金纳米空心半球壳膜的可调谐光学性质研究

以单层聚苯乙烯微球阵列为模板,通过控制其表面金膜蒸镀时间,制备了具有不同厚度的空心半球壳结构的金纳米膜.利用扫描电子显微镜和自制光谱仪分别测量了金膜表面形貌和其透射光谱,并分析了金膜形貌与其光学性质间的关系,同时以4-巯基苯胺为探针分子测定了金膜的表面增强喇曼散射效应.结果表明,该金纳米膜的表面等离子体共振波长随膜厚度增大而发生红移,在可见与近红外波段较宽范围内可调谐,并且,当金膜共振波长与入射激发光波长较近时,探针分子可产生出较强的表面增强喇曼信号.同时,对该现象的产生机制也进行了理论解释.     

大口径衍射望远系统公差分析及测量

由于薄膜衍射元件表面质量密度低、面形公差宽松,可将其作为空间大口径衍射望远系统的主镜,构成具有超大口径、轻质量、高集光率的光学载荷,提高对地球不受干扰、实时观测能力.本文分析了衍射元件的加工公差、衍射望远系统两部分空间相对位置的系统公差,提出了衍射望远系统两部分空间相对位置测量方法,并分析了测量准确度.该方法利用两种不同结构的计算全息元件,将激光光源在CMOS有源探测器上形成两个聚光光斑,实时分析两光斑的相对位置,可以精确测量偏心量和倾斜量,测量准确度分别可达50μm和0.003°,为未来大口径衍射望远系统在空间的实施奠定了基础.     

Pb(Mg1/3Nb2/3)O3-PbTiO3/CoFe2O4复合薄膜 电学、磁学性能的研究

利用射频磁控溅射技术在LaNiO3/SiO2/Si基底上制备了Pb(Mg1/3Nb2/3)O3-PbTiO3/CoFe2O4和Pb(Mg1/3Nb2/3)O3-PbTiO3/CoFe2O4/Pb(Mg1/3Nb2/3)O3-PbTiO3两种复合薄膜.我们采取了三种退火条件对复合薄膜进行退火处理,研究两种复合薄膜的晶体结构、电学和磁学性能.通过对两种复合薄膜的结构的分析,发现两步法退火后得到复合薄膜同时存在纯钙钛矿相和尖晶石相两种结构.铁电性能测试表明:两种复合薄膜均具有较好的铁电性能,其中三层复合薄膜的剩余极化强度Pr最大可以达到14.9 μC/cm2,这要归因于多层复合薄膜内部的应力-应变效应和界面耦合效应.在电场强度为80kV/cm的漏电流密度数量级仅10-5A/cm2,其导电机制在高电场区满足Schottky机制.介频性能测试表明:复合薄膜的介频特性较差,双层复合薄膜的介电性能较好,其介电常数εr为1078,其介电损耗tgδ较大,约为0.43.此外,对复合薄膜的磁滞回线测试表明:两种复合薄膜中均存在磁学性能,且双层结构复合薄膜的铁磁性能较大,其饱和磁化强度Ms为119 emu/cm3,剩余磁化强度Mr达到31.6 emu/cm3,矫顽场Hc为1360 Oe. 以上测试结果表明,铁电有序和磁有序可以存在于钙钛矿-尖晶石结构当中,通过多层复合和合适退火方式可以增强其铁电和介电性能.     

Low temperature effects on electrical and optical properties of TTBNc thin films

Electrical and optical properties of thermally evaporated air annealed Tetra-Tert-Butyl 2,3 Naphthalocyanine (TTBNc) thin films are studied. From the Arrhenius plot, the thermal activation energy is calculated for intrinsic and extrinsic region. Different hopping conduction parameters are tabulated using the Variable Range Hopping (VRH) model in the low temperature region. The studies on the optical absorption spectra lead to the determination of optical band gap energy and Urbach’s energy of TTBNc thin films. Also the temperature dependence of steepness parameter is explained.     

Oxidation and biodegradation of polyethylene films containing pro-oxidant additives: Synergistic effects of sunlight exposure, thermal aging and fungal biodegradation

Synergistic effects of sunlight exposure, thermal aging and fungal biodegradation on the oxidation and biodegradation of linear low density poly(ethylene) PE-LLD films containing pro-oxidant were examined. To achieve oxidation and degradation, films were first exposed to the sunlight for 93 days during the summer months followed by their incubation with fungal strains previously isolated from the soil based on the ability to grow on the oxidized PE-LLD as a sole carbon source. Some films were also thermally aged at temperatures ranging between 45°C and 65 °C, either before or after fungal degradation. Films with pro-oxidant additives exhibited a higher level of oxidation as revealed by increase in their carbonyl index (COi). In addition to increase in the COi, films showed a slight increase in crystallinity and melting temperature (T_m), considerably lower onset degradation temperatures, and a concomitant increase in the % weight of the residues. The level of oxidation observed in thermally aged films was directly proportional to the aging temperature. The PE-LLD films with pro-oxidant exposed to sunlight followed by thermal aging showed even higher rate and extent of oxidation when subsequently subjected to fungal biodegradation. The higher oxidation rate also correlated well with the CO₂ production in the fungal biodegradation tests. Similar films oxidized and aged but not exposed to fungal biodegradation showed much less degradation. Microscopic examination showed a profuse growth and colonization of fungal mycelia on the oxidized films by one strain, while another spore-producing strain grew around the film edges. Data presented here suggest that abiotic oxidation of polymer's carbon backbone produced metabolites which supported metabolic activities in fungal cells leading to further biotically-mediated polymer degradation. Thus, a combined impact of abiotic and biotic factors promoted the oxidation/biodegradation of PE-LLD films containing pro-oxidants.     

聚合物PMMA/DR1薄膜棱镜的制备

本文研究了用光漂白方法制备ＰＭＭＡ／ＤＲ１聚合物光棱镜的方法,测量了这种波导棱镜对１．０６４μｍ光的ＴＥ模和ＴＭ模在波导内传播光束的方向改变,并从理论上对测量结果进行了分析。     

Tuning of the electronic properties of self-assembling and highly sensitive chromic polyalkylthiophenes

The solvatochromic behaviour of different functional group-bearing and self-interacting polyalkylthiophenes with strong chromic responses in solution and self-assembling capacity in the solid state is investigated here. The menagerie of species deriving from the conformational freedom of the conjugated chains in solution has been examined in different solvent mixtures as their physico-chemical nature sensibly affects final material morphology in the solid (film) state. Memory of solution curling shape and of the degree of aggregation is in fact retained through casting or spin-coating procedures and permanently endures in the polymeric film. The efficiency of the final device based on the ICP (inherent conducting polymer) film may therefore be improved by simply acting on its morphology, which is directly determined by polymer dissolution conditions.     

Studying surfaces and thin films using Mössbauer spectroscopy

Using a series of bi-layer samples, we show how Conversion Electron Mössbauer Spectroscopy (CEMS) and X-ray Backscatter Mössbauer Spectroscopy (XBS) can be done with the same experimental set up. The penetration depths of the K and L conversion electrons are measured as 51(6) and 330(240) nm, respectively, with relative contributions of 88(9) and 12(9)%. The penetration depth of the Fe-K _α X-ray signal is determined to be 3.6(2) μm. As a demonstration we show data on surface damage effects in electropolished TRIP steels, and by comparing CEMS and XBS Mössbauer patterns we estimate the thickness of a damaged layer (created by sanding) to be 550(50) nm.