Characterization of Cd1−xFexS diluted magnetic semiconductors grown at near phase conversion temperature

Fe-based cadmium sulfide alloy thin films have been grown on c-plane sapphire substrates by a low-pressure metalorganic chemical vapor deposition technique at different growth temperatures. From X-ray diffraction and absorption spectra of the samples, the evolutions with growth temperature show an inflexion at the growth temperature of 300 ^°C. This was attributed to the phase transformation from zinc-blende to wurtzite. With increasing growth temperature from 270 ^°C to 360 ^°C, Fe concentration in the films increases monotonously. The electronic states of Cd_1−xFe_xS were investigated by X-ray photoelectron spectroscopy. Magnetic measurement shows Van Vleck paramagnetism of the Cd_1−xFe_xS thin film in the temperature region below 7 K.     

First-principles studies of magnetic properties and electronic structure of EuC60

The full potential linearized augmented plane wave (FP-LAPW) method with the GGA+U approach was applied to study the electronic structures of the compound Eu₆C₆₀. Present calculations show that the hybridization between the Eu s, d state and the C₆₀ π states plays an essential role in its FM exchange interactions between the 4f electrons and metallic properties.     

Use of elemental size distributions in identifying particle formation modes

The chemical composition of particles generated during pulverized coal combustion is the consequence of their formation processes. This work aims to use the size resolved elemental composition of coal-derived particles to identify their formation modes. A size-classified bituminous coal is burnt in a laboratory drop tube furnace at 1150, 1250, and 1350 °C, respectively. The elemental composition of the size-segregated particles from coal combustion is analyzed and the total mass fraction size distributions of Si and Al are obtained. Three particle formation modes are observed in these distribution profiles. The coarse mode has the highest value of the total mass fraction of Si and Al while the ultrafine mode has the lowest one. The total mass fraction of Si and Al in these two modes is nearly independent of particle size. It is believed that the coarse mode is formed by the mineral coalescence mechanism and the ultrafine mode by the vaporization–condensation mechanism. The difference in the total mass fraction of Si and Al between the central mode and the other two indicates that the central mode is formed by different mechanisms. Based on the observation that the total mass fraction of Si and Al in this mode increases with increasing particle size, heterogeneous condensation of vaporized species on existing fine residual ash particles is proposed to account for the formation of these particles. The study of the elemental composition of the three modes represented in five categories verifies the proposed formation mechanisms for them to some extent.     

Dynamics of Efficiency Change by Temperature in Diode Pumped Nd：YAG Heat Capacity Laser

We investigate the influence of temperature on the efficiency of diode pumped Nd：YAG heat capacity laser is studied. It is shown that the efficiency of such a laser system is greatly reduced at higher temperature. This bad behaviour is mainly caused by the doped-ion redistribution among various Stark levels of the ground state, and by a thermal equilibrium between the upper laser level and the pump level. Meanwhile, the thermal excitations from the ground state to the lower laser level also play a role. We derive a model to describe those effects, with the considerations of emission spectrum of laser diodes, the subtle Stark structures and the linewidth of absorption and of simulated-emission.     

Laser-induced damage of high reflectors for Ti:sapphire laser system

A broadband (～ 176 nm, R ＞ 98%, λ0 = 800 nm) and high laser-induced damage threshold (LIDT =2.4 J/cm2) TiO2/HfO2/SiO2 high reflector (HR) for Ti:sapphire chirped-pulse amplification (CPA) laser system is fabricated by the electron beam evaporation. The refractive index and extinction coefficient of TiO2 and HfO2 films are calculated from single-layer films' transmittance spectra. The properties of HR are mainly determined by the high refractive index material. The high refractive index leads to wide bandwidth. A low extinction coefficient indicates low absorption and high LIDT. The possible damage mechanism of HR is discussed.     

Synthesis of two dihydropyrroloindoledione‐based copolymers for organic electronics

Two novel dihydropyrroloindoledione (DPID)‐based copolymers have been synthesized in a two directional approach and characterized (gel permeation chromatography (GPC), ultraviolet‐visible (UV–vis), cyclic voltammetry, and computational models). These planar, broad absorption copolymers show promise for use in organic electronics, with deep energy levels and low bandgaps. The two‐directional Knoevenagel condensation used demonstrates the versatility of DPID as a useful yet underexploited conjugated unit. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Combining renewable gum rosin and lignin: Towards hydrophobic polymer composites by controlled polymerization

Rosin polymer–grafted lignin composites were prepared via “grafting from” atom transfer radical polymerization (ATRP) with the aid of 2‐bromoisobutyryl ester‐modified lignin as macroinitiators. Three different monomers derived from dehydroabietic acid (DA) were used for execution of grafting from ATRP, while DA was separately attached onto lignin by a simple esterification reaction. Kinetic studies indicated controlled and “living” characteristics of all monomer polymerizations. Thermal studies indicated that rosin polymer–grafted lignin composites exhibited glass transition temperatures in a broad temperature range from ～20 to 100°C. The grafting of both DA and rosin polymers significantly enhanced hydrophobicity of lignin. Static contact angle measurement of water droplets showed ～90° for all these rosin modified lignin composites. X‐ray photoelectron spectroscopy demonstrated that the surface of rosin–lignin composites was dominated with chemical compositions originating from the hydrocarbon rich rosin moiety. The impartation of hydrophobicity of rosin into lignin provided excellent water resistance of this class of renewable polymers, as all rosin‐modified lignin composites showed water uptake below 1.0 wt %. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Novel perfluorocyclobutyl aryl ether‐based well‐defined amphiphilic block copolymer

A series of fluorine‐containing amphiphilic diblock copolymers comprising hydrophobic poly(p‐(2‐(p‐tolyloxy)perfluorocyclobutoxy)phenyl methacrylate) (PTPFCBPMA) and hydrophilic poly(2‐(diethylamino)ethyl methacrylate) (PDEAEMA) segments were synthesized via successive reversible addition fragmentation chain transfer (RAFT) polymerizations. RAFT homopolymerization of p‐(2‐(p‐tolyloxy)perfluorocyclobutoxy)phenyl methacrylate was first initiated by 2,2′‐azobisisobutyronitrile using cumyl dithiobenzoate as chain transfer agent, and the results show that the procedure was conducted in a controlled way as confirmed by the fact that the number‐average molecular weights increased linearly with the conversions of the monomer while the polydispersity indices kept below 1.30. Dithiobenzoate‐capped PTPFCHPMA homopolymer was then used as macro‐RAFT agent to mediate RAFT polymerization of 2‐(diethylamino)ethyl methacrylate, which afforded PTPFCBPMA‐b‐PDEAEMA amphiphilic diblock copolymers with different block lengths and narrow molecular weight distributions (M_w/M_n ≤ 1.28). The critical micelle concentrations of the obtained amphiphilic diblock copolymers were determined by fluorescence spectroscopy technique using N‐phenyl‐1‐naphthylamine as probe. The morphology and size of the formed micelles were investigated by transmission electron microscopy and dynamic light scattering, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Palladium(II)-catalyzed oxidative Heck coupling of thiazole-4-carboxylates

Oxidative Heck coupling of thiazole-4-carboxylates via palladium(II)-catalyzed C-H bond activation has been achieved in moderate to good yields. No ligand, and no acidic additive were used in the reaction. The results showed that this protocol tolerated a series of substitutions on the thiazole ring. A preliminary attempt of direct arylation with p-xylene via Pd(II)-catalyzed C-H bond activation has also been done.