In order to lower the boriding temperature of hot work steel H13, method of surface mechanical attrition treatment （SMAT）, which can make the grain size of the surface reach nano-scale, was used before pack boriding...In order to lower the boriding temperature of hot work steel H13, method of surface mechanical attrition treatment （SMAT）, which can make the grain size of the surface reach nano-scale, was used before pack boriding. The growth of the boride layer was studied in a function of boriding temperature and time. By TEM （transmission electron microscopy）, SEM （scanning electron microscopy）, XRD （x-ray diffraction） and microhardness tests, the grain size, thermal stability of the nano-structured （NS） surface and the thickness,appearance, phases of the surface boride layer were studied. Kinetic of boriding was compared between untreated samples and treated samples. Results showed that after SMAT, the boride layer was thicker and the hardness gradient was smoother. Furthermore, after boriding at a low temperature of 700℃ for 8 h, a boride layer of about 5 μm formed on the NS surface. This layer was toothlike and wedged into the substrate, which made the surface layer combine well with the substrate. The phase of the boride layer was Fe2B. Research on boriding kinetics indicated that the activation energy was decreased for the treated samples.展开更多
Microwave boriding layer microstructure of carbon steels and its diffusion mechanics were studied. The results show that the existence of microwave field in the boriding can＇t change the growth mechanics of boriding ...Microwave boriding layer microstructure of carbon steels and its diffusion mechanics were studied. The results show that the existence of microwave field in the boriding can＇t change the growth mechanics of boriding layer. Compared with conventional boriding, if the treatment temperature and time remain constantly, the descend rate of the boriding layer thickness with the increase of carbon content of steel is smaller. The diffusion activation energy ofT8 steel is 2.6× 10^5 J/mol between the temperature of 750 ℃ and 900 ℃ in microwave field, which is in the same order of conventional boriding.展开更多
Gas-boriding in N2-H2-BCl3 atmosphere resulted in the formation of a thick layer on Inconel 600 alloy.The microstructure of layer produced at 920℃for 2 h consisted of a mixture of chromium borides and nickel borides....Gas-boriding in N2-H2-BCl3 atmosphere resulted in the formation of a thick layer on Inconel 600 alloy.The microstructure of layer produced at 920℃for 2 h consisted of a mixture of chromium borides and nickel borides.The objective of investigations was to determine the influence of the chemical and phase compositions of borided layer on its mechanical properties.The nanoindentation was carried out using Berkovich diamond tip under a load of 50 m N.The gas-borided layer was characterized by high indentation hardness HIT from 1542.6 HV to 2228.7 HV and high elastic modulus EIT from 226.9 to 296.4 GPa.It was found that the mixture with higher percentage of chromium borides was the reason for the increase in HIT and EIT values.The fracture toughness(KC)was measured using Vickers microindentation technique under a load of 0.98 N.The presence of high compressive stresses in normal direction to the top surface caused the strong anisotropy of the borided layer,in respect of fracture toughness.The high difference between the lowest(0.5763 MPa·m^1/2)and the highest(4.5794 MPa·m^1/2)fracture toughness was obtained.This situation was caused by the differences in chemical and phase compositions of tested areas,presence of porosity and residual stresses.Generally,the higher KC values were obtained in areas with lower chromium content.展开更多
Plasma boriding treatment was carried out at low temperature for the hot work die steel H13 assisted by surface nanocrystallization technology in this paper.At the same time,the thermal fatigue property of it was inve...Plasma boriding treatment was carried out at low temperature for the hot work die steel H13 assisted by surface nanocrystallization technology in this paper.At the same time,the thermal fatigue property of it was investigated through thermal fatigue testing with 3000 continuous cycles from room temperature to 700℃.The changes of structure and grain size in surface layer were characterized by high-resolution transmission electron microscopy(HRTEM).After plasma boriding at 580℃ for 4 h,the phase composition,morphology and in-situ nanomechanical property of boride layer were investigated by X-ray diffraction spectroscopy(XRD),scanning electron microscope(SEM),nanoindentation test,respectively.The results show that the boride layer with about thickness of 5μm is composed with two phases of Fe2B and FeB.The nanohardness of boride layer is as high as 21 GPa.Furthermore,thermal fatigue testing shows that the boride layer with excellent oxidation resistance and mechanical strength at elevated temperatures could effectively delay the crack initiation and impede the crack propagation.Therefore,the thermal fatigue property of H13 can be remarkably improved.展开更多
To improve the surface performance of TB2 alloy,pack boriding was performed at 1100℃ for 20 h with 4 wt.%La_(2)O_(3).The composition and thickness of boride layer and corrosion and wear properties of borided TB2 allo...To improve the surface performance of TB2 alloy,pack boriding was performed at 1100℃ for 20 h with 4 wt.%La_(2)O_(3).The composition and thickness of boride layer and corrosion and wear properties of borided TB2 alloy were measured.The results show that La_(2)O_(3) can promote the growth,continuity,and compactness of boride layer,and the length of TiB whisker increases from 16.80 to 21.84μm.The reason is that La_(2)O_(3) can react with B to form La−B active groups and further to improve the growth of the boride layer.The wear and corrosion resistances of TB2 alloy are enhanced by boriding with La_(2)O_(3).The wear mechanisms are adhesive wear and abrasive wear for unborided and borided TB2 alloys,respectively,and the corrosion mechanism is changed from local corrosion(unborided TB2 alloy)to uniform corrosion(borided TB2 alloy).展开更多
Boriding of the Ti-Al intermetallic GE48-2-2 at 1273 K for 10 hours was performed. In order to ensure that no any serious alteration occurred in the substrate, it was previously examined with X-Ray Diffractometry (XRD...Boriding of the Ti-Al intermetallic GE48-2-2 at 1273 K for 10 hours was performed. In order to ensure that no any serious alteration occurred in the substrate, it was previously examined with X-Ray Diffractometry (XRD), after it has undergone an annealing process at the temperature of boronizing. Subsequently, we examined the coating with XRD and Scanning Electron Microscopy, in order to characterize its structure and morphology. A dense TiΒ2 layer, 10 - 15 μm thick, was formed, but also Cr2B3 and NbN, BN and some Ti-Al phases were detected. Efforts were undertaken to focus on influence of the substrate modification, towards the quality of the coating.展开更多
The mechanical behavior and wear of the different hardened phases with bore-induced changes in AISI 4340 and AISI D2 steels were investigated. The hardness and modulus of elasticity were measured by nanoindentation an...The mechanical behavior and wear of the different hardened phases with bore-induced changes in AISI 4340 and AISI D2 steels were investigated. The hardness and modulus of elasticity were measured by nanoindentation and the values obtained for the layers in AISI D2 steel were 18 GPa and 325 GPa in the Fe<sub>2</sub>B boride phase, and 20 GPa and 360 GPa in the FeB boride phase, respectively. The AISI 4340 steel presented mainly the Fe<sub>2</sub>B phase. It was then possible to analyze the coefficient of friction obtained in the Fe<sub>2</sub>B phase of the steel AISI 4340 presented a range of 0.04 to 0.06. The AISI D2 steel presents two different phases in the boride layer being the coefficient of friction higher for the test in the FeB phase than for Fe<sub>2</sub>B, and the values vary from 0.065 to 0.075. These parameters were obtained with micro-wear tests. No adhesion failures were observed after the sliding tests in the interface of the two different boride layers. Cracks in the FeB phase after the sliding test were much more frequent.展开更多
A nanostructured layer was fabricated on the surface of steel Q235 by using fast multiple rotation rolling( FMRR). The Cr-Rare earth-boriding process was carried out followed at different temperatures.Experimental res...A nanostructured layer was fabricated on the surface of steel Q235 by using fast multiple rotation rolling( FMRR). The Cr-Rare earth-boriding process was carried out followed at different temperatures.Experimental results showed that the thickness of the boride layer was significantly increased by surface nanocrystallization. The morphology of the boride layer was saw-toothed. An uniform,continuous and dense boride layer was obtained and adhered well to the substrate. The penetrating speed of FMRR specimens was enhanced by 1.9,1.7 and 1.5 times when the Cr-Rare earth-boriding temperature was 843,873 and 923 K.Severe plastic deformation,which grain size was approximately 100 nm,was observed on steel Q235 surface.Mechanism of Cr-Rare earth-boriding was also studied.展开更多
Selective laser melting(SLM)is a cost-effective 3 D metal additive manufacturing(AM)process.However,AM 316 L stainless steel(SS)has different surface and microstructure properties as compared to conventional ones.Bori...Selective laser melting(SLM)is a cost-effective 3 D metal additive manufacturing(AM)process.However,AM 316 L stainless steel(SS)has different surface and microstructure properties as compared to conventional ones.Boriding process is one of the ways to modify and increase the surface properties.The aim of this study is to predict and understand the growth kinetic of iron boride layers on AM 316 L SS.In this study,the growth kinetic mechanism was evaluated for AM 316 L SS.Pack boriding was applied at 850,900 and 950℃,each for 2,4 and 6 h.The thickness of the boride layers ranged from(1.8±0.3)μm to(27.7±2.2)μm.A diffusion model based on error function solutions in Fick’s second law was proposed to quantitatively predict and elucidate the growth rate of FeB and Fe_(2)B phase layers.The activation energy(Q)values for boron diffusion in FeB layer,Fe_(2)B layer,and dual FeB+Fe_(2)B layer were found to be 256.56,161.61 and 209.014 kJ/mol,respectively,which were higher than the conventional 316 L SS.The findings might provide and open new directions and approaches for applications of additively manufactured steels.展开更多
Two-dimensional(2D)transition metal borides(MBenes)have emerged as a rising star and hold great potential promise for catalysis and metal ion batteries owing to a well-defined layered structure and ex-cellent electric...Two-dimensional(2D)transition metal borides(MBenes)have emerged as a rising star and hold great potential promise for catalysis and metal ion batteries owing to a well-defined layered structure and ex-cellent electrical conductivity.Unlike well-studied graphene,perovskite and MXene materials in various fields,the research about MBene is still in its infancy.The inadequate exploration of efficient etching methods impedes their further study.Herein,we put forward an efficient microwave-assisted hydrother-mal alkaline solution etching strategy for exfoliating MoAlB MAB phase into 2D MoB MBenes with a well accordion-like structure,which displays a remarkable electrochemical performance in sodium ion batter-ies(SIBs)with a reversible specific capacity of 196.5 mAh g^(-1)at the current density of 50 mA g^(-1),and 138.6 mAh g^(-1)after 500 cycles at the current density of 0.5 A g^(-1).The underlying mechanism toward excellent electrochemical performance are revealed by comprehensive theoretical simulations.This work proves that MBene is a competitive candidate as the next generation anode of sodium ion batteries.展开更多
Lithium-sulfur(Li-S)batteries hold great promise for next-generation energy storage,yet suffer from sluggish redox kinetics and polysulfide shuttling.Herein,a novel Ni_(3)S_(2)/Ni_(2)B heterostructure is developed to ...Lithium-sulfur(Li-S)batteries hold great promise for next-generation energy storage,yet suffer from sluggish redox kinetics and polysulfide shuttling.Herein,a novel Ni_(3)S_(2)/Ni_(2)B heterostructure is developed to improve sulfur electrochemistry by synergistically enhancing polysulfide fixation and catalytic conversions.Fabricated through mild sequential boronation and sulfurization,this hybrid nanocatalyst integrates the strong polysulfide adsorbability and high conductivity of Ni_(2)B with the high catalytic activity of Ni_(3)S_(2).More importantly,the as-constructed heterointerface inspires new,highly catalytic sites that smooth consecutive sulfur conversions with lower energy barriers,while the built-in electric fields promote directional charge transfer,collectively contributing to fast-kinetic and highly efficient sulfur redox reactions.As a result,Li-S cells incorporating the Ni_(3)S_(2)/Ni_(2)B nanocatalyst exhibit excellent cyclability,with minimal capacity decay of 0.017%per cycle over 900 cycles at 1 C and a superb rate capability of up to 5 C.Even under demanding conditions,such as a high sulfur loading of 5.0 mg cm^(-2)and a low electrolyte-to-sulfur(E/S)ratio of 4.8 mL g^(-1),high capacity and cyclability are maintained,highlighting the great potential of this unique heterointerface engineering in advancing high-performance and practically viable Li-S batteries.展开更多
Transition metal borides(TMBs)are a new class of promising electrocatalysts for hydrogen generation by water splitting.However,the synthesis of robust all-in-one electrodes is challenging for practical applications.He...Transition metal borides(TMBs)are a new class of promising electrocatalysts for hydrogen generation by water splitting.However,the synthesis of robust all-in-one electrodes is challenging for practical applications.Herein,a facile solid-state boronization strategy is reported to synthesize a series of self-supported TMBs thin films(TMB-TFs)with large area and high catalytic activity.Among them,MoB thin film(MoB-TF)exhibits the highest activity toward electrocatalytic hydrogen evolution reaction(HER),displaying a low overpotential(η10=191 and 219 mV at 10 mA cm^(−2))and a small Tafel slope(60.25 and 61.91 mV dec^(−1))in 0.5M H_(2)SO_(4)and 1.0M KOH,respectively.Moreover,it outperforms the commercial Pt/C at the high current density region,demonstrating potential applications in industrially electrochemical water splitting.Theoretical study reveals that both surfaces terminated by TM and B atoms can serve as the active sites and the H*binding strength of TMBs is correlated with the p band center of B atoms.This work provides a new pathway for the potential application of TMBs in largescale hydrogen production.展开更多
The energy density of thin-film lithium batteries(TFLBs)is predominantly determined by the average voltage and specific capacity,however,the mechanism of regulating the voltage plateaus of the film electrodes is not w...The energy density of thin-film lithium batteries(TFLBs)is predominantly determined by the average voltage and specific capacity,however,the mechanism of regulating the voltage plateaus of the film electrodes is not well understood.In this study,three boride films(Co–B,Fe–B,and Co–Fe–B alloys)with different thick-nesses were fabricated to enhance the specific capacity and voltage stability of TFLBs.By analyzing the cycling performance,redox peak evolution,and capacitive contribution,the thickness-dependent lithiation behavior of the thin/thick films was elucidated.Theoretical simulations and electrochemical analysis were conducted to investigate how the lithiation behaviors affected the voltage profiles of the film electrodes.In addition,the various-thickness CoB films were compared in all-solid-state TFLBs,demonstrating the universality and practicability of this simple regulation strategy to develop high-performance energy storage devices.展开更多
Multi-component transition group metal borides(MMB_(2))have become a research hotspot due to their new composition design concepts and superior properties compared with conventional ceramics.Most of the current method...Multi-component transition group metal borides(MMB_(2))have become a research hotspot due to their new composition design concepts and superior properties compared with conventional ceramics.Most of the current methods,however,are complicated and time-consuming,the mass production remains a chal-lenge.Herein,we proposed a new high-efficiency strategy for synthesis of MMB_(2)using molten aluminum as the medium for the first time.The prepared Al-containing multi-component borides(TiZrHfNbTa)B_(2)microcrystals had a homogeneous composition with a hexagonal AlB_(2)structure and ultra-high hardness value of∼35.3 GPa,which was much higher than data reported in the literature and the rule of mix-ture estimations.Furthermore,combined with the First-principles calculation results,we found that the Poisson’s ratio(v)values exhibit a clearly ascending trend from 0.17 at VEC=3.5 to 0.18 at VEC=3.4,then to 0.201 at VEC=3.2 with the increasing of Al content.This indicates that the intrinsic toughness of multi-component boride microcrystals is obviously enhanced by the trace-doped Al elements.Besides,the fabricated Al-containing multi-component boride microcrystals have superior oxidation activation en-ergy and structural stability.The enhanced oxidation resistance is mainly attributed to the formation of a protective Al2 O3 oxide layer and the lattice distortion,both of which lead to sluggish diffusion of O_(2).These findings propose a new unexplored avenue for the fabrication of MMB_(2)materials with supe-rior comprehensive performance including ultra-hardness and intrinsically improved thermo-mechanical properties.展开更多
Owing to the orbital hybridization between the transition metal and the B element and the electron-trapping effect of the B ele-ment,transition metal borides are considered very promising materials for energy catalysi...Owing to the orbital hybridization between the transition metal and the B element and the electron-trapping effect of the B ele-ment,transition metal borides are considered very promising materials for energy catalysis.In this work,an amorphous scaly high-entropy boride(HEB)with electron traps was designed and fabricated via a facile reduction method to improve the hydrogen storage properties of magnesium hydride(MgH_(2)).For dehydrogenation,the onset temperature of MgH_(2)+10wt%HEB was dropped to 187.4℃;be-sides,the composite exhibited superior isothermal kinetics and the activation energy of the composite was reduced from(212.78±3.93)to(65.04±2.81)kJ/mol.In addition,MgH_(2)+10wt%HEB could absorb hydrogen at 21.5℃,and 5.02wt%H_(2) was charged in 50 min at 75℃.For reversible hydrogen storage capacity tests,the composite maintained a retention rate of 97%with 6.47wt%hydrogen capacity after 30 cycles.Combining microstructure evidence with hydrogen storage performance,the catalytic mechanism was proposed.During ball milling,scaly high-entropy borides riveted a large number of heterogeneous active sites on the surface of MgH_(2).Driven by the cocktail effect as well as the orbital hybridization of metal borides,numerous active sites steadily enhanced the hydrogen storage reactions in MgH_(2).展开更多
Multifunctional carbon fibers(C_(f))/ZrB_(2) based composites were synthesized through a series of processes termed as IVI including sequential slurry injection,vacuum impregnation,pyrolysis and reimpregnation cycles,...Multifunctional carbon fibers(C_(f))/ZrB_(2) based composites were synthesized through a series of processes termed as IVI including sequential slurry injection,vacuum impregnation,pyrolysis and reimpregnation cycles,which facilitated the effective incorporation of ZrB_(2) powder into the carbon fiber preform.A single IVI cycle reduced the porosity of the preform from∼77%to∼40%.Microstructural analysis revealed a preferential distribution of ZrB2 powders within random layers and pyrolytic carbon effectively bridging the ceramic particles and fibers.Due to the hierarchical 0°/90°carbon fiber architecture,as fabricated Cf/ZrB_(2) composites exhibited anisotropy in mechanical and physical properties.Vertically oriented com-posites demonstrated higher compressive strain and low thermal conductivity(1.00-2.59 W m^(−1) K^(−1) from 298 to 1173 K).In contrast,horizontally oriented specimens exhibited higher compressive strength(60.77±20.30 MPa)and thermal conductivity(1.6-4.5 W m^(−1) K^(−1) from 298 to 1173 K).Furthermore,the continuous Cf endowed the composites with a positive temperature-dependent electrical conductiv-ity characteristic,not only contributed to their higher electrical conductivity values,but also was helpful for maintaining the excellent EMI shielding effectiveness(19.80-22.51 dB)of Cf/ZrB_(2) up to 800℃without obvious degradation.Considering the low-density characteristics of as-prepared composites,their specific performance metrics demonstrate good competitiveness compared to those fabricated via alternative processes.展开更多
Amorphous bimetallic borides,as a new generation of catalytic nanomaterials with modifiable electronic properties,are of great importance in the design of high-efficiency catalysts for NaBH_(4) hydrolysis.This study s...Amorphous bimetallic borides,as a new generation of catalytic nanomaterials with modifiable electronic properties,are of great importance in the design of high-efficiency catalysts for NaBH_(4) hydrolysis.This study synthesizes an amorphous Co_(3)B-Mo_(2)B_(5) catalyst using a self-sacrificial template strategy and NaBH_(4) reduction for both NaBH_(4) hydrolysis and the reduction of 4-nitrophenol.The catalyst delivers an impressive hydrogen generation rate of 7690.5 mL min^(-1) g^(-1) at 25℃,coupled with a rapid reaction rate of 0.701 min^(-1) in the reduction of 4-nitrophenol.The enhanced catalytic performance is attributed to the unique amorphous structure and the electron rearrangement between Co_(3)B and Mo_(2)B_(5).Experimental and theoretical analyses suggest electron transfer from Co_(3)B to the Mo_(2)B_(5),with the electron-deficient Co_(3)B site favoring BH_(4)^(-) adsorption,while the electron-rich Mo_(2)B_(5) site favoring H_(2)O adsorption,Furthermore,Co_(3)B-Mo_(2)B_(5) demonstrated potential for energy applications,delivering a power output of 0.3 V in a hydrogen-air fuel cell.展开更多
The Mg(NH_(2))_(2)-2LiH composite system is a promising vehicle-mounted hydrogen sto rage material,but its application is limited due to serious thermodynamic and kinetic barriers.Adding additives can effectively opti...The Mg(NH_(2))_(2)-2LiH composite system is a promising vehicle-mounted hydrogen sto rage material,but its application is limited due to serious thermodynamic and kinetic barriers.Adding additives can effectively optimize their hydrogen absorption and desorption kinetics and thermodynamic performance.In this work the comprehensive hydrogen storage performance of Mg(NH_(2))_(2)-2LiH with extremely small nano rare earth borides is improved,and a series of characterization methods and density functional theory(DFT)calculation systems was combined to study its hydrogen storage improvement mechanism.The research results show that the method of adding 5 wt%molten salt to prepare nano CeB_(6)(24.5 nm)can significantly reduce the initial hydrogen absorption/release temperature of Mg(NH_(2))_(2)-2LiH from 110/130to 45/90℃,inhibit the generation of ammonia by-products,and improve hydrogen purity.Under lowtemperature hydrogen absorption conditions at 120℃,the improved sample can absorb 2.81 wt%hydrogen gas,with a hydrogen absorption capacity more than 3.5 times of the unmodified sample.The amount of hydrogen released at 150℃reaches 3.35 wt%,which is more than twice that of the pristine sample,demonstrating excellent hydrogen absorption and release kinetics performance.After 10 consecutive hydrogen cycles,4.64 wt%hydrogen can still be released,and the cycle retention rate can be increased from 85%before improvement to nearly 100%,demonstrating good reversibility.Mechanism studies show that nano CeB_(6)can effectively weaken the Mg-N and N-H bonds of Mg(NH_(2))_(2)and inhibit the polycrystalline transformation of the hydrogen evolution product Li_(2)MgN_(2)H_(2)at high temperatures.It can also provide nucleation active sites for hydrogen absorption and desorption in the material,making the system possess superior hydrogen absorption and desorption performance and cycling stability.This study provides new insights into the role of rare earth borides in Mg(NH_(2))_(2)-2LiH hydrogen storage materials,both experimentally and theoretically.展开更多
The first-principle calculations are performed to investigate the structural,mechanical and electronic properties of titanium borides （Ti2B,TiB and TiB2）.Those calculated lattice parameters are in good agreement wit...The first-principle calculations are performed to investigate the structural,mechanical and electronic properties of titanium borides （Ti2B,TiB and TiB2）.Those calculated lattice parameters are in good agreement with the experimental data and previous theoretical values.All these borides are found to be mechanically stable at ambient pressure.Compared with parent metal Ti （120 GPa）,the larger bulk modulus of these borides increase successively with the increase of the boron content in three borides,which may be due to direction bonding introduced by the boron atoms in the lattice and the strong covalent Ti-B bonds.Additionally,TiB can be regarded as a candidate of incompressible and hard material besides TiB2.Furthermore,the elastic anisotropy and Debye temperatures are also discussed by investigating the elastic constants and moduli.Electronic density of states and atomic Mulliken charges analysis show that chemical bonding in these titanium borides is a complex mixture of covalent,ionic,and metallic characters.展开更多
文摘In order to lower the boriding temperature of hot work steel H13, method of surface mechanical attrition treatment （SMAT）, which can make the grain size of the surface reach nano-scale, was used before pack boriding. The growth of the boride layer was studied in a function of boriding temperature and time. By TEM （transmission electron microscopy）, SEM （scanning electron microscopy）, XRD （x-ray diffraction） and microhardness tests, the grain size, thermal stability of the nano-structured （NS） surface and the thickness,appearance, phases of the surface boride layer were studied. Kinetic of boriding was compared between untreated samples and treated samples. Results showed that after SMAT, the boride layer was thicker and the hardness gradient was smoother. Furthermore, after boriding at a low temperature of 700℃ for 8 h, a boride layer of about 5 μm formed on the NS surface. This layer was toothlike and wedged into the substrate, which made the surface layer combine well with the substrate. The phase of the boride layer was Fe2B. Research on boriding kinetics indicated that the activation energy was decreased for the treated samples.
基金the National Natural Science Foundation of China(No.50371064)Natural Science Foundation of Hubei(No.2003ABA032)
文摘Microwave boriding layer microstructure of carbon steels and its diffusion mechanics were studied. The results show that the existence of microwave field in the boriding can＇t change the growth mechanics of boriding layer. Compared with conventional boriding, if the treatment temperature and time remain constantly, the descend rate of the boriding layer thickness with the increase of carbon content of steel is smaller. The diffusion activation energy ofT8 steel is 2.6× 10^5 J/mol between the temperature of 750 ℃ and 900 ℃ in microwave field, which is in the same order of conventional boriding.
基金financially supported by Ministry of ScienceHigher Education in Poland as a part of the “02/24/DSPB” Project
文摘Gas-boriding in N2-H2-BCl3 atmosphere resulted in the formation of a thick layer on Inconel 600 alloy.The microstructure of layer produced at 920℃for 2 h consisted of a mixture of chromium borides and nickel borides.The objective of investigations was to determine the influence of the chemical and phase compositions of borided layer on its mechanical properties.The nanoindentation was carried out using Berkovich diamond tip under a load of 50 m N.The gas-borided layer was characterized by high indentation hardness HIT from 1542.6 HV to 2228.7 HV and high elastic modulus EIT from 226.9 to 296.4 GPa.It was found that the mixture with higher percentage of chromium borides was the reason for the increase in HIT and EIT values.The fracture toughness(KC)was measured using Vickers microindentation technique under a load of 0.98 N.The presence of high compressive stresses in normal direction to the top surface caused the strong anisotropy of the borided layer,in respect of fracture toughness.The high difference between the lowest(0.5763 MPa·m^1/2)and the highest(4.5794 MPa·m^1/2)fracture toughness was obtained.This situation was caused by the differences in chemical and phase compositions of tested areas,presence of porosity and residual stresses.Generally,the higher KC values were obtained in areas with lower chromium content.
基金Supported by Shanghai Leading Academic Discipline Project(S30107)
文摘Plasma boriding treatment was carried out at low temperature for the hot work die steel H13 assisted by surface nanocrystallization technology in this paper.At the same time,the thermal fatigue property of it was investigated through thermal fatigue testing with 3000 continuous cycles from room temperature to 700℃.The changes of structure and grain size in surface layer were characterized by high-resolution transmission electron microscopy(HRTEM).After plasma boriding at 580℃ for 4 h,the phase composition,morphology and in-situ nanomechanical property of boride layer were investigated by X-ray diffraction spectroscopy(XRD),scanning electron microscope(SEM),nanoindentation test,respectively.The results show that the boride layer with about thickness of 5μm is composed with two phases of Fe2B and FeB.The nanohardness of boride layer is as high as 21 GPa.Furthermore,thermal fatigue testing shows that the boride layer with excellent oxidation resistance and mechanical strength at elevated temperatures could effectively delay the crack initiation and impede the crack propagation.Therefore,the thermal fatigue property of H13 can be remarkably improved.
基金the financial support from the National Natural Science Foundation of China (No. 51761023)。
文摘To improve the surface performance of TB2 alloy,pack boriding was performed at 1100℃ for 20 h with 4 wt.%La_(2)O_(3).The composition and thickness of boride layer and corrosion and wear properties of borided TB2 alloy were measured.The results show that La_(2)O_(3) can promote the growth,continuity,and compactness of boride layer,and the length of TiB whisker increases from 16.80 to 21.84μm.The reason is that La_(2)O_(3) can react with B to form La−B active groups and further to improve the growth of the boride layer.The wear and corrosion resistances of TB2 alloy are enhanced by boriding with La_(2)O_(3).The wear mechanisms are adhesive wear and abrasive wear for unborided and borided TB2 alloys,respectively,and the corrosion mechanism is changed from local corrosion(unborided TB2 alloy)to uniform corrosion(borided TB2 alloy).
文摘Boriding of the Ti-Al intermetallic GE48-2-2 at 1273 K for 10 hours was performed. In order to ensure that no any serious alteration occurred in the substrate, it was previously examined with X-Ray Diffractometry (XRD), after it has undergone an annealing process at the temperature of boronizing. Subsequently, we examined the coating with XRD and Scanning Electron Microscopy, in order to characterize its structure and morphology. A dense TiΒ2 layer, 10 - 15 μm thick, was formed, but also Cr2B3 and NbN, BN and some Ti-Al phases were detected. Efforts were undertaken to focus on influence of the substrate modification, towards the quality of the coating.
文摘The mechanical behavior and wear of the different hardened phases with bore-induced changes in AISI 4340 and AISI D2 steels were investigated. The hardness and modulus of elasticity were measured by nanoindentation and the values obtained for the layers in AISI D2 steel were 18 GPa and 325 GPa in the Fe<sub>2</sub>B boride phase, and 20 GPa and 360 GPa in the FeB boride phase, respectively. The AISI 4340 steel presented mainly the Fe<sub>2</sub>B phase. It was then possible to analyze the coefficient of friction obtained in the Fe<sub>2</sub>B phase of the steel AISI 4340 presented a range of 0.04 to 0.06. The AISI D2 steel presents two different phases in the boride layer being the coefficient of friction higher for the test in the FeB phase than for Fe<sub>2</sub>B, and the values vary from 0.065 to 0.075. These parameters were obtained with micro-wear tests. No adhesion failures were observed after the sliding tests in the interface of the two different boride layers. Cracks in the FeB phase after the sliding test were much more frequent.
基金Sponsored by Higher Educational Science and Technology Program of Shandong Province(Grant No.J17KA017)Doctoral Research Foundation of Shandong Jianzhu University(Grant o.XNBS1625)
文摘A nanostructured layer was fabricated on the surface of steel Q235 by using fast multiple rotation rolling( FMRR). The Cr-Rare earth-boriding process was carried out followed at different temperatures.Experimental results showed that the thickness of the boride layer was significantly increased by surface nanocrystallization. The morphology of the boride layer was saw-toothed. An uniform,continuous and dense boride layer was obtained and adhered well to the substrate. The penetrating speed of FMRR specimens was enhanced by 1.9,1.7 and 1.5 times when the Cr-Rare earth-boriding temperature was 843,873 and 923 K.Severe plastic deformation,which grain size was approximately 100 nm,was observed on steel Q235 surface.Mechanism of Cr-Rare earth-boriding was also studied.
文摘Selective laser melting(SLM)is a cost-effective 3 D metal additive manufacturing(AM)process.However,AM 316 L stainless steel(SS)has different surface and microstructure properties as compared to conventional ones.Boriding process is one of the ways to modify and increase the surface properties.The aim of this study is to predict and understand the growth kinetic of iron boride layers on AM 316 L SS.In this study,the growth kinetic mechanism was evaluated for AM 316 L SS.Pack boriding was applied at 850,900 and 950℃,each for 2,4 and 6 h.The thickness of the boride layers ranged from(1.8±0.3)μm to(27.7±2.2)μm.A diffusion model based on error function solutions in Fick’s second law was proposed to quantitatively predict and elucidate the growth rate of FeB and Fe_(2)B phase layers.The activation energy(Q)values for boron diffusion in FeB layer,Fe_(2)B layer,and dual FeB+Fe_(2)B layer were found to be 256.56,161.61 and 209.014 kJ/mol,respectively,which were higher than the conventional 316 L SS.The findings might provide and open new directions and approaches for applications of additively manufactured steels.
基金supported by the National Key Re-search and Development Program of China(No.2020YFC1909604)SZIIT Startup Fund(No.SZIIT2022KJ072)+1 种基金Shenzhen Peacock Project Startup Fund(No.RC2023-002)Shenzhen Steady General Projects(No.KJ2024C010).
文摘Two-dimensional(2D)transition metal borides(MBenes)have emerged as a rising star and hold great potential promise for catalysis and metal ion batteries owing to a well-defined layered structure and ex-cellent electrical conductivity.Unlike well-studied graphene,perovskite and MXene materials in various fields,the research about MBene is still in its infancy.The inadequate exploration of efficient etching methods impedes their further study.Herein,we put forward an efficient microwave-assisted hydrother-mal alkaline solution etching strategy for exfoliating MoAlB MAB phase into 2D MoB MBenes with a well accordion-like structure,which displays a remarkable electrochemical performance in sodium ion batter-ies(SIBs)with a reversible specific capacity of 196.5 mAh g^(-1)at the current density of 50 mA g^(-1),and 138.6 mAh g^(-1)after 500 cycles at the current density of 0.5 A g^(-1).The underlying mechanism toward excellent electrochemical performance are revealed by comprehensive theoretical simulations.This work proves that MBene is a competitive candidate as the next generation anode of sodium ion batteries.
基金supported by the National Natural Science Foundation of China(22379069,22109072)the Fundamental Research Funds for the Central Universities(30922010304)。
文摘Lithium-sulfur(Li-S)batteries hold great promise for next-generation energy storage,yet suffer from sluggish redox kinetics and polysulfide shuttling.Herein,a novel Ni_(3)S_(2)/Ni_(2)B heterostructure is developed to improve sulfur electrochemistry by synergistically enhancing polysulfide fixation and catalytic conversions.Fabricated through mild sequential boronation and sulfurization,this hybrid nanocatalyst integrates the strong polysulfide adsorbability and high conductivity of Ni_(2)B with the high catalytic activity of Ni_(3)S_(2).More importantly,the as-constructed heterointerface inspires new,highly catalytic sites that smooth consecutive sulfur conversions with lower energy barriers,while the built-in electric fields promote directional charge transfer,collectively contributing to fast-kinetic and highly efficient sulfur redox reactions.As a result,Li-S cells incorporating the Ni_(3)S_(2)/Ni_(2)B nanocatalyst exhibit excellent cyclability,with minimal capacity decay of 0.017%per cycle over 900 cycles at 1 C and a superb rate capability of up to 5 C.Even under demanding conditions,such as a high sulfur loading of 5.0 mg cm^(-2)and a low electrolyte-to-sulfur(E/S)ratio of 4.8 mL g^(-1),high capacity and cyclability are maintained,highlighting the great potential of this unique heterointerface engineering in advancing high-performance and practically viable Li-S batteries.
基金National Natural Science Foundation of China,Grant/Award Number:52172058Outstanding Youth Fund of Natural Science Foundation of Inner Mongolia Autonomous Region,Grant/Award Number:2023JQ15+4 种基金Fundamental Research Funds for the Inner Mongolia Normal University,Grant/Award Numbers:2022JBBJ010,2022JBTD008Major Project Cultivation Fund for the Inner Mongolia Normal University,Grant/Award Number:2020ZD01Funds for Reform and Development of Local Universities Supported by The Central Government(Cultivation of First-Class Disciplines in Physics)Postdoctoral Fellowship Program of CPSF,Grant/Award Number:GZB20240101China Postdoctoral Science Foundation,Grant/Award Number:2024M750304.
文摘Transition metal borides(TMBs)are a new class of promising electrocatalysts for hydrogen generation by water splitting.However,the synthesis of robust all-in-one electrodes is challenging for practical applications.Herein,a facile solid-state boronization strategy is reported to synthesize a series of self-supported TMBs thin films(TMB-TFs)with large area and high catalytic activity.Among them,MoB thin film(MoB-TF)exhibits the highest activity toward electrocatalytic hydrogen evolution reaction(HER),displaying a low overpotential(η10=191 and 219 mV at 10 mA cm^(−2))and a small Tafel slope(60.25 and 61.91 mV dec^(−1))in 0.5M H_(2)SO_(4)and 1.0M KOH,respectively.Moreover,it outperforms the commercial Pt/C at the high current density region,demonstrating potential applications in industrially electrochemical water splitting.Theoretical study reveals that both surfaces terminated by TM and B atoms can serve as the active sites and the H*binding strength of TMBs is correlated with the p band center of B atoms.This work provides a new pathway for the potential application of TMBs in largescale hydrogen production.
基金supported by National Natural Science Foundation of China(Grant Nos.52101273 and U22A20118)Natural Science Foundation of Fujian Province of China(Grant No.2022J01042)Fundamental Research Funds for Central Universities of China(Grant No.20720242002).
文摘The energy density of thin-film lithium batteries(TFLBs)is predominantly determined by the average voltage and specific capacity,however,the mechanism of regulating the voltage plateaus of the film electrodes is not well understood.In this study,three boride films(Co–B,Fe–B,and Co–Fe–B alloys)with different thick-nesses were fabricated to enhance the specific capacity and voltage stability of TFLBs.By analyzing the cycling performance,redox peak evolution,and capacitive contribution,the thickness-dependent lithiation behavior of the thin/thick films was elucidated.Theoretical simulations and electrochemical analysis were conducted to investigate how the lithiation behaviors affected the voltage profiles of the film electrodes.In addition,the various-thickness CoB films were compared in all-solid-state TFLBs,demonstrating the universality and practicability of this simple regulation strategy to develop high-performance energy storage devices.
基金financially supported by the National Natural Science Foundation of China(Nos.52271033 and 52071179)the Key program of National Natural Science Foundation of China(No.51931003)+2 种基金Natural Science Foundation of Jiangsu Province,China(No.BK20221493)Jiangsu Province Leading Edge Technology Basic Research Major Project(No.BK20222014)Foundation of“Qinglan Project”for Colleges and Universities in Jiangsu Province.
文摘Multi-component transition group metal borides(MMB_(2))have become a research hotspot due to their new composition design concepts and superior properties compared with conventional ceramics.Most of the current methods,however,are complicated and time-consuming,the mass production remains a chal-lenge.Herein,we proposed a new high-efficiency strategy for synthesis of MMB_(2)using molten aluminum as the medium for the first time.The prepared Al-containing multi-component borides(TiZrHfNbTa)B_(2)microcrystals had a homogeneous composition with a hexagonal AlB_(2)structure and ultra-high hardness value of∼35.3 GPa,which was much higher than data reported in the literature and the rule of mix-ture estimations.Furthermore,combined with the First-principles calculation results,we found that the Poisson’s ratio(v)values exhibit a clearly ascending trend from 0.17 at VEC=3.5 to 0.18 at VEC=3.4,then to 0.201 at VEC=3.2 with the increasing of Al content.This indicates that the intrinsic toughness of multi-component boride microcrystals is obviously enhanced by the trace-doped Al elements.Besides,the fabricated Al-containing multi-component boride microcrystals have superior oxidation activation en-ergy and structural stability.The enhanced oxidation resistance is mainly attributed to the formation of a protective Al2 O3 oxide layer and the lattice distortion,both of which lead to sluggish diffusion of O_(2).These findings propose a new unexplored avenue for the fabrication of MMB_(2)materials with supe-rior comprehensive performance including ultra-hardness and intrinsically improved thermo-mechanical properties.
基金supported by the National Natural Science Foundation of China(No.22179054)the Jiangsu Province Innovation Support Project,China(No.BZ2023010)+1 种基金the Project of Jiangsu University High-Tech Ship Collaborative Innovation Center(No.1174871801-11)the Ministry of Science and Technology of the People’s Republic of China(No.G2023014022L).
文摘Owing to the orbital hybridization between the transition metal and the B element and the electron-trapping effect of the B ele-ment,transition metal borides are considered very promising materials for energy catalysis.In this work,an amorphous scaly high-entropy boride(HEB)with electron traps was designed and fabricated via a facile reduction method to improve the hydrogen storage properties of magnesium hydride(MgH_(2)).For dehydrogenation,the onset temperature of MgH_(2)+10wt%HEB was dropped to 187.4℃;be-sides,the composite exhibited superior isothermal kinetics and the activation energy of the composite was reduced from(212.78±3.93)to(65.04±2.81)kJ/mol.In addition,MgH_(2)+10wt%HEB could absorb hydrogen at 21.5℃,and 5.02wt%H_(2) was charged in 50 min at 75℃.For reversible hydrogen storage capacity tests,the composite maintained a retention rate of 97%with 6.47wt%hydrogen capacity after 30 cycles.Combining microstructure evidence with hydrogen storage performance,the catalytic mechanism was proposed.During ball milling,scaly high-entropy borides riveted a large number of heterogeneous active sites on the surface of MgH_(2).Driven by the cocktail effect as well as the orbital hybridization of metal borides,numerous active sites steadily enhanced the hydrogen storage reactions in MgH_(2).
基金financially supported by the National Natural Science Foundation of China(Nos.52332003,52293373,52022072 and 52202067)the Hubei Provincial Natural Science Foundation of China(Distinguished Young Scholars No.2022CFA042)Independent Innovation Projects of Hubei Longzhong Laboratory(No.2022ZZ-10).
文摘Multifunctional carbon fibers(C_(f))/ZrB_(2) based composites were synthesized through a series of processes termed as IVI including sequential slurry injection,vacuum impregnation,pyrolysis and reimpregnation cycles,which facilitated the effective incorporation of ZrB_(2) powder into the carbon fiber preform.A single IVI cycle reduced the porosity of the preform from∼77%to∼40%.Microstructural analysis revealed a preferential distribution of ZrB2 powders within random layers and pyrolytic carbon effectively bridging the ceramic particles and fibers.Due to the hierarchical 0°/90°carbon fiber architecture,as fabricated Cf/ZrB_(2) composites exhibited anisotropy in mechanical and physical properties.Vertically oriented com-posites demonstrated higher compressive strain and low thermal conductivity(1.00-2.59 W m^(−1) K^(−1) from 298 to 1173 K).In contrast,horizontally oriented specimens exhibited higher compressive strength(60.77±20.30 MPa)and thermal conductivity(1.6-4.5 W m^(−1) K^(−1) from 298 to 1173 K).Furthermore,the continuous Cf endowed the composites with a positive temperature-dependent electrical conductiv-ity characteristic,not only contributed to their higher electrical conductivity values,but also was helpful for maintaining the excellent EMI shielding effectiveness(19.80-22.51 dB)of Cf/ZrB_(2) up to 800℃without obvious degradation.Considering the low-density characteristics of as-prepared composites,their specific performance metrics demonstrate good competitiveness compared to those fabricated via alternative processes.
基金supported by the National Natural Science Foundation of China(Nos.52363028,21965005)Natural Science Foundation of Guangxi(Nos.2021GXNSFAA076001,2018GXNSFAA294077)Guangxi Technology Base and Talent Subject(Nos.GUIKE AD23023004,GUIKE AD20297039)。
文摘Amorphous bimetallic borides,as a new generation of catalytic nanomaterials with modifiable electronic properties,are of great importance in the design of high-efficiency catalysts for NaBH_(4) hydrolysis.This study synthesizes an amorphous Co_(3)B-Mo_(2)B_(5) catalyst using a self-sacrificial template strategy and NaBH_(4) reduction for both NaBH_(4) hydrolysis and the reduction of 4-nitrophenol.The catalyst delivers an impressive hydrogen generation rate of 7690.5 mL min^(-1) g^(-1) at 25℃,coupled with a rapid reaction rate of 0.701 min^(-1) in the reduction of 4-nitrophenol.The enhanced catalytic performance is attributed to the unique amorphous structure and the electron rearrangement between Co_(3)B and Mo_(2)B_(5).Experimental and theoretical analyses suggest electron transfer from Co_(3)B to the Mo_(2)B_(5),with the electron-deficient Co_(3)B site favoring BH_(4)^(-) adsorption,while the electron-rich Mo_(2)B_(5) site favoring H_(2)O adsorption,Furthermore,Co_(3)B-Mo_(2)B_(5) demonstrated potential for energy applications,delivering a power output of 0.3 V in a hydrogen-air fuel cell.
基金Project supported by the National Natural Science Foundation of China(51971199,51771171)。
文摘The Mg(NH_(2))_(2)-2LiH composite system is a promising vehicle-mounted hydrogen sto rage material,but its application is limited due to serious thermodynamic and kinetic barriers.Adding additives can effectively optimize their hydrogen absorption and desorption kinetics and thermodynamic performance.In this work the comprehensive hydrogen storage performance of Mg(NH_(2))_(2)-2LiH with extremely small nano rare earth borides is improved,and a series of characterization methods and density functional theory(DFT)calculation systems was combined to study its hydrogen storage improvement mechanism.The research results show that the method of adding 5 wt%molten salt to prepare nano CeB_(6)(24.5 nm)can significantly reduce the initial hydrogen absorption/release temperature of Mg(NH_(2))_(2)-2LiH from 110/130to 45/90℃,inhibit the generation of ammonia by-products,and improve hydrogen purity.Under lowtemperature hydrogen absorption conditions at 120℃,the improved sample can absorb 2.81 wt%hydrogen gas,with a hydrogen absorption capacity more than 3.5 times of the unmodified sample.The amount of hydrogen released at 150℃reaches 3.35 wt%,which is more than twice that of the pristine sample,demonstrating excellent hydrogen absorption and release kinetics performance.After 10 consecutive hydrogen cycles,4.64 wt%hydrogen can still be released,and the cycle retention rate can be increased from 85%before improvement to nearly 100%,demonstrating good reversibility.Mechanism studies show that nano CeB_(6)can effectively weaken the Mg-N and N-H bonds of Mg(NH_(2))_(2)and inhibit the polycrystalline transformation of the hydrogen evolution product Li_(2)MgN_(2)H_(2)at high temperatures.It can also provide nucleation active sites for hydrogen absorption and desorption in the material,making the system possess superior hydrogen absorption and desorption performance and cycling stability.This study provides new insights into the role of rare earth borides in Mg(NH_(2))_(2)-2LiH hydrogen storage materials,both experimentally and theoretically.
基金Project(2010JK404) supported by the Education Committee Natural Science Foundation of Shaanxi Province,ChinaProjects(ZK0918,ZK0915) supported by the Baoji University of Arts and Sciences Key Research,China
文摘The first-principle calculations are performed to investigate the structural,mechanical and electronic properties of titanium borides （Ti2B,TiB and TiB2）.Those calculated lattice parameters are in good agreement with the experimental data and previous theoretical values.All these borides are found to be mechanically stable at ambient pressure.Compared with parent metal Ti （120 GPa）,the larger bulk modulus of these borides increase successively with the increase of the boron content in three borides,which may be due to direction bonding introduced by the boron atoms in the lattice and the strong covalent Ti-B bonds.Additionally,TiB can be regarded as a candidate of incompressible and hard material besides TiB2.Furthermore,the elastic anisotropy and Debye temperatures are also discussed by investigating the elastic constants and moduli.Electronic density of states and atomic Mulliken charges analysis show that chemical bonding in these titanium borides is a complex mixture of covalent,ionic,and metallic characters.
