TiO2粒径对PTFE基复合材料介电损耗和吸水率的影响

PTFE/TiO_2复合材料的微观界面结合性直接影响其介电损耗和吸水率性能。本文从增大TiO_2填料粒径的角度出发,以D_(50)为6.258,24.122和34.191μm的TiO_2陶瓷粉分别制备PTFE/TiO_2复合材料样品,测试其在X波段的介电常数、介电损耗和吸水率,结合不同陶瓷粉的特性,分析讨论了TiO_2填料粒径变化对复合材料性能的影响规律。当TiO_2填料粒径增大时,制备的复合材料内部界面比例降低,由界面结合性差导致的高吸水率得到明显的改善。以D_(50)为34.191μm的TiO_2陶瓷粉制备的PTFE基复合材料的相对介电常数为9.97,介电损耗为0.0021,吸水率降低至0.038%。     

SiO2粒径对PTFE/SiO2复合材料性能的影响

采用化学旋蒸工艺,制备了无定形SiO2填充聚四氟乙烯(PTFE)复合材料,并对其进行了热、介电性能测试和SEM分析表征.系统研究了PTFE-SiO2复合介质材料中,不同粒径的SiO2(φ4μm,φ9 μm,φ13 μm,φ20μm)对材料结构和性能的影响.结果表明,复合材料的密度、热膨胀系数、介电常数随着SiO2粒径的增大而增加,而介电损耗则随着SiO2粒径的增大而减小.当SiO2的粒径为φ20μm时,PTFE能很好的在SiO2表面形成一层包覆层,此时复合材料具有合适的热膨胀系数(17.58×10-6/℃)、介电常数(2.82)和低介电损耗(0.001 2).     

TiO_2掺杂量对PTFE/SiO_2复合材料性能的影响

采用新型化学工艺,制备了SiO2与TiO2共同填充的PTFE复合材料,系统研究了TiO2掺杂量对所制复合材料显微结构、微波介电性能和热膨胀系数的影响。结果表明,复合材料的密度、介电常数和热膨胀系数都随着掺杂量的增大而增加,吸水率随着掺杂量的增大而减小,介电损耗随着掺杂量的增大先减小后增大。当TiO2掺杂量为质量分数7%时,PTFE很好地包覆在SiO2表面,复合材料结构致密,具有与铜箔较为匹配的线膨胀系数(17.76×10–6/℃),且介电性能优良(εr=2.94,tanδ=0.000 82)。     

SiO2含量及粒径对SiO2/聚烯烃复合材料性能的影响

采用溶液法制备了SiO_2填充聚烯烃复合材料,系统研究了SiO_2含量及粒径对SiO_2/聚烯烃复合材料显微结构、力学性能、吸水率、介电性能的影响。结果表明,随着SiO_2含量的增加,复合材料的拉伸强度先增大到一个最大值然后减小,断裂伸长率先稍有增大后逐渐减小,介电常数、介电损耗和吸水率则随SiO_2含量的增加而增加;相同SiO_2填充量时,复合材料拉伸强度、断裂伸长率、介电常数、介电损耗和吸水率均随SiO_2粒径的增大而减小,当SiO_2的粒径为10μm时,复合材料具有最低的介电常数、介电损耗和吸水率。     

SiO2粒径对PTFE/SiO2复合材料性能的影响

采用化学旋蒸工艺,制备了无定形SiO2填充聚四氟乙烯(PTFE)复合材料,并对其进行了热、介电性能测试和SEM分析表征。系统研究了PTFE SiO2复合介质材料中,不同粒径的SiO2 (4 μm,9 μm,13 μm,20 μm)对材料结构和性能的影响。结果表明,复合材料的密度、热膨胀系数、介电常数随着SiO2粒径的增大而增加,而介电损耗则随着SiO2粒径的增大而减小。当SiO2的粒径为20 μm时,PTFE能很好的在SiO2表面形成一层包覆层,此时复合材料具有合适的热膨胀系数(17.58×10-6/℃)、介电常数(2.82)和低介电损耗(0.001 2)。     

CaTiO_3含量对PTFE/TiO_2复合材料性能的影响

采用类似于粉末冶金的工艺,制备了金红石型TiO2填充的聚四氟乙烯(PTFE)复合材料,研究了CaTiO3掺杂量对所制复合材料热学、介电性能的影响。结果表明:随着CaTiO3含量的增加,复合材料的密度减小,吸水率增大,介电常数和损耗增大,线膨胀系数增大到一个最大值后减小;当CaTiO3添加量达到质量分数16%时,复合材料的相对介电常数达到最大值11.60,损耗为0.002 0。     

TiO2含量对PTFE/TiO2微波介质复合材料性能的影响

采用机械搅拌、冷压成型和烧结相结合的方法制备了TiO2填充聚四氟乙烯(PTFE)微波介质复合材料,通过扫描电镜表征了TiO2颗粒存PTFE中的分散情况及复合材料的微观形貌,测定了材料的热膨胀系数、介电性能及吸水率等参数.重点研究了不同含量TiO2对复合材料热、介电性能的影响.结果表明,随着TiO2含量的增加,复合介质板的密度先增大到一个最大值然后减小,吸水率、介电常数和介电损耗随着TiO2含量的增加而增加,热膨胀系数则呈相反趋势.TiO2含量增加约65％时,复合材料的密度达到最大值(2.802 g/cm3),此时介电常数为8.89,介电损耗为0.002 5.     

热压成型温度对PTFE/SiO2复合材料性能的影响

采用热压工艺制备了PTFE/SiO2微波复合基板材料,研究了热压温度对PTFE/SiO2复合材料的性能及显微结构的影响。差示扫描量热法分析表明PTFE结晶度随热压成型温度上升而升高,熔限先变宽后变窄。同时通过扫描电镜观察发现,热压成型温度升高使复合材料表面出现气孔,材料内部气孔数目增多,从而导致材料密度、相对介电常数下降,吸水率A升高。由于PTFE树脂结晶度与材料显微结构共同作用,介电损耗先降低后增高,热导率Kc则先增高后降低。热压温度为370℃时,复合材料性能较好(εr=2.90,tanδ=0.001 1,A=0.58‰,Kc=0.566W/(m·℃))。     

Dy2O3对钛酸锶钡基陶瓷结构及介电性能的影响

采用传统固相法制备Dy2O3掺杂(Ba0.7Sr0.3)TiO3系电容器介质陶瓷,通过扫描电镜、X线衍射仪及LCR测试系统,研究不同含量的Dy2O3对体系微观结构及介电性能的影响.结果表明,随着Dy2O3添加量的增大,(Ba0.7Sr0.3)TiO3陶瓷平均粒径减小且Dy2O3掺杂(Ba0.7Sr0.3)TiO3陶瓷均为钙钛矿结构单相固溶体.Dy2O3通过占据钙钛矿晶格A、B位引起(Ba0.7Sr0.3)TiO3陶瓷晶格畸变,体系自发极化能力降低,进而显著降低了体系室温相对介电常数及介电损耗.随着Dy2O3添加量的增大,(Ba0.7Sr0.3)TiO3陶瓷居里温度向负温方向移动,且体系的相对介电常数及介电损耗随温度变化显著.     

SiO2含量对PTFE/SiO2复合材料性能的影响

采用类似于粉末冶金工艺,制备了无定形SiO2填充聚四氟乙烯(PTFE)复合材料,并对其进行了热、介电性能测试和SEM分析表征。系统研究了(1-x)PTFE-xSiO2(x为质量比)复合介质材料中,不同x值(x=0.35,0.40,0.45,0.50,0.55)对材料结构和性能的影响。结果表明,复合材料的密度随着SiO2含量的增加而减少,吸水率、热膨胀系数、介电常数和介电损耗随着SiO2含量的增加而增加。当SiO2质量分数为50%时,PTFE能很好地在SiO2表面形成一层包覆层,此时复合材料具有合适的热膨胀系数(17μ℃-1)、介电常数(2.74)和低介电损耗(0.002)。     

低红外发射率TiO2/Ag/TiO2纳米多层膜研究

利用磁控溅射在玻璃衬底上制备了具有良好的光谱选择性透过率的TiO2/Ag/TiO2纳米多层膜.通过用X射线衍射、扫描电子显微镜、UV-VIS-NIR分光光度计、傅里叶红外光谱仪对样品进行表征,优化了薄膜的制备工艺,研究了多层膜的光学特性.结果表明,当Ag膜的厚度为12nm时,多层膜具有高的可见光透过率和优良的导电性能.样品在555nm波长处的透过率最高达93.5%,红外波段平均反射率为90%左右,8μm～14μm波段红外发射率ε＜0.2.Ag层厚度的增加使可见光高透过率波段变窄,透过率下降.内层及外层TiO2厚度的变化引起薄膜可见光透过峰的位置及强度发生变化,外层的影响高于内层.     

The Influence of TiO2 Particle Size in TiO2/CuInS2 Nanocomposite Solar Cells

The recently developed CuInS₂/TiO₂ 3D nanocomposite solar cell employs a three‐dimensional, or “bulk”, heterojunction to reduce the average minority charge‐carrier‐transport distance and thus improve device performance compared to a planar configuration. 3D nanocomposite solar‐cell performance is strongly influenced by the morphology of the TiO₂ nanoparticulate matrix. To explore the effect of TiO₂ morphology, a series of three nanocomposite solar‐cell devices are studied using 9, 50, and 300 nm TiO₂ nanoparticles, respectively. The photovoltaic efficiency increases dramatically with increasing particle size, from 0.2 % for the 9 nm sample to 2.8 % for the 300 nm sample. Performance improvements are attributed primarily to greatly improved charge transport with increasing particle size. Other contributing factors may include increased photon absorption and improved interfacial characteristics in the larger‐particle‐size matrix.     

PANI/TiO2和PANI/TiO2/HCSA纳米复合材料的光电性能

采用原位聚合的方法制备了PANI/TiO2纳米复合材料,用樟脑磺酸掺杂PANI/TiO2(EB)得到纳米复合膜.使用红外光谱、紫外光谱、荧光光谱及透射电镜探讨了复合材料的光电性能.     

Effect of TiO2 nanoparticle content in sol–gel derived TiO2 paste on the photovoltaic properties of TiO2 photoanode of dye-sensitized solar cells

In the present work, the effect of the amount of TiO₂ nanoparticles, added to the sol–gel derived paste, on the photovoltaic properties of fabricated dye-sensitized solar cells (DSSCs) was investigated. A titanium sol (Ti-sol) was synthesized using a Pechini type sol–gel method, and different pastes were prepared by adding various amounts of TiO₂ nanoparticles to the obtained Ti-sol. The pastes were used to fabricate the mesoporous TiO₂ semiconducting layers for DSSCs. It was observed that by increasing the mass ratio (MR) of TiO₂ nanoparticles to Ti-sol the thickness of TiO₂ layer increases. This led to the more adsorption of dye molecules per unit area of active TiO₂ layer, which were determined by UV–vis spectrophotometry. Also, micro-cracks were observed in TiO₂ layers obtained from pastes with low MR values. But their amount and size decreased with increasing MR, which was due to the decrease of paste surface tension (σ). As a result, short circuit current density (I_sc) showed continuous increase with increasing MR, which was due to the more dye adsorption. Open circuit voltage (V_oc) first increased and then decreased by enhancing MR, which was explained by considering the electron–hole recombination rate. Finally, the DSSC fabricated from the paste with MR=0.65 showed the maximum conversion efficiency (η).     

Different depositing amount of CuInS2 on TiO2 nanoarrays for polymer/CuInS2–TiO2 solar cells

This paper reports the deposition of CuInS₂ on TiO₂ nanoarrays, with different depositing amounts and demonstrates the application of TiO₂–CuInS₂ composites in polymer-based solar cells. The composites of TiO₂–CIS1 and TiO₂–CIS2 were prepared by the deposition of CuInS₂ on TiO₂ with one-step or two-step solvethermal reactions, respectively, and characterized by XRD, SEM, TEM, absorption spectrum and PL spectrum. Results showed that TiO₂–CIS1 displayed the higher light-harvesting ability and PL quenching efficiency compared to TiO₂–CIS2, although less CuInS₂ was deposited on TiO₂ surface. As a result, polymer/TiO₂–CIS1 solar cells displayed much higher J_sc correlated with the increased absorptivity and charge separation efficiency, and the higher V_oc was originated from the presence of strong interaction between TiO₂ and CuInS₂ in TiO₂–CIS1 resulting in the effective modification of TiO₂ surface by CuInS₂.     

Enhanced photocatalytic performance of platinized CdS/TiO2 by optimizing calcination temperature of TiO2 nanotubes

TiO₂ nanotubes were prepared by hydrothermal treatment of TiO₂ powder in NaOH aqueous solution and then calcined at various temperatures. The post-calcination treated TiO₂ nanotubes were decorated with CdS by wetness impregnation and subsequently sulfurization to fabricate CdS/TiO₂ composites. The photocatalytic performance of CdS/TiO₂ composites toward hydrogen production from water splitting was investigated. The results show that the calcination temperature of TiO₂ nanotubes has a significant effect on the photocatalytic performance of CdS/TiO₂. With the increase of calcination temperature from 300 to 500 °C, the crystallinity of TiO₂ nanotubes is increased resulting in the enhanced photocatalytic performance of CdS/TiO₂. When the calcination temperature is higher than 500 °C, TiO₂ nanotubes gradually transform into nanorods and finally completely collapse, which leads to the decrease of photocatalytic performance of CdS/TiO₂. The CdS/TiO₂ composite with TiO₂ nanotubes calcined at 500 °C exhibits the highest hydrogen evolution rate, which could be attributed to its 1 D nanotubular structure and good crystallinity.     

草酸氧钛酸分解法制备纳米金红石型TiO_2粉体

用硫酸钛与草酸按比例配合 ,析出草酸氧钛酸晶体 ,将其洗涤后在 75 0～ 82 0℃焙烧 ,因草酸氧钛酸分解时 ,其分子中较大部分成分以气体 :CO2 、CO、水蒸气形式挥发到空气中 ,从而固态产物成为纳米级的金红石型二氧化钛粉体。用透射电子显微镜 (TEM)测定 ,其粒径范围为 10～ 35 nm;用 X射线衍射 (XRD)测定 ,其晶型为金红石型。     

Efficient TiO2 Photocatalysts from Surface Hybridization of TiO2 Particles with Graphite‐like Carbon

Surface hybridization of TiO₂ with graphite‐like carbon layers of a few molecular layers thickness yields efficient photocatalysts. Photoelectrochemical measurements confirm an electronic interaction between TiO₂ and the graphite‐like carbon. A TiO₂ photocatalyst with a carbon shell of three molecular layers thickness (～1 nm) shows the highest photocatalytic activity which is about two times higher than that of Degussa P25 TiO₂ under UV light irradiation. The mechanism of the enhanced photocatalytic activity under UV irradiation is based on the high migration efficiency of photoinduced electrons at the graphite‐like carbon/TiO₂ interface, which is due to the electronic interaction between both materials. In addition, a high activity under visible light irradiation is observed after graphite‐like carbon hybridization. TiO₂'s response is extended into the visible range of the solar spectrum due to the electronic coupling of π states of the graphite‐like carbon and conduction band states of TiO₂.