R2O—A12O3—B2O3—SiO2系统玻璃、超细α—Al2O3对羟基磷灰石陶瓷的烧结和相变的影响

系统地研究了R2O-A12O3-B2O3-SiO2系统玻璃和超细α—Al2O3对羟基磷灰石(HAP)陶瓷的烧结和相变及机械性能的影响。结果表明α—Al2O3对HAP的烧结有阻碍作用，使烧结温度提高；在烧结过程中能抑制玻璃与羟基磷灰石作用，使羟基磷灰石在烧结温度下避免脱去羟基而分解。同时使用超细α—Al2O3和玻璃复合增强HAP可以取得较好的效果，当α-Al2O3含量为10％(wt)，玻璃含量为20％(wt)时，在1200℃下烧结1h可以获得弯曲强度高达106MPa的复相HAP陶瓷。     

云母基高强度可切削微晶玻璃的研究

着重研究了以钙氟金云母为主相的可切削微晶玻璃的组成、结构和性能。 XRD和 EDS的分析结果表明 ,微晶玻璃以钙氟金云母、t- Zr O2 为主相 ,另有 Kx Ca( 1 - x) /2 Mg2 Si4 O1 0 F2 和 m- Zr O2 存在。微晶玻璃强度达 2 35MPa,比目前临床用同类材料强度提高近一倍 ;断裂韧性最高为 2 .17MPa· m1 /2 ;显微结构对材料性能影响尤为显著。理论分析和实验结果表明 ,具有大量细小晶粒的材料 ,其强度较高。本研究研制的微晶玻璃具有典型的可切削微晶玻璃的显微结构和良好的可切削性     

可切削渗透陶瓷(MIC)渗透玻璃的研究

讨论可切削渗透陶瓷（ＭＩＣ）渗透玻璃的制备技术及性能表征。采用氧化铝坩埚于１４５０℃熔融成玻璃，筛选玻璃生成范围，采用热分析仪测定玻璃的热学性能，对晶化后的微晶玻璃采用Ｘ射线衍射分析进行物相鉴别，用三点弯曲法测定力学性能。确立了母体玻璃的化学组成，对传统氟金云母玻璃进行了改进，增加了Ｂ２Ｏ３的用量，并添加了Ｌａ２Ｏ３及Ｌｉ２Ｏ３，生成了具有较低熔点的玻璃，晶化后析出氟金云母晶相，氟金云母玻璃可按性     

R2O-Al2O3-B2O3-SiO2系统玻璃、超细α-Al2O3对羟基磷灰石陶瓷的烧结和相变的影响

系统地研究了 R2 O- Al2 O3- B2 O3- Si O2 系统玻璃和超细α- Al2 O3对羟基磷灰石 (HAP)陶瓷的烧结和相变及机械性能的影响。结果表明α- Al2 O3对 HAP的烧结有阻碍作用 ,使烧结温度提高 ;在烧结过程中能抑制玻璃与羟基磷灰石作用 ,使羟基磷灰石在烧结温度下避免脱去羟基而分解。同时使用超细α- Al2 O3和玻璃复合增强 HAP可以取得较好的效果 ,当α- Al2 O3含量为 10 % (wt) ,玻璃含量为 2 0 % (wt)时 ,在 12 0 0℃下烧结 1h可以获得弯曲强度高达 10 6 MPa的复相 HAP陶瓷     

添加剂对可切削生物微晶玻璃结构的影响

本研究分析了ZnO、Fe2O3和ZrO2添加剂对KO-MgO-CaO-SiO2-P2O5-F系统可切削微晶玻璃的结构和性能的影响,并初步探讨了添加剂影响的机理.     

HAP-玻璃-α-Al2O3复合梯度生物陶瓷涂层的显微结构及其附着强度

利用涂覆烧结法在 α- Al2 O3陶瓷基体表面制备了 HAP-玻璃 (α- Al2 O3)梯度生物活性涂层 ,并研究了涂层组成对显微结构和附着强度的影响。梯度涂层中玻璃组成采用低膨胀低软化温度的 R2 O- Al2 O3- B2 O3- Si O2 系统 ;涂层中的 HAP含量由里到外逐渐增多 ,并在涂层中添加了适量的超细 α- Al2 O3粉体。实验结果表明 ,使用 R2 O-Al2 O3- B2 O3- Si O2 系统玻璃有利于涂层低温烧结和涂层与基体结合 ,在涂层中添加 α- Al2 O3超细粉有利于提高涂层与基体结合强度 ,所制备的梯度涂层与基体的结合强度为 4 8.2 MPa。     

牙用遮色瓷热处理制度的研究

首次选用双相成核剂CaF2和TiO2为制备遮色瓷的成核剂，以SiO2-Al2O3-K2O-Na2O系统为其基质成分，采用差热分析仪，扫描电镜和x衍射分析仪等实验手段来探讨本体系遮色瓷制备的热处理制度。结果表明阶梯制度的热处理方式适用于本体系的遮色瓷。瓷粉经过如下的热处理制度：从室温以8℃／min的加热速度升温至750℃保温1h，然后再以4℃／min的升温速度升至960℃，保温2h后冷淬，其白榴石晶体的析晶行为良好，且晶体尺寸较小（约1μm左右）。该热处理制度的确定为改善遮色瓷与金属的热匹配性和提高遮色瓷的理化性能提供了基础。     

三种纳米Fe2O3的制备方法研究

目的:通过固相研磨、化学加热沉淀以及均匀沉淀三种不同方法制备纳米氧化铁粒子Fe2O3,从中选择具有超顺磁性特质的纳米粒子晶型,为药物包被做前期准备,并对制备方法从制备时间、粒子粒度以及纯度等方面进行比较。方法:利用化学分析纯级别的FeCl3.6H2O、FeCl2.4H2O、NaOH、Fe(NO3)3.9H2O等作为初始原料,分别采用固相研磨法、化学沉淀法以及均匀沉淀法制备出磁性纳米粒子,利用XRD衍射比较粒子晶型,选出超顺磁性纳米粒子(γ-Fe2O3),并通过扫描电子显微镜观察粒径等特质。结果:固相研磨法可能会使粒子晶格畸变、团聚现象严重,化学加热沉淀法所得粒子粒径好、但是受影响因素较多,均匀沉淀法可以调节纳米粒子核形成速率、粒径大小可以控制。结论:通过比较分析,化学沉淀法操作简单适合于实验室制备实验用超顺磁性纳米粒子(γ-Fe2O3)。     

牙科Al2O3/ZrO2复合陶瓷的低温烧结研究

以5％的CaO—MgO—SiO2—TiO2复合物为烧结助剂，研究了Al2O3／ZrO2牙科复合陶瓷的烧结性能。着重考察烧结温度对材料力学性能和显微结构的影响。结果表明，在(1250—1400)℃之间，材料的密度、线收缩和抗弯强度呈上升趋势，1400℃保温2h，材料的抗弯强度为466MPa。液相传质是促进烧结，降低烧结温度的主要原因。     

Na_2O-CaO-SiO_2-P_2O_5系统生物玻璃析晶对其生物活性及强度的影响

Na2 O- Ca O- Si O2 - P2 O5系统生物活性玻璃具有较高的生物活性 ,是一种理想的骨缺损填充材料。为了提高该生物玻璃的力学强度 ,对其进行了微晶化处理 ,并利用 XRD、SEM、FTIR分析及 SBF浸泡等技术对其生物活性与母体玻璃进行了分析比较 ,并测定和比较了晶化前后材料的抗折强度和断裂韧性 ,对材料的生物活性机理进行了理论分析     

Effect of sodium content on the crystallization behavior of fluoramphibole glass-ceramics.

The purpose of this study was to evaluate the effect of sodium content on the crystallization behavior of glass-ceramics in the system SiO(2)-MgO-CaO-Na(2)O-K(2)O-F. Five glass compositions were prepared with increasing sodium content. The compositions were melted at 1400 degrees C for 2 h and cast into 60 x 12-mm ingots. Differential thermal analyses were performed on the glasses up to 1400 degrees C. Discs (1.5 x 12 mm) were cut from the ingots, nucleated in the temperature range 600-650 degrees C for 1-2 h, and crystallized in the temperature range 900-1000 degrees C for 0.5-4 h. The crystalline phases were analyzed by x-ray diffraction. The microstructure was investigated by scanning electron microscopy. Differential thermal analyses showed that the crystallization exotherm occurred in the temperature range 600-750 degrees C. There was a linear relationship between the amount of sodium and the transformation temperatures. X-ray diffraction revealed the presence of mica and diopside as major crystalline phases in the sodium-free composition. Mica, diopside, and fluorrichterite were present in all other glass-ceramics. The microstructure of the sodium-free glass-ceramic was characterized by the presence of hexagonal mica crystals and prismatic diopside crystals. All other compositions exhibited needle-shaped fluorrichterite crystals (2-5 microm in length) in addition to mica and diopside crystals.     

Role of acid attack in the in vitro bioactivity of a glass-ceramic of the 3CaO.P2O5-CaO.SiO2-CaO.MgO.2SiO2 system.

A non-bioactive glass-ceramic (GC13) that contains hydroxyapatite (Ca5(PO4)3OH), diopside (CaMg(SiO3)2) and althausite (Mg2 PO4OH) as crystalline phases has been obtained by thermal treatment of a parent bioactive glass (G13) of nominal composition (wt%) 40.0 CaO-34.5 SiO2-16.5 P2O5-8.5 MgO-0.5CaF2. To induce bioactivity, GC13 was chemically treated with 1 M HCl for different periods of time. After chemical etching the in vitro studies showed formation of an apatite-like surface layer. In this article the influence of etching time both on the surface composition of the glass-ceramic and on the growth rate of the apatite layer is studied. It is concluded that the presence of hydroxyapatite in the glass-ceramic, associated to microstructural fluctuations, can favour apatite deposition in vitro.     

In vitro bioactivity of glass and glass-ceramics of the 3CaO x P2O5-CaO x SiO2-CaO x MgO x 2SiO2 system

A glass of nominal composition (wt%) 40.0 CaO-34.5 SiO2-16.5 P2O5-8.5 MgO-0.5 CaF2 has been obtained (G13). The glass showed in vitro bioactivity evidenced by the formation on its surface of a calcium phosphate-rich layer when soaked in a solution with ionic composition analogous to human plasma. By thermal treatments of G13, a glass-ceramic (GC13) containing apatite, diopside, althausite and akermanite as crystalline phases was developed. GC13 as-made did not show in vitro bioactivity. However, after chemical treatment of GC13 with 1 M HCl (GC13-HCl), the in vitro studies showed the formation of an apatite-like layer covering certain areas of the material surface. The influence of both chemical and morphological factors on the in vitro bioactivity has been studied.     

Structure and properties of bioactive eutectic glasses based on the Ca3(PO4)2-CaSiO3-CaMg(SiO3)2 system

Taking into account the phase equilibrium relationships within the Ca3(PO4)2-CaSiO3-CaMg(SiO3)2 ternary system, three bioactive glasses with a eutectic composition and analogous amounts of Ca3(PO4)2 (～40 wt.%) have been prepared. The structure of the glasses was investigated by 31P and 29Si magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. The glasses exhibited thermal expansion coefficients (50-600 °C) of 11.8-13.3×10(-6) °C(-1), a glass transition temperature of 790-720 °C and a softening temperature of 811-750 °C. The mechanical properties of the glasses were as follows: bending strength ～100 MPa, Young's modulus 94-83 GPa, Vickers microhardness 7.1-4.1 GPa and toughness 0.8 MPa m1/2. The bioactive properties were discussed in terms of their structure deduced by MAS-NMR spectroscopy and the field strength of the network modifiers (Mg2+ and Ca2+). A knowledge of the glass structure was important in predicting its bioactivity.     

Effect of magnesium content on the microstructure and crystalline phases of fluoramphibole glass-ceramics

The purpose of this study was to evaluate the effect of magnesium content on the microstructure and crystalline phases of glass-ceramics in the system SiO(2)-MgO-CaO-Na(2)O-K(2)O-F. Four glass compositions were prepared with magnesium content varying from 12-18 wt%. The compositions were melted at 1400 degrees C for 2 h and cast into 30 x 8 mm ingots. Differential thermal analyses were performed on the powdered glasses at a heating rate of 20 degrees C/minute up to 1400 degrees C. Bars (4 x 8 x 25 mm) were cut from the ingots with a low-speed diamond saw, nucleated in the temperature range 600-650 degrees C for 1-2 h and crystallized in the temperature range 900-1000 degrees C for 4-6 h. The crystalline phases were analyzed by X-ray diffraction. The microstructure was investigated by scanning electron microscopy. The Vickers hardness was determined after indentation under a 9.81 N load. Differential thermal analyses revealed that crystallization occurred in the temperature range 700-800 degrees C. X-ray diffraction showed the presence of fluorrichterite as major crystalline phase regardless of the magnesium content in the parent glass or heat treatment temperature. The microstructure consisted of interlocked acicular crystals (5-10 micrometers). The highest magnesium content led to the coexistence of both a mica phase and fluorrichterite. This microstructure promoted crack deflections and arrest.     

Bioactivity of gel-glass powders in the CaO-SiO2 system: a comparison with ternary (CaO-P2O5-SiO2) and quaternary glasses (SiO2-CaO-P2O5-Na2O)

Bioactive glasses react chemically with body fluids in a manner that is compatible with the repair processes of the tissues. This results in the formation of an interfacial bond between the glasses and living tissue. Bioactive glasses also stimulate bone-cell proliferation. This behavior is dependent on the chemical composition as well as the surface texture of the glasses. It has been recently reported that gel-derived monolith specimens in the binary SiO2 - CaO are bioactive over a similar molar range of SiO2 content as the previously studied ternary CaO-P2O5-SiO2 system. In this report, the preparation and bioactivity of the binary gel-glass powder with 70 mol % SiO2 is discussed and its bioactivity is compared with the melt-derived 45S5 (quaternary) Bioglass and sol-gel-derived 58S (ternary) bioactive gel-glass compositions. Dissolution kinetic parameters K(1) and K(2) were also computed based on the silicon release for all glass powders. It was shown that the simple two-component SiO2-CaO gel-glass powder is bioactive with comparable dissolution rates as the clinically used melt-derived 45S5 Bioglass powder and extensively studied sol-gel-derived 58S gel-glass powder.     

Microstructural dependence on relevant physical-mechanical properties on SiO2-Na2O-CaO-P2O5 biological glasses

Bioactive glasses of the system SiO2-Na2O-CaO-P2O5 have been prepared by the normal melting and annealing technique. The elastic moduli, attenuation, Vickers hardness, fracture toughness and fracture surface energy have been obtained using the known method at room temperature. The temperature dependence of elastic moduli and attenuation measurements have been extended over a wide range of temperature from 150 to 500 K. The SiO2 content dependence of velocities, attenuation, elastic moduli, and other parameters show an interesting observation at 45 wt% of SiO2 by exhibiting an anomalous behaviour. A linear relation is developed for Tg, which explores the influence of Na2O on SiO2-Na2O-CaO-P2O5 bioactive glasses. The measured hardness, fracture toughness and fracture surface energy show a linear relation with Young's modulus. It is also interesting to note that the observed results are functions of polymerisation and the number of non-bridging oxygens (NBO) prevailing in the network with change in SiO2 content. The temperature dependence of velocities, attenuation and elastic moduli show the existence of softening in the glass network structure as temperature increases.     

Calcium phosphate formation on porous sol-gel-derived SiO2 and CaO-P2O5-SiO2 substrates in vitro.

Sol-gel-derived SiO2 and CaO-P2O5-SiO2 have been shown to be bioactive and bone bonding. In this study bioactive sol-gel-derived SiO2 and CaO-P2O5-SiO2 systems were tested for in in vitro bioactivity. The calcined ceramic monoliths were immersed in a simulated body fluid and analyzed to follow the hydroxyapatite formation on the ceramic surface. Apatite-forming ability was investigated in terms of structural changes by changing the composition and the preparation method. The role of Ca and P dopants in the substrate structure is complicated, and careful characterization is needed. The composition and structure together determine the in vitro bioactivity. The pore structure was analyzed using N2-adsorption/desorption isotherms. The results indicate that a great mesopore volume and a wide mesopore size distribution favor hydroxycarbonate apatite nucleation and a great surface area is not needed. The performed preparation process for silica in a basic environment provides a convenient way to prepare a mesoporous material.     

A new model formulation of the SiO2-Al2O3-B2O3-MgO-CaO-Na2O-F glass-ceramics

Mono-phase glass-ceramics of akermanite were successfully produced from a Ca-mica and wollastonite via low-temperature sintering and crystallization. Doping with P(2)O(5) considerably improves sintering behaviour since P(2)O(5) increases the stability of glass against crystallization at the temperature of sintering onset. The resulting glass-ceramics feature good in vitro acceptance from osteoblasts, and moderate bioactivity due to the enrichment of the glassy phase with Ca and Si. The good quality of the white colour at the surface and throughout the bulk, the matching of microhardness with tooth enamel, and the possibility to coat other biomaterials such as ZrO(2), Ti or hydroxyapatite make these materials promising for medical applications.     

Physicochemical degradation studies of calcium phosphate glass ceramic in the CaO-P2O5-MgO-TiO2 system

The aim of this work was to evaluate the in vitro degradation behaviour of a 45CaO-37P(2)O(5)-5MgO-13TiO(2) (mol.%) glass ceramic, under two different simulated physiological conditions: normal physiological pH 7.4, and pH 3.0, which was designed to simulate the acidic conditions produced by osteoclast cells. The in vitro testing was carried out at 37 degrees C for up to 42 days for the pH 7.4 solution and for up to 1 day for the pH 3.0 solution. The incorporation of TiO(2) into the glass structure leads to the precipitation of specific crystalline phases in the glass matrix, namely alpha- and beta-Ca(2)P(2)O(7), TiP(2)O(7) and CaTi(4)(PO(4))(6). The degradation testing at pH 3.0 showed a higher weight loss compared with degradation testing at pH 7.4; the weight loss under the acidic condition after 1 day (24 h) was about 10 times higher than the weight loss after 42 days of immersion at pH 7.4. The ionic release profile of Ca(2+), PO(4)(3-), Mg(2+) and Ti(4+) showed a continuous increase in concentration over all immersion times for both testing solutions. After 1 day of immersion at pH 3.0, the concentration levels of Mg(2+), Ca(2+), PO(4)(3-) were about six times higher than the levels achieved after 42 days of immersion at pH 7.4. The glass ceramic showed similar degradation to hydroxyapatite, and therefore has potential to be used in certain clinical applications where relatively slow resorption of the implant and replacement by bone is required, e.g. cranioplasty.