Preparation,structure, and properties of flexible polyurethane foams filled with fumed silica

Flexible polyurethane (PU) foams with different load-ing mass fraction (0%-2.0%) of fumed silica were synthesized by free-rising foaming method. The addition of 1.4% fumed silica makes the cells diffuse more uniform in the PU foam and the temperature of degradation occurring with a maximum weight loss rate is about 7℃ higher than that of pure PU foam. Most signifi-cantly,the sound absorption peaks of the filled PU foams shift to the low frequency region (from 997 Hz to 711 Hz) with increasing fumed silica content (0%-2.0%). The average sound absorption coefficients of filled PU foams increase except the content of 0.35% fumed silica. The experimental results show that flexible PU foams filled with fumed silica have excellent sound absorption characteristics in low-frequency regions.     

A Novel Polymethyl Methacrylate （PMMA）TiO2 Nanocomposite and Its Thermal and Photic Stability

A new kind of polymethyl methacrylate （PMMA）-TiO2 nanocomposite was synthesized through polymerization. The thermal and photic stability of this PMMA TiO2 nanocomposites were investigated. The as prepared samples were characterized by scanning electron microscopy （SEM）, UV-Vis spectroscopy, differential thermal analysis （DTA） and the photo-induced weight loss, The results show that the photostability of the PMMA-TiO2 nanocomposite is higher than that of the pure PMMA under UV-light irradiation, The weight loss of the pure PMMA reaches 30 % after 300 h UVirradiation, while the composite only 0.3% under the identical experimental condition. The glass transition temperature （TR） of pure PMMA is only 80℃, while the Tg of the composite reaches 258℃. Compared with pure PMMA, the thermal stability of the composite is greatly enhanced.     

Synthesis and characterization of monoclinic TiO<Subscript>2</Subscript> nanosheets

A novel two-step method for the synthesis of monoclinic titanium oxide （i.e. TiO2（B）） nanosheets is presented in this report. The method is featured by two steps： 1） synthesis of hydrogen titanate nanosheets, followed by 2） calcination of the titanate nanosheets at elevated temperatures. The hydrogen titanate nanosheets were prepared first by autoclaving anatase TiO2 powders, obtained by air cal- cining an ethanol-gel of Ti（OH）4 at 500℃, in aqueous NaOH （10 mol/L） at 150-200℃, and then by washing with hydro- chloric acid under supersonic irradiation. While sizes of the nanosheets were found to increase with increasing the temperature of the hydrothermal treatment, the calcination at 400-500℃ of the hydrogen titanate nanosheets that were synthesized at higher autoclaving temperatures （180-200℃） produced monoclinic TiO2 nanosheets with a uniform morphology. By contrast, the same calcination of the titanate nanosheets synthesized at the autoclaving temperature 180℃ led to anatase TiO2 nanoparticles.     

聚氨酯/蜂窝铝复合材料的压缩力学行为及缓冲吸能特性

对空芯蜂窝铝(六边形孔)、聚氨酯、聚氨酯/蜂窝铝复合材料进行压缩试验,分析蜂窝铝和聚氨酯复合后的压缩力学行为及缓冲吸能特性.结果表明：复合材料的应力-应变曲线表现出弹性、屈服和密实三个阶段,初始刚度和屈服应力较空芯蜂窝铝有很大提高;蜂窝铝的加入使聚氨酯的变形回复降低25%;复合材料的最大吸能效率是单纯聚氨酯的1.47倍,且较大应力下复合材料具有比单纯聚氨酯更好的吸能效率;聚氨酯填充1 mm孔径蜂窝铝复合材料的最大吸能效率是聚氨酯填充2 mm孔径蜂窝铝复合材料的1.37倍;加载速率越大,吸能效率的峰值越大,且在达到最大吸能效率时的应力越大.     

聚氨酯改性聚氯乙烯复合乳液树脂的研究

由甲苯二异氰酸酯、聚醚和二羟甲基丙酸合成了自乳化阴离子水性聚氨酯(PU),以此为种子在高压釜中进行氯乙烯原位接枝共聚制备PU/PVC复合乳液树脂.考察了不同分子量PU对PU/PVC复合材料力学性能以及耐热稳定性能的影响,通过激光粒度分析仪、透射电子显微镜、扫描电子显微镜等手段,对复合胶乳粒子及其复合材料进行了测试和表征.结果表明:PU/PVC复合胶乳粒子具有较为清晰的规整核壳结构;综合力学性能提高,但热稳定性有所下降;经PU改性的PVC复合材料的断面表现为明显的韧性断裂.     

Properties improvement of SPEEK based proton exchange membranes by doping of ionic liquids and Y2O3

The membranes of sulfonated poly(etheretherketone) with 65％ sulfonation degree were prepared by doping of Y2O3 and ionic liquids,such as 1-ethyl-3-methylimidazole tetrafluoroborate (EB) or 1-butyl-3-me...     

Bulk Al-Al3Zr composite prepared by mechanical alloying and hot extrusion for high-temperature applications

Bulk Al/Al₃Zr composite was prepared by a combination of mechanical alloying (MA) and hot extrusion processes. Elemental Al and Zr powders were milled for up to 10 h and heat treated at 600℃ for 1 h to form stable Al₃Zr. The prepared Al₃Zr powder was then mixed with the pure Al powder to produce an Al-Al₃Zr composite. The composite powder was finally consolidated by hot extrusion at 550℃. The mechanical properties of consolidated samples were evaluated by hardness and tension tests at room and elevated temperatures. The results show that annealing of the 10-h-milled powder at 600℃ for 1 h led to the formation of a stable Al₃Zr phase. Differential scanning calorimetry (DSC) results confirmed that the formation of Al₃Zr began with the nucleation of a metastable phase, which subsequently transformed to the stable tetragonal Al₃Zr structure. The tension yield strength of the Al-10wt%Al₃Zr composite was determined to be 103 MPa, which is approximately twice that for pure Al (53 MPa). The yield stress of the Al/Al₃Zr composite at 300℃ is just 10% lower than that at room temperature, which demonstrates the strong potential for the prepared composite to be used in high-temperature structural applications.     

Rapid reactive synthesis of TiAl3 intermetallics by thermal explosion and its oxidation resistance at high temperature

Porous TiAl₃ intermetallics were synthesized from Ti-75 at.% Al elemental powder mixtures using an energy-saving and rapid reactive method of thermal explosion (TE). The results demonstrated that the actual temperature of the compact climbed rapidly from 673 °C to 1036 °C within 24 s, indicating that an obvious TE reaction occurred during sintering process. The video graphs suggested that the TE in Ti–Al system behaved instant occurrence and overall heating whether from axial or radial direction. The silver wires and NaCl particles that pressed on the surface of the sample disappeared due to the heavy heat released during TE reaction. Only pure TiAl₃ phases were synthesized in TE products and the open porosity of 55.4% was easy to obtain. After high-temperature treatment at 1000 °C, large amounts of sintering-neck formed and then improved the compressive strength of porous TiAl₃ materials. Moreover, the mass gain curve of porous TiAl₃ intermetallics oxidized at 650 °C for 120 h exhibited the parabolic oxidation rate law. XPS analysis confirmed that the strong O 1s peak was 531.4 eV which was the typical binding energy of Al₂O₃. Therefore, the excellent oxidation resistance of porous TiAl₃ foams would be considered as good candidate materials for prolonging the service life at high temperatures.     

Novel approaches to produce Al2O3– TiC/TiCN– Fecomposite powders directly from ilmenite

Al2O3 –TiC/TiCN–Fe composite powders were successfully prepared directly from ilmenite at 1300–1400℃.The effects of Al/C ratio,sintering atmosphere,and reaction temperature and time on the reaction products were investigated.Results showed that the nitrogen atmosphere was bene cial to the reduction of ilmenite and the formation of Al2O3 –TiC/TiCN–Fe composite powders.When the reaction temperature was between 600 and 1100℃,the intermediate products,TiO2,Ti3O5 and Ti4O7 were found,which changed to TiC or TiCN at higher temperature.Al/C ratio was found to affect the reaction process and synthesis products.When Al addition was 0.5 mol,the Al2O3 phase did not appear.The content of carbon in TiCN rose when the reaction temperature was increased.     

Preparation of graphene and TiO2 layer by layer composite with highly photocatalytic efficiency

A process for fabricating graphene and TiO₂ layer by layer composite was introduced to improve the photocatalytic activity by controlling the layers, thickness and the mass ratio between graphene and TiO₂. The graphene oxide (GO) was synthesized from natural graphite powder by the modified Hummers method. Large-area uniform GO and TiO₂ thin films were made by a spin-coating process in turn. After exposure of the TiO₂/GO multilayer film to UV light irradiation which allows the reduction of GO to graphene, a novel photocatalytic structure as graphene and TiO₂ layer by layer composite was synthesized. The cross-sectional SEM image showed that a clear layer by layer microstructure with a single layer thickness of graphene or TiO₂ was in the range of about 50 nm. The total thickness of the film was around 5 μm which was varied according to the layer number of spin coating process. Raman spectra revealed that significant structural changes occurred through UV light irradiation. Photodegradation for methylene blue (MB) exhibited that the layer by layer composite is of higher photocatalytic activity than the pure TiO₂ layer.     

Structure and photocatalytic properties of TiO<Subscript>2</Subscript>-Graphene Oxide intercalated composite

TiO2-Graphene Oxide intercalated composite (TiO2-Graphene Oxide) has been successfully prepared at low temperature (80°C) with graphite oxide (GO) and titanium sulfate (Ti(SO4)2) as initial reactants.GO was firstly exfoliated by NaOH and formed single and multi-layered graphite oxide mixture which can be defined as graphene oxide,[TiO]2+ induced by the hydrolysis of Ti(SO4)2 diffused into graphene oxide interlayer by electrostatic attraction.The nucleation and growth of TiO2 crystallites took place at low temperature and TiO2-Graphene Oxide composite was successfully synthesized.Furthermore,the photocatalytic properties of TiO2-Graphene Oxide under the irradiation of UV light were also studied.The results show that the degradation rate of methyl orange is 1.16 mg min-1 g-1(refer to the efficiency of the initial 15 min).Compared with P25 powder,this kind of intercalation composite owns much better efficiency.On the other hand,the reusable properties and stable properties of TiO2-Graphene Oxide intercalated composite are also discussed in this paper.At last,crystalline structure,interface status,thermal properties and microscopic structure of TiO2-Graphene Oxide were characterized by X-ray diffraction (XRD),X-ray photoelectron spectroscopy (XPS),thermogravimetric analysis (TGA),field emission scanning electron microscopy (FESEM) and high-resolution Transmission Electron Microscopy (HRTEM).Also,we have analyzed major influencing factors and mechanism of the composite structures which evidently improve the photocatalytic properties.     

磨碎玻璃纤维/聚氨酯/环氧灌封材料的形态结构与力学性能

采用真空灌注工艺,制备磨碎玻璃纤维(MG)／聚氨酯(PU)／环氧(EP)灌封材料,并对其力学性能和微观结构进行研究。研究结果表明:随着PU含量的增加,PU／EP共混聚合物的拉伸和冲击强度呈先升后降的变化趋势。当PU含量为15％时,共混聚合物的综合力学性能最佳,拉伸强度为60．57 MPa,冲击强度为23．56 kJ／m2,与EP相比分别提高32．77％和115％。为进一步提高材料的强度,并保持良好韧性,采用添加MG的方法来增强PU／EP。当MG与EP的质量比为1:1时,材料的拉伸强度达到79．72 MPa,与PLJ／EP相比提高31．95％,而冲击强度为17．83 kJ／m2,仍保持较高水平;同时,与相同含量的活性硅微粉相比增强PU／EP材料的拉伸强度和冲击强度分别提高18．91％和11．51％。     

聚氨酯／石墨烯纳米复合物的制备、力学及温度-电阻率行为研究

采用改进的hummers法,并以NaBH4还原制得还原石墨烯（RGO）．以蓖麻油（CO）和2,4-甲苯二异氰酸酯（2,4-TDI）为原料合成蓖麻油基聚氨酯预聚体．利用原位聚合法将聚氨酯预聚体与还原石墨烯反应（不完全还原）,制得不同石墨烯含量的聚氨酯／石墨烯纳米复合物．采用x线衍射、傅里叶变换红外光谱、拉曼光谱、热重分析以及力学和热-电阻特性测试对复合物薄膜的结构和性能进行研究．实验结果显示聚氨酯／石墨烯复合物薄膜具有优良的热力学性能,特别是当石墨烯质量分数为1．5％时,聚氨酯／石墨烯纳米复合物出现正的电阻率-温度效应（PTC效应）．     

Preparation of transparent TiO2 nanocrystalline film for UV sensor

Nanocrystalline TiO2 is a very important inorganic semiconductor function material with a wild band gap of 3.0-3.2 eV. Owing to its characteristics of selectiveabsorption for UV light, it has been extensively applied in photocatalysts, dye-sensitized sola…     

Investigation of functional, physical, mechanical and thermal properties of TiO2 embedded polyester hybrid composites: A design of experiment (DoE) study

This paper presents a study on the Design of Experiments(Do E) approach to optimize the fabrication parameters of titania(TiO_2) embedded glass fiber reinforced polyester hybrid composites(HCs). HCs of unsaturated polyester resin(UPR) were fabricated using methyl ethyl ketone peroxide(MEKP) as the curing agent by hand lay-up process(HLUP) and compression molding technique(CMT). The fabrication parameters were optimized by Taguchi Do E(an orthogonal array of L25) using 3 control factors(concentration of TiO_2, concentration of MEKP and curing temperature) having 5 levels each. Statistical tools were employed to identify significant factors affecting tensile strengths and its reproducibility during HLUP. It was found that the concentration of TiO_2 in HCs significantly influenced the tensile strength(TS) followed by MEKP concentration and curing temperature. The highest value of TS was obtained at 3 wt% TiO_2, 2 wt% MEKP and 80 °C. Nevertheless, the sensitivity of TiO_2 concentration was basis for fabrication of polyester titania glass fiber hybrids(PTGFHs), which were further investigated for density and void fractions, linear shrinkage, flexural strength, impact strength, hardness and thermal behaviors. Moreover, cross-linking and hydrogen-bonding between polymeric chains, styrene, silica content of glass fiber and TiO_2 particles in PTGFHs were confirmed by Fourier transform infrared spectroscopy.     

Elastic anomalies near phase transitions of lead-free （Na,Bi）TiO3 and （Ba,Zr）TiO3 ferroelectric ceramics

We have investigated the temperature dependence of elastic modulus for various ferroelectric ceramics in the temperature range of 20–90°C.The Na0.5Bi0.5TiO3(NBT)ceramics has a phase transition at 200°C,thus exhibits minimal change in elastic modulus up to 90°C,while the elastic modulus of the BaZr0.07Ti0.93O3(BZT-7)shows 12.5%change at the phase transition temperature of70°C and that of the BaZr0.15Ti0.85O3(BZT-15)ceramics shows 34.6%change at the phase transition temperature of60°C.The variations of elastic modulus will affect the temperature stability of devices made by these lead-free ferroelectric ceramics.     

聚氨酯/环氧树脂互穿网络硬泡循环压缩

制备了聚氨酯(PU)/环氧树脂(ER)互穿聚合物网络硬泡，研究了互穿聚合物网络(IPN)硬泡的化学结构及微观结构形态.傅里叶红外光谱(FTIR)分析表明，IPN硬泡的网络间存在接枝反应.扫描电子显微镜(SEM)分析发现，IPN硬泡泡孔结构形状都比较均一.循环压缩实验研究表明：随循环次数增加，应力下降，单次循环的能量损耗下降；随ER含量增加，IPN硬泡的压缩模量和强度提高，相同应变下应力增加，每次循环耗能增加；循环压缩的加卸载应力 应变曲线可用改进的Ogden模型表示；累积能量损耗可用Weibull方程表示.     

一步法合成耐久性水基超疏水TiO2/DTMS涂层

为制备具有优异自清洁功能的耐久性水基超疏水涂层，以十二烷基三甲氧基硅烷(n-dodecyltrimethoxysilane, DTMS)为有机改性物，通过一步法在纳米TiO₂表面嫁接长链烷基官能团得到超疏水TiO₂/DTMS涂层。分析了TiO₂涂层及TiO₂/DTMS涂层的表面润湿性、形貌和化学组成，并对所得超疏水TiO₂/DTMS涂层的自清洁性能、机械及化学稳定性进行了测试。结果表明：超疏水TiO₂/DTMS涂层表面水接触角(water contact angle, WCA)达到159°；以亚甲基蓝粉末作模拟污染物，涂覆有超疏水TiO₂/DTMS涂层的玻璃具有优异的自清洁性能；经机械磨损(10 min)、酸碱液(pH=1、3、5、7、9、11、13)浸泡、高低温(−20、30、60、90、120、150 ℃)处理后超疏水TiO₂/DTMS涂层的WCA仍大于150°，表明其具有优异的机械和化学稳定性，可用于室外防污，如建筑物外墙、玻璃、太阳能电池板等。     

核—壳结构水性丙烯酸—聚氨酯微乳液膜表面结构

采用Ｘ射线光电子能谱（ＸＰＳ）技术对具有核－壳结构的水性丙烯酸－聚氨酯微乳液（ＡＣ－ＰＵ）,包括非交联型和两种核－壳交联型的膜表面结构进行了研究。ＸＰＳ元素组成测定和电子计算机自动拟合分峰技术对谱峰的数学处理以及不同膜的上下表面的研究结果均表明,纯ＰＵ乳液膜的表面软段含量多于内层,非交联型ＡＣ－ＰＵ乳液膜的表面为富ＰＵ相,而交联型ＡＣ－ＰＵ乳液膜较为均一,研究还表明ＸＰＳ及其价带谱可用来表征核与壳     

Microwave sintering of Ca<Subscript>0.6</Subscript>La<Subscript>0.2667</Subscript>TiO<Subscript>3</Subscript> microwave dielectric ceramics

Ca_0.6La_0.2667TiO₃ ceramics were prepared by conventional and microwave sintering techniques and their sinterability, microstructure, and microwave dielectric properties were investigated in detail for comparison. Densified Ca_0.6La_0.2667TiO₃ ceramics were obtained by microwave sintering at 1350°C for 30 min and by conventional sintering at 1450°C for 4 h. An unusual phenomenon was found that some larger grains (grain size range: 8–10 μm) inclined to assemble in one area but some smaller ones (grain size range: 2–4 μm) inclined to gather in another area in the microwave sintered ceramics. The microwave dielectric properties of Ca_0.6La_0.2667TiO₃ ceramics prepared by microwave sintering at 1350°C were as follows: dielectric constant (ɛ _r) = 119.6, quality factor (Qf) = 17858.5 GHz, and temperature coefficient of resonant frequency (τ _f) = 155.5 ppm/°C. In contrast, the microwave dielectric properties of the ceramics prepared by conventional sintering at 1450°C were ɛ _r = 117.4, Qf = 13375 GHz, and τ _f = 217.2 ppm/°C.