共查询到20条相似文献,搜索用时 15 毫秒
1.
Yifei Gu Wei Xiao Linnan Lu Wenhai Huang Mohamed N. Rahaman Deping Wang 《Journal of Materials Science》2011,46(1):47-54
Borate bioactive glasses are receiving increasing attention as scaffold materials for bone repair and regeneration. In this
study, the kinetics and mechanisms of converting three groups of sodium–calcium–borate glasses with varying CaO:B2O3 ratio to hydroxyapatite (HA) in 0.25 M K2HPO4 solution were investigated at 10–70 °C. Glass disks with the composition 2Na2O·(2 − x)CaO·(6 + x)B2O3 (x = 0, 0.5, and 1.0) were immersed for up to 8 days in the potassium phosphate solution. The conversion kinetics to HA were
monitored by measuring the weight loss of the glass, while X-ray diffraction, scanning electron microscopy, and Fourier transform
infrared spectroscopy were used to study structural and compositional changes. All three groups of glasses formed HA on their
surfaces, showing that the glasses were bioactive. At 10–37 °C, the conversion kinetics was well fitted by the contracting
sphere model. Also, the contracting sphere model has a good fit for the early stage of conversion at 70 °C, whereas a three-dimensional
(3D) diffusion model provided a good fit to the data of the later stage. The results of this study provide kinetic and structural
data for the design of borate bioactive glasses for potential applications in bone tissue engineering. 相似文献
2.
Xin Liu Mohamed N. Rahaman Delbert E. Day 《Journal of materials science. Materials in medicine》2013,24(3):583-595
Microfibrous bioactive glasses are showing a considerable capacity to heal soft tissue wounds, but little information is available on the mechanism of healing. In the present study, the conversion of microfibrous borate bioactive glass (diameter = 0.2–5 μm) with the composition designated 13-93B3 (5.5 Na2O, 11.1 K2O, 4.6 MgO, 18.5 CaO, 3.7 P2O5, 56.6 B2O3 wt%) was evaluated in vitro as a function of immersion time in a simulated body fluid (SBF) at 37 °C using structural and chemical techniques. Silicate 45S5glass microfibers (45 SiO2, 24.5 Na2O, 24.5 CaO, 6 P2O5 wt%) were also studied for comparison. Microfibrous 13-93B3 glass degraded almost completely and converted to a calcium phosphate material within 7–14 days in SBF, whereas >85 % of the silica remained in the 45S5 microfibers, forming a silica gel phase. An amorphous calcium phosphate (ACP) product that formed on the 13-93B3 microfibers crystallized at a slower rate to hydroxyapatite (HA) when compared to the ACP that formed on the 45S5 fibers. For immersion times >3 days, the 13-93B3 fibers released a higher concentration of Ca into the SBF than the 45S5 fibers. The fast and more complete degradation, slow crystallization of the ACP product, and higher concentration of dissolved Ca in SBF could contribute to the capacity of the microfibrous borate 13-93B3 glass to heal soft tissue wounds. 相似文献
3.
Huang W Day DE Kittiratanapiboon K Rahaman MN 《Journal of materials science. Materials in medicine》2006,17(7):583-596
Bioactive glasses with controllable conversion rates to hydroxyapatite (HA) may provide a novel class of scaffold materials
for bone tissue engineering. The objective of the present work was to comprehensively characterize the conversion of a silicate
bioactive glass (45S5), a borate glass, and two intermediate borosilicate glass compositions to HA in a dilute phosphate solution
at 37°C. The borate glass and the borosilicate glasses were derived from the 45S5 glass by fully or partially replacing the
SiO2 with B2O3. Higher B2O3 content produced a more rapid conversion of the glass to HA and a lower pH value of the phosphate solution. Whereas the borate
glass was fully converted to HA in less than 4 days, the silicate (45S5) and borosilicate compositions were only partially
converted even after 70 days, and contained residual SiO2 in a Na-depleted core. The concentration of Na+ in the phosphate solution increased with reaction time whereas the PO43– concentration decreased, both reaching final limiting values at a rate that increased with the B2O3 content of the glass. However, the Ca2+ concentration in the solution remained low, below the detection limit of atomic absorption, throughout the reaction. Immersion
of the glasses in a mixed solution of K2HPO4 and K2CO3 produced a carbonate-substituted HA but the presence of the K2CO3 had little effect on the kinetics of conversion to HA. The kinetics and mechanisms of the conversion process of the four
glasses to HA are compared and used to develop a model for the process. 相似文献
4.
Wang Q Huang W Wang D Darvell BW Day DE Rahaman MN 《Journal of materials science. Materials in medicine》2006,17(7):641-646
The preparation of hollow hydroxyapatite (HA) microspheres as potential drug-delivery vehicles was investigated. A lithium-calcium-borate
(10Li2O-15CaO-75B2O3) (mol%) glass, made by fusing the components at 1100°C for 1 h, was ground to a powder and passed through a flame at ∼1400°C
to spheroidize the particles. The resulting glass microspheres (106–125 μm in diameter) were reacted in 0.25 M K2HPO4 solution for 5 days at 37°C and pH 10–12, resulting in the formation of porous, hollow microspheres of a calcium phosphate
(Ca-P) material with external diameters similar to those of the original glass particles. Heat treatment at 600°C for 4 h
partially converted the Ca-P material to HA, as confirmed by X-ray diffraction, and also increased the strength of the hollow
microspheres. 相似文献
5.
K. V. Shah M. Goswami S. Manikandan V. K. Shrikhande G. P. Kothiyal 《Bulletin of Materials Science》2009,32(3):329-336
The degradation behaviour of phosphate glass with nominal composition, 40Na2O-10BaO-xB2O3-(50-x)P2O5, where 0 ≤ x ≤ 20 mol%, was studied in water, HCl and NaOH solutions at room temperature to 60°C for different periods extending up to
300 h. These glasses were synthesized by conventional melt-quench technique. Dissolution rates were found to increase with
B2O3 content in the glass. The dissolution rates for the glass having 10 mol% B2O3 were found to be 0·002 g/cm2 and 0·015 g/cm2 in distilled water and 5% NaOH solution, respectively, at room temperature after 225 h of total immersion period, whereas
it increased considerably to 0·32 g/cm2 in 5% NaOH at 60°C after 225 h. However, glass samples with x = 15 and 20 mol% B2O3 were dissolved in 5% HCl solution after 5 h immersion. The degradation behaviour has been correlated with the structural
features present in the glass. The optical microscopy of the corroded surface revealed that the corrosion mechanism were different
in acid and alkali media. 相似文献
6.
Raman spectra of sodium borosilicate glasses with a wide range of Na2O/B2O3 ratios were systematically measured. Variations of the spectra with glass composition were studied to interpret the implied
distribution of Na+ ions between silicate and borate units. When Na2O/B2O3 is less than 1, all Na+ ions are associated with borate units as indicated by the absence of the 1100 cm−1 band of Si-O− non-bridging bond stretching. For the (1−x)Na2O · SiO2 ·xB2O3 glass withx≦0.4 the peak-height ratio of the 950 cm−1 band to the 1080 cm−1 band was used to analyse semiquantitatively the distribution of the Na+ ions between silicate and borate units. Sodium ions are divided between silicate and borate units approximately in proportion
to the amount of SiO2 and B2O3 present in these glasses. Some of the high sodium content glasses were crystallized and their spectra were compared with
the bulk glass spectra. The distribution of Na+ ions in the glass was quite different from their distribution after crystallization. Spectra of high silica glasses that
had been heat-treated for phase separation indicated exclusion of borate units from the silica network and the formation of
borate groups. For high boron content glasses, no change was observed on heat treatment. Raman bands due to borate groups
seem to be little affected by their environments.
Also affiliated with the Department of Geosciences. 相似文献
7.
Behnamghader A Bagheri N Raissi B Moztarzadeh F 《Journal of materials science. Materials in medicine》2008,19(1):197-201
The composites of hydroxyapatite (HA) with 2.5 and 5 wt% of a double oxide (50 mol% CaO and 50 mol% P2O5) glass were prepared using the conventional powder mixing and sintering method. The addition of the glass significantly enhanced
the decomposition process of HA into alpha tricalcium phosphate (α-TCP) for bodies sintered at 1,300 and 1,350 °C and β-TCP
phases for the ones sintered at 1,200, 1,250 and 1,300 °C. Microstructural characteristics, phase development and thermal
behaviour were studied by SEM, XRD and STA. The effects of TCP phase content and phase transformation from β-TCP to α-TCP
on the sintering are discussed. The characterizations revealed considerable content of TCP in the form of large semi-islands
due to important reactions between the fine HA and the glass mixed powders. 相似文献
8.
Xin Liu Zongping Xie Changqing Zhang Haobo Pan Mohamed N. Rahaman Xin Zhang Qiang Fu Wenhai Huang 《Journal of materials science. Materials in medicine》2010,21(2):575-582
The objective of this work was to evaluate borate bioactive glass scaffolds (with a composition in the system Na2O–K2O–MgO–CaO–B2O3–P2O5) as devices for the release of the drug Vancomycin in the treatment of bone infection. A solution of ammonium phosphate,
with or without dissolved Vancomycin, was used to bond borate glass particles into the shape of pellets. The in vitro degradation
of the pellets and their conversion to a hydroxyapatite-type material in a simulated body fluid (SBF) were investigated using
weight loss measurements, chemical analysis, X-ray diffraction, and scanning electron microscopy. The results showed that
greater than 90% of the glass in the scaffolds degraded within 1 week, to form poorly crystallized hydroxyapatite (HA). Pellets
loaded with Vancomycin provided controlled release of the drug over 4 days. Vancomycin-loaded scaffolds were implanted into
the right tibiae of rabbits infected with osteomyelitis. The efficacy of the treatment was assessed using microbiological
examination and histology. The HA formed in the scaffolds in vivo, resulting from the conversion of the glass, served as structure
to support the growth of new bone and blood vessels. The results in this work indicate that bioactive borate glass could provide
a promising biodegradable and bioactive material for use as both a drug delivery system and a scaffold for bone repair. 相似文献
9.
Hezhou Ye Xing Yang Liu Hanping Hong 《Journal of materials science. Materials in medicine》2009,20(4):843-850
Fourier transform infrared (FTIR) spectroscopy was employed to characterize the phase changes of hydroxyapatite (Ca10(PO4)6(OH)2, HA) in a titanium/HA biocomposite during sintering. The effects of sintering temperature and the presence of Ti on the decomposition
of HA were examined. It was observed that pure HA was stable in argon atmosphere at temperatures up to 1,200°C, although the
dehydroxylation of pure HA was promoted by the increase in sintering temperature. In the Ti/HA system, on the other hand,
the presence of Ti accelerated dehydroxylation and the decomposition of HA was detected at a temperature as low as 800°C.
Tetracalcium phosphate (Ca4P2O9, TTCP) and calcium oxide (CaO) were the dominant products of the decomposition, but no tricalcium phosphate (Ca3(PO4)2, TCP) was detected due to phosphorus diffusion and possible reactions during the thermal process. The main decomposed constituents
of HA in Ti/HA system at high temperatures (≥1,200°C) would be CaO and amorphous phases. 相似文献
10.
《Materials science & engineering. C, Materials for biological applications》2006,26(8):1434-1438
The biodegradable hydroxyapatite (HA) was synthesized by hydrolysis and characterized using high temperature X-ray diffraction (HT-XRD), differential thermal analysis and thermogravimetry (DTA/TG), and scanning electron microscopy (SEM). The in situ phase transformation of the HA synthesized from CaHPO4·2H2O (DCPD) and CaCO3 with a Ca / P = 1.5 in 2.5 M NaOH(aq) at 75 °C for 1 h was investigated by HT-XRD between 25 and 1500 °C. The HA was crystallized at 600 °C and maintained as the major phase until 1400 °C. The HA steadily transformed to the α-tricalcium phosphate (α-TCP) which became the major phosphate phase at 1500 °C. At 700 °C, the minor CaO phase appeared and vanished at 1300 °C. The Na+ impurity from the hydrolysis process was responsible for the formation of the NaCaPO4 phase, which appeared above 800 °C and disappeared at 1200 °C. 相似文献
11.
A hydroxyapatite (HA, Ca10(PO4)6(OH)2), transformed from a calcium-containing borate glass, has been investigated for its protein adsorption and chromatographic
characteristics. Microspheres of the borate glass were transformed into HA by reacting them with a 0.25 M phosphate (K2HPO4) solution for 24 h at 37 °C (pH 9.0). The HA microspheres with a diameter of 45–90 μm were hand packed into a steel column
(4.6 mm × 80 mm) and used to separate a binary protein mixture of bovine serum albumin (BSA) and lysozyme. HA microspheres,
with a diameter <45 μm, were used for separating a protein mixture of BSA, myoglobin, and lysozyme. These microspheres had
a diameter that was 20–30 times larger than commercial HA column packing spherical particles, 2–3 μm, but these microspheres
had a six times larger surface area and a more uniform spherical shape. These advantages compensated for their larger size
and the separation results were comparable to those commercially available HA columns in the separation of the proteins studied.
These unique HA microspheres, made from microspheres of a borate glass, are considered to be useful as packing materials for
protein separation in chromatography. 相似文献
12.
Macroporous calcium phosphate glass-ceramic with an initial glass composition of 60CaO ⋅ 30P2O5⋅ 3TiO2⋅ 7Na2O in mol% was successfully prepared by sintering the mixture compact consisting of calcium phosphate glass and sucrose powders, which was formed using a two-step pressing technique. After burning off the sucrose phase, a 3D interconnected macroporous structure was formed in the sintered body, in which the skeleton consisting of the calcium phosphate glass-ceramic (including β -calcium pyrophosphate and β -tricalcium phosphate as the crystalline phases) was transformed from the initial glass during the sintering. The macropores with several hundred microns in diameter and the large interconnection size (∼ 100 μ m), which result from the controllably large-sized sucrose particles and the hot-pressing at a little higher temperature than the sucrose’s melting point, are believed to meet the requirements for cell adhesion and bone tissue regeneration well. Moreover, in vitro dissolution behavior study indicates that the calcium phosphate glass-ceramic is soluble to an acetic acid solution of pH 5–7. These, together with the simplicity and feasibility of the innovative fabrication method itself, show that the formed porous glass-ceramic has a promising potential for application to a scaffold for bone tissue engineering. 相似文献
13.
O P Thakur Devendra Kumar O M Parkash Lakshman Pandey 《Bulletin of Materials Science》1995,18(5):577-585
65(SrO·TiO2)−35(2SiO2·B2O3) wt% glass was synthesized. Differential thermal analysis study shows one exothermic peak which shifts towards higher temperature
with increasing heating rate. Glass ceramics prepared by controlled crystallization of strontium titanate borosilicate glass
produce uniform distribution of crystallites in a glassy matrix. Attempt was made to crystallize strontium titanate phase
in this glass ceramic. Different phases precipitated out during ceramization have been identified by X-ray diffraction. It
appears that due to high reactivity of SrO with B2O3, strontium borate crystallizes as principal phase followed by TiO2 (rutile) and Sr3Ti2O7 phases. Dielectric constant of these glass ceramics was observed to be more or less temperature independent over wide range
of temperatures with low values of dielectric constant and dissipation factor. 相似文献
14.
《Materials Letters》1988,6(10):347-350
For fabricating glass ceramics containing calcium apatite as the major phase, a series of glasses of composition 50[xCaO-(1−x)P2O5]-25Al2O3-25B2O3 (mol%; 0.667 <x< 0.773) were heat-treated at various temperatures. X-ray diffraction and DTA study indicated that calcium apatite is precipitated at about 725°C from all glasses but it is decomposed to β-tricalcium phosphate at about 900°C. AlPO4 is found as the major phase for the lower CaO content. Dependence of the precipitated phases on the glass composition is tentatively interpreted in relation to the glass structure. 相似文献
15.
Anthony L. B. Maçon Sungho Lee Gowsihan Poologasundarampillai Toshihiro Kasuga Julian R. Jones 《Journal of Materials Science》2017,52(15):8858-8870
The effect of the substitution of strontium for calcium in the tertiary the SiO2–CaO–P2O5 sol–gel bioactive glass 58S (60SiO2·36CaO·4P2O5, mol%) on its structure and its chemical durability on soaking in simulated body fluids was investigated. 58S was selected as a starting composition, and substitution for calcium was carried out from 0 to 100% with an increment of 25%. A novel phosphate source of diethylphosphatoethyltriethoxysilane, which consists of Si and P connected with ethylene group, was used in this work. XRD and FTIR showed that the gels obtained following drying at 130 °C had a typical sol–gel structure, where a continuous amorphous silica gel network and surface bound mineral salts of Ca(NO3)2 and Sr(NO3)2. Once the gels were heat stabilised to decompose nitrates and incorporate the cations into the network, samples containing Sr formed a strontium silicate crystalline phase. With increasing levels of Sr in the composition, the overall crystallinity of the glass–ceramic increased, while, at the maximum substitution of 100% SrO, macroscopic phase separation was observed, characterised by needle-like crystals of strontium apatite (Sr5(PO4)3OH) and strontium silicate (Sr2SiO4) phases in addition to amorphous regions. Dissolution experiments in Tris-buffered solution showed Sr successfully released into the media even though it existed as a crystalline phase in the glass–ceramic. Further, the glass–ceramics induced nucleation and growth of carbonated hydroxyapatite (HA) on their surface suggesting potential bioactivity of the materials. At higher substitutions (75 and 100% SrO for CaO), HA nucleation was not found to occur this may have been due to low amount of phosphate released from the original glass–ceramic as a result of it being locked up in the strontium apatite phase. 相似文献
16.
Zhu Q De With G Dortmans LJ Feenstra F 《Journal of materials science. Materials in medicine》2004,15(11):1187-1191
Near net-shape fabrication of hydroxyapatite (HA) glass composites has been attempted by infiltrating a glass into porous HA performs. Main efforts were put to develop glasses that are chemically compatible with HA at elevated temperatures. After extensive investigations in the phosphate and borosilicate systems, glasses of (50-55)SiO2-(20-25)B2O3-(10-20)Li2O-(0-6)CaO (wt%) composition were successfully developed. The glass shows good chemical compatibility with HA at elevated temperatures. Dense HA/glass composites can be fabricated at 850–950 C by the melt infiltration process. Investigations demonstrated a good near net-shape capability of the process, where the linear shrinkage induced by the infiltration process is less than 0.1%. Preliminary mechanical tests showed that the fracture strength and toughness of the infiltrated HA/glass composite are comparable with dense HA. 相似文献
17.
N. J. Lakhkar E. A. Abou Neel V. Salih J. C. Knowles 《Journal of materials science. Materials in medicine》2009,20(6):1339-1346
This preliminary study focuses on the effect of adding SrO to a Ti-containing quaternary phosphate glass system denoted by
P2O5–Na2O–CaO–TiO2. The following four different glass compositions were manufactured: 0.5P2O5–0.17Na2O–0.03TiO2–(0.3−x)CaO–xSrO where x = 0, 0.01, 0.03 and 0.05. Structural characterisation revealed glass transition temperatures in the range 427–437°C and the
presence of sodium calcium phosphate as the dominant phase in all the glasses. Degradation and ion release studies conducted
over a 15-day period revealed that the Sr-containing glasses showed significantly higher degradation and ion release rates
than the Sr-free glass. Cytocompatibility studies performed over a 7-day period using MG63 cells showed that the addition
of 5 mol% SrO yielded glasses with cell viability nearly equivalent to that observed for quaternary TiO2 glasses. 相似文献
18.
H. A. Abo-Mosallam H. Darwish S. M. Salman 《Journal of Materials Science: Materials in Electronics》2010,21(9):889-896
The crystallization behaviour of some soda lime silicate glasses modified by ZnO/CaO replacement to give the composition (Na2O)2·CaO1−x
·(ZnO)
x
·3SiO2 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been investigated using differential scanning calorimetry (DSC) and X-ray diffraction
analysis (XRD). The thermal expansion coefficients and AC electrical properties in the frequency range 40 Hz–5 MHz of the
obtained crystalline products were determined. Two forms of sodium calcium silicate (Na4CaSi3O9 & Na2Ca2Si3O9), sodium metasilicate-Na2SiO3, two types of sodium zinc silicate (Na1.31Zn0.655Si1.345O4 & Na2ZnSiO4) and α-quartz phases were mostly developed in the crystallized glasses using various heat-treatment processes. The coefficient
of thermal expansion of the obtained glass–ceramic materials are between 120 × 10−7°K−1 and 168 × 10−7°K−1 in the 25°–600 °C temperature range. The increase of frequency generally resulted in the increase of the conductivity and
decrease the dielectric constant together with the loss tangent of the glass–ceramic materials. 相似文献
19.
《Materials Letters》2006,60(17-18):2110-2114
Nanoparticle zinc phosphate dihydrate was prepared by solid-state reaction at ambient temperature from Na3PO4·12H2O and ZnSO4·7H2O, and characterized by X-ray, Raman, FT-IR spectra and TEM. Thermochemical study was performed by a RD496-III microcalorimeter at 298.15 K. The results reveal that the obtained product is Zn3(PO4)2·2H2O with spherical shape and particle size is between 40–50 nm. The standard enthalpy value for above reaction is calculated as − 45.793 kJ·mol− 1. The standard enthalpy of formation for zinc phosphate dihydrate is recommended as − 3788.607 kJ·mol− 1. 相似文献
20.
O P Thakur Devendra Kumar O M Parkash Lakshman Pandey 《Bulletin of Materials Science》1996,19(2):393-404
Glass of the nominal composition 64 wt%(SrO·TiO2)·35 wt%(2SiO2·B2O3)-1 wt%(CoO) was prepared. The glass samples were subjected to heat treatment at 900 and 950 C. The phase progression in these
glass ceramics from X-ray diffraction studies shows the formation of Sr2B2O5 as primary crystalline phase followed by rutile (TiO2), Sr3Ti2O7, SrB2Si2O8 and Sr3B2SiO8 as secondary phases. The first DTA exothermic peak of glass corresponds to the crystallization of Sr2B2O5, rutile and Sr3Ti2O7 phase while second crystallization peak may be assigned to the formation of SrB2Si2O8 and Sr3B2SiO8 phases. From microstructure studies we find that strontium borate grows with larger grain size whereas the other phases like
Sr3Ti2O7, TiO2 appear smaller in size. Cobalt oxide content in the strontium titanate borosilicate glass ceramic gives the thermal stability
to dielectric behaviour and decreases the dielectric loss.
Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995 相似文献