LABORATORY OF THE MONTH
Glass and m a n y other inorganic and composite materials challenge the ingenuity of the technical staff in instrumental analyses, chemical analyses, and physical measurements in this materialsand process-oriented company
T the HE
TECHNICAL
STAFFS DIVISION o f
Corning Glass Works, located a t Sullivan Park, near Corning, Ν . Υ., is unique in t h a t t h e Division encom passes not only Research and Develop ment but also Engineering and Process Research. T h e broad scope a n d r e sponsibilities of t h e Division a r e d e signed for smooth and rapid channeling of research findings through develop ment, engineering, and process or pilot plant operation, into final production. M a n y of Technical Staffs analytical, physical measurement, a n d other m a terial characterization requirements are handled b y three separate, though coordinated, departments : Chemical Analysis Research, Instrumental Analy sis Research, a n d Physical Properties Research. These three departments provide both service a n d research in method development, and they function under the Director of Technical Staffs Services. Since Corning is a materialsand process-oriented company, analyt ical requirements of t h e three depart ments are concerned not only with com position, structural, and physical p r o p erties of glass b u t also with many other inorganic and composite materi als as well. T h e Instrumental Analysis Research D e p a r t m e n t employs m a n y physical techniques to assist in the characteriza tion of materials and processes. X - r a y diffraction and electron and optical mi croscopy a r e extensively employed t o study the relationships between struc ture a n d properties of polycrystalline
Wet chemistry, combining the best of classical and new separation and determi nation techniques, continues to be a mainstay in meeting the diverse analytical problems associated with Coming's broad materials research program. Laid out in a configuration designed to promote greater efficiency, the laboratory arrange ment provides for maximal freedom of movement and accessibility to central facilities such as balances, chemicals, muffle furnaces, and instrumentation
Sullivan Park, new Corning Glass Works research complex, lies in a sylvan setting about five miles from downtown Corning, Ν. Υ. At center is the fundamental research building, with twin six-story towers and 147,300 square feet. At left is the 144 χ 792-foot development building, soon to be expanded. At right is the process research center, with its distinctive claw-like ventilator indicating glass-melting operations underneath. Complex also includes a cafeteria—libraryauditorium building. Sullivan Park is dedicated to the memory of the late Dr. Eugene C. Sullivan, the company's first scientist VOL. 39, NO. 12 OCTOBER 1967 · 1 0 9
Technician is shown operating the highly adaptable Jarrell Ash 3.4 meter spectrograph-spectrometer. An indispensable and highly versatile analytical tool, this spectrometer can function either as a multichannel direct reader, a single-fixedslit scanning spectrometer, or as a spectrograph
Pertinent optical characteristics of experimental photochromic glasses are evaluated in the optical properties area. One of the several spectrophotometers employed for this work is shown behind the physicist in the picture
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ANALYTICAL CHEMISTRY
glass-ceramics, fused-cast and bonded refractories, single crystals, a n d thin metal or oxide films. Replica and direct transmission electron microscopy techniques have given insight into the nature, size, and shape of photoactive crystallites responsible for photosensitive and photochromic properties of glasses. These techniques have also furnished information concerning the early phase separation a n d crystal nucleation stages in glass-ceramics where the microseparation size ranges down to about 60 A. While microstructural changes in polycrystalline glass-ceramics are observed by replica electron microscopy, the accompanying crystal growth and crystal transformations which occur on heat t r e a t m e n t are identified b y x-ray diffraction techniques. Often the crystal phases encountered are not found in nature, and extensive solid-solution series are evident in certain silicate systems. Crystal orientation in polycrystalline materials and thin films, as well as crystal size and stress, are also studied by x-ray diffraction. Trace impurity analyses of crystals and films produced in the search for materials with unique electronic a n d semiconductor properties are carried out by spark source mass spectrometry. Analytical mass spectrometers are utilized for gas analysis a n d for studies of outgassing produced b y heat, electron bombardment, and neutron or ultraviolet irradiation. Elemental analysis of microvolumes with the electron microprobe is used to provide information concerning glass inhomogeneities, semiconductor and microcircuit devices, glass-to-metal interfaces, segregation in alloys and refractories, and ion exchange and diffusion processes. A typical application of the electron microprobe is the study of diffusion of certain glass constituents into specific phases of refractories to help elucidate glass-refractory contact p r o b lems. T h e application of x-ray emission for the determination of low atomic n u m b e r elements, such as sodium, magnesium, aluminum, and silicon in glass and refractory materials, and for the determination of thickness and element ratios in thin films, is a continuing program. M a n y compositional problems arising in the course of research and developmental studies of new materials and processes are not directly solvable by the aforementioned instrumental methods. T h e Chemical Analysis R e search Department, through utilization of m o d e m wet chemistry, provides compositional information, often of an u n usu'al nature, in support of m a n y phys-
LABORATORY
Use of a cryosorption pump in the source region of the spark source mass trometer (shown here outside the source) can establish a vacuum of / "" torr in one hour. A computer program has been developed to eliminate consuming calculations and provide flexibility of analysis interpretation. conducting and nonconducting inorganic materials are analyzed for impurities
ical and chemical investigations of ma terials, processes, and products. T o handle adequately current problems as well as to develop future capabilities, about one third of the staff's time is committed to development and explo ration of new techniques. Not infre quently, "customer" requests become extended applied research projects. Problems of trace analysis, micro sampling, analysis of thin films, crystallinity determination of the constitu ent phases of glass-ceramics, unusual elemental separations, and redox states of certain elements in different glass and ceramic materials have been sucessfully solved. The determination of re dox couple equilibria in glasses and ceramics is a particularly noteworthy example of a n analysis which so far has been accomplished successfully only b y chemical means. Such redox informa tion is critical to photosensitive and photochromic glasses, neodymium glass laser pumping efficiency, the optical transmission of many glasses, "fining" of glasses, and the stability of certain refractory systems. Through the stim ulus of such problems, complexometry,
spec 10~ 9 timeBoth trace
ion-exchange separations, pyrohydrolysis, combustion, inert gas fusion, gas chromatography, coulometry, and spec trochemistry have been explored and utilized. Investigation of m a n y of these techniques continues, particularly in elemental separations and titrimetry, and in spectrochemical and electroanalytical methods. T h e solution proce dures which have proved so highly suc cessful in the determination of a wide variety of elements b y emission and atomic absorption spectroscopy are currently being adapted to a n optical emission spectrograph-spectrometer. Potentiostatic coulometry and other voltammetric techniques are employed for assay as well as trace level analyses. Studies of chemical durability and weathering are also a responsibility of the Chemical Analysis Research D e p a r t m e n t . This work involves a com prehensive program of research and testing aimed at evaluating and p r e dicting the chemical properties of glass, of glass-ceramics, and of ceramic sur faces when placed in contact with v a r i ous chemical environments. Much of the work to date has been related to
OF THE
MONTH
effects of atmospheric weathering (in cluding industrial atmospheres) and of solutions—e.g., water, acids, and bases—on glass surfaces. Aiding in these studies is a B E T surface areapore volume analyzer which permits accurate determination of low (less than 0.1 m 2 / g ) specific areas with krypton. The Physical Properties Research D e p a r t m e n t provides a wide range of facilities for the measurement of me chanical, thermal, Theological, optical, and electrical properties. In the area of mechanical properties, routine and nonroutine strength measurements are carried out, stress-strain relationships are investigated, elastic moduli are de termined over a wide temperature range, and fatigue effects in glass and glass-ceramics are studied. Measurements of optical properties include absorption and reflectance spectrophotometry from 0.165 to 35 microns, and spectroradiometry of light and heat sources. Programs are in progress for the determination of spec tral transmittance, reflectance and emittance a t high temperatures, of the change of refractive index of glass with temperature, and of absorption coeffi cient and refractive index of films. I n strumentation includes spectrophotom eters and accessories, N B S calibrated lamps, calibrated radiometer, and pre cision refractometers. High-temperature rheological proper ties are determined by two methods: For viscosities from one-half to 10 7 poises, the rotating cylinder technique is employed; from 10 8 to 10 15 poises a bending-beam technique is used. T h e thermal expansion of glasses, ceramics, and metals is determined by laser ihterferometry with a sensitivity of 10~7 c m / c m , and b y dilatometers which are accurate from 10~5 to 10~e c m / c m . Dilatometer information can be ob tained from —200° to 1500°C. M u c h of the rheological and expansion equip ment has been designed and built b y department personnel. Other thermal property measurements carried out in clude differential thermal analysis, thermal gravimetric analysis, thermal conductivity, thermal diffusivity, and specific heat. Facilities to provide electrical p r o p erty measurements include equipment for determining dielectric constant and loss tangent from room temperature to 700°C a t frequencies, from ΙΟ" 2 to 8.6 Χ 10~9 cycle per second, direct current resistivity from room temperature to 1000°'C, and direct current and 60 cy cle per second dielectric strength from room temperature to 700°C.
α VOL 39, NO. 12 OCTOBER 1967 ·
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