共查询到20条相似文献,搜索用时 31 毫秒
1.
Marc Bohner † Jacques Lemaitre ‡ Terry A. Ring 《Journal of the American Ceramic Society》1996,79(6):1427-1434
Several additives were selected to increase the setting time of calcium phosphate cements made of β-tricalcium phosphate (β-TCP; β-Ca3 (PO4 )2 )-phosphoric acid-water mixtures. The effects of the additives, i.e., sulfate, pyrophosphate, and citrate ions, are presented in this study. The results show that they all increased the setting time of the cement. Their effectiveness at increasing the setting time is in the order pyrophosphate > citrate > sulfate. The effect of sulfate ions on the setting time is increasingly large below a concentration of 0.1 M . Above that concentration, calcium sulfate dihydrate (CSD; CaSO4 -2H2 O) crystals nucleate and act as nuclei for dicalcium phosphate dihydrate (DCPD; CaHPO4 -2H2 O) crystals, which are the normal product of the setting reaction. This decreases the setting time and decreases the DCPD crystal size, resulting in an increase of the tensile strength of the cement. 相似文献
2.
Maria-Pau Ginebra Enrique Fernández Ferdinand C. M. Driessens Josep A. Planell 《Journal of the American Ceramic Society》1999,82(10):2808-2812
Some of the formulations of apatitic calcium phosphate bone cements are based on the hydrolysis of α-tricalcium phosphate (α-Ca3 (PO4 )2 , α-TCP). In this work the hydrolysis kinetics of α-TCP are studied, taking into account the particle-size distribution of the initial powder, to identify the mechanisms that control the reaction in its successive stages. The temporal evolution of the depth of reaction is calculated from the degree of reaction data, measured by X-ray diffractometry. A kinetic model is proposed, which suggests the existence of two rate-limiting mechanisms: initially, the surface area of the reactants and, subsequently, the diffusion through the hydrated layer formed around the reactants. For the specific particle size and preparation used, the controlling mechanism changeover takes place after 16 h of reaction. 相似文献
3.
The hydrolysis of α-tricalcium phosphate (α-TCP) in a simulated body fluid (SBF) at 37°C was investigated. The hydration rate was found to be slower in SBF than that in deionized water. The concentration of ions in SBF was monitored by ICP. The hydrolysis product, which was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infra red, and X-ray photoelectron spectroscopy, was determined to be carbonate-containing, calcium-deficient hydroxyapatite (CO3 −CDHAp) with Mg2+ , Na+ , and Cl− impurities similar to the biological apatite. An amorphous layer on the α-TCP surface was found to be the precursor of the apatite phase, which may either form crystalline apatite or may decompose back to α-TCP at a lower temperature. 相似文献
4.
Liam M. Grover Uwe Gbureck Adrian J. Wright Jake E. Barralet 《Journal of the American Ceramic Society》2005,88(11):3096-3103
Despite numerous reports of calcium phosphate cement materials, a calcium cement that sets to form a matrix consisting of a pyrophosphate phase has not been reported. The formulation of such a material from the mixture of α-tricalcium phosphate (TCP), β-TCP, or tetracalcium phosphate with a solution containing pyro- and orthophosphoric acid is reported in this study. The effects of liquid and solid compositions on the setting times, compressive strengths and phase compositions of the resultant cements were investigated. It was found that cements could be produced that set to form up to 28 wt% dicalcium pyrophosphate, which appeared by comparison with Rietveld refinement and chemical methods to be entirely amorphous in nature. The solubilities of the different solid components were shown to have a marked effect on the composition of the cements. The strongest cement formulations exhibited compressive strengths comparable with those previously reported in the literature for brushite cements and set within clinically relevant time scales. This class of cement would appear to demonstrate potential as a bone replacement material. 相似文献
5.
A mechanistic model for the kinetics of hydrolysis of α-tricalcium phosphate (α–Ca3 (PO4 )2 or α-TCP) to hydroxyapatite (Ca10− x (HPO4 ) x (PO4 )6− x (OH)2− x or HAp) has been developed. The model is based on experimental hydrolysis rate data obtained using isothermal calorimetry. Analysis of the kinetic data according to the general kinetics models in terms of the fractional degree of reaction and time suggests the hydrolysis to be controlled by different rate-limiting mechanisms as reaction proceeds. Initially, the hydrolysis kinetics depend on the surface area of the anhydrous α-TCP. Subsequently, they change to a dependence on the rate of HAp product formation controlled by a nucleation and growth mechanism. The model predicts that HAp nuclei form at essentially one time and growth occurs in two dimensions, leading to a platelike morphology. The change in the reaction mechanism occurs at a fractional degree of hydrolysis, which does not change significantly with temperature in the range of 37°–56°C. 相似文献
6.
Masatomo Yashima Yoichi Kawaike Masahiko Tanaka 《Journal of the American Ceramic Society》2007,90(1):272-274
Unit-cell parameters of the α-tricalcium phosphate [TCP; Ca3 (PO4 )2 ] were investigated using high-resolution synchrotron powder diffraction and the Rietveld method. The diffraction experiment was conducted at 29°C at the BL-15XU experimental station of SPring-8, Japan. Precise unit-cell parameters of the α-TCP were obtained; a =12.87271 (9), b =27.28034(8), c =15.21275(12) Å, α=γ=90°, and β=126.2078(4)°. The calculated density of α-TCP (2.8677 g/cm3 ) is smaller than that of β-TCP, indicating the "looser" structure of α-TCP. 相似文献
7.
Submicrometer-sized, pure calcium hydroxyapatite (HA, (Ca10 (PO4 )6 (OH)2 )) and β-tricalcium phosphate (β-TCP, Ca3 (PO4 )2 ) bioceramic powders, that have been synthesized via chemical precipitation techniques, were used in the preparation of aqueous slurries that contained methyl cellulose to manufacture porous (70%–95% porosity) HA or β-TCP ceramics. The pore sizes in HA bioceramics of this study were 200–400 μm, whereas those of β-TCP bioceramics were 100–300 μm. The pore morphology and total porosity of the HA and β-TCP samples were investigated via scanning electron microscopy, water absorption, and computerized tomography. 相似文献
8.
Theresa Brückner Katrin Hurle Anja Stengele Jürgen Groll Uwe Gbureck 《Journal of the American Ceramic Society》2018,101(5):1830-1834
Magnesium phosphate cements have attracted an increasing attention for biomedical applications in the past years due to their high mechanical performance and fast in vivo degradation at bony implantation sites. Cements are usually multicomponent mixtures of cement raw powders and setting regulators, whereas the latter may have a detrimental effect on the biocompatibility. Here, we demonstrate that following prolonged grinding of trimagnesium phosphate (Mg3(PO4)2, farringtonite), a mechanically induced disordering reaction strongly altered farringtonite reactivity such that self‐setting cements without further components were formed with a compressive strength of up to 11 MPa. Time‐resolved X‐ray diffraction analysis revealed that the formation of a nanocrystalline magnesium phosphate phase during grinding was responsible for cement setting to the highly hydrated magnesium phosphate mineral cattiite (Mg3[(PO4)2?22H2O), whereas crystalline farringtonite showed practically no setting reaction. 相似文献
9.
Marie-Noëlle de Noirfontaine Sandrine Tusseau-Nenez Marcel Signes-Frehel Gilles Gasecki Caroline Girod-Labianca 《Journal of the American Ceramic Society》2009,92(10):2337-2344
Alite is the major compound of anhydrous Portland cement: it is composed of tricalcium silicate Ca3 SiO5 (C3 S) modified in composition and crystal structure by ionic substitutions. Alite is also the main hydraulic phase of cement and the most important for subsequent strength development. Using raw meals (rich in Ca3 P2 O8 ) as alternative fuels in cement plants raises the question about the effect of phosphorus on C3 S and its consequences on reactivity with water. This paper deals with a systematic study of C3 S triclinic T1 polymorph doped with P2 O5 in the range 0–0.9 wt%. All the samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and electron-microprobe analysis. The appearance of a phase rich in phosphorus is shown. It displays a structure derivative of the α'H –Ca2 SiO4 polymorph, noted α'H –C2 S(P). As phosphorus content increases, C3 S is more and more decomposed into free lime and α'H –C2 S(P). The α'H phase was detected from 0.1 wt% P2 O5 and located at the interfaces of C3 S grains. Two identification keys are proposed in order to highlight the α'H –C2 S(P) phase: the XRD angular window at 2θCu =32.8°–33.2° and a smooth aspect on SEM micrographs. 相似文献
10.
Takayuki Nagano Shinji Fujisaki Koji Sato Koji Hataya Yuji Iwamoto Mikihiro Nomura Shin-Ichi Nakao 《Journal of the American Ceramic Society》2008,91(1):71-76
An amorphous silica membrane with an excellent hydrogen/nitrogen (H2 /N2 ) permselectivity of >10 000 and a He/H2 permselectivity of 11 was successfully synthesized on a γ-alumina (γ-Al2 O3 )-coated α-alumina (α-Al2 O3 ) porous support by counter diffusion chemical vapor deposition using tetramethylorthosilicate and oxygen at 873 K. An amorphous silica membrane possessed a high H2 permeance of >1.0 × 10−7 mol·(m2 ·s·Pa)−1 at ≥773 K. The dominant permeation mechanism for He and H2 at 373–873 K was activated diffusion. On the other hand, that for CO2 , Ar, and N2 at 373–673 K was a viscous flow. At ≥673 K, that for CO2 , Ar, and N2 was activated diffusion. H2 permselectivity was markedly affected by the permeation temperature, thickness, and pore size of a γ-Al2 O3 mesoporous intermediate layer. 相似文献
11.
Wenhai Huang Delbert E. Day Mohamed N. Rahaman 《Journal of the American Ceramic Society》2008,91(6):1898-1904
In our earlier work, it was found that particles of a ternary alkali-borate glass, containing either CaO or BaO, converted completely to a crystalline phosphate of calcium or barium when reacted in an aqueous phosphate solution at 37°C. The present work is an extension of our earlier work to investigate the conversion of tetranary borate glass with the composition 10Li2 O·10CaO·10(AeO or T2 O3 )·60B2 O3 (weight percent), where Ae is the alkai-earth metal Mg or Ba, and T is the transition metal La, Sm, or Dy. In the experiments, particles of each glass (150–300 μm) were reacted in 0.25 M K2 HPO4 solution with a starting pH of ∼9.0 at 37°C. Weight loss and pH measurements indicated that the reaction was complete after 30–50 h, yielding an amorphous product. X-ray fluorescence showed that the as-formed product consisted of a calcium phosphate phase that contained the alkali-earth metal or transition metal present in the starting glass. Heating the as-formed material for 8 h at 600°–700°C produced a mixture of two crystalline phosphates: calcium phosphate and an alkali-earth or transition metal phosphate. The kinetics and mechanism of converting tetranary borate glass to phosphate materials are discussed and compared with data from earlier work for the conversion of ternary borate glass. 相似文献
12.
Recently, premixed calcium phosphate cement pastes have been proposed as biomaterials for bone tissue repair and regeneration. Use of premixed pastes saves the time and removes an extra step during a medical operation. α-Tricalcium phosphate (α-TCP) based cements set to form calcium deficient hydroxyapatite which has a moderate bioresorbtion speed. α-TCP cements require a setting aid, usually a sodium or potassium phosphate salt, to speed up the setting process. Within the current research we investigated which setting aid has significant advantage, if α-TCP is used in form of non-aqueous premixed paste. This approach offers the application of simple ingredients to produce a premixed calcium phosphate cement. The following properties of cement formulations were evaluated: cohesion, phase composition, microstructure, pH value of the liquid surrounding the cement, and compressive strength.Compositions using mixture of basic and acidic potassium phosphate salts (KH2PO4 and K2HPO4) in sufficient amounts give the best overall results (adequate cohesion and pH of the surrounding liquid, hydrolysis of starting materials within 48 h, and compressive strength of 12 ± 3 MPa). Cement prepared with basic sodium phosphate salt (Na2HPO4) as setting aid had considerably higher compressive strength 22 ± 1 MPa, but the pH of the surrounding liquid was basic (9.0). 相似文献
13.
Fine hydroxyapatite (HA) powders were prepared by mechanically activating a mixture of calcium oxide and brushite powders in a high-energy shaker mill. A defective HA phase was formed when the starting powder mixture was activated for ≤20 h. When the mixture was calcined at 800°C, it was converted to β-tricalcium phosphate. In contrast, a nanocrystalline HA phase was formed when the mechanical activation was extended to 30 h. The material was transformed to a HA compound (Ca10 (PO4 )6 (OH)2 ) of high crystallinity when it was calcined at 800°C. 相似文献
14.
Hirotaka Fujimori Naoya Sato Koji Ioku Seishi Goto Tetsuo Yamada 《Journal of the American Ceramic Society》2000,83(9):2251-2254
The spin-lattice relaxation times, T 1 , in α-, β-, and amorphous Si3 N4 have been obtained for the first time, using a multiple-pulse saturation recovery method. The saturation recovery of the 29 Si magnetization follows exponential behavior under magic-angle spinning conditions, within the limits of experimental error. A rather wide dispersion of T 1 values is observed for the phases of Si3 N4 : 284 ± 29 min (–46.686 ppm) and 260 ± 23 min (–48.812 ppm) for the α-phase, 36 ± 4 min for the β-phase, and 11 ± 1 min for the amorphous phase, assuming an exponential recovery. The values obtained for the exponent in the power-law fitting are 0.599(9) (–46.686 ppm) and 0.61(1) (–48.812 ppm) for the α-phase, 0.52(2) for the β-phase, and 0.53(3) for the amorphous phase. 相似文献
15.
Toshifumi Sugama Marita Allan Janet M. Hill 《Journal of the American Ceramic Society》1992,75(8):2076-2087
We investigated the characteristics of calcium phosphate cements (CPC) prepared by an exothermic acid–base reaction between NH4 H2 PO4 -based fertilizer (Poly-N) and calcium aluminate compounds (CAC), such as 3CaO · Al2 O3 (C3 A), CaO · Al2 O3 (CA), and CaO · 2Al2 O3 (CA2 ), in a series of integrated studies of reaction kinetics, interfacial reactions, in-situ phase transformations, and microstructure development. Two groups were compared: untreated and hydrothermally treated CPC specimens. The extent of reactivity of CAC with Poly-N at 25°C was in the following order: CA > C3 A ≫ CA2 . The formation of a NH4 CaPO4 · x H2 O salt during this reaction was responsible for the development of strength in the CPC specimens. The in-situ phase transformation of amorphous NH4 CaPO4 · x H2 O into crystalline Ca5 (PO4 )3 (OH) and the conversion of hydrous Al2 O3 gel →γ-AIOOH occur in cement bodies during exposure in an autoclave to temperatures up to 300°C. This phase transformation significantly improved mechanical strength. 相似文献
16.
Gaoxiang Chen Wanwan Li Bingxia Zhao Kang Sun 《Journal of the American Ceramic Society》2009,92(4):945-948
Calcium polyphosphate (CPP) was added to hydroxyapatite (HA) to develop a novel biphasic calcium phosphate (BCP). The effects of varying CPP dosage on the sintering property, the mechanical strength, and the phase compositions of HA were investigated. Results showed that CPP reacted with HA and produced β-calcium phosphate (β-TCP) and H2 O and that an excessive dosage of CPP (>10 wt%) obtained a novel BCP of β-TCP/amorphous-CPP, while a lesser dosage of CPP (<10 wt%) obtained a traditional BCP (HA/β-TCP). The porous β-TCP/amorphous-CPP scaffolds (porosity of 66.7%, pore diameter of 150–450 μm, and compressive strength of 6.70±1.5 MPa) were fabricated and their in vitro degradation results showed a significant improvement of degradation with the addition of CPP. 相似文献
17.
Hideki Ishida Satoru Yamazaki Kaori Sasaki Yoshihiko Okada Takeshi Mitsuda 《Journal of the American Ceramic Society》1993,76(7):1707-1712
α-C2 SH can be synthesized by hydrothermal treatment of lime and silicic acid for 2 h at 200°C. When heated to 390–490°C, α-C2 SH dissociates through a two-step process to form an intermediate phase plus some γ-C2 S. This appears to be a new dicalcium silicate different from known dicalcium silicates—α, α'L , α'H , β, and γ phase—and is stable until around 900°C. At 920–960°C, all the phases are transformed to the α'L phase. The intermediate phase has high crystallinity and is stable at room temperature. 29 Si MAS NMR measurements indicate the possibility that it contains both protonated and unprotonated monosilicate anions. The intermediate phase that has passed through the α'phase at higher temperature yields β-C2 S on cooling. The intermediate phase is highly active, and completed its hydration in 1 day ( w/s = 1.0, 25°C). Among the crystalline calcium silicate hydrates with Ca/Si = 2.0, it is hillebrandite that yields β-C2 S at the lowest temperature. 相似文献
18.
Mechanical-Activation-Triggered Gibbsite-to-Boehmite Transition and Activation-Derived Alumina Powders 总被引:2,自引:0,他引:2
Mechanical activation of monoclinic gibbsite (Al(OH)3 ) in nitrogen led to the formation of nanocrystalline orthorhombic boehmite (AlOOH) at room temperature. The boehmite phase formed after merely 3 h of mechanical activation and developed steadily as the mechanical-activation time increased. Forty hours of mechanical activation resulted in essentially single-phase boehmite, together with α-alumina (α-Al2 O3 ) nanocrystallites 2–3 nm in size. The sequence of phase transitions in the activation-derived boehmite was as follows: boehmite to γ-Al2 O3 and then to α-Al2 O3 when flash-calcined at a heating rate of 10°C/min in air. γ-Al2 O3 formed at 520°C, and flash calcination to 1100°C led to the formation of an α-Al2 O3 phase, which exhibited a refined particle size in the range of 100–200 nm. In contrast, the gibbsite-to-boehmite transition in the unactivated gibbsite occurred over the temperature range of 220°–330°C. A flash-calcination temperature of 1400°C was required to complete the conversion to α-Al2 O3 phase, with both δ-Al2 O3 and θ-Al2 O3 as the transitional phases. The resulting alumina powder consisted of irregularly shaped particles 0.4–0.8 μm in size, together with an extensive degree of particle agglomeration. 相似文献
19.
Carolyn Moorlag Quanzu Yang Tom Troczynski Jeremy Bretherton Colin Fyfe 《Journal of the American Ceramic Society》2004,87(11):2064-2071
Aluminum phosphate products formed by the reactions of alumina and alumina-gel systems with acidic phosphates were analyzed. Drying of alumina-gel to form microcrystalline boehmite and conversion to γ-alumina by thermal treatment was indicated by the appearance of octahedral, pentacoordinate, or tetrahedral sites, which were established using 27 Al magic-angle-spinning solid-state nuclear magnetic resonance spectroscopy. Crystalline aluminum phosphate products and amorphous material were identified using this technique. α-alumina and heat-treated alumina-gel that were reacted with phosphate in an Al:P ratio of 1:1 yielded dramatically different aluminum orthophosphate:aluminum metaphosphate product ratios of 8.2:1 and 1:1.1, respectively. When alumina-gel was heat-treated with phosphate, an abundance of aluminum orthophosphate, aluminum metaphosphate, and hydrated aluminum phosphate products were affected by varying conditions of temperature and time of heat treatment and by the amount of phosphate present. An α-alumina/alumina-gel composite sol–gel phase that was reacted with phosphoric acid (H3 PO4 ) in a Al:P ratio of 1:1 exhibited an increased quantity of aluminum metaphosphate products compared with an α-alumina:H3 PO4 ratio of 1:1 and a higher percentage of reaction (79%) compared with the reactions of an α-alumina:H3 PO4 ratio of 1:1 or an alumina-gel:H3 PO4 ratio of 1:1. The morphologies of aluminum triphosphate hydrate and aluminum metaphosphate product phases were observed using scanning electron microscopy. 相似文献
20.
《Ceramics International》2023,49(6):9219-9230
The use of liquid phase additives is a strategy to improve the physicochemical, mechanical, and biological properties of calcium phosphate cements. In this study, TTCP and α-TCP particles were synthesized using the solid-state reaction method. Apatite cements were prepared by mixing TTCP/DCPD/α-TCP powders and liquid phases containing chondroitin sulfate with various additives of carboxylic acids and phosphate salts. The formation of hydroxyapatite and consumption of raw materials as well as the acceleration and deceleration periods through cementation process were investigated by XRD and DSC experiments, respectively. In addition, the morphology, setting time, porosity, compressive strength, degradation, in-vitro bioactivity and cytotoxicity were studied. The results showed that the approximate amount of hydroxyapatite resulting from the cementation process was divergent in the presence of liquid phase additives. The use of phosphate salt additives presented better results compared to carboxylic acid ones regarding hydroxyapatite cement product formation, compressive strength, hardening, setting, and cytotoxicity. All cements showed, generally a similar tendency to form dense hydroxyapatite on their outer surfaces through immersion in the simulated body fluid. The cement containing Na2HPO4 salt exhibited the lowest cytotoxicity and highest strength. The ALP assay and the morphological behavior of MG63 cells indicated the good activity and proper cell adhesion of this cement. 相似文献