DEVELOPMENT OF CERAMIC USES FOR NEPHELINE SYENITE TAILINGS DISSERTATION Presented In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy in the Graduate School of The Ohio State University By Robert Charles Wilson, B. A., M.Sc. The Ohio State University 1958 Approved by Adviser Department of Ceramic Engineering PREFACE The author wishes to express gratitude to his adviser, Dr. J. 0. Everhart, for his help and advice. He also wishes to thank Dr. C. J. Koenig for his suggestions and guidance throughout his graduate career. The author is indebted to the American Nepheline Limited, sponsors of the research program of which this investigation is a part. ii TO MY FATHER AND MOTHER AND MOST ESPECIALLY MY WIFE Hi TABLE OF CONTENTS Pago INTRODUCTION 1 USE OF NEPHELINE SYENITE TAILINGS lu VlTnlFIED CLa Y p i p e b o d i e s Introduction 4 Raviow of Literature 6 Procedure 8 Results 9 Discussion 26 Conclusions 28 USE OF NEPHELINE SYENITE TAILINGS IN VITRIFIED CLAY PIPE GLAZES Introduction 29 Review of Literature 32 Fusibility Tests 34 Cone 3 to 4 Glazes 39 Cone 04 to 03 Glazes 52 Conclusions 58 APPENDIX 64 REFERENCES 66 AUTOEIOGRAPHY 68 iv LIST OF TABLES Number Title Page 1 Chemical Analyses of Body Materials 10 2 Screen Analyses of the Various Grinds of Nepheline Syenite Tailings 11 3 Body Compositicus and Physical Properties for Body A 12 4 Body Compositions and Physical Properties for Body B 15 5 Body Compositions and Physical Properties for Body C 17 6 Body Compositions and Physical Properties for Body D 13 7 Body Compositions and Physical Properties for Body E 2 Q 8 Body Compositions and Physical Properties for Body F 22 9 Body Compositions and Physical Properties for Body G 23 10 Body Compositions and Physical Properties for Body H 25 11 Chemical Analyses of Glaze Materials 3 5 12 Compositions Evaluated for Fusibility by the Inclined Plane Flux Block Test Method 37 13 Molecular Formulae of Cone 4 Glazes 42 14 Batch Formulae of Cone 4 Glazes 43 15 The Effect of Glazes Studied on the Flexural Strength of a Cone 4 Vitrified Clay Pipe Body 44 16 Molecular Formulae of Cone 04 Glazes 53 v LIST OF TABLES (Continued) Number Title Page 17 Batch Formulae of Cone 04 Glazes 54 18 The Effect of Glazes Studied on the Flexural Strength of a Cone 04 Vitrified Clay Pipe Body 55 vi LIST OF ILLUSTRATIONS Figure Subject Page I Thermal expansion curves for body A. Body AC, no additive; body A 6 , 6 per cent addition of coarse-ground nepheline syenite tailings. 59 II Triaxial diagram for the pellet fusion study of B-200 nepheline syenite - talc - Gerstley Borate. 60 III Per cent Flexural Strength changes imparted by cone 4 glazes for firings 1 through V. 61 IV Per cent Flexural Strength changes Imparted by cone 4 glazes for firings VI through X. 62 V Per cent Flexural Strength changes Imparted by cone 04 glazes. 63 vll INTRODUCTION Nepheline syenite is an igneous rock, resembling granite in texture, hardness, and general appearancef1 )• The chief* mineral constituents of the rock are albite { soda feldspar ), mocrocline ( potash feldspar ), and nepheline. The mineral nepheline is higher in alkali and alumina, and lower in silica than either albite or microcline. The mineral nepheline, instead of albite, crystal­ lizes from the magma as a result of an insufficient amount of silica to form albite. The fact that it is " hungry " for silica, so to speak, enhances Its vitrifying activity in ceramic bodies. The fluxing action of nepheline syenite is unique because of the presence of the mineral nepheline. Nepheline, mineralogically, is a sodium aluminum silicate which contains, in the natural mineral, an appreciable amount of potash. An artifically prepared nepheline Is a pure sodium aluminum silicate with the formula f^O'A^O^* 2SIQ2 * The natural nepheline containing potash has the formula K2 0 »3 Na2 0 *4Al2 0 3 *9 SI0 2 . Natural nepheline has a hardness in the Moh's scale of 5.5 to 6 , specific gravity 2.55 to 2.65 and indices of refraction of 1.538 and 1.542. Research and subsequent commercial utilization 1 2 have shown not only that nepheline syenite can be used as a substitute for potash feldspar but that It is superior to feldspar in many respects{2 ). Extensive deposits of nepheline syenite occur In Canada, Russia, and India. In the United States, deposits of nepheline syenite are located in Arkansas, Montana, New Hampshire, New Jersey, and Virginia. Some excellent deposits are located at Blue Mountain, Ontario, and in the vicinity of Bancroft, Ontario, Canada. The Bancroft deposits are higher in nepheline content than the former. The Blue Mountain deposit is a long ridge rising to an elevation of about 350 feet above the surrounding country. The rock of the Blue Mountain central alkaline Intrusive is fine grained, light colored, and of granite-like texture. The solidified mass consists predominantly of the minerals albite, nepheline, and microcline in order of abundance(3). These minerals account for approximately 95 per cent of the rock. Although this deposit Is somewhat variable mineral- ogically, the chemical composition is uniform. When the iron, mostly in the form of magnetite, is removed during processing, a remarkably uniform product is obtained(4,5). Geological surveys have disclosed many million tons of nepheline syenite in the Blue Mountain deposit(6 ). Diamond drilling in the area where mining is now being carried out Indicates a block of about ten million tons. In refining nepheline syenite, it has been found Impracticable to remove the iron from a certain percentage of the rock. Approximately 75 per cent of the ore fed to the processing mill at Nephton, Ontario, is recovered as a low iron content material. This material has found appli­ cation in many branches of ceramics; namely, as a vitrifying agent in whltewares and as a source of alumina in glasses, glazes, and porcelain enamels. The remaining 25 per cent of the ore has about the same chemical composition as the lower Iron content product but contains higher amounts of iron oxides. The high iron content ore is efficiently separated from the lower iron content ore by high intensity magnetic separators. Recently there has been an increased interest by vitrified clay pipe manufacturers in using additives to improve the finished physical and working properties of their pipe bodies, and in developing ceramic glazes to replace salt glazes for their ware. Developments of the use of the higher iron content nepheline syenite ore ( nepheline syenite tailings ) in the aforementioned applications have been the aim of this study. USE OP NEPHELINE SYENITE TAILINGS IN VITRIFIED CLAY PIPE BODIES Introduction The manufacturers of vitrified clay pipe have shown an increased interest in adding low cost additives to their fire clay and shale bodies. Some of the principal improvements sought when experimenting with additives in pipe production are lower absorption to inhibit percolation, higher initial pipe strength and less deterioration in strengths during yard storage, longer firing ranges, and reduced air checking due in part to free silica. The additive investigated here was ground nepheline syenite tailings• In the processing of nepheline syenite, the high iron- bearing product is separated from the low iron-bearing product by high intensity magnetic separators. For efficient high-intensity separation, it is necessary to remove the dust from the head feed to the magnetic separators. Until recent years, the dust varied somewhat in fineness and in iron content. Processing the dust through Sweco screens and Eriez-type magnetic separators now yields a minus 1 0 0 -mesh product with five tenths per cent iron oxide. This product, however, is still not as fine as desired in a body flux. Previous work with nepheline 4 5 syenite as an additive to structural clay bodies has been with this type of material. This study dealt with the minus 30-mesh tailings from the high-intensity separators. These tailings were ground to various degrees of fineness and contained from 2 to 3 per cent of iron oxide. From the standpoint of costs, there are two stipu­ lations which must be met oy materials added to the clays and shales used in making vitrified clay pipe: the activity of the material must be great so that small additions will suffice; and the cost of the material must be low. The ground tailings are a low-cost commodity that can be shipped at a low freight rate because of the relatively high iron content. Information was therefore desired to establish the effect of several percentages of iron oxide and fineness of grind on the fluxing characteristics of nepheline syenite in pipe bodies. Careful consideration was given to the selection of representative pipe bodies. Review of Literature Nepheline syenite has found application in all branches of ceramics. In whitewares, advantage is taken of the low fusion characteristics of nepheline syenite to lower firing temperatures of the various products. This permits savings in fuel, in refractories, and In kiln furniture, and provides a wider color palette for single fire production. In 1939, Chilcote and Koenig{7) Investigated the influence of small additions of the previously described dust by-product, and combinations of this by-product with dolomite, on the physical properties of fire clay and shale brick. It was found that the addition of small amounts lowered the absorption and increased the fired shrinkage and flexural strength. Realizing that some vitrified clay pipe bodies fall to develop a sufficiently low absorption even when fired to the maximum safe temperature, Everhart(8 ) investigated the effect of 17 fluxing materials on such bodies.