Nitrogen-doped carbon materials with a large specific surface area,high conductivity,and adjustable microstructures have many prospects for energy-related applications.This is especially true for N-doped nanocarbons u...Nitrogen-doped carbon materials with a large specific surface area,high conductivity,and adjustable microstructures have many prospects for energy-related applications.This is especially true for N-doped nanocarbons used in the electrocatalytic oxygen reduction reaction(ORR)and supercapacitors.Here,we report a low-cost,environmentally friendly,large-scale mechanochemical method of preparing N-doped porous carbons(NPCs)with hierarchical micro-mesopores and a large surface area via ball-milling polymerization followed by pyrolysis.The optimized NPC prepared at 1000°C(NPC-1000)offers excellent ORR activity with an onset potential(Eonset)and half-wave potential(E1/2)of 0.9 and 0.82 V,respectively(vs.a reversible hydrogen electrode),which are only approximately 30 mV lower than that of Pt/C.The rechargeable Zn–air battery assembled using NPC-1000 and the NiFe-layered double hydroxide as bifunctional ORR and oxygen evolution reaction electrodes offered superior cycling stability and comparable discharge performance to RuO2 and Pt/C.Moreover,the supercapacitor electrode equipped with NPC prepared at 800℃ exhibited a high specific capacity(431 F g^−1 at 10 mV s^−1),outstanding rate,performance,and excellent cycling stability in an aqueous 6-M KOH solution.This work demonstrates the potential of the mechanochemical preparation method of porous carbons,which are important for energy conversion and storage.展开更多
The preparation of nano sized La 2O 3 powder by mechanochemical reaction of lanthanum carbonate with sodium hydroxide and subsequent heat treatment was studied using X ray diffraction, differential thermal and ther...The preparation of nano sized La 2O 3 powder by mechanochemical reaction of lanthanum carbonate with sodium hydroxide and subsequent heat treatment was studied using X ray diffraction, differential thermal and thermo gravimetric analysis and transmission electron microscopy. It was found that the mechanochemical reaction process can be divided into two steps: the first step is the multi phases mechanochemical reaction of lanthanum carbonate with NaOH to form amorphous lanthanum basic carbonate and lanthanum hydroxide, and the second step is the crystallization of basic lanthanum carbonate with the formula of La 2(OH) 2(CO 3) 2·H 2O under a quasi hydrothermal synthesis condition caused by the mechanical ball milling. The synthesized La 2O 3 powder appears clearly separated spherical like monodisperse nano size particles in which particle size ranges from 30 to 50 nm.展开更多
In this study, a powder mixture with an Al/TiO2 molar ratio of 10/3 was used to form an r-Al2Ti intermetallic matrix composite （IMC） reinforced with α-Al2O3 ceramic by a novel milling technique, called discontinuou...In this study, a powder mixture with an Al/TiO2 molar ratio of 10/3 was used to form an r-Al2Ti intermetallic matrix composite （IMC） reinforced with α-Al2O3 ceramic by a novel milling technique, called discontinuous mechanical milling （DMM） instead of milling and ignition of the produced thermite. The results of energy dispersive X-ray spectroscopy （EDX） and X-ray diffraction （XRD） of samples with varying milling time indicate that this fabrication process requires considerable mechanical energy. It is shown that Al2Ti-α-Al2O3 IMC with small grain size was produced by DMM after 15 h of ball milling. Peaks for γ-TLA1 as well as Al2Ti and Al2O3 are observed in XRD patterns after DMM followed by heat treatment. The microhardness of the DMM-treated composite produced after heat treatment was higher than Hv 700.展开更多
铬铁矿液相氧化法可以得到铬酸钠和高浓度碱的混合物,前期研究表明,采用氢氧化钡可以较好地实现从高碱介质中分离铬酸根,形成铬酸钡中间体。然而,钡盐在传统的加热搅拌模式下转化制备重铬酸钠,存在反应过程时间长、效率低的问题。在分...铬铁矿液相氧化法可以得到铬酸钠和高浓度碱的混合物,前期研究表明,采用氢氧化钡可以较好地实现从高碱介质中分离铬酸根,形成铬酸钡中间体。然而,钡盐在传统的加热搅拌模式下转化制备重铬酸钠,存在反应过程时间长、效率低的问题。在分析铬酸钡固液反应控制步骤的基础上,研究了球磨搅拌反应模式对该固液转化反应过程的强化作用。系统考察了反应温度、时间、液固比(液固体积质量比)、料球比(物料和磨球的质量比)、物料配比(铬酸钡与硫酸氢钠的物质的量比)、固液混合速率对铬酸钡转化率的影响,并得到了较好的工艺参数:反应温度为180℃、反应时间为120 min、液固比为10 m L/g、料球比为2∶1、物料配比为1∶1、固液混合速率为50 r/min,在此条件下得到铬酸钡的转化率为93%。展开更多
In this paper, TiAl alloy powders were prepared successfully by high-energy ball milling and diffusion reaction in vacuum at low temperature. The titanium powder, aluminum powder, and titanium hydride powder were used...In this paper, TiAl alloy powders were prepared successfully by high-energy ball milling and diffusion reaction in vacuum at low temperature. The titanium powder, aluminum powder, and titanium hydride powder were used as raw materials. The samples were characterized by scanning electron microscopy（SEM）, X-ray diffraction（XRD）, field-emission scanning electron microscopy（FESEM）, and differential thermal analysis（DTA）. The results show that the alloy powders with the main intermetallic compounds of TiAl are obtained using Ti-Al powders and TiH2-Al powders after heated for 2 h at 500 ℃,3 h at 600 ℃,and 3 h at 750 ℃,respectively.The average grain sizes of alloy powder are about 45 and20 μm with irregular shape, respectively. The prepared TiAl alloy powders are relatively pure, and the average quality content of oxygen in the alloy powders is0.33 wt%. The forming process of alloy powder contains both the diffusion reaction of Ti and Al,which gives priority to the diffusion reaction of aluminum.展开更多
基金financial support from NSFC(51602332)the National Key Research and Development Program of China(2016YFB0700204)+4 种基金Science and Technology Commission of Shanghai Municipality(15520720400,16DZ2260603)Equipment Research Program(6140721050215)the National 1000 Youth Talents program of Chinafinancial support from Ningbo 3315 programDST Solar Energy Harnessing Centre(DST/TMD/SERI/HUB/1(C)),DST Materials for Energy Storage program,Ministry of Electronics and Information Technology(India)(Project ID:ELE1819353MEITNAK)
文摘Nitrogen-doped carbon materials with a large specific surface area,high conductivity,and adjustable microstructures have many prospects for energy-related applications.This is especially true for N-doped nanocarbons used in the electrocatalytic oxygen reduction reaction(ORR)and supercapacitors.Here,we report a low-cost,environmentally friendly,large-scale mechanochemical method of preparing N-doped porous carbons(NPCs)with hierarchical micro-mesopores and a large surface area via ball-milling polymerization followed by pyrolysis.The optimized NPC prepared at 1000°C(NPC-1000)offers excellent ORR activity with an onset potential(Eonset)and half-wave potential(E1/2)of 0.9 and 0.82 V,respectively(vs.a reversible hydrogen electrode),which are only approximately 30 mV lower than that of Pt/C.The rechargeable Zn–air battery assembled using NPC-1000 and the NiFe-layered double hydroxide as bifunctional ORR and oxygen evolution reaction electrodes offered superior cycling stability and comparable discharge performance to RuO2 and Pt/C.Moreover,the supercapacitor electrode equipped with NPC prepared at 800℃ exhibited a high specific capacity(431 F g^−1 at 10 mV s^−1),outstanding rate,performance,and excellent cycling stability in an aqueous 6-M KOH solution.This work demonstrates the potential of the mechanochemical preparation method of porous carbons,which are important for energy conversion and storage.
文摘The preparation of nano sized La 2O 3 powder by mechanochemical reaction of lanthanum carbonate with sodium hydroxide and subsequent heat treatment was studied using X ray diffraction, differential thermal and thermo gravimetric analysis and transmission electron microscopy. It was found that the mechanochemical reaction process can be divided into two steps: the first step is the multi phases mechanochemical reaction of lanthanum carbonate with NaOH to form amorphous lanthanum basic carbonate and lanthanum hydroxide, and the second step is the crystallization of basic lanthanum carbonate with the formula of La 2(OH) 2(CO 3) 2·H 2O under a quasi hydrothermal synthesis condition caused by the mechanical ball milling. The synthesized La 2O 3 powder appears clearly separated spherical like monodisperse nano size particles in which particle size ranges from 30 to 50 nm.
文摘In this study, a powder mixture with an Al/TiO2 molar ratio of 10/3 was used to form an r-Al2Ti intermetallic matrix composite （IMC） reinforced with α-Al2O3 ceramic by a novel milling technique, called discontinuous mechanical milling （DMM） instead of milling and ignition of the produced thermite. The results of energy dispersive X-ray spectroscopy （EDX） and X-ray diffraction （XRD） of samples with varying milling time indicate that this fabrication process requires considerable mechanical energy. It is shown that Al2Ti-α-Al2O3 IMC with small grain size was produced by DMM after 15 h of ball milling. Peaks for γ-TLA1 as well as Al2Ti and Al2O3 are observed in XRD patterns after DMM followed by heat treatment. The microhardness of the DMM-treated composite produced after heat treatment was higher than Hv 700.
文摘铬铁矿液相氧化法可以得到铬酸钠和高浓度碱的混合物,前期研究表明,采用氢氧化钡可以较好地实现从高碱介质中分离铬酸根,形成铬酸钡中间体。然而,钡盐在传统的加热搅拌模式下转化制备重铬酸钠,存在反应过程时间长、效率低的问题。在分析铬酸钡固液反应控制步骤的基础上,研究了球磨搅拌反应模式对该固液转化反应过程的强化作用。系统考察了反应温度、时间、液固比(液固体积质量比)、料球比(物料和磨球的质量比)、物料配比(铬酸钡与硫酸氢钠的物质的量比)、固液混合速率对铬酸钡转化率的影响,并得到了较好的工艺参数:反应温度为180℃、反应时间为120 min、液固比为10 m L/g、料球比为2∶1、物料配比为1∶1、固液混合速率为50 r/min,在此条件下得到铬酸钡的转化率为93%。
基金financially supported by the National Natural Science Foundation of China (No. 51274039)the Guangdong Foundation of Research (No. 2011A090200091)
文摘In this paper, TiAl alloy powders were prepared successfully by high-energy ball milling and diffusion reaction in vacuum at low temperature. The titanium powder, aluminum powder, and titanium hydride powder were used as raw materials. The samples were characterized by scanning electron microscopy（SEM）, X-ray diffraction（XRD）, field-emission scanning electron microscopy（FESEM）, and differential thermal analysis（DTA）. The results show that the alloy powders with the main intermetallic compounds of TiAl are obtained using Ti-Al powders and TiH2-Al powders after heated for 2 h at 500 ℃,3 h at 600 ℃,and 3 h at 750 ℃,respectively.The average grain sizes of alloy powder are about 45 and20 μm with irregular shape, respectively. The prepared TiAl alloy powders are relatively pure, and the average quality content of oxygen in the alloy powders is0.33 wt%. The forming process of alloy powder contains both the diffusion reaction of Ti and Al,which gives priority to the diffusion reaction of aluminum.
