Chemistry of Non-Sag Tungsten (eBook)

Front Cover 1
The Chemistry of Non-Sag Tungsten 4
Copyright Page 5
Table of Contents 6
Dedication 8
Foreword 10
Chapter 1. Aspects of Effective Doping and the Incorporation of Dopant 14
1 INTRODUCTION 14
2 BASIC MATERIALS SUITABLE FOR PRODUCING NS TUNGSTEN 15
3 THE REDUCTION OF THE DOPED OXIDE TO METAL POWDER 20
4 INTERMEDIATE AND END PRODUCTS IN THE INDUSTRIAL REDUCTION PROCESS 20
5 THE EFFECT OF THE DOPANT FROM THE CHEMICAL POINT OF VIEW 29
6 THE ROLE OF NITROGEN (NH3) IN THE PRODUCTION OF NS METAL FROM APT 32
7 THE ROLE OF PHOSPHORUS (ASH3PO4) IN THE REDUCTION OF WO3 AND APT IN HYDROGEN 33
8 THE FORMATION OF GASEOUS HYDROXIDES FROM TUNGSTEN OXIDES AND THE EFFECTS OF As AND OF Mo ON THIS TYPE OF CVT 34
9 THE EFFECTS OF DIFFERENT ADDITIVES ON THE MORPHOLOGY OFW02 AND ON THE FORMATION OF OXIDEBRONZES AND ß-TUNGSTEN 35
10 TESTING OF NS TUNGSTEN METAL POWDER 'IN ITSELF' 41
11 SPECIFIC CHEMICAL EFFECTS INFLUENCING THE PERFORMANCE AND USE OF NS TUNGSTEN PRODUCTS 42
REFERENCES 45
APPENDIX 46
Chapter 2. From Tungsten Concentrates and Scrap to Highly Pure Ammonium Paratungstate (APT) 48
1 INTRODUCTION 48
2 RAW MATERIALS 49
3 PRETREATMENT OF RAW MATERIALS PRIOR TO DIGESTION 50
4 DIGESTION (DISSOLUTION) 51
5 PURIFICATION STEPS 53
6 CONVERSION OF SODIUM TUNGSTATE TO AMMONIUM POLYTUNGSTATE 54
7 AMMONIUM PARATUNGSTATE (APT)CRYSTALLIZATION 56
8 AMMONIUM PARATUNGSTATE (APT) 56
REFERENCES 57
Chapter 3. Effluent-Free Manufacture of Ammonium Paratungstate (APT) by Recycling the Byproducts 58
1 INTRODUCTION 58
2 SPECIAL ENVIRONMENTAL CONSIDERATIONS IN THE MANUFACTURE OF APT AND TUNGSTIC ACID 58
3 ELECTRODIALYSISOFTHENa2W04 SOLUTION 61
4 ENERGY CONSUMPTION OF THE ELECTRODIALYTIC RECOVERY OF NaOH 62
5 KEY PARTS OF THE ELECTRODIALYZERS AND THEIR RELIABILITY 64
6 COUPLING OF ELECTRODIALYTIC NaOH RECOVERY WITH SOLVENT EXTRACTION AND OTHER PROCESSES 65
7 HYDROMETALLURGICAL PROCESSING OF TUNGSTEN SCRAP 67
8 IMPLEMENTATION STAGES OF THE PROCESSES AND EQUIPMENT 68
9 DEVELOPMENT POTENTIALS FOR THE APT MANUFACTURING PROCESSES 69
ACKNOWLEDGEMENTS 71
REFERENCES 71
Chapter 4. Crystallisation and Processing of Ammonium Paratungstate (APT) 74
1 CRYSTALLISATION OF AMMONIUM PARATUNGSTATE 74
2 PROCESSING OF APT TO TUNGSTEN BLUE OXIDE 77
REFERENCES 87
Chapter 5. Chemistry of Tungsten Oxide Bronzes 90
1 INTRODUCTION 90
2 GENERAL CHARACTERIZATION OF OBs 91
3 PREPARATION METHODS FOR OBs 92
4 STRUCTURAL DESCRIPTION OF TOB 95
6 THERMAL DECOMPOSITION OF TOBs 98
7 ION EXCHANGE PROPERTIES OF TOB 100
8 A(H)TOB–A DECOMPOSITION PRODUCT OF APT 100
9 SURFACE CHEMICAL REACTIONS OF THE ATOB ON DOPING 100
10 THE MORPHOLOGY OF TOB 101
REFERENCES 102
Chapter 6. The Crystal Chemistry of the Higher Tungsten Oxides 106
INTRODUCTION 106
TUNGSTEN TRIOXIDE AND THE TUNGSTATES 107
TUNGSTEN BRONZES WITH THE PEROVSKITE STRUCTURE 108
CRYSTALLOGRAPHIC SHEAR STRUCTURES 110
STRUCTURES CONTAINING PENTAGONAL BIPYRAMIDS 112
CRYSTALLOGRAPHIC SHEAR VERSUS PENTAGONAL BIPYRAMIDS 115
THE HEXAGONAL TUNGSTEN BRONZES AND RELATED STRUCTURES 116
PYROCHLORE TUNGSTEN TRIOXIDE AND RELATED STRUCTURES 118
THE PHOSPHATE 'BRONZES' AND RELATED PHASES 119
CONCLUSIONS: STRUCTURES AND REACTIONS 120
REFERENCES 121
Chapter 7. Tungsten Blue Oxide 124
1 INTRODUCTION AND HISTORY 124
2 INDUSTRIAL PRODUCTION OF TBO 125
3 CHEMICAL COMPOSITION 126
PHYSICAL CONSTITUTION: MORPHOLOGY OF TBO 127
5 HOMOGENEITY 128
6 TBO CHARACTERIZATION 128
7 CONCLUSION 129
REFERENCES 130
Chapter 8. Formation and Incorporation of Dopant Phases during Technical Reduction of NS-Doped Tungsten Blue Oxide 132
1 INTRODUCTION 132
2 THE INDUSTRIAL PROCESS OF NS TUNGSTEN MANUFACTURE 133
3 DOPANT INTERACTIONS DURING HYDROGEN REDUCTION OF NS-DOPED TBO 138
4 INCORPORATION OF FOREIGNELEMENT PHASES IN OTHER ME-W-O SYSTEMS 144
5 CONCLUSIONS 148
ACKNOWLEDGEMENTS 148
REFERENCES 148
Chapter 9. The Formation and the Role of Potassium Bubbles in NS-Doped Tungsten 150
1 INTRODUCTION 150
2 SINTERING TECHNOLOGY 152
3 INGOT DENSIFICATION AND MICROSTRUCTURE EVOLUTION 153
4 BULK CHEMISTRY CHANGES AND POTASSIUM BUBBLE EVOLUTION DURING SINTERING 158
5 EVOLUTION OF THE BUBBLES IN THE TUNGSTEN ROD AND WIRE 162
ACKNOWLEDGEMENTS 171
REFERENCES 171
Afterword 174
CRYSTAL SIZE AND CRYSTAL SIZE DISTRIBUTION OF APT 174
THE APPROPRIATE OXIDE 175
DOPING OF TBO 175
REDUCTION TO WO2 175
REDUCTION TO TUNGSTEN METAL AND INCORPORATION OF THE DOPING ELEMENTS 176
SINTERING 176
CONCLUSION 176
Author Index 178
Subject Index 184