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

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GRA<strong>IN</strong> SIZE - um - 73 - % OF TOTAL WEIGHT > 76 10 44-76 40 37-44 15 < 37 35 These powders were prepared from two grades of aluminium wire. The purer grade was obtained from Johnson Matthey Chemicals and had a quoted maximum impurity content of 50 ppm, the majority constituent of which was magnesium. The other grade of wire was as supplied directly by Metallisation Limited for industrial use and had a purity of approximately 99.5%. In a second method of sample preparation a tungsten carbide coated file was used to file powder from a5 9's pure aluminium ingot obtained from Koch-Light Laboratories. After sieving, the powder was passed several times through a high inhomogeneous magnetic field in an attempt to remove all ferromagnetic impurities. The aluminium specimens were annealed by subjecting them to a temperature of 250°C for a period of two hours, under a vacuum of better than 2x 10-6 torr. No problems of sintering were ßxper- ienced, so the powders were annealed loose in small glass boats and then allowed to cool down overnight. Surface oxidation of the metals afforded electrical insulation between neighbouring crystallites in the loose powders. However, with the exception of aluminium, the stresses induced by rapid rotation of the powder samples resulted in a welding together of the individual grains. To overcome this effect the powders were
- 74 - combined with a low viscosity resin mix - araldite 753/HY 951 hardener. In order to maximize the specimen density the uncured mixt- ure of resin and powder was centrifuged in cylindrical teflon moulds. After curing under an infra-red lamp, the solid slugs of powder and resin formed at the bottom of the moulds were machined to size, etched with acid and then pressed into the rotor sample chambers.
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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 +
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- 13 - In powdered samples a weak i
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- 15 - This contact term manifests
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- 17 - where 0 is the angle between
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- 19 - termed pseudo-dipolar. It is
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- 21 - the non-secular terms of the
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- 23 - to the lattice directly via
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- 25 - (2.25), can then be assumed
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- 27 - quadrupole moments to produc
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- 29 - where En are the Zeeman ener
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3.1 INTRODUCTION - 31 - CHAPTER 3 N
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Aý T. B a A"T"B " - 33 - It is a g
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(-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 and 74: 4.4.4 COMMENTS - 55 - For completen
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: a° P/'rvu - 72 - p is the resistiv
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
Page 125 and 126: - 97 - TABLE 7.1. COMPUTED SECOND A
Page 127 and 128: - 99 - and Slichter(104) reported t
Page 129 and 130: - 101 - of this value would be requ
Page 131 and 132: N JL I F- 0 z J I0 0123456789 ROTAT
Page 133 and 134: -103- results obtained at a tempera
Page 135 and 136: T10 ms 3. O 2.5 2'C H 1"C o.. v 234
Page 137 and 138: 0 - 106 - CHAPTER 8 MEASUREMENTS ON
Page 139 and 140: - 108 - process for vanadium the me
Page 141 and 142: - 109 - in the same way to the prec
Page 143 and 144: Qv == , 2 28 kHz -111- which is sli
Page 145 and 146: - 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
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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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NNR IN RAPIDLY ROTATED METALS By - Nottingham eTheses ...

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