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Voltage stability is one of the critical factors for the stable operation of DC microgrids (MG). For the communication free DC MG, the DC voltage is more vulnerable due to the DC voltage deviation caused by the droop characteristics. When facing the transient power fluctuation caused by multiple electric vehicles (EVs) connected to the grid, PV shedding, etc., the DC bus will have a large voltage sag. The voltage quality degradation will bring adverse effects to the DC MG. However, most energy storage systems like battery energy storage systems (BESS) are not suitable for suppressing transient large power fluctuation. In this paper, the SMES is introduced to a DC MG to form a power regulation system. A voltage-based segmented (VBS) control is designed for the SMES-based power regulation system to suppress transient large power fluctuation in the DC MG. The voltage deviation caused by power distribution can be tolerant by VBS controlled SMES. Meanwhile, the dynamic recovery capability of the DC voltage is improved. The control method of SMES is independent of other devices in DC MGs, hence it is not dependent on communication. The control strategy of the SMES is further verified by simulation results.

Recent optical stimulation suggests a vital non-contact pathway to manipulate both macroscopic and microscopic ferroelectric properties and paves the foundation for optoelectronics devices. However, up to date, most optical-related manipulation of ferroelectric properties is restricted due to their intrinsic bandgap and limited visible light spectrum absorption. Here, we reveal non-oxide Sn2P2S6 single crystal possesses full-visible-spectrum absorption (from 300 to 800 nm) with a unique disproportionation mechanism of photoexcited Sn ions and Urbach tail, which is not contradicting to the intrinsic band gap. Interestingly, we observed the existence of conductive domain walls (c-DW) and the light illumination induced significant enhancement of the domain wall conductivity caused by such disproportionation reaction. In addition, the domains separated by c-DW also exhibited noticeable electrical conductivity difference in the presence of optical illumination owing to the interfacial polarization charge with opposite signs. The result provides a novel opportunity for understanding the electrical conductivity behavior of the domains and domain walls in ferroelectrics with full-visible-spectrum absorption and achieving greatly enhanced performances for optoelectronics.

The study investigated the effect of fibre laser processing (1060 nm, 240 ns pulse duration) on tungsten carbide (WC). Fluence, frequency, and the interaction effect of these were the most influential factors on the surface integrity and crack formation. In this paper, a crack classification system was developed, and a crack density variable was introduced to estimate the number of cracks and crack type within a 1 mm2 area size. ANOVA was used to analyse how fluence (0.05–0.20 J/cm2) and frequency (5–100 kHz) altered the crack density. The crack density increased between 0.050–0.099 J/cm2 across all frequency settings then decreased as the fluence increased to 0.20 J/cm2. Superficial cracks were present in all frequency settings but particularly with lower fluence settings. Micro-cracks were more likely to form between 0.050–0.135 J/cm2. Deep cracks did not present until 40 kHz or above 0.099 J/cm2 across the frequency settings and were situated around balling and splatter defects. The crack density was minimised at 0.149 J/cm2 fluence and 52.5 kHz. To the author’s knowledge for the first time a quantitative analysis of the crack formation mechanism for brittle materials is proposed (post laser processing). In addition, a linear model generated to predict surface roughness performed best at moderate to medium level of processing (fluences in the region of 0.050–0.099 J/cm2) with an error between 1 % to 10 %. The model failed to predict the material response as accurately at higher fluences with percentage errors between 15 % to 36 %.

MnBi$_8$Te$_{13}$ is an intrinsic ferromagnetic (FM) topological insulator with different complex surface terminations. Resolving the electronic structures of different termination surfaces and manipulation of the electronic state are important. Here, by using micrometer spot time- and angle-resolved photoemission spectroscopy ($\mu$-TrARPES), we resolve the electronic structures and reveal the ultrafast dynamics upon photoexcitation. Photoinduced filling of the surface state hybridization gap is observed for the Bi$_2$Te$_3$ quintuple layer directly above MnBi$_2$Te$_4$ accompanied by a nontrivial shift of the surface state, suggesting light-tunable interlayer interaction. Relaxation of photoexcited electrons and holes is observed within 1-2 ps. Our work reveals photoexcitation as a potential control knob for tailoring the interlayer interaction and surface state of MnBi$_8$Te$_{13}$.

A couple of enantiomers of 2, 6-diaminotriptycene ( R, R - 1 and S, S - 1 ) are split by chiral HPLC and their absolute configurations are identified by single-crystal X-ray diffraction technology. Using the enantiomers as monomers, a couple of chiral porous polyimides ( R - FTPI and S - FTPI ) are prepared by polycondensation reactions and display good heat stability, high BET surface area and good solubility in organic solvents. Moreover, both of R - FTPI and S - FTPI can be cast into robust, free-standing films suitable for enantioselective separation with symmetrical chiral selectivity.

Semiconductor photocatalysis technology is a promising method to solve the antibiotics pollution in water. Herein, a series of Sn-doped In2.77S4 (Sn-In2.77S4) hybrid photocatalysts for tetracycline degradation have been fabricated via a one-step hydrothermal process. The analytic results exhibit that doping Sn can improve the photocatalytic performance of In2.77S4 nanosheets under the visible light illumination and the doping amount obviously affects the photocatalytic performance of the samples. When the theoretical molar ratio of Sn4+ to In3+ is 0.04:1 (4%), the photocatalytic efficiency of the Sn-In2.77S4 photocatalyst exhibits the highest of 87.4% in comparison with 39.2% of pure In2.77S4 in 20 min. Moreover, its band gap energy has been reduced to 1.56 eV from 1.75 eV and the light absorption range has been broadened. The transfer rate and separation efficiency of photo-generated electron and hole pairs of the samples have also been enhanced. In addition, the holes play a leading role in the photocatalytic degradation process.

Surface friction plays a significant role in the machining performance and life of cutting tools. This investigation examines the influences of laser produced periodic textures on lubrication across the tool’s rake face and the influence on cutting forces when orthogonal turning steels exhibiting ductile chip behaviour. Laboratory tribology and orthogonal turning experiments on TiCN/Al2O3/TiN CVD coated tool inserts enhance understanding of the role of textures in the reduction of cutting forces and coolant film behavior in the sliding pairs by showingshifts in lubrication regimes from boundary to mixed and hydrodynamic, depending on operating parameters, texture design and coverage.

In the present work, machining performance of a new solid carbide end mill has been investigated during side milling of Ti-6Al-4V. It is observed that adding cooling grooves on the clearance side of the cutting tool improves the tool performance by decreasing tool wear. Tool temperature measurements by infrared camera showed that these grooves decreased the tool temperature during the machining process. In order to understand the mechanisms behind this improvement, simulations of the coolant flow around the tool with and without these grooves are performed. Modelling and simulation results showed that these cooling grooves lead to an increase in the velocity of fluid at the head of the tool, which results in more efficient cooling and consequently the temperature along the cutting edge is decreased.

The SrCO3/AgI photocatalysts were prepared via a co-precipitation method by using SrCO3 as a co-photocatalyst and AgI as a photo sensitizer. X-ray diffraction, field emission scanning electron microscope, X-ray photoelectron spectrometer, UV-vis diffuse reflectance spectroscopy and electrochemical impedance spectroscope were used to analyze the structure, micro-morphology, chemical compositions, optical properties and photo-generated carrier behaviors of the as-prepared samples, respectively. The photocatalytic degradation mechanism of the as-developed composites was also proposed. Analysis results show SrCO3, an insulator, can improve the photocatalytic performances and recyclability of AgI for degrading tetracycline under visible light. As the theoretical molar ratio of Sr(NO3)2 to AgNO3 increases, the degradation efficiency of the hybrids first increases and then descends. When the theoretical molar ratio of that is 1: 1, it acquires the maximum of 66.6% within 8 min. This is higher than 32.0% of pure AgI and 34.0% of SrCO3. Moreover, after three times degradations it is 63.0%, which is higher than 13.6% of AgI. The improvement of the photocatalytic performance of the sample is attributed to the construction of hybrids. The main activated species in catalysis process are superoxide radicals.

Ag2WO4 is a typically noble metal based photocatalyst with highly efficient photocatalytic activity. However, due to photocorrosion, the pristine Ag2WO4 is prone to inactivation during illumination. Constructing composite photocatalyst may be a useful method to promote the stability of Ag2WO4. In this work, Ag2WO4/graphitic carbon nitride nanotubes (g-C3N4 NTs) composite photocatalyst was prepared by adopting an in-situ composite strategy. The photocatalytic performance of the samples was discussed by the degradation of rhodamine B under visible light, and the catalytic mechanism was also analyzed. The characterization results show that the photocatalytic efficiency of the as-prepared Ag2WO4/g-C3N4 NTs composite increases firstly and then decreases along with the increase of the Ag2WO4 content. When the theoretical molar ratio of Ag2WO4:g-C3N4 NTs reaches 3:2, the photocatalytic degradation efficiency achieves the optimal value, that is 92.4% within 20 min, which obviously exceeds 2.8% of pure Ag2WO4 and 48.9% of pure g-C3N4 NTs. Moreover, the separation and migration efficiency of photoelectron–hole pairs of the composites can be accelerated in comparison with pure samples. In addition, superoxide radicals and hydroxyl radicals play major roles in the photocatalytic degradation process.

The SnO2 quantum dots (SnO2QDs)/ZnS nanosheets (ZnSNs) heterojunction was fabricated via an in-situ synthetic method at room temperature. Rhodamine B, potassium dichromate, and tetracycline were used to discuss the photocatalytic activities of the as-prepared samples under the visible light illumination. The photocatalytic mechanism of the as-prepared samples was also proposed. The experimental results indicate that the degradation efficiency of the as-prepared SnO2QDs/ZnSNs heterojunction first increases and then decreases with increasing the usage of ZnSNs. When the mass ratio of SnO2QDs to ZnSNs is 1: 2 in 180 min, the asprepared samples have the highest degradation efficiency of 89.1% for rhodamine B, 97.7% for potassium dichromate, and 83.8% for tetracycline, which are much higher than 51.7%, 26.8%, and 0.9% of pure SnO2QDs as well as 37.9%, 87.1%, and 19.1% of pure ZnSNs, respectively. After it is repeatedly degraded for 3 times, it possesses the degradation efficiency of 62.5% for rhodamine B, which increases by 200.5% in comparison with 20.8% of the pure SnO2QDs. Moreover, the enhanced photocatalytic performances of the as-prepared hybrids are attributed to the formation of heterojunction between the SnO2QDs and ZnSNs. In addition, hydroxyl radicals and superoxide anion radicals play major roles during the photocatalytic degradation process, while holes play a minor role.

The AgBrO3/few-layer g-C3N4 composite photocatalyst has been developed via an in-situ synthetic method. The structure, morphology, light response range, separation and migration efficiency of the photogenerated electron–hole pairs and element valence state of the as-obtained samples have been characterized. The tetracycline was used to discuss the photocatalytic activities of the samples. The photocatalytic degradation mechanism of the as-obtained composites was also researched. The analysis results show that the photocatalytic degradation property of the asobtained composite photocatalyst appears to the tendency of first increasing and then decreasing with increasing the amount of AgBrO3 under visible light illumination. When the mass ratio of AgBrO3 to g-C3N4 is 4:3, in 60 min, the photocatalytic degradation efficiency of the as-obtained composites reaches the maximum of 79%. It is 37% and 45% higher than that of pure AgBrO3 and g-C3N4, respectively. Moreover, the separation and migration efficiency of the photogenerated electron–hole pairs of the as-prepared composites are also enhanced. In addition, superoxide radicals and holes are the dominant active species during the photocatalytic degradation process.

It is a great challenge to tune the porosity of porous materials. As most porous organic cages are soluble, solution processability can be a possible way to regulate the porosity of such materials. Herein, a triptycene-based cage (TC) is demonstrated to be stable in acid, base or boiling water. Meanwhile, its porosity can be tuned by adjusting the solution-state assembly processes. TC molecules crystallized slowly from solution exhibit nearly no porosity to nitrogen (off-state). While, after rapid precipitating from methanol/dichloromethane solution, the obtained TC (TC-rp) is in a porous state and exhibit a high BET surface area of 653 m2 g−1 (on-state).

The performance thresholds of cutting tool geometries, tool materials and machining systems are often restricted by surface friction from work material engagement and flow across the tool surfaces. This study investigates the influences of geometrically defined surface textures of the tool rake face on forces encountered during two dimensional orthogonal turning. Regular textures featuring highly uniform profiles and inter-surface blending, exhibiting no measurable recast material were produced using a multi-scanning strategy of a femtosecond pulsed laser of near IR wavelength, in specially profiled flat rake faces of cemented carbide cutting tool inserts. A series of complementary tests were carried out on open ended grooved and equivalently sized closed dimpled surface textures of defined area ratios in the presence of a cutting fluid to investigate their effects on cutting and frictional forces when machining a Chromium steel material exhibiting ductile long chip behaviour. Data captured from a purpose designed in-situ lathe based friction test to simulate chip flow during machining, orthogonal turning experiments using a zero degree rake angle setup and laboratory tribometer oscillatory tests using an identical cutting tool and workpiece material tribo-pair and lubrication fluid, highlight the influences of closed and open structured textures on surface lubrication regimes and the consequent friction forces. The results of the study reveal that surface texturing of uncoated cemented carbide tool surfaces can reduce friction when employed with coolant within the tools’ typical operating range. It has also been shown that textures having closed dimple structures produce the lowest friction forces under these conditions and reduced surface wear. The reduction of the measured surface friction produced by the dimpled textures also suggest desirable shifts in the boundary and hydrodynamic lubrication regimes towards the tools’ cutting edge.

Based on the difference of thermal expansion coefficient between Si and Ge, low-intensity tensile stress can be introduced into Ge epitaxial layer on Si substrate. S-Ge/Si semiconductor (as known as low tensile strained Ge grown on Si substrate) has a higher carrier mobility when compared with unstrained-Ge or Si material, so that s-Ge/Si is appropriate for the production of high-speed circuit. At the same time, transformation from indirect bandgap semiconductor Ge into Pseudo-Direct bandgap semiconductor (which is also called PD-Ge) will be happen after s-Ge/Si is heavy doped, which makes LED produced of PD-Ge material perform a higher luminous efficiency because the radiative recombining probability of carriers in PD-Ge material is greatly improved compared with unstrained one. Taking the advantages referred of s-Ge/Si into account, s-Ge/Si has the potential to PD-Ge monolithic optoelectronic integration. Carrier mobility of the semiconductor is one of the key physical parameters during the design and simulation of PD-Ge monolithic optoelectronic integrated system. While as far as the authors are aware, carrier mobility model of s-Ge/Si is still rarely reported to date. In view of that all above, based on the E-k relation in both conduction band and valence band of s-Ge/Si material, the analytical models of physical parameters in energy band are established, and the models are verified by experiments. Then the s-Ge/Si carrier models are further established based on our band structure model, and the Monte Carlo method is used to verify our s-Ge/Si carrier mobility model. The quantificational results of our paper will help understand s-Ge/Si material physics and provide an important theoretical basis for the design of PD-Ge monolithic optoelectronic integration.

Polycrystalline diamonds, polycrystalline cubic boron nitrides and tungsten carbides are considered difficult to process due to their superior mechanical (hardness, toughness) and wear properties. This paper aims to review the recent progress in the use of lasers to texture hard and ultra-hard materials to a high and reproducible quality. The effect of wavelength, beam type, pulse duration, fluence, and scanning speed is extensively reviewed, and the resulting laser mechanisms, induced damage, surface integrity, and existing challenges discussed. The cutting performance of different textures in real applications is examined, and the key influence of texture size, texture geometry, area ratio, area density, orientation, and solid lubricants is highlighted. Pulsed laser ablation (PLA) is an established method for surface texturing. Defects include melt debris, unwanted allotropic phase transitions, recast layer, porosity, and cracking, leading to non-uniform mechanical properties and surface roughness in fabricated textures. An evaluation of the main laser parameters indicates that shorter pulse durations (ns—fs), fluences greater than the ablation threshold, and optimised multi-pass scanning speeds can deliver sufficient energy to create textures to the required depth and profile with minimal defects. Surface texturing improves the tribological performance of cutting tools in dry conditions, reducing coefficient of friction (COF), cutting forces, wear, machining temperature, and adhesion. It is evident that cutting conditions (feed speed, workpiece material) have a primary role in the performance of textured tools. The identified gaps in laser surface texturing and texture performance are detailed to provide future trends and research directions in the field.

A dual-phase Mg-Li-Zn alloy was processed by a severe plastic deformation method which is a method of combination of extrusion and rolling processes and enables production of a very fine grain structure. After this processing, the Mg-Li-Zn alloy exhibited a significantly large fracture elongation of 1400% at 473 K at 0.001 s−1. Moreover, an elongation of more than 600% was observed at 473 K even at high strain rate of 0.01 s−1. Also, at a lower temperature of 423 K, the alloy exhibited a large fracture elongation of 720% at 0.001 s−1. The values of the strain rate sensitivity were approximated to 0.5, which suggested that the superplastic deformation is based on grain boundary sliding. Dislocation glide is identified to be an accommodation mechanism according to the texture evolution during the superplastic deformation. The different trends of the changes of the textures in the α and β phases indicated an inhomogeneity of grain boundary sliding between phases.

Additive manufacturing offers the advantage of infinite freedom to design and fabricate complex parts at reduced lead-time. However, the surface quality of additively manufactured parts remains well behind the conventionally processed counterparts. This paper aims to systematically investigate the impact of varying surface inclination angles with respect to the build direction on the resultant surface textures. A bespoke metal truncheon artifact with inclination angles varying from 0 deg to 180 deg was built by selective laser melting. Focus variation microscopy was used to measure the topography of inclined surfaces with a tilt angle of up to 132 deg. The measurement data were then analyzed to characterize the staircase effect and the particles adherent to the artifact surface. Areal surface texture parameters, including height parameters, spatial parameters, functional parameters, and feature parameters, were explored to quantify the general surface topography, the staircase effect, and the particle features. The areal surface texture characterization and particle analysis reveal the resulted surface topographies are strongly correlated with the surface inclination angles.

Tribological performance of systems in boundary lubrication is dependent on contact and lubricant conditions such as temperature, lubricant additive concentration, surface characteristics, contact pressure and additive-additive interactions. Although past parametric studies have investigated these various factors, there are limited studies on the effect of surface topography on the performance of boundary lubrication additives. This is pertinent because of the increased use of surface texturing in lubricated contacts. This study has employed laser surface texturing to achieve surfaces with different topographies. The influence of the different surface topographies on the tribological performance of a friction modifier additive, molybdenum dialkyldithiocarbamate (MoDTC), was investigated. Results show that laser-textured surfaces in some instances can offer improved friction performance compared to non-textured (polished) surfaces when working positively with a friction modifier additive. Anisotropic surfaces resulted in improved friction. The mechanism for the improved performance of the laser-textured surfaces is believed to be through the augmented local contact pressures at the asperities that accelerate additive decomposition to form protective low-friction tribofilms. This study demonstrates the feasibility of surface texturing in improving the performance of boundary additives.

Sandblasting is an established technique in generating surface textures on titanium and other metal alloys; these surfaces are desirable in the field of biomedical engineering as they promote osseointegration of medical implants. However, this process has significant limitations including, the embedment of abrasive particles causing changes to surface composition, lack of automation, and health hazards. Laser processing is becoming more common in the medical industry as a method to generate surface textures. Nanosecond laser systems are generally used in surface processing for their benefits of productivity and cost; however, the ultra-short pulsed lasers induce less thermal damage. This study probes the use of stochastic laser processing (laser-blasting) as an alternative to sandblasting to modify surfaces of Ti6Al4V. Laser processing parameters such as power and pulse durations were investigated in both nanosecond and femtosecond laser systems operating in the IR region. Surface morphology and microstructural changes of laser blasted samples were inspected using a variety of techniques (confocal microscopy, SEM and EDX) and then compared with those that had been sandblasted. The results obtained show that through careful selection of parameters, laser-blasting is capable of generating similar surfaces produced by sandblasting with limiting thermal damage.

Anti-wetting, or superhydrophobic surfaces have been a subject of significant interest in the engineering field for many years, particularly due to the potential to create self-cleaning surfaces. A droplet of water landing on a superhydrophobic surface will roll or slide away, whilst taking with it any surface debris. Such surfaces exist in nature, and there have been many reports where ultra-short pulsed lasers have been used to generate surfaces with similar feature sizes and hydrophobic performance. However it is also possible to produce superhydrophobic surfaces with short (nanosecond) laser pulses. In this paper we report our work in which flat sheets of SS304S15 were textured using a nanosecond pulsed fibre laser operating at 1064 nm. Quantitative analysis of the wettability of the laser structured surfaces was carried out by measuring the static contact angle of a droplet of deionized water with a volume in the microliter range. As with other reports, these surfaces are initially hydrophilic, and after a time delay of some days to weeks transition to hydrophobic, and in some cases to superhydrophobic. In order to realise a practical process, our work has concentrated in speeding up this transition from weeks to days, and to this end we have studied the role of the processing environment during laser texturing.

Laser-induced ripples that are also known as laser-induced periodic surface structures (LIPSS) have gained a considerable attention by researchers and industry due to their surface functionalization applications. However, texturing large areas or batch manufacture of parts that incorporate LIPSS surfaces require the development of tools for monitoring the LIPSS generation and potentially for controlling their main geometrical characteristics, i.e., spatial periodicity, orientation, and amplitude. In this context, the focus of the research reported in this paper is on developing process monitoring and inspection methods for identifying shifts and changes in these characteristics. One of the well-known and widely used by industry method for characterizing and inspecting surfaces is light scattering, and this research investigates the capabilities of this method for inline monitoring of LIPSS optical response. A simple setup was designed and implemented for measuring the diffraction angle and intensity of the reflected light from LIPSS surfaces. The capabilities of this concept for determining relative shifts in the optical response on surfaces processed with known disturbances, such as incident angle deviations and focus offset, were investigated. Sensitivity of the method proved to be sufficient to detect shifts/deviations from LIPSS reference and thus potentially to monitor their generation in line with a simple sensor, e.g., the LIPSS treatment of larger tool surfaces or serial manufacture of holograms.

Diamond-like carbon (DLC) coatings have very attractive mechanical and tribological properties, i.e. high hardness, low friction and high wear resistance. Therefore, DLC is often used as a solid lubricant in moulds for injection moulding. Laser processing of DLC with ultrashort lasers, i.e. femtosecond lasers, can be performed both at micron and sub-micron scales, namely by producing laser-induced periodic surface structures (LIPSS). In this research, the effects of laser structuring/texturing on DLC properties are investigated. First, the laser-processing parameters were optimised to produce uniform LIPSS without damaging a thin DLC film and then the properties of the textured DLC-coated substrates were studied. It was determined that the tribological properties of the processed surfaces remained unchanged, but the hardness of the structured/textured DLC layers was reduced significantly. Although GAXRD and Raman spectroscopy did not show any significant crystallisation of the DLC coating after the laser irradiation, the analysis indicated that a thin graphitised layer had been formed on the surface as a result of the femtosecond laser processing.

Plasmonic structures are renowned for their capability to efficiently convert light into heat at the nanoscale. However, despite the possibility to generate deep sub-wavelength electromagnetic hot spots, the formation of extremely localized thermal hot spots is an open challenge of research, simply because of the diffusive spread of heat along the whole metallic nanostructure. Here we tackle this challenge by exploiting single gold nanocones. We theoretically show how these structures can indeed realize extremely high temperature gradients within the metal, leading to deep sub-wavelength thermal hot spots, owing to their capability of concentrating light at the apex under resonant conditions even under continuous wave illumination. A three-dimensional Finite Element Method model is employed to study the electromagnetic field in the structure and subsequent thermoplasmonic behaviour, in terms of the three-dimensional temperature distribution. We show how the latter is affected by nanocone size, shape, and composition of the surrounding environment. Finally, we anticipate the use of photoinduced temperature gradients in nanocones for applications in optofluidics and thermoelectrics or for thermally induced nanofabrication.

In materials chiral fermions such as Weyl fermions are characterized by nonzero chiral charges, which are singular points of Berry curvature in momentum space. Recently, new types of chiral fermions beyond Weyl fermions have been discovered in structurally chiral crystals CoSi, RhSi and PtAl. Here, we have synthesized RhSn single crystals, which have opposite structural chirality to the CoSi crystals we previously studied. Using angle-resolved photoemission spectroscopy, we show that the bulk electronic structures of RhSn are consistent with the band calculations and observe evident surface Fermi arcs and helical surface bands, confirming the existence of chiral fermions in RhSn. It is noteworthy that the helical surface bands of the RhSn and CoSi crystals have opposite handedness, meaning that the chiral fermions are reversed in the crystals of opposite structural chirality. Our discovery establishes a direct connection between chiral fermions in momentum space and chiral lattices in real space., Exotic chiral fermions beyond Weyl fermions have recently been discovered in a series of chiral crystals such as CoSi. Here, the authors report the evidences of chiral fermions in RhSn with opposite handedness compared to those observed in CoSi, where the structural chirality is also opposite.

An Al-coated Mg-8 mass% Li alloy rectangular bar was fabricated by hot extrusion, and then, it was hot-rolled into a thin sheet. The Al coating was uniform in thickness and had good bonding with the substrate during all the processing. This Al-coated Mg–Li alloy exhibited a good corrosion resistance in a 0.5 mass% HCl aqueous solution. No intermetallic compound was observed at the Al/Mg–Li interface after the extrusion and the rolling. The Al-coated Mg–Li alloy sheet exhibited an elongation to fracture of 35% at room temperature at a strain rate of 0.001 s−1 without any debonding between the coating and the substrate. When tensile tested at 573 K at 0.001 s−1 in the air, the Al coating remained undamaged even until an elongation of about 150%. Further elongation generated cracks on the coating and the specimen fractured at an elongation of about 200%. In an Ar atmosphere, the specimen exhibited a fracture elongation of over 400% under the same conditions at 573 K at 0.001 s−1, although a large number of cracks generated on the Al coating.

Although the particle adhesion is a classic problem in cyclones, it is not clearly understood in previous studies. This study was set out to determine factors affecting the micro-particle adhesion in an acrylonitrile butadiene styrene cyclone by developing a mesh-free simulation method to predict the dynamic motion of a single particle in a 2D horizontal section of the cyclone with the presence of the wall boundary layer. Simulation results showed that the centrifugal force played a minor role on the particle adhesion but it was important on the transportation of the particle. In contrast, the electrostatic force was important on the particle adhesion but it was not important on the transportation of the particle. Moreover, simulation results suggested that the particle adhesion can be reduced by increasing the inlet velocity of the cyclone or by increasing the coefficient of restitution of the particle–wall collision. In contrast, the particle adhesion can be increased by increasing the radius of the cyclone, the particle charge and the coefficient of friction. Furthermore, simulation results on the effect of the inlet velocity and particle charge were validated by experimental results.

TiO2/reduced graphene oxide (rGO) nanocomposites were prepared via a facile one-step hydrothermal method using TiCl3 as the TiO2 precursor. Cetyltrimethyl ammonium bromide (CTAB) was introduced as a stabilizer for GO in solution. The effects of GO content, Ti3+ concentration and urea additive on phase constituent and morphology of the TiO2 crystallites in the nanocomposites were systematically investigated. UV–vis absorption ability of the as-made composites was further tested and discussed. Ag nanocrystals (NCs) were photocatalytically grown on the surfaces of biphasic (anatase + brookite) and triphasic (anatase + brookite + rutile) TiO2/rGO nanocomposites to evaluate their surface-enhanced Raman scattering (SERS) performances. Morphology evolution of the Ag NCs in response to different photocatalytic ability of the TiO2/rGO nanocomposite was also investigated in detail. The nanocomposite with triphasic TiO2 of proper phase constituents was confirmed to favor the growth of Ag particles of two distinctly different sizes and to produce SERS substrates of substantially better performance.

The development of cheap and highly dispersed nano-catalyst is one of the key technologies for low temperature steam reforming (SR) of biomass tar. This work used acid-washed and oxidized Shengli lignite char (OXAWSL) as carbon precursor to load Co (Co/OXAWSL) and Ni (Ni/OXAWSL) via ion exchange method to SR of toluene and biomass tar. The Co/OXAWSL was more active and stable than Ni/OXAWSL during the 30 h test with a final toluene conversion of 85% at a relatively low temperature of 450 °C and steam to carbon ratio (S/C) of 3.4, which resulted from its small particle size (5.6 nm) and high dispersion (12.3%) of Co. The relatively high H2 production (42.59 mmol/g-biomass) over Co0.1/OXAWSL (450 °C, S/C = 3.4) in SR of tar was also obtained. A low Ea (22.0 kJ/mol) value of Co/OXAWSL and good affinity to oxygen for Co explained its excellent performance. The low-temperature tar cracking process can provide theoretical and technical support for the large-scale industrial utilization of biomass pyrolysis and gasification.

Visible-light-driven WO3and#183;0.33H2O/Ag2MoO4 composites have been prepared by using an in-situ growth of Ag2MoO4 nanoparticles on the surfaces of WO3and#183;0.33H2O. The photocatalytic activities of the samples were studied by degradation of rhodamine B and levofloxacin dilute solution. The synergistic photocatalytic mechanism was also analyzed. Experimental results reveal that the as-developed hybrids have higher photocatalytic activity than pure samples. When the theoretical molar ratio of WO3and#183;0.33H2O to Na2MoO4and#183;2H2O is 1:0.15, the as-developed hybrids have the highest photocatalytic degradation efficiency of 99.0% for rhodamine B in 45 min and 40.9% for levofloxacin in 120 min. Furthermore, there are chemical bonds between WO3and#183;0.33H2O and Ag2MoO4. In addition, the super oxide radicals play the leading role during the photocatalytic degradation process of the samples. This work will provide reference for treatment of organic dyes and antibiotics pollution in water with using solar energy.

A novel porous carbon catalyst was prepared by carbonization of D151 resin exchanged with nickel ion (Ni/RC). TEM images and XRD patterns manifest that nickel crystallite size (NCS) relies greatly on solution pH value and carbonization temperature. The as-prepared Ni/RC in pH 11 at 650 °C achieved the maximal specific surface area of 213 m 2 /g and metallic nickel particles are highly dispersed with a NCS of 5.7 nm. Ni/RC exhibited higher activity for corncob tar reforming than commercial Ni/Al 2 O 3 and produced a gas yield of 46.8 mmol/g at 650 °C. The nickel particles growth above 650 °C causes the decline in catalytic activity of Ni/RC. In the presence of steam, a high tar-free gas of 84.5 mmol/g was obtained at 650 °C. This study sheds light on the possibility of Ni/RC as a promising candidate for H 2 -rich gas production from biomass under mild conditions.

This paper presents an investigation on the titanium aluminium nitride (TiAlN) coating removal from tungsten carbide (WC-Co) substrate using a diode pump solid state (DPSS) ultraviolet (UV) laser with maximum average power of 90 W, wavelength of 355 nm and pulse width of 50 ns. The TiAlN coating of 1.5 μm thickness is removed from the WC-Co substrate with laser fluence of 2.71 J/cm2 at 285.6 number of pulses (NOP) and with NOP of 117.6 at 3.38 J/cm2 fluence. Titanium oxide formation was observed on the ablated surface due to the re-deposition of ablated titanium residue and also attributed to the high temperature observed during the laser ablation process. Crack width of around 0.2 μm was observed over both TiAlN coating and WC-Co substrate. The crack depth ranging from 1 to 10 μm was observed and is related to the thickness of the melted carbide. The crack formation is a result of the thermal induced stresses caused by the laser beam interaction with the material as well as the higher thermal conductivity of cobalt compared to WC. Two cleaning regions are observed and is a consequence of the Gaussian distribution of the laser beam energy. The surface roughness of the ablated WC-Co increased with increasing laser fluence and NOP.

An investigation on ablation characteristics of 1024 and H10F cobalt cemented tungsten carbide (WC-Co) with a DPSS nanosecond UV laser (50 ns pulse width, 355 nm wavelength, 90 W average power and 10 kHz repetition rate) is presented. The ablation characteristic parameters such as ablation threshold, incubation effect and optical penetration depth were evaluated based on the spot ablation diameter and depth. It was observed that the ablation threshold is significantly influenced by the number of pulses (NOP) and it decreases with increase NOP which is attributed to the incubation effect. Only one ablation region is observed at low laser fluence and an additional molten ablation region is observed at high laser fluence accompanied with cracks. The cracks formation is due to the thermal induced stress and changes in WC microstructure during laser beam irradiation. The crack depth is proportional to the thickness of the molten WC region. The ablation threshold of 1024 WC-Co and H10F WC-Co were found to be Fth1 =4.32 J/cm2 and Fth1 =4.26 J/cm2 respectively. The difference in chemical composition has insignificant effect on the ablation threshold value of the material. The incubation factor and optical penetration depth values of 1024 WC-Co and H10F WC-Co were found to be ξ=0.73, α−1 =411 nm and ξ=0.75, α−1 =397 nm respectively.

Different sizes of hexagonal spherical NaGdF4:Eu3+ particles are synthesized via a facile hydrothermal method with the use of ethylene glycol (EG), propylene glycol (PG) or butylene glycol (BG) as another solvent. The particle size decreases with the addition of EG, PG or BG and the decreasing trend in BG/H2O system is significantly more than that in the other two systems. Meanwhile, results show that luminescent properties of NaGdF4:Eu3+ are enhanced along with the decrease of particle size. Besides, the energy transfer from Dy3+ to Eu3+ is directly observed in the PL spectra of NaGdF4:Eu3+/Dy3+.

pH responsive polymeric nanoparticles have emerged as a promising technology platform for targeted and controlled drug delivery in recent years. In this paper, endosomal pH-activatable doxorubicin (DOX) and core-crosslinked polymeric nanoparticles (DCNPs) were prepared and investigated for potent growth inhibition of human cancer cells in vitro. In vitro drug release studies, DOX conjugated nanoparticles with hydrazone bond showed a pH sensitive release phenomenon, that is, the releasing is significantly faster at mildly acidic condition with pH of 5.5 than that at physiological condition. Confocal laser scanning microscope (CLSM) observations revealed that DOX conjugated nanoparticles delivered and released DOX into the cytosols as well as cell nuclei of Hela cells following 6 h incubation. MTT assays demonstrated that these pH-sensitive DOX nanoparticles exhibited high antitumor effect to HeLa cells. The conjugated DOX polymeric nanoparticles may be a promising candidate as a nanoscale and pH-sensitive drug delivery vehicle for cancer therapy.

The greater structural versatility of two-dimensional polymeric nanosheets could be available through the development of a bottom-up polymerization strategy compared with top-down nanosheets (such as graphene and metal chalcogenides). However, rational synthesis by solution polymerization has been a long-standing challenge. Considering that Glaser coupling is catalyzed by cuprous (I) salts with the participation of oxygen, an air/liquid interfacial coupling reaction has been designed and used to prepare a two-dimensional porous triptycene-based polymeric nanosheet (2D-PTNS). This 2D-PTNS shows a high BET surface area, good gas adsorption ability and excellent selective adsorption of C2H6/CH4 at ambient temperature and pressure.

We report the effects of cobalt doping on the magnetic properties of two-dimensional van der Waals ferromagnet Fe3GeTe2. Single crystals of (Fe{1-x}Cox)3GeTe2 with x=0-0.78 were successfully synthesized and characterized with x-ray diffraction, energy dispersive x-ray spectroscopy and magnetization measurements. Both the Curie-Weiss temperature and ferromagnetic (FM) ordered moment of Fe3GeTe2 are gradually suppressed upon Co doping. A kink in zero-field-cooling low field M(T) curve which is previously explained as an antiferromagnetic transition is observed for samples with x=0-0.58. Our detailed magnetization measurements and theoretical calculations strongly suggest that this kink is originated from the pinning of magnetic domain walls. The domain pinning effects are suddenly enhanced when the doping concentration of cobalt is around 50%, both the coercive field Hc and the magnetic remanence to saturated magnetization ratio MR/MS are largely improved and a hard magnetic phase emerges in bulk single crystal samples. The strong doping dependent magnetic properties suggest more spintronic applications of Fe3GeTe2., 6 pages, 4 figures, accepted by PRB

AlGaN/GaN HEMT epistructures were grown on SI-SiC using different doping concentrations of carbon in GaN buffer layer to study the effects of carbon on various device parameters. The carbon doping was tuned by adjusting different growth parameters, and SIMS analysis was performed to determine the carbon doping density. HEMTs with $0.25 \mu \mathrm {m}$ gate length were fabricated and characterized. Some of the parameters studied include buffer leakage current, drain current density, OFF-state breakdown voltage and drain current collapse.

Van der Waals (vdW) layered materials have rather weaker interlayer bonding than the intra-layer bonding, therefore the exfoliation along the stacking direction enables the achievement of monolayer or few layers vdW materials with emerging novel physical properties and functionalities. The ferroelectricity in vdW materials recently attracts renewed interest for the potential use in high-density storage devices. As the thickness going thinner, the competition between the surface energy, depolarization field and interfacial chemical bonds may give rise to the modification of ferroelectricity and crystalline structure, which has limited investigations. In this work, combining the piezoresponse force microscope scanning, contact resonance imaging, we report the existence of the intrinsic in-plane polarization in vdW ferroelectrics CuInP2S6 (CIPS) single crystals, whereas below a critical thickness between 90-100 nm, the in-plane polarization disappears. The Young's modulus also shows an abrupt stiffness at the critical thickness. Based on the density functional theory calculations, we ascribe these behaviors to a structural phase transition from monoclinic to trigonal structure, which is further verified by transmission electron microscope technique. Taken together, these findings demonstrate the foundational importance of structural phase transition for enhancing the rich functionality and broad utility of vdW ferroelectrics.

Tribological performance of mating surfaces can be improved by developing surfaces with predefined textures and it is crucial to understand their role in modifying the performance and action of boundary lubrication additives. An isotropic texture T1, intermediate texture T2 and anisotropic texture, T3, were imported into our mixed simulation framework. It was found that T3 outperforms by providing the most feasible conditions for the activation of the lubricant additive, molybdenum dithiocarbamate (MoDTC) i.e. generating higher pressure peaks (shear), making more lubricant (reactant) available and providing greater load bearing area (greater reaction probability). Hence, facilitating the formation of functional boundary films. T2 seems to generate highest pressure peaks but its performance is worst due to its inability to sustain lubricant within the contact.

Adhesion of viscous liquids on packaging surfaces could lead to wastage, an increase of recycling costs, and even customers' dissatisfaction in applications related to food, cosmetics and agrochemical industries. Lubricant-impregnated surfaces (LIS) gained much attention recently over other surface functionalisation technologies due to their non-sticking response to highly viscous liquids. This work reports an investigation into anti-adhesive properties of LIS, with an emphasis on their durability. It provides an insight into the rationale design of LIS topographies in order to maximise their lubricant retention in potential food packaging applications. Femtosecond laser processing and hot embossing were employed to produce two types of topographies for LIS on stainless steel, polypropylene and polystyrene surfaces. The first type was single-scale sub-micron laser induced periodic surface structures (LIPSS), while the second one was multi-scale (MS) structures with both micron and sub-micron features. Droplet shedding characteristics of such LIPSS-LIS and MS-LIS substrates with water, milk and honey were examined under vibration and shear. The critical sliding angles at which liquid droplets attained motion on LIS were observed to be less than 32° for all investigated liquids. However, the LIPSS-LIS substrates retained their functionality even after subjecting them to severe vibration, while the MS-LIS substrates partially lost their anti-adhesive characteristics. At the same time, the MS-LIS substrates exhibited premature pinning of droplets as compared to LIPSS-LIS substrates, under shear forces. Both vibration- and shear-induced loss of lubricant impacted the MS-LIS functionality.

Conventionally, effective mechanical vibration energy harvesting is based on (Pb,Zr)TiO3 (PZT) ceramics, poly(vinylidene fluoride) (PVDF) polymers or PVDF/PZT or other piezoelectric composite materials, and their working temperature is normally limited to room temperature (R-T) or below 150 °C. Here, bismuth scandium lead titanate (BiScO3-PbTiO3, abbreviated as BSPT) ceramic is reported which has a high Curie temperature point around 450 °C and its application for high-temperature (H-T) vibration energy harvesting. Experimental results show that it exhibits an excellent H-T piezoelectricity, converting mechanical vibration energy into electric power effectively in a wide temperature range from R-T till 250 °C. This research shows the BSPT piezoelectric energy harvester having the potential application for self-power source of wireless sensor network system in high temperature circumstance.

The optical, thermal and electrical properties of ultra-thin two-dimensional (2D) crystal materials are highly related to their thickness. Therefore, identifying the atomic planes of few-layer crystal materials rapidly is crucial to fundamental study. Here, a simple technique was demonstrated based on optical contrast for counting atomic planes (n) of few-layer MoSe2 on SiO2/Si substrates. It is found that the optical contrast of single-layer MoSe2 depends on light wavelength and thickness of SiO2 on Si substrate. The data calculated based on a Fresnel law-based model as well as atomic force microscopy (AFM) measurements fit well with the values measured by spectroscopic ellipsometer. Furthermore, the calculated and measured contrasts were integral and plotted, which can be used to determine the MoSe2 atomic planes (1 ≤ n ≤ 4) accurately and rapidly. The optical contrast of thin-layer (1 ≤ n ≤ 4) MoSe2 sample was calculated by Fresnel’s law, and the contrast was measured by OM image. By combining these two group data, a function of layer numbers and contrast was developed: C (contrast) = 0.07N + 0.177. This proves that contrast is linear to layer numbers of MoSe2 when layer number is less than 4.

Galvanic growth of Ag nano/micro-structures on Cu micro-grid was systematically studied for surface-enhanced Raman scattering (SERS) applications. Detailed characterizations via FE-SEM and HR-TEM showed that processing parameters, (reaction time, Ag+ concentration, and PVP addition) all substantially affect thermodynamics/kinetics of the replacement reaction to yield substrates of significantly different microstructures/homogeneities and thus varied SERS performances (sensitivity, enhancement factor, and reproducibility) of the Ag substrates in the detection of R6G analyte. PVP as an additive was shown to notably alter nucleation/growth behaviors of the Ag crystals and promote the deposition of dense and uniform Ag films of nearly monodisperse polyhedrons/nanoplates through suppressing dendrites crystallization. Under optimized synthesis (50 mM of Ag+, 30 s of reaction, and 700 wt.% of PVP), Ag substrates exhibiting a high Raman signal enhancement factor of ~ 1.1 × 106 and a low relative standard deviation of ~ 0.13 in the repeated detection of 10 μM R6G were obtained. The facile deposition and excellent performance reported in this work may allow the Ag microstructures to find wider SERS applications. Moreover, growth mechanisms of the different Ag nano/micro-structures were discussed based on extensive FE-SEM and HR-TEM analysis.

Iron-based superconductors have the second-highest superconducting transition temperature next to cuprate superconductors. There are many electronic phases such as superconducting, antiferromagnetic and nematic phases, coexisting in the family of iron pnictides. The charge/spin orders are the key factors for understanding the mechanism of high-temperature superconductivity. In this paper we have performed a Raman scattering study of parent compound BaFe2As2. A relatively strong electron–phonon coupling is observed for B1g phonon mode and is weakened after the structural transition at ∼140 K. Through a careful symmetry analysis, we revealed the possibility that B1g mode can be effectively coupled with dxz and dyz orbits. The coupling can remove the degeneracy of the two orbits and further cause the fluctuations of electronic nematic phases. The study suggests that electron–phonon coupling can be a possible origin of nematic phase.

Bismuth layer-structured ferroelectric (BLSF) compound strontium bismuth titanate (SrBi 4 Ti 4 O 15 , SBT) with cerium modifications have been synthesized using conventional solid-state processing. X-ray powder diffraction (XRPD) analyses reveal that the cerium-modified SBT ceramics have a pure four-layer Aurivillius-type structure. The dielectric, ferroelectric, and piezoelectric properties of the cerium-modified SBT ceramics are investigated in detail. The results indicate that the cerium modifications into SBT increase the densities, decrease the sintering temperature, lower the dielectric loss tan δ , and reduce the coercive filed E c . The piezoelectric measurements show that cerium is very effective in promoting the piezoelectric properties of SBT ceramics. The SBT ceramics modified with 4 mol% CeO 2 (SBT-4Ce) exhibit the optimized piezoelectric properties, with a piezoelectric constant d 33 of 27 pC/N, which is the highest value among the modified SBT-based piezoelectric ceramics ever reported. The temperature-dependent electrical impedance and electromechanical coupling coefficients ( k p and k t ) reveal that the electromechanical coupling characteristics have a significant deterioration at ~400 °C because of the high conductivity at high temperature. But the temperature-dependent frequency constants ( N p and N t ) and thermal annealing analyses indicate the cerium-modified SBT ceramics have good thermal stabilities of piezoelectric properties up to 450 °C. These results demonstrate that the cerium-modified SBT ceramics are promising materials for high temperature piezoelectric sensors applications.

This paper presents a study of the influence of gradient doping on solar cell performance. The gradient doping of the emitter layer of a a-Si:H(n)/a-Si:H(i)/c-Si(P) solar cell was simulated using the AFORS-Het software simulation package. Band structure adjustment due to gradient doping was studied. The adjustment manifests itself in two separate ways: the gradient quasi-Fermi level splitting (ΔeF) and the gradient band slope. The relationship between ΔeF and doping concentrations has been theoretically deduced and simulated using the AFORS-Het software package. The study shows that the ΔeF caused by gradient doping can improve the spectral response of the cell at long wavelengths and enhance the open circuit voltage. The steeper energy band caused by the higher doping gradient, G, promotes the effective separation of the carriers and reduces their recombination by 2–3 orders of magnitude compared to that of the uniform band. The photovoltaic conversion efficiency of the silicon heterojunction solar cell increases from 13.65% (uniform doping) to 20.86% for the gradient doping cell with the highest G and steepest energy band. This numerical simulation shows that the band structure adjustment caused by gradient doping can achieve higher utilization of solar energy and suppress the recombination of the carriers at the heterojunction interface. The study will guide practical preparation of future solar cells.

In this study, we prepared gold nanoparticles by electrochemical synthesis and inlaid in the photo-electrode of dye-sensitized solar cells (DSSCs) to study the surface plasma resonant (SPR) and light-scattering effects on the properties of dye-sensitized solar cells. The analyses of field emission scanning electron microscopy (FE-SEM) show that the average diameter of gold nanoparticles is 50nm. The results of ultraviolet-visible absorption spectra show that the absorption wavelength is about 533nm for gold nanoparticles. The conversion efficiency with different amounts of gold nanoparticles in TiO2 photo-electrodes is 5.42%, 5.92%, 6.06%, and 5.51% with the amounts of 0µL, 300µL, 400µL, and 500µL, respectively. The best conversion efficiency of the dye-sensitized solar cells with gold nanoparticles added is 6.06%, and is higher than that the cells without gold nanoparticles, which is 5.42%. In addition, in order to study light-scattering effects on the photo-electrode, different thicknesses of large particle size TiO2 (~250nm) coated onto photo-electrode to form double layer structure. The best conversion efficiency of the dye-sensitized solar cells with gold nanoparticles added and with the thickness of 3.3µm light scattering layer is 7.10%, which is higher than that of the cell without light-scattering layer, which is 6.06%. This result indicates that the effect of gold nanoparticles on the photo-electrode can increase the conductivity and reduce the recombination of charges in the photo-electrode, and the light-scattering structure can enhance light transmission path in TiO2 films and the absorption of photons in the photo-electrode, resulting in the increase of the photoelectric conversion efficiency for DSSCs. The addition of gold nanoparticles leads to a linear increase in conversion efficiency of the DSSC. When the volume of added gold nanoparticles is 500µL, the Jsc begins to decrease.Display Omitted The effect of gold nanoparticles can increase the conductivity and reduce the recombination of charges in the photo-electrode.The light-scattering structure can enhance light transmission path in TiO2 films and the absorption of photons.Gold nanoparticles result in the increase of the photoelectric conversion efficiency for DSSCs.