多孔ZnO/羟基磷灰石生物复合材料的制备与性能

利用放电等离子烧结技术制备多孔ZnO/羟基磷灰石（HA）生物复合材料,研究不同纳米ZnO含量对ZnO/HA复合材料微观结构、孔隙特征、力学性能、矿化和降解性能的影响。结果表明:烧结后ZnO/HA复合材料主要由HA相和ZnO相组成;随着ZnO含量提高,多孔ZnO/HA复合材料孔隙率缓慢增大,抗压强度略有减小,弹性模量变化不大;多孔ZnO/HA复合材料的孔隙率>40%,孔径在50～500 μm之间,抗压强度>148 MPa,弹性模量为6.5 GPa左右,能够满足骨修复材料的要求;模拟人工体液中矿化和降解实验表明,多孔ZnO/HA复合材料浸泡7天后表面开始形成大量类骨磷灰石层,且随着ZnO含量增加,磷灰石形成能力明显增强而降解速率加快。      

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。     

东方龙虱鞘翅内表皮层及断面硬度和弹性模量

研究了东方龙虱去除外表皮后的鞘翅内表皮层及其鞘翅断面的力学性能。利用纳米压痕仪测得鞘翅内表皮层硬度和弹性模量分别为(0.065±0.007) GPa和(0.704±0.013) GPa, 均远远小于鞘翅外表皮层的硬度和弹性模量。鞘翅断面的力学性能测试结果表明: 在鞘翅横断面上, 靠近联接部位的硬度和弹性模量略大于鞘翅中部和外侧; 而在鞘翅纵向断面上, 鞘翅中部的硬度和弹性模量明显大于头部和尾部, 其断面力学性能呈现一定的分布规律。      

Ti35Nb7Zr-xHA生物复合材料的微观组织与性能研究

为了改善Ti-Nb-Zr合金的生物活性,采用放电等离子烧结(SPS)技术制备了不同羟基磷灰石(HA)含量的Ti35Nb7Zr-xHA(x=0、5、10、20(质量分数,%))生物复合材料,研究了HA含量对复合材料微观组织、力学性能及体外生物活性的影响。结果表明,复合材料主要由β-Ti、α-Ti、HA及陶瓷相(Ti_xP_y、CaTiO_3、Ti_2O、CaO)组成;HA含量增加会导致β-Ti减少而α-Ti和陶瓷相明显增多;与Ti-35Nb-7Zr合金(E:45GPa,σ:1 736 MPa)相比,HA含量为5%和10%时,复合材料的抗压强度分别为1 662MPa和1 593MPa,弹性模量分别为48GPa和49GPa,综合力学性能与Ti-35Nb-7Zr合金接近,展现出良好的力学性能,而过高的HA含量(20%)会导致复合材料弹性模量明显升高(E:55GPa)、抗压强度急剧下降(σ:958 MPa),复合材料的力学性能降低;体外生物活性实验表明,加入10%HA的复合材料在人工模拟体液(SBF)中浸泡7d后表面生成了大量的类骨磷灰石层,与Ti-35Nb-7Zr合金相比,其显示出更优异的体外生物活性。     

Cu含量对脉冲偏压电弧离子镀TiN-Cu纳米复合薄膜硬度的影响

用脉冲偏压电弧离子镀技术在高速钢(HSS)基体上制备了一系列不同Cu含量的TiN-Cu纳米复合薄膜,用EPMA、SEM、GIXRD和纳米压痕等方法分别测试了薄膜的成分、形貌、相组成、硬度和弹性模量,重点考察薄膜成分对其硬度和弹性模量的影响.结果表明,Cu含量对薄膜的硬度和弹性模量影响显著,随着Cu含量的增加,薄膜硬度和弹性模量先增大后减小,在Cu含量为1.28 at％时,硬度和弹性模量达到最大值,分别为45.0 GPa和562.0 GPa.最后对TiN-Cu纳米复合薄膜的非晶-纳米晶强化机制进行了讨论.     

Al含量对CrAlN涂层微观结构和力学性能的影响

采用不同Al含量的AlCr合金靶,在高速钢(M2)上通过直流反应磁控溅射的方式沉积不同的CrAlN涂层;分别用EDS、XRD、纳米压痕仪、高速往复摩擦磨损试验机和台阶仪测量出涂层的化学成分、物相组成、力学性能、磨损性能和磨损量,研究了不同Al含量对CrAlN涂层微观结构和力学性能的影响。XRD分析表明涂层主要为NaCl结构,纳米压痕仪测得力学性能随Al含量的提升先提高后降低,在Al含量为60%时获得最高硬度和弹性模量分别为36.8 GPa和459.5 GPa和最佳的磨损性能。磨损机制为磨料磨损和微动磨损。     

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。     

应用纳米压痕技术研究表面纳米化后316L不锈钢力学性能

316L不锈钢经表面纳米化(SNC)处理后,表面形成一层纳米层。样品表面晶粒细化至纳米级大约12nm左右,随着深度的增加,晶粒尺寸逐渐增大。该文应用纳米压痕技术分析了纳米层力学性能,结果表明:纳米层的纳米硬度和弹性模量分别为6.05GPa和227GPa,是基体硬度和弹性模量的1.4倍和1.2倍。随距表面距离的增加而降低,并逐步趋近于一个稳定值。同时测得纳米层的应变硬化指数为0.44为基体的1.5倍。     

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。     

Gradually varying mechanical properties of in situ synthesized NbC–Fe-graded composite coating

NbC–Fe-graded composite coating was fabricated by in situ synthesis using a pure niobium plate and grey cast iron as the raw materials. SEM analysis demonstrates that the thickness of coating is about 400?μm. From the surface to the matrix, the volume fraction of NbC particulates continuously decreases from 95 to 0%, while the average particulate diameter gradually increases from 200?nm to 1?μm. Along the depth towards the matrix, the nano-hardness and elastic modulus of the graded coating decrease from 23.5 to 3?GPa and from 435 to 150?GPa, respectively. In addition, the fracture toughness (K_C) of 8.62?MPa?m^1/2 is obtained on the surface of the coating by the Vickers indentation technique. And the fracture mechanism is intergranular cracking.     

Mechanical and tribological characterization of human tooth

In order to develop new dental restorative materials, it is imperative to evaluate and understand the structure–property relationships of the human tooth. Three major structural parts of human tooth i.e. enamel, dentin and dentin–enamel junction have been characterized in the present work in terms of microstructure, phase analysis and compositional gradient. It has been observed that microindentation hardness varies from enamel to dentin with the highest hardness observed for enamel at the outermost surface (around 3.5 GPa). Hardness values monotonically decrease with depth to less than 1 GPa, measured at the interior dentin. Furthermore, the measured hardness variation is found to have a noticeable correlation with the compositional variation.

In order to evaluate the tribological properties of the human tooth, fretting wear tests were carried out against sintered alumina under a load of 1 N for 2000 to 10,000 cycles. A variation in coefficient of friction (ranging from 0.12 to 0.55) was measured in our experiments. The wear mechanism is dominated by fretting fatigue and adhesive wear, involving the formation of oxidized calcium phosphate based compounds and its subsequent transfer from tooth to alumina surface. The experimental results also reveal that the human tooth is more susceptible to adhesion wear than abrasion or attrition at fretting contacts.     

基于SLM的梯度多孔牙种植体力学特性

目的 确定既满足强度要求又能够有良好长期稳定性的梯度多孔牙种植体最佳孔隙值。方法 设计4组不同孔隙率(G30、G40、G50、G60)的梯度多孔结构样件及均质多孔样件S30,选区激光熔化(SLM)成型后通过准静态压缩试验对其力学性能进行研究,测量出样件的弹性模量和屈服强度。通过有限元分析评估不同孔隙率种植体及对应下颌骨组织的应力分布。结果 相较于实体钛合金结构(110 GPa),多孔结构的弹性模量(13.47~15.88 GPa)已完全符合人体自然骨组织(2~20 GPa)范围,多孔结构屈服强度(484.81~834.47 MPa)远高于皮质骨(180.5~211.7 MPa);梯度多孔结构样件弹性模量相较于均质多孔结构略有提升,屈服强度(834.47 MPa)比均质多孔结构样件(730.56 MPa)提高了约14%。梯度多孔种植体周围皮质骨最大等效应力值分布在43.362 9~45.015 4 MPa之间,松质骨最大等效应力值分布在4.756 58~ 5.055 6 MPa之间,完全满足2~60 MPa范围内的最大应力,适合骨组织生长。种植体与下颌骨之间的应力差值随着孔隙率的增大而逐渐变大,孔隙率为30%的TPMS–G型梯度多孔牙种植体与下颌骨应力差值最小,生物力学特性最佳,有利于形成稳定的骨整合。结论 通过试验及仿真模拟,确定了适用于种植体的最佳梯度多孔结构,既满足强度要求,又具有良好的长期稳定性。     

Interfacial stress distribution between bovine dentine and resin composite in dentine bonding systems

In finite element stress analysis, the principal interfacial stress at a tensile bond strength of 10 MPa during tensile loading was estimated for the resin composite/dentine material including the bonding area with elastic moduli of 0.03, 0.3, 3.0 and 12.0 GPa assumed in this study. Interfacial stress along the resin composite/bonding area interface or bonding area/dentine interface increased with increasing elastic modulus. The interfacial stress distributed non-uniformly and locally at the most sensitive sites, that is, the edge of the resin composite/bonding area interface with the lowest elastic modulus (0.03 GPa) and the edge of bonding area/dentine interfaces with other elastic modulus values (0.3, 3.0 and 12.0 GPa). The maximum value of interfacial stress increased linearly with increasing elastic modulus of bonding area from 0.03 to 12.0 GPa. This study showed that the distribution of interfacial stress was highly non-uniform along the interfaces of the bonded areas in dentinal adhesives.     

轮胎模具无氢DLC涂层的制备及表征

为探究轮胎模具类金刚石(DLC)涂层的应用前景,提高模具表面的硬度和疏水性,按照模具加工工艺制备35钢基体试样,利用电弧离子镀在基体上沉积无氢DLC涂层,对涂层粗糙度、三维表面形貌、断面结构、元素组成及含量、Raman光谱、纳米硬度和疏水性进行了分析.结果表明:通过改变粗糙度可以改善涂层的疏水性,涂层疏水性随粗糙度增大而显著增加,水接触角最高可达96°,且涂层硬度可达30.3 GPa.无氢DLC涂层可满足轮胎模具耐磨性和易清洁的使用要求,为制造高性能轮胎模具提供了一种可行的工艺选择.     

Measuring the Radiopacity of Flowable Resin Composites Using Scanned Radiograph Images

Radiopacity is a requirement for dental restorative materials that permits evaluation of the integrity and adaptation over time to the restoration of the tooth structure. This work was to investigate amount of fillers and radiopacity of flowable resin composites using scanned radiograph images. Radiographs of samples (8 mm diameter and 1 mm thickness) were taken with a dental x-ray at 60 kv, 7 mA, for 0.32 sec. exposure time, with a target-film distance at 40 cm. After development, dental films (Kodak D-Speed) were scanned for digitalisation and average gray value was recorded for every sample using Image J software. Percentage of filler by weight and volume were assessed by combustion analysis. The filler percentages of the flowable composites determined was ranged from 52.26 to 69.74 wt%. All materials investigated were more radiopaque than dentin and two materials were more radiopaque than enamel. The usage of low radiopaque materials should be avoided because it may lead to incorrect diagnosis. Future flowable resin composites are recommended to have higher radiopacity than dentin and perhaps ideally similar to or slightly higher than that of enamel for improved clinical detection. Digital imaging could be an alternative to transmission densitometry for the evaluation of the radiopacity of dental composites.     

The designable elastic modulus of 3-D fabric reinforced biocomposites

The three-dimensional (3-D) carbon fiber fabric is used to reinforce a hydroxyapatite (HA)/epoxy biocomposite. The elastic modulus calculation of the 3-D fabric reinforced composite by the stiffness average method and the finite element method shows that the elastic modulus of the composite is designable, and can be adjusted to the range of a human cortical bone (7-30 GPa) by varying the micro-structural parameters of the woven fabric to fulfill the nonisotropic requirement of the composite implants. The calculated elastic modulus is comparable with the flexural modulus of the 3-D fabric reinforced composites prepared by resin transfer molding. The incorporation of HA has decreased the flexural modulus of the composites for the weakened fiber-matrix interface, but the flexural modulus (22-36 GPa) is still close to that of the human cortical bone, which favors the avoidance of ‘stress shielding’ and the sequent bone absorption caused by implant materials with a high elastic modulus.     

镍-钛合金弹性模量的测定

采用静态拉伸法和纳米压入法对具有伪弹性行为的镍-钛合金的弹性模量进行了研究.结果表明,镍-钛合金的弹性模量随其相组成的变化而变化,母相状态时的弹性模量为24.5 GPa,而马氏体相状态时的弹性模量为11.6 GPa.多次重复拉伸使其弹性模量降低并呈现非线性的变化趋势.纳米压入法测量镍-钛合金的弹性模量同拉伸法测量结果有较大的偏差,其原因同纳米压入法未考虑伪弹性变形行为有关.     

Effects of cola drinks on the morphology and elastic modulus of dentin

The mechanical and morphological degradation that human dentin undergoes after prolonged exposure in cola drinks was examined using nanoindentation and AFM. The elastic modulus of the dentin prior cola exposure was 18.28 ± 1.7 GPa, while after exposure it had decreased to 4.25 ± 1.4 GPa on the surface that was in direct contact with the drink, and to 13.38 ± 2.9 GPa on the surface that was in indirect contact with the drink. AFM documented the corrosion effects of the cola through topography images and histograms of the RMS roughness.