蜜胺甲醛树脂／聚乙烯醇复合物单晶

三聚氰胺甲醛树脂(MF)为非晶态高聚物,有广泛用途,已有许多改性的MF树脂产品。我们曾认为三聚氰胺甲醛树脂和聚乙烯醇(PVA)复合物中可能有单晶存在。本文对此单晶作进一步的确认。试样制备见前报。 将试样切成约50nm的薄片,用真空镀膜     

三聚氰胺-1,4-环己烷二甲酸结合物微粒体系的共振散射光谱研究及其分析应用

在pH 3.6的乙酸盐缓冲溶液中和聚乙烯醇(PVA)存在下,三聚氰胺(MA)与1,4-环己烷二甲酸(CHDA)发生结合反应形成结合物微粒,该结合物微粒在480 nm处有一个较强的共振散射峰。三聚氰胺质量浓度在0.67～20.0μg/mL范围内与480 nm处的共振散射光强度呈线性关系,其检出限为12μg/L。研究了共存物质对CHDA共振散射测定三聚氰胺的影响,方法的选择性比较好,应用于合成废水测定,测定结果的相对标准偏差为2.3%～3.7%(n=5),回收率在94.8%～103.8%之间。     

C3N6H6(H3BO3)2的合成及晶体结构

以三聚氰胺和硼酸为原料在水溶液中反应合成出了一种新的BCN化合物先驱体C3N6H6(H3BO3)2。XRD表征结果表明三聚氰胺和硼酸的最佳配比为1∶3(物质的量比)。用单晶X-射线衍射分析法测定了该化合物的晶体结构。该化合物属单斜晶系,空间群为P21/C,晶胞参数为a=0.3597(7)nm,b=2.0105(4)nm,c=1.4112(3)nm,α=90,°β=92.07(3),°γ=90,°V=1.0199(3)nm3,Z=4,D c=1.627g.cm-3,μ(MoKα)=0.144mm-1,F(000)=520。晶体结构经全矩阵最小二乘法修正,最终可靠因子R1=0.0519,wR2=0.1361。该化合物是由C3N6H6分子和H3BO3分子通过氢键加合组装形成的三维超分子结构化合物。     

发光配合物1,2-二(2-吡啶甲酰胺基)苯锌的研究

合成了发光配合物1,2-二(2-吡啶甲酰胺基)苯锌(1)及其双分子-4,4'-联吡啶复合物(2).用X射线单晶衍射分析方法得到了配合物2的单晶结构.该晶体属三斜晶系,P1空间群,晶胞参数为a=0.96251(6)nm,b=1.50122(9)nm,c=1.64252(12)nm,α=106.958(2)°,β=105.362(3)°,γ=102.978(2)°,V=2.0685(2)nm³,Z=2,D_c=1.563g/cm³,F(000)=1000,R₁=0.0367,wR₂=0.0898.研究表明,晶体2由1个4,4'-联吡啶通过配位键连接2个化合物1分子构成.晶体2是由沿晶体学b和c轴方向的一维分子柱堆积而成.考察了配合物1的发光性质,配合物1可作为发光材料效率很高的电致发光器件制备.     

直接置换插层法0.85 nm水合高岭石的制备

以高岭石/尿素插层复合物作为中间相,利用简单的直接置换插层法制备了d001=0.85 nm的水合高岭石。利用X射线衍射、红外光谱、扫描电镜表征处理前后高岭石结构与形貌的变化。结果表明:尿素插层后的高岭石层间距从d001=0.72 nm增大到d001=1.08 nm,经不同温度酸洗或水洗后,插层复合物转变成层间有水分子的水合高岭石(d001=0.85 nm),且高岭石晶粒厚度明显从约25 nm减小到约10 nm。在高温条件下形成的水合高岭石含量最高,90℃水洗时d001=0.85 nm水合高岭石的转化率接近70%,这种水合高岭石具有进一步的置换插层能力,是一种制备其他高岭石插层复合物很好的前驱体。与乙二醇形成d001=1.10nm乙二醇/高岭石插层复合物,其置换率达到100%。     

非共价型弱作用NAH+·Pic-有机复合物的合成及结构与量子化学研究

烟酰胺(NA)与苦味酸钴[Co(Pic)2·4H2O]在乙醇水混合液中反应,制得氢键连接的有机复合物单晶,该晶体属单钭晶系,空间群为P-1,晶胞参数为a=0.7810(1)nm,b=2.5079(4)nm,c=0.8138(2)nm,β=118.41(10)°,V=1.3968(4)nm3,Z=4,Dc=1.670g/cm3,F(000)=720.运用Gaussian 98量子化学程序包,对该化合物进行从头算研究,探讨了化合物的各原子净电荷分布、稳定性、一些前沿的分子轨道能量和组成特征,并对分子识别、分子间和分子内交互作用进行了讨论.     

嘧霉胺合成、晶体结构及量子化学计算

用自制的嘧霉胺在无水乙醇溶液中培养出单晶,首次采用X射线单晶衍射法测定了嘧霉胺晶体结构,其晶体属三斜晶系,空间群为P2（1）/n.晶胞参数为：a=0.7532（1）nm,b=1.1701（1）nm,c=1.4640（2）nm,α=68.361（2）°,β=85.554（2）°,γ=71.291（2）°,V=1.1348...     

9,9-二甲基-2-(4-硝基苯基)-4-苯基-9H-吡啶并[1,2-a]吲哚高氯酸盐的微波合成及晶体结构

在微波辐射条件下,由2,3,3-三甲基-3H-吲哚高氯酸盐、1-苯基-3-(4'-硝基苯基)-2-丙烯-1-酮与哌啶合成了标题化合物.在甲醇/乙醇=1/1(V/V)中培养出单晶,通过X射线单晶结构分析法测定了分子结构和晶体结构,晶体属于单斜晶系,P2(1)/n空间群,其晶胞参数为:a=1.2507(4)nm,b=1.4378(4)nm,c=1.3033(4)nm,V=2.3366(12)nm3,Dc=1.401g/cm3,μ=0.210mm-1,F(000)=1024,Z=4,R1=0.0553,wR2=0.0732.     

亚甲基蒽苯乙烯吡啶盐的合成、结构及双光子吸收性质

以氯化4-甲基-N-9-亚甲基蒽吡啶盐为原料,合成了一种新型的苯乙烯吡啶盐,通过红外、核磁共振氢谱、碳谱、电喷雾质谱、单晶X射线衍射等测试技术对化合物的结构进行了表征。单晶X射线衍射结果表明,该化合物属于单斜晶系,空间群为P21/c,晶胞参数a=1.255 7(1)nm,b=1.539(1)nm,c=2.220 2(8)nm,β=101.099(1)°,V=4.210 5(4)nm3,Z=4,Dc=1.159 g/cm3。用1 064 nm皮秒脉冲激光研究其三阶非线性光学特性,双光子吸收系数β=0.028 cm/GW,吸收截面为σ=8.68×10-48cm4.s.photon-1,表明目标化合物具有良好的三阶非线性光学性质。     

二水合L－精氨酸顺丁烯二酸加合物的制备和晶体结构

制备了具有非线性特性的标题化合物,以降温法培养出25mm×40mm×13mm大尺寸单晶,该单晶在1064nm的Nd³⁺:YAG激光束照射下,产生绿色的532nm倍频光,以X射线衍射法测定了此1:1:2加合物的晶体结构,晶体属P₁空间群,a=0.5269(1)nm,b=0.8040(1)nm,c=0.9783(2)nm,α=106.14(1)°,β=97.27(1)°,γ=101.64(1)°,Z=1,R=0.062.L-精氨酸与顺丁烯二酸之间以氢键相联,形成三维氢键网络。     

纳米羟基磷灰石/聚乙烯醇/明胶复合材料的结构和力学性能

采用机械共混法、原位化学合成法、原位水热法制备了一系列纳米羟基磷灰石/聚乙烯醇/明胶(n-HA/PVA/GEL)复合材料;利用X射线衍射仪、透射电镜及傅立叶变换红外光谱仪等分析了复合材料的结构;利用材料试验机测定了复合材料的力学性能.结果表明,利用原位水热法可使n-HA有效地在PVA高分子中均匀分散,并提高n-HA颗粒...     

Synthesis and characterization of perovskite-type La1-yCayMn1-xB″xO3±δ nanomaterials (B″ = Ni,Fe; x = 0.2, 0.5; y = 0.4, 0.25)

Perovskite-type nanomaterials of the compositions La_1-yCa_yMn_1-xB″_xO_3±δ with B’’ = Ni, Fe; x = 0.2, 0.5 and y = 0.4, 0.25 were prepared using two different preparation routes (synthesis by precipitation and the PVA/sucrose method) at 500 °C–700 °C. The calcined products of the syntheses were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and physisorption measurements. The materials from the PVA/sucrose method contain particles with diameters from 33 nm to 48 nm, generate specific surface areas up to 33 m²/g and form pure compared to 45 nm–93 nm and up to 18 m²/g from precipitation method which contain a significant amount of sodium ions. The agglomeration process was analyzed for one nanomaterial (B’’ = Fe, x = 0.2, y = 0.4) from the PVA/sucrose method using temperature dependent XRD showing only a slight growth (4.3%) of nanoparticles at 600 °C. The materials from the PVA/sucrose method turned out to be more suitable as electrode materials in electrochemical applications (SOFC, sensors) because of smaller particle sizes, higher specific surface areas and purity.     

热塑性淀粉/聚乙烯醇/蒙脱土三元纳米复合材料

用熔融挤出的方法制备了甘油塑化热塑性淀粉（TPS）/聚乙烯醇（PVA）/蒙脱土（MMT）纳米复合材料,添加蒙脱土和聚乙烯醇用以提高热塑性淀粉材料的力学性能。 在相对湿度50%的条件下,复合材料的XRD衍射谱图和透射电子显微镜测试表明,MMT以剥离状态均匀分布在TPS/PVA基体中;力学测试表明,当MMT的质量分数从0％增至5％时,复合材料的力学性能明显提高。 当蒙脱土的质量分数为3%时,复合材料最大抗张强度达到13.24 MPa,杨氏模量达到61.46 MPa。 这说明蒙脱土在复合材料中可以起到物理交联点的作用,提高了复合材料的力学性能。     

The effect of silica morphology on properties of PVA/silica nano-composites

Two kinds of poly(vinyl alcohol)(PVA)-silica composites were prepared with different methods. One composite was prepared by directly mixing PVA with 80 nm silica nano-particles which were made from tetraethoxysilane(TEOS). The another was obtained by the mixing PVA and hydrolyzed TEOS in the presence of acid-catalyst. The properties of the two PVA/silica hybrids were characterized by means of scanning electron microscopy(SEM), UV-Visible spectroscopy,solubility tests, limiting oxygen index(LOI) test, tensile test and dynamical mechanical analysis(DMA), respectively. The results indicate that PVA-TEOS composites(PT for short) display more transparency than PVA-silica nano-particles hybrids(PS for short). At the same time, The PT composites presented more excellent performance than PS in water resistance, fire resistance and mechanical properties. Moreover, the Tg of PT increased with increasing TEOS content, while that of PS decreased.     

细菌纤维素(BC)增强PVA/PVP复合水凝胶的制备及性能表征

通过冷冻-熔融法制备了细菌纤维素/聚乙烯醇/聚乙烯吡咯烷酮(BC/PVA/PVP)双网络复合水凝胶,并采用X射线衍射,红外光谱,扫描电镜,力学性能测试等手段对凝胶的结构和性能进行表征.研究发现PVA、PVP通过氢键作用均匀地吸附于纤维微丝周围,将BC纤维有效地分开,因而干燥后的复合凝胶在热水中浸泡后仍可恢复原状;X射线...     

Surface modified graphene oxide/poly(vinyl alcohol) composite for enhanced hydrogen gas barrier film

A series of novel polyethyleneimine (PEI) modified graphene oxide (PEI-mGO) filled poly(vinyl alcohol) (PVA) nanocomposite (PEI-mGO/PVA) films were prepared by solution-casing for hydrogen gas barrier applications. Hydrophilic PEI was used to simultaneously reduce and modify graphene oxide sheets, thereby facilitating a homogeneous dispersion of PEI-mGO in the PVA matrix. The effects of PEI-mGO on the morphology and properties of the nanocomposite films were examined by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and field emission scanning electron microscopy. Analogous GO/PVA composites were also prepared and characterized for comparative purposes. The PEI-mGO/PVA nanocomposites showed higher thermal and mechanical stability as well as remarkable improvement in hydrogen gas barrier properties compared to the PVA film; specifically, the PEI-mGO/PVA film having 3.0 wt% of PEI-mGO content exhibited almost 95% decrease in GTR and permeability values compared to PVA film.     

A novel form-stable paraffin-based hydroxyl-terminated polybutadiene binder containing microencapsulated paraffin wax

Leakage and incompatibility of paraffin wax (PW) in hydroxyl-terminated polybutadiene (HTPB) binders is a major obstacle to its application in polymer-bonded explosives (PBX). In order to solve this issue, we designed a microencapsulated PW (MePW)/PW/HTPB composite in this paper. Melamine–formaldehyde-shelled MePW (MF MePW)/PW/HTPB composites with different contents of MePW and PW were prepared by cast molding method. The chemical composition, crystallinity and microstructure of MePW/PW/HTPB composites were analyzed with Fourier transformed infrared spectroscopy, X-ray diffraction and scanning electron microscope, respectively. The results showed that PW and MF MePW have been uniformly dispersed in HTPB without any chemical interaction. Moreover, differential scanning calorimeter analysis, thermal gravimetric analyzer, thermal cycling test, leaking test, tensile and compressive test were used to investigate the thermal and mechanical properties of these composites. The composites have high latent heat and good thermal reliability. The thermal stability, tensile and compressive strength of MePW/PW/HTPB composites were dramatically increased with the increasing mass fraction of MePW. The introduction of MePW can obviously prevent the leakage of PW in both HTPB binders and PBX. Consequently, it is anticipated that MePW can be used in the next-generation of paraffin-based high-temperature PBX systems.

     

PVA/PEG/Mg(OH)_2复合材料体系的非等温结晶行为

采用熔融共混法,以聚乙二醇(PEG)为增塑剂、Mg(OH)2为稳定剂制备了聚乙烯醇(PVA)/PEG/Mg(OH)2复合材料。利用差示扫描量热仪(DSC)考察了PVA/PEG/Mg(OH)2复合体系中PVA的非等温结晶行为。结果表明:在熔融过程中PEG与PVA大分子形成的分子间氢键,破坏了PVA分子内或分子间的氢键,改善了PVA的热塑性能,使研究其熔融结晶行为成为可能。     

层状钙钛矿型氧化物BaYb_xMn_(1-x)O_3的制备与结构分析

以BaCO_3,MnCO_3和Yb_2O_3为原料,采用传统固相烧结法,在1300 ℃下合成了两种新的化合物12R-Ba_4YbMn_3O_(11.5)和10H-Ba_5YbMn_4O_(14.5).用X射线能谱(EDS)微区成分分析和氧化还原滴定法确定两种化合物的化学式,用选区电子衍射(SAED)以及粉末X射线衍射Rietveld结构精修等手段分析测定了对化合物的晶体结构.12R-Ba_4YbMn_3O_(11.5)的空间群为R-3m,晶胞参数为a=0.578 nm,c=2.850 nm;10H-Ba5 YbMn_4O_(14.5)的空间群为P63/mmc,晶胞参数为a=0.575 nm,C=2.377 nm.     

Preparation of Ag/C fiber with nanostructure through in situ thermally induced redox reaction between PVA and AgNO3 and its catalysis for 4‐nitrophenol reduction

A novel synthesized Ag/C fibrous catalyst based on in situ thermally induced redox reaction of PVA/AgNO₃ composite fibers was proposed. Utilizing the plasticization and complexation of AgNO₃ solution, the melt spinning of PVA/AgNO₃ composites was accomplished. Through the in situ thermally induced redox reaction on PVA/AgNO₃ composite fibers combined with carbonization of PVA and reduction of Ag+, the synthesized Ag/C fibrous catalyst was prepared with nanosilver particles with average diameter of 130 nm immobilized on the loose microstructural carbon layers. The synthesized Ag/C fibrous catalyst exhibited excellent catalytic activity and reused for at least five cycles for the reduction of 4‐nitrophenol, which may hold great promise in effective and eco‐friendly waste water treatment.