pH值和缓冲剂对水热电化学沉积HA/TiO_2涂层的影响

以微弧氧化后的钛合金为基体,采用水热电化学法制备了HA/TiO2涂层。利用SEM、XRD对涂层的表面形貌、物相组成进行了表征分析,通过pH微探针原位探测电极/电解液界面pH值的变化,研究了pH值和缓冲剂对水热电化学沉积HA/TiO2涂层的影响。研究结果表明,微弧氧化膜有利于水热电化学沉积HA,得到的HA晶体分布均匀、致密。当电解液pH值在2~8时,pH值升高有利于提高水热电化学沉积HA的结晶度,并促使HA沿(002)晶面生长。在水热电化学沉积HA过程中,电极表面的pH值随沉积时间的增加先升高后逐渐降低;而溶液中的pH值随沉积时间的增加逐渐降低。pH值和缓冲剂对涂层HA晶体形貌有明显影响,加入缓冲剂后得到的HA晶体端面呈六边形棒状结构,晶体表面光滑、结晶完整。     

氨基酸对水热合成羟基磷灰石纤维形貌的影响

以Ca(NO_3)_2·4H_2O和(NH_4)_2HPO_4的水溶液为前驱体,基于生物矿化的基本原理,利用水热法制备结晶度较高的羟基磷灰石(HA)纤维,重点研究酸性氨基酸L-谷氨酸(Glu)、中性氨基酸L-苯丙氨酸(Phe)和碱性氨基酸L-赖氨酸(Lys)的添加对产物物相和形貌的影响。结果表明:添加这3种氨基酸均对产物的物相影响不大,制得样品的主要组成相都是HA,部分样品含有少量碳酸钙。3种氨基酸的加入均改变纤维沿c轴生长的趋势:加入Glu后得到球状形貌的HA,Lys的加入使得产物形貌变得不均匀,而加入Phe后得到分散性较好的棒状纤维。     

pH值对水热合成钒酸铋及性能的影响

以硝酸铋和偏钒酸铵为无机源,NaOH为pH值调节剂,利用水热法制备了多种结构和形貌的BiVO4,并利用X射线衍射(XRD)、扫描电子显微镜(SEM)和紫外-可见吸收光谱(UV-vis DRS)等分析手段表征了其物化性质。结果表明前驱液的pH值对制得BiVO4产物的晶型和粒子形貌有很大影响。考察了BiVO4样品在可见光(λ>420nm)下降解罗丹明B的催化活性和总有机碳(TOC)浓度的变化,结果表明前驱液pH值为6.7时所得BiVO4具有最好的光催化活性,可见光催化4h后,罗丹明B的降解率达到95.3%。TOC值随着光解反应时间的延长而减小,表明罗丹明B发生了矿化。另外,对BiVO4光催化剂的晶型、形貌和性能之间的联系也进行了简单的探讨。     

纳米羟基磷灰石粉体的水热合成

采用Ca(NO3)2·4H2O和(NH4)3PO4·3H2O作为反应前驱物,通过水热合成颗粒尺寸在100nm以下的短棒状或针状HA晶体.X射线衍射(XRD)、透射电镜(TEM)和红外光谱(FTIR)分析讨论水热温度、反应时间、表面活性剂和烧结与物相组成、晶粒尺寸和晶体形貌的关系.实验结果表明升高反应温度和延长反应时间有利于HA的生成;表面活性剂有助于改善粉体的分散性能;烧结能提高晶体的结晶程度,但粉体易团聚,当温度高于800℃时HA发生分解.     

水热合成羟基磷灰石纳米粉体的研究

采用ＣａＣＯ３和ＣａＨＰＯ_４·２Ｈ_２Ｏ的混合物为前驱物,通过水热合成得到晶粒完整、分散性好、端面粒度在１００ｎｍ以下的ＨＡ粉体,并借助ＸＲＤ和ＳＥＭ分析讨论了前驱物配比、水热温度、反应时间与物相组成、粒度变化和晶体形貌的关系．     

聚乙烯吡咯烷酮对羟基磷灰石结晶和形貌的影响

采用化学均相沉淀法,在水热条件下以Ca(NO3)2.4H2O和(NH4)2HPO4为原料,合成了具有特殊形貌的羟基磷灰石(HA)微球。在合成过程中加入聚乙烯吡咯烷酮(PVP)为模板剂,研究了PVP的加入和浓度对HA晶体形貌和粒径的影响。结果表明,PVP的加入改变了HA晶体的生长方式,颗粒是由针片状HA晶体组成的微球;HA颗粒的形貌和粒径可以通过调节PVP浓度来控制,当PVP浓度从0%(质量分数,下同)增加到12%时,HA颗粒的形貌逐渐由不规则的絮状团聚物转变为规整的微球,组成微球的结构单元也随PVP浓度的变化有所不同。     

pH值对溶胶凝胶法制备莫来石纳米粉体微观形貌的影响

以氧化钨为催化剂,利用溶胶-凝胶方法制备了具有高长径比的一维莫来石纳米粉体.研究表明,溶胶前驱体的pH值对氧化钨的催化作用有重要的影响.只有当溶胶前驱体的pH值小于7时,才能形成AlWO₄生长模板引导一维莫来石颗粒的形成.随着溶胶前驱体pH值的逐渐升高,前驱体的化学均匀度降低,导致γ-Al₂O₃形成温度升高,WO₃在生成AlWO₄之前已经大量挥发.生长模板的缺失使莫来石粉体的微观形貌从各向异性向各向同性发展.     

水热合成磷酸铁锂粉体的形貌控制

以氢氧化锂、硫酸亚铁、磷酸为原料,采用水热法合成磷酸铁锂.研究了表面活性剂,加料温度、降温速度对产物形貌及性能的影响.用X射线衍射(XRD)、扫描电子显微镜(SEM)和激光粒度仪、恒流充放电测试表征材料的性能.结果表明:表面活性剂选择CTAB,40℃加料,降温速度选择5℃·min-1,可以得到平均粒径为1.5μm的粉体,在30℃的环境温度下,材料0.2C、1C和5C首次充放电比容量分别为157、152和136mAh·g-1,经过35次5C倍率充放电循环后,比容量无衰减.     

等离子喷涂/水热合成HA涂层的制备和模拟体液及体内实验

等离子喷涂磷酸氢钙涂层经过水热处理转化为羟基磷灰石 (HA)涂层 ,该涂层由高纯度的缺钙HA组成 ,结晶性高。水热合成HA涂层在模拟体液中的溶解性和结合强度衰减均低于等离子喷涂HA涂层 ,体内实验表明水热合成HA涂层的生物学性能良好     

合成条件对羟基磷灰石粉体形貌和煅烧后组成的影响

通过溶液法制备羟基磷灰石粉体,研究了反应体系与分散剂、溶液浓度、反应温度、pH值和陈化时间等工艺因素对羟基磷灰石粉体粒度和形貌的影响.研究表明,高浓度(1mol/L)乙醇-水溶液条件下,也可通过控制工艺因素获得不同形态(如颗粒状、针状)的羟基磷灰石粉体.粉体煅烧可得仅含羟基磷灰石和磷酸钙的生物陶瓷粉.提高pH值、延长陈化时间可以提高煅烧产物中羟基磷灰石的含量.     

Influence of temperature and aging time on HA synthesized by the hydrothermal method

The influence of temperature and aging time on the morphology and mechanical properties of nano-sized hydroxyapatite (HA) synthesized by a hydrothermal method is reported here. The pre-mixed reactants were poured into a stirred autoclave and reacted at temperatures between 25–250°C for 2–10 h. HA powders thus obtained were examined using X-ray diffraction (XRD), high-resolution field emission scanning electron microscopy (FESEM) and a particle size analyzer. It was found that the aspect ratio of the particles increased with the reaction temperature. The length of the HA particles increased with the reaction temperature below 170°C, but it decreased when the temperature was raised above 170°C. The agglomerates of HA particles were formed during synthesis, and their sizes were strongly dependent on reaction temperatures. As the reaction temperature increased, the agglomerate size decreased (p = 0.008). The density of the discs pressed from these samples reached 85–90% of the theoretical density after sintering at 1200°C for 1 h. No decomposition to other calcium phosphates was detected at this sintering temperature. A correlation existed (p = 0.05) between the agglomerate sizes of HA particles synthesized at various conditions and their sintered densities. With the increase of the agglomerate size, the sintered density of the HA compact decreased. It was found that both the sintered density and flexural strength increased with increasing aging time and reaction temperature. A maximum flexural strength of 78 MPa was observed for the samples synthesized at 170°C for 5 h with the predicted average at these conditions being 65 MPa. These samples attained an average sintered density of 88%.     

Effect of pH value on particle morphology and electrochemical properties of LiFePO4 by hydrothermal method

Lithium iron phosphate was prepared by hydrothermal synthesis using LiOH·H₂O, FeSO₄·7H₂O and H₃PO₄ as raw materials. The effects of pH value of reaction solution on particle morphology and electrochemical property were investigated. The pH value of the reaction solution was adjusted in the range of 2.5-8.8 by dilute sulfuric acid and ammonia water. The samples were characterized by field-emission scanning electronic microscope (FE-SEM), X-ray powder diffraction (XRD), constant-current charge/discharge cycling tests and chemical analysis. The results indicated that the particles exhibited acute angle diamond flake-like morphology at pH = 2.5, and as the pH value increased, the particle became hexagon flake-like, round flake-like and irregular flake-like morphology gradually. The optimal sample synthesized at pH = 6.4 exhibited discharge capacities of 151.8 mAh g⁻¹ at 0.2 C rate and 129.3 mAh g⁻¹ at 3 C rate. It was found that pH value affected the morphologies and properties of the product by means of different crystal growth rates.     

水热法合成羟基磷灰石晶须的工艺研究

纳米羟基磷灰石（HAP）增强聚合物基复合材料是替换硬组织的最理想材料，是植入材料的研究重点之一。为了制备与天然骨结构非常相似的复合材料，必须首先制备出性能优良的的纳米HAP粉体。对水热法制备HAP纳米晶须的工艺进行了研究，研究了反应时间、温度、起始反应物的浓度、钙磷比以及反应体系的pH值对合成HAP纳米晶须形貌的影响。用X射线衍射（XRD）、扫描电镜（SEM）和红外光谱（FT-IR）法，对制备的羟基磷灰石进行了表征和分析。结果表明：生成的HAP晶须的长度及长径比随反应时间的延长而增大。温度〈150℃时，得到HAP晶须；温度〉180℃，则得到细小HAP晶体的聚集产物。当反应物的pH=9时，得到的是缺钙型的HAP；当反应物的pH〈4时，产物中出现新相磷酸氢钙；当pH=2时，得到纯的磷酸氢钙。     

反应pH值对原位水热沉积法制备纳米羟基磷灰石/壳聚糖复合材料的影响

为避免羟基磷灰石(HA)在壳聚糖(CS)基体中分子出现分布不均的现象,在结合原位沉析法和水热法二者优点的基础上,发展了原位水热沉析法来制备HA/CS复合材料,并深入研究不同的反应pH值对该复合材料的影响。研究表明,在不同反应pH值下制备的复合材料,均由CS晶体和低结晶度的纳米HA晶体所组成,2种晶体均出现沿c轴方向上的择优生长。随着反应pH值的增大,复合材料中HA和CS分子的结晶度均增大,HA晶体尺寸增大,CS分子排列有序化程度增高,且二者之间发生较强的化学键合作用。当反应pH值增大到12时,复合材料中纳米HA的晶体尺寸约为27.63 nm,且均匀地分布在CS分子中;CS分子为高结晶度的α晶型,且分子排列规整,有序化程度高;存在于HA与CS分子间的化学键合作用最强。     

Influence of anions on the morphology of nanophase alpha-MnO2 crystal via hydrothermal process

The alpha-MnO2 nanocrystal nanowires, nanoplates, and nanoflowers have been successfully synthesized by a common hydrothermal treatment of different solutions containing KMnO4 and NH4X (X = Cl-, Ac-, NO3-, SO4(2-), and PO4(3-)) at 140 degrees C for 24 h. The influence of anions on the morphology of final product is discussed. According to our experimental results, we proposed a possible mechanism of the formation of different morphologies of nano-phase alpha-MnO2 and considered that the growing process was due to the initial plate-like MO(x) absorbing different anions and cooperation with them, which contributes to the final morphology of the product.     

pH值对水热法制备ZnGa2O4粉体的影响

采用水热法制备了ZnGa2O4纳米粉体,使用XRD、SEM、TEM及AFM对不同pH值条件下产物的结构及微观形貌进行了表征.结果表明pH值调节严重影响ZnGa2O4的晶相及粒度:当pH≥7.5时,可得到纯相的ZnGa2O4纳米粉体;随着pH的增加,晶胞参数增加,所得样品的平均粒径不断减小,其粒径范围为6～11nm,发射峰位置在450nm左右.所得样品的晶型很完整,GaO(OH)为细长棒状,ZnGa2O4晶粒为四方形和圆形.     

Synthesis and formation of alumina whiskers from hydrothermal solution

Al₂O₃ whiskers with an average length of 5 μm have been synthesized from hydrothermal solution. Al(NO₃)₃ and urea were mixed and put into a Teflon-lined stainless steel autoclave and then treated at 120 °C to fabricate precursor whiskers NH₄Al(OH)₂CO₃ (AACH). AACH whiskers were heated at 1200 °C in a furnace to obtain Al₂O₃ whiskers. The time-dependent examinations revealed that the formation process of AACH whiskers involves two sequential processes: a short liquid–solid deposition process in the initial stage and a long Ostwald ripening process. During calcinations, AACH transforms to amorphism then to α-Al₂O₃. The escape of NH₃ and CO₂ induced the distortion and toothlike morphology on the surface of the Al₂O₃ whiskers.     

水热电沉积HA/Ti复合涂层的研究

在水热电沉积HA涂层的电解液中加入Ti粉,制备了HA/Ti复合涂层,探讨了Ti粉的加入对涂层结合强度和生物活性的影响,并研究了涂层的热稳定性.结果表明,HA/Ti复合涂层的结合强度明显高于纯HA涂层;模拟体液浸泡7天后,涂层表层形成一层碳磷灰石.Ti粉的加入明显提高了涂层的结合强度,又不降低涂层的生物活性.     

pH值和无机盐添加剂对水热合成钨酸铋的影响

在170℃的温和水热条件下,用Na2WO4·2H2O、Bi(NO3)3·5H2O为原料,硝酸钠为添加剂辅助制备了三维(3D)花球状钨酸铋粉体。通过改变添加剂的浓度,发现硝酸钠在诱导花球状钨酸铋的生长和自组装过程中起到关键作用。在合适添加剂浓度的基础上,pH值的变化会对产物的物相和微观形貌有很大的影响。研究结果表明,当pH值≤10.8时,产物为Bi2WO6,当pH值=12.4时,产物转变为Bi3.84W0.16O6.24。当pH值=1.2,硝酸钠浓度为4 mol/L时,获得粉体的比表面积为33.427m2/g。