高压电缆缓冲层烧蚀缺陷的超声检测实验

高压电缆缓冲层烧蚀故障是近年来频发的电缆故障类型，然而目前的烧蚀缺陷检测手段难以满足存量电缆的检测需求。本文首次研究了基于铝护套内表面粗糙度的高压电缆缓冲层烧蚀缺陷的超声检测方法。首先，开展了潮湿条件下的缓冲层烧蚀模拟实验，并对烧蚀后的铝片开展了激光共聚焦显微镜测试以及电化学阻抗谱分析，发现随着烧蚀时间的增加，铝片的表面粗糙度逐渐增大，同时铝片表面的腐蚀程度逐渐加深，对应的缓冲层烧蚀缺陷逐渐加重，表明铝片的表面粗糙度与潮湿条件下缓冲层的烧蚀程度存在关联。其次，对烧蚀后的铝片开展了超声检测实验，并通过相邻超声回波信号的幅值比推算出了铝片腐蚀面的粗糙度，与实验测得的粗糙度具有相同的变化趋势。本文结果表明超声检测可用于检测缓冲层烧蚀缺陷的严重程度，为高压电缆缓冲层烧蚀缺陷超声检测方法的应用奠定了研究基础。     

Femtosecond-laser-induced nanostructure formation and surface modification of diamond-like carbon film

This paper reports the pump and probe experiment for in situ reflectivity measurements in the femtosecond laser ablation that brings about nanoscale modification of diamond-like carbon (DLC) film. The characteristic reflectivity changes observed demonstrate that the formation of periodic nanostructure is preceded by a change in bonding structure of DLC in the ablation at low fluences. We have observed a coherent nonlinear wave-mixing signal that can resolve the ultrafast interaction processes for the nanoscale modification on the film surface. Based on the results obtained, a model of the interaction process is proposed.     

Encapsulation of fresh silicon nanocrystals in carbon nanotube cavity

An approach for filling the carbon nanotubes (CNTs) with silicon nanocrystals (Si-ncs) during the fragmentation process of silicon micrograins in de-ionized water is presented. An efficient fragmentation of homogenously aqueous dispersed micrograins and filling of the CNTs cavity with Si-ncs is demonstrated by nanosecond pulsed-laser irradiation. Direct laser ablation has a unique surface Si-ncs chemistry in water and following aqueous in-situ CNT cavity stabilization prevents pollution, agglomeration of Si-ncs and can lead to 1D nano-composite material.     

Room-temperature growth of high-purity titanium nitride by laser ablation of titanium in a nitrogen atmosphere

Thin films of titanium nitride (TiN) were deposited on glass substrates by KrF excimer laser ablation of titanium over a very broad nitrogen pressure range with different target–substrate distances at room temperature. The as-deposited TiN thin films were analyzed by X-ray diffraction and transmission electron microscopy. It was found that the as-deposited thin films are normally a mixture of TiN and metallic titanium, and the TiN-to-Ti ratio of the as-deposited thin film depends on both the nitrogen pressure and the target–substrate distance. High-purity TiN thin films can be obtained only in a very narrow deposition parameter range. A compound parameter (the product of the nitrogen pressure and the target–substrate distance) is proposed to optimize the deposition of high-purity TiN thin films, and the possible mechanism is also discussed. It was also revealed that the as-deposited TiN thin films are polycrystalline with an average grain size of about 20 nm.     

Synthesis of Yb nanoparticles by laser ablation of ytterbium target in sodium bis(2-ethylhexyl)sulfosuccinate reverse micellar solution

Surfactant-coated ytterbium nanoparticles were produced by Nd:YAG laser ablation of a Yb bulk target immersed in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/n-heptane micellar solution. In our experimental conditions, as highlighted by IR spectroscopy, AOT molecules are not decomposed by the intense laser pulses but play a pivotal role in the stabilisation of Yb nanoparticles. The formation of Yb nanoparticles in the liquid phase was monitored by UV-Vis spectroscopy whereas the Yb/AOT composites obtained by evaporation of the organic solvent were characterised by XPS and TEM. Data analysis consistently shows the presence of surfactant-coated, nearly spherical and non-interacting Yb nanoparticles of mean diameter of 3 nm.Moreover, the presence of bigger polycrystalline nanoparticles (about 30%) in coexistence with smaller mono crystalline ones indicates that, after the rapid formation of the pristine Yb nanoparticles from plume condensation, two processes effectively compete for their size distribution: nanoparticle agglomeration and surfactant adsorption.     

石墨的含量对硅橡胶/石墨复合材料的影响

以热硫化硅橡胶为基体,添加石墨制备硅橡胶/石墨复合材料,研究了石墨的含量对硅橡胶/石墨复合材料力学性能、耐烧蚀性能及摩擦磨损性能的影响。试验结果表明:随着石墨量从0份增加到12份,材料的抗拉强度及硬度变化不大,而石墨的增加使硅橡胶的质量烧蚀率从0.056g/s降低到0.051g/s,耐烧蚀性提高了10%;摩擦磨损量从0.0042g减小到0.0032g,耐磨性提高了24%左右。     

一种燃速可调的光控固体推进剂燃烧特性

为了研究光控固体推进剂在激光辐照下的可控燃烧特性以及推力性能,采用高速摄影、高精度压力传感器、R型热电偶以及微推力测试平台等装置分别获取了不同激光功率密度下,光控固体推进剂的燃速、点火延迟时间、燃烧室压强、燃烧火焰温度以及微推力等性能参数.结果表明:光控固体推进剂的燃速与燃烧室压强均随激光功率密度的增加而线性升高,与之相反,其点火延迟时间随激光功率密度的增加呈下降趋势.结合热电偶测温曲线,发现光控固体推进剂的燃烧过程主要分为五个区域:预热区、凝聚相区、三相区、气相区以及火焰区,与此同时,在1.343 W·mm-2的激光功率密度下,推进剂的燃烧火焰温度为1202.3℃.光控固体推进剂燃烧状态对于激光功率密度的依赖性对于实现推力的精确控制具有重要意义,通过改变激光功率密度的大小,成功实现了光控固体推进剂的推力控制;随着激光功率密度由0.344 W·mm-2增加到1.343 W·mm-2,光控固体推进剂的推力由1.58 mN上升至2.28 mN.     

近域爆炸瞬态温度场作用下聚脲涂层灼烧损伤特性

为研究爆炸瞬态温度场作用下聚脲抗爆涂层的灼烧损伤特性,针对不同厚度(1 mm、4 mm和6 mm)的聚脲材料涂覆胶囊式储液容器进行近距爆炸条件下的实验测试。通过爆炸实验获得了聚脲涂层遭受爆炸瞬态高温灼烧后的宏-微观损伤特性,并结合比色测温技术及数值模拟方法分析了爆炸温度场对聚脲材料的灼伤机制。研究结果表明：本研究实验条件下,钝化黑索今(RDX)爆炸温度最大值约为3792 K,大于聚脲材料的初始分解温度(231.2℃)。灼烧现象主要发生在聚脲材料表层,当表层与内部孔洞之间薄层被贯穿破坏时,爆轰产物进入材料内部孔洞导致聚脲的灼烧深度明显增加,并形成斑点状的灼烧外层。聚脲的灼烧程度与爆轰产物密度、爆轰产物沿聚脲层厚度方向传播速度正相关,爆轰产物作用于聚脲层的单位面积质量达到0.0195 g·cm^-2时发生灼烧,且热传导是造成聚脲发生热分解的主要原因。研究方法及结论可为工程防护评估及抗爆聚脲改性提供参考。     

脉冲激光沉积制备TiN/AlN多层薄膜的研究

采用脉冲激光沉积(PLA)法,在单晶Si试样表面沉积制备了一系列TiN/AlN硬质多层膜,并采用基于免疫算法的免疫径向基函数(IRBF)神经网络对AlN厚度建立预测模型,设计出具有可控调制周期和调制比的TiN/AlN多层膜。X射线衍射(XRD)结果表明,小调制层周期下,过高或过低的工艺条件下薄膜通常为非晶态,适当的工艺条件下TiN、AlN形成具有强烈织构的超晶格柱状晶多层膜;与此相应,纳米多层膜产生了硬度和弹性模量异常增高;随着调制比增加,使纳米多层膜形成非晶AlN层和纳米晶TiN层的多层结构,多层膜的硬度和弹性模量逐渐下降。XPS结果表明,薄膜界面由Ti+4、Ti+3离子组成,N的负二价、三价亚谱结构预示着非当量TiN、AlN的形成。AFM研究显示,薄膜的调制周期均在10~200 nm范围内,且薄膜表面较均匀;当多层薄膜调制周期在50 nm以下时,薄膜的纳米硬度值明显高于TiN和AlN的混合硬度值,达30 Gpa。