Humin-like substances formed under the conditions of industrial hydrolysis of wood
Pathways of formation of humin-like substances from carbohydrates and furan compounds under the conditions of acid hydrolysis of wood were studied.
Materials Literature
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MOCVD growth mechanisms of ZnO nanorods
ZnO is a promising material for the fabrication of light emitting devices. One approach to achieve this goal is to use ZnO nanorods because of their expected high crystalline and optical quality. Catalyst free growth of nanorods by metalorganic chemical vapour deposition (MOCVD) was carried out on (0001) sapphire subs…
First-principles study of ultrathin (2×2) Gd nanowires encapsulated in carbon nanotubes
Using density-functional calculations, we investigate the structural and magnetic properties of ultrathin Gd and Gd-carbide nanowires (NWs) encapsulated in narrow carbon nanotubes (CNTs). The equilibrium geometry of an encapsulated (2 x 2) Gd-NW is markedly different from that of bulk Gd crystals. The charge-density a…
Electronic structure and magnetism of the diluted magnetic semiconductor Fe-doped ZnO nanoparticles
We have studied the electronic structure of Fe-doped ZnO nanoparticles, which have been reported to show ferromagnetism at room temperature, by x-ray photoemission spectroscopy, resonant photoemission spectroscopy, x-ray absorption spectroscopy, and x-ray magnetic circular dichroism (XMCD). From the experimental and c…
Transport in organic semiconductors in large electric fields: From thermal activation to field emission
Understanding charge transport in organic semiconductors in large electric fields is relevant to many applications. We present transport measurements in organic field-effect transistors based on poly(3-hexylthiophene) and 6,13-bis(triisopropyl-silylethynyl) (TIPS) pentacene with short channels, from room temperature d…
A versatile scanning acoustic platform
We present a versatile and highly configurable scanning acoustic platform. This platform, comprising of a high frequency transducer, bespoke positioning system and temperature-regulated sample unit, enables the acoustic probing of materials over a wide range of length scales and with minimal thermal aberration. In its…
Surface-induced magnetism in C-doped SnO2
The magnetism of C-doped SnO2 (001) surfaces is studied using first-principles calculations. It is found that carbon does not induce magnetism in bulk SnO2 when located at the oxygen site but shows a large magnetic moment at the SnO2 (001) surface. The magnetic moment is mainly contributed by the carbon atoms due to e…
Energetics of excited states in the conjugated polymer poly(3-hexylthiophene)
There is an enormous potential in applying conjugated polymers in novel organic optoelectronic devices such as light-emitting diodes and solar cells. Although prototypes and first products exist, a comprehensive understanding of the fundamental processes and energetics involved during photoexcitation is still lacking…
Crystal and electronic structure of the room temperature organometallic ferrimagnet V(TCNE)$_2$. Analysis of numerical DoS and magnetic properties as related to orbital and spin-Hamiltonian models
We present a detailed analysis of the results of our numerical study of the crystal and electronic structure of the room temperature organometallic ferrimagnet of general composition V(TCNE)$_{x}$ with $% x\approx 2$. The results of the LSDA+$U$ study show that the experimentally determined structure complies with the…
Negative refraction at deep-ultraviolet frequency in monocrystalline graphite
Negative refraction is such a prominent electromagnetic phenomenon that most researchers believe it can only occur in artificially engineered metamaterials. In this article, we report negative refraction for all incident angles for the first time in a naturally existing material. Using ellipsometry measurement of the…
Electronic structure, phonons, and thermal properties of ScN, ZrN, and HfN: A first-principles study
With a motivation to understand microscopic aspects of ScN, ZrN, and HfN relevant to the thermoelectric properties of nitride metal/semiconductor superlattices, we determine their electronic structure, vibrational spectra and thermal properties using first-principles calculations based on density functional theory wit…
From Natural Attapulgite to Mesoporous Materials: Methodology, Characterization and Structural Evolution
In this paper, we report the synthesis of hexagonally ordered aluminum-containing mesoporous silica, Al-MCM-41, from natural attapulgite (Al-substituted Si(8)O(20)Mg(5)(OH)(2)(H(2)O)(4) x 4 H(2)O) without addition of silica or aluminum reagents. A pretreatment process involving sequential mechanical grinding and acid…
Processing of polysiloxane-derived porous ceramics: a review
Because of the unique combination of their attractive properties, porous ceramics are considered as candidate materials for several engineering applications. The production of porous ceramics from polysiloxane precursors offers advantages in terms of simple processing methodology, low processing cost, and easy control…
Factors responsible for crystal-chemical variations in the solid solutions from illite to aluminoceladonite and from glauconite to celadonite
Several finely dispersed low-temperature dioctahedral micas and micaceous minerals that form solid solutions from (Mg,Fe)-free illite to aluminoceladonite via Mg-rich illite, and from Fe 3+ -rich glauconite to celadonite have been studied by X-ray diffraction and chemical analysis. The samples have 1M and 1Md structur…
Charge migration in Pb(Zr,Ti)O3 ceramics and its relation to ageing, hardening, and softening
The dielectric response of hard (Fe-doped) and soft (Nb-doped) rhombohedral Pb(Zr0.58Ti0.42)1−xMexO3 (Me=Fe or Nb) ceramics was studied at subswitching conditions over a wide range of temperatures (50–450 °C) and frequencies (10 mHz to 10 kHz). The results show qualitative differences in the behavior of the acceptor-…
Partial discharge source discrimination using a support vector machine
Partial discharge (PD) measurements are an important tool for assessing the health of power equipment. Different sources of PD have different effects on the insulation performance of power apparatus. Therefore, discrimination between PD sources is of great interest to both system utilities and equipment manufacturers.…
Development of novel thermoelectric materials by reduction of lattice thermal conductivity
Thermal conductivity is one of the key parameters in the figure of merit of thermoelectric materials. Over the past decade, most progress in thermoelectric materials has been made by reducing their thermal conductivity while preserving their electrical properties. The phonon scattering mechanisms involved in these str…
Rapid Separation and Purification of Nanoparticles in Organic Density Gradients
Nanoseparation and concomitant purification of nanoparticles by ultracentrifugation in a nonhydroxylic organic density gradient has been demonstrated by separating several typical colloidal nanoparticles, including Au, Ag, and CdSe. Successful separation of Au nanowires from their spherical counterparts showed that co…
Wide-bandgap Zn2GeO4 nanowire networks as efficient ultraviolet photodetectors with fast response and recovery time
Ultraviolet (UV) photodetectors based on ternary Zn2GeO4 nanowire (NW) networks are demonstrated. The devices show fast response and recovery time, which is attributed to the unique NW-NW junction barrier dominated conductance for network devices. The UV-light induced barrier height modulation is much faster than the…
Ring-Opening Polymerization of Lactides Catalyzed by Natural Amino-Acid Based Zinc Catalysts
A series of chiral NNO-tridentate Schiff base ligands derived from natural amino acids were reacted with zinc(bis-trimethylsilylamide)(2) to provide metal complexes which have been fully characterized. One of these derivatives was further reacted with p-fluorophenol to yield a phenoxide complex. X-ray crystallographic…