Preliminary Research on Structure and Properties of Nano-cellulose

The structure of bacterial cellulose （BC） produced by Acetobacter xylinum NUST4 （A.xylinum NUST4） under static （SBC） and shake culture condition （ABC） was studied by means of transmission electron microscopic （TEM）, X-ray diffraction （XRD） and Fourier transform-infrared spectrum （FT-IR）. It was revealed that BC is I crystal cellulose and the proportion of cellulose I, exceeds 80% and BC diameter is 10-80 nm. Mechanical properties and water absorption capacity were also determined. These properties could result from crystalline and nanometer structure of BC.     

Effect of La Dopant on the Structure and Electrochemical Properties of LiCoO_2

1Introduction AgreatdealofdevelopmenthasbeenmadeforLi ionsecondarybatterysinceitwasinventedin1990[1].As apartofpowersources,thecathodeplaysacriticalrole foritsproperties.Lithiatedtransitionmetaloxidessuchas LiCoO2,LiMn2O4andLiNiO2areusuallyusedascathode m…     

Effect of La Dopant on the Structure and Electrochemical Properties of LiCoO2

The cathode material LiCo1-xLaxO2（x=0,0.01,0.02,0.05）for Li-ion battery was prepared in solid phase,Effects of La dopant on the structure were analyzed by X-ray diffraction.and the morphology of the samples was observed by scanning electron microscopy.The results show that the structure of LiCoO2 becomes more and more non-perfect with the4 increasing comtent of La and some impurity peaks appear in the XRD pattern when the La content reaches 0.05.Meamchile,a high synthesis temperature is advantageous to the intact and unitary compound,The initial discharge capacity of doped material containing La（x=0.01）synthesized at 900℃ reaches 160 mAh/g by charge-discharge test.which prior to that of non-doped material synthesized under the same condition.However,the increasing La content deteriorates the cycling performance.Therefore,the appropriate content of La is 0.01 and the optimum synthesis temperature is 900℃.     

Effect of Nb on the Mechanical Properties of Ti／Al2O3 Composite

1　IntroductionMetallic Titanium and alloy are necessary to theaerospace materials because they have excellent propertiesof low density, high strength, and resistance to high tem perature and erosion. And alumina has fine properties ofcalorifics, m…     

Properties and Structure of Magnesium Matrix Composite Reinforced with CNTs

By using high pure Magnesium (99.9 wt% ) as matrix and multi-walled bended carbon nanotubes ( CNTs ) as reinforced phase, carbon nanotubes/magnesium matrix composite was prepared to the foundry method under the argon gas protection, and its mechanical properties were tested. The interface structure and component of plating and un-plating carbon nanotubes were analyzed by TEM and EDS , and the action mechanism was discussed. The experiment results show that the CNTs con strengthen mechanical properties of the nano-tube-reinforced Mg matrix composite, the tensile strength and elongation ratio are greatly improved. Furthermore, the plating CNTs are better than un-plating CNTs in strengthening effects. The tensile strength is inereased by 150% and the elongation ratio is increased by 30% than that of matrix when content of CNTs is 0.67 wt%.     

Research on Composite Errors of Long Gage Blocks

ompcnoRecenily,precisemeasurementoflonglengthisanimPOrtantsubjectforeitensivestudy.TherearemanymethedsdeveloPed,sofar,measurementoflonglengthusinglaserinpaIticularmeasurementofhighaccuracycanbeachievedusinggagblocks.Atpresent,thelengthofstandanlgagblockisnotlargerthanlmbecauseofman-ufactUringandverificationlndtahons.ItisdifficulttoaP-plythemethedtomeasurementoflengthlargerthanlmusingcOInpositegagblocks.Toacertaindegree,themethedhasitSsuPeriorityinactualmeasurementanditissignificanttostudym…     

Preliminary Research on Strueture and Properties of Nano-cellulose

The structure of bacterial cellulose(BC)produced by Acetobacter xylinum NUST~4(A.xylinum NUST~4)under static(SBC)and shake culture condition(ABC)was studied by means of transmission electron microscopic(TEM),X-ray diffraction(XRD)and Fourier transform-infrared spectrum(FT-IR).It was revealed that BC isⅠcrystal cellulose and the proportion of celluloseⅠ_αexceeds 80% and BC diameter is 10-80 nm. Mechanical properties and water absorption capacity were also determined.These properties cottld result from crystalline and nanometer structure of BC.     

Effect of Cold-rolling on Hardness of SiCw／Al Composite

A SiCw|A| compostie was fabricated through a squeeze cast route and cold rolled to about 30%,50% and 70% reduction in thickness.respectively.The length of whiskers in the composite before and after rolling was examined using SEM.Some of the rolled composites were annealed by recrystallizing to remove the work hardening of the matrix alloy.The hardness of the rolled and annealed SiC A SiCw|A| composites was examined and then associated with the change of the whisker length and the work hardening of the matrix alloy.It was found that the hardness was a function of the degree of cold rolling .For the cold rolled composites .with the increase in the degree of cold rolling .the hardness increases at first,and decreases when the degree of cold rolling excecds 50%.For the annealed ones .however,the hardness monotonously with the increase in rolling degree.The different changes in hardness beticeen the rolled and annealed composites coukl be attributed to a result of the competition benceen the work hardening of the matrix resulting from the cold rolling and the work softening arising from the change of whisker length.     

Effect of Cold-rolling on Hardness of SiC_w/Al Composite

1　IntroductionDiscontinuouslyreinforcedaluminummetalmatrixcomposites (AMCs)arenowrecognizedasimportantstructuralmaterials[1,2 ] .Oneoftheprimeadvantagesofthesematerialsisthattheycanbeprocessedandshapedbyconventionalmetalworkingtechniques ,suchasextru sio…     

Investigation on Mechanical Properties and Microstructure of Hydroxyapatite-SiCw Composite Bioceramics

Hydroxyapatite-SiCw composite micropowder was synthesized using in-situ composite method, and hydroxyapatite- SiCw composite bioceramics with different content of SiCw were produced by hot pressing sintering method. The microstructures of the materials were analyzed by SEM, and the relative density, bending strength and fracture toughness of the materials were tested. The results show that the mechanical properties of composite material are best when the whisker content is 20- 23.7% . The mechanical properties of the material are the best when the tensile stress acted on the composite material is parallel with the hot pressing plane, and they are the worst when the tensile stress acted on the composite material is normal to the hot pressing plane.     

螺栓连接层合板结构失效模式多尺度数值分析

为充分发挥螺栓连接层合板结构的力学潜能,构建宏-细观多尺度数值方法,从细观组分材料性能出发准确地预测结构的失效载荷,模拟局部损伤的产生、扩展过程,指导结构设计。基于有限元软件ABAQUS提供的用户自定义子程序（ USDFLD）,引入改进的单胞模型（ GMC模型）,建立考虑细观组分材料损伤／失效的宏-细观多尺度数值分析模型,模拟预报螺栓连接层合板结构在双剪切载荷作用下的损伤模式及挤压强度,模型的预报结果与文献及实验结果吻合较好,充分证明模型的预报能力。利用该模型进一步分析试件的几何尺寸对结构损伤模式及挤压强度的影响。结果表明：结构宽度与孔径比尺寸的变化对结构的损伤模式及挤压强度均有影响,且对挤压强度的影响较大,在结构的设计过程中应给予充分的考虑。     

复合材料层板冲击后剩余压缩性能声发射分析

利用声发射技术对复合材料层合板的低速冲击和压缩破坏进行了分析.测试过程中用声发射技术进行实时监测,结合载荷—位移曲线,分析了声发射能量,幅值和波形经过快速傅里叶变换后的峰值频率,并对典型信号的波形进行了频谱分析.结果表明:AE参数能很好的描述复合材料层合板低速冲击及其剩余压缩行为.     

锚固岩体复合材料力学性质的数值模拟研究

将岩体锚-杆支护系统看作一种由岩体（基体）法和观点建立锚杆、锚杆（增强材料）和砂浆（粘结材料）组成的复合材料，利用复合材料力学的方加固岩体的细观力学等效模型，建立岩体-锚杆支护系统复合材料的宏观力学性质与其组分材料性能及细观结构之间的定量关系，从整体上评价该支护系统的增强效果。同时。在ANSYS分析软件的基础上利用APDL进行二次计算程序开发，选取岩体-锚杆复合材料代表单元体，通过对单元体进行单轴和三轴数值模拟试验，得到锚固岩体复合材料的等效应力-应变关系，并研究了其等效强度性质。     

化学刻蚀法制备硅微纳米复合结构及其光反射性能影响

提出一种改进的金属辅助化学蚀刻技术(metal-assisted electroless etching, MAEE)来制备硅基微纳米(silicon micropillar/nanowire, MP/NW)复合结构,技术结合了传统MAEE及旋涂法,实验腐蚀液由KMnO_4/AgNO_3/HF组成,探究了腐蚀温度、旋涂速度及腐蚀时间对复合结构的表面形貌特征的影响,并分析了制备条件对反射率与吸收率的影响规律。结果表明,腐蚀温度改变时,复合结构的高度差、MP的直径和NW的长度都随着温度的增加而减少,而反射率随之增大,吸收率随之减小;当旋涂速度改变时,旋涂速度的增加会导致复合结构的高差、MP直径和NW长度减小,反射率随速度增加而增大,吸收率随之减小;腐蚀时间延长时,复合结构的高度差、MP的直径、吸收率随之减小,而NW高度与其反射率随之增加。     

板桁组合结构分析的超级有限元法

针对板－桁组合结构的静力分析问题，根据桁梁弯曲扭转理论，将复杂的离散型结构进行三维化处理，使其离散成一系列梁段单元－超级元。考虑到弯曲扭转拉伸压缩等多种变形效应，再将超级元离散成板单元和空间杆单元，按一般有限元法选取其自由度，通过采用构件自由度向超级元自由度转换，把复杂多构件问题的求解，变为少量一维节点问题的求解。     

复合防护结构的动力响应及破坏规律研究

采用中间含吸能层的复合防护结构，其抗爆防护能力可大幅度提高，但目前对该种复合结构在爆炸作用下动力响应及破坏规律的研究较少。利用ANSYS／LS—DYNA对复合防护结构在爆炸载荷作用下的动力响应和破坏规律进行了数值计算．结果表明：外拱结构的破坏基本上属于冲切破坏，而内拱结构基本上属于拱的压弯破坏；复合结构的破坏是以牺牲外拱和泡沫混凝土为代价来保护整体防护结构；与常规防护结构相比，复合防护结构的抗爆能力明显加强．     

轻钢-秸秆混凝土组合结构体系整体性能分析

轻钢-混凝土组合结构是由冷弯薄壁型钢与混凝土组合而成的新型结构体系.本文采用有限单元法对七层冷弯C型钢秸秆混凝土组合结构进行静力分析,为将来实际工程应用与实践提供理论依据.     

砂桩复合地基室内模型试验研究

通过自行研发的试验装置,对砂桩群桩复合地基进行室内模型试验,得出砂桩复合地基的一些工作性状:砂桩复合地基的荷载沉降曲线特征、桩和土的应力特点、桩土应力比特点、荷载分担比曲线特征等。本室内静载荷试验模型虽然不能完全模拟现场砂桩复合地基的工作性状,但从定性上分析砂桩复合地基的工作性状是可行的。从试验结果可以看出,在处理粉细砂类土时,砂桩发挥的作用是比较显著的。     

新型梁柱-钢管混凝土板柱混合结构试验研究

新型梁柱-钢管混凝土板柱混合结构的特点是钢管混凝土柱-板节点处只承担竖向荷载,不出现或者出现较小的不平衡弯矩,同时提高节点抗侧移能力,避免地震时楼板发生冲切破坏,水平荷载则全部由抗震墙和梁柱框架承担.通过1个1/2比例钢筋混凝土梁柱-钢管混凝土柱无梁楼盖异型板(跨数少于3跨)结构模型试验,研究其在受竖向均布荷载和水平荷载作用下结构的受力性能.试验结果表明,楼盖系统的竖向承载力超出设计荷载的2倍以上,具有较高的安全储备;在重力荷载产生的剪力与板抗冲切承载力的比值(gravity shear ratio,GSR)超过0.8时,弹塑性层间位移角限值不小于2.25%,满足中国《建筑抗震设计规范》(GB50011—2010)中大震下结构侧移的要求,优于普通的无梁楼盖系统.     

墙趾可更换组合剪力墙抗震性能试验研究

为研究墙趾可更换组合剪力墙的抗震性能,设计并制作了2片带有可更换墙趾构件的波形钢板–混凝土组合剪力墙试件.采用拟静力试验和ABAQUS有限元软件模拟的方法,分析了内置波形钢板波纹方向对墙趾可更换组合剪力墙抗震性能的影响.试验结果表明:各试件墙趾构件先于主体构件破坏,且在达到极限位移角前其破坏主要集中于可更换墙趾构件;墙...