Search Results

You are looking at 1 - 2 of 2 items for

  • Author or Editor: J. Townsend x
  • All content x
Clear All Modify Search

The radioluminescence spectrum of Ge-silica fibres doped with Nd is found to change by the effect of pre-irradiation and thermal annealing. Originally the spectrum consists of a gaussian band centred near 3.1 eV (400 nm). Following the irradiation and heating an additional asymmetric band appears near 2.4 eV (520 nm). On top of this band there is a line spectrum, which can be ascribed to internal transitions of the Nd3+. On the basis of the spectroscopic data and previous results of thermoluminescence measurements, a model is suggested for the luminescence and the effect of the thermal annealing. The blue and green bands are ascribed to an O2 molecular ion and a hole centre near the Nd3+ ion, respectively.

Restricted access

Abstract  

The use of non-aqueous deacidification procedures as a preventive conservation measure to assist in retarding the deterioration of painting canvases has been suggested by the Conservation Department of the Tate Gallery [1]. The reverse sides of paintings are treated with commercially available MMC solution (methoxy magnesium methyl carbonate). The aim of this paper is to describe how dynamic mechanical thermal analysis can be used to evaluate the effects of this treatment. Measurements are described on modern commercially primed canvas samples [2] which show that the MMC treatment does cause an increase in the modulus or stiffness of the primed canvas materials but that the effect on theT g is minimal. The response of the treated materials to variations in relative humidity has also been studied and indications are that the response of treated canvases to variations in relative humidity differs from those of the untreated canvases.

Restricted access