鳌合剂对溶胶凝胶制备纳米羟基磷灰石的影响

采用硝酸钙(Ca(NO3)2.4H2O)、磷酸三甲酯(PO(CH3O)3,简称TMP)作为钙与磷的先驱体,用溶胶凝胶法合成纳米羟基磷灰石粉体.探讨了工艺过程中添加乙二醇、柠檬酸、甘氨酸三种鳌合剂对粉体制备及其特性的影响.实验结果表明,在合适配比下,鳌合剂的加入影响干凝胶的形态,并促使碳酸钙晶相出现.柠檬酸和甘氨酸会改变体系pH值,影响酯的水解反应,同时通过鳌合作用及表面电荷作用影响粉体粒径.研究表明甘氨酸是低温下制备纳米羟基磷灰石粉体合适的鳌合剂.     

化学沉淀法快速制备纳米羟基磷灰石粉体工艺研究

以Ca(OH)_2和Ca(H_2PO_4)2·H_2O为原材料,采用化学沉淀法制备纳米羟基磷灰石(HA)粉体。改变不同反应物量、加入方法及后续反应时间等去探索快速制备纳米HA粉体的工艺。利用X射线衍射(XRD)、扫描电镜(SEM)、能谱仪(EDS)测试手段对样品的成分、组织形貌等进行分析。研究结果表明碱性环境有利于加快氢氧化钙和磷酸二氢钙在溶液中的反应速度,从而提高HA的生产效率;20倍反应物量,将Ca(H_2PO_4)_2溶液分20次以1分钟为间隔加入Ca(OH)_2过饱和溶液中并保持后续反应时间30分钟为本研究实验条件下最快制备纳米HA粉体的工艺,和原始制备工艺相比,可提高生产效率60倍。     

纳米级羟基磷灰石粒子的可控制备

文中以硝酸钙和磷酸氢二铵作为前驱体,在水溶液体系中成功合成出纳米级羟基磷灰石粒子。研究了溶液的pH值、陈化时间、反应温度、热处理温度、Ca-P摩尔比、加料方式及速度等因素对所制得粒子颗粒大小、晶型、分散度、纯度等性能的影响,探索出制备纳米级羟基磷灰石粒子简单的工艺条件,基本实现了纳米级羟基磷灰石粒子的可控制备。     

纳米羟基磷灰石(HAP)的制备研究

综述了生物医用材料纳米羟基磷灰石(HAP)的合成方法及应用前景.在比较现有制备方法的基础上,采用珍珠粉、珍珠层粉等无毒无害且生物活性较高的物质为原料,克服了现有实验方法的一些缺陷,对pH值、NaOH的加入方式、温度等实验条件进行了一系列探索,得出了最佳工艺条件,用湿法制备出了纳米羟基磷灰石.     

双十二烷基二甲基溴化铵对羟基磷灰石粒度的影响

在沉淀法生成的纳米羟基磷灰石(HA)胶体中加入阳离子表面活性剂双十二烷基二甲基溴化铵(DDAB)制备纳米级HA粉体,研究其在制备过程中对颗粒大小的作用,分别用激光粒度分析仪、SEM和TEM检测了HA粉体的粒度、形态和相组成,结果表明,表面活性剂可以得到粒度小,但分布较宽的纯羟基磷灰石。     

蛋壳水热法合成羟基磷灰石

以蛋壳为主要原料,利用水热合成工艺,成功制备了羟基磷灰石(HA)粉体.实验结果表明,合成的HA粉体具有与天然骨骼HA相似的结构特征,组分包括OH-,H2O,CO32-等基团.单个HA粒子为纳米尺寸,并团聚为微米级大颗粒.该工艺提供了环境友好和低成本的羟基磷灰石制备方法,可有效提高蛋壳加工利用技术的附加值.     

纳米羟基磷灰石的制备及工艺优化

以Ca（OH）2和H3PO4为原料，采用沉淀法制备了羟基磷灰石纳米粒子（n—HA）；讨论了H3PO4的滴加速率、反应时间、反应温度、溶液的pH值、搅拌强度，以及干燥方法对纳米羟基磷灰石结构和性能的影响。利用红外光谱（FTIR）、X-射线衍射（XRD）、扫描电镜（SEM）等分析测试手段对产物结构与形貌进行了表征。实验结果表明，溶液在搅拌强度为2000r／min反应10h，并结合冷冻干燥，可得到结晶尺寸小、纯度和分散性较好的纳米羟基磷灰石粒子。     

光固化3D打印羟基磷灰石工艺参数优化

采用光固化3D打印技术,以羟基磷灰石、光敏树脂和分散剂为原料,成型后通过脱脂烧结得到支架样品,研究了球磨时间、粉体粒径尺寸、配比及不同种类分散剂对浆料黏度的影响．通过优化工艺参数及热重分析,扫描电子显微镜和黏度测试等技术方法对制备的支架试样进行了分析．结果表明:浆料的最佳球磨时间为120 min;采用油酸作为分散剂,羟基磷灰石采用15 wt%的纳米羟基磷灰石+85 wt%的微米羟基磷灰石的粉体配比可获得最佳的流动性,以此光固化3D打印后烧结制备的HAP支架材料具有较好性能．     

微弧氧化法制备镁基羟基磷灰石/碳纳米管复合生物涂层及其性能研究

 通过化学沉淀法制备了羟基磷灰石/碳纳米管纳米(HA/CNTs)复合粉体,并作为电解液的添加剂,采用微弧氧化方法(MAO)制备了镁合金表面MAO/HA/CNTs 复合活性涂层。分别采用扫描电子显微镜(SEM)、X 射线衍射分析(XRD)、傅里叶红外光谱(FTIR)和电化学工作站,研究所制备的复合粉体的形貌和物相组成、复合粉体对微弧氧化涂层表面形貌和在模拟体液(SBF)中耐腐蚀性能和生物活性的影响。结果表明,所制备的HA/CNTs 复合粉体结晶良好,无其他杂质相;复合粉体在微弧氧化过程中沉积在样品表面,对微弧氧化涂层起到封孔作用。MAO/HA/CNTs 样品的腐蚀电位为-1.50 V,经过30 天的SBF 浸泡后,表面沉积了大量的亚微米级别的颗粒沉积物,相比于镁基体和MAO 样品具有更好的生物活性和耐腐蚀性。     

超临界流体干燥法制备医用纳米羟基磷灰石

应用超临界流体干燥法制备医用纳米羟基磷灰石.以 Ca(NO3)2·4H2O和(NH4)2HPO4 为原料,采用超临界流体干燥法(SCFD)制备了纳米羟基磷灰石,并用 XRD,TEM,FTIR等手段进行了表征.超临界干燥法制备的羟基磷灰石具有结晶性好、分散性好、尺寸分布均匀,呈针状结晶,长度为 100~200 nm,宽度 10~15 nm.用溶胶凝胶结合超临界流体干燥法可以制备出颗粒大小均匀、分散性好的纳米羟基磷灰石.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the