《晶胞参数的测定优秀课件.ppt》由会员分享，可在线阅读，更多相关《晶胞参数的测定优秀课件.ppt（19页珍藏版）》请在taowenge.com淘文阁网|工程机械CAD图纸|机械工程制图|CAD装配图下载|SolidWorks_CaTia_CAD_UG_PROE_设计图分享下载上搜索。
1、晶胞参数的测定第1页，本讲稿共19页OutlineExperimental Goal1.Background and Theory2.Example3.第2页，本讲稿共19页Experimental Goal Determine the precise lattice parameters of materials第3页，本讲稿共19页Background and TheoryImportance Useful in determining solid solubility limits of one component in another,coefficients of thermal e
2、xpansion,and true densities of materials.The magnitudes of changes in the lattice parameters due to a change in solute content or temperature are so small.第4页，本讲稿共19页Background and TheoryA material with a cubic structure第5页，本讲稿共19页Background and TheoryMethodsDebye-Scherrer CamerasDiffractometersMath
3、ematizationExtrapolation Debye-Scherrer Cameras Bradley-Jay Nelson-Riley Diffractometers The least-square method第6页，本讲稿共19页Background and TheoryDebye-Scherrer CamerasSources of error:Film shrinkage Incorrect camera radius Off-centering of specimen Absorption in specimen Divergence of the beam第7页，本讲稿
4、共19页Background and TheoryDiffractometersSources of error:Misalignment of the instrument Use of a flat specimen instead of a specimen curved to conform to the focusing circle Absorption in the specimen Displacement of the specimen from the diffractometer axis Vertical divergence of the incident beam第
5、8页，本讲稿共19页Background and TheoryExtrapolation1.Since varies differently with different errors，a single extrapolation function is not satisfactory in this case2.It is necessary to have as many reflections as possible in the high-angle region of the diffraction pattern so that you will have many Points
6、enabling you to draw the best possible straight line第9页，本讲稿共19页Background and TheoryThe least-square methodNormal Equations Drift constant第10页，本讲稿共19页ExampleFIG 1X-ray diffraction pattern of aluminum showing only the high-angle regionThe least-square method-Aluminum第11页，本讲稿共19页ExampleTable 1 Calcula
7、tion of the Lattice Parameter of Aluminum第12页，本讲稿共19页ExampleTABLE 2 Data Required for Cohens Analytical Method第13页，本讲稿共19页Example 2674A+858.9C=96.77139858.9A+313.14C=31.08341A=0.0361895 C=7.810-7 第14页，本讲稿共19页ExampleFIG2 X-ray diffraction pattern of silicon showing only the highangle regionExtrapolat
8、ion-Silicon第15页，本讲稿共19页ExampleTABLE 3 Work Table for Indexing the Diffraction Pattern of Silicon第16页，本讲稿共19页Examplea0=0.5430nmTrue value a0=0.5431 nmFIG 3 The straight line by extrapolating lattice parameters against 第17页，本讲稿共19页Examplea0=0.5430nmTrue value a0=0.5431 nmFIG 4 The straight line by extrapolating lattice parameters against 第18页，本讲稿共19页第19页，本讲稿共19页