碳纤维网络增强环氧树脂基复合材料的制备与表征

为提高碳纤维/环氧树脂复合材料的刚性和热尺寸稳定性,首先利用短切碳纤维制备了碳纤维网络增强体(CFNR),并将其与环氧树脂复合制备了CFNR/环氧树脂新型复合材料。然后,分别利用扫描电镜和热机械分析仪对CFNR/环氧树脂复合材料的微观结构和热力学性能进行了表征。结果表明:CFNR/环氧树脂复合材料中有明显的网络节点,即碳质粘结点;CFNR/环氧树脂复合材料具有较好的导电性、较高的刚性和较低的热膨胀性,其弹性模量分别为常规短切碳纤维/环氧树脂复合材料及纯环氧树脂的3倍和6倍,平均热膨胀系数(60~200℃)分别为常规短切碳纤维/环氧树脂复合材料的1/15及纯环氧树脂的1/40;随着温度升高,CFNR/环氧树脂复合材料、常规短切碳纤维/环氧树脂复合材料及纯环氧树脂的弹性模量均因环氧树脂变软而降低,当温度高于80℃时,CFNR/环氧树脂复合材料的弹性模量分别约为常规短切碳纤维/环氧树脂复合材料的7倍和纯环氧树脂的近70倍。研究结论可以为开发高刚性、低膨胀聚合物基复合材料提供实验依据和理论指导。     

Fabrication and characterization of carbon fiber reinforced clay/epoxy composite

In this study, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and flexural tests were performed on unfilled, 1, 2, 3, and 4 wt% clay filled SC-15 epoxy to identify the effect of clay weight fraction on thermal and mechanical properties of the epoxy matrix. The flexural results indicate that 2.0 wt% clay filled epoxy showed the highest improvement in flexural strength. DMA studies also revealed that 2.0 wt% system exhibit the highest storage modulus and T _g as compared to neat and other weight fraction. However, TGA results show that thermal stability of composite is insensitive to the clay content. Based on these results, the nanophased epoxy with 2 wt% clay was then utilized in a vacuum assisted resin transfer molding set up with carbon fabric to fabricate laminated composites. The effectiveness of clay addition on thermal and mechanical properties of composites has been evaluated by TGA, DMA, tensile, flexural, and fatigue test. 5 °C increase in glass transition temperature was found in nanocomposite, and the tensile and flexural strengths improved by 5.7 and 13.5 %, respectively as compared to the neat composite. The fatigue strength was also improved significantly. Based on the experimental result, a linear damage model combined with the Weibull distribution function has been established to describe static failure processing of neat and nanophased carbon/epoxy. The simulated stress–strain curves from the model are in good agreement with the test data. Simulated results show that damage processing of neat and nanophased carbon/epoxy described by bimodal Weibull distribution function.     

Fabrication and characterization of nano filler-filled epoxy composites for underfill application

The present research aims to fabricate and characterize different nano filler types and filler loadings in epoxy composites for underfill application. The nano filler types were synthetic diamond (SD), boron nitride (BN), and silica (S). The filler loadings which were considered in the study were varied from 1 to 4 vol%. Sonication process was used to facilitate filler dispersion. The results showed that BN had a good flow ability, with higher flow rates than the other filler types. The thermal conductivity of the composites increased with the addition of fillers, and higher thermal conductivity value is observed in SD system. The coefficient of thermal expansion (CTE) of composites decreased with the addition of filler with lower CTE value shown by BN system. Generally, SD showed higher flexural strength and flexural modulus compared with BN and S. A high filler loading also resulted in decreased flexural strength but increased flexural modulus.     

环氧基倍半硅氧烷的合成与表征

以八乙烯基倍半硅氧烷(OvPOSS)为原料,过氧乙酸为氧化剂,采用官能团衍生法制备了环氧基倍半硅氧烷(epoxy-POSS)。讨论了过氧化氢浓度、反应时间、反应温度、酸体积比对OvPOSS环氧化程度的影响。结果表明,当酸体积比CH3COOH∶H2O2=0.5∶1,反应温度60℃,回流反应12h,OvPOSS上参加反应的乙烯基平均数为4,并用FT-IR、NMR对产物结构进行了表征。     

Fabrication and characterization of nanopore array

A nanopore array with diameter of approximately 30 nm was fabricated by use of focused ion beam (FIB) scanning and thin film coating on Si(100). A thin film of SiO2 with thickness of 200 nm (used as sacrificial layer) was coated by physical evaporation deposition (PVD) first. Next, the thin films of Aluminum with thickness of 500 nm were coated on the surface of SiO2 thin film. A window with an area of 2 x 2 mm2 was opened by reactive ion etching from bottom side and reached to the thin film of SiO2. After that, a fine controlled FIB milling with bitmap function (milling according to a designed pattern in a defined area) was used to scan the area. Signal is obtained by a sensor inside the vacuum chamber collecting secondary electrons emitted from the sputtered material when the beam reach the layer of SiO2. Stopping the milling process at this moment, the nanopore array was derived after removing the sacrificial layer by wet chemical etching. The nanopore arrays were characterized using transmission electron microscopy (TEM) after the FIB drilling.     

Fabrication and characterization of SiC-AIN alloys

SiC-AIN alloys were prepared by the carbothermal reduction of silica and alumina, derived from an intimate mixture of silica, aluminium chloride and starch. The resulting single-phase SiC-AIN powder was hot-pressed without additives to a high density. The dense bodies had a fine-grained uniform microstructure. The Young's elastic modulus, microhardness, fracture toughness, thermal expansion and thermal conductivity were measured as functions of composition. The creep behaviour of the SiC-AIN alloy was compared with that of silicon carbide.     

典型纳米结构制备及其测量表征

针对纳米器件中的典型几何特征,制备了3种纳米结构,采用扫描电子显微镜(SEM)、原子力显微镜(AFM)等测量工具对所制备的纳米样板进行了测量、分析和表征。提出转换薄膜厚度为线宽的公称值、基于多层薄膜淀积技术制备纳米宽度结构的方法,制备出了具有名义线宽尺寸分别为20 nm、25 nm、35 nm的纳米栅线结构。用离线的图像分析算法对所制备的纳米线宽样板的线边缘粗糙度/线宽粗糙度(LER/LWR)以及栅线线宽的一致性进行了评估。实验表明所制备纳米线宽样板的栅线具有较好的一致性,LER/LWR值小,且具有垂直的侧壁。采用电子束直写技术(EBL)和感应耦合等离子体刻蚀(ICP)制备了名义高度为220 nm的硅台阶样板。实验表明刻蚀后栅线边缘LER/LWR的高频成分减少,相关长度变长,均方根偏差值(σ)增大。采用聚焦离子束(FIB)制备了纳米单台阶和多台阶结构,并对Z方向的尺度与加工能量之间的关系进行了分析。     

Fabrication and characterization of electrospun titania nanofibers

Titania (TiO₂) nanofibers were fabricated by electrospinning three representative spin dopes made of titanium (IV) n-butoxide (TNBT) and polyvinylpyrrolidone (PVP) with the TNBT/PVP mass ratio being 1/2 in three solvent systems including N,N-dimethylformamide (DMF), isopropanol, and DMF/isopropanol (1/1 mass ratio) mixture, followed by pyrolysis at 500 °C. The detailed morphological and structural properties of both the as-electrospun precursor nanofibers and the resulting final TiO₂ nanofibers were characterized by SEM, TEM, and XRD. The results indicated that the precursor nanofibers and the final TiO₂ nanofibers made from the spin dopes containing DMF alone or DMF/isopropanol mixture as the solvent had the common cylindrical morphology with diameters ranging from tens to hundreds of nanometers, while those made from the spin dope containing isopropanol alone as the solvent had an abnormal concave morphology with sizes/widths ranging from sub-microns to microns. Despite the morphological discrepancies, all precursor nanofibers were structurally amorphous without distinguishable phase separation, while all final TiO₂ nanofibers consisted of anatase-phased TiO₂ single-crystalline grains with sizes of approximately 10 nm. The electrospun TiO₂ nanofiber mat is expected to significantly outperform other forms (such as powder and film) of TiO₂ for the solar cell (particularly dye-sensitized solar cell) and photo-catalysis applications.     

Fabrication and characterization of Ge-doped flat fibres

In this paper, we demonstrate fabrication and characterization of Ge-doped flat fibres. The Ge-doped flat fibre was fabricated from a 6 mol% Ge-doped preform. The flat fibre was successfully fabricated using dual stage drawing. Near field characterization was done and results show similar modal profile patterns as simulated using the software COMSOL. The results confirmed that with dual stage drawing and optimized drawing parameters, flat fibres with no defect holes can be fabricated.     

Fabrication and characterization of electrospun mullite nanofibers

Continuous mullite (3Al₂O₃·2SiO₂) nanofibers were fabricated by a sol-gel electrospinning technique. The detailed crystallization development and micromorphological evolution of both the as-electrospun nanofibers and the sintered mullite nanofibers were investigated. Results indicated that the spinnability and micromorphological evolution of mullite nanofibers are largely dependent on the viscosity η of the mullite sol, which can be adjusted by polyvinylprrolidone (PVP) content. Mullite nanofibers with common cylindrical morphology and diameters ranging from 400 nm to 800 nm could be obtained easily and rapidly when PVP content is ranged from 5 wt.% to 8 wt.%. High purity polycrystalline mullite nanofibers with diameters of about 200 nm were obtained after sintering at 1200 °C for 2 h. All sintered nanofibers consisted of single crystalline grains with size of approximately 100 nm.     

Fabrication and characterization of sputtered-carbon microelectrode arrays

This paper describes a robust and reliable process for fabricating a novel sputter-deposited, thin-film carbon microelectrode array using standard integrated circuit technologies and silicon micromachining. Sputter-deposited carbon films were investigated as potential candidates for microelectrode materials. The surface properties and cross section of the microelectrode arrays were studied by atomic force microscopy and scanning electron microscopy, respectively. Electrical site impedance, crosstalk, and lifetime (dielectric integrity) of microelectrodes in the array were characterized. Electrochemical response of the microelectrodes to hexaammineruthenium(III) chloride and dopamine were investigated by fast-scan cyclic voltammetry and high-speed, computer-based chronoamperometry; results show that thin-film carbon microelectrodes are well-behaved electrochemically. The thin carbon films offer extremely good electrical, mechanical, and chemical properties and thus qualify as viable candidates for various electroanalytical applications, particularly acute neurophysiological studies.     

Fabrication and characterization of a concentric cylindricalmicrotransformer

This paper describes the use of a nonphotolithographic technique-microcontact printing-to fabricate a concentric cylindrical microtransformer having an outer diameter of ~350 μm. For frequencies of up to 20 kHz, this microtransformer has a high coupling coefficient (>0.9). At higher frequencies, properties of the ferromagnetic material used in the construction of the microtransformer limit performance     

碱催化多孔二氧化硅薄膜的制备和性能表征

以水为介质,NH3·H2O为催化剂,丙三醇(C3H5(OH)3和聚乙烯醇(PVA)为添加剂,正硅酸乙脂(TEOS)溶胶 凝胶工艺可制备纳米多孔二氧化硅薄膜。体系的H2O/TEOS>15,TEOS的水解 聚合过程可通过添加剂效应,pH效应等控制。碱催化会使二氧化硅的溶解度增大,也能使二氧化硅胶粒带负电荷,抑制了二氧化硅胶粒之间的聚合长大,而丙三醇与TEOS的水解中间Si(OR)4-x(OH)x结合,抑制其与二氧化硅胶粒的聚合。聚乙烯醇(PVA)能使二氧化硅溶胶具有网状结构,使二氧化硅溶胶易于成膜。该工艺制备的多孔二氧化硅薄膜具有纳米多孔结构。其Vicker硬度在600～800N/mm2,热导率<0.2W·m-1K-1。     

纳米多孔二氧化硅薄膜的制备及性能

以N(C_8H_(15))_4~+OH~-为催化剂,用正硅酸乙脂(TEOS)溶胶-凝胶工艺制备出纳米多孔二氧化硅薄膜。体系的H_2O/TEOS>25,强碱催化使二氧化硅的溶解度增大并使二氧化硅胶粒带负电荷,抑制了二氧化硅的聚合。丙三醇与TEOS的水解中间体Si(OC_2H_5)_4-x(OH)_x及二氧化硅胶粒Si_xO_y(OH)_z~(+n)表面Si-OH形成氢键,抑制了二氧化硅的聚沉。聚乙烯醇(PVA)使粒状二氧化硅溶胶具有网状结构,易于成膜。薄膜由致密结构转化为均匀纳米多孔结构是构成薄膜的二氧化硅胶粒在热处理时聚集和塑性形变的结果。多孔二氧化硅薄膜的折射率为1.27～1.42,介电常数为1.578～2.016,热导率为0.2W/(m·K)。     

Fabrication and mechanical properties of well-dispersed multiwalled carbon nanotubes/epoxy composites

Multiwalled carbon nanotubes (MWCNTs)/epoxy nanocomposites were fabricated by using ultrasonication and the cast molding method. In this process, MWCNTs modified by mixed acids were well dispersed and highly loaded in an epoxy matrix. The effects of MWCNTs addition and surface modification on the mechanical performances and fracture morphologies of composites were investigated. It was found that the tensile strength improved with the increase of MWCNTs addition, and when the content of MWCNTs loading reached 8 wt.%, the tensile strength reached the highest value of 69.7 MPa. In addition, the fracture strain also enhanced distinctly, implying that MWCNTs loading not only elevated the tensile strength of the epoxy matrix, but also increased the fracture toughness. Nevertheless, the elastic modulus reduced with the increase of MWCNTs loading. The reasons for the mechanical property changes are discussed.     

Synthesis and characterization of petroleum resins with epoxy groups

Pyrolysis of petroleum hydrocarbons (including diesel pyrolysis) aimed at obtaining polyethylene also creates certain liquid products which can be used for making so-called petroleum resins (PRs). The C₉ fraction from pyrolysis contains among others, styrene and its derivatives, indene and pentanodiene. Petroleum resins with epoxy groups (PREs) have been synthesized by oligomerization of unsaturated components of the C₉ fraction in the presence of 4,4′-azo-bis-[2,3-epoxypropoxy-4-cyano-pentanenitrile] (AEPCP) used as an azoinitiator. The influence of azoinitiator quantity, temperature and time of oligomerization upon the yield and characteristics of the resulting functional petroleum resins has been evaluated. The structure of the products was confirmed by IR-spectroscopy. Our PREs have potential applications as active additives to industrial epoxy resins based on Bisphenol A.     

环氧树脂/二氧化硅杂化材料的制备与性能表征

溶胶-凝胶法制备环氧树脂/SiO2杂化材料,利用FTIR、SEM和综合热分析仪对杂化材料的结构、显微形态及热性能进行了表征.结果表明,杂化材料中SiO2与环氧树脂两相间存在氢键作用;SiO2质量分数＜7%时SiO2与环氧树脂之间无明显相界面,可获得有机聚合物链段与无机网络互穿的有机/无机杂化材料;SiO2质量分数为11%时材料具有最佳耐热性能.