镍纤维管改善锂硫电池性能

为了改善锂硫电池的比容量和循环稳定性等电化学性能,以聚丙烯腈纤维为基体,采用无钯活化化学镀法在其表面镀一层镍,制备得到复合纤维.通过热处理去除复合纤维中的聚丙烯腈,得到氧化镍中空纤维,然后在氢等离子体气氛中对氧化镍中空纤维进行还原制备中空镍纤维管,并以它作为锂硫电池正极材料活性物质的承载体,制备含镍纤维管的硫电极来改善锂硫电池的电化学性能.采用扫描电子显微镜和X射线能谱仪表征镍纤维管的表面形貌和成分,结果表明:所制备的纤维管主要是镍,但含有少量的磷,可能是镀液中次磷酸盐中的磷元素被还原,且管径为10～15μm,管壁厚度均匀,约0.7μm.采用恒流充放电和交流阻抗谱对含镍纤维管硫电极的电化学性能进行表征,结果表明:添加镍的纤维管能够增强锂硫电池的电化学性能,在充放电电流密度为每平方厘米0.2mA的条件下,镍纤维管增强硫电极的首次放电比容量为941.6mAh/g,20次循环后的放电比容量仍保持在593.3mAh/g,表现出较高的放电比容量和良好的循环稳定性.     

微波法制备纳米碳管-碳化钛复合粉体

以钛铁矿为原料,通过等离子体化学气相沉积,生长纳米碳管.再通过微波加热强制碳化得到碳化钛-纳米碳管(TiC-CNTS)复合粉体.研究纳米碳管的生长工艺和微波碳化处理工艺,得出合理的制备工艺条件:纳米碳管的制备条件为微波功率600 W,腔体气压5.5 kPa,甲烷流量3.3 mL·min-1,氢气流量55 mL·min-1,生长时间40 min.碳化条件:微波功率700 W,处理时间10 min.     

微波等离子体化学气相沉积法制备的新型纳米片状碳膜

在甲烷和氢气的混合系统中,利用石英管型微波等离子体化学气相沉积方法,在硅片上制备了新型的纳米片状碳膜．利用场发射扫描电子显微镜和拉曼光谱仪对碳膜的结构进行了表征,结果表明碳膜是由长1μm、宽100nm的纳米碳片相互缠绕而成．最后简单讨论了新型碳纳米片的形成机理．     

MPCVD实验条件对碳氮纳米管薄膜场发射性能的影响

通过正交设计试验法研究了微波等离子体化学气相沉积(MPCVD)实验条件对碳氮纳米管薄某》⑸湫阅艿挠跋?结果表明,当微波功率为1 500W、反应气压为8.5kPa、甲烷、氮气和氢气的流量比为8:20:80时,制备的碳氮纳米管薄膜场发射特性最好,其开启电场强度为3.2 V/μm,电场强度为8.0V/μm时的电流密度为3.5 mA/cm2.     

多孔镍/碳纳米管中空纤维膜的制备与结构表征

泡沫镍作为电极活性材料的常用骨架,其孔径在500μm以上,为了制备出孔径小、空间利用率高的多孔金属集流体材料,探索了多孔镍/碳纳米管(Ni/CNTs)中空纤维膜的制备新工艺.首先配制包含金属镍粉的铸膜液,通过干-湿纺丝工艺得到中空纤维生坯材料,经烧蚀掉有机物后,金属粉末烧结自组装成多孔镍中空纤维膜;然后以镍膜为基体负载催化剂后,采用化学气相沉积法在镍膜上直接生长CNTs制得多孔Ni/CNTs中空纤维复合膜.通过实验可知:铸膜液配比为wNi∶wPAN∶wPVP∶wNMP=50∶8∶1∶41,纺丝参数为采用插入管式喷丝头,其芯液流量为50 m L/min,计量泵泵供量为8 m L/min,釜内氮气压力为0.1 MPa,喷丝孔直径为1.5 mm,插入管外径为2.5 mm;在950℃还原性气氛下,烧结可以得到孔径5μm左右的多孔镍中空纤维膜.采用0.001 mol/L的Ni/Y催化剂,550℃下混合气体比例vAr∶vH2∶vC2H2=200∶50∶8时进行化学气相沉积,可在中空纤维Ni膜表面可生长出直径20~30 nm的CNTs.     

等离子体辅助热丝化学气相沉积金刚石复合膜

运用等离子体辅助热丝化学气相沉积设备分别进行了金刚石膜和金刚石 /碳化钛复合膜的沉积。实验条件 :甲烷流量与氢气流量比为 1∶5 0 ,基体温度 860℃ ,等离子体偏压 30 0V ,沉积气压 4kPa。运用扫描电子显微镜 (SEM )分别观察了沉积膜的表面和断面形貌 ;运用能量扩散电子谱 (EDX)对沉积的复合膜进行分析 ,观察到Ti元素峰和C元素峰 ;运用X射线衍射 (XRD)得到相应的金刚石衍射峰和碳化钛衍射峰。实验表明 ,用等离子体辅助热丝化学气相沉积法可以制备出晶型良好的金刚石复合膜     

一种碳纳米纤维的大面积连续制备方法

为了实现碳纳米材料的大面积连续制备,采用卷对卷化学气相沉积法,通过等离子体催化乙炔在Cu箔表面裂解,制备均匀连续的碳纳米纤维(CNFs)。结果表明:当等离子体功率为40 W时,合成的CNFs直径约为50～60 nm,且纯度较高;随着合成温度从550℃增加到700℃时,碳纳米产物由直壁状CNFs逐渐向单螺旋状CNFs转变,且直径不断增加;随着通入乙炔的气流量从5 m L/min增加到40 mL/min时,碳纳米产物由不均匀直壁状CNFs逐渐转变为均匀直壁CNFs,并在高的乙炔气流量下转变为单螺旋CNFs,且CNFs的直径及螺旋角呈逐渐增大的趋势。     

表面覆盖钛薄膜的纳米片状碳膜场发射特性(英文)

利用石英管型波等离子体化学气相沉积装置在Si衬底上沉积了纳米片状碳膜,然后采用电子束蒸镀方法在碳膜表面沉积了一层2 nm厚的Ti膜,并在高真空系统中测量了覆盖Ti膜前后的纳米片状碳膜的场发射特性.研究表明:覆盖Ti膜的纳米片状碳膜因表面生成碳化钛而改性,使得场发射特性得到改善;表面覆盖Ti膜后,阈值电场由2.6 V/μm下降到2.0 V/μm,当电场增加到9 V/μm时,场发射电流由12.4 mA/cm2增加到20.2 mA/cm2.     

热丝CVD法制备金刚石管

以钨丝作为基体,用氢气和丙酮作为反应气体,在热丝化学气相沉积装置中制备出了金刚石管,其生长速度达到了4μm／h．扫描电镜和激光拉曼光谱的测试结果表明制备出的金刚石管质量较好．     

基片预处理对CVD金刚石薄膜形核的影响

微波辅助等离子体化学气相沉积法是目前低压气相合成金刚石薄膜方法中应用最普遍、工艺最成熟的方法,形核是CVD金刚石沉积的第一步．利用微波辅助等离子体化学气相沉积装置,研究了硅基片预处理方式对金刚石薄膜形核密度的影响．在工作气压为5-8kPa,微波功率为2500—5000W,甲烷流量为4-8cm^3／min,氢气流量为200em3／min,沉积温度为500℃-850℃的条件下,在单晶Si基片上沉积金刚石薄膜．通过扫描电子显微镜形貌观察表明,基片预处理能够显著提高金刚石形核密度,同时用拉曼光谱表征了金刚石薄膜的质量,     

纳米碳纤维薄膜的制备及其疏水性能

采用化学气相沉积(CVD)方法,以乙炔(C2H2)为碳源,直接于铜基板上生长碳纤维薄膜。铜基板只进行简单的打磨处理。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)对产物的形貌、结构进行了表征,并用接触角测量仪(CA)对制备的碳纤维薄膜进行疏水性测试。结果表明:在铜基板表面制备了一层直径为100～200nm,厚度为40～50μm的碳纤维薄膜。疏水测试结果显示,这种薄膜有较好的疏水性能,且随纳米碳纤维合成温度变化而变化。经多次试验表明,铜片具有良好的循环使用性能,可多次用于制备碳纤维薄膜。     

Growth of graphite film over the tops of vertical carbon nanotubes using Ni/Ti/Si substrate

A substrate with Ni/Ti/Si structure was used to grow vertical carbon nanotubes (CNTs) with a graphite film over CNT tops by thermal chemical vapor deposition with CH4 gas as carbon source.The carbon nanotubes and the substrate were character-ized by a field emission scanning electron microscope for the morphologies,a transmission electron microscope for the microstruc-tures,a Raman spectrograph for the crystallinity,and an Auger electron spectrometer for the depth distribution of elements.The re-sult shows that when the thickness ratio of Ni layer to Ti layer in substrate is about i,a graphite film with relatively good quality canbe formed on the CNT tops.     

Morphological,Mechanical and Thermal Properties of Poly(lactic acid)(PLA)/Cellulose Nanofibrils(CNF) Composites Nanofiber for Tissue Engineering

Composite nanofiber membranes based on biodegradable poly(lactic acid)(PLA) and cellulose nanofibrils(CNF) were produced via electrospinning. The influence of CNF content on the morphology, thermal properties, and mechanical properties of PLA/CNF composite nanofiber membranes were characterized by field scanning electron microscopy(FE-SEM), differential scanning calorimetry(DSC), thermogravimetric analysis(TGA), and dynamic mechanical analysis(DMA), respectively. The results show that the PLA/CNF composite nanofibers with smooth, free-bead surface can be successfully fabricated with various CNF contents. The introduction of CNF is an effective approach to improve the crystalline ability, thermal stability and mechanical properties for PLA/CNF composite fibers. The Young's moduli and tensile strength of the PLA/CNF composite nanofiber reach 106.6 MPa and 2.7 MPa when the CNF content is 3%, respectively, which are one times higher and 1.5 times than those of pure PLA nanofiber. Additionally, the water contact angle of PLA/CNF composite nanofiber membranes decreases with the increase of the CNF loading, resulting in the enhancement of their hydrophilicity.     

镍基纳米碳管/二氧化钛复合镀层的制备及性能

为了改善金属基材的表面性能,以钛铁矿为原料,利用微波等离子体化学气相沉积法制备了纳米碳管/二氧化钛复合粉体.采用复合电泳电沉积法在不锈钢基体表面制备了镍基纳米碳管/二氧化钛复合镀层;利用扫描电镜、X射线衍射仪、数显维氏硬度计和电化学测试等手段研究了纳米碳管/二氧化钛复合粉体对复合镀层结构和性能的影响.结果表明纳米碳管/二氧化钛复合粉体的加入有效地减小了复合镀层中镍的晶粒尺寸,促进了金属镍沿(111)晶面择优取向生长,改变了镍的电沉积层结构,提高了镀层的硬度,改善了镀层的耐腐蚀性能;在复合粉体的作用下,复合镀层的硬度与纯镍镀层相比提高了110%,腐蚀电位正移了23mV,腐蚀电流密度减少了0.991微安/平方厘米.     

结构化纳米碳纤维催化材料的制备及表征

采用堇青石型蜂窝陶瓷(monolith)为基材,在其表面浸涂二氧化钛,得到含二氧化钛涂层的新型结构化基材,提高了基材的比表面及抗腐蚀性。以甲烷为碳源,在结构化基材表面生长纳米碳纤维(CNF),制备出结构化复合纳米碳纤维催化材料(CNF/TiO2/monolith)。扫描电镜(SEM)和物理吸附仪(BET)表征结果表明,CNF粗细均匀、直径-70 nm,比表面-180 m2/g。并以CNF/TiO2/monolith为载体负载金属钯,制备出结构化纳米碳纤维负载型催化剂(Pd/CNF/TiO2/monolith),其催化加氢活性明显优于成型活性炭负载型Pd催化剂。     

碳包覆粒子的制备与表征

通过热处理在多壁纳米碳管上负载2种金属氧化物颗粒,以其为催化剂,用化学气相沉积法制备碳包覆金属粒子,并利用XRD、TEM、FESEM和EDS对催化剂和产物的物相组成、形貌和结构进行表征。结果表明,金属氧化物颗粒均匀地负载于纳米碳管的管壁上,所制备的碳包覆金属粒子粒径较为均匀,具有明显的核一壳结构。     

Effect of chemical vapor infiltration treatment on the wave-absorbing performance of carbon fiber/cement composites

Short carbon fibers were treated at high temperatures around 1100℃ through chemical vapor infiltration technology. A thinner layer ofpyrocarbon was deposited on the fiber surface. The dispersion of carbon fibers in a cement matrix and the mechanical properties of carbon fiber/cement composites were investigated by scanning electron microscopy （SEM） and other tests. The reflec- tivity of electromagnetic waves by the composites was measured in the frequency range of 8.0-18 GHz for different carbon fiber contents of 0.2wt%, 0.4wt%, 0.6wt%, and 1.0wt%. The results show that the reflectivity tends to increase with the increase of fiber content above 0.4wt%. The minimum reflectivity is -19.3 dB and the composites exhibit wave-absorbing performances. After pyrocarbon is deposited on the fiber, all the refiectivity data are far greater. They are all above -10 dB and display mainly wave-reflecting performances.     

Structure and Composition of Crystalline Carbon Nitride Films Synthesized by Microwave Plasma Chemical Vapor Deposition

Crystalline carbon nitride thin films were prepared on Si (100) substrates by a microwave plasma chemical vapor deposition method, using CH4/N2 as precursor gases. The surface morphologies of the carbon nitride films deposited on Si substrate at 830℃ are consisted of hexagonal crystalline rods. The effect of substrate temperature on the formation of carbon nitrides was investigated. X-ray photoelectron spectroscopy analysis indicated that the maximum value of N/C in atomic ratio in the films deposited at a substrate temperature of 830℃ is 1 .20, which is close to the stoichiometric value of C3N4. The X-ray diffraction pattern of the films deposited at 830℃ indicates no amorphous phase in the films, which are composed of β- and α-C3N4 phase containing an unidentified C-N phase. Fourier transform infrared spectroscopy supports the existence of C-N covalent bond.     

Structure and Composition of Crystalline Carbon Nitride Films Synthesized by Microwave Plasma Chemical Vapor Deposition

Crystalline carbon nitride thin films were prepared on Si (100) substrates by a microwave plasma chemical vapor deposition method, using CH4/N2 as precursor gases. The surface morphologies of the carbon nitride films deposited on Si substrate at 830℃ are consisted of hexagonal crystalline rods. The effect of substrate temperature on the formation of carbon nitrides was investigated. X-ray photoelectron spectroscopy analysis indicated that the maximum value of N/C in atomic ratio in the films deposited at a substrate temperature of 830℃ is 1.20, which is close to the stoichiometric value of C3N4. The X-ray diffraction pattern of the films deposited at 830℃ indicates no amorphous phase in the films, which are composed of - and -C3N4 phase containing an unidentified C-N phase. Fourier transform infrared spectroscopy supports the existence of C-N covalent bond.