Surface morphology,elastic modulus and hardness of thin film cathodes for Li-ion rechargeable batteries

In this study, surface morphology, elastic modulus and hardness of two thin film cathode materials, namely layered structured LiNi_1/3Co_1/3Mn_1/3O₂ and spinel structured LiMn₂O₄, during the charge/discharge cycles, are measured by using Scanning Electron Microscopy, Atomic Force Microscopy and nanoindentation experiments. Furthermore, the effects of depth of discharge (DOD) and charging rate (current density) on the changes of elastic modulus and hardness of the spinel structured LiMn₂O₄ are also investigated. The results have shown that both elastic modulus and hardness of the thin film cathodes have been significantly affected by the charge/discharge cycles as well as the condition of the charge/discharge processes. These results suggest the importance of the mechanical properties of the cathode materials to the reliability and integrity of the cathode materials to be used for the Li-ion batteries. The possible mechanisms of the changes in mechanical properties are also discussed.     

Evaluation of interphase properties in a cellulose fiber-reinforced polypropylene composite by nanoindentation and finite element analysis

The hardness and elastic modulus of the cellulose fiber and polypropylene (PP) matrix in a cellulose fiber-reinforced PP composite were investigated by nanoindentation with a continuous stiffness technique. Nanoindentation with different indentation depths and spacings was conducted to measure hardness and elastic modulus in the interphase region, which was modified by maleic anhydride-grafted PP and γ-amino propyltrimethoxy silane (γ-APS) sizing. A line of indents was produced from the fiber to the matrix. There was a gradient of hardness and modulus across the interphase region. The distinct properties of the transition zone were revealed by 1–4 indents, depending on nanoindentation depth and spacing. Based on the results of nanoindentation, it was assumed that the width of the property transition zone is less than 1 μm. However, three dimensional finite element analysis shows that even a perfect interface without property transition has almost same interphase width as that measured by nanoindentation. Using existing nanoindentation techniques, it will be difficult to calculate exact mechanical properties without the effect of neighboring material property in at least 8 times smaller region than indent size.     

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。     

Ti-12Mo-6Zr-2Fe钛合金的纳米压入特征

利用纳米压入测量仪测试了Ti-12Mo-6Zr-2Fe钛合金的硬度和模量.测试表明,Ti-12Mo-6Zr-2Fe钛合金的硬度比Ti-6Al-4V ELI高,而模量比后者低,与常规方法得到的规律一致,表明该方法能很好地表征钛合金的力学特性.对测试过程的分析表明这种方法得到的结果不能与传统方法得到的结果互换,表面状态对测量结果有一定影响.     

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.     

An improved method for the measurement of mechanical properties of bone by nanoindentation

Nanoindentation is widely used to measure the mechanical properties of bio-tissues. However, viscoelastic effects during the nanoindentation are seldom considered rigorously, although they are in general very significant in bio-tissues. In this study, a recently developed method for correcting the viscoelastic effects during nanoindentation is applied to mice bone samples. This method is found to yield reliable elastic modulus and hardness results from forelimb and femur cortical bone samples of C57 BL/6N and ICR mice. The creep properties of the samples are also characterized by a novel procedure using nanoindentation. The measured mechanical properties correlate well with the calcium content of the bone samples.     

Effects of drying on the mechanical properties of bovine femur measured by nanoindentation

Effects of drying on the measurement of mechanical properties of bone by nanoindentation methods have been examined. Tests were conducted to measure the elastic modulus and hardness of two cross-sectional cortical specimens obtained from adjacent areas of bovine femur. One specimen was thoroughly dried in air prior to testing while the other was stored in deionized water. The properties of osteons and interstitial lamellae showed statistically significant differences (plt; 0.0001) and were therefore investigated separately. Drying was found to increase the elastic modulus by 9.7% for interstitial lamellae and 15.4% for osteons. The hardness was also found to increase by 12.2% for interstitial lamellae and 17.6% for osteons.     

Mechanical properties of human enamel as a function of age and location in the tooth

Aging and the related changes in mechanical behavior of hard tissues of the human body are becoming increasingly important. In this study the influence of aging on the mechanical behavior of human enamel was evaluated using 3rd molars from young (18 < or = age < or = 30 years) and old (55 < or = age) patients. The hardness and elastic modulus were quantified using nanoindentation as a function of distance from the Dentin-Enamel Junction (DEJ) and within three different regions of the crown (i.e. cervical, cuspal and inter-cuspal enamel). Results of the evaluation showed that the elastic modulus and hardness increased with distance from the DEJ in all three regions examined, regardless of patient age. The largest increases with distance from the DEJ occurred within the cervical region of the old enamel. Overall, the results showed that there were no age-dependent differences in properties of enamel near the DEJ. However, near the tooth's surface, both the hardness (p < 0.025) and elastic modulus (p < 0.0001) were significantly greater in the old enamel. At the surface of the tooth the average elastic modulus of "old" enamel was nearly 20% greater than that of enamel from the young patients.     

On the measurement of pile-up corrected hardness based on the early Hertzian loading analysis

Nanoindentation has been used to gain insight into the elastic/plastic contact responses of material at very small scales. The Oliver and Pharr's analysis (W.C. Oliver and G.M. Pharr, J. Mater. Res. 7 (1992) 1564) on the nanoindentation curve, however, can be meaningless when plastically deformed material piles around the indented points. This study suggests a measuring methodology of the real contact area enlarged by the material pile-up and its corresponding mechanical properties; the pile-up corrected contact area can be calculated inversely from the reduced modulus formulation with input information of the independently determined Young's modulus based on the Hertzian loading analysis. This contact correction relaxed overestimates in the elastic modulus and hardness interpreted from the nanoindentation curve and yielded actual mechanical properties comparable to the literature values of a (100) tungsten monocrystal. In addition, theoretically estimated upheaval amount of the contact boundary in this study was nearly consistent with the average pile-up height measured from an atomic-force microscope.     

纳米压入测试中面积函数测量方法综述

在纳米压入法材料力学性能测试中,面积函数的准确测量对保证测量结果的准确性非常重要。本文对纳米压入测试中常用的面积函数确定方法进行了分类介绍,并对各种方法的特点进行了分析,指出了为提高纳米硬度和弹性模量等力学性能参数的测量准确性对面积函数进行校准的必要性。     

基于纳米压痕法的羟基磷灰石/聚乳酸复合材料力学性能表征

采用准静态和动态纳米压痕技术研究了羟基磷灰石/聚乳酸（HA/PLA）复合材料在微纳尺度的表面力学性能。在静态模式下研究了保载和卸载时间对模量和硬度测试结果的影响。结果发现,当保载时间小于45 s时,由于蠕变使保载和卸载时间对测试结果产生显著影响;保载时间短且卸载时间长时,在卸载段会形成"鼻子",为了避免"鼻子"选择保载时间为45 s。在动态模式下研究了材料的动态力学性能,结果表明,存储模量和硬度均随着压入深度的增加而减小。压痕和划痕实验结果均表明：HA显著提高了PLA的力学性能,与纯PLA相比,9wt% HA/PLA复合材料的模量增加了35.5%,硬度增加了44.7%,蠕变深度下降了9.5%,相同载荷下的最大划痕深度和残余深度均小于纯PLA,表现出良好的弹性恢复能力和抗变形能力。     

Characterization of Plasma Nitrided and PVD-TiN Duplex Treated Armco Iron and En40B Steel by Nanoindentation

The nanoindentation test has been applied to evaluate the mechanical properties such as hardness, elastic moduli and deformation behaviors of Fe₄N iron nitride layers produced on Armco iron and En40B steel by plasma nitriding, and PVD-TiN coatings deposited on En40B with or without prior plasma nitriding treatment. Results showed that the Fe₄N layer produced on En40B exhibits higher hardness than that on Armco iron. This is attributed to the effect of the alloy compositions, especially Cr element. However, similar elastic modulus values to that of bulk ferrous alloys have been found for Fe₄N layers produced on both Armco iron and En40B. Under lower loads, TiN coatings on nitrided substrate behave quite the same in hardness and elastic modulus as TiN coatings on untreated En40B. Whilst with increasing indentation load and depth, duplex treated (i.e., combined plasma nitriding and PVD-TiN coating) En40B possesses higher composite hardness, elastic modulus and load bearing capacity than TiN coated base material.     

空位对Hf-Ta-C体系的结构、力学性质及电子性质影响的第一性原理研究

本研究理论预测了三元Hf-Ta-C空位有序结构以及空位对力学性质的影响.采用第一性原理进化晶体结构预测软件USPEX,预测得到了5种热力学稳定和3种亚稳的(Hf,Ta)C1–x空位有序结构,这些结构都属于岩盐结构.采用第一性原理方法,计算了(Hf,Ta)C1–x空位有序结构的力学性质,并分析了力学性质随空位浓度的变化....     

Biomechanical evaluation of regenerating long bone by nanoindentation

It is crucial to measure the mechanical function of regenerating bone in order to assess the mechanical performance of the regenerating portion as well as the efficiency of the regeneration methods. In this study, nanoindentation was applied to regenerating and intact rabbit ulnae to determine the material properties of hardness and elasticity; viscoelasticity was also investigated to precisely evaluate the material properties. Both intact and regenerating bones exhibited remarkable viscoelasticity manifested as a creep behavior during load hold at the maximum load, and the creep was significantly greater in the regenerating bone than the intact bone. The creep resulted in an overestimation of the hardness and Young’s modulus. Hence, during nanoindentation testing of bones, the effect of creep should be eliminated. Moreover, the regenerating bone had lower hardness and Young’s modulus than the intact bone. The nanoindentation technique proved to be a powerful approach for understanding the mechanical properties of regenerating bone.     

Effect of Styrene–Butadiene Rubber Latex on Mechanical Properties of Cementitious Materials Highlighted by Means of Nanoindentation

Abstract: In this paper, micro‐mechanical properties of styrene–butadiene rubber (SBR) latex‐modified cement pastes identified by means of the nanoindentation (NI) technique are related to macro‐mechanical properties of SBR latex‐modified mortars obtained from standard test methods, considering an SBR latex/cement ratio varying from 0% to 20%. For this purpose, the average value of the hardness and the so‐called indentation modulus of the different material phases of the cement paste, i.e. calcium–silicate–hydrate (CSH), portlandite, anhydrous cement, etc., obtained from NI are compared with the compressive and flexural strengths, on the one hand, and the dynamic elastic modulus of SBR latex‐modified mortars, on the other hand. This comparison revealed a linear correlation between the dynamic elastic modulus and the indentation modulus and between the compressive strength, flexural strength and hardness. Thus, the obtained results clearly indicate the finer‐scale origin of the macroscopic elastic and strength properties, linking the mechanical properties at the so‐called mortar scale to the cement‐paste scale.     

The microstructural mechanism for mechanical property of LY2 aluminum alloy after laser shock processing

This paper described nanoindentation techniques for measuring thin films mechanical properties, including elastic modulus and nano-hardness. The effects of laser shock processing (LSP) on elastic modulus and nano-hardness of the sample manufactured by LY2 aluminum alloy were experimentally investigated by nanoindentation techniques. Transmission electron microscope (TEM) observations of the microstructures in different regions after LSP are carried out. Experimental results showed that the values of nano-hardness and elastic modulus in the laser-shocked region were obviously increased by 58.13% and 61.74% compared to those in the non-shocked region, respectively. The influences of LSP on microstructure and grain size of LY2 aluminum alloy were discussed, and the enhancement mechanism of LSP on nano-hardness and elastic modulus was also addressed.     

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。     

Investigation of mechanical properties of diatom frustules using nanoindentation

Diatom frustules have been identified as potential candidate materials for nanotechnology applications. However, for successful engineering applications, their mechanical properties must be fully determined. Toward this end, indentation hardness and elastic properties frustules of the centric diatom Coscinodiscus concinnus were evaluated using nanoindentation. A series of nanoindentation tests were performed on the outer surfaces of frustules at various locations. Analysis of the indentations revealed that the Young's modulus and hardness values appear to be strongly dependent on the location of the indentation. The modulus varied from 0.591 to 2.768 GPa in the center and 0.347 to 2.446 GPa at locations away from the center. Similarly, frustule hardness varied between 0.033 and 0.116 GPa in the center and between 0.076 and 0.12 GPa away from the center. Another series of nanoindentation tests were performed on the frustules (positioned in both concave and convex orientations) at various locations to analyze the failure mode. It was found that the failure modes in each of the orientations were also drastically different. In convex orientation, cracks initiated along the sharp edges of the indentation were followed by circular ring cracks, whereas in concave orientation only cracks along the sharp edges (corresponding to the three edges of the indenter) were revealed. The porosity and the nonplanar nature of the frustules make it difficult to extract the mechanical properties accurately at each location.     

Anisotropic nanomechanical properties of bovine horn using modulus mapping

Bovine horns are durable that they can withstand an extreme loading force which with special structures and mechanical properties. In this study, the authors apply quasi‐static nanoindentation and modulus mapping techniques to research the nanomechanical properties of bovine horn in the transverse direction (TD) and longitudinal direction (LD). In quasi‐static nanoindentation, the horn''s modulus and hardness in the inner layer and the outer layer demonstrated a gradual increase in both TD and LD. Laser scanning confocal microscopy revealed microstructure in the horn with wavy morphology in the TD cross‐section and laminate in the LD cross‐section. When using tensile tests or quasi‐static nanoindentation tests alone, the anisotropy of the mechanical properties of bovine horn were not obvious. However, when using modulus mapping, storage modulus (E ′), loss modulus (E ″) and loss ratio (tan δ) are clearly different depending on the position in the TD and LD. Modulus mapping is proposed as accurately describing the internal structures of bovine horn and helpful in understanding the horn''s energy‐absorption, stiffness and strength that resists forces during fighting.Inspec keywords: laser applications in medicine, proteins, molecular biophysics, high‐speed optical techniques, biomedical optical imaging, viscoelasticity, elastic moduli, biomechanics, biological tissues, nanoindentation, laminates, tensile testing, tensile strengthOther keywords: resists forces, stiffness, energy‐absorption, internal structures, loss ratio, loss modulus, storage modulus, modulus mapping, quasistatic nanoindentation testing, tensile testing, LD cross‐section, laminate, TD cross‐section, wavy morphology, microstructure, laser scanning confocal microscopy, hardness, longitudinal direction, transverse direction, modulus mapping techniques, quasistatic nanoindentation, loading force, bovine horns, modulus mapping, anisotropic nanomechanical properties