Data mining and accelerated electronic structure theory as a tool in the search for new functional materials

A highly accelerated electronic structure implementation and data mining algorithms have been combined with structural data from the inorganic crystal structure database to generate materials properties for about 22,000 inorganic compounds. It is shown how data mining algorithms employed on the database can identify new functional materials with desired materials properties, resulting in a prediction of 136 novel materials with potential for use as detector materials for ionizing radiation. The methodology behind the automatized ab initio approach is presented, results are tabulated and a version of the complete database is made available at the internet web site <http://gurka.fysik.uu.se/ESP/> (Ref. [1]).     

关于多孔材料的新模型

指出了多孔材料的经典性模型-Gibson-Ashby模型的不足,如孔隙单元非密积、棱柱状态不等价等,提出了一个能弥补Gibson-Ashby模型这些不足的新模型．应用这个新模型,可获得与实验结果符合良好的三维网状泡沫材料电阻率关系和力学关系的表征．实验结果证明,应用于多孔材料时,由新模型所得的有关数理关系明显优于Gibson-Ashby模型。     

Silicon-metal clusters: Nano-templates for cluster assembled materials

The structure, cohesive energy and electronic properties of MSi_n clusters were studied by first-principles calculations as a function of size (n) and species (M). We investigated 168 different clusters, containing from 1 to 14 Si atoms together with one transition metal atom among 12 different elements: Ti, Zr, Hf, V, Nb, Ta, Ni, Pd, Pt, Cu, Ag, Au. Clusters with n = 7, 10, 12 appear as local maxima in cohesive energy, independently of the metal involved. This, together with our previous findings for MSi_n (containing 12 other transition metal elements), establishes a systematic behavior. For most metals, MSi₁₂ and MSi₁₀ (the smallest endohedral species) are highly symmetric and exhibit local (with respect to their neighbors in size) stability. Thus, besides practically all MSi₁₂ clusters (exceptions being HfSi₁₂, ZrSi₁₂), also some MSi₁₀ such as VSi₁₀, NiSi₁₀, PdSi₁₀, NbSi₁₀ and AgSi₁₀, are promising candidates as building blocks for cluster assembled materials. Electronic properties of structurally equivalent clusters depend markedly on the transition metal involved, providing the means to tailor pre-defined properties when designing extended phases.     

Sol-gel processing of materials for electronic and related applications

Various techniques of sol-gel processing for the preparation of electronic and related materials are described and reviewed. Typical examples are chosen from thin films and coatings of gels, crystalline materials and glasses as also bulk glasses to illustrate the variations in processing parameters and material properties.     

高性能聚苯硫醚电子封装材料

本文介绍了高性能电子封装材料对特种工程塑料聚苯硫醚(PPS)树脂的要求,特别是离子含量、树脂分子量(粘度)的要求,并给出了国外PPS电子封装材料的性能指标。     

Nanostructured electronic and magnetic materials

Research and development in nanostructured materials is one of the most intensely studied areas in science. As a result of concerted R & D efforts, nanostructured electronic and magnetic materials have achieved commercial success. Specific examples of novel industrially important nanostructured electronic and magnetic materials are provided. Advantages of nanocrystalline magnetic materials in the context of both materials and devices are discussed. Several high technology examples of the use of nanostructured magnetic materials are presented. Methods of processing nanostructured materials are described and the examples of sol gel, rapid solidification and powder injection moulding as potential processing methods for making nanostructured materials are outlined. Some opportunities and challenges are discussed.     

PMN–PT based relaxor ferroelectrics as very smart materials

The basic classification of smart materials and structures is reviewed briefly. The role of nonlinear response for achieving field-tunability of properties is described in simple terms. The observation of the two-way shape-memory effect in a solid solution of lead magnesium niobate (PMN) and lead titanate (PT) for the nominal atomic composition 65:35 is reported. Possible factors influencing the occurrence of the two-way effect are discussed. It is argued that such relaxor ferroelectric ceramics can function as smart materials (rather than serving merely as components of smart structures), because they can meet the “information-reduction” criterion. And they qualify to be called very smart because they have a fairly large number of smartness attributes, including the two-way shape-memory attribute reported here.     

Block copolymers as templates for functional materials

There are applications and devices which require controlled distribution of material functionality (electrical, optical, catalytic, magnetic) in two or three dimensions. At the nanometer length scale, attempts to meet this challenge have included template-mediated materials chemistry [1] in which track-etched membranes, porous alumina and zeolites serve as the nanoscale reaction vessels for the synthesis of the functional materials. The ability to control both the length scale and the spatial organization of block copolymer morphologies makes these materials particularly attractive candidates for use as templates in the synthesis of functional nanocomposites. Appropriate choices of the repeat units of the block sequences renders them capable of selectivity sequestering preformed inorganic nanoclusters or selectively solubilizing inorganic reagents for in-situ cluster synthesis. Methods exist to produce nanoscale voids which percolate through the structure, leading to processes which coat or backfill the channels with functional materials.     

Graphene/MnO2 hybrid nanosheets as high performance electrode materials for supercapacitors

Graphene/MnO₂ hybrid nanosheets were prepared by incorporating graphene and MnO₂ nanosheets in ethylene glycol. Scanning electron microscopy and transmission electron microscopy analyses confirmed nanosheet morphology of the hybrid materials. Graphene/MnO₂ hybrid nanosheets with different ratios were investigated as electrode materials for supercapacitors by cyclic voltammetry (CV) and galvanostatic charge–discharge in 1 M Na₂SO₄ electrolyte. We found that the graphene/MnO₂ hybrid nanosheets with a weight ratio of 1:4 (graphene:MnO₂) delivered the highest specific capacitance of 320 F g⁻¹. Graphene/MnO₂ hybrid nanosheets also exhibited good capacitance retention on 2000 cycles.     

蛋白质-无机纳米杂化制备新型胶原蛋白材料

通过溶胶 凝胶法制备了胶原蛋白 SiO2有机 无机纳米杂化材料。FT IR研究表明:正硅酸乙酯(前驱体)水解产生的高表面活性微粒和精氨酸、组氨酸、色氨酸侧基的—CN基团发生了键合反应,并生成了新的化学键Si—C,同时前驱体水解产生的Si—OH和蛋白质分子的侧基CH—OH间也可发生缩合反应,因而在有机相和无机相之间产生强烈的相互作用。纳米粒子的尺寸随介质pH值和SiO2含量的改变而改变,当SiO2含量<3%且控制pH值3～3.5,生成纳米粒子的尺寸均在50～80nm之间;前驱体水解后产生的SiO2粒子在蛋白质中分散均匀,未发现明显的团聚现象;当SiO2含量高且水解速度较快时,无机粒子的尺寸分布略宽且高于100nm。无机纳米粒子的引入,使得胶原蛋白的水溶性降低,耐酸、碱稳定性、耐酶水解稳定性和耐热稳定性得到了明显的提高。     

Rational design of new materials for spintronics: Co2FeZ (Z=Al,Ga, Si,Ge)

Abstract

Spintronic is a multidisciplinary field and a new research area. New materials must be found for satisfying the different types of demands. The search for stable half-metallic ferromagnets and ferromagnetic semiconductors with Curie temperatures higher than room temperature is still a challenge for solid state scientists. A general understanding of how structures are related to properties is a necessary prerequisite for material design. Computational simulations are an important tool for a rational design of new materials. The new developments in this new field are reported from the point of view of material scientists. The development of magnetic Heusler compounds specifically designed as material for spintronic applications has made tremendous progress in the very recent past. Heusler compounds can be made as half-metals, showing a high spin polarization of the conduction electrons of up to 100% in magnetic tunnel junctions. High Curie temperatures were found in Co₂-based Heusler compounds with values up to 1120 K in Co₂FeSi. The latest results at the time of writing are a tunnelling magnet resistance (TMR) device made from the Co₂FeAl_0.5Si_0.5 Heusler compound and working at room temperature with a (TMR) effect higher than 200%. Good interfaces and a well-ordered compound are the precondition to realize the predicted half-metallic properties. The series Co₂FeAl_{1- x}Si_x is found to exhibit half-metallic ferromagnetism over a broad range, and it is shown that electron doping stabilizes the gap in the minority states for x=0.5. This might be a reason for the exceptional temperature behaviour of Co₂FeAl_0.5Si_0.5 TMR devices. Using x-ray diffraction (XRD), it was shown conclusively that Co₂FeAl crystallizes in the B2 structure whereas Co₂FeSi crystallizes in the L2₁ structure. For the compounds Co₂FeGa or Co₂FeGe, with Curie temperatures expected higher than 1000 K, the standard XRD technique using laboratory sources cannot be used to easily distinguish between the two structures. For this reason, the EXAFS technique was used to elucidate the structure of these two compounds. Analysis of the data indicated that both compounds crystallize in the L2₁ structure which makes these two compounds suitable new candidates as materials in magnetic tunnel junctions.     

Preparation of porous materials as catalysts for isomerization reactions

The preparation of platinum on tungsten oxide promoted zirconia using different procedures has been studied. Zirconium oxyclhoride, ammonium hydroxide, ammonium metatungstate, and hexachloroplatinic acid solutions were used as raw materials. Tungsten oxide promoted zirconium hydroxide (obtained using the three first reagents) was calcined at different temperatures before platinum incorporation. The solids were characterized by different techniques and used as catalysts for the isomerization of n-hexane at 200 °C. According to the preparation procedure, the solids have different properties: surface area, pore size distribution, X-ray diffraction patterns and activity for the isomerization reaction. Received: 30 March 2000     

Informatics derived materials databases for multifunctional properties

Abstract

In this review, we provide an overview of the development of quantitative structure–property relationships incorporating the impact of data uncertainty from small, limited knowledge data sets from which we rapidly develop new and larger databases. Unlike traditional database development, this informatics based approach is concurrent with the identification and discovery of the key metrics controlling structure–property relationships; and even more importantly we are now in a position to build materials databases based on design ‘intent’ and not just design parameters. This permits for example to establish materials databases that can be used for targeted multifunctional properties and not just one characteristic at a time as is presently done. This review provides a summary of the computational logic of building such virtual databases and gives some examples in the field of complex inorganic solids for scintillator applications.     

仿生结构材料的研究进展

综述了贝壳珍珠层、蛛丝结构、毛竹外密内疏结构、骨骼哑铃型结构、植物的根部网状结构以及木材的年轮结构等天然生物材料的结构特征及其相应的仿生材料近年来的研究进展；展望了结构仿生材料的前景，认为应对现有生物体的结构特征与其性能的相关性进行进一步的研究，并对已经解析的结构从不同的角度构筑模型，在实际应用中寻找模型和仿生材料设计的结合点，以推动仿生材料学的发展．     

Metallo-supramolecular modules as a paradigm for materials science

Abstract

Metal ion coordination in discrete or extended metallo-supramolecular assemblies offers ample opportunity to fabricate and study devices and materials that are equally important for fundamental research and new technologies. Metal ions embedded in a specific ligand field offer diverse thermodynamic, kinetic, chemical, physical and structural properties that make these systems promising candidates for active components in functional materials. A key challenge is to improve and develop methodologies for placing these active modules in suitable device architectures, such as thin films or mesophases. This review highlights recent developments in extended, polymeric metallo-supramolecular systems and discrete polyoxometalates with an emphasis on materials science.     

固体氧化物燃料电池LaxSr1-xTiO3阳极材料的电导性能

用高温固相合成法制备了LaxSr1-xTiO3,系统地研究了掺杂量、制备气氛和烧结温度对La掺杂SrTiO3性能的影响.研究表明,温度对La在SrTiO3中掺杂量的影响很大,La的掺杂极限在1300℃时为30 mol%,1500℃时为40 mol%左右.La的掺杂极大地提高了材料的电导率,La0.4Sr0.6TiO3表现出最佳的电导性能,其在800℃的电导率为160 S/cm.制备气氛与烧结温度也对LaxSr1-xTiO3电导性能有很大的影响,还原气氛与高的致密度有利于材料电导率的提高.     

Complex metallic alloys as new materials for additive manufacturing

Additive manufacturing processes allow freeform fabrication of the physical representation of a three-dimensional computer-aided design (CAD) data model. This area has been expanding rapidly over the last 20 years. It includes several techniques such as selective laser sintering and stereolithography. The range of materials used today is quite restricted while there is a real demand for manufacturing lighter functional parts or parts with improved functional properties. In this article, we summarize recent work performed in this field, introducing new composite materials containing complex metallic alloys. These are mainly Al-based quasicrystalline alloys whose properties differ from those of conventional alloys. The use of these materials allows us to produce light-weight parts consisting of either metal–matrix composites or of polymer–matrix composites with improved properties. Functional parts using these alloys are now commercialized.