Influence of Compacted Hydrophobic and Hydrophilic Colloidal Silicon Dioxide on Tableting Properties of Pharmaceutical Excipients

The effect of noncompacted and compacted hydrophilic as well as hydrophobic colloidal silicon dioxide (CSD) on tableting properties of three different pharmaceutical excipients used for direct compression, namely, Avicel® PH 101, Starch 1500®®, and Tablettose® 80, was investigated. Binary powder mixtures containing 0.5% CSD and 99.5% excipient were compressed on an instrumented single-punch tablet press, and the radial tensile strength/compaction load profiles were examined. The Ryshkewitch-Duckworth relationship shows that the influence of CSD on tablet strength was dependent on the hydrophobic and hydrophilic nature of the CSD and on the compaction characteristics of the excipients. Tablets from each excipient with and without CSDs were subjected to different levels of relative humidity at 20°C for 7 days. The sorption isotherms and the radial tensile strengths of the tablets after the storage period showed that neither hydrophilic nor hydrophobic CSD influenced the tablet properties of Avicel® PH 101, Starch 1500®®, and Tablettose® 80. Moreover, ternary powder mixtures containing magnesium stearate as a third component were compressed in order to study the influence of CSD on the deleterious effect of magnesium stearate on the interparticle bonding. The radial tensile strength/compaction load profiles and the residual and ejection forces of tablets made from ternary mixtures showed that CSD eliminated the negative effect of magnesium stearate on interparticle bonding while maintaining the lubrication action, in a manner that was affected by its hydrophobicity/hydrophilicity and by the particle deformation properties of the excipient upon compression.     

Charge migration on hydrophobic and hydrophilic silicon dioxide

Experimental results are presented which shed light on the properties of thin discontinuous metal films as chemical sensing elements. They demonstrate further some interesting differences between hydrophilic and hydrophobic sensing structures. Two different methods are used to study the migration of charges out onto the oxide surface outside the metal gate of metal–oxide–semiconductor capacitors after treatment of the surface with hydrochloric acid. The charge migration is observed either as a time dependent increase of the inversion capacitance or as a possibility to generate a photocapacitive current by a chopped light beam hitting the oxide surface at a distance from the contact. It is concluded that the charge migration occurs only if the surface was hydrophilic before the HCl-treatment. For a hydrophobic surface neither the inversion capacitance nor the photocapacitive current changed upon ion-treatment. An explanation for an observed increase of the capacitance level of hydrophilic structures immersed in electrolytes is also given.     

硅树脂/二氧化硅高温相变及介电性能研究

采用氧乙炔喷枪对含有少量有机硅树脂的二氧化硅素坯进行单面烧蚀处理,利用XRD、SEM和SAED表征其高温物相变化.研究发现,高温烧蚀后的二氧化硅中有少量α-方石英析出,并伴有α-SiC、β-SiC新相生成,在此基础上研究了物态变化对材料高温介电性能的影响.     

Directed growth of colloidal crystals on a hydrophobic polymer film by using hydrophilic traps

Deposition of colloidal crystal films onto a hydrophobic surface using capillary force-induced self-assembly is difficult to achieve because of wetting problems of the aqueous colloids with the substrate. We present here a method to overcome this problem. By introducing a hydrophilic trench around the hydrophobic polymer, uniform crystalline colloidal films can be deposited onto the surface of the polymer, provided a sufficient volume of suspension is used. The hydrophilic area around the polymer acts like an artificial trap that can help pin the colloidal suspension on the surface of the hydrophobic polymer surface and direct the self-assembly of colloidal spheres, which is the key to fabricate a uniform colloidal crystal film on the polymer surface.     

纤维增强石英复合材料的改性处理及性能研究EI北大核心CSCD

采用气相接枝方法对纤维增强石英复合材料进行改性处理,对材料的微观形貌、比表面积、介电性能、力学性能和吸湿率等进行测试和分析。结果表明,改性处理和后续热处理对材料的微观形貌和比表面积影响很小,且对材料的介电性能和力学性能没有损伤。改性处理后,材料的介电损耗随频率的变化范围从4.7×10^-3~6.8×10^-3明显降低到1.7×10^-3~2.9×10^-3,拉伸强度从48.58 MPa明显提高到63.49 MPa。改性处理的优选处理条件为(T bp+30℃)/72 h/80%M。材料的极限吸湿率在改性处理后从6.35%降低到0.32%,说明该方法具有优异的防潮效果。     

二氧化硅/木材复合材料的微观结构与物理性能

为了明确二氧化硅/ 木材复合材料的微观结构与物理性能, 通过EDAX 及XRD 的测定分析了溶胶2凝胶法制备的二氧化硅/ 木材复合材料的微观结构, 通过应力松弛、介电性质、热重、表面显微硬度的测定分析了该材料的物理性能。结果表明: 生成的二氧化硅与增重率呈正相关, 在纤维饱和点以下, 生成的二氧化硅存在于细胞壁中。XRD 衍射峰位置没有改变, 增重率增大, 峰强减弱, 结晶度减小。应力松弛量变小, 材料内部的结合力增强, 分子间产生了交联结合。介电常数值增大, 介电损耗随着频率的增加呈先增加后减小的趋势, 室温下, 出现最大峰值的频率均在log f = 6. 5 Hz 附近。热失重过程中, 快速失重的起始温度提高, 残余质量增加, 表面显微硬度提高。      

粘结剂对石英基复合材料电磁性能的影响研究

研究对比了水玻璃和聚乙烯醇两种粘结剂对石英基复合材料电磁屏蔽效能、吸波性能和抗压强度的影响。实验结果表明，在150MHz～1．5GHz频率范围内，水玻璃作粘结剂的试样其屏蔽效能要明显高于聚乙烯醇试样；在2.6～3．85GHz和8．5～12．4GHz频率内，水玻璃作为粘结剂的试样，其吸波曲线比较平缓，而聚乙烯醇试样则存在较为明显的吸收峰。水玻璃作粘结剂时，试样的抗压强度要高于聚乙烯醇试样。     

应用纳米二氧化硅改进外墙涂料性能的研究

对不同添加量纳米二氧化硅 (SiO2 )对外墙涂料性能产生的不同效能进行了表征 ,从而找到纳米SiO2 对外墙涂料影响的相关参数。     

球磨作用对改性二氧化硅热行为的影响

对天然二氧化硅分别经不同条件球磨改性,并分别采用TGA、X射线衍射分析、红外光谱分析和粒度分析等对改性二氧化硅样品进行表征,研究了球磨作用对改性二氧化硅热行为的影响.结果表明,在TGA曲线上,原料二氧化硅失重率很低,而球磨后二氧化硅失重率都较大.从TGA曲线可知,经球磨后硅烷偶联剂KH-560并不是简单的物理吸附而是化学吸附于改性二氧化硅表面.结构表征结果表明,不同球磨条件下所得改性二氧化硅的结构有显著差异.因此,不同球磨条件下所得改性二氧化硅的热行为差异主要是由相应改性二氧化硅的结构变化差异所引起的.     

纳米SiO2改性低分子环氧树脂的研究

采用纳米SiO2对低分子液态环氧树脂进行改性,讨论了纳米SiO2与环氧树脂间偶联形成的环氧树脂-偶联剂-纳米SiO2的层间结构.实验指出,当环氧树脂与纳米SiO2比例为100∶3(质量比)时,其综合物理机械性能达到最大值.     

二氧化硅/木材复合材料的晶胞与Matrix区域的变化

为了弄清楚由于二氧化硅介入木材细胞壁引起结晶区与Matrix区域的变化,通过二氧化硅/木材复合材料细胞壁膨胀率、XRD测定及分析其结晶度、结晶区长度、宽度,研究结晶区与Matrix区域的形态变化及二氧化硅凝胶粒子介入木材细胞壁的空间位置.结果表明:溶胶-凝胶法制备的二氧化硅/木材复合材料,细胞壁的膨胀率随着增重率的增加而增大,且有两个不同的增大过程,相同增重率条件下,加硅烷偶联剂法制备的细胞壁膨胀率比直接溶胶-凝胶法制备的大.XRD谱分析表明,结晶度随着增重率的增加而减小,有两个不同的减小过程,衍射峰的位置不变,晶胞不变;Scherrer公式计算表明结晶区的宽度及长度均不变.     

Electron cyclotron resonance (ECR) plasma-enhanced chemical vapour deposition of silicon dioxide on strained-SiGe films using tetraethylorthosilicate

Silicon dioxide films on strained Si_1−x Ge _x have been deposited by electron cyclotron resonance (ECR) plasma-enhanced chemical vapour deposition technique using tetraethylorthosilicate (TEOS) at room temperature. The deposition rate as a function of time and substrate temperature has been studied. MOS capacitors fabricated using deposited oxides have been used to characterize the electrical properties of silicon dioxide films. Deposited oxide film shows its suitability for microelectronic applications.     

Influence of pressure annealing on electrical properties of Mn implanted silicon

The effect of annealing at 610-720 K under enhanced hydrostatic pressure (HP) on electrical properties of manganese implanted Czochralski grown silicon (CzSi:Mn) and floating zone grown silicon (FzSi:Mn) (doses up to 1×10¹⁶ cm⁻¹, E=160 keV) was investigated by electrical C-V, I-V and admittance measurements. Mn⁺ implantation produces both donor-like and acceptor-like implantation-induced defects. The stress-induced decrease in the hole concentration was detected in CzSi implanted by Mn⁺ and annealed at temperatures 610-670 K. The effect of changing initial conductivity of CzSi:Mn samples of high concentration of interstitial oxygen, from p type to n type, due to thermal donors (TDs) generation has been observed. The electron concentration after type conversion depends on annealing conditions and Mn⁺ dose. The TDs generation has not been detected in FzSi:Mn samples containing lower oxygen concentration, however, the FzSi:Mn samples annealed at 720 K under 10⁵ Pa for 10 h indicate at the implanted side the increased carrier concentration due to the defects produced by Mn⁺ implantation. The heat treatment of FzSi:Mn under HP at 720 K for 10 h results in further increase of carrier concentration due to the defect generation.     

Synthesis,structure and photocatalytic properties of nanoparticles from a carbon-containing composite based on silicon oxide modified with titanium dioxide

A pulsed plasmochemical method was used to obtain carbon-containing nanocomposites based on silicon oxide modified with titanium dioxide. The material contained a Si_xC_yO_z carrier with an average size of 50–150?nm and a shell of fine particles with an average size of 5–10?nm. The phase composition and morphology of the synthesized composites was studied by X-ray diffraction and transmission electron microscopy. The optical and photocatalytic properties of the nanoparticles from the carbon-based composite based on silicon oxide encapsulated in titanium dioxide were studied. The synthesized composite showed a high photocatalytic activity due to the decomposition of methylene blue under the influence of visible light in the wavelength range of 460–630?nm.     

蒙脱土对硅橡胶基磁流变弹性体性能的影响

考察蒙脱土对硅橡胶基磁流变弹性的动态力学特性和磁流变性能的影响，通过调节体系中蒙脱土的含量优化硅橡胶磁流变弹性体的综合性能。研究结果表明，当弹性体中蒙脱土的含量在4．6％时，硅橡胶基磁流变弹性体／蒙脱土复合材料的模量比纯弹性体的模量提高了近345％，硅橡胶磁流变弹性体的磁致模量达到1.76MPa，磁流变效应为63．7％。     

The effect of silicon dioxide content of natural stones on their strength properties,material removal rate and power consumption in diamond grinding

The paper addresses the influence of silicon dioxide content of natural stones on their Mohs hardness, ultimate uniaxial compression strength, microhardness as well as on the removal rate and power consumption in diamond grinding of these materials. An increase in the amount of this constituent in natural stones is demonstrated to have an effect on strength properties and power consumption in grinding and a considerable effect on removal rate in diamond grinding.     

Influence of microstructure and hydrogen concentration on amorphous silicon crystallization

Hydrogenated amorphous silicon samples were deposited on glass substrates at different temperatures by high frequency plasma-enhanced chemical vapor deposition. In this way, samples with different hydrogen concentrations and structures were obtained. The transition from an amorphous to a crystalline material, induced by a four-step thermal annealing sequence, has been followed. Effusion of hydrogen from the films plays an important role in the nucleation and growth mechanisms of crystalline silicon grains. Measurements of hydrogen concentrations, Raman scattering, X-ray diffraction and UV reflectance showed that an enhanced crystallization was obtained on samples deposited at lower substrate temperatures. A correlation between these measurements allows to analyze the evolution of structural properties of the samples. The presence of voids in the material, related to disorder in the amorphous matrix, results in a better quality of the resulting nanocrystalline silicon thin films.     

Influence of thermal oxidation on the interfacial properties of ultrathin strained silicon layers

In this work we examine the influence of thermal oxidation on the electrical characteristics of ultra-thin strained silicon layers grown on relaxed Si_0.78Ge_0.22 substrates under moderate to high thermal budget conditions in N₂O ambient at 800 °C. The results reveal the presence of a large density of interfacial traps which depends on the oxidation process. As long as the strained silicon layer remains between the growing oxide and the underlying Si_0.78Ge_0.22 layer, the density of interface traps increases with increasing oxidation time. When the oxidation process consumes the s-Si layer the interface state density undergoes a significant reduction of the order of 40%. This experimental evidence signifies that the strained silicon-Si_0.78Ge_0.22 interface is a major source of the measured interfacial defects. This situation can be detected only when the front SiO₂-strained silicon interface and the rear strained silicon-Si_0.78Ge_0.22 interface are in close proximity, i.e. within a distance of 5 nm or less. Finally, the influence of the material quality deterioration—as a result of the thermal treatment—to the interfacial properties of the structure is discussed.     

Influence of colloidal silica sol on fresh properties of cement paste as compared to nano-silica powder with agglomerates in micron-scale

Influence of colloidal silica sol (SS) with mono-dispersed nano-particles on fresh properties of cement paste was investigated as compared to nano-silica powder (NS) with agglomerates in micron-scale. The SS addition showed a much greater influence on sedimentation and rheological behavior of the paste than the NS incorporation, because the nano-particles in SS coagulate immediately once cement is mixed into water containing SS, forming loose floc and coating layer around cement particles. The loose floc cannot function as fillers to release free water, but possesses a more open microstructure, leading to a higher free water retention capacity than the agglomerates in NS. However, addition of SS presented an obviously better accelerating effect on cement hydration than that of NS, though the nano-particles in SS are nearly the same as those in NS in primary particle size and the flocs in the paste with SS addition are typically larger than the agglomerates in NS, implying that the acceleration may have nothing to do with the seeding effect. Through detecting calcium-absorbing properties of NS and SS, it is found that the accelerating effect is highly dependent on the rapid depletion of calcium ions in the paste. Finally, it was interestingly found that the CH crystals are even more prone to grow along (0001) plane with larger size in the paste with SS addition, because the coagulated gel network in the paste slows down the diffusion rate of the released ions and eliminate the convection in the system, thus the 3D nucleation and growth of the CH crystals were suppressed.