Internal friction peaks due to a coating effect

Abstract

It is well known that artefact internal friction peaks appear when the atmosphere surrounding the tested specimen is not perfectly controlled o r i t s surface is not sufficiently cleaned. F o r example, humidity o r residual nitrogen /1, 2/ and also oil coating /3/ could induce such peaks.The purpose of this note is to give other examples of friction peaks due to a coating effect (which are sometimes erroneously attributed in the literature to a bulk effect).The specimen is a high purity, strongly cold worked iron wire. The internal friction of such a specimen is well known /4/ and composed of an cz peak (27 K) and a slowly increasing background from 30 to 300 K. The specimen coated by oil is an equiatomic Copt alloy in ordered state with a very low background of internal friction /5/. The torsion pendulum is an inverted one, oscillating a t 1 Hz and with an axial saturating magnetic field.Coating by oil oil (less than 0.1 ym) an asymmetric peak, with an associated modulus defect appears at a temperature Tm = 210 K (curve a, Fig. 1 ) and anneals out after heating at a temperature Td % 570 K. Tm and Td appear to be the melting temperature and the decomposition temperature, respectively, of the tested oil.Cleaning tests are made: after cleaning at room temperature, benzene, acetone, methanol, CHC13, and Rl3S 25 could not remove the peak. The peak is reduced by (C2H5)20, 20 min a t 300 K and suppressed when treated by ultrasounds. imen a mixture of helium and CH4 (curve a, b, Fig. 2) o r C7H16 (curve c, After covering the sample by a thin layer of vacuum paraffinCoating by solidified gas-The layer is obtained by cooling around the spec-1) ul. Majakowskiego 11/12, 80-952 Gdadsk, Poland.2) 85 X -3804l Grenoble C6dex, France.

Hydrogen in Fe40Ni40P14B6 amorphous alloy studied by magnetic after effect, internal friction, and positron annihilation

“…This peak is removed either by cleaning as mentioned or by heating a t a temperature above the oil deconiposition temperature. These peaks are probably similar t o those reported previously with crystalline specimens [9]. I n the present case, they are bigger because the ratio surface/volunie is larger.…”

Internal Friction Investigations of Electrolytically Deposited Thin Layers

“…These maxima occur in the temperature range 200 -250 K, in which range lies the melting temuerature of the oil. IF peaks were observed in [2] the surface micropores of the molybdenum sample. The IF method was used in [7]to study the electrical resistance of a silver layer deposited on mica by vacuum evaporation, and two peaks were observed at temperatures 373 and 503 K. After heating the sample for two hours at temperature 723 K the maximum at 373 K disappeared.…”