Thermophysical Properties of Industrial Sugar Cane Juices for the Production of Bioethanol

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Mechanical, thermal and colorimetric properties of LLDPE coloured with a blue nanopigment and conventional blue pigments

Purpose – This research deals with a new kind of nanopigment, obtained from the combination of organic dyes and layered nanoclays, that the authors call nanoclay-colorant pigment (NCP). Whilst they have already been employed in inks and coatings, to date these nanopigments have not been used as pigments for polymers. The existing lack of knowledge surrounding them must be redressed in order to bridge the gap between current academic studies and commercial exploitation. Therefore, the main purpose of this paper is to examine the hitherto unknown aspects of the NCP, which relate specifically to their applicability as a new type of colorant for polymers. Design/methodology/approach – A blue NCP has been prepared at the laboratory according to the patented method of synthesis (patent WO0104216), using methylene blue and montmorillonite nanoclay. It has then been applied to a thermoplastic polymer (linear low-density polyethylene – LLDPE) to obtain a coloured sample. Furthermore, samples with the same polymer but using conventional blue colorants have been prepared under the same processing conditions. The mechanical, thermal and colorimetric properties of these materials have been compared. Findings – The thermal stability of the sample coloured with NCP is reduced to some extent, while the mechanical strength is slightly increased. Moreover, this sample has better colour performance than the conventionally pigmented samples. Originality/value – In this paper, a blue NCP has been synthesised and successfully employed with polyethylene and the obtained sample shows better colour performance than polyethylene with conventional pigments.

The properties of advanced alumimium alloy systems

2XXX and 7XXX series aluminium alloys have been the accepted materials for airframe construction for many decades. However, only minor improvements in properties have been possible by the development of these alloys since the early 1970's. The constant need to reduce weight in aircraft has therefore led to a resurgence in the research for higher performance aluminium alloys. The reason for this investigation was to evaluate possible alternatives for the existing conventional aluminium alloy 2014 for aircraft wheel applications. Three new technologies in alloy development were considered: a metal matrix composite, an aluminium-lithium alloy and a powder metallurgical alloy. The basic mechanical properties of these advanced materials have already been established to an extent, but their fatigue behaviour has yet to be fully understood. The purpose of this work was to investigate the fatigue properties of the materials concerned, in both air and an aerated 3.5% NaCl solution, and compare these properties to 2014-T6. As well as the basic mechanical properties, fatigue crack propagation data is presented for all of the materials concerned. Additionally, fatigue crack initiation data is presented for the aluminium-lithium alloy and 2014. The D.C. electrical potential method was used to monitor crack growth. Of the materials investigated, the most promising was the aluminium-lithium alloy. However, short transverse properties need to be increased and the commercial cost of the material needs to be decreased before it can be considered as a direct replacement for 2014 for aircraft structural applications. It was considered that the cost of the powder metallurgical alloy would limit its further use. The metal matrix composite material proved to be unsuitable for most ambient temperature applications

无机材料的结构与物理性能：第一性原理计算

本论文的研究方向是通过密度泛函理论研究各种材料的物理化学性质。近年来相关理论和数值算法的飞速发展，使得基于密度泛函理论的第一性原理方法成为凝聚态物理、量子化学和材料科学中的常规计算研究手段。本论文对无机材料进行第一性原理研究，研究涉及材料物性包括几何构型、电子结构、磁性能、和力学性质等等。 第一章简要地介绍了密度泛函理论的基本框架和近年来的理论发展。密度泛函理论的发展以及寻找合适的交换相关能量泛函为主线。从最初的局域密度近似（LDA）、广义梯度近似（GGA）到现在的非局域泛函、自相互作用修正，多种泛函形式的出现使得密度泛函理论可以提供越来越精确的计算结果。除了改进交换相关泛函，近年来密度泛函理论向动力学平均场和含时理论等方面扩展也很活跃。这些扩展式的密度泛函理论的应用领域不断扩大。在本章的最后，我们介绍一些密度泛函理论的应用程序。 第二章我们通过第一性原理从头算系统的研究了5d过渡金属二硼化物TMB2 (TM = Hf, Ta, W, Re, Os and Ir, Pt)在假想的Pmmn空间群中的结合能、生成焓、力学常数和电子能带结构。我们的计算结果表明在力学常数和价电子浓度之间存在一种关系：即当价电子浓度在6.8到7.2之间时，体模量和剪切模量达到最大值。再者，这种力学常数与价电子浓度之间的关系可以通过电子能带结构分析，如费米面附近价电子的占据情况，决定了体系的结合能和力学性能。最大的体模量和剪切模量的获得归因于TM d-B p成键态的几乎完全占据和反键态的未占据。依据上述这种关系，我们预测了在正交结构OsB2合金化W和Re将比合金化Ir元素更容易和更硬。事实上，我们的进一步计算证实了我们的期望。 通过第一性原理计算研究了ReB2和WB2的结构、弹性力学，和电子性质。计算结果表明：ReB2的平衡态结构参数和报导的实验结构一致。在常温常压下，WB2在P63/mmc空间群比在P6/mmm更稳定。依据我们计算的多晶聚集体的体模量、剪切模量，ReB2和WB2可以被看作是具有前景的低压缩率和硬材料。再者，化合物的力学各项异性通过计算得到的弹性力学常数来详细的分析讨论。态密度和电子密度分析揭示过渡金属和硼原子之间的共价键是材料具有高的体模量、剪切模量和小的Poisson比率的原因。 第四章，采用WIEN2k程序包中的缀加平面波+局域轨道方法的第一性原理计算，研究了层状钙钛矿化合物Cs2AgF4的结构、电子结构和磁性等性质。我们的计算结果表明Cs2AgF4的基态为正交相，能量比四方相低。我们同时发现Cs2AgF4应该表现出一种强的二维铁磁性，铁磁层之间为弱的反铁磁性耦合，这一结果与实验观察相一致。更主要的是，通过分析态密度图和自旋电子密度等密度面的分析，可以清楚地看出体系中存在 和 轨道的反铁电弹性有序现象。 第五章中，采用WIEN2k程序包中的缀加平面波+局域轨道方法的第一性原理计算，研究了YBaFe2O5的晶体结构、电子和磁性等方面的物理性能，特别是有关电荷和轨道有序的情况。尽管总的3d电荷不均衡程度很小，以Fe2+ 和Fe3+阳离子t2g轨道占据数的差别所定义的轨道有序序参量相当大（0.73），无可非议的显示YBaFe2O5中存在电荷和轨道有序。O 2p和Fe eg轨道之间的强的杂化作用使得Fe2+ 和Fe3+阳离子之间总电荷差别几乎完全消失。此外，我们讨论了轨道有序和电荷有序以及磁有序之间的关系。dxz轨道有序决定了G型反铁磁性自旋有序的稳定性和电荷有序模式。

地幔压力下CaSiO3 Perovskite状态方程和弹性常数的第一性原理研究

In the past decade density functional theory (DFT) has made its way from a peripheral position in quantum chemistry to center. Of course the often excellent accuracy of the DFT based methods has provided the primary driving force of this development. This dissertation is devoted to the study of physical and chemical properties of planetary materials by first-principle calculation. The concerned properties include the geometry, elastic constants and anisotropy. In the first chapter, we give a systematic introduction to theoretical background and review its progress. Development of quantum chemistry promotes the establishment of DFT. Theorem of Hohenberg-Kohn is the fundament of DFT and is developed to Kohn-Sham equation, which can be used to perform real calculations. Now, new corrections and extensions, together with developed exchange-correlation, have made DFT more accurate and suitable for larger systems. In the second chapter, we focus on the calculational methods and technical aspects of DFT. Although it is important to develop methods and program, external package are still often used. At the end of this chapter, we briefly some widely used simulation package and the application of DFT. In the third chapter, we begin to focus on properties of real materials by first principles calculation. We study a kind of minerals named Ca perovskite, investigate its possible structure and anisotropy at Earth’s mental condition. By understanding and predicting geo-physically important materials properties at extreme conditions, we can get the most accurate information to interpret seismic data in the context of likely geophysical processes.

Integration Principles of Russian and Japanese Databases on Inorganic Materials

The methods and software for integration of databases (DBs) on inorganic material and substance properties have been developed. The information systems integration is based on known approaches combination: EII (Enterprise Information Integration) and EAI (Enterprise Application Integration). The metabase - special database that stores data on integrated DBs contents is an integrated system kernel. Proposed methods have been applied for DBs integrated system creation in the field of inorganic chemistry and materials science. Important developed integrated system feature is ability to include DBs that have been created by means of different DBMS using essentially various computer platforms: Sun (DB "Diagram") and Intel (other DBs) and diverse operating systems: Sun Solaris (DB "Diagram") and Microsoft Windows Server (other DBs).

Effect of silver nanoparticles on luminescent properties of europium complex in di-ureasil hybrid materials

Organic-inorganic hybrids containing luminescent lanthanide complex Eu(tta)(3)Phen (tta = thenoyltrifluoroaceton, phen = 1,10-phenanthroline) and silver nanoparticles have been prepared via mixing rare earth complex and nanoparticles with the precursors of di-ureasil using a sol-gel process. The obtained hybrid materials with transparent and elastomeric features were characterized by transmission electron microscope, solid-state Si-29 magic-angle spinning NMR spectra, diffuse reflectance, UV-visible absorption and photoluminescence spectroscopies. The effect of the silver nanoparticles on the luminescence properties was investigated. The experimental results showed that the luminescence intensity of the Eu(tta)(3)phen complex could be enhanced by less than ca. 9.5 nM of silver nanoparticles with the average diameter of 4 nm, and reached its maximum at the concentration of ca. 3.6 nM. Further increasing the concentration of the silver nanoparticles (> 9.5 nM) made the luminescence quenched. The enchancement and quench mechnism was discussed.

Comparison of the effect of processing parameters and degradation on the DC and microwave properties of thin films and polycrystalline bulk high-Tc superconducting materials

The sharp increase in microwave power loss (the reverse of what has previously been reported) at the transition temperature in high-Tc superconducting systems such as YBaCu oxide (polycrystalline bulk and thin films obtained by the laser ablation technique) and BiPbSrCaCu oxide is reported. The differences between DC resistivity ( rho ) and the microwave power loss (related to microwave surface resistance) are analysed from the data obtained by a simultaneous measurement set-up. The influence of various parameters, such as preparation conditions, thickness and aging of the sample and the probing frequency (6-18 GHz), on the variation of microwave power loss with temperature is outlined.

Effect of TiO2 electrode thickness on photovoltaic properties of dye sensitized solar cell based on randomly oriented Titania nanotubes

Anatase titania nanotubes (TNTs) have been synthesized from P25 TiO2 powder by alkali hydrothermal method followed by post annealing. The microstructure analysis by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed the formation of anatase nanotubes with a diameter of 9-10 nm. These NTs are used to make photo anode in dye-sensitized solar cells (DSSCs). Layer by layer deposition with curing of each layer at 350 C is employed to realize films of desired thickness. The performance of these cells is studied using photovoltaic measurements. Electrochemical impedance spectroscopy (EIS) is used to quantitatively analyze the effect of thickness on the performance of these cells. These studies revealed that the thickness of TiO2 has a pronounced impact on the cell performance and the optimum thickness lies in the range of 10-14 mu m. In comparison to dye solar cells made of P25, TNTs based cells exhibit an improved open circuit voltage and fill factor (FF) due to an increased electron lifetime, as revealed by EIS analysis. (C) 2011 Elsevier B.V. All rights reserved.

Combustion synthesis and properties of the NASICON family of materials

The fine-particle NASICON family of materials, MZr2P3O12(where M = Na, K, ½Ca and ¼Zr) and NbZrP3O12, have been prepared by the combustion of aqueous heterogeneous mixtures of stoichiometric amounts of metal nitrate, zirconyl nitrate, niobium phosphate, diammonium hydrogen phosphate, ammonium perchlorate and carbohydrazide (CH) at 400 °C. The formation of NASICON materials was confirmed by powder X-ray diffraction (XRD), IR, solid-state (31P) NMR spectroscopy and thermal expansion coefficient measurements. The combustion-synthesized NASICON powders have an average agglomerate size of 9�13 µm with a specific surface area varying from 8 to 28 m2 g�1. The powders pelletized and sintered in the range 1100�1200 °C for 5 h achieved 95�97% theoretical density and showed fine-grain microstructure. The coefficient of thermal expansion of a sintered compact was measured up to 500 °C and ranged from �1.5 × 10�6°C�1 to 1.0 × 10�6°C�1 depending on the composition.

Non-destructive evaluation of porosity and its effect on mechanical properties of carbon fiber reinforced polymer composite materials

In this work, an attempt is made to induce porosity of varied levels in carbon fiber reinforced epoxy based polymer composite laminates fabricated using prepregs by varying the fabrication parameters such as applied vacuum, autoclave pressure and curing temperature. Different NDE tools have been utilized to evaluate the porosity content and correlate with measurable parameters of different NDE techniques. Primarily, ultrasonic imaging and real time digital X-ray imaging have been tried to obtain a measurable parameter which can represent or reflect the amount of porosity contained in the composite laminate. Also, effect of varied porosity content on mechanical properties of the CFRP composite materials is investigated through a series of experimental investigations. The outcome of the experimental approach has yielded interesting and encouraging trend as a first step towards developing an NDE tool for quantification of effect of varied porosity in the polymer composite materials.

Non-destructive evaluation of porosity and its effect on mechanical properties of carbon fiber reinforced polymer composite materials

Structural adhesive bonding is widely used to execute assemblies in automobile and aerospace structures. The quality and reliability of these bonded joints must be ensured during service. In this context non destructive evaluation of these bonded structures play an important role. Evaluation of adhesively bonded composite single lap shear joints has been attempted through experimental approach. Series of tests, non-destructive as well as destructive were performed on different sets of carbon fiber reinforced polymer (CFRP) composite lap joint specimens with varied bond quality. Details of the experimental investigations carried out and the outcome are presented in this paper.