纳米压痕技术对比研究DNAN和TNT晶体的微观力学性能

通过溶剂挥发法制备了DNAN和TNT晶体;利用纳米压痕技术研究了DNAN和TNT晶体的微观力学性能(硬度和弹性模量);通过原位扫描探针成像技术(SPM)研究了DNAN和TNT晶体的压痕形貌随时间的变化差异。结果表明,DNAN晶体的平均硬度和弹性模量分别为7.82GPa和0.22GPa,TNT晶体的平均硬度和弹性模量分别为12.19GPa和0.48GPa,表明TNT抵抗变形的能力优于DNAN;随着压痕深度由118nm增至856nm,DNAN的硬度从0.61GPa降至0.22GPa;随着压痕深度由27nm增至481nm,TNT的硬度从2.9GPa降至0.48GPa,表明DNAN和TNT均存在尺寸效应。随着时间由0增至50.4min,DNAN的压痕深度由-270.99nm减至-44.28nm,TNT的压痕深度由-415.12nm减至-369.21nm,表明DNAN晶体比TNT晶体具有更明显的慢回弹性,DNAN具有更强的冲击能量吸收能力。     

烧结温度对ZrO2薄膜表面形貌及力学性能的影响

采用溶胶-凝胶法在玻璃基体表面制备了经300℃,400℃和500℃烧结热处理的ZrO2薄膜.利用X射线衍射仪、原子力显微镜和纳米压痕仪研究了烧结温度对ZrO2薄膜表面形貌和力学性能的影响.实验结果表明,随着烧结温度的增加,ZrO2的晶体结构由少量的单斜晶相逐渐转变为单斜晶相和四方晶相的混合相.薄膜表面形貌逐渐改善,薄膜的表面粗糙度和颗粒度依次减小,薄膜的表面粗糙度分别为10.5 nm、7.2 nm和5.6 nm,ZrO2的粒径分别为188 nm、153 nm和130 nm.ZrO2薄膜的弹性模量和硬度都显著提高,薄膜的弹性模量分别为89.6 GPa、114.2 GPa和128.9 GPa,薄膜的硬度分别为7.6 GPa、10.3 GPa和15.1 GPa.     

应变率对硬化水泥净浆微观力学性能及徐变行为的影响

采用连续刚度测试研究应变率对硬化水泥净浆微观力学性能及徐变行为的影响,结合扫描电镜技术分析水泥净浆的微观结构对连续刚度测试结果的影响。结果表明:通过30μm压入深度的连续刚度测试可以得到水泥净浆均匀的力学性能,当压入深度(荷载)大于临界最小深度(荷载)时,测试得到的弹性模量和压痕硬度基本保持不变,反映了水泥净浆均匀的力学性质;在0.01 s~(–1)~0.50 s~(–1)应变率范围内,应变率变化对硬化水泥净浆弹性模量的影响可忽略不计,但压痕硬度随着应变率的增大而增大,且二者具有幂型函数关系;应变率影响持载阶段的接触徐变函数,应变率越大,持载阶段的接触徐变函数越大,这与应变率越大时加载阶段的徐变发展越不充分有关。为了准确测试水泥净浆的微观徐变,需尽可能减小加载阶段的用时。     

纳米压痕技术测试纤维束内沥青炭和粗糙层热解炭的力学性能

为了研究纤维束内沥青炭和粗糙层热解炭的力学性能,以2.5D针刺炭毡为增强体,分别通过中温煤沥青浸渍炭化和化学气相沉积制备得到C/C复合材料。使用G200型纳米压痕仪对C/C复合材料纤维束内基体进行纳米压痕测试,采用连续刚度测试方法,利用Oliver和Pharr模型获得试样弹性模量随测试深度的变化,利用弹性模量和硬度两参数Weibull分布函数对纳米压痕测试结果进行统计分析。结果表明,沥青炭和粗糙层热解炭的弹性模量平均值分别为(14.92±2.02) GPa和(12.87±1.35)GPa;硬度的平均值分别为(0.64±0.14) GPa和(0.67±0.17) GPa。沥青炭和粗糙层热解炭的弹性模量的Weibull分布模数分别为8.60和9.18,弹性模量的特征值分别为15.63 GPa和13.40 GPa。     

脉冲电沉积纳米晶Zn涂层的结构表征与摩擦学性能

采用脉冲电沉积法,通过调节电流密度控制涂层的晶粒尺寸,在铜基体上制备了平均晶粒尺寸为6~32 nm的Zn涂层,采用XRD, SEM和显微硬度、摩擦实验等手段,表征了涂层的微观结构,并研究了其力学性能与摩擦学性能. 结果表明,纳米晶Zn涂层的表面平整致密,平均晶粒尺寸随电流密度增大而减小,随着晶粒尺寸减小,涂层的显微硬度增大,摩擦系数降低. 当电流密度从0.3 A/cm2增大至2.4 A/cm2时,平均晶粒尺寸从32 nm下降为6 nm,显微硬度从低于0.5 GPa增大至2.0 GPa以上,在大气环境中与Si3N4球之间的滑动摩擦系数从0.18降低至0.05. 硬度随晶粒尺寸的变化规律符合经典的Hall-Petch关系.     

浮法玻璃在线镀复合膜的力学性能

用化学气相沉积法在浮法玻璃上制备了复合薄膜.用台阶仪、纳米压痕和X射线衍射分别测定了薄膜厚度、弹性模量、纳米硬度和室温时薄膜的残余应力.实验结果表明:薄膜厚度为560.7nm,弹性模量为48.33GPa,纳米硬度值为10.65GPa,计算得到薄膜的残余应力值为-0.19GPa.对膜厚、气体的配比、流量、玻璃板的厚度、玻璃基体的化学成分等因素对薄膜残余应力的影响进行了讨论.     

溅射功率对二氧化锆薄膜结构及力学性能的影响研究

为了研究溅射功率对二氧化锆薄膜结构及力学性能的影响,使用射频反应磁控溅射技术在常温下以玻璃为基底使用不同功率镀制了800 nm左右的ZrO2薄膜.利用X射线衍射仪(XRD)和扫描电子显微镜(SEM)对样品结晶情况,表面和断面形貌进行表征,结果显示镀制的ZrO2薄膜均为单斜晶体,晶粒尺寸变化不大;随着功率的升高,薄膜从纳米晶结构转变为柱状晶结构.使用纳米压痕仪对薄膜表面进行硬度和弹性模量测试,发现随着功率升高,硬度和弹性模量均出现上升趋势,进一步增加功率出现下降,再上升的变化;在沉积功率为65 W时,可得到厚度为800 nm,弹性恢复量,硬度,弹性模量和塑性指数均最高,分别为88.55％,25.42 GPa,228.6 GPa和0.314的ZrO2薄膜.不同的溅射功率会镀制出不同结构的二氧化锆薄膜,在常温低功率溅射条件下二氧化锆薄膜结构是影响其力学性能的重要因素.     

~(60)Co γ射线辐照改性As_2S_3玻璃的纳米压痕试验（英文）

采用纳米压痕技术对~(60)Coγ-射线辐照改性10年后As_2S_3玻璃的表面机械性能(即硬度和弹性模量)进行超纳硬度仪(UNHT)测试,压痕深度为200~1 600 nm。结果表明:经平均量子能1.25 Me V、累计剂量2.41 MGy的~(60)Coγ-射线辐照后,g-As_2S_3(g-表示玻璃态)的表面硬度和弹性模量与辐照前相比得以提高。对于g-As_2S_3表面机械性能的长期辐照诱导改性,具有辐照诱导氧化层的辐照样品与经过清洗和抛光处理除去氧化层的辐照样品相比,其实验数据显示宽分布特性。     

自组装ANFs/GO复合薄膜的结构与纳米压痕力学性能

将氧化石墨烯(GO)在氢氧化钾/二甲基亚砜中分散并与对位芳纶聚对苯二甲酰对苯二胺(PPTA)聚阴离子分散液混合得到稳定分散的复合分散液,将该复合分散液通过去离子水处理并利用自组装方法制备由直径为40 nm左右的高长径比芳纶纳米纤维(ANFs)和表面无羧基、羟基含量相对增多的部分脱氧GO(DGO)组成的复合薄膜。对系列复合薄膜进行电子显微镜观察和光谱学分析发现ANFs与DGO间通过氢键和π–π堆叠相互作用紧密结合形成多层结构。采用纳米压痕技术测试旋涂自组装方法制备的薄膜的微观力学性能,发现薄膜弹性模量和纳米硬度在GO用量为PPTA质量的1.5%时,分别达到了32 GPa和1.5 GPa,较未加GO的ANFs提升了104%和87.5%,表明ANFs与GO形成的DGO之间具有较强的协同增强作用。这种具有高硬度、高弹性模量的新型复合材料有望在个体防护、船壳材料、航空航天等领域发挥重要作用。     

一种太阳能单晶硅片的清洗工艺

本发明涉及一种太阳能单晶硅片的清洗工艺,其特征在于将太阳能单晶硅片依次经过喷淋、脱胶、自来水漂洗、清洗剂超洗、纯水漂洗工序,之后,先在离子水和氢氟酸的混合液中浸泡一定时间,     

电热爆炸定向喷涂NiCr/WC-Co复合涂层的特性

用电热爆炸定向喷涂技术在45钢基体上制备了NiCr／WC-17％Co复合涂层。用扫描电镜以及能谱仪对涂层显微组织和界面情况进行了观察分析。借助纳米硬度计测定了涂层的硬度和模量。结果表明：涂层颗粒细小且分布均匀,可分辨颗粒尺寸在200～300nm;涂层致密,孔隙率为1％;涂层与基体结合良好,界面附近存在元素扩散现象;弹性模量在涂层内最大为290GPa;涂层硬度达到17．7GPa。涂层硬度和弹性模量沿横截面平稳下降,体现出了复合涂层的特征。     

Mechanical properties of PECVD thin ceramic films

Silicon dioxide (thickness 350 nm and 969 nm) and silicon nitride (thickness 218 nm) films deposited on silicon substrate using plasma enhanced chemical vapor deposition process were investigated using a Berkovich nanoindenter. The load-depth measurements revealed that the oxide films have lower modulus and hardness compared to the silicon substrate, where as the nitride film has a higher hardness and slightly lower modulus than the substrate. To delineate the substrate effect, a phenomenological model, that captures most of the ‘continuous stiffness measurement’ data, was proposed and then extended on both sides to determine the film and substrate properties. The modulus and hardness of the oxide film were around 53 GPa and 4–8 GPa where as those of the nitride film were around 150 GPa and 19 GPa, respectively. These values compare well with the measurements reported elsewhere in the literature.     

Influence of porosity on the mechanical properties of microporous β-TCP bioceramics by usual and instrumented Vickers microindentation

Beta-tricalcium phosphate [Ca₃(PO₄)₂, β-TCP] is a bioresorbable material showing an excellent biocompatibility. However, sintering of β-TCP is difficult and the material presents poor mechanical strength and a low resistance to crack-growth propagation. In this study, influence of the porosity on the hardness and the elastic modulus is studied by means of usual and instrumented microindentation tests. Nevertheless, indentation diagonals measurement by optical observations is not accurate due to the crack formation around the residual indent. That is why instrumented indentation test which allows deducing the hardness and the bulk modulus from the load-depth curve analysis is used as an alternative method. The corresponding hardness number can be calculated by using the maximum indentation depth (Martens Hardness) or the contact depth determined by Oliver and Pharr's method (Contact Hardness). But in order to give representative values when comparing classical and instrumented hardness measurements, Martens hardness is preferred because its value can be directly related to the value of the Vickers hardness number by simple geometrical considerations.In this work, bioceramics were produced by conventional sintering of β-TCP powders synthesized by aqueous precipitation. Different process conditions were chosen to obtain microporous ceramics with a porosity rate between 0 and 14% in volume. As main results, the elastic modulus is found decreasing between 166 GPa and 108 GPa and the hardness number from 4.4 GPa to 2.2 GPa when increasing the porosity rate. A model connecting mechanical properties to porosity rate and grain arrangement is validated for the elastic modulus whereas deviation is observed for the hardness number. However, we propose an original approach where the relative variation of the two mechanical properties can be expressed with a unique relation as a function of the porosity volume fraction.     

Evaluation of the elastic-plastic properties of SiCN coating system by finite element simulations

The elastic properties of SiCN coating on substrates can be evaluated by nano-indentation test, however, it is challenging for experiments to evaluate the plastic performance of SiCN coating. Finite element (FE) is a numerical method for investigating in-depth mechanical behavior of various structures. In this paper, a contact model between Berkovich indenter and SiCN/Si system is established by FE method. The stress-strain behavior of SiCN coating is obtained by comparing the calculated P-h curves with experimental results. The indentation depth dependent elastic modulus and hardness of the SiCN coating are calculated from the P-h curves and are close to the experimental data. When the indentation depth is in excess of 10% of the coating thickness, the mechanical properties of SiCN coating tend to be influenced by the Si substrate, which also consists with experiments. The proposed approach provides an efficient tool to predict the mechanical properties of SiCN coating.     

Mechanical properties of MWPECVD diamond coatings on Si substrate via nanoindentation

The mechanical properties of polycrystalline diamond coatings with thickness varying from 0.92 to 44.65 μm have been analysed. The tested samples have been grown on silicon substrates via microwave plasma enhanced chemical vapour deposition from highly diluted gas mixtures CH₄-H₂ (1% CH₄ in H₂). Reliable hardness and elastic modulus values have been assessed on lightly polished surface of polycrystalline diamond films.The effect of the coating thickness on mechanical, morphological and chemical-structural properties is presented and discussed. In particular, the hardness increases from a value of about 52 to 95 GPa and the elastic modulus from 438 to 768 GPa by varying the coating thickness from 0.92 to 4.85 μm, while the values closer to those of natural diamond (H = 103 GPa and E = 1200 GPa) are reached for thicker films (> 5 μm). Additionally, the different thickness of the diamond coatings permits to select the significance of results and to highlight when the soft silicon substrate may affect the measured mechanical data. Thus, the nanoindentation experiments were made within the range from 0.65% to 10% of the film thickness by varying the maximum load from 3 to 80 mN.     

Nanoindentation behavior of ultrathin polymeric films

Measurement of the mechanical properties of nanoscale polymeric films is important for the fabrication and design of nanoscale layered materials. Nanoindentation was used to study the viscoelastic deformation of low modulus, ultrathin polymeric films with thicknesses of 47, 125 and 3000 nm on a high modulus substrate. The nominal reduced contact modulus increases with the indentation load and penetration depth due to the effect of substrate, which is quantitatively in agreement with an elastic contact model. The flow of the nanoscale films subjected to constant indentation loads is shear-thinning and can be described by a linear relation between the indentation depth and time with the stress exponent of 1/2.     

Study of the mechanical properties of tetrahedral amorphous carbon films by nanoindentation and nanowear measurements

Nanoindentation and nanowear measurements, along with the associated analysis suitable for the mechanical characterization of tetrahedral amorphous carbon (ta-C) films are discussed in this paper. Films of approximately 100-nm thick were deposited on silicon substrates at room temperature in a filtered cathodic vacuum arc evaporation system with an improved S-bend filter that yields films with high values of mass density (3.2 g/cm³) and sp³ content (84–88%) when operating in a broad bias voltage range (−20 V to −350 V). Nanoindentation measurements were carried out on the films with a Berkovich diamond indenter applying loads in the 100 μN–2 mN range, leading to maximum penetration depths between 10 and 60 nm. In this measurement range, the ta-C thin-films present a basically elastic behavior with high hardness (45 GPa) and high Young's modulus (340 GPa) values. Due to the low thickness of the films and the shallow penetration depths involved in the measurement, the substrate influence must be taken into account and the area function of the indenter should be accurately calibrated for determination of both hardness and Young's modulus. Moreover, nanowear measurements were performed on the films with a sharp diamond tip using multiple scans over an area of 3 μm², producing a progressive wear crater with well-defined depth which shows an increasing linear dependence with the number of scans. The wear resistance at nanometric scale is found to be a function of the film hardness.     

Mechanical properties of thermally sprayed porous alumina coating by Vickers and Knoop indentation

Depending on the thermal spraying conditions, coatings obtained can present different defects, like pores, cracks and/or unmelted particles, and different surface roughnesses, that can affect the determination of the hardness and elastic modulus. The present work investigates the mechanical properties, determined by means of Knoop and Vickers indentations, of a plasma as-sprayed alumina coating, obtained with a nano-agglomerated powder sprayed using a PTF4 torch, in order to highlight how the surface defects interfere into the indentation process. As a main result, Knoop indentation compared to Vickers one gives less dispersive results (15% and 33%, respectively), that are, in addition, more representative of the coating properties. The mean values obtained are 110 ± 40 GPa for the elastic modulus and 1.75 ± 0.42 GPa for the hardness. In addition, and for the two indenter types used, multicyclic indentation has been performed because it allows a more appropriate characterization of such heterogeneous coatings due to the representation of the mechanical properties as a function of the indentation load and/or the penetration depth, leading to more reliable results according to the depth-variability of the coating microstructure.     

Mechanical behaviour of the constituents inside carbon-fibre/carbon-silicon carbide composites characterised by nano-indentation

The Young's modulus, hardness, fracture toughness and ductility of the key constituents were characterised using nano-indentation for three types of carbon-fibre/carbon silicon carbide composite manufactured through different routes and/or using different carbonaceous raw materials. Under indentation, all of the carbon constituents demonstrated much less ductile deformation than the silicon carbide and silicon did in these composites. Between two types of PAN-based carbon fibre, as well as of pyrolytic carbon, a difference of around a factor of two was evident in the Young's modulus and hardness. For the silicon carbide, a difference of around 100 GPa and 5 GPa was recorded for the mean Young's modulus and hardness respectively; for silicon, only a small variation was evident. The estimated mean fracture toughness of the silicon carbide ranged between 0.7 and 1.2 MPa.m^1/2, whilst the silicon was approximately 0.6 MPa.m^1/2. Results for the constituents were discussed in terms of their elastic/plastic behaviour.