Silica

Otto W. Flörke

Otto W. Flörke

Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität, Bochum, Federal Republic of Germany

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Heribert A. Graetsch

Heribert A. Graetsch

Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität, Bochum, Germany

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Fred Brunk

Fred Brunk

Dr. C. Otto Feuerfest Gmbh, Bochum, Federal Republic of Germany

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Leopold Benda

Leopold Benda

Niedersächsisches Landesamt für Bodenforschung, Hannover, Federal Republic of Germany

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Siegfried Paschen

Siegfried Paschen

Kieselgur- und Kalksandsteinindustrie, Henrich Meyer-Werke Breloh GmbH & Co. KG, Munster, Federal Republic of Germany

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Horacio E. Bergna

Horacio E. Bergna

E. I. du Pont de Nemours & Company Inc., Wilmington, Delaware 19 880–0262, United States

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William O. Roberts

William O. Roberts

E. I. du Pont de Nemours & Company Inc., Wilmington, Delaware 19 880–0262, United States

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William A. Welsh

William A. Welsh

Grace Davison, W. R. Grace & Co.-Conn., Columbia, Maryland, United States

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David M. Chapman

David M. Chapman

Grace Davison, W. R. Grace & Co.-Conn., Columbia, Maryland, United States

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Manfred Ettlinger

Manfred Ettlinger

Degussa-Hüls AG, Standort Wolfgang, Hanau, Federal Republic of Germany

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Dieter Kerner

Dieter Kerner

Degussa-Hüls AG, Standort Wolfgang, Hanau, Federal Republic of Germany

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Monika Maier

Monika Maier

Degussa-Hüls AG, Standort Wolfgang, Hanau, Federal Republic of Germany

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Walter Meon

Walter Meon

Degussa-Hüls AG, Standort Wolfgang, Hanau, Federal Republic of Germany

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Ralf Schmoll

Ralf Schmoll

Degussa-Hüls AG, Werk Weeseling, Wesseling, Federal Republic of Germany

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Hermann Gies

Hermann Gies

Ruhr-Universität, Bochum, Federal Republic of Germany

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Dietmar Schiffmann

Dietmar Schiffmann

Institut für Toxikologie, Universität Würzburg, Würzburg, Federal Republic of Germany

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First published: 15 April 2007
Citations: 1

Abstract

Silica (SiO2) is a commonly occurring compound in nature. Various crystalline and noncrystalline silica minerals of inorganic and biogenic origin are known. Depending on temperature, pressure, composition of the precursor phases, etc., several different crystalline modifications are formed. Quartz is the most abundant and well-known polymorph. Silica occurs as meter-sized quartz crystals or as amorphous masses made up of submicroscopic crystallites having different microstructures or growth fabrics. In addition, synthetic polymorphs have been produced for which no natural counterparts exist. In industry, quartz sand and silica rocks are widely used as raw materials for production of glass, ceramics, and silicon. Single crystals of quartz are grown artificially for application as resonator crystals in clocks, communication technology, and computer electronics. Both natural and synthetic silica powders are used as fillers to improve the mechanical properties of plastics.

The article contains sections titled:

1.

Silica Modifications and Products

1.1.

Occurrence and Geochemistry

1.2.

Si-O Bond and Crystal Structures

1.3.

Crystalline Silica Phases

1.3.1.

Crystalline Silica Minerals

1.3.2.

Crystalline Nonmineral Silica Phases

1.4.

Noncrystalline Silica Minerals

1.5.

Colored Silica Minerals

1.6.

Silica Rocks

1.7.

Crystalline Silica Products

1.7.1.

Cultured Quartz Single Crystals

1.7.2.

Polycrystalline Silica Products

1.8.

Noncrystalline Silica Products

2.

Quartz Raw Materials

2.1.

Physical Forms and Occurrence

2.2.

Processing

2.3.

Uses

3.

Diatomites

3.1.

Introduction

3.2.

Formation, Composition, and Quality Criteria

3.3.

Occurrence and Mining

3.4.

Processing

3.5.

Analysis

3.6.

Storage and Transport

3.7.

Environmental and Health Protection

3.8.

Uses

3.9.

Recycling

4.

Colloidal Silica

4.1.

Introduction

4.2.

Structure of Colloidal Silica Particles

4.3.

Physical and Chemical Properties

4.4.

Stability

4.5.

Production

4.6.

Analysis and Characterization

4.7.

Uses

4.8.

Storage, Handling, and Transportation

4.9.

Economic Aspects

5.

Silica Gel

5.1.

Introduction

5.2.

Structure, Properties, and Characterization

5.3.

Production

5.4.

Uses

5.5.

Economic Aspects

5.6.

Legal Aspects

6.

Pyrogenic Silica

6.1.

Flame Hydrolysis

6.1.1.

Production Process

6.1.2.

Morphology

6.1.3.

Solid-State Properties

6.1.4.

Surface Chemistry

6.1.5.

Surface Modification with Silicon Compounds

6.1.6.

Characterization

6.1.7.

Uses

6.1.8.

Industrial Hygiene and Safety

6.2.

Electric-Arc Process

6.3.

Plasma Process

7.

Precipitated Silicas

7.1.

Introduction

7.2.

Production

7.3.

Properties

7.3.1.

Physicochemical Properties

7.3.2.

Surface Chemistry and Surface Modification

7.3.3.

Chemical Composition and Analysis

7.4.

Uses

7.5.

Industrial Hygiene and Safety

8.

Porosils

8.1.

Introduction

8.2.

Physical and Chemical Properties

8.2.1.

Zeosils

8.2.2.

Clathrasils

8.3.

Manufacture of Porosils

8.3.1.

Synthesis of Porosils

8.3.2.

Dealumination of Aluminosilicate Zeolites

8.3.3.

Formation of Melanophlogite

9.

Toxicology

9.1.

Experiences with Humans

9.2.

Animal Experiments

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