Knowledge Dissemination Series

Brief resume of Prof. T.R. Ramachandran

Dr. T.R. Ramachandran received his B.E. degree in Metallurgy from the Indian Institute of Science Bangalore in 1960, his M.Sc. from the McMaster University Canada in 1965 and Ph.D. from the University of Wales UK in 1969. He had been on the Faculty of the Indian Institute of Technology Kanpur for two decades, 1969-89. He was the Head of the Department of Metallurgical Engineering at lIT Kanpur during 1986-88 and the Head of the Materials Science Programme in 1987-89. Almost all the research projects that he had supervised during his stint at lIT Kanpur were related to structure-property relationship in aluminium alloys.

He was the Founder - Director of the Jawaharlal Nehru Aluminium Research Development and Design Centre (JNARDDC) Nagpur during the period 1989-99. He was also the National Project Director of the UNDP project on the establishment of the Jawaharlal Nehru Aluminium Research Development and Design Centre (1989-96). He was an Emeritus Scientist at the Nonferrous Materials Technology Development Centre Hyderabad from 1999 where his main interests were in the development of grain refiners and specialized master alloys for the aluminium industry.

He has been closely associated with the Indian aluminium industry, serving as part-time Director of the National Aluminium Company (1991-93), the Bharat Aluminium Company (1994-97), Paradeep Carbons (2002-2006) and presently Alufluoride. He has served on several committees set up by the Government assessing the performance of some major aluminium producers in the country. As the Founder-Director of JNARDDC he was involved in organizing a number of research projects and workshops on topics covering bauxite, alumina and aluminium production, molten metal processing and downstream activities. He has lectured extensively in these areas both in India and abroad. He has been a Consultant to several industries in the areas of molten metal processing and alloy development. He has organized a number of courses on electron microscopy in JIT Kanpur; in the last year and a half, he has conducted electron microscopy courses in NML Jamshedpur, NIFFT Ranchi, IGCAR Kalpakkam, lIT Roorkee, lIT Kharagpur, NIT Surathkal, NIT Trichy and lIT Bombay ..

For his outstanding contributions in the field of nonferrous metals, he has been awarded the Hindustan Zinc Gold Medal (in 1994) and the NALCO Gold medal (in 2006, the first year of its inception) by the Indian Institute of Metals.

His research interests are in the areas of energy conservation and environmental control in aluminium industry, physical metallurgy of aluminium alloys and applications of electron optical techniques to metallic materials.

Chief Editor's special note :

The inner urge of Prof. TRR, as he is fondly known in scientific community, for knowledge dissemination is something superb and remarkable. There is no age boundary for him, neither the distance for knowledge dissemination. His rich experience in Characterization Techniques backed up by sound knowldge in Physical Metallurgy are twin advantages for the users who have become beneficiaries of his expertise.

Now we look forward to his technical article.

Characterization Techniques in Corrosion and Surface Engineering

T.R. Ramachandran

Nonferrous Materials Technology Development Centre

Kanchanbagh   Hyderabad 500 058

Abstract

Characterization techniques used in the study of corrosion and surface engineering are dealt with in detail in a series of presentations in this Newsletter, with emphasis on optical and electron optical techniques. The topics covered range from chronological developments in the field, principles of the techniques, instrumental details, optimum conditions for obtaining the desired information, theoretical background for analysis and applications. The present article is concerned with developments in the field of microscopy over the last six centuries which have contributed to commendable progress in the field.  

Introduction

A variety of techniques can be used for the study of surfaces and subsurfaces in materials for obtaining information on microstructure, crystallography and chemical composition. Measurement of thickness of coatings forms an essential aspect of surface engineering. Important methods for analysis of materials can broadly be divided into the following categories:

Image analysis: Optical microscopy, Confocal microscopy, Scanning electron microscopy (SEM), Scanning probe microscopy (SPM), Atomic force microscopy (AFM) and Transmission electron microscopy (TEM).

Surface analysis: Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS),  Time of flight static secondary ion mass spectroscopy (TOF-SSIMS) and Low energy electron diffraction (LEED)

Structural analysis: XRD – X-Ray diffraction, XAX/EXAFS - X-ray absorption spectroscopy  and Extended X-Ray absorption fine structure, Raman spectroscopy, TEM – Transmission electron microscopy, EELS – Electron energy loss spectroscopy (typically combined with TEM)

Organic analysis: Fourier transform infrared spectroscopy (FTIR), Gas chromatography with mass spectroscopy (GC/MS), High performance liquid chromatography (HPLC) and Raman spectroscopy (structural organic)

Elemental analysis: Inductively coupled plasma (ICP), X-Ray fluorescence (XRF), Particle-induced X-ray emission (PIXE), detection of gases such as carbon, hydrogen or nitrogen

Structural information can be based on macroscopic, microscopic and or nanolevel examination, using magnifying glass (or a stereo microscope with typical magnification of 10X) optical or electron microscopes. While optical microscopes provide information mainly on the microstructure, the electron optical instruments provide information on microstructure, chemical composition, and crystallographic features and under special conditions on type of bonding. The developments in the last century have resulted in the availability of sophisticated equipment, facilitated reproducible specimen preparation methods, examination of the samples under well defined conditions, quantitative characterization of the features and storage of digital images which can be easily retrieved and processed. On the flip side “key board” operation of many of the equipments has the disadvantage of an operator not understanding what is happening when a particular key is actuated. The objective of this series of articles is to bring to the attention of the reader how the techniques have evolved over the last few centuries, the basic features of the equipments, operational details, methods of analysis of measured parameters and applications. The present write-up will concentrate on historical developments, the pioneering work of several scientists (or even laymen) and how theoretical postulates have been turned into operating realities. Optical and electron-optical techniques will be dealt with in the first few articles, followed by electron diffraction, X-ray microanalysis and energy loss spectroscopy. Subsequent topics will be devoted to Auger and photo electron spectroscopy and thickness measuremnts.

Milestones

Microscopic techniques have evolved over the last several centuries; some important land marks are summarized in Table I. 

Table I: Chronological Developments in the Field of Microscopy

Period	Developments
Circa 1000AD	Invention of reading stone –  a glass sphere that magnified when laid on top of reading materials.
Circa 1284	Salvino D'Armate invented the first wearable  eye glasses
1590	The Dutch father and son combination, Zaccharias and Hans Janssen used several lenses placed in a tube for obtaining magnified images of objects – forerunner of compound microscope and telescope
1665	English physicist, Robert Hooke looked at a sliver of cork through a microscope lens and noticed some "pores" or "cells" in it.
1674	Anton van Leeuwenhoek built a simple microscope with only one lens to examine blood, yeast, insects and many other tiny objects – father of microbiology; he invented new methods for grinding and polishing microscope lenses that provided magnifications of up to 270 X.
18th century	Technical innovations for improved microscopes, combination of lenses to reduce lens aberrations “chromatic effect”, that lead to disturbing halos in the image.
1830	Reduction of chromatic effect by using several weak lenses at certain distance by Joseph Jackson Lister to obtain good magnification without blurring the image – the forerunner for the compound microscope
1872-73	Hermann von Helmholtz and Ernst Abbe demonstrated that optical resolution depends on the wavelength of the illumination source - possibilities of using UV light and electrons for obtaining better resolution.
1896	Existence of electrons demonstrated in  experiments of J.J. Thomson and colleagues
1903	Development of ultramicroscope by Richard Zsigmondy for studying objects below the wavelength of light; Nobel Prize winner in Chemistry in 1925.
1924	de Broglie’s doctoral thesis, introducing his theory of electron waves; any moving particle or object has an associated wave, with wavelength given by λ = h / mv where λ is the wavelength, h is  Planck's constant,  m is  mass and v is velocity (for an electron at 100kV, λ is ~ 0.004 nm).
1926	H. Busch - magnetic or electric fields act as lenses for electrons
(contd.)
Table I (contd.)
Period	Developments
1929	E. Ruska - Ph.D thesis on magnetic lenses
1931	Davisson and Calbrick - Properties of electrostatic lenses
1931	Invention of electron microscope by Ernst Ruska and Max Knoll; Ruska won the Nobel Prize in Physics in 1986.
1932	Invention of phase-contrast microscope by Frits Zernike; this allowed the study of colorless and transparent biological materials; Nobel Prize winner in Physics in 1953.
1938	Development of scanning electron microscope (SEM) by Von Ardenne; von Borries and Ruska built the first practical electron microscope (Siemens) with 10 nm resolution
1940	RCA - Commercial EM with 2.4 nm resolution
1981	Gerd Binnig and Heinrich Rohrer invented the scanning tunneling microscope that gives three-dimensional images of objects down to the atomic level. Binnig and Rohrer won the Nobel Prize in Physics in 1986.
1986	Invention of atomic force microscope by Binnig, Quate and Gerber; excellent tool for imaging, measuring and manipulating matter at nanoscale.

Some interesting points presented in the Table are worth elaboration. Antony van Leeuwenhoek (1632-1723) came from a family of tradesmen and had no formal higher education or training. With excellent skill, perseverance, endless curiosity, and an open mind (free of the scientific dogma of his day), he succeeded in making some of the most important discoveries in the history of biology.  He is well known for his work on the improvement of the microscope and for his contributions towards the establishment of microbiology. He is the first to observe and describe single-celled organisms, which he termed as “animalcules”, and now referred to as microorganisms. He made more than 500 optical lenses and at least 25 microscopes, of differing types. On September 17, 1683, Leeuwenhoek wrote to the Royal Society about his observations on the plaque between his own teeth, "a little white matter, which is as thick as if 'twere batter." – in this regard he is the first person to examine surface films. The lack of suitable imaging facilities in his days is amply reflected in his letter to the Royal Society in 1674 in which he described Euglenaveridis, the “animalcules” found in a lake water sample "green in the middle, and before and behind white”.

Louis de Broglie’s 1924 Recherches sur la théorie des quanta (Research on the Theory of the Quanta), introduced his theory of electron waves – the duality of wave-particle nature of matter. His thesis examiners were unsure of the material presented and passed on the thesis to Einstein for evaluation who endorsed his wave–particle duality proposal wholeheartedly. He created a new field in physics, the mécanique ondulatoire, or wave mechanics, uniting the physics of energy (wave) and matter (particle). For this he won the Nobel prize in Physics in 1929. Ernst Ruska’s Ph.D. thesis was related to magnetic lenses which form an essential component of the electron microscopes. He won the Nobel prize in 1986 (55 years after the development of the electron microscope), sharing it with Binnig and  Rohrer who invented the Scanning tunneling microscope.

We are all used to seeing/operating some of the most sophisticated microscopes but it may be a sobering experience to be exposed to the earliest models – photographs of Robert Hooke’s (1665) optical microscope and the 1930 transmission electron microscope are shown in Fig. 1.


 
 

Fig. 1a): Robert Hooke’s microscope (1665) with parts made of wood and brass and with tubes of leather covered pasteboard.

Fig. 1(b): 1930 Vintage transmission electron microscope

Abbe’s theory (which will be covered in detail in the next issue) indicates that the resolution of the microscope depends on wavelength of light used and refractive index. The use of ultraviolet light or electrons energized by high potential reduces wavelength. Refractive index in the case of the optical microscope can be increased by using oil-immersion objective. Both these factors contribute to improved resolution. Several modes of operation of the optical microscope - reflected and transmitted light, phase contrast, interference, and polarized light- enable us to collect detailed information about the sample. Sustained efforts have been made to improve the resolution of the electron microscope, from the 1 nm level in the 1950s to 0.05 nm in the recently developed aberration corrected electron microscopes. In this regard it is worth recalling the words of Richard Feymann; in his lecture on “There's Plenty of Room at the Bottom” at an American Physical Society meeting on December 29, 1959 he pointed out "The electron microscope is not quite good enough, with the greatest care and effort, it can only resolve about 10 angstroms ... Is there no way to make the electron microscope more powerful?"  

We end this write-up by including a few quotations on microscopy.

“As long as there is a hunger for knowledge and a deep desire to uncover the truth, microscopy will continue to unveil Mother Nature’s deepest and most beautiful secrets”. Lelio Orci and Michael Pepper

“A weak mind is like a microscope, which magnifies trifling things, but cannot receive great ones” – Lord Chesterfield.

“When you employ the microscope, shake off all prejudice, nor harbor any favorite opinions; for, if you do, ‘tis not unlikely fancy will betray you into error, and make you see what you wish to see”. -  Henry Baker

(to be continued... )