硬硅钙石晶须对高温下油井水泥强度的影响

针对稠油热采过程中高温下固井水泥环强度下降严重的问题,以SiO₂为硅源,Ca(OH)₂为钙源,采用水热合成法制备了硬硅钙石晶须(C₆S₆H),并将其应用在油井水泥中抑制水泥石在高温下的强度衰退。通过热重分析仪(TG)、红外光谱仪(FTIR)、X-射线衍射仪(XRD)、扫描电子显微镜(SEM)和X-射线光电子能谱仪(EDS)表征了C₆S₆H晶须的结构。TG分析表明：所制备的C₆S₆H晶须热稳定性好,在900℃时质量损失仅为3.57%。FT-IR和XRD分析结果表明：所制备的C₆S₆H晶须晶型完整,结晶度高;通过SEM观察所制备的C₆S₆H晶须呈针状纤维形态,利用图像处理软件分析C₆S₆H晶须SEM图,计算得出C₆S₆H晶须长度范围在1～16μ...     

CaSO_4晶须补强增韧聚氨酯弹性体机理的研究

提高聚氨酯弹性体的力学性能是聚氨酯研究领域里普遍关心的课题之一,一般采用刚性粒子和纤维类无机填料增强聚氨酯弹性体,但上述填料在提高强度的同时,会导致韧性降低,空易造成脆性断裂,因此填料能否同时补强增韧聚氨酯弹性体具有重要的实际应用价值,晶须是一种单晶纤维状材料,其直径极小,几乎不存在任何缺陷,由于内在的完整性,高度有序的原子排列,使其强度接近晶体理论－－原子间价键的强度,晶须凭借微细的直径、较短的长度、极高的强度,成为一种新型补强增韧剂,目前晶须的复合基体多为陶瓷基、金属基和树脂基,有关复合基体多为陶瓷基、金属基和树脂基,有关复合聚氨酯弹性体的理论及应用研究报道很少,本文制备了具有较高强度和韧性的CaSO4晶须／聚氨酯弹性体复合材料,通过微观分析揭示了CaSO4晶须对聚氨酯弹性体补强增韧的机理,并对其影响因素进行了讨论。     

无机晶须材料的合成与应用

本文综述了无机晶须材料的合成与应用研究现状.近年来我国在这一研究领域取得了很大发展,以"硼酸铝晶须产业化"项目为代表的无机晶须材料的工业化生产,无疑将对我国高技术新材料的发展起极大的促进作用.本文还对几种典型的无机晶须材料--SiC晶须、Al18B4O33晶须、K2Ti6O13晶须、CaCO3晶须、Mg2B2O5晶须、莫来石晶须的合成与应用研究现状作了概述,并就其研究前景作了展望.     

莫来石晶须/堇青石表面层的制备及准超疏水性能

采用溶胶-凝胶法制备了硅铝混合凝胶粉体, 再通过熔盐反应在堇青石陶瓷基体上生长莫来石晶须, 制得莫来石晶须/堇青石表面层微结构. 表征结果表明, 莫来石晶须紧密生长在堇青石基体上, 晶须直径为100~300 nm, 长度可达几个微米. 莫来石晶须表面含有大量Si—OH和Al—OH极性亲水基团, 采用十二烷基三甲氧基硅烷与活性基团间的偶联反应将非极性基团引入莫来石晶须表面, 获得了静态润湿角为146°的莫来石晶须/堇青石表面层. 动态润湿研究表明, 合成的莫来石晶须增大了堇青石陶瓷的表面粗糙度, 使亲水的莫来石晶须/堇青石表面更加亲水, 而硅烷偶联剂修饰的堇青石/莫来石晶须表面则成为准超疏水表面.     

细菌纤维素晶须/聚(丙烯酸-丙烯酰胺)复合高吸水性树脂

利用硫酸水解细菌纤维素(BC)的方法制备具有一定长径比的细菌纤维素晶须(BCW),利用TEM对其进行表征,发现BCW具有较好的单分散性.将细菌纤维素晶须(BCW)与丙烯酸、丙烯酰胺复合制备高吸水性树脂.根据Box-Behnken中心组合实验设计原理,采用三因素三水平的响应面分析法,对交联剂、引发剂以及晶须投加量进行优化组合,确定最佳配比,并构建了以饱和吸水倍率为函数,以各影响因素为变量的回归模型.经吸水性测试发现,添加量仅为0.05 wt%的BC晶须在合适的条件下吸水倍率可达自身重量的600倍左右,在盐溶液中也有较高的吸水性能.SEM形貌表征显示细菌纤维素晶须(BCW)的加入使得树脂网孔结构更加蓬松.红外光谱显示高吸水性树脂由聚丙烯酸、聚丙烯酰胺与纤维素晶须复合而成.     

半水硫酸钙晶须的水化机理及稳定性调节

通过探讨半水硫酸钙晶须(HCSW)贮存过程在空气中形貌和晶形的变化,研究了半水硫酸钙晶须的水化机理,分析了不同处理方法对其稳定性的调节。研究发现,HCSW的水化是由晶须表面的-OH基团和Ca^2+活性位点以及HCSW存在的内部通道引起的,煅烧和二元醇改性均可提高硫酸钙晶须的耐水性。结果表明,煅烧后,半水硫酸钙晶须转化为无水可溶硫酸钙晶须和无水死烧硫酸钙晶须,易于水化的内部通道消失,耐水性增强;水热合成过程二元醇的加入,可利于醇羟基吸附在HCSW的(200)、(020)和(220)表面,阻止H2O分子中羟基在晶须表面的吸附,进而提高晶须的耐水性,当添加剂为三乙二醇(TEG)且浓度为18.8 mmol·L^-1时,HSCW在空气中耐水稳定性不小于7 d。     

半水硫酸钙晶须的水化机理及稳定性调节（英文）

通过探讨半水硫酸钙晶须(HCSW)贮存过程在空气中形貌和晶形的变化,研究了半水硫酸钙晶须的水化机理,分析了不同处理方法对其稳定性的调节。研究发现,HCSW的水化是由晶须表面的-OH基团和Ca~(2+)活性位点以及HCSW存在的内部通道引起的,煅烧和二元醇改性均可提高硫酸钙晶须的耐水性。结果表明,煅烧后,半水硫酸钙晶须转化为无水可溶硫酸钙晶须和无水死烧硫酸钙晶须,易于水化的内部通道消失,耐水性增强;水热合成过程二元醇的加入,可利于醇羟基吸附在HCSW的(200)、(020)和(220)表面,阻止H_2O分子中羟基在晶须表面的吸附,进而提高晶须的耐水性,当添加剂为三乙二醇(TEG)且浓度为18.8 mmol·L~(-1)时,HSCW在空气中耐水稳定性不小于7 d。     

尿素水解法制备晶须碳酸钙

采用尿素水解法合成了晶须碳酸钙,研究了原料配比、反应时间等合成条件对晶须产率的影响,采用SEM、TG和X-射线衍射技术等方法对晶须进行了表征。结果表明,本方法体系简单,条件易于控制,且随尿素比例的增加、反应时间的延长,晶须的产率得以提高。     

T-ZnO晶须化学镀铜复合粉体的制备及其电磁性能的研究

采用化学镀的方法制备了Cu包覆四脚状氧化锌晶须(T-ZnO晶须)的复合粉体.使用X射线衍射分析仪(XRD)进行了物象分析,扫描电镜(SEM)观察了粉体的形貌.运用能谱仪(EDS)进行了成份分析.结果表明,晶须为纯氧化锌,晶体结构为六方晶系纤锌矿结构,镀层为纯铜. SEM观察晶须外观形貌为四脚状结构.同时使用波导法对T-ZnO晶须和化学镀铜得到的Cu/T-ZnO晶须复合粉体进行了电磁参数的测量.微波电磁性能试验表明,化学镀后晶须的微波吸收性能明显增加,在频率为13 GHz处反射率可达－12 dB左右,而且最大吸收峰的频率随铜析出量的不同而发生改变,这样有利于实现吸收频带的展宽.     

短纤维/硅树脂复合材料的性能研究

分别用ＰＥＴ短纤维和硅灰石（无机针状晶须）增强甲基乙烯基硅树脂,研究了纤维长度、含量与复合材料力学性能的关系,并考察了增强纤维对硅树脂热稳定性的影响。结果表明：ＰＥＴ短纤维增强硅树脂复合材料的拉伸强度、模量和硬度显著提高,断裂伸长率下降;ＰＥＴ纤维长径比在１８０～３００范围内时,复合材料的拉伸强度增大;硅灰石增强的复合材料强度、模量及硬度提高相对较小,断裂伸长率随强体用量增多,先增加而后降低,存在     

电化学法沉积氧化锌晶须

应用阳极氧化法沉积氧化锌(ZnO)松针状晶须,SEM和XRD观察、表征样品形貌与结构.结果表明,电沉积氧化锌晶须直径为20～50 nm、长度200～300 nm、长径比10～15,纯度高,结晶度好,属六方晶系纤锌矿(JCPDS 36-1451).循环伏安法研究了该氧化锌结晶过程,并考察了电解液的锌酸盐[Zn(OH)4]2-浓度和基底表面氧化膜对晶须生成的影响.     

利用浮区法在高氧压下生长ZnO晶须

采用浮区法在高温高氧压下生长出大尺寸的ZnO晶须. X射线衍射和拉曼光谱分析结果表明, 生长的ZnO晶须结晶良好, 具有六方结构, 沿(001)方向有明显的择优生长取向. 光致发光光谱测量结果表明, 晶须在室温下有较高的紫外光致发光效率和较低的缺陷, 生长时选择大于0.3 MPa的氧压对提高IUV/Igreen有益.     

丙三醇-变频微波-水热法制备氢氧化镁晶须

以MgCl₂·6H₂O和NaOH为原料, 采用丙三醇-变频微波-水热法制备了优质氢氧化镁晶须. 采用XRD, SEM和TEM进行了物相、粒度、晶体形貌和结构分析. 考察了丙三醇-变频微波-水热法工艺对氢氧化镁晶须晶形、结构及分散性的影响. 实验发现, 在水热反应体系中加入体积分数为15%的丙三醇, 用变频微波加热, 在180 ℃反应6 h, 可获得粒度分布均匀、晶形和分散性好、表面光滑及缺陷少的优质氢氧化镁晶须. 在透射电镜下估算晶须直径约为0.1～0.3 μm, 长度约为80～110 um. 初步分析了变频微波和丙三醇对氢氧化镁晶须生长的作用.     

Single crystalline β-SiAlON nanowhiskers: preparation and enhanced properties at high temperature

Single crystalline β-SiAlON (z = 1.0) nanowhiskers with uniform morphology were prepared using a reaction sintering method at 1773 K for 6 h under flowing nitrogen atmosphere. The as-synthesized whiskers were well-crystallized with about 100-200 nm in diameter and a few hundred microns in length. According to the thermodynamic calculation, Al(g) and SiO(g) are important intermediate reactants to synthesize β-SiAlON whiskers. In the experiment, the two phases was controlled by changing the flow rate of nitrogen to make β-SiAlON whiskers grow in a stable way. The formation of β-SiAlON whiskers occurred through a vapor-solid (VS) mechanism. SiAlON was found to grow as a single crystal whisker from the (10 ?10) plane of the granule. Furthermore, an enhanced oxidation resistance for β-SiAlON whiskers at high temperature was also observed using the thermogravimetry method (TG), demonstrating that β-SiAlON whiskers with uniform morphology is a promising candidate as a reinforcing agent in composite.     

The first fluoride one-dimensional nanostructures: microemulsion-mediated hydrothermal synthesis of BaF2 whiskers

A convenient microemulsion-mediated hydrothermal process was employed for the first synthesis of BaF2 whiskers with lengths up to 50 mum and aspects ratios as high as 1000, each of which is a single crystal with a growth direction of (111). A directed aggregation growth process mediated by the microemulsion droplet building blocks is proposed for the formation of BaF2 whiskers.     

The effect of drying method on the properties and nanoscale structure of cellulose whiskers

Cellulose whiskers were prepared from wood- and cotton-based microcrystalline cellulose and dried by two methods: freeze-drying or air-drying. The effect of drying method on the properties and structure of the whiskers were studied. Furthermore, the influence of the source of cellulose on the nanoscale structure was investigated. Drying method was observed to slightly influence the thermal stability of cellulose whiskers, whereas the char residue varied significantly depending on the drying process performed. Small- and wide-angle X-ray scattering and solid state nuclear magnetic resonance spectroscopy were used to examine the crystallinity and nanoscale structure of the dried whiskers. It was observed that the crystal structure and crystallinity of cellulose whiskers remained during all treatments, whereas their nanoscale structure was significantly influenced by drying method, neutralization, and source of cellulose. Relationships between thermal behavior and nanoscale structure were reported and discussed.     

Surface treatment of magnesium oxysulfate whiskers through plasma polymerization

The surface of magnesium oxysulfate (MOS) whiskers was treated through plasma polymerization to increase the compatibility between the MOS whiskers and a polymer matrix. Different plasma parameters were chosen to determine the most hydrophobic coating. The surface structure of the plasma-treated MOS whiskers was examined. The MOS whiskers retained their crystal structure after plasma treatment, as shown by X-ray powder diffraction (XRD) analyses. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) spectroscopy analyses revealed that a polymer sheath was formed on the surface of the MOS whiskers, and interfacial chemical bonds were generated between the polymer sheath and the MOS whiskers. The thin-layer polymer sheath was uniform around the entire surface of the MOS whiskers and exhibited a typical amorphous structure, as determined by transmission electron microscopy (TEM) combined with selected area electron diffraction (SAED) analyses. The possible reaction mechanism on the surface of the MOS whiskers under plasma treatment was then proposed. Finally, the effect of surface treatment was evaluated by scanning electron microscopy (SEM), measurement of the contact angle and contact angle hysteresis, and torque rheometer. Results showed that plasma treatment could markedly increase the hydrophobicity of the MOS whiskers' surface, effectively reducing the agglomeration and improving the dispersibility of the MOS whiskers in the matrix, which results in the improved compatibility between the MOS whiskers and the polyvinyl matrix, as well as the processability of the composites.     

Ni催化剂上甲烷部分氧化制合成气反应性能与碳物种的关系

In the partial oxidation of methane (POM) to syngas, carbon deposition on the catalyst causing catalyst deactivation or reactor plugging was reported[1～3]. Our previous work showed that methane dissociation on metallic sites to H2 and NixC is an initial step of POM over Ni/Al2O3[4]. If NixC can not be consumed immediately after its formation, it has a tendency to dissolve into the nickel crystal to form carbon whiskers. The bulk carbon and carbon whiskers are more difficult to be oxidized than NixC. Therefore, prohibiting the transformation of NixC to bulk carbon and carbon whiskers can depress the formation of carbon deposition effectively.     

Preparation and budding growth of whiskers in a homogeneous system

Ca₁₀(PO₄)₆(OH)₂ (HAP) and NH₄Al(OH)₂CO₃·H₂O (AACHH) whiskers were prepared by a homogeneous precipitation method based on urea hydrolysis reaction. To clarify the growth process of whiskers in the homogeneous system, XRD and SEM results of the products obtained at different reaction time were investigated in detail. A novel observation about budding growth in preparing both whiskers was described. It was indicated that the growth of whiskers went through three stages, which were oversaturation, nucleation, and budding growth. The growth units of whiskers budded from the surfaces of substrates, which were crystallized flakes for HAP preparation and amorphous spherical nuclei for AACHH preparation. Subsequently, the whiskers grew up accompanying with the disappearing substrates. One-dimensional whiskers with fine morphology and large slenderness ratio were finally obtained. Besides, according to the crystal growth and the interface diffusion theories, the effects of the templates and the budding growth mechanism were discussed.     

Polymer-assisted growth of molybdenum oxide whiskers via a sonochemical process

Whiskers of molybdenum oxides with high aspect ratios were synthesized from peroxomolybdate precursor solutions in the presence of small amounts of poly(ethylene glycol) (PEG) via a sonochemical process at temperatures of 25-70 degrees C. Irradiation with ultrasound reduces the time needed for the growth of micrometer-sized whiskers from weeks to a few hours. The simplicity of the sonochemical approach also compares favorably to a hydrothermal/solvothermal process. The morphology, crystal structure, and other characteristics of the whiskers were characterized by scanning electron microscopy, transmission electron microscopy, selective area electron diffraction, energy-dispersive X-ray spectroscopy, wide-angle X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and the Brunauer-Emmett-Teller method. The surface area of the calcified molybdenum oxide whiskers (55.4 m2/g) was found to be much higher than those of molybdenum oxide nanofibers (35 m2/g) or nanorods (13.4 m2/g) The growth rate of various crystal faces could be postulated to be controlled by the binding of peroxomolybdate ions to pseudo-crown ether cavities formed by PEG. The reduction of molybdenum oxide to produce mixed-valent oxides and their growth could also be controlled by the reducing ability of PEG. The aspect ratio of the molybdenum oxide whiskers increased with decreasing concentration in the initial peroxomolybdate precursor solution. Whether the precursor solution species was H2Mo2O3(O2)4(H2O)2, H2MoO2(O2)2, or MoO2(OH)(OOH), the peroxide group in all the species disproportionates to give the final product MoO3 by a catalytic process. On the basis of experimental evidence of the dual role of glycols, a mechanism for the growth of the molybdenum oxide whiskers is proposed.