三氟氯乙烯与乙烯辐射共聚合的研究

本文报导利用⁶⁰Coγ射线引发以三氟三氯乙烷为溶剂的三氟氯乙烯与乙烯溶液共聚合的研究.聚合有诱导期(小于40伦/秒时)而无后效应.平均聚合速率比本体辐射聚合快一倍以上.聚合初速率与辐照强度成0.5次方关系,DPPH完全抑制聚合反应,聚合按自由基机制进行.聚合总活化能为3.5千卡/克分子.求得单体竞聚率γ_OTFE·E=0.025,γ_E·CTFE=0.20,所得共聚物为交替共聚物.共聚物熔点随单体配比中三氟氯乙烯含量的增加而增加,随聚合温度的升高而降低,而与辐照强度和溶剂比关系不大.聚合率(P%)与辐照强度(I)、除去诱导期的辐照时间(t)和溶剂FC-113比例(φ)的关系近似地由下式表示:P%=10⁽-1.28·t^1.23·I^1.12·φ^-0.508熔融指数(M.I.)与辐照温度(T)和溶剂FC-113比例(φ)的关系近似地由下式表示:M.I.=1.586·10^-4·φ^3.3·T^1.78(克/10分).     

甲烷无氧脱氢芳构化双促进W/MCM-22基催化剂研究

以MCM-22分子筛为载体,H₂SO₄酸化的(NH₄)₂WO₄为W组分前驱物,以Zn和/或Ca,Co,Mo为促进剂,研制两系列促进型W/MCM-22基催化剂.在常压固定床连续流动反应器-GC测试系统评价其对CH₄无氧脱氢芳构化的催化性能,结果显示,在双促进的W-Co-Mo(或W-Ga-Zn)/MCM-22催化剂上,常压、1073 K、原料气空速GHSV=1500 mL(STP)·h^-1·(g-cat.)^-1的反应条件下,苯选择性最高达到70%～72%,相应甲烷转化率为～15%;反应450 min后,甲烷转化率降低到～5%水平;7.5 h平均积炭选择性～20%.H₂-TPR和NH₃-TPD表征研究显示,在W/MCM-22基质催化剂中适当添加少量Co^3+/2+/Mon⁺或Ga³⁺/Zn²⁺,一方面导致Wⁿ⁺物种还原活化温度下降及可还原W⁶⁺物种数量增加,另一方面消去最强的一些B酸位同时诱生相当数量的中强酸位,这两方面的促进效应都对催化剂活性、选择性提高及结炭减缓作出贡献.     

Ni2P-NiS双助剂促进g-C3N4光催化产氢动力学

本文通过简单的一步水热法得到Ni₂P-NiS双助催化剂,之后采用溶剂蒸发法将Ni₂P-NiS与g-C₃N₄纳米片结合构建获得无贵金属的Ni₂P-NiS/g-C₃N₄异质结。研究结果表明,优化后的复合材料具有良好的光催化产氢活性,其产氢速率最高可到6892.7 μmol·g^-1·h^-1,分别为g-C₃N₄ (150 μmol·g^-1·h^-1)、15%NiS/g-C₃N₄ (914.5 μmol·g^-1·h^-1)和15%Ni₂P/g-C₃N₄ (1565.9 μmol·g^-1·h^-1)的46.1、7.5和4.4倍。这主要归因于Ni₂P-NiS相比Ni₂P和NiS单体具有更好的载流子转移能力,其与g-C₃N₄形成的肖特基势垒能有效促进光生载流子在二者界面上的分离,同时Ni₂P-NiS能进一步降低析氢过电势,进而显著增强了表面析氢反应动力学。本研究为开发稳定、高效的非贵金属产氢助剂提供了实验基础。     

电气石粉对制备纳米TiO2及光催化氧化甲苯气相污染物的影响

用浸渍、烧结方法制备了不锈钢网(3×15cm)负载催化剂:由溶胶-凝胶法制备含(400目)电气石粉的二氧化钛催化剂,并与直接混合电气石粉、P-25 TiO₂的复合负载催化剂进行对照;利用X射线衍射、扫描电镜、透射电镜等表征催化剂结构;研究了催化剂在反应器(14L)中由20W紫外杀菌灯照射下光催化氧化去除气相甲苯污染物的效果.结果表明,在制溶胶过程中添加微米级电气石粉,得到催化剂粒径较小,其负载量和催化活性均有提高,平均催化比活性达到1.90mg·m^-2·min^-1或0.11mg·g^-1·min^-1,该催化剂在静态条件下反应4h,对初始浓度为180mg·m^-3和70mg·m^-3的甲苯去除率分别达到87%和82%;而同样的高初始浓度下,负载P-25仅可去除21%甲苯,复合负载P-25、电气石可去除58%甲苯,其催化比活性达到1.35mg·m^-2·min^-1或0.18mg·g^-1·min^-1.     

锂在嵌入物LixTio2中的扩散行为

本文利用电化学方法测定了薄膜电极Li_xTiO₂中锂离子的化学扩散系数,室温下其数量级为10^-11～10^-12cm²·S^-1(x=0.10～0.20)。通过₄-T关系,测得其扩散激活能E≈0.59eV,频率因子₀≈O.54cm²·s^-1.故其一般式可表为:₄=O.54exp(-6785/T)cm²·s^-1(t=15～50℃).利用D₄值和库仑滴定曲线测得了Li⁺在Li_xTiO₂薄膜电极中的迁移率和电导率分别为10^-10cm²·V^-1·s^-1和10^-7～10^-8Ω^-1·cm^-1数量级。比较了Li_xTiO₂体系与其他锂嵌入物的₄值,发现其与隧道化合物Li_xWO₃的₄值相近,而比层状化合物Li_xTiS₂的₄值小3～4个数量级。D₄值较大的嵌入物在作为锂电池的正极时,可以经受较大的充放电流。     

脂族酰基过氧化物分解动力学研究 Ⅰ.过氧化月桂酰在苯中的分解动力学

进行了过氧化月桂酰(1)在脱氧的苯中的分解动力学研究,当起始浓度0.1～0.2克分子·升^-1,温度30℃、40℃时,1不是严格地按一级反应分解的.在50℃下起始浓度0.04～0.34克分子·升^-1时,实验结果符合一级加二分之三级的反应规律:-(da/dt)=k₁a+k₁a^3/2.求出的自发分解速率常数k₁=0.0115小时^-1,诱导分解速率常数k₁=0.014克分子^-1.2·升^1/2·小时^-1.     

HS+HO2气相反应机理及主通道速率常数的理论研究

采用CCSD(T)/6-311++G(3df, 2pd)//B3LYP/6-311+G(2df, 2p)双水平计算方法构建了HO₂+HS反应体系的单、三重态反应势能面,并对该反应主通道的速率常数进行了研究。研究结果表明,标题反应经历了八条反应通道,其中三重态反应通道R1是标题反应主通道。此通道包含路径Path 1 (R → ³IM1 → ³TS1 → P1(³O₂+H₂S))和Path 1a (R → ³IM1a → ³TS1a → P1(³O₂+H₂S))两条路径。利用经典过渡态理论(TST)与变分过渡态理论(CVT)并结合小曲率隧道效应模型(SCT),分别计算了主路径Path 1和Path 1a在200-800 K温度范围内的速率常数k^TST、k^CVT和k^CVT/SCT,在此温度区间内路径Path 1和Path 1a具有负温度系数效应。速率常数计算结果显示,对主路径Path 1和Path 1a而言,变分效应在计算温度段内有一定影响,与此同时量子力学隧道效应在低温段有显著影响。路径Path 1和Path 1a的CVT/SCT速率常数的三参数表达式分别为k₁^CVT/SCT(200-800 K) = 1.54×10^-5T^-2.70exp(1154/T) cm³ ·molecule^-1·s^-1和k_1a^CVT/SCT(200-800 K) = 5.82×10^-8T^-1.84exp(1388/T) cm³·molecule^-1·s^-1。     

LiCl-KCl-CeCl3熔盐结构与热力学的分子动力学模拟

采用分子动力学模拟的方法,研究了LiCl-KCl-CeCl₃熔盐中CeCl₃的结构性质和热力学,获得了LiCl-KCl-CeCl₃熔盐中密度与组成、密度与温度的关系数据;径向分布函数g_Ce-Cl(r)的第一个峰位置为0.259nm, Ce³⁺对应的第一个配位数约为6.9;混合熔盐中计算数据与纯熔盐中数据的差异可以解释为混合熔盐中Ce³⁺和Cl^-的相互作用比纯的CeCl₃更强; LiCl-KCl熔盐中Ce³⁺的自扩散活化能为22.5 kJ·mol^-1,从活化能的本质来说, Ce³⁺自扩散所需要克服的能垒要略低于U³⁺(25.8 kJ·mol^-1)。当Ce³⁺的摩尔分数从0.005增加到0.05时,其指前因子从31.9×10^-5 cm²·s^-1减少到21.8×10^-5 cm²·s^-1;随着Ce³⁺摩尔分数从0.005增长到0.05,单位体积内(忽略总体积的变化)Ce³⁺的增加意味着其扩散阻力增加,而自扩散的能力降低,导致了指前因子的减小。     

球状介孔锆铝复合氧化物甲醇催化剂载体的制备及性能

以Zr(NO₃)₄·5H₂O和Al(NO₃)₃·9H₂O为原料,采用葡萄糖水热法制备了一系列球状介孔复合氧化物(ZrO₂)_xAl₂O₃(x=0、 0.18、 0.42、 0.76和1.26),其结构和性能经扫描电子显微镜、低温N₂吸脱附、NH₃吸脱附表征。以(ZrO₂)_xAl₂O₃为载体,制备了铜锌基甲醇催化剂,其结构经X 射线衍射和N₂O化学滴定表征,并考察了催化剂在合成气合成甲醇反应中的催化性能。结果表明：当n(ZrO₂)/n(Al₂O₃)=0.42时,复合氧化物ZA2具有较大的孔径和较弱的表面酸强度,以其作为载体合成的铜锌基甲醇催化剂CZn/ZA2的活性铜比表面积较高。在5 MPa、 250 ℃反应条件下,甲醇的时空收率达到1.44 g·mL^-1·h^-1,活性比传统C307甲醇合成催化剂提高约2.1%。     

Pd-Cu/ZrO2催化CO2加氢制甲醇的性能

采用溶胶-凝胶法制备了n(Cu):n(Zr)=1:1、1:2、1:4和1:8的Cu/ZrO₂催化剂。 实验结果表明,当n(Cu):n(Zr)=1:4时,催化剂表现出较高的CO₂转化率(8.0%)和甲醇选择性(59.5%),为了增加CO₂的转化率,提高甲醇选择性,在n(Cu):n(Zr)=1:4的催化剂中添加质量分数1%的Pd,采用浸渍法制备了Pd-Cu/ZrO₂催化剂。 在250 ℃、2 MPa、12000 mL/(g·h)和V(H₂):V(CO₂)=3:1的反应条件下,CO₂转化率和CH₃OH收率相比Cu/ZrO₂催化剂(n(Cu):n(Zr)=1:4)分别提高了40.0%和80.9%。 通过X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FT-IR)、N₂吸附-脱附(BET)、X射线光电子能谱仪(XPS)和程序升温还原化学吸附仪(H₂-TPR)等仪器表征证明Pd的添加提高了催化剂的分散性和比表面积。 催化剂中Pd和Cu之间强相互作用,使Cu2p轨道结合能向低处偏移,还原温度的降低,说明Pd-Cu/ZrO₂催化剂还原能力增强,使得CO₂加氢活性提高。     

甲醇在Pd基电催化剂上的氧化

以多壁碳纳米管(MWCNT)和碳黑为载体, 用交替微波加热的方法制备了担载型Pd电催化剂, 并表征了其微观形貌和电化学性能. 透射电镜(TEM)和X射线衍射(XRD)结果显示, Pd在MWCNT载体上有较好的分散度, 平均粒径为4 nm. 循环伏安、计时电位和交流阻抗的测试结果表明, 在碱性溶液中, Pd/MWCNT显示出良好的甲醇氧化性能. 在Pd/MWCNT催化剂上, 甲醇氧化的起始电位比在Pt/C上负移100 mV 左右. Pd/MWCNT高的催化活性不仅与它的高的活性表面积有关, 而且和Pd与载体MWCNT之间的协同作用有关.     

Thermal and electrical behaviors of acid functionalized MWCNT/ABC-type triblock copolymer grafted-MWCNT nanocomposites

In this work, ABC-type triblock copolymer grafted onto the surface of the MWCNT/acid functionalized MWCNT (MWCNT-COOH) composites were prepared and the properties of nanocomposites were characterized extensively using differential scanning calorimetry (DSC), scanning electronic microscopy (SEM), thermogravimetric analysis (TGA), ac electrical conductivity and dielectrical measurements.

DSC study showed that the glass transition temperatures of the nanocomposites are a some higher than that of the matrix polymer. The increase in oxidized MWCNT in the nanocomposite improved the thermal stability of the composite, according to initial decomposition temperatures. The ac electrical conductivity has increased moderately with increasing frequency, but has increased slowly with increase in the oxidized MWCNT content in the nanocomposites. The electrical conductivity increases slowly with increasing temperature to about the glass transition temperature, then it increases faster. The dielectric constants for the matrix polymer and all the composites decreases slightly with increasing frequency from 0.1 kHz to 2.0 kHz. The dielectric constant increases slightly with increasing temperature up to about the glass transition temperature region and then the increase in temperature is accelerated the increase in the dielectric constant.     

Thermodynamics and kinetics of adsorption of Cu(II) from aqueous solutions onto multi-walled carbon nanotubes

Release of heavy metals into water as a result of industrial activities may pose a serious threat to the environment. The objective of this study is to assess the uptake of Cu²⁺ from aqueous solutions onto multi-walled carbon nanotubes (MWCNT). The potential of the t-MWCNT to remove Cu²⁺ cations from aqueous solutions was investigated in batch reactor under different experimental conditions. The processing parameters such as initial concentration of Cu²⁺ ions, temperature, and adsorbent mass were also investigated. Copper uptake was quantitatively evaluated using the Langmuir, Freundlich and Dubinin–Kaganer–Radushkevich (DKR) models. In addition, the adsorption equilibrium was described well by the Langmuir isotherm model with maximum adsorption capacity of 12.34 mg/g of Cu²⁺ cations on t-MWCNT. Various thermodynamic parameters, such as ΔG⁰, ΔH⁰ and ΔS⁰ were calculated. The thermodynamics of Cu²⁺ cations adsorption onto t-MWCNT system pointed at spontaneous and endothermic nature of the process. Using the second-order kinetic constants, the activation energy of adsorption (E_a) was determined as 27.187 kJ/mol according to the Arrhenius equation.     

Improved Catalytic Performance of Pt Supported on Multi‐Wall Carbon Nanotubes as Cathode for Direct Methanol Fuel Cell Applications Prepared by Dual‐Stepped Surface Thiolation Processes

This study develops a simple surface modification process for modifying the MWCNT surface by thiolation reaction after the conventional nitric acid treatment for strong interface attachment of Pt NPs and improved dispersion onto MWCNTs. The thiolated MWCNTs (Pt/MWCNTs) showed significant improvement of methanol electro‐oxidation activity compared with that treated only by nitric acid solution. The prepared electrode with thiolated MWCNTs was used as the cathode for assembling MEA for DMFC single‐cell applications. Testing results indicate that the thiolated MWCNT cathode can improve the power density of MEA by more than 300% (from 4.6 to 20.6 mW cm^?2) compared with that treated only by conventional nitric acid reactions. The dual‐step modification process for MWCNT surface treatment showed significant improvement over the convention nitric acid treatment and can be successfully used in DMFC applications.     

The improvement in interfacial shear strength of wood fiber/epoxy composite by sizing with epoxy sizing agent containing MWCNTs

This paper discloses a feasible and high efficient strategy for wood fiber treatment to introducing multi‐wall carbon nanotubes (MWCNTs) to the surface of wood fibers for the aim of improving the interfacial shear strength of wood fiber/epoxy composite. Briefly, a layer of MWCNT was deposited on wood fibers through sizing wood fibers with epoxy sizing agent containing amine‐treated MWCNTs (MWCNT‐PEI). The surface functional groups, morphology, wettability, and interphase properties of MWCNTs on the surface of wood fiber were studied. The remarkable enhancements were achieved in interfacial shear strength of reinforced composites by dipping wood fiber in MWCNTCOOH suspension and wood fiber sizing containing MWCNT‐PEI.     

Synergic effect in electrical conductivity using a combination of two fillers in PVDF hybrids composites

The objective of this work was to prepare novel conductive blends of poly(vinylidene fluoride) (PVDF) with polypyrrole (PPy) and to compare their performance with PVDF/multiwall carbon nanotube (MWCNT) composites and novel PVDF/PPy/MWCNT hybrid systems. All the compositions were prepared by melt mixing using a miniature mixer. The mixtures were characterized by Fourier transformed infrared (FTIR), wide angle X-ray diffraction (WAXD), thermogravimetric analyses (TGA), scanning and transmission electron microscopy (SEM and TEM, respectively) and volume electrical resistivity. For the binary PVDF/PPy and PVDF/MWCNT systems, percolation thresholds of 10 and 0.3 wt%, respectively, were found. In the hybrid systems, however, the percolation threshold for each filler was lower than in the binary systems, but the electrical conductivities were always much higher at all concentrations than the conductivities of the binary systems. Therefore, the addition of both fillers had a synergistic effect on the hybrid system conductivity, which was attributed to its morphology: the PPy increased the homogeneity of the MWCNT distribution and decreased the available free volume for the MWCNT; as a result the MWCNT rolled around the PPy particles bridging them through the PVDF matrix, increasing the quantum tunneling effect and thus, the electrical conductivity of the system.     

Electro-optical and dielectric study of multi-walled carbon nanotube doped polymer dispersed liquid crystal films

The self-organising property of nematic liquid crystals (LCs) was used to align multi-walled carbon nanotubes (MWCNT) dispersed in them. MWCNT not only well integrate in the matrix but also, even at very low concentration, have a detectable effect on the LC properties that can be very attractive for display applications. In the present work, MWCNT were doped (0–0.5% wt/wt) in two different types of LCs. These MWCNT doped polymer dispersed LC (CPDLC) films were studied comprehensively using fundamental techniques. Polarising optical microscope (POM) and scanning electron microscope (SEM) techniques used for morphological study reveal that the LC droplet size remains unchanged with increase in MWCNT concentration. The electro-optical (EO) study performed by increasing voltage in steps of 10 V up to 100 V at an optimised frequency of 200 Hz and at temperature 25°C shows that the low MWCNT concentration films show good optical response than the higher one. The dielectric behaviour of CPDLC films in the frequency range 20 Hz to 20 MHz was investigated using precision impedance analyser. The obtained data were modelled with Debye and Cole-Cole methods to calculate relaxation time and distribution parameter (α). The zero value of α indicates Debye type relaxation processes.     

The defluoridation of drinking water using multi-walled carbon nanotubes

In this study, the potential sorption capacity of multi-walled carbon nanotubes (MWCNTs) was investigated as a means of removing fluoride from the drinking water of a number of regions in Iran and from experimental solutions. The test was conducted in both batch and continuous operation modes. Batch mode experiments were used to study the effect of parameters such as pH, contact time, ionic strength, adsorbent dose, adsorbent capacity, and the presence of foreign anions on the efficiency of fluoride removal. The results showed that the highest level of sorption occurs at pH 5 (about 94% at 18 min). The ionic strength of the solutions and the presence of co-anions such as chloride, nitrate, sulfate, hydrogen carbonate, perchlorate had a negligible effect on the sorption of F⁻ onto MWCNTs. Sorption capacity measurements revealed that MWCNTs have a saturation capacity of 3.5 mg of F⁻ per gram. Sorption data were best fitted with the Fruendlich sorption isotherm equation, which indicates that F⁻ tends to be adsorbed on MWCNTs in a multilayered manner. Experiments using Kohbanan city drinking water, which contains the highest level of F⁻ among the drinking water samples studied, showed that MWCNTs can remove over 85% of fluoride content.     

Development An Amperometric Microbial-enzyme Hybrid Cholesterol Biosensor Based On Ionic Liquid MWCNT Carbon Paste Electrode

In this study we report the development of an amperometric cholesterol biosensor based on cholesterol oxidase from Pseudomonas sp. and catalase immobilized in carbon paste electrode (CPE) modified with multiwall carbon nanotubes (MWCNT) and ionic liquid (IL). The working electrode (CPE/MWCNT-IL/Microorganism (MO)-Catalase) was characterized by impedance spectroscopy and cyclic voltammetry at different stages of its construction. This proposed cholesterol biosensor performed linear relationship in the range of 5–600 μM with a low detection limit of 1.52 μM. The biosensor showed good sensitivity and high selectivity and it was successfully applied for the measurement of cholesterol levels in lyophilized serum samples.     

Nanotubes as polymer composite reinforcing additive materials – A comparative study

Nitrogen-doped bamboo-shaped carbon nanotubes (N-BCNTs) and their non-doped conventional counterparts, multiwalled carbon nanotubes (MWCNTs) were compared as polymer reinforcing additives in polyvinyl chloride (PVC) matrix. The nanotubes were synthetized by catalytic chemical vapor deposition (CCVD) method. The purity of both nanotubes was measured by thermogravimetric analysis (TGA) and found to be >91%. Further analysis on the morphology and size of the carbon nanotubes (CNTs) were performed by transmission electron microscopy (TEM). The PVC powder was impregnated with CNTs in ethanol by using tip ultrasonicator. The dispersion media was evaporated, and the CNT/PVC powder was used to produce polymer fibers. The orientation of carbon nanotubes in the PVC matrix was characterized by scanning electron microscopy (SEM), and the presence of nanotubes were confirmed in case of all PVC samples. It can be observed on the SEM images that the nanotubes are fully covered with PVC. The tensile strength of the nanotube containing samples was tested and the N-BCNT/PVC composite was found to be better in this sense, thanks to the extraordinary structure of the nanotube. In case of the N-BCNT/PVC composite the measured young modulus was 39.7% higher, while the elongation at brake decreased by 33.6% compare to the MWCNT/PVC composite. These significant differences in the mechanical properties of the composites can be explained with the stronger interaction between N-BCNTs and PVC.