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

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N x9 } U w8 W cx V. öý 12 10 ä H ' 0 A FIGURE 4.8 0 20 40 60 80 100 PRESSURE p. s. i. : Rotation rates attained by a metal foil bearing rotor for air and helium driving gas 120
4.4.4 COMMENTS - 55 - For completeness we include at this point a few general comments about the foil bearing rotor system. It was found that at speeds up to 7 kHz the foil bearing rotors were extremely reliable. Every rotor constructed as described in Section 4.4.2 rotated stably even with full-sized liquid samples. Not all the conical rotors would rotates even on air. Although it is not a normal requirement of any NMR rotation system, it is worth noting that the Bernoulli rotors would not spin with liquid samples of any reasonable volume. Because of the heating effect upon rotation, use of the foil bearing system appears to be limited to those cases where the temperature of the sample is relatively unimportant. As the attainment of rotation rates above 7 kHz was limited only by the failure of the alumina axles, silicon nitride might well prove a more suitable axle material. Its tensile strength is typically the same as alumina, but its density is only about 2.6 gm/cm3 compared to 3.8 gm/cm 3. The coefficient of thermal expansion in silicon nitride is half that of alumina(64) so upon rotation both the induced thermal and mechanical stresses should be less. If the use of this or any other material does result in a consider- able improvement in performance it might prove possible to use a much simpler rotor design in a foil bearing, such as a single hollow tube.
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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
Page 21 and 22: - 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: PTFE Tape_ FIGURE 4.7 rotors SCALE
Page 75 and 76: Clamp Pf-£-- SECTION II SECTION 11
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
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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
Page 147 and 148:
- 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
Page 157 and 158:
- 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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NNR IN RAPIDLY ROTATED METALS By - Nottingham eTheses ...

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