Microweighing in Vacuum and Controlled Environments

Preface

Chapter 1. Introduction and Microbalance Review

I. Introduction

II. History

III. Definitions

IV. Classifications of Various Types of Microbalance

A. Introduction: The Ideal Microbalance

B. Types of Instruments

C. Methods of Monitoring Mass Changes

D. Methods for Automatic Sensing of Movement from the Null Point

E. Materials for Microbalance Fabrication

F. Conclusion: The Ultimate Microbalance

V. Calibration Techniques

VI. Auxiliary Equipment for Operation of a Vacuum Microbalance

A. Introduction

B. Vacuum Operation

C. Vibrational Mounts

D. Thermostatic Operation

E. Automatic Operation

F. Manual Operation

G. High Temperature Operation

H. Low Temperature Operation

VII. Undesirable Disturbances or Forces

A. Adsorption and Desorption Effects

B. Temperature Fluctuations

C. Static Charge Forces

D. Convection Currents

E. Buoyancy Forces

F. Radiometric Forces that Result from the Thermomolecular Flow of Gases

G. Water Vapor Effects

VIII. Applications

A. Classic Operation

B. Simultaneous Measurement of Mass and Other Physical Parameters

C. Future

D. Thermogravimetry

Acknowledgments

References

Chapter 2. Beam Microbalance Design, Construction and Operation

I. Introduction

II. Some General Theoretical Considerations in Beam Microbalance Design

III. Microbalance Selection Considerations

A. Environmental and Experimental Considerations

B. Advantages and Disadvantages of Various Beam Microbalances

IV. Microbalance Construction

A. Materials Considerations

B. Beam and Suspension Construction

V. Microbalance Operation

A. Deflection Detectors

B. Compensation and Null Techniques

C. Automatic Damping and Nulling Systems

D. System Sensibility or Resolution

E. Microbalance Calibration

VI. Summary

References

Chapter 3. Sources of Error in Micro Weighing in Controlled Environments

I. Introduction

II. Brownian Motion

A. The Undamped Balance Without Feedback

B. The Critically Damped Balance without Feedback

C. The Automated Balance

III. Knudsen Forces

IV. Cavity Forces

V. Armlength Effect

VI. Radiation Pressure

VII. Gravitational Forces

VIII. Electrostatic Forces

IX. Magnetostatic Forces

X. Building Vibrations

References

Chapter 4. Physical Adsorption Studies with the Vacuum Microbalance

I. Introduction

II. Instrumentation

A. Sorption Balances

B. Instruments for Pressure Measurement and Control

C. Instruments for Temperature Measurement and Control

D. Determination of the Saturation Vapor Pressure

E. Gravimetric Sorption Measuring Instruments

III. Measuring Techniques

A. Measuring Procedure

B. Pretreatment of the Materials

C. Pretreatment of the Instrument

D. Special Recommendations for the Measurements

E. Reducing the Measuring Time

IV. Examples of Physisorption Measurements and their Evaluation

A. Evaluation of Adsorption Isotherms

B. Determination of Specific Surface Area, Particle Size and Roughness

C. Isotherms of Porous Materials

D. Mesopore Analysis

E. Micropore Analysis

F. Determination of the Isosteric Heat

References

Chapter 5. Chemisorption Studies with the Vacuum Microbalance

I. Introduction

II. Probing the Surface Phase

III. Quantitative Information from Adsorption and Desorption

A. Adsorption Parameters

B. Isosteric Heat of Adsorption

C. Activation Energy of Adsorption

D. Desorption Kinetics

IV. Experimental

A. Overview

B. Apparatus

C. Technique

V. Chemisorption Results Obtained on Silver Powders

A. The Effectiveness of Outgassing, Oxygen Adsorption, and Chemical Reduction for Cleaning the Surface and Producing Reproducible Chemisorptive Behavior

B. Adsorption and Desorption of Oxygen on Silver

C. Adsorption of Carbon Dioxide on Oxygen Covered Silver

VI. Chemisorption Results Obtained on Other Solids

VII. Concluding Remarks

Acknowledgments

References

Chapter 6. Simultaneous Microgravimetric and Residual Gas Analyzer Measurements

I. Introduction

II. Instrumentation

A. Mass Spectrometers

III. Experimental

A. System Design

B. Methods

IV. Applications

A. Review

B. Future Applications

Acknowledgments

References

Chapter 7. The Simultaneous Measurement of Mass Change and Infrared Spectra

I. Introduction

II. Experimental

III. Results

IV. Conclusion

References

Chapter 8. Microgravimetric Studies of Catalysts and Catalytic Processes

I. Introduction

II. Vacuum Microbalances

A. Equipment and Apparatus

B. Assembly and Operation

III. Selected Examples

A. Surface Area Determination: Variation with Pretreatment

B. Surface Area Determination: Mixed Physical and Chemical Adsorption

C. Chemisorption: Rehydration

D. Support Information: Heat of Adsorption from Heat of Wetting

E. Sorption Energetics and Mechanism: Lunar Soils

IV. Areas of Additional Research

V. Conclusions

Acknowledgments

References

Chapter 9. High Temperature Reaction Studies

I. Introduction

A. Types of Chemical Reactions

B. Purpose of Chapter

C. Preliminary Thermochemical Analyses

D. Extent of Reaction

E. Units

II. Empirical and Theoretical Rate Laws

A. General

III. Apparatus and Methods

A. Static Reaction Systems

B. Flow Reaction Systems

C. Special Problems

IV. Applications

A. Vapor Pressure of Silicon

B. Oxidation of Graphite Using the Static Reaction System

C. Oxidation of Graphite Using the Flow Reaction System

D. Oxidation of Molybdenum-Static Reaction System

E. Oxidation of Tungsten

V. General Comments

VI. Appendix 1: Theory of Surface Interface Reactions with no Oxides Present

A. Processes

B. Kinetic Theory

C. Absolute Reaction Rate Theory

VII. Appendix 2: Furnaces for Temperatures Up to 1650°C

A. Mechanical and Physical Properties of Molybdenum Disilicide Elements

B. Electrical Supply Equipment

C. Useful Life

D. Atmospheric Effects

E. Furnace Design: Refractories

VIII. Appendix 3: Furnace Tubes and Reaction Systems

A. Criteria of Furnace Tube Performance

B. Types of Furnace Tubes

C. Specimen Supporting Wires

References

Chapter 10. Unusual Applications of the Vacuum Microbalance

I. Introduction

II. Permeation of Water Vapor through Plastic Membranes

A. Theory of Permeation

B. Measurement of Permeation

III. Measurement of Dust Concentration

A. The Basic Concept of the Dust Balance

B. Combination of Electrostatic Precipitation and Electromagnetic Weighing

C. Mass Determination by Vibrations of a Very Thin Band

IV. Determination of Grain Size Distributions by Weighing

A. Theory of Sedimentation Analysis

B. Grain Size Distribution by Sedimentation in Liquids

C. Grain Size Distribution by Sedimentation in Air

D. Grain Size Distribution by Sedimentation in Partial Vacuum

E. General Considerations

V. Measurement of Surface Tension

A. Basic Facts

B. Measurement of Surface Tension with the Aid of Wire Loops and Rings

C. Measurement of Surface Tension with the Aid of an Immersed Solid Plate

D. Measurement of Surface Tension with the Aid of a Cylinder or of a Solid Plate Touching the Surface

E. Adaptation of the Vacuum Microbalance to Measurement of Surface Tension

VI. Measurement of Permittivity and Dielectric Loss Factor

A. Theory of Electrostatic Forces on Dielectric Bodies

B. Measurement of Dielectric Permittivity

C. Measurement of the Dielectric Loss Factor

VII. Precision Measurement of Pressure Using the Principle of Automatic Compensation

A. Objective of the Development

B. A Self Compensating Bodenstein Manometer

VIII. Simultaneous Measurement of Components of Force and Combinations of Force and Torque

A. Measurement of Lift and Drag in a Gas Stream by a Two Component Microbalance

B. Simultaneous Determination of Mass Flow and Reaction Force of a Vapor Stream from a Heated Sample

C. Simultaneous Measurement of Weight and Torque by Magnetic Suspension

IX. Conclusion

References

Index