Improvement of Thermal Stability and Tribological Performance of Diamond-Like Carbon Composite Thin Films

Diamond-like carbon (DLC) is a metastable amorphous film that exhibits unique properties. However, many limitations exist regarding the use of DLC, for example, its tribological characteristics at high temperature, as well as its limited thermal stability. In this study, silicon/oxygen and silicon/nitrogen co-incorporated diamond-like carbon (Si-O-DLC and Si-N-DLC) films are studied, taking into account the thermal stability and tribological performance of these films compared with pure DLC. All the films were prepared on Si wafers, WC-Co materials, and aluminum foils using a plasma-based ion implantation (PBII) technique using acetylene (C2H2), tetramethylsilane (TMS, Si(CH3)4), oxygen (O2) and nitrogen (N2) as plasma sources. The structure of the films was characterized using Raman spectroscopy. The thermal stability of the films was measured using thermogravimetric and differential thermal analysis (TG-DTA). The friction coefficient of the films was assessed using ball-on-disk friction testing. The results indicate that Si-N-DLC films present better thermal stability due to the presence of Si-O networks in the films. The Si-N-DLC (23 at.%Si, 8 at.%N) film was affected using thermal annealing in an air atmosphere with increasing temperature until 500°C. The film can also resist thermal shock by cycling 10 times between the various temperatures and air atmosphere until 500°C. Further, Si-O-DLC and Si-N-DLC films exhibit excellent tribological performance, especially the Si-N-DLC (23 at.%Si, 8 at.%N) film, which exhibits excellent tribological performance at 500°C in an air atmosphere. It is concluded that Si-O-DLC and Si-N-DLC films improve upon the thermal stability and tribological performance of DLC.

Structure and Mechanical Performance of Nitrogen Doped Diamond-like Carbon Films

Nitrogen doped diamond-like carbon （DLC：N） films were prepared by electron cyclotron resonance chemical vapor deposition （ECR-CVD） on polycrystalline Si chips. Film thickness is about 50 nm. Auger electron spectroscopy （AES） was used to evaluate nitrogen content, and increasing N2 flow improved N content from 0 to 7.6%. Raman and X-ray photoelectron spectroscopy （XPS） analysis results reveal CN-sp^3C and N-sp^2C structure. With increasing the N2 flow, sp^3C decreases from 73.74% down to 42.66%, and so does N-sp^3C from 68.04% down to 20.23%. The hardness decreases from 29.18 GPa down to 19.74 GPa, and the Young＇s modulus from 193.03 GPa down to 144.52 GPa.

Relationship Between Thermal Stability and Optical Bandgap of Fluorinated Amorphous Carbon Films

Fluorinated amorphous carbon films were deposited using microwave electron cyclotron resonance chemical vapor deposition (ECR-CVD) reactor with CF4 and C8H6 as source gas and were annealed in nitrogen ambience for the investigating of their thermal stability .The relative concentration of C=C bond and optical bandgap were obtained by Fourier Transform Infrared (FTIR) spectroscopy and Ultraviolet-Visible (UV-VIS ) spectrum, respectively. It has been demonstrated that there is a close relationship between relative concentration of C=C bond and optical bandgap, and the films deposited at a higher microwave power have a lower optical bandgap and a better thermal stability.

Influence of nitrogen doping on thermal stability of fluorinated amorphous carbon thin films

Nitrogen doping fluorinated amorphous carbon (a-C∶F) films were deposited using radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) and annealed in Ar environment in order to investigate their thermal stability. Surface morphology and the thickness of the films before and after annealing were characterized by AFM and ellipsometer. Raman spectra and FTIR were used to analyze the chemical structure of the films. The results show that the surface of the films becomes more homogeneous either by the addition of N2 or after annealing. Deposition rate of the films increases a little at first and then decreases sharply with the increase of N2 source gas flux. It is also found that the fraction of aromatic rings structure increases and the thermal stability of the films is strengthened with the increase of N2 flux. Nitrogen doping is a feasible approach to improve the thermal stability of a-C∶F films.

Interposition fixing structure of TiO_2 film deposited on activated carbon fibers

The immobilized photocatalyst, TiO2 film supported on activated carbon fibers (TiO2/ACFs) prepared with molecular adsorption-deposition (MAD), exhibits high stability in cyclic photodegradation runs. The interposition fixing structure between TiO2 film and carbon fiber was investigated by means of SEM-EDX, XRD, XPS and FTIR, and a model was proposed to explain this structure. With SEM examination of carbon fiber surface after removing the deposited TiO2 film, a residual TiO2 super-thin film was found to exist still. By determining surface groups on ACFs, titanium sulfate (Ti2(SO4)3) in burnt remainders of the TiO2/ACFs was thought to be formed with an interfacial reaction between TiO2 film and carbon fibers. These provide some evidence of firm attachment of TiO2 film to carbon fiber surface. In the consideration of characteristics of the MAD, the deposition mechanism of TiO2 film on ACFs was proposed, and the interposition fixing structure was inferred to intercrossedly form between TiO2 film and ACFs’ surface. This structure leaded to firm attachment and high stability of the TiO2 film.

Thermal Stability and Tribological Properties of Fluorinated Amorphous Carbon Thin Films Doped With Nitrogen

Nitrogen doped fluorinated amorphous carbon thin films(a-C:N:F)were prepared by radio frequency plasma enhanced chemical vapor deposition(rf-PECVD)under different deposited condition usingCH_4,CF_4,and N_2 as source gases.The thin films were annealed at different temperature.The influence of doped nitrogen on the chemical structure, tribological and thermal properties of thin films were investigated by Atomic force microscopy(AFM),Fourier transform infrared absorption spectrometry(FTIR),X-ray photoelectron spectrum spectra(XPS),and thermogravimetry(TG).The results indicated that the thin films presence a compact and smooth morphology surface after the nitrogen doped.After incorporation of nitrogen,the H atoms are replaced partially by the N atoms in the thin films.The degree of cross-linking of the carbon network in the thin films is enhanced.The chemical bonds of C=N,C≡N,and C—N_x(x=1,2,3) have formed in the films.The relative content of sp^2 graphite phase increases.The thermal stability temperature of the films deposited at r=0.5(r=N_2/[CF_4+CH_4+N_2])is 420℃.The tribological properties improve greatly,and the friction coefficient of the a-C:N:F thin films ranges approximately from 0.20 to 0.36.

高导热沥青基碳纤维复合材料在航天器中的应用现状及展望

随着新一代航天器不断朝着超大型化、微小型化、高效能化方向发展,航天器对轻质高强高模高导热材料的需求日益迫切。相比传统的聚丙烯腈(PAN)基碳纤维,高导热沥青基碳纤维具有超高的热导率、更高的拉伸模量以及更低的热膨胀系数,是实现承载/传热/热尺寸稳定性功能一体化的理想材料,在航天领域得到了重要应用并展现出巨大应用前景。本文介绍了高导热沥青基碳纤维及其复合材料的性能特点、发展现状以及在航天器中的应用现状,重点从航天器热管理结构、热防护结构、高尺寸稳定性结构、多功能结构、电子设备外壳等方面综述了其应用现状,最后对高导热沥青基碳纤维复合材料的发展及应用前景进行了展望。

碳纳米管-铜复合薄膜材料的抗辐照损伤性能研究

利用磁控溅射沉积技术获得的碳纳米管-金属复合材料是一种新型的纳米多孔材料,涂覆碳纳米管-金属复合材料的结构组件在新型核反应堆中具有广阔的应用前景。但是目前的报道中对碳纳米管-金属复合材料抗辐照损伤性能的研究还很少。因此,本工作通过磁控溅射沉积技术,制备了两种不同厚度的碳纳米管-铜复合薄膜,结合室温下的He离子辐照对石蜡基矿物油有机蒸汽的脱氢效应在复合薄膜表面包覆碳层,研究了碳层包覆前后碳纳米管-铜复合薄膜的抗辐照损伤性能。结果表明,随着辐照剂量和辐照温度升高,样品内逐渐产生孔洞等缺陷,且孔洞尺寸较小,这与碳纳米管-铜复合薄膜较高的晶界体积分数和比表面积以及降低的缺陷迁移速率有关。与平面基底上沉积的铜薄膜相比,复合薄膜在室温和高温辐照后,晶粒尺寸明显减小,这与一维碳纳米管基底可显著限制碳纳米管轴向垂直方向上的晶界迁移有关。碳层包覆后的碳纳米管-铜复合薄膜的高温结构稳定性和抗辐照损伤性能明显增强,这得益于碳包覆碳纳米管-铜复合薄膜较高的晶界体积分数和比表面积以及稳定的纳米晶粒。

框架镂空结构微小卫星热控设计方法

针对框架镂空结构微小卫星无传统散热面的问题,文章提出一种在极低成本和极低重量约束下的小卫星热控设计方法:将低成本的工业级碳纳米铜箔贴装于设备与卫星结构之间,构建柔性导热通道;在镂空结构外侧贴装镀锗聚酰亚胺膜,利用其红外透射率特性使得设备部分热耗辐射至深空冷背景。采用该方法设计的“仰望一号”卫星的在轨遥测数据表明:整星设备温度为13~30℃,满足设计指标要求。所提方法可为此类镂空结构卫星提供热控设计参考。

Structural stability of C_(60) films under the bombardment of 1.95 GeV Kr ions

The structural stability of C60 films under the bombardment of 1.95 GeV Kr ions is investigated.The irradiated C60 films were analyzed by Fourier Transform Infrared(FTIR) spectroscopy and Raman scattering technique.The analytical results indicate that the irradiation induced a decrease of icosahedral symmetry of C60 molecule and damage of C60 films;different vibration modes of C60 molecule have different irradiation sensitivities;the mean efficient damage radius obtained from experimental data is about 1.47 nm,which is in good agreement with thermal spike model prediction.

Preparation and thermal properties of layered porous carbon nanotube/epoxy resin composite films

A floating-catalyst spray pyrolysis method was used to synthesize carbon nanotube(CNT)thin films.With the use of ammonium chloride as a pore-former and epoxy resin(EP)as an adhesive,CNT/EP composite films with a porous structure were prepared through the post-heat treatment.These films have excellent thermal insulation(0.029–0.048 W·m^−1·K^−1)at the thickness direction as well as a good thermal conductivity(40–60 Wm^−1·K^−1)in the film plane.This study provides a new film material for thermal control systems that demand a good thermal conductivity in the plane but outstanding thermal insulation at the thickness direction.

基于微波热解技术制备生物炭的研究进展

随着社会和经济的发展,农林废弃物、生活垃圾、市政污泥及其他有机固体废弃物的无害化处理受到广泛关注。有机固体废弃物中含有大量碳源,通常的处理方法多是填埋、焚烧和作物残余物还土还田,既造成环境污染,又导致碳源资源的浪费。微波热解(MP)是一种比较新颖的生物质热解处理方式,其具有升温速率快、生物质受热均匀、加热效率高等优点。MP可能会以不同于传统管式炉加热的方式影响生物炭的性质,这是因为在不同的加热方式下,传热和传质方式是不同的。主要总结归纳了MP废弃生物质过程中得到的固体生物炭的性质,包括MP方式及特点的描述,对比不同生物质在不同的微波功率和温度影响下,其热解产物的分布和产率变化。着重比较了不同废弃生物质原料经MP后所得生物炭的形貌差异、生物炭表面官能团变化、生物炭孔结构和比表面积的差异、生物炭中各元素的变化及生物炭热稳定性,以及微波生物炭和常规生物炭的差异。

不同碳酸钙填充PVC压延膜性能探究

本文通过色差计、光度计、电子万能试验机以及扫描电子显微镜对比重质碳酸钙、轻质碳酸钙以及纳米碳酸钙填充PVC压延膜的热稳定性、力学性能和喷绘效果的影响进行研究。结果表明,三种碳酸钙均能确保PVC压延膜的热稳定性,而纳米碳酸钙喷绘效果最好。纳米碳酸钙的填充的PVC压延膜拉伸强度为14.7 MPa、断裂伸长率为279.9%,而重质碳酸钙和轻质碳酸钙的为13.2%、256.6%和11.9 MPa、243.1%,这是由于纳米碳酸钙颗粒比表面积大、分散性好,能均匀分散在PVC基体中,与PVC基体中的界面接触面积大,界面附着力增强所致。

碳酸钙三级红外光谱研究

采用红外(IR)光谱技术开展了碳酸钙的结构研究。实验发现,碳酸钙的红外吸收模式包括碳酸钙CO3不对称伸缩振动模式(νasCO3-碳酸钙)、碳酸钙CO3对称伸缩振动模式(νsCO3-碳酸钙)、碳酸钙CO3面外弯曲振动模式(rCO3-碳酸钙)和碳酸钙CO3面内弯曲振动模式(βCO3-碳酸钙)等。采用变温红外(TD-IR)光谱开展了碳酸钙的热稳定性研究。在293~393 K的温度范围内,碳酸钙主要官能团对应的吸收强度及频率都有一定的改变。采用二维红外(2D-IR)光谱进一步研究了碳酸钙νasCO3-碳酸钙、rCO3-碳酸钙和βCO3-碳酸钙吸收峰变化快慢的信息,证明了三级红外(IR)光谱在重要的无机盐(碳酸钙)结构及热稳定性研究中的重要作用。

水杨醛缩苯胺锌及其薄膜的谱学性能

合成了一种新型的发光材料水杨醛缩苯胺锌(SAZ),利用真空热蒸镀制备了高质量、纳米级薄膜,利用红外光谱、差热-热重谱、X射线衍射谱、UV-Vis吸收谱、荧光光谱研究了水杨醛缩苯胺锌及其薄膜的结构、晶态、热稳定性以及光学特性,并利用循环伏安法、UV-Vis吸收谱确定了该材料的能级结构。结果表明,水杨醛缩苯胺锌无定性薄膜具有较高的热稳定性,在紫外光激发下产生绿色荧光,色纯度高,亮度高。水杨醛缩苯胺锌薄膜在大气环境下存放,荧光衰减比8-羟基喹啉铝快,但受紫外光照射时,荧光衰减比8-羟基喹啉铝慢。水杨醛缩苯胺锌的HOMO能级为-5.659eV,LUMO能级为-3.054eV,禁带宽度为2.604eV。

磁控溅射非晶CN_x薄膜的热稳定性研究

为了研究非晶CNx薄膜的热稳定性,采用射频磁控溅射方法沉积了非晶CNx薄膜样品,并在真空中退火至900℃,利用FTIR,Raman和XPS谱探讨了高温退火对CNx薄膜化学成分及键合结构的影响.研究表明:CNx薄膜样品中N原子分别与sp、sp2和sp3杂化状态的C原子相结合,退火处理极大地影响了CN键合结构的稳定性;当退火温度低于600℃时,膜内N含量的损失较少,CNx薄膜的热稳定性较好,退火温度超过600℃时,将导致CNx膜中大多数C、N间的键合分离,造成N大量损失,膜的热稳定性下降;退火可促使膜内sp3型键向sp2型键转变,在膜中形成大量的sp2型C键,导致CNx膜的石墨化.

聚氨酯/多壁碳纳米管复合薄膜的制备及其热稳定性研究

通过溶液共混的方法制备出聚氨酯(PU)/多壁碳纳米管(MWNTs)纳米复合薄膜,重点研究了MWNTs的加入对PU热稳定性能的影响。结果表明,加入质量分数3%的MWNTs,使PU的耐热性得到一定的提高;用Kissinger方法得出的降解活化能由198.01kJ/mol提高到250.05kJ/mol,薄膜的力学性能得到改善,拉伸强度提高了63.5%,伸长率提高了4.2%;TEM分析表明,质量分数3%的MWNTs在PU/MWNTs纳米复合薄膜中得到均匀分散。

FCVA法沉积的超薄类金刚石薄膜的结构与热稳定性

采用FCVA方法沉积了厚度分别为2nm、5nm、10nm和30nm的类金刚石薄膜。在氩气保护下对类金刚石薄膜进行了180、300、400和600℃,保温6h的退火处理。用Raman光谱和宽光谱变角度椭偏仪研究了DLC薄膜的结构和热稳定性。实验结果表明,随着薄膜厚度增大,FCVA法沉积的DLC薄膜中的sp3键含量增加,薄膜热稳定性逐渐改善。当DLC薄膜的厚度为30nm时,薄膜中的sp3键含量达到最高值,薄膜具有最好的热稳定性。当退火温度为600℃时,厚度为2nm和5nm的DLC薄膜结构由非晶态转变为微晶态;厚度为10nm和30nm的DLC薄膜结构发生转变但仍保持非晶态。随着退火温度的升高,各个厚度的DLC薄膜的光学带隙Eg均先增大后减小。

航天器高稳定结构的热控设计及验证

高稳定结构对温度场的稳定性、均匀性有较高要求,为达到在轨温度场精稳控制,文章提出了一种基于高导热柔性材料的分区控温设计方法,采用面内导热系数达750W/(m·K)的柔性石墨材料,进行了二维均温扩热,增强结构自身导热能力,减小温度梯度;强化隔热设计,减小外部热扰动对温度场的影响。以某测绘卫星载荷适配结构为例,进行了分析及试验验证,结果表明:全生命周期内,载荷适配结构核心部件温度控制在20.0~24.5℃范围内,温度波动≤0.4℃,温度梯度≤4℃,同时验证了设计方法的正确性。该方法可为有高精度控温需求的部件的热设计提供参考。

微器件用Ni-W合金薄膜热稳定性的研究

研究了低应力柠檬酸胺-1-羟基乙烷二膦酸(HEDP)镀液体系中电流密度、pH值、脉冲参数和热处理条件等对Ni-W合金薄膜硬度的影响。结果表明,电镀工艺条件对硬度提高有限,热处理对Ni-W合金薄膜的硬度有明显提高。同时研究对比了沉积态及550℃热处理后Ni和Ni-W硬度、干摩擦条件下耐磨性以及微观结构的变化。实验发现:多晶的Ni薄膜经过热处理后,晶粒尺寸显著长大,硬度、耐磨性约下降2/3;而Ni-W合金薄膜经过热处理后,微观结构由非晶转变成纳米晶,薄膜仍保持良好的耐磨性,硬度提高了1倍。Ni-W合金薄膜优异的热稳定性,有望在特殊环境下取代Ni薄膜在MEMS器件上获得应用。