首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到19条相似文献,搜索用时 62 毫秒
1.
Mechanism of AIN combustion synthesis was studied by DSC analysis and “quenching” experiment of combustion wave. In preheating region, Al powder melted at 660℃ and became spherical because of surface tension. In reaction region, Al volatilized rapidly at 1000℃ and Al vapor reacted with N2 to form AlN, which nucleated and grew on the surface of AlN formed precedently as a diluent. Based on the experiment analysis,kinetics equations and modeling were established. Analysis showed the dramatic effect of temperature, aluminum particle size and nitrogen pressure on the reaction speed.  相似文献   

2.
0 INTRODUCTIONAluminumnitride (AlN)isamaterialwhichpossess esoutstandingelectricalandthermalpropertiessuchashighthermalconductivity ,lowthermalexpansion ,gooddielectricstrength ,goodresistancetocorrosionandero sion ,andhighhardness .Presently ,AlNceramicisfind ingincreasedusageinsubstratesandpackaging ,cru cibles ,firingtilesandthermalfillersinpolymers ,adhe sivesandpottingcompounds[1] .Thetypicalcombustionsynthesis ,orself propagatinghigh temperaturesynthesis ,istheoldestandmostwell kn…  相似文献   

3.
Mechanism of hybrid-magnetic-circuit multi-couple motor   总被引:1,自引:0,他引:1  
0 INTRODUCTIONInapermanent magnetinductormotor ,theaxiallymagnetizedpermanentmagnetisgenerallysandwichedbe tweentwosegmentsofironcores .Theintervalbetweenlaminationsmakestheair gapmagneticfieldproducedbythepermanentmagnetveryunevenintheaxialdirection .Wit…  相似文献   

4.
The effect of operating conditions on the aluminium content of Ni - Al allay deposit and the catalytic function of NaF on electrodeposition in the nonaqueous solution containing aluminium are investigated.The results indicate that the plated aluminuim content will be increased with the rise of current density in a given range. When the current density is 2.5A/dm^2, nickle-aluminium alloy conl, oJlurtg 13.1 wt% aluminium will be deposited. The plated aluminium content will be increased by 2wt% as 0. 1 mol/ L NaF is added to the bath.  相似文献   

5.
Electronic structure of Ag-Cu alloys   总被引:15,自引:0,他引:15  
Inordertoadvancematerialsscienceintoasystematicscienceofmaterialsandempiricaldesignofmaterialsintoascientificdesignofmaterials,wefirstestablishedtheoneatomtheoryofpuremetals(simplyOAtheory)[1—6]andthendevelopedthecentralatomsmodelinthestatisticthermodyn…  相似文献   

6.
1 INTRODUCTIONCopperandcopperalloysarewidelyusedinelectricindustryduetotheirexcellentelectricalcon ductivity .ButtheimpuritiesandtraceelementsinCudecreasetheirelectricalconductivity ,especiallynon metalimpuritiessuchasoxygenandsulfurwhichaf fecttheirmechanicalproperties[14 ] .P ,MnandBecanbeusedasdeoxidant ,buttheresiduainCude creasetheelectricalconductivitydramatically[57] .ItwasreportedthatLicanrefinetheimpuritiesinCuandincreasethetensilestrengthofCuwithouttheelectricalconductivityd…  相似文献   

7.
In this study a measurement instrument of scrooping sound has been develope.Thefollowing results were obtained by means of measurement and analysis for the frequencyspetrums of scrooping sound of silk : 1 The scrooping vibration is mainly composed of S- S( stick-slip vibration) ,F- V(free damping vibration) and S- C( characteristic high frequency vibration) vibrations. 2 The scrooping sound of silk mainly depends on F- V and S- S vibrations and be-longs to lower frequency sound,while the effect of S- C vibration is limited. 3 The wave and the vibration equations as well as some fromulas of relative physicalproperties have been established on the discussion about the stick- slip vibration. 4 The critical condition producing stick- slip vibration is( μs- μd)> 0.  相似文献   

8.
The reduction action mechanism of the unsatrurated polyester resin reducer is analysed by the free space volume theory. Through measuring the reduction magnitude in each phase of solidification, the authors predicted the rate of reduction is in concordance with the results from experiments. From this we presented corresponding solutions to different causes of the reduction action of the unsatwated polyester resin.  相似文献   

9.
Hydrogen could be enriched on grain boundaries by stress induction and other traps.The enriched hydrogen facilitated emission and movement of dislocations and lowered plastic work.Consequently,fracture occurred easily along grain boundary.A normalized threshold value of hydrogen-induced cracking (HIC) along grain boundary is given as (KIH/KIC)2=1-0.162×10-3 βHCc(H)GH/(2γs-γb-0.16×103∑β CiGi),where βH and βi are the enrichment factors of hydrogen and other elements on grain boundaries,respectively;Cc(H) is hydrogen concentration induced by stress;C,is the average concentration of an element in the steel;GH and Gi are factors of fracture work along grain boundary with hydrogen and other elements,and γs and γb are surface free energy and grain boundary energy of Fe.For tubular steel,the calculated KH/KIC is 0.23 while the determined value is 0.26.The theoretical threshold value is well consistent with the experimental one.  相似文献   

10.
CorrosiveWearMechanismofStainlessSteelsFanAiming;TaoZiyun;LongJinming(DepartmentofMetallicMaterialsKunmingInstituteofTechnolo...  相似文献   

11.
The effects of trace silver and magnesium additions on the microstracture and mechanical properties of the Al-Cu-Li alloys were investigated. The experimental results indicate that the effect of combined additions of Ag and Mg is the most obvious , the next is that of individual addition of Mg , and that of individual addition of Ag is the least. The addition of Ag and Mg in Al-Cu-Li alloy accelerates the precipitation of T1 and results in increasing the ageing hardness and strength. Prior cold work significantly improves the tensile strength by enhancing T1 precipitation in all the alloys investigated.  相似文献   

12.
Micro-inhomogeneous structure of liquid Al-Fe alloys   总被引:5,自引:0,他引:5  
BoththeFerichalloysandtheAlrichalloysareimportantinpractice.ThereareseveralintermetalliccompoundsintheAlFesystem,suchasFe3Al,Al3FeandAl5Fe2.MuchattentionhasbeenpaidtoFe3Al[1];Al3Feisaphasethataffectsthepropertiesofthematrixstrongly[2].Thestudyofthemeltstructu…  相似文献   

13.
LixMn2O4 was synthesized rapidly by microwa heaing,the product phases of the microwave synthesis and comventional solid-solid-state synthesis were comparatively inesitigated,The capacity of microwave synthesis product decreases relatively slow,The lithium ion can be inserted into and extracted from the spinel framework structure fluently after cycling .But the capacity of the conventional solid-state synthesis product is more remarkably lowered.The spinel framework structure was destroyed which hindered the lithium ion from inserting and extracting,Tehe influential factors of the process parameters are discussed such as heat preservation time,pre-heating at 400℃ for 24 h and coupled agent.  相似文献   

14.
C-Mn segregation and its effect on phase transformation and plastic deformation in Fe-Mn-C alloys were studied through the calculation of valence electron structure, the microregion composition detection and TEM in-situ dynamic tensile deformation test The experimental results show that in Fe-8Mn-1.2C alloyed austenite, nA of units with C Mn involved is 3 98 times that of units without C involved and 1.4 times that of units with C involved; aCD of units with C-Mn involved is 2 21 times that of units with C involved. In Fe-Mn-C alloyed austenites, there exists microsegrcgation of C-Mn, forming the randomly distributed Fe-Mn-C atomic cluster segregation zone linked with the -C-Mn-C-Mn- strong bond network, which will effectively slow down the motion of atoms and retard the initiation of the slip system and the movement of dislocation, and thus will severely influence the phase transformation and deformation of the alloy  相似文献   

15.
Ti-based AB2-type hydrogen storage alloys are a group of promising materials, which will probably replace the prevalent rare earth-based AB5-type alloys and be adopted as the main cathode materials of nickelmetal hydride (Ni-MH) batteries in the near future. Alloying in side B is a major way to improve the performance of Ti-based AB2-type alloys. Based on recent studies, the effects of alloying elements in side B upon the performance of Ti-based AB2-type hydrogen storage alloys are systematically reviewed here. These performance sare divided into two categories, namely PCI characteristics, including hydrogen storage capacity (HSC), plateau pressure (PP), pressure hysteresis (PH) and pressure plateau sloping (PPS), and electrochemical properties, including discharge capacity (DC), activation property ( AP), cycling stability (CS) and high-rate dischargeability (HRD). Furthermore, the existing problems in these investigations and some suggestions for future research are proposed.  相似文献   

16.
The reaction process of combustion synthesis for TiB2 -Cu was investigated in detail using combustion-wave arresting experiment, X-ray diffraction ( XRD ) analysis, SEM analysis and differential thermal analysis ( DTA ). The XRD analysis results for the different parts of the quenched specimen show that TiCux intermetallic phase firstly forms with the propagation of combustion wave, and then Ti1.87 B50 and Ti3B4 metastable phases come forth due to the diffusion of B atoms and finally the stable TiB2 phase forms because of the continuous diffusion of B atoms. The formation of TiB2 phase is uot completed by one step, but undergoes several transient processes. The process of reaction synthesis for Ti-B-Cu ternary system can be divided into three main stages: melting of Cu and Ti , and the formation of Cu- Ti melt and few TiCux , TiBx intermetallic phases ; large numbers of TiCux intermetallic phases formation and some fine TiB2 particles precipitation ; and the TiB2 particles coarsening and the stable TiB2 and Cu two phases formation in the final product.  相似文献   

17.
甲烷部分氧化制合成气的反应机理探索姜玄珍(化学系)近年来,甲烷部分氧化制合成气(CO+H2)成为十分吸引人的课题[1-3]。因为它(CH4+1/2O2→CO+2H2……(1),△H=-8.5koal.mol-1)是温和放热反应,所制合成气之比H2/C...  相似文献   

18.
1IntroductionNi-based heat-resistant superalloys are widely usedto make critical components in gas-turbine engines,suchas bladeetc.But they are very hard and difficult to bemachined,the net-shape machining of these materials isveryimportant.Computer simul…  相似文献   

19.
One of the main disadvantages of combustion synthesis of ceramic/metal composite materials is the relatively high level of porosity present in the products. To synthesize TiC/ Al composites with a dense structure, this paper proposes a novel application of an elevated-temperature Al-melt to directly ignite and simultaneously in-filtrate Al-Ti-C preform dipped in the melt. The emphasis was placed on the combustion synthesis process and mi-crostructural evolution of the preform in the melt, by a liquid quenching test combined with the measurtment of the temperatwe history of the dipped preform. The results show that the combustion synthesis process of the preform in the elevated-temperature melt involves a series of reactions, and that higher temperature of the melt is favourable for the formation of TiC. The synthesized TiC / Al composites exhibit a dense strucame, which is attributed to the infiltration of the melt into the preform.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号