稻壳二氧化硅/环氧树脂纳米复合材料机械性能研究

将稻壳用10%的盐酸处理后在600℃焚烧得到纯度为99.3%的SiO_2,将SiO_2用偶联剂γ-氨丙基三乙氧基硅烷(KH550)改性后与环氧树脂(EP)复合,探讨了SiO_2质量分数在0～5%范围内复合材料的力学性能.研究结果显示:经硅烷偶联剂KH550改性后稻壳SiO_2粒子为无定形态,尺寸在30～50 nm且能显著提高环氧树脂的力学性能.当稻壳SiO_2质量分数为3%时,材料的拉伸性能以及弯曲性能的提高率最大,拉伸强度、拉伸模量、弯曲模量和弯曲强度的提高率分别为27.25%、6.54%、61.7%和24.56%.SEM研究结果显示:复合材料中SiO_2与基体树脂之间有较好的相容性.     

Synergistic Toughening in Ternary Silica/Hollow Glass Spheres/Epoxy Nanocomposites

Herein, the fracture toughness of ternary epoxy systems containing nanosilica and hollow glass microspheres (HGMS) is investigated. The experimental measurements reveal synergistic fracture toughness in some hybrid compositions: The incorporation of 10 phr of HGMS and nanosilica alone modify the fracture toughness of epoxy by 39% and 91%, respectively. However, use of 10 phr hybrid modifier can enhance the fracture toughness of the resin up to 120%. Observations reveal different toughening mechanisms for the blends i.e., plastic deformation for silica nanoparticles and crack bifurcation for HGMS. Both of these toughening mechanisms additively contribute to the synergism in ternary epoxies.     

Thermal Stability Investigation of Synthesized Epoxy-Polyurethane/Silica Nanocomposites

Silicon - In this research, epoxy polyurethane-nano silica nanocomposites have been synthesized using an in-situ method, for which SiO2 nanocomposites had been initially ready in N,...     

环氧树脂/稻壳SiO2纳米复合材料的热性能及拉伸性能研究

将稻壳用酸处理后在600 ℃焚烧得到纯度为99.3%、比表面积为212 m2/g的SiO2。经硅烷偶联剂γ-氨丙基三乙氧基硅烷（KH550）改性后的SiO2为无定形态,尺寸在30~50 nm之间。将改性后的稻壳SiO2与环氧树脂复合,利用热分析方法考察了纳米复合材料在N2气氛中的热性能,并采用万能材料试验机测试其拉伸性能。结果表明：稻壳SiO2的加入能有效增加环氧树脂/稻壳SiO2纳米复合材料的热稳定性,复合材料的起始分解温度（Ti）、分解速率最大时的温度（Tmax）以及失重50 %的分解温度（T50 %）均高于纯环氧树脂,并随稻壳SiO2含量的增加而增加。当环氧树脂/稻壳SiO2纳米复合材料的组成相同时,KH550改性的复合材料的Ti、Tmax和T50 %均比未经过KH550改性的高。随KH550用量增加,复合材料T50 %向高温方向移动。此外,复合材料的拉伸强度、断裂伸长率和模量也高于纯环氧树脂。     

Development and Experimental Study of Milling Electrochemical Spark Micromachining (M-ECSMM) of Silicon

Silicon - Milling Electrochemical Spark Micromachining (M-ECSMM) is hybrid micromachining process which is used to create microfeatures in non-conducting materials. Silicon is one of the abundantly...     

盐雾对环氧涂层防腐蚀性能影响的电化学研究

制备了新型环氧富锌、环氧铁红、环氧云铁3种有机涂层材料。在此基础上，采用交流阻抗技术，对各种环氧涂层在盐雾前后进行了阻抗谱测定，并研究了涂层在盐雾环境中的失效机理。结果表明：3种涂层材料在盐雾实验后，阻抗圆直径均大幅减小，涂层耐腐蚀性能较盐雾前降低。盐雾实验后各涂层的耐腐蚀性能由强到弱依次是环氧云铁、环氧铁红、环氧富锌。通过对盐雾实验前后涂层阻抗谱的分析，比较了几种涂层材料的性能，提出了可能的腐蚀破坏机制。     

聚酰胺11/白炭黑纳米复合材料的非等温结晶动力学研究

采用原位聚合法制备了聚酰胺11（PA11）及PA11/白炭黑纳米复合材料,利用差示扫描量热仪研究了PA11及其纳米复合材料的非等温结晶过程,用经Jeziorny修正的Avrami方程、Mo法对其非等温结晶动力学进行了研究,计算并得到了非等温结晶动力学参数。结果表明,Avrami方程和Mo法都适用于处理PA11及其纳米复合材料的非等温结晶过程;在其非等温结晶过程中,PA11及其纳米复合材料都包括初期结晶和二次结晶两个阶段;Mo法表明,复合材料的结晶速率比PA11的小。此外,用Huffman-Lauritzen理论计算了PA11及其纳米复合材料非等温结晶的结晶活化能,结果表明,纳米复合材料的结晶活化能的绝对值小于PA11。     

Nickel and Lanthanum Hydroxide Nanocomposites with Much Improved Electrochemical Performance for Supercapacitors

By developing a facile low temperature hydrothermal process, we demonstrate the direct growth of nickel and lanthanum hydroxide nanocomposites on Ni‐foam substrate. The hydroxide nanocomposites thus derived show much enhanced overall electrochemical capacitance and improved stability of the alpha nickel hydroxide phase in alkaline solution. By adjusting the initial molar ratio between nickel and lanthanum nitrates from 1:0 to 1:2, the electrochemical behavior, such as specific capacitance, shows a dramatic change, while the nickel hydroxide phase evolves from beta nickel hydroxides (1:0) to alpha nickel hydroxide (1:2). Lanthanum hydroxide is not expected to contribute to the pseudocapacitance as it only shows a capacitance of <10 F/g. The specific capacitance is increased from 970 F/g (Ni:La = 1:0) to 1874 F/g (Ni: La = 1:2) at the discharging current of 1 A/g. At high discharging currents (e.g. 10 A/g), the Ni:La = 1:2 sample can retain a capacitance of 1055 F/g. An excellent cycling performance is demonstrated for the Ni:La = 1:2 nanocomposite sample upon 2000 cycles at the discharging current density of 2 A/g, where the stability of alpha nickel hydroxide in the alkaline solution is improved. The low temperature hydrothermal method compares favorably to other previously documented preparation processes, such as chemical coprecipitation and electrochemical deposition, for lanthanum‐doped nickel hydroxides, where the specific capacitance is typically less than 1000 F/g (1 A/g).     

Experimental Investigation of Epoxy Bonded Polymethylmethacrylate Joints

This paper presents an experimental investigation into various aspects of epoxy-bonded polymethylmethacrylate (PMMA) and PMMA-to-aluminium joints. The effects of adhesive thickness, overlap area, surface roughness, and environmental exposure on the joint strength were studied. Results indicated that the joint strength was not directly proportional to the overlap area, while sanding had a positive effect on the joint strength. A negative effect was observed when adhesive thickness was increased. The fatigue behaviour of adhesively-bonded joints under dynamic loading was found to be independent of frequency, for the range of values tested; however, it was dependent on the test temperature with greater reduction in fatigue life observed in PMMA-to-aluminium joints at higher temperature. Empirical equations from which the fatigue life of joints can be predicted were obtained by regression analysis. Intermittent fatigue testing of the joints was also performed. The epoxy adhesive tested proved to be a satisfactory choice for outdoor exposure. The rate of degradation of the adhesive was slow with the adherend itself degrading at a faster rate than the adhesive or the bondline.     

Experimental Investigation of Epoxy Bonded Polymethylmethacrylate Joints

This paper presents an experimental investigation into various aspects of epoxy-bonded polymethylmethacrylate (PMMA) and PMMA-to-aluminium joints. The effects of adhesive thickness, overlap area, surface roughness, and environmental exposure on the joint strength were studied. Results indicated that the joint strength was not directly proportional to the overlap area, while sanding had a positive effect on the joint strength. A negative effect was observed when adhesive thickness was increased. The fatigue behaviour of adhesively-bonded joints under dynamic loading was found to be independent of frequency, for the range of values tested; however, it was dependent on the test temperature with greater reduction in fatigue life observed in PMMA-to-aluminium joints at higher temperature. Empirical equations from which the fatigue life of joints can be predicted were obtained by regression analysis. Intermittent fatigue testing of the joints was also performed. The epoxy adhesive tested proved to be a satisfactory choice for outdoor exposure. The rate of degradation of the adhesive was slow with the adherend itself degrading at a faster rate than the adhesive or the bondline.     

Experimental and Analytical Investigation of Epoxy/MWCNT Nanocomposites: Electrical,Thermal Properties,and Electric Heating Behavior

The epoxy–matrix nanocomposite films filled with multiwalled carbon nanotubes (MWCNTs, ~10 nm in out diameter and ~4 μm long) were fabricated by a shear-dispersing and thermal curing technology. Whereafter, their microstructure, electrical, and thermal properties, as well as electric heating behavior were characterized as a function of MWCNT content. Unlike the electrical improvement filled with MWCNTs, in which an electrical percolation threshold was observed, the thermal properties showed only some improvements as filler content was increased. The electric heating behavior was studied by considering different environmental conditions, temperature response rapidity, and electric heating efficiency. With an aid of temperature data processing software, Flir Reporter, we performed a comparative analysis for the electric heat distribution on prepared nanocomposite and conventional PI-Kanthal film surface, which demonstrated that the nanocomposite film could provide a more uniform, rapider heating function for deicing application. Moreover, the stable operating temperature (~120°C) for the nanocomposite was determined by cyclic heating–cooling test and dynamic mechanical analysis. Finally, we observed the ice melting process under the action of the electric heating function of the nanocomposite film using an infrared thermal camera. POLYM. ENG. SCI., 60: 233–242, 2019. © 2019 Society of Plastics Engineers     

具有抗菌活性的氧化锌/环氧树脂基纳米复合材料的研究

为了提高环氧树脂(EP)的抗菌性能,延长其使用寿命,采用纳米氧化锌(ZnO)粉末对脂环族EP进行改性,利用溶液浇注法制备了纳米ZnO/EP抗菌复合材料。研究了不同含量的纳米ZnO经硅烷偶联剂表面处理后,对复合材料的抗菌性能及力学性能的影响。结果表明:硅烷偶联剂处理后的纳米ZnO能够在EP中均匀分散;复合材料的抗菌性能随着纳米ZnO用量的增加而显著增大,加入1%纳米ZnO对大肠杆菌的抗菌率达到99.06%,对金黄色葡萄球菌的抗菌率达到99.00%;加入3%纳米ZnO时达到抗菌饱和,且弯曲强度出现极值,为EP的1.66倍;而纳米ZnO的加入对EP原有的固化温度和玻璃化转变温度几乎没有影响。     

KDP晶体金刚石线锯切入方向的研究

KDP晶体具有强烈的各向异性,为了使锯切时锯丝的偏移量较小,获得好的切片表面质量,本文对金刚石线锯切入方向进行了研究.锯丝两边材料去除率差异性的变化是导致锯丝偏移量变化的重要因素,因此本文基于保持锯切时锯丝两边材料去除率差异性最小的原则,分析得出:锯切(001)晶面时,锯丝切入方向的改变不影响锯丝偏移量的大小,锯切二倍频晶面时选择[110]、[-1-10]晶向、锯切三倍频晶面时选择[100]、[-100]晶向,此时锯丝两边材料去除率差异性最小.该线锯切入方向的提出对于KDP晶体的线锯切片技术的研究具有重要的意义.     

环氧树脂/有机蒙脱土复合材料的制备与力学性能研究

利用插层聚合法制备了环氧树脂/有机蒙脱土(EP/OMMT)复合材料.采用XRD对复合材料进行了表征,并研究了复合材料力学性能.实验表明:环氧树脂/有机蒙脱土形成了剥离型的纳米复合材料结构;环氧树脂中加入适量的有机蒙脱土,可以提高环氧树脂的拉伸强度和冲击强度.当经过改性的OMMT质量分数为5%时,EP/钛酸酯偶联剂(Coupler)-OMMT复合材料的拉伸强度达到51.21 MPa,提高了40.26%;当OMMT质量分数为3%时,EP/Coupler-OMMT复合材料冲击强度达25.31 kJ/m2,提高了34.56%.     

PA11/白炭黑纳米复合材料非等温结晶动力学研究

采用原位聚合法制备了聚酰胺(PA)11/白炭黑纳米复合材料,利用差示扫描量热仪研究了PA11纳米复合材料的非等温结晶过程,用经Jeziorny修正的Avrami方程、Mo法对其非等温结晶动力学进行了分析,计算并得到了非等温结晶动力学参数。结果表明,Avrami方程、Mo法都适用于处理PA11及其纳米复合材料的非等温结晶过程;在非等温结晶过程中,PA11及其纳米复合材料都包括初期结晶和二次结晶两个阶段;Avrami方程和Mo法表明,白炭黑含量较低时可提高复合材料的结晶速率,含量过高时则阻碍晶体的生长。     

PA11/白炭黑纳米复合材料等温结晶动力学的研究

采用差示扫描量热法(DSC)研究了原位聚合尼龙11/白炭黑纳米复合材料的等温结晶行为,并应用Avrami方程分析了其等温结晶动力学过程。结果表明,纳米白炭黑对尼龙11基体起到异相成核作用,使其原位纳米复合材料动力学常数变大。Hoffman成核结晶理论计算结果表明,原位纳米复合材料的Kg大于尼龙11且随着纳米含量的增加而增加,说明纳米白炭黑阻碍了尼龙11分子链的运动,同时尼龙11有晶核生长占主导地位逐渐向成核机制占主导地位转变。     

Investigation on the Mechanical and Thermal Properties of Intercalated Epoxy/Layered Silicate Nanocomposites

Epoxy resin/layered silicate nanocomposites with various clay contents were prepared. The structural studies showed the intercalation of epoxy polymer chains into the clay galleries. The adhesion analysis of nanocomposite coating films on metallic substrates showed the excellent adhesion of epoxy-based nanocomposite coatings on iron plates, especially in lower clay loadings. According to the hardness test results, the organoclay minerals caused the increasing of the hardness of epoxy nanocomposites. The thermal properties of nanocomposites were evaluated by means of DSC and TGA analysis. The tensile and compression strengths of cured epoxy/clay systems were also investigated.     

Preparation and Investigation of Novel PVA/Silica Nanocomposites with Potential Application in NLO

This research describes the synthesis of organomodfied sillica nanoparticles (NP)s /polyvinyl alcohol (PVA) nanocomposites (NC)s through consecutive three-steps. In the first step the surface modifier, namely 1-(benzo[d]thiazol-2-yl)-3-(3-(triethoxysilyl)propyl)urea, was prepared from the reaction of benzo[d]thiazol-2-amine and 3-isocyanatopropyl triethoxysilane. With success in the first step, the surface modifications of silica NPs were achieved by sol-gel procedure and at the final step, the preparation of PVA/silica NCs were targeted. The optical properties and morphology of the NPs and NCs were characterized. This investigation clearly showed that the new coupling agent could effectively prevent the agreggation of NPs.     

粘土/环氧树脂纳米复合材料的性能研究

利用改性蒙脱土制备粘土/环氧树脂纳米复合材料,并对材料的结构和性能进行测试和表征.结果表明,少量蒙脱土的加入可以较大地提高材料的力学性能和耐热性能,对环氧树脂同时起到了增韧增强的作用.     

Nanoindentation and Morphological Studies of Epoxy Nanocomposites

Summary: This paper investigates the mechanical properties of the epoxy–organoclay nanocomposites by the nanoindentation technique. The nanocomposites were prepared by in situ polymerization and a mixture of exfoliated and intercalated composites structure was obtained as evidenced by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The hardness, elastic modulus, and the creep behavior of the nanocomposites have been evaluated as a function of clay concentration. It has been found that incorporation of 7.5 wt.‐% of clay nanofiller enhances the elastic modulus and hardness of the epoxy matrix by about 20 and 6%, respectively. The elastic modulus data calculated from indentation experiments are comparable with those obtained from a tensile test. An optimum clay loading level was found to be 2.5 wt.‐% to maximum enhance the creep resistance of the epoxy matrix. The lowered creep resistance with higher clay loading could be due to the reduced crosslinking density near the clay surface caused by the plasticizing effect from the pending of alkyl ammonium chains on the clay surface. An attempt has been made to correlate the fracture toughness of the nanocomposites with the ratio of modulus to hardness obtained from nanoindentation experiments.

Ratio of modulus to hardness (E/H) and the fracture toughness (K_IC) versus clay loading for the epoxy nanocomposites.