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In this work, the Si3N4 nano-particles were dispersed in organic hybrid damping materials to enhance the mechanical properties, and the effect of surface silylation on Si3N4 was also studied. The hydrogen bond networks were formed via the interactions of AO-80 small organic molecules (phenolic hydroxyl groups). In the composites, the Young’s modulus and hydrogen bond interaction were verified by molecular dynamics simulation, which was in high consistent with the experimental results. For the surface-treated fillers, there were hydrogen bond networks in both XNBR/sin system and XNBR/AO-80 system, and the hydrogen bond network in the composites could contribute to better dispersion of Si3N4 and improvement of mechanical properties.

Novel physical properties emerge when the thickness of charge density wave (CDW) materials is reduced to the atomic level, owing to the significant modification of the electronic band structure and correlation effects. Here, we investigate the layer-dependent CDW phase transition and evolution of the nonequilibrium state of 1T-TaS2 nanoflakes using pump-probe spectroscopy. Both the low-energy single-particle and collective excitation relaxations exhibit sharp changes at ~ 210 K, indicating a phase transition from commensurate CDW to nearly commensurate CDW state. The single particle process reveals that the phase transition stiffness (PTS) is thickness-dependent. Moreover, a small PTS is observed in thin nanoflakes, which is attributed to the reduced thickness that increases the fluctuation and inhibits the nucleation and growth of discommensurations. In addition, the phase mode vanishes when the discommensuration network appears. Our results suggest that the carrier dynamics could be an efficient operational approach to measuring the quantum phase transition in correlated materials.

MoS2/C nanocomposite coatings were deposited on a 304 stainless steel plate by unbalanced magnetron sputtering from carbon and molybdenum disulfide targets, and the target current of MoS2 was varied to prepare for coating with different carbon contents. The mechanical and tribological properties of the MoS2/C nanocomposite coating with different carbon contents were studied using a low-velocity impact wear machine based on kinetic energy control, and the substrate was used as the comparison material. The atomic content ratio of Mo to S in the MoS2/C coating prepared by unbalanced magnetron sputtering was approximately 1.3. The dynamic response and damage analysis revealed that the coating exhibited good impact wear resistance. Under the same experimental conditions, the wear depth of the MoS2/C coating was lower than that of the substrate, and the coating exhibited a different dynamic response process as the carbon content increased.

Thermodynamic analysis and optimization for the steam methane reforming (SMR) hydrogen production system using the high temperature gas-cooled reactor pebble-bed module power plant (HTR-PM) are investigated in this work. Based on the thermodynamic-equilibrium model, parameters of thermal efficiency (��), hydrogen production (YH2/methane), methane conversion rate (X1) and carbon monoxide conversion rate (X2) are calculated under the specified temperature (T), pressure (P) and water-to-carbon ratio (S). The influence of S, T, P on ��, YH2/methane, X1 and X2 is then analyzed. It considers a wide range of operating conditions (T = 400���1200��C; P = 2���7 MPa and S = 2���10). The results show that the influence of on the system performance is significant. When T > 950��C, �� and YH2/methane increases slowly (4 S ��� 6) or reduces (S > 6). For the operating conditions of HTR-PM (P = 7 MPa; S = 6 and T = 950��C), the maximum value of �� is 63.44% and the maximum YH2/methane is 3.3 mol. At last, system optimized parameters are illustrated.

Proton exchange membrane fuel cell (PEMFC) is a new type of fuel cell developed after alkaline fuel cell, phosphoric acid fuel cell, molten carbonate fuel cell and solid oxide fuel cell. In this paper, the dynamic parameter model of PEMFC electric reactor is established based on the experience of proton exchange membrane fuel cells. On the basis of this parameter model, the intelligent method is used to identify the system, and the identification model of voltage and temperature is established. Finally, based on fuzzy logic, the operating performance of the battery system was simulated, a comprehensive PEMFC simulation model was established, a PEMFC voltage identification model was established, and a PEMFC temperature identification model was established by using fuzzy logic network, so as to reduce the fluctuation range as much as possible to reach the research purpose.

The viscoelastic materials exhibit different tribological responses when compared to the stiff materials, due to the intermediate mechanical properties between viscous liquid and elastic solid. In this work, the effect of damping materials viscoelasticity on sliding friction under dry condition was investigated. However, it was difficult to change its damping properties only while other properties (strength or surface hardness) remain unchanged, since viscoelasticity was one of its intrinsic properties. Therefore, the attention of interactions between the material components was closely paid. To achieve this, the experimental groups of damping materials with various viscoelasticity were established by adding various fillers and adjusting their surface properties. Additionally, a viscoelastic property determined friction coefficient model was obtained and validated by the molecular dynamic method. The results show that the test model is in good agreement with the experimental results. Meanwhile, tribo-pairs with higher proportion of viscous character had greater oscillations in friction. They also exhibited higher friction coefficient due to the increased contribution of viscoelastic hysteresis losses to friction.

The shearing performance and strength of the interface between rock foundations and structural concrete is a key issue for safety estimation in geotechnical engineering containing rock-concrete interface. In this paper, we focused on the effects of concrete wall strength and normal stress on the unbonding performances of sandstone-concrete interface. First, many sandstone-concrete specimens containing a natural dam bedrock interface had been produced by using “3D optical scanning technology + 3D digital engraving technology + pouring concrete” method. Subsequently, after the sandstone-concrete specimens were prepared, a series of shear tests for these sandstone-concrete specimens were carried out under different normal loading conditions. Finally, the shear characteristics of sandstone-concrete interface were discussed, and an improved rock-concrete shear strength formula was proposed based on the exposed experimental tests and theoretical derivation. Three primary outcomes are as follows: (i) shear damage only occurred at some special positions of the concrete wall, and its degree of shear damage gradually increased with increasing normal stress; (ii) the damage degree of the concrete surface performed obvious localization and nonuniformity was affected by the concrete strength; (iii) the global shear strength and residual strength of the rock-concrete interface were affected by the concrete strength and the normal load. Moreover, an improved rock-concrete shear strength formula was proposed based on the experimental cognition. This strength formula considers both the interface roughness and the mechanical strength of rock/concrete materials, and is more reasonable for estimating the shear strength of rock-concrete interfaces in geotechnical engineering.

A numerical simulation method by using the realizable k-ε model of computational fluid dynamics (CFD) proposed by establishing the model of hydrogen leakage of a high-pressure hydrogen storage container is presented in this paper. By setting different environmental wind speeds, leakage apertures, and leakage locations, multiple simulation calculations are performed to compare test results. As the wind speed increases, the degree of turbulence of hydrogen increases. Large aperture and bottom side leakage cause more serious hazardous area of personnel than small aperture and top leakage do. Base on the results, it can provide reference for dealing with the leakage of high-pressure hydrogen storage containers.

Given the current situation that there is no parallel experiment of multiple stacks in China, this paper uses a fuel cell test platform independently designed and produced by a company to study the performance of three fuel cells. This article describes the construction of the experimental test platform and the multi-stack load-up experiment. The experimental results show that the power generation of the three fuel cells is almost the same, which are 9475W, 9385W, and 9512W. When carrying out multi-stack load-up experiments, it was found that as the number of stacks increased, the voltage efficiency continued to decrease. The Analysis revealed that the parallel gas supply method caused uneven gas distribution, which caused some fuel cells to be in a state of hydrogen deficiency. This article proposes amendments to this problem.

This study adopted PPy/PAN-based carbon fiber felt composite as a new electrode for desalination experiment. The result shows that this kind of composite electrode can significantly reduce the outlet conductivity when inlet chemical oxygen demand (COD) is over 300 mg/l. It additionally reduces COD to the value obtained with other electrodes.

With the dramatic requirements of high power and high integrity in field of power devices, the study of novel interconnection materials and packaging methods has been paid an extremely attention. Presently, the most candidates for the chip bonding are Zn-based, Bi-based, noble-metal-based (such as Au-Sn, Au-Ge, Au-Si), nano-metal particles (Ag or Cu nanoparticles) and transient-liquid-phase (TLP) bonding. However, a high bonding temperature and poor ductility for Zn-based solder (more than 420°C) causing irreversible damages or accelerated aging affects to the electronic devices; Bi-based solder alloys are still under way mainly due to their inferior thermal and electrical conductivity as well as poor workability; It's worth noting that nano-silver sintering and TLP bonding technology have been proven to be the potential solutions to the power electronic packaging, because their processing temperatures are relatively low and the produced joints are of high re-melting temperatures. However, Ag is expensive and easy to electromigration, which will influence the stability/reliability of the joints and hinder to universal industry applications. For the TLP bonding, the process to produce full intermetallic compounds (IMCs) is time-consuming, commonly more than 60 min, due to relatively low reaction velocity. To solve the problem of time-consuming of the TLP, an enhanced and low-cost auxiliary energy is necessary. Ultrasonic-assisted soldering has been proven able to solder dissimilar metals at low temperatures within a very short time. In our previous work, a full Cu6Sn5/Cu3Sn IMCs joint through TLP assisted by ultrasound was obtained. Because of the acoustic cavitation and streaming effect created by ultrasonic waves propagating in molten alloys, the atom diffusion and physical-chemical interactions were accelerated at the liquid/solid interfaces. However, a sole IMC joint with single phase has not been fabricated so far. High re-melting temperature joint consisted of nearly sole Ni 3 Sn 4 with a high shear strength of 43.4 MPa was achieved with Sn-24 wt.%Ni by ultrasonic-assisted soldering for 10 s. This rapidly formed intermetallic joint was phase-stable as isothermally aged at 300 °C for 72 h in air and its shear strength was 33.4 MPa due to the Ni 3 Sn 4 grains coarsening. These results demonstrate that the less time-consuming ultrasonic-assisted soldering has wide potentials for high-temperature power electronic packaging.

Sintering of low-cost Cu nanoparticles (NPs) for interconnection of chips to substrate at low temperature and in atmosphere conditions is difficult because they are prone to oxidation, but dramatically required in semiconductor industry. In the present work, we successfully synthesized Cu@Ag NPs paste, and they were successfully applied for joining Cu/Cu@Ag NPs paste/Cu firstly in air by the ultrasonic-assisted sintering (UAS) at a temperature of as low as 160 °C. Their sintered microstructures featuring with dense and crystallized cells are completely different from the traditional thermo-compression sintering (TCS). The optimized shear strength of the joints reached to 54.27 MPa, exhibiting one order of magnitude higher than TCS at the same temperature (180 °C) under the UAS. This ultra-low sintering temperature and high performance of the sintered joints were ascribed to ultrasonic effects. The ultrasonic vibrations have distinct effects on the metallurgical reactions of the joints, resulting in the contact and growth of Cu core and the stripping and connection of Ag shell, which contributes to the high shear strength. Thus, the UAS of Cu@Ag NPs paste has a great potential to be applied for high-temperature power device packaging.

The chemical vapor deposition method is used to prepare CNT (carbon nanotube)/PCF (PAN-based carbon fiber felt) composite electrodes in this paper, with the surface morphology of CNT/PCF composites and electroadsorption desalination performance being studied. Results show such electrode materials with three-dimensional network nanostructures having a larger specific surface area and narrower micropore distribution, with a huge number of reactive groups covering the surface. Compared with PCF electrodes, CNT/PCF can allow for a higher adsorption and desorption rate but lower energy consumption; meanwhile, under the condition of the same voltage change, the CNT/PCF electrodes are provided with a better desalination effect. The study also found that the higher the original concentration of the solution, the greater the adsorption capacity and the lower the adsorption rate. At the same time, the higher the solution’s pH, the better the desalting; the smaller the ions’ radius, the greater the amount of adsorption.

Hydrogen is an ideal clean energy source that can be used as an energy storage medium for renewable energy sources. The water electrolysis hydrogen production technology, which is one of the mainstream hydrogen production methods, can be used to produce high-purity hydrogen and other energy sources can be converted into hydrogen storage by electrolysis. Hydrogen production by alkaline water electrolysis and hydrogen production by PEM electrolysis are all water electrolysis hydrogen production technologies that have been industrially applied. From the application point of view, the paper compares the working principle of the two kinds of electrolyzers, the process flow of hydrogen production equipment, advantages and disadvantages. This article provides a reference for relevant researchers.

The corrosion failure of 1Cr18Ni9Ti stainless steel pressure vessel was studied with the aid of metallurgical microscopes, scanning electron microscopes, scanning Auger energy spectra and X-ray diffraction meters. The main causes of the failure included: inter-crystalline corrosion initiated at or near welding position between head and body of cylinder, electrochemical corrosion due to chloride ions in electrolyte and corrosive action formed by oxygen separator and hydrogen separator. Some measures of corrosion resistance and design improvement were proposed.

Nonlinear 2D layered crystals provide ideal platforms for applications and fundamental studies in ultrathin nonlinear optical (NLO) devices. However, the NLO frequency conversion efficiency constrained by lattice symmetry is still limited by layer numbers of 2D crystals. In this work, 3R MoS2 with broken inversion symmetry structure are grown and proved to be excellent NLO 2D crystals from monolayer (0.65 nm) toward bulk-like (300 nm) dimension. Thickness and wavelength-dependent second harmonic generation spectra offer the selection rules of appropriate working conditions. A model comprising of bulk nonlinear contribution and interface interaction is proposed to interpret the observed nonlinear behavior. Polarization enhancement with two petals along staggered stacking direction appears in 3R MoS2 is first observed and the robust polarization of 3R MoS2 crystal is caused by the retained broken inversion symmetry. The results provide a new arena for realizing ultrathin NLO devices for 2D layered materials.

The chemical oxygen?iodine laser (COIL) has wide application prospects in military, industrial and medical treatment fields as a second generation gas chemical laser to follow the first HF/DF chemical laser. However, a COIL releases large amounts of gas, such as helium, oxygen, chlorine and iodine. Chlorides have a serious corrosive effect on the system, especially iodine vapor crystallization, which seriously endangers the normal use of vacuum systems, and radioactive methyl iodide, which is hazardous to operators and pollutes the environment. The use of soaked coal-based activated carbon as an adsorbent for removing methyl iodine is proposed, while it is proposed that coal-based activated carbon is an effective adsorbent for removing stable iodine. The research conducted in this work shows that iodine residues are less than 0.5??g?ml?1 after the adsorption treatment and the decontamination factor of the coal-based activated carbon for removing stable iodine is more than 1000. Using this method can achieve the purpose of removing harmful iodine, satisfy the requirements for engineering applications, and also be applied to other nuclear power plant flue gas treatments.