Cellular Ceramics / front

Contents XIII

4.3.5.1Nusselt/Reynold Correlations and Comparison with Theoretical Data 354

4.3.6Summary 359

4.4Electrical Properties 361

Hans-Peter Martin and Joerg Adler

4.4.2.1Honeycombs 367

4.4.2.3Ceramic Foams 369

4.4.2.4Ceramic Fibers 374

4.4.4Summary 379

4.5Acoustic Properties 381

Iain D. J. Dupère, Tian J. Lu, and Ann P. Dowling

4.5.1Introduction 381

4.5.2Acoustic Propagation 381

4.5.2.2Wave Equation 382

4.5.2.3Relationships between Acoustic Parameters under Inviscid Conditions 383

4.5.2.4Acoustic Energy 384

4.5.3Acoustic Properties 384

4.5.3.2Acoustic Wavenumber 386

4.5.3.3Reflection Coefficient, Transmission Coefficient, and Transmission

Loss 386

4.5.3.4Absorption Coefficient 387

4.5.4Experimental Techniques 387

4.5.5Empirical Models 389

4.5.6Theoretical Models 390

4.5.6.2Acoustic Damping by an Array of Elements Perpendicular to the Propagation Direction 391

4.5.6.3Generalized Models 392

XIV Contents

4.5.6.6Biot’s Model 395

4.5.6.7Lambert’s Model 396

4.5.8Summary 398

5.1.1Introduction 403

5.1.3Commercial Applications 408

5.1.3.1Aluminum 408

5.1.3.2Iron Foundry 410

5.1.3.3Steel 412

5.1.4Summary 414

5.2.1Introduction 416

5.2.3Applications 418

5.2.4Modeling 433

5.2.5Summary 436

5.3Kiln Furnitures 439

Andy Norris and Rudolph A. Olson III

5.3.1Introduction 439

5.3.2.1Longer Life 441

5.3.2.4Chemical Inertness 447

5.3.2.5Cost Benefits 448

Contents XV

5.4Heterogeneously Catalyzed Processes with Porous Cellular Ceramic Monoliths 454

Franziska Scheffler, Peter Claus, Sabine Schimpf, Martin Lucas, and Michael Scheffler

5.4.1Introduction 454

5.4.2.3Zeolite Coating: A Combination of High Surface Area and Catalytic

5.4.3.1Automotive Catalysts 461

5.4.3.4Applications of Honeycomb Catalysts for Other Gas Phase

5.4.4.1Improvement of Technical Processes for Base Chemicals Production 474

5.4.4.2Hydrogen Liberation from Liquid Precursors/Hydrogen Cleaning for

5.4.5Summary 479

5.5Porous Burners 484

Dimosthenis Trimis, Olaf Pickenäcker, and Klemens Wawrzinek

5.5.1Introduction 484

5.5.2Flame Stabilization of Premixed Combustion Processes in Porous Burners 486

5.5.2.2Flame Stabilization under Steady Operation by Convection and Cooling 489

5.5.2.3Flame Stabilization under Steady Operation by Thermal

5.5.5Volumetric Porous Burners with Flame Stabilization by Thermal

XVI Contents

5.5.6Summary 506

5.6.1Introduction 509

5.6.2Acoustic Transfer 511

5.6.3Analytical Model 512

5.6.4.1Numerical Results 515

5.6.4.2Measurements 518

5.6.5Summary 521

5.7.1Introduction 523

5.7.3Optical, Thermodynamic, and Fluid-Mechanical Requirements of

5.7.4.2Ceramic Foams 533

5.7.4.5Material Combinations 536

5.7.5Absorber Tests 536

5.7.6Physical Restrictions of Volumetric Absorbers and Flow Phenomena in

5.7.7Summary 545

5.8.1Introduction 547

Contents XVII

5.9Interpenetrating Composites 571

Jon Binner

5.9.1Introduction 571

5.9.4Summary 578

5.10.1Introduction 580

5.10.2Novel Engine Combustion Concepts with Homogeneous Combustion

5.10.4The PM Engine Concept: Internal Combustion Engine with Mixture

5.10.5An Update of the MDI Engine Concept: Intelligent Engine Concept with

5.10.7Summary 594

5.11.8.2Armour Systems 608

5.11.9Heat Exchangers 609

5.11.11Duplex filters 611

5.11.12Lightweight Structures 612

5.11.17Sound Absorbers 616

5.11.18Bacteria/Cell Immobilization 617

5.11.19Light Diffusers 617

5.11.20Summary 618

Concluding Remarks 621

Index 625

XIX

Preface

Porosity in materials can be arranged in a well-defined and homogeneous manner or heterogeneously. It can be oriented, separated, or interconnected. From these possibilities pores of different shape, size, and interconnectivity arise. The three-dimen- sional assemblage of a large number of pores possessing a specific shape leads to a solid monolith displaying what can be termed a cellular structure.

A close analysis of materials found in nature reveals that most of them have a cellular structure and thus contain a significant amount of porosity, which plays a key role in optimizing their properties for a specific function. Indeed, Robert Hooke (1635–1703), a natural philosopher, experimental scientist, inventor, and architect, realized this in his investigations of the natural world and coined the term “cell” for describing the basic unit of the structure of cork, which reminded him of the cells of a monastery. In “Observation XVIII” of his book “Micrographia: or Some Physiological Descriptions of Minute Bodies Made by Magnifying Glasses with Observations and Inquiries Thereupon” (London: J. Martyn and J. Allestry, 1665), he wrote:

“... I could exceedingly plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular ... these pores, or cells, ... were indeed the first microscopical pores I ever saw, and perhaps, that were ever seen, for I had not met with any Writer or Person, that had made any mention of them before this ...”

Similarly, with an updated pool of knowledge and equipped with higher resolution analytical instruments, 300 years or so later researchers around the globe are interested in investigating and exploiting the advantages and peculiarities of cellular materials. Indicators of the increasing importance of this field are the numerous international conferences devoted to all three classes of cellular materials (metals, plastics, and ceramics), special issues of various scientific journals, and a rising number of specific books discussing either cellular structures in general or, more specifically, cellular metals and cellular plastics, among them:

L.J. Gibson, M.F. Ashby, Cellular Solids: Structure and Properties, Cambridge University Press, 1999;

D.L. Weaire, The Physics of Foams, Oxford University Press, 2001;

S. Perkowitz, Universal Foam: From Cappuccino to the Cosmos, Walker & Co., New York, 2000;

Cellular Ceramics: Structure, Manufacturing, Properties and Applications.

Michael Scheffler, Paolo Colombo (Eds.)

Copyright © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

ISBN: 3-527-31320-6