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Surface roughness is an important factor that affects the wetting of molten metal on ceramics. The effect of surface roughness of the alumina substrate on the contact angle, contact diameter, drop height and surface tension of molten lead was investigated in the temperature range of 923–1123 K. The microstructure of the lead/substrate interface was observed by SEM. The surface free energy of alumina substrates was calculated by the geometrical average method. When the surface roughness of the substrate increased from 0.092 to 2.23 μm, the surface free energy increased gradually, ranging from 13.356 to 39.998 mJ/m2. The contact diameter of lead droplets decreased from 9.111 to 7.19 mm. The lead drop height increased from 3.41 to 3.85 mm. The contact angle increased from 113.05° to 137.15°. Moreover, the surface depression of the alumina substrate was filled with lead, and no obvious change was observed. The results demonstrated that the wetting of lead drop on alumina substrates was consistent with the Wenzel state.

ZnO nanopowders with hexagonal wurtzite structure were synthesized by hydrothermal method with different concentrations of Fe. X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spe...

Slag movement on SiO2-based prism refractories in different slag systems was observed. The cross section shape evolution mechanism was discussed. Two types of shape evolution appear. For PbO−SiO2 slag whose surface tension improves with SiO2 concentration, slag film flows up along four edges under axial Marangoni shear force and wettability. Then, it flows down along four lateral faces under gravity. Corrosion rate at edges is larger than that on lateral faces due to different SiO2 solubilities of ascending and descending flow. Prism cross section shape changes from square to round. For FetO−SiO2 slag whose surface tension reduces with the increase of SiO2 concentration, slag film flows up under the inflence of wettability. Then, it flows down under Marangoni shear force and gravity. Compared to four edges, slag is mainly up and down on four lateral faces due to larger surface tension and size. So, prism cross section shape keeps square.

During the operation of a coke dry quenching system of coking plant, wear-proofing cover of the boiler was seriously eroded, and even the ceiling tube of the boiler was worn and torn. Thus, attentions were paid to the research, development and application of the wear-resistant coating spraying technique for wear-proofing cover of the coke dry quenching furnace. The Cr3C2–NiCr coatings for wear-proofing cover were fabricated via supersonic arc spraying process, and the residual coating of wear-proofing cover would be sampled for being analyzed after two years. The coating presents a dense microstructure with few pores and micro-cracks (the porosity is 4.65%). After thermal spraying of the wear-proofing cover, the hardness and the wear resistance of the surface are improved. The remaining coating is continuous and compact, with an average thickness of about 147 μm. Transverse micro-cracks parallel to the spreading direction of the coating surface are displayed on different areas of the coating, which demonstrates its serious erosion wear effect. The main chemical component of white zone is Fe–18Cr–Ni. The Cr level of light gray phase is about 77.57 wt.% and the O level is 22.43 wt.%. And the main chemical components of dark gray phase are C, O, Al, Si and Ca. X-ray diffraction patterns were adopted to implement phase analysis on the surface of coating sample, which indicated that the coating was composed of a large amount of Cr3O2 and a small amount of metal Cr.

The effect of alumina ceramics surface roughness on the wetting characteristics of liquid lead was investigated by the sessile drop method. The surface 3D appearance and surface roughness of the alumina substrate were measured by confocal laser scanning microscope (CLSM). The interface micrographs of lead and alumina substrates were characterized by scanning electron microscope (SEM). The results show that as the alumina substrate surface roughness increases, the contact angle of the lead drop increases, the drop height increases, the contact diameter decreases, and the adsorption work decreases. An obvious pinning effect was observed during the wetting process, and the potential mechanism of the wetting behavior was described on the basis of Wenzel equation. This work provides a theoretical basis for the application of alumina ceramics in the lead industry.

A porous tubular-type ultra-high molecular weight polyethylene (UHMWPE) membrane with good filtration effect for turbid circulating water was designed and prepared. The physical-chemistry properties such as surface microstructure and tensile strength of tubular-type UHMWPE membrane were investigated. UHMWPE membrane consists of agglomerated particles with diameters of 127–229 μm. The UHMWPE membrane has a porous structure with pore diameter of 40–152 μm, which can enhance the permeability of UHMWPE membrane. The accumulation and distribution of oxide scale particles in UHMWPE membrane after having been used for 5 years were also analyzed. Oxide scale particles are mainly accumulated on the surface layer of UHMWPE membrane. And the fouling layer is about 2.052 mm. The accumulation of oxide scale particles decreases with the increase of distance from the inner surface of the UHMWPE membrane. The accumulation is about 0.96% at L = 0.342 mm, and the accumulation is about 0.36% at L = 2.052 mm in the UHMWPE membrane. UHMWPE membrane exhibits excellent antifouling property for long-term use.

The structural, mechanical, and thermodynamic properties of R-3m ReB4 under high pressure were investigated by using the density functional theory in combination with the quasi-harmonic Debye model in this work. The calculated structure parameters and bulk moduli of R-3m ReB4 at zero pressure are in good agreement with previous theoretical data. The calculated single crystal elastic constants and phonon spectra revealed that R-3m ReB4 is mechanically and dynamically stable at least 100 GPa. The pressure dependence of elastic constants and elastic modulus (B, G, and E) have been determined. Based on the obtained elastic modulus, two theoretical models were used to predict the Vickers hardness of R-3m ReB4. Furthermore, through plotting the directional dependent of bulk moduli, Young’s moduli, and shear moduli, the elastic anisotropy has been investigated in detail. Moreover, using the quasi-harmonic Debye model, some basic thermodynamical quantities such as the heat capacity, Gruneisen parameter, and the thermal expansion coefficients of R-3m ReB4 were explored under high temperature and high pressure. The obtained results can provide valuable reference for future synthesis and application R-3m ReB4 material.

Purpose This research aims to provide a theoretical method and data supports for a future study on interfacial reaction mechanism and spreading mechanism between molten solder and V-shaped substrate, which also gives guidance for those complicated welding operation objects in brazing technique. Design/methodology/approach Wetting experiments were performed to measure the contact angles at different temperatures of molten Sn-3.0Ag-0.5Cu wetting on the quartz substrate with an included angle of 90°. According to the experimental results, the theoretical spreading morphology of molten solder on V-shaped substrate at corresponding temperature was simulated by Surface Evolver. Findings The theoretical morphology profiles of the molten solder sitting on the V-shaped substrate are simulated using Surface Evolver when the molten solder reaches spreading equilibrium. The spreading mechanisms as well as the impact of surface tension and gravity on interfacial energy of the molten solder wetting on the V-shaped groove substrate are also discussed where theoretical results agree well with experiment results. The contact area between the gas and liquid phases shows a tendency of first increasing and later decreasing. Otherwise, the spreading distance and the height of the molten solder increases as the droplet volume increases as the included angle and the contact angle are given as constants, and both the interfacial energy and the gravitational energy increase as well. This research has a wide influence on predicting the outcomes in commercial impact and also gives guidance for those complicated welding operation objects in brazing technique. Research limitations/implications It is of very important significance in both science and practice to investigate the differences between the flat surface and V-shaped surface. Some necessary parameters including intrinsic contact angle and surface tension need to be directly measured when the droplet spreads on the flat surface. The relevant simulation conclusions on the inherent characteristics can be given based on these intrinsic parameters. Compared with the flat surface, the V-shaped substrate is chosen for further discuss on the effects of gravity on the droplet spreading behavior and the changes of apparent contact angle which can only occurs as the substrate is inclined. Therefore, this research provides theoretical method and data supports for a future study on interfacial reaction mechanism and spreading mechanism between molten solder and substrate. Practical implications The research is developed for verifying the accuracy of the model built in Surface Evolver. Based on this verified model, other researches on the spreading distance along y-axis and the contact area that are especially difficult to be experimentally measured can be directly simulated by Surface Evolver, which can provides a convenient method to discuss the changes of horizontal spreading distance, droplet height and contact area with increasing the included angle of V-shaped substrate or with increasing the droplet volume. Actually, the modeling results are calculated for supplying the theoretical parameters and technical guidance in the welding process. Social implications This research provides theoretical method and data supports for a future study on interfacial reaction mechanism and spreading mechanism between molten solder and substrate, which has a wide influence on prediction the outcomes in commercial impact and also gives guidance for those complicated welding operation objects in brazing technique. Originality/value Surface Evolver, can also be used to discuss the structure and spreading mechanism of droplets on V-shaped substrates, which have not been discussed before.

The self-driving of water droplets on textured substrate is momentous for understanding the directional transport of water on biological surface. In this paper, a novel design of monolayer graphene-covered wedge-shaped copper substrate (GWCS) is put forward to realize the directional and ultrafast spontaneous driving of water droplets from the tip of the wedge-shaped substrate to the wide end. The self-driving behaviors of water droplets on GWCS are studied by classical molecular dynamics. The results show that the maximum spontaneous driving velocity of water droplet driven by surface wetting gradient and Young-Laplace pressure gradient can reach 73.8 m/s. The law of energy variation during the whole droplet self-driving on GWCS indicates that there is a competitive relationship between the potential energy of water droplet and the interaction energy between the droplet and GWCS, i.e. the interaction energy between water droplet and GWCS is partially converted into the potential energy of water droplet. The relationship of the maximum displacement of water droplet with the wedge angle, wettability of GWCS and the droplet surface tension is proposed in theory, and the influence of the discontinuous linear increase of the wedge-shaped substrate width on a nanoscale on the self-driving is analyzed and used to explain the little difference between the theoretical and simulation results. Furthermore, a smaller droplet is easier to obtain larger spontaneous driving velocity, and the influence of long-distance decelerating motion of high-speed small droplet on the non-wetting gradient substrate on the droplet displacement law is clarified. Finally, the mechanism of graphene suspended on both sides of the wedge-shaped copper structure to enhance the droplet transport efficiency is determined. The results will have theoretical significance in designing the functional texture surface covered by monolayer graphene to realize droplet self-driving.

Because of the high water flux and excellent ion rejection, the pores graphene is considered as a promising candidate material for fabricating the membranes in reverse osmosis (RO) process. Unfortunately, water molecules cannot pass through the perfect graphene, and how to effectively create a large number of nanopores with controllable size remains a challenge, which seriously prevents the practical application and development of graphene membrane for desalination. Recently, the emergence of pillared graphene (PGN) might open a new way for designing the graphene-based membranes, which can compensate for the deficiency of porous graphene membrane. The PGN has been extensively studied in gas storage and separation, and its RO characteristics and mechanism still remain unclear because the limitation of large area preparation in desalination. In this paper, the RO process of seawater through PGN membranes is investigated by molecular dynamics simulations, and the influences of the pressure within feed solution, temperature and the shearing of membrane on the desalination properties are considered. It is found that the water flux increases linearly with the pressure within feed solution increasing, and the PGN membrane with nanopore diameter of 0.8 nm can conduct water molecules but completely rejects high-concentration ions. As the diameter of nanopores increases to 1.2 nm, the rise of temperature can increase the permeability of water molecules, whereas the salt rejection is not appreciably sensitive to the temperature. Particularly, the shearing membrane can improve the salt rejection and hinder the water molecules from permeating at the same time. The designed PGN membrane exhibits excellent performance of water purification, and the ultrahigh water flux obtained in this work reaches 56.15 L·cm–2·day–1·MPa–1 with a salt rejection of 88.9%. Subsequently, the hydrogen bond dynamics is calculated in order to explain the variation of water permeability under different conditions. The result shows that the rise of temperature reduces the stability of hydrogen bonds and leads the water flux to increase, while the increase of shearing speed will enhance the stability of hydrogen bonds and inhibit water seepage. Furthermore, the analysis results of hydrogen bond and ionic hydration structure show that the shear motion on RO membrane will improve the stability of ionic hydration shell, which makes it more difficult for the ions to pass through nanopores by weakening the hydration shell. On the contrary, rising temperature will impair the strength of ionic hydration shell, leading more ions to pass through the RO membrane. The simulation results can provide an in-depth understanding of the desalination performance of PGN membrane under different key conditions, and further demonstrate the promising applications of graphene-based membrane in water desalination.

In this paper, the 795-nm vertical cavity surface emitting laser (VCSEL) with sub-wavelength grating coupled cavity is proposed and designed based on the theory of resonant coupled cavity, and the mechanism of multi-cavity coupling linewidth narrowing and influencing factors are analyzed in detail by using the COMSOL software finite element method. The analysis results show that when photonic resonance takes place in a multi-coupled cavity, the grating-coupled cavity with reasonable design parameters and the multi-coupled cavity formed by precisely controlled lasers are phase-matched, which greatly strengthens the narrowing effect of the spectral linewidth resonance, and a 795-nm VCSEL laser with high beam quality and ultra-narrow linewidth output is obtained, finally. Theoretical results display that the reflection spectrum cold cavity linewidth Δλc of the coupling cavity with a thickness of 180nm of the spacer layer can reach 7 pm, which lays a theoretical foundation for achieving a kHz-level spectral linewidth output of VCSEL lasers.

First-principles calculations of plane wave ultra-soft pseudo-potential method based on the density functional theory (DFT) were used to study lattice constants, band structure, density of states and optical properties of wurtzite InxGa1-xN alloys. The calculated results indicate that the lattice constant gradually increases, the conduction band shifts to low energy direction and the band gap becomes narrower with the increase in In-doped concentration. Meanwhile, the dielectric function moves towards low energy direction, which is red-shift. The first dielectric peak appears near 2.0 eV, and the maximum dielectric peak close to 4.76 eV is found. There are two intersection points at about 5.6 and 9.2 eV. When the photon energy is less than 5.6 eV or higher than about 9.2 eV, the absorption coefficient of InxGa1-xN in low doping concentration (less than 50%) is smaller than that of high doping concentration of InxGa1-xN. However, when the photon energy is located between 5.6 and 9.2 eV, the absorption spectra of InxGa1-xN in low doping concentration are greater than those of high doping concentration. Therefore, the study result shows that InxGa1-xN alloys can be applied as solar cell and the transparent conductive materials.

Chrysanthemum-like ZnO nanowire clusters were prepared by hydrothermal process, then were transferred to Ti substrate by electrophoresis method, and uniform ZnO nano-film with certain thickness was formed. Finally ZnO field emission cathode sample was fabricated after vacuum heat treatment. The microstructure and the morphology of chrysanthemum-like ZnO nanowire clusters were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM), respectively. Field emission tests were conducted for cathode samples after heat treatment, results reveal that the low turn-on field is 2.0 V/μm for the chrysanthemum-like ZnO, and the threshold field is 5.5 V/μm. Moreover, the field emission current density is 200 μA/cm2 under the condition of electric field of 7.5 V/μm, and the field emission current density and its stability can be effectively improved by appropriate enlarging the thickness of the ZnO coating. The field emission mechanism was also explored.

The structure electronic and optical properties of rutile-type SnO2 were studied based on plane-wave pseudopotential density functional theory (DFT) adopting GGA, LDA, B3LYP and PBE0, respectively. The computing results show that the properties calculated by GGA and LDA are very close, which correspond to those by ultra-soft pseudopotential and norm conserving pseudopotential, respectively, and the properties calculated by B3LYP are near to those by PBE0. The band gap obtained from B3LYP and PBE0 is much more consistent with the available experimental data than that from GGA and LDA, whose band gap calculated by norm conserving pseudopotential is bigger than that by ultra-soft pseudopotential. However, the density of state and optical properties calculated from every type are basically similar in qualitative analysis, and the numerical values have a little difference. From the whole results calculated by the six methods, we can see that the structure, electronic and optical properties of rutile-type SnO2 calculated by B3LYP and PBEO are more near to the available experimental data than those by other methods.

To study the structural characteristics and physical properties of droplets sitting on the inclined substrates and cylindrical surfaces, wetting experiments are conducted in different cases. The profile curves of the droplets are recorded and extracted by a CCD camera and image processing, respectively. Contact angles are figured out by fitting the profile curves and taking the derivative at the front and rear triple points. Based on the experimental results, a Surface Evolver is employed to simulate the morphological changes by minimizing the total energy of the system. Furthermore, theoretical shapes and feature parameters, including the heights and the spreading distances of the droplets, which are hard to obtain by normal experimental measurements are provided. The contact-angle hysteresis when the heavy droplet sitting on the inclined substrate is discussed. Meanwhile, the evolutions of the contour of the three-phase contact line are predicted when heavy droplets spread on the convex and concave cyli...

Graphene-based materials have aroused great interest for their potential applications in water desalination and purification membranes attributed to their ultrathin thickness, high mechanical strength, and anti-foiling properties. Reverse osmosis (RO) technology is currently the most progressive, energy-saving and efficient separation technology by membranes, therefore the new materials with high strength, strong pollution resistance and excellent performance are urgently needed. The ability of porous graphene to serve as a kind of novel advanced RO membrane is due to two major potential strengths of this atomically thin two-dimensional material, i.e., ultrahigh permeability and super selectivity. Thus, the reverse osmotic properties of the porous graphene membranes should be further investigated theoretically. In this paper, classical molecular dynamics method is used to investigate the reverse osmosis characteristics of brine in hydrogenated porous graphene reverse osmosis membrane. The results show that the water permeation rate increases with the driving force, pore size and temperature increasing, for the pore diameter larger than the hydration radius. The ion rejection rate decreases with the driving force and temperature increasing. Interestingly, as the porous graphene moves in the tangential direction to perform a shearing process, the interception rate of the salt ions can be effectively improved and the concentration difference polarization phenomenon can be reduced with the tangential velocity increasing, although the water flux decreases slightly. The influence mechanism of each parameter on permeability and on water flux are explored by analyzing the hydrogen bond distribution, the ionic hydration in feed solution, and the energy barrier of the water molecules in penetrating process. In order to further evaluate the effects of various parameter changes on the benefits of reverse osmosis membranes, both the selectivity and permeability are calculated to evaluate the tradeoff between permeability and selectivity, indicating that the increase of the pore diameter can obtain both high permeability and selectivity under the shearing circumstance of the membrane. The research results in this paper will provide a theoretical understanding of porous graphene-based desalination membrane and also may be helpful in designing the shearing graphene-based water filtration devices.

In order to generate low frequency acoustic wave and minish the ratio of the length to diameter, it is appropriate to instead the circular jet by annular jet as the high pressure gas power. So the larger diameter of jet and resonator are got in the condition of the same pressure and flux. Flow simulations and experiments have been performed in order to better understand the behavior of the powered resonance tube (PRT) driven by annular. Simulation and experiment results show the PRT can be excited by a annular jet, and produce low frequency high-amplitude dynamic pressures and acoustic emission. The compression wave and expansion wave transmit into and out of the resonance tube alternately in a cycle and a cycle can be decomposed to two distinct stages of filling and evacuation. In experiment PRT can work in the low frequency at very low pressure, and PRT can generate intense sound wave at frequency from 50~3200Hz.

We describe a fiber-optic sinusoidal phase modulating (SPM) interferometer for three-dimensional (3D) profilometry, which is insensitive to external disturbances such as mechanical vibration and temperature fluctuation. Sinusoidal phase modulation is created by modulating the drive voltage of the piezoelectric transducer (PZT) with a sinusoidal wave. The external disturbances that cause phase drift in the interference signal and decrease measuring accuracy are effectively eliminated by building a closed-loop feedback system. The phase stability can be measured with a precision of 2.75 mrad, and the external disturbances can be reduced to 53.43 mrad for the phase of fringe patterns. By measuring the dynamic deformation of the rubber membrane, the RMSE is about 0.018 mm, and a single measurement takes less than 250 ms. The feasibility for real-time application has been verified.

Wetting behavior and interfacial characteristic of the Sn-3.5Ag/Ni system are investigated by sessile drop method at the temperature range of 523~773K. The reactive wetting processes demonstrate that: contact angles between the solder and Ni substrate decrease as exponential decay and the equilibrium contact angles decrease monotonously with the temperature increasing. Triple-line mobility is enhanced as the temperature increases. Compositions of the Sn-3.5Ag/Ni interface are identified by EPMA and EDS analysis as Ni3Sn4adjacent to the solder and Ni3Sn adjacent to the Ni substrate, respectively. The formation of the interface IMC was known to greatly improve the reliability of the solder joints in integrated circuits.

TiO2 thin films deposited by magnetron sputtering possess excellent optical transmittance, high refractive index, good adhesion and chemical stability. In this manuscript, TiO2 thin films deposited by magnetron sputtering was used for the first time as an electron extraction layer in inverted polymer solar cells (IPSCs), and the effect of the TiO2 thickness on the photovoltaic performance of P3HT:PC61BM IPSCs was investigated. The highest PCE value of 3.75% was obtained when the thickness of TiO2 thin films was in the range between 42 nm and 73 nm. The absorption properties, morphology and structure of the TiO2 films were characterized by UV-Vis spectroscopy, SEM and Raman spectroscopy, and were related to the device performance of P3HT:PC61BM IPSCs. The results indicate that TiO2 films deposited by magnetron sputtering are an excellent electron extraction layer for IPSCs.

Using the first-principles calculations, we studied the geometric structures, electronic structures and optical properties of the single-walled (n, 0) ZnO nanotubes (NTs). The calculated results show that all the bind energies of the single-walled (n, 0) ZnO NTs are of negative values, which indicate that the ZnO NTs can exist stably as single-walled NTs. While the calculated results of electronic structure indicate that the single-walled (n, 0) ZnO NTs are a type of direct wide band-gap semiconductor materials, the whole valence bands are spread and drift to low-energy direction with the increase of the NT diameter. The defect energy levels caused by quantum size and surface effects emerge on the top of the valence bands. Furthermore, the calculated results of optical properties reveal that the dielectric peaks have a blue shift and the edge of absorption band corresponds to ultraviolet band with the decrease of the NT diameter. The single-walled (n, 0) ZnO NTs can be applied to ultraviolet semiconductor systems.

A new type of organic visible-blind ultraviolet(UV) photodetector based on tri(dibenzoylmethane)(4, 7-biphenyl-1,10-phenanthroline)europium(III) [Eu(DBM)3 BPhen] as an electron donor and [6,6]-phenyl- C-61-butyric acid methyl ester([60]PCBM) as an electron acceptor was fabricated. A peak response of 26 mA W-1and external quantum efficiency of 9.1% were obtained under illumination with 360 nm UV light at 2.1 mW cm-2. This was because of the high UV absorption of Eu(DBM)3 BPhen and the long lifetime, 300 μs, of Eu3 +ions, resulting in high exciton dissociation efficiency. Distinct photoluminescence quenching and photoconductivity of Eu(DBM)3 BPhen were obtained by doping with [60]PCBM. A strong persistent photoconductivity was observed, which could be attributed to low charge carrier transportation and slow release of trapped exciton states in the blend films after the UV light is turned off.

Wettability and interfacial characteristic of the Sn-3.0Ag-0.5Cu/Ni system are investigated by sessile drop method at the temperature range of 503~673K. The reactive wetting processes demonstrate that: contact angles between the solder and Ni substrate decrease as exponential decay and the equilibrium contact angles decrease monotonously with the temperature increasing. Triple-line mobility is enhanced as the temperature increases. Interface of the Sn-3.0Ag-0.5Cu /Ni interface are identified by EPMA and EDS analysis as (Cu,Ni)6Sn5 adjacent to the solder and Ni3Sn4 adjacent to the Ni substrate, respectively. Cu is condensed at the interface, the composition of (Cu,Ni)6Sn5 is (23.16~23.46)Ni- (36.56~37.52) Cu-(39.02~40.27)Sn (atom %). The formation of the (Cu,Ni)6Sn5 IMC was known to greatly improve the reliability of the solder joints in integrated circuits.

The luminescent properties of bis[(4,6-difluorophenyl)-pyridinato-N,Cʹ]c(picolinate)iridium(III) (FIrpic) dependence on the doping concentrations and different annealing treatments were investigated. The color of emission from thin films and organic light emitting diodes (OELDs) could be adjusted from blue to yellow-green by controlling the FIrpic doping concentration. There was good spectral overlap from 440 to 480 nm between the FIrpic photoluminescence (PL) spectra and its absorption spectra. The 476 nm emission intensity decreased as the FIrpic doping concentration increased, and this effect could be attributed to FIrpic self-absorption. The PL and electroluminescence (EL) spectra were measured under different excitation power densities and in different doping concentrations, respectively. The intensity of emission peak at 530 nm was enhanced as the excitation power density or FIrpic doping concentration increased. This suggests that the emission peak at 530 nm originates from the excimer emission between FIrpic molecules. The morphologies of the thin film and changes in the EL spectra were analyzed before and after annealing treatment. This demonstrated that FIrpic molecular aggregation promoted by annealing [Article] www.whxb.pku.edu.cn 物理化学学报(Wuli Huaxue Xuebao) Acta Phys. -Chim. Sin. 2012, 28 (4), 949-956 April Received: November 23, 2011; Revised: January 5, 2012; Published on Web: January 16, 2012. ∗Corresponding author. Email: fjzhang@bjtu.edu.cn; Tel: +86-10-51684908. The project was supported by the National Key Basic Research Program of China (973) (2010CB327704), National Natural Science Foundation of China (10804006, 60576016), National Outstanding Young Scientists Foundation of China (60825407), Natural Science Foundation of Beijing, China (1102028), Program of Introducing Talents of Discipline to Universities, China (B08002), Fundamental Research Funds for the Central Universities, China (2011JBM123, 2010JBZ003), and Talent Plan of Red Berry of Beijing Jiaotong University, China. 国家重点基础研究发展规划(973) (2010CB327704),国家自然科学基金(10804006, 60576016),国家杰出青年基金(60825407),北京市自然科学 基金(1102028),高等学校学科创新引智计划(B08002),高等学校基本科研业务基金(2011JBM123, 2010JBZ003)及北京交通大学红果园人才计 划资助 C Editorial office of Acta Physico-Chimica Sinica doi: 10.3866/PKU.WHXB201201163 949 Acta Phys. ⁃Chim. Sin. 2012 Vol.28 treatment could increase the intensity of excimer emission between FIrpic molecules. The emission color of OLEDs could be adjusted from blue to yellow-green by changing the FIrpic doping concentration, optimizing the device structure, and using annealing treatment on the devices.

Nanocomposite WC–8Co (mass%) powders with different CeB 6 contents were prepared using the planetary ball milling method. Effects of CeB 6 on the microstructures and mechanical properties of WC–8Co cemented carbides were investigated by X-ray diffraction, scanning electron microscope and mechanical properties testing. The results show that the grain growth and regularization of WC particles occur simultaneous with the addition of CeB 6 . CeB 6 addition improves the density and fracture toughness and decreases the volume fraction of the η (Co 3 W 3 C) phase in the materials.

Several polymer solar cells consisting of ITO/PEDOT:PSS/P3HT:PCBM/Al (indium tin oxide/ poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methyl ester/aluminum cathode) were fabricated by spin coating. The influence of annealing temperature on the performance of the polymer solar cells was studied using absorption spectra, photoluminescence spectra, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and atomic force microscopy (AFM). These devices were treated at 120 °C for 10 min in an ambient atmosphere and the best power conversion efficiency (PCE) of 2.00% was obtained at an open circuit voltage (Voc) of 0.64 V, a short circuit current density (Jsc) of 10.25 mA·cm-2, and a fill factor (FF) of 38.1% . The intensities of the absorption peaks at 560 and 610 nm increased because of the increased absorption π→π transition of P3HT after annealing treatment. XRD spectra showed that the intensity of the diffraction peaks at (100) for P3HT increased 1.8 times by comparison with that of the cells that did not undergo annealing treatment. The P3HT:PCBM phase separation increased markedly after annealing treatment, which is valuable for 875 Acta Phys. ⁃Chim. Sin. 2011 Vol.27 exciton dissociation. FTIR results also showed that the polymer materials did not deteriorate during the annealing treatment process.

Based on spin-polarized density functional theory we studied the electronic structures, magnetic and optical properties of Ni-doped ZnO nanowires. The magnetic results show that three magnetic coupling states are present: ferromagnetic (FM), antiferromagnetic (AFM), and paramagnetic (PM) states for the six kinds of Ni-doped configurations. The calculated energy results indicate that antiferromagnetic coupling is more stable when Ni atoms substitute for Zn atoms in the ZnO nanowires on the outside surface along the (0001) direction. AFM coupling has a metallic nature. The FM results from the density of states show that the spin polarization phenomenon appears near the Fermi level and causes strong hybridization between Ni 3d and O 2p. Moreover, the magnetic moments mainly originate from the unpaired electrons of the Ni 3d orbitals and the electrons of the O 2p orbitals contribute a little to the magnetic moments. The coupling of FM has a half-metal nature. In addition, the optical properties indicate that the absorption peaks show a significant red shift and good emission in the far UV band while a blue shift is apparent for the near UV band (380 nm). These results indicate that the Ni-doped ZnO nanowires are promising magneto-optical electronic materials and they can be used for nanoscale spintronics device materials.

In traditional aqueous slurry freezing casting processing, the growth method of ice crystals is hard to control, resulting in the uncontrollable pore's morphologies of the porous ceramics. In the experimental, the pure Al 2 O 3 sol was used to substitute water as a medium for preparing ceramic slurry. With Al 2 O 3 sol addition, it becomes easy to control the microstructure and pore's morphologies of the porous Al 2 O 3 ceramics via adjusting of the solid loading, composition of the ceramic slurries, as well as the cooling methods. The SEM micrographs showed that the sol-contained ceramic slurry combined with freeze casting processing can easily prepare the porous Al 2 O 3 ceramics with different pore sizes and different morphologies. The porous Al 2 O 3 ceramics prepared from 70 wt.% to 90 wt.% solid loading sol-contained Al 2 O 3 slurries and sintered at 1500 °C for 2 h have open porosities from 81.7% to 64.6%.

Ca-α-sialons with low oxygen content were fabricated at 1800°C by hot pressing. The phase and microstructure were characterized by XRD and SEM. The calculated lattice parameter reveals that 20~30% Ca2+ ions still exist in the grain boundary phase of Ca-α′. A large amount of Ca-containing liquid phase efficiently promotes the anisotropic growth of α′ grains in Ca-rich composition. Reinforced only by elongated α′ grains, the fracture toughness of Ca-α′ can reach 4.96 MPa•m1/2.

With the aim of understanding the relationships between organic small molecule field-effect transistors (FETs) and organic conjugated polymer FETs, we investigate the thickness dependence of surface morphology and charge carrier mobility in pentacene and regioregular poly (3-hexylthiophene) (RR-P3HT) field-effect transistors. On the basis of the results of surface morphologies and electrical properties, we presume that the charge carrier mobility is largely related to the morphology of the organic active layer. We observe that the change trends of the surface morphologies (average size and average roughness) of pentacene and RR-P3HT thin films are mutually opposite, as the thickness of the organic layer increases. Further, we demonstrate that the change trends of the field-effect mobilities of pentacene and RR-P3HT FETs are also opposite to each other, as the thickness of the organic layer increases within its limit.

In order to enhance the performance of regioregular poly(3-hexylthiophene) (RR-P3HT) field-effect transistors (FETs), RR-P3HT FETs are prepared by the spin-coating method followed by vacuum placement and annealing. This paper reports that the crystal structure, the molecule interconnection, the surface morphology, and the charge carrier mobility of RR-P3HT films are affected by vacuum relaxation and annealing. The results reveal that the field-effect mobility of RR-P3HT FETs can reach 4.17 × 10−2 m2/(V · s) by vacuum relaxation at room temperature due to an enhanced local self-organization. Furthermore, it reports that an appropriate annealing temperature can facilitate the crystal structure, the orientation and the interconnection of polymer molecules. These results show that the field-effect mobility of device annealed at 150 °C for 10 minutes in vacuum at atmosphere and followed by placement for 20 hours in vacuum at room temperature is enhanced dramatically to 9.00 × 10−2 cm2/(V · s).

Through hydrothermal process, the chrysanthemum-like ZnO particles are prepared with zinc acetate dihydrate (Zn(CH3COO)22H2O) and sodium hydroxide (NaOH) used as main resources under the different concentrations of surfactant polyacrylamide (PAM). The microstructure, morphology and the electromagnetic properties of the as-prepared products are characterized by high-resolution transmission electron microscopy (HRTEM), field emission environment scanning electron microscope (FEESEM) and microwave vector network analyzer, respectively. The experimental results indicate that the as-prepared products are ZnO single crystalline with hexagona wurtzite structure, that the values of slenderness ratio Ld are different in different PAM concentrations, and that the good magnetic loss property is found in the ZnO products, and the average magnetic loss tangent tan δu increases with PAM concentration increasing, while the dielectric loss tangent tan δe decreases.

This paper investigates the effects of concentration on the crystalline structure, the morphology, and the charge carrier mobility of regioregular poly(3-hexylthiophene) (RR-P3HT) field-effect transistors (FETs). The RR-P3HT FETs with RR-P3HT as an active layer with different concentrations of RR-P3HT solution from 0.5 wt% to 2 wt% are prepared. The results indicate that the performance of RR-P3HT FETs improves drastically with the increase of RR-P3HT weight percentages in chloroform solution due to the formation of more microcrystalline lamellae and bigger nanoscale islands. It finds that the field-effect mobility of RR-P3HT FET with 2 wt% can reach 5.78 ? 10?3 cm2/Vs which is higher by a factor of 13 than that with 0.5 wt%. Further, an appropriate thermal annealing is adopted to improve the performance of RR-P3HT FETs. The field-effect mobility of RR-P3HT FETs increases drastically to 0.09 cm2/Vs by thermal annealing at 150 ?C, and the value of on/off current ratio can reach 104.

Fabrication of ambipolar organic field-effect transistors (OFETs) is essential for the achievement of an organic complementary logic circuit. Ambipolar transports in OFETs with heterojunction structures are realized. We select pentacene as a P-type material and N,N'-bis(4-trifluoromethylben-zyl)perylene-3,4,9,10-tetracarboxylic diimide (PTCDI-TFB) as a n-type material in the active layer of the OFETs. The field-effect transistor shows highly air-stable ambipolar characteristics with a field-effect hole mobility of 0.18 cm2/(V.s) and field-effect electron mobility of 0.031 cm2/(V.s). Furthermore the mobility only slightly decreases after being exposed to air and remains stable even for exposure to air for more than 60 days. The high electron affinity of PTCDI-TFB and the octadecyltrichlorosilane (OTS) self-assembly monolayer between the SiO2 gate dielectric and the organic active layer result in the observed air-stable characteristics of OFETs with high mobility. The results demonstrate that using the OTS as a modified gate insulator layer and using high electron affinity semiconductor materials are two effective methods to fabricate OFETs with air-stable characteristics and high mobility.

The geometric, energetic, electronic structures and optical properties of ZnO nanowires (NWs) with hexagonal cross sections are investigated by using the first-principles calculation of plane wave ultra-soft pseudo-potential technology based on the density functional theory (DFT). The calculated results reveal that the initial Zn-O double layers merge into single layers after structural relaxations, the band gap and binding energies decrease with the increase of the ZnO nanowire size. Those properties show great dimension and size dependence. It is also found that the dielectric functions of ZnO NWs have different peaks with respect to light polarization, and the peaks of ZnO NWs exhibit a significant blueshift in comparison with those of bulk ZnO. Our results gives some reference to the thorough understanding of optical properties of ZnO, and also enables more precise monitoring and controlling during the growth of ZnO materials to be possible.

The microstructures and the phases of the Mg–6Zn–3Sn–2Al alloy in the different states were characterized by OM, XRD and TEM. Almost all the MgZn phase was dissolved in the alloy after solutionizing, while part of the Mg2Sn phase was retained. In addition, no visible grain growth was detected. The long rod-like β ′ 1 phase, the hexagonal tablet-like β ′ 2 phase, the lath-like MgZn phase, the coarse particle-like MgZn2 phase and the short rod-like Mg2Sn phase were observed in the as-aged alloy. The Sn addition had no obvious effect on the morphology and crystal structure of the precipitates in the Mg–Zn system. The as-aged alloy exhibited higher strength but lower elongation than the as-cast alloy at ambient temperature and 150 °C. With the increment of temperature, the strength of the alloys in both states decreased, while their elongations increased. Moreover, the former showed a slighter decrease in strength than the latter with the temperature increasing. It can be mainly ascribe to the strengthening of thermally stable β ′ 1 and Mg2Sn precipitates along grain boundaries and within the matrix.

We synthesize and purify 9, 9'-bianthracene with the purity up to 96.4%. The electronic and crystallographic structures of 9, 9'-bianthracene are studied. The results of a joint experimental investigation based on a combination of x-ray diffraction (XRD) spectra, hydrogen nuclear magnetic (HNMR) spectra, infrared absorption (FT-IR) spectra, and mass spectra (MS) of 9,9'-bianthracene are obtained. The uniform compact film is observed by an atomic-force microscope (AFM). Organic field effect transistors (OFETs) with an active layer based on the synthesized 9, 9'-bianthracene are fabricated for the first time. Its field-effect mobility is as large as 0.067cm2/(V-s) and the on/off ratio is above 5 × 10.4 The result demonstrates that the oligomerization of a small semiconductor molecule is an effective method to develop high-mobility organic semiconductors.

Effects of Sn and Ca additions on microstructure, mechanical properties, and corrosion resistance of the as-cast Mg-6Zn-2Al-based alloy were investigated by SEM, XRD, tensile tests, electrochemical measurements, etc. The higher the Sn content, the higher the yield strength of the Mg-6Zn-2Al-based alloy. Trace Ca addition refined both grains and divorced eutectics in the Mg-Zn-Sn-Al alloys, leading to the best combination of strength and plasticity. Moreover, its influence was more significant for the alloy with a higher Sn content. Furthermore, the combined addition had a beneficial effect on the corrosion resistance improvement of the Mg-6Zn-2Al alloy. The Mg-6Zn-2Al-3Sn-0.2Ca alloy was the most corrosion-resistant alloy among the nine alloys studied, better than AZ91 and ZA85. It could be ascribed to the decrease and the refinement of divorced eutectics, the higher hydrogen overvoltage of Sn and the Ca grain refinement.

The geometric structure, electronic structure, optical properties and the formation energy of Sb-doped ZnO with the wurtzite structure are investigated using the first-principles ultra-soft pseudo-potential approach of plane wave based upon the density functional theory. The calculated results indicate that the volume of ZnO doped with Sb becomes larger, and the doping system yields the lowest formation energy of Sb on the interstitial site and the oxygen site. Furthermore, Sb dopant first occupies the octahedral oxygen sites of the wurtzite structure. It is found that Sb substituting on oxygen site behaves as a deep acceptor and shows the p-type degenerate semiconductor character. After doping, the electron density difference demonstrates the considerable electron charge density redistribution, which induces the effect of Sb-doped ZnO to increase the charge overlap between atoms. The density of states move towards lower energy and the optical band gap is broadened. Our calculated results are in agreement with other experimental results and could make more precise monitoring and controlling possible during the growth of ZnO p-type materials.

This paper investigates the morphology and crystallization properties of the two crystalline phases of pentacene grown by thermal evaporation on p+-Si substrates at room temperature by the methods of atomic force microscopy and x-ray diffraction. This kind of substrate induces a thin film phase and a triclinic phase which are formed directly onto p+-Si substrates and constitute a layer consisting of faceted grains with a step height between terraces of 15.8 A (1 A=0.1 nm) and 14.9 A, respectively. Above the critical thickness of the thin film phase, lamellar structures are found with an increasing fraction with the increase of the film thickness. When the film thickness is fixed, the fraction of lamellar structures increases with the increase of annealing temperature. These lamellar structures are identified as the second phase with a interplanar distance of 14.9 A corresponding to the pentacene triclinic phase. Furthermore, the thin film phase consisting of several micrometre sized uniformly oriented grains at an annealing temperature of less than 80°C and a deposition rate of 0.6 A/s is observed.

Adsorption and reaction of CO on two possible terminations of SrTiO3 (100) surface are investigated by the first-principles calculation of plane wave ultrasoft pseudopotential based on the density function theory The adsorption energy, Mulliken population analysis, density of states (DOS) and electronic density difference of CO on SrTiO3 (100) surface, which have never been investigated before as far as we know are performed. The calculated results reveal that the Ti-CO orientation is the most stable configuration and the adsorption energy (0.449 eV) is quite small. CO molecules adsorb weakly on the SrTiO3 (100) surface, there is predominantly electrostatic attraction between CO and the surface rather than a chemical bonding mechanism.

Three novel tri-dimensional phthalocyanine polymers, with lanthanum (LaPPc), gadolinium (GdPPc) and ytterbium (YbPPc) as centric atoms, have been synthesized from a tetranuclear phthalonitrile. Third-order optical nonlinearities of these compounds in DMF solution are measured by a picosecond Z-sacn technique at 532nm. It is found that all the compounds show reverse saturation absorption and nonlinear self-focus refraction effect. The second-order molecular hyperpolarizabilities are calculated to be 1.82× 10 29 , 1.48× 10 29 and 1.45× 10 29 esu for LaPPc, GdPPc and YbPPc, respectively. The differences among their nonlinear optical properties are attributed to the special tri-dimensional structure and the variation in rare earth atoms.