中空铜纳米线的拉伸断裂分布与初始滑移分布的关系

构建了系列球形中空结构的纳米线(NW),采用分子动力学(MD)对每个模型300个不同初始态的样本开展拉伸形变模拟。并利用基于密度的噪声应用空间聚类(density-based spatial clustering of applications with noise,DBSCAN)机器学习算法,获得了初始滑移面的位置。基于大数据统计,分析了初始滑移位置分布以及断裂位置分布两者之间的相关性。研究结果表明：当内部中空半径较小时,断裂位置分布形成于塑性形变阶段,初始滑移分布与断裂位置分布之间无显著的相关性;但是对于脆性特征明显的大中空半径的NW,高能内表面诱导产生的滑移面迅速积累,产生颈缩并导致最终的断裂。因此当内部中空结构达到一定尺寸时初始滑移位置的分布与最终断裂位置的分布之间有明确的因果关系。     

中空铜纳米线的拉伸断裂分布与初始滑移分布的关系

构建了系列球形中空结构的纳米线(NW)，采用分子动力学(MD)对每个模型300个不同初始态的样本开展拉伸形变模拟。并利用基于密度的噪声应用空间聚类(density-based spatial clustering of applications with noise，DBSCAN)机器学习算法，获得了初始滑移面的位置。基于大数据统计，分析了初始滑移位置分布以及断裂位置分布两者之间的相关性。研究结果表明：当内部中空半径较小时，断裂位置分布形成于塑性形变阶段，初始滑移分布与断裂位置分布之间无显著的相关性；但是对于脆性特征明显的大中空半径的NW，高能内表面诱导产生的滑移面迅速积累，产生颈缩并导致最终的断裂。因此当内部中空结构达到一定尺寸时初始滑移位置的分布与最终断裂位置的分布之间有明确的因果关系。     

介观模拟方法研究高分子表面活性剂在水介质中的聚集行为

高分子表面活性剂已广泛应用于许多领域, 其构型复杂、分子量大等特点使其聚集行为不同于小分子表面活性剂. 从微观上认识其聚集行为可为应用提供指导, 因而此方面的研究倍受关注. 计算机模拟技术的发展使我们能成功地在微观或介观水平上获得高分子表面活性剂聚集行为的信息. 本文综述了耗散粒子动力学(DPD)和介观动力学(MesoDyn)在高分子表面活性剂聚集行为研究中的应用. 着重介绍了这两种介观模拟方法研究单一高分子表面活性剂溶液的相行为及其与低分子表面活性剂之间的相互作用, 揭示了实验中难以观测的微观相分离及聚集体结构形态的变化规律. 这些信息可以为实验研究提供指导和补充.     

高内相乳液模板法制备淀粉基大孔材料及表征

首先将水溶性淀粉结构中的部分羟基用甲基丙烯酸酐功能化,得到淀粉基大分子单体(S-MA);然后以聚乙烯醇-1788为表面活性剂、以二氧化碳为分散相、以S-MA的水溶液为连续相,制备了水包二氧化碳型高内相乳液(内相体积分数大于74.05%);最后利用乳液模板聚合法制备了大孔材料。采用傅里叶变换红外光谱仪(FT-IR)、核磁共振波谱仪(~1H-NMR)、扫描电镜(SEM)等分析测试手段对S-MA的结构、大孔材料的孔径及分布进行了表征,研究了内相体积分数对材料孔径的影响。结果表明:所得高内相乳液具有优良的稳定性,能够稳定存在超过24h;所得大孔材料的平均孔径在10μm以上,且存在相互贯穿的孔结构,该结构有利于细胞的黏附和生长。     

金属纳米线中凸凹微结构对初始形变的影响

构建了具有代表性的系列凸纳米线和凹纳米线,利用分子动力学模拟研究了2种微结构对拉伸形变的影响.结果表明,微凸纳米线与单晶纳米线表现出类似的行为,其能量和应力应变曲线等均无显著差异.改变不同的凸起高度未发现显著差别.沿z轴的应力分布分析表明凸微结构使局域应力降低,不能诱导产生初始位错滑移;微凹纳米线表现更明显的塑性形变特征,小应变时能量上升的幅度低于单晶和凸纳米线,但大应变条件下能量上升更高,微凹纳米线的第一屈服点早于单晶和凸纳米线,且其屈服应力不是最大应力,沿z轴的应力分布表明凹陷处产生增加的局域应力,凹陷附近可以诱导产生初始位错滑移.原子排布位图从微观上进一步阐述了上述形变特征.     

HDPE/CB导电复合材料电-热平衡态电学行为

研究了ＨＤＰＥ／ＣＢ导电复合材料在不同环境温度下电－热平衡态的电学行为,发现其电流密度－电场强度－电导率（Ｊ－Ｅ－σ）关系曲线经临界点参量约化后可有效地重叠。根据自发热临界电流密度、电场强度以及电导率与材料线性电导率之间的标度关系,揭示了复合材料在不同温度下的导电机理的一致性及宏观电学行为与微观导电网络结构的相互关联性。     

双联齿轮断裂分析

机床传动系统双联直齿轮投入运行不久即发生齿面断裂事故,造成较大经济损失.传动系统所用双联齿轮未达到设计使用寿命,属于早期断裂失效.对现场收集到的断裂齿轮残块进行化学成分分析和硬度测试,对齿廓工作面及断裂形成的断口用扫描电镜进行微观观察,对齿轮残块上出现的裂纹用光学金相显微镜观察其形貌和微观特征,依据检测实验数据和结果,...     

聚苯基单醚喹噁啉薄膜的性能与物理老化

研究了物理老化对聚苯基单醚喹啉薄膜的结构与力学性能的影响 .用差示扫描量热计 (DSC)及正电子湮没寿命谱 (PALS)方法表征了两种不同物理老化条件试样的凝聚结构以及自由体积的差别 .结果表明 ,物理老化使聚苯基单醚喹啉薄膜玻璃化转变温度移向高温 ,在其末端出现热焓吸收峰 ,分子链堆砌紧密使自由体积减小 ,分子可动性降低 .用动态力学分析 (DMTA)以及静态拉伸性能测试等方法研究了两类试样的力学性能 ,结果表明 ,物理老化后 ,试样的动态储能模量稍有增加 ,力学损耗降低 .而静态拉伸实验的断裂应变降低 ,屈服应力增加 ,断裂能降低 ,试样在宏观上由韧性断裂变为明显的脆性断裂 .     

可逆加成-断裂链转移活性自由基聚合的应用研究进展

可逆加成-断裂链转移(Reversible addition-fragmentation chain transfer,RAFT)自由基聚合是活性自由基聚合领域的一次突破.由于该方法具有适用单体范围广、反应条件温和以及聚合实施方法多样等优点,已成为一种有效的分子设计和材料设计手段.它不但可实现聚合物链端及链段侧基的功能化和制备特定空间拓扑结构的大分子,比如嵌段、星型、梳状及链端氨基聚合物等,还可用于修饰固体材料表面及生物大分子来赋予其特殊的功能.本文综述了RAFT技术在实际应用中的实施研究进展.     

手性金团簇的制备、性质及应用

手性作为生命体固有的自然属性广泛存在于从微观到宏观的自然界中,其现象包括具有高度手性偏好的生物小分子(如L-氨基酸和D-糖),具有不对称空间构象的生物大分子(如DNA双螺旋链),以及其他所有由手性分子或手性结构参与的生理和生化过程。研究者们成功地把分子手性引入到金团簇的表面诞生了一种新的材料——手性金团簇,这种新型纳米级的手性材料实现了手性信号从分子尺度到纳米尺度的跨越。作为一类集表面手性、特殊光学活性和金团簇独特性质于一体的新型纳米材料,手性金团簇在手性催化、手性识别、分子检测等领域具有广泛的应用前景。本文主要综述了手性金团簇的制备、表征、性质及应用,并对其发展前景及面临的挑战进行了总结与展望。     

Environmentally Friendly Green Materials from Plant-Based Resources: Modification of Soy Protein using Gellan and Micro/Nano-Fibrillated Cellulose

Fully biodegradable micro/nano-composite resins were prepared by reinforcing soy protein concentrate (SPC) with micro/nano-fibrillated cellulose (MFC) and then blending with gellan. The composite resins showed excellent mechanical and physical properties under testing conditions. Due to the high aspect ratio of MFC, excellent mechanical properties of MFC and MFC/SPC interfacial properties, the SPC (100 parts) reinforced with glycerol (1.5 parts) and MFC (40 parts) showed fracture stress of 88.2 MPa and Young's modulus of about 4.1 GPa, which are higher than those of many conventional petroleum-based plastics. MFC reinforced SPC composite resins were then further modified by blending with gellan to obtain further improvement in fracture stress and Young's modulus. SPC resin containing glycerol (1.5 parts), gellan (40 parts) and MFC (40 parts) had fracture stress of over 122 MPa and Young's modulus of about 5.8 GPa. Although the moisture sensitivity of the specimens was high, they have the potential to replace petroleum-based materials in many fields, particularly for indoor applications.     

A tensile testing machine for a scanning electron microscope; Its structure,properties and applications

This work introduces a micro tensile testing machine built in to an ISI 40 SEM scanning electron microscope. With additional accessories (an anticontamination system and a Robinson detector), the machine is suitable for studying non-conductive materials, such as polymers, plastics and non-metallic composites, without coating, during tension or compression.With regard to its properties, the micro tensile testing machine developed in this context can structurally be compared in all aspects to normal mechanical universal tensile testing machines. The difference is that in this case, in addition to the conventional information (force, deformation), a continuing picture of the surface of test materials can be recorded from the area where the most interesting changes are happening. With the micro tensile testing machine it has been possible to retain all movements of the specimen stage, which enables the efficient observation of the specimen in a scanning electron microscope.The examples of applications presented in this paper show that the tensile machine is suitable and useful in studies of plastics and plastic-based composites in a very wide area.     

煤与废塑料共焦化基础研究Ⅲ. 协同作用的热重研究

采用加压热天平研究煤与废塑料共焦化过程中,不同废塑料对太钢焦煤的热解行为,以及德国废塑料对不同煤种的热解行为的影响。认为不同的废塑料对太钢焦煤热重行为的影响不尽相同;不同的煤种在与德国塑料共热解时的协同作用也不相同,德国废塑料与焦煤的相互作用更大些。共热解中废塑料与煤的协同作用受煤与废塑料二者之间的热解温区、失重峰温、失重速率的重叠程度及煤所形成的胶质体数量的影响。废塑料与煤之间的相互作用使得两者     

Processing and properties of engineering plastics recycled from waste electrical and electronic equipment (WEEE)

The characteristics of engineering plastics used in the preparation of electrical and electronic equipment were studied. More specifically, their thermal response was recorded by DSC experiments, the rheological properties were investigated via MFI tests and the mechanical properties were evaluated with tensile tests. The aim was to establish a procedure for recycling the same engineering plastics deriving from waste of electrical and electronic equipment (WEEE), which offers the additional advantage of using the as-received waste stream as a recyclable mixture, i.e. without sorting and classification of its components.The experimental results showed that blends of PC with ABS or ABS/HIPS can be prepared by direct mixing and this, would allow easy handling of the engineering plastics coming from WEEE, i.e. blending without the need of sorting. These mixtures can be easily processed and display acceptable mechanical properties with reasonable cost. Therefore, the processing characteristics and properties of the systems studied in this work could be the key for the design of an interesting approach for handling solid plastic waste from electrical and electronic devices.     

Simulation of processing the “Power” composition in a mixer with oval rotors

The main dependence for determining the energy-power parameters of processing the compositions, whose behavior under load is described by a power rheological law in the operation gap of mixers with oval rotors. In the proposed method of calculating the power of the mixer drive motor an attempt was made to account for movement of a treated material not only in circular but also in the axial direction of the mixing chamber. These dependences for determining the pressure and power supplied to the rotors for rotation thereof may be recommended for engineering calculations of mixing equipment for plastics and rubber mixtures.     

Rheological and mechanical properties of ABS plastics prepared by bulk polymerization

A series of ABS plastics prepared by bulk polymerization was studied. The test samples contained almost equal amounts of PB but mostly differed in the molecular mass of a styrene-acrylonitrile copolymer. It was shown that the molecular mass of the copolymer strongly affects the rheological and mechanical properties of ABS plastics. An increase in molecular mass leads to a rise not only in the non-Newtonian viscosity of plastics but also in their yield point, storage modulus under periodic steady-state shear flow in the low-frequency plateau region, and impact strength. Quantitative correlations between these rheological and mechanical characteristics of the copolymers and their M _w values were established. As opposed to homophase polymer systems, a marked increase in the shear stress has no effect on viscosity in relation to the molecular mass of ABS plastics. In the case of melts, the influence of the M _w of the styrene-acrylonitrile copolymer on the rheological behavior of ABS plastics is apparently related to a change in the interaction of PB particles with the copolymer that controls the structural framework of the system. The relationship between the impact strength of the copolymer and its M _W may be explained by the fact that the latter parameter influences orientational effects in crazes that arise during steady-state shear flow of ABS plastics in the solid state.     

Effect of temperature on the rupture behavior of highly stretchable acrylic elastomer

Dielectric elastomer has been recently explored extensively to make diverse soft actuators and energy harvesting devices. The lack of study on the rupture behavior under the influence of temperature hinders further applications where heat generation and accumulation are unavoidable. In this paper, an experimental study has been carried out to investigate the effect of temperature on the rupture behavior of acrylic dielectric elastomer. By using VHB 4910 films with and without an initial crack, the fracture energy at different temperature and stretch rate is measured by pure shear test. The storage modulus and phase angle have been investigated by dynamic mechanical analysis (DMA). The images of defects and rupture surface are provided by scanning electron microscope (SEM). It is found that the stretch at rupture is insensitive to the temperature for both pristine and precut samples. In addition, the maximum nominal stress and fracture energy linearly decrease with environmental temperature, especially at high stretch rate. Furthermore, we measure the stretch at rupture for rectangular strips with a single edge-notch under uniaxial tension and compare them with the theoretical prediction using nonlinear fracture mechanics based on the measured fracture energy. The results obtained in this paper will give a reference to the engineering design and applications of dielectric elastomer, especially for those working at different temperatures.     

乙炔基封端液晶-含硅芳炔共聚树脂的固化机理

将热致性乙炔基封端液晶单体(MPBE)与含硅芳炔树脂(PSA)进行共聚,制得乙炔基封端液晶改性含硅芳炔树脂(PSA-MPBE)。采用FT-IR在线表征了PSA-MPBE树脂固化过程的结构变化,用裂解-气相色谱-质谱联用仪(Py-GC-MS)分析了其高温裂解产物,研究了其固化机理,用偏光显微镜(POM)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)分析了共混树脂的相结构、断裂形貌和微观结构。结果表明:MPBE与PSA发生了共聚反应,使介晶域固定在交联网络中,形成结构均匀的以介晶相为小岛的海岛结构,PSA-MPBE树脂的断裂行为从典型的脆性断裂转变为微塑性断裂。     

Fracture and crack profile fictitious crack modeling of porous poly(methyl methacrylate)

This article presents the fracture behavior and applicability of the fictitious crack (FC) model to describe the fracture of a porous poly(methyl methacrylate) material. Two test geometries, wedge‐opening load and single‐edge‐notched beam, were employed under two different test conditions (room temperature and in water at 45 °C); all presented quasibrittle fracture behavior. The crack profile of a wedge‐opening load sample was visualized and measured with the digital image correlation technique. The mechanical response of all the samples, including the crack profile, was successfully modeled with the FC model, and this showed the good applicability of this model to the fracture of this granular poly(methyl methacrylate) material. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1112–1122, 2003     

高性能工程塑料的流变和加工性能──Ⅰ.酞侧基聚芳醚酮的毛细管挤出行为

酚测基聚芳醚酮（PEK－C）和酞侧基聚芳醚矾（PES－C）〔‘·‘I是我国在80年代自行开发的高性能工程塑料．这两种材料在其主链结构上都附有酚酞侧基，而且几乎不含脂肪族基团，都呈无定形结构，具有耐热性好（T。＞220C），强度高（室温下拉伸强度大于100MPa）的特点．PEK－C、PES－C的特点是加工温度高、熔体粘度大，使其加Xi与通用塑料相比要困难得多．本文报道了PEK－C的挤出流动行为的研究结果．白色粉末状的PEK－C由长春应用化学研究所徐州工程塑料公司提供，在25C氯仿中的增比粘度为O．49，先将其放在140℃的真空烘箱中…