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Measurements of the Thermal Conductivity and Electrical Resistivity of Platinum from 373 to 1373° K

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Measurements of the Thermal Conductivity and Electrical Resistivity of Platinum from 373 to 1373° K NATIONAL BUREAU OF STANDARDS REPORT 9387 MEASUREMENTS OF THE THERMAL CONDUCTIVITY AND ELECTRICAL RESISTIVITY OF PLATINUM FROM 373 TO 1373° K by D. R. Flynn Environmental Engineering Section Building Research Division Institute for Applied Technology National Bureau of Standards and M. E. O' Hagan School of Engineering and Applied Science The George Washington University DO NOT REFERENCE THIS DOCUMENT U. S. DEPARTMENT OF COMMERCE NATIONAL BUREAU OF STANDARDS — THE NATIONAL BUREAU OF STANDARDS The National Bureau of Standards 1 provides measurement and technical information services essential to the efficiency and effectiveness of the work of the Nation’s scientists and engineers. The Bureau serves also as a focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. To accomplish this mission, the Bureau is organized into three institutes covering broad program areas of research and services: THE INSTITUTE FOR BASIC STANDARDS . provides the central basis within the United States for a complete and consistent system of physical measurements, coordinates that system with the measurement systems of other nations, and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation’s scientific community, industry, and commerce. This Institute comprises a series of divisions, each serving a classical subject matter area: —Applied Mathematics—Electricity—Metrology—Mechanics—Heat—Atomic Physics—Physical 2 - 2 Chemistry—Radiation Physics—Laboratory Astrophysics —Radio Standards Laboratory , which includes Radio Standards Physics and Radio Standards Engineering—Office of Standard Refer- ence Data. THE INSTITUTE FOR MATERIALS RESEARCH . conducts materials research and provides associated materials services including mainly reference materials and data on the properties of ma- terials. Beyond its direct interest to the Nation’s scientists and engineers, this Institute yields services which are essential to the advancement of technology in industry and commerce. This Institute is or- ganized primarily by technical fields: —Analytical Chemistry—Metallurgy—Reactor Radiations—Polymers—Inorganic Materials—Cry- ogenics 2—Materials Evaluation Laboratory-—Office of Standard Reference Materials. APPLIED . provides technical services to promote the THE INSTITUTE FOR TECHNOLOGY . use of available technology and to facilitate technological innovation in industry and government. The principal elements of this Institute are: —Building Research—Electronic Instrumentation—Textile and Apparel Technology Center Technical Analysis—Center for Computer Sciences and Technology—Office of Weights and Meas- ures—Office of Engineering Standards Services—Office of Invention and Innovation—Clearing- 3 house for Federal Scientific and Technical Information . 1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D. C., 20234. 2 Located at Boulder, Colorado, 80302. 3 Located at 5285 Port Royal Road, Springfield, Virginia, 22151. NATIONAL BUREAU OF STANDARDS REPORT NBS PROJECT NBS REPORT 421.03-40-4212231 9387 August 22, 1966 MEASUREMENTS OF THE THERMAL CONDUCTIVITY AND ELECTRICAL RESISTIVITY OF PLATINUM FROM 373 TO 1373 °K by D. R. Flynn Environmental Engineering Section Building Research Division Institute for Applied Technology National Bureau of Standards and M. E. O' Hagan School of Engineering and Applied Science The George Washington University DO NOT REFERENCE THIS DOCUMENT IMPORTANT NOTICE NATIONAL BUREAU OF ST l s accounting documents intended for use within the Government, Approved for public release by the subjected to additional evaluation and review. For this reason, the Director of the National Institute of listing of this Report, either in whole or in part, is not author! Office of the Director, National (NIST) Bureau of Standards, Washingto Standards and Technology the Government agency for which the Report has been specifically on October 9, 2015 pies for its own use. U. S. DEPARTMENT OF COMMERCE NATIONAL BUREAU Of STANDARDS ABSTRACT Measurements have been made of the thermal conductivity and the electri- cal resistivity of commercial grade platinum (99.98% pure) in the temperature range 373 to 1373 °K. The measurements have been made with a view to providing accurate data on the thermal conductivity of platinum to serve as a basis for establishing platinum as a thermal conductivity standard reference material. Two methods of measuring the thermal conductivity have been employed, one an electrical method and the other a non-electrical method. In the electri- cal method, a direct current passed through a necked-down portion of the speci- men and the thermal conductivity was determined in terms of the temperature and electrical potential distribution in the necked-down region. The second method was of the absolute guarded longitudinal heat flow type. The experiment was designed to permit measurements by both methods in the same apparatus and on the same specimen thereby providing as direct a comparison as possible between the methods. The data given by the two methods agree within experimental error and show the thermal conductivity of platinum to be a smoothly increasing function of temperature in the measured range. The data are considered to be accurate to better than 1% and indicate that platinum could be adopted as a thermal conductivity standard reference material. ii TABLE OF CONTENTS Page ACKNOWLEDGMENTS v LIST OF TABLES . ....... V £ LIST OF ILLUSTRATIONS vii INTRODUCTION .................. 1 Chapter I. PREVIOUS INVESTIGATIONS 4 II. DESCRIPTION OF THE APPARATUS ....... 24 Mechanical Configuration 27 Specimen 27 Furnace 34 Environmental System 36 Thermal Configuration 37 Specimen 37 Guard 42 Instrumentation 45 Temperature Control 45 Temperature Measurement 46 Power Measurement 46 Resistance Measurement 46 III. THEORY OF THE INDIRECT METHOD 50 IV. CALCULATION PROCEDURES 63 Indirect Method 63 Direct Method 73 V. SPECIMEN CHARACTERIZATION 85 Source 85 Fabrication and Thermal History 85 Hardness 88 Spectrographic Analysis . 88 Metallography 89 Density 89 Residual Resistance 91 Ice-Point Resistivity 92 EMF vs Pt 27 93 - iii - VI. TEST PROCEDURES 94 Direct Method 95 Resistivity 97 Indirect Method 98 VII. RESULTS 101 Electrical Resistivity 101 Thermal Conductivity ....... ....... 106 VIII. DISCUSSION OF RESULTS 116 Accuracy ....... ..... 116 Electrical Resistivity . 116 Thermal Conductivity ....... 117 Comparison with Other Investigations . 130 Electrical Resistivity ..... ..... 130 Thermal Conductivity 131 Appendix A. Machining the Neck and Wiring the Specimen . 138 B. Potential Perturbations . ..... 141 C. The Thomson Effect . 148 D. Alternative Calculation Procedure for the Indirect Method . 150 E. A Simplified Expression for the Maximum Temperature Rise in the Neck in the Presence of Heat Losses 152 F. Derivation of the Equation for Heat Flow in the Current Leads of the Specimen Heater 154 G. Errors in Temperature Measurements Due to Heat Conduction along Thermocouple Wires 157 H. Departures from One -Dimensional Heat Flow in the Direct Method 160 I. Tempering of the Heater Current Leads 162 References 164 - iv - ACKNOWLEDGMENTS This research was the subject of a dissertation submitted by Malcolm O'Hagan to the Faculty of The School of Engineering and Applied Science, The George Washington University, in partial satisfaction of the requirements for the degree of Doctor of Science. This work was supported in part by Engelhard Industries, Inc., Newark, New Jersey, who supplied the platinum and financial assistance in the form of a Grant to the National Bureau of Standards. We thank Henry G. Albert and A. V. Lincoln, both of Engelhard Industries, Inc., for their support and advice. Malcolm E. O'Hagan was supported in part by Grant AFOSR-1025-66 from the Air Force Office of Scientific Research and in part by the Institute for Industrial Research and Standards, Dublin, Ireland. We thank Henry E„ Robinson, Chief, Environmental Engineering Section, NBS, and Adjunct Professor of Engineering, The George Washington University for his advice and support. The intricate and difficult machining required for this project was done by Raymond Chidester, Section 145.01 NBS. Much good advice in matters of fabrication came from John Hettenhouser , Section 145.01 NBS. - v - LIST OF TABLES Table Page 1. Sample characterization of platinum samples used by various investigators 17 2. Thermal conductivity of platinum in the temperature range 273-373 °K as reported by several investigators ... 18 3. Hardness values as measured on the platinum bar .... 88 4. Spectrographic analysis as determined on platinum wire No. 175105 89 5. Resistance values for three samples of platinum at ice- point and helium-point temperatures and the computed re- sistance ratios at zero current 92 6. EMF vs Pt 27 as determined on 20-mil platinum wire. 93 7. Experimental values for the thermal conductivity of platinum as determined by the direct method 107 8. Typical set of data from measurements of the thermal con- ductivity by the direct method 108 9. Experimental values for the thermal conductivity of platinum as determined by the indirect method .... 113 10. Comparison of smoothed resistivity values for platinum with those of other investigators 130 11. Thermal conductivity of platinum 132 12. Values for the relative magnitude of the Thomson Term . 149 U(T) 13. Values of o 0 m) for
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