO2 has been observed for irradiated membrane with increasing etching time. The permeability increases with increasing etching
time for both gases. There was a sudden change in permeability for both the gases when observed at 18 min etching. At this
stage the tracks are visible with optical instrument, which confirms that the pores are generated. Most of pores seen in the
micrograph are circular cross-section ones. 相似文献
17.
Microstresses developed in the crystallites of polymeric material due to irradiation of high-energy particle causes peak broadening
and shifting of X-ray diffraction lines to lower angle. Neutron irradiation significantly changes the material properties
by displacement of lattice atoms and the generation of helium and hydrogen by nuclear transmutation. Another important aspect
of neutron irradiation is that the fast neutron can produce dense ionization at deep levels in the materials. The polyethylene
terephthalate (PET) fibre of raw denier value, 78.2, were irradiated by fast neutron of energy, 4.44 MeV, at different fluences
ranging from 1×109 n/cm2 to 1 × 1012 n/cm2. In the present work, the radiation heating microstresses developed in PET micro-crystallites was investigated applying X’Pert-MPD
Philips Analytical X-ray diffractometer and the effects of microstresses in tensile strength of fibre measured by Instron
have also been reported. The shift of 0.45 cm−1 in the Raman peak position of 1614.65 cm{−1} to a higher value confirmed the development of microstresses due to neutron irradiation using micro-Raman technique. The
defects due to irradiation were observed by SEM micrographs of single fibre for virgin and all irradiated samples. 相似文献
18.
Fatigue and life-time of bioactive glass-ceramic A-W containing apatite and wollastonite 总被引:1,自引:0,他引:1
T. Kokubo S. Ito M. Shigematsu S. Sanka T. Yamamuro 《Journal of Materials Science》1987,22(11):4067-4070
High-strength bioactive glass-ceramic A-W containing apatite and wollastonite shows the least dynamic fatigue among glass and glass-ceramics of the same composition and of different structure in a simulated body fluid at 38.5° C. An avenge life-time estimated from the fatigue of glass-ceramic A-W is 10 yews under continuous loading of bending stress of 65 MPa in the simulated body fluid, whereas that of a sintered dense hydroxyapatite ceramic is only 1 min. Articles of the glass-ceramic which withstand the stress of 215 M Pa in an inert atmosphere are guaranteed for 10 years life-time in the body environment. The glass-ceramic shows an increase in strength, without having an appreciable change in fatigue, when placed in the simulated body fluid without being loaded. Its practical life-time can therefore be expected to be much longer than that estimated above. 相似文献
19.
G. Willmann 《Materialwissenschaft und Werkstofftechnik》2003,34(2):198-202
Sterilization can change properties of bioceramics Bioceramics made of bioinert alumina or zirconia and bioactive hydroxyapatite are well established implant materials. Implants have to be cleaned and sterilized. When sterilized some bioceramics change their color. This may effect their properties. No decrease of mechanical strength is observed when sterilizing alumina and the novel ceramic biocomposite AMC (Alumina Matrix Composite) with steam or Co60 Gamma irradiation. When sterilizing Y‐TZP zirconia with steam a decrease of strength is observed. 相似文献
20.
S. Chatterjee S. K. Samanta H. D. Banerjee C. K. Maiti 《Bulletin of Materials Science》2001,24(6):579-582
ZrO
2
films on silicon wafer were deposited by microwave plasma enhanced chemical vapour deposition technique using zirconium tetratert
butoxide (ZTB). The structure and composition of the deposited layers were studied by fourier transform infrared spectroscopy
(FTIR). The deposition rates were also studied. MOS capacitors fabricated using deposited oxides were used to characterize
the electrical properties of ZrO
2
films. The films showed their suitability for microelectronic applications. 相似文献