Institute of Chemistry
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Controlling the synthesis and assembly of fluorescent Au/Ag alloy nanoclusters
No full textSelf-assembly of water-soluble fluorescent thiolated Au/Ag alloy NCs into 1D nanostructure in water is demonstrated. Fluorescent Au/Ag alloy NCs with high stability were synthesized through galvanic replacement, starting from nonemissive and unstable AgNC precursors. Then a facile ultrasound method was used to induce a thiolate-driven self-assembly process
Facile Preparation of Molybdenum Bronzes as an Efficient Hole Extraction Layer in Organic Photovoltaics
No full textWe proposed a facile and green one-pot strategy to synthesize Mo bronzes nanoparticles to serve as an efficient hole extraction layer in polymer solar cells. Mo bronzes were obtained through reducing the fractional self-aggregated ammonium heptamolybdate with appropriate reducing agent ascorbic acid, and its optoelectronic properties were fully characterized. The synthesized Mo bronzes displayed strong n-type semiconductor characteristics with a work function of 5.2-5.4 eV, matched well with the energy levels of current donor polymers. The presented gap states of the Mo bronzes near the Fermi level were beneficial for facilitating charge extraction. The as-synthesized Mo bronzes were used as hole extraction layer in polymer solar cells and significantly enhanced the photovoltaic performance and stability. The power conversion efficiency was increased by more than 18% compared with the polyethylene dioxythiophene:polystyrenesulfonate-based reference cell. The excellent performance and facile preparation render the as-synthesized solution-processed Mo bronzes nanoparticles a promising candidate for hole extraction layer in low-cost and efficient polymer solar cells
Phosphonated conjugated polymers for polymer solar cells with a non-halogenated solvent process
No full textNormal photovoltaic polymers must be processed with halogenated solvents, which are harmful to the environment and cannot be used for the mass production of polymer solar cells (PSCs). We report a novel approach to develop photovoltaic polymers suitable for non-halogenated solvent processing by attaching a polar and inert phosphonate moiety to the side chain of conventional photovoltaic polymers. The pendant phosphonate moiety does not obviously affect the electronic structure of the conjugated polymer backbone but greatly changes the solubility of the polymers. The phosphonated polymers are soluble in several polar non-halogenated solvents, such as methoxybenzene (MOB), methylbenzoate (MBz), o-dimethoxybenzene (o-DMOB), etc. PSCs of the phosphonated polymers processed with MOB exhibit better photovoltaic performances than those of the devices processed with common halogenated solvents. A power conversion efficiency (PCE) of 2.11% is achieved with the device processed with MOB, in comparison to the PCE of 0.90% with chlorobenzene (CB) as the processing solvent and the PCE of 1.59% with o-dichlorobenzene (o-DCB) as the processing solvent. These results indicate that a pendant phosphonate moiety is an effective approach to developing photovoltaic polymers towards the production of PSCs fabricated using environmentally friendly solvents
Efficient synthesis of diverse well-defined functional polypropylenes with high molecular weights and high functional group contents via thiol-halogen click chemistry
No full textThe thiol-halogen click chemistry between halogenated isotactic polypropylenes (iPPs) and thiols was systematically investigated for the first time. The order of copolymer reactivity can be summarized as iodinated >> brominated > chlorinated iPP, while for different thiols, the reactivity depended on not only the acidity of the sulfhydryl but also the competition of the polar group in the thiols with -SH to participate in the nucleophilic substitution reaction. In this case, various polar groups including hydroxyl, ester, aryl, thiazolyl and amino have been successfully introduced into iPP in a quantitative way, by employing iodinated iPP as the highly reactive intermediate. The content of polar groups in the high molecular weight functional iPPs (M-w > 100 kg mol(-1)) could be tuned in a wide range of 0-11 mol%. More notably, this new strategy offers an effective route to prepare the well-defined graft copolymer iPP-g-PCL from the halogen functionalized iPP and poly(e-caprolactone)s with highly reactive -SH end (PCL-PhSH). Initiated by the resulting hydroxyl-containing iPP, ring-opening polymerization of L-lactide (LLA) provided another kind of graft copolymer, iPP-g-PLLA
Simple hydrothermal synthesis of mesoporous spinel NiCo2O4 nanoparticles and their catalytic behavior in CH3OH electro-oxidation and H2O2 electro-reduction (vol 3, pg 3207, 2013)
No full text溶液法铜基薄膜太阳能电池的制备
No full text铜基半导体材料由于高的光吸收系数以及合适的光学帶隙而被广泛应用于薄膜太阳能电池的吸光层，具有潜在的市场价值。铜基薄膜吸收层材料制备过程主要分为真空法和溶液法。前者需要较高的真空度和昂贵的器械设备，使得器件制备成本下降空间十分有限。溶液法由于操作简单，提供了低成本、大量生产的可能性。在溶液法制备薄膜电池中，纳米晶溶液法和分子前驱体体系两种方法被广泛研究。纳米晶成膜方法涉及复杂的纳米晶合成过程，此外，长碳链的有机配体也对电池性能产生不良的影响。肼溶液法是分子前驱体溶液的代表，也是溶液法最高电池效率的创造者。然而，无水肼本身的易爆炸和剧毒成为阻碍其进一步发展的关键因素。本论文主要针对当前国际上溶液法制备铜基薄膜电池存在的一些问题，致力于发展操作简单，低价低毒的溶液法，并成功地制备了几种常见的铜基薄膜太阳能电池，详细研究如下： 1. 发展了一种简单、低毒的制备CuInS2(CIS)分子前驱体溶液的...Abstract Copper-based semiconductor thin films pose a promising commercial value due to their high light absorption coefficient and suitable optical bandgaps, which have been applied in preparation of photovoltaic device. At present, the deposition methods of copper-based thin films absorbing layer fall into two classes: vacuum-based and solution-based processes. The former requires high vacuum and expensive equipment, which leads to a high manufacturing cost. Solution-based process provides a possibility of low-cost and mass production owing to simple operation. Among the solution-based processes, nanocrystal-based and molecule-based precursor approaches received a great deal of attention. Nanocrystal-deposited thin film absorbing layer needs complex and tedious synthesis, in addition, lo..
面向人工软骨的POSS改性聚氨酯的合成及性能研究
No full text聚碳酸酯型聚氨酯（PCU）凭借其优异的生物相容性、生物稳定性和耐磨性及弹性模量和润滑性与天然软骨相近的优点成为一种理想的人工软骨置换材料。但是PCU预聚体黏度较大，不得不采用传统溶液法制备。溶液法容易残留有机溶剂，将限制PCU的临床应用，所以急需开发一种新颖的适合于高黏度预聚体聚氨酯体系的合成方法。另外，作为长期植入体内的人工软骨材料，PCU是在反复承载和摩擦的复杂条件下表现出生物功能的，仍面临着环境应力作用下的降解和受压挤出的问题。因此研究生物稳定性和相关机械性能更优的聚氨酯弹性体十分必要。 针对上述问题，本论文开发一种新颖的适用于高黏度预聚体聚氨酯体系的合成方法，采用该方法制备了具有良好生物稳定性和生物相容性的有机/无机分子内杂化纳米材料POSS复合的PCU（可简称为POSS-PCU）；率先研究POSS-PCU作为人工软骨类材料时环境应力作用下的降解行为和相关机械性能，有望成为下一代新...Polycarbonate urethane (PCU) is an attractive material for artificial cartilage application since it offers excellent biocompatibility, biostability, wear resistance, low elasticity modulus, tribological properties comparable to those of cartilage. However, PCU with high-viscosity prepolymer has to be synthesized by solution casting. Solution casting tends to have organic solvent residues and limits the clinical applications of PCU. So it is necessary to develop a novel method, which is suitable for the high-viscosity prepolymer reaction systems. In addition, as long-term artificial cartilage implant material, PCU shows biological function in repeated load and friction conditions, but it is faced with degradation and radial expansion. Therefore, it is necessary to study polyurethane elasto..
稀土荧光性质在热障涂层失效机理研究中的应用-博士论文
No full text热障涂层被用来保护金属基底免受高温氧化和腐蚀，提高发动机热效率并延长其寿命，在航空、航天、汽车和大型火力发电等方面都有重要应用。目前广泛使用的涂层材料是6-8wt%Y2O3部分稳定的ZrO2（8YSZ）。由于8YSZ的长期使用温度低于1473K，高温易发生相变和烧结导致涂层失效，已难满足涡轮发动机进口温度进一步提高的需求。为了提高涂层的使用温度，延长涂层的使用寿命，使用新的涂层材料和优化涂层结构成为两个主要研究方向。 应力检测对于涂层失效机理的研究有重要意义。传统的无损应力检测方法有X射线衍射（XRD）、中子衍射（ND）和红宝石荧光光谱法，但是以上方法无法满足热障涂层热循环过程中应力测试的要求。采用掺Eu3+荧光亚层来指示涂层的脱落位置和脱落模式，用Eu3+离子荧光探针来指示涂层体系中内层的应力分布情况。Eu3+是常用的荧光离子，能发射单色性好和量子效率高的红色荧光。掺Eu3+的8YSZ荧光层在254nm紫外线照射下有发射峰在592nm和606nm的红色荧光产生，将荧光亚层的这一特性用于指示双陶瓷层热障涂层的脱落位置和脱落程度。Eu3+离子的5D0→7F2跃迁峰峰位与离子所处应力环境有线性关系。根据此关系，测得涂层5D0→7F2跃迁峰峰位从而求得涂层的应力分布情况。 研究稀土的荧光性质在热障涂层失效机理中的应用。采用大气等离子喷涂（APS）制备了8YSZ:Eu单陶瓷层涂层、La2(Zr0.7Ce0.3)2O7/8YSZ:Eu （LZ7C3/8YSZ:Eu）双陶瓷层涂层、LaMgAl11O19/8YSZ:Eu（LaMA/8YSZ:Eu）双陶瓷层涂层和LZ7C3/8YSZ功能梯度涂层，并且研究了Eu3+离子掺杂对于8YSZ高温相变稳定性的影响。 对LZ7C3/8YSZ:Eu涂层在1250±50℃条件下进行热循环实验，7370次后失效。在热循环过程中，随着LZ7C3外层的逐渐脱落，内层8YSZ:Eu荧光亚层逐渐暴露于空气中，在紫外灯照射下可以看到有明显的红色荧光。荧光亚层可以用来简单有效的指示LZ7C3/8YSZ:Eu双陶瓷层热障涂层体系的脱落和失效程度。LZ7C3/8YSZ:Eu双陶瓷层热障涂层的寿命远远大于传统8YSZ涂层和其他双陶瓷层涂层，这主要是因为LZ7C3和8YSZ相似的热膨胀系数。LZ7C3/8YSZ涂层失效的主要原因是热生长氧化物的生成，LZ7C3外层材料的烧结和相变以及8YSZ的老化。 在LZ7C3/8YSZ:Eu双陶瓷层热障涂层的基础上发展了LZ7C3/8YSZ功能梯度热障涂层，涂层从内到外依次为100%8YSZ, 75%8YSZ+25%LZ7C3，50%8YSZ+50%LZ7C3，25%8YSZ+75%LZ7C3，100%8YSZ。相应块材料的热膨胀系数依次为10.97×10-6K-1、10.92×10-6K-1、10.77×10-6K-1、10.64×10-6K-1和10.10×10-6K-1。LZ7C3/8YSZ梯度热障涂层在1250±50℃热循环寿命是880次，小于LZ7C3/8YSZ:Eu双层。粘结层的反常氧化、LZ7C3的重结晶和烧结是涂层点状脱落的主要原因。 将Eu3+压力荧光探针技术应用到LaMA/8YSZ:Eu双陶瓷层热障涂层中，激发波长为532nm。测得涂层荧光发射曲线5D0→7F2跃迁峰峰位，根据Eu3+离子的5D0→7F2跃迁峰峰位与离子所处应力环境有线性关系，计算得相应荧光测试点的应力情况。喷涂后LaMA/8YSZ:Eu涂层中8YSZ:Eu层既有压缩应力又有拉伸应力，总体平均值为55MPa的拉伸应力。随着热循环的进行，压缩应力逐渐消失拉伸应力逐渐增大。另外，8YSZ:Eu荧光亚层在依然可以用来指示LaMA/8YSZ:Eu热障涂层的脱落和失效。 使用高温固相法合成了8YSZ:Eu粉末，并通过大气等离子方法制备了8YSZ:Eu涂层，对涂层的相变、荧光性质进行分析，在8YSZ中添加Eu3+可以提高8YSZ的高温相稳定性。在氧化锆晶格中掺杂不同价态的离子，可以将氧空穴引入到晶格中。而氧空穴可以提高四方相在高温煅烧过程中的相稳定性。发射光谱中5D0→7F2能级跃迁发射峰随着粉末和涂层高温老化的进行，除了刚开始的不规律变化之外，变化情况为：峰位值发生红移；半峰宽度呈现增大的趋势；发射峰强度不断降低。Thermal barrier coatings (TBCs), which are applied to protect substrate materials against thermal corrosion and oxidation, have been widely used in the hot section of gas turbine engines to improve the fuel efficiency and prolong the lifetime of components. The state-of-art topcoat material typically used is yttria partially stabilized zirconia (YSZ), especially 8YSZ. 8YSZ performs well up to about 1200oC, but it cannot be used above 1200oC for long term due to sintering and phase transformation, which will result in failure of TBCs. In order to increase the operation temperature and lifetime of TBCs, new TBCs structures were designed and new materials were developed. Non-destructive diagnostic tools could assess the damage of TBCs, which would alleviate the risk of TBC premature failure by prompting its replacement before the level of TBC damage threatens performance of safety. It is necessary and important to evaluate and predict the development of the residual stress for the study of failure mechanism of TBCs. Several non-destructive techniques such as X-ray diffraction (XRD) techniques, neutron diffraction (ND), ruby fluorescence spectroscopy (RFS) have been applied to investigate the coating stresses. However, all of them have some limitations. It is highly demanded to develop a new method to overcome the limitation of these techniques in order to monitor the residual stress in the ceramic layer of the TBCs. Eu3+ is one of the most typical luminescent rare-earth ions, which provides a very intense and sharp luminescence spectrum when doped into the host material. 8YSZ:Eu coating has intense emission peak at 592 nm and 606 nm for excitation at 254 nm. 8YSZ:Eu luminescence sublayer is applied to indicate the spallation and damage degree of double-ceramic-layer coatings. Eu3+ photoluminescence piezo-spectroscopy based on the relationship between the stress and peak position of 5D0→7F2 transition of Eu3+ ions in 8YSZ is used to detect the residual stress of the inner ceramic layer of the TBCs. The property of rare-earth photoluminescence is applied in the study of TBC failure mechanism. 8YSZ:Eu coating, La2(Zr0.7Ce0.3)2O7/8YSZ:Eu (LZ7C3/8YSZ:Eu) double-ceramic-layer coating, LaMgAl11O19/8YSZ:Eu (LaMA/8YSZ:Eu) double-ceramic-layer coating, and LZ7C3/8YSZ:Eu five-layer ceramic-ceramic functionally graded TBCs (FG-TBCs) have been prepared by atmospheric plasma srpraying (APS). Furthermore, the effect of Eu3+ ions addition on the phase stability of 8YSZ has been studied. Thermal cycling test has been carried out on the LZ7C3/8YSZ:Eu coating, and the coating failed after 7370 cycles. As thermal cycling test going on, LZ7C3 top layer spalled bit by bit and the inner 8YSZ:Eu luminescence layer exposed. Red luminescence can be observed from the exposed 8YSZ:Eu layer under 254 nm UV illumination. The application of Eu3+-doped luminescence sublayer can be a useful non-destructive technique to indicate the spallation and damage degree of DCL coatings. LZ7C3/8YSZ:Eu coating has a much longer lifetime than that of dual layer LZ/8YSZ, LC/8YSZ coating and single layer LZ7C3, 8YSZ coating. It can be concluded that LZ7C3/8YSZ:Eu TBCs showed a promising thermal cycling performance at 1250±50oC. This could be due to the thermal expansion coefficient (TEC) of LZ7C3, which is about 10.66×10-6 K-1 and similar to that of 8YSZ. The similar TEC of LZ7C3 and 8YSZ can reduce the thermal residual stress during thermal cycling and prolong the lifetime of LZ7C3/8YSZ:Eu coating. The phase transition and sintering of LZ7C3, formation of thermally grown oxides (TGO), and the sintering of 8YSZ:Eu, are the primary factors for the spallation of DCL coating. LZ7C3/8YSZ FG-TBC consists of 100%8YSZ, 75%8YSZ+25%LZ7C3, 50%8YSZ+50%LZ7C3, 25%8YSZ+75%LZ7C3 as the interlayer, 100%LZ7C3 as the top coat. The average TEC values of bulk samples of each layer are 10.97×10-6，10.92×10-6，10.77×10-6，10.64×10-6，10.10×10-6K-1. The graded coating failed after 880 thermal cycle
IR Spectral Study of Mesoscale Process during Urea Crystallization from Aqueous Solution
No full textUnravelling the mesoscale process and the dynamic heterogeneous structures that appear nil the mesoscale in a crystallization system is important in designing and fabricating functional crystalline materials. Recent experimental observations show the existence of stable dusters and amorphous intermediates before the formation of a crystalline solid, which seems to contradict classical nucleation theory. Here we show by in situ infrared Spectroscopy and theoretical calculation that the liquid/solid phase transformation of urea proceeds through the agglomeration of primary clusters. The phase transformation pathway of urea in solution has been identified; in which urea molecules initially aggregate into one-dimensional (1D) molecular chains, and then these 1D molecular chains assemble to 2D plane-like and 3D net-like clusters. Crystalline urea with P-42(1)m symmetry can be formed when these 3D net-like clusters overcome a critical size. Both experimental and. calculated results demonstrate that the liquid/solid. phase transformation of urea in aqueous solution obeys the classical nucleation theory. Finally, a morphology diagram of urea is provided on the basis of relative chemical bonding energy density. This morphology diagram can be used to understand the multiple anisotropic geometries, for how urea crystals in an aqueous solution system can be laid out. Our results demonstrate the concept of identifying a particular mesoscale process in a urea crystallization system by both in situ vibration spectroscopy observations and chemical bonding calculations
Trimetallic PtPdRu Dendritic Nanocages with Three-Dimensional Electrocatalytic Surfaces
No full textControl over composition and structure on the nanoscale level is critical for designing highly active and durable catalyst to implement in electrochemical energy conversion. Herein, we report a facile strategy for an efficient synthesis of trimetallic PtPdRu dendritic nanocages with hollow cavity and porous dendritic shell by eroding the interior of the starting PtPdRu nanodendrites in acidic solution. The newly discovered trimetallic dendritic nanocages with an open-framework surface afford 3D molecular accessibility and can be used as highly active and durable catalysts for oxygen reduction reaction due to the synergetic effect derived from their unique porous structure and multimetallic composition