Herein,cure characteristics,morphology,and mechanical properties of natural rubber filled with activated carbon-based materials were investigated.Carbon-based materials were prepared from bagasse,coffee grounds and pi...Herein,cure characteristics,morphology,and mechanical properties of natural rubber filled with activated carbon-based materials were investigated.Carbon-based materials were prepared from bagasse,coffee grounds and pineapple crowns by the pyrolysis method at temperatures in the range of 300℃.As-synthesized carbon materials were characterized by optical microscopy(OM),scanning electron microscopy(SEM),and Fourier-transform infrared spectroscopy(FTIR)to analyze size distribution,morphology,and functional groups,respectively.OM and SEM analysis revealed that particles,flakes,and a small quantity of fiber-like carbon were obtained using bagasse and pineapple crown as raw materials,while honeycomb-like carbon materials can be derived from coffee grounds.To investigate the mechanical properties,natural rubber was filled with carbon black and as-synthesized carbon materials by the internal mixing and compression molding process.Transmission electron microscopy(TEM)was utilized to characterize the dispersion of carbon materials in the rubber matrix.The results of tensile testing showed that the natural rubber mixed with as-synthesized carbon materials from pineapple crowns exhibited 54%and 74%improvement in the ultimate tensile strength and Young’s modulus,respectively,compared with natural rubber without filled carbon materials.The enhancement in mechanical properties by activated carbon materials derived from pineapple crowns can be attributed to the flake-and fiber-like structures and good dispersion of carbon materials in the rubber matrix.In addition,it is higher than that of rubber mixed with carbon black.The results demonstrated that as-synthesized carbon materials from pineapple crowns have the potential materials to substitute carbon black in the rubber compound industry.展开更多
Cu/Al bar clad material was fabricated by a drawing process and a subsequent heat treatment.During these processes,intermetallic compounds have been formed at the interface of Cu/Al and have affected its bonding prope...Cu/Al bar clad material was fabricated by a drawing process and a subsequent heat treatment.During these processes,intermetallic compounds have been formed at the interface of Cu/Al and have affected its bonding property.Microstructures of Cu/Al interfaces were observed by OM,SEM and EDX Analyser in order to investigate the bonding properties of the material.According to the microstructure a series of diffusion layers were observed at the interface and the thicknesses of diffusion layers have increased with aging time as a result of the diffusion bonding.The interfaces were composed of 3-ply diffusion layers and their compositions were changed with aging time at 400 °C.These compositional compounds were revealed to be η2,(θ+η2),(α+θ) intermetallic phases.It is evident from V-notch impact tests that the growth of the brittle diffusion layers with the increasing aging time directly influenced delamination distance between the Cu sleeve and the Al core.It is suggested that the proper holding time at 400 °C for aging as post heat treatment of a drawn Cu/Al bar clad material would be within 1 h.展开更多
Understanding the material flow facilitated by tool geometry in friction stir welds is challenging for quality weld production in industrial applications.The optimal tool shoulder and pin design combination,which play...Understanding the material flow facilitated by tool geometry in friction stir welds is challenging for quality weld production in industrial applications.The optimal tool shoulder and pin design combination,which plays a vital role in material flow was addressed.The flow of plasticized material was analyzed using a marker insert technique.The results show that the knurling shoulder design with square and hexagonal pin design facilitated constant stability force with reference to weld length/time.The uniform mixing and distribution of plasticized material were facilitated by the knurling shoulder design with square tool pin shape(TK)S(sticking length minimum)below which fragmented copper was observed.(TK)S tool facilitated higher mechanical properties for the welds,i.e.strength(182 MPa)and hardness(HV 78)in stir zone.展开更多
Employing Li2CO3, NiO, Co3O4, and MnCO3 powders as starting materials, Li[Ni1/3Co1/3Mn1/3]O2 was synthesized by solid-state reaction method. Various grinding aids were applied during milling in order to optimize the s...Employing Li2CO3, NiO, Co3O4, and MnCO3 powders as starting materials, Li[Ni1/3Co1/3Mn1/3]O2 was synthesized by solid-state reaction method. Various grinding aids were applied during milling in order to optimize the synthesis process. After successive heat treatments at 650 and 950 ℃, the prepared powders were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy, and transmission electron microscopy. The powders prepared by adding salt (NaCl) as grinding aid exhibit a clear R3m layer structure. The powders by other grinding aids like heptane show some impurity peaks in the XRD pattern. The former powders show a uniform particle size distribution of less than 1 μm average size while the latter shows a wide distribution ranging from 1 to 10 μm. Energy dispersive X-ray (EDX) analysiss show that the ratio of Ni, Co, and Mn content in the powder is approximately 1/3, 1/3, and 1/3, respecively. The EDX data indicate no incorporation of sodium or chlorine into the powders. Charge-discharge tests gave an initial discharge capacity of 160 mAh·g-1 for the powders with NaCl addition while 70 mAh·g-1 for the powders with heptane.展开更多
The effects of hydro co-extrusion on the microstructure changes of aluminum hybrid duo-cast Al 3003/Al 4004 clad materials were studied. The specimen of duo-cast Al 3003/Al 4004 clad materials was in circle shape, and...The effects of hydro co-extrusion on the microstructure changes of aluminum hybrid duo-cast Al 3003/Al 4004 clad materials were studied. The specimen of duo-cast Al 3003/Al 4004 clad materials was in circle shape, and was composed of Al 3003(outside) and Al 4004(inside) materials. The specimen was extruded by the hydro co-extrusion equipment. The manufacturing conditions of the specimen were 423 K in temperature and 5 in extrusion ratio. The dimensions of the specimen were 80 mm in diameter of the Al 4004 material and 35 mm in thickness of the Al 3003 material before the hydro co-extrusion process, and 30 mm in diameter and about 5 mm in thickness after the extrusion process, respectively. The microstructure and the hardness for two specimens were investigated. The hardness value of cross section in the duo-cast Al 3003/Al 4004 clad materials before the extrusion process was increased in form of the parabola toward the center. However, after the extrusion process, it was almost constant in the portion of Al 4004 material. Lots of big voids above 1 mm in diameter in the specimen existed in the interfacing region of Al 3003 and Al 4004 materials before the extrusion process. These big voids disappeared after the process of hydro co-extrusion.展开更多
Heteroatom-doped transition metal oxides have attracted great attention as advanced anode materials for lithium-ion batteries due to their high theoretical capacity and superior properties.However,the limited resource...Heteroatom-doped transition metal oxides have attracted great attention as advanced anode materials for lithium-ion batteries due to their high theoretical capacity and superior properties.However,the limited resource availability has led to a substantial rise in prices for valuable metals such as Ni and Co,posing a significant challenge for their application.To address this issue,recycling of these metals from waste materials have gained prominence,and particularly the recovery of Co has been mostly focused on its economic benefits.Herein,we introduced a novel recycling strategy for fabrication of heteroatomdoped CoO_(x)(comprising mainly Co_(3)O_(4)with a minor CoO phase)anode with a yolk–shell structure for lithium-ion batteries,by separating Co from cemented tungsten carbide waste.By employing a simple leaching process and subsequent spray pyrolysis,the yolk–shell structured microsphere comprising CoO_(x)was successfully synthesized.Moreover,the presence of other waste metals in the leachate facilitated multi-heteroatom doping during synthesis.Interestingly,the introduction of various dopants into CoO_(x)induced oxygen vacancy formation,thereby enhancing the electrochemical properties of the CoO_(x)anode.As a result,compared with the phase-pure(undoped)CoO_(x)yolk–shell,the heteroatom-doped CoO_(x)yolk–shell exhibited robust cycling stability(602 mAh·g^(-1)for 200 cycles at 1 A·g^(-1))and excellent rate capability(210 mAh·g^(-1)at 10 A·g^(-1)).展开更多
K–Se batteries have been identified as promising energy storage systems owing to their high energy density and cost-effectiveness.However,challenges such as substantial volume changes and low Se utilization require f...K–Se batteries have been identified as promising energy storage systems owing to their high energy density and cost-effectiveness.However,challenges such as substantial volume changes and low Se utilization require further investigation.In this study,novel N-doped multichannel carbon nanofibers(h-NMCNFs)with hierarchical porous structures were successfully synthesized as efficient cathode hosts for K–Se batteries through the carbonization of two electrospun immiscible polymer nanofibers and subsequent chemical activation.Mesopores originated from the decomposition of the polymer embedded in the carbon nanofibers,and micropores were introduced via KOH activation.During the activation step,hierarchical porous carbon nanofibers with enhanced pore volumes were formed because of the micropores in the carbon nanofibers.Owing to the mesopores that enabled easy access to the electrolyte and the high utilization of chain-like Se within the micropores,the Se-loaded hierarchical porous carbon nanofibers(60 wt%Se)exhibited a high discharge capacity and excellent rate performance.The discharge capacity of the nanofibers at the 1,000th cycle was 210.8 mA.h.g^(-1)at a current density of 0.5C.The capacity retention after the initial activation was 64%.In addition,a discharge capacity of 165 mA.h.g^(-1)was obtained at an extremely high current density of 3.0C.展开更多
Retained austenite plays a significant role in third-generation advanced high-strength steels (AHSS 3. Gen.), renowned for their excellent combination of strength and ductility. Silicon (Si) is a key element in stabil...Retained austenite plays a significant role in third-generation advanced high-strength steels (AHSS 3. Gen.), renowned for their excellent combination of strength and ductility. Silicon (Si) is a key element in stabilizing retained austenite. However, it introduces challenges in galvannealing and welding processes in Zn-coated steels, such as inhibited Fe-Zn alloying and increased susceptibility to liquid metal embrittlement (LME). This study investigated the mechanism of Si enrichment at the Zn/steel interface and its role in suppressing Fe-Zn interdiffusion during annealing. Using advanced techniques such as high-resolution transmission electron microscopy and atomic probe tomography, and Thermo-Calc DICTRA simulations, we analyzed the diffusion behavior and microstructural evolution in Zn-coated steels with varying Si contents. Si, driven by its low solubility in liquid Zn and Fe-Zn intermetallic phases, accumulates at the interface, forming a Si-enriched region that significantly suppresses Zn diffusion while permitting limited Fe diffusion. Numerical simulations revealed that the Si-enriched layer forms via the drag effect of the Fe-Zn reaction line, progressively concentrating Si at the interface as Zn diffuses. As annealing progresses, the morphology of the Si-enriched region evolves from layered, cloud-like structures to droplets and elongated dendritic forms, driven by Zn penetration and Fe consumption. These findings provide novel insights into the role of Si enrichment in mitigating LME and optimizing the Zn-coated AHSS 3. Gen., paving the way for advancements in automotive material design.展开更多
Seawater is the most abundant source of molecular hydrogen.Utilizing the hydrogen reserves present in the seawater may inaugurate innovative strategies aimed at advancing sustainable energy and environmental preservat...Seawater is the most abundant source of molecular hydrogen.Utilizing the hydrogen reserves present in the seawater may inaugurate innovative strategies aimed at advancing sustainable energy and environmental preservation endeavors in the future.Recently,there has been a surge in study in the field addressing the production of hydrogen through the electrochemical seawater splitting.However,the performance and durability of the electrode have limitations due to the fact that there are a few challenges that need to be addressed in order to make the technology suitable for the industrial purpose.The active site blockage caused by chloride ions that are prevalent in seawater and chloride corrosion is the most significant issue;it has a negative impact on both the activity and the durability of the anode component.Addressing this particular issue is of upmost importance in the seawater splitting area.This review concentrates on the newly developed materials and techniques for inhibiting chloride ions by blocking the active sites,simultaneously preventing the chloride corrosion.It is anticipated that the concept will be advantageous for a large audience and will inspire researchers to study on this particular area of concern.展开更多
Aqueous zinc-ion batteries(AZIBs)have emerged as promising,practical energy storage devices based on their non-toxic nature,environmental friendliness,and high energy density.However,excellent rate characteristics and...Aqueous zinc-ion batteries(AZIBs)have emerged as promising,practical energy storage devices based on their non-toxic nature,environmental friendliness,and high energy density.However,excellent rate characteristics and stable long-term cycling performance are essential.These essential aspects create a need for superior cathode materials,which represents a substantial challenge.In this study,we used MXenes as a framework for NH_(4)V_(4)O_(10)(NVO)construction and developed electrodes that combined the high capacity of NVO with the excellent conductivity of MXene/carbon nanofibers(MCNFs).We explored the electrochemical characteristics of electrodes with varying NVO contents.Considering the distinctive layered structure of NVO,the outstanding conductivity of MCNFs,and the strong synergies between the two components.NVO-MCNFs exhibited better charge transfer compared with earlier materials,as well as more ion storage sites,excellent conductivity,and short ion diffusion pathways.A composite electrode with optimized NVO content exhibited an excellent specific capacitance of 360.6mAh g^(-1) at 0.5 A g^(-1) and an outstanding rate performance.In particular,even at a high current density of 10 A g^(-1),the 32NVO-MCNF exhibited impressive cycling stability:88.6%over 2500 cycles.The mechanism involved was discovered via comprehensive characterization.We expect that the fabricated nanofibers will be useful in energy storage and conversion systems.展开更多
Nitrogen-doped activated carbon(N-AC)was successfully prepared by KOH-activation and nitrogen doping using ammonia(NH3)heat treatment.Coconut shell-derived activated carbon(AC)was heat-treated under NH3 gas in the tem...Nitrogen-doped activated carbon(N-AC)was successfully prepared by KOH-activation and nitrogen doping using ammonia(NH3)heat treatment.Coconut shell-derived activated carbon(AC)was heat-treated under NH3 gas in the temperature range of 700℃-900℃.Likewise,the mixture of potassium hydroxide(KOH)and AC was heated at 800℃,followed by heat treatment underNH3 gas at 800℃(hereafter referred to asKOH-N-AC800).Scanning electron microscopy(SEM),Raman spectroscopy,X-ray photoelectron spectroscopy(XPS)and Brunauer-Emmett-Teller(BET)method were utilized to analyze morphology,crystallinity,chemical bonding,chemical composition and surface area.The surface area and porosity of N-AC increased with increasing NH3 heat treatment.Similarly,the nitrogen content in the N-AC increased from 3.23%to 4.84 at%when the NH3 heat treatment was raised from 700℃ to 800℃.However,the nitrogen content of N-AC decreased to 3.40 at% after using NH3 heat treatment at 900℃.The nitrogen content of KOH-N-AC800 is 5.43 at%.KOH-N-AC800 and N-AC800 exhibited improvements of 33.66% and 26.24%,respectively,in CO_(2) adsorption compared with AC.The enhancement of CO_(2) adsorption of KOH-N-AC800 is attributed to the synergic effect of the nitrogen doping,high surface area,and porosity.The results exhibited that nitrogen sites on the surface play a more significant role in CO_(2) adsorption than surface area and porosity.This work proposes the potential synergistic effect of KOH-activation and nitrogen doping for enhancing the CO_(2) adsorption capacity of activated carbon.展开更多
Titanium-based nitride coatings on cutting tools,press molds and dies can be used to prolong their life cycle because of their superior corrosion and oxidation resistance.TiAlN/ZrN and TiCrN/ZrN multilayer coatings we...Titanium-based nitride coatings on cutting tools,press molds and dies can be used to prolong their life cycle because of their superior corrosion and oxidation resistance.TiAlN/ZrN and TiCrN/ZrN multilayer coatings were prepared by RF magnetron sputtering,and their microstructural evolution and corrosion resistance during heat treatment were investigated.The TiAlN/ZrN and TiCrN/ZrN multilayer coatings are degraded by heating up to 600 ℃ with the formation of oxides particles on the surface.During the heat treatment,the TiCrN/ZrN and TiAlN/ZrN multilayer coatings show the lowest corrosion current density and the highest polarization resistance at temperature range of 400-500 ℃.Consequently,the TiAlN/ZrN and TiCrN/ZrN multilayer coatings show good corrosion resistance at temperature range of 400-500 ℃ during heating.展开更多
The applicability of Ce and Y as promising candidate elements to form irreversible traps in weld metal was investigated by thermal desorption spectroscopy(TDS) with gas chromatography(GC). The precise nature of the pr...The applicability of Ce and Y as promising candidate elements to form irreversible traps in weld metal was investigated by thermal desorption spectroscopy(TDS) with gas chromatography(GC). The precise nature of the precipitate particles newly formed in the weld metal by the addition of Ce and Y to a certain alloy system was characterized. Moreover,the hydrogen trapping efficiency expressed as the reduction of the diffusible hydrogen in the weld metal was analyzed. The results showed that the addition of Ce and/or Y to this alloy system led to the formation of a mixed type of(Ce,Ti)-based oxide,(Y,Ni)-based carbide,or(Ce,Y,Ti)-based oxide particles. Because of the high activation energy of the mixed type of particles(≥ 150 k J/mol),the trapping efficiency for hydrogen was considered to be sufficiently high to effectively reduce the diffusible hydrogen content.展开更多
Mg alloys exhibit a number of good properties such as low density, good castability and high specific strength. However, molten Mg and Mg alloys are ignited without the melt protective gases during melting and casting...Mg alloys exhibit a number of good properties such as low density, good castability and high specific strength. However, molten Mg and Mg alloys are ignited without the melt protective gases during melting and casting process due to their high reactivity. The purpose of this study is to investigate effects of Ca and CaO on pure Mg through microstructure observation, ignition test and phase analysis. With increasing Ca and CaO contents, the ignition resistance of Ca or CaO added pure Mg is increased and the grains are refined. As results of XRD and EDS, CaO is reduced to Ca in CaO added pure Mg. Mg2Ca phase is formed even in 0.1 wt.%CaO added pure Mg by reduction mechanism, while Mg2Ca phase is formed over 1.35 wt.% Ca added pure Mg.展开更多
Wetting phenomena between MgO C and CaO SiO2 slags were investigated by varying carbon content.A sessile drop technique was adopted to study the wetting phenomena in conjunction with a high speed camera for the observ...Wetting phenomena between MgO C and CaO SiO2 slags were investigated by varying carbon content.A sessile drop technique was adopted to study the wetting phenomena in conjunction with a high speed camera for the observation of intrinsic wetting phenomena.The results show that the high content of SiO2 and the presence of Al2O3 in slags enhance the diffusion of Mg2+,leading to the promotion of reactive wetting.The carbon in MgO C refractory impedes the penetration of slags by repelling the slag and slowing the diffusion of Mg2+.This accounts for the non-wetting behavior of the slag on MgO C refractory with 17% (mass fraction) carbon similar to that of graphite.展开更多
The effects of alloying elements(Co,Cr,Mo,W,Al,Ti,and Ta)on the oxidation resistance of Ni-(0-15)Co-(8-15)Cr-(0-5)Mo-(0-10)W-(3-8)Al-(0-5)Ti-(0-10)Ta-0.1 C-0.01 B alloys were studied.The sample compositions were desig...The effects of alloying elements(Co,Cr,Mo,W,Al,Ti,and Ta)on the oxidation resistance of Ni-(0-15)Co-(8-15)Cr-(0-5)Mo-(0-10)W-(3-8)Al-(0-5)Ti-(0-10)Ta-0.1 C-0.01 B alloys were studied.The sample compositions were designed by the Box-Behnken method of design of experiments(DOE).The alloying elements show complicated effects on the mass gain due to oxidation,depending on the alloy composition.Al reduces the mass gain largely.The other elements except Al do not appear to exert a strong effect on the oxidation rate on average,but their influences are shown clearly in the alloys with a low Al content.Co,W,and Ta reduce the oxidation rate,while Cr,Mo,and Ti promote oxidation.Ta is the most effective element in reducing the oxidation rate of the alloy with a low Al concentration.It is confirmed that a continuous Al2O3 layer is essentially required for high oxidation resistance.The oxide scale of easily oxidized alloys has various oxides such as NiCr2O4,NiAl2O4,NiO,Cr2O3,CrTaO4,and TiO2.展开更多
A small amount of misch metal was added to Cu-Zn-Al alloy in order to study its effect on grain refinement,mechanical properties,phase transformation behavior and stabilization of martensite.It is found that the addit...A small amount of misch metal was added to Cu-Zn-Al alloy in order to study its effect on grain refinement,mechanical properties,phase transformation behavior and stabilization of martensite.It is found that the addition of misch metal is very effective for reducing the grain size.The coarse grains over 1 000 μm are refined to the size of 30 μm by the addition of 0.43%(mass fraction) misch metal.The grain size of thermo-mechanically treated alloys is barely affected by cold working.The fracture strength and ductility increase significantly with the increase of misch metal content when tensile test is carried out below Mf temperature.Also,the fracture strength is larger in the case of post-quench ageing treatment than that in the case of direct quench ageing treatment.The fracture mode is changed from transgranular brittle fracture to ductile fracture with void formation and coalescence by the addition of misch metal.展开更多
Mg-Al-Zn-M M （misch metal） alloy powders were manufactured by inert gas atomization and the characteristics of alloy powders were investigated.In spite of the low fluidity and easy oxidation of the magnesium melt,th...Mg-Al-Zn-M M （misch metal） alloy powders were manufactured by inert gas atomization and the characteristics of alloy powders were investigated.In spite of the low fluidity and easy oxidation of the magnesium melt,the spherical powder was made successfully with the improved three piece nozzle systems of gas atomization unit. It was found that most of the solidified powders with particles size of less than 50μm in diameter were single crystal and the solidification structure of rapidly solidified powders showed a typical dendritic morphology because of supercooling prior to nucleation.The spacing of secondary denrite arms was deceasing as the size of powders was decreasing.The rapidly solidified powders were consolidated by vacuum hot extrusion and the effects of misch metal addition to AZ91 on mechanical properties of extruded bars were also examined.During extrusion of the rapidly solidified powders,their dendritic structure was broken into fragments and remained as grains of about 3μm in size.The Mg-Al-Ce intermetallic compounds formed in the interdendritic regions of powders were finely broken,too.The tensile strength and ductility obtained in as-extruded Mg-9 wt pct Al-1 wt pct Zn-3 wt pct MM alloy wereσ-（T.S.） =383 MPa andε=10.6%,respectively.All of these improvements on mechanical properties were resulted from the refined microstructure and second-phase dispersions.展开更多
In this work,a simple synthesis of sulfur doped graphitic carbon nitride(S-g-C3N4)act as a support cum stabilizers for gold nanoparticles(Au)and its was characterized by UV–vis and XRD to measure the absorbance and c...In this work,a simple synthesis of sulfur doped graphitic carbon nitride(S-g-C3N4)act as a support cum stabilizers for gold nanoparticles(Au)and its was characterized by UV–vis and XRD to measure the absorbance and crystallinity,respectively.The functional group and morphology of the samples were identified using FT-IR and TEM.Finally,the Au@S-g-C3N4 nanocatalyst exhibits good catalytic performance and stability in the reduction of hazardous 4-nitrophenol(NP)compared to S-g-C3N4 using Na BH4.Moreover,the Au@S-g-C3N4 nanocomposite holds a good catalytic efficiency(near 100%)achieved by within 5 min.The highest catalytic reduction of NP is due to the synergistic effect of Au nanoparticles decorated on S-g-C3N4.The fast electron transfer reduction mechanism was elucidated and discussed.Excellent reusability and stability of the developed nanocomposites were also observed in consecutive reduction experiments.The filtering and catalyzing device was used for the direct conversion of NP polluted water.This method can open a new avenue for the metal nanoparticles based carbon materials heterogeneous catalyst and its reduction of toxic contaminants.展开更多
The alpha-case formation reactions between Ti and investment molds （Al-2O-3,ZrSiO-4,ZrO-2,CaO stabilized ZrO-2） were evaluated in a plasma arc melting furnace.Regardless of thermodynamic approaches,there were distin...The alpha-case formation reactions between Ti and investment molds （Al-2O-3,ZrSiO-4,ZrO-2,CaO stabilized ZrO-2） were evaluated in a plasma arc melting furnace.Regardless of thermodynamic approaches,there were distinct alpha-case formations.The reaction products were characterized by electron probe micro-analysis and transmission electron microscopy.Theα-case generation between Ti and Al-2O-3 mold was not able to be explained by the conventionalα-case formation mechanism,which is known to be formed by the interstitials,especially oxygen dissolved from mold materials.However,from our experimental results and thermodynamic calculations,it was confirmed that theα-case is formed not only by an interstitial element but also by substitutional metallic elements dissolved from mold materials.Our newly establishedα-case formation mechanism will surely lead to a variety of significant applications of theα-case controlled Ti casting.展开更多
基金funded by Faculty of Engineering,Burapha University,grant number 003/2567.
文摘Herein,cure characteristics,morphology,and mechanical properties of natural rubber filled with activated carbon-based materials were investigated.Carbon-based materials were prepared from bagasse,coffee grounds and pineapple crowns by the pyrolysis method at temperatures in the range of 300℃.As-synthesized carbon materials were characterized by optical microscopy(OM),scanning electron microscopy(SEM),and Fourier-transform infrared spectroscopy(FTIR)to analyze size distribution,morphology,and functional groups,respectively.OM and SEM analysis revealed that particles,flakes,and a small quantity of fiber-like carbon were obtained using bagasse and pineapple crown as raw materials,while honeycomb-like carbon materials can be derived from coffee grounds.To investigate the mechanical properties,natural rubber was filled with carbon black and as-synthesized carbon materials by the internal mixing and compression molding process.Transmission electron microscopy(TEM)was utilized to characterize the dispersion of carbon materials in the rubber matrix.The results of tensile testing showed that the natural rubber mixed with as-synthesized carbon materials from pineapple crowns exhibited 54%and 74%improvement in the ultimate tensile strength and Young’s modulus,respectively,compared with natural rubber without filled carbon materials.The enhancement in mechanical properties by activated carbon materials derived from pineapple crowns can be attributed to the flake-and fiber-like structures and good dispersion of carbon materials in the rubber matrix.In addition,it is higher than that of rubber mixed with carbon black.The results demonstrated that as-synthesized carbon materials from pineapple crowns have the potential materials to substitute carbon black in the rubber compound industry.
基金Project supported by the Fundamental Materials Development funded by the Korean Ministry of Knowledge Economy
文摘Cu/Al bar clad material was fabricated by a drawing process and a subsequent heat treatment.During these processes,intermetallic compounds have been formed at the interface of Cu/Al and have affected its bonding property.Microstructures of Cu/Al interfaces were observed by OM,SEM and EDX Analyser in order to investigate the bonding properties of the material.According to the microstructure a series of diffusion layers were observed at the interface and the thicknesses of diffusion layers have increased with aging time as a result of the diffusion bonding.The interfaces were composed of 3-ply diffusion layers and their compositions were changed with aging time at 400 °C.These compositional compounds were revealed to be η2,(θ+η2),(α+θ) intermetallic phases.It is evident from V-notch impact tests that the growth of the brittle diffusion layers with the increasing aging time directly influenced delamination distance between the Cu sleeve and the Al core.It is suggested that the proper holding time at 400 °C for aging as post heat treatment of a drawn Cu/Al bar clad material would be within 1 h.
文摘Understanding the material flow facilitated by tool geometry in friction stir welds is challenging for quality weld production in industrial applications.The optimal tool shoulder and pin design combination,which plays a vital role in material flow was addressed.The flow of plasticized material was analyzed using a marker insert technique.The results show that the knurling shoulder design with square and hexagonal pin design facilitated constant stability force with reference to weld length/time.The uniform mixing and distribution of plasticized material were facilitated by the knurling shoulder design with square tool pin shape(TK)S(sticking length minimum)below which fragmented copper was observed.(TK)S tool facilitated higher mechanical properties for the welds,i.e.strength(182 MPa)and hardness(HV 78)in stir zone.
基金This research was supportedby a grant under‘Development of Key Materials and Fundamental Tech-nology for Secondary Battery’Program of the Ministry of Commerce,Industry and Energy,Korea.
文摘Employing Li2CO3, NiO, Co3O4, and MnCO3 powders as starting materials, Li[Ni1/3Co1/3Mn1/3]O2 was synthesized by solid-state reaction method. Various grinding aids were applied during milling in order to optimize the synthesis process. After successive heat treatments at 650 and 950 ℃, the prepared powders were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy, and transmission electron microscopy. The powders prepared by adding salt (NaCl) as grinding aid exhibit a clear R3m layer structure. The powders by other grinding aids like heptane show some impurity peaks in the XRD pattern. The former powders show a uniform particle size distribution of less than 1 μm average size while the latter shows a wide distribution ranging from 1 to 10 μm. Energy dispersive X-ray (EDX) analysiss show that the ratio of Ni, Co, and Mn content in the powder is approximately 1/3, 1/3, and 1/3, respecively. The EDX data indicate no incorporation of sodium or chlorine into the powders. Charge-discharge tests gave an initial discharge capacity of 160 mAh·g-1 for the powders with NaCl addition while 70 mAh·g-1 for the powders with heptane.
基金supported by the project of Fundamental Materials Development funded by the Korean Ministry of Knowledge Economy
文摘The effects of hydro co-extrusion on the microstructure changes of aluminum hybrid duo-cast Al 3003/Al 4004 clad materials were studied. The specimen of duo-cast Al 3003/Al 4004 clad materials was in circle shape, and was composed of Al 3003(outside) and Al 4004(inside) materials. The specimen was extruded by the hydro co-extrusion equipment. The manufacturing conditions of the specimen were 423 K in temperature and 5 in extrusion ratio. The dimensions of the specimen were 80 mm in diameter of the Al 4004 material and 35 mm in thickness of the Al 3003 material before the hydro co-extrusion process, and 30 mm in diameter and about 5 mm in thickness after the extrusion process, respectively. The microstructure and the hardness for two specimens were investigated. The hardness value of cross section in the duo-cast Al 3003/Al 4004 clad materials before the extrusion process was increased in form of the parabola toward the center. However, after the extrusion process, it was almost constant in the portion of Al 4004 material. Lots of big voids above 1 mm in diameter in the specimen existed in the interfacing region of Al 3003 and Al 4004 materials before the extrusion process. These big voids disappeared after the process of hydro co-extrusion.
基金financially supported by the National Research Foundation of Korea(NRF)from the Korea Government(MEST,No.NRF-2022R1F1A1070886MSIT,No.RS2023-00217581)the Commercialization Promotion Agency for R&D Outcomes(COMPA)from the Korea Government(MEST,No.1711175258)。
文摘Heteroatom-doped transition metal oxides have attracted great attention as advanced anode materials for lithium-ion batteries due to their high theoretical capacity and superior properties.However,the limited resource availability has led to a substantial rise in prices for valuable metals such as Ni and Co,posing a significant challenge for their application.To address this issue,recycling of these metals from waste materials have gained prominence,and particularly the recovery of Co has been mostly focused on its economic benefits.Herein,we introduced a novel recycling strategy for fabrication of heteroatomdoped CoO_(x)(comprising mainly Co_(3)O_(4)with a minor CoO phase)anode with a yolk–shell structure for lithium-ion batteries,by separating Co from cemented tungsten carbide waste.By employing a simple leaching process and subsequent spray pyrolysis,the yolk–shell structured microsphere comprising CoO_(x)was successfully synthesized.Moreover,the presence of other waste metals in the leachate facilitated multi-heteroatom doping during synthesis.Interestingly,the introduction of various dopants into CoO_(x)induced oxygen vacancy formation,thereby enhancing the electrochemical properties of the CoO_(x)anode.As a result,compared with the phase-pure(undoped)CoO_(x)yolk–shell,the heteroatom-doped CoO_(x)yolk–shell exhibited robust cycling stability(602 mAh·g^(-1)for 200 cycles at 1 A·g^(-1))and excellent rate capability(210 mAh·g^(-1)at 10 A·g^(-1)).
基金financially supported by the Materials/Parts Technology Development Program(No.RS-202400456324)funded by the Ministry of Trade,Industry&Energy(MOTIE,Korea)by the National Research Foundation(NRF)of Korea grant(No.RS-2024-00454367)funded by the Ministry of Science and ICT(MSIT,Korea)。
文摘K–Se batteries have been identified as promising energy storage systems owing to their high energy density and cost-effectiveness.However,challenges such as substantial volume changes and low Se utilization require further investigation.In this study,novel N-doped multichannel carbon nanofibers(h-NMCNFs)with hierarchical porous structures were successfully synthesized as efficient cathode hosts for K–Se batteries through the carbonization of two electrospun immiscible polymer nanofibers and subsequent chemical activation.Mesopores originated from the decomposition of the polymer embedded in the carbon nanofibers,and micropores were introduced via KOH activation.During the activation step,hierarchical porous carbon nanofibers with enhanced pore volumes were formed because of the micropores in the carbon nanofibers.Owing to the mesopores that enabled easy access to the electrolyte and the high utilization of chain-like Se within the micropores,the Se-loaded hierarchical porous carbon nanofibers(60 wt%Se)exhibited a high discharge capacity and excellent rate performance.The discharge capacity of the nanofibers at the 1,000th cycle was 210.8 mA.h.g^(-1)at a current density of 0.5C.The capacity retention after the initial activation was 64%.In addition,a discharge capacity of 165 mA.h.g^(-1)was obtained at an extremely high current density of 3.0C.
基金supported by the Fundamental Research Program of the Korea Institute of Materials Science(No.PNK9820).
文摘Retained austenite plays a significant role in third-generation advanced high-strength steels (AHSS 3. Gen.), renowned for their excellent combination of strength and ductility. Silicon (Si) is a key element in stabilizing retained austenite. However, it introduces challenges in galvannealing and welding processes in Zn-coated steels, such as inhibited Fe-Zn alloying and increased susceptibility to liquid metal embrittlement (LME). This study investigated the mechanism of Si enrichment at the Zn/steel interface and its role in suppressing Fe-Zn interdiffusion during annealing. Using advanced techniques such as high-resolution transmission electron microscopy and atomic probe tomography, and Thermo-Calc DICTRA simulations, we analyzed the diffusion behavior and microstructural evolution in Zn-coated steels with varying Si contents. Si, driven by its low solubility in liquid Zn and Fe-Zn intermetallic phases, accumulates at the interface, forming a Si-enriched region that significantly suppresses Zn diffusion while permitting limited Fe diffusion. Numerical simulations revealed that the Si-enriched layer forms via the drag effect of the Fe-Zn reaction line, progressively concentrating Si at the interface as Zn diffuses. As annealing progresses, the morphology of the Si-enriched region evolves from layered, cloud-like structures to droplets and elongated dendritic forms, driven by Zn penetration and Fe consumption. These findings provide novel insights into the role of Si enrichment in mitigating LME and optimizing the Zn-coated AHSS 3. Gen., paving the way for advancements in automotive material design.
基金supported by the Nano&Material Technology Development Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(RS-2024-00436563)supported by Brain Pool program funded by the Ministry of Science and ICT through the National Research Foundation of Korea(Grant No.RS-2023-00284361).
文摘Seawater is the most abundant source of molecular hydrogen.Utilizing the hydrogen reserves present in the seawater may inaugurate innovative strategies aimed at advancing sustainable energy and environmental preservation endeavors in the future.Recently,there has been a surge in study in the field addressing the production of hydrogen through the electrochemical seawater splitting.However,the performance and durability of the electrode have limitations due to the fact that there are a few challenges that need to be addressed in order to make the technology suitable for the industrial purpose.The active site blockage caused by chloride ions that are prevalent in seawater and chloride corrosion is the most significant issue;it has a negative impact on both the activity and the durability of the anode component.Addressing this particular issue is of upmost importance in the seawater splitting area.This review concentrates on the newly developed materials and techniques for inhibiting chloride ions by blocking the active sites,simultaneously preventing the chloride corrosion.It is anticipated that the concept will be advantageous for a large audience and will inspire researchers to study on this particular area of concern.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean Government(MSIT)(Nos.RS-2023-00217581 and RS-2023-00304768)the National Research Council of Science&Technology(NST)grant by the Korean Government(MSIT)(No.CAP 22073-000).
文摘Aqueous zinc-ion batteries(AZIBs)have emerged as promising,practical energy storage devices based on their non-toxic nature,environmental friendliness,and high energy density.However,excellent rate characteristics and stable long-term cycling performance are essential.These essential aspects create a need for superior cathode materials,which represents a substantial challenge.In this study,we used MXenes as a framework for NH_(4)V_(4)O_(10)(NVO)construction and developed electrodes that combined the high capacity of NVO with the excellent conductivity of MXene/carbon nanofibers(MCNFs).We explored the electrochemical characteristics of electrodes with varying NVO contents.Considering the distinctive layered structure of NVO,the outstanding conductivity of MCNFs,and the strong synergies between the two components.NVO-MCNFs exhibited better charge transfer compared with earlier materials,as well as more ion storage sites,excellent conductivity,and short ion diffusion pathways.A composite electrode with optimized NVO content exhibited an excellent specific capacitance of 360.6mAh g^(-1) at 0.5 A g^(-1) and an outstanding rate performance.In particular,even at a high current density of 10 A g^(-1),the 32NVO-MCNF exhibited impressive cycling stability:88.6%over 2500 cycles.The mechanism involved was discovered via comprehensive characterization.We expect that the fabricated nanofibers will be useful in energy storage and conversion systems.
基金funded by Burapha University,grant number SDG 4/2568.
文摘Nitrogen-doped activated carbon(N-AC)was successfully prepared by KOH-activation and nitrogen doping using ammonia(NH3)heat treatment.Coconut shell-derived activated carbon(AC)was heat-treated under NH3 gas in the temperature range of 700℃-900℃.Likewise,the mixture of potassium hydroxide(KOH)and AC was heated at 800℃,followed by heat treatment underNH3 gas at 800℃(hereafter referred to asKOH-N-AC800).Scanning electron microscopy(SEM),Raman spectroscopy,X-ray photoelectron spectroscopy(XPS)and Brunauer-Emmett-Teller(BET)method were utilized to analyze morphology,crystallinity,chemical bonding,chemical composition and surface area.The surface area and porosity of N-AC increased with increasing NH3 heat treatment.Similarly,the nitrogen content in the N-AC increased from 3.23%to 4.84 at%when the NH3 heat treatment was raised from 700℃ to 800℃.However,the nitrogen content of N-AC decreased to 3.40 at% after using NH3 heat treatment at 900℃.The nitrogen content of KOH-N-AC800 is 5.43 at%.KOH-N-AC800 and N-AC800 exhibited improvements of 33.66% and 26.24%,respectively,in CO_(2) adsorption compared with AC.The enhancement of CO_(2) adsorption of KOH-N-AC800 is attributed to the synergic effect of the nitrogen doping,high surface area,and porosity.The results exhibited that nitrogen sites on the surface play a more significant role in CO_(2) adsorption than surface area and porosity.This work proposes the potential synergistic effect of KOH-activation and nitrogen doping for enhancing the CO_(2) adsorption capacity of activated carbon.
文摘Titanium-based nitride coatings on cutting tools,press molds and dies can be used to prolong their life cycle because of their superior corrosion and oxidation resistance.TiAlN/ZrN and TiCrN/ZrN multilayer coatings were prepared by RF magnetron sputtering,and their microstructural evolution and corrosion resistance during heat treatment were investigated.The TiAlN/ZrN and TiCrN/ZrN multilayer coatings are degraded by heating up to 600 ℃ with the formation of oxides particles on the surface.During the heat treatment,the TiCrN/ZrN and TiAlN/ZrN multilayer coatings show the lowest corrosion current density and the highest polarization resistance at temperature range of 400-500 ℃.Consequently,the TiAlN/ZrN and TiCrN/ZrN multilayer coatings show good corrosion resistance at temperature range of 400-500 ℃ during heating.
文摘The applicability of Ce and Y as promising candidate elements to form irreversible traps in weld metal was investigated by thermal desorption spectroscopy(TDS) with gas chromatography(GC). The precise nature of the precipitate particles newly formed in the weld metal by the addition of Ce and Y to a certain alloy system was characterized. Moreover,the hydrogen trapping efficiency expressed as the reduction of the diffusible hydrogen in the weld metal was analyzed. The results showed that the addition of Ce and/or Y to this alloy system led to the formation of a mixed type of(Ce,Ti)-based oxide,(Y,Ni)-based carbide,or(Ce,Y,Ti)-based oxide particles. Because of the high activation energy of the mixed type of particles(≥ 150 k J/mol),the trapping efficiency for hydrogen was considered to be sufficiently high to effectively reduce the diffusible hydrogen content.
文摘Mg alloys exhibit a number of good properties such as low density, good castability and high specific strength. However, molten Mg and Mg alloys are ignited without the melt protective gases during melting and casting process due to their high reactivity. The purpose of this study is to investigate effects of Ca and CaO on pure Mg through microstructure observation, ignition test and phase analysis. With increasing Ca and CaO contents, the ignition resistance of Ca or CaO added pure Mg is increased and the grains are refined. As results of XRD and EDS, CaO is reduced to Ca in CaO added pure Mg. Mg2Ca phase is formed even in 0.1 wt.%CaO added pure Mg by reduction mechanism, while Mg2Ca phase is formed over 1.35 wt.% Ca added pure Mg.
基金supported by the R&D Center for Valuable Recycling(Global-Top Environmental Technology Development Program)funded by the Ministry of Environment(Project No.:11-C22-ID)
文摘Wetting phenomena between MgO C and CaO SiO2 slags were investigated by varying carbon content.A sessile drop technique was adopted to study the wetting phenomena in conjunction with a high speed camera for the observation of intrinsic wetting phenomena.The results show that the high content of SiO2 and the presence of Al2O3 in slags enhance the diffusion of Mg2+,leading to the promotion of reactive wetting.The carbon in MgO C refractory impedes the penetration of slags by repelling the slag and slowing the diffusion of Mg2+.This accounts for the non-wetting behavior of the slag on MgO C refractory with 17% (mass fraction) carbon similar to that of graphite.
基金financially supported by the Fundamental R&D Program for Core Technology of Materials(No.10041233)the Human Resources Program in Energy Technology of the Korea Institute of Energy Technology Evaluation and Planning(KETEP)(No.20174030201620)。
文摘The effects of alloying elements(Co,Cr,Mo,W,Al,Ti,and Ta)on the oxidation resistance of Ni-(0-15)Co-(8-15)Cr-(0-5)Mo-(0-10)W-(3-8)Al-(0-5)Ti-(0-10)Ta-0.1 C-0.01 B alloys were studied.The sample compositions were designed by the Box-Behnken method of design of experiments(DOE).The alloying elements show complicated effects on the mass gain due to oxidation,depending on the alloy composition.Al reduces the mass gain largely.The other elements except Al do not appear to exert a strong effect on the oxidation rate on average,but their influences are shown clearly in the alloys with a low Al content.Co,W,and Ta reduce the oxidation rate,while Cr,Mo,and Ti promote oxidation.Ta is the most effective element in reducing the oxidation rate of the alloy with a low Al concentration.It is confirmed that a continuous Al2O3 layer is essentially required for high oxidation resistance.The oxide scale of easily oxidized alloys has various oxides such as NiCr2O4,NiAl2O4,NiO,Cr2O3,CrTaO4,and TiO2.
基金supported by research funds from Chosun University,Korea,2001
文摘A small amount of misch metal was added to Cu-Zn-Al alloy in order to study its effect on grain refinement,mechanical properties,phase transformation behavior and stabilization of martensite.It is found that the addition of misch metal is very effective for reducing the grain size.The coarse grains over 1 000 μm are refined to the size of 30 μm by the addition of 0.43%(mass fraction) misch metal.The grain size of thermo-mechanically treated alloys is barely affected by cold working.The fracture strength and ductility increase significantly with the increase of misch metal content when tensile test is carried out below Mf temperature.Also,the fracture strength is larger in the case of post-quench ageing treatment than that in the case of direct quench ageing treatment.The fracture mode is changed from transgranular brittle fracture to ductile fracture with void formation and coalescence by the addition of misch metal.
文摘Mg-Al-Zn-M M （misch metal） alloy powders were manufactured by inert gas atomization and the characteristics of alloy powders were investigated.In spite of the low fluidity and easy oxidation of the magnesium melt,the spherical powder was made successfully with the improved three piece nozzle systems of gas atomization unit. It was found that most of the solidified powders with particles size of less than 50μm in diameter were single crystal and the solidification structure of rapidly solidified powders showed a typical dendritic morphology because of supercooling prior to nucleation.The spacing of secondary denrite arms was deceasing as the size of powders was decreasing.The rapidly solidified powders were consolidated by vacuum hot extrusion and the effects of misch metal addition to AZ91 on mechanical properties of extruded bars were also examined.During extrusion of the rapidly solidified powders,their dendritic structure was broken into fragments and remained as grains of about 3μm in size.The Mg-Al-Ce intermetallic compounds formed in the interdendritic regions of powders were finely broken,too.The tensile strength and ductility obtained in as-extruded Mg-9 wt pct Al-1 wt pct Zn-3 wt pct MM alloy wereσ-（T.S.） =383 MPa andε=10.6%,respectively.All of these improvements on mechanical properties were resulted from the refined microstructure and second-phase dispersions.
基金supported financially by the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science,ICT and Future Planning(No.NRF-2017R1E1A1A01074266)the Industrial Fundamental Technology Development Program(No.10076350)funded by the Ministry of Trade,Industry and Energy(MOTIE)of Korea.
文摘In this work,a simple synthesis of sulfur doped graphitic carbon nitride(S-g-C3N4)act as a support cum stabilizers for gold nanoparticles(Au)and its was characterized by UV–vis and XRD to measure the absorbance and crystallinity,respectively.The functional group and morphology of the samples were identified using FT-IR and TEM.Finally,the Au@S-g-C3N4 nanocatalyst exhibits good catalytic performance and stability in the reduction of hazardous 4-nitrophenol(NP)compared to S-g-C3N4 using Na BH4.Moreover,the Au@S-g-C3N4 nanocomposite holds a good catalytic efficiency(near 100%)achieved by within 5 min.The highest catalytic reduction of NP is due to the synergistic effect of Au nanoparticles decorated on S-g-C3N4.The fast electron transfer reduction mechanism was elucidated and discussed.Excellent reusability and stability of the developed nanocomposites were also observed in consecutive reduction experiments.The filtering and catalyzing device was used for the direct conversion of NP polluted water.This method can open a new avenue for the metal nanoparticles based carbon materials heterogeneous catalyst and its reduction of toxic contaminants.
文摘The alpha-case formation reactions between Ti and investment molds （Al-2O-3,ZrSiO-4,ZrO-2,CaO stabilized ZrO-2） were evaluated in a plasma arc melting furnace.Regardless of thermodynamic approaches,there were distinct alpha-case formations.The reaction products were characterized by electron probe micro-analysis and transmission electron microscopy.Theα-case generation between Ti and Al-2O-3 mold was not able to be explained by the conventionalα-case formation mechanism,which is known to be formed by the interstitials,especially oxygen dissolved from mold materials.However,from our experimental results and thermodynamic calculations,it was confirmed that theα-case is formed not only by an interstitial element but also by substitutional metallic elements dissolved from mold materials.Our newly establishedα-case formation mechanism will surely lead to a variety of significant applications of theα-case controlled Ti casting.
