氮掺杂二氧化钛/聚吡咯（TiO2@Polypyrrole）纳米球的制备及其超声催化性能研究

本文介绍了氮掺杂TiO2纳米球的制备方法,并对TiO2纳米球的超声催化性能进行改进,提高它的超声催化活性。改变方法是利用原位聚合法对TiO2纳米球进行聚吡咯(PPy)包覆来制备TiO2@PPy纳米球,并且在制备TiO2纳米球的过程中引入N离子,以此来提高它的催化效率(本实验超声催化降解罗丹明B),通过透射电镜(TEM)、红外光谱(FT-IR)、X射线衍射(XRD)和热重分析(TGA)对其结构和形貌进行了表征,并利用紫外可见光谱(UV-VIS)表征了其在超声条件下对罗丹明B的超声催化降解性能。结果表明:氮掺杂TiO2@PPy纳米球对罗丹明B有很好的超声催化降解性能。     

电化学沉积铁-非晶碳磁性纳米复合薄膜北大核心CSCD

利用液相电化学方法,以乙酰丙酮铁的甲醇溶液为碳源,在单晶硅表面制备了铁-非晶碳磁性纳米复合薄膜。通过扫描电子显微镜、X射线衍射、X射线光电子能谱和Raman光谱技术分析了薄膜组成、形貌和结构。结果表明:Fe掺杂的非晶碳膜为含有Fe、Fe_3O_4纳米晶和非晶碳基的复合结构。和未掺杂非晶碳膜相比,Fe掺杂的薄膜具有更高的sp2碳含量和无序度。磁滞回线显示Fe掺杂的薄膜具有软磁特性,沿薄膜表面方向为易磁化方向。     

电化学沉积铁-非晶碳磁性纳米复合薄膜

利用液相电化学方法,以乙酰丙酮铁的甲醇溶液为碳源,在单晶硅表面制备了铁-非晶碳磁性纳米复合薄膜。通过扫描电子显微镜、X射线衍射、X射线光电子能谱和Raman光谱技术分析了薄膜组成、形貌和结构。结果表明:Fe掺杂的非晶碳膜为含有Fe、Fe_3O_4纳米晶和非晶碳基的复合结构。和未掺杂非晶碳膜相比,Fe掺杂的薄膜具有更高的sp2碳含量和无序度。磁滞回线显示Fe掺杂的薄膜具有软磁特性,沿薄膜表面方向为易磁化方向。     

机械激活工艺对TiO2碳热还原合成纳米TiC的影响

以纳米TiO2/碳黑为原料,通过机械激活-碳热还原法合成纳米TiC粉末,研究了机械激活工艺对TiO2碳热还原反应的影响.产物经XRD分析表明,激活时间延长、球料比增大、球磨机转速加快都有利于促进纳米TiO2碳热还原反应进行得更完全,但最终TiC产物中(Fe,C)杂质含量也随之上升.综合考虑,球磨时间4～8h,球料比10:1,转速250r/min对后续碳热还原合成纳米TiC是较合适的工艺选择.     

碳纳米管增强的陶瓷基复合材料

利用聚合物前驱体热裂解工艺制备了碳纳米管增强的陶瓷基复合材料.制备了含1.3%和6.4%(体积分数)碳纳米管的硅碳氮复合材料.SEM和HRTEM微观结构表明碳纳米管被均匀地分布在陶瓷基体中.采用纳米压痕测量了材料的力学性能,结果表明碳纳米管增强陶瓷复合材料的力学性能明显提高.     

氮掺杂对碳纳米颗粒缓蚀性能的影响

通过热分解方法,以柠檬酸为碳源制备出无氮碳纳米颗粒(CNPs);以柠檬酸为碳源、尿素为氮源制备出氮掺杂碳纳米颗粒(N-CNPs)。采用原子力显微镜、红外光谱和Raman光谱表征碳纳米颗粒的结构,利用失重实验、电化学测试、激光共聚焦扫描显微镜观察等研究碳纳米颗粒在1 mol/L HCl溶液中对Q235钢缓蚀性能。结果表明:两种碳纳米颗粒均属于混合型缓蚀剂,50 mg/L CNPs的缓蚀效率为37.6%;而N-CNPs的缓蚀效率明显提高,达到90.96%。     

金属掺杂及多孔化Bioglass@CNFs的制备与结构分析

以溶胶-凝胶法、静电纺丝法以及高温烧结相结合的方法,将金属离子Mg、Zn掺杂到生物活性玻璃中制备了掺杂Mg、Zn的Bioglass@CNFs,以聚甲基丙烯酸甲酯(PMMA)为致孔剂制备了多孔化Bioglass@CNFs。扫描电子显微镜(SEM)、X射线衍射(XRD)等表征手段研究表明,不同的处理阶段碳纳米纤维的形貌发生变化,在热牵伸和化学反应的共同影响下,碳纳米纤维的直径会逐渐变小,但其取向度会有所改善;在高温烧结即碳化后,碳纳米纤维的表面生长出生物活性玻璃纳米粒子;Mg、Zn掺杂Bioglass@CNFs的表面都有生物活性玻璃纳米粒子生长,且Mg掺杂Bioglass@CNFs表面粒子组成以硅灰石(CaSiO3)和透辉石(MgCaSi2O6)为主,呈方形、数量多、大小均一,Zn掺杂Bioglass@CNFs表面粒子为无定形态,数量少、大小均一,这与Mg、Zn参与碳纳米纤维不同热处理阶段中发生的环化、脱氢和氧化等一系列化学反应的机制有关。此外,PMMA具有显著的制孔作用,高温烧结后Bioglass@CNFs内部出现中空管道结构,表面也出现大量微孔,大大提高了纤维的比表面积和粗糙度,且表面生长出的生物活性玻璃纳米粒子组成以硅灰石(β-CaSiO3)和假硅灰石Ca3(Si3O9)为主。     

含纳米Al_2O_3/Fe_3O_4的FeS固体润滑复合层的摩擦学性能

采用离子氮碳共渗与离子渗硫复合处理技术在45钢表面制备FeS固体润滑复合层,复合层中硫化物表层厚度约为10μm,其硫化物颗粒与孔隙均在微纳米量级且分布均匀。复合层相组成主要为FeS、FeS2和Fe3N。在含0.1%n-Al2O3＋0.08%n-Fe3O4液体石蜡润滑下,复合层与纳米Al2O3/Fe3O4复合添加剂产生协同作用,磨损表面形成了由硫化物、硫酸盐、氮化物等组成的化学反应膜,使FeS固体润滑复合层表面摩擦因数最低,始终保持在0.07左右,体积磨损量最小,比未渗表面降低了92%,比渗硫表面和氮碳共渗表面分别降低了85%和44%。     

铈铁复合氧化物纳米空心球的制备与催化性能

用水热法制备的碳球(CS)作为模板,利用Ce~(4+)与碳球表面的静电吸附以及高铁酸钾(K_2Fe O_4)的强氧化性在碳球表面进行包覆,煅烧去除模板后得到铈铁复合氧化物(Ce_(1-x )Fe_(x )O_2)纳米空心球。通过SEM、TEM、XRD、Raman、BET等手段对材料的结构进行了表征。结果表明,纳米空心球平均直径约300 nm,壁厚20~25 nm,Fe的含量对空心球的形貌有较大的影响。用CO催化氧化反应来测试材料的催化性能。结果表明Ce_(0.95)Fe_(0.05)O_2具有良好的催化性能,可以在297℃实现对CO的完全氧化,并且具有非常高的催化稳定性。     

添加Fe3+对二氧化钛薄膜吸收光谱及光催化活性的影响

用阳极氧化法制备多孔状的纳米晶二氧化钛薄膜 ,通过往阳极氧化的电解液中添加Fe3 使Fe3 进入二氧化钛薄膜中。研究了掺杂Fe3 对二氧化钛薄膜吸收光谱和光催化活性的影响 ,发现掺杂Fe3 使二氧化钛薄膜对入射光的吸收带边发生红移 ,讨论了其作用机制。     

Electrocatalytic efficiency of polyaniline by cyclic voltammetry and electrochemical impedance spectroscopy studies

Electrochemical redox reactions of ferrous/ferric (Fe²⁺/Fe³⁺) and hydroquinone/quinone (H₂Q/Q) were studied on Pt and polyaniline (PANI)-deposited Pt electrodes in 0.5 M H₂SO₄-supporting electrolyte by cyclic voltammetry and ac impedance spectroscopy. A comparison of the experimental data obtained with the Pt and PANI/Pt electrodes suggested that the reactions were catalyzed by the PANI. Based on a relative increase in peak currents of cyclic voltammograms, catalytic efficiency (γ_cv) of the PANI was defined. There was an increase in γ_cv with an increase of scan rate and a decrease of concentration of Fe²⁺/Fe³⁺ or H₂Q. The complex plane impedance spectrum of the electrode consisted of a semicircle in high frequency range and a linear spike in low frequency range. The exchange current density (i₀) calculated using the semicircle part of the impedance showed Butler–Volmer kinetics with respect to concentration dependence. From a relative increase of i₀ on the PANI/Pt electrode, catalytic efficiency (γ_eis) was evaluated.     

Microstructure and mechanical properties of 3D fine-woven punctured C/C composites with PyC/SiC/TaC interphases

The 3D fine-woven punctured C/C-(P_yC/SiC/TaC) composites, composed of P_yC/SiC/TaC interphases and pyrocarbon (PyC) matrix, were synthesized by isothermal chemical vapor infiltration (ICVI) methods. The alternating layers and the structure of these composites were examined by polarized light microscopy (PLM), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). It is found that the P_yC matrix has rough laminar (RL) structure, the TaC layer has NaCl-type cubic structure, and the SiC layer has few wurtzite type 10H-SiC besides β-SiC structure. The effects of fiber coating and the bulk density on the tensile and flexural properties of composites along X or Y and Z direction were investigated. It is shown that fiber coated 3D woven punctured C/C composites have good tensile and flexural strength, and the maximum of flexural strength is 375 MPa in X or Y direction at density of 1.89 g/cm³, which is about three times higher than that of samples without TaC/SiC fiber coating. The flexural strength and bending strength increase with increasing the density of the composites. The analysis of fracture surfaces reveals that fibers and fiber bundles are pulled out in composites, indicating that the composite exhibits a non-linear failure behavior through propagation and deflection of the cracks.     

Nanocomposites of polyaniline,its derivatives and platinum prepared using aqueous Pt sol

Polyaniline (PANI), poly(o-methoxyaniline) (POMA) and poly(o-toluidine) (POT) have been used as matrices for incorporation of Pt nanoparticles from the previously prepared aqueous Pt sol. Polymer–Pt nanocomposites thus obtained have been characterized by X-ray diffraction, transmission electron microscopy and IR spectroscopy. It has been revealed that metal nanoparticles (predominantly of sizes in the range between 2 and 4 nm) have been present in all the composites. It can be postulated that the polymers prevent Pt nanoparticles from agglomeration, i.e. act as their stabilizers. As has been found, charge transfer interactions between polymer chains and Pt nanoparticles are responsible for this stabilization. Among the polymers studied, POT shows the weakest stabilizing effect.Catalytic isopropyl alcohol conversion has shown that PANI–Pt nanocomposite obtained using aqueous Pt sol exhibits strong redox properties. Its overall catalytic activity is ca. three times higher than that of PANI–Pt composite containing larger Pt particles. This is connected with better dispersion of Pt particles in the composite prepared using aqueous Pt sol.     

V，Ru共掺杂NiS2 高尔夫微球作为碱性介质析氢反应的高效电催化剂

通过溶剂热法和滴钌法(室温)将钒和钌引入到NiS₂中,并制备了包覆在泡沫镍上的V,Ru共掺杂NiS₂微球(V, Ru)-NiS₂/NF电催化剂。通过硫化过程产生粗糙的高尔夫球状结构暴露出丰富的活性位点,此外,钒和钌的协同作用可以优化NiS₂的电子结构,提供额外的催化活性位点,进一步增强本征催化活性。泡沫镍的加入对催化材料起到支撑作用,避免聚集,同时提高导电性。结果表明,(V, Ru)-NiS₂/NF电催化剂在碱性条件下表现出优异的电催化性能和优异的析氢反应稳定性。在10 mA·cm^-2的电流密度下,(V, Ru)-NiS₂/NF提供了38 mV的过电位,小于商业Pt/C的过电位,并且具有较低的Tafel斜率(80.3 mV·dec^-1)、较高的电化学活性表面(ECSA)和在KOH溶液中24 h出色的稳定性。     

高密度预制体制备炭/炭复合材料的弯曲力学性能与断裂机制

以丙烯作为碳源,氮气作为载气,采用初始密度为0.94g/cm3三维正交PAN基12K炭纤维预制体,利用自制的快速CVI炉制备基体热解炭结构为带状结构的C/C复合材料。力学性能测试结果表明,材料的弯曲断裂特征与制备过程中受到的高温热处理次数有关。从载荷-位移曲线来看,当C/C复合材料经过两次热处理时,C/C复合材料呈明显假塑性断裂特征。当C/C复合材料经过三次热处理时,载荷-位移曲线趋于稳定平滑,抗弯强度降低。从C/C复合材料断面的SEM图可以观察到材料断裂可以分为层间断裂和层内断裂,而层内断裂又因热解炭填充密度变化呈明显的分区断裂。由于热解炭和纤维含量在C/C复合材料中分布的差异,材料在不同的区域表现出不同的断裂特征,从而使得材料具备良好的弯曲强度同时具有一定的韧性特征。     

Electrocatalytic properties of polypyrrole films prepared with platinate(II) counter-ions

Polypyrrole/PtCl₄²⁻ composites were studied with respect to their possible use as a hydrogen electrode, e.g. for fuel cell applications. The impact of composite conditioning on its electrochemical activity for the hydrogen oxidation reaction (HOR) was studied. The cathodic polarization of samples containing a high amount of PtCl₄²⁻ ions after synthesis leads to the formation of polypyrrole/Pt composites active for HOR. Their behavior is, however, different from that of bulk Pt and strongly depends on the potential at which the reduction proceeds. Both electrochemical and IR measurements displayed the self-degradation of composites exposed to cathodic potentials exceeding a certain level. The presence of metallic Pt is proved by means of X-ray photoelectron spectroscopy (XPS) and the extent of platinate ions reduction/motion is discussed. Subsequently the possibility of tuning composite activity by changing the thickness or using a competing counter-ion during synthesis was tested.     

高分数GNFs/6061Al基复合材料的放电等离子体烧结制备及其显微组织与性能

采用放电等离子体烧结(SPS)工艺在610℃制备30％～50％(质量分数)纳米石墨片(GNF)/6061Al基复合材料,研究烧结压力及GNF含量对复合材料显微组织和力学、热学性能的影响.结果表明,SPS有效抑制GNFs/6061Al基复合材料中Al4C3等界面反应产物的生成.随着GNF含量的增加,GNFs团聚程度增加,...     

碳载PtNi合金催化剂的制备、表征及氧还原催化性能研究

以乙酰丙酮铂(Pt(acac)₂)、乙酰丙酮镍(Ni(acac)₂)为前驱体,三正辛基氧膦(TOPO)为表面修饰剂,油胺(OAm)为还原剂,N,N-二甲基甲酰胺(DMF)为助剂,超导碳科琴黑ECP为载体,采用液相合成法制备了碳载PtNi合金纳米催化剂(Pt_2.7Ni/C)。通过TEM对其形貌进行表征,ICP-AES进行定性和定量分析,XRD对其结构进行表征,并进行电化学阴极氧还原催化性能研究。研究表明：所制备的Pt_2.7Ni/C纳米催化剂粒径分布在3～11 nm之间,平均粒径为6.25 nm;在酸性条件下,当电位在0.9 V(vs.RHE)时,Pt_2.7Ni/C纳米催化剂的质量比活性为796.08 mA·mg_Pt^-1,为商业Pt/C(JM)催化剂的约4.0倍,面积比活性为3.60 mA·cm^-2,为商业Pt/C(JM)催化剂的约11.3倍。同时在经过5000和10 000次的加速耐久性实验后,Pt_2.7...     

Synthesis and study of λ-MnO_2 supported Pt nanocatalyst for methanol electro-oxidation

A λ-MnO2 supported Pt nanocatalyst(5 wt.% Pt/λ-MnO2) was synthesized using a facile approach.X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), scanning electronic microscope(SEM), transmission electron microscopy(TEM), and energy disperse spectroscopy(EDS) were used for catalyst structure and morphology characterization, which showed that the metallic Pt particles were attached on a λ-MnO2 surface through the interaction between Pt and λ-MnO2.Cyclic voltammetry(CV) was used to test the catalytic activity of Pt/λ-MnO2 toward methanol oxidation, which showed that Pt/λ-MnO2 catalyst has much higher catalytic activity than baseline Pt/C catalyst.     

One-pot synthesis of polyaniline/Fe3O4 nanocomposites with magnetic and conductive behaviour. Catalytic effect of Fe3O4 nanoparticles

Polyaniline/Fe₃O₄ nanocomposites were prepared by a one-pot synthesis using N-(4-aminophenyl)aniline as the reagent, molecular oxygen or hydrogen peroxide as the oxidizing agents in the presence of Fe₃O₄ nanoparticles (NPs) in powder and ferrofluid form. Both magnetic NPs in powder and ferrofluid form showed similar catalytic behaviour. The catalytic effect is particularly evident when molecular oxygen was used as the oxidizing agent. However, concerning the morphological aspects, only the composites prepared in the presence of ferrofluid-type Fe₃O₄ NPs showed a preferential morphology of nanorods (between 30 and 110 nm in diameter). All the composites are superparamagnetic at room temperature but at low temperature they are in a blocked state. Inter-particle interactions significantly affect the magnetic properties of the composites. The electrical conductivity of the composites is about 10⁻² S cm⁻¹, in agreement with the values obtained for polyaniline prepared by chemical route. A mechanism of the nanorods formation is proposed.