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Coatings technology handbook
Books & publications
Coatings technology handbook D Satas (Editor) Marcel Dekker, 1991, 800 pp, hardcover, $201.25. ISBN: 0-8247-8410-3 Coatings have today permeated practically all areas of manufacturing, and it would be difficult to find a finished product that has escaped the application of a coating. Coatings are applied to protect bulk materials from corrosion and other detrimental effects of the ambient atmosphere. They are used to change surface properties and colour, gloss, and general appearance. Adhesive coatings are used in laminating and in the preparation of composites. Coatings are used as barriers for gases and liquids. Application techniques, coating types and their purposes make coating technology today an extremely diverse field. The transferable nature of coating technology, from one application to another, makes a handbook practicable from a technical and economic standpoint - there is a large enough pool of authors and purchasers; and a person practising one aspect of coating technology may not be at all familiar with techniques or materials used for another application. Mr Satas has gathered together 91 contributors, the majority of them from the USA but with representatives from Germany (8), Lithuania (3), Sweden, The Netherlands and the UK. The subject coverage is comprehensive and the quality of contributions is generally good. More than half of the contributors have supplied references for further specialist information but few of these are as recent as 1987 and many are much older. This matters less for some of the more traditional coating areas but is clearly a disadvantage for anyone wishing to read up on diamond and diamond-like films or optical fibre coatings. Therein lies a problem with almost all multi-authored reference books. The timeliness of each contribution is only as good as the last, invariably late, contributor allows it to be. Publication schedules are based around the last contribution regardless of when the first was written and submitted. Since this is a general problem it is only fair, then, to judge these books on their accessibility and 'user-friendliness' as much as their content. On that score the handbook is quite successful. Chapters are arranged into four sections: fundamentals and testing (9 chapters); coating and processing techniques (25); materials (29); and surface coatings (26). It is not clear why these distinctions have been drawn, or why certain chapters appear where they do, but a clear contents list at the front
120
and accurate, though brief, index at the back allow topics to be found easily. The appearance is clean; the text is easy to absorb and illustrations, both photographs and line diagrams, are clear and large. Contributors are predominantly from an industrial background and the short, practical discussions of techniques, processes and materials reflect this. Overall the handbook achieves the aims of its Editor: "to expose those practising coating technology to techniques and materials used in related technologies, and perhaps offer some useful ideas".
S.S.
Micromachining silicon patent awarded to Sandia
US
Researchers at Sandia National Laboratories, Albuquerque, have developed an improved process for uniformly etching silicon to create miniature parts used in micromechanical devices. A patent has been awarded on the process (No. 4, 995, 954) and a further patent application has been filed for a humidity sensor fabricated by the process. Single crystal silicon has long been used to produce integrated circuits, and its exceptional strength also makes it an ideal material for fabricating miniature sensors, motors, accelerometers, and other microdynamic devices. The sculpting of these tiny operating structures - measured in microns and often having complex three-dimensional geometries - is a relatively new engineering field known as micromachining.
Silicon removal techniques for crafting silicon wafers involve photolithology and chemical etching. With these techniques, the area to be removed is defined by a patterned mask and the material to be removed is dissolved in hydroxide baths at elevated temperatures. For three-dimensional structures, these techniques are less desirable. Because the etch rate is dependent upon the temperature and bath composition, it is difficult to control precisely the amount of silicon to be removed. Chemical etching also tends to give the etched area a matte finish rather than the preferred mirror finish. The Sandia process uses electrolysis of silicon in hydrofluoric acid to make porous a very thin layer of silicon on the top of the silicon wafer. Since the etching rate is directly proportional to the current passed in the electrochemical cell, the depth of the porous silicon can be easily regulated by controlling the charge passed through the cell. The wafer is then removed from the cell, and the porous silicon is etched by immersing it in a hydroxide solution at room temperature. Because the pore depths are so uniform, the resultant etch finish is mirror rather than matte. According to Terry Guilinger, a member of the Sandia research team: "the greatest attraction of this method is the assurance of a uniform product when fabricating multiple structures. This intermediate, porous phase allows the volume to be etched away precisely and in a repeatable manner. We have demonstrated that we can duplicate the process repeatedly with no more than 0.3 percent variance in results." Further information from: Terry Guilinger, Sandia National Laboratories, Albuquerque, NM 87185, USA. Tel: +1 505 845 9043.
Electroslag technology B I Medovar, G A Boyko (Translated from the Russian by O Gavrilovic) Springer-Verlag, 1991, 270 pp, hardcover, DM 148. ISBN: 3-540-97333-8 Electroslag technology is a method of melting and casting steel and alloys that produces highly pure and strong metals. The development of this method in the Soviet Union was an effort to catch up with the technology of Vacuum and Remelting (VAR) previously developed and tested in the USA for complex, high alloy systems. Electroslag casting has become highly successful for a wide range of products and compositions and is now used in the USA, Europe and Japan. The book describes key applications of electroslag technology as well as a
number of practical recommendations. It provides an excellent discussion of the refining slags employed, their stability and refining abilities for an extremely wide range of alloys. Mechanical properties and the extensive equipment modifications that makes EST attractive are discussed in detail. Components from small castings to extremely large rotors, truck and equipment beds are reported. The book also covers the development of EST in other countries, including Austria, Germany, Canada, USA, France, Japan, Italy, Yugoslavia, Hungary, Czechoslovakia and China.
MATERIALS & DESIGN Vol. 13 No. 2 APRIL 1992
Coatings technology handbook D Satas (Editor) Marcel Dekker, 1991, 800 pp, hardcover, $201.25. ISBN: 0-8247-8410-3 Coatings have today permeated practically all areas of manufacturing, and it would be difficult to find a finished product that has escaped the application of a coating. Coatings are applied to protect bulk materials from corrosion and other detrimental effects of the ambient atmosphere. They are used to change surface properties and colour, gloss, and general appearance. Adhesive coatings are used in laminating and in the preparation of composites. Coatings are used as barriers for gases and liquids. Application techniques, coating types and their purposes make coating technology today an extremely diverse field. The transferable nature of coating technology, from one application to another, makes a handbook practicable from a technical and economic standpoint - there is a large enough pool of authors and purchasers; and a person practising one aspect of coating technology may not be at all familiar with techniques or materials used for another application. Mr Satas has gathered together 91 contributors, the majority of them from the USA but with representatives from Germany (8), Lithuania (3), Sweden, The Netherlands and the UK. The subject coverage is comprehensive and the quality of contributions is generally good. More than half of the contributors have supplied references for further specialist information but few of these are as recent as 1987 and many are much older. This matters less for some of the more traditional coating areas but is clearly a disadvantage for anyone wishing to read up on diamond and diamond-like films or optical fibre coatings. Therein lies a problem with almost all multi-authored reference books. The timeliness of each contribution is only as good as the last, invariably late, contributor allows it to be. Publication schedules are based around the last contribution regardless of when the first was written and submitted. Since this is a general problem it is only fair, then, to judge these books on their accessibility and 'user-friendliness' as much as their content. On that score the handbook is quite successful. Chapters are arranged into four sections: fundamentals and testing (9 chapters); coating and processing techniques (25); materials (29); and surface coatings (26). It is not clear why these distinctions have been drawn, or why certain chapters appear where they do, but a clear contents list at the front
120
and accurate, though brief, index at the back allow topics to be found easily. The appearance is clean; the text is easy to absorb and illustrations, both photographs and line diagrams, are clear and large. Contributors are predominantly from an industrial background and the short, practical discussions of techniques, processes and materials reflect this. Overall the handbook achieves the aims of its Editor: "to expose those practising coating technology to techniques and materials used in related technologies, and perhaps offer some useful ideas".
S.S.
Micromachining silicon patent awarded to Sandia
US
Researchers at Sandia National Laboratories, Albuquerque, have developed an improved process for uniformly etching silicon to create miniature parts used in micromechanical devices. A patent has been awarded on the process (No. 4, 995, 954) and a further patent application has been filed for a humidity sensor fabricated by the process. Single crystal silicon has long been used to produce integrated circuits, and its exceptional strength also makes it an ideal material for fabricating miniature sensors, motors, accelerometers, and other microdynamic devices. The sculpting of these tiny operating structures - measured in microns and often having complex three-dimensional geometries - is a relatively new engineering field known as micromachining.
Silicon removal techniques for crafting silicon wafers involve photolithology and chemical etching. With these techniques, the area to be removed is defined by a patterned mask and the material to be removed is dissolved in hydroxide baths at elevated temperatures. For three-dimensional structures, these techniques are less desirable. Because the etch rate is dependent upon the temperature and bath composition, it is difficult to control precisely the amount of silicon to be removed. Chemical etching also tends to give the etched area a matte finish rather than the preferred mirror finish. The Sandia process uses electrolysis of silicon in hydrofluoric acid to make porous a very thin layer of silicon on the top of the silicon wafer. Since the etching rate is directly proportional to the current passed in the electrochemical cell, the depth of the porous silicon can be easily regulated by controlling the charge passed through the cell. The wafer is then removed from the cell, and the porous silicon is etched by immersing it in a hydroxide solution at room temperature. Because the pore depths are so uniform, the resultant etch finish is mirror rather than matte. According to Terry Guilinger, a member of the Sandia research team: "the greatest attraction of this method is the assurance of a uniform product when fabricating multiple structures. This intermediate, porous phase allows the volume to be etched away precisely and in a repeatable manner. We have demonstrated that we can duplicate the process repeatedly with no more than 0.3 percent variance in results." Further information from: Terry Guilinger, Sandia National Laboratories, Albuquerque, NM 87185, USA. Tel: +1 505 845 9043.
Electroslag technology B I Medovar, G A Boyko (Translated from the Russian by O Gavrilovic) Springer-Verlag, 1991, 270 pp, hardcover, DM 148. ISBN: 3-540-97333-8 Electroslag technology is a method of melting and casting steel and alloys that produces highly pure and strong metals. The development of this method in the Soviet Union was an effort to catch up with the technology of Vacuum and Remelting (VAR) previously developed and tested in the USA for complex, high alloy systems. Electroslag casting has become highly successful for a wide range of products and compositions and is now used in the USA, Europe and Japan. The book describes key applications of electroslag technology as well as a
number of practical recommendations. It provides an excellent discussion of the refining slags employed, their stability and refining abilities for an extremely wide range of alloys. Mechanical properties and the extensive equipment modifications that makes EST attractive are discussed in detail. Components from small castings to extremely large rotors, truck and equipment beds are reported. The book also covers the development of EST in other countries, including Austria, Germany, Canada, USA, France, Japan, Italy, Yugoslavia, Hungary, Czechoslovakia and China.
MATERIALS & DESIGN Vol. 13 No. 2 APRIL 1992