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1.
Herein, we report the results of the in vitro dissolution tests, which were carried out by immersing the selected glass-ceramic samples in artificial saliva (AS) for various time periods of up to 42 days. In our experiments, the SiO(2)-MgO-Al(2)O(3)-K(2)O-B(2)O(3)-F glass ceramics with different crystal morphology and crystal content were used and a comparison is also made with the baseline glass samples (without any crystals). The bioactivity of the samples was probed by measuring the changes in pH, ionic conductivity and ionic concentration of AS following in vitro dissolution experiments. High resistance of the selected glass-ceramic samples against in vitro leaching has been demonstrated by minimal weight loss (<1%) and insignificant density change, even after 6 weeks of dissolution in artificial saliva. While XRD analysis reveals the change in surface texture of the crystalline phase, FT-IR analysis weakly indicated the Ca-P compound formation on the leached surface. The experimental measurements further indicate that the leaching of F(-), Mg(2+) ions from the sample surface commonly causes the change in the surface chemistry. Furthermore, the presence of (Ca, P, O)-rich mineralized deposits on the leached glass-ceramic surface as well as the decrease in Ca(2+) ion concentrations in the leaching solutions (compared to that in the initial AS solution) provide evidences of the moderate bioactive or mild biomineralisation behaviour of investigated glass-ceramics. 相似文献
2.
Rajendra Kumar Singh A. Srinivasan G. P. Kothiyal 《Journal of materials science. Materials in medicine》2009,20(1):147
Magnetic bioglass ceramics (MBC) are being considered for use as thermoseeds in hyperthermia treatment of cancer. While the bioactivity in MBCs is attributed to the formation of the bone minerals such as crystalline apatite, wollastonite, etc. in a physiological environment, the magnetic property arises from the magnetite [Fe3O4] present in these implant materials. A new set of bioglasses with compositions 41CaO · (52 ? x)SiO2 · 4P2O5 · xFe2O3 · 3Na2O (2 ≤ x ≤ 10 mol% Fe2O3) have been prepared by melt quenching method. The as-quenched glasses were then heat treated at 1050°C for 3 h to obtain the glass-ceramics. The structure and microstructure of the samples were characterized using X-ray diffraction and microscopy techniques. X-ray diffraction data revealed the presence of magnetite in the heat treated samples with x ≥ 2 mol% Fe2O3. Room temperature magnetic property of the heat treated samples was investigated using a Vibrating Sample Magnetometer. Field scans up to 20 kOe revealed that the glass ceramic samples had a high saturation magnetization and low coercivity. Room temperature hysteresis cycles were also recorded at 500 Oe to ascertain the magnetic properties at clinically amenable field strengths. The area under the magnetic hysteresis loop is a measure of the heat generated by the MBC. The coercivity of the samples is another important factor for hyperthermia applications. The area under the loop increases with an increase in Fe2O3 molar concentration and the. coercivity decreases with an increase in Fe2O3 molar concentration The evolution of magnetic properties in these MBCs as a function of Fe2O3 molar concentration is discussed and correlated with the amount of magnetite present in them. 相似文献
3.
Hui-Juan Wang Tilman Zscheckel Bo-Tao Li Hui-Xing Lin Christian Bocker Christian Rüssel Lan Luo 《Journal of Materials Science》2017,52(3):1330-1347
Crystallization and microstructure of glasses with the molar compositions 1MgO·1.2Al2O3·2.8SiO2·1.2TiO2·xLa2O3 (x = 0.1 and 0.4) were thermally treated at different temperatures in the range from 950 to 1250 °C and then analyzed by X-ray diffraction and scanning electron microscopy, in combination with energy-dispersive X-ray spectroscopy and electron backscatter diffraction. It was found that the microstructure is first homogeneous with the precipitation of randomly distributed crystals and then indialite domains with embedded perrierite and rutile crystals are formed. For higher temperatures or prolonged times, more domains appear and expand into the bulk of the sample. Finally, the entire sample consists of the indialite domains and the boundaries that are enriched in rutile, perrierite, and magnesium aluminotitanate. Nevertheless, very distinct differences are observed between the samples with different La2O3 concentrations. For the sample with x = 0.4, the domains were detected at lower temperatures, while the quantity and size of the domains increase faster due to the promoted precipitation of indialite. For the sample with x = 0.1, in addition to the domain boundaries, secondary boundaries between the “regions” (assemblages of the domains) are observed in a larger length scale. The average size of the crystalline phases found between the “regions” is larger than that typically observed at the domain boundaries. The sizes of the crystals at the boundaries decrease with higher concentrations of La2O3, and the crystals (especially perrierite) within the domains become larger, resulting in a more homogeneous microstructure. This results in better dielectric properties, i.e., much higher quality factor for the sample with x = 0.4 in comparison to that with x = 0.1 after heat-treatment at 1150 or 1250 °C. 相似文献
4.
X. H. Zheng X. C. Jiang D. P. Tang C. Zhang 《Journal of Materials Science: Materials in Electronics》2011,22(7):781-784
CaO–SrO–Li2O–Ln2O3–TiO2 ceramics were prepared by solid state reaction method, where Ln2O3 consists of equal proportions of Nd2O3 and Sm2O3. Dielectric properties and crystal structure were investigated with respect to the content of TiO2. Single phase with an orthorhombic perovskites structure was formed within the composition range of investigation. The frequency
dependence of dielectric properties of the present ceramics was extensively investigated. Dielectric constant was less sensitive
to frequency. However, dielectric loss and temperature coefficients were both very sensitive to frequency and gradually decreased
with increasing frequency, such as the variation was more than ten times between 1 MHz and several GHz. The relationship between
the temperature coefficient and dielectric loss was also discussed at different frequencies. And the mechanism of the frequency
dependence was discussed in term of the role of Li ions. 相似文献
5.
In view of the potential engineering applications requiring machinability and wear resistance, the present work focuses to
evaluate hardness property and to understand the damage behavior of some selected glass–ceramics having different crystal
morphologies with SiO2–MgO–Al2O3–K2O–B2O3–F composition, using static micro-indentation tests as well as dynamic scratch tests, respectively. Vickers hardness of up
to 5.5 GPa has been measured in glass–ceramics containing plate like mica crystals. Scratch tests at a high load of 50 N in
artificial saliva were carried out in order to simulate the crack–microstructure interaction during real-time abrasion wear
and machining operation. The experimental observations indicate that the novel “spherulitic-dendritic” shaped crystals, similar
to the plate like crystals, have the potential to hinder the scratching induced crack propagation. In particular, such potential
of the ‘spherulitic-dendritic’ crystals become more effective due to the larger interfacial area with the glass matrix as
well as the dendritic structure of each mica plate, which helps in crack deflection and crack blunting, to a larger extent.
While modest damage tolerant behavior is observed in case of ‘spherulitic-dendritic’ crystal containing material, severe brittle
fracture of plate like crystals were noted, when both were scratched at 50 N load. 相似文献
6.
HIMANSHU TRIPATHI AREPALLI SAMPATH KUMAR S P SINGH 《Bulletin of Materials Science》2016,39(2):365-376
The aim of the present investigation was to study the role of Al2O3 in the Li2O–CaO–P2O5–SiO2 bioactive glass for improving the bioactivity and other physico-mechanical properties of glass. A comparative study on structural and physico-mechanical properties and bioactivity of glasses were reported. The structural properties of glasses were investigated by X-ray diffraction, Fourier transform infrared spectrometry, scanning electron microscopy and the bioactivity of the glasses was evaluated by in vitro test in simulated body fluid (SBF). Density, compressive strength, Vickers hardness and ultrasonic wave velocity of glass samples were measured to investigate physical and mechanical properties. Results indicated that partial molar replacement of Li2O by Al2O3 resulted in a significant increase in mechanical properties of glasses. In vitro studies of samples in SBF had shown that the pH of the solution increased after immersion of samples during the initial stage and then after reaching maxima it decreased with the increase in the immersion time. In vitro test in SBF indicated that the addition of Al2O3 up to 1.5 mol% resulted in an increase in bioactivity where as further addition of Al2O3 caused a decrease in bioactivity of the samples. The biocompatibility of these bioactive glass samples was studied using human osteoblast (MG-63) cell lines. The results obtained suggested that Li2O–CaO–Al2O3–P2O5–SiO2-based bioactive glasses containing alumina would be potential materials for biomedical applications. 相似文献
7.
Shaaban M. Salem E. M. Antar A. G. Mostafa S. M. Salem S. A. El-badry 《Journal of Materials Science》2011,46(5):1295-1304
(10Li2O–20GeO2–30ZnO–(40-x)Bi2O3–xFe2O3 where x = 0.0, 3, 6, and 9 mol%) glasses were prepared. A number of studies, viz. density, differential thermal analysis, FT-IR spectra,
DC and AC conductivities, and dielectric properties (constant ε′, loss tan δ, AC conductivity, σ
ac, over a wide range of frequency and temperature) of these glasses were carried out as a function of iron ion concentration.
The analysis of the results indicate that, the density and molar volume decrease with an increasing of iron content indicates
structural changes of the glass matrix. The glass transition temperature T
g and onset of crystallization temperature T
x increase with the variation of concentration of Fe2O3 referred to the growth in the network connectivity in this concentration range, while glass-forming ability parameter ΔT decrease with increase Fe2O3 content, indicates an increasing concentration of iron ions that take part in the network-modifying positions. The FT-IR
spectra evidenced that the main structural units are BiO3, BiO6, ZnO4, GeO4, and GeO6. The structural changes observed by varying the Fe2O3 content in these glasses and evidenced by FTIR investigation suggest that the iron ions play a network modifier role in these
glasses while Bi2O3, GeO2, and ZnO play the role of network formers. The temperature dependence of DC and AC conductivities at different frequencies
was analyzed using Mott’s small polaron hopping model and, the high temperature activation energies have been estimated and
discussed. The dielectric constant and dielectric loss increased with increase in temperature and Fe2O3 content. 相似文献
8.
S. M. Abo-Naf R. L. Elwan M. A. Marzouk 《Journal of Materials Science: Materials in Electronics》2012,23(5):1022-1030
SiO2–PbO–Bi2O3 glasses having the composition of 35SiO2–xPbO–(65−x)Bi2O3 (where x = 5, 10, 15, 20, 25, 35, 45; in mol%) have been prepared using the conventional melting and annealing method. Density, molar
volume and Vickers microhardness of the prepared glasses were measured. Infrared (IR) and UV–visible spectroscopic techniques
were used for structural studies of these glasses. Density as well as the microhardness increase systematically and, conversely,
the molar volume decreases with increasing the lead oxide content. This behavior can be explained by the correlation with
the glass structure. Increasing the lead oxide content (≥20 mol%) increases the network former PbO4 groups which can play an important role in increasing the connectivity and compactness of the glass matrix via increasing
the cross-linking with the other constituent silicate and bismuthate structural units. The increased compactness may explain,
in turn, the increase of the density and microhardness. IR spectra reinforce the idea that bismuth participates in the glassy
network predominantly as BiO6 octahedral structural units. UV–VIS optical absorption spectra revealed UV-charge transfer absorption bands related to the
contribution of Pb2+ ions in the region 350–385 nm; in addition to the extrinsic absorption of trace iron impurities in the range 220–290 nm.
In the visible region, three optical bands in the ranges 415–435, 605–650 and 880–890 nm were correlated with the contribution
of electronic transitions in Bi3+ ions. Calculation of the optical mobility gap and the width of the energy tail of glass from the UV–VIS absorption indicated
a slight increase followed by a decrease in their values. The behavior change occurred at the glass in which PbO content is
20 mol% where lead oxide starts to participate into the glassy matrix as a network former. The combination of analytical FTIR
and UV–visible spectroscopy provided a consistent picture of structure–property relations in this glass system. 相似文献
9.
Tulyaganov DU Agathopoulos S Valerio P Balamurugan A Saranti A Karakassides MA Ferreira JM 《Journal of materials science. Materials in medicine》2011,22(2):217-227
New compositions of bioactive glasses are proposed in the CaO–MgO–SiO2–Na2O–P2O5–CaF2 system. Mineralization tests with immersion of the investigated glasses in simulated body fluid (SBF) at 37°C showed that
the glasses favour the surface formation of hydroxyapatite (HA) from the early stages of the experiments. In the case of daily
renewable SBF, monetite (CaHPO4) formation competed with the formation of HA. The influence of structural features of the glasses on their mineralization
(bioactivity) performance is discussed. Preliminary in vitro experiments with osteoblasts’ cell-cultures showed that the glasses
are biocompatible and there is no evidence of toxicity. Sintering and devitrification studies of glass powder compacts were
also performed. Glass-ceramics with attractive properties were obtained after heat treatment of the glasses at relatively
low temperatures (up to 850°C). 相似文献
10.
S. Bindra Narang Shalini Bahel S. Dash 《Journal of Materials Science: Materials in Electronics》2010,21(11):1186-1190
The influences of Bi substitution on microwave dielectric properties of Ba4(La0.5Sm0.5)9.33Ti18O54 solid solutions were investigated. Dielectric ceramics with general formula Ba4(La(0.5−z)Sm0.5Bi
z
)9.33Ti18O54, z = 0.0–0.2 were prepared by conventional solid state route. The structural analysis of all the samples was carried out by
X-ray diffraction and scanning electron microscopy. The dielectric properties were investigated as a function of Bi contents
using open-ended coaxial probe method in the frequency range 0.3–3.0 GHz at room temperature. Dielectric constant varies from
83 to 88 and loss tangent from 2.1 × 10−3 to 5.5 × 10−3 at 3 GHz with temperature coefficient of resonant frequency changing from 106.7 to −8.4 ppm/oC as Bi contents increases from
z = 0.00–0.20. It has been found that dielectric constant and temperature coefficient of resonant frequency improve whereas
loss tangent is adversely affected with increase in Bi substitution. 相似文献
11.
Dehua Xiong Hong Li Jinshu Cheng 《Journal of Materials Science: Materials in Electronics》2010,21(9):882-888
Temperature and frequency dependence on electrical properties (dielectric constant, dielectric loss and conductivity) of Li2O–Na2O–K2O–Al2O3–SiO2(R2O–Al2O3–SiO2) system glass–ceramics used as anodic bonding materials were discussed. The results showed that the main crystal phase of
glass–ceramics was lithium metasilicate (Li2SiO3). Compared with the parent glass, both the dielectric constant and dielectric loss of glass–ceramics decreased, the dielectric
constant and dielectric loss increased gradually with the increasing of the test temperature from room temperature to 400 °C,
Testing frequency (30–300 MHz) had very little influence on the dielectric properties of samples. The electrical conductivity
of glass–ceramics showed a trend of first decrease and then increase with the increasing of temperature. The glass–ceramics
which has a lower dielectric constant, dielectric loss and better stability under high frequency was obtained after an appropriate
heat treatment; it could be used as anodic bonding materials under very high frequency. 相似文献
12.
The Tl2Te–Tl5Te3–Tl9TbTe6 system has been studied using differential thermal analysis, X-ray diffraction, and microhardness measurements. We have mapped out a number of vertical sections, the 680 K isothermal section of its phase diagram, and projections of its polythermal projections of its liquidus and solidus surfaces. The field of solid solutions with the Tl5Te3 structure (δ-phase) has been shown to account for more than 90% of the area of the composition triangle. Tl2Te-based solid solutions (α-phase) exist in a narrow composition region. 相似文献
13.
S. Z. Imamaliyeva T. M. Gasanly V. P. Zlomanov M. B. Babanly 《Inorganic Materials》2017,53(7):685-689
Phase equilibria in the Tl5Te3–Tl9BiTe6–Tl9TbTe6 system have been studied using differential thermal analysis, X-ray diffraction, and microhardness measurements. We have mapped out a number of vertical sections, the 760-K isothermal section of its phase diagram, and projections of its liquidus and solidus surfaces. The composition dependences of lattice parameters and microhardness have been obtained. The system has been shown to contain a continuous series of solid solutions, which crystallize in a tetragonal structure (Tl5Te3 type, sp. gr. I4/mcm). 相似文献
14.
The possibility of using phytic acid as a precursor to synthesize CaO–P2O5–SiO2 glasses by sol–gel method has been explored and the pseudo ternary phase diagram has been established. It was shown that
gel-glasses over a broader range of compositions could be prepared compared to other phosphorus precursors or melt-quenching
method. Furthermore, phytic acid was found to assist calcium being incorporated into glass networks. In vitro tests in simulated
body fluid (SBF) were performed on the above gel–glasses and it was found that they were bioactive over a much broader compositional
range especially at high phosphate content, thus enabling one to design bioactive materials with various degradation rates
by adjusting the phosphate content. 相似文献
15.
D. S. Lipatov A. N. Guryanov M. V. Yashkov M. M. Bubnov M. E. Likhachev 《Inorganic Materials》2018,54(3):276-282
An all-vapor phase MCVD process has been proposed for the fabrication of fiber preforms with a Yb2O3–Al2O3–P2O5–SiO2 multicomponent glass core. We have investigated the tubular preform collapse into a rod and demonstrated approaches capable of preventing P2O5 losses in the central part of the core during the collapse process. Preforms with a flat, perfect step-index profile have been fabricated. 相似文献
16.
Song Chen Shuren Zhang Xiaohua Zhou Bo Li 《Journal of Materials Science: Materials in Electronics》2011,22(3):238-243
The low-temperature co-fired ceramic (LTCC) composites containing quartz based on the eutectic system BaO–Al2O3–SiO2–B2O3 are fabricated at the sintering temperature below 980 °C. Preparation process and sintering mechanism were described and
discussed, respectively. The results indicated that the addition of quartz to the eutectic system can availably improve dielectric
properties of the LTCC composites. In addition, The LTCC composites with optimum compositions, which were obtained by the
regulation of an Al2O3 content in the composite, can express excellent dielectric properties (permittivity: 5.94, 5.48; loss: 7 × 10−4, 5 × 10−4), considerable CTE values (11.7 ppm. °C−1, 10.6 ppm. °C−1) and good mechanical properties (128 MPa,133 MPa). 相似文献
17.
Bo Li Quanyin Long Dinan Duan 《Journal of Materials Science: Materials in Electronics》2016,27(3):2206-2211
BaO–B2O3–SiO2–Al2O3 (BBSA) glass/silica composites synthesized by solid-state reaction method were developed for CBGA packages, and the effects of sintering temperature (900–950 °C) on the phase transformation, microstructure, thermal, mechanical and electrical properties were investigated. XRD results show that the major phases quartz and cristobalite, and the minor phase BaSi2O5 are detected in BBSA composites. Furthermore, it was found that the quartz phase transforms to cristobalite phase at 930–940 °C. The formation of cristobalite phase with higher coefficient of thermal expansion (CTE) led to the increase of CTE value of BBSA composites. However, excessive cristobalite phase content would degrade the mechanical properties and the linearity of thermal expansion of the ceramics. BBSA composites sintered at 920 °C exhibited excellent properties: low dielectric constant and loss (εr = 6.2, tanδ = 10?4 at 1 MHz), high bending strength (179 MPa), high CTE (12.19 ppm/°C) as well as superior linearity of the thermal expansion. 相似文献
18.
Mechanical treatment of Fe2O3, Al and Fe powder mixtures was carried out in a high energy ball mill to synthesize Fe3Al–Al2O3 intermetallic matrix nanocomposite. Different compositions including 3Fe + Al, Fe2O3 + 2Al, 3Fe2O3 + 8Al and Fe2O3 + 3Al+Fe were chosen in this study. Phase development and structural changes occurring during ball milling were investigated
by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results showed that during MA, Fe2O3, Al, and Fe react to give a nanocrystalline Fe3Al intermetallic compound matrix. The presence of pure Fe in initial powder mixture changed the modality of mechanochemical
process from sudden to gradual reaction. The Fe3Al–Al2O3 compound had a finer microstructure and particles size compared to the Fe3Al compound. 相似文献
19.
Bin Li Wenqin Luo Yongya Wang Yanhui Zhang Haiyan Wu 《Journal of Materials Science》2018,53(11):8030-8038
The glass and glass ceramics containing SiO2–CaO–Fe2O3–P2O5 were prepared by sol–gel method. The influence of the Fe contents on the crystallization and local structure of the glass and glass ceramics was systematically investigated. The crystal structure of the glass ceramics was identified by XRD characterization. Hematite phase can be precipitated from the glass matrix in all glass ceramics with various Fe contents, and the crystallographic parameters of hematite were determined by XRD Rietveld refinement. The crystallization kinetics of the glasses was investigated in detail. Relative low activation energies were obtained at low Fe contents. The local structure evolution of the glass and glass ceramics has been studied in-depth by means of FTIR and Mössbauer spectroscopy. Fe element is present both as network former and network modifier which significantly influenced the crystallization activation energies of the glasses. The results of this work may be of great significance for the material design and practical applications of bioactive magnetic glass ceramics for hyperthermia. 相似文献
20.
TiO2–NiO and TiO2–WO3 nanocomposites were prepared by hydrothermal and surface modification methods. The samples were analyzed using X-ray diffraction, Scanning Electron Microscope images, Transmission Electron Microscope, Energy dispersive analysis, Zeta potential, Electrophoretic mobility and Photocatalysis activity measurement. XRD data sets of TiO2–NiO, TiO2–WO3 powder nanocomposite have been studied for the inclusion of NiO, WO3 on the anatase-rutile mixture phase of TiO2 by Rietveld refinement. The cell parameters, phase fraction, the average grain size, strain and bond lengths between atoms of individual phases have been reported in the present work. Shifted positional co-ordinates of individual atoms in each phase have also been observed. 相似文献