A Review on Binderless Tungsten Carbide: Development and Application

WC-Co alloys have enjoyed great practical significance owing to their excellent properties during the past decades.Despite the advantages,however,recently there have been concerns about the challenges associated with the use of Co,i.e.price instability,toxicity and properties degeneration,which necessitates the fabrication of binderless tungsten carbide(BTC).On the other hand,BTC or BTC composites,none of them,to date has been commercialized and produced on an industrial scale,but only used to a limited extent for specialized applications,such as mechanical seals undergoing high burthen as well as high temperature electrical contacts.There are two challenges in developing BTC:fully densifying the sintered body together with achieving a high toughness.Thus,this review applies towards comprehensively summarize the current knowledge of sintering behavior,microstructure,and mechanical properties of BTC,highlighting the densification improving strategies as well as toughening methods,so as to provide reference for those who would like to enhance the performance of BTC with better reliability advancing them to further wide applications and prepare the material in a way that is environment friendly,harmless to human health and low in production cost.This paper shows that the fabrication of highly dense and high-performance BTC is economically and technically feasible.The properties of BTC can be tailored by judiciously selecting the chemical composition coupled with taking into careful account the effects of processing techniques and parameters.

Quantum cascade superluminescent light emitters with high power and compact structure

Quantum cascade(QC)superluminescent light emitters(SLEs)have emerged as desirable broadband mid-infrared(MIR)light sources for growing number of applications in areas like medical imaging,gas sensing and national defense.However,it is challenging to obtain a practical high-power device due to the very low efficiency of spontaneous emission in the intersubband transitions in QC structures.Herein a design of^5μm SLEs is demonstrated with a two-phonon resonancebased QC active structure coupled with a compact combinatorial waveguide structure which comprises a short straight part adjacent to a tilted stripe and to a J-shaped waveguide.The as-fabricated SLEs achieve a high output power of 1.8 mW,exhibiting the potential to be integrated into array devices without taking up too much chip space.These results may facilitate the realization of SLE arrays to attain larger output power and pave the pathway towards the practical applications of broadband MIR light sources.

Preparation and characterization of calcium aluminate by chemical synthesis

Saturated Ca（OH）2 and AlCl3 solutions were used to synthesize calcium aluminate hydrate precipitates at room temperature; high purity calcium aluminate powders with stable phases were made by calcination of the precursors at a temperature as low as 1100℃. PSD and BET analysis revealed the particles with sizes ranging from submicrometer to several micrometers and with a specific area of 13 m^2/g. The measurement of hydraulic exotherm revealed that the exothennal rate is in peak for about 2 h. The exothermal quantities are 449.24 J/g at 12 h and 488.38 J/g at 24 h. Its strength development is quick and the 1 day curing strength is almost equal to 100% of the 3 days curing strength in the mortar test.

Research on the Fe-silicon nitride material self-producing N_2 at high temperature

The Fe silicon nitride synthesized by flashing combustion process was studied to determine the reaction temperature between Fe and silicon nitride, the account of N2 given out in the course of the reaction, and the change of the microstructure during calcination. The results showed that at 1127.2℃ the Fe-silicon nitride self-reacts and releases N2 and under 101.3 kPa the volume of N2 given out in the course of the reaction is 20 times more than that of the starting material. N2 is produced quickly, and completes in several decade seconds. With the producing of N2, the structure of Silicon Nitride around Fe becomes loose and porous, or cracks are formed by the reaction between Fe and silicon nitride. So if it is made use of that Fe-silicon nitride self-producing N2 at the high temperature, the performance of the material on a base of Fe-silicon nitride could be greatly improved.

Research on rail wear of small radius curve in EMU depot

Purpose–With the help of multi-body dynamics software UM,the paper uses Kik–Piotrowski model to simulate wheel-rail contact and Archard wear model for rail wear.Design/methodology/approach–The CRH5 vehicle-track coupling dynamics model is constructed for the wear study of rails of small radius curves,namely 200 and 350 m in Guangzhou East EMU Depot and those 250 and 300 m radius in Taiyuan South EMU Depot.Findings–Results show that the rail wear at the straight-circle point,the curve center point and the circlestraight point follows the order of center point>the circle-straight point>the straight-circle point.The wear on rail of small radius curves intensifies with the rise of running speed,and the wearing trend tends to fasten as the curve radius declines.The maximum rail wear of the inner rail can reach 2.29 mm,while that of the outer rail,10.11 mm.Originality/value–With the increase of the train passing number,the wear range tends to expand.The rail wear decreases with the increase of the curve radius.The dynamic response of vehicle increases with the increase of rail wear,among which the derailment coefficient is affected the most.When the number of passing vehicles reaches 1 million,the derailment coefficient exceeds the limit value,which poses a risk of derailment.

Effect of a Magnetic Field on the Preparation of Silver Nanowires Using Solid Electrolyte Thin Films

在 silvernanowires 的准备的一个外部磁场的效果是 studied.The 银 nanowires 被两个都使用一个直接电流( DC )电场和磁性的 field.The RbAg_4I_5 thinfilms 用稳固的电解质 RbAg_4I_5 thinfilms 综合，它被免职在 NaCIsubstrate 上在房间温度和气压准备，在 preparationprocess.When 期间被用于在二个 Ag 电极之间的Ag^+离子的转移仅仅 DC 电场被使用，

Advances in Research on Hypoglycemic Functions of Polysaccharides from Medicinal and Edible Plants

Plant polysaccharides have an excellent hypoglycemic effect through various ways such as promoting insulin secretion,improving insulin resistance,regulating related enzyme activities,improving sugar,protein and fat metabolism,promoting hepatic glycogen synthesis,inhibiting gluconeogenesis,and improving immune system function and resistance.At present,more than 200 polysaccharides derived from traditional Chinese medicines have been reported,and most of them are isolated and purified from plants.With the deepening of research on plant polysaccharides,more and more attention has been paid to the development of safe and economical natural hypoglycemic products.This paper first introduced the hypoglycemic effects of Folium Mori polysaccharides,Cucurbita moschata polysaccharides,Momordica charantia polysaccharides,Dioscoreae Rhizoma polysaccharides and Camellia sinensis O.Kuntze polysaccharides.Besides,it discussed the utilization ways of hypoglycemic plant polysaccharides,and the prospects of applying polysaccharide hypoglycemic effect to diabetes treatment,so as to provide reference for the research and utilization of plant polysaccharide hypoglycemic effects and the development of natural hypoglycemic foods.

High-performance multifunctional(Hf^(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)Zr_(0.2))C high-entropy ceramic reinforced with low-loading 3D hybrid graphene–carbon nanotube

There has been growing interest in the high-entropy ceramic(HEC)recently owing to its tailorable compositions and microstructures,versatile properties,together with promising structural and functional applications.However,inferior fracture toughness(KIC)and damage tolerance restricted many practical applications of the HEC.Herein,we addressed this challenge by incorporating a threedimensional graphene–carbon nanotube(3D G–CNT)as toughening agent in(Hf_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)Zr_(0.2))C.The resulting enhanced 3D G–CNT/(Hf_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)Zr_(0.2))C featured an outstanding toughness of 8.23 MPa·m^(1/2),while remaining superior strength(763 MPa)and hardness(24.7 GPa).An ultralow friction coefficient(0.15)coupled with an ultralow wear rate(w,2.6×10^(−7) mm^(3)/(N·m))in the 3D G–CNT/(Hf_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)Zr_(0.2))C was obtained primarily as a function of lubricating scrolls,in which two-dimensional(2D)graphene acted as a tribolayer,and one-dimensional(1D)carbon nanotubes acted as nano ball bearings embedded inside.Strikingly,the 3D G–CNT/(Hf_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)Zr_(0.2))C exhibited rather low thermal conductivity(κ)yet excellent electrical conductivity(σ,1.3×10^(6) S/m)in comparison with the pure(Hf_(0.2)Nb_(0.2)Ta_(0.2)Ti_(0.2)Zr_(0.2))C.This study provided great potential for maximizing the physical and functional properties of the HEC for various applications.

Progress in densification and toughening of high entropy carbide ceramics

High entropy carbide ceramics(HECC)are solid solution of inorganic compounds with five or more prin-cipal metal cations.Research interests in HECC are dramatically sparked by the enormous possibilities in composition-microstructure-property tailoring.As widely acknowledged,HECCs enjoy higher hardness and oxidation/corrosion/wear resistance,as well as lower thermal conductivity than conventional engi-neering carbide ceramics,making them the most potential candidates for state-of-the-art structural and functional applications in extreme service conditions.Despite the advantages,however,the poor den-sification coupled with low fracture toughness significantly limited the practical applications of HECC.Adding to the difficulty,the literature available for toughening HECC is woefully limited.In considera-tion of this insufficiency,we apply towards offer a comprehensive,critical review of the mechanical be-havior of HECC,highlighting the densification enhancing strategies(carbon content,sintering techniques,grain size,sintering aids,etc.)as well as toughening methods including particle toughening,whisker/fiber toughening,synergistic toughening,graphene-carbon nanotube toughening,to further the service reliabil-ity of HECC in practical industrial applications.Furthermore,despite some significant successes,important directions for further development of HECC are given as multi-dimensional gradient HECC,additive man-ufacturing of HECC,processing-composition-microstructure-property relationship prediction and genomes of HECC based on machine learning,and high-throughput computing,etc.

In situ establishment of Co/MoS_(2) heterostructures onto inverse opal‐structured N,S‐doped carbon hollow nanospheres:Interfacial and architectural dual engineering for efficient hydrogen evolution reaction

Rational design of low‐cost and high‐efficiency non‐precious metal‐based catalysts toward the hydrogen evolution reaction(HER)is of paramount significance for the sustainable development of the hydrogen economy.Interfacial manipulationinduced electronic modulation represents a sophisticated strategy to enhance the intrinsic activity of a non‐precious electrocatalyst.Herein,we demonstrate the straightforward construction of Co/MoS_(2) hetero‐nanoparticles anchored on inverse opal‐structured N,S‐doped carbon hollow nanospheres with an ordered macroporous framework(denoted as Co/MoS_(2)@N,S-CHNSs hereafter)via a templateassisted method.Systematic experimental evidence and theoretical calculations reveal that the formation of Co/MoS_(2) heterojunctions can effectively modulate the electronic configuration of active sites and optimize the reaction pathways,remarkably boosting the intrinsic activity.Moreover,the inverse opal‐structured carbon substrate with an ordered porous framework is favorable to enlarge the accessible surface area and provide multidimensional mass transport channels,dramatically expediting the reaction kinetics.Thanks to the compositional synergy and structural superiority,the fabricated Co/MoS_(2)@N,S-CHNSs exhibit excellent HER activity with a low overpotential of 105mV to afford a current density of 10 mA/cm^(2).The rationale of interface manipulation and architectural design herein is anticipated to be inspirable for the future development of efficient and earth‐abundant electrocatalysts for a variety of energy conversion systems.

Pharmacokinetic study of salvianolic acid D after oral and intravenous administration in rats

A sensitive,specific and rapid LC-MS method was developed and validated for the determination of salvianolic acid D(Sal D) in rat plasma.This method used a single quadrupole mass spectrometer with an electrospray ionization(ESI) source.A single ion monitoring scanning(SIM) mode was employed.It showed good linearity over the concentration range from 3.3 to 666.7 ng/m L for the determination of Sal D.The R.S.D.% of intra-day and inter-day precision values were no more than7.69%,and the accuracy was within 91% 104% at all quality control levels.This LC-MS method was applied to the pharmacokinetic study of Sal D in rats.A two-compartmental model analysis was employed.The plasma concentrations at 2 min(C2min) were 5756.067719.61,11,073.0171783.46 and21,077.5875581.97 μg/L for 0.25,0.5 and 1 mg/kg intravenous injection,respectively.The peak plasma concentration(Cmax) was 333.08761.21 μg/L for 4 mg/kg oral administration.The area under curve(AUC0 t) was 14,384.37978443.184,22,813.369711,860.823,46,406.122727,592.645 and8201.74074711.961 μg/L h for intravenous injection(0.25,0.5 and 1 mg/kg) and oral administration(4 mg/kg),respectively.The bioavailability of Sal D was calculated to be 4.159%70.517%.

Synthesis and evaluation of peptide-fentanyl analogue conjugates as dualμ/δ-opioid receptor agonists for the treatment of pain

Novel peptide-fentanyl analogue conjugates were synthesized by the covalent coupling of carfentanyl derivatives to the C-terminus or N-terminus of the conformationally constrained dermorphin tetrapeptide BVD03 via a chemical linker.The carfentanyl-related analogues displayed distinct binding and functional activities atμ/δopioid receptors(MOR/DOR)and antinociceptive effects when conjugated to the peptide.The most potent compound,SW-LJ-11,displayed mixed MOR/DOR agonist properties in the low nanomolar range and significant analgesic efficacy in vivo in four classic mouse models of pain.Interestingly,SW-LJ-11 did not exhibit any physical dependence or respiratory depression,in contrast to an equipotent analgesic dose of morphine or BVD03,indicating that the use of opioid peptide-fentanyl analogue conjugates as dual MOR/DOR agonists may be a promising strategy for obtaining safer opioids.

Differential effects of Rho-kinase inhibitor and angiotensin Ⅱ type-1 receptor antagonist on the vascular function in hypertensive rats induced by chronic L-NAME treatment

Little attention has been paid to the effect of Rho-kinase inhibitor on the vascular dysfunction of nitric oxide-deficient hypertension.We aimed to investigate whether the Rho-kinase inhibitor fasudil showed beneficial effect on the vascular dysfunction of the N^(G)-nitro-L-arginine methyl ester(L-NAME)treated rat,as well as to compare the differential effects of fasudil and angiotensin Ⅱ receptor antagonist valsartan on vascular function.In the present study,both valsartan and fasudil exerted antihypertensive action on the L-NAME-treated rats,while only va lsartan attenuated the cardiac hypertrophy.Treatment with valsartan showed improvement on vascular reactivity to norepinephrine,KCl and CaCl_(2),whereas fasudil therapy showed little effect on vasoconstriction.Endothelium-dependent vasodilation to acetylcholine was reduced in the NO-deficient group but was normalized by the fasudil therapy.The increased expression of RhoA and Rho-kinase(ROCK)in the vasculature was corrected well to normal level by either valsartan or fasudil administration,which seemed to be at least partially responsi ble for the beneficial effect of the drug infusion.These findings suggest that the angiotensin Ⅱ receptor antagonist interferes more with the contractile response than Rho-kinase inhibitor,whereas inhibition of Rho-kinase activity exhibits a better improvement on vasorelaxation than blockade of angiotensin Ⅱ receptor.

Microstructure, mechanical properties and toughening mechanism of directional Fe2B crystal in Fe-B alloy with trace Cr addition

Exploring the effective way to improve Fe2 B's toughness has always been the hot topic in the researches of Fe-B wear resistant alloys.In the present work,the effects of Cr on the microstructure,mechanical properties and lattice structure of directional Fe2 B have been investigated.The affecting mechanism of Cr addition has been discussed according to the experimental and first-principle calculation analysis.The results show Cr addition can improve the toughness of directional Fe2 B on the longitudinal sections perpendicular to(002) crystal plane,without sacrificing the hardness distinctly.The toughening mechanism by Cr substitution has been revealed:Cr addition enriches the electron density between the B atoms along [002] direction,contributing to the shrinkage of the bond length and the enhancement of the bond strength of B-B bonds.The obtained results provide insight into the intrinsic reason for toughening Fe2 B by Cr doping.