POSS纳米杂化材料压痕实验的分子力学模拟

本文通过分子力学模拟方法研究了聚苯乙烯和丙基POSS纳米杂化聚苯乙烯两种薄膜在压痕实验中的力学行为.计算得到了两种材料的载荷-位移曲线.曲线表明随着压头位移的增加,两种材料的载荷响应呈锯齿状增长.结合材料的载荷-位移曲线和模拟过程中材料的形变计算了两种材料的硬度.进而,采用一个简单的表达式描述材料硬度与压痕深度之间的关系.我们通过对多种聚合物硬度-压痕深度的拟合验证了公式的合理性.根据此公式计算出了聚苯乙烯及其POSS杂化材料极限硬度的比值,结果表明POSS单体可以有效地提高聚苯乙烯的硬度.     

钛合金表面TiAlN膜层的制备

为了研究不同偏压对TiAlN薄膜性能的影响以及薄膜体系膜基硬度比随载荷的变化关系,采用多弧离子镀的方法在Ti6Al4V合金表面制备TiAlN薄膜,利用扫描电子显微镜、x 射线衍射仪、全自动显微硬度计等设备对膜层的微观组织结构和力学性能进行了测试.结果表明,TiAlN膜层由Ti2AlN(hcp)相组成.在恒定载荷条件下,体系的膜基硬度比随载荷的增加而减小.当载荷小于300g时,偏压对膜基硬度比与载荷关系曲线呈不规则影响.载荷超过300g以后,几乎没有影响.     

脉冲激光沉积制备TiN/AlN多层薄膜的研究

采用脉冲激光沉积(PLA)法,在单晶Si试样表面沉积制备了一系列TiN/AlN硬质多层膜,并采用基于免疫算法的免疫径向基函数(IRBF)神经网络对AlN厚度建立预测模型,设计出具有可控调制周期和调制比的TiN/AlN多层膜。X射线衍射(XRD)结果表明,小调制层周期下,过高或过低的工艺条件下薄膜通常为非晶态,适当的工艺条件下TiN、AlN形成具有强烈织构的超晶格柱状晶多层膜;与此相应,纳米多层膜产生了硬度和弹性模量异常增高;随着调制比增加,使纳米多层膜形成非晶AlN层和纳米晶TiN层的多层结构,多层膜的硬度和弹性模量逐渐下降。XPS结果表明,薄膜界面由Ti+4、Ti+3离子组成,N的负二价、三价亚谱结构预示着非当量TiN、AlN的形成。AFM研究显示,薄膜的调制周期均在10~200 nm范围内,且薄膜表面较均匀;当多层薄膜调制周期在50 nm以下时,薄膜的纳米硬度值明显高于TiN和AlN的混合硬度值,达30 Gpa。     

超薄纳米薄膜的划痕硬度评价方法及应用

纳米压痕是一种常用的薄膜硬度评价方法.然而,当薄膜厚度10 nm时,该方法难以去除基体对薄膜硬度的影响,因而无法获得薄膜自身的硬度,限制了纳米结构与硬度之间关系的认知,阻碍了超薄纳米结构薄膜的应用.本研究提出一种基于纳米压痕硬度标定下的纳米划痕硬度评价方法,并将其应用于纳米结构碳膜的硬度研究.首先,利用自行设计搭建的纳米刻划装置,通过对比碳膜在纳米划痕和纳米压痕方法下的残余变形深度,分析不受基体影响的临界薄膜厚度,得到纳米划痕深度不受基体影响的临界薄膜厚度.其次,采用压头形状等效接触模型,利用划痕的残余顶角、宽度和深度,通过计算压头前端的接触压力分布得到硅基体的纳米划痕硬度,与纳米压痕硬度标定结果一致.最后,将纳米划痕硬度方法应用在电子回旋共振等离子体溅射方法制备的3种不同纳米结构碳膜上,得到交联结构碳膜和非晶碳膜的硬度分别约为19. 1 GPa和14. 6 GPa,高于硅基体11. 2 GPa的硬度,而石墨烯嵌入式碳膜的硬度约为2. 7GPa.分析不同纳米结构碳膜的刻划机理表明,在sp2含量较高的纳米结构碳膜中,sp3含量并不是决定碳膜力学特性的唯一因素,小尺度、多石墨烯层间交联结构能够有效增加层间的剪切强度,薄膜展现出较好的耐刻划特性.研究结果有助于进一步拓展纳米划痕方法的应用,也为不同纳米结构碳膜的应用提供了理论基础.     

压痕对不锈钢材料表面残余应力的影响

为研究自动球压痕过程残留压痕残余应力分布情况,以压力容器常用的奥氏体不锈钢板材S30408、S32168、 S31603 和 S30403为对象,通过常规拉伸试验获得材料的本构关系及自动球压痕试验获得压痕过程的载荷-位移曲线,采用有限元软件ABAQUS进行模拟。试验结果表明:压头卸载后,压痕凹坑底部材料承受的残余压应力达到最大,Mises应力状态下最大残余应力约为700 MPa左右,压痕残余应力影响范围在受压面上大约占球形压头半径的1.3%。同时,对材料施加一定大小的外载荷拉应力,研究残余应力和外载荷共同作用下压痕周围材料的应力分布状况,结果显示最大叠加应力出现在压痕材料堆积区域,但是应力影响区域很小,影响深度为所受影响平面半径的6%以内。     

基于纳米压痕技术及有限元模拟的薄膜力学性能研究

采用纳米压痕技术结合有限元模拟和量纲分析方法分析薄膜材料的弹塑性性能．用有限元模 拟纳米压痕过程,结合量纲分析方法将纳米压痕的加卸载过程与被测材料的力学性能联系起来,建 立起两者间的无量纲函数关系结构式,进而结合实际纳米压痕试验所得薄膜的弹性模量和载荷— 位移曲线计算出了材料的应力—应变关系．经检验,有限元模拟所得到载荷—位移曲线和纳米压痕 试验所得载荷—位移曲线吻合得比较好,因此验证了有限元模型的正确性和材料模拟的正确性．     

颗粒体系错流微滤过程临界点研究——临界点的数值识别

以传统的滤饼层阻力和与诱导扩散相结合的浓差极化模型为基础,建立了刚性颗粒悬浮液体系错流微滤过程中模拟临界点的数学模型。模型的模拟和预测结果与实验值吻合很好。用该模型不仅能计算错流微滤过程中临界点的临界压力、临界错流速度和临界滤饼层厚度,还可以对临界点的性质与微滤中各项参数的关系进行预测。模型的提出为更好地理解颗粒体系错流微滤中的膜污染机理,并在实际应用中通过控制过滤操作参数来减小或消除此类膜面污染提供了理论依据。     

大载荷连续压入及整体材料弹塑性行为的研究

用自制的具有新颖性的压入仪,对ＧＣｒ１５,４０Ｃｒ,２０Ｃｒ和退火纯铝等块状材料进行了大载荷连续加载,卸载压入实验,实验结果表明,大载荷压入时,加载曲线的载荷戌压入深度具有幂函数关系,卸载曲线的为自变量的幂函数,;材料硬度的测定值与载荷大小或压入深度无关,即不存在硬度的压痕尺寸效应。由大载荷连加载卸载曲线可得被测材料的塑性功、弹性功,性比和硬度等材料性能指标。     

基于单晶硅各向异性特征的纳米压痕过程有限元仿真研究

本文采用各向异性弹塑性材料本构关系,利用非线性有限元软件MSC.Marc建立了单晶硅纳米压痕过程的三维模型,分别用玻氏、维氏、圆锥形和球形压头对单晶硅（100）晶面进行了纳米压痕过程的仿真分析,研究了单晶硅对于不同形状的压头、不同压头半锥角、不同最大加载力的加、卸载响应特性。仿真结果表明,压入相同深度时,圆锥形压头所需载荷最小,材料对圆锥形和球形压入产生的应力应变分布呈现出各向异性,体现了单晶硅在不同晶向上的材料性能存在差异。当最大加载力为25mN时,仿真得出维氏压头在单晶硅（100）晶面产生的压痕深度约为300nm,与相应实验结果基本相符。     

Ti过渡层厚度对Ti—TiN薄膜结合强度的影响

薄膜脱落的主要原因之一是受薄膜与基体上的界面应力影响,TiN薄膜和钢基体由于其力学性能差异较大,在界面上有很大的应力集中,在钢基体上沉积Ti过渡层能减小其界面应力。研究Ti过渡层厚度对膜基体系结合强度的影响．并借助有限元方法对不同过渡层厚度的膜基体系的界面应力进行分析,研究表明,适当厚度的过渡层能提高Ti-TiN膜层的结合强度。     

Load Dependence of Nanohardness in Nitrogen Ion Implanted Ti6Al4V Alloy and Fractal Characterization

Three different nitrogen ion doses were implanted into a Ti6Al4V alloy to improve its mechanical surface properties for the application of artificial joints. The titanium nitride phase and nitrogen element distribution profile were characterized with X-ray photoelectron spectroscopy (XPS). Nano-indentation tests were carried out on the surface of the Ti6Al4V alloy and implanted samples on a large scale of applied loads. The XPS analysis results indicate that nitrogen diffuses into the titanium alloy and forms a hard TiN layer on the Ti6Al4V alloy. The nanohardness results reveal that nitrogen ion implantation effectively enhances the surface hardness of Ti6Al4V. In addition, the nanohardness clearly reveals load dependence over a large segment of the applied loads. Thus a concept of nanohardness fractal dimension is first proposed and the dual fractal model can effectively describe nonlinear deformation in indentation areas on the Ti6Al4V surface. The fractal dimension shows a decreased trend in two regions of applied loads, indicating a decrease of the self-similarity complexity in surface indentation owing to an increase in nanohardness after nitrogen ion implantation.     

Load Dependence of Nanohardness in Nitrogen Ion Implanted Ti6AI4V Alloy and Fractal Characterization

Three different nitrogen ion doses were implanted into a Ti6A14V alloy to improve its mechanical surface properties for the application of artificial joints. The titanium nitride phase and nitrogen element distribution profile were characterized with X-ray photoelectron spectroscopy （XPS）. Nano-indentation tests were carried out on the surface of the Ti6A14V alloy and implanted samples on a large scale of applied loads. The XPS analysis results indicate that nitrogen diffuses into the titanium alloy and forms a hard TiN layer on the Ti6A14V alloy. The nanohardness results reveal that nitrogen ion implantation effectively enhances the surface hardness of Ti6A14V. In addition, the nanohardness clearly reveals load dependence over a large segment of the applied loads. Thus a concept of nanohardness fractal dimension is first proposed and the dual fractal model can effectively describe nonlinear deformation in indentation areas on the Ti6A14V surface. The fractal dimension shows a decreased trend in two regions of applied loads, indicating a decrease of the self-similarity complexity in surface indentation owing to an increase in nanohardness after nitrogen ion implantation.     

连续压入法评定等离子体增强化学气相沉积(PECVD)TiN膜基结合强度

介绍了一种新型涂层压入仪。对比了压入法、划痕法、接触疲劳法测定不同处理基体、同类ＰＥＣＶＤ ＴｉＮ 膜基结合强度的变化规律。结果表明采用该压入仪, 运用连续加载压入法, 可方便地定性或半定量测定ＰＥＣＶＤ ＴｉＮ 膜基结合优劣。该法所测临界载荷Ｐｃ 不仅反映膜基结合的优劣, 还反映了膜基体系的承载能力。     

Compressional Deformation in Indentation Process for Microlens Array Mold

The structure of a microlens array (MLA) can be formed on copper by an indentation process which is a new manufacture approach we applied here instead of a traditional method to test the material property,thereby work time can be saved.Single-indentation and multi-indentation are both conducted to generate a single dimple and dimples array,namely micro lens and MLA.Based on finite element simulation method,factors affecting the form accuracy,such as springback at the compressed area of one single dimple and compressional deformation at the adjacent area of dimples arrays,are determined,and the results are verified by experiments under the same conditions.Meanwhile,indenter compensation method is proposed to improve form accuracy of single dimple,and the relationship between pitch and compressional deformation is investigated by modelling seven sets of multi-indentations at different pitches to identify the critical pitch for the MLA's indentation processing.Loads and cross-sectional profiles are measured and analyzed to reveal the compressional deformation mechanism.Finally,it is found that MLA at pitches higher than 1.47 times of its diameter can be manufactured precisely by indentation using a compensated indenter.     

Compressional Deformation in Indentation Process for Microlens Array Mold

The structure of a microlens array (MLA) can be formed on copper by an indentation process which is a new manufacture approach we applied here instead of a traditional method to test the material property,thereby work time can be saved.Single-indentation and multi-indentation are both conducted to generate a single dimple and dimples array,namely micro lens and MLA.Based on finite element simulation method,factors affecting the form accuracy,such as springback at the compressed area of one single dimple and compressional deformation at the adjacent area of dimples arrays,are determined,and the results are verified by experiments under the same conditions.Meanwhile,indenter compensation method is proposed to improve form accuracy of single dimple,and the relationship between pitch and compressional deformation is investigated by modelling seven sets of multi-indentations at different pitches to identify the critical pitch for the MLA's indentation processing.Loads and cross-sectional profiles are measured and analyzed to reveal the compressional deformation mechanism.Finally,it is found that MLA at pitches higher than 1.47 times of its diameter can be manufactured precisely by indentation using a compensated indenter.     

脉冲偏压对铝合金上TiN膜生长的影响

为了研究在铝合金上硬质膜的性能,促进硬质TiN膜在铝合金构件上的应用,利用电弧离子镀在7075铝合金上沉积TiN膜层,并通过改变脉冲偏压幅值研究其对薄膜生长过程的影响.结果表明,生长的TiN膜具有柱状特征,在无偏压或低偏压时,柱状特征明显,但随着负偏压值的增大,柱状特征变得不明显,膜层中Ti和N的原子比率增加,由无偏压、低偏压时近似为1.0增加到-200V偏压时的1.2.在0～-200V偏压范围内,沉积膜的平均生长速率由1.5μm/h增加到11.3μm/h.随着负偏压的增加,TiN膜的(111)方向的择优取向越来越明显,而(200)方向强度越来越小.沉积膜呈柱状生长,具有明显的择优取向,其程度受脉冲偏压影响.     

Nanoindentation analysis of TiN,TiAlN,and TiAlSiN coatings prepared by cathode ion plating

The TiN,TiAlN and TiAlSiN coatings were deposited on H13 hot-worked mold steel by cathodic arc ion plating(CAIP).The morphologies,phase compositions,and nanoindentation parameters,such as creep hardness,elastic modulus and plastic deformation energy of the coatings were analyzed with field emission scanning electron microscopy(FESEM),X-ray diffraction(XRD) and nanoindentation testing,respectively,and the test results were compared with equation describing the indentation model.The results show that the TiN,TiAlN and TiAlSiN coating surfaces were dense and composed of TiN,TiN + TiAlN,TiN + Si3N4 + TiAlN phases,respectively.There was no spalling or cracking on the indentation surface.The creep hardness of the TiN,TiAlN and TiAlSiN coatings was 7.33,13.5,and 15.2 GPa,respectively;the corresponding hardness measured by nanoindentation was 7.09,15.6,and 21.7 GPa,respectively;and the corresponding elastic modulus was 201.93,172.79,and 162.77 GPa,respectively.The contact depth and elastic modulus calculated by the indentation model were close to those of the test results,but the remaining indentation parameters showed discrepancies.The sequence of plastic deformation energy was TiN TiAlNTiAlSiN.     

Determination of Young''''s modulus by nanoindentation

Loadanddepthsensingindentationtechniqueisveryusefulinprobingthemechanicalpropertiesofmaterialsonsmallscales[1—5].Youngsmodulusisoneofthemostcommonlyconcernedmaterialpropertiesmeasuredbythiskindoftechnique.Conventionally,itisachievedonthebasisofthemethodproposedbyOliverandPharr[4]usingthewell-knownrelationship:whereSuistheinitialslopeofunloadingcurve,EristhereducedmodulusandrelatedwiththeYoungsmodulusEandPoissonsratioνoftheindentedmaterialandthose(Ei,ni)oftheindenterbytheequation1/Er=(1-n2…     

铜合金表面Ti/TiN多层膜的制备、结构及其性能

为了研究多层膜的腐蚀性能,促进多层膜在生产中的应用,采用电弧离子镀技术,通过调整环境N₂和Ar气的时间比例在铜衬底上成功制备了不同调制周期的Ti/TiN多层膜.利用x 射线衍射谱和交流阻抗谱研究了该多层膜的结构和腐蚀性能.表面形貌显示,沉积的Ti/TiN多层膜具有明显的周期性,环境中N2和Ar气的时间比例决定了多层膜的调制周期,N₂气时间越长,多层膜中TiN相层越厚.腐蚀性能测定表明,多层膜的调制周期影响其耐蚀性,当调制周期为550nm时,沉积膜的耐腐蚀性最好.