激光诱导化学气相沉积法制备纳米氮化硅及粉体光谱特性研究

氮化硅是优良的陶瓷材料,应用广泛.本文研究了激光诱导化学气相沉积法制备纳米氮化硅的工作原理,提出了减少游离硅的措施,利用双光束激发制备了超微的、非晶纳米氮化硅粉体.实验证明,纳米氮化硅粉体具有一些特殊的物理性能和光谱特性.     

纳米氮化硅粉体的制备

本文用碳热还原法制备了纳米氮化硅粉体,研究了纳米氮化硅颗粒的表面形貌及其电子自旋共振谱。     

纳米氮化硅对氯磺化聚乙烯橡胶耐磨性能的影响

采用低相对分子质量氯磺化聚乙烯改性的纳米氮化硅填充氯磺化聚乙烯橡胶(CSM)制备纳米氮化硅/CSM复合材料,并对其性能进行研究.结果表明,低相对分子质量氯磺化聚乙烯与纳米氮化硅质量比为0.08时,改性效果较好,可有效地阻止纳米氮化硅的团聚;1份改性纳米氮化硅填充的CSM胶料耐磨性能比未加改性氮化硅的CSM胶料提高了1.8倍,其余物理性能变化不大.     

加入纳米氮化硅对氮化硅陶瓷性能与结构影响

本文以亚微米级氮化硅为起始原料，加入纳米氮化硅来增强基体，添加氧化铝和氧化钇为烧结助剂，等静压成型，采用无压烧结的方式来制备具有优良性能的氮化硅陶瓷。主要研究了纳米氮化硅的分散；纳米氮化硅的加入量对氮化硅陶瓷力学性能的影响；纳米氮化硅的加入量对氮化硅陶瓷使用性能的影响；纳米氮化硅的加入量对氮化硅陶瓷显微结构的影响。研究结果表明：乙醇作为溶剂在分散介质为聚乙二醇的情况下，超声波震荡40分钟时，纳米氮化硅分散效果最好；随纳米氮化硅加入量的增加，显气孔率增加，吸水率增大；加入3wt％的纳米氮化硅时，试样的体积密度最大，抗弯强度、洛氏硬度、断裂韧性最好，具有较理想的显微结构。     

改性纳米氮化硅/FKM复合材料的制备和性能研究

采用甲基丙烯酸六氟丁酯-甲基丙烯酸甲酯-甲基丙烯酸缩水甘油酯三元共聚物对纳米氮化硅进行表面改性,制备改性纳米氮化硅/氟橡胶(FKM)复合材料,并对其性能进行研究.结果表明:改性纳米氮化硅在FKM基体中分散均匀;当改性纳米氮化硅用量为1.5份时,改性纳米氮化硅/FKM复合材料的综合物理性能、耐磨性能、耐热空气老化性能和耐油性能较好.     

纳米氮化硅/三元乙丙橡胶复合材料的制备与性能

用甲基丙烯酸锌原位聚合改性纳米氮化硅,再将改性纳米氮化硅填充到三元乙丙橡胶中以制备纳米橡胶复合材料,研究了复合材料的基本力学性能、耐热老化性能、耐油性能和耐磨性能等。结果表明,添加改性的纳米氮化硅在一定程度上提高了三元乙丙橡胶的撕裂强度、扯断伸长率和拉伸强度,邵尔A硬度也小幅上升。当改性纳米氮化硅的添加量为1.0份(质量)时,纳米氮化硅/三元乙丙橡胶复合材料的耐热老化性能和耐油性能有一定程度的提高,其综合性能也达到最佳。用甲基丙烯酸锌原位聚合改性可以改善纳米氮化硅与三元乙丙橡胶基质间的界面作用,提高其在三元乙丙橡胶中的分散效果。     

LMPB-g-KH-570改性纳米氮化硅/丙烯酸酯橡胶复合材料的制备与性能研究

采用溶液聚合法将硅烷偶联剂KH-570接枝到低相对分子质量的聚丁二烯液体橡胶(LMPB)分子长链中,合成了新型大分子表面处理剂LMPB-g-KH-570,用其对纳米氮化硅进行表面改性,制备改性纳米氮化硅/丙烯酸酯橡胶(ACM)复合材料,并对其结构和性能进行研究。结果表明:LMPB-g-KH-570与纳米氮化硅发生了化学键合;在复合材料中加入适量LMPB-g-KH-570,可以改善纳米氮化硅在复合材料中的分散性,提高复合材料的物理性能。     

改性纳米氮化硅/EPDM复合材料的制备与性能研究

分别采用液体聚丁二烯接枝甲基丙烯酸缩水甘油酯(LMPB-g-GMA)和无规聚丙烯接枝马来酸酐(APP-gMAH)对纳米氮化硅进行改性,制备改性纳米氮化硅/EPDM复合材料,并对复合材料的性能进行研究.结果表明:改性纳米氮化硅对EPDM具有良好的补强作用;随着改性纳米氮化硅用量的增大,复合材料邵尔A型硬度变化不大,定伸应力、拉伸强度和撕裂强度总体呈先增大后减小的趋势; LMPB-g-GMA改性纳米氮化硅/EPDM复合材料的拉伸性能和压缩永久变形优于APP-g-MAH改性纳米氮化硅/EPDM复合材料,但耐热空气老化性能略差.     

改性纳米氮化硅/NR/SBR复合材料的制备与性能研究

采用甲基丙烯酸甲酯(MMA)-丙烯酸丁酯(BA)-乙烯基三乙氧基硅烷(VTES)三元共聚物对纳米氮化硅进行表面改性,制备改性纳米氮化硅/NR/SBR复合材料,并对复合材料的性能进行研究.结果表明,采用MMA-BA-VTES三元共聚物改性后,纳米氮化硅的平均粒径明显减小,分散性改善;当改性纳米氮化硅用量为2.5份时,复合材料的综合物理性能最优.     

纳米氮化硅陶瓷的抗热震性能研究

研究了由热压法制备的晶粒尺寸为 100nm 左右的氮化硅陶瓷抗热震性能.研究结果表明,纳米氮化硅陶瓷表现出原始短裂纹扩展特征;起始粉末粒度对氮化硅陶瓷的力学性能和抗热震性有一定影响.在纳米尺度范围内,晶粒较粗大的氮化硅陶瓷具有较好的抗热震性能;随起始粉末中仪 α-Si3N4 含量的增加,氮化硅陶瓷的抗热震性能得到明显提高.     

A multilayered approach of Si/SiO to promote carrier transport in electroluminescence of Si nanocrystals

The electroluminescence (EL) and photoluminescence of Si nanocrystals (Si-nc) from multilayered samples of Si/SiO are investigated. Si-nc are formed within Si and SiO layers after furnace annealing. It is found that the presence of Si interlayers creates extra carrier paths for EL emission. A comparative study is further performed on a multilayered Si/SiO sample and a single-layered one with Si and SiO homogeneously mixed. Both samples have the same ratio of Si to O and the same contents of Si and O. The multilayered sample is found to have higher EL intensity, less turn-on voltage, lower resistance, and higher current efficiency than the single-layered one. The results indicate that Si interlayers in Si/SiO may act as carrier channels, which promote carrier transport and enhance the EL emission of Si-nc.     

不同Si/B比含银可溶性玻璃结构与抗菌性能

利用XRD测试分析手段对制备的Si-B-Zn-Ca-P-Ag-O系统分析,实验结果表明:随着体系中Si/B比的不同,抗菌材料结构发生从晶体到玻璃体的变化过程,并且在Si/B=3和5(molar ratio)时具有良好的抗菌效果,MIC(最小抑菌浓度)值分别为50mg/L和100mg/L.同时把生成的抗菌材料放在80℃的水中做耐久性实验,实验结果表明Ag离子是随着时间缓慢释放出来的,Si/B=3和5时的溶出量(3.00mg/L和2.35mg/L)明显高于Si/B=1和8.4时的溶出量(0.85 mg/L和0.53 mg/L).     

Novel modification of cyanate ester by epoxidized polysiloxane

A novel modification of cyanate ester (CE) resin by epoxidized polysiloxane (E‐Si) has been developed, and the modified system is coded as CE/E‐Si. E‐Si was prepared by the reactions among octamethylcyclotetrasiloxane, hexamethyldisiloxane, (3‐aminopropyl)‐methyldiethoxysilane, and diglycidyl ether of bisphenol‐A resin. Six formulations were designed to evaluate the effect of the weight ratio between CE and E‐Si on performance parameters. Results reveal that the addition of E‐Si in CE resin cannot only significantly decrease the curing temperature of the CE resin but also improve the water resistance and toughness of original CE resin. Moreover, these positive effects increase with the increase of E‐Si concentration in CE/E‐Si systems. Thermal property investigation shows that the glass‐transition temperature and initial degradation temperature of CE/E‐Si systems are lower than that of original CE resin. For the flexural properties of the CE/E‐Si systems, the E‐Si concentration in the system exists a threshold, that is, when the E‐Si concentration is smaller than the threshold, original CE and CE/E‐Si systems have similar flexural properties, whereas when the E‐Si concentration is higher than the threshold, CE/E‐Si systems have lower flexural properties than original CE resin. All these changes of properties are closely correlated to the structure alteration from neat CE to CE/E‐Si networks. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

显微结构对Si_3N_4(Si_2ON_2)结合SiC质棚板性能的影响

通过X射线衍射、扫描电镜、压汞议、立体显微镜等检测手段,对Si3N4(Si2ON2)结合SiC质棚板的显微结构进行了剖析,揭示了显微结构对SiC质棚板宏观性能的影响。认为结合相的抗氧化性及氧化“釉层”的稳定性是决定棚权使用寿命的关键;气孔结构及分布是影响Si3N4(Si2ON2)结合棚极热震稳定性的重要因素。     

Structure,morphology, and photoluminescence of porous Si nanowires: effect of different chemical treatments

The structure and light-emitting properties of Si nanowires (SiNWs) fabricated by a single-step metal-assisted chemical etching (MACE) process on highly boron-doped Si were investigated after different chemical treatments. The Si nanowires that result from the etching of a highly doped p-type Si wafer by MACE are fully porous, and as a result, they show intense photoluminescence (PL) at room temperature, the characteristics of which depend on the surface passivation of the Si nanocrystals composing the nanowires. SiNWs with a hydrogen-terminated nanostructured surface resulting from a chemical treatment with a hydrofluoric acid (HF) solution show red PL, the maximum of which is blueshifted when the samples are further chemically oxidized in a piranha solution. This blueshift of PL is attributed to localized states at the Si/SiO₂ interface at the shell of Si nanocrystals composing the porous SiNWs, which induce an important pinning of the electronic bandgap of the Si material and are involved in the recombination mechanism. After a sequence of HF/piranha/HF treatment, the SiNWs are almost fully dissolved in the chemical solution, which is indicative of their fully porous structure, verified also by transmission electron microscopy investigations. It was also found that a continuous porous Si layer is formed underneath the SiNWs during the MACE process, the thickness of which increases with the increase of etching time. This supports the idea that porous Si formation precedes nanowire formation. The origin of this effect is the increased etching rate at sites with high dopant concentration in the highly doped Si material.     

Electrochemical behaviour of three- to nine-membered cyclic polysilanes

The electrochemical behaviour of cyclic polysilanes, namely, hexamesitylcyclotrisilane (Mes2Si)3 (I), 1,2,3,4-tetra-tert-butyltetramethyl-cyclotetrasilane [t-Bu(Me)Si]4 (II), decaethylcyclopentasilane (Et2Si)5 (III), decapropylcyclopentasilane (Pr2Si)5 (IV), dodecamethylcyclohexasilane (Me2Si)6 (V), tetradecaethylcycloheptasilane (Et2Si)7 (VI), hexadecamethylcyclooctasilane (Me2Si)8 (VII) and octadecamethylcyclononasilane (Me2Si)9 (VIII), have been studied by cyclic voltammetry and preparative scale electrolysis. The effects of electrolyte, ring size and nature of substitutes both on oxidation peak potential and upon reactivity as well as style of product are discussed.     

The modulation on luminescence of Er3+-doped silicon-rich oxide films by the structure evolution of silicon nanoclusters

A series of silicon-rich oxide (SRO) and erbium-doped SRO (SROEr) films imbedded with structural tunable silicon nanoclusters (Si NCs) have been fabricated using sputtering followed by post-annealing. The coalescence of Si NCs is found in the films with large Si excess. The energy transfer rate between Si NCs and Er³⁺ is enhanced, but the luminescence efficiencies of both Si NCs and Er³⁺ are reduced by the coalescent microstructures. Optimization of the microstructures of Si NCs is performed, and the preferential optical performance for both Si NCs and Er³⁺ could be achieved when Si NCs were separated in microstructures.     

Property approach of Si based ZnO films under thermal shock

ZnO and Al-doped ZnO (AZO) films were deposited on p-Si(100) wafers using magnetron sputtering, the effect of thermal shock on Si based films and its interface were evaluated by various characterization methods such as in-situ nanoscratch, atomic force microscope (AFM), X-ray diffraction (XRD), fourier transform infrared (FTIR) spectra and ultraviolet–visible diffuse reflectance spectroscopy (UV-DRS). The results show the adhesion strength of Si/ZnO interface is relatively stable under thermal shock, the surface grains of Si coated ZnO form dense clusters then refine them. XRD and FTIR show Si based films exhibit (002) orientation with good structural stability related to Zn–O bond, the interfacial reactions of Si based films could experience strong interaction through Si, Zn and O atoms located at Si/ZnO interface during thermal shock. Moreover, some comparatively prominent peaks are observed by UV-DRS, which caused by Si interacted with ZnO, the AZO films deposited on quartz glass substrates illustrate the optical properties are obviously influenced and degraded after thermal shock.     

Low-Temperature Purification of Silicon by Dissolution and Solution Growth in Sodium Solvent

Efficient low-cost processes for solar-grade Si production are needed to overcome the deficiency in the supply of Si. We have demonstrated a new method for the purification of Si crystal. Low-purity Si powder was dissolved in a Na melt (solvent), and Si grains were crystallized by Na evaporation from the Na-Si solution at 1173 K. Glow discharge mass spectrometry analysis revealed that the concentrations of impurity elements, except Na and B, were decreased in the crystallized Si grain. In particular, the concentration of Fe which was mainly included in the Si powder decreased from 3200 ppm by mass to 1.5 ppm by mass in a refined Si grain. Iron disilicide was crystallized from the solution before the crystallization of Si. It was suggested that impurities were reduced not only by crystallization from the Na-Si melt but also by the dissolution of Si into the melt. Na contaminating the refined Si grain was eliminated down to 0.055 mass ppm by heating at 1723 K under vacuum.     

Preparation of hybrid composite microspheres containing nanosilicon via microsuspension polymerization

Hybrid composite microspheres with nano‐Si as the core and poly(styrene‐co‐acrylonitrile) as a shell are successfully prepared by a two‐step polymerization technique, which includes dispersion polymerization of styrene and 3‐methacryloxypropyl trimethoxysilane in ethanol for surface modification of nano‐Si followed by microsuspension polymerization of styrene and acrylonitrile in an aqueous phase for encapsulating nano‐Si into an SAN copolymer matrix. The structure and surface properties of modified nano‐Si are investigated by Fourier transform infrared spectroscopy (FTIR) and contact angle. The hybrid composite microspheres are systematically characterized by energy dispersive spectroscopy, thermogravimetric analysis, and transmission electron microscopy (TEM). According to the FTIR spectra and the contact angle experiments, it was determined that a hydrophobic polymer layer was formed on the surface of nano‐Si. TEM showed that nano‐Si was homogeneously dispersed in SAN particles when the loading capacity of nano‐Si in the hybrid composite microspheres was less than 20 wt %. Moreover, scanning electron microscopy and X‐ray photoelectron spectroscopy revealed that there were large amounts of nano‐Si absorbed on the surface of the hybrid composite microspheres, and the mean particle size became much larger when the loading amounts of nano‐Si reached 25 wt %. From this, it can be inferred that nano‐Si overflows from the inner core to the outside surface in the emulsification process and acts as an inorganic dispersant. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43101.