A simple experimental arrangement for measuring the vapour pressures and sublimation enthalpies by the Knudsen effusion method: Application to DNA and RNA bases

We measured the vapour pressure of several DNA and RNA bases—uracil, adenine, guanine, thymine and cytosine—in the 300–450 K range. In each case the sample mass loss rate was measured as function of temperature with a simple setup consisting of a commercial film deposition system and a homemade oven. Afterwards vapour pressure values were extracted from these data using the Knudsen effusion method. Sublimation enthalpy values, obtained from vapour pressure data by applying the Clausius–Clapeyron equation, are in very good agreement with literature values. The results suggest that crystal-based film thickness monitors may be useful in on-line cross-section measurements, monitoring the gas target thickness. They also show the viability of using this oven for producing a biomolecular gas target.     

Ferroelectrics: new wide-gap materials for UV detection

Photoconductive properties of some sol-gel deposited, ferroelectric thin films are investigated in the ultraviolet (UV) domain. The investigated materials are: Bi₄Ti₃O₁₂ (BiT)_; SrBi₂Ta₂O₉ (SBT) and Pb(Zr_0.45Ti_0.55)O₃ (PZT). It was found that all these materials exhibit pronounced photoconductivity in the 250–500 nm domain. The best current responsivity was obtained for Bi₄Ti₃O₁₂ (BiT) films.     

Characterization of multilayered materials for optoelectronic components by high-resolution X-ray diffractometry and reflectometry: contribution of numerical treatments

Both X-ray reflectometry and X-ray diffractometry techniques are used for the assessment of individual layer thicknesses inside complicated semi-conductor heterostructures, in particular for opto-electronic applications. The use of Fast Fourier transform-based numerical treatments applied to the reflectivity curve allows a fast determination of the individual layer thicknesses. We demonstrate the capability of this method by reporting X-ray reflectometry study on superlattices, multiple quantum wells, and other complicated structures. Typical layer thicknesses from 0.5 nm to 500 nm were successfully investigated. Fast Fourier transform-based procedure has also been employed successfully on high resolution X-ray diffraction spectra. We finally show the complementary of both techniques.     

Ultrafast lasers: A new frontier for optical materials processing

In the last years, ultrashort laser pulses have gone through the laboratory walls to burst into the industrial arena as a tool for material micro- and nanoprocessing. The number of industrial fields and specific applications is steadily growing, reaching the nanotechnology applications. Now, we celebrate the 25th anniversary of the CPA (chirped pulse amplification) technique which made available intense ultrashort (subpicosecond) pulses able to induce ablation of any material. This contribution tries to review the fundamentals of ultrafast lasers as well as some of their applications, emphasizing the processing of optical materials.     

NSF cyberinfrastructures: A new paradigm for advancing materials simulation

This paper discusses the motivation for the creation of cyberinfrastructures to enhance specific technical areas of research. It then goes on to provide a review of two cyberinfrastructures supported by the National Science Foundation, OpenKIM and CAMS, which are geared towards enhancing materials modeling at the atomic scale. Their objectives, accomplishments, and future goals are discussed. Lastly, the future outlook for cyberinfrastructures such as these to impact materials modeling is discussed.     

Photonic metamaterials: a new class of materials for manipulating light waves

Abstract

A decade of research on metamaterials (MMs) has yielded great progress in artificial electromagnetic materials in a wide frequency range from microwave to optical frequencies. This review outlines the achievements in photonic MMs that can efficiently manipulate light waves from near-ultraviolet to near-infrared in subwavelength dimensions. One of the key concepts of MMs is effective refractive index, realizing values that have not been obtained in ordinary solid materials. In addition to the high and low refractive indices, negative refractive indices have been reported in some photonic MMs. In anisotropic photonic MMs of high-contrast refractive indices, the polarization and phase of plane light waves were efficiently transformed in a well-designed manner, enabling remarkable miniaturization of linear optical devices such as polarizers, wave plates and circular dichroic devices. Another feature of photonic MMs is the possibility of unusual light propagation, paving the way for a new subfield of transfer optics. MM lenses having super-resolution and cloaking effects were introduced by exploiting novel light-propagating modes. Here, we present a new approach to describing photonic MMs definitely by resolving the electromagnetic eigenmodes. Two representative photonic MMs are addressed: the so-called fishnet MM slabs, which are known to have effective negative refractive index, and a three-dimensional MM based on a multilayer of a metal and an insulator. In these photonic MMs, we elucidate the underlying eigenmodes that induce unusual light propagations. Based on the progress of photonic MMs, the future potential and direction are discussed.     

Chemically complex intermetallic alloys: A new frontier for innovative structural materials

Intermetallic materials are bestowed by diverse ordered superlattice structures together with many unusual properties. In particular, the advent of chemically complex intermetallic alloys (CCIMAs) has received considerable attention in recent years and offers a new paradigm to develop novel metallic materials for advanced structural applications. These newly emerged CCIMAs exhibit synergistic modulations of structural and chemical features, such as self-assembled long-range close-packed ordering, complex sublattice occupancy, and interfacial disordered nanoscale layer, potentially allowing for superb physical and mechanical properties that are unmatched in conventional metallic materials. In this paper, we critically review the historical developments and recent advances in ordered intermetallic materials from the simple binary to chemically complex alloy systems. We are focused on the unique multicomponent superlattice microstructures, nanoscale grain-boundary segregation, and disordering, as well as the various extraordinary mechanical and functional properties of these newly developed CCIMAs. Finally, perspectives on the future research orientation, challenges, and opportunities of this new frontier are provided.     

Phase separation micromolding: a new generic approach for microstructuring various materials

Phase separation micromolding (PSmicroM) is a versatile microfabrication technique that can be used to structure a very broad range of polymers, including block copolymers and biodegradable and conductive polymers without the need for clean-room facilities. By incorporating a subsequent process step, carbon, ceramic, and metallic microstructures can also be fabricated from a polymeric or hybrid precursor. The replication process is straightforward and cost-effective. It relies on phase separation of a polymer solution while in contact with a structured mold. Intrinsic shrinkage during the phase separation facilitates the release of the replica from the mold, which increases the reliability of the process even at small feature sizes, thin polymer films, or high aspect ratios. Under suitable circumstances perforation of the polymer film can be obtained, resulting in completely open "through" microstructures. Furthermore, porosity can be introduced in a microstructure, which may result in unknown functionalities.     

Autoclaved aerated concrete (AAC) rubble for new recycling building products: In dry premixed mortars for masonry,in masonry blocks and in lightweight blocks

In cooperation of Bremen Institute for Materials Testing (MPA Bremen), a Department of Leibniz Institute for Materials Engineering IWT, Bremen University of Applied Sciences and the Research Association RWB Bremen building products for masonry structures were developed on the basis of AAC rubble from C&D wastes. Granulates from processed AAC rubble were introduced as aggregates in dry premixed masonry mortars, in masonry blocks and lightweight building blocks and elements to replace completely natural aggregates. These recycling products exhibit beneficial technical properties, at the same time large volumes of AAC wastes may be re‐used. On the basis of the achieved R&D‐results from laboratory experiments, trial batches of dry premixed mortar and masonry blocks were produced in the building materials industry on their available industrial equipment, minor adjustments in the mix composition were necessary. After a sufficient amount of dry premixed mortar and masonry blocks were produced, the recycling products were used to erect indoor masonry walls in a building project in Bremen.     

高温原位测试材料相变的新方法:高温法拉第磁秤

高温原位磁化率测试法利用顺磁性材料在相变时磁化率变化的原理,直接测试出材料相变时的转变温区,是研究顺磁性材料相变的一种新的尝试.我们采用高温法拉第磁秤测试了Ag2O和CuO在升温和降温中磁化率的变化曲线,通过磁化率的转变演示了Ag2O和CuO相变的动态过程.以此介绍了原位观测顺磁性材料晶体学相变的高温法拉第磁秤方法.高...     

Mineralized structures in nature: Examples and inspirations for the design of new composite materials and biomaterials

Through the natural evolutionary process, organisms have been improving amazing mineralized materials for a series of functions using a relatively few constituent elements. Biomineralization has been widely studied in the last years. It is important to understand how minerals are produced by organisms and also their structure and the corresponding relationship with the properties and function. Moreover, one can look at minerals as a tool that could be used to develop high performance materials, through design inspiration and to find novel processing routes functioning at mild conditions of temperature, pressure and solvent type. As important as the molecular constituents are structural factors, which include the existence of different levels of organization and controlled orientation. Moreover, the way how the hierarchical levels are linked and interfacial features plays also a major role in the final behavior of the biogenic composite. The main aim of this work is to review the latest contributions that have been reported on composite materials produced in nature, and to relate their structures at different length scales to their main functions and properties. There is also an interest in developing new biomimetic procedures that could induce the production of calcium phosphate coatings, similar to bone apatite in substrates for biomedical applications, namely in orthopedic implants and scaffolds for tissue engineering and regenerative medicine; this topic will be also addressed. Finally, we also review the latest proposed approaches to develop novel synthetic materials and coatings inspired from natural-based nanocomposites.     

Zr(IV) basic carbonate complexes as precursors for new materials: synthesis of the zirconium-surfactant mesophase

Soluble anionic carbonate complexes of Zr(IV) are produced by addition of Zr(IV) salts to the excess of an alkali metal or ammonium carbonate. The solutions are metastable at pH 7-10 and can be used as the precursors for the synthesis of new materials, as illustrated by the example of the surfactant containing mesophase with a wormhole-like structure, prepared by means of reaction with cetyltrimethylammonium bromide.     

The 3D Amlouk-Boubaker expansivity-energy gap-Vickers hardness abacus: A new tool for optimizing semiconductor thin film materials

In this study, we propose a new abacus based on a synthetic parameter: the Amlouk-Boubaker expansivity ψ_AB. This abacus gathers the band gap energy E_g., Vickers microhardness and ψ_AB. This abacus is presented as a guide to evaluate and optimize photovoltaic-thermal semiconductor thin films thermal and optical performance. The definition of this parameter ψ_AB takes into account the thermal diffusivity and the optical effective absorptivity of the material. As a first approximation, this parameter, could be considered as a 3D velocity of the transmitted heat inside the material.New functional semiconductor materials have been significantly classified using this abacus.     

The Gibson-Ashby model for additively manufactured metal lattice materials: Its theoretical basis,limitations and new insights from remedies

The Gibson-Ashby (G-A) model has been instrumental in the design of additively manufactured (AM-ed) metal lattice materials or mechanical metamaterials. The first part of this work reviews the proposition and formulation of the G-A model and emphasizes that the G-A model is only applicable to low-density lattice materials with strut length-to-diameter ratios greater than 5. The second part evaluates the applicability of the G-A model to AM-ed metal lattice materials and reveals the fundamental disconnections between them. The third part assesses the deformation mechanisms of AM-ed metal lattices in relation to their strut length-to-diameter ratios and identifies that AM-ed metal lattices deform by concurrent bending, stretching, and shear, rather than just stretching or bending considered by the G-A model. Consequently, mechanical property models coupling stretching, bending and shear deformation mechanisms are developed for various lattice materials, which show high congruence with experimental data. The last part discusses new insights obtained from these remedies into the design of strong and stiff metal lattices. In particular, we recommend that the use of inclined struts be avoided.     

Environmental advantage by choice: Ex-ante LCA for a new Kraft pulp fibre reinforced polypropylene composite in comparison to reference materials

This study analyses the circumstances of environmental advantage by benchmarking a novel Kraft pulp fibre reinforced polypropylene against its matrix material and two other composites with talcum and glass fibres. With one exception, all composites use less non-renewable energy (−1% to −29%), but only the Kraft pulp fibre reinforced polypropylene achieves a reduction in global warming potential (14% to 35%) considering different functional units compared to polypropylene. The comparisons on basis of function–strength and stiffness in this case study–show that the adequate application of specific material properties, are key to achieve environmental advantages.     

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.     

Room temperature plasma oxidation: A new process for preparation of ultrathin layers of silicon oxide, and high dielectric constant materials

In this paper we present basic features and oxidation law of the room temperature plasma oxidation, (RTPO), as a new process for preparation of less than 2 nm thick layers of SiO₂, and high-k layers of TiO₂. We show that oxidation rate follows a potential law dependence on oxidation time. The proportionality constant is function of pressure, plasma power, reagent gas and plasma density, while the exponent depends only on the reactive gas. These parameters are related to the physical phenomena occurring inside the plasma, during oxidation. Metal-Oxide-Semiconductor (MOS) capacitors fabricated with these layers are characterized by capacitance-voltage, current-voltage and current-voltage-temperature measurements. Less than 2.5 nm SiO₂ layers with surface roughness similar to thermal oxide films, surface state density below 3 × 10¹¹ cm^− 2 and current density in the expected range for each corresponding thickness, were obtained by RTPO in a parallel-plate reactor, at 180 mW/cm² and pressure range between 9.33 and 66.5 Pa (0.07 and 0.5 Torr) using O₂ and N₂O as reactive gases. MOS capacitors with TiO₂ layers formed by RTPO of sputtered Ti layers are also characterized. Finally, MOS capacitors with stacked layers of TiO₂ over SiO₂, both layers obtained by RTPO, were prepared and evaluated to determine the feasibility of the use of TiO₂ as a candidate for next technology nodes.