X射线衍射（PPT课件讲稿）X-ray Diffraction（XRD）

X-ray Diffraction (XRD) What is X-ray Diffraction Properties and generation of x-ray Braggs Law Basics of Crystallography XRD Pattern Powder Diffraction · Applications of XRD http://www.matter.org.uk/diffraction/x-ray/default.htm

X-ray Diffraction (XRD) • What is X-ray Diffraction Properties and generation of X-ray • Bragg’s Law • Basics of Crystallography • XRD Pattern • Powder Diffraction • Applications of XRD http://www.matter.org.uk/diffraction/x-ray/default.htm

http://www.youtubecom/watch?v=vyztzilj3ds at~0:40-3:10 X-ray and x-ray diffraction X-ray was first discovered by W. C. roentgen in 1895. Diffraction of X-ray was discovered by W.H. Bragg and W.L. Bragg in 1912 Bragg's law: n2=2dsine X-ray machine Photograph of the hand of an old man using X-ray WADAM

X-ray and X-ray Diffraction X-ray was first discovered by W. C. Roentgen in 1895. Diffraction of X-ray was discovered by W.H. Bragg and W.L. Bragg in 1912 Bragg’s law: n=2dsin Photograph of the hand of an old man using X-ray. http://www.youtube.com/watch?v=vYztZlLJ3ds at~0:40-3:10

Properties and Generation of X-ray X-rays are Name of enery, ey wavclength angstroms electromagnetic 10--1 x-unit XU radiation with very Gumma mys short wavelength( (Hard) 000 108-1012m) (Soft) 10—1 I:aKInete,uu The energy of the x- 0—1 mIcron,gt ray can be calculated Infrared visible light with the equation UH)+104 103—1 centimeter,cm E= hv= hc/a 000 eg. the x-ray photon:r+】算签+oi t02 1013-1, kilometer, km with wavelength 1A 04 Long wave has energy 12.5 kevI (VLF

Properties and Generation of X-ray ▪ X-rays are electromagnetic radiation with very short wavelength ( 10-8 -10-12 m) ▪ The energy of the x￾ray can be calculated with the equation E = h = hc/ ▪ e.g. the x-ray photon with wavelength 1Å has energy 12.5 keV

http://www.youtube.com/watch?v=lwv5wcbh9a0tow1:08 A Modern automated X-ray Diffractometer X-ray Tube Detector Sample stage Cost: $560K to 1. 6M

A Modern Automated X-ray Diffractometer Cost: $560K to 1.6M X-ray Tube Sample stage Detector http://www.youtube.com/watch?v=lwV5WCBh9a0 to~1:08

http://www.youtube.com/watch?v=bcoeojwkxputow1:10ProductionofX rays Production of X-rays Cross section of sealed-off filament X-ray tube copper vacllIrt glass X-ra vs tungsten flament CA p423 electrons Filament cooling w to transformr target X-rays Vacuum beryllium window X-ruvs netul focusing eup X-rays are produced whenever high-speed electrons collide with a metal target A source of electrons- hot w filament a high accelerating voltage(30-50k) between the cathode (w and the anode, which is a water-cooled block of Cu or Mo containing desire target metal https://www.youtubecom/watch?v=3_bzca7tlfqHowdoesX-raytubework

Production of X-rays Cross section of sealed-off filament X-ray tube target X-rays W Vacuum X-rays are produced whenever high-speed electrons collide with a metal target. A source of electrons – hot W filament, a high accelerating voltage (30-50kV) between the cathode (W) and the anode, which is a water-cooled block of Cu or Mo containing desired target metal. http://www.youtube.com/watch?v=Bc0eOjWkxpU to~1:10 Production of X￾rays https://www.youtube.com/watch?v=3_bZCA7tlFQ How does X-ray tube work filament + -

http://www.youtube.com/watch?v=bcoeojwkxpuatw1:06-3:10 X-ray Spectrum a spectrum of x-ray is produced as a result of the I Mo interaction between the incoming electrons and the nucleus or inner shell characterist radiation electrons of the target continuous element radiation Two components of the spectrum can be identified, namely the continuous spectrum caused by bremsstrahlung(German SWI. word: braking radiation) 0 and the characteristic WAVELENGTH (angstroms) spectrum SWL-short-wavelength limit http://www.youtube.com/watch?v=3fe6rhnhkuYBremsstrahlung http://www.youtube.com/watch?v=n9fklbakteycharacteristicX-ray

X-ray Spectrum ▪ A spectrum of x-ray is produced as a result of the interaction between the incoming electrons and the nucleus or inner shell electrons of the target element. ▪ Two components of the spectrum can be identified, namely, the continuous spectrum caused by bremsstrahlung (German word: braking radiation) and the characteristic spectrum. SWL - short-wavelength limit continuous radiation characteristic radiation k k I  Mo http://www.youtube.com/watch?v=n9FkLBaktEY characteristic X-ray http://www.youtube.com/watch?v=Bc0eOjWkxpU at~1:06-3:10 http://www.youtube.com/watch?v=3fe6rHnhkuY Bremsstrahlung

Short-wavelength Limit The short-wavelength limit (SWL or AswD) corresponds to those x-ray photons generated when an incoming electron yield all its energy in one impact. hc ev=hv max min hc1.240×104 SWL A e V- applied voltage

Short-wavelength Limit • The short-wavelength limit (SWL or SWL) corresponds to those x-ray photons generated when an incoming electron yield all its energy in one impact. min max   hc eV = h =  A 1.240 104 min eV V hc SWL   =  = = V – applied voltage

Characteristic x-ray spectra Sharp peaks in the spectrum can be seen if the (e. g. 25 kV for molybdenum/ir/ accelerating voltage is high cha target) These peaks fall into sets which are given the names, KL M lines with swI increasing wavelength WAVELENGTH (angstroms)

Characteristic x-ray Spectra ▪ Sharp peaks in the spectrum can be seen if the accelerating voltage is high (e.g. 25 kV for molybdenum target). ▪ These peaks fall into sets which are given the names, K, L, M…. lines with increasing wavelength. Mo

Excitation of kl m and n shells and Formation of Ka to Ma Characteristic X-rays If an incoming electron has sufficient kinetic energy for knocking out an electron of the K shell (the inner-most shell), it may excite the atom to an K high-energy state(k state) One of the outer electron falls subshells into the K-shell vacancy emitting the excess energy as Energ Kstate (shell a X-ray photon Characteristic X-ray energy L state x-ray Et final-cinitial K excitation中 M state EK>EL>EM excitation EKB>EKa N state ground state

2/9/2021 ▪ If an incoming electron has sufficient kinetic energy for knocking out an electron of the K shell (the inner-most shell), it may excite the atom to an high-energy state (K state). ▪ One of the outer electron falls into the K-shell vacancy, emitting the excess energy as a x-ray photon. ▪ Characteristic x-ray energy: Ex-ray=Efinal-Einitial Excitation of K, L, M and N shells and Formation of K to M Characteristic X-rays K L M N K K L Energy K state (shell) L state M state N state ground state K K L L K1 K2 I II III M subshells EK>EL>EM EK>EK K excitation L excitation M

Characteristic x-ray spectra Excitation (weighted very strong, strong, A weak, A Absorptionpotential Element average),A A edge. A (kv) A g 0.5608409410.563800.497070.4859 Mo0.7107300.7093000.71359006322880.6198 20.00 Cu 1.5418381.5405621.5443901.392218 1.3806 1.659191.65791 1.661751.50014 14881 Co 17902601.789651.7928501.6207916082 7.71 19373551.93604219399801.756611.7435 Cl 2.29100 2289702.2936062.08487 2.0702

Element K (weighted average), Å K1 very strong, Å K2 strong, Å K weak, Å K Absorption edge, Å Excitation potential (kV) Ag 0.56084 0.55941 0.56380 0.49707 0.4859 25.52 Mo 0.710730 0.709300 0.713590 0.632288 0.6198 20.00 Cu 1.541838 1.540562 1.544390 1.392218 1.3806 8.98 Ni 1.65919 1.65791 1.66175 1.50014 1.4881 8.33 Co 1.790260 1.788965 1.792850 1.62079 1.6082 7.71 Fe 1.937355 1.936042 1.939980 1.75661 1.7435 7.11 Cr 2.29100 2.28970 2.293606 2.08487 2.0702 5.99 Characteristic x-ray Spectra Z