The+doping+effect+of+Mo+on+FeAl2O3+catalyst+for+methane+decomposition+reaction

Journal of Alloys and Compounds 492 (2010) 496–499Contents lists available at ScienceDirectJournal of Alloys andCompoundsj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /j a l l c omMixing of iron and molybdenum and photo-doping effect on Sr 2FeMoO 6Y.C.Hu a ,Q.Ji a ,J.J.Ge a ,R.B.Xie a ,Z.S.Jiang a ,X.S.Wu a ,∗,G.F.Cheng b ,Hairui Liu c ,Qingfeng Lu caNanjing National Laboratory of Microstructures,Key Lab of Solid State Microstructures,Department of Physics,Nanjing University,Hankou Road,Nanjing 210093,China bShanghai Institute of Ceramics,CAS,1295Dingxi Road,Shanghai 200050,China cDepartment of Physics,Henan Normal University,Xinxiang 453007,Henan,Chinaa r t i c l e i n f o Article history:Received 17August 2009Received in revised form 19November 2009Accepted 20November 2009Available online 26 November 2009Keywords:Magnetically ordered materials X-ray diffraction Crystal structurePositron spectroscopya b s t r a c tThe structure and photo-doping effect on Sr 2FeMoO 6are investigated using the X-ray powder diffraction and positrons annihilation technique,respectively.Anti-site defect is about 8.8%,can be estimated directly from the XRD pattern,which is well consistent with that of obtained from the XRD refinements.The integral intensity ratio of the reflection (101)and the reflections (200)and (112)may used to estimate the concentration of the anti-site defect.The positron annihilation lifetime in Sr 2FeMoO 6is sensitive to photo-doping.The average lifetime and the electron density n e vary with photo-doping.© 2009 Elsevier B.V. All rights reserved.1.IntroductionThe double perovskite compound Sr 2FeMoO 6(SFMO),with a high magnetic transition temperature (T c ≈410K)[1]and a remarkable magneto-resistance around room temperature,has become one of the most promising candidates in magnetic storage materials [2].SFMO is a typical ordered double perovskite structure A 2BB O 6,where A is the alkali-earth ion,B and B are the transition metals.As reported in [3,4],the crystal structure of SFMO is cubic or tetragonal,where the alternating FeO 6and MoO 6octahedral are arranged regularly in a rock salt superlattice with the voluminous Sr cation occupying the voids among the octahedral.The existence of anti-site defects (Mo on Fe site and vice versa)has great influence on the magnetic and transport properties of Sr 2FeMoO 6[5,6].Defects are important structural information in understanding the properties of material [7].Positron annihilation technique (PAT)can provide unique information about defects and has many advan-tages in structural characteristic.It is a nondestructive and effective method to detect the information of defects [8],whereas there are few studies about SFMO using this technique recently.Photo-doping,which remains the component and structure of material unchanged,is an effective way to improve the property [9,10].It has been extensively used in semiconductor material [11,12],but∗Corresponding author.Tel.:+862583594402;fax:+862583595535.E-mail address:xswu@ (X.S.Wu).seldom studies are performed on magnetic materials.In order to understand the photo-doping effect on defects in SFMO,we synthe-size the compounds using standard solid-state reaction.The crystal structure and photo-doping effect on defects have been studied by means of X-ray powder diffraction and the positrons annihilation technique,respectively.2.ExperimentalSample of Sr 2FeMoO 6is prepared by standard solid-state reaction.Stoichiomet-ric powders of SrCO 3,Fe 2O 3and MoO 3are mixed,ground and heated at 900◦C for 10h in air.The pre-reacted mixture is then finely ground,pressed into pellets and sintered at 1280◦C in a stream of 5%H 2/Ar gas for 15h with several intermediate grindings.The samples are heated and cooled at a rate of 5◦C/min under the same atmosphere.Structure of the sample is examined by X-ray powder diffraction (XRD)using a Rigaku D/max 2500diffractometer with CuK ␣radiation (50kV 250mA)and a graphite monochromator.The XRD pattern shows that the sample crystallizes in sin-gle phase.The XRD data are analyzed by means of the Rietveld refinement program GSAS [13].Sample is illuminated by halogen lamp (60mW/cm 2)with varying illumina-tion time from 0min to 40min in a space of 10min.Power of the lamp is 100W and distance between sample and lamp is 7.9cm.The sample temperature values reached at 28±1◦C after 40min irradiation.The heating rate of the samples is about 2±1◦C/10min through the illumination.We use pieces of the samples at the same time.After each illumination,the positron lifetime measurements are carried out using a conventional fast–fast coincidence ORTEC-100U system with a prompt time resolution of 228ps (FWHM,full width at half maximum)and 10␮Ci 22Na source in sandwich geometry with the pellets.The total count for spectrum is 1million with the counting rate of 1000cps.Lifetime spectrum is analyzed by the PATFIT computer program with necessary source corrections.The measurements of positron lifetime are all performed at room temperature (20±1◦C).0925-8388/$–see front matter © 2009 Elsevier B.V. All rights reserved.doi:10.1016/j.jallcom.2009.11.148Y.C.Hu et al./Journal of Alloys and Compounds492 (2010) 496–499497Fig. 1.Observed(circles)and calculated(continuous line)XRD pattern for Sr2FeMoO6.The lowest curve is the difference between the observed and the calcu-lated XRD patterns.The vertical bars at the bottom indicate the Bragg reflection positions.(101)is the Bragg reflection at2Â≈19◦and(200)+(112)is that at 2Â≈32◦.3.Results and discussionFig.1presents the XRD pattern for Sr2FeMoO6.The excellent crystalline quality of sample used in this work can be appreci-ated.The XRD data can be used to refine the structure of the sample and abundance of information could be revealed due to precise counting statistics.Rietveld refinements of XRD diffraction pattern are carried out using the I4/m and the corresponding Wyck-off positions:Sr,4d(1/2,0,1/4);Fe1,2a(0,0,0);Fe2,2b(0,0,1/2); Mo1,2b(0,0,1/2);Mo2,2a(0,0,0);O1,8h(x,y,0);O2,4e(0,0,z). The refinement is performed according to the following group order[14,15]:(1)scale factor;background;zero point shift/sample displacement,transparency coefficient;(2)cell parameters;(3) peak shape;half width;asymmetry parameter and preferred ori-entation;(4)atom position parameter;(5)site occupancies;(6) overall thermal parameters;(7)isotropic thermal parameters.The Gaussian function is considered to refine the profile.No absorp-tion correction is taken into account.The wavelengths of CuK␣1, CuK␣2and the intensity ratio arefixed as1.5406A,1.5444A,and 0.497A,respectively.Full occupancy at every site in the unit cell is assumed during the refinements,i.e.the occupancies of Fe and Mo at2a and2b in total are1,respectively.The preferred orien-tations are very small and the temperature factors B Sr,B Fe1,B Fe2,B Mo1,B Mo2,B O1,and B O2are0.01304Å2,0.00611Å2,0.00611Å2,0.00392Å2,0.00392Å2,0.02301Å2,and0.01271Å2,respectively. The refinement process is smooth and leads to good quality fac-tors Rwp=10.00%and Rp=7.26%.All reflections can be indexed and a=b=5.58235(1)Å,c=7.87965(4)Å.The occupancy of Fe on Mo site (which is the occupancy of Fe2,equivalent in value to that of Mo on Fe site)is8.8%,which means the order concentrationÁis82.4% due toÁ=1−2x,where x is fraction of Fe on Mo site.Superstructure reflection(101)at2Â≈19◦can be seen clearly,which may indicate the existence of cation order-ing between Fe/Mo.Fig.2is the sketch of the unit cell of Sr2FeMoO6,in which Fe and Mo are completely ordered.Each unit cell is composed of10ions and the coordinates ofthe Fig.2.The unit cell of Sr2FeMoO6,in which Fe and Mo is completely ordered. ions are as following:Sr(1/2,1/2,1/4),(1/2,1/2,3/4),Fe(0,0,1/2), Mo(0,0,0),and O(1/2,0,0),(0,1/2,0),(0,0,1/4),(0,0,3/4),(1/2,0,1/2), (0,1/2,1/2).Based on the structure factor formula F(h k l)= nj=1f j e2 i(hx j+ky j+lz j),we can calculate the F(h k l)of Sr2FeMoO6as:F(h k l)=f Sre2 i(h/2+k/2+l/4)+e2 i(h/2+k/2+(3/4)l)+f Oe2 i(h/2)+e2 i(k/2)+e2 i(l/2)+e2 i(3/4)l+e2 i(h/2+l/2)+e2 i(k/2+l/2)+f Fe e2 i(l/2)+f Mo e2 i0when(h k l)=(101),F(101)=f Sr(e(3/2) i+e(5/2) i)+f O(e i+e0i+e(1/2) i+e(3/2) i+e2 i+e i)+f Mo−f Fe =f Mo−f FeSo we can obtain:I101∝P101|F(101)|2=P101|f Mo−f Fe|2,whereP101=(1+cos22Â)/(4sin2ÂcosÂ)is the Lorentz polarization fac-tor.The reflection of(101)is indeed observed at2Â≈19◦.Infact,as reported in Ref.[16],there is a fraction of Mo atoms onthe B site,equivalent in value to that of Fe atoms on the B site,which is defined as the anti-site defect.Suppose there are x Moions on Fe sites in the unit cell.The F(101)can be modified as:F(101)=(1−x)f Mo+xf Fe−(1−x)f Fe−xf Mo=(1−2x)f Mo−(1−2x)f Fe=(1−2x)(f Mo−f Fe)Four interesting results can be seen from above consequences.Firstly,the intensity of(101)reflection decreases with the increaseof the anti-site defect.Secondly,the integral intensity ratio betweenthe reflection peak of about2Â≈19◦and the reflection peak ofabout2Â≈32◦,I19◦/I32◦,which is used to indicate the order of Fe/Mo[17],can be interpreted as following:I32◦=I200+I112I200∝P200F2002,I112∝P112F1122,Thus,I32◦∝P200F2002+P112F1122Due to F(200)=(f Fe+f Mo)+2(f Sr+3f O),F(112)=(f Fe+f Mo)−2(f Sr+3f O).So I32◦∝P200|(f Fe+f Mo)+2(f Sr+3f O)|2+P112|(f Fe+f Mo)−2(f Sr+3f O)|2,which has no relation to Fe/Mo order.I19◦/I32◦can498Y.C.Hu et al./Journal of Alloys and Compounds 492 (2010) 496–499indicate the Fe/Mo order concentration as I 19◦is induced by Fe/Mo order.The larger I 19◦/I 32◦,the higher order of Fe/Mo.Thirdly,we define R is the integral intensity ratio of I 19◦/I 32◦for ideal sample without anti-site defect and R e as that for our sample which is prepared by standard solid-state reaction.R =I 19◦I 32◦∝P 101 F (101)2P 200F 2002+P112F1122∝P 101 f Mo −f Fe2P 200 (f Fe +f Mo )+2(f Sr +3f O ) 2+P 112 (f Fe +f Mo )−2(f Sr +f O )2When consider the fraction of anti-site defect x ,R e ∝(1−2x )2P 101 f Mo −f Fe2P 200(f Fe +f Mo )+2(f Sr +3f O ) 2+P 112(f Fe +f Mo )−2(f Sr +f O )2,soR e /R =1−2x .Due to Á=1−2x ,thus Á=R e /R .R e =I 19◦/I 32◦=2.56%from our experiment and we cancalculate R =3.76%[18,19]as sin Â(101)/ =0.11and sin Â(200)/ ≈sin Â(112)/ =0.18.ThusR e /R =82.5%,which is also similar with the order concentration Áfrom Rietveldrefinement.So we think Á=R e /R is a convenient method to calculate the order concentration approximately.Fourthly,based on the third result,we can define the disorder concentration as:=⎧⎨⎩2x,0<x ≤12(1−x )+(1−x ),12≤x <1.When x =1/2,F (101)=0, =100%.This means that the peak at 19◦will disappear as Fe/Mo complete disorder.When x =0or 1,the Fe/Mo is perfect ordered.Analysis on the positron lifetime spectra usually tells us three meaningful components of 1, 2and 3in the ratio I 1+I 2+I 3=100%.The second lifetime component 2with the typ-ical value of 278–280ps and a relative intensity of 1.5–2%,is due to the partial trapping of positrons at residual extrinsic vacancy-type defects. 2suggests that photo-doping has little effect on vacancy-type defect,according to our experiments [20],we here do not consider for further discussion.Fig.3(a)left shows the short lifetime component 1against different illumination time in the Sr 2FeMoO 6.The short lifetime component 1,having a value of 180–200ps,is due to the free annihilation of positrons.Anti-site defect is not open volume defect and contributes to 1.Electrons in the sample are activated by photo-doping and the concentration of electrons at the site of free annihilation increases,which improves the annihilation rate 1. 1decreases because of 1=1/ 1.The increase of 1is due to the decrease of the electron concentration at the site of free annihilation when t ≥30min.The longest lifetime component 3against different illumina-tion time in SFMO is shown in Fig.3(a)right.The longest component 3,with the typical value >0.5ns,results from positronium formed and annihilated through the ‘pick-off’process.The three main mod-els that describe the positronium formation in condensed matter are the Ore model (OM)[21],the spur model (SM)[22]and the free volume model (FVM)[23].Our work can be better explained according to FVM.Illumination may make electrons transit into the free volume and improve the annihilation rate 3. 3decreases because of 3=1/ 3. 3continually decreases because more elec-trons might locate the free volume.This is similar with Ref.[24],which suggests that two or more electrons can locate one vacancy.The concentration of electron at the free volume is saturated when t =30min due to Coulomb compel potential betweenelectrons.Fig.3.Positron lifetime parameters (a)left 1,right 3;(b)left I 1,right I 3;and (c)left AV ,right n e against different illumination time in the Sr 2FeMoO 6.The solid lines are guides for the eyes.Fig.3(b)shows I 1(left)and I 3(right)against different illu-mination time in the Sr 2FeMoO 6.I 1is found first to increase (0min ≤t ≤30min)and then decrease (t >30min)with a relative intensity of 85–88%,which is the main part of the positron lifetime spectra.This can be explained in light of the following scenario:electrons at the site of free annihilation is easier to active by illu-mination than at the free volume.When t =30min,electrons at the site of free annihilation is completely activated.When t >30min,electrons at the free volume is continually activated but at the site of free annihilation has already saturated,thus the intensity of 1decreases.Fig. 4.Observed (circles)and calculated (continuous line)XRD pattern for Sr 2FeMoO 6after 30min illumination,which is the representative XRD pattern for illuminated samples.The lowest curve is the difference between the observed and the calculated XRD patterns.The vertical bars at the bottom indicate the Bragg reflection positions.Y.C.Hu et al./Journal of Alloys and Compounds 492 (2010) 496–499499Table 1Unit cell parameters for Sr 2FeMoO 6after irradiation obtained from Rietveld refinement of XRD data.0min10min 20min 30min 40mina 5.58235(1) 5.58246(9) 5.58236(5) 5.58250(5) 5.58261(9)c7.87965(4)7.87968(8)7.87982(4)7.87985(6)7.87990(6)v245.55084(2)245.56228(3)245.55737(1)245.57068(5)245.58227(3)Rwp (%)10.0010.4110.289.9210.12Rp (%)7.267.596.866.767.41We have calculated the average positron lifetime AV ,defined as AV =I i i ,where I i is the relative intensity of the i th lifetime com-ponent. AV is better to describe the mean size of the defects in the samples.As shown in Fig.3(c)left, AV of the photo-doped is smaller than that of photo-free.According to Navarro et al.[25],Sr 2FeMoO 6may be unstable when heated,and that may have important oxida-tion effects if exposure it to air for several days.We measured the structure of the samples after PALS measurements.Fig.4shows the XRD pattern for Sr 2FeMoO 6after 30min illumination,which is the representative XRD pattern for illuminated samples.There is no trace of SrMoO 4is detected,due to that 40min might be a very short time for oxidation procedure.Structure parameters after irra-diation obtained from Rietveld refinement are shown in Table 1.The increase of unit cell makes the size of defects small.This might be important reason for decrease of average lifetime.Ions may absorb photons and occupy part of defects,thus also reduce the mean size of defects.We calculated the electron density n e ,defined asn e =1/(¯ r 20c ),where c is the speed of light and r 0is classical elec-tron radius.The variation of n e against illumination time is shown in Fig.3(c)right.The minimum value of AV suggests the maximum of electrons density when t =30min.4.ConclusionTo investigate the structure and photo-doping effect on defect in SFMO,we performed X-ray powder diffraction and the positrons annihilation technique.The result of X-ray powder diffraction sug-gests that the superstructure reflection (101)appearing due to the Fe/Mo order on the B/B site can index the concentration of anti-defect.Positron lifetime measurements after illumination suggest that the positron annihilation lifetime is sensitive to photo-doping.The minimum of defects size and the maximum of electrons den-sity when t =30min indicate that photo-doping may be an effective way to improve the property of the material.AcknowledgementsThis work is supported by NNSFC (10774065,10523001)and NKPBRC (2006CB921802,2010CB923404).Professor QFL thanks for the financial support from Henan Education foundation (No.2007140008).References[1]K.-I.Kobayashi,T.Kimura,H.Sawada,K.Terakura,Y.Tokura,Nature 395(1998)677.[2]A.Gary,Prinz,J.Magn.Magn.Mater.200(1999)57.[3]F.K.Patterson,C.W.Moeller,R.Ward,Inorg.Chem.2(1963)196.[4]F.S.Galasso,F.C.Douglas,R.J.Kasper,J.Chem.Phys.44(1966)1672.[5]D.Stoeffler,S.Colis,Mater.Sci.Eng.B 126(2006)133.[6]M.F.LÜ,J.P.Wang,J.F.Liu,W.Song,X.F.Hao,D.F.Zhou,X.J.Liu,Z.J.Wu,J.Meng,J.Alloy Compd.428(2007)214.[7]Z.Bajnok,Zs.Simon,Nucl.Phys.B 802(2008)307.[8]X.J.Hu,J.S.Ye,H.J.Liu,S.Mariazzi,R.S.Brusa,Thin Solid Films 516(2008)1699.[9]J.H.Hao,W.D.Si,X.X.Xi,Appl.Phys.Lett.76(2000)3100.[10]J.H.Hao,X.T.Zeng,H.K.Wong,J.Appl.Phys.79(1996)1810.[11]M.Idrish Miah,Mater.Chem.Phys.111(2008)249.[12]O.V.Prezhdo,Chem.Phys.Lett.460(2008)1.[13]B.H.Toby,J.Appl.Crystallogr.34(2001)210.[14]X.S.Wu,W.M.Chen,X.Jin,S.S.Jiang,Physica C 273(1996)99–106.[15]X.S.Wu,S.S.Jiang,N.Xu,F.M.Pan,X.R.Huang,W.Ji,Z.Q.Mao,G.J.Xu,Y.H.Zhang,Physica C 266(1996)296–302.[16]M.T.Anderson,K.B.Greenwood,G.A.Taylor,K.R.Poppelmeier,Prog.Solid StateChem.22(1993)197.[17]Ll.Balcells,J.Navarro,M.Bibes,A.Roig,B.Martínez,J.Fontcuberta,Appl.Phys.Lett.78(2001)781.[18]/xray/comp/scatfac.htm .[19]A.Guinier,X-ray Diffraction,W.H.Freeman and Company,San Francisco,1963.[20]Y.C.Hu,P.F.Wang,B.Lv,Q.Ji,X.S.Wu,Q.F.Lu,J.Appl.Phys.105(2009)07D726.[21]A.Ore,Univ.Bergen Arbok,Naturvet Rekke,1949,p.9.[22]O.E.Mogensen,J.Chem.Phys.60(1974)998.[23]W.Brandt,S.Berko,W.W.Walker,Phys.Rev.120(1960)1289.[24]P.Hautojarvt,Positrons in Solid,Springer-Verlag,Berlin,Heidelberg/New York,1979.[25]J.Navarro,C.Frontera,D.Rubi,N.Mestres,J.Fontcuberta,Mater.Res.Bull.38(2003)1477–1486.。

碳化程度( degree of carbonation, DOC) 的定义为硅酸钙矿物实际吸收 CO2 的质量与其理论上最大吸收
CO2 质量的比值。 具体操作步骤为:将坩埚放入高温炉在 1 000 ℃ 煅烧 2 h 至恒重称其质量,记为 m0 ,再取
10 g 左右的样品置于坩埚中在 300 ℃ 保温 2 h 后冷却至室温称其质量,记为 m1 ,然后在 1 000 ℃ 保温 2 h 后
按照 0. 15 的水固比称取 γ-C2 S 粉体和水溶液,将二者置于玛瑙研钵中搅拌均匀。 称取 12 g 混合好的物 料置于 ϕ20 mm 的模具中,成型压力为 30 MPa,保压 1 min,成型后的试样为尺寸 ϕ20 mm × 20 mm 的圆柱体。 将制备好的圆柱体试样放入不锈钢制的压力容器内进行碳化养护。 碳化养护的条件参数为 CO2 浓度为 100% ,相对湿度 RH≥95% ,容器内相对压强为 0. 3 MPa,初始温度为室温,容器内通入 CO2 之前进行抽真空 处理。 1. 3. 3 力学性能测试
压强度更高。
关键词:Al2 O3 ; γ-C2 S; 碳化; 碳酸钙; 力学性能; 半峰宽
中图分类号:TQ172. 1
文献标志码:A
文章编号:1001-1625(2021)06-2003-08
Effect of Al2O3 Doping on Carbonation Performance of γ-C2S
烧成熟料粉化后利用激光衍射 粒 度 分 析 方 法 测 试 其 粒 径 分 布 情 况, 选 用 英 国 马 尔 文 公 司 生 产 的 Mastersizer 2000 激光粒度仪。 应用理论为全量程完全的米氏理论,原理为当光线穿过物料时,反射光和透射 光与物料粒径大小有关,根据入射光的偏离角度可以计算出粒径分布。 累积分布曲线上 50% 处的对应粒径 值为物料的 D50 ,其可以表示熟料粒径大小。 1. 3. 2 碳化试样的制备及其碳化养护

小学上册英语第四单元测验卷(有答案)考试时间：80分钟（总分:100）B卷一、综合题(共计100题共100分)1. 填空题：I enjoy riding my ______ around the neighborhood.2. 填空题：When I help others, I feel ______ (满足). It’s important to be kind and ______ (乐于助人).3. 选择题：What is the largest organ in the human body?A. BrainB. HeartC. SkinD. Liver答案:C4. 听力题：Friction can slow down a ______.5. 填空题：The ancient Romans established ________ to provide public services.6. 选择题：What is the name of the fairy tale character who had long hair?A. CinderellaB. RapunzelC. Sleeping BeautyD. Snow White答案: B7. 填空题：I like to play ______ (视频游戏).8. 填空题：The frog croaks loudly during the ______ (春天).9. 听力题：The color of cabbage juice changes with pH; it can be red or ______.10. 选择题：What is 5 + 5?A. 8B. 9C. 10D. 1111. 填空题：The _____ (果树) produces sweet fruit.12. 填空题：My friend is very __________ (乐观的) about life.13. 选择题：What is 15 7?A. 6B. 7C. 8D. 9答案:C14. 听力题：The flower pot is ______ (colorful) and bright.15. 填空题：I love to watch ______ movies.16. 听力题：The _______ can be used for decoration.17. 选择题：What do you call a baby jackal?A. KitB. PupC. CalfD. Cub18. 听力题：The _______ of a wave can be described as its height.19. ssance was marked by advancements in ________ (科学). 填空题：The Rock20. 选择题：What is the name of the first spacecraft to fly by Jupiter?A. Pioneer 10B. Voyager 1C. Voyager 2D. Galileo21. 填空题：My mom loves to _______ (动词) to relax. 她觉得这个很 _______ (形容词).22. 选择题：What is a synonym for "fast"?A. SlowB. QuickC. LazyD. Tired23. 填空题：My mom is a wonderful __________ (家长) who teaches me well.24. 选择题：What do you call the sound a cow makes?A. MeowB. BarkC. MooD. Quack25. of Hammurabi is one of the oldest known ______ (法律). 填空题：The Cold26. 听力题：I see a ___ in the sky. (bird)27. 听力题：A ____ is often seen leaping gracefully through the air.28. 听力题：The chameleon changes ______ to blend in.29. 听力题：The dog is ______ at the squirrel. (barking)The flowers are ___. (colorful)31. 选择题：What do we call the person who teaches students?A. EngineerB. TeacherC. DoctorD. Chef答案:B32. 选择题：Which food is made from milk?A. BreadB. CheeseC. RiceD. Pasta答案: B33. 选择题：What do we call the act of making something happen?A. CreationB. InnovationC. ProductionD. Action答案:D34. 填空题：My brother loves __________ (学习) different instruments.35. 听力题：A mineral's ______ refers to the color of its powder when scraped on a surface.36. 听力题：They go to _____ (school/market) every day.37. 选择题：What is the capital of Brunei?A. Bandar Seri BegawanB. Kuala BelaitC. TutongD. Seria答案:A38. 听力题：The pizza is ______ and cheesy. (hot)The ____ is a favorite among children and loves to play in the grass.40. 听力题：The capital city of Sweden is __________.41. 听力题：The process of forming a precipitate occurs in a _______ reaction.42. 填空题：_____ (farming) can be both rewarding and challenging.43. 选择题：What is the capital city of Germany?A. MunichB. BerlinC. FrankfurtD. Hamburg44. 听力题：The children are _______ (drawing) pictures.45. 听力题：The _______ of a pendulum can be affected by air resistance.46. 听力题：When water freezes, it becomes ______.47. 选择题：What is the capital of Portugal?A. LisbonB. MadridC. ParisD. Rome答案:A48. 选择题：What do we call the process of changing from a liquid to a solid?A. MeltingB. FreezingC. BoilingD. Evaporating答案:B49. 选择题：What do you call a group of fish?A. SchoolB. FlockC. PackD. Pride答案: A50. 选择题：What is the chemical symbol for gold?A. AuB. AgC. PbD. Fe51. 听力题：She has ___ (ten) fingers.52. 填空题：The ______ (狐狸) is very clever and sly.53. 听力题：I like to _____ on weekends. (relax)54. 填空题：A chicken lays ______.55. 听力题：She is _______ (studying) for her exam.56. 填空题：My cat loves to chase after ______ (线).57. 填空题：I enjoy drawing _____ (树木) in art class.58. 选择题：What is the primary color of a pumpkin?A. GreenB. OrangeC. YellowD. Brown答案: B. Orange59. 听力题：The squirrel is very ___ (quick).The __________ (热带雨林) is rich in biodiversity.61. 听力题：The apple tree is _______ (full) of fruit.62. 选择题：What is the capital of Sweden?A. StockholmB. OsloC. HelsinkiD. Copenhagen答案: A. Stockholm63. 选择题：What do we call the hard outer layer of the Earth?A. CrustB. MantleC. CoreD. Lithosphere64. 填空题：The ________ (生态研究) reveals insights.65. 填空题：The crow is known for its black ______ (羽毛).66. 填空题：The _____ (birch) tree has beautiful bark.67. 听力题：The chemical symbol for francium is ______.68. 听力题：A saturated solution can no longer dissolve ______.69. 听力题：The __________ point is the temperature at which a solid becomes a liquid.70. 选择题：What do you call the person who studies stars and planets?A. BiologistB. GeologistC. AstronomerD. Physicist答案:CI have a toy _______ that makes me giggle.72. 选择题：What do we call a person who studies history?A. BiologistB. HistorianC. ScientistD. Researcher答案:B73. 听力题：My ______ likes to cook delicious food.74. 听力题：My mom makes _____ for breakfast. (pancakes)75. 填空题：The ________ grow in the garden.76. 选择题：Which sport uses a net and a ball?A. SoccerB. TennisC. BaseballD. Golf答案: B77. 填空题：在古代，________ (leaders) 的决策对国家未来有着重大影响。

基金项目："十三五"国家重点研发计划项目（2016YFB0303500）
Байду номын сангаас
2实验
2.1原料及样品制备 所用原料均为分析纯试剂。将CaCO3, AI2O3与SQ 按照2： 1： 1摩尔比配料，其他杂质分别以MgO、BaO 及MgO与AIQ3复掺等形式引入，其中MgO、BaO的 掺量分别为1 %、2%和3%。MgO与Abd复掺是通过 调整氧化钙、氧化铝、氧化镁二氧化硅之间的摩尔比，使 之形成C2oA,3Mg3S3o将生料充分混合均匀磨细后，加水 压片并烘干，在1350T®烧3h,电风扇速冷磨细备用。 2.2测试 采用德国布鲁克公司的D8X射线衍射仪对样品在 2 8角度（10-70° ）范围內进行分析，所使用步长为 0.02° /min。采用美国FEI公司生产的Quanta 250FEG 场发射环境扫描电子显微镜在高真空模式下观察样品新鲜 断面的形貌特征。采用TAM Air八通道等温微量热仪测定 了样品的水化放热速率和放热量。实验温度为20°C水灰 比为0.5,水化热测量持续7d。
关键词:掺杂；硅铝酸二钙；结构；水化活性 Abstract: Effect of MgO, BaO and MgO+Al2O3 doping on Structure and Hydration Reactivity of dicalcium aluminosilicate (C2AS) was studied by X-ray diffraction, scanning electron microscopy and isothermal calorimetry. The results showed that BaO doping has almost no effect on the structure of C?AS, and 3% MgO can promote the diffraction peak intensity of a crystal plane of GAS. MgO and AkO； doping can promote the formation of Q phase. Compared with MgO and BaO single doping, MgO and ALO^ doping can greatly improve the hydration activity of C?AS, and the total hydration heat of 7d can reach 400J/g. Keywords: doping; dicalcium aluminosilicate; structure; hydration activity 中图分类号:TQ172.1文献标识码：A 文章编号:1003-8965(2019)02-0047-03