Search

Layup temperature is a vital factor that affects the production quality of automated fiber placement for thermoset composites. For high quality production, this paper proposes a new prediction model of layup temperature by considering the structure of infrared heater of automatic fiber placement equipment. The model was first verified by comparing with the temperature results of layup experiments. Then a prediction on the effects of heater structure arrangement on layup temperature was conducted in the model. The research shows that the length of infrared tube and the radian of reflective-film have significant influences, rather than other parameters. According to this investigation, a heater structure-based heating strategy was presented in the paper to efficiently achieve constant temperature control in variable speed layup process.

Two-dimensional (2D) ferromagnets with out-of-plane (OOP) magnetic anisotropy are potential candidates for realizing the next-generation memory devices with ultra-low power consumption and high storage density. However, a scalable approach to synthesize 2D magnets with OOP anisotropy directly on the complimentary metal-oxide semiconductor (CMOS) compatible substrates has not yet been mainly explored, which hinders the practical application of 2D magnets. This work demonstrates a cascaded space confined chemical vapor deposition (CS-CVD) technique to synthesize 2D FexGeTe2 ferromagnets. The weight fraction of iron (Fe) in the precursor controls the phase purity of the as-grown FexGeTe2. As a result, high-quality Fe3GeTe2 and Fe5GeTe2 flakes have been grown selectively using the CS-CVD technique. Curie temperature (TC) of the as-grown FexGeTe2 can be up to ∼ 280 K, nearly room temperature. The thickness and temperature-dependent magnetic studies on the Fe5GeTe2 reveal a 2D Ising to 3D XY behavior. Also, Terahertz spectroscopy experiments on Fe5GeTe2 display the highest conductivity among other FexGeTe2 2D magnets. The results of this work indicate a scalable pathway for the direct growth and integration of 2D ternary magnets on CMOS-based substrates to develop spintronic memory devices.

Propagation of ultrasonic wave in Carbon Fiber Reinforced Polymer (CFRP) is greatly influenced by the material’s matrix, resins and fiber volume ratio. Laser ultrasonic broadband spectral technique has been demonstrated for porosity and fiber volume ratio extraction on unidirection aligned CFRP laminates. Porosity in the matrix materials can be calculated by longitudinal wave attenuation and accurate fiber volume ratio can be derived by combined velocity through the high strength carbon fiber and the matrix material with further consideration of porosity effects. The results have been benchmarked by pulse-echo ultrasonic tests, gas pycnometer and thermal gravimetric analysis (TGA). The potentials and advantages of the laser ultrasonic technique as a non-destructive evaluation method for CFRP carbon fiber volume fraction evaluation were demonstrated.

A high-speed (HS) permanent magnet (PM) synchronous motor (HSPMSM) with a carbon fiber-reinforced plastic (CFRP) protective sleeve in the surface-mounted rotor was explored in this study. In view of retaining the PMs at HS operations, the high-strength CFRP sleeve was designed on the basis of a process that could be summarized as follows. First, a multi-physics analysis of the rotor was conducted. The requirements to the CFRP sleeve were obtained from electromagnetic analysis, loss analysis, heat flow coupling computational fluid dynamics analysis, structural analysis, and rotor dynamics analysis. Second, the CFRP sleeve was designed by theoretical analysis. From the results, the thickness values of the carbon fibers in the circumferential and helical directions were chosen to be 4 and 1 mm, respectively, while the helical angle of carbon fibers was chosen to be 70°. Then, a plate-shaped CFRP product and a cylindrical CFRP product were fabricated to verify the strength and stiffness of the CFRP sleeve. The performance test results show that the hoop strength and elastic modulus and the axial strength and elastic modulus of the plate-shaped CFRP products at 20 °C are 1963 MPa @ 156 GPa and 550 MPa @ 36 GPa, respectively. The hoop strain and axial strain of the cylindrical CFRP product under 35 MPa are about 3000 and 1900 μe, which meet the design requirements of the HSPMSM.

A robust fiber sensor for salinity measurement based on encapsulated long-period grating in microfiber is proposed. The long-period grating is fabricated in microfiber by inducing periodical deformation with CO2 laser, which is then encapsulated in a holey capillary tube. The encapsulation tube is designed to effectively protect the microfiber from external interference, but does not change the optical properties of the fiber and the response speed of the sensor, which makes the sensor more robust for real applications. Experimental results show that the sensor can achieve a sensitivity of 2.16 nm/% with a good linearity for concentration from 0% to 20%. It is theoretically proved that the sensitivity can be further improved by optimizing the diameter parameters. Such structure may be used as low loss evanescent-wave-coupled optical absorption, fluorescent and gain cells, photoacoustic cells, and etc.

A Novel scalable approach using Terahertz (THz) waves together with the electromagnetic field simulation was applied to investigate four rabbits of eight rabbit corneas in vivo. One eye of each rabbits' corneas was edema induced; the other eye of the corneas served as the control. The simulation revealed the propagation of THz waves at a certain distance along the sub-surface of the cornea. THz spectra have been collected close to the corneal surface by deviating the direct reflection of the THz beam for the edema cornea, the reflected wave intensity for edema corneas is generally larger compared with the control cornea. Upon edema becomes severe at the end of the observation, the reflected wave intensities obtained by detector corresponding to the corneal deep stroma layer approach to the same value for all observed corneas. Good correlation is observed between central corneal thickness measurements and THz wave reflection signal intensities. Our results demonstrated that THz spectroscopy technique could obtain the information from different corneal sublayers.

Significance: Corneal diseases is a major cause of reversible blindness in the world. Monitoring the progression of human corneal edema or corneal scarring to prevent the disease entering into the end stage is crucial. Aim: We present a method for sensing human corneal composition at different depths, namely focused on the epithelium and stromal layer, using high-sensitivity terahertz (THz) broadband spectroscopy. Approach: From the proposed methodology, the THz temporal and absorption spectra of human corneas at different edema stages have been studied. THz wave signals were collected from the direct reflection and four other collection points along the THz wave propagation direction as reviewed from the simulation THz electrical field. Result: Our results show that the epithelium layer acts as a good barrier to maintain hydration level of the stroma, and the quality of the epithelium can be used to predict the level of corneal swelling in corneal edema. At the detection points near to the incident point, the THz frequency spectra demonstrated interference oscillation behavior. At the final edema observing time, results showed that the epithelium lose its barrier properties. The intactness of the epithelium can be used to predict the edema severity in the final stage. When the detection points are further away from the incident point, the THz spectra are believed to contain information from stromal layer. Stromal absorption spectra demonstrated correlation with optical coherence tomography thickness results. Conclusion: The hydration concentration from stromal layer was further quantitatively calculated. At the end of the experiment, all the corneal hydration levels reach to the same value which shows that the edema hydration has reached maximum saturation. The information of individual sublayers of the cornea is obtained by characterizing noninvasively with the use of THz spectroscopy. To our knowledge, this is the first report of using THz for noninvasive characterization of sublayers of the cornea.

We report the fabrication of long period gratings in fluid-cladding microfibers by directly focusing a femtosecond laser beam on the microfibers surface to induce periodical modification a long one side of the microfibers. A long period grating is fabricated in a water-cladding microfiber with a diameter of ~ 5 μm, which demonstrates a resonant attenuation of 28.53 dB at wavelength of 1588.1 nm with 10 pitches. When water cladding is changed to be refractive index oil of n= 1.33 and alcohol solution with concentration of 5%, the resonance wavelength shifts to 1575.1 nm with resonant attenuation of 24.91 dB and 1594.1 nm with resonant attenuation of 35.9 dB, respectively. The long period grating demonstrates different temperature sensitivities of–0.524 nm/°C,–0.767 nm/°C and–1.316 nm/°C for water, alcohol solution and refractive index oil cladding microfibers, respectively, which means the alterable liquid cladding allows the availability of tunable wavelength and sensitivity. The fluid-cladding protects the microfibers from external disturbance and contamination and allows more flexibility in controlling the transmission property and sensing characteristics of long period gratings, which can be used as fiber devices and sensors for chemical, biological, and environmental applications.

Two complexes, [Cu6I6(L1)3]n (I) and [Cu4I4(L2)2]n (II) (L1 = 1,4-bis(phenylthio)but-2-yne; L2 = 1,4-bis(phenylthio)butane), as precursors for thermoelectric composites were prepared using a literature procedure. During the preparation of I, an unexpected 3-D polymorph [Cu4I4(L1)2]n (1) with a triclinic space group and an infinite [CuI]n staircase structure was obtained. This new polymorph (1) exhibited the same structure at both room temperature and 173 K. Complexes 1 and II were therefore pyrolysed to composites 2 and 3, respectively, at 400 °C under a nitrogen gas flow. Composite 3 was pale in color with a low carbon content (0.05 wt%) and easily disassembled during handling. By comparison, the high carbon containing (10.2 wt%) composite 2 can be compressed into a robust, light pellet (density 3.58 g cm-3), which showed a moderate to high Seebeck coefficient (543-1308 μV K-1) over the temperature range 70-240 °C.

It is demanded a non-contact, non-destructive and reliable system and method of porosity measurement because conventional techniques are contact and cubersome. We have developed a method by using THz inspection system, which allows measuring the porosity rapidly and non-invasively, by introducing an external perturbation. The embodiments of the external perturbation can be mechanical or pulsed laser.

Liposomes, the biocompatible lipid bilayer vesicles, have attracted immense attention due to their distinctive features such as efficient vehicle for the delivery of a wide range of therapeutic agents, adjustable formulation properties, and high drug entrapment efficiency. In this contribution, we present a simple method for the preparation of liposomes using glass beads and compared the potential of this method with conventional methods of liposome preparation. The prepared liposomes were characterized by different analytical techniques (HPLC, DLS, TEM, differential scanning calorimetry, and in vitro drug release). Our findings revealed that the particle size of liposomes is mainly dependent on the size of the glass beads and the glass bead shearing time. An average liposome size of 67.7 ± 25.5 nm was obtained using 2-mm glass beads after 24-h incubation at 200 rpm. The liposomes prepared under the optimized conditions exhibited a high encapsulation efficiency of 92.1 ± 1.7% with 31.08% drug release after 360 min at 37°C. In conclusion, the developed method is a simple and convenient process of liposome preparation of different sizes with desirable entrapment efficiency capacity.

We study the junction behavior of poly (3,4-ethylenedioxythiophene):polystyrenesulphonate/n-Si hybrid organic/inorganic heterojunction by reverse recovery transient (RRT) characterization. RRT response for PEDOT:PSS/n-Si hybrid junction is reported for various n-Si doping concentration and forward bias current injection level. The presence of settling time of 8.3–23.5 μs in the RRT response in contradiction to Schottky junction model commonly assumed for PEDOT:PSS/n-Si hybrid structure. The decrease in the minority carrier lifetime from 126.8 μs to 39.5 μs with increased n-Si doping concentration, suggests that minority carriers are stored at n-Si side of the junction, which is consistent with a p+-n junction model for the hybrid structure. The minority carrier lifetime is found to depend on forward bias current injection level, attributed to trap-saturation effect of the recombination-centers at the PEDOT:PSS/n-Si junction. The DC-IV characteristics of the PEDOT:PSS/n-Si hybrid junction are also consistent with the notion of diffusion and trap assisted recombination dominated dark current. The diffusion dominated transport of PEDOT:PSS/n-Si leads to an ideal p+-n junction behavior that leverages on the good transport properties of Si. Our findings are important in the modeling and optimization of the characteristics of electronic devices based on the organic/Si hybrid junction.

Organic solar cells based on P3HT:PCBM without annealing process, with annealing process before and after cathode deposition have been investigated in dark and under light by using high magnitude and phase resolution impedance spectrometer. The impedance data in dark can be interpreted as the properties and positions of layers and interfaces of the sample to nanoscale range. Therefore, the fabrication process and device nanoscale layer and interface quality can be monitored. Under light conditions, the impedance data obtained were fitted into equivalent circuit and electronic parameters such as diffusion time of electrons, τd and effective carrier lifetime, τn were calculated. Correlation of the nanoscale layers and interface parameters to the dynamic carrier performance parameters were established. Applying the high magnitude and phase resolution impedance method to understand the properties of organic thin-film solar cells in both static and dynamic status will give useful insights not only on the device performance improvement in terms of process, layer morphology and interfaces quality; but also deeper understanding of how the device kinetic characteristics at the interface states induced correlate with the improvement of current-potential characteristics under device operation conditions.

Colloidal quantum dot light-emitting diodes (QLEDs) are reported with improved external quantum efficiencies (EQE) and efficiency roll-off under high current densities by introducing a thermally-evaporated organic cathode interfacial material (CIM) Phen-NaDPO. QLEDs with this new CIM modified Al cathode were fabricated, giving an upwards of 25% enhancement in the EQE relative to the bare Al device. Ultraviolet photoemission spectroscopy (UPS) suggests that this material can effectively lower the work function of Al, therefore facilitating the electron injection in QLEDs. Furthermore, Phen-NaDPO was introduced into the LiF/Al device to afford better balanced hole/electron injection in the emitting layer. Consequently, the QLEDs with the organic CIM/LiF/Al cathode further increased EQE and current efficiency by 44% and 52%, respectively, with higher luminance and lower efficiency roll-off under high current densities.

A Zn(II)-based metal–organic frameworks (MOFs) containing azo-functionalized pores was synthesized by solvothermal process. Batch adsorption experiments for the removal of U(VI) were performed with the MOFs. The adsorption data were successfully modeled by the Langmuir and D–R isotherms, suggesting a chemisorption with monolayer homogeneous adsorption. The thermodynamics research shows the adsorption being a feasible and endothermic process. The larger experimental adsorption capacity of 312.32 mg g−1 suggests that MOFs may be a potential adsorbent material for removal of U(VI) ions from waste water and further development would be warranted in future.

This article establishes a reliable constitutive model to describe the behaviors of fiber-reinforced polymer composites under quasi-static and dynamic loading. This model integrates the contributions of all the three phases of a composite: the fiber, the matrix, and the fiber/matrix interphase, which make it capable of capturing the key micromechanical effect of the interphase on the macroscopic mechanical properties of composites. The interphase is taken as a transversely isotropic material together with the fiber. By analyzing glass/epoxy and carbon/epoxy composites, it was found that the model predictions agree well with the experimental data and the model is more effective particularly when the fiber volume fraction is high. The dynamic three-phase model was also established by using the coupling of the elastic and Maxwell elements for the viscoelasticity of the matrix as well as the interphase. The article concludes that the three-phase model with consideration of the interphase influence can precisely characterize the static and dynamic mechanical properties of a FRP composite.

The red oxide phosphors activated by Mn4+ have become a research hotspot because of their excellent physical/chemical stability, which can be applied in the field of light-emitting diodes (LED) plant growth lighting. Here, a new type of Sr9Gd2W4O24 (SGWO):Mn4+ red phosphor was prepared by traditional high temperature solid state reaction method. The phase compositions and morphologies of powders were analyzed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The luminescent properties of the samples with varying Mn4+ concentrations were investigated, and the photoluminescence excitation (PLE) spectra illustrate that samples can be effectively excited by near-ultraviolet/blue light. Furthermore, typical concentration quenching occurs when the doping concentration of Mn4+ exceeds 0.4 mol%. In addition, the thermal activation energy of the sample was calculated to be 0.3641 eV. Importantly, under the excitation of near-UV light at 365 nm, SGWO:0.004Mn4+ phosphor can emit bright far-red light. All the results indicated that SGWO:Mn4+ phosphors have potential application value in indoor plant cultivation.

The dinuclear complex [Cu2 I2 (L1)2 ] (1) (L1=3-((4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl)methyl)benzonitrile) is characterized by single-crystal X-ray diffraction (XRD), powder XRD, IR, photoluminescence spectroscopy, and thermogravimetric analysis. Unlike other related, known copper iodide complexes, it exhibits strong yellow emission in the solid state at both room temperature and 77 K. Showing good compatibility with PMMA, it is blended with the polymer in different weight ratios to prepare luminescent composite fibers.

Shelf lifetime of organic solar cells based on P3HT:PCBM has been investigated using high magnitude and phase resolution impedance spectrometer. From the traditional current–voltage degradation curve, several stages of changes causing the device performance degradation are discussed. Degradation process of the devices has been monitored using impedance spectrometer under light, and dynamic parameters changes have been derived by model fitting, which are unable to provide information regarding the different stages of device changes though. However, layer analysis tested using impedance spectrometer in dark, provided exact information of device’s layers and interfaces changes during degradation process. Higher capacitance at PEDOT-ITO interface and higher resistance at PEDOT-P3HT interface, and PEDOT bulk layer’s performance fluctuations contributed to the beginning stages of device degradation. The degradation of P3HT:PCBM layer indicates the starting of the final device irreversible degradation.

The degradation mechanism of Alq 3 -based OLED is investigated using low-frequency noise measurements. Devices are driven at constant current mode and constant voltage mode. Our results show that device under constant current mode has a longer lifetime and the device under constant voltage mode generates defects and interface charges much faster. The differences show that the interfacial building up of traps and defects occurs at different pace.

Shearography is an optical non-destructive testing technique which has been used as a practical tool in industrial applications due to its suitability for large area and fast inspections. Shearography is based on the differential of two interferometric patterns obtained when the test samples are under stress loading and when the stress loading is removed. Conventional loading methods for shearography testing include loadings by vacuum, thermal and vibration excitations. Currently, shearography testing has been mainly used for detection of delamination in composite structures. For damage detection in metallic structures, it is difficult for shearography with those conventional loading methods to detect defects, especially sub-surface fatigue cracks in metals, due to the high rigidity and/or the high thermal conductivity of metals.

In this report, we showed the existence of RET induced intermolecular pairing force by comparing their fluorescence behaviors under room illumination vs standing in dark area for either PFluAnt solution or PFluAnt&PFOBT mixture. Their prominent emission attenuation under room illumination brought out the critical role of photo, i.e. RET induced intermolecular pairing force in induction of polymer aggregation. Constant UV-Vis absorption and fluorescence spectra in terms of both peak shapes and maximum wavelengths implied no chemical decomposition was involved. Recoverable fluorescence intensity, fluorescence lifetime as well as NMR spectra further exclude photo induced decomposition. The controllable on/off state of RET induced intermolecular pairing force was verified by the masking effect of outside PFluAnt solution which function as filter to block the excitation of inside PFluAnt and thus off the RET induced intermolecular pairing force. Theoretical calculation suggest that magnitude of RET induced intermolecular pairing force is on the same scale as that of van der Waals interaction. Although the absolute magnitude of RET induced intermolecular pairing force was not tunable, its effect can be magnified by intentionally turn it “on”, which was achieved by irradiance with 5 W desk lamp in this report.

We present an improved efficiency of polymer solar cell by incorporating single-wall carbon nanotubes (SWCNTs). A power conversion efficiency of 2.66% was achieved for the device with 0.125 wt% SWCNTs, which is 16% improvement over control device without SWCNTs, primarily due to the increase in the photocurrent and fill factor. The results reveal that SWCNTs serve as effective and additional electron pathways, facilitating the electron transport and improving the interface contact between active layer and electrode. The improved contact area was evidenced by the increased root-mean-square surface roughness as SWCNTs concentration increases. However, the increased peak-to-valley value also indicates the possibility of short circuit in device, thus the concentration of SWCNTs has to be optimized. Published version

The usage of zinc oxide (ZnO)-based nanostructures in photoelectrochemical (PEC) water splitting has been well investigated yet still in keen exploration for further performance enhancement. Multi-walled carbon nanotubes (MWCNTs)-modified ZnO nanorods were prepared via hydrothermal route followed by simple solution deposition. MWCNTs were self-anchored onto the ZnO nanorods and acted as a hole-attracting phase. The PEC performance of MWCNTs-modified ZnO nanorods, including photocurrent density and photo current conversion efficiency (PCE), was found to be significantly improved compared with unmodified ones. The maximum value of PCE (0.646%), which was 2.1 times higher than that of pristine ZnO nanorods, was achieved with a MWCNTs/ethanol suspension concentration of 0.002 wt%. The performance enhancement is attributed to increasing of light absorption from rougher surface and effective charge carrier transport from the excellent conductivity of the incorporated MWCNTs.

Most fatigue failures in aeronautical structures occur at fastened joints due to stress concentration (SC). Since more and more advanced composites are applied in aircrafts instead of conventional alloys, SC in CFRP composite plates with zigzag-arranged multiple holes has been investigated by finite element method in this paper. It is found that the static SC factor (SCF) of CFRP plates varies with the dimensionless bore and zigzag angle by a greater change than isotropic plates, and that the dynamic response amplitude and frequency of the SCF depend on the dimensionless bore and the dimensionless wave number related with material properties and the exciting frequency.

A series of thermally stable cyclotriphosphazenes, hexakis(4-(9,9-dihexthyl-fluoren-2-yl)phenoxy)cyclotriphosphazene ( CPZ1 ), hexakis(4′-(9,9-dihexyl-fluoren-2-yl)-[1,1′-biphenyl]-4-oxy)cyclotriphosphazene ( CPZ2 ), hexakis(4-(9,9,9′,9′-tetrahexyl-[2,2′-bifluoren]-7-yl)phenoxy)cyclotriphosphazene ( CPZ3 ), and hexakis-(4′-(9,9,9′,9′-tetrahexyl-[2,2′-bifluoren]-7-yl)-[1,1′-biphenyl]-4-oxy)cyclotriphosphazene ( CPZ4 ), were prepared by reacting hexachlorocyclotriphosphazene with suitable precursors in high yields. The chemical structures and properties of the compounds CPZ1-4 were characterized by thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, and UV–Vis and fluorescence spectroscopy. All CPZ compounds were amorphous in nature and showed very good thermal stability with decomposition temperatures of more than 429 °C in nitrogen and around 400 °C in air. CPZ3-4 emitted blue light with maxima of 403 and 416 nm with quantum yields of 0.69–0.56 in THF solution, respectively. Study on the thermal aging effect on the optical properties of CPZ2-4 revealed that three-dimensional hybrid organic–inorganic cyclotriphosphazene ring could suppress the undesirable green emission by obstructing π – π stacking. In addition, light-emitting diode devices of CPZ3 and CPZ4 were fabricated.

A highly efficient and stable QLED using an inorganic WO3 nanoparticle film as a hole injection layer is demonstrated.The resulting WO3 nanoparticle-based QLEDs also exhibit superior performance compared to that of the present PEDOT:PSS-based QLEDs. The results indicate that WO3 nanoparticles are promising solution-processed buffer layer materials and serve as a strong candidate for QLED technology towards the practical applications in the next-generation lighting and displays. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly porous three-dimensional (3D) hierarchical nanostructures suspended in aqueous media were facilely prepared via electrospinning of polyacrylonitrile (PAN)/indium tin oxide (ITO) nanofibers and collection of the hybrid nanofibers by water, followed by hydrothermally growing ZnO nanorods from the nanofibers. The large inter-fiber distances facilitated the uniform growth of the ZnO nanorods throughout the whole system. The suspended PAN/ITO nanofibers process excellent light trapping capability due to their centimeter-sized dimensions and hence large light penetration path. This significantly increases the probability of multiple-reflections, leading to high absorption with almost zero transmission when the size of the sample reaches 10 mm in the direction parallel to incident light. High photocurrent was generated when the nanorods-on-nanofibers was used as a photoanode. The high photocurrent density generated by the anode can be attributed to its excellent light-trapping capability brought by the large amount of interaction sites between the ZnO nanorods and light, its large contact area with electrolyte, as well as the conduction path constructed by high-content ITO nanoparticles. Accepted version

The diamond films deposition experiment is carried out with MPCVD system. Some technology problems are discussed respectively, such as the substrate pretreatment, gases source compositions and deposition temperature. XRD pictures with different peaks illustrated that diamond film has good crystal orientation. A density of film crystal is observed and a thickness uniformity in detected by Scanning Electron Microscopy (SEM). The pureness of the diamond film was measured by Raman spectroscopy. The parameter coincidence rate is 90% based on the 10 prepared samples

Superiorly high photoconductivity is desirable in optoelectronic materials and devices for information transmission and processing. Achieving high photoconductivity via bandgap engineering in a bandgap-graded semiconductor nanowire has been proposed as a potential strategy. In this work, we report the ultrahigh photoconductivity of bandgap-graded CdSxSe1−x nanowires and its detailed analysis by means of ultrafast optical-pump terahertz-probe (OPTP) spectroscopy. The recombination rates and carrier mobility are quantitatively obtained via investigation of the transient carrier dynamics in the nanowires. By analysis of the terahertz (THz) spectra, we obtain an insight into the bandgap gradient and band alignment to carrier transport along the nanowires. The demonstration of the ultrahigh photoconductivity makes bandgap-graded CdSxSe1−x nanowires a promising candidate as building blocks for nanoscale electronic and photonic devices.

Although sub-diffraction-limit-resolution optical imaging has been attained via superlenses in the UV regime, the corresponding resist profile in general exhibits a very poor contrast, far below the minimum requirement for photolithography. Here, it is experimentally demonstrated thin flat silver superlenses, engineered through refining interfacial roughness to reduce scattering loss, capable of resolving grating features of sub-50 nm resolution with a high contrast of about 2.2. The seed layer effect on the superlens performance at a wavelength of 365 nm has been probed through both experimental and analytical methods. The performance of Ag, Ag/Ni and Ag/Ge superlenses agrees well with theoretical predications. The results show that a smooth interface is a key factor for realizing high performance superlensing, while damping losses become dominant when the roughness is reduced to less than 2 nm. This work verifies that a superlens is a potential tool for sub-diffraction limit nano-photolithography.

Uniform and well adhesive nanostructured hydrated tungsten trioxide (3WO 3•H 2O) films were grown on fluorine doped tin oxide (FTO) substrate via a facile and template-free crystal-seed-assisted hydrothermal method by addition of ammonium sulfate ((NH 4) 2SO 4) and hydrogen peroxide (H 2O 2). X-ray diffraction (XRD) studies indicated that the films are of orthorhombic structure. Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) analysis showed that the film was composed of brick-like nanostructures with a preferred growing direction along (002). The influence of seed layer, (NH 4) 2SO 4 and H 2O 2 on the products were also studied. The film showed good cyclic stability, comparable switching speed and coloration efficiency (30.1 cm 2 C -1). A complementary electrochromic device based on the film and Prussian blue depicted highly improved color contrast, coloration/bleaching response (1.8 and 3.7 s respectively) and coloration efficiency (164.6 cm 2 C -1).

Photolithography is the technology of choice for mass patterning in semiconductor and data storage industries. Superlenses have demonstrated the capability of subdiffraction-limit imaging and been envisioned as a promising technology for potential nanophotolithography. Unfortunately, subdiffraction-limit patterns generated by current superlenses exhibited poor profile depth far below the requirement for photolithography. Here, we report an experimental demonstration of sub-50 nm resolution nanophotolithography via a smooth silver superlens with a high aspect profile of ~45 nm, as well as grayscale subdiffraction-limit three-dimensional nanopatterning. Theoretical analysis and simulation show that smooth interfaces play a critical role. Superlens-based lithography can be integrated with conventional UV photolithography systems to endow them with the capability of nanophotolithography, which could provide a cost-effective approach for large scale and rapid nanopatterning.

We report a fast-switching negative photoelectrochromic cell composed of a dye-sensitized nanocrystalline TiO 2 electrode and Prussian blue counter electrode sandwiching a LiI electrolyte. The cell can be bleached under illumination with shorted TiO 2 and Prussian blue electrodes, and re-colored by applying an appropriate external voltage. The photo-bleaching and electric-coloring processes are fast and reversible. A maximum absorbance modulation of 0.44 recorded at 700 nm is obtained between bleached and colored states for the cell when the PB films thickness is 452 nm. Illuminated under different levels of light intensity or durations of time, the shorted cell shows adjustable optical absorption from 470 to 840 nm. The in-situ transmittance response depicts that the photo-bleaching response is 6.2 s for 70% transmittance change under 100 mW/cm 2 illumination in short circuit configuration, and the re-coloration time is about 600 ms under 2 V bias recorded at 780 nm, with an electrochromic coloration efficiency of 103.4 cm 2/C. The cell shows a good reversible stability and can be potentially applied in erasable displays. © 2011 Elsevier B.V. All rights reserved.

Poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) layers are used as the nucleation (seed) layer to reduce surface roughness of the overlying silver (Ag). The technique leads to ultrasmooth Ag thin films with a minimum surface roughness of 0.8 nm. The mechanism contributing to the improvement is explained on the basis of better wetting of Ag on PEDOT:PSS, and properties of the nucleation layer on the aspects of surface energy, surface adhesive force, and surface morphology influencing Ag wetting and growth pattern are being discussed. The surface plasmon resonance (SPR) shows significant improvement, in terms of the Figure of Merits (FOM), as the surface roughness on Ag films is reduced. A lower light scattering and longer plasmon propagation of maximum 15.3 μm are also realized on a smoother Ag surface. The results indicate great potential on the application of combined PEDOT:PSS/Ag structure as an effective and economically feasible design solution for plasmonic and optical metamaterials devices.

Based on the history of multi-step stamping, an advanced analysis method is proposed to analyze the structural properties of metal part. This method combines multi-step stamping forming and structure analysis together. The forming of metal blank is simulated to obtain the shape (thickness) variation, spring-back, residual stress and hardening material properties by multi-step stamping using the Abaqus/Explicit software; then the non-uniform thickness stamped part obtained is used to analyze the subsequent structure properties through mapping residual stress and hardening material using the Abaqus/Standard software. The terminal of connector is taken as an example and its normal force is analyzed with the above proposed method to demonstrate its analysis process. The method presented here conduces to improving the precision and ability of structural analysis.

An amphiphilic graft copolymer with poly(acrylamide-methacrylate) as a main chain and octylphenyl polyoxyethylene as side chains (P(AM-MA)-g-C8PhEO10) was successfully synthesized via free radical copolymerization. The structure and the composition of the graft copolymer were characterized by FTIR, 1H-NMR and elemental analysis (EA) in detail. The absolute molecular weight of the copolymer is 1.304×106, as determined by static light scattering (SLS). The molar ratio of acrylamide monomer to the macromonomer is 33:1 in the copolymer and 53 C8PhEO10 branch chains attach to a P(AM-MA) backbone. The micellar behavior of P(AM-MA)-g-C8PhEO10 was preliminarily studied by means of surface tension measurements, transmission electron microscope (TEM) in aqueous solution. It was found that the stable spherical micelles with core-shell structure are formed and polymolecular micelles are larger and more compact than monomolecular micelles. In addition, the graft copolymer has favorable thermal stability.

Inverted tandem organic solar cells, consisting of two bulk heterojunction sub-cells with identical poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) active layer and a MoO3/Ag/Al/Ca intermediate layer, have been presented and optimized. Indium tin oxide (ITO) modified by Ca acts as a cathode for electron collection and Ag is used as the anode for hole collection for the tandem device. A proper thickness of Ca (3 nm) forms a continuous layer, working as a cathode for the top sub-cell. MoO3 as the anode buffer layer prevents exciton quenching and charge loss at the anode side, which could result in increase in interfacial resistance. The variance of sub-cell thickness adjusts the optical field distribution in the entire device, facilitating light absorption and good current matching in both sub-cells. The optimal inverted tandem device achieves a maximum power conversion efficiency of 2.89% with a short-circuit current density of 4.19 mA/cm2, an open-circuit voltage of 1.17 V, and a fill factor of 59.0% under simulated 100 mW/cm2 (AM 1.5G) solar irradiation.

The dependence of morphology and polymer-chain orientation of regioregular poly(3-hexylthiophene) (rrP3HT) thin films on processing conditions have been widely studied. However, their possible variation across the film thickness direction remains largely unknown. We report here a marked difference in the optical dielectric (n,k) spectra between the top and bottom interfaces of spin-cast (sc) rrP3HT films deposited from chlorobenzene solutions. These spectra were obtained from reflection variable-angle spectroscopic ellipsometry using a self-consistent graded optical model with self-imposed Kramers-Krönig consistency. The top interface shows a red-shifted absorption that is characteristic of better order than at the bottom, across a wide range of film thicknesses. This disparity diminishes in drop-cast (dc) and multipass inkjet-printed (ijp) films, and disappears in amorphous films such as those of polystyrene and of a green-emitting phenyl-substituted poly(p-phenylenevinylene). The (n,k) spectra also reveal that crystallinity increases across scdcijp films. This is supported by cross section scanning electron microscopy of the cleaved edges and measurement of the microroughness of both the film interfaces. Furthermore, optical anisotropy decreases across scdcijp films. Finally, near-edge X-ray absorption fine structure spectroscopy also shows the frontier chains in ijp and dc films are more isotropically oriented than those in sc films. These results suggest that semicrystalline conjugated polymer films can be produced far from equilibrium. This explains the marked variation in their (opto)electronic properties between the top and bottom surfaces that has sometimes been found depending on the film deposition method. In particular, an unusually pronounced crystallization is induced by ijp. We label this marked ijp-induced crystallization the "ijp morphology", which appears to be general, as it is found also in single-inkjet-droplet films. It appears also to be responsible for the lower field-effect mobility measured for ijp films deposited on a variety of linear and circular electrode arrays. This however can fortuitously be reversed by annealing in solvent vapor. As all films were deposited in the low Peclet-number regime, we can rule out surface skin formation. We attribute the extensive crystallization to the non-uniform drying of picoliter droplets, further promoted by repeated film swelling-deswelling cycles in multipass-ijp films.

The effects of time durations for ZnO nanorod growth and dye loading on a ZnO-based dye-sensitized solar cell's efficiency and 1/f low-frequency noise (LFN) spectral were analyzed. Sufficient time durations for ZnO growth and dye loading were required for achieving optimum photoconversion efficiency. Extending these two time parameters beyond the optimal, however, reduced the efficiency due to nanorod defects and dye agglomerations. The mechanisms inducing the change in the efficiency was reflected in the LFN spectral and explained on the basis of Kleinpenning's noise equation and excessive noises in the presence of structural defects.

An inverted organic solar cell, consisting of an ultrathin Ca layer for electron transport, the blend of poly(3-hexylthiophene) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 for photon absorption, and a MoO3 layer for hole transport, is optimized. The insertion of MoO3 layer between photoactive layer and Ag anode has been demonstrated to improve both the photocurrent and the fill factor. By optical modeling and experiment, we find that the MoO3 layer also functions as an optical spacer for thin devices. For the optimized device with an active layer thickness of 85 nm, Ca thickness of 0.5 nm, and MoO3 layer thickness of 5 nm, a maximum power conversion efficiency of 3.86% was achieved.

The degradation process in pentacene-based organic thin-film transistors (OTFTs) is investigated. Pentacene-based OTFTs were fabricated with and without octadecyl trichlorosilane (OTS) treatment, and their device characteristics during lifetime test are evaluated using low-frequency-noise (LFN) spectroscopy. It is found that the devices exhibited the 1/f type of noise behavior with generation and recombination noise superimposed. The drain-current noise was found to vary proportionally with drain current according to Hooge's empirical relation of flicker noise. Devices without any treatment show obvious interface traps and deep-level traps, while devices with OTS treatment show nonexistence of interface traps and suppression of deep-level traps. The LFN intensity is found to decrease during the device lifetime test initially, while upon the device failure, the noise level is observed to increase again. The viability of using LFN as a diagnostic tool in the organic transistor is demonstrated.

To inhibit chips burning in the high-speed cutting of Ti-6Al-4V, nitrogen gas with 0.7 MPa pressure was ejected at the milling zone. The high speed flowing of nitrogen gas speeds up the chips leaving, and prevents the chips from burning at the same time. By this method the cutting force is reduced. Especially, the temperature increment of the finished surface is smaller than 5 °C. This prevents the increase of hardness, improves the roughness of the finished surface, and reduces the tools wear. Comparing and analyzing the morphology and color of chips, which are obtained from the high-speed machining of Ti-6Al-4V with and without nitrogen gas ejection, show the action mechanism of nitrogen gas during the high-speed machining of titanium alloy, and it is concluded that nitrogen gas can be used to realize the proper high-speed milling of Ti-6Al-4V titanium alloy.

We fabricated three optically compensated bend (OCB) polymer-dispersed nematic liquid crystal (PDLC) cells doped with a minute amount of multiwalled carbon nanotubes (MWCNTs) and observed the eletrohydrodynamic (EHD) behaviors of LCs in these three MWCNT-doped OCB PDLC cells at 5 or 12 V AC voltage with a frequency of 1 kHz or 60 Hz, respectively. Using the polarizing microscope, we discovered many kinds of domain patterns, including the fingerprint-like domain pattern, the uniform domain pattern, the bean-like domain pattern, the irregular big spot domain pattern, the hexagonal short period lattice domain pattern, and the rectangular period lattice domain pattern. This suggests that some domain patterns differ from the Kapustin–William's domain pattern while others were somewhat similar to the Kapustin–William's domain pattern.

A semi-artificial thermocouple device is developed to explore the dynamic cutting temperature variation rules in high-speed milling of Al7050-T7451 aluminum alloy. Both the aluminum-constantan thermocouple calibration diagram and cutting temperature curves are obtained. The cutting temperature empirical formula is constructed by means of orthogonal experimental design and multivariate linear regression analyses. It shows a reasonable good match between the theoretical predicted values and the measured temperatures. This allows for the optimization of cutting parameters and the exploration of machining deformation induced by the cutting heat in high-speed milling of aerospace aluminum monolithic constructions.

On the base of analyzing material constitutive model, chip-tool contact friction, and chip separation and fracture, a finite element model (FEM) was built to study the high-speed machining process of alloy cast-iron. The shaping process of serrated chip in high-speed milling alloy cast-iron was simulated and analyzed in detail. It was shown that machining parameters affect the serrated chip forming greatly. The model can be used to optimize machining parameters, prolong tool life and improve machining surface quality.