Showing papers in "Journal of Materials Research in 2017"
TL;DR: The cold sintering process as mentioned in this paper can consolidate a broad set of inorganic powders between room temperature and 300 °C using a standard uniaxial press and die.
Abstract: This manuscript describes, defines, and discusses the process of cold sintering, which can consolidate a broad set of inorganic powders between room temperature and 300 °C using a standard uniaxial press and die. This temperature range is well below that needed for appreciable bulk diffusion, indicating immediately the distinction from the well-known and thermally driven analogue, allowing for an unconventional method for densifying these inorganic powders. Sections of this report highlight the general background and history of cold sintering, the current set of known compositions that exhibit compatibility with this process, the basic experimental techniques, the current understanding of physical mechanisms necessary for densification, and finally opportunities and challenges to expand the method more generically to other systems. The newness of this approach and the potential for revolutionary impact on traditional methods of powder-based processing warrants this discussion despite a nascent understanding of the operative mechanisms.
165 citations
TL;DR: TENG based active sensors have been extensively spread into a variety of fields for self-powered high-performance sensing, featured as being lightweight, extremely cost-effective, and environmentally friendly.
Abstract: Personal, multifunctional, and smart electronic devices/systems are indispensable components of the internet of things for modern information collection and exchange, which play a key role in facilitating the development of human civilization Traditional technique for powering these sensor nodes mainly relies on batteries, which may not be favorable owing to the limited battery lifetime, large sensor population, wide distribution, as well as the potential of environmental detriment Extricated from external power sources, triboelectric nanogenerators (TENGs) based active sensors have been extensively spread into a variety of fields for self-powered high-performance sensing, featured as being lightweight, extremely cost-effective, and environmentally friendly In this article, current progress of TENGs as smart sensors for self-powered touch detection, vibration and acoustic sensing, biomedical applications, as well as human-machine interfacing, has been comprehensively reviewed, from aspects of materials usage, device fabrication to practical applications The latest representative achievements regarding the TENG based self-powered sensing systems were also systematically presented In the end, some perspectives and challenges for the TENG based self-powered smart sensors were also summarized
136 citations
TL;DR: In this article, the interface between n-type c-Si (n-Si) and three thermally evaporated transition metal oxides (TMOs) was investigated by transmission electron microscopy, secondary ion-mass, and x-ray photoelectron spectroscopy.
Abstract: Transition metal oxides (TMOs) have recently demonstrated to be a good alternative to boron/phosphorous doped layers in crystalline silicon heterojunction solar cells. In this work, the interface between n-type c-Si (n-Si) and three thermally evaporated TMOs (MoO3, WO3, and V2O5) was investigated by transmission electron microscopy, secondary ion-mass, and x-ray photoelectron spectroscopy. For the oxides studied, surface passivation of n-Si was attributed to an ultra-thin (1.9–2.8 nm) SiOx ∼1.5 interlayer formed by chemical reaction, leaving oxygen-deficient species (MoO, WO2, and VO2) as by-products. Carrier selectivity was also inferred from the inversion layer induced on the n-Si surface, a result of Fermi level alignment between two materials with dissimilar electrochemical potentials (work function difference Δϕ ≥ 1 eV). Therefore, the hole-selective and passivating functionality of these TMOs, in addition to their ambient temperature processing, could prove an effective means to lower the cost and simplify solar cell processing.
123 citations
TL;DR: In this article, the electronic, mechanical, and optical properties of monolayer C3N, a newly synthesized two-dimensional carbon-graphene crystal, were investigated using first-principles calculations.
Abstract: Carbon–nitrogen compounds have attracted enormous attention because of their unusual physical properties and fascinating applications on various devices. Especially in two-dimension, doping of nitrogen atoms in graphene is widely believed to be an effective mechanism to improve the electronic and optoelectronic performances of graphene. In this work, using the first-principles calculations, we systematically investigate the electronic, mechanical, and optical properties of monolayer C3N, a newly synthesized two-dimensional carbon-graphene crystal. The useful results we obtained are: (i) monolayer C3N is an indirect band-gap semiconductor with the gap of 1.042 eV calculated by the accurate hybrid functional; (ii) compared with graphene, it has smaller ideal tensile strength but larger in-plane stiffness; (iii) the nonlinear effect of elasticity at large strains is more remarkable in monolayer C3N; (iv) monolayer C3N exhibits main absorption peak in visible light region and secondary peak in ultraviolet region, and the absorbing ratio between them can be effectively mediated by strain.
110 citations
TL;DR: In this paper, high-porosity metakaolin-based geopolymer foams (GFs) were fabricated by a gelcasting technique using hydrogen peroxide (foaming agent) in combination with Tween 80 (surfactant).
Abstract: High-porosity metakaolin-based geopolymer foams (GFs) were fabricated by a gelcasting technique using hydrogen peroxide (foaming agent) in combination with Tween 80 (surfactant). Slurries processed in optimized conditions enabled to fabricate potassium based GFs with a total porosity in the range of ∼67 to ∼86 vol% (∼62 to ∼84 vol% open), thermal conductivity from ∼0.289 to ∼0.091 W/mK, and possessing a compressive strength from ∼0.3 to ∼9.4 MPa. Moreover, factors that influence the compressive strength, the porosity, the thermal conductivity, and the cell size distribution were investigated. The results showed that the cell size and size distribution can be controlled by adding different content of surfactant and foaming agent. The foamed geopolymer can also be used as adsorbents for the removal of copper and ammonium ions from wastewater. The foams, due to their low thermal conductivity, could also be used for thermal insulation. It was also possible to produce geopolymer formulations that could be printed using additive manufacturing technology (Direct Ink writing), which enabled to produce components with nonstochastic porosity.
106 citations
TL;DR: In this paper, the current understanding of graphene ceramic matrix composites (GCMC) with three particular topics: (i) principles and techniques for graphene dispersion, (ii) processing of GCMC, and (iii) effects of graphene on properties ofGCMC.
Abstract: Research on graphene has been developing at a relentless pace as it holds the promise of delivering composites with exceptional properties. In particular, the excellent mechanical properties of graphene make it a potentially good reinforcement ingredient in ceramic composites while their impressive electrical conductivity has roused interest in the area of multifunctional applications. However, the potential of graphene can only be fully exploited if they are homogenously embedded into ceramic matrices. Thus, suitable processing route is critical in obtaining ceramic composites with desired properties. This paper reviews the current understanding of graphene ceramic matrix composites (GCMC) with three particular topics: (i) principles and techniques for graphene dispersion, (ii) processing of GCMC, and (iii) effects of graphene on properties of GCMC. Besides, toughening mechanisms and percolation phenomenon that may occur in these composites are elaborated with appropriate examples. Challenges and perspectives for future progress in applications are also highlighted.
104 citations
TL;DR: In this article, the fundamental basis for texture-engineered ceramics properties is outlined and a review of recent contributions to the field of texture-engineering is provided with an update on the properties of textured lead-free and lead-based piezoelectrics.
Abstract: Texture-engineered ceramics enable access to a vast array of novel texture-property relations leading to property values ranging between those of single crystals and isotropic bulk ceramics. Recently developed templated grain growth and magnetic alignment texturing methods yield high quality crystallographic texture, and thus significant advances in achievable texture-engineered properties in magnetic, piezoelectric, electronic, optical, thermoelectric, and structural ceramics. In this paper, we outline the fundamental basis for these texture-engineered properties and review recent contributions to the field of texture-engineered ceramics with an update on the properties of textured lead-free and lead-based piezoelectrics. We propose that further property improvements can be realized through development of processes that improve crystallographic alignment of the grain structure, create biaxial texture, and explore a wider array of crystallographic orientations. There is a critical need to model the physics of texture-engineered ceramics, and more comprehensively characterize texture, thus enabling testing of texture orientation-property relations and materials performance. We believe that in situ measurements of texture evolution can lead to a more fundamental and comprehensive understanding of the mechanisms of texture development.
101 citations
TL;DR: Graphene has emerged as a champion material for a variety of applications cutting across multiple disciplines in science and engineering as discussed by the authors, and this review is intended to assess why graphene is suitable to build better biosensors, the working of existing biosensing schemes and their current status toward commercialization for wearable diagnostic and prognostic devices.
Abstract: Graphene has emerged as a champion material for a variety of applications cutting across multiple disciplines in science and engineering. Graphene and its derivatives have displayed huge potential as a biosensing material due to their unique physicochemical properties, good electrical conductivity, optical properties, biocompatibility, ease of functionalization, and flexibility. Their widespread use in making biosensors has opened up new possibilities for early diagnosis of life-threatening diseases and real-time health monitoring. Following an introduction and discussion on the significance of fabrication protocols and assembly, this review is intended to assess why graphene is suitable to build better biosensors, the working of existing biosensing schemes and their current status toward commercialization for wearable diagnostic and prognostic devices. We believe this review will provide a critical insight for harnessing graphene as a suitable biosensor for the clinical diagnostics, its future prospects and challenges ahead.
96 citations
TL;DR: In this article, a novel strain compensation model enabling the epitaxial growth of two-phase nanocomposites having large lattice mismatch with substrates is proposed, and out-of-plane strain coupling between the two phases is also discussed in terms of designing strain states for desired functionalities.
Abstract: Self-assembled oxide-based vertically aligned nanocomposite (VAN) thin films have aroused tremendous research interest in the past decade. The interest arises from the range of unique nanostructured films which can form and the multifunctionality arising from these forms. Hence, a large number of oxide VAN systems have been demonstrated and explored for enhancing specific physical properties, such as strain-enhanced ferroelectricity, tunable magnetotransport, and novel electrical/ionic transport properties. The epitaxial growth of the nanocomposite thin films and the coupling at the heterogeneous interfaces are critical considerations for future device applications. In this review, the advantages of strain coupling along vertical interfaces and film-substrate interfaces in nanocomposite films over conventional single phase films are discussed. Specifically, a unique strain compensation model enabling the epitaxial growth of two-phase nanocomposites having large lattice mismatch with substrates is proposed. Out-of-plane strain coupling between the two phases is also discussed in terms of designing strain states for desired functionalities.
84 citations
TL;DR: In this article, the photocatalytic performance of MoO3/g-C3N4 composite in converting CO2 to fuels under simulated sunlight irradiation was investigated.
Abstract: This research was designed for the first time to investigate the photocatalytic activities of MoO3/g-C3N4 composite in converting CO2 to fuels under simulated sunlight irradiation. The composite was synthesized using a simple impregnation-heating method and MoO3 nanoparticles was in situ decorated on the g-C3N4 sheet. Characterization results indicated that the introduction of MoO3 nanoparticles into g-C3N4 fabricated a direct Z-scheme heterojunction structure. The effective interfacial charge-transfer across the heterojunction significantly promoted the separation efficiency of charge carriers. The optimal CO2 conversion rate of the composite reached 25.6 µmol/(h gcat), which was 2.7 times higher than that of g-C3N4. Additionally, the synthesized MoO3/g-C3N4 also presented excellent photoactivity in RhB degradation under visible-light irradiation.
78 citations
TL;DR: In this article, the electron density dependence of the electron mobility in β-Ga2O3 is studied in the bulk material form and also in the form of a two-dimensional electron gas.
Abstract: This work reports an investigation of electron transport in monoclinic β-Ga2O3 based on a combination of density functional perturbation theory based-lattice dynamical computations, coupling calculation of lattice modes with collective plasmon oscillations, and Boltzmann theory-based transport calculations. The strong entanglement of the plasmon with the different longitudinal optical (LO) modes makes the role LO-plasmon coupling crucial for transport. The electron density dependence of the electron mobility in β-Ga2O3 is studied in the bulk material form and also in the form of a two-dimensional electron gas. Under high electron density, a bulk mobility of 182 cm2/V s is predicted, while in the 2DEG form, the corresponding mobility is about 418 cm2/V s when remote impurities are present at the interface and improves further as the remote impurity center moves away from the interface. The trend of the electron mobility shows promise for realizing high-electron mobility in dopant-isolated electron channels. The experimentally observed small anisotropy in mobility is traced through a transient Monte Carlo simulation. It is found that the anisotropy of the IR-active phonon modes is responsible for giving rise to the anisotropy in low-field electron mobility.
TL;DR: In this article, a Cu 0.13Cr-0.074Ag alloy has been synthesized by nonvacuum melting and casting followed by thermal-mechanical treatment, and microstructure and mechanical properties have been tailored to make a trade-off between the strength and the electrical conductivity.
Abstract: A Cu–0.13Cr–0.074Ag (wt%) alloy has been synthesized by the nonvacuum melting and casting followed by thermal-mechanical treatment, and microstructure and mechanical properties have been tailored to make a trade-off between the strength and the electrical conductivity. Results illuminated that the designed alloy has a tensile strength of 473 MPa, a hardness of 140 HV, a yield strength of 446 MPa, an elongation of 10.5%, and an electrical conductivity of 94.5% IACS. Microstructure observations of the samples aged at 480 °C showed that: an fcc structure Cr-phase with a cube-on-cube orientation relationship with the Cu matrix was formed as aged for 15 min, while an ordered bcc structure Cr phase with B2 structure formed as aged for 2 h. The 3DAP results revealed that the Cr was formed to be precipitates and the Ag was formed as solutes distributing evenly in matrix. The high electrical conductivity was ascribed to the Cr element precipitated from the Cu matrix, Ag dissolved in the Cu matrix had little effect on the scattering of Cu electron.
TL;DR: A review of research on nanostructured high-entropy alloys with emphasis on those made by the severe plastic deformation methods of mechanical alloying and high-pressure torsion is presented in this paper.
Abstract: This article is a review of research on nanostructured high-entropy alloys with emphasis on those made by the severe plastic deformation methods of mechanical alloying and high-pressure torsion. An example of thin film refractory metal alloys made by magnetron sputtering is also presented. The article will begin with a discussion of the seminal research of B.S. Murty and co-workers who first produced nanocrystalline high-entropy alloys by mechanical alloying of powders. This will be followed by a listing of research, in mostly chronological order, of mainly 3d transition metal alloys made nanocrystalline by mechanical alloying. Research on the well-studied Cantor alloy, from the literature and the author’s laboratory will be presented. The author’s and co-worker’s research on a low-density high-entropy alloy with single-phase fcc or hcp structure and an extremely high strength (hardness)-to-weight ratio will be described.
TL;DR: In this article, the authors discuss the measurement technique of X-ray beam induced current and point out fundamental differences between measurements of wafer-based silicon and thin-film solar cells.
Abstract: In situ and operando measurement techniques combined with nanoscale resolution have proven invaluable in multiple fields of study. We argue that evaluating device performance as well as material behavior by correlative X-ray microscopy with <100 nm resolution can radically change the approach for optimizing absorbers, interfaces and full devices in solar cell research. In this article, we thoroughly discuss the measurement technique of X-ray beam induced current and point out fundamental differences between measurements of wafer-based silicon and thin-film solar cells. Based on reports of the last years, we showcase the potential that X-ray microscopy measurements have in combination with in situ and operando approaches throughout the solar cell lifecycle: from the growth of individual layers to the performance under operating conditions and degradation mechanisms. Enabled by new developments in synchrotron beamlines, the combination of high spatial resolution with high brilliance and a safe working distance allows for the insertion of measurement equipment that can pave the way for a new class of experiments. Applied to photovoltaics research, we highlight today’s opportunities and challenges in the field of nanoscale X-ray microscopy, and give an outlook on future developments.
TL;DR: In this article, a review of the benefits and methods for interlayer modification of layered transition metal oxides, which include the presence of structural water, solvent cointercalation and exchange, cation exchange, polymers, and small molecules, exfoliation, and exfoliated heterostructures, is presented.
Abstract: Layered transition metal oxides are some of the most important materials for high energy and power density electrochemical energy storage, such as batteries and electrochemical capacitors. These oxides can efficiently store charge via intercalation of ions into the interlayer vacant sites of the bulk material. The interlayer can be tuned to modify the electrochemical environment of the intercalating species to allow improved interfacial charge transfer and/or solid-state diffusion. The ability to fine-tune the solid-state environment for energy storage is highly beneficial for the design of layered oxides for specific mechanisms, including multivalent ion intercalation. This review focuses on the benefits as well as the methods for interlayer modification of layered oxides, which include the presence of structural water, solvent cointercalation and exchange, cation exchange, polymers, and small molecules, exfoliation, and exfoliated heterostructures. These methods are an important design tool for further development of layered oxides for electrochemical energy storage applications.
TL;DR: Carbon aerogels (CAs) are a unique class of high surface area materials derived by sol-gel chemistry as mentioned in this paper, and their high mass-specific surface area and electrical conductivity, environmental compatibility, and chemical inertness make them very promising materials for many applications.
Abstract: Carbon aerogels (CAs) are a unique class of high surface area materials derived by sol–gel chemistry. Their high mass-specific surface area and electrical conductivity, environmental compatibility, and chemical inertness make them very promising materials for many applications, such as energy storage, catalysis, sorbents, and desalination. Since the first CAs were made via pyrolysis of resorcinol–formaldehyde (RF)-based organic aerogels in the late 1980s, the field has really grown. Recently, in addition to RF-derived amorphous CAs, several other carbon allotropes have been realized in aerogel form: carbon nanotubes (CNTs), graphene, graphite, and diamond. Furthermore, the popularity of graphene aerogels has inspired research into aerogels made of a host of graphene analog materials (e.g., boron nitride, transition metal dichalcogenides, etc.), with potential for an even wider array of applications. Finally, the development of three-dimensional-printed aerogels provides the potential for CAs to have an even broader impact on energy-related technologies. Here, we will present recent work covering the novel synthesis of RF-derived, CNT, graphene, graphite, diamond, and graphene analog aerogels.
TL;DR: In this paper, the behavior of extruded Mg-Gd-Al-Zn magnesium alloys at elevated temperatures was studied to elucidate the effect of intermetallic compounds on thermal stability, grain coarsening mode, and grain growth kinetics.
Abstract: The behavior of extruded Mg–Gd–Al–Zn magnesium alloys at elevated temperatures was studied to elucidate the effect of intermetallic compounds on thermal stability, grain coarsening mode, and grain growth kinetics. The presence of the fine and widely distributed intermetallic (Mg,Al)3Gd phase in the extruded microstructure of the Mg–4.8Gd–1.2Al–1Zn alloy was found to be quite effective in inhibiting grain growth. This was not the case for the Mg–3Gd–3Al–1Zn alloy, where the extruded microstructure showed that the grain boundaries are not effectively pinned by the main Al2Gd intermetallic phase. The grain coarsening situation was found to be more severe for the Mg–6Al–1Zn alloy because no second phases were present to pin the grain boundaries at elevated temperatures. The simultaneous presence of Al and Gd was found to be helpful in increasing the solidus temperature, and in this way, it further contributes to increasing thermal stability of the magnesium alloys. The abnormal grain growth occurred by penetrating into grain boundaries of smaller grains and by the formation of discrete islands inside large abnormal grains, which provided evidence for the occurrence of the solid-state wetting mechanism in this magnesium alloy.
TL;DR: A great variety of applications envisaged for native and modified frustules are described, highlighting the material scientists’ benefit to avail of nature in the construction of highly ordered biohybrid architectures for nanotechnology.
Abstract: Diatoms microalgae can be regarded as living factories producing nanostructured and mesoporous biosilica shells (frustules) having a highly ordered hierarchical architecture. These unique, morphological, chemical and mechanical properties make diatoms’ biosilica a very attractive nanomaterial for a wide variety of applications. Methods of purification of frustules that preserve their nanostructured morphology have been set up as well as in vivo or in vitro chemical modification protocols of the biosilica with functional molecules to generate biohybrid active materials for photonics, sensing, drug delivery and electronics. Herein we describe, with some selected examples, the great variety of applications envisaged for native and modified frustules, highlighting the material scientists’ benefit to avail of nature in the construction of highly ordered biohybrid architectures for nanotechnology. New concepts for the biotechnological production of nanomaterials are opened by the use of diatoms as living factories.
TL;DR: In this paper, wire electro discharge machining of Ti50Ni40Co10 shape memory alloy has been carried out and machining performances such as surface roughness (SR), and material removal rate (MRR) have been evaluated.
Abstract: Shape memory alloys (SMAs) are unique class of smart materials with excellent physical, mechanical and biomedical properties, which have wide applications in several fields such as aerospace, robotics, biomedical, and dental etc. These alloys are well known for exhibiting shape memory effect (SME) and pseudoelasticity (PE), it is a well-established fact that they are required to be processed into functioning parts. The conventional machining affects the internal properties of shape memory alloys and hence, it is reported that nonconventional machining techniques are more suitable. Wire electro discharge machining (WEDM) is one of the nonconventional machining processes for machining complicated shapes without hampering the internal properties of such type of materials. In the present experimental investigation, wire electro discharge machining of Ti50Ni40Co10 shape memory alloy (SMA) has been carried out and machining performances such as surface roughness (SR), and material removal rate (MRR) have been evaluated. Experimental results exposed that pulse on time, pulse off time and servo voltages are most influential process parameters on the responses. The machined surface has been characterised with respect to microstructure, microhardness, and phases formed.
TL;DR: In this paper, a short review on computational modeling on the formation, thermodynamics, and elasticity of single-phase high-entropy alloys (HEAs) was provided.
Abstract: This article provides a short review on computational modeling on the formation, thermodynamics, and elasticity of single-phase high-entropy alloys (HEAs). Hundreds of predicted single-phase HEAs were re-examined using various empirical thermo-physical parameters. Potential BCC HEAs (CrMoNbTaTiVW, CrMoNbReTaTiVW, and CrFeMoNbReRuTaVW) were suggested based on CALPHAD modeling. The calculated vibrational entropies of mixing are positive for FCC CoCrFeNi, negative for BCC MoNbTaW, and near-zero for HCP CoOsReRu. The total entropies of mixing were observed to trend in descending order: CoCrFeNi > CoOsReRu > MoNbTaW. Calculated lattice parameters agree extremely well with averaged values estimated from the rule of mixtures (ROM) if the same crystal structure is used for the elements and the alloy. The deviation in the calculated elastic properties from ROM for select alloys is small but is susceptible to the choice used for the structures of pure components.
TL;DR: In this paper, the properties and absorption behavior of different kinds of microwave absorbing materials based on graphene were reviewed and discussed in detail, and the perspective of the current challenges and key issues for achieving better microwave absorption performance of the graphene-based materials are provided.
Abstract: With the rapid development of electronic information and technology, especially the explosive advance of novel electronic devices, ultra-wideband radar detector and satellite communication, the elimination of adverse electromagnetic waves (EWs) effectively is very necessary both for electronic safety and national defense security. As one of the important material basis for controlling adverse EW pollution, compatibility, shielding, and stealth capability of weaponry, microwave absorbing materials has long been an area of intense research activity. Graphene-based materials have attracted great interests for microwave absorption in recent years due to the unique structure and physicochemical properties of graphene, such as high specific surface area, ultrathin thickness, large interface, optical transmittance, and tunable conductive properties, etc. In this paper, the properties and absorption behavior of different kinds of microwave absorbing materials based on graphene were reviewed and discussed in detail. In addition, the perspective of the current challenges and key issues for achieving better microwave absorption performance of the graphene-based materials are provided.
TL;DR: A review of the state-of-the-art in functionalization of carbon-based nanomaterials can be found in this paper, where the authors present an objective analysis of the various approaches reported in the literature, using metrics such as the agent of functionalization, number of steps, and time required, the need for special instruments, effect on properties, scalability, reproducibility and applications.
Abstract: Carbon-based nanomaterials (CANOMATs), including fullerenes, carbon nanotubes, graphene, and their derivatives, are widely considered to be the next-generation materials for a broad range of biomedical applications, owing to their unique opto-electronic, chemical, and mechanical properties. However, for bio-applications, CANOMATs need to be surface-functionalized, to render them passive, non-toxic, and water-soluble. Here, we review the current state-of-the-art in the methods of functionalization of CANOMATs. In contrast to other Reviews, we present an objective analysis of the various approaches reported in the literature, using metrics such as the agent of functionalization, number of steps, and time required, the need for special instruments, effect on properties, scalability, reproducibility, and applications. Our Review offers a way for researchers to make a rational selection of the process of functionalization to best suit their desired application. This opens up new opportunities for developing targeted functionalization strategies, based on the need to excel at the above metrics.
TL;DR: In this article, the progress made toward hybrid photodetector based on metal dichalcogenides with various sensitizers from metal to large band-gap semiconductor in architectures from zero-dimensional quantum dot to two-dimensional crystal.
Abstract: Atomically thin transition metal dichalcogenides (TMDCs), such as WS2 and MoS2, have opened up new opportunities for the next generation of optoelectronics owing to their unique properties such as optical transparency, high carrier mobility, widely tunable band gap, and strong light–matter interaction. The photodetection performance relies primarily on the light absorption efficiency and separation efficiency of photoexcited electron–holes. The photodetectors with all broadband response, high photoconductive gain, high response speed, and high detectivity is arduous challenge to realize using one photo-active material. Building of photodetectors composed of two or more light absorber materials of different band gaps was an efficient route to realize high performance light detection. The application of a thin sensitizing layer atop the TMDCs has proven to be a viable route to improve the photodetection performance due to the efficient charge separation at the interface, and fast charge transfer process due to the high carrier mobility. In this article, we review the progress made toward hybrid photodetector based on TMDCs with various sensitizers from metal to large band-gap semiconductor in architectures from zero-dimensional quantum dot to two-dimensional crystal.
TL;DR: In this paper, the authors rekindled the research of oxygen behavior in Ti with the purpose of developing Ti alloys with high strength and suitable ductility by using no expensive and poisonous element.
Abstract: Oxygen is known to have a significant impact on the strength of Ti alloys, whereas it can also reduce the ductility substantially. Thus, the usage of oxygen to strengthen Ti is restricted in the industry. In this study, we rekindled the research of oxygen behavior in Ti with the purpose of developing Ti alloys with high strength and suitable ductility by using no expensive and poisonous element. To this end, experiments of producing high performance commercially pure Ti using only oxygen solid solution were carried out. The oxygen element was introduced into the Ti by two different powder metallurgy methods. The microstructural examination and mechanical test were performed for the samples, which indicated a strong hardening effect of oxygen in spite of the processing routes. Most importantly, the results suggested that a high elongation to failure of over 20% can still be obtained in the samples having yield stress over 800 MPa, up to an oxygen content of 0.8 wt%, which is far beyond the previously recognized limit.
TL;DR: Freeze casting of traditional ceramic suspensions and freeze casting of preceramic polymer solutions were directly compared as methods for processing porous ceramics as discussed by the authors, and the pore sizes were smaller for solution freeze casting than for suspension freeze casting under identical processing conditions.
Abstract: Freeze casting of traditional ceramic suspensions and freeze casting of preceramic polymer solutions were directly compared as methods for processing porous ceramics. Alumina and polymethylsiloxane were freeze cast with four different organic solvents (cyclooctane, cyclohexane, dioxane, and dimethyl carbonate) to obtain ceramics with ∼70% porosity. Median pore sizes were smaller for solution freeze casting than for suspension freeze casting under identical processing conditions. The pore structures, which range from foam-like to lamellar, were correlated to the Jackson α-factor of the solvent; solvents with low α-factors yielded nonfaceted pore structures, while high α-factors produced more faceted structures. Intermediate α-factors resulted in dendritic pore structures and were most sensitive to the processing method. Small suspended particles ahead of a solid–liquid interface are hypothesized to destabilize the dendrite tip in suspension freeze casting resulting in more foam-like structures. Differences in processing details were highlighted, particularly regarding the improved freezing front observation possible with solution-based freeze casting.
TL;DR: In this article, a microwave-assisted hydrothermal synthesis of high performance nanoparticles and thin films of Nb2O5 by microwave assisted synthesis is reported, which shows a kinetic curve similar to that of a reference TiO2-P25 thin film.
Abstract: A new rapid and energy saving method for the obtention of high performance nanoparticles and thin films of Nb2O5 by microwave-assisted hydrothermal synthesis is reported. The hydrothermal treatment of a sol–gel precursor solution in a microwave oven at 180 °C for 20 min was enough to obtain amorphous nanoparticles with average sizes of 40 nm. The calcination promotes the formation of different phases of Nb2O5 (TT and T) with pseudohexagonal and orthorhombic structure, respectively, that transform at higher temperatures in a mixture of orthorhombic and monoclinic phases. Crystalline phase composition was found to have a significant influence on the photocatalytic activity. The best photocatalytic performance was observed for the material mainly constituted by the TT-Nb2O5 phase. Thin films constituted by the TT phase were prepared by dip-coating. Photocatalytic experiments confirmed the high photocatalytic activity of this material, which showed a kinetic curve similar to that of a reference TiO2-P25 thin film.
TL;DR: In this paper, the synthesis, characterization, and corrosion behavior of AA6063 composites with the inclusion of micron-sized titanium carbide (TiC) particles with different weight percentages were investigated.
Abstract: This study investigates the synthesis, characterization, and corrosion behavior of AA6063 composites with the inclusion of micron-sized titanium carbide (TiC) particles with different weight percentages. AA6063/TiC particulate composites containing 0, 3, 6, 9, and 12 weight percent of TiC particles were produced by stir casting. The homogeneous dispersion of TiC particles in the AA6063/TiC composites was revealed from the scanning electron microscopy analysis. Energy dispersive X-ray spectroscopy analysis was conducted to ensure the presence of reinforcement particles in the matrix. Mechanical and corrosion properties of the produced composites are evaluated. The addition of TiC particles to the AA6063, the mechanical, electrical, and corrosion properties are initially increased and then decreased. Mechanical and corrosion study shows that the presence of 9 wt% of TiC particles in the matrix improved mechanical properties than other combination of TiC with the matrix material.
TL;DR: In this paper, a roll-to-roll (R2R) line with two slot-die coating stations is discussed, which can deposit two uniform layers consecutively in a single run (tandem coating) at web speeds up to 30 m/min.
Abstract: The large volume production of flexible electronics by solution based roll-to-roll (R2R) manufacturing technologies is a promising upscaling strategy for the organic electronics industry. Typical optoelectronic devices like organic light emitting diodes (OLEDs) consist of a complex stack of functional layers. Solution deposition of these structures eliminates the need for expensive vacuum processing. This contribution presents approaches for solution based R2R production methods of functional OLED layers on flexible polymer substrates. The development of a R2R line with two slot-die coating stations is discussed which can deposit two uniform layers consecutively in a single run (“tandem coating”) at web speeds up to 30 m/min. Furthermore, it offers the unique feature that there is no contact between the rollers and the top side of the substrate where the functional coating is deposited. Thereby, an important source of particle contamination and other damage to the device is eliminated. In addition to continuous deposition, stripe and intermittent coating techniques have been developed, allowing the production of patterned layers. Finally, examples will be shown of OLEDs where two functional materials are deposited by R2R processing from solution.
Abstract: Composite magnetoelectrics implemented as thin film heterostructures are discussed in view of their applicability as highly sensitive magnetic field sensors. Here, either PZT or AlN served as piezoelectric component. The magnetostrictive phase consisted of layer systems based on FeCo or (Fe90Co10)78Si12B10. All functional layers were deposited with thicknesses of a few micrometers on Si cantilever structures with typical lateral dimensions of 25 mm by 2.2 mm. Magnetoelectric coefficients as large as 6900 V/cm Oe and a limit of detection as low as 1 pT/(Hz)1/2 were measured. Currently, the best result demonstrates a detection limit of 500 fT/(Hz)1/2 at 958 Hz frequency using a set of two sensors for external noise suppression. A frequency conversion technique is proposed to broaden the applicability of resonant magnetoelectric sensors to a wider frequency range. Finally, the achieved sensor performance is evaluated with regard to typical magnetic field amplitudes in medical applications.
TL;DR: In this paper, the authors present analytical results for efficiency potential of high-efficiency solar cells based on external radiative efficiency (ERE), open-circuit voltage loss and fill factor loss.
Abstract: The present status of R&D for various types of solar cells is presented by overviewing research and development projects for solar cells in Japan as the PV R&D Project Leader of the New Energy and Industrial Technology Development Organization (NEDO) and the Japan Science and Technology Agency (JST). Developments of high-efficiency solar cells such as 44.4% (under concentration) and 37.9% (under 1-sun) InGaP/GaAs/InGaAs 3-junction solar cells by Sharp, 26.6% crystalline Si heterojunction back-contact (HBC) solar cells by Kaneka, 22.3% CIGS solar cells by Solar Frontier have been demonstrated under the NEDO PV R&D Project. 15.0% efficiency has also been attained with 1 cm2 perovskite solar cell by NIMS under the JST Project. This article also presents analytical results for efficiency potential of high-efficiency solar cells based on external radiative efficiency (ERE), open-circuit voltage loss and fill factor loss. Crystalline Si solar cells, GaAs, III–V compound 3-junction and 5-junction, CIGSe, and CdTe solar cells have efficiency potential of 28.5%, 29.7%, 42%, 43%, 26.5%, and 26.5% under 1-sun condition, respectively, by improvements in ERE.