Novel gel polymer electrolytes (GPEs) composed of polyvinyl alcohol (PVA) and sodium thiocyanate were developed via a solution casting technique. An ionic liquid (IL), 1-ethyl-3-methyl-imidazolium tricyanomethanide ([EMIM][TCM]), was doped into a polymer–salt complex system (PVA + NaSCN) to further enhance the conductivity. IL-doped polymer electrolyte (ILDPE) films were characterized using X-ray diffraction (XRD), polarized optical microscopy (POM), Fourier-transform infrared (FTIR) spectroscopy, and conductivity measurements. XRD was performed to check the degree of crystallinity and amorphicity of the ILDPE films, and the amorphicity of GPEs increased with the increase of the IL content. POM was employed to evaluate the changes in the surface morphology due to the inclusion of salt and IL in the PVA. The compositional nature of the GPE films was examined via FTIR studies. The electrical and electrochemical properties were characterized by cyclic voltammetry and electrochemical impedance spectroscopy. The maximum conductivity for the GPE film was estimated to be 1.10 × 10^-5 S/cm for 6% (mass fraction) of IL in the polymer–salt complex. The ionic transference number was approximately 0.97. An electrochemical double-layer capacitor (EDLC) was built from optimized GPE films and reduced graphene oxide-based electrodes. The specific capacitance calculated from the cyclic voltammograms of the EDLC cells was 3 F/g.

Undoped and copper (Cu) doped zinc oxide (Zn1-xCuxO, where x = 0—0.065) nano crystal thin films have been deposited on glass substrate via RF/DC reactive co-sputtering technique. The aim of this work is to investigate the crystal structure of ZnO and Cu doped ZnO thin films and also study the effect of Cu doping on optical band gap of ZnO thin films. The identification and confirmation of the crystallinity, film thickness and surface morphology of the nano range thin films are confirmed by using X-ray diffractometer (XRD), scanning electron microscope and atomic force microscope. The XRD peak at a diffractive angle of 34.44° and Miller indices at (002) confirms the ZnO thin films. Crystallite size of undoped ZnO thin films is 27 nm and decreases from 27 nm to 22 nm with increasing the atomic fraction of Cu (x_Cu) in the ZnO thin films from 0 to 6.5% respectively, which is calculated from XRD (002) peaks. The different bonding information of all deposited films was investigated by Fourier transform infrared spectrometer in the range of wave number between 400 cm^-1 to 4 000 cm^-1. Optical band gap energy of all deposited thin films was analyzed by ultraviolet visible spectrophotometer, which varies from 3.35 eV to 3.19 eV with the increase of x_Cu from 0 to 6.5% respectively. Urbach energy of the deposited thin films increases from 115 meV to 228 meV with the increase of x_Cu from 0 to 6.5% respectively.

This paper designs the thermal crystals composed of alloy materials with air holes and analyzes their properties of band structures, heat transmission, and flux spectra. Thermal crystals composed of Si-A (A=Ge, Sn, Pb) alloys as background materials and air holes with square array are used to construct an elastic-constant periodic structure and their high-frequency phononic band is calculated by deploying finite element methods. Moreover, this paper investigates heat transmission through a finite array of thermally excited phonons and presents the thermal crystal with maximum heat transport. The results show that a wider bandgap could be achieved by increasing the air hole radius and decreasing the lattice constant. In the alloy materials, with increasing atomic radius and thus atomic mass (Ge, Sn, Pb), the frequency range (contributed to thermal conductivity) shifts towards lower frequency. Hence, the bandgap frequencies also shift toward low frequency, but this decreasing rate is not constant or in order, so former may have a faster or slower decreasing rate than the later. Thus, the frequency range for the contribution of heat transportation overlaps with the bandgap frequency range. The development of thermal crystals is promising for managing heat and controlling the propagation of the thermal wave.

With the development of integrate circuit and artificial intelligence, many kinds of transistors have been invented. In recent years, wide attention has been paid to the oxide thin film transistors due to its ease preparation, low cost, and suitability for mass production. Traditionally used gate dielectric film (such as silicon dioxide film) in oxide thin film transistor owns low dielectric constant, which leads to weak capacitive coupling between the gate dielectric layer and the channel layer. As a result, high voltage (10 V or more) needs to be applied on the gate electrode in order to achieve the purpose of regulating the current of channel layer. Therefore, new oxide thin film needs to be developed. In this work, silane coupling agents (3-triethoxysilypropyla-mine) KH550 solid electrolyte film was obtained by spin coating-process. The KH550 solid electrolyte was used as gate dielectric layer to fabricate low-voltage indium zinc oxide thin film transistor. The surface topography and thickness of KH550 solid electrolyte film were characterized by atomic force microscope and field emission scanning electron microscope, respectively. The capacitance-frequency curve of the sample was measured by impedance analyzer (Soloartron 1260A), and the electrical characteristics of the sample were analyzed by a semiconductor parameter analyzer (Keithley 4200 SCS). A maximum specific capacitance of about 7.3 μF/cm² is obtained at 1 Hz. The transistor shows a good stability of pulse operation and negative bias voltage, the operation voltage is only 2 V, the current on/off ratio is about 1.24 × 10⁶, and the subthreshold swing is 169.2 mV/dec. The development of KH550 solid electrolyte gate dielectric provides a novel way for the research of oxide thin film transistor.

A method was developed and proposed to fabricate graphene-enhanced hollow microlattice materials, which include the three-dimensional (3D) printing, nanocomposite electroless plating, and polymer etching technologies. The surface morphology and uniformity of as-deposited coatings were systematically characterized and analyzed. Moreover, the mechanical properties of the microlattices were investigated through quasi-static compression tests. The results demonstrated that a uniform Nickel-phossphorous-graphene (Ni-P-G) coating was obtained successfully, and the specific modulus and strength were increased by adding graphene into the microlattice materials. The optimal mass concentration of graphene nanoplatelets was obtained after comparing the specific modulus and strength of the materials with different densities of graphene, and the strength mechanism was discussed.

This study proposes a novel design and micromachining process for a dual-cantilever accelerometer. Comb and curved-surface structures are integrated into the sensing structure to modulate the squeeze-film damping, thus effectively optimizing the response frequency bandwidth. Owing to the high stress concentration on the dual-cantilever integrated with a fully sensitive piezoresistive Wheatstone bridge, a high sensitivity to acceleration is achieved. In addition, the dual-cantilever accelerometer is fabricated using a specifically developed low-cost and high-yield (111)-silicon single-side bulk-micromachining process. The test results show that the proposed dualcantilever accelerometer exhibits a sensitivity of 0.086—0.088 mV/g/3.3 V and a nonlinearity of ±(0.09%—0.23%) FS (full-scale). Based on dynamic characterization, an adequate frequency bandwidth of 2.64 kHz is verified. Furthermore, a resonant frequency of 4.388 kHz is measured, and a low quality factor (Q) of 7.62 is obtained, which agrees well with the design for air-damping modulation. The achieved high performance renders the proposed dual-cantilever accelerometer promising in applications such as automotive and consumer electronics.

The Ca-Sn co-substituted yttrium iron garnet (YIG) ferrite materials were prepared by the traditional oxide solid-state reaction method, and the influence of forming pressure on the density, morphology and magnetic properties of YIG ferrite was systematically studied. The results show that the density of YIG ferrite green body increases with the increase of the forming pressure, while the density of its sintered body shows a trend of first increasing and then decreasing. At the same time, the ferromagnetic resonance (FMR) linewidth of YIG sample first decreases and then increases. Meanwhile, the effects of forming pressure on the saturation magnetization, remanence and coercivity of the sample can be ignored. This study proves that the density and FMR linewidth of YIG materials can be controlled by regulating the forming pressure and the best performance is obtained for the sample prepared under a forming pressure of 5 MPa.

This paper presents a new approach to evaluating the electrostatic/magnetic adhesion force between two adjacent objects separated by a thin gap. In this approach, instead of generating mesh for the gap, a contact boundary is introduced in the finite element modeling to obtain a reasonable field distribution; then the field in the gap is approximated based on the continuity condition at their interface, so that the adhesion force can be properly calculated. Moreover, a simple equivalent circuit model is introduced to explain how the thin gap influences the adhesion force significantly. Numerical experiments are given to demonstrate the validity of the proposed method and the significance of the thin gap.

A representative volume element method and a novel mesomechanical-based polyline model are proposed to describe the misalignment of in-plane fibers induced by the insertion of stitch thread. A multi-scale mathematical model of in-plane elastic parameters for stitched composite laminate is established with ply-angle and stitch parameters as well as material parameters taken into account. Based on the fabrication of specimens and the verification of experimental platform, the superposition influences of stitch on structural anisotropy are revealed by the developed theoretical model. Results indicate that the stitch orientation can increase the structural anisotropy. The decreases of stitch pitch and spacing as well as the increase of thread diameter obviously reduce the elastic and shear moduli of laminates. Furthermore, the elastic and shear moduli as well as Poisson’s ratios show sinusoidal changes with a period of 90° as the ply-angle increases. The theoretical model not only analyzes the in-plane mechanical properties of stitched laminate with ply-angle, but also lays a foundation for the dynamic studies of stitched sandwich structures with ribs in the future.

The mechanical state of cantilever gearbox housing is different from ordinary ones due to the long arm of force caused by cantilever structure. Conventional mechanical analysis methods either took cantilever gearbox housing as ordinary ones or cantilever beam. Few published papers have specially focused on mechanical analysis method for cantilever gearbox housing. This paper takes a longwall shearer cutting unit gearbox (SCUG) as an example and the mechanical analysis method is investigated according to the causes of fatigue for SCUG. Force analysis model is established for finding out regions of static fatigue caused by low-frequency loads, and local resonance analysis is used for finding out regions of vibration fatigue caused by high-frequency loads. Not only bending moment but also torque caused by gear meshing forces is taken into account in the force analysis model. Vibration response is obtained from cutting experiment, and dominant frequencies of local resonance are obtained by frequency domain analysis. Finite element model of SCUG is established, and natural frequencies and strain modes are analyzed for obtaining the main vibration modes corresponding to dominant frequencies. Hence, large stress regions caused by low and high frequency loads are obtained. Results show that the worst working condition is oblique cutting, and the stress of B-B in 600 mm cutting depth can reach 166 MPa. Obviously, 950 Hz, 1 250 Hz, and 1 400 Hz are dominant frequencies of SCUG (23rd, 25th and 27th natural frequencies). Generally, this paper proposes some principles for mechanical analysis method of cantilever gearbox housing.

Rotor clearance is necessary for the safe operation of twin-screw compressors, and it has a major impact on the performance of twin-screw compressors. The purpose of this study was to obtain a rotor tooth profile with reasonable meshing clearance on the rotor end surface, so that the clearance on the rotor contact line would be uniform and the rotor could be smoothly meshed. Under ideal conditions, the rotor of a screw compressor should have no clearance or interference. However, owing to assembly errors, thermal compression, stress deformation, and other factors, a rotor without backlash modification will inevitably produce interference during operation. A new design method based on the Alpha shape solution was proposed to achieve an efficient and high-precision design of the clearance of the twin-screw rotor profile. This method avoids the complex analytical calculations in the traditional envelope principle. The best approximation of the points on the rotor conjugate motion sweeping surface in the points is illuminated using a specific color. The sweeping surface of the screw rotor single-tooth profile is roughly scanned to capture the base point set of the sweeping surface boundary points. The chord length and tilt angle of each interval are calculated using the value of the base point set to adjust the position, phase, and magnification of each interval sweeping surface. Finally, the data point set is converted to the same coordinate system to generate the conjugated rotor profile. An example was used to verify the feasibility and adaptability of this method. Based on the equidistant profile method, the clearance between male and female rotors of a screw compressor was obtained under actual operation conditions. Therefore, this study provides a basis for the meshing clearance design in the machining of twin-screw compressor rotors.

Solution heat treatment combined with a rapid quenching operation, which can effectively suppress the decomposition of the supersaturated solid solution in the matrix, is a vital process step for producing large precipitation-hardenable aluminum alloy thick plates with desired properties. However, large thermal gradients that result from the non-uniform cooling rates during quenching usually give rise to severely heterogeneous distributions of residual stress in thick plates. The presence of roller-hearth furnaces makes it possible to achieve continuous and integral solution-quenching treatment for large aluminum alloy thick plates. The conveyor velocity of the roller table in the roller-hearth furnace is a key parameter but its influence is less addressed in literature. Thus, in the present work, finite element thermal-mechanical simulations taking into account different conveyor velocities of the roller table were employed to predict the temperature variations and residual stress distributions in large aluminum alloy thick plates during quenching process. Four different velocities were utilized in the simulations. The modeling results showed that the temperature evolutions as well as the distributions of the induced internal stresses in those large thick plates during quenching treatments were indeed affected by the conveyor velocities. Slower velocities were demonstrated to be favorable for gaining thick plates being with relatively homogeneous residual stress distributions in the plates.

Using fast multiple rotation rolling (FMRR), a nanostructure layer was fabricated on the surface of Ti6Al4V alloy. The microstructure of the surface layer was investigated using optical microscopy, transmission electron microscopy, scanning electron microscopy, and X-ray diffraction. The results indicated that a nanostructured layer, with an average grain size of 72—83 nm, was obtained in the top surface layer, when the FMRR duration was 15 min. And the average grain size further reduced to 24—37 nm when the treatment duration increased to 45 min. High density dislocations, twins, and stacking faults were observed in the top surface layer. The microhardness of FMRR specimen, compared with original specimen, was significantly increased. A uniform, continuous and thicker compound layer was obtained in the top surface of FMRR sample, and the diffusion speed of N atom in the top surface layer was accelerated. FMRR treatment provides corrosion improvement.

To obtain better strength-toughness balance of 15-5PH stainless steel, a double aging treatment is proposed to investigate the mechanical properties and microstructure evolution. In this study, Cu precipitates and reversed austenite played a determining role to improve strength-toughness combination. The microstructure was observed using electron backscattered diffraction, transmission electron microscopy and scanning transmission electron microscopy. The volume fractions of Cu precipitates and reversed austenite were calculated with Thermo-Calc software and measured by X-ray diffraction. The results showed that the reversed austenite is formed at the martensitic lath boundaries and its volume fraction also increases with the increase of the aging temperature. At the same time, the size of the Cu precipitates gradually increases. Compared with the traditional single aging and double aging treatment, double aging treatment of 15-5PH stainless steel can increase the toughness while retaining the necessary strength. During double aging of 550 ℃ × 4 h + 580 ℃ × 1 h, 15-5PH stainless steel has the best strength and low-temperature (- 40 ℃) toughness match. Its yield strength, ultimate tensile strength and the Charpy impact energy are 1.037 GPa, 1.086 GPa and 179 J, respectively.

On the multi-layer forging die used in daily life, stressed ring can strength the die structure within elastic deformation and the die material can be self-strengthened through uniform plastic deformation by autofrettage effect, whereas the thermal effect generated during forging process can directly influence the stress state and dimension of the forging die in service. In this study, an analytical solution of the thermo-elastic-plastic deformation in the forging die is derived. The relationships between the radial and circumferential stresses and the temperature distribution, which are directly related to geometric parameters, material properties and working pressure, are determined. This helps to better understand the thermo-elastic-plastic deformation behavior of the die and design the combined forging die to achieve long service life and high accuracy product.