独角仙鞘翅微结构及其纳米力学性能

利用SEM对独角仙鞘翅的微结构进行了观测, 并借助纳米压痕仪测试分析了鞘翅的纳米力学性能。SEM试验表明独角仙鞘翅是一种具有拱形空腔的中空轻质生物复合材料, 其断面占空比为26.36%。鞘翅由外表皮和内表皮构成, 而内表皮又通过11~12层纤维层采用45°角正交叠加铺设, 层间辅以许多微纤维丝交叉连接方式编织在一起, 形成层合板结构。试验测得鞘翅外表皮纳米力学性能分别为: 硬度(0.28±0.13) GPa, 弹性模量(5.62±1.21) GPa, 接触刚度 (1.67±0.14)×10⁴ N/m。其纳米力学性能呈现拓扑分布规律, 由头部至尾部区域有增大趋势。试验测试结果为后续研究中设计一种基于独角仙鞘翅的新型轻质仿生结构提供了仿生学模型和理论参考。     

四种甲虫鞘翅的力学参数测定及微结构观测

研究了4种甲虫(白星花金龟、 东方龙虱、 独角仙、 毛黄鳃金龟)鞘翅的材料力学参数及其微结构。鞘翅截面微观结构观察表明, 这4种甲虫鞘翅均由鞘翅背壁、 中空夹芯层和鞘翅腹壁构成, 背、 腹壁之间由桥墩状几丁质纤维空心柱体结构连接, 两鞘翅间以凹凸啮合结构联接。用纳米压痕仪测得这4种甲虫鞘翅背壁致密层的弹性模量均值分别为9.08、 8.21、 4.76、 6.00GPa, 硬度分别为0.44、 0.48、 0.18、 0.18GPa。用多功能材料性能实验机测定白星花金龟、 东方龙虱、 独角仙鞘翅之间的联接强度分别为46.43、 7.38、 11.34mN/mm。该研究为轻质结构的设计提供了仿生学基础。      

HfN/HfB_2纳米多层膜结构调制及其力学性能

为了进一步了解调制周期对HfN/HfB2纳米多层膜力学性能的影响,利用多靶磁控溅射技术,在Si(100)基底上制备了一系列具有相同厚度不同调制周期的HfN/HfB2纳米多层膜。利用XRD、TEM、XP-2台阶仪、纳米压痕仪及摩擦试验机分别分析了多层膜的结构特征、力学性能和室温下摩擦性能。结果表明,室温下沉积的多层膜呈现出结晶/非晶的混合结构;随着调制周期的增大,多层膜的结晶程度先增加后降低,其硬度和弹性模量也呈现出先升高后降低的趋势;当调制周期为40nm时,多层膜的硬度和弹性模量均达到最大值,分别为(36.72±1.3)和(378.41±5.6)GPa,并且此时多层膜具有较高的膜基结合力(Lmax=67.3mN)和较低的平均摩擦系数(0.061);在调制周期为20nm时,多层膜的残余应力达到最小值为-0.82GPa;经过高温退火后,多层膜的硬度和弹性模量均无明显变化,说明其具有良好的热稳定性;多层膜的结构和力学性能随调制周期的变化归因于晶粒的细化。     

无铅焊料Sn3.0Ag0.5Cu/Cu界面过渡层金属间化合物性能研究

根据实际工业工艺流程和服役工况,制备接近真实服役状态下的微电子封装中无铅焊点界面化合物试样;采用扫描电镜(SEM)和能量色散X射线荧光光谱仪(EDX)确定IMC的形貌厚度和化学成分;根据W.C.Olive算法,利用连续刚度测量(CSM)技术,实现了IMC层、焊料和Cu的弹性模量、硬度随压痕深度变化的连续测量,得到IMC层材料的硬度和弹性模量分别为(5.2±0.2)GPa和(104.51±2.62)GPa。根据纳米压痕结果,焊料、Cu和IMC蠕变应力指数从小到大分别为15.129、61.463和70.27。     

人体牙齿的显微组织及纳米力学性能

采用光学显微镜、能谱扫描电镜、高分辨透射电镜以及纳米力学探针等设备对人体牙齿的显微组织及纳米力学性能进行了研究。结果表明: 牙本质由规则排列的牙本质小管和基质组成,牙釉质由不同方向的釉柱及柱间质组成,牙本质与牙釉质之间有明显的界面;牙釉质中的Ca和P含量明显高于牙本质中的含量,而C含量明显低于牙本质中的含量。牙釉质中发现有大量的磷灰石晶体结构,而牙本质中则明显缺少。力学性能结果显示,牙釉质的纳米硬度平均为4.4 GPa,弹性模量为81 GPa,而牙本质的纳米硬度平均为1.0 GPa,弹性模量为26 GPa。牙釉质高的硬度和弹性模量与含有大量的羟基磷灰石晶体组织有关,Ca和P促进了该晶体组织形成。      

超音速火焰喷涂参数及粉末粒度对WC-12Co涂层弹性模量的影响

利用多功能超音速火焰喷涂(HVO-AF)焰流温度的特点(1400~2800℃)分别在三种条件下(HVOF,HVO-AF和HVAF)制备WC-12Co涂层。用Knoop压痕法对涂层的弹性模量进行测试,并测量涂层的显微硬度。采用扫描电镜(SEM)、能谱分析(EDS)、X射线衍射(XRD)探讨涂层的显微结构、成分和相组成。结果表明:与微米结构涂层相比,纳米结构涂层组织均匀、致密,孔隙率低,显微硬度与弹性模量均大幅提高,其中HVO-AF状态下制备的纳米结构WC-Co涂层平均硬度与弹性模量最高,分别为1515MPa和308GPa,而HVOF与HVAF状态下的纳米WC-Co涂层平均硬度与弹性模量分别为1390MPa,286GPa和1469MPa,270GPa;HVO-AF状态下的微米结构涂层平均硬度与弹性模量为1065MPa和242GPa。在HVO-AF状态下,焰流温度适中,可有效控制纳米WC-12Co粉末的分解,测得的涂层弹性模量最高。     

钨与钒掺杂类金刚石薄膜的温度适应摩擦磨损机制研究

通过非平衡磁控溅射技术,改变沉积工艺参数,在不锈钢及单晶硅基体上制备未掺杂、钨(W)掺杂以及钒(V)掺杂类金刚石(DLC)薄膜。采用拉曼光谱,纳米压痕法对薄膜结构和力学性能进行表征。在室温、250℃、500℃进行磨损实验,研究其不同温度范围的摩擦磨损性能。研究结果表明:适量掺杂W元素,可显著地提高W-DLC膜力学与摩擦性能,在W靶电流为0.6A条件下,W-DLC膜具有最优的综合性能,纳米硬度和弹性模量分别为11.11GPa和169.25GPa,其中在250℃条件下摩擦系数低至0.044,室温磨损率为1.27×10-7 mm~3/Nm,但W-DLC薄膜难以适应高温;适量掺杂V元素,可以显著提高V-DLC膜的纳米硬度和弹性模量,并能改善高温摩擦性能,在V靶功率为1.2kW条件下,V-DLC薄膜的纳米硬度和弹性模量分别为37.36GPa和379.89GPa,其中在500℃高温摩擦条件下,V-DLC薄膜的摩擦系数最低为0.35。     

高温超高压烧结纳米 SiC的研究

采用高温超高压(HT-HP)技术在4.5GPa/1250°C/20min工艺条件下制备了添加2wt%Al2O3助烧结剂的纳米SiC陶瓷.采用X射线粉末衍射(XRD)、X光电子能谱(XPS)、扫描电镜(SEM)、X射线能谱(EDX)、纳米压痕(Nano indenter)研究了烧结SiC陶瓷的物相组成、晶粒大小、化学成分、微观结构、纳米压痕力学性能等.结果表明:采用超高压烧结,可以在较低温度(1250±50°C)、较少烧结助剂用量下实现纳米SiC的致密烧结.烧结体未发生相转变,结构致密,无孔隙,晶粒尺寸为22nm,晶格常数为4.355A;显微硬度为33.7GPa,弹性模量为407GPa.     

感应熔覆原位自生TiC增强钛基复合涂层的纳米力学性能EI北大核心

为揭示感应熔覆原位TiC/Ti复合涂层微观结构与力学性能的对应关系,利用单一纳米压痕测试方法研究涂层内不同相结构的纳米力学性能变化规律,利用点阵压痕测试方法研究涂层微区结构的力学性能。单一压痕结果显示原位TiC增强相的纳米压痕硬度和弹性模量分别为21.3 GPa和275 GPa,富α-Ti与富β-Ti区域的基质相平均纳米硬度分别为4 GPa和6 GPa,平均弹性模量分别为130 GPa和155 GPa。点阵压痕与单一压痕测试结果之间具有较好的对应关系,对点阵纳米压痕测试结果进行三峰高斯拟合得到的最小峰值代表了涂层基质相的力学性能,中间峰值反映涂层的综合力学性能,最大峰值因受增强体尺寸与压痕位置的影响低于原位TiC增强体的真实力学性能。在考虑涂层微观结构与增强体尺寸的情况下,通过合理设置点阵压痕测试条件,选择适当的测试区域,可以在获得原位钛基复合涂层不同相结构真实力学性能的同时,揭示涂层的综合性能。     

感应熔覆原位自生TiC增强钛基复合涂层的纳米力学性能

为揭示感应熔覆原位TiC/Ti复合涂层微观结构与力学性能的对应关系，利用单一纳米压痕测试方法研究涂层内不同相结构的纳米力学性能变化规律，利用点阵压痕测试方法研究涂层微区结构的力学性能。单一压痕结果显示原位TiC增强相的纳米压痕硬度和弹性模量分别为21.3 GPa和275 GPa,富α-Ti与富β-Ti区域的基质相平均纳米硬度分别为4 GPa和6 GPa,平均弹性模量分别为130 GPa和155 GPa。点阵压痕与单一压痕测试结果之间具有较好的对应关系，对点阵纳米压痕测试结果进行三峰高斯拟合得到的最小峰值代表了涂层基质相的力学性能，中间峰值反映涂层的综合力学性能，最大峰值因受增强体尺寸与压痕位置的影响低于原位TiC增强体的真实力学性能。在考虑涂层微观结构与增强体尺寸的情况下，通过合理设置点阵压痕测试条件，选择适当的测试区域，可以在获得原位钛基复合涂层不同相结构真实力学性能的同时，揭示涂层的综合性能。     

Investigating the nanomechanical properties and reversible color change properties of the beetle <Emphasis Type="Italic">Dynastes</Emphasis> <Emphasis Type="Italic">tityus</Emphasis>

The wing cases (elytra) of Dynastes tityus are able to change coloration from yellow-green in a dry state to deep brown in a wet state due to different degrees of water absorption. An environmental scanning electron microscope was used to investigate the elytra’s reversible color change properties. Because the elytra cuticle has a spongy structure that is composed of laminated chitin and protein, a UV–Vis–NIR spectrophotometer was used to investigate the elytra’s optical properties. The width of the curve peak gradually decreased from 60 to 10 nm when the color of the elytra varied from deep brown to yellow-green. In a humid environment, air between the voids was replaced by water with a higher refractive index that induced an elytra color changed from yellow-green to deep brown. Interestingly, when both humidity and elytra color changed, the elytra’s mechanical properties varied too. When the humidity of the environment changed from 100 to 34%, the reduced modulus (E _r) and hardness (H) of the elytra increased 230 and 440%, respectively. The storage modulus (E′) of the elytra is 1.98 ± 0.65 and 1.17 ± 0.22 GPa in yellow-green and deep brown color at 10 Hz, respectively, while their loss modulus (E″) is similar. tan δ of deep brown elytra is 0.072 ± 0.017, which is nearly two times higher than that of yellow-green. It can be demonstrated that when the elytra’s color turns to yellow-green, they are more elastic with less energy loss. The relationship between the elytra’s mechanical properties and structure color will not only help us gain insight into the biological functionality of the color change but also inspire the designs of artificial biomimetic devices.     

Application of nano-indenter for investigation of the properties of the elytra cuticle of the dung beetle (Copris ochus Motschulsky)

The nanomechanical properties of the multilayer elytra cuticle of the dung beetle (Copris ochus Motschulsky) were investigated in the vertical and transverse directions using a nano-indenter. The reduced modulus Ev and hardness Hv of the surface cuticle in the vertical direction obtained by nano-indentation were 3.54+/-0.12 GPa and 0.20+/-0.01 GP, respectively. The nano-indentation result showed that the reduced modulus E(t) and hardness Ht of each layer were gradually reduced from the outer layer to the inner layer in the transverse direction. Ev was less than the largest Et presented at the outer layer (7.06+/-0.54 GPa). It was supposedly formed as a result of the composite effect of the multilayer. Without consideration of the anisotropy of chitin, an experimental model was proposed to describe the nanomechanical properties of the elytra cuticle.     

Mechanical properties of conventional and nanostructured plasma sprayed alumina coatings

The hardness and the elastic modulus measured by microindentation of three different types of plasma sprayed alumina coatings have been compared. Usually, such coatings present porosity and heterogeneity which affect the measurement of the mechanical properties. To take such effects into account along with the indentation size effect which is relevant to all hardness studies, the Proportional Specimen Resistance model is applied. The three alumina coatings show closely similar mechanical properties at indentation loads exceeding 1 N, i.e., macrohardness around 5.7 GPa, indentation size effect parameter around 5.5 MPa mm and elastic modulus around 160 GPa. For loads below 1 N, the extrapolated values of the macrohardness of crushed and agglomerated alumina coatings increased to 8.5 GPa, while the indentation size effect parameter has the same value, and the elastic modulus increased to 320 GPa. However, no significant change in the measured values of hardness and the elastic modulus of the nanostructured alumina coating has been observed. This result is attributed to porosity and the bimodal microstructure of the nanostructured coating where a semimolten phase coexists along with the fully molten phases.     

Study on mechanical properties of a new type micro/nano metal material based on bacteria shape

The functional groups and mechanical properties of Nocadia, a kind of bacteria with submicrometer in diameter and 3-10 microm in length, before and after metallization are determined by fourier transform infrared spectroscopy (FT-IR) and nanoindentation technology. The group -COOH exists on surface of Nocadia and the function groups of Nocadia decreases due to metallization. The elastic modulus of metallized Nocadia, Nocadia and resin is 42.583 GPa, 9.501 GPa and 5.723 GPa, respectively, and the hardness is 1.940 GPa, 0.265 GPa and 0.301 GPa, respectively. There is a great improvement of 5 times in elastic modulus and 9 times in hardness compared with bare Nocadia.     

纯钛表面微弧氧化膜纳米压入法研究

微弧氧化是一项较新的等离子体化学-电化学成膜技术，硬度和弹性模量是膜的基本微区力学性能。采用交流微弧氧化方法的铝酸盐溶液中在TA2纯钛表面制备出较厚的氧化膜，利用纳米压入法测定了膜的硬度和弹性膜量，并探讨了微弧放电对氧化膜相组成和性能的影响。研究结果表明：膜的显微硬度和弹性模量分布有相似的变化规律，从膜表层到膜内部，硬度和弹性模量逐渐增加，并在内层膜达到最大值，分别为9.78GPa和176GPa，比钛基体高的多；膜不同浓度处TiO2金红石和TiAl2O5相的相对含量变化决定了硬度和弹性模量的分布。     

c-AIN的生长对AIN/(Ti,Al)N纳米多层膜力学性能的影响

采用反应磁控溅射制备了具有不同调制周期的AIN/(Ti,Al)N纳米多层膜,研究了亚稳相立方氮化铝(c-AIN)在纳米多层膜中的生长条件及其对薄膜力学性能的影响。结果表明:在小调制周期下AIN以立方结构存在,并与(Ti,Al)N层形成同结构共格外延生长,使纳米多层膜产生较大的晶格畸变。与此相应,AIN/(Ti,Al)N纳米多层膜硬度和弹性模量随调制周期的减小呈单凋上升的趋势,当调制周期小于8～10 nm时其增速明显增大,并在调制周期为1.3 nm时达到最高硬度29.0GPa和最高弹性模量383 GPa.AIN/(Ti,Al)N纳米多层膜的硬度和弹性模量在小调制周期时的升高与亚稳相c-AIN的产生并和(Ti,Al)N形成共格结构有关。     

Large flexibility of high aspect ratio carbon nanostructures fabricated by electron-beam-induced deposition

The mechanical properties of free-standing electron beam deposited amorphous carbon structures have been studied using atomic force microscopy. The fabricated carbon blades are found to be extraordinarily flexible, capable of undergoing vertical deflection up to ～ 75% of their total length without inelastic deformation. The elastic bending modulus of these structures was calculated to be 28 ± 10 GPa.     

砌浆层状复合材料珍珠层的应变率效应

为了分析具有砌浆结构的层状复合材料的应变率效应,以珍珠层为研究对象,采用纳米压入法测试珍珠层力学性能,利用连续刚度测量法得到不同加载速率下材料的硬度值和弹性模量。利用扫描电子显微镜观察珍珠层不同方向的砌浆微结构形貌,并结合微观结构对比分析不同压入深度和不同应变率两种工况下,珍珠层表层与横断面方向的力学性能。结果表明:在相同加载条件下,珍珠层表层方向的弹性模量小于其横断面方向的弹性模量,而表层方向硬度值则大于横断面方向的硬度值;当应变率恒定时,珍珠层弹性模量与硬度随压入深度增加而增加,当压入深度达到750nm后,弹性模量不再随压入深度变化而变化;当压入深度恒定时,硬度值、弹性模量和弹性回复率均随着应变率的增加而变大。