台湾乳白蚁对昆虫病原真菌的防御机制

单头饲养的台湾乳白蚁对昆虫病原真菌,玫烟色拟青霉、布氏白僵菌、金龟子绿僵菌具有高度的敏感性,而群体饲养的台湾乳白蚁则对其有很高的抗性。用荧光显微镜进行定量的分析,研究结果表明：三种昆虫病原真菌的孢子在白蚁表皮的附着量具有明显的差异。相比于金龟子绿僵菌,布氏白僵菌和玫烟色拟青霉的孢子能更加有效地侵入台湾乳白蚁的表皮。我们的研究结果还表明,自吮舐行为并不能有效的移除白蚁表皮的孢子,但是相互的吮舐可以有效的移除同伴体表的孢子。移除速率的统计分析表明,布氏白僵菌和金龟子绿僵菌比玫烟色拟青霉的孢子能更加迅速地从昆虫体表被移除。     

Catalyst-free growth of nanographene films on various substrates

We have developed a new method to grow uniform graphene films directly on various substrates, such as insulators, semiconductors, and even metals, without using any catalyst. The growth was carried out using a remote plasma enhancement chemical vapor deposition (r-PECVD) system at relatively low temperatures, enabling the deposition of graphene films up to 4-inch wafer scale. Scanning tunneling microscopy (STM) confirmed that the films are made up of nanocrystalline graphene particles of tens of nanometers in lateral size. The growth mechanism for the nanographene is analogous to that for diamond grown by PECVD methods, in spite of sp2 carbon atoms being formed in the case of graphene rather than sp3 carbon atoms as in diamond. This growth approach is simple, low-cost, and scalable, and might have potential applications in fields such as thin film resistors, gas sensors, electrode materials, and transparent conductive films.     

Self-Assembly and Ordering of C60 on the WO2/W（110） Surface

The growth and ordering of C₆₀ molecules on the WO₂/W(110) surface have been studied by low-temperature scanning tunnelling microscopy and spectroscopy (STM and STS), low-energy electron diffraction (LEED), and density functional theory (DFT) calculations. The results indicate the growth of a well-ordered C₆₀ layer on the WO₂/W(110) surface in which the molecules form a close-packed hexagonal structure with a unit cell parameter equal to 0.95 nm. The nucleation of the C₆₀ layer starts at the substrate’s inner step edges. Low-temperature STM of C₆₀ molecules performed at 78 K demonstrates well-resolved molecular orbitals within individual molecules. In the C₆₀ monolayer on the WO₂/W(110) surface, the molecules are aligned in one direction due to intermolecular interaction, as shown by the ordered molecular orbitals of individual C₆₀. STS data obtained from the C₆₀ monolayer on the WO₂/W(110) surface are in good agreement with DFT calculations.     

橡树岭国家实验室的科学家揭示了在纳米尺度下锂离子电池的行为

美国的橡树岭国家实验室能源部利用显微镜对高效锂离子电池的功能提出了前所未有的看法。一个研究小组研发了一种称之为电化学应力显微镜（ESM）的新型扫描探针显微镜,用它成功绘制了锂离子在锂电池正极周围运动的影像。用ESM探针对电池的层状正极表面进行了探测。通过测定相应的电化学应力或体积变化,研究小组明确了锂离子在材料内的迁移情况并使之形象化。     

低碳钢在高温共焦激光扫描显微镜下马氏体相变的原位观察研究

利用高温共焦激光扫描显微镜,对低碳钢进行了马氏体相变的原位动态观察。结果表明,实验用低碳钢在连续冷却过程中形成板条马氏体,Ms点约为373 ℃,Mf点约为300 ℃。板条马氏体主要在退火孪晶处以及奥氏体晶界及其角隅处形核,或者在先形成的板条处形核,再以60°或120°角向奥氏体晶内生长。板条束的形成也有两种类型,一类以先形成的板条为基准逐步形成彼此平行的板条束,另一类则由先形成的板条触发60°或120°方向的板条。最终构成正三角形、平行四边形等几何形状。     

压电陶瓷激励微悬臂梁的动态特性

结合流体中微悬臂梁振动频率响应的理论模型,通过实验、理论计算和基于流固耦合的有限元仿真3种方法,分析了在空气和去离子水中不同结构、尺寸的微悬臂梁的谐振频率、品质因子以及幅频响应曲线,并对3种方法得到的结果进行了对比.结果显示,空气中各种方法得到的谐振频率较为吻合,相对于实验值的偏差在1%以内.去离子水中,梁谐振频率的理论值和仿真值基本一致,而实验值则较大,前两者相对于实验值的偏差在13.9%～27.3%之间;对于品质因子,理论值和仿真值依然较一致,但相对于实验值出现较大偏差,最大达70.5%.分析表明,对于液体环境下压电陶瓷激励的微悬臂梁,频率响应曲线中干扰峰的存在会严重影响微悬臂梁品质因子的准确测量.微悬臂梁动态特性的研究对基于微悬臂梁的传感器的设计优化和液相原子力显微术的应用具有一定意义.     

一种消除AFM中悬臂梁横向扭转串扰误差的修正技术

串扰效应始终存在于原子力显微镜(AFM)的测量过程中,并影响其测量精度.在对串扰效应的产生机理进行分析,并建立了悬臂梁形变与光斑位置检测器(PSPD)输出信号之间的数学关系的基础上,提出了一种可消除横向扭转串扰影响的修正方法.在该方法中AFM系统可由输出信号直接获得悬臂梁的实际形变量,进而获得原子间作用力的实际值,并通过保持作用力的恒定对样品进行测量.该方法可有效地将悬臂梁扭转导致的纵向信号的变化从系统测得的纵向信号中剔除出去.仿真结果表明,在恒力接触模式下,串扰效应严重影响测量结果,导致测量误差,且针尖.样品夹角导致的串扰效应比摩擦力导致的串扰效应更严重.为验证本文方法消除串扰效应的效果,在应用该修正方法前后分别对标准梯形样品进行测量.实验对比结果表明,在普通恒力接触模式下的样品表面最大测量误差范围为21.2 nm～32.0 nm;对串扰效应进行修正后,最大测量误差范围降低至5.5 nm～10.2 nm.这表明该方法可有效降低AFM中串扰效应导致的测量误差,提高其测量精度.     

Formation Characteristics of Calcium Ferrite in Low Silicon Sinter

 Influence of sintering temperature, basicity and MgO content on the formation characteristics of calcium ferrite in low silicon sinter of Baotou Iron and Steel Company was studied by means of mini-sintering test and mineralographic microscope analysis. In addition, the suitable sintering parameters such as temperature and basicity were explored. The results found that optimum temperature for the formation of calcium ferrite is 1280 ℃, the basicity of 25-28 is helpful to the development of acicular or columnar calcium ferrite, and MgO content in the low silicon sintering raw materials should be lower than 28% because MgO can intensively inhibit the formation of calcium ferrite. And calcium ferrite in the sinter belongs to calcium ferrite with low calcium, which is different from that in ordinary sinter at home and abroad. So, it provided theoretical basis for promoting formation of calcium ferrite in low silicon sinter and improving properties of sinter.     

超光滑光学基底表面原子力显微镜测试方法

原子力显微镜(AFM)是评价亚纳米级表面粗糙度σRMS最主要的测试仪器,但其测试结果会因采样条件(采样间距、采样点数)及测量点位置变化而改变。以AFM测试超光滑光学基底随机表面为例,应用累积功率谱理论建立了确定合理采样条件的方法,避免了采样条件选取不当带来的数据丢失或冗余;通过全局优化选取测量点和局部优化选取测量点相结合,降低了样品表面区域性差异给测试结果带来的不确定性,并大大减少了获得可靠测试结果所需的测试量。上述工作为超光滑光学基底AFM测试提供了有效方案。     

SAM扫描器件芯/焊结合空洞的失效分析

超声无损检测是70种无损探伤技术的最热点。扫描声学显微镜(SAM)的原理是声阻抗成像,要求缺陷尺度大于超声波的波长。结合SAM技术中的A-扫描波形分析和C-扫描特征成像,针对由封装引入的分层和空洞缺陷进行失效分析。研究发现:分层定位的关键是A-扫描波形分析中对各界面处反射波的时间位置的判断;基于分层定位的芯/焊结合空洞缺陷的判别,关键是C-扫描图像中灰阶色带的区分(反射率差值)。