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1.
Therehavebeenconsiderableinvestigationsonintrinsictoughening.Theatentionhasbenpaidprogresivelytothemechanismofextrinsictoughe...  相似文献   

2.
MechanismofCeriumIonsScavengingSuperoxideRadicalWangJinsheng(王金胜),GuoChunrong(郭春绒)(DepartmentofBasicScience,ShanxiAgricultura...  相似文献   

3.
The order of adsorbability of three kinds of clay minerals and their selectivity of adsorption tocommon cations and RE ions have been studied by quantum chemical calculation.They are as follows:montmorilionite>halloysite>kaolinite,RE~(3+)>Al~(3+)>Ca~(2+)>Mg~(2+)>K~+>NH_4~+>Na~+,Sc~(3+)>La~(3+)>Ce~(3+)>Pr~(3+)>Nd~(3+)>Sm~(3+)>Eu~(3+)>Gd~(3+)>Tb~(3+)>Dy~(3+)>Ho~(3+)>Y~(3+)>Er~(3+)>Tm~(3+)>Yb~(3+)>Lu~(3+).Based onthese orders,the facts that RE is preferentially adsorbed in weathered residual type of clay mineral and lightRE and heavy RE are enriched at the upper layer and at the lower layer respectively in ore body have beenexplained.  相似文献   

4.
ntermetalicsbasedonFe3Alafordexcelentoxidationresistancepropertiesatrelativelylowcostandmaterialsdensity,makingthemcandidates...  相似文献   

5.
The utilization of pure hydrogen as an energy source in fuel cells gave rise to renewed interest in developing active and stable water-gas shift catalysts. Gold catalysts have proven to be very efficient for water-gas shift reaction at low temperature. The aim of the present study was to investigate the effect of:(i) different preparation methods(impregnation and coprecipitation) to obtain a modified ceria support,and(ii) the amount of Y_2 O_3(1.0 wt%, 2.5 wt%, 5.0 wt% and 7.5 wt%) as dopant on the water-gas shift activity of Au/CeO_2 catalysts. An extended characterization by means of S_(BET), XRD, HRTEM/HAADF, FTIR,H_2-TPR and CO-TPR measurements in combination with careful evaluation of the catalyst behavior allowed to shed light on the parameters governing the water-gas shift activity. The catalysts show very high activity(90% CO conversion) in the temperature range 180-220 ℃,with a slightly better performance of the gold catalysts on supports prepared by impregnation. The decreased activity with increasing Y_2 O_3 concentration is related to the hindering of oxygen mobility due to ordering of surface oxygen vacancies in vicinity of segregated Y~(3+). The effect of catalyst pre-treatments and the stability of the best performing samples were examined as well.  相似文献   

6.
COshiftprocessisoneessentialprocessinthechemicalfertilizerindustryaswellasotherindustry .Inthepresenttime ,theironcatalystscontainingchromiumisstillwidelyusedinindustry .Asthereasonpointedoutinthepreviousarticle[1] ,thereisagreatinterestintheworldtodevelo…  相似文献   

7.
The performance of Co supported over ceria and doped ceria (by Sm and Pr) catalysts towards the water gas shift reaction was studied for the removal of CO from syngas to produce high purity hydrogen for a fuel cell application. It is found that 1%Co/Ce-5%Sm-O yields the highest catalytic performance towards this reaction compared with undoped-Sm and doped-Pr. An addition of Sm onto ceria support reveals a small crystallite size with high surface area and well dispersed cobalt on ceria surface. Moreover, a presence of Sm increases the reducibility of cobalt species and surface oxygen. The positive effect of Sm on increasing the WGS activity of Co/CeO2 is because Sm contributes to the reduction of Ce4+ to Ce3+ which gives rise to oxygen vacancies and facilitates the electron movement at the surface leading to an ease of surface reduction.  相似文献   

8.
Experimental data on As(III) adsorption by rusted zero valent iron (ZVI) could be modeled using a simple Langmuir isotherm model. However, the adsorption equilibrium was observed to shift with time, as continued rusting produced additional sites on the rusted ZVI surface for potential arsenic adsorption. A modified Langmuir isotherm model was formulated taking into consideration the temporal variation in the site concentration for potential arsenic adsorption on the rusted ZVI surface. This model simulated the long-term experimental data on As(III) adsorption quite well. The model was further refined by apportioning the arsenic adsorbed on the rusted ZVI surface into labile and irreversibly adsorbed fractions. Finally, the developed model was used to simulate the performance of an adsorption column. The simulation results indicate that an adsorption column of length 0.4 m and diameter 0.056 m, i.e., containing 0.001?m3 of rusted ZVI weighing 4.76 kg, and operated at an empty bed contact time of 12 min, can treat 2,375–2,525 L of water containing 100?μg?L?1 of As(III) such that the effluent As(III) concentration from the column is less than 10?μg?L?1.  相似文献   

9.
Clay minerals are inferred to be the primary host materials for ion-exchangeable rare earth in ion adsorption type rare earth ore(IAREO).During the rare earth leaching process,the adsorption and desorption reactions of the cations controlling the leaching process continue to occur at the clay minerals-leaching agent solution interface.In order to understand the leaching mechanism and behavior of rare earth and co-leached aluminum,adsorption,competitive adsorption,and desorption experiments were ...  相似文献   

10.
Asanewtypecatalyst,complexoxidesofperovskitetypehavewonextensiveattentioninthefundamentalandappliedresearch.Forthisreasontheyareofwelldefinedstructure,specialcatalyticpropertiesandhighstabilities[1].Forexample,LaNiO3istheonlymetalliccompoundwithord…  相似文献   

11.
Hydrousoxidesofsomemetals,suchasCe,Nb,La,Tietc.,showexcelentadsorptioncapacitiesandselectivityforF-[1],whichmakesitposibletou...  相似文献   

12.
LuminescencePropertiesofCe3+inKMF3(M=Mg,Ca,Sr,Ba)HostswithPerovskiteStructureZhangJilin(张吉林)(LiaoyangPetrochemicalEnginering...  相似文献   

13.
Recently ,manymaterialresearchershavecometorealizethattheelectroniccharacterhasadecisionalroleonmaterialpropertiesandmicrostructure[1~ 3] .Theseworksrevealanewmechanismtomaterialbehaviorandanewun derstandingelectrontheoryofalloy .Addition aly,theeffectofane…  相似文献   

14.
EffectsofRE-SbonGrayCastIronXiongZhong-Ming(熊仲明);ZhangSuo-Mei(张锁梅),ShiDong-ya(石东崖);SongWei-Xi(宋维锡)(DepartmentofMetailurgy,Uni...  相似文献   

15.
Effect of Cerium on the Properties of CuPNiSn Amorphous Alloys   总被引:1,自引:0,他引:1  
CuPNiSn amorphous alloys are good brazing materials at medium temperature for replacementof silver bearing brazing materials.The crystallization temperature,wettability,tensile strength of Cu-Cujoints and the microstructure of joints for three compositional series are reported.Some rare earth elementswere added in two series.It has been found that grains are refined and the tensile strengths increase as in-creasing rare earth content.The results also show that the brittle fracture turns to plastic one for the jointswith reducing amount of(Ni+Sn),and the tensile strength is increased.  相似文献   

16.
EffectofCeriumonStructureandPropertiesofGranularBainiticSteel¥WangFuming(王福明),LiJinhui(李景慧),HanQiyong(韩其勇)(DepartmentofPhysic...  相似文献   

17.
Study was made on the effect of surface modification on the behaviors of cerium oxide nanopowders.A surfactant-sodium dodecyl sulfate(C12H25SO4Na)was used to modify the surface of CeO2 powder particles.The unmodified and modified CeO2 powders were characterized by using a powder comprehensive characteristic tester,laser particle size analyzer,specific surface area tester,X-ray diffraction tester,and a scanning electron microscope.The testing and analysis results showed that C12H25SO4Na surface modification might increase the flowability and dispersity,and decrease the specific surface area and agglomeration of CeO2 powders.The mechanism of the surface modification of CeO2 powder particles was also discussed.  相似文献   

18.
Effect of RE Oxide on Cracking Resistance of Hardfacing Metal   总被引:4,自引:0,他引:4  
Sincenotonlythehotrolandhotdiewithhigherpriceareconsumedinlargequantitiesbutalsotheirqualityafectstheproductivity,theyarecrit...  相似文献   

19.
Mesoporous CeMnOx composite oxides catalysts were prepared by surfactant-assisted co-precipitation method and used for the catalytic oxidation of toluene.The effect of different cerium precursors[Ce(NO_3)_3 and(NH_4)_2 Ce(NO_3)_6] on catalyst structure,surface properties and toluene combustion activities of mesoporous CeMnO_x catalysts were investigated.The Ce(Ⅲ)MnO_x catalyst prepared from Ce(NO_3)_3 precursor shows higher catalytic activity,with a 90% conversion temperature of 240℃,which is better than the Ce(Ⅳ)MnO_x catalyst derived from(NH_4)_2 Ce(NO_3)_6] precursor.On the basis of characterizations,it reveals that abundant surface content of Mn~(4+),better redox behavior and larger concentration of surface active oxygen species are responsible for the excellent catalytic performance.  相似文献   

20.
ItiswelknownthatthemechanicalpropertiesofgraycastironcanbeimprovedbyaddingsuitableamountofREandN.Tohighcarbonequivalent(CE)gr...  相似文献   

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