Browsing by Author "S.K. Agrawal"

Now showing 1 - 9 of 9

A simple set-up for in-situ observation of the critical dose of blistering during ion implantation in polymers
(1984) V. Shrinet; U.K. Chaturvedi; S.K. Agrawal; A.K. Nigam
A simple set-up was designed and fabricated for in-situ studies of the critical dose of blistering and changes on the surface morphology of the polymers during ion-implantation. Mylar, a very important polymer, stable at high temperatures, which shows severe blistering at dose level ∼- 7 × 1015, 250 keV H+ ions cm-2, was chosen for study with this set-up. The design of t some initial results are discussed here. Some major limitations are also described. © 1984.
A technique for preparing mechanically strong ohmic contacts on glass slides
(1981) U.K. Chaturvedi; S.K. Agrawal; A.K. Nigam; S.P. Singh
[No abstract available]
A technique using a Wheatstone bridge to study the minute differences in nucleation and growth of two metallic films
(1983) U.K. Chaturvedi; S.K. Agrawal; A.K. Nigam
A technique has been developed to study the differences in the nucleation and growth of metallic films during their vacuum thermal deposition. The “P” and “Q ” resistance arms of a Wheatstone bridge are made equal and arms “R ” and “S” are replaced by two substrates having proper contacts, facing the vapor source in the vacuum chamber. During deposition, if nucleation and growth conditions of the films on these substrates are exactly identical, no voltage difference is developed across the junctions “PQ” and “R S ” of the bridge throughout the growth of the films. If, however, there is even a minute difference in the nucleation and growth sequence of these films, the critical time at which the films become conductive may be different for both the films which ultimately gives a rectangular pulse-type signal which is recorded by the X-Y recorder. As the critical thickness at which the metal film becomes suddenly conductive is dependent on a large number of factors, e.g., flux and species of vapor, structure and temperature of the substrate, residual gas pressure and its nature, fields present on or nearby the substrate etc., this technique has potential applications in metallic thin film technology. © 1983, American Vacuum Society. All rights reserved.
Blistering observed in Mylar due to H+-ion bombardment
(1983) V. Shrinet; U.K. Chaturvedi; S.K. Agrawal; Vakil Singh; A.K. Nigam
So far the blistering phenomenon due to ion implantation has been observed in metals and alloys, but no blistering has been reported in polymers like Mylar etc. A severe blistering in Mylar (polyethylene teraphthalate) has been observed by us, due to 250 keV H+-ion bombardment up to a dose level of 7×1015 ions/cm2, at ambient temperature. In metals and alloys the blistering is due to the pressure built up by the coalescence of the implanted gaseous species. However, in Mylar the cause is entirely different. In fact, it is attributed to the hydrogen gas released on account of the breakage of aliphatic C-H bonds of monomer, due to ion implantation. Very interesting features, like uniform unexfoliated circular blisters, circular rings (Karnavalayas) and black dots of different sizes along with their development sequence, have been observed. The observed features are explained on the basis of the aliphatic CH bond breakage theory due to ion bombardment. © 1983.
EFFECT OF NEUTRON AND PROTON IRRADIATION ON SOME PROPERTIES OF KAPTON.
(Plenum Press, 1984) V. Shrinet; U.K. Chaturvedi; S.K. Agrawal; V.N. Rai; A.K. Nigam
[No abstract available]
Enzymes in the epidermis of a fresh-water teleost Barbus sophor (Cyprinidae, Pisces). pisces). A histochemical investigation
(1979) S.K. Agrawal; T.K. Banerjee; A.K. Mittal
[No abstract available]
Increase of the electrical resistance of thin aluminium film due to 14 MeV neutron irradiation
(1978) S.K. Agrawal; U. Kumar; S.P. Singh
[No abstract available]
Increase of the electrical resistance of thin copper film due to 14 MeV neutron irradiation
(1981) S.K. Agrawal; U. Kumar; S.P. Singh; A.K. Nigam
The variation in the electrical resistance of thin copper film (500 thick), grown on the glass slide has been measured with increasing 14 MeV neutron Irradiation time. The electrical resistance vs irradiation time curveshows an interesting behaviour after an irradiation of 40 minutes. However, there is a net increase in the electrical resistance with increasing neutron dose. The maximum increase in the observed electrical resistance after an irradiation of 115 mins, is 4.45%. The microstructural studies of irradiated film were made using TEM & TED techniques. The TEM patterns upto an irradiation time of 1.00 hr do not show any appreciable change in the microstructure. The TED patterns also do not show any appreciable change in the diffraction pattern upto an irradiation time of 1.0 hr. But after an irradiation time of 1.5 hrs, two extra rings appear in the TED pattern which disappear with increasing neutron irradiation time. Copyright © 1981 by The Institute of Electrical and Electronics Engineers. Inc.
Recovery of the electrical insulation of a van de Graaff accelerator's charging belt by vacuum drying
(1985) V. Shrinet; N.L. Singh; S.K. Agrawal; G.P. Mishra; A.K. Nigam
The insulation of a moisture exposed “leaky” charging belt of AN-400 Van-de-Graaff Accelerator was successfully restored by vacuum drying. Although the drying time is of nearly one week, the technique is comparatively easy, risk free and superior to other alternative techniques and does not require dismantling of the belt. Copyright © 1986 by The Institute of Electrical and Electronics Engineers, Inc.