多孔氧化铝模板的纳米力学性能测试与分析

为了掌握多孔氧化铝模板的纳米力学性能,采用二次氧化法制备孔径在30～40nm之间且高度有序的纳米阵列氧化铝模板,并使用扫描电子显微镜(SEM)对其形貌进行表征;在原位纳米力学测试系统上进行微压痕实验,对样品表面力学性能(纳米硬度、模量)进行测试;利用原子力成像功能对实验区域扫描成像,在纳米尺度下观察和分析样品形貌.结果表明,AAO模板在同一深度处对应的硬度、模量值明显高于相应的基体材料铝,膜基体系的抗载能力明显提高;在压入深度为70～240nm时,AAO膜板的硬度和模量值分别为5.8GPa和106GPa,但从深度250nm时开始出现减小趋势;单晶铝与压针的接触为理想刚塑性接触,AAO模板与压针的接触为弹塑性接触.     

不同厚度纳米Ti薄膜的力学性能

通过直流磁控溅射方法制备出四个不同厚度的纳米Ti薄膜,并分别采用纳米压痕仪、电子薄膜应力分布测试仪研究了Ti薄膜的力学性能和残余应力大小,结合分形维数方法和原子力显微镜对薄膜表面粗糙度和表面形貌进行了分析。实验结果表明:随Ti薄膜厚度的增加,薄膜晶粒尺寸逐渐增大,表面粗糙度和残余应力值随厚度的增加先增大后减小,而Ti薄膜弹性模量和硬度随薄膜厚度增加呈现出先减小随后增大的趋势。当薄膜厚度为600,2400,3600nm时薄膜中存在残余压应力,厚度为1200nm时存在残余拉应力,薄膜中残余应力分布最为均匀,但此时薄膜具有较低的硬度和弹性模量值。分析得出Ti薄膜中存在残余拉应力会使薄膜硬度和弹性模量值变小,残余压应力反之。     

多壁碳纳米管增强水泥基复合材料的纳米力学性能

采用纳米压痕技术探讨了多壁碳纳米管(MWCNTs)对有骨料水泥基复合材料纳米尺度上力学性能的影响,分别对压痕模量(M)小于50 GPa和压痕硬度(H)小于4.0 GPa的数据进行了统计,对其频率分布进行了Gaussian函数(PDF)的解卷积分峰处理,并对低密度水化硅酸钙凝胶(LD C-S-H)和高密度水化硅酸钙(HD C-S-H)凝胶进行了定量的体积分数计算。结果表明,除LD C-S-H、 HD C-S-H、 Ca(OH)2(CH)外,还出现了一个假相。MWCNTs降低了水化产物中LD C-S-H的体积分数,提高了HD C-S-H的体积分数,提高了C-S-H凝胶的压痕模量,但利用压痕模量和压痕硬度统计结果计算出的各相体积分数存在一定的差异。MWCNTs作为一种纳米晶核,对HD C-S-H凝胶形成起到了一定的诱导作用,从纳观尺度阐释了MWCNTs对水泥基材料的改性机制。     

电热爆炸喷涂层的纳米力学性能研究

采用英国Micro Materials公司生产的Nano Test 600型纳米多功能测试仪,对电热爆炸喷涂方法制备的FeAl、FeCrAl、FeCrAlRE 3种电爆喷涂层,进行力学性能测试,通过3种涂层加卸载曲线的对比,以及每种涂层的硬度、弹性模量的测取,分析铁基3种电爆喷涂层的力学性能及涂层表面规律,从而优化电爆喷涂工艺参数.     

氧化铝／碳化硅纳米复合材料的力学性能和强化机理

热压合成的氧化铝／碳化硅纳米复合材料的四点弯曲强度随纳米尺寸的碳化硅的含量增加而增大。这一增大被部分地解释为晶粒细化的结果。与具有相同晶粒尺寸的纯氧化铝基体材料相比，复合材料的强度提高约２０％。维氏压痕对样品表面应力的探测以及裂纹／粒子互作用的透射电镜观察表明，这一强化应归之于断裂模式的改变，即从氧化铝的沿晶断到复合的穿晶断裂。晶界上的碳化硅粒子在改变断裂模式上可能起着重要作用。     

多孔氧化铝膜的纳米力学性能研究

采用二次铝阳极氧化技术, 制备了高度有序的铝阳极氧化膜(AAO膜), 孔径为50nm. 利用纳米压缩仪结合纳米压痕仪对不同压缩位移条件下的AAO膜进行了纳米力学测试和卸载后的压痕原位扫描实验. 通过测量加载-卸载曲线并用Oliver-Pharr模型分析计算得到, 在压缩位移为0、3.3、6.6、9.9μm时, AAO膜的纳米硬度和弹性模量分别为1.49、1.79、1.69、1.55GPa和11.79、12.32、12.82、13.19GPa. 由卸载曲线和原位扫描的压痕形貌可以看出, 压缩位移为6.6和9.9μm时的压痕在压缩力的作用下发生了明显的塑性变形, 因而AAO膜的纳米硬度减小, 而弹性模量一直增大.     

金属纳米多层膜力学性能研究进展

新型功能材料及器件向小型化,集成化和复合化发展的趋势,使得尺寸在纳米尺度的层状材料和柔性多层器件在使用过程中的服役行为成为其发展的关键科学问题。本文结合作者近几年对Ag/M系列和Cu/M系列多层膜力学性能的研究工作,对金属纳米多层膜的微结构特征及其对力学性能的影响进行了回顾和总结,主要包括多层膜的晶粒形貌对其强化机制和塑性变形行为的影响,组元强度错配对多层膜硬化行为的影响,界面结构与其强度极值的关系、不对称界面结构引起的异常弹性模量增强和多层膜的室温蠕变机制及界面结构对蠕变性能的影响等几个方面,并对多层膜的力学性能研究进行了展望。     

应用纳米压痕技术测试沥青炭的力学性能

以高温煤沥青为前驱体,采用液相浸渍技术制备了4D炭/炭复合材料.利用纳米压痕技术研究了后处理温度和炭基体位置对沥青炭力学性能的影响.研究结果表明,在同一工艺状态下,束内沥青炭的硬度和模量要远低于束间沥青炭的硬度和模量.经过900℃后处理的沥青炭的模量出现小幅降低,而硬度则出现一定的增加.     

聚碳酸酯透明材料表面耐磨涂层的纳米力学性能和耐磨性研究

利用纳米压痕和划痕技术对不同纳米硅溶胶含量的两种有机硅耐磨涂层的表面与体相的纳米力学性能和耐磨性分别进行了对比实验研究。结果表明:纳米硅溶胶会增加涂层Si-O-Si网络结构的刚性,提高涂层的力学性能和耐磨性,并且涂层近表面区的硬度、模量以及耐磨性明显优于体相的性质。     

用纳米压痕法研究玻璃表面复合薄膜的力学性能

采用溶胶凝胶法在玻璃基体上制备了CeO2-TiO2单层膜、TiO2-SiO2单层膜和CeO2-TiO2/TiO2-SiO2双层膜,采用纳米压痕和划痕法对薄膜的机械性能(纳米硬度、弹性模量、临界载荷、摩擦系数)进行了分析.实验结果表明,双层膜与玻璃基体的附着力以及弹性模量、硬度等指标均大于单层膜,由TiO2-SiO2组成的内层,对强化附着力起到了关键作用.     

Nanomechanical properties of silicon surfaces nanostructured by excimer laser

Abstract

Excimer laser irradiation at ambient temperature has been employed to produce nanostructured silicon surfaces. Nanoindentation was used to investigate the nanomechanical properties of the deformed surfaces as a function of laser parameters, such as the angle of incidence and number of laser pulses at a fixed laser fluence of 5 J cm^?2. A single-crystal silicon [311] surface was severely damaged by laser irradiation and became nanocrystalline with an enhanced porosity. The resulting laser-treated surface consisted of nanometer-sized particles. The pore size was controlled by adjusting the angle of incidence and the number of laser pulses, and varied from nanometers to microns. The extent of nanocrystallinity was large for the surfaces irradiated at a small angle of incidence and by a high number of pulses, as confirmed by x-ray diffraction and Raman spectroscopy. The angle of incidence had a stronger effect on the structure and nanomechanical properties than the number of laser pulses.     

Nanomechanical properties of silicon surfaces nanostructured by excimer laser

Excimer laser irradiation at ambient temperature has been employed to produce nanostructured silicon surfaces. Nanoindentation was used to investigate the nanomechanical properties of the deformed surfaces as a function of laser parameters, such as the angle of incidence and number of laser pulses at a fixed laser fluence of 5 J cm⁻². A single-crystal silicon [311] surface was severely damaged by laser irradiation and became nanocrystalline with an enhanced porosity. The resulting laser-treated surface consisted of nanometer-sized particles. The pore size was controlled by adjusting the angle of incidence and the number of laser pulses, and varied from nanometers to microns. The extent of nanocrystallinity was large for the surfaces irradiated at a small angle of incidence and by a high number of pulses, as confirmed by x-ray diffraction and Raman spectroscopy. The angle of incidence had a stronger effect on the structure and nanomechanical properties than the number of laser pulses.     

Nanomechanical Characterisation of Graded NiTi Films Fabricated Through Diffusion Modification

Abstract:  Ni₄₇Ti₅₃ films of varying thickness were deposited onto Ni₅₆Ti₄₄ substrates. Annealing the films produced compositional gradients through diffusion modification. Nanoindentation measurements were used to probe the mechanical properties at various depths into the film. The films exhibited a variation in elastic modulus as a function of indentation depth that depended on the thickness of the film. A self-similarity principle permitted the mechanical properties of the graded NiTi films to be resolved further into substrate, beyond the contact depth of the tip. The observed variation of elastic modulus with indentation depth in the graded NiTi films was considered to be a combined response from changes in microstructure, substrate effects, and mechanically-induced phase transformations. This variation was predicted using an analysis that accounted for the transformation effects occurring under the tip during loading and the graded distribution of martensite volume fraction obtained from diffusion modification.     

Toxicity Assessments of Multisized Gold and Silver Nanoparticles in Zebrafish Embryos

The potential toxicity of nanoparticles is addressed by utilizing a putative attractive model in developmental biology and genetics: the zebrafish (Danio rerio). Transparent zebrafish embryos, possessing a high degree of homology to the human genome, offer an economically feasible, medium‐througput screening platform for noninvasive real‐time assessments of toxicity. Using colloidal silver (cAg) and gold nanoparticles (cAu) in a panoply of sizes (3, 10, 50, and 100 nm) and a semiquantitative scoring system, it is found that cAg produces almost 100% mortality at 120 h post‐fertilization, while cAu produces less than 3% mortality at the same time point. Furthermore, while cAu induces minimal sublethal toxic effects, cAg treatments generate a variety of embryonic morphological malformations. Both cAg and cAu are taken up by the embryos and control experiments, suggesting that cAg toxicity is caused by the nanoparticles themselves or Ag⁺ that is formed during in vivo nanoparticle destabilization. Although cAg toxicity is slightly size dependent at certain concentrations and time points, the most striking result is that parallel sizes of cAg and cAu induce significantly different toxic profiles, with the former being toxic and the latter being inert in all exposed sizes. Therefore, it is proposed that nanoparticle chemistry is as, if not more, important than specific nanosizes at inducing toxicity in vivo. Ultimately such assessments using the zebrafish embryo model should lead to the identification of nanomaterial characteristics that afford minimal or no toxicity and guide more rational designs of materials on the nanoscale.     

骨组织工程支架材料及其力学性能

骨组织工程的研究是组织工程最为活跃的领域之一,如何制备理想的骨支架材料是当前的一个研究热点.通过人们的努力,目前已有多种骨组织工程支架材料问世.综述了各类骨组织工程支架材料的优缺点,对比了它们的力学性能,并对骨组织工程的前景进行了展望.     

纳米HAP改性PMMA骨水泥力学性能的研究

PMMA骨水泥存在力学强度及弹性模量不高、聚合温度、生物相容性有待进一步改进等问题.本文利用水热法合成了纳米HAP粉体,研究HAP粉体对PMMA基骨水泥改性方法及其对力学性能、微观结构的影响.结果表明,当HAP含量在5-10%时,骨水泥的拉伸强度、弹性模量、硬度、冲击韧性等性能均有一定程度的提高.通过粉体的表面改性,界面结合性能得到改善.     

Nanomechanical evaluation of nickel-titanium surface properties after alkali and electrochemical treatments.

In this paper, the suitability of alkali treatment followed by heat treatment at 600 degrees C, and spark oxidation for nickel-titanium, intended for medical applications such as pins, wires and clamps, was evaluated on the basis of nanomechanical and wear testing. In addition, the chemical composition and topography of the surface layer, wetting ability, corrosion resistance and influence of the heat treatment on structure of the alloy were also investigated. The results showed that the highest hardness was observed for alkali-treated samples, and this could be correlated with the structure of the sample that contained martensite and a higher phase transformation temperature. This treatment caused a very large increase of nickel in the top layer and decreased resistance in pitting corrosion. These results disqualified the treatment to be considered as useful for medical applications. On the other hand, the hardness of the oxidized samples was at the same level as that obtained for ground reference samples. Moreover, the oxide layer was enriched with phosphorus, and it was predominantly composed of TiO2 and phosphorus oxides. This 3.1 microm thick layer had good adhesion to the substrate as indicated by scratch testing and wear resistant in nanowear testing. However, the oxidation did not significantly increase the corrosion resistance of the alloy compared with reference samples.     

Comparative Evaluation of Intestinal Nitric Oxide in Embryonic Zebrafish Exposed to Metal Oxide Nanoparticles

Nanoparticle (NP) exposure may induce oxidative stress through generation of reactive oxygen and nitrogen species, which can lead to cellular and tissue damage. The digestive system is one of the initial organs affected by NP exposure. Here, it is demonstrated that exposure to metal oxide NPs induces differential changes in zebrafish intestinal NO concentrations. Intestinal NO concentrations are quantified electrochemically with a carbon fiber microelectrode inserted in the intestine of live embryos. Specificity of the electrochemical signals is demonstrated by NO‐specific pharmacological manipulations and the results are correlated with the 4,5‐diaminofluorescein‐diacetate (DAF‐FM‐DA). NPs are demonstrated to either induce or reduce physiological NO levels depending on their redox reactivity, type and dose. NO level is altered following exposure of zebrafish embryos to CuO and CeO₂ NPs at various stages and concentrations. CuO NPs increase NO concentration, suggesting an intestinal oxidative damage. In contrast, low CeO₂ NP concentration exposure significantly reduces NO levels, suggesting NO scavenging activity. However, high concentration exposure results in increased NO. Alterations in NO concentration suggest changes in intestinal physiology and oxidative stress, which will ultimately correspond to NPs toxicity. This work also demonstrates the use of electrochemistry to monitor in vivo changes of NO within zebrafish organs.