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氢氧化钙-磷酸体系在沉淀法合成羟基磷灰石过程中原料粒度的影响 总被引:1,自引:0,他引:1
采用化学沉淀法,分别以3种不同颗粒尺寸的氢氧化钙[Ca(OH)2]与磷酸(H3PO4)反应制备羟基磷灰石(hydroxyapatite,HA)粉末,研究了原料粒度对合成HA的影响.测定了合成过程中溶液的pH值和不同反应时间内合成产物的摩尔比n(Ca)/n(P),并表征了所得粉末的组成、颗粒形貌和粒度分布.研究表明:在采用粒度为57~88 μm的中等尺寸的原料时,合成过程中,溶液大部分时间处于较高的碱性范围,得到的HA粉末的纯度高、颗粒尺寸分布范围较窄.采用较大尺寸的原料时,溶液的碱性较低,合成的HA粉末中存在磷酸钙β-Ca3(PO4)2(β-TCP)和氧化钙(CaO)且尺寸分布范围较宽.采用较小尺寸原料时,HA粉末存在较严重的团聚现象,团聚体尺寸较大.Ca(OH)2-H3PO4体系用化学沉淀法制备HA粉末时,Ca(OH)2颗粒尺寸是影响合成过程的重要因素之一. 相似文献
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采用化学沉淀法将硝酸钙、磷酸氢二铵按摩尔比5:3配成溶液,加入不同质量非离子表面活性剂聚乙二醇(PEG)、聚乙烯醇(PVA),使其质量占羟基磷灰石(HA)质量分别为1%、2%、3%、4%、5%,经750℃热处理2 h,从而制取表面活性剂改性的HA粉末.对粉末进行粒度分布测量、FT-IR测试、XRD衍射分析和SEM表征.结果表明:常压60℃下制备改性的HA粉末纯度高,结晶度低.其中PEG改性HA粉末物相为Ca10(PO4)6(OH)2、Ca3(PO4)2和Ca2P2O7,添加3%PEG粉体中位径(D50)为13.55μm,OH-吸收峰最强,HA含量为纯相,结晶程度趋于完善;PVA改性HA粉末物相只有Ca10(PO4)6(OH)2,添加3%PVA粉体中位径(D50)为7.068μm,结晶程度趋于完善,HA粉末的团聚程度最小,比表面积最大为607.4 m2/kg.PVA对HA团聚程度的分散性优于PEG. 相似文献
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采用超声共聚法制备含硅羟基磷灰石Si-HA纳米粉体,并用柠檬酸与丙烯酸制成的固化液与之按一定比例调制成含硅羟基磷灰石骨水泥Si-HAC。采用XRD和FESEM对Si-HA纳米粉体的晶相、粒度、结构和表面形貌进行分析表征,并用万能材料试验机测定了所得Si-HAC骨水泥的力学性能。研究结果表明,将硅源TEOS加入到具有较强碱性的Ca(OH)2氨水前驱液中,能有效避免TEOS的水解漂浮,使钙硅均匀混合;将超声空化作用施加于Ca(OH)2和H3PO4外加硅源的反应体系,进行超声共聚,能够有效防止次生相的形成,合成纳米粉体纯度高,结晶细腻而均匀;将硅掺杂的Si-HA纳米粉体与柠檬酸/丙烯酸固化液调制成Si-HAC骨水泥能有效提高其力学性能,尤以4%Si最佳。 相似文献
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以四水硝酸钙[Ca(NO3)2·4H2O]、磷酸氢二铵[(NH4)2HPO4]、十二水合砷酸钠[Na3AsO4·12H2O]为原料,在200℃下水热反应8h制得掺砷羟基磷灰石[Ca10(PO4)6-x(AsO4)x(OH)2].考察了反应液中不同砷含量对合成砷羟基磷灰石结构的影响.采用X射线衍射分析(XRD)、扫描电镜结合电子能谱分析(SEM/EDS)、傅立叶变换红外光谱分析(FTIR)等测试手段对产物的晶相、化学组成和形貌进行分析.结果表明:As取代部分磷(P)进入羟基磷灰石的晶格中,没有改变其晶体结构,但羟基磷灰石的晶胞参数发生了变化,随着As含量的增加,砷羟基磷灰石的晶体尺寸呈增大的趋势,晶体形状为短棒状. 相似文献
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论述了共沉淀法制备羟基磷灰石粉体的过程,以Ca(OH)2和H3PO4为原料,控制适当Ca/P的比、H3PO4的滴加速率、溶液的pH值、反应温度和时间以及煅烧温度等条件,采用电子显微镜、X射线衍射仪和红外光谱仪对目标产物的结构和粒度进行了分析。结果表明,溶液在40℃下反应6 h,煅烧温度为900℃,产物用无水乙醇洗涤可获得纯度、结晶度、颗粒度和分散性均较好的羟基磷灰石粉体。 相似文献
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以FeCl3·6H2O,FeCl2·4H2O为原料,通过水热法制备磁性四氧化三铁粒子.并以合成的磁性四氧化三铁粒子,Na3PO4 ·12H2O和Ca(NO3)2 ·4H2O为原料,在80 ℃恒温水浴条件下,采用共沉淀法制备磁性羟基磷灰石.通过X射线衍射(XRD),红外(FTIR)对制备样品的结构和化学组成进行表征,并用Materials Studio 4.0(MS)模拟软件,对制备的样品进行结构分析.结果表明,四氧化三铁取代羟基磷灰石中平行于c轴的OH进入羟基磷灰石晶格中,从而引起羟基磷灰石 (210)和(212)晶面发生变化,但所得的样品具备羟基磷灰石的晶体结构特征和化学组成. 相似文献
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A model is developed for the sedimentation from a suspension of two particle species of unequal densities and of different sizes. The composition and the thickness of various layers in the sediments are predicted using graphical and analytical methods. The model predictions were in excellent agreement with experimental results, when the particle size ratio was ≥ 108. When size ratio of the particles was 2.60 and 4.31 the agreement occurred in about 50 percent of the cases. 相似文献
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面对日益激烈的市场竞争,摩托车油箱外观质量越来越成为影响销售的因素之一。文章介绍了改进工艺后的油箱涂装,该涂装体系提高了油箱外观的丰满度,降低了油箱涂装的生产成本。 相似文献
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P. P. Budnikoff 《Journal of the American Ceramic Society》1924,7(11):817-820
The different analytical methods proposed for the evaluation of gypsum have been subjected to an experimental test. A combination method, consisting of a fusion with KHCO3 and determination of CaO by KMnO4 titration, the SO3 by Andrews method of titration of BaCrO4 has been found to give very reliable results with the least consumption of time. 相似文献
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A novel technique serves to monitor instantaneous rates of loss of a volatile solute from a suspended drop during drying. A highly sensitive electron capture detector is used to monitor concentrations of SF6 released into a flowing gas stream from a suspended, drying drop. Simultaneously, the appearance and morphological development of the drop are monitored with a video camera. This provides the wherewithal of relating instantaneous rates of loss of the volatile solute to particular events during the development of particle morphology.
Initial experiments have been carried out with drops of aqueous solutions of glucose, sucrose, maltodextrin and coffee extract. The results clearly display the onset of the volatiles-retentive selective diffusion phenomenon. There is also substantial loss of the volatile component later in the drying process, when the drops undergo repeated ex ansion, bursting and cratering due to the formation of internaf bubbles. These experiments appear to be the first quantitative demonstration of major losses accompanying changes in drop morphology. 相似文献
Initial experiments have been carried out with drops of aqueous solutions of glucose, sucrose, maltodextrin and coffee extract. The results clearly display the onset of the volatiles-retentive selective diffusion phenomenon. There is also substantial loss of the volatile component later in the drying process, when the drops undergo repeated ex ansion, bursting and cratering due to the formation of internaf bubbles. These experiments appear to be the first quantitative demonstration of major losses accompanying changes in drop morphology. 相似文献
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用两个形状指数表征粉煤灰颗粒形貌的研究 总被引:5,自引:0,他引:5
引用两个形状指数表征颗粒形状的概念,即先将颗粒形状近似为椭圆,再将椭圆图像分离:以圆为基准的颗粒宏观形状指数δ;以光滑椭圆为基准的颗粒轮廓凹凸度,即微观形状指数ζ。分析和发展了近似椭圆模型。并运用图像分析仪对粉煤灰、水泥样品进行实验。结果表明,粉煤灰颗粒的两个形状指数δ和ζ都大于水泥颗粒。证明粉煤灰颗粒的球形度、表面光滑度优于水泥,而且,随着粒径增大,δ和ζ呈下降趋势,表明磨制颗粒越粗。(?)粒形状越不规则。文中还运用近似椭圆模型再现了颗粒的模拟图像。 相似文献
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本文以三种典型煤的碳燃烧为研究对象,分别采用简单一维沉降燃烧方式和等温加热燃烧方式,实验研究了煤在快速加热条件下,其碳的初期和中,后期燃烧过程。以实验为基础,建立了煤的碳燃烧模型,变工况数值模拟了煤的碳燃烧过程,揭示了煤不同条件下的单颗粒碳燃烧特性。 相似文献
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ONACCURACYOFANALYSISOFOFHYDROGEN1前言我公司目前应用的氢气纯度分析方法有两种,一种是爆炸反应法,另一种是焦性没食子酸吸收法。几年来,人们对两种分析方法的准确性曾有过褒贬不一的评论。这里我们也谈谈自己粗浅的观点。2爆炸法测定氢气纯度一定量的氢气样品与适量的空气之均匀混合物因反应后生成液体水而引起气体体积减少,减少的体积等于参加反应气体体积之和。其中l/3为氧气,2/3为氢气。根据氢气取样量和反应前后混气体体积之差,以及氢气在反应中的体积比例关系,可计算出样品的氢气纯度。计算公式式中:A一混… 相似文献
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ANALYSIS OF RECENT MEASUREMENTS OF THE VISCOSITY OF GLASSES 总被引:5,自引:0,他引:5
Viscosity of Simple Soda-Silicate 500° to 1400°C Comparison of the results given by English with those of Washburn, Shelton and Libman, indicates a discrepancy in the absolute values of log10 viscosity amounting to 0.6, those of Washburn et al., being relatively too high. If correction for this is made, the isothermal curves of log10 viscosity as a function of soda content are smooth up to 50% Na2O, showing no inflection. The observations as a function of temperature T are all represented within accidental error by an equation of the type where all three constants vary regularly with the composition. Change of Viscosity of Glass (6SiO2, 2Na2O) due to Molecular Substitution of CaO, MgO and Al2O3 for Na2O The effect is clearly brought out by plotting (from the results of English) the change of log10η due to the substitution as a function of temperature. The curves each show a sharp bend at a temperature between 840° and 1050°C, which is designated the aggregation temperature Ta. If we divide these curves by the corresponding percentage substituted, we get curves for each oxide which are straight and parallel below the aggregation temperatures, the slopes (increase of change of log10η per 100°C) being −0.056 (CaO), −0.055 (MgO), −0.018 (A12O3) per per cent oxide substituted. For substitution of 1/2 molecule the slopes are −0.325 (CaO), −0.23 (MgO) and −0.18 (Al2O3) per 100°. At the aggregation temperature the change of log10η per per cent is a minimum, 0.03 to 0.06 for CaO, 0.12 for MgO, 0.07 for Al2O3. Evidence of Aggregation in Glasses, from viscosity Measurements The sharp bends in the plots of change of log10η due to substitution of an oxide for Na2O, suggest the beginning of molecular aggregation at these temperatures. These aggregation temperatures are close to the devitrification temperatures, but the effect on the viscosity curves cannot be due to actual devitrification since it does not change with time. Taking the aggregation temperatures as equal to devitrification temperatures, additional isotherms are roughly sketched into the equilibrium triangle of the system Na2O-CaO-SiO2. Change of Viscosity of Glass (4SiO2, 2Na2O) due to of Substitution of B2O3 for SiO2 The change of log10η (from the results of English) is plotted as a function of temperature, and also the change of log10η per per cent B2O3. The curves are more complex than for the substitution for Na2O. 相似文献
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