牙科纳米氧化锆陶瓷粉体的制备

目的 :探讨用于增韧牙科氧化铝陶瓷的纳米氧化锆陶瓷粉体的制备方法。方法 :应用沉淀法 ,比较不同前驱物浓度和 pH值等条件下 ,所制备氧化锆粉体的物理性能。 结果 :ZrOCl2 ·8H2 O浓度为 0 .3～ 0 .5mol/L、pH 8.5时 ,经 70 0℃煅烧 2h后 ,可获得性能优良、粒径约为 10 0nm的氧化锆陶瓷粉体。 结论 :选择适当的条件 ,该方法可制得粒径小、团聚少的纳米氧化锆陶瓷粉体。     

牙科用氧化锆增韧纳米复相铝瓷粉体的制备与性能研究

目的 研制牙科用氧化锆增韧纳米复相铝瓷粉体并测试其理化性能，探讨影响铝瓷粉体性能的制备工艺。方法 表面诱导沉淀法制备纳米复相铝瓷粉体，记录分散剂加入量及pH值对氧化铝悬浮液沉降物体积的影响；观察超声时间对粉体团聚的影响；X射线衍射分析添加稳定剂前后粉体晶相的组成，扫描电子显微镜下观察其形貌。结果 pH=9、分散剂加入量wt=0．2％～0．3％时，悬浮液分散性好；超声处理后粉体粒径下降；稳定剂处理后复相铝瓷粉体含有单斜相和四方相氧化锆。在原始颗粒较大的氧化铝表面均匀分布着直径约80～100nm的氧化锆细颗粒。结论 控制制备工艺，采用表面诱导沉淀法可得到粒度细、分散好的氧化锆增韧纳米复相铝瓷粉体；经稳定剂处理后，复相铝瓷中的氧化锆成为部分稳定氧化锆。     

氧化锆增韧的纳米复合渗透陶瓷粉体性能的研究

目的：研制合成Al2O3/nZrO2纳米复合陶瓷粉体，以获得其粉体体系全面而真实的粉体颗粒信息。方法：采用包裹共沉淀法与湿法球磨相结合的方法合成Al2O3/nZrO2纳米复合陶瓷粉体，对Al2O3/nZrO2纳米复合粉体的颗粒形状/尺寸、粒度分布、晶相组成、化学成分等重要表征进行研究分析。并与GI-Ⅱ型α-Al2O3及In-Ceram^Rzirconia等两种氧化铝陶瓷粉体的性能进行比较研究。结果：①XRD衍射图剖析结果，所研制合成的Al2O3/nZrO2纳米复合渗透陶瓷粉体晶相组成为α-Al2O3、t-ZrO3及m-ZrO2；②Al2O3/nZrO2纳米复合渗透陶瓷粉体密度为4.12g/cm^2；③粉体粒度分布范围为0.02-3.0μm之间，并且粒径小于0.5μm的超细颗粒的相对体积含量达20％左右；④SEM观察及粒度分布测试结果表明Al2O3/nZrO2纳米复合渗透陶瓷粉体的微观形貌较规则，纵横比接近1.2。结论：所合成Al2O3/nZrO2粉体化学组成稳定，均质性好；粉体粒度级配合理，利于提高粉体的堆积密度。     

牙科纳米氧化铝陶瓷的烧结研究

目的 :探讨干压成型、低温烧结制备牙科纳米氧化铝陶瓷的工艺方法。方法 :采用Al2 O3-CaO -MgO -SiO2 系统来研制纳米氧化铝陶瓷 ,通过扫描电子显微镜 (SEM)及力学性能测试 ,比较了不同MgO含量、成型压力及烧结温度对氧化铝陶瓷的密度及力学性能的影响。结果 :1.2 9wt%MgO试样组的陶瓷晶粒均匀且发育比较完全 ;随着粉料成型压力的升高 ,烧结后瓷体的密度及维氏硬度均增大 ;在 130 0℃烧结后 ,晶体发育差且气孔较多 ,随着烧结温度的升高 ,晶粒逐渐增大 ,在 145 0℃时可见瓷体晶形发育较完全。结论 :选择适当的复合烧结助剂、成型压力及烧结温度可制得较理想的纳米氧化铝陶瓷     

超声波-化学沉淀法制备牙科纳米氧化铝陶瓷粉体

目的:制备分散性好,粒度均匀的纳米α-A l2O3粉体。方法:应用超声波-化学沉淀法,制备氢氧化铝前驱体,经900℃、1 000℃、1 100℃、1 200℃煅烧后测试粉体性能。结果:1 200℃煅烧得到的A l2O3粉体为α-A l2O3,其晶粒平均粒径为D202=31.44 nm。结论:以乙醇为反应溶剂,在低频超声波作用下可制备出分散性好、粒度均匀的纳米级α-A l2O3粉体。     

氧化锆增韧的纳米复合渗透陶瓷(Al2O3-nZrO2)粉体合成的研究

目的　研究Al2 O3 -nZrO2 纳米复合陶瓷粉体的合成。方法　采用包裹共沉淀与湿法球磨相结合的方法合成Al2 O3 -nZrO2 纳米复合陶瓷粉体。结果　①采用观察沉降情况与沉降物体积的方法来评价分散效果 ,粉体分散系沉降过程极慢 ,观察 2 4h后悬浮液的颗粒仍由上而下呈逐渐增浓的弥散分布 ,最后即使经高速离心所得到的沉积物体积亦较小。②SEM观察粉体颗粒分散较好 ,超细颗粒粒径为纳米级。③衍射图剖析结果经稳定剂处理后 ,粉体晶相由单斜相和四方相共同构成 ,即成为有增韧作用的部分稳定ZrO2 粉体。结论　所合成Al2 O3 -nZrO2 粉体的分散效果、粉浆流动性良好且适于操作     

氧化锆增韧的纳米复合渗透陶瓷（AlO3—nZrO2）粉体合成的研究

目的 研究AlO3-nZrO2纳米复合陶瓷粉体的合成。方法 采用包裹共沉淀与湿法球磨相结合的方法合成AlO3-nZrO2纳米复合陶瓷粉体。结果 （1）采用观察沉降情况与沉降物体积的方法来评价分散效果，粉体分散系沉降过程极慢，观察24h后悬浮液的颗粒仍由上而下呈逐渐增浓的弥散分布，最后即使经高速离心所得到的沉积物体积亦较小。（2）SEM观察粉体颗粒分散较好，超细颗粒粒径为纳米级。（3）衍射图剖析结果经稳定剂处理后，粉体晶相由单斜盯和四方相共同构成，即成为有增韧作用的部分稳定ZrO2粉体。结论 所合成AlO3-nZrO2粉体的分散效果，粉浆流动性良好且适于操作。     

牙科纳米氧化铝复合树脂的制备与性能研究

目的 制备一种新型的光固化纳米氧化铝复合树脂,探讨其用于口腔临床的可行性。方法 以双酚A双甲基丙烯酸缩水甘油酯(Bis-GMA)为树脂基质,甲基丙烯酸羟乙酯(HEMA)为活性稀释剂,添加纳米氧化铝填料对树脂基质进行增强增韧改性,制备一种新型牙科纳米氧化铝复合树脂,并表征其固化程度、弯曲强度、硬度、断面形貌、耐磨性、吸水性与水溶解性。结果 添加纳米氧化铝能提高复合树脂材料的刚性和硬度,当添加量达到3wt%时,复合树脂的力学性能、吸水和溶解性能均为最优。结论 复合树脂中加入一定比例的纳米氧化铝可达到增韧和耐磨的效果,该研究为开发新型牙科复合树脂提供了理论和实验基础。     

纳米氧化铝陶瓷对成骨细胞功能代谢影响的研究

目的 :比较纳米氧化铝 (nAl2 O3 )和常规氧化铝 (cAl2 O3 )对成骨细胞功能代谢方面影响。方法 :采用压制成型和无压烧结工艺制备nAl2 O3 和cAl2 O3 的块体材料 ,将体外原代分离培养成骨细胞分别接种于nAl2 O3 和cAl2 O3 的表面 ,分别在 7、14、2 1、2 8d时检测细胞内总蛋白、ALP活性及细胞基质钙含量。结果 :所制备的nAl2 O3 和cAl2 O3 的平均粒径分别为 60nm和 1.80 μm。 14、2 1和 2 8d时 ,nAl2 O3 表面附着的成骨细胞ALP活性和细胞基质钙含量均高于cAl2 O3 。结论 :与相应的cAl2 O3 比较 ,nAl2 O3 更能增强成骨细胞的功能及代谢活动     

牙科纳米氧化铝陶瓷的烧结研究

目的：探讨干压成型、低温烧结制备牙科纳米氧化铝陶瓷的工艺方法。方法：采用Al2O3-CaO-MgO-SiO2系统来研制纳米氧化铝陶瓷,通过扫描电子显微镜（SEM）及力学性能测试,比较了不同MgO含量、成型压力及烧结温度对氧化铝陶瓷的密度及力学性能的影响。结果：1．29wt% MgO试样组的陶瓷晶粒均匀且发育比较完全;随着粉料成型压力的升高,烧结后瓷体的密度及维氏硬度均增大;在1300℃烧结后,晶体发育差且气孔较多,随着烧结温度的升高,晶粒逐渐增大,在1450℃时可见瓷体晶形发育较完全。结论：选择适当的复合烧结助剂、成型压力及烧结温度可制得较理想的纳米氧化铝陶瓷。     

Al2O3-氮化硼纳米晶包覆的3%氧化钇稳定的四方氧化锆多晶复合陶瓷粉体的制备

目的 研究非均相沉淀法制备3%氧化钇稳定的四方氧化锆多晶陶瓷(3Y-TZP)/3%Al₂O₃复合粉的最佳pH值;3Y-TZP/3%Al₂O₃/10%BN双相包覆中,合成Al₂O₃及非晶氮化硼（BN）的最佳热处理温度。方法 不同pH值（6.5、7.5、8.5、9.5）下,通过非均相沉淀法合成Al₂O₃前驱体包覆3Y-TZP粉,通过透射电镜（TEM）选出包覆形貌较均匀的一组。将此pH下制备的复合粉经不同的温度（800、1 000、1 200、1 400 ℃）处理后,硼酸尿素反应烧结法（N₂保护下,850 ℃煅烧5 h,850 ℃煅烧3 h及800 ℃煅烧5 h,800 ℃煅烧3 h）合成10%BN包覆3Y-TZP/3%Al₂O₃粉,通过TEM、能谱分析及X射线衍射（XRD）选出形貌及相组成最佳的一组。结果 当pH值为8.5时,3%Al₂O₃前驱体均匀地包覆在3Y-TZP颗粒周围;3%Al₂O₃前驱体经1 200 ℃煅烧,再包覆10%BN,在N₂保护下800 ℃煅烧5 h,此时可见3Y-TZP颗粒周围包覆Al₂O₃及非晶BN,3Y-TZP/3%Al₂O₃/10%BN复合粉中Al-B-O化合物较少,且t-ZrO₂所占的比例最多。结论 合成Al₂O₃前驱体包覆3Y-TZP的最佳pH值为8.5;双相包覆中,Al₂O₃前驱体的最佳处理温度为1 200 ℃,合成非晶BN的适宜条件为N₂保护下800 ℃煅烧5 h。     

Effects of preparation conditions in aqueous solution on properties of hydroxyapatites

Hydroxyapatite powders (HAP: Ca10(PO4)6(OH)2) were prepared from calcium nitrate and di-ammonium hydrogen phosphate at various temperatures in aqueous solution in the absence and presence of carbon dioxide. In the absence of carbon dioxide, the crystallinities as well as the calcium to phosphate ratio (Ca/P ratio) of HAP powders increased with an increase in the preparation temperature. Calcium ion deficiency caused low Ca/P ratios of HAP powders. Such HAP powders decomposed thermally to beta-tricalcium phosphate (beta-TCP: Ca3(PO4)2) at 800 degrees C in 3 hours whereas HAP powders with sufficient calcium were stable at 1200 degrees C for 3 hours. In the presence of carbon dioxide as well the crystallinities of HAP powders increased with an increase in the preparation temperature, but carbonate-bearing HAPs were obtained instead of pure HAP. In addition, calcium carbonate was obtained along with carbonate-bearing HAP prepared below 60 degrees C.     

Effect of Sintering Temperature on Flexural Properties of Alumina Fiber-Reinforced, Alumina-Based Ceramics Prepared by Tape Casting Technique

PURPOSE: The purpose of this study was to investigate the effect of sintering temperature on flexural properties of an alumina fiber-reinforced, alumina-based ceramic (alumina-fiber/alumina composite) prepared by a tape casting technique. MATERIALS AND METHODS: The alumina-based ceramic used a matrix consisting of 60 wt% Al(2)O(3) powder and 40 wt% SiO(2)-B(2)O(3) glass powder with the following composition in terms of wt%: 33 SiO(2), 32 B(2)O(3), 20 CaO, and 15 MgO. Prepreg sheets of alumina-fiber/alumina composite in which uniaxial aligned alumina fibers were infiltrated with the alumina-based matrix were fabricated continuously using a tape casting technique employing a doctor blade system. Four sintering temperatures were investigated: 900 degrees C, 1000 degrees C, 1100 degrees C, and 1200 degrees C, all for 4 hours under atmospheric pressure in a furnace. The surface of the alumina-fiber/alumina composite after sintering was observed with a field-emission scanning electron microscope (FE-SEM). A three-point bending test was carried out to measure the flexural strength and modulus of alumina-fiber/alumina composite specimens. In addition, sintered alumina fiber was characterized by X-ray diffraction (XRD). RESULTS: FE-SEM observation showed that alumina-fiber/alumina composite was confirmed to be densely sintered for all sintering temperatures. Three-point bending measurement revealed that alumina-fiber/alumina composite produced at sintering temperatures of 1100 degrees C and 1200 degrees C exhibit flexural strengths lower than those of alumina-fiber/alumina composite produced at sintering temperatures of 900 degrees C and 1000 degrees C; alumina-fiber/alumina composite produced at sintering temperatures of 1100 degrees C and 1200 degrees C exhibit flexural moduli lower than that of alumina-fiber/alumina composite produced at a sintering temperature of 1000 degrees C. Additional XRD pattern of alumina fiber indicated that with increasing sintering temperature, the crystallographic structure of gamma-alumina transformed to mullite. CONCLUSIONS: There were significant differences in the flexural properties between the alumina-fiber/alumina composite sintered at the four temperatures. This indicates that the choice of optimum sintering temperature is an important factor for successful dental applications of alumina-fiber/alumina composite developed by the tape casting system.     

氧化铝颗粒大小对氧化铝玻璃复合体力学性能的影响

研究氧化铝颗粒大小对氧化铝玻璃复合体力学性能的影响。方法采用两种不同大小颗粒的氧化铝原料,经等静压成型,１４００℃小时的低温烧结,制作了部分烧结的多孔氧化铝,经镧硼玻璃渗透形成了氧化铝玻璃复合体。结论氧化铝玻璃复合体中氧化铝的体积百分数和气孔率对其强度和断裂韧性起关键性作用。     

Release of organic matrix components from bovine incisor roots during in vitro lesion formation

The solubilization of organic matrix components during demineralization of powdered and intact root sections from adult bovine incisors was investigated. Root powder was demineralized with 0.1 mol/L acetic acid, pH 4.0, at 4 degrees C and 37 degrees C. Surfaces of intact root sections were subjected to 0.1 mol/L acetic acid, pH 4.0 (for production of erosive lesions), or to 0.1 mol/L lactic acid, 0.2 mmol/L methane hydroxy diphosphonate, pH 5.0 (for production of subsurface lesions at 37 degrees C). The solubilized organic material was analyzed for collagen, total noncollagenous protein (NCP), organic phosphate (Po), and proteoglycans (PGs), which were measured as chondroitin 4-sulfate (C-4-S). For root powder, a maximal release of NCPs and PGs was found only after neutralization of the extraction mixture. For both temperatures tested, the average amounts of liberated noncollagenous components (NCCs) were the same, i.e., 0.68 micrograms [NCP - Po], 0.11 microns Po, and 0.10 micrograms C-4-S per mumols released calcium. The amino acid composition of the NCP fraction revealed relatively high amounts of aspartic acid and serine. These findings indicate that the NCCs were easily liberated from the tissue, and that the NCP fraction consisted mainly of phosphoprotein. Demineralization of intact root sections resulted in average amounts of solubilized NCCs of 0.21 micrograms [NCP - Po], less than 0.01 micrograms Po, and less than 0.01 micrograms C-4-S per mumols released calcium, independent of incubation time and lesion type. The amino acid composition of all NCP fractions was virtually the same, high in glutamic acid, but lower in aspartic acid and serine when compared with the neutralized powder extracts. For both demineralization solutions, the amounts of solubilized collagen were 0.07 and 0.16 micrograms per micromol released calcium after three and 28 days of incubation, respectively. Our experiments indicate that phosphoprotein and proteoglycans may be released from root surfaces during the periods of neutral pH that follow acid demineralization.     

Shrinkage and strength characterization of an alumina-glass interpenetrating phase composite for dental use.

OBJECTIVE: The aim of the study was to investigate the influence of temperature and time during partial-sintering (i.e. initial-stage sintering) on the shrinkage and strength of an alumina-glass dental composite. METHODS: The alumina slip and infiltrating glass were prepared for fabrication of an interpenetrating phase composite by melt-infiltration technology. Partial-sintering temperatures for the alumina body ranged from 1050 to 1200 degrees C (2 h) and at 1125 degrees C, the time was varied from 2 to 8 h. Partially sintered alumina preform were then infiltrated with melted glass at 1125 degrees C for 6h except for one group treated at 1100 degrees C for 6 h. RESULT: The composite demonstrated shrinkage not only during initial-stage sintering of the alumina but also during infiltration of glass into the alumina preform. Higher temperatures and longer times for alumina sintering led to greater shrinkage for the alumina preform and overall for the alumina-glass infiltrated composite. However, shrinkage during the infiltration stage was lower for alumina compacts having the highest initial-stage sintering shrinkage (1200 degrees C for 2 h or at 1125 degrees C for 6 and 8 h). Strength of the composite was not influenced when sintering temperatures and times were increased. SIGNIFICANCE: Shrinkage during both alumina sintering and glass infiltration must be taken into account for the overall shrinkage of the alumina-glass interpenetrating phase composite. Strength does not appear to be influenced by the changes in density or preform microstructure occurring during more extensive initial-stage sintering.     

GI-Ⅱ型渗透陶瓷氧化铝粉体的研究

目的:研究GI-Ⅱ型渗透陶瓷氧化铝粉体和坯体的特征,分析其形成氧化铝多孔结构的机制。方法:X衍射分析氧化铝粉体的晶型,粒度分析仪测试其粒度组成,扫描电镜观察坯体的微观结构。结果:氧化铝晶体是结构最紧密、最稳定的纯A型氧化铝晶型。氧化铝粉体中小于015Lm的细颗粒占9 wt%,粗颗粒集中在115~315Lm,占 75 wt%。扫描电镜观察坯体断面发现许多细小的颗粒均匀地附着在大颗粒表面,大小颗粒分散均匀,堆积较为密实。结论:氧化铝的晶型、粒度分布、颗粒分散,有利于形成多孔可渗透氧化铝骨架,是GI-Ⅱ型渗透陶瓷预制体的材料基础,也是复合体强度提高的关键。     

Degradation of bovine incisor root collagen in an in vitro caries model.

The effects of pH, ionic strength and proteinases on the destruction of bovine incisor root collagen were studied. Experiments were done with powdered and intact root specimens. Completely demineralized root powder was subjected to solutions of varying pH and ionic strength: (a) 0.1 M acetic acid, pH 4.0, (b) 0.1 M acetic acid + 0.15 M KCl, pH 4.0, (c) 0.1 M Hepes, pH 7.0 or to (d) 0.1 M Hepes + 0.15 M KCl, pH 7.0 at 37 degrees C. The surfaces of intact root specimens were exposed to 0.1 M acetic acid, pH 4.0 (which resulted in erosive lesions) or to 0.1 M lactic acid, 0.2 mM methane hydroxy diphosphonate, pH 5.0 (which produced subsurface lesions) at 37 degrees C. After incubation, the extracts were analysed for soluble collagen and the insoluble matrices were treated with trypsin at 15 degrees C to determine the denatured collagen. To estimate sensitivity to non-specific proteinases, demineralized root powder was also treated with trypsin under physiological conditions of temperature, pH and ionic strength. The denaturation and subsequent solubilization of collagen material from the fibrils could be influenced by variations in pH and ionic strength but these effects were small when compared to proteolytic degradation under physiological conditions. This supports the hypothesis that, in root caries, destruction of exposed matrix collagen depends largely on the presence and activity of proteinases.     

Electrochemical features of zirconia polymorphs. The interplay between structure and surface OH species

Zirconia powders were prepared by heating at 470°C hydrothermal precursors obtained by precipitation at increasing pH (from 2 to 12). The phase composition of the calcined products varied from pure monoclinic (at the acid extreme) to pure tetragonal (neutral-alkaline range). For the mixed phase samples, the relative enrichment in the two polymorphs was estimated by interpretation of X-ray diffractograms. Electrochemical determinations of the double layer reactivity of the pure and mixed phase oxides were performed and combined with characterisations of the surface state by X-ray photoelectron spectroscopy (XPS). Interpretations of the distinctive electrochemical features shown by the different polymorphs are proposed.