钢渗铬层上金刚石薄膜的表面、界面结构及附着性

在钢渗铬层表面用化学气相沉积(CVD))法制备了金刚石薄膜.使用扫描电镜(SEM)、透射电镜(TEM)和压痕法研究了金刚石膜的表面、界面结构及附着力.用拉曼光谱分析了金刚石膜的纯度及非金刚石碳相.甲烷含量超过0.6%(体积分数)后,金刚石膜为球形纳米晶,形核密度＞107cm-2.用甲烷含量为0.6%(体积分数)沉积的金刚石膜表面的残余压应力为1.22 Gpa,而膜背面的残余压应力更高,达2.61 Gpa.压痕显示在19.6 N载荷下膜发生开裂.TEM观察发现,膜/基界面为微观非平面,有利于提高金刚石膜的附着力.     

摩擦条件对掺钨DLC膜摩擦磨损性能的影响

本研究利用SEM、AES、XRD、Raman谱仪、纳米压痕仪、划痕仪和球-盘磨损实验机对掺钨DLC膜的微观结构和摩擦学性能进行了研究,结果表明:掺钨DLC膜光滑致密,具有纳米晶碳化钨和非晶碳组成的复相结构;其硬度和弹性模量为19-23GPa和200-228GPa,膜/基结合力好;摩擦系数随着载荷的增加略有增加,转速对摩擦系数的影响较小;当载荷大于1.96N时,磨损率随着载荷增加急剧增大,磨损率随着转速的增加存在一个极小值;DLC膜的磨损主要是由基体塑性变形引起的梯度掺钨DLC膜内部不同亚层之间的剥离和DLC膜的断裂引起的。     

WC—Co硬质合金基体上金刚石薄膜的附着机理研究

金刚石涂层在硬质合金(WC-Co)基体上的附着力,是影响金刚石涂层刀具切削性能和使用寿命的关键因素.采用微波等离子体化学气相沉积(CVD)法在经酸浸蚀脱Co的硬质合金基体上生长金刚石薄膜.通过对金刚石膜/基界面的微观形貌和成分分析,初步认识了金刚石薄膜的附着机理:机械锁合作用对金刚石膜/基附着力有较大贡献;界面热应力和弱中间相的存在是导致金刚石膜自发剥离的主要原因.     

硼酸铵改性碳纳米纤维负极材料制备及储钠性能研究

通过合理的合成路线与微观结构设计，开发具有高比容量和柔性的钠离子电池负极材料，是当前的难点。采用静电纺丝制备自支撑碳纳米纤维膜，利用不同浓度的硼酸铵溶液对纤维膜进行改性，研究了浸渍溶液浓度和热处理温度对碳纳米纤维膜相组成、微观形貌及储钠性能的影响。结果表明：低浓度硼酸铵溶液改性并未改变纤维膜三维相互交错的空间结构，但纤维膜表面粗糙程度增加，使改性后的碳纳米纤维缺陷和活性点位增多并减小了碳层间距。采用0.02mol/L硼酸铵溶液浸渍改性和600℃热处理后得到的碳纳米纤维膜作为钠离子电池自支撑负极时，可获得最优的储钠性能。在100mA/g电流密度下，该电池初始充比容量为354.7mAh/g,循环100周后电池的可逆充放电比容量为316.8mAh/g,表现出优异的储钠性能。     

化学气相沉积制备纳米结构碳化钨薄膜

采用氟化钨(WF6)和甲烷(CH4)为前驱体,采用等离子体增强化学气相沉积(PECVD)方法制备具有纳米结构的碳化钨薄膜。采用SEM、XRD、EDS等方法表征了碳化钨薄膜的形貌、晶体结构和化学组成。通过表征,表明在前驱体混合气体中的甲烷与氟化钨气体的流量比(碳钨比)为20、基底温度为800℃的条件下得到的碳化钨薄膜是由直径为20～35nm的圆球状纳米晶构成。通过分析影响薄膜的晶体结构、化学组成的因素后,认为要得到具有纳米晶结构的碳化钨薄膜,主要应控制前驱体气体中的碳钨比以及基底温度。     

改性纳米金刚石增强增韧医用口腔复合树脂的研究

以爆轰法合成的纳米金刚石作为填料,加入到双酚A型口腔用光固化复合树脂中,研究了纳米金刚石对树脂性能的影响.金刚石用硅烷偶联剂进行表面改性.结果发现:偶联剂化学接枝到金刚石表面,改性后的金刚石在乙醇中的分散稳定性得到提高;加入0.2%(质量分数)的改性纳米金刚石后,复合树脂的挠曲强度和硬度分别提高35.4%和29.8%,改性金刚石的增强作用明显优于未经改性的金刚石;同时金刚石的加入也改善了树脂的韧性.     

C基薄膜电子场发射的一般特性及发射模型

介绍了几种碳基材料的场发射特性及其发射模型.金刚石表面具有较低的或负的电子亲和势,因无法实现N型掺杂,难以用作电子发射材料.类金刚石膜及非晶碳膜材料经过"激活"后在表面形成具有较大场增强因子的熔坑,在几～几十V/μm的低阈值电场下得到非本征的电子发射,纳米结构的碳和碳纳米管本身具有较大的场增强因子,是较有前途的平面阴极场发射材料.碳基材料的导电性不同,遵循的发射模型不同.     

Ti掺杂及Ti应力缓和层对类金刚石薄膜附着力的影响

研究了Ti掺杂对磁控溅射类金刚石(DLC)薄膜附着力及硬度的影响,同时在Ti掺杂类金刚石(Ti-DLC)薄膜的基础上,通过引入Ti应力缓和层制备了Ti/Ti-DLC/Ti/Ti-DLC……软硬交替多层薄膜,研究了Ti应力缓和层对进一步提高薄膜附着力特性的作用.采用纳米划痕仪和显微硬度计分析测试了薄膜的附着力和硬度.研究表明,金属Ti的掺杂有利于DLC薄膜附着力特性的改善,但对硬度有一定的影响.Ti应力缓和层的导入进一步改善了Ti-DLC薄膜的附着力特性,使其达到或超过了TiN薄膜的水平,对于附着力的改善Ti应力缓和层存在最佳的厚度值.采用特殊的变周期多层结构设计即在应力集中的膜基界面附近采用较小的调制周期,薄膜项层附近采用较大的调制周期不但可以保持足够的附着力,还可维持Ti-DLC薄膜原有的硬度.     

改性纳米SiO2/环氧树脂涂料的制备及其性能

为提高纳米SiO2在环氧树脂中的分散程度,充分发挥纳米SiO2的力学性能和耐热性,采用乙烯基三乙氧基硅烷与丙烯酸对纳米SiO2表面进行接枝改性,利用红外光谱对改性纳米SiO2的结构进行了表征;将改性纳米SiO2添加到环氧树脂中混合固化,得到改性纳米SiO2/环氧树脂复合涂料(SAE),并通过附着力、吸水率、电化学试验等方法对SAE涂层的耐蚀性能进行了评价。结果表明:改性后的纳米SiO2出现新的吸收峰;SAE具有附着力高、抗渗透性强、极化电流小等优良的耐腐蚀性能。     

脉冲激光沉积技术生长铜材碳基保护膜EI北大核心CSCD

用脉冲激光沉积技术制备三种结构的金属铜材碳基保护膜,分析了失效样品剥离面的微结构。结果表明,在室温条件下生长的碳基复合膜,碳化硅层增强了界面间结合力、避免了类金刚石内应力积累导致的脱落。优化的碳基复合膜牢固地附着在金属铜材上,通过了国军标《光学薄膜通用规范(GJB 2485-95)》中附着力和中度摩擦测试。碳基复合膜使金属铜基材样品表面的纳米硬度比铜基材提高了4倍,增强了铜基材的抗划伤能力。     

Adhesion Enhancement of Diamond Films on Various Substrates by Carbide Interlayer

Diamond films were prepared on various substrates by a combustion flame technique using an oxyacetylene torch. During the deposition, a carbide interlayer was formed between the surface of the substrate and deposited diamond. The hard interlayers were seen on the molybdenum, tungsten as well as silicon substrates. The adhesion of diamond on the molybdenum substrate was improved with increase in the hardness of the carbide layer. This result strongly supports the premise that the carbide interlayer and/or carbon diffused layer enhances the adhesion of diamond to substrates.     

DEPOSITION OF DIAMOND FOR CUTTING TOOL APPLICATIONS

The poor adhesion of diamond film to substrates is one of the major problems for practical use in a cutting tool (1-4). in this study, sintered tungsten carbide (WC) body without Co metal, not cemented carbide, was used as the substrate (5), and the effects of surface decarburization of the substrate for improvement in the adhesion of diamond films were investigated. The surface decarburization and diamond coating were carried out in a microwave plasma CVD system. From the results of several adhesion tests, including the cutting tests, it is concluded that the good adhesion is obtained by surface decarburization of the substrate before diamond coating. The reasons for improvement in adhesion are considered by observing the interface structure between the film and the substrate. The damage mechanism of diamond coating on cutting an AI-18%Si alloy with increasing cutting speed is also discussed.     

等离子体刻蚀处理对金刚石膜粘附性能的影响

采用直流等离子体射流ＣＶＤ法在ＹＧ８质合金基体上成功地合成了多晶金刚薄膜。通常基体表面经金刚石磨盘研磨、稀硝酸化学侵蚀脱钴预处理后，沉积的金刚石薄膜的的粘附性能仍不理想。本文首次采用原位的Ａｒ－Ｈ２等离子体射流对基体表面进行适当的轰击、刻蚀处理，显著粗化了基体表面，并使基体表面显微组织和化学成分发生重大变化，并且在合适的沉积工艺条件下，沉积的金刚石膜的粘附性能显著提高。借助ＸＲＤ、ＳＥＥＭ、ＴＥＭ     

Stress and phase purity analyses of diamond films deposited through laser-assisted combustion synthesis

Diamond films were deposited on silicon and tungsten carbide substrates in open air through laser-assisted combustion synthesis. Laser-induced resonant excitation of ethylene molecules was achieved in the combustion process to promote diamond growth rate. In addition to microstructure study by scanning electron microscopy, Raman spectroscopy was used to analyze the phase purity and residual stress of the diamond films. High-purity diamond films were obtained through laser-assisted combustion synthesis. The levels of residual stress were in agreement with corresponding thermal expansion coefficients of diamond, silicon, and tungsten carbide. Diamond-film purity increases while residual stress decreases with an increasing film thickness. Diamond films deposited on silicon substrates exhibit higher purity and lower residual stress than those deposited on tungsten carbide substrates.     

Chemically vapour deposited diamond coatings on cemented tungsten carbides: Substrate pretreatments, adhesion and cutting performance

Chemical vapour deposition (CVD) of diamond films onto Co-cemented tungsten carbide (WC-Co) tools and wear parts presents several problems due to interfacial graphitization induced by the binder phase and thermal expansion mismatch of diamond and WC-Co. Methods used to improve diamond film adhesion include substrate-modification processes that create a three-dimensional compositionally graded interface. This paper reviews substrate pretreatments and adhesion issues of chemically vapour deposited diamond films on WC-Co. The combined effect of pretreatments and substrate microstructure on the adhesive toughness and wear rate of CVD diamond in dry machining of highly abrasive materials was analyzed. The role of diamond film surface morphology on chip evacuation in dry milling of ceramics was also investigated by comparing feed forces of coated and uncoated mills. The overall tribological performance of diamond coated mills depended on coating microstructure and smoothness. The use of smother films did allow to reduce cutting forces by facilitating chip evacuation.     

Influence of WC-Co substrate pretreatment on diamond film deposition by laser-assisted combustion synthesis

The quality of diamond films deposited on cemented tungsten carbide substrates (WC-Co) is limited by the presence of the cobalt binder. The cobalt in the WC-Co substrates enhances the formation of nondiamond carbon on the substrate surface, resulting in a poor film adhesion and a low diamond quality. In this study, we investigated pretreatments of WC-Co substrates in three different approaches, namely, chemical etching, laser etching, and laser etching followed by acid treatment. The laser produces a periodic surface pattern, thus increasing the roughness and releasing the stress at the interfaces between the substrate and the grown diamond film. Effects of these pretreatments have been analyzed in terms of microstructure and cobalt content. Raman spectroscopy was conducted to characterize both the diamond quality and compressive residual stress in the films.     

Adhesion improvement of diamond films on cemented carbides with copper implant layer

The deposition of diamond films on cemented carbides is strongly influenced by the catalytic effect of cobalt under typical deposition conditions. Decreasing the content of Co on the surface of the cemented carbide is often used for the diamond film deposition. But the leaching of Co from the WC-Co substrate leads to a mechanical weak surface, often causing poor adhesion. In this paper we adopt a copper implant layer to improve the mechanical properties of the Co leached substrate. The copper implant layer is prepared with vaporization. The diamond films are grown by microwave plasma chemical vapor deposition from the CH₄/H₂ gas mixture. The morphology and the quality of the diamond films have been characterized by scanning electron microscopy and Raman spectroscopy. A Rockwell apparatus has evaluated the adhesion of the diamond on the substrate. The results indicate that the diamond films have good adhesion to the cemented carbide substrate due to the recovery of the mechanical properties of the Co depleted substrate after the copper implantation and less graphite formation between the substrate and the diamond film.     

The nature of stresses in hot-filament chemical vapour deposited diamond thin films on WC substrates

The nature of film stresses in hot-filament chemical vapour deposited (HFCVD) diamond thin films on tungsten carbide substrates, is reported. Commercial WC substrates were subjected to various surface treatments. Subsequently, they were coated with a diamond film and examined for stresses using X-ray diffraction. All but one of the stress measurements indicated various levels of compressive stresses in the film and at the film–substrate interface. These stresses are compared with those obtained by other researchers. Intrinsic film stresses were also computed for diamond films and found to be tensile. WC drills, of 0.125 in. diameter, were also diamond coated and the stress levels measured along drill flanks and flutes. Significant variations were found in these stresses, and the results were analysed from a film–substrate adhesion perspective.     

Diamond coated dental bur machining of natural and synthetic dental materials

Diamond coatings are attractive for cutting processes due to their high hardness, low friction coefficient, excellent wear resistance and chemical inertness. The application of diamond coatings on cemented tungsten carbide (WC-Co) burs has been the subject of much attention in recent years in order to improve cutting performance and tool life. WC-Co burs containing 6% Co and 94% WC with an average grain size 1–3 micron were used in this study. In order to improve the adhesion between diamond and the bur it is necessary to etch away the surface Co to prepare it for subsequent diamond growth. Hot filament chemical vapour deposition (H.F.C.V.D.) with a modified vertical filament arrangement has been employed for the deposition of diamond films. Diamond film quality and purity has been characterised using scanning electron microscopy (S.E.M.) and micro-Raman spectroscopy. The performance of diamond coated WC-Co burs, uncoated WC-Co burs, and diamond embedded (sintered) burs have been compared by drilling a series of holes into various materials such as human teeth, and model tooth materials such as borosilicate glass and acrylic. Flank wear has been used to assess the wear rates of the burs when machining natural and synthetic dental materials such as those described above.     

The diamond-tungsten carbide polycrystalline composite material

The sintering of a diamond composite from diamond and tungsten powders of submicron and nanosizes at high pressure and temperature has been discussed. It has been shown that as a result of the diamond and tungsten interaction tungsten carbide particles, which are chemically bonded to diamond particles, form in spaces between them. Over the whole volume of the composite the structure has been observed, where tungsten carbide and diamond grains are regularly placed and are uniform in size. An addition of a coarse diamond component to the composite has been found to contribute to an increase of the composite wear resistance. The optimal sintering parameters and formulation of this composite have been defined.