电纺聚酰亚胺/氧化石墨烯复合纳米纤维膜的制备及性能研究

采用静电纺丝技术制备了氧化石墨烯(GO)不同含量的聚酰亚胺/氧化石墨烯(PI/GO)复合纳米纤维膜,并研究其结构、表面润湿性、热氧化特性、力学性能和过滤性能。结果表明,添加GO有利于纳米纤维的直径分布趋于均匀,在GO用量为0.5%(wt,质量分数)条件下,PI/GO复合纳米纤维膜平均纤维直径最小为(231±36)nm,孔隙率高达89.61%,拉伸强度为14.43MPa,杨氏模量为1.36GPa,断裂伸长率为10.84%,热氧化稳定性较纯PI纳米纤维膜提高了15℃,过滤效率最高达到96.5%,较纯PI纳米纤维膜提高了8%。添加GO能有效提高PI/GO复合纳米纤维膜的疏水性、力学性能及热氧化稳定性。     

静电纺丝素/聚左旋乳酸复合纳米纤维膜的制备及性能研究

采用静电纺丝技术成功制备丝素(SF)/聚左旋乳酸(PLLA)复合纳米纤维膜,对其理化性能进行研究。本实验以六氟异丙醇(HFIP)为溶剂,将SF与PLLA按100∶0、70∶30、50∶50、30∶70、0∶100的质量比共混进行电纺,制备的5种材料用戊二醛(GTA)蒸汽交联48h。通过扫描电镜(SEM)、拉伸性能测试、X射线衍射(XRD)、热重分析(TG)和亲水角等方法对其理化性能进行表征。结果显示制备的SF/PLLA复合纳米纤维平均直径在162~680nm之间,并随着PLLA含量的增加而增加;交联后纤维虽有溶胀,但仍然保持了纤维形貌;SF/PLLA复合纳米纤维膜的力学性能、结晶度、热稳定性和疏水性较纯SF明显提高,且随着PLLA含量的增加而增加,有望成为一种新型的组织工程支架材料。     

PBT/PVA复合纳米纤维膜的制备及性能研究

通过将聚乙烯醇(PVA)与聚对苯二甲丁二醇酯(PBT)不同比例混合进行静电纺丝,对所得PBT/PVA复合纳米纤维膜通过扫描电子显微镜(SEM)、单轴拉伸测试以及水接触角测试进行了表征。结果显示:PBT/PVA混合溶液的可纺性和所得纤维膜形貌随PVA含量增加而变化;纯PBT纳米纤维膜表现为较低的力学性能和疏水性(水接触角为135°),而少量PVA的混入(PBT/PVA=20/1或10/1)可以有效提高所得纤维膜力学性能和亲水性,尤其10/1的PBT/PVA复合纤维膜在力学性能提高的同时表现为超亲水特性(水接触为0°)。     

取向TSF/PLLA静电纺纳米纤维毡的制备及其生物相容性

利用静电纺丝技术制备了取向的柞蚕丝素/左旋聚乳酸(TSF/PLLA)纳米纤维毡。通过扫描电子显微镜(SEM)、X射线衍射分析(XRD)和拉伸测试分别对TSF/PLLA纳米纤维的形貌、结晶结构及力学性能进行了研究。将人成骨肉瘤细胞(MG-63)种植在TSF/PLLA纳米纤维上,通过荧光显微镜分析和MTT(四甲基偶氮噻唑蓝比色法),观察细胞在材料表面的生长情况,评价纳米纤维的生物学性能。结果表明,TSF含量为10%时,纤维直径分布均匀,结晶度高。但是,TSF含量超过10%后,纤维直径粗细不匀明显,纤维的力学性能下降。与无规纤维毡相比,取向的纳米纤维毡力学性能优异,初始模量高,更能够促进细胞增殖,对细胞的生长行为影响大。     

含有石墨烯和纳晶纤维素的聚氨酯复合纳米纤维

以N,N-二甲基甲酰胺/丙酮(DMF/CP)为混合溶剂,纳晶纤维素(NCC)辅助还原的氧化石墨烯(r GO)和热塑性聚氨酯(TPU)为原料,采用静电纺丝法制备了rGO/TPU复合纳米纤维,通过扫描电子显微镜、透射电子显微镜、激光粒度仪观察了rGO、NCC、复合纳米纤维膜的尺寸和形貌结构,并测试分析了纳米纤维膜的力学性能、热性能和亲水性。结果表明,当m(rGO)/m(TPU)=1.5/100时,复合纳米纤维表面光滑、直径均一,相应的复合纳米纤维膜断裂强度最大(31.98MPa),比纯TPU纳米纤维膜断裂强度(7.92 MPa)提高了303.79%。此外,随着rGO和NCC的加入,复合纳米纤维膜的热稳定性和亲水性增强。     

含环氧-SiC复合微/纳米纤维的层合板制备及其力学性能

应用同轴静电纺丝技术制备环氧包覆纳米SiC 复合微/ 纳米纤维, 将该复合微/ 纳米纤维收集成无纺布薄膜引入层合板层间界面并固化成型, 研究其对层合板力学性能的影响。采用扫描电子显微镜(SEM) 和透射电子显微镜( TEM) 分析了微/ 纳米纤维的形貌和结构, 并测试了微/ 纳米纤维薄膜的拉伸性能。应用三点弯曲、短梁剪切和简支式冲击实验测定了层合板的弯曲性能、层间剪切强度和冲击韧性。结果表明, 一定厚度及一定SiC 含量的微/ 纳米纤维无纺布薄膜对层合板的力学性能无显著影响。      

静电纺丝聚乳酸/磷酸钙复合纳米纤维的力学性能

运用静电纺丝技术制备了聚乳酸纳米纤维和聚乳酸/磷酸钙复合纳米纤维.对两种电纺纳米纤维的表面形态进行了扫描电子显微镜(SEM)的表征及单轴拉力测试表征.讨论了聚乳酸纳米纤维和聚乳酸/磷酸钙复合纳米纤维的力学性能.结果表明掺加了磷酸钙的聚乳酸纳米纤维的力学性能得到明显提高.     

层间环氧纳米纤维薄膜对层合板力学性能的影响

应用静电纺丝技术制备环氧纳米纤维, 将收集的纳米纤维无纺布薄膜插入层合板的层间界面并固化成型, 研究其对层合板力学性能的影响。采用扫描电子显微镜(SEM) 和透射电子显微镜( TEM) 分析了纳米纤维的形貌和尺寸, 并测试了纳米纤维薄膜的拉伸性能; 应用三点弯曲和短梁剪切方法测试了层合板的力学性能。结果表明, 一定厚度的纳米纤维无纺布薄膜对层合板的力学性能无显著影响。因此, 应用该方法可以制备一种新型的功能复合材料。      

MWNTs/PU复合微/纳米纤维的形态及力学性能

应用静电纺丝技术制备多壁碳纳米管/聚氨酯(MWNTs/PU)复合微/纳米纤维 , 将该复合纤维收集成无纺布薄膜 , 采用扫描电子显微镜 (SEM)和透射电子显微镜 (TEM)观察了纤维的微观形貌和结构 , 分别利用X射线衍射(XRD)和差示扫描量热法(DSC)测试了复合纤维的结晶行为及玻璃态转变温度 , 并测试了纤维薄膜的拉伸力学性能随 MWNTs含量的变化关系。结果表明 , 一定含量的 MWNTs能有效地分散于 PU 溶液中 , 并能成功地纺出 MWNTs/PU 复合微/纳米纤维。随 MWNTs在 PU 纤维中含量的增加 , 纤维的直径变细 , 复合纤维的玻璃态转变温度提高。在所研究的含量范围内 , 无纺布的拉伸强度和断裂伸长率随 MWNTs 含量的增加而有所增大。      

PLGA/TSF静电纺纳米纤维的仿生矿化及生物相容性

利用静电纺丝和模拟体液仿生矿化技术制备了聚乳酸-羟基乙酸共聚物/柞蚕丝素/羟基磷灰石((PLGA/TSF/HA)骨组织工程复合支架。通过扫描电子显微镜(SEM)、透射电子显微镜(TEM)、X射线衍射测试(XRD)和热重分析(TG)对复合纳米纤维的形貌结构进行了表征。此外,在复合纳米纤维支架材料上接种人骨髓间充质干细胞(hMSCs),通过四甲基偶氮噻唑蓝比色(Four methyl azo thiazole blue colorimetric,MTT)法,观察细胞在材料表面的生长情况评价纳米纤维的生物相容性。结果显示,PLGA/TSF纳米纤维毡具有精细的三维结构,纤维直径分布均匀,表面光滑。矿化后HA颗粒均匀地分布在PLGA/TSF纳米纤维表面,矿物含量约占63%。与PLGA/TSF纳米纤维支架相比,PLGA/TSF/HA纳米纤维支架的亲水性、生物相容性都得到显著提高。     

Dielectric and pyroelectric properties of Ba-modified lead lanthanum zirconate stannate titanate ceramics

(Pb_0.97−xLa_0.02Ba_x)(Zr_0.75Sn_0.12Ti_0.13)O₃ ceramics in the composition range 0.1 ≤ x ≤ 0.16 were prepared by conventional solid state reaction process. On increasing Ba content from 0.1 to 0.16 mol, the specimens underwent phase transition from the first order to the second order and the Curie temperature decreased from 85 to 35 °C. With x = 0.16, the specimen showed good pyroelectric properties for practical applications. When a 500 V/mm dc bias field was applied, the specimen showed the maximum pyroelectric coefficient of 5800 μC/m² K and figure of merit of 58 × 10⁻⁵ Pa^−0.5 at Curie temperature.     

Microstructure and optical properties of plasmapolymer thin films with embedded silver nanoparticles

Plasmapolymer thin films with embedded silver nanoparticles were deposited by simultaneous plasma polymerization and metal evaporation. The particle size and shape were determined by transmission electron microscopy (TEM) and analysed by optical image processing. The optical properties in the UV/ VIS/NIR spectral region were determined by the plasma resonance absorption of the silver particles. Transmittance spectra were calculated with the Bergman effective medium theory and compared with experimental spectra.     

Engineering properties of concrete containing natural zeolite as supplementary cementitious material: Strength,toughness, durability,and hygrothermal performance

A complex analysis of engineering properties of concrete containing natural zeolite as supplementary cementitious material in the blended Portland-cement based binder in an amount of up to 60% by mass is presented. The studied parameters include basic physical characteristics, mechanical and fracture–mechanics properties, durability characteristics, and hygric and thermal properties. Experimental results show that 20% zeolite content in the blended binder is the most suitable option. For this cement replacement level the compressive strength, bending strength, effective fracture toughness, effective toughness, and specific fracture energy are only slightly worse than for the reference Portland-cement concrete. The frost resistance, de-icing salt resistance, and chemical resistance to MgCl₂, NH₄Cl, Na₂SO₄, and HCl are improved. The hygrothermal performance of hardened mixes containing 20% natural zeolite, as assessed using the measured values of water absorption coefficient, water vapor diffusion coefficient, water vapor sorption isotherms, thermal conductivity, and specific heat capacity, is satisfactory.     

Facile preparation of poly(vinyl alcohol) nanocomposites with pristine layered double hydroxides

In this paper, nano-sized Mg–Al layered double hydroxide (LDH) was synthesized by a fast nucleation and slow aging method. The structures of LDH were characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM) and photon correlation spectroscopy (PCS). Poly(vinyl alcohol) (PVA) nanocomposites with different LDH loadings were prepared by water solution casting method. TEM observations show that the LDH nanoplatelets are uniformly dispersed in the PVA matrix. Tensile tests indicate that the elastic modulus and the tensile strength of PVA are improved by about 15% and 54%, respectively, when incorporating with 2 wt% LDH. The improvement of mechanical properties of PVA can be attributed to fine dispersion of LDH, good compatibility and strong interaction between PVA and LDH. In addition, the presence of LDH decreases the decomposition rates at the second stage and improves the amount of residues of PVA. Meanwhile, the transparency of the nanocomposite films is maintained compared with neat PVA.     

X-cor夹层结构的力学性能试验研究

X-cor夹层结构比强度高,比刚度大,有望取代传统蜂窝夹层结构作为航空航天器的主承力结构材料。采用真空固化成型工艺,通过改变Z-pin的植入参数制备了X-cor夹层结构,研究了Z-pin植入角度、植入间距和直径对其平压、剪切和拉伸性能的影响。研究结果表明,Z-pin的植入参数对X-cor夹层结构的力学性能影响显著。随Z-pin植入角度的增加X-cor夹层结构的平压性能降低,剪切性能增强,拉伸模量减小,拉伸强度先增加后减小。随Z-pin植入间距和直径增加,X-cor夹层结构力学性能均增加。与泡沫夹层结构相比,X-cor夹层结构压缩、剪切和拉伸模量的测试值分别提高了1.26～5.15倍、2.50～13.56倍和1.90～2.71倍,压缩、剪切和拉伸测试值分别提高了1.63～9.20倍、1.28～2.03倍和1.01～2.30倍。     

Properties of high performance concrete containing fine-ground ceramics as supplementary cementitious material

This paper presents experimental work regarding the basic physical characteristics, mechanical and fracture-mechanics properties, durability characteristics, hydric and thermal properties of high performance concrete (HPC) with up to 60% of Portland cement replaced by fine-ground ceramics. Experimental results show that the amount of the ceramics in the mix is limited mainly by the resistance against de-icing salts which is found satisfactory only up to the cement replacement level of 10%. The mechanical and water transport properties are not significantly impaired by ceramic additions of up to 20%, whereas the effective fracture toughness, specific fracture energy, and chemical resistance (to MgCl₂, NH₄Cl, Na₂SO₄, HCl) are effectively maintained up to 40%. The frost resistance, water vapor transport and storage parameters and thermal properties are not significantly impaired even up to a 60% replacement level.     

Mechanochemical synthesis,structural, magnetic,optical and electrooptical properties of CuFeS2 nanoparticles

The rapid mechanochemical synthesis of nanocrystalline CuFeS₂ particles prepared by high-energy milling for 60?min in a planetary mill from copper, iron and sulphur elements is reported. The CuFeS₂ nanoparticles crystallize in tetragonal structure with mean crystallite size of about 38?±?1?nm determined by XRD analysis. HRTEM study also revealed the presence of nanocrystals with the size of 5–30?nm with the tendency to form agglomerates. The Raman spectrum confirms the chalcopyrite structure. Low temperature magnetic data for CuFeS₂ support the coexistence of antiferromagnetic and paramagnetic spin structure. Moreover, the hysteresis loops taken at temperatures from 5?K to 300?K revealed a presence of very small amount of ferromagnetic phase, which seems to be associated with the non-consumed elemental Fe in as-prepared nanoparticles. The optical band gap of CuFeS₂ nanoparticles has been detected to be 1.05?eV, larger than band gap of the bulk material. The wider gap possibly resulted from the nano-size effect. Photoresponses of CuFeS₂ nanoparticles were confirmed by I-V measurements under dark and light illumination. It was demonstrated that mechanochemical synthesis can be successfully employed in the one step preparation of nanocrystalline CuFeS₂ with good structural, magnetic, optical and electrooptical properties.     

基于第一性原理研究Heusler合金Fe2CuGa的结构和性能

采用基于密度泛函理论的第一性原理,系统研究了Heusler合金Fe2CuGa的结构、磁性、弹性性能和电子性质.计算结果表明:立方相的基态结构是铁磁态的Hg2CuTi结构.立方到四方的相变几乎是体积不变的,这是形状记忆合金的特性.奥氏体和马氏体的磁矩分别是4.48和4.56μB/f.u..另外,预测了Fe2CuGa的弹性系数.Fe2CuGa的立方结构在力学上是不稳定的而四方结构是稳定的.根据体模量和剪切模量的比值,发现Fe2CuGa在本质上是可延展的.利用态密度的方法解释了Fe2CuGa马氏体相变的来源.     

Preparation and characterization of organic pigments and their fluorescence properties depending on bulk structure

Fluorescent pigments, based on the optical or electrooptical properties of dyes, are the main component in fluorescent coatings and inks. In this study, three kinds of dyes (Rhodamine B, Light Green SF Yellowish, Coumarin) with four different ratios (2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%) were employed as luminophor, and the melamine-formaldehyde (MF) resin was used as curing resin to prepare fluorescent pigments in different color. Fourier transform infrared spectroscopy and X-ray diffractometry were carried out to analyze the structure of the fluorescent pigments. Scanning electron microscopy and particle size distribution were used to present the morphology of fluorescent pigments. UV–vis and fluorescence spectrum were used to demonstrate the optical properties. It can be concluded that, coumarin pigments possessed consecutive structure in MF resin while rhodamine B might be the best for the preparation of printing inks among the three kinds of dyes from the view of particle size. The TG results presented that all the pigments showed good thermal stability, which might possess potential application in high speed printing industry.