Surface science
Surface science is the study of physical and chemical phenomena that occur at the interface of two phases, including solid-liquid interfaces, solid-gas interfaces, solid-vacuum interfaces, and liquid-gas interfaces. It includes the fields of surface chemistry and surface physics.[1] Some related practical applications are classed as surface engineering. The science encompasses phenomena such as heterogeneous catalysis, semiconductor device fabrication, fuel cells, self-assembled monolayers, adhesion, adsorption, friction, and lubrication.
Surface science is closely related with Interface and Colloid Science.[2] Interfacial chemistry and physics are common subjects for both. Methods are different. In addition, Interface and Colloid Science studies macroscopic phenomena that occur in heterogeneous systems due to peculiarities of interfaces.
The science and technology of interacting surfaces in relative motion is known as tribology.
- "Biological issues often involve interface phenomena. The majority of pharmaceuticals, for example, work through the active molecule interacting with substances on cell surfaces. In the course of events that controls this process surface chemical issues are of major significance. For the rapidly growing area of biomaterials the significance of surface chemistry is more obvious. The interaction between the surface and biological substances is vital to the performance of the biomaterials."
History
The field of surface chemistry started with heterogeneous catalysis pioneered by Paul Sabatier on hydrogenation and Fritz Haber on the Haber process.[3] Irving Langmuir was also one of the founders of this field, and the scientific journal, Langmuir, on surface science bears his name. The Langmuir adsorption equation is used to model monolayer adsorption where all surface adsorption sites have the same affinity for the adsorbing species.
Gerhard Ertl in 1974 described for the first time the adsorption of hydrogen on a palladium surface using a novel technique called LEED.[4] Similar studies with platinum,[5] nickel[6][7], and iron [8] followed. Most recent developments in surface sciences include the 2007 Nobel Prize of Chemistry winner Gerhard Ertl's advancements in surface chemistry, specifically his investigation of the interaction between carbon monoxide molecules and platinum surfaces.
Surface chemistry
Surface chemistry can be roughly defined as the study of chemical reactions at interfaces. It is closely related to surface functionalization, which aims at modifying the chemical composition of a surface by incorporation of selected elements or functional groups that produce various desired effects or improvements in the properties of the surface or interface. Surface chemistry also overlaps with electrochemistry. Surface science is of particular importance to the field of heterogeneous catalysis.
The adhesion of gas or liquid molecules to the surface is known as adsorption. This can be due to either chemisorption or by physisorption. These too are included in surface chemistry.
The behaviour of a solution based interface is affected by the surface charge, dipoles, energies and their distribution within the electrical double layer.
Surface physics
Surface physics can be roughly defined as the study of physical changes that occur at interfaces. It overlaps with surface chemistry. Some of the things investigated by surface physics include surface diffusion, surface reconstruction, surface phonons and plasmons, epitaxy and Surface enhanced Raman scattering, the emission and tunneling of electrons, spintronics, and the self-assembly of nanostructures on surfaces.
Analysis techniques
The study and analysis of surfaces involves both physical and chemical analysis techniques.
Several modern methods probe the topmost 1-10 nm of the of surfaces exposed to vacuum. These include X-ray photoelectron spectroscopy, Auger electron spectroscopy, low-energy electron diffraction, electron energy loss spectroscopy, thermal desorption spectroscopy, ion scattering spectroscopy, secondary ion mass spectrometry, and other surface analysis methods included in the list of materials analysis methods. Many of these techniques require vacuum as they rely on the detection of electrons or ions emitted from the surface under study.
Purely optical techniques can be used to study interfaces under a wide variety of conditions. Reflection-Absorption Infrared, Surface Enhanced Raman and Sum Frequency Generation spectroscopies can be used to probe solid-vacuum as well as solid-gas, solid-liquid, and liquid-gas surfaces.
Modern physical analysis methods include scanning-tunneling microscopy (STM) and a family of methods descended from it. Two of these are atomic force microscopy (AFM) and SPM. These microscopies have considerably increased the ability and desire of surface scientists to measure the physical structure of many surfaces. This increase is related to a more general interest in nanotechnology.
Adhesion
The strength of attachment between an adhesive and its substrate depends on many factors, including the mechanism by which this occurs and the surface area over which the two materials contact each other. Materials that wet each other tend to have a larger contact area than those that don't. Five mechanisms have been proposed to explain adhesion.
- Mechanical Adhesion: Two materials may be mechanically interlocked, as when the adhesive works its way into small pores of the materials.
- Chemical Adhesion: Two materials may form a compound at the join.
- Dispersive Adhesion: In dispersive adhesion (also known as adsorption), two materials are held together by what are known as "van der Waals forces." These are weak (but numerous) interactions between molecules of the materials, arising by electron movements or displacements within the molecules.
- Electrostatic Adhesion: Some conducting materials may pass electrons to form a difference in electrical charge at the join. This gives rise to a structure similar to a capacitor and creates an attractive electrostatic force between the materials.
- Diffusive Adhesion: Some materials may merge at the joint by diffusion. This may occur when the molecules of both materials are mobile and soluble in each other.
Tribology
Tribology deals with the interactions of surfaces in relative motion. It includes the study and application of the principles of friction, lubrication, and wear. Any product in which one material slides over or rubs against another is affected by complex tribological interactions.
The study of tribology is commonly applied in the design of mechanical bearings, but it extends to such products as hip implants, hair conditioners, lipstick, powders, and lipgloss.
in high temperature sliding wear in which conventional lubricants can not be used but in which the formation of compacted oxide layer glazes have been observed to protect against wear.
Tribology plays an important role in manufacturing. In metal-forming operations, friction increases tool wear and the power required to work a piece. This results in increased costs due to more frequent tool replacement, loss of tolerance as tool dimensions shift, and greater forces are required to shape a piece. A layer of lubricant which eliminates surface contact virtually eliminates tool wear and decreases needed power by one third.
See also
- Surface finishing
- Tribology
Notes
- ↑ Prutton, Martin. 1994. Introduction to Surface Physics. Oxford University Press. ISBN 0198534760.
- ↑ Lyklema. J. 1995-2005. Fundamentals of Interface and Colloid Science. vol. 1-5. Academic Press.
- ↑ Scientific Background on the Nobel Prize in Chemistry 2007 Chemical Processes on Solid Surfaces Håkan Wennerström, Sven Lidin http://nobelprize.org/nobel_prizes/chemistry/laureates/2007/chemadv07.pdf
- ↑ Adsorption of hydrogen on palladium single crystal surfaces Surface Science, Volume 41, Issue 2, February 1974, Pages 435-446 H. Conrad, G. Ertl and E. E. Latta DOI:10.1016/0039-6028(74)90060-0
- ↑ Adsorption of hydrogen on a Pt(111) surface Surface Science, Volume 54, Issue 2, February 1976, Pages 365-392 K. Christmann, G. Ertl and T. Pignet DOI:doi:10.1016/0039-6028(76)90232-6
- ↑ Adsorption of hydrogen on nickel single crystal surfaces K. Christmann, O. Schober, G. Ertl, and M. Neumann The Journal of Chemical Physics — June 1, 1974 — Volume 60, Issue 11, pp. 4528-4540 DOI:10.1063/1.1680935
- ↑ Chemisorption geometry of hydrogen on Ni(111): Order and disorder The Journal of Chemical Physics — May 1, 1979 — Volume 70, Issue 9, pp. 4168-4184 DOI:10.1063/1.438041
- ↑ Phase transitions of a two-dimensional chemisorbed system-H on Fe(110) Surface Science, Volume 117, 1982, Pages 257-266 R.Imbihl, R.J. Behm, K. Christmann, G.Ertl, and T. Matsushima DOI:doi:10.1016/0039-6028(82)90506-4
ReferencesISBN links support NWE through referral fees
- Ibach, Harald. 2006. Physics of Surfaces and Interfaces. Berlin: Springer. ISBN 978-3540347095.
- Kolasinski, Kurt W. 2002. Surface Science: Foundations of Catalysis and Nanoscience. Chichester: Wiley. ISBN 0471492450.
- McCash, Elaine M. 2004. Surface Chemistry. Oxford, UK: Oxford Univ. Press. ISBN 0198503288.
- Prutton, Martin. 1994. Introduction to Surface Physics. Oxford University Press. ISBN 0198534760.
- Somorjai, Gabor A. 1994. Introduction to Surface Chemistry and Catalysis. New York: Wiley. ISBN 0471031925.
- Woodruff, D. P., and T. A. Delchar. 1994. Modern Techniques of Surface Science. 2nd ed. Cambridge Solid State Science Series. Cambridge, UK: Cambridge University Press. ISBN 0521424984.
External links
- An Introduction to Surface Chemistry. Retrieved October 19, 2008.
- Surface chemistry awarded Nobel. BBC News. Retrieved October 19, 2008.
- Gabor Somorjai, the father of modern surface chemistry. Retrieved October 19, 2008.
- Applied Surface Chemistry. Retrieved October 19, 2008.
Credits
New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:
The history of this article since it was imported to New World Encyclopedia:
Note: Some restrictions may apply to use of individual images which are separately licensed.
