High‐pressure synthesis of cyclic mesitylacetylene oligomer

Reaction of mesitylacetylene was carried out by annealing under high pressure (0.13 and 0.52 GPa). The products obtained were classified into soluble and insoluble products in chloroform. The insoluble product reacted under 0.13 GPa was the mesitylacetylene polymer. The soluble product reacted under 0.13 GPa was classified as the monomer and the oligomer [number‐average molecular weight (M̄_n): 390, weight‐average molecular weight (M̄_w): 453, Oligomer yield (O_y): 36%]. The oligomer yield was accelerated by pressure [pressure: 0.13–0.52 GPa, M̄_n: 390–315, M̄_w: 453–968, O_y: 36–98%]. Field desorption mass spectrum showed that the oligomer had cyclic structure. The result of the elementary analysis revealed that the insoluble product reacted under 0.52 GPa was a polycyclic aromatic compound. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1539–1542, 1999     

PET环状低聚物的表征及其开环聚合研究

以对苯二甲酸双(2-羟乙基)酯(BHET)为原料,通过悬浮法合成了聚对苯二甲酸乙二醇酯(PET)的环状低聚物(COET),对COET的结构和性能进行了表征;研究了COET的开环聚合及其在PET熔体中的开环聚合,探究了开环聚合工艺条件对其聚合产物的影响.结果表明:由核磁共振氢谱和碳谱表征悬浮法合成产物为COET,其主要以...     

Lipase-catalyzed synthesis and characterization of a novel linear polyamidoamine oligomer

A linear polyamidoamine oligomer was obtained by polymerization of ethyl acrylate and N-methyl-1,3-diaminopropane, catalyzed by the Candida antarctica lipase. Depending on the reaction conditions such as substrates concentration, solvent and enzyme:substrate ratio, the enzyme catalyzes the polymerization reaction or Michael adducts formation. The polymeric material, characterized by FTIR, ¹H and ¹³C NMR and UV-MALDI-TOF-MS, shows low molecular weight and high monodispersity. The activity showed by C. antarctica lipase in the polymerization reaction is highly selective and allows to obtain a product with potential biomedical applications in mild condition reactions and low environmental impact.     

Preparation,dielectric property and microwave absorption property of Cu doped SiC nanopowder by combustion synthesis

Abstract

Cu doped SiC nanopowders have been prepared via combustion synthesis, using silicon powder and carbon black as the raw materials, copper powder as the doping source and polytetrafluoroethylene as the chemical activator respectively. The microstructure of prepared nanopowders has been characterised by X-ray diffraction and scanning electronic microscope. The electric permittivities of prepared SiC nanopowders in the frequency range of 8·2–12·4 GHz have been determined. Results show that prepared β-SiC nanopowders have fine spherical particles and narrow particle size distribution, and a quantity of SiC whisker increases with increasing Cu doping content. The Cu₃Si impurity has been generated when Cu content is up to 10%. The β-SiC doped with 10% Cu has the highest real part ?′ and dielectric loss tanδ values. The 5% Cu doped SiC nanopowder with matching thickness of 2 or 2·5 mm exhibits the best microwave absorption properties in the frequency range of 8·2–12·4 GHz.     

新型齐聚物的合成与性能研究

以水为溶剂,将马来酸酐、次磷酸或它的盐,按一定物质的量比加入反 应溶液中,并且滴加引发剂进行反应,所制所的齐聚物经过预膜试验发现有膜下腐蚀,加入亚磷酸进行膦化便可解决上述问题。所制成的新型齐聚物具有高密度支链膦酸基官能团,该产品经过阻垢、预膜、绘蚀测定后,认为可作为水处理的阻垢缓蚀剂。     

High-pressure synthesis of TaN compacts with high hardness and thermal stability

High-hardness TaN compacts with a diameter and height of 6 mm were synthesized through the phase transformation of CoSn-type into WC-type TaN under experimental conditions of high temperature and high pressure. The Vickers hardness of WC-type TaN compacts obtained at the pressure of 5 GPa and the temperature of 1873 K is found to be ~21.5 ± 1.5 GPa with a load of 3 Kg, which is comparable to that of the pure tungsten carbide compact (~20 GPa) and higher than those of ultrahigh temperature ceramics ZrB₂ and HfB₂ under the same load. The high hardness of WC-type TaN compacts presented in this work is attributed to the deviatoric strain and well-bonded nanograins. The synthesized WC-type TaN compacts also possess a high oxidation temperature (1072 K). These results suggest that the WC-type TaN with high hardness and high thermal stability holds great promise for industrial applications.     

聚羰基脲低聚物的绿色合成研究

在充入CO2的高压釜中,以尿素和碳酸二甲酯为原料通过酯的氨解反应合成了聚羰基脲低聚物,产率最高达88.32%,副产物甲醇可以与CO2利用已有技术再转化为碳酸二甲酯,因而本工艺原料利用率高、成本较低。目标产物通过13C-NMR、傅里叶变换红外光谱仪(FT-IR)、元素分析确定是平均聚合度为5的聚羰基脲。探究了CO2通入压力、反应温度、反应时间对产率的影响并初步探讨了CO2的作用机理。     

Role of surface defects in the third order nonlinear optical properties of pristine NiO and Cr doped NiO nanostructures

Pristine NiO and 2% Cr doped NiO nanostructures are successfully synthesized by the modified auto–combustion method for the determination and improvement of linear and nonlinear optical behaviours, and for identifying them as suitable materials for optical limiting applications. Vibrational and linear optical properties of both nanostructures are investigated, and structural and morphological studies are carried out using XRD, FE-SEM, and HR-TEM. From the Kubelka-Munk model, the energy band gaps for pristine and doped samples are found to be 3.52 eV and 3.44 eV, respectively. Both pristine as well as Cr-doped NiO nanostructures reveal substantial nonlinear optical behaviour at the excitation wavelength of 532 nm, arising from the presence of strong reverse saturable absorption. The third order nonlinear absorption coefficients have values of the order of 10^?10 m/W and 10^?6 m/W, under pulsed (5 ns) and continuous wave laser excitations, respectively. These values confirm the suitability of these nanostructures for fabricating efficient optical limiting devices for safeguarding human eyes and optical sensors from hazardous laser radiation.     

Synthesis, properties of fullerene-containing polyurethane-urea and its optical limiting absorption

Based on the typical two step polyurethane-urea synthesis, self-crosslinkable polyurethane-urea compounded of poly(tetramethylene oxide), MDI (4,4′-diphenylmethane diisocyanate) and extended by AEAPS (aminoethylaminopropyltrimethoxysilane) were prepared. On the other hand, a C60-amine adducts by reacting C60 with excessive APES (aminopropyltrimethoxysilane) were synthesized and introduced into the polyurethane-urea to form the homogenous and transparent C60 containing polyurethane-urea films. FT-IR, UV, Electron Spectroscopy for Chemical Analysis, Wide-angle X-ray diffractions, dynamic mechanical thermal analysis and mechanical properties of samples were recorded. The optical limiting properties were also measured. The results show that the C60 containing polyurethane-urea is a kind of homogenous material with the ranging of C60 content. The solution state before processing makes it easy to be cast as variety configurations. With the difference in C60 content in polymers, the optical limiting properties are various and the required transmittance and transmitted energy can be altered with the C60 contents in polymers.     

Mechanical and optical property assessment of irradiated SiC with displaced atoms

Explicit method to emulate neutron radiation effects on key ceramic materials is lacking, with most literatures stressing direct comparison between radiation parameters while underestimating the defect-property correlation. Herein, the evolutionary correlation between defects of displaced atoms and properties in 6H-SiC was systematically investigated, aiming to found the basis for performance assessment of neutron irradiated material. The point defect accumulation, defect cluster growth, and homogeneous crystalline-amorphous (c-a) transition were recognized, with different stages of Young’s modulus reduction and optical absorption enhancement accordingly triggered. Specifically, the relaxation process accompanying the c-a transition was believed to induce the final reduction stage of Young’s modulus and account for the conflict between existing research results. Average lattice disorder, regarded as the average density of displaced atoms, was proved to be the success reference in the property assessment approach, paving the way for the extension into high temperature radiation where more defect types coexist.     

脱氢枞酰胺乙基磺酸盐表面活性剂合成与性能研究

以脱氢枞酸为主要原料合成了脱氢枞酰胺乙基磺酸钠表面活性剂,用红外光谱对其结构进行了表征。在25℃下测定了其表面张力,得到cmc=1.0×10-4mol/L,cγmc=31.99 mN/m。在25℃下用改进Ross-Miles法测定其泡沫性能,ρ(活性剂)=0.6 g/L时,起泡高度达到150 mm以上,稳泡性t1/2=16 min。在45℃条件下测定活性剂与大庆采油四厂脱水脱气原油的界面张力,w(活性剂)=0.2%时,体系的界面张力达到9.3×10-3mN/m;考察了NaCl对界面性能的影响,(ρNaCl)=0.3 g/L时,界面张力降低至2.0×10-3mN/m。     

High-pressure synthesis and characterization of diamond from a sulfur–carbon system

Diamond crystallization in the sulfur–graphite system has been studied at P=7 GPa and T=1750–1850°C in experiments with a duration up to 7 h. It has been found that diamond nucleation and crystallization occur both at the interface between the graphite and sulfur melt and directly within the carbon–saturated sulfur melt. Diamond crystals with maximum size up to 500 μm were synthesized. The crystals had cube–octahedral morphology with minor faces of trapezohedron. Goniometric measurements revealed that crystallographic indexes of the trapezohedron faces are {411} and {944}. Spectroscopic characterization of sulfur–synthesized diamonds by means of infrared absorption microscopy and cathodoluminescence has been made for the first time. It was found that crystals contain nitrogen impurity in the form of A aggregates with concentration up to approximately 700 at. ppm. An absorption band with a maximum at 1050 cm⁻¹, whose origin is not clear, was observed in the IR spectra. The cathodoluminescence spectra of these diamonds were found to comprise of the well-known H3 and 575-nm systems as well as a broad emission band.     

应用微反应器合成环状碳酸酯的工艺与模拟

应用分子内双功能催化剂，设计了利用环氧烷烃和CO2偶合反应合成环状碳酸酯的连续微通道工艺，考察了催化剂用量、反应温度、反应压力、CO2与环氧烷烃比例对反应的影响。实验结果显示，即使在较温和条件（120 ℃、1.5 MPa）和较低催化剂用量下（0.5‰ mol），环氧烷烃仍可高效地转化为相应的环状碳酸酯，反应30 s环氧烷烃转化率可达78%。在相同条件下，微通道反应工艺转化速率是传统釜式反应工艺的1.8倍。这表明所设计的微通道反应工艺对反应过程中气液混合传质具有显著强化作用。通过fluent软件模拟微通道中气液混合情况，研究了不同工况对环氧烷烃与CO2混合效果的影响。结合实验结果分析表明，影响气液混合的关键因素为气体扰动。     

循环伏安法沉积Bi-Te合金及其光学性能的研究

采用循环伏安法成功在Ti膜上沉积得到了可见光到近红外波段低反射率的Bi-Te合金镀层,并研究了镀层的结构、形貌和光学性质。X射线衍射分析结果表明沉积得到的镀层是以Bi2Te3为主的多晶结构;扫描电子显微镜分析显示利用循环伏安法可以得到类似"黑硅"的有序粗糙表面;紫外可见近红外分光光度计对其光学性能的测试表明该镀层在300～1 700 nm整个波段的反射率在5%以内。     

丙烯酸酯系共聚物高吸油树脂的合成及性能研究

以甲基丙烯酸十八酯（SMA）、丙烯酸丁酯（BA）和苯乙烯（St）为单体，二乙烯苯（DVB）为交联剂，过氧化苯甲酰（BPO）作引发剂，采用悬浮聚合法合成高吸油性树脂。以吸油率作为性能指标，利用正交试验分析各种反应因素对树脂吸油率的影响，得出最佳工艺条件，并系统研究了体系中单体组成及配比、交联剂、引发荆、分散剂及致孔剂用量等因素对吸油树脂性能的影响。结果表明，当m（SMA）：m（BA）：m（St）=42：58：8，ω（BPO）=1.0％，ω（DVB）=1．2％，ω（PVA）=0．2％，ω（CHCl3）=10％时，树脂吸油率达到最大，可吸收四氯化碳23．61g／g，甲苯22．58g／g，笨18．85g／g，柴油14.8g／g。树脂的保油率在90％以上。经过热重分析可知，树脂的稳定性比较好，分解温度在333．7℃。     

两性纤维素醚的合成及流变性能的研究

以二甲基烯丙基胺(DMAA)、氯乙酸钠和次氯酸为原料合成两性醚化剂3-氯-2羟-丙基二甲铵基乙酸盐(CCAH)。后在自制碱催化剂存在下,与工业羟乙基纤维素(HEC)干法制备两性纤维素醚(AHEC),同时探讨了两性离子羟乙基纤维素醚在水溶液中的流变性能。结果表明,两性羟乙基纤维素醚的溶液呈现非牛顿流体特征,具有剪切变稀特性。随着溶液质量浓度增大其表观粘度增大,在一定浓度的盐溶液中,AHEC具有明显的反聚电解质溶液性质。     

纳米二氧化钛粉的水热合成与光催化性能研究

以钛酸四丁酯(TBOT)为钛源,NH4Cl为分散剂,不经高温煅烧,直接低温水热合成纳米TiO2粉。采用FT-IR,XRD,TEM等方法研究了低温高压水热条件和NH4Cl浓度对TiO2粉的相组成、组织形貌的影响,并研究了其对甲基橙光催化降解的性能。结果表明,纳米TiO2具有锐钛矿相结构且无有机物残留。晶粒尺寸随着水热合成温度增高(120~180℃)而增大,随着NH4Cl/TBOT的摩尔比(0.1~0.5)增加而减小,但纳米粉逐渐出现团聚现象。水热温度为160℃以及NH4Cl/TBOT=0.25条件下合成的锐钛矿相纳米TiO2具有良好的分散性,其颗粒尺寸约为14 nm,且有高的光催化降解甲基橙的能力。     

Molten salt synthesis and antioxidation property of SiC-coated mesocarbon microbeads

Mesocarbon microbead (MCMB) is a prospective candidate as the raw material for nuclear graphite. However, the poor resistance to high-temperature oxidation limits its application. Herein, a dense SiC coating was prepared by molten salt synthesis on the surface of MCMB to improve its antioxidation performance. The effect of molten salt synthesis reaction time on the phase composition, microstructure, and antioxidation performance of the SiC-coated MCMB particles was investigated. A theoretical model was established to explain the SiC coating growth rule well, in conformity with the carbon vacancy diffusion mechanism in SiC coating. The SiC coating synthesized for 7 h with the thickness of .385 µm remarkably promoted the high-temperature antioxidation property of MCMB. The kinetics analysis indicated that the SiC coating obstructed the oxygen diffusion effectively during the oxidation process. The as-fabricated SiC-coated MCMBs with good oxidation resistance show great promise for application in nuclear industry and other antioxidative fields.     

马来松香聚甘油酯的合成及性能研究

马来松香与聚甘油反应,合成了一种非离子表面活性剂马来松香聚甘油酯(PGMRE)。对产品结构进行了红外光谱分析,测定了产品的表面物理化学性能,合成产品临界表面张力为39 9mN/m～46 0mN/m,临界胶束浓度在9 4×10-4mol/L～2 3×10-3mol/L数量级,钙皂分散指数是9 0%～26 7%,与松节油之间的界面张力为8 0mN/m～13 9mN/m,对松节油乳化力为38s～100s,泡沫性能是11mm～65mm,润湿力为70s～102s。系统研究了甘油聚合度对产品表面物理化学性能的影响。并与聚甘油硬脂酸酯(PGSE)和聚甘油异硬脂酸酯(PGISE)的表面物理化学性能进行了比较。结果表明PGMRE是一种性能优良的非离子表面活性剂,可作为乳化剂、破乳剂和缓蚀剂等使用。     

几种席夫碱化合物的室温固相合成及二阶非线性光学性质的理论计算

以对乙酰苯胺和6种单取代基苯甲醛为原料,通过室温固相反应合成了6个席夫碱类化合物,用元素分析1、HNMR确定了产物的结构,并对产物做了定性SHG响应以及固体紫外反射光谱的测试。利用密度泛函理论的B3LYP方法,在6-31G水平上对6种化合物进行几何结构优化,在获得稳定构型的基础上,用TDHF/6-31G方法计算了它们的分子二阶非线性光学系数β值。