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The present study investigated the effect of TiB2 on the tribological properties of CuSn10Bi3 bimetallic bearing materials. CuSn10Bi3 samples with different contents of TiB2 were fabricated by powd...

In this work, a novel lubricating additive was designed and synthesized via self-assembling of wrapped PTFE nanoparticles by exfoliated MXene nanosheets. Then the pMXene@polytetrafluoroethylene (pMXene@PTFE) hybrid was introduced into epoxy coating and painted to substrate. The composite with PTFE would effectively alleviate the oxidation of MXene sheets. The research results show that the epoxy-based composite coating has excellent friction-reduction and wear-resistance properties in dry air, humid air (RH = 80%), and vacuum (3 × 10−5 Mbar) environments, achieving multi-environmental stability binary composite coating. The performance improvement of composite coating mainly depends on the following points: (a) the lubricating synergistic effect of MXene sheets and PTFE hybrid additive with core-shell structure; (b) the good dispersibility and adhesion of composite additive in the epoxy matrix; (c) the formation of protective film on the upper counterpart. The obtained friction results demonstrate that self-assembled pMXene@PTFE epoxy coatings greatly enhance the lubricating and anti-wear properties in multiple environments, establishing a promising platform for the design and application of novel high-performance additive with environmental insensitivity.

Ionogels is a kind of hybrid materials composed of ionic liquids (ILs) and solid polymer network matrix, has been extensively investigated in the most recent decade. Due to the excellent mechanical properties and ionic conductivity, their promising applications in flexible stress and strain sensors have been proposed and explosively developed. In this review, we briefly summarize research progresses on ionogel based flexible stress and strain sensors (IFSSs) from five aspects, including material synthesis, device fabrication, working principles, characteristics and performances, and potential applications. Some outlooks and perspectives are also proposed at the end of review. The review is expected to provide reference and new insights into the research of IFSS.

There are intensive needs for scaffolds with new designs to meet the diverse requirements of bone repairing. Biodegradable microspheres are highlighted as injectable micro-scaffolds thanks to their advantages in filling irregular defects

The equivalent series resistance (ESR) is an important parameter for determining the quality of a capacitor. In general, the value of the ESR can be obtained only at a single frequency point during mass production testing, because obtaining the whole ESR curve by means of scanning the frequency range is time consuming. We present a novel method to investigate how the ESR varies with frequency during batch testing. We use the multi-frequency synthesis excitation waveform to obtain the ESR at multiple frequency points. This allows the entire ESR curve to be obtained during one measurement period, thus greatly improving the measurement speed. The mathematical principle, the circuit realisation and the signal processing algorithm are discussed. Furthermore, a principle verification test is conducted, and the ESR values at seven frequency points are synchronously measured. The obtained results are consistent with those acquired from a standard LCR meter, and the entire measurement is completed within 10 ms, which confirms that our method is efficient and suitable for measurements in the mass production testing.

Nano-ZrO2 and PEEK particles were synergistically filled in unfilled PTFE to improve the wear resistance and maintain a relatively low friction coefficient, and the materials were studied using a reciprocating sliding friction and wear tester. In the friction tests, the evolution of various tribological characteristics in both the contact interfaces and debris was observed, and the wear mechanism of the PTFE composites was investigated. The results showed that the wear rate of the PTFE composites synergistically filled with nano-ZrO2 and PEEK was lower and its friction coefficient was slightly higher than that of the unfilled PTFE; the uniformity and continuity of the transfer film generated by the composite with nano-ZrO2 and PEEK were the best, and the particle size of the debris was minimal in comparison to that in other sample systems.

Organic molybdenum (e.g., molybdenum dialkyldithiocarbamate, Mo-DTC) is a typical additive for liquid lubricants which can produce a significant anti-wear role with only a minor addition. I...

In order to study the tribological properties of PTFE modified by hard nanoparticles and soft polymer under dry friction conditions, the tribological properties of polytetrafluoroethylene (PTFE) fi...

Polytetrafluoroethylene (PTFE) is a commonly used seal material for oil-free engine that is well known for its excellent tribological properties. In this work, the nano-ZrO2 particles were used as the friction modifiers to improve the friction and wear performance of PTFE-PPS composites. The friction and wear characteristics of PTFE/PPS-nano-ZrO2 composites were investigated by a block-on-ring tester under dry friction sliding condition. The worn surfaces, counterpart transfer films and wear debris were studied by scanning electron microscopy and X-ray photoelectron spectroscopy. It was found that the increase of nano-ZrO2 content could effectively reduce the coefficient of friction and enhance the anti-wear ability of PTFE-PPS composites. Especially, the best tribological properties of the composites were obtained when the particle content of nano-ZrO2 was 10 vol%, the anti-wear performance of composite is 195 times better than that of the unfilled PTFE-PPS composite. Under different conditions, the coefficient of friction of PTFE/PPS-nano-ZrO2 composites was more affected by the applied load while the wear rate was more affected by the sliding velocity.

Cesium tungsten bronze (Cs0.33WO3) coatings can effectively depress solar heat gain and air-conditioning energy consumption of buildings, because of their highly selective near infrared (NIR) absorbing ability. However, the absorbed solar energy may overheat the window glasses due to the high photothermal conversion efficiency of Cs0.33WO3 coatings, discounting their transparent heat insulating performance. To solve this issue, we design a new energy-efficient composite window by integrating NIR-shielding Cs0.33WO3 with phase change materials (PCMs, paraffin wax in our case). In the composite window, the hexagonal-phase Cs0.33WO3 is prepared by a solid-state reaction method, and then coated onto commercial float glass as Cs0.33WO3–SiO2 composite films via a sol–gel process. Afterwards, a homemade double-plane window consisting of a float glass and a Cs0.33WO3–SiO2-coated glass is filled by molten commercial paraffin wax to obtain the paraffin wax–Cs0.33WO3 composite window. Cs0.33WO3 in the window can reduce solar heat gain of the buildings. Meanwhile, the paraffin wax component can accumulate the Cs0.33WO3-captured thermal energy by its endothermic molting processes, protecting the window from overheating. When the ambient temperature drops low enough, the stored thermal energy in the paraffin wax can be gradually released back by reverse solidifying processes. Therefore, this paraffin wax–Cs0.33WO3 composite window should be very effective to keep indoor temperature stable and comfortable. Performed on a homemade house model, the paraffin wax–Cs0.33WO3 composite window can depress indoor temperature variation from 24.2 down to 7.3 °C, compared with a bare glass window. This composite window is expected to improve energy efficiency of buildings locating in areas with high day–night or summer–winter temperature fluctuations.

According to the reflection behavior of the fiber Bragg grating, the monitoring method of reinforced concrete was presented in this paper. A postprocessing method to extract crack openings from a three-dimension finite element computation was proposed. The three-axial stresses of the FBG were extracted also from the same finite element computation, and then, were converted as a wavelength deformation of the FBG reflected spectrum. The three-dimension computation result of crack width versus the FBG spectrum deformation was investigated using laboratory experiments. The results showed that the numerical values approximated the experimental ones.

In this study, we evaluate the effect of co-doping with TiO2 nanoparticles and sisal cellulose nanocrystals (CNCs) on the physical and biological properties of a conventional glass-ionomer cement (GIC). Test samples were characterized by scanning electron microscopy, and Fourier-transform infrared spectroscopy, and subjected to mechanical tests to evaluate the mechanical performances. Antimicrobial activity was evaluated against Candida albicans, and cytotoxicity experiments were conducted using L-929 cells. Unmodified GIC served as a control. Compared with the control group, the co-doped group demonstrated an increased compressive strength of 18.9%, an increased shear bond strength of 51%, the dissolution decreased by 18.3%, the volume wear rate was reduced by 5%. The antifungal effect against C. albicans was increased by 22%. In cytotoxicity experiments, the co-doped group had a slightly negative effect on the viability of L-929 cells.

Soft electronic skins (e-skins) with superior sensing performance have attracted significant attention in numerous applications. However, most of the reported e-skins have been prepared based on an inert polymer substrate without completely considering its self-healing ability; this severely limits the practical application of these e-skins. In addition, the fabrication of most of the e-skins is conducted via photolithography and other tedious processes; therefore, it is difficult to equilibrate high sensing performance and preparation simplification. Herein, a simple and general fabrication strategy of self-healable and highly sensitive electrical sensor, consisting of a sensing component, i.e. Au-deposited toothbrush-hair micro-prick arrays, and a substrate component, i.e. a P-TDI-IP elastomer obtained via the block polymerization of polytetramethylene glycol (P), 2,4′-tolylene diisocyanate (TDI), and isophorone diisocyanate (IP), is reported. The self-healable P-TDI-IP elastomer acting as a substrate endows the reported electrical sensor with an excellent self-healing capability (96% with 6 h) and an outstanding stretchability (1200%). Importantly, due to the presence of unique micro-prick arrays, the electrical sensor could detect multiaxial tactile stimuli including pressing and shearing. Moreover, this device exhibited high sensitivities (3.32 kPa−1 for pressing, GF = 2.82 for shearing), the rapid response time of 25 ms, and the low detection limit of 5 Pa. Owing to these prominent properties, the electrical sensor presented anticipated abilities for distinguishing ultrafine surfaces with different roughnesses and monitoring various human motions.

Following the fast development of microelectronic systems, multifunctional microelectronic components featuring high sensitivity, large stretchability, and a wide sensing range have attracted a huge surge of interest. Here, pressure sensors based on a novel three-dimensional (3D) network structure are introduced, which consist of a 3D ordered reduced graphene oxide (rGO) sponge microstructure and polyaniline (PANI) nanoarrays via interfacial polymerization and hydrothermal self-assembly processes. The nano-scaled PANI arrays greatly enhance the strength and electrical conductivity of the 3D microarchitectural rGO sponge, endowing the pressure sensor with 0.77 kPa−1 of a high sensitivity within 6 kPa, a wide reliable sensing range up to 10.22 kPa, a rapid response time of 50 ms, and an excellent stability of 3000 cycles. Accordingly, a flexible pressure sensor is fabricated based on the as-prepared sponge, which can be used as a wearable device for real-time and high-accuracy detection of subtle physiological and external stimuli, as well as large motions from the facial expression of the eye, the knee, and the finger. The outstanding piezoresistive sensing performance of this pressure sensor makes it a promising candidate for developing advanced microelectronic systems.

In order to solve the problems of poor dispersibility and wettability, as well as unsatisfactory wear resistance and load capacity of polytetrafluoroethylene (PTFE) as water lubricating additive, a new type of PTFE@silica (PTFE@SiO2) core-shell nanoparticles was prepared by encapsulating SiO2 layer on the surface of PTFE via chemical bonding. Electron microscope analysis showed that the synthesized particles had well-defined core-shell morphology. Special double/multi-core structure and a reduced thickness of the intermediate shell were found, and the formation mechanisms were also explored in detail. The water contact angle measurement proved that the wettability of PTFE could be greatly enhanced by coating SiO2 layer. The friction tests were performed to investigate the water lubrication properties of PTFE@SiO2 additive, the results indicated that the core-shell PTFE@SiO2 nanoparticles possessed the superior tribological properties, and the maximum friction coefficient and wear volume were respectively decreased by 75% and 99% when compared with pure water and water with PTFE/SiO2. Based on the analysis of worn surface, it was believed that the existence of core-shell structure and the formation of robust transfer film were the key to its excellent performance, and a possible lubrication mechanism was also proposed.

GaAs is an important short-wave near-infrared photocathode material. In this paper, the first-principles plane wave pseudopotential method based on the density functional theory framework is used to study the influence mechanism of external electric field on the electronic structure of GaAs. Applying an electric field in different directions to GaAs shows that the (011) electric field direction has the strongest effect on opening the GaAs energy gap. Then, the electric fields of different strength are applied along the (011) direction. The results show that the energy gap of GaAs is 0.937eV when no electric field is applied. With increasing the electric field strength in the (011) direction, the energy gap of GaAs decreases gradually, when the electric field strength reaches 1eV/A/e, the energy gap of GaAs is almost zero. Notice that in the conduction band region where the total density of state of GaAs gradually shifts to Fermi surface and the Span gradually decrease with increasing the electric field strength, while valence band is the opposite of the conduction band.

To obtain a high resolution of the reflection-mode AlGaN photocathode by establishing the modulation transfer function (MTF) model of this photocathode, the influence of emission layer thickness T e , electron diffusion length L d , recombination velocity at back-interface V b , and optical absorption coefficient α on MTF for varied-doping and uniform-doping Al0.42Ga0.58N photocathodes have been given. The computational results suggest that varied-doping structure has great potentiality in improving both resolution and quantum efficiency of the reflection-mode Al0.42Ga0.58N photocathode. This improvement is mainly attributed to the reduced lateral diffusion of photoelectrons, which is caused by an electric field generated by the varied-doping structure, and hence the photoelectron transportation towards photocathode surface is promoted.

In this paper, the wear and transfer behaviors of polytetrafluoroethylene@silica (PTFE@SiO2) core-shell composite particles filled epoxy resin (PTFE@SiO2-EP) coating during the sliding were studied in detail. The main results indicated that: firstly, the addition of PTFE@SiO2 particles can result in favorable plastic deformation on the worn surface; secondly, the morphology of PTFE@SiO2 particles in-situ changes from pressed to broken to flattened, and the average friction coefficient, wear rate as well as the transfer film thickness of the PTFE@SiO2-EP coating all conform to the following regularity: run-in period > steady-state period > transition period. Besides, except that FeF2 is not contained in the transition period, the compositions of the transfer film are basically unchanged during the whole friction process, which all consist of PTFE, ploy (methylmethacrylate-co-3-(trimethoxysilyl) propylmethacrylate) (P(MMA-co-MPS)), SiO2, EP and FeF2. Additionally, no wear debris is observed during the whole sliding. It is expected that this study can provide instructive scientific guidance for the lubrication behaviors of soft@hard core-shell additives, and further enrich the tribological theories of solid lubricants with core-shell structure.

Environmental-friendly polytetrafluoroethylene@silica (PTFE@SiO2) composite particles characterized by core-shell structure were synthesized. The tests demonstrated that the synthesized particles had good dispersibility and stability in poly-α-olefin 6 (PAO6) and its corrosion resistance was better than zinc dialkyl dithiophosphate (ZDDP). The extreme pressure (EP) and tribological tests evidenced that PTFE@SiO2 particles possessed superior EP and anti-wear (AW) properties, which could enhance the wear-resistance and load-bearing capacities of PAO6 in high efficiency, whereas the tribological performance was greatly affected by the load. Besides, EP tests for different kinds of base oils demonstrated that the addition of PTFE@SiO2 particles could significantly improve the bearing capacity of these base oils, and the corresponding performances were also better than ZDDP. Scanning electron microscope and X-ray photoelectron spectrum characterizations proved that there was an organic-inorganic co-extruded transfer film generated on the worn surface, and a possible lubrication mechanism on this basis was also put forward.

Nanoparticles are increasingly being used to improve the friction and wear performance of polymers. In this study, we investigated the tribological behavior and energy dissipation characteristics of nano-Al2O3-reinforced polytetrafluoroethylene-polyphenylene sulfide (PTFE-PPS) composites in a sliding system. The tribological behaviors of the composites were evaluated under different normal loads (100–300 N) at a high linear velocity (2 m/s) using a block-on-ring tester. Addition of the nano-Al2O3 filler improved the antiwear performance of the PTFE-PPS composites, and the friction coefficient increased slightly. The lowest wear rate was obtained when the nano-Al2O3 content was 3% (volume fraction). Further, the results indicated a linear correlation between wear and the amount of energy dissipated, even though the wear mechanism changed with the nano-Al2O3 content, independent of the normal load applied.

In practice, for a higher signal to noise ratio of the solar-blind ultraviolet (UV) image intensifier, one of the most meaningful work is to effectively evaluate its noise characteristics and to obtain suitable work voltages. In this paper, we have proposed an evaluation method and then implemented an effective evaluation of the noise characteristics of a typical solar-blind Cs 2 Te UV image intensifier, through the measurement of signal to noise ratio at the output end (SNR out ) of this image intensifier in different work conditions. The evaluation results show that the SNR out of a Cs 2 Te UV image intensifier increases as the photocathode voltage and the voltage across MCP increase within an appropriate range. Additionally, the voltage across phosphor screen has almost no impact on the SNR out . More specifically, the suitable values of Cs 2 Te photocathode voltage, the voltage across MCP and the voltage across phosphor screen are −300 V, 800 V, and 4500 V, respectively.

Two dimensional (2D) MoS 2 nanosheets are firstly exfoliated by high shear mixing technique and then incorporated into PAA precursors to form the MoS 2 /PI nanocomposite films, and the preparation can be accomplished via in-situ polymerization, tape casting and thermal imidization processes. As a result, the mechanical and thermal properties of the prepared MoS 2 /PI nanocomposite films are significantly enhanced by incorporation of a small amount of MoS 2 nanosheets without any surface modification. Especially, 43% and 47% increases in tensile strength and Young’s modulus can be respectively achieved upon adding certain small amount of MoS 2 (0.75 wt% or so). Meanwhile, the glass transition temperature ( T g ) can be effectively improved by 11 °C by taking advantages of unique superior thermal stability of MoS 2 nanosheets. This desirable fabrication of MoS 2 /PI nanocomposite films is expected to offer a new avenue on the development of high strength PI-based nanocomposites with comprehensive performances.

The effects of solid loading on the fabrication of ceramic microparts by soft molding were studied. Alumina microchannel parts of different dimensions (60–160 µm) were fabricated from well-dispersed suspensions with different solid loadings (70, 75 and 80 wt%). The structural integrity of the green microchannel parts was examined to study the moldability of the suspensions. It was found that the minimum feature size and linear shrinkage of the microchannel parts decreased with increasing solid loading, while the green density and sintered density showed the opposite trend. The reasons for incomplete filling and demolding failures were also discussed.

Development of high-performance polymer composites exposed to water lubrication conditions is of increasing interests for numerous applications, where high durability and reliability are demanded. However, formation of a protective boundary reaction layer on the rubbing surfaces can be problematic with the presence of water. The roles of hexagonal boron nitride (h-BN) nanoparticles on the tribological performance of polyoxymethylene (POM) and POM composite reinforced with short carbon fibers were investigated. It is identified that the addition of low loading h-BN greatly improves the tribological performance, e.g. wear resistance of POM is enhanced by one order of magnitude. Moreover, h-BN and carbon fibers play a synergetic role in enhancing the wear resistance. Tribo-chemistry and nanostructures of the boundary film were comprehensively investigated. It is revealed that H3BO3 and B2O3 generated as products of tribo-chemical reactions are arrayed in a closely packed outmost layer of the boundary film and exert an important influence on the tribological performance. Our work gives the evidence that the basal planes of H3BO3 and B2O3 are aligned parallel to the sliding direction, leading to low friction and wear. Keywords: POM, Water lubrication, Tribo-chemical reaction, h-BN nanoparticles, Boundary film

The selective decomposition of formic acid (FA) traditionally needs to be carried out under high temperature with the noble metal-based catalysts. Meanwhile, it also encounters a separation of H2 and CO2 for pure H2 production. The photocatalytic FA dehydrogenation under mild conditions can meet a growing demand for sustainable H2 generation. Here, we reported a photocatalytic selective H2 release from FA decomposition at low temperature for pure H2 production by Pt/g-C3N4. Low-cost and easy-to-obtained urea was utilized to produce carbon nitride as the metal-free semiconductor photocatalyst, along with a photodeposition to obtain Pt/g-C3N4. The electrochemical evidences clearly demonstrate the photocatalytic activity of Pt/g-C3N4 to produce H2 and CO2 in one-step FA decomposition. And, the impedance is the lowest under simulated solar light of 70 mW cm−2 with a faster electron transfer kinetic. Under simulated solar light, H2 production rate is up to 1.59 mmol · h−1 · g−1 for FA with concentration at 2.65 mol l−1, 1700 000 times larger than that under visible light and 1928 times under ultraviolet (UV) light. DFT calculations further elucidate that nitrogen (N) active site at the g-C3N4 has an excellent adsorption towards CO2 molecule capture. Then, H2 molecules are selectively released to simultaneously separate H2 and CO2 in solution. Platinum (Pt) at Pt/g-C3N4 as the catalytic site contributes into the acceleration of H2 production.

In this work, monomer casting nylon-6 (MCPA6)/melamine foam (Me)/graphene oxide (GO)/paraffin wax (PW) composites were synthesized using Me foam as a three-dimensional template and adsorbing GO and PW on the Me foam skeleton. The microstructure and tribological behaviors of the MCPA6/Me/GO/PW composites were determined and the interaction of PW with GO were theoretical investigated. The results showed that the addition of both GO and PW significantly improved the tribological properties of the composites. Compared with pure MCPA6, the friction coefficient and specific wear rate of the composite with the ratio of 2:3.5 (GO to PW) were reduced by 82% and 84%, respectively. The improvement of tribological performance was attributed to the synergistic lubrication and anti-wear effects of PW and GO.

Tribological studies have shown that polytetrafluoroethylene @ phenolic resin core/shell (PTFE@PR) composite maintained excellent tribological properties under harsh working conditions (120 °C, 0.1 m/s, 100 N, friction pair with roughness of 2.528 μm), suggesting the core/shell composite would be a candidate lubricating material with multi-environmental adaptability. The friction-induced transfer film with long-range ordered crystal structure and fiber-like morphology was observed by scanning electron microscope, while the strong chemical bonding between the PTFE-PR transfer film and friction pair was confirmed by X-ray photoelectron spectroscopy. The crystallinity of the long-range ordered transfer film and wear debris under the shear force is higher than that of the original specimens by attenuated total reflection Fourier transform infrared spectroscopy. Besides, the wear life of the PTFE@PR transfer film was six times higher than that of PTFE, reflecting its long durability.

CsPbI3 thin films with orthorhombic phase were prepared on Si (100) substrates by the pulse laser deposition (PLD). The photoelectric characteristics of the CsPbI3 films had been investigated. The photodetector based on CsPbI3/n-Si heterojunction was sensitive to red wavelengths, showing the peak responsivity of 51.9 mA/W (695 nm). The excellent photoelectric characteristics of the CsPbI3 films grown by PLD are clearly demonstrated and should be widely applicable to optoelectronic devices.

Based on first-principle study, the adsorption mechanism of Cs on (100) crystal plane of GaN nanowire surface with coverage of 1/12 monolayer is explored. It is discovered that the most stable adsorption site is BN because of its lowest adsorption energy. The work function of GaN nanowire surface is reduced by 1.69 eV and will be further reduced with increasing Cs adsorption, which promotes the development of negative electron affinity (NEA) state of the materials. Furthermore, Cs adatom will make a great influence on the surface atomic structure, oppositely, little influence on the center atomic structure. There appears a dipole moment valued −6.93 Debye on the nanowire surface contributed to the formation the heterojunction on the surface, which is beneficial to the photoelectrons liberation. After Cs adsorption, the valence band and conduction band both move to lower energy side. The surface states mainly result from the hybridization of Cs 5s state with Ga 4p state and N 2p state. This study can help us to further experiment on the Cs adsorption processing on GaN nanowire and improve the photoemission performance of GaN nanowire devices.

The damage effect experiment is carried out to the low noise amplifiers (LNAs) based on Bipolar Junction Transistor (BJT) and Pseudomorphic High Electronic Mobility Transistor (PHEMT) by microwave pulse injection experiment platform. The essence of the LNA damage with microwave pulses is the damage to the core semiconductor device. The influence rule upon the damage power of the LNA by different microwave pulse widths and pulse numbers is obtained. The injection, reflection and output waveforms are measured by high frequency oscilloscope and the typical damage waveforms of the LNA are analyzed. Inspection is made on the damaged semiconductor device by a scanning electron microscope (SEM) and the microscopic damage images of the semiconductor devices with different pulse widths and pulse numbers are analyzed in comparison.

Using plane-wave ultrasoft pseudopotential method based on density functional theory (DFT), the influence of Zn atoms on Cs activation process of NEA GaAlAs photocathodes is researched. The Zn-induced E-Mulliken population and ionicity change are analyzed, the influence of Zn on average dipole moment and work function are researched and the density of state and band structure of Cs adsorbed Ga 0.5 Al 0.5 As (0 0 1)β 2 (2 × 4) reconstruction surface before and after Zn doping are compared. Results show that Zn doped Ga 0.5 Al 0.5 As (0 0 1)β 2 (2 × 4) reconstruction surface shows Negative Electron Affinity (NEA) state when Cs coverage is 0.75 mL.

The nonlinear and damage properties of silicon bipolar junction transistors (Si BJTs) injected with microwave pulses (MWPs) from base are studied in this paper. The experimental results of this injection research show that the feature of the output power of the Si BJT is from linear increase, saturation, reduction to increase again as the input power increases; the feature of the measured output voltage waveform is from linear increase, saturation, reduction to reversion and increase again as the input power increases. Permanent damage occurs to the BJT when the input power is high enough. The 3-D simulation model is established with Technology Computer Aided Design (TCAD) to further analyze the nonlinear and damage properties of the Si BJT injected with MWPs. The simulation results match with the experimental results.

The tribological properties of polyimide (PI) and PI/fluorinated graphene (FG) nanocomposites, as a new class of graphene reinforced polymer, are investigated using a ball-on-disk configuration under different lubricated conditions of dry sliding, water lubrication and oil lubrication. Experimental results reveal that single incorporation of FG can effectively improve the tribological performance of PI under all the three conditions. In addition, compared to the results under dry sliding, the phenomenon that the friction coefficient decreases while the wear rate increases under water lubrication condition is observed and researched in detail. The worst anti-wear performance under water-lubricated condition can be ascribed to the fact that the water can be adsorbed by the polar imide radicals of the PI and PI/FG nanocomposite, therefore leading to the property deterioration of the PI and PI/FG nanocomposite coatings.

In 0.53 Ga 0.47 As is an important material for the shortwave near-infrared negative electron affinity photocathodes. As we all known, doping is a necessary step for the formation of the negative electron affinity and zinc is a traditional substitutional element to generate the P-type semiconductor. The In 0.53 Ga 0.44 Zn 0.03 As and In 0.50 Ga 0.47 Zn 0.03 As were formed from In 0.53 Ga 0.47 As by a zinc atom substituting a gallium atom or an indium atom in the article. The atom structures, the band structures and the populations were studied by the first principle method for these two supercell models. Two problems, how the zinc-doping change the characters of intrinsic In 0.53 Ga 0.47 As and the differences between In 0.53 Ga 0.44 Zn 0.03 As and In 0.50 Ga 0.47 Zn 0.03 As, were solved by the research. Firstly, the atom structures were changed and the band gaps were narrowed after zinc doping. The ionicity was enhanced which is agreed with the character of P-type semiconductor. Secondly, there were small differences between the two supercells in electronic structures. Therefore, there is no need to consider which kind of atom to be substituted during the material growth for the near-infrared InGaAs photocathode.

This work presented a feasible strategy to generate molybdenum disulfide (MoS2) nanosheets by a direct liquid shear exfoliation technique in a green mixed solvent system of ethanol/water. The volume ratio of ethanol/water and the initial concentration of the bulk MoS2 powders were found to have significant impacts on the final exfoliation yield. The best ratio and initial concentration for optimal shear exfoliation were finally selected as 45 vol% and 10 mg mL−1, respectively. According to the proper shear strength and matching viscosity, systematic analysis on the exfoliation mechanism indicated that shear and collision effects would play the major role when the shearing occurred at a high speed of 10 000 rpm. The higher cumulative yield and better quality (up to 30% after 10 times of shear cycling, comparatively large sizes d ∼ 4 μm) were confirmed by detailed experimental characterizations. Moreover, the photothermal performance was also investigated and the prepared MoS2 nanosheets exhibited great efficiency in transforming near-infrared light into heat. It is expected to be a promising strategy for large-scale production of MoS2 nanosheets with excellent properties in a low-cost and green solvent system.

Surface photovoltage (SPV) in p+-GaAs/p-GaAlAs/p-GaAs has been studied by establishing a multilayer model and measuring the SPV at room temperature. The model mainly considers surface recombination velocity, interface recombination velocity and the space charge region (SCR) at the surface of p+-GaAs. The SPV of the multilayer structure is shown to originate predominantly from the minority carrier diffusion, which caused photovoltage between the surface and bottom. Subsequently, the minority carrier diffusion lengths in p+-GaAs and in p-GaAs are obtained from fitting experimental data to the theoretical model. At the same time, the minority carrier diffusion length in p-GaAs is obtained by illuminating the backside (illuminating on p-GaAs) of the p+-GaAs/p-GaAlAs/p-GaAs. The p+-GaAs in p+-GaAs/p-GaAlAs/p-GaAs structure with different thickness are measured to show the variation of SPS with different thickness, but the experimental parameters are not affected. In multi-layer structure, the SPV contributed by different layers has a great difference with different dark saturation current density.

In order to improve the service life of Si devices applied in micro-electro-mechanical systems (MEMS), anti-wear octadecyltrichlorosilane/silica nanoparticles (OTS/SiO2) composite films were prepared on silicon by sol-gel and self-assembly techniques. The structure, morphology, chemical composition, wettability, anti-adhesion and tribological properties of the films were characterized. The prepared OTS/SiO2 composite films were hydrophobic with water contact angle of 119.0 ± 0.5° and textured by OTS modified SiO2 nanoparticles with long chain structures. Compared with Si substrate and OTS self-assembled monolayer (SAM), OTS/SiO2 composite films could not only reduce adhesive force to 17.7 ± 0.5 nN but also reduce friction coefficient to 0.18 ± 0.02 under a load of 1 N. The anti-wear lifetime was prolonged to 40,897 s, while OTS SAM was gradually worn out in 104 s under the same friction conditions. The synergistic effect of the transferring of OTS SAM as lubrication films and the repairing of abrasive areas by SiO2 nanoparticles accounted for the preeminent wear resistance. OTS/SiO2 composite films are expected to be effectively used in MEMS as high-performance lubrication films.

Polytetrafluoroethylene @ phenolic resin (PTFE@PR) core-shell particles were successfully synthesized through a versatile one-pot method, which were investigated in tribological characteristics. The core-shell structure was characterized by transmission electron microscopy (TEM), fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS). The results demonstrated that core-shell composites possess the lower friction coefficient and better anti-wear performance. Friction coefficient of the composite is about 0.178 as low as pure PTFE at 50 N and 0.033 m/s. Meanwhile, the wear volume of the composite was measured at 0.59 mm3 by rubbing 1 h, which is merely a fifteenth of pure PTFE (8.94 mm3). The chemical action of core-shell composites resulted in the uniform and integrate transfer film, so that outstanding tribological performances of core-shell composites were exhibited.

The optical properties of alternating ultrathin Ti0.91O2 nanosheets and CdS nanoparticle hybrid spherical structures designed by the layer-by-layer (LBL) assembly technique are investigated. From the photoluminescence (PL) spectral measurements on the hybrid spherical structures, a spectrum-shifted fluorescence emission occurs in this novel hybrid material. The time-resolved PL measurements exhibit a remarkably increased PL lifetime of 3.75 ns compared with only Ti0.91O2 spheres or CdS nanoparticles. The novel results were attributed to the enhanced electron-hole separation due to the new type II indirect optical transition mechanism between Ti0.91O2 and CdS in a charge-separated configuration. Electronic supplementary material The online version of this article (10.1186/s11671-018-2488-3) contains supplementary material, which is available to authorized users.

In order to study the influence of interstitial point defects on the optical properties of Ga0.75Al0.25N, three Ga0.75Al0.25N bulk models with Ga, Al, and N interstitial defects were built. And the band structure, dielectric function, complex refractive index, absorption coefficient, reflectivity, and loss function of pure Ga0.75Al0.25N and the Ga0.75Al0.25N with interstitial defects were calculated based on first principles. Results show that the band gap values of Ga0.75Al0.25N with interstitial defects are smaller than that of the pure Ga0.75Al0.25N. And Ga0.75Al0.25N crystals with Ga and Al interstitial defects show n-type property, meanwhile Ga0.75Al0.25N crystal with N interstitial defect show p-type property. The static dielectric constants of crystals with defects are much bigger than that of the pure one. And the metal reflective regions of the crystals shift to lower energy because of the interstitial defects.

The structure properties and work function of reflection-mode GaN photocathodes are investigated by using first-principles calculation within density-function theory (DFT). Seven different GaN (0001) (1×1) surface models are used in this paper to simulate cesium and oxygen activation process. Before starting the surface models calculations, clean bulk GaN surface is first optimized, when compared with the models before optimization, the correctness of the calculations method is verified. Next, change of work function of different surface models caused by adsorption is calculated and analyzed, the results show that over-cesiuminizd atmosphere is not only benefit for work function declining but also conductive to the formation of negative electron affinity (NEA), the optimal ratio of Cs to O for activation is between 3:1 and 4:1, excess Cs or O modules increase the work function and undermine the photocathode. Then a series of experiments are performed to verify the calculation results. First of all, NEA GaN photocathode activation and evaluation system is established, “yo-yo” activation method is verified. Then, an activation experiment is performed on high quality p-type Mg-doped reflection-mode GaN substrate grown by metal organic chemical vapor deposition (MOCVD), the photocurrent is controlled and monitored by multi-information on-line monitoring system, the results are consistent with our calculation models. Finally, combined with the data provided by Stanford University, schematic energy band variation of the GaN photocathode after only-Cs and Cs/O activations is given. Our result opens the possibility to engineer the activation properties of GaN photocathode.

As advanced semiconductor materials, GaN, AlN, and GaAlN alloys are widely used in optoelectronic devices. In order to research the optoelectronic properties of GaN, AlN, and Ga1−xAlxN with different Al component, models of GaN, Ga0.875Al0.125N, Ga0.750Al0.250N, Ga0.625Al0.375N, Ga0.500Al0.500N, and AlN were built, then the atomic structure, band structure, density of states, Mulliken charge distribution, and optical properties of the six crystals were calculated based on first principle calculations. Results show that the lattice parameters decrease while the band gap increases with the increase of Al component. The GaN, AlN, and GaAlN alloys are all semiconductors with direct band gap. The global transfer index increases with the increase of Al component. When the Al component is bigger and bigger, the absorption peak shifts to higher energy, and the threshold wavelength of Ga1−xAlxN decreases.

The nonlinear and transient responses of gallium arsenide pseudomorphic high electron mobility transistor (GaAs PHEMT) injected with microwave pulses are studied in this paper. The experimental research results show that the feature of the output power of the GaAs PHEMT is from linear increase to saturation to linear increase again as the input power increases; and the feature of the measured output time domain waveforms is from linearity to saturation to reversion as the input power increases. The simulation model for analyzing the GaAs PHEMT with microwave pulses is established by TCAD. The nonlinear feature of GaAs PHEMT analyzed through simulation is consistent with measurement. In addition, the field, current density, and temperature distribution inside the transistor injected with microwave pulses are discussed.

Graphene-wrapped Ni(OH)2 hollow spheres were prepared via electrostatic interaction between poly(diallyldimethylammonium chloride) (PDDA) modified Ni(OH)2 and graphene oxide (GO) in an aqueous dispersion, followed by the reduction of GO. Morphological and structural analysis by field-emission scanning electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis confirmed the successful coating of graphene on Ni(OH)2 hollow spheres with a content of 3.8 wt%. And then its application as electrode material for supercapacitor has been investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge tests. Results show that the sample displays a high capacitance of 1368 F g(-1) at a current density of 1 A g(-1), much better than that of pure Ni(OH)2, illustrating that such composite is a promising candidate as electrode material for supercapacitors.

In0.53Ga0.47As is a new near-infrared material for negative electron affinity photocathodes. Geometry optimization combined generalized gradient approximation based on the density functional theory is adopted to calculate the bulk In0.53Ga0.47As. Lattice constant of bulk In0.53Ga0.47As after geometry optimization is compared with the theoretical one based on the Vigard law, which proves the reliability of the parameters of the geometry optimization. The energy bands, electronic structures and optical properties of the bulk ternary In0.53Ga0.47As for near-infrared photocathode are analyzed. Electron transition way which is closely related with the photoemission is analyzed from the energy bands and the density of electrons. The dielectric function and the optical absorption coefficient are made clear based on the partial density of states. It is found that optical absorption coefficient of bulk In0.53Ga0.47As is bigger than that of GaAs in the near-infrared band, which is in keeping with the experiments. The analysis provides a theoretical foundation to design a better near-infrared negative electron affinity photocathode from the point of microscopic atoms.