Developing various approaches for preparing high performance materials has long been topics and tasks both for scientists and for engineers.Despite that many methods have been developed for preparing nanomaterials,dev...Developing various approaches for preparing high performance materials has long been topics and tasks both for scientists and for engineers.Despite that many methods have been developed for preparing nanomaterials,developing simple and environment-friendly ways for preparing nanomaterials is very attractive.Here a simple approach of synthesizing Fe3O4 nanoparticles by arc-discharge submerging in water was reported.The results showed that by this method Fe3O4 nanoparticles can be synthesized at large scale.The as-prepared Fe3O4 nanoparticles exhibited uniform spherical shape and their diameters varied with arc-discharging parameters.The experimental results showed that the size of the synthesized Fe3O4 nanoparticles can be controlled through adjusting the processing parameters.Since no vacuum system has been used,the synthesizing process is greatly simplified.In addition,only cheap deionized water and industrial iron bar are used and no pollution or harmful byproducts are found in the synthesis process.It indicated that the present approach is a simple,low-cost and environment-friendly one for preparing nanoparticles.展开更多
The Zr41Ti14Cu12.5Ni10Be22.5(at.%)bulk metallic glass composites with various crystallization fractions were prepared by pretreating the bulk metallic glassy samples with pulsing current,and then by isothermal anneali...The Zr41Ti14Cu12.5Ni10Be22.5(at.%)bulk metallic glass composites with various crystallization fractions were prepared by pretreating the bulk metallic glassy samples with pulsing current,and then by isothermal annealing at near initial crystallization temperature for different periods of time.The precipitations and crystallization fractions were studied by X-ray diffraction(XRD)and differential scanning calorimetry(DSC),and their effects on mechanical properties of the composite were studied by microhardness,uniaxial compression test and scanning electron microscopy(SEM).The experimental results show that the primary precipitate is quasicrystalline phase and other metastable phases including Be2Zr,Zr2Cu and FCC would precipitate subsequently.In the initial crystallization process,in which the crystallization fraction increases from 0 to 8.2%,both fracture strength and plastic strain increase,with the maximum plastic strain up to 6.4%.When the crystallization fraction is larger than 8.2%,the fracture strength and the plastic strain decrease sharply.Furthermore,the alloy with low crystallization fraction is fractured by shearing,while for high crystallization fraction it is fractured by splitting and cleavage.The results show that the mechanical properties of the glassy alloy could be optimized by controlling the processing parameters.展开更多
The effect of thermal cycling treatment on mechanical properties and thermal stability of a Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass is investigated.The metallic glassy samples are sealed into quartz tubes under h...The effect of thermal cycling treatment on mechanical properties and thermal stability of a Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass is investigated.The metallic glassy samples are sealed into quartz tubes under high vacuum condition,and liquid nitrogen together with electric furnace are used to control a periodical temperature variation between 196℃ and 150℃.The structure and properties of the tested samples for different thermal cycles have been examined by X-ray diffraction analysis,mechanical properties measurement and thermal analysis.It has been found that the structure and properties of the samples do not show a significant change even after 200 cycles,which suggests Zr41Ti14Cu12.5Ni10Be22.5 alloy as having potential in aerospace environment.展开更多
A series of Ti-Zr-Be-Fe bulk metallic glasses(BMGs)with good glass-forming ability(GFA)and high specific strength have been developed.With different alloying routes and content of Fe,it is found that these alloys exhi...A series of Ti-Zr-Be-Fe bulk metallic glasses(BMGs)with good glass-forming ability(GFA)and high specific strength have been developed.With different alloying routes and content of Fe,it is found that these alloys exhibit different GFA and mechanical properties.The effects of Fe addition on the GFA and mechanical properties of Ti-Zr-Be alloy are systemically investigated.The possible mechanisms for the improvement or damage to the GFA by addition of Fe can be interpreted in view of the mixing enthalpy,atomic size differences and electronegativity differences of the alloys,while the mechanical properties strongly depend on the Poisson’s ratio and free volume concentration.The experimental results also show that alloying technology is an effective method to improve the GFA and mechanical properties of Ti-Zr-Be glassy alloy.展开更多
A bulk metal/ceramic composite material with a honeycomb-like micro-cell structure has been prepared by sintering the spherical Al90Mn9Ce1 alloy powders clad by Al2O3 nano-powder with the spark plasma sintering (SPS) ...A bulk metal/ceramic composite material with a honeycomb-like micro-cell structure has been prepared by sintering the spherical Al90Mn9Ce1 alloy powders clad by Al2O3 nano-powder with the spark plasma sintering (SPS) technique. The as-prepared material consists of Al90Mn9Ce1 alloy cell and closed Al2O3 ceramic cell wall. The diameter of the cells is about 20―40 μm, while a thickness of the cell wall is about 1―2 μm. The ultimate compressive strength of the as-sintered materials is about 514 MPa, while its fracture strain is up to about 0.65 %. This composite material might possess good anti-corrosion, thermal endurance and other potential properties due to its unique microstructure. The result shows that the Al90Mn9Ce1/Al2O3 composite powders can be sintered by spark plasma sintering technique despite the large difference in their sintering temperature. This work offers a way of designing and preparing metal/ceramic composite material with functional property.展开更多
Pd80+xSi20-x (x=0,1,and 2) binary metallic glasses with the diameter ranging from 7 to 8 mm were prepared by a combination of fluxing and water quenching or air cooling. Thermal analysis results show that with increas...Pd80+xSi20-x (x=0,1,and 2) binary metallic glasses with the diameter ranging from 7 to 8 mm were prepared by a combination of fluxing and water quenching or air cooling. Thermal analysis results show that with increasing Si content,the glass transition temperature Tg,the initial crystallization temperature Tx and the onset crystalliza-tion temperature Tp of Pd-Si binary glassy alloys increase. Moreover,the super-cooled liquid region reaches 61 K. It indicates that Pd-Si binary alloys possess large glass forming ability,which can be greatly improved by fluxing treatment.展开更多
文摘Developing various approaches for preparing high performance materials has long been topics and tasks both for scientists and for engineers.Despite that many methods have been developed for preparing nanomaterials,developing simple and environment-friendly ways for preparing nanomaterials is very attractive.Here a simple approach of synthesizing Fe3O4 nanoparticles by arc-discharge submerging in water was reported.The results showed that by this method Fe3O4 nanoparticles can be synthesized at large scale.The as-prepared Fe3O4 nanoparticles exhibited uniform spherical shape and their diameters varied with arc-discharging parameters.The experimental results showed that the size of the synthesized Fe3O4 nanoparticles can be controlled through adjusting the processing parameters.Since no vacuum system has been used,the synthesizing process is greatly simplified.In addition,only cheap deionized water and industrial iron bar are used and no pollution or harmful byproducts are found in the synthesis process.It indicated that the present approach is a simple,low-cost and environment-friendly one for preparing nanoparticles.
基金supported by the National Basic Research Program of China(Grant No.2007CB613905)the National Natural Science Foundation of China(Grant Nos.50671050 and 50971073)
文摘The Zr41Ti14Cu12.5Ni10Be22.5(at.%)bulk metallic glass composites with various crystallization fractions were prepared by pretreating the bulk metallic glassy samples with pulsing current,and then by isothermal annealing at near initial crystallization temperature for different periods of time.The precipitations and crystallization fractions were studied by X-ray diffraction(XRD)and differential scanning calorimetry(DSC),and their effects on mechanical properties of the composite were studied by microhardness,uniaxial compression test and scanning electron microscopy(SEM).The experimental results show that the primary precipitate is quasicrystalline phase and other metastable phases including Be2Zr,Zr2Cu and FCC would precipitate subsequently.In the initial crystallization process,in which the crystallization fraction increases from 0 to 8.2%,both fracture strength and plastic strain increase,with the maximum plastic strain up to 6.4%.When the crystallization fraction is larger than 8.2%,the fracture strength and the plastic strain decrease sharply.Furthermore,the alloy with low crystallization fraction is fractured by shearing,while for high crystallization fraction it is fractured by splitting and cleavage.The results show that the mechanical properties of the glassy alloy could be optimized by controlling the processing parameters.
基金supported by the National Basic Research Program of China(Grant No.2007CB613905)the National Natural Science Foundation of China(Grant Nos.50971073,51101090 and 51271095)Beijing Natural Science Foundation(Effect of pre-cyclic loading on mechanical behaviors of bulk amorphous alloys)
文摘The effect of thermal cycling treatment on mechanical properties and thermal stability of a Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass is investigated.The metallic glassy samples are sealed into quartz tubes under high vacuum condition,and liquid nitrogen together with electric furnace are used to control a periodical temperature variation between 196℃ and 150℃.The structure and properties of the tested samples for different thermal cycles have been examined by X-ray diffraction analysis,mechanical properties measurement and thermal analysis.It has been found that the structure and properties of the samples do not show a significant change even after 200 cycles,which suggests Zr41Ti14Cu12.5Ni10Be22.5 alloy as having potential in aerospace environment.
基金supported by the National Basic Research Program of China(Grant No.2007CB613905)the National Natural Science Foundation of China(Grant Nos.51271095,51101090 and 50971073)
文摘A series of Ti-Zr-Be-Fe bulk metallic glasses(BMGs)with good glass-forming ability(GFA)and high specific strength have been developed.With different alloying routes and content of Fe,it is found that these alloys exhibit different GFA and mechanical properties.The effects of Fe addition on the GFA and mechanical properties of Ti-Zr-Be alloy are systemically investigated.The possible mechanisms for the improvement or damage to the GFA by addition of Fe can be interpreted in view of the mixing enthalpy,atomic size differences and electronegativity differences of the alloys,while the mechanical properties strongly depend on the Poisson’s ratio and free volume concentration.The experimental results also show that alloying technology is an effective method to improve the GFA and mechanical properties of Ti-Zr-Be glassy alloy.
基金This work was supported by the China Postdoctoral Science Foundation(No.2003033133)the Basic Science Research Foundation of Tsinghua University(Grant No.091201107)the National Center for Nanoscience and Technology of China.
文摘A bulk metal/ceramic composite material with a honeycomb-like micro-cell structure has been prepared by sintering the spherical Al90Mn9Ce1 alloy powders clad by Al2O3 nano-powder with the spark plasma sintering (SPS) technique. The as-prepared material consists of Al90Mn9Ce1 alloy cell and closed Al2O3 ceramic cell wall. The diameter of the cells is about 20―40 μm, while a thickness of the cell wall is about 1―2 μm. The ultimate compressive strength of the as-sintered materials is about 514 MPa, while its fracture strain is up to about 0.65 %. This composite material might possess good anti-corrosion, thermal endurance and other potential properties due to its unique microstructure. The result shows that the Al90Mn9Ce1/Al2O3 composite powders can be sintered by spark plasma sintering technique despite the large difference in their sintering temperature. This work offers a way of designing and preparing metal/ceramic composite material with functional property.
基金the National Basic Research Program of China (Grant No. 2007CB613905)the National Natural Science Foundation of China (Grant Nos. 50671050 and 50431030)
文摘Pd80+xSi20-x (x=0,1,and 2) binary metallic glasses with the diameter ranging from 7 to 8 mm were prepared by a combination of fluxing and water quenching or air cooling. Thermal analysis results show that with increasing Si content,the glass transition temperature Tg,the initial crystallization temperature Tx and the onset crystalliza-tion temperature Tp of Pd-Si binary glassy alloys increase. Moreover,the super-cooled liquid region reaches 61 K. It indicates that Pd-Si binary alloys possess large glass forming ability,which can be greatly improved by fluxing treatment.
