NNR IN RAPIDLY ROTATED METALS By - Nottingham eTheses ...

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4.5 OTHER TURB<strong>IN</strong>E SYSTEMS - 56 - 4.5.1 THE AXLE SUPPORTED ROTOR This rotor system has been used by a number of workers (34,39,44) The hollow cylindrical rotor with a snap-on lid is supported about its axis by a fine phosphor-bronze wire and propelled by a single gas jet impinging against a ring of flutes about the rotor circum- ference. Using compressed helium rotation rates of 8 kHz have been reached. However these rotors are apparently only capable of stable operation when the diameter/length ratio is greater than one, which limits the volume of the sample chamber. Unfortunately the filling factor of the rf coil is relatively poor in this system. 4.5.2 THE PRAGUE ROTOR SYSTEM A rotor of a more conventional design has been used for the measurement of proton magnetic resonance (50,65) . The rotor suspended in two externally pressurized conical gas bearings and driven by two pairs of jets placed against flutes on the main body, as shown in Figure 4.9. Using rotors machined from poly- mers rotation speeds of 10 kHz have been achieved but, for samples placed in hollow glass or sapphire rotors of internal diameter 3.5 mm the speeds were limited to 5 kHz. These spinning frequencies were reportedly dependent on machining tolerances of less than 0.003 mm. An investigation has been carried out on a similar system directly copied from this design. When propelled by compressed air at a pressure of 100 psi a solid nylon rotor reached a spinning is .
Clamp Pf-£-- SECTION II SECTION 11-]I Rotor FIGURE 4.9 : The 'Prague' rotor system (twice size) 3ring Jet ving t Jet raring Jet Driving Jet
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NNR IN RAPIDLY ROTATED METALS By R.
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I wish to express my thanks to: ACK
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quadrupole relaxation. However theo
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2.3.5 Quadrupole Relaxation 26 (i)
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5.9 Sample Preparation 71 5.9.1 Cup
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1.1 BASIC THEORY -i- CHAPTER 1 INTR
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-3- Transforming to the rotating fr
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-5- lattice and T2 is the spin-spin
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and -7- Vd(t) f(w1)cos w't dw Sao -
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-9- where the terms represent the Z
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- 11 - If rii = nrij = (Xli + X2j +
Page 23 and 24: - 13 - In powdered samples a weak i
Page 25 and 26: - 15 - This contact term manifests
Page 27 and 28: - 17 - where 0 is the angle between
Page 29 and 30: - 19 - termed pseudo-dipolar. It is
Page 31 and 32: - 21 - the non-secular terms of the
Page 33 and 34: - 23 - to the lattice directly via
Page 35 and 36: - 25 - (2.25), can then be assumed
Page 37 and 38: - 27 - quadrupole moments to produc
Page 39 and 40: - 29 - where En are the Zeeman ener
Page 41 and 42: 3.1 INTRODUCTION - 31 - CHAPTER 3 N
Page 43 and 44: Aý T. B a A"T"B " - 33 - It is a g
Page 45 and 46: (-Ur Ho FIGURE 3.1. : Co-ordinate s
Page 47 and 48: D, (t) = 331 2 + 3YI2 sin 2a 4 - 36
Page 49 and 50: - 38 - X (t) = cos a cos ßp + sin
Page 51 and 52: - 40 - 3.7 THE EFFECT OF ROTATION O
Page 53 and 54: - 42 - observations are inconsisten
Page 55 and 56: - 44 - that it apparently offered n
Page 57 and 58: - 46 - bearings suffer from instabi
Page 59 and 60: SI FIGURE 4.1 SCALE il cm : The con
Page 61 and 62: N to 9 . ýC 8 Ü7 Z w D 06 w ax U.
Page 63 and 64: - 50 - The rotors used in this work
Page 65 and 66: Ip IJýi O 1 t - 1 - 1 p OI ý I ý
Page 67 and 68: - 52 - at rotation speeds around 4
Page 69 and 70: - 53 - the manufacture of which was
Page 71 and 72: PTFE Tape_ FIGURE 4.7 rotors SCALE
Page 73: 4.4.4 COMMENTS - 55 - For completen
Page 77 and 78: 5.1 EQUIPMENT - 58 - CHAPTER 5 EXPE
Page 79 and 80: - 59 - the range ±1 V are digitise
Page 81 and 82: SCALE 3 cm j Cooling Gas ; tainiess
Page 83 and 84: Trensmitter EXL, FIGURE 5.3 : The s
Page 85 and 86: FIGURE $. 4 s The spectrometer prob
Page 87 and 88: Gas Tuning ransmi tter Input Receiv
Page 89 and 90: - 64 - phase can then be set so tha
Page 91 and 92: -66- The transient nuclear signals
Page 93 and 94: - 68 - 5.7.1 THE SOLID ECHO PULSE S
Page 95 and 96: - 70 - sequence may be repeated. In
Page 97 and 98: a° P/'rvu - 72 - p is the resistiv
Page 99 and 100: - 74 - combined with a low viscosit
Page 101 and 102: 6.2 RESULTS AND DISCUSSION - 76 - A
Page 103 and 104: IC 1 I. FIGURE 6.2 : Measured T1 va
Page 105 and 106: - 78 - TABLE 6.1. DEBYE TEMPERATURE
Page 107 and 108: - 80 - TABLE 6.2. RATIO OF TI VALUE
Page 109 and 110: - 82 - TABLE 6.3. DEPENDENCE OF T1
Page 111 and 112: - 84 - provides further evidence th
Page 113 and 114: - 86 - CHAPTER 7 EXPERIMENTAL RESUL
Page 115 and 116: - 88 - Lorentzian NMR lineshape of
Page 117 and 118: - 90 - at the top with epoxy glue.
Page 119 and 120: - 92 - (c) Bulk Susceptibility Effe
Page 121 and 122: - 94 - aluminium nuclei in the meta
Page 123 and 124: FIGURE 7.1 : 27A1 F. I. Ds and corr
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- 97 - TABLE 7.1. COMPUTED SECOND A
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- 99 - and Slichter(104) reported t
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- 101 - of this value would be requ
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N JL I F- 0 z J I0 0123456789 ROTAT
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-103- results obtained at a tempera
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T10 ms 3. O 2.5 2'C H 1"C o.. v 234
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0 - 106 - CHAPTER 8 MEASUREMENTS ON
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- 108 - process for vanadium the me
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- 109 - in the same way to the prec
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Qv == , 2 28 kHz -111- which is sli
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- 113 - from Cerac Inc. (USA). The
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- 115 - 8.4.3 SPIN-LATTICE RELAXATI
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tv D Xm =o N O Ul- X- z N O FIGURE
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which gives K=0.048 an ± 0.002 - 1
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- 118 - Lifetime broadening alone g
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- 120 - cannot be spun at low tempe
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- 122 - 11. L. E. Orgel, J. Phys. C
Page 159 and 160:
- 124 - 59. P. J. Randall, Ph. D. T
Page 161 and 162:
- 126 - 101. H. R. Khan, J. M. Reyn
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