Doping-enhanced robustness of anomaly-related magnetoresistance in WTe_(2±α)flakes

We study systematically the negative magnetoresistance(MR)effect in WTe_(2±α)flakes with different thicknesses and doping concentrations.The negative MR is sensitive to the relative orientation between electrical-/magnetic-field and crystallographic orientation of WTe_(2±α).The analysis proves that the negative MR originates from chiral anomaly and is anisotropic.Maximum entropy mobility spectrum is used to analyze the electron and hole concentrations in the flake samples.It is found that the negative MR observed in WTe_(2±α)flakes with low doping concentration is small,and the high doping concentration is large.The doping-induced disorder obviously inhibits the positive MR,so the negative MR can be more easily observed.In a word,we introduce disorder to suppress positive MR by doping,and successfully obtain the negative MR in WTe_(2±α)flakes with different thicknesses and doping concentrations,which indicates that the chiral anomaly effect in WTe_(2)is robust.

Improving Crude Oil Flow Using Graphene Flakes under an Applied Electric Field

Graphene flakes(GF)have been prepared and assessed as a material for improving flow in oil pipelines under the effect of an electric field.In particular,different amounts of GFs have been considered in order to determine the optimal flow conditions.The GFs were prepared from graphite foam,derived from the dehydration of sugar with a particle size of 500-600μm,which was dispersed in ethanol and exfoliated in a ball mill under a shear force.After 15 h of exfoliation,sonication,and subsequent high-speed centrifugation at 3000 rpm,irregular-shaped GFs of 50-140 nm were produced and characterized using scanning electron microscopy,X-ray diffractometry,atomic force microscopy,and Raman spectroscopy.The prepared graphene sheets have been found to display excellent morphology and good graphitic structure.Experiments on flow improvement were conducted using the central composite rotatable design method for three parameters:stimulation time(15,30,45,and 60 s),applied voltage(150,170,200,and 220 V),and concentration of the GFs(0,100,200,and 400 mg/L).The optimal conditions for improved crude oil flow were then determined using the STATISTICA and WinQSB software packages.The results have confirmed the effectiveness of the use of the prepared GFs as a flow improver for crude oil,where the flow improvement is essentially a result of a reduction in viscosity and suppression of friction in the crude oil system.

Enhanced Thermal Conductivity and Bending Strength of Graphite Flakes/aluminum Composites Via Graphite Surface Modification

The effect of graphite surface modification on the thermal conductivity(TC) and bending strength of graphite flakes/Al composites(Gf/Al) prepared by gas pressure infiltration were investigated. Al3 Ni and Al4C3 phase may form at the interface in Ni-coated Gf/Al and uncoated Gf/Al composites, respectively, while the Al-Cu compound cannot be observed in Cu-coated Gf/Al composites. The Cu and Ni coatings enhance TC and the bending strength of the composites in the meantime. TC of Cu-coated Gf/Al composites reach 515 Wm^-1·K^-1 with 75 vol% Gf, which are higher than that of Ni-coated Gf/Al. Meanwhile, due to Al3 Ni at the interface, the bending strength of Ni-coated Gf/Al composites are far more than those of the uncoated and Cu-coated Gf/Al with the same content of Gf. The results indicate that metal-coated Gf can effectively improve the interfacial bonding between Gf and Al.

Unusual Normal and Superconducting State Properties Observed in Hydrothermal Fe_(1-δ)Se Flakes

The electronic and superconducting properties of Fe_(1-δ)Se single-crystal flakes grown hydrothermally are studied by the transport measurements under zero and high magnetic fields up to 38.5 T.The results contrast sharply with those previously reported for nematically ordered Fe Se by chemical-vapor-transport(CVT)growth.No signature of the electronic nematicity,but an evident metal-to-nonmetal crossover with increasing temperature,is detected in the normal state of the present hydrothermal samples.Interestingly,a higher superconducting critical temperature T_c of 13.2 K is observed compared to a suppressed T_c of 9 K in the presence of the nematicity in the CVT Fe Se.Moreover,the upper critical field in the zero-temperature limit is found to be isotropic with respect to the field direction and to reach a higher value of-42 T,which breaks the Pauli limit by a factor of 1.8.

Magneto-transport properties of thin flakes of Weyl semiconductor tellurium

As an elemental semiconductor,tellurium has recently attracted intense interest due to its non-trivial band topology,and the resulted intriguing topological transport phenomena.In this study we report systematic electronic transport studies on tellurium flakes grown via a simple vapor deposition process.The sample is self-hole-doped,and exhibits typical weak localization behavior at low temperatures.Substantial negative longitudinal magnetoresistance under parallel magnetic field is observed over a wide temperature region,which is considered to share the same origin with that in tellurium bulk crystals,i.e.,the Weyl points near the top of valence band.However,with lowering temperature the longitudinal magnetoconductivity experiences a transition from parabolic to linear field dependency,differing distinctly from the bulk counterparts.Further analysis reveals that such a modulation of Weyl behaviors in this low-dimensional tellurium structure can be attributed to the enhanced inter-valley scattering at low temperatures.Our results further extend Weyl physics into a low-dimensional semiconductor system,which may find its potential application in designing topological semiconductor devices.

Resistance Anomaly and Linear Magnetoresistance in Thin Flakes of Itinerant Ferromagnet Fe_(3)GeTe_(2)

Research interests in recent years have expanded into quantum materials that display novel magnetism incorporating strong correlations,topological effects,and dimensional crossovers.Fe_(3)GeTe_(2)represents such a twodimensional van der Waals platform exhibiting itinerant ferromagnetism with many intriguing properties.Up to date,most electronic transport studies on Fe_(3)GeTe_(2)have been limited to its anomalous Hall responses while the longitudinal counterpart(such as magnetoresistance)remains largely unexplored.Here,we report a few unusual transport behaviors on thin flakes of Fe_(3)GeTe_(2).Upon cooling to the base temperature,the sample develops a resistivity upturn that shows a crossover from a marginally-ln T to a-T^(1/2)dependence,followed by a lowertemperature deviation.Moreover,we observe a negative and non-saturating linear magnetoresistance when the magnetization is parallel or antiparallel to the external magnetic field.The slope of the linear magnetoresistance also shows a nonmonotonic temperature dependence.We deduce an anomalous contribution to the magnetoresistance at low temperatures with a scaling function proportional-HT^(1/2),as well as a temperature-independent linear term.Possible mechanisms that could account for our observations are discussed.

Graphene Flakes in Arc Plasma: Conditions for the Fast Single-Layer Growth

The results of systematic numerical studies of graphene flakes growth in low-temperature arc discharge plasmas are presented. Diffusion-based growth model was developed, verified using the previously published experiments, and used to investigate the principal effects of the process parameters such as plasma density, electron temperature, surface temperature and time of growth on the size and structure of the plasma-grown graphene flakes. It was demonstrated that the higher growth temperatures result in larger graphene flakes reaching 5 μm, and simultaneously, lead to much lower density of the carbon atoms adsorbed on the flake surface. The low density of the carbon adatoms reduces the probability of the additional graphene layer nucleation on surface of growing flake, thus eventually resulting in the synthesis of the most valuable single-layered graphenes.

Influence of shape anisotropy on microwave complex permeability in carbonyl iron flakes/epoxy resin composites

To explore the mechanism of carbonyl iron flake composites for microwave complex permeability, this paper investigates the feature of the flakes. The shape anisotropy was certified by the results of the magnetization hysteresis loops and the Mossbauer spectra. Furthermore, the shape anisotropy was used to explain the origin of composite microwave performance, and the calculated results agree with the experiment. It is believed that the shape anisotropy dominates microwave complex permeability, and the natural resonance plays main role in flake.

Detection of heavy metals in water samples by laser-induced breakdown spectroscopy combined with annular groove graphite flakes

The use of laser-induced breakdown spectroscopy(LIBS) for the analysis of heavy metals in water samples is investigated. Some factors such as splashing, surface ripples, extinction of emitted intensity, and a shorter plasma lifetime will influence the results if the water sample is directly measured. In order to avoid these disadvantages and the ‘coffee-ring effect', hydrophilic graphite flakes with annular grooves were used for the first time to enrich and concentrate heavy metals in water samples before being analyzed by LIBS. The proposed method and procedure have been evaluated to concentrate and analyze cadmium, chromium, copper, nickel, lead,and zinc in a water sample. The correlation coefficients were all above 0.99. The detection limits of 0.029, 0.087, 0.012, 0.083, 0.125, and 0.049 mgl^(-1) for Cd, Cr, Cu, Ni, Pb, and Zn,respectively, were obtained in samples prepared in a laboratory. With this structure, the heavy metals homogeneously distribute in the annular groove and the relative standard deviations are all below 6%. This method is very convenient and suitable for online in situ analysis of heavy metals.

Synthesis Method and Absorption Application of Nanocrystalline Alloy Flakes

The soft magnetic Fe-Si-B nanocrystalline/ amorphous flakes were fabricated by ball milling from the elemental powders and annealing the amorphous precursor, respectively. The microstructure, magnetic and microwave properties were evaluated by different synthesis methods. By computation, ball-milled Fe78Si13B9 flakes demonstrated potential appfication in absorption.

Salt-assisted vapor-liquid-solid growth of high-quality ultrathin nickel oxide flakes for artificial synapses in image recognition applications

Transition metal oxides have attracted intense interest owing to their abundant physical and chemical properties.The controlled preparation of large-area,high-quality two-dimensional crystals is essential for revealing their inherent properties and realizing high-performance devices.However,fabricating two-dimensional(2D)transition metal oxides using a general approach still presents substantial challenges.Herein,we successfully achieve highly crystalline nickel oxide(NiO)flakes with a thickness as thin as 3.3 nm through the salt-assisted vapor-liquid-solid(VLS)growth method,which demonstrated exceptional stability under ambient conditions.To explore the great potential of the NiO crystal in this work,an artificial synapse based on the NiO-flake resistive switching(RS)layer is investigated.Short-term and long-term synaptic behaviors are obtained with external stimuli.The artificial synaptic performance provides the foundation of the neuromorphic application,including handwriting number recognition based on artificial neuron network(ANN)and the virtually unsupervised learning capability based on generative adversarial network(GAN).This pioneering work not only paves new paths for the synthesis of 2D oxides in the future but also demonstrates the substantial potential of oxides in the field of neuromorphic computing.

Dried bonito flakes-inspired moisture-responsive actuator with a gradient structure for smart devices

Exploring high-performance soft actuators from biomass resources is significant for developing eco-friendly smart devices.Dried bonito(DB)flake is a common food as well as a biomass material,and it can produce irregular motion in changed moisture,just like dancing.Inspired by this intriguing phenomenon,a cost-effective,biocom patible,and biodegradable moisture-responsive DB film actuator with a gradient structure is developed.The DB film actuator exhibits rapid and reversible bending deformation triggered by a humidity gradient with a high bending speed(40°s-1)and a maximum bending angle(180°).More-over,the DB film actuator shows large bending deformation(-71°to+51°)with a high actuation force(214.7 Pa)in response to changes in relative humidity.Furthermore,the actuation performance can be also tuned by adjusting the thickness of the film.Potential applications of this actuator,including smart grippers,crawling robots,and biomimetic flowers for visible humidity sensing,are demonstrated.More importantly,smart sweat-responsive wearables that automatically deform to promote sweat evaporation and convection during exercise are constructed based on the actuator,making it promising for adaptive personal thermal management.This work offers an easily processable,cost-effective,and environmentally benign strategy to construct moisture-responsive actuators for future eco-friendly smart devices.

Preparation of quasi-isotropic thermal conductive composites by interconnecting spherical alumina and 2D boron nitride flakes

Achieving thermal management composite material with isotropic thermal dissipation property by using an environmentally friendly and efficient method is one of the most challenging techniques as a traditional approach tending to form a horizontally arranged network within the polymer matrix or the preparation steps which are unduly cumbersome.What presented here is a closestack thermally conductive three-dimensional(3D)hybrid network structure prepared by a simple and green strategy that intercalating the modified aluminum oxide(m-Al_(2)O_(3))spheres of different sizes into the modified two-dimensional(2D)boron nitride(m-h-BN)flakes.An effective 3D network is created by the multi-dimensional fillers through volume exclusion and synergistic effects.The m-h-BN flakes facilitate in-plane heat transfer,while the variously sized m-Al_(2)O_(3)spheres insert into the gaps between adjacent m-h-BN flakes,which is conducive to the heat transfer in the out-of-plane direction.Additionally,strong interactions between the m-Al_(2)O_(3)and m-h-BN promote the effective heat flux inside the 3D hybrid network structure.The 3D hybrid composite displays favorable quasi-isotropic heat dissipation property(through-plane thermal conductivity of 2.2 W·m^(-1)·K^(-1)and in-plane thermal conductivity of 11.6 W·m^(-1)·K^(-1))in comparison with the single-filler composites.Furthermore,the hybrid-filler composite has excellent mechanical properties and thermal stability.The efficient heat dissipation capacity of the hybrid composite is further confirmed by a finite element simulation,which indicates that the sphere-flake hybrid structure possesses a higher thermal conductivity and faster thermal response performance than the single-filler system.The composite material has great potential in meeting the needs of emerging and advancing power systems.

Bioactive and nutritional characterization of modeled and optimized consumer-ready flakes from pseudocereal(Amaranthus viridis), high-protein soymeal and modified corn starch

Flake is consumed in many parts of the world.Flakes are majorly prepared from cereals.However,most flakes are deficient in protein and some other healthful substances.High-protein soymeal is rich in protein,mineral,amino acids,antioxidants,and other healthful substances.Formulating flakes with high-protein soymeal would improve the health status of consumers.This work investigated consumer-ready flake from amaranth,high-protein soymeal,and modified corn starch produced under the optimized condition and characterized with the aim to develop models that would give a healthful consumer-ready flake.Amaranthus viridis,corn,and soybean grains were sorted,wet-cleaned,and dried.Soybean grains were processed into high-protein soymeal,starch was extracted from corn grains while A.viridis grains were processed into flour.Formulated flour mixtures were developed into flakes using three-level factorial categoric factor design of response surface methodology.The flakes were analyzed using standard procedures.Optimal flour mixtures of high-protein soymeal(34.78 g/100 g),amaranth(56.52 g/100 g),and modified corn starch(8.70 g/100 g)were established.Results showed the optimized flakes contained per 100 g:29.05 g protein,6.00 g fat,4.10 g fibre,3.84 g ash,8.96 g moisture,249.74 mg calcium,272.35 mg magnesium,12.08 mg iron,618.42 mg phosphorus,6.41 mg niacin,4.85 mg pyridoxine,0.21 g tannin,1.85 mg phytate,2.96 mg alkaloids,908.24GAE total phenolics and 12.75mgRE flavonoids with good quality characteristics in amino acids.The study illustrated the feasibility of formulating quality consumer-ready flakes from amaranth,high-protein soymeal,and modified corn starch.The production process is scalable and could be employed for both domestic and industrial purposes.

Governing the Inclination Angle of Graphite Flakes in the Graphite Flake/Al Composites by Controlling the Al Particle Size via Flake Powder Metallurgy

The inclination angle of the flake particle has a significant impact on the in-plane thermal conductivity of composites.The graphite flake/Al composites(50 vol%)with different inclination angles were fabricated via flake powder metallurgy,and the results show that with increasing the size of Al particle from 25.6 to 50.7μm,the inclination angle of graphite flake decreases from 7.3°to 4.4°,while the in-plane thermal conductivity of composites increases from 473 to 555 Wm-1 K-1.Based on the rules of mixture,an effective model was established to qualify and quantify the relation between the inclination angle and the in-plane thermal conductivity of the corresponding composites.This model can also be applied to other flake particle-reinforced composites.

Achieving high yield of Ti3C2Tx MXene few-layer flakes with enhanced pseudocapacior performance by decreasing precursor size

Ti3C2Tx,a most studied member of MXene family,shows promise as a candidate electrode for pseudocapacitor due to its electronic conductivity and hydrophilic surface.However,the unsatisfactory yield of Ti3C2Tx few-layer flakes significantly restricted it in real applications.Here,we proposed a simple solution to boost the yield of Ti3C2Tx few-layer flakes by decreasing precursor size.When using the small500 mesh Ti3AlC2 powders as raw material,high yield of 65%was successfully achieved.Moreover,the asreceived small flakes also exhibit an enhanced pseudocapacior performance owing to their excellent electrical conductivity,expanded inte rlayer space and more O content on the surface.This work not only sheds light on the cost effective mass production of Ti3C2Tx few-layer flakes,but also provides an efficient solution for the design of MXene electrodes with high pseudocapacior performance.

Incorporating the magnetic alignment of GO composites into Pebax matrix for gas separation

The mixed matrix membranes(MMMs) were developed by incorporating graphite oxide(GO) flakes functionalized with iron oxide(Fe_3O_4) into Pebax matrix. The Pebax/Fe_3O_4–GO MMMs were used to separate CO_2/CH_4 and CO_2/N_2 gas mixture. The results showed that the MMMs with magnetic alignment presented the better gas separation performance than that of random arrangement of Pebax/Fe_3O_4–GO mixed matrix membranes. The reason was that the Fe_3O_4–GO flakes arranged magnetically in the membrane played a multiple role in improving the performance of MMMs. Firstly, under the action of the magnetic field,the magnetic alignment of Fe_3O_4–GO flakes in Pebax matrix constructed the shorter transfer path for gas molecule, increasing the CO_2 permeability. Secondly, the hydroxyl groups in GO flakes and the presence of Fe_3O_4 have stronger binding force for water, improving the CO_2 solubility selectivity. Thirdly, the better interaction between the magnetic alignment of GO composites and polymer matrix, reduced the interface defects. Especially, the optimum gas separation performance was obtained at the Fe_3O_4–GO flakes content of 3 wt% in Pebax matrix at vertical arrangement with selectivity of 47 and 75 for CO_2/CH_4 and CO_2/N_2, respectively, and CO_2 permeability of 538 Barrer at 0.2 MPa and room temperature.

Flexible Waterproof Piezoresistive Pressure Sensors with Wide Linear Working Range Based on Conductive Fabrics

Developing flexible sensors with high working performance holds intense interest for diverse applications in leveraging the Internet-of-things(IoT)infrastructures.For flexible piezoresistive sensors,traditionally most efforts are focused on tailoring the sensing materials to enhance the contact resistance variation for improving the sensitivity and working range,and it,however,remains challenging to simultaneously achieve flexible sensor with a linear working range over a high-pressure region(>100 kPa)and keep a reliable sensitivity.Herein,we devised a laserengraved silver-coated fabric as"soft"sensor electrode material to markedly advance the flexible sensor's linear working range to a level of 800 kPa with a high sensitivity of 6.4 kPa^-1 yet a fast response time of only 4 ms as well as long-time durability,which was rarely reported before.The integrated sensor successfully routed the wireless signal of pulse rate to the portable smartphone,further demonstrating its potential as a reliable electronic.Along with the rationally building the electrode instead of merely focusing on sensing materials capable of significantly improving the sensor's performance,we expect that this design concept and sensor system could potentially pave the way for developing more advanced wearable electronics in the future.

A Universal Atomic Substitution Conversion Strategy Towards Synthesis of Large‑Size Ultrathin Nonlayered Two‑Dimensional Materials

Nonlayered two-dimensional(2D)materials have attracted increasing attention,due to novel physical properties,unique surface structure,and high compatibility with microfabrication technique.However,owing to the inherent strong covalent bonds,the direct synthesis of 2D planar structure from nonlayered materials,especially for the realization of large-size ultrathin 2D nonlayered materials,is still a huge challenge.Here,a general atomic substitution conversion strategy is proposed to synthesize large-size,ultrathin nonlayered 2D materials.Taking nonlayered CdS as a typical example,large-size ultrathin nonlayered CdS single-crystalline flakes are successfully achieved via a facile low-temperature chemical sulfurization method,where pre-grown layered CdI2 flakes are employed as the precursor via a simple hot plate assisted vertical vapor deposition method.The size and thickness of CdS flakes can be controlled by the CdI2 precursor.The growth mechanism is ascribed to the chemical substitution reaction from I to S atoms between CdI2 and CdS,which has been evidenced by experiments and theoretical calculations.The atomic substitution conversion strategy demonstrates that the existing 2D layered materials can serve as the precursor for difficult-to-synthesize nonlayered 2D materials,providing a bridge between layered and nonlayered materials,meanwhile realizing the fabrication of large-size ultrathin nonlayered 2D materials.

片状气体放电电子束强度与能量分布的实验研究

片状气体放电电子束强度与能量分布的实验研究罗宗南，崔一平，陈松生，杨正名（东南大学电子工程系．南京２１００１８）气体放电电子束强度高，能量大，在微电子、光电子、加工、材料科学、等离子化学以及表面处理等方面有着广泛的应用前景，加以成本低廉、操作方便，是...