Dialkylated dibenzotetrathienoacene derivative as semiconductor for organic field effect transistors

A novel semiconductor material based on dialkylated thienoacene is designed and synthesized. The dihexyl-substituted dibenzotetrathienoacene derivative C6-DBTTA exhibits high stability which is evidenced by thermogravimetric analysis (TGA), UV–vis spectroscopy and electrochemistry. X-ray diffraction measurements of the vacuum-evaporated thin films show strong diffraction and indicate that the molecules are stacked nearly perpendicular to the substrate. AFM images reveal that the morphology of thin films depended on the deposition temperature. Thin film FETs devices based on C6-DBTTA were constructed and showed high mobility up to 0.48 cm² V⁻¹ s⁻¹ and an on/off ratio over 10⁷. These results suggest that this new dihexylated thienoacene is an important organic semiconductor for field effect transistors.     

Microstructure evolution and interface structure of Al-40 wt% Si composites produced by high-energy ball milling

High silicon content Al-Si composites with a composition of Al-40 wt% Si were fabricated via a highenergy ball milling method. The microstructure evolution of Al-40 wt% Si milled powders and sintered composites has been thoroughly studied by scanning electron microscopy, X-ray diffraction, energydispersive spectrometry and high-resolution transmission electron microscopy. The mechanism of ball milling Al-40 wt% Si powders has been disclosed in detail: fracture mechanism dominating in the early stages, followed by the agglomeration mechanism, finally reaching the balance between the fragments and the agglomerates. It has been found that the average particle sizes of mixed Al-Si powders can be refined to the nanoscale, and the crystallite sizes of Al and Si have been reduced to 10nm and 62nm upon milling for 2h–50h, respectively. The finally formed Al-Si interfaces after ball milling for 50h are wellcohesive. A dense and homogenous Al-40 wt% Si composite have been achieved by solid-state sintering at550?C. The results thus provide an effective support for producing bulk nanostructured Al-Si composites.     

The improved mechanical properties of Al matrix composites reinforced with oriented β-Si3N4 whisker

The β-Si₃N₄ whiskers (β-Si₃N₄w) reinforced Al matrix composites were first fabricated by hot pressing, then treated through hot extrusion. The microstructure characterization demonstrated the preferred orientations of both β-Si₃N₄w and Al grains in the as-extruded composites. It indicated that β-Si₃N₄w were aligned along the extrusion direction and Al grains exhibited a distinct <111>_Al texture. The interface between β-Si₃N₄w and Al was in a good bonding status without voids and reaction products. Effects of extrusion process on the mechanical properties of composites were also investigated. The results indicated the extrusion process had a prominent strengthening effect on the mechanical properties of composites. The maximum yield strength and ultimate tensile strength of composites reached up to 170 and 289 MPa, respectively, accompanied by a 12.3% elongation at fracture when the whisker fraction was 15 vol.%. This improvement was collectively attributed to the densification of composites, the strong interface, and the preferred orientation inside composites. The yield strength of the composites reinforced with 5 vol.% β-Si₃N₄w corresponded well with the theoretical value from different strengthening mechanisms.     

Oxidation of amorphous alloys

Owing to their unique short- or medium-range ordered microstructures and excellent mechanical, physical, and chemical properties, amorphous alloys have attracted significant interest in recent years. For the application of amorphous alloys, clarifying their oxidation processes and mechanisms is necessary since many of the surface-related properties of amorphous alloys largely depend on the surface oxide layer. The aim of this paper is to review the recent research on the thermal oxidation behaviors of amorphous alloys under pure oxygen or air condition. The contents are divided into three categories according to the number of components the research considers, i.e., the oxidation of binary, ternary, and multi-component (>3) amorphous alloys. Each section discusses the thermal stability of the amorphous matrix, oxidation kinetics, and the oxide layer and amorphous substrate, which are strongly affected by internal factors (i.e., alloy elements and microstructure) and external factors (i.e., oxidation temperature, duration, and oxygen partial pressure, etc.). The general features of the oxidation of amorphous alloys – from simple binary to complex multi-component amorphous alloys – will be summarized. This overview of the current scientific understanding on the fundamentals of these materials may provide guidelines for the development of strongly corrosion-resistant amorphous alloys.     

Morphology modulation of organic photovoltaics with block copolymer additive based on rational design strategies

Organic photovoltaics are a promising alternative to silicon-based solar cells with benefits of low-cost production and large scalability. However, its performance is restricted by a non-equilibrium phase-separated morphology. Additive compositions of block copolymer P3HT-b-PFTBT are most likely to mix up and form donor and acceptor morphologies. The parallel bulk-heterojunction model was proposed to show the characteristic photovoltaic parameters and the effect of the parallel cascading heterojunction formation made up of isolated PCBM acceptor domains. We demonstrate block copolymer-based stretchable solar cells on plastic foil substrates, with good power conversion efficiency. To compare the efficiency and stretchability, organic photovoltaic devices were constructed using P3HT/PC₆₁BM, PTB7/PC₇₁BM and P3HT/P3HT-b-PFTBT/PCBM active layer combinations. We find that through rational design of the component ratio, the block-copolymer-based solar cell can withstand tensile strain up to 37%.     

金属诱导晶化基础与应用研究进展

将非晶半导体与金属相接触,可以诱导非晶半导体在极低的温度下结晶,这一现象被称为金属诱导晶化。薄膜状态的晶体半导体是用于众多先进技术中的关键材料,被广泛应用于微电子、光电子、显示技术和光伏技术等领域。金属诱导晶化为低温晶体半导体器件的制造、纳米多孔金属材料的合成以及金属材料界面工程提供了一种崭新的途径,引起了学术界和工业界的广泛关注。本文综述了金属诱导晶化的研究进展,对不同金属/非晶半导体体系中存在的金属诱导晶化现象进行了归纳分类总结,对其热力学原理和动力学机制进行了详细的计算与分析,突出了界面热力学在薄膜体系的固→固相变中的作用,最终阐明了金属诱导晶化过程的内在机理,并对金属诱导晶化过程未来的研究趋势进行了展望。     

Preparation and electrochemical properties of some (Sc1−xTix)Ni alloys

A series of (Sc_1−xTi_x)Ni alloys and their hydrides (Sc_1−xTi_x)NiH_y, where x=0, 0.1, 0.3, 0.5, and y=2.9, 2.58, 2.23 and 1.55, have been prepared. The ability to store hydrogen gradually decreases with increasing Ti content in line with the reduction of the unit cell volume from 32.16 ų for ScNi to 29.68 ų for (Sc_0.5Ti_0.5)Ni. The electrochemical discharge capacity, however, varies in a more complex manner with (Sc_0.7Ti_0.3)Ni composition displaying the highest value of 231 mAh/g. The discharge capacity losses after 10 electrochemical charge–discharge cycles also vary non-linearly between 46% for (Sc_0.9Ti_0.1)Ni and 5% for (Sc_0.5Ti_0.5)Ni.     

Lignocellulose to bio-hydrogen: An overview on recent developments

Production of hydrogen from lignocellulosic biomass using biological methods is an alluring approach to generate green and clean energy. However, the challenges levied by structural and compositional aspects of lignocellulosic biomass block the way to harness their complete energy potential. The review revisits the available methods of pretreatment to augment the accessibility of carbon source required for microorganism to perform biomass to hydrogen conversion. The fermentation methods that have been employed for years for bio-hydrogen production are discussed in brief to provide the background of biological routes of hydrogen production. The review further highlights the latest research trends and upgrades in technologies including the identified novel microbial strains, reactor configurations, integrated schemes of fermentations, nanocatalysts addition and the genetic engineering tactics to enhance the competence of hydrogen producing bacteria.     

A novel photovoltaic maximum power point tracking technique based on grasshopper optimized fuzzy logic approach

The maximum power point tracking (MPPT) in the PV system has become complex due to the stochastic nature of the load, intermittency in solar irradiance and ambient temperature. To address this problem, a novel Grasshopper optimized fuzzy logic control (FLC) approach based MPPT technique is proposed in this paper. In this proposed MPPT, grasshopper optimization is used to tune the membership functions (MFs) of FLC to handle all uncertainties caused by variable irradiances and temperatures. The performance of the proposed grasshopper optimized FLC based MPPT is studied under rapidly changing irradiance and temperature. The proposed MPPT overcomes the limitations such as slow convergence speed, steady-state oscillations, lower tracking efficiency as encountered in conventional methods viz. perturb & observed (P&O) and FLC techniques. The feasibility of the proposed MPPT is validated through experimentation. The effectiveness of the proposed scheme is compared with P&O and also with FLC MPPT.