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Based on the attribute of asbestos tailings rich in silicon and magnesium, the powder of asbestos tailings was pre-calcined followed by MgO addition in the green body and finally sintered to develo...

During magnetron sputtering process, the common structure of cathode target is planar target and cylindrical rotating target. In this study, cylindrical rotating target is used and two kinds of cathode targets were investigated by COMSOL Multiphysics software (The official network of COMSOL Multiphysics software. https://uk.comsol.com/). We will elucidate the difference between the two types of cathode target and determine the type of cathode target used in the final experiment. We explore the plasma distribution in the radio frequency cavity, so the simulation process was divided into two steps: building RF cavity model and setting up plasma discharge parameters. The main part of the model included the radio frequency cavity substrate (divided into two tube parts and middle ellipsoid part), the cathode and the magnet. And the plasma discharge parameters are as follows: Ar gas was used with 1.5 Pa; magnetic field strength of iron core was set to 1000 Gs; the applied voltage of cathode was set to − 160 V; and anode was set to 0 V. For the long cathode target and the short cathode target, the main difference is the electric field distribution. Because the electric field lines are denser for the long cathode target, the electric field intensity is stronger, and then the initial energy obtained by electrons is higher. During the plasma discharge process, because of the high electron energy, the plasma density produced is more than the simulation of the short cathode target. And under the same simulation time, the residual energy of electrons is more for the long cathode target, which is the reason for the higher electron temperature. From the previous experimental experience, we know that the film quality formed by higher electron energy is better. The simulation in this work shows that the electron energy corresponding to the long cathode target is higher than that of the short cathode target, so we choose the long cathode target as the experimental target in the subsequent coating experiments.

The extreme mechanical strength of fibrous connective tissues in the human body, such as ligaments and tendons, has always been challenging for hydrogel scientists. Here, we created extremely strong, purely cellulose-based hydrogels (DCC-E gels). The fracture stress and Young’s modulus of the gels were improved to the level of an Achilles tendon even at their equilibrium swollen state. To make DCC-E gels, regenerated cellulose gels were first prepared with ethanol as the anti-solvent. DCC-E gels were then prepared by applying Drying in Confined Condition method, where regenerated cellulose gels were prestretched and dried while their length was fixed. Although strength improvement of materials is typically only achieved at the expense of toughness, a significant increase in strength was achieved while maintaining high levels of toughness. The high strength and toughness of the DCC-E gels were realized by optimizing the cellulose fibril arrangement from nanoscale to macroscale, which was done by selection of an appropriate solvent used for cellulose regeneration. Parallel aggregated fibrous structures observed in the DCC-E gels are thought to play a central role in the enhancement of both toughness and strength. This study can assist in expanding the application of biopolymer-based hydrogels in tissue engineering and soft electronics.

Niobium is extremely important in SRF cavities because of its superconducting properties. However, there are some intrinsic limits of Nb cavities that cannot meet the requirements of future accelerators. It is therefore of utmost importance to look into materials offering SRF performances beyond niobium. Nb3Sn is the most promising material. In our work, the cathode target is cylindrical and rotatable, containing both Nb and Sn elements, which are simultaneously charged, aiming to explore the area ratios of the two elements required in the cathode target by simulation and experiments, respectively. This work will provide the basis for the subsequent Nb3Sn cathode target fabrication. In the simulation, we calculated stoichiometric ratio and sputtering yield to obtain the area ratios of Nb and Sn. In the experiment, we calculated the rotation rate of the target, deposition thickness of films on substrates and deposition rate to obtain the area ratio of Nb and Sn. In conclusion, we compared the simulation and experimental results and found that they are in good agreement. The simulation and experimental results also showed that the area ratio of Nb to Sn in the target is close to 9:1. These results lay the foundation for the subsequent Nb3Sn cathode target fabrication and multilayer deposition of Nb3Sn thin films.

Three-point bending specimen with fixed constraints (TPBSF) can be used to obtain uniaxial creep parameters from small samples of material. Conversion relationships between TPBSF and uniaxial creep data are based on the beam bending model. For large loads and longtime creep test, the specimen deformation can be large, which may be contrary to the small deformation assumption of the beam bending model. So it is necessary to define the critical deformation, below which the beam bending model holds. In this study, a new method to define this critical deformation was proposed by displacement. Based on the relationship between the maximum rotation angle and displacement at the elastic and creep stages, three procedures to determine the critical displacement were first proposed. Then it was verified by the creep test of P91 steel at 566 °C and 66 N. The results show that the critical displacement obtained by finite element method is in good agreement with the experimental result, and the maximum error is 4.5%. Creep parameters were regressed and compared with those in the literature on the basis of critical displacement, it can be seen that creep parameters regressed by the new proposed method are much closer to uniaxial creep than the literature, which indicates that beam bending model holds below this critical displacement. Finally, the finite element method was used to investigate the relationship between the time correction parameter and specimen geometric parameters. It can be found that the specimen width has little influence on the time correction parameter. However, the influence of specimen thickness and span can be significant.

Small specimen test methods have distinct advantages in life prediction of components operating at high temperatures. Yet some factors which can be ignored in traditional bulk material creep tests should be considered in the small specimens. In the present paper four different miniature specimens used to evaluate high-temperature creep properties of materials, such as small punch, impression, three-point bending and cantilever beam specimens, are discussed. Combined with Kachanov–Rabotnov creep damage constitutive equations, finite element models are established and applied to analyze the creep properties of small specimens. The effect of friction on the steady and tertiary creep properties is further investigated for four different small specimen tests. The results show that the friction existing between the specimen and clamp has a significant influence on the evaluation of creep properties and is more pronounced than that between the specimen and punch. In comparison with the small punch, impression, and three-point bending specimens with friction constraints the three-point bending specimens with fixed ends and the cantilever beam specimens give better results. Smaller ratio of characteristic punch size to gauge length, fixed constraint and smaller or no sliding between the punch and specimen are accordingly recommended.

In this letter, an atomistic-level simulation model of bipolar TiO2 RRAM is addressed, which adopts the typical MIM structure and combines the equation of oxygen vacancy transport, current continuity and Joule heating. Based on the model, the dynamic formation and rupture of conductive filament are described in a 3D geometry model of COMSOL. Besides, the electro-thermal model with a conical shape conductive filament achieved is carried out to actually reflect the dynamic resistive switching processes and increase the understanding of conductive mechanism.

A TiN/SiOx/Pt structure was fabricated at room temperature and its resistive switching behaviors were investigated. The device demonstrated a bipolar resistive switching behavior, good stability and excellent scalability. The size effect of resistance and the resistive memory behavior can be explained based on conducting filaments (CFs) composed of oxygen vacancies. The resistive switching behavior is then explained by the rupture and the formation of filaments near the TiN electrode. It is found that the electric field and temperature have played an important role in ion migration.

A new nano-sized NiAl reinforced FeNiCr–TiC composite coating was fabricated using a thermite reaction technique in centrifugal field. All of the consisted phases in the composite coating were obtained in situ from the reaction product melt. The microstructure investigation showed that the composite coating consisted of ferrite (α-FeNiCr), NiAl and TiC. The NiAl phase appeared in whisker with a diameter of about 100 nm and it was coherent with the ferrite matrix. The present composite coating exhibited excellent oxidation resistance and the mass gain after 100 h isothermal exposure at 1000 °C in air was less than 1 mg/cm 2 which is about 1/130 of that for CrNi1Mo steel. The coating had a good wear resistance, its relative wear resistance was 30–40 to the CrNi1Mo steel substrate at room temperature. As compared to NiCr1Mo steel, a significant increase of the composite coating in wear resistance at high temperature was observed. The volumetric wear rate of the composite coating was only about 1/7 of that for the NiCr1Mo steel.

Natural structural materials (such as tendons and ligaments) are comprised of multiscale hierarchical architectures, with dimensions ranging from nano- to macroscale, which are difficult to mimic synthetically. Here a bioinspired, facile method to fabricate anisotropic hydrogels with perfectly aligned multiscale hierarchical fibrous structures similar to those of tendons and ligaments is reported. The method includes drying a diluted physical hydrogel in air by confining its length direction. During this process, sufficiently high tensile stress is built along the length direction to align the polymer chains and multiscale fibrous structures (from nano- to submicro- to microscale) are spontaneously formed in the bulk material, which are well-retained in the reswollen gel. The method is useful for relatively rigid polymers (such as alginate and cellulose), which are susceptible to mechanical signal. By controlling the drying with or without prestretching, the degree of alignment, size of superstructures, and the strength of supramolecular interactions can be tuned, which sensitively influence the strength and toughness of the hydrogels. The mechanical properties are comparable with those of natural ligaments. This study provides a general strategy for designing hydrogels with highly ordered hierarchical structures, which opens routes for the development of many functional biomimetic materials for biomedical applications.

The axial vector R is selected as the order parameter of the antiferroelectric phase transition of Lead Zirconate. This order parameter can adequately reflect the symmetry change of the paraelectric-antiferroelectric (PE-AFE) phase transition of PbZrO3 by using Curie principle. The axial vector R of the single-crystal PbZrO3 is calculated. R = 1.09× 10− 9 k (C/m).

The symmetry of the antiferroelectric phase of PbZrO3 was mainly regarded as C 2v 8 or D 2h 9 in the previous literatures. Both of them belong to the orthorhombic system. It is reinvestigated in this paper by symmetry element analysis based on the projective figures given in the related literatures. We find that the symmetry group of this antiferroelectric (AFE) phase is C 2h 1, and the antiferroelectric crystal PbZrO3 belongs to the monoclinic system. The dielectric tensor measurement was proposed to distinguish the space group C 2h 1 from C 2v 8 and D 2h 9.

The phenomenological theory has been applied to investigate the phase transition of the Rochelle salt crystal. The Helmholtz free energy expansion of the Rochelle salt crystal is obtained by using the basis functions of all the irreducible representations of the paraelectric phase group D 2 . An appropriate explanation of the existence of two Curie temperatures in the ferroelectric phase transition of the Rochelle salt crystal is put forward. The temperature dependence of the spontaneous polarization is obtained. The independent components of the reciprocal susceptibility in both the paraelectric phase and the ferroelectric phase are calculated out. The theoretical curves of the spontaneous polarization and the main reciprocal susceptibility ζ 11 varying with the temperature accord with the experimental results of other literatures.

The shortage of the order parameter of the antiferroelectric phase in the previous reference is pointed out. An axial vector R = ∑ iqi ri × Δ ri/V was proposed as the order parameter of the displacive antiferroelectric phase. This vector is of the symmetry groupC ∞ i . Using R as the order parameter, we reinvestigated the antiferroelectric model of Kittle type. We find that the vector can adequately reflect the symmetry change of the paraelectric-antiferroelectric phase transition by using Curie principle.

The relationship between the slowness curved surface and the softening of the acoustic mode is discussed. The acoustic mode softening of hexagonal system corresponds to the maximum slowness. The eigenvector of soft mode corresponds to the polarization of acoustic mode. By solving the Christoffel equation, the maximum slowness and the polarization of the acoustic mode can be obtained. The symmetry change of proper ferroelastic phase transition can be determined by analyzing the solutions of the Christoffel equation and by using Curie principle.

We first demonstrate the laser performance of a Cr2+:CdSe passively Q-switched (PQS) 2.09 μm Ho: YAG laser resonantly pumped by a thulium-doped fiber laser. The maximum output pulse energy of 1.766 mJ, corresponding to a repetition frequency of 685 Hz, was obtained with a pulse duration of 15.4 ns. The pulse peak power was 114.7 kW, while the PQS efficiency was 21.45% against the continuous-wave output. The laser wavelength in the PQS operation was precisely measured to be 2090.2 nm.

Recuperator is one of the key components in high temperature gas cooled reactors. Although cross-corrugated plates have been used to increase the thermal performance of the recuperators, the fundamental mechanisms of fluid flow and heat transfer are generally not clear. Fluid dynamics simulations and experiments are hence carried out to study the performance of the recuperators. A periodic cell is employed as the control volume. The flow field and heat transfer in sine-wave crossed-corrugated channels are investigated based on the Navier–Stokes and energy equations in the laminar flow regime between Re = 84 and 1168. The numerical results of the heat transfer factors and friction factors in different operating conditions show a fairly good agreement with the experimental measurements. The influence factors on the heat transfer and the hydraulic performance are also discussed in the paper. It is found that the heat transfer factor j and friction factor f decrease with the increase of the pitch-height ratio for a given Reynolds number.

The formation of anodic oxide films on Cu–Co (5 to 40 wt %) alloys in borate buffer solutions is studied by voltammetry and photocurrent measurements. It is shown that cobalt oxide Co2O3 is photosensitive; the formation of oxide films on the alloy surface and their composition depend on the alloy composition and the solution temperature.

The combined effect of purge/coolant e ow rate and nonwhirling, rotor-casing radial eccentricity on the gasturbinewheelspace cavity thermal environmentwas determined from a computational study. In this study, a series ofReynolds-averaged,Navier ‐Stokesnumericalexperimentswasundertakentoobtainanimprovedunderstanding ofmassingresscavityheating.Arecentlydevelopedandheavilytestedthree-scale k-"turbulencemodelwasutilized. The temperature, pressure, Mach number, and Reynolds number of a typical commercial gas-turbine engine were specie ed as appropriate for the mainstream, purge/coolant stream, and turbine wheel. At engine nominal conditions, no mass ingress (100% rim seal effectiveness ) was found for the concentric-rotor case. However, for 50% rotor-casing eccentricity, large mass ingress and only 53% rim seal effectiveness were found. In addition, the minimum purgee ow to prevent mass ingress increased markedly, i.e., from 8000 to 23,500 as the rotoreccentricity increased from 5 to 50%.

To research the resistance temperature characteristic of large deformation sensor element produced by the conductive composite materials based on rubber. A series of tests on resistance temperature characteristic of carbon fiber filled conductive silicone rubber are carried out. the results shows that it appears transition temperature during heating-cooling cycle range from 0D to 40D. The composite materials shows Negative Temperature Coefficient of resistance(NTC) phenomenon at temperatures below the transition temperature while it shows Positive Temperature Coefficient of resistance(PTC) phenomenon at temperatures above the transition temperature. The resistance of composite materials gradually decreases, and finally reaches a steady as the temperature cycle.

The heat transfer between airway and airflow is an unsteady problem. Three experimental schemes (1, Variable wind temperature, the temperature of air flow are 15°C, 20°C, 25°C, 30°C; 2, Variable speed, wind speed are 1m/s, 2m/s, 3m/s; 3, Periodic wind temperature, 15°C∼25°C and 20°C∼30°C) are used to simulate the actual heat transfer process between airway and airflow. Test results show that it exists obvious unstable heat transfer characteristics; the temperature of airway is stable in the last. And the temperature increased with the decreasing difference in temperature between air flow and surrounding rock; and the time required to reach a steady was reduced; with the increase of airflow speed, the stable temperature of the soil was lower and the time required to reach a steady was reduced; when airflow temperature periodic changes, the heat transfer in the soil has obvious "lag" effect. The entire heat transfer process can be divided into severe heat section, excessive heat segment and stable heat section.

From the intensity ratio of the folded longitudinal acoustic phonons with respect to the longitudinal acoustic phonon in a Ge0.51 Si0.49/Si superlattice (SL), we obtained a photoelastic constant ratio of 6.6 for Ge0.51 Si0.49 alloy with respect to Si in the SL at wavelength 5145 A, which is 2.6 times greater than that obtained by [He Phys. Rev. B 39 (1989) 5919] in a Ge0.5 Si0.5/Si SL.

The 30 at.% Ho: BaY2F8 crystals were grown by the Czochralski method, and their spectroscopic properties are analyzed systematically by standard Judd–Ofelt theory. The Judd–Ofelt intensity parameters are estimated to be Ω2 = 6.74 × 10−20 cm2, Ω4 = 1.20 × 10−20 cm2, and Ω6 = 0.66 × 10−20 cm2, and the fluorescence branching ratios and radiative lifetimes for a series of excited state manifolds are also determined. The emission cross sections with our measured infrared luminescence spectra, especially important for 4.1 μm, are calculated to be about 4.37 × 10−21 cm2. The crystal quality is preliminarily tested through a mid-infrared laser emission experiment.

In this paper, an experimental instrument for large-scale optics grinding is introduced, which is a three-axis CNC precision grinding machine. After resolving several essential technological problems (grinder dressing and dynamic balancing, positioning of large-scale optics and profile measurement) in precision grinding of large-scale optics, many experiments are carried on the workpiece of 330mm square K9 optics by applying the experimental instrument. Typical process values in grinding flat and spherical optics include: X-axis feed rate is 15-200mm/min, grinding depth 2-30μm, 1400-2000 rpm spindle speed for grinder and workpiece spindle speed of 40-150 rpm. The grinders are 250mm diameter resin bond with 8-10μm to 80-90μm diamond abrasives, used in rough or finish grinding. Experiment results are presented. The PV surface form of flat and spherical optics is 3-4μm, 4-5μm respectively.