t~icrogravity research, a new field originating from the accessibility of space, has reached the age of adolescence. An impressive set of results has emerged from the fi rst Space 1 ab fl i ght, whi ch by now has been fully evaluated. In view of this and the wealth of information available from other space experiments, ground based research, and short-term microgra­ vity experiments in ai rp 1 anes, rockets or fall towers, it was felt that the time was ripe for a comprehensive review of the field. The initiative of the US to build a permanent station in space, which was soon followed by a European decision to join this venture, further focussed attention onto microgravity materials sciences. This originates from the interesting prospects of a commercial space uti 1 ization, which would heavily rely on the results of scientific or technical experiments in space. From this point of view it also seemed timely and essential to provi de prospective commerci a 1 users with the necessary i nformat i on on previous experience, and more importantly, with a sound scientific basis for space processing. The aim of the present volume consequently is twofold, namely - to stimulate new scientific experiments in space in order to expand our knowledge gained from microgravity research, and to provide industry with the information obtained from space experi­ ments sofar and to contribute to the scientific background for commer­ cial space utilization.

I: Microgravity Materials Sciences.- 1 Introduction.- 1.1 The Space Utilization.- 1.2 The Scientific Basis.- 1.3 Present State and Future Developments.- 2. Historical Development.- 2.1 Motivation for Microgravity Experiments.- 2.2 First Experiments.- 2.2.1 Drop Tower and Aircraft Experiments.- 2.2.2 Apollo Experiments.- 2.3 Sky lab and Apollo-Soyus Test Project Experiments.- 2.3.1 Crystal Growth Experiments.- 2.3.2 Metallurgical Experiments.- 2.3.3 Electrophoresis Experiments.- 2.3.4 Skylab and Apollo-Soyus Experiments in Perspective.- 2.4 SPAR Experiments.- 2.5 Creation of the Science Base.- 3. Stimulation of Weightlessness.- 3.1 Free Fall: The Principle to Simulate Weightlessness.- 3.2 Free Fall Trajectories.- 3.3 The Orbital Flight.- 3.3.1 Atmospheric Drag.- 3.3.2 Solar Radiation Pressure.- 3.3.3 The Extended Spacecraft.- 3.3.4 G-jitter.- 3.4 Other Free-Fall Methods.- 3.4.1 Sounding Rockets.- 3.4.2 Research Aircrafts.- 3.4.3 Drop Tubes and Drop Towers.- II: Physical Phenomena.- 4. Convectionon and Bulk Transport.- 4.1 Bulk Fluid Flow.- 4.2 Scalings for Flow and Species Transport.- 4.3 Transport Phenomena in Directional Solidification.- 4.4 Transport Phenomena in the Floating Zone.- 4.5 Drop Dynamics.- 4.6 Summary and Perspective.- 5. Diffusion and Atomic Transport.- 5.1 Thermodynamics of Irreversible Processes.- 5.1.1 Phenomenological Equations.- 5.1.2 Diffusion.- 5.1.3 Transport Effects.- 5.1.4 Influence of Gravity on Transport.- 5.2 Diffusion and Transport in Simple Systems.- 5.2.1 Reference System.- 5.2.2 Simple Solutions of the Continuity Equation.- 5.2.3 The Boltzmann-Matano Method.- 5.2.4 Experimental Methods and Problems.- 5.3 Theories of Diffusion Processes in Liquids.- 5.3.1 Diffusion and Viscosity.- 5.3.2 Quasicrystalline Models.- 5.3.3 Model of Critical Volume.- 5.3.4 Fluctuation Theory.- 5.3.5 New Concepts and the Dynamic Structure of Liquid.- 5.3.6 Theories of Transport Processes in Liquids.- 5.3.7 Isotope Effect in Diffusion and Transport.- 5.4 Influence of Diffusion on Related Experiments.- 5.4.1 Solidification and Eutectic Alloys.- 5.4.2 Ostwald-Ripening.- 5.4.3 Separation of Immiscible Liqifids.- 5.4.4 Crystallization.- 5.5 Conclusions.- 6. Capillarity and Wetting.- 6.1 Surfaces.- 6.1.1 The Gibbs Model.- 6.1.2 Determination of Surface Tension.- 6.1.3 Surface Tension and Other Properties.- 6.2 Surface Tension of Solutions.- 6.3 Surface Tension of Solids.- 6.4 Wetting and Spreading.- 6.4.1 Contact Angles: Measurement and Character.- 6.5 Capillarity.- 6.5.1 Hydrostatic Equilibrium.- 6.5.2 Diffusional Equilibrium.- 6.5.3 Capillary Stability.- 6.6 Practical Conclusions.- 7. Solidification.- 7.1 Objectives for Solidification Research Under Microgravity.- 7.2 Solidification Front Dynamics.- 7.3 Complex Interactions of Different Transport Processes.- 7.4 Gravity-Independent Convective Processes.- 7.5 Effect of Convection on Microstructure and Properties.- 7.6 Towards Novel Materials and Technologies.- 8. Nucleation and Undercooling.- 8.1 Nucleation Theory.- 8.1.1 Clusters and Nuclei.- 8.1.2 Homogeneous and Heterogeneous Nucleation.- 8.1.3 The Nucleation Rate.- 8.2 Nonequilibrium Solidification.- 8.2.1 Undercooling and Hypercooling.- 8.2.2 Thermodynamic Conditions.- 8.2.3 Influence of Solidification Kirfetics.- 8.2.4Microstructure Refinement.- 8.3 Experimental Approaches.- 8.3.1 Rapid Cooling.- 8.3.2 Amorphous Containment.- 8.3.3 Dispersion Techniques.- 8.3.4 Container less Undercooling.- 8.4 Microgravity Prospects.- 9. Critical Phenomena.- 9.1 Universality of the Critical Behavior. Scaling Laws.- 9.1.1 Broken Symmetry ¿ Order Parameter.- 9.1.2 The Landau Free Energy.- 9.1.3 Scaling Laws. The Renormalization Group Approach.- 9.1.4 Critical Fluid Dynamics.- 9.2 Non Equilibrium Phenomena.- 9.2.1 Fluids Under Shear Flow. Change of Upper Critical Dimensionality.- 9.2.2 Phase Separation Process: Nucleation, Spinodal Decomposition.- 9.2.3 Ionic Conductivity Measurements.- 9.3 Finite Size Effects: Wetting and Prewetting Transitions.- 9.3.1 In the 2-Phases Region: Wetting.- 9.3.2 In the 1-Phase Region: Prewetting.- 9.3.3 Near the Critical Point: The Critical Adsorption.- 9.4 Gravity Dependence.- 9.4.1 The Liquid-Vapor Transition.- 9.4.2 The Phase Separation Process.- 9.4.3 Wetting Layers.- 9.4.4 The x-Point of Helium.- 9.5 Experiments Under Microgravity Conditions.- 9.5.1 Microgravity to Obtain a Bulk Critical Cell at the Gas-Liquid Critical Point.- 9.5.2 Microgravity to Avoid Stratification.- 9.6 General Conclusion.- III: Experimental Hardware.- 10. Funmices.- 10.1 Special Requirements to Furnaces in Space Laboratories.- 10.2 Review of Heating Techniques and Their Potential for Space Furnaces.- a. Resistance Heating.- b. Electron Beam Heating.- c. Inductive Heating.- d. Electrical Discharge Heating.- e. Heat Pipe Heating.- f. Mirror Heating.- g. Direct Current Passage Heating.- h. Laser Heating.- i. Microwave Heating.- k. Chemical Reaction Heating.- 10.3 Practical Spaceborn Furnace Configurations and Their Characteristics.- a. Isothermal Heating Furnaces.- b. Gradient Furnaces.- c. Zone Heating Furnaces.- d. Universal Furnaces.- 10.4 Peripheral Devices.- 10.5 Future Trends in Space Furnace Development.- 11. Fluid Experiments.- 11.1 Introduction.- 11.2 Particular Characteristics of Fluid Instrumentation.- 11.3 The Spacelab Facilities.- 11.4 Concluding Remarks.- 12. Containerless Processing Technologh.- 12.1 Drop Facilities.- 12.1.1 The MSFC Drop Tubes t.- 12.1.2 The JPL Drag-Free Drop Facility.- 12.2 Acoustical Levitators.- 12.2.1 Single-Axis Tuned Cavity Acoustic Levitator Furnace.- 12.2.2 Three-Axis Levitator.- 12.2.3 Single-Axis Interference Levitator.- 12.3 Aerodynamic Levitators.- 12.4 Electromagnetic Levitators.- 12.5 Electrostatic Levitation.- 12.6 Prospectus for Containerless Processing.- IV: Case Studies and Results.- 13. Metals and Composites.- 13.1 Metallurgical Technologies.- 13.2 Test of Theories.- 13.2.1 Eutectic Growth.- 13.2.2 Directional Solidification.- 13.3 Elaboration of New or Improved Materials.- 13.3.1 Particle Redistribution.- 13.3.2 Systems of Interest.- 13.3.3 Skin Technology.- 13.4 Characteristic Future Experiments.- 13.4.1 The ¿GETS¿ Experiment.- 13.4.2 The Mephisto Project.- 13.5 Conclusions.- 14. Binary, Systems with, Miscibility, gap in the Liquid State.- 14.1 Binary Systems with Miscibility Gap in the Liquid State.- 14.2 Minimum Free Energy Configurations.- 14.3.1 Simulation of Spinodal Decomposition and Growth of Nuclei.- 14.3.2 Nucleation.- 14.3.3 Terrestrial Observation of the Early Stages of Spinodal Decomposition and Nucleation.- 14.4 Results of Microgravity Investigations.- 14.5 Conclusions.- 15. Crystal Growth.- 15.1 Introduction.- 15.2 Space Relevant Growth Techniques.- 15.2.1 Floating Zone Melting.- 15.2.2 Bridgman Growth.- 15.2.3 Growth from Metal Solution by the Travelling Heater Method (THM).- 15.2.4 Growth from Aqueous Solution.- 15.2.5 Vapour Growth.- 15.3 Discussion.- 15.4 Future Potential.- 15.5 Conclusions.- 16. Fluid Dynamics.- 16.1 Capillarity.- 16.2 Stability.- 16.3 Microgravity Experiments on Liquid Bridges and Drops.- 16.4 Dynamic Models.- 16.5 Wetting and Spreading.- 16.6 Interface Convection.- 16.7 Microgravity Experiments on Interface Convection.- 17. Themophysical Properties.- 17.1 Overview on Properties with Gravity Influence.- 17.2 Design of Experiments for Reduced Gravity (Diffusion and Atomic Transport).- 17.2.1 Container Design.- 17.2.2 Temperature Control.- 17.2.3 Analysis of Diffusion Components.- 17.3 Diffusion Experiments in Space.- 17.3.1 Self diffusion in Zn (Skylab).- 17.3.2 Solute Diffusion of Au in Pb (Apollo-Soyuz).- 17.3.3 Self diffusion in Sn (Spacelab-1).- 17.3.4 Self- and Interdiffusion in Sn/In (D1 Flight).- 17.3.5 Interdif fusion in Pb/Zn (D1 Flight).- 17.3.6 Interdif fusion in Salt Melts (D1 Flight).- 17.4 Transport Experiments in Space.- 17.4.1 Thermotransport of Co in Sn (Spacelab-1 and D1).- 17.4.2 Thermotransport in AgI/KI (D1 Flight).- 17.5 Summary and Outlook.- 18. Glasses.- 18.1 Uses and Types of Glass.- 18.2 Melting of Glass.- 18.3 Glass Formation and Crystallization.- 18.4 Diffusion.- 18.5 Bubbles.- 18.6 Processing of Glass in Low Gravity.- 18.7 Measurement of Properties of Glass in Low Gravity.- 18.8 Summary.- 19. Separation Techniques.- 19.1 Electrophoresis.- 19.2 Continuous Flow Electrophoresis on Earth.- 19.3 Continuous Flow Electrophoresis in Space.- 19.4 Isoelectric Focusing.- 19.5 Phase Partitioning.- 19.6 Conclusions.