The reaction behavior between CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags and La-bearing FeCrAl melt was quantitatively characterized,which was further compared with the reaction behavior of CaO–SiO_(2)-based slags.Bas...The reaction behavior between CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags and La-bearing FeCrAl melt was quantitatively characterized,which was further compared with the reaction behavior of CaO–SiO_(2)-based slags.Based on this,the new type of mold flux for La-bearing FeCrAl alloy continuous casting was designed and its basic properties were evaluated.The results showed that the order of reaction degree of fluxing agents in CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags is(Na_(2)O)>(B_(2)O_(3))>(Li_(2)O),and the percentages of mass change of fluxing agents were 85.8,54.29 and 42.35 wt.%,respectively.Moreover,the addition of(Li_(2)O)and(Na_(2)O)promoted the reaction between(CaO)and[Al],and the reaction degree of the former was weaker than that of the latter,which was due to the greater effect of(Na_(2)O)on the activity of(CaO)and(Al_(2)O_(3))than(Li_(2)O).Compared with the reactivity of CaO–SiO_(2)-based slags,the percentages of mass change of Al and La caused by slag–steel reaction decreased by 10.63–14.36 and 39.78–50.49 wt.%,respectively.The percentages of mass change of(Al_(2)O_(3)),(La_(2)O_(3))and(CaO)in slags highest increased by 17.71,17.98,and 7.81 wt.%,respectively.The reactivity of CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags was significantly weakened.Ultimately,the new type of mold flux was designed and the composition range was determined.The fundamental properties of new mold flux basically meet the theoretical requirements for La-bearing FeCrAl alloy continuous casting.展开更多
To understand the mechanism of the interfacial reaction between high-Mn and high-Al steel and MgO refractory,a series of laboratory experiments as well as thermodynamic calculations were performed.The effects of Mn an...To understand the mechanism of the interfacial reaction between high-Mn and high-Al steel and MgO refractory,a series of laboratory experiments as well as thermodynamic calculations were performed.The effects of Mn and Al contents in the steel and the reaction time on the interfacial reaction were investigated.It was observed that the erosion of the MgO refractory is caused by the reaction of Al and Mn in the steel with MgO in the refractory,which would lead to the formation of(Mn,Mg)O·Al_(2)O_(3) spinel and(Mn,Mg)O solid solution.The formation mechanism of the spinel and solid solution is as follows.The Al in the steel firstly reacts with MgO in the refractory to generate MgO·Al_(2)O_(3) spinel,and then,the spinel reacts with Mn in the steel to form(Mn,Mg)O·Al_(2)O_(3) spinel.Finally,the MnO in the spinel reacts with the MgO in the inner refractory to form(Mn,Mg)O solid solution.In addition,only(Mn,Mg)O·Al_(2)O_(3) spinel is present in the interfacial reaction layer of the refractory when the Al content in the steel is sufficient.展开更多
Reaction behaviors occurring in Ti/Al foil metallurgy were systematically investigated.Particular emphasis was focused on the reaction between solid Al and Ti as well as subsequent reaction between TiAland Ti layer.In...Reaction behaviors occurring in Ti/Al foil metallurgy were systematically investigated.Particular emphasis was focused on the reaction between solid Al and Ti as well as subsequent reaction between TiAland Ti layer.In the solid reaction between Al and Ti,the presence of residual Al is mainly caused by inhomogeneous growth of TiAllayer and micro-voids existing at the interface.However,through reaction between molten Al and Ti,TiAl/Ti multilayer can be achieved with complete consumption of Al.During subsequent high-temperature heat treatment,TiAl/Ti multilayer will eventually turn into TiAl/TiAl multilayer accompanying with simultaneous formation and successive disappearance of intermediate phases,such as TiAland TiAl.Moreover,it is found that the growth direction of TiAl layer changes as a function of annealing time between different couples in multi-intermetallics system.展开更多
In order to develop limonite and decrease CO_(2) emissions,siderite is proposed as a clean reductant for suspension magnetization roasting(SMR) of limonite.An iron concentrate(iron grade:65.92wt%,iron recovery:98.54wt...In order to develop limonite and decrease CO_(2) emissions,siderite is proposed as a clean reductant for suspension magnetization roasting(SMR) of limonite.An iron concentrate(iron grade:65.92wt%,iron recovery:98.54wt%) was obtained by magnetic separation under the optimum SMR conditions:siderite dosage 40wt%,roasting temperature 700℃,roasting time 10 min.According to the magnetic analysis,SMR achieved the conversion of weak magnetic minerals to strong magnetic minerals,thus enabling the recovery of iron via magnetic separation.Based on the phase transformation analysis,during the SMR process,limonite was first dehydrated and converted to hematite,and then siderite decomposed to generate magnetite and CO,where CO reduced the freshly formed hematite to magnetite.The microstructure evolution analysis indicated that the magnetite particles were loose and porous with a destroyed structure,making them easier to be ground.The non-isothermal kinetic results show that the main reaction between limonite and siderite conformed to the two-dimension diffusion mechanism,suggesting that the diffusion of CO controlled the reaction.These results encourage the application of siderite as a reductant in SMR.展开更多
In order to ascertain the reaction behavior of rare earth minerals in coal-based reduction, X-ray diffraction（XRD）, scanning electron microscopy（SEM）, and energy dispersive spectroscopy（EDS） analyses were applie...In order to ascertain the reaction behavior of rare earth minerals in coal-based reduction, X-ray diffraction（XRD）, scanning electron microscopy（SEM）, and energy dispersive spectroscopy（EDS） analyses were applied to investigate the rare earth minerals in Bayan Obo.The occurrence state and regularity of rare earth elements were analyzed under different reduction time. The results reveal that rare earth elements in rare earth minerals exist in RE（CO3）F（bastnaesite） and REPO4（monazite）. In this research, at 1,498 K with a C/O molar ratio（i.e., molar ratio of fixed carbon in the coal to reducible oxygen in the ore） of2.5, rare earth minerals primarily decompose into RE2O3at5 min. When the time is extended to 10 min, solid-phase reactions occur among RE2O3, CaO, and SiO2, and the resultant is cerium wollastonite（CaO·2RE2O3·3SiO2）. At reaction time 〉20 min, rare earth elements mainly exist in cerium wollastonite（CaO·2RE2O3·3SiO2）, and the grain size varies in the range of 10–30 μm. The results show that coal-based reduction is efficient to recover rare earth minerals in reduced materials.展开更多
The formation mechanism of calcium vanadate and manganese vanadate and the difference between calcium and manganese in the reaction with vanadium are basic issues in the calcification roasting and manganese roasting p...The formation mechanism of calcium vanadate and manganese vanadate and the difference between calcium and manganese in the reaction with vanadium are basic issues in the calcification roasting and manganese roasting process with vanadium slag.In this work,CaO–V_(2)O_(5) and MnO_(2)–V_(2)O_(5) diffusion couples were prepared and roasted for different time periods to illustrate and compare the diffusion reaction mechanisms.Then,the changes in the diffusion product and diffusion coefficient were investigated and calculated based on scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) analysis.Results show that with the extension of the roasting time,the diffusion reaction gradually proceeds among the CaO–V_(2)O_(5) and MnO_(2)–V_(2)O_(5) diffusion couples.The regional boundaries of calcium and vanadium are easily identifiable for the CaO–V_(2)O_(5) diffusion couple.Meanwhile,for the MnO_(2)–V_(2)O_(5) diffusion couple,MnO_(2) gradually decomposes to form Mn_(2)O_(3),and vanadium diffuses into the interior of Mn_(2)O_(3).Only a part of vanadium combines with manganese to form the diffusion production layer.CaV_(2)O_(6) and MnV_(2)O_(6) are the interfacial reaction products of the CaO–V_(2)O_(5) and MnO_(2)–V_(2)O_(5) diffusion couples,respectively,whose thicknesses are 39.85 and 32.13μm when roasted for 16 h.After 16 h,both diffusion couples reach the reaction equilibrium due to the limitation of diffusion.The diffusion coefficient of the CaO–V_(2)O_(5) diffusion couple is higher than that of the MnO_(2)–V_(2)O_(5) diffusion couple for the same roasting time,and the diffusion reaction between vanadium and calcium is easier than that between vanadium and manganese.展开更多
In this paper,the ballistic impact experiments,including impact test chamber and impact double-spaced plates,were conducted to study the reaction behaviors of a novel functionally graded reactive material(FGRM),which ...In this paper,the ballistic impact experiments,including impact test chamber and impact double-spaced plates,were conducted to study the reaction behaviors of a novel functionally graded reactive material(FGRM),which was composed of polytetrafluoroethylene/aluminum(PTFE/Al)and PTFE/Al/bismuth trioxide(Bi_(2)O_(3)).The experiments showed that the impact direction of the FGRM had a significant effect on the reaction.With the same impact velocity,when the first impact material was PTFE/Al/Bi_(2)O_(3),compared with first impact material PTFE/Al,the FGRM induced higher overpressure in the test chamber and larger damaged area of double-spaced plates.The theoretical model,which considered the shock wave generation and propagation,the effect of the shock wave on reaction efficiency,and penetration behaviors,was developed to analyze the reaction behaviors of the FGRM.The model predicted first impact material of the FGRM with a higher shock impedance was conducive to the reaction of reactive materials.The conclusion of this study provides significant information about the design and application of reactive materials.展开更多
At the molar ratio of CaO to SiO2 of 1, with calcium hydroxide and sodium silicate, calcium silicate hydrate was synthesized at 50, 100, 170 ℃, respectively. The results show that temperature favors the formation of ...At the molar ratio of CaO to SiO2 of 1, with calcium hydroxide and sodium silicate, calcium silicate hydrate was synthesized at 50, 100, 170 ℃, respectively. The results show that temperature favors the formation of calcium silicate hydrate with perfect structure. When calcium silicate hydrate reacts with caustic solution, the decomposition rate of calcium silicate hydrate increases with the increasing caustic concentration and decreases with the raising synthesis temperature and the prolongation of reaction time. The decomposition rate is all less than 1.2% in caustic solution, and XRD pattern of the residue after reaction with caustic solution is found as the same as that of original calcium silicate hydrate, which indicates the stable existence of calcium silicate hydrate in caustic solution. When reacted with soda solution, the decomposition rate increases with the increasing soda concentration and reaction time, while decreases with the synthesis temperature. The decomposition rate is more than 2% because （CaO·SiO2·H2O（CSH（Ⅰ））,） except (Ca5（OH）2Si6O16·4H2O) and (Ca6Si6O17（OH）2,) is decomposed. So the synthesis temperature and soda concentration should be controlled in the process of transformation of sodium aluminosilicate hydrate into calcium silicate hydrate.展开更多
The effects of different Bi contents on the properties of Sn solders were studied. The interfacial reaction and growth behavior of intermetallic compounds（IMCs） layer（η-Cu6 Sn5 + e-Cu3 Sn） for various soldering t...The effects of different Bi contents on the properties of Sn solders were studied. The interfacial reaction and growth behavior of intermetallic compounds（IMCs） layer（η-Cu6 Sn5 + e-Cu3 Sn） for various soldering time and the influence of Bi addition on the thermal behavior of Sn-x Bi solder alloys were investigated. The Cu6 Sn5 IMC could be observed as long as the molten solder contacted with the Cu substrate. However, with the longer welding time such as 60 and 300 s, the Cu3 Sn IMC was formed at the interface between Cu6 Sn5 and Cu substrate. With the increase of soldering time, the thickness of total IMCs increased, meanwhile, the grain size of Cu6 Sn5 also increased. An appropriate amount of Bi element was beneficial for the growth of total IMCs,but excessive Bi（≥ 5 wt%） inhibited the growth of Cu6 Sn5 and Cu3 Sn IMC in Sn-x Bi/Cu microelectronic interconnects. Furthermore, with the Bi contents increasing（Sn-10 Bi solder in this present investigation）, some Bi particles accumulated at the interface between Cu6 Sn5 layer and the solder.展开更多
The influence of barium addition to a Ni/Al2O3 catalyst on the reaction intermediates formed,the activity,resistance of the catalyst to coking,and properties of the coke formed after acetic acid steam reforming were i...The influence of barium addition to a Ni/Al2O3 catalyst on the reaction intermediates formed,the activity,resistance of the catalyst to coking,and properties of the coke formed after acetic acid steam reforming were investigated in this study.The results showed the drastic effects of barium addition on the physicochemical properties and performances of the catalyst.The solid-phase reaction between alumina and BaO formed BaAl2O4,which re-constructed the alumina structure,resulting in a decrease in the specific surface area and an increase in the resistance of metallic Ni to sintering.The addition of barium was also beneficial for enhancing the catalytic activity,resulting from the changed catalytic reaction network.The in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study of the acetic acid steam reforming indicated that barium could effectively suppress the accumulation of the reaction intermediates of carbonyl,formate,and C=C functional groups on the catalyst surface,attributed to its relatively high ability to cause the gasification of these species.In addition,coking was considerably more significant over the Ba-Ni/Al2O3 catalyst.Moreover,the Ba-Ni/Al2O3 catalyst was more stable than the Ni/Al2O3catalyst,owing to the distinct forms of coke formed (carbon nanotube form over the Ba-Ni/Al2O3 catalyst,and the amorphous form over the Ni/Al2O3 catalyst).展开更多
The influence of Cu content on the reaction process, reaction behavior and obtained products in the Cu-ZrC system, as well as their relationships, were investigated. The results showed that Zr C was synthesized throug...The influence of Cu content on the reaction process, reaction behavior and obtained products in the Cu-ZrC system, as well as their relationships, were investigated. The results showed that Zr C was synthesized through the diffusion and dissolution of C into a Cu-Zr liquid. Increasing the Cu content enhanced the amount of Cu-Zr liquid formed at the early stage but decreased the amount of C atoms dissolving into the melt at unit time. Consequently, the ignition time initially decreased and then increased. Conversely, with an increased Cu content, the energy required for igniting the neighboring unreacted powders increased,while the heat released by the reaction and the dwell time of the compact at high temperatures decreased.These effects then resulted in the reduction of combustion wave velocity, combustion temperature and Zr C particle size. Furthermore, the synthesis of ZrC is a multistage process, which provides a nonuniform distributed Zr C particle size. The sub-μm Zr C particle reinforced Cu matrix composite was fabricated by adding a ZrC-Cu master alloy prepared through a self-propagating high-temperature synthesis reaction into liquid Cu.展开更多
The thermal decomposition behavior and nonisothermal reaction kinetics of the double-base gun propellants containing the mixed ester of triethyleneglycol dinitrate（TEGDN） and nitroglycerin（NG） were investigated by...The thermal decomposition behavior and nonisothermal reaction kinetics of the double-base gun propellants containing the mixed ester of triethyleneglycol dinitrate（TEGDN） and nitroglycerin（NG） were investigated by thermogravimetry（TG） and differential thermogravimetry（DTG）, and differential scanning calorimetry（DSC） under the high-pressure dynamic ambience. The results show that the thermal decomposition processes of the mixed nitric ester gun propellants have two mass-loss stages. Nitric ester evaporates and decomposes in the first stage, and nitrocellulose and centralite II（C2） decompose in the second stage. The mass loss, the DTG peak points, and the terminated temperatures of the two stages are changeable with the difference of the mass ratio of TEGDN to NG. There is only one obvious exothermic peak in the DSC curves under the different pressures. With the increase in the furnace pressure, the peak temperature decreases, and the decomposition heat increases. With the increase in the content of TEGDN, the decomposition heat decreases at 0.1 MPa and rises at high pressure. The variety of mass ratio of TEGDN to NG makes few effect on the exothermic peak temperatures in the DSC curves at different pressures. The kinetic equation of the main exothermal decomposition reaction of the gun propellant TG0601 was determined as： dα/dt=1021.59（1-α）3e-2.60×104/T. The reaction mechanism of the process can be classified as chemical reaction. The critical temperatures of the thermal explosion（Tbe and Tbp） obtained from the onset temperature（Te） and the peak temperature（Tp） are 456.46 and 473.40 K, respectively. ΔS≠, ΔH≠, and ΔG≠ of the decomposition reaction are 163.57 J·mol^-1·K^-1, 209.54 kJ·mol^-1, and 133.55 kJ·mol^-1, respectively.展开更多
The energy-dispersive spectroscopy （ EDS ） , X-ray diffraction analysis （ XRD ） and differential thermal analysis （DTA） were used to analyze the melting, spreading process, and reaction mechanism of non-corrosiv...The energy-dispersive spectroscopy （ EDS ） , X-ray diffraction analysis （ XRD ） and differential thermal analysis （DTA） were used to analyze the melting, spreading process, and reaction mechanism of non-corrosive flux on the surface of aluminum. The result indicates that the whole process can be divided into three stages. In the first stage, flux is heated from room temperature to its melting point, which is called the endothermic stage, mainly absorbs heat and generates a small amount of liquid flux. When the temperature exceeds the melting point of flux, a large amount of liquid flux is generated and reacts with oxide films on the surface of aluminum. This stage is called the reaction stage. The third stage is a spreading and cleaning process, in which residues and reaction products quickly flow out from the center with liquid flux. The different compositions of flux perform different functions in brazing. K3AlF6 can remove oxide film us a cleaner. Only in liquid or molten state can flux remove oxide film on the substrate.展开更多
A class of initial boundary value problems for the reaction diffusion equations are considered.The asymptotic behavior of solution for the problem is obtained using the theory of differential inequality.
基金supported by the National Natural Science Foundation of China(Grant Nos.52174321,52274339 and 52074186).
文摘The reaction behavior between CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags and La-bearing FeCrAl melt was quantitatively characterized,which was further compared with the reaction behavior of CaO–SiO_(2)-based slags.Based on this,the new type of mold flux for La-bearing FeCrAl alloy continuous casting was designed and its basic properties were evaluated.The results showed that the order of reaction degree of fluxing agents in CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags is(Na_(2)O)>(B_(2)O_(3))>(Li_(2)O),and the percentages of mass change of fluxing agents were 85.8,54.29 and 42.35 wt.%,respectively.Moreover,the addition of(Li_(2)O)and(Na_(2)O)promoted the reaction between(CaO)and[Al],and the reaction degree of the former was weaker than that of the latter,which was due to the greater effect of(Na_(2)O)on the activity of(CaO)and(Al_(2)O_(3))than(Li_(2)O).Compared with the reactivity of CaO–SiO_(2)-based slags,the percentages of mass change of Al and La caused by slag–steel reaction decreased by 10.63–14.36 and 39.78–50.49 wt.%,respectively.The percentages of mass change of(Al_(2)O_(3)),(La_(2)O_(3))and(CaO)in slags highest increased by 17.71,17.98,and 7.81 wt.%,respectively.The reactivity of CaO–Al_(2)O_(3)–La_(2)O_(3)-based slags was significantly weakened.Ultimately,the new type of mold flux was designed and the composition range was determined.The fundamental properties of new mold flux basically meet the theoretical requirements for La-bearing FeCrAl alloy continuous casting.
基金the support of the National Natural Science Foundation of China(Grant Nos.52274337 and 52174317)。
文摘To understand the mechanism of the interfacial reaction between high-Mn and high-Al steel and MgO refractory,a series of laboratory experiments as well as thermodynamic calculations were performed.The effects of Mn and Al contents in the steel and the reaction time on the interfacial reaction were investigated.It was observed that the erosion of the MgO refractory is caused by the reaction of Al and Mn in the steel with MgO in the refractory,which would lead to the formation of(Mn,Mg)O·Al_(2)O_(3) spinel and(Mn,Mg)O solid solution.The formation mechanism of the spinel and solid solution is as follows.The Al in the steel firstly reacts with MgO in the refractory to generate MgO·Al_(2)O_(3) spinel,and then,the spinel reacts with Mn in the steel to form(Mn,Mg)O·Al_(2)O_(3) spinel.Finally,the MnO in the spinel reacts with the MgO in the inner refractory to form(Mn,Mg)O solid solution.In addition,only(Mn,Mg)O·Al_(2)O_(3) spinel is present in the interfacial reaction layer of the refractory when the Al content in the steel is sufficient.
基金financially supported by the National Basic Research Program of China(No.2011CB605501)the National Natural Science Foundation of China(Nos.U1204508 and 51171015)the Project of State Key Laboratory for Advanced Metals and Materials,University of Science and Technology Beijing(No.2012Z-11)
文摘Reaction behaviors occurring in Ti/Al foil metallurgy were systematically investigated.Particular emphasis was focused on the reaction between solid Al and Ti as well as subsequent reaction between TiAland Ti layer.In the solid reaction between Al and Ti,the presence of residual Al is mainly caused by inhomogeneous growth of TiAllayer and micro-voids existing at the interface.However,through reaction between molten Al and Ti,TiAl/Ti multilayer can be achieved with complete consumption of Al.During subsequent high-temperature heat treatment,TiAl/Ti multilayer will eventually turn into TiAl/TiAl multilayer accompanying with simultaneous formation and successive disappearance of intermediate phases,such as TiAland TiAl.Moreover,it is found that the growth direction of TiAl layer changes as a function of annealing time between different couples in multi-intermetallics system.
基金financially supported by the National Natural Science Foundation of China(Nos.51874071 and 52022019)。
文摘In order to develop limonite and decrease CO_(2) emissions,siderite is proposed as a clean reductant for suspension magnetization roasting(SMR) of limonite.An iron concentrate(iron grade:65.92wt%,iron recovery:98.54wt%) was obtained by magnetic separation under the optimum SMR conditions:siderite dosage 40wt%,roasting temperature 700℃,roasting time 10 min.According to the magnetic analysis,SMR achieved the conversion of weak magnetic minerals to strong magnetic minerals,thus enabling the recovery of iron via magnetic separation.Based on the phase transformation analysis,during the SMR process,limonite was first dehydrated and converted to hematite,and then siderite decomposed to generate magnetite and CO,where CO reduced the freshly formed hematite to magnetite.The microstructure evolution analysis indicated that the magnetite particles were loose and porous with a destroyed structure,making them easier to be ground.The non-isothermal kinetic results show that the main reaction between limonite and siderite conformed to the two-dimension diffusion mechanism,suggesting that the diffusion of CO controlled the reaction.These results encourage the application of siderite as a reductant in SMR.
基金financially supported by the National Natural Science Foundation of China (Nos. 51204033 and 51134002)
文摘In order to ascertain the reaction behavior of rare earth minerals in coal-based reduction, X-ray diffraction（XRD）, scanning electron microscopy（SEM）, and energy dispersive spectroscopy（EDS） analyses were applied to investigate the rare earth minerals in Bayan Obo.The occurrence state and regularity of rare earth elements were analyzed under different reduction time. The results reveal that rare earth elements in rare earth minerals exist in RE（CO3）F（bastnaesite） and REPO4（monazite）. In this research, at 1,498 K with a C/O molar ratio（i.e., molar ratio of fixed carbon in the coal to reducible oxygen in the ore） of2.5, rare earth minerals primarily decompose into RE2O3at5 min. When the time is extended to 10 min, solid-phase reactions occur among RE2O3, CaO, and SiO2, and the resultant is cerium wollastonite（CaO·2RE2O3·3SiO2）. At reaction time 〉20 min, rare earth elements mainly exist in cerium wollastonite（CaO·2RE2O3·3SiO2）, and the grain size varies in the range of 10–30 μm. The results show that coal-based reduction is efficient to recover rare earth minerals in reduced materials.
基金supported by the National Natural Science Foundation of China(Nos.52174277 and 51874077)the Fundamental Funds for the Central Universities,China(No.N2225032)+1 种基金the China Postdoctoral Science Foundation(No.2022M720683)the Postdoctoral Fund of Northeastern University,China。
文摘The formation mechanism of calcium vanadate and manganese vanadate and the difference between calcium and manganese in the reaction with vanadium are basic issues in the calcification roasting and manganese roasting process with vanadium slag.In this work,CaO–V_(2)O_(5) and MnO_(2)–V_(2)O_(5) diffusion couples were prepared and roasted for different time periods to illustrate and compare the diffusion reaction mechanisms.Then,the changes in the diffusion product and diffusion coefficient were investigated and calculated based on scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) analysis.Results show that with the extension of the roasting time,the diffusion reaction gradually proceeds among the CaO–V_(2)O_(5) and MnO_(2)–V_(2)O_(5) diffusion couples.The regional boundaries of calcium and vanadium are easily identifiable for the CaO–V_(2)O_(5) diffusion couple.Meanwhile,for the MnO_(2)–V_(2)O_(5) diffusion couple,MnO_(2) gradually decomposes to form Mn_(2)O_(3),and vanadium diffuses into the interior of Mn_(2)O_(3).Only a part of vanadium combines with manganese to form the diffusion production layer.CaV_(2)O_(6) and MnV_(2)O_(6) are the interfacial reaction products of the CaO–V_(2)O_(5) and MnO_(2)–V_(2)O_(5) diffusion couples,respectively,whose thicknesses are 39.85 and 32.13μm when roasted for 16 h.After 16 h,both diffusion couples reach the reaction equilibrium due to the limitation of diffusion.The diffusion coefficient of the CaO–V_(2)O_(5) diffusion couple is higher than that of the MnO_(2)–V_(2)O_(5) diffusion couple for the same roasting time,and the diffusion reaction between vanadium and calcium is easier than that between vanadium and manganese.
基金National Natural Science Foundation of China[grant number U1730112],China.
文摘In this paper,the ballistic impact experiments,including impact test chamber and impact double-spaced plates,were conducted to study the reaction behaviors of a novel functionally graded reactive material(FGRM),which was composed of polytetrafluoroethylene/aluminum(PTFE/Al)and PTFE/Al/bismuth trioxide(Bi_(2)O_(3)).The experiments showed that the impact direction of the FGRM had a significant effect on the reaction.With the same impact velocity,when the first impact material was PTFE/Al/Bi_(2)O_(3),compared with first impact material PTFE/Al,the FGRM induced higher overpressure in the test chamber and larger damaged area of double-spaced plates.The theoretical model,which considered the shock wave generation and propagation,the effect of the shock wave on reaction efficiency,and penetration behaviors,was developed to analyze the reaction behaviors of the FGRM.The model predicted first impact material of the FGRM with a higher shock impedance was conducive to the reaction of reactive materials.The conclusion of this study provides significant information about the design and application of reactive materials.
文摘At the molar ratio of CaO to SiO2 of 1, with calcium hydroxide and sodium silicate, calcium silicate hydrate was synthesized at 50, 100, 170 ℃, respectively. The results show that temperature favors the formation of calcium silicate hydrate with perfect structure. When calcium silicate hydrate reacts with caustic solution, the decomposition rate of calcium silicate hydrate increases with the increasing caustic concentration and decreases with the raising synthesis temperature and the prolongation of reaction time. The decomposition rate is all less than 1.2% in caustic solution, and XRD pattern of the residue after reaction with caustic solution is found as the same as that of original calcium silicate hydrate, which indicates the stable existence of calcium silicate hydrate in caustic solution. When reacted with soda solution, the decomposition rate increases with the increasing soda concentration and reaction time, while decreases with the synthesis temperature. The decomposition rate is more than 2% because （CaO·SiO2·H2O（CSH（Ⅰ））,） except (Ca5（OH）2Si6O16·4H2O) and (Ca6Si6O17（OH）2,) is decomposed. So the synthesis temperature and soda concentration should be controlled in the process of transformation of sodium aluminosilicate hydrate into calcium silicate hydrate.
基金Funded by the National Natural Science Foundation of China(No.51465039)Natural Science Foundation of Jiangxi Province(No.20151BAB206041,20161BAB206122)Fund of the State Key Laboratory of Solidification Processing in NWPU(No.SKLSP201508)
文摘The effects of different Bi contents on the properties of Sn solders were studied. The interfacial reaction and growth behavior of intermetallic compounds（IMCs） layer（η-Cu6 Sn5 + e-Cu3 Sn） for various soldering time and the influence of Bi addition on the thermal behavior of Sn-x Bi solder alloys were investigated. The Cu6 Sn5 IMC could be observed as long as the molten solder contacted with the Cu substrate. However, with the longer welding time such as 60 and 300 s, the Cu3 Sn IMC was formed at the interface between Cu6 Sn5 and Cu substrate. With the increase of soldering time, the thickness of total IMCs increased, meanwhile, the grain size of Cu6 Sn5 also increased. An appropriate amount of Bi element was beneficial for the growth of total IMCs,but excessive Bi（≥ 5 wt%） inhibited the growth of Cu6 Sn5 and Cu3 Sn IMC in Sn-x Bi/Cu microelectronic interconnects. Furthermore, with the Bi contents increasing（Sn-10 Bi solder in this present investigation）, some Bi particles accumulated at the interface between Cu6 Sn5 layer and the solder.
基金supported by the National Natural Science Foundation of China(No.51876080)the Strategic International Scientific and Technological Innovation Cooperation Special Funds of National Key Research and Development Program of China(No.2016YFE0204000)+3 种基金the Program for Taishan Scholars of Shandong Province Governmentthe Recruitment Program of Global Experts(Thousand Youth Talents Plan)the Natural Science Foundation of Shandong Province(ZR2017BB002)the Key Research and Development Program of Shandong Province(2018GSF116014)。
文摘The influence of barium addition to a Ni/Al2O3 catalyst on the reaction intermediates formed,the activity,resistance of the catalyst to coking,and properties of the coke formed after acetic acid steam reforming were investigated in this study.The results showed the drastic effects of barium addition on the physicochemical properties and performances of the catalyst.The solid-phase reaction between alumina and BaO formed BaAl2O4,which re-constructed the alumina structure,resulting in a decrease in the specific surface area and an increase in the resistance of metallic Ni to sintering.The addition of barium was also beneficial for enhancing the catalytic activity,resulting from the changed catalytic reaction network.The in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) study of the acetic acid steam reforming indicated that barium could effectively suppress the accumulation of the reaction intermediates of carbonyl,formate,and C=C functional groups on the catalyst surface,attributed to its relatively high ability to cause the gasification of these species.In addition,coking was considerably more significant over the Ba-Ni/Al2O3 catalyst.Moreover,the Ba-Ni/Al2O3 catalyst was more stable than the Ni/Al2O3catalyst,owing to the distinct forms of coke formed (carbon nanotube form over the Ba-Ni/Al2O3 catalyst,and the amorphous form over the Ni/Al2O3 catalyst).
基金supported by the National Key Research and Development Program (No. 2017YFB0305300)the National Natural Science Foundation of China (Nos. 51404157, 51374144)+1 种基金Public Welfare Projects of Science and Technology Department of Zhejiang Province (Grant No. 2017C31118)the Natural Science Foundation of Zhejiang Province (Grant No. LY17E050003)
文摘The influence of Cu content on the reaction process, reaction behavior and obtained products in the Cu-ZrC system, as well as their relationships, were investigated. The results showed that Zr C was synthesized through the diffusion and dissolution of C into a Cu-Zr liquid. Increasing the Cu content enhanced the amount of Cu-Zr liquid formed at the early stage but decreased the amount of C atoms dissolving into the melt at unit time. Consequently, the ignition time initially decreased and then increased. Conversely, with an increased Cu content, the energy required for igniting the neighboring unreacted powders increased,while the heat released by the reaction and the dwell time of the compact at high temperatures decreased.These effects then resulted in the reduction of combustion wave velocity, combustion temperature and Zr C particle size. Furthermore, the synthesis of ZrC is a multistage process, which provides a nonuniform distributed Zr C particle size. The sub-μm Zr C particle reinforced Cu matrix composite was fabricated by adding a ZrC-Cu master alloy prepared through a self-propagating high-temperature synthesis reaction into liquid Cu.
基金the National Natural Science Foundation of China(No.20573098)the Foundation of Key Laboratory of Science and Technology for National Defence of Propellant and Explosive of China(No.9140C3503020605).
文摘The thermal decomposition behavior and nonisothermal reaction kinetics of the double-base gun propellants containing the mixed ester of triethyleneglycol dinitrate（TEGDN） and nitroglycerin（NG） were investigated by thermogravimetry（TG） and differential thermogravimetry（DTG）, and differential scanning calorimetry（DSC） under the high-pressure dynamic ambience. The results show that the thermal decomposition processes of the mixed nitric ester gun propellants have two mass-loss stages. Nitric ester evaporates and decomposes in the first stage, and nitrocellulose and centralite II（C2） decompose in the second stage. The mass loss, the DTG peak points, and the terminated temperatures of the two stages are changeable with the difference of the mass ratio of TEGDN to NG. There is only one obvious exothermic peak in the DSC curves under the different pressures. With the increase in the furnace pressure, the peak temperature decreases, and the decomposition heat increases. With the increase in the content of TEGDN, the decomposition heat decreases at 0.1 MPa and rises at high pressure. The variety of mass ratio of TEGDN to NG makes few effect on the exothermic peak temperatures in the DSC curves at different pressures. The kinetic equation of the main exothermal decomposition reaction of the gun propellant TG0601 was determined as： dα/dt=1021.59（1-α）3e-2.60×104/T. The reaction mechanism of the process can be classified as chemical reaction. The critical temperatures of the thermal explosion（Tbe and Tbp） obtained from the onset temperature（Te） and the peak temperature（Tp） are 456.46 and 473.40 K, respectively. ΔS≠, ΔH≠, and ΔG≠ of the decomposition reaction are 163.57 J·mol^-1·K^-1, 209.54 kJ·mol^-1, and 133.55 kJ·mol^-1, respectively.
基金Acknowledgements The authors are grateful to the National Natural Science Foundation of China （ No. 51465032） for financial support.
文摘The energy-dispersive spectroscopy （ EDS ） , X-ray diffraction analysis （ XRD ） and differential thermal analysis （DTA） were used to analyze the melting, spreading process, and reaction mechanism of non-corrosive flux on the surface of aluminum. The result indicates that the whole process can be divided into three stages. In the first stage, flux is heated from room temperature to its melting point, which is called the endothermic stage, mainly absorbs heat and generates a small amount of liquid flux. When the temperature exceeds the melting point of flux, a large amount of liquid flux is generated and reacts with oxide films on the surface of aluminum. This stage is called the reaction stage. The third stage is a spreading and cleaning process, in which residues and reaction products quickly flow out from the center with liquid flux. The different compositions of flux perform different functions in brazing. K3AlF6 can remove oxide film us a cleaner. Only in liquid or molten state can flux remove oxide film on the substrate.
基金the National Natural Science Foundation of China( 90 2 1 1 0 0 4 ,1 0 4 71 0 39) ,and by the"Hundred Talents Project"of Chinese Academy of Sciences
文摘A class of initial boundary value problems for the reaction diffusion equations are considered.The asymptotic behavior of solution for the problem is obtained using the theory of differential inequality.
