双马来酰亚胺-聚醚砜复相树脂固化与相行为

采用非等温DSC研究了双马来酰亚胺-聚醚砜（BMI-PES）复相树脂体系的固化行为和固化动力学,根据Kissinger方程计算BMI-PES复相树脂固化的表观活化能和指前因子,利用Crane方程计算反应级数,得到反应动力学方程,进行了实验固化度与理论固化度对比验证,通过SEM研究BMI-PES复相树脂微观相结构随固化温度和时间的演化规律。树脂固化行为显示:BMI-PES复相树脂固化反应存在自催化现象,PES参与了BMI固化;随着升温速率增大,BMI-PES复相树脂固化特征温度均向高温移动,但固化热焓基本不变;随着PES添加量增多,反应速率增大,BMI-PES复相树脂固化热焓降低,而峰值固化温度无变化。固化动力学研究表明:随着PES添加量增多,BMI-PES复相树脂固化表观活化能增大,但指前因子和反应级数无变化,固化为一级反应;BMI-PES树脂在200℃固化时,反应前期固化度实验数据与理论值吻合度很高。SEM结果表明,BMI-PES树脂经180℃固化处理后产生了相反转结构。      

乳化炸药中硝酸铵-亚硝酸钠的发泡动力学研究

为了了解和控制乳化炸药中硝酸铵-亚硝酸钠反应的发泡速率,采用减重法和量气法研究了该反应过程的反应机理和反应动力学。结果表明,酸可作为催化剂,对整个反应过程起促进作用;其次,在酸作为催化剂条件下,反应速率随着实验温度的增加而增加,且反应符合Arrhenius模型。其中,反应活化能为57.87 kJ/mol,指前因子为1.48×10~6 mol/L·s。对比实验值和计算值可知,反应动力学方程合理。为实际生产中化学敏化反应速率的控制提供了理论依据。     

铁粉表面置换镀铜的动力学

通过对硫酸铜溶液中铜置换包覆铁粉的研究,发现置换速率明显受到温度、搅拌速率、初始铜浓度以及溶液pH值的影响.置换速率随温度、搅拌速率和初始铜浓度的增加而增加.溶液pH值在弱酸性时,有利于置换反应的进行.该体系的置换反应机理符合扩散控制机理.动力学数据服从一级反应速率的规律.     

铁粉表面置换镀铜的动力学

通过对硫酸铜溶液中铜置换包覆铁粉的研究，发现置换速率明显受到温度、搅拌速率、初始铜浓度以及溶液pH值的影响。置换速率随温度、搅拌速率和初始铜浓度的增加而增加。溶液pH值在弱酸性时，有利于置换反应的进行。该体系的置换反应机理符合扩散控制机理。动力学数据服从一级反应速率的规律。     

1,3—戊二烯阳离子聚合反应动力学

研究了以Ａｌ（ＯＴｆ）３引发的１，３－戊二烯（ＰＤ）在二氯甲烷和正己烷中的阳离子聚合动力学。根据聚合反应引发速度快并呈现转化率不完全的实验事实，提出了快速引发活性中心浓度逐渐降低的非稳态假定，根据这个假定推导出的非稳态动力学方程能较好地与实验数据相吻合。在二氯甲烷中链增长反应速度大于在正己烷中的速度，而链终止反应在二氯甲烷中的速度小于正己烷中的速度，因此在二氯甲烷中聚合反应呈现较高的反应速率及转化     

固化剂种类对PBX粘结剂固化反应动力学的影响

采用非等温DSC方法,研究了TDI和IPDI做固化剂时,塑料粘结炸药(PBX)粘结剂固化行为的差异,获得了不同固化剂胶液体系的固化反应动力学方程。结果表明,以TDI做固化剂的粘结剂体系的活化能是55.87kJ/mol,反应级数是0.88,指前因子是4.70×104s-1,以IPDI做固化剂的粘结剂体系的活化能是62.29kJ/mol,反应级数是0.92,指前因子是1.23×105s-1,同一温度,同一固化度时,以TDI做固化剂体系的固化速率大于以IPDI做固化剂体系的固化速率。     

以甘蔗渣为原料的聚氨酯合成反应动力学

利用二丁胺滴定法研究了甘蔗渣液化产物与多次甲基多苯基异氰酸酯(PAPI)在30℃、40℃、50℃和60℃于二氧六环溶液中的反应速率;计算了这四个温度的反应速率常数;按照阿仑尼乌斯公式计算了该反应的活化能为101.6 kJ/mol,指前因子为3.99×1015g/mol.s。     

改性海绵铁除氧影响因素与机理研究

采用反应动力学分析、表面分析、扫描电镜(SEM)和X射线能谱仪(EDS)研究了诸外因对改性海绵铁除氧行为的影响及除氧相关机理.结果表明:改性海绵铁表面铜含量增加对除氧能力的促进作用大于比表面积减小使除氧能力降低的影响.改性海绵铁除氧过程为反应控制过程并符合一级反应动力学方程.另外,诸外因中溶液初始pH值和初始电导率对除氧速率常数的影响规律是先增后减.增加改性海绵铁投加量和溶液温度对除氧速率常数的提高具有促进作用,但继续增加改性海绵铁的投加量并不能无限提高除氧速率常数,速率常数存在极限值为0.3663min-1.     

乙烯-醋酸乙烯共聚乳液水解动力学研究Ⅱ. 乳胶粒内部水解反应动力学

当乙烯-醋酸乙烯共聚物乳液(EVA)胶粒表面水解完成后,水解反应将继续在胶粒内部进行,采用滴定法跟踪测试体系碱的浓度进行动力学研究,并建立一数学模型对其进行描述.研究表明,胶粒内部水解反应呈现前后两个阶段 ,反应速率主要由OH-在胶粒内部的扩散速率所控制.前半阶段反应活化能为53.21 kJ/m ol,指前因子为1.525×107 min-1,后半阶段反应活化能为44.86 kJ/mol, 指前因子为3.411×105 min-1.甲醇的加入能加速内部水解反应的进行.     

85 nmUV降解水中二苯甲酮和孔雀石绿的动力学研究

研究了185 nmUV降解水中 二苯甲酮和孔雀石绿的动力学,主要 包括185 nmUV降解水中有机物的动力 学分析,反应速率常数的理论分析, 各种因素如温度、浓度、pH值以及流 速等影响反应速率常数的因素分析, 并建立化学反应动力学方程;讨论185 nmUV降解水中的二苯甲酮和孔雀石绿的 动力学规律;从理论和实验讨论185 nmUV 降解水中的二苯甲酮和孔雀石绿是符合准 一级动力学规律。     

Gel polymer electrolytes based on polyacrylonitrile and a novel quaternary ammonium salt for dye-sensitized solar cells

Gel polymer electrolytes were prepared by incorporating polyacrylonitrile (PAN) in a mixture of polysiloxane with quaternary ammonium side groups (PSQAS), ethylene carbonate (EC), propylene carbonate (PC) and iodine. The influence of PAN content on the ionic conductivity of gel polymer electrolytes and the charge-transfer kinetic performance in counterelectrode-electrolyte interface was investigated. The dye-sensitized solar cell with the gel polymer electrolyte containing 5 wt.% PAN showed the best photovoltaic performance; a maximum incident photon conversion efficiency of 63% at 520 nm was obtained, the short-circuit photocurrent density (J_sc), the open-circuit voltage (V_oc) and the fill factor (FF) were 7 mA cm⁻², 0.565 V and 0.65, respectively. The corresponding overall conversion efficiency (η) is 4.3%.     

Production new chelating fibers of polyacrilonitrile for removing metal ions

In this work, raw acrylic fibers (RAF) have been modified with ethanolamine to provide new chelating fibers and prepared polyacrylonitrile‐monoethanolamine (PAN‐MEA). PAN‐MEA fiber was prepared by conversion nitrile groups into hydroxyle groups using ethanolamine solution with different concentration under refluxing at different temperatures and different times. The fiber structure has been investigated by different experimental techniques of characterization such as Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and the physical and mechanical properties has also been investigated in this study. The PAN‐MEA was examined as chelating material in a series of batch adsorption experiments for removal Cu (II), Pb (II) and Ni (II) ions. The ion adsorption of PAN‐MEA was determined with the atomic adsorption method. PAN‐MEA show adsorption metal ions more than usual fiber because of the modification.     

Preparation of porous polyacrylonitrile fibers by electrospinning a ternary system of PAN/DMF/H2O

Polyacrylonitrile (PAN) porous fibers were prepared in one step by electrospinning a ternary system of PAN/N, N-dimethylformamide (DMF)/water at ambient environment. The formation of porous structures was mainly due to the spinodal decomposition phase separation occurred during the electrospinning process. The concentration of PAN varied from 3 to 10 wt.% with the water content changing from 2 to 8 wt.%. When PAN concentration was above 5 wt.%, the composition of the ternary system was close to the “cloud point” and fibers with porous structures were obtained. In addition, the surface tension and viscosity of PAN solutions increased with water which may lead to the diameter increase of the fibers. The Brunauer-Emmett-Teller (BET) surface area of porous PAN nanofibers obtained from 8 wt.% PAN solution containing 7 wt.% of water was 46.4 m² g⁻¹, which was 3 times higher than that of nonporous PAN nanofibers prepared under the same conditions from a solution without water.     

偕胺肟基螯合纳米纤维的制备

以静电纺聚丙烯腈(PAN)纳米纤维为原料,与盐酸羟胺的水溶液反应,将腈基转化为偕胺肟基团,从而制备出偕胺肟基螯合纤维。探讨了盐酸羟胺浓度、pH值、反应时间及温度对转化率的影响,并分别采用扫描电子显微镜和傅里叶变换红外光谱(FT-IR)对PAN纳米纤维膜反应前后的形貌和分子基团进行分析。结果表明:PAN在pH值为7时,腈基转化率最高;-CN转化率随着浓度、反应时间及温度的增大而提高。红外光谱分析表明,PAN分子中有部分腈基转化为偕胺肟基团。     

OPA oxidation rates in supercritical water

Supercritical water oxidation can effectively destroy a large variety of high-risk wastes resulting from munitions demilitarization and complex industrial chemical. An important design consideration in the development of supercritical water oxidation is the information on the oxidation rate. In this paper, the oxidation rate of isopropyl amine (OPA), one of high-risk wastes resulting from munitions demilitarization, was investigated under supercritical water oxidation (SCWO) conditions in an isothermal tubular reactor. H2O2 was used as the oxidant. The reaction temperatures were ranged from 684 to 891 K and the residence times varied from 9 to 18s at a fixed pressure of 25 MPa. The conversion of OPA was monitored by analyzing total organic carbon (TOC) on the liquid effluent samples. The initial TOC concentrations of OPA varied from 7.21 to 143.78 mmol/l at the conversion efficiencies from 88.94 to 99.98%. By taking into account the dependence of reaction rate on oxidant and TOC concentration, a global power-law rate expression was regressed from 38 OPA experimental data. The resulting pre-exponential factor was 2.46(+/-0.65)x10(3)l(1.37)mmol(-0.37)s(-1); the activation energy was 64.12+/-1.94 kJ/mol; and the reaction orders for OPA (based on TOC) and oxidant were 1.13+/-0.02 and 0.24+/-0.01, respectively.     

Ion adsorption studies of micro and nano acrylic fibers modified by ethanolamine

Micro and nano polyacrylonitrile fibers were modified to polyacrylonitrile‐monoethanolamine (PAN‐MEA) through reaction PAN with ethanolamine. The modified PAN fiber was prepared by conversion nitrile groups into hydroxyle groups using ethanolamine solution with different concentration under refluxing at 91°C. Modified raw acrylic fibers (RAF) with submicrometer diameters ranging from 120 to 300 nm were produced using electrospinning in N,N‐dimethyl formamide (DMF). The PAN‐MEA micro and nano fibers were examined as chelating material in a series of batch adsorption experiments for removal of Cu (II), Pb (II) and Ni (II) ions. The fiber structure has been investigated by different experimental techniques of characterization such as Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). Also, the physical and mechanical properties has been investigated in this study. Nano fibers show adsorption metal ions more than the usual fiber because of high ratio of surface to mass.     

Synthesis of polyacrylonitrile using AGET-ATRP in emulsion

The technique of activators generated by electron transfer for atom transfer radical polymerization (AGET-ATRP) of acrylonitrile (AN) has been first attempted in emulsion using the procedure of “one-pot”, “two-step” with polyethylene glycol monooleyl ether (Brij 35) as surfactant, cupric chloride (CuCl₂) as catalyst, hexamethylenetetramine (HMTA) as ligand, carbon tetrachloride (CCl₄) as initiator and ascorbic acid (VC) as reducing agent. The polymerization proceeds in controlled/living manner as indicated by first-order kinetics of the polymerization rate with respect to the monomer concentration, linear increase of the molecular weight of polyacrylonitrile (PAN) with monomer conversion and narrow polydispersity. Monomer conversion increases initially with the increase of ligand HMTA and then decreases. The ratio of [AN1] to [AN2] at 1:3 not only gives better control on the molecular weight and the molecular weight distribution, but also provides a more rapid polymerization rate. The rate of polymerization shows a trend of increase along with CCl₄ content. The apparent activation energy of the polymerization is calculated to be 46.6 kJ/mol. Chain extension of PAN with AN was also carried out and the chain extended PAN with 20520 molecular weight and 1.36 polydispersity was successfully obtained.     

Preparation,characterization, and mechanical properties of polyacrylonitrile (PAN)/graphene oxide (GO) nanofibers

Abstract

Mostly, water filters are designed based on the steady state conditions “Laminar flow”, while the actual case is a turbulent flow as a result of chaotic changes in pressure and flow velocity, which can be lead to rapid failure thus decrease its service time. Also, the surface roughness of the synthesized filter was neglected, which has been classified as the main cause of shear failure. In this work, Polyacrylonitrile (PAN) nanofibers were enhanced by graphene oxide (GO) with different fractions in order to increase its performance, in terms of mechanical behavior. At the same time, GO was employed as a surface refining of the synthesized filter in order to decrease the friction between flow and filter surface thus delays the occurrence of shear failure. In this work, PAN/GO composite nanofibers were fabricated by electrospinning process. Different volume concentration of GO (0.05, 0.5, 1, and 1.5?wt%) have been investigated. PAN/GO composite nanofibers were characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). As demonstrated by the results of tensile testing, mechanical properties of PAN can be effectively enhanced with the addition of GO filler. At 1?wt% of GO filler nanofibers membranes achieved 64.4% rise of tensile strength and 71.4% improvement of Young’s modulus.     

The impact of electronic theses and dissertations: a study of the institutional repository of a university in South Africa

This paper investigates the academic and societal impacts of the engineering electronic theses and dissertations (ETDs) at the North-West University. The citation counts obtained through Google Scholar (GS) and the altmetrics data obtained from Dspace on the North-West University institutional repository are used to determine these impacts. Further, the conversion rates of ETDs from an educational output into an academic research output are determined using data from GS and the North-West University institutional repository. The results show that the 612 theses and dissertations attracted 931 citations which translates to 1.52 citations per thesis on average. A total of 41.2% theses and dissertations received at least one citation and the conversion rate into academic research output was 16.8%. The conversion rates in the last 3 years that are part of this research is 27.3% which suggests an improvement. An average of 323 PDF views were received per thesis. The citation and PDF views data show that the Engineering ETDs have commendable academic and societal impacts. Nonetheless, the academic impacts show scant correlation with the societal impacts although some positive trends are noticeable when looking at the origin of PDF views and citations by country.     

高分子量聚丙烯腈中空纤维膜铸膜液流变性能的研究

采用气压式毛细管流变仪对聚丙烯腈/二甲基乙酰胺/聚乙烯吡咯烷酮(PAN/DMAc/PVP)中空纤维铸膜液的流变性能进行了研究.实验结果表明,该铸膜液属假塑型流体.物料性质,如PAN分子量、PAN质量分数、添加剂质量分数会影响体系的流动性能.PAN分子量为Mη=13.1×104、PAN质量分数为14%、添加剂PVP质量分数为10%时,该铸膜液的流动性最好.另外,温度对体系的流动性也有影响.对特定的PAN铸膜体系来说,升高温度使体系的黏度降低,流动性变好;而当体系中PAN分子量增大、PAN质量分数增加时,体系的黏度增大,活化能变大,因而对温度的敏感性也增强.