贵东岩体X荧光光谱、等离子体质谱分析结果及其对岩体演化的指示意义

粤北贵东岩体是由形成于早侏罗世(燕山一期)的粗粒黑云母花岗岩、晚侏罗世(燕山三期)的中细粒二云母或白云母花岗岩、早白垩世(燕山四期)石英正长岩组成的复式岩体。不同期次花岗岩进行X荧光光谱和等离子体质谱测试结果显示：(1)同期岩体自上而下具有硅碱组分降低,铁镁含量组分和LREE,LREE/HREE及(La/Yb),N值总体升高的变化趋势;(2)复式岩体从早期到晚期,岩体的硅碱组分逐渐升高,而∑REE,LREE/HREE,(La/Yb)_N及δEu值则逐渐降低,稀土配分曲线由右倾型向海鸥型过渡,表明复式岩体的形成是地壳岩石多次原地熔融(重熔)的结果;(3)微量元素组成同样反映复式岩体形成是地壳岩石多次原地熔融(重熔)的结果;多次熔融(重熔)导致晚期岩体U丰度和U/Th比值升高,故该区铀矿床的形成多与燕山晚期的熔融(重熔)事件有关。     

Efficient Hybrid Photovoltaic Devices Based on in-situ Electrochemical Copolymerization of 3-Methylthiophene and Bithiophene into Pores of Nanocrystalline TiO2

Novel organic and inorganic hybrid photovoltaic devices were thbricated by in-situ electrochemical copolymerization of 3-methylthiophene（3MT） and bithiophene（BT） into the pores of nanostructured TiO2 sintered on fluorine-doped tin oxide（FTO） substrate. The photoactive layer was investigated by Fourier transform infrared（FTIR） spectroscopy, ultraviolet-visable（UV-Vis） spectrometer, scanning electron microscope（SEM） and cyclic voltammo- gram characterization. Device efficiency based on different molar feed ratios of 3MT and BT during electrochemical polymerization, and the effect of in-situ copolymer state（doped by electrolyte and de-doped） were measured and compared. Under the solar illumination of 100 mW/cm2（AM 1.5）, an optimized device efficiency of 0.938% was obtained when the molar ratio of 3MT to BT was 500：1, polymerization time was 500 s and the system was in doped copolymer state, respectively. The mechanism of overall photovoltaic parameter improvement was discussed.     

Unusual plastic deformation and damage features in titanium: Experimental tests and constitutive modeling

In this paper, we present an experimental study on plastic deformation and damage of polycrystalline pure HCP Ti, as well as modeling of the observed behavior. Mechanical characterization data were conducted, which indicate that the material is orthotropic and displays tension-compression asymmetry. The ex-situ and in-situ X-ray tomography measurements conducted reveal that damage distribution and evolution in this HCP Ti material is markedly different than in a typical FCC material such as copper. Stewart and Cazacu (2011) anisotropic elastic/plastic damage model is used to describe the behavior. All the parameters involved in this model have a clear physical significance, being related to plastic properties, and are determined from very few simple mechanical tests. It is shown that this model predicts correctly the anisotropy in plastic deformation, and its strong influence on damage distribution and damage accumulation. Specifically, for a smooth axisymmetric specimen subject to uniaxial tension, damage initiates at the center of the specimen, and is diffuse; the level of damage close to failure being very low. On the other hand, for a notched specimen subject to the same loading the model predicts that damage initiates at the outer surface of the specimen, and further grows from the outer surface to the center of the specimen, which corroborates with the in-situ tomography data.     

Controllable synthesis of high aspect ratio Mg_2B_2O_5 nanowires and their applications in reinforced polyhydroxyalkanoate composites

Highly pure magnesium borate （Mg2B2O5） nanowires with an average diameter of - 30 nm, an average length of 15 μm, and a high aspect ratio of - 500 have been synthesized on a large scale via a two-step method. MgBO2（OH） nanowires with high aspect ratios were first prepared via a PVP-assisted hydrothermal technique. Using these nanowires as precursors, single crystalline Mg2B205 nanowires were synthesized by post-annealing treatment at a relatively low temperature of 700 ℃. The important effect of the MgBO2（OH）-Mg2B2O5 conversion process on the morphology of the Mg2B2O5 nanowires was investigated and it was indicated that the recrystallization process plays an important role in the protection of the one-dimensional （1D） nanostructure. Moreover, the rigidity and the toughness of the Mg2B2O5 nanowire- reinforced PHA composites were tremendously improved compared to those of the pure PHA. Our results demonstrate the effectiveness of Mg2B2O5 nanowires for reinforcement applications in polymer composites.     

聚吡咯/碳纳米管复合物的制备及电性能研究

用原位聚合法制备了聚吡咯／碳纳米管（ PPy／MWNTs）复合物．采用XRD、TGA、FT－IR、SEM、四探针测试仪和网络分析仪表征了PPy／MWNTs复合物的组成、结构、形貌和电性能．研究了不同制备条件,如质子酸及其浓度、MWNTs的质量分数（ωMWNTs ）、引发剂和单体的物质的量比（ nAPS／nPy ）和反应时间对PPy／MWNTs复合物电性能的影响．结果表明,当磷酸浓度为0．1 mol／L、nAPS／nPy为1：1、ωMWNTs等于45 wt％、反应时间12 h时,制备的PPy／MWNTs复合物的导电性和介电损耗性能最好．     

一种尼龙老化评价的新方法

作为一种广泛使用的工程塑料,尼龙的老化备受关注。当作为电力系统芯片的封装材料时,尼龙在自然环境下的老化有可能会导致封装失效,从而影响芯片使用的可靠性,严重时甚至导致芯片的失效,给电力行业带来巨大损失。常规的自然老化和人工加速老化评价周期非常漫长,不同因素对尼龙老化的影响机理十分复杂,且这种影响难以研究,使得评价尼龙的老化稳定性成为一大难题。采用自主开发的原位老化评价系统,对尼龙6（PA6）和尼龙66（PA66）的老化稳定性及湿度对老化的影响进行了研究。该系统可以实现光照/温度/湿度/氧气等环境因素的加载,通过高灵敏度地测定材料在综合环境因素作用下产生的气相降解产物来评价材料的老化稳定性,评价时间缩短到几小时。实验表明,PA6和PA66的气相降解产物以H₂O和CO₂为主,由于H₂O在气相中的浓度不稳定,因此以CO₂的产生量作为老化评价指标。通过对不同自然老化时间PA6和PA66的原位老化评价,并与其ATR-FTIR红外光谱图进行对照,证明了原位老化评价方法能够较好地反映尼龙的老化程度,自然老化时间越长,PA6和PA66的稳定性越低,CO₂的产生量越大。进一步,采用该方法研究了湿度对PA6和PA66老化反应的影响,证明增大湿度对尼龙老化存在促进作用,而且升高温度会进一步促进湿度对老化的促进作用。研究表明,原位老化评价方法是一种快速评价尼龙老化稳定性及环境因素影响的有力手段。     

碳纳米管改性聚苯硫醚熔纺纤维的结构与性能研究

将多壁碳纳米管(MWCNTs)和聚苯硫醚(PPS)经过熔融挤出后制备成复合材料切片,并采用熔融纺丝法制得碳纳米管改性聚苯硫醚复合纤维.采用扫描电镜(SEM)、拉曼光谱、示差扫描量热分析(DSC)、动态机械分析(DMA)以及力学性能测试等表征手段研究了复合纤维中碳管的分散状态,与基体的界面作用,复合纤维的结晶性能以及力学性能,从而探讨了聚苯硫醚/碳纳米管复合纤维体系的微观结构与宏观性能之间的关系.研究表明,聚苯硫醚分子结构与碳纳米管之间具有的π-π共轭作用使碳管较为均匀的分散在基体中,界面结合较为紧密.同时熔融纺丝过程中的拉伸作用使碳管进一步解缠并使碳管沿纤维拉伸方向取向.另一方面,拉曼光谱显示拉伸作用有效地增强了界面作用,有利于外界应力的传递.碳管的良好分散以及强的界面作用使复合纤维力学性能得到大幅度的提高,当碳管含量达到5 wt%时,复合纤维的模量有了明显的提高,拉伸强度较纯PPS纤维提高了近220%.     

不同形貌镍纳米粒子-石墨烯复合材料的制备及微波吸收性能

采用原位化学还原方法制备出了两种不同形貌的镍纳米粒子-石墨烯(Ni-GNs)复合材料, 并研究了形貌对复合材料电磁吸收性能的影响. 制备过程中通过改变反应物的加入顺序, 制备出球形和刺球形镍纳米粒子-石墨烯复合材料. 利用X射线衍射(XRD)仪、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和矢量网络分析仪(VNA)对复合材料的形貌、结构和微波吸收性能进行了表征. 结果表明: 刺球形镍纳米粒子-石墨烯复合材料相比于球形镍纳米粒子-石墨烯复合材料具有优异的电磁吸收性能, 其原因是由于复合材料中刺球形镍纳米粒子独特的各向同性天线形貌引起的尖端放电效应. 因此利用简单的原位化学还原制备不同形貌镍纳米粒子-石墨烯复合材料的方法可以作为其他复合材料制备的总体路线.     

孔口缝合补强对含孔复合材料层板应力集中影响的数值模拟

提出的一种缝合线计算模型,通过数值模拟计算与实验结果比较,得到缝合线计算模型中相关的弹性参数.对复合材料开口缝合补强结构进行有限元模拟计算,分析了孔边及邻近区域应变、应力的分布规律,得到不同缝合参数、孔边不同位置以及不同载荷条件下的应变、应力集中系数,并给出合理的孔口缝合参数设计方法及相关结论.研究结果表明:含孔拉伸试件在孔边θ=0°处,切向拉伸应力最大;在θ=90°处,切向压缩应力最大;在孔口0°和90°之间存在拉应力与压应力的转换点,缝合补强后,此转换点大约在θ=56°左右.     

Torsional Swelling of a Hyperelastic Tube with Helically Wound Reinforcement

This paper examines the combination of radial deformation with torsion for a circular cylindrical tube composed of a transversely isotropic hyperelastic material subject to finite deformation swelling. The stored energy function involves separate matrix and fiber contributions such that the fiber contribution is minimized when the fiber direction is at a natural length. This natural length is not affected by the swelling. Hence swelling preferentially expands directions that are orthogonal to the fiber. The swelling itself is described via a swelling field that prescribes the local free volume at each location in the body. Such a treatment is a relatively simple generalization of the conventional incompressible theory. The direction of transverse isotropy associated with the fiber reinforcement is described by a helical winding about the tube axis. The swelling induced preferential expansion orthogonal to this direction induces the torsional aspect of the deformation. For a specific class of strain energy functions we find that the twist increases with swelling and approaches a limiting asymptotic value as the swelling becomes large. The fibers reorient such that fibers at the inner portion of the tube assume a more circumferential orientation whereas, at least for small and moderate swelling, the fibers in the outer portion of the tube assume a more axial orientation. For large swelling the fibers in the outer portion of the tube reorient beyond the axial orientation, and so are described by helices with orientation in the opposite sense to that in the reference configuration.