一种用于自然辐射冷却的光谱选择性透过薄膜

本文介绍了溶胶凝胶法制备光谱选择性透过薄膜，通过对样品的光谱透过率的测试，分析和研究这些样品薄膜的性能，结果表明：掺杂碳黑浓度为0.12%，厚度约为0.3μm的二氧化钛薄膜样品的光谱透过性能较优，其在8～12μm波段的透过率超过80%，在可见光波段内的透过率低于15%，作为自然辐射冷却应用的选择性透过覆盖材料，它具有阻挡太阳光中可见光加热其下的物体，同时又允许物体的热以辐射方式穿透该薄膜散发到大气外层空间的双重作用。

Design and operation of integrated pilot-scale dimethyl ether synthesis system via pyrolysis/gasification of corncob

The integrated pilot-scale dimethyl ether (DME) synthesis system from corncob was demonstrated for modernizing utilization of biomass residues. The raw bio-syngas was obtained by the pyrolyzer/gasifier at the yield rate of 40-45 Nm(3)/h. The content of tar in the raw bio-syngas was decreased to less than 20 mg/Nm(3) by high temperature gasification of the pyrolysates under O-2-rich air. More than 70% CO2 in the raw bio-syngas was removed by pressure-swing adsorption unit (PSA). The bio-syngas (H-2/CO approximate to 1) was catalytically converted to DME in the fixed-bed tubular reactor directly over Cu/Zn/Al/HZSM-5 catalysts. CO conversion and space-time yield of DME were in the range of 82.0-73.6% and 124.3-203.8 kg/m(cat)(3)/h, respectively, with a similar DME selectivity when gas hourly space velocity (GHSV, volumetric flow rate of syngas at STP divided by the volume of catalyst) increased from 650 h(-1) to 1500 h(-1) at 260 degrees C and 4.3 MPa. And the selectivity to methanol and C-2(+) products was less than 0.65% under typical synthesis condition. The thermal energy conversion efficiency was ca. 32.0% and about 16.4% carbon in dried corncob was essentially converted to DME with the production cost of ca. (sic) 3737/ton DME. Cu (111) was assumed to be the active phase for DME synthesis, confirmed by X-ray diffraction (XRD) characterization.

Bleaching kinetics of indoly-benzylfulgimide in PMMA

Indoly-benzlfulgimide belongs to the photochromic fulgide family and follows photochemical first order kinetics. Its bleaching kinetics is investigated at 633 nm and 640 nm by spectroscopy, by the time dependence of transmission and of diffraction from holographically induced gratings. The non-exponential decay law resulting for diffraction experiments with a Gaussian beam profile is calculated and verified experimentally. For a quasi-homogeneous beam profile the time constant determined from diffraction decay is half the one for absorbance decay. The photochemical reaction rate of indoly-benzylfulgimide in PMMA is (3.9 +/- 0.3) cm(2)/J at 650 nm. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dual-wavelength photochromic fulgides for parallel recording memory

Two photochromic fulgides, 2-{2-[4-(N,N-dimethylnilino)-5-methyl-4-oxazoly]}ethylidene-4-(1-methylethylidene) tetrahydrofuran-2,5-dione (A) and 3-(1,2-dimethyl-5-phenyl-3-pyrolloethylidene)-4-(1-methylethylidene)tetrahydrofuran-2,5-dione (B), doped in PMMA as candidates of dual-wavelength optical memory for parallel recording has been investigated. With 488 nm-laser and 650 nm-laser, both "cross" and "star" images are recorded on the fulgides-PMMA film and read out clearly, respectively. Crosstalk between two fulgides in PMMA matrix and nondestructive readout has also been explored. The results show that no significant cross-talk is detected between them, and nondestructive readout is up to 201 times. (C) 2005 Elsevier B.V. All rights reserved.

Optical image processing using the photoinduced anisotropy of pyrrylfulgide

A synthesized photochromic compound-pyrrylfulgide-is prepared as a thin film doped in a polymethylmethacrylate (PMMA) matrix. Under irradiation by UV light, the film converts from the bleached state into a colored state that has a maximum absorption at 635 nm and is thermally stable at room temperature. When the colored state is irradiated by a linearly polarized 650 nm laser, the film returns to the bleached state; photoinduced anisotropy is produced during this process. Application of optical image processing methods using the photoinduced anisotropy of the pyrrylfulgide/PMMA film is described. Examples in non-Fourier optical image processing, such as contrast reversal and image subtraction and summation, as well as in Fourier optical image processing, such as low-pass filtering and edge enhancement, are presented. (c) 2006 Optical Society of America.

Kinetics of photoinduced anisotropy in bacteriorhodopsin film under two pumping beams

Photoinduced anisotropy in bacteriorhodopsin (BR) film arises from the selective bleaching of BR molecules to linearly polarized light. The kinetics of photoinduced anisotropy excited by single and two pumping beams are investigated theoretically and experimentally. Compared with a single pumping beam (650 nm), which produces comparatively small photoinduced anisotropy, dual-wavelength linearly polarized pumping beams (650 and 405 nm) can obviously change the photoinduced anisotropy. When the polarization orientation of the 405 ran pumping beam is perpendicular to that of the 650 nm pumping beam, the peak and steady values of the photoinduced anisotropy kinetic curves are remarkably enhanced. But when the two pumping beams have parallel polarization orientation, the peak and steady values are restrained. At a fixed intensity of the 650 nm pumping beam, there exists an optimal intensity for the 405 nm pumping beam to maximize the value of the photoinduced anisotropy. The photoinduced transmittance of the polarizer-BR-analyzer system is modulated by the polarization angle of the 405 nm pumping beam in an approximate-cosine form. (C) 2008 Optical Society of America.

钙催化剂在生物降解脂肪族聚酯合成中的应用

生物降解高分子在环境保护以及组织工程、药物控制释放、骨固定等医药领域有着广泛的应用。特别是以聚丙交酷（PLA）、聚乙交酯（PGA）、聚。一己内酯（PCL）以及它们的共聚物为代表的化学合成生物降解高分子材料，由于具有优异的性能、可以大规模生产、成本较低等优点，得到了人们广泛的关注。作为生物医用材料，对无毒性的要求很严。而现在所用的脂肪族聚酯大都是用金属盐、金属有机化合物等作为催化剂合成出来的，不可避免残留一些催化剂所用的金属元素。研究表明，即使是已经获得美国FDA批准的，现在用得最普遍的辛酸亚锡所残留的锡也可能引起一些细胞毒性。因此对毒性小且活性高的催化剂的研究是非常有意义。钙离子对人体是没有毒性的，因而这几年已引起了人们的兴趣，但文献中报道的钙催化剂，如CaHZ等，催化活性尚不够让人满意。本文对高效的钙催化剂在生物降解脂肪族聚酯中的应用进行详细的研究，得到了一些有意义的结论：1、用EO和PO处理的有机氨钙催化剂（Ca／EO和Ca／PO）聚合了CL和LLA。发现CL聚合速度很快，M／I=650时70℃反应3h后收率已达到90％以上，LLA的聚合速度比CL要慢，M／I=650、70℃反应10h后收率才达到90％以上。以上聚合反应有明显的活性聚合的特点：反应初期Mv和收率和聚合时间呈线性关系；Mv在一定范围内和M／I成线性关系。2、用红外、原子吸收和核磁共振等分析手段阐明了有机氨钙催化剂的结构：结构，而且这两个催化剂的活性中心分别是均是Ca-O键。CL和LLA的开环聚合可能是以配位一插入的机理进行的。3、用C。／PO催化剂聚合LLA时有一定程度的消旋化反应发生，曳NMR研究表明相当于88％的LLA和12％外消旋以共聚。提高反应温度到110℃时比旋光度只有-125℃说明消旋化反应比较严重。4、用C。／PO催化剂先聚合CL再聚合LLA的方法合成了PCL-PLA两嵌段共聚物，并用泊NMR，13C NMR，GPC，DSC，WAXD进行了表征。其绝对和相对分子量可以通过M／I和投料比进行控制。定量碳谱图表明有较严重的消旋化反应发生，相当于84％的LLA和16％外消旋LA共聚。DSC和似XD分析表明，PLA段的分子量小时PLA段不结晶，当PLA段的分子量达到一定程度（3000以上）后PCL一PLA嵌段共聚物有相分离现象发生。5、以各种分子量的PEG为引发剂用氨钙催化剂和开环聚合CL，合成了一系列PCL-PEG-PCL三嵌段共聚物，并用妞NMR，laCNMR，GPC，DSC，做XD进行了表征。聚合物的结构可以通过改变PEG的分子量和CL／PEG投料比来调整。从DSC和wAXD分析可以得出以下几个结论：PCL-PEG-PCL嵌段共聚物有相分离现象发生，形成PCL和PEG微相区域；PEG段的结晶行为受先结晶的PCL段的影响；PCL段的分子量越大PEG段的Tc和Tm越低，其结晶度越低。6、以各种分子量的PEG为引发剂用氨钙催化剂80℃下开环聚合LLA24小时，合成了一系列PLA-PEG-PLA三嵌段共聚物，和别的催化剂比起来温度低得多，反应时间也短得多。可以通过改变PEG的分子量和CL／PEG投料比来调整聚合物的结构。DSC和WAXD分析表明，PLA-PEG-PLA三嵌段共聚物中PEG段的结晶能力受PLA段的影响非常大：当PEG段的分子量很小时（如1000）很难结晶；即使当PEG段的分子量较大时如果PLA段的分子量达到一定程度时PEG段同样也不结晶；而且PLA段的结晶行为受本身分子量的影响比较大，其Tc和伽随着分子量增加有较大的提高。7、合成了MPEG-PLA两嵌段共聚物，发现合成PLA段的分子量大的聚合物比较困难，MPEG-PCL两嵌段共聚物很难合成。DsC和WAXD分析表明，PLA段对MPEG段结晶有一定程度的影响，但是比三嵌段共聚物的影响要小得多。8、用荧光光谱和IHNMR研究了上面合成出的几个样品的胶束行为。发现cmc由大到小的顺序为MPEG（5000）-PLA（5100），PLA（3050）-PEG（4600）-PLA（3050），PCL（2270）-PEG（5000）-PCL（2270），PCL（4600）-PEG（4600）-PCL（4600）。PCL-PEG-PCL三嵌段共聚物在水中形成了具有核一壳结构的胶束。9、以苯甲醇处理的有机氨钙催化剂开环聚合了CL。泊NMR谱图表明得到的聚合物具有苯端基。这一结果为用硝苯基乙醇代替苯甲醇制备催化剂，然后开环聚合CL或LA得到硝基苯端基的脂肪族聚酯打下了实验基础。

液结Hg_(1-x)CaxTe太阳能电池的研究

多晶富镉HerxCdsoTe的电阻率较低，禁带宽度可调，是一种很有希望的半导体光电转换材料。本论文通过对Hg_(1-x)CdxTe(MCT)电沉积的研究，找出了多晶富镉MCT电况积的最佳条件，并对它的结构，组份以及在多硫体系溶液的光电化学性能进行了研究，观察到良好的光响应，在此基础上，进一步深入地研究了不同X值的系列MCT电极的结构，性能。结果表明，不同X值的系列MCT具有相同的闪锌矿型晶体结构，多晶晶粒大小，分布，形态等均没有明显的变化。但随着1－X值的增大，MCT的电导率增高，在多硫电解液中的短路光电流大大上升，但开路光电压却有所下降，这与φ_(fb)随1－X的升高而正移这一实验事实是一致的。即开路光电压的下降是由φ_(fb)的正移，由光谱响应实验得到的Eg值表明：当MCT中的汞含量增大（1-X值升高），禁带宽度下降.经分析，导致Eg变窄的因素在于Ec位置的下降，价带Ev的位置基本保持不变。过高的表面态密度和施主掺杂浓度，大大降低了MCT电极在多硫体系溶液中的Voc,Isc,η,FF。本实验中，未经任何处理MCT沉积膜在多硫电解液中的Voc可达300mV, Isc为3.55mAcm~(-2)，η达0.43%.对MCT／多硫体系在光照下的稳定性进行了热力学分析，表明此体系易于分解，不是稳定体系，实验结果证实了这一点。为了解决以上存在的问题，本论文分别探索了能够影响电极性能的几个因素。MCT的退火处理能够增大多晶晶粒，减少晶粒间界，使Isc大大提高。采用Ni或650 ℃热处理后的Ti作基底呈现出较好的光活性，它的短路光流Isc。开路光电压Voc等比使用经10％HF浸刻的Ti作基底要提高数倍。与多硫体系相比，MCT电极在Fe(CN)_6~(4-)/Fe(CN)_6~(3-)体系中的Voc, Isc提高近二倍，但填充因子F，F未能得到改善。单晶HgIn_2S_4是有明显的n型半导体特征，由光谱响应实验确定出它的禁带宽度为2.0eV，与太阳光谱匹配差。在光极化特性测量中，暗态扫描与光刻至关得要，它能使电极在多硫体系中的光电流提高十多倍。在这种体系HgIn_2S_4的功率效率η=0.1%。稳定性实验表明单晶HgIn_2S_4在多硫体系中的光腐蚀小，光电流稳定。

Si衬底减薄及氧化对硅基二氧化硅波导应力双折射影响的数值分析

采用有限元法对硅基二氧化硅波导在玻璃化过程中的应力与Si衬底厚度和背面氧化层厚度的关系进行了系统的分析;在此基础上,应用全矢量有限差分束传播法(FD-BPM) 对应力光波导的双折射进行了分析.结果表明随着Si衬底厚度的减薄,波导附近水平方向和垂直方向所受应力趋于一致,双折射系数B可小于10~(-4);Si衬底背面氧化层的存在使双折射系数略有增大,但随氧化层厚度的增加可减缓其增加量.

PLD工艺制备高质量ZnO/Si异质外延薄膜

采用脉冲激光沉积工艺在不同条件下以Si(111)为衬底制备了Zno薄膜.通过对不同氧压下(0～50Pa)沉积的样品的室温PL谱测试表明,氧气氛显著地提高了薄膜的发光质量,在50Pa氧气中沉积的ZnO薄膜具有最强的近带边UV发射.XRD测试说明在氧气氛中得到的薄膜结晶质量较差,没有单一的(002)取向.利用-低温(500℃)沉积的ZnO薄膜作缓冲层,得到了高质量的ZnO外延膜.与直接沉积的ZnO膜相比,生长在缓冲层上的ZnO膜展现出规则的斑点状衍射花样,而且拥有更强的UV发射和更窄的UV峰半高宽(98meV).对不同温度下沉积的缓冲层进行了RHEED表征,结果表明,在600～650℃之间生长缓冲层,有望进一步改善ZnO外延膜的质量.