Optical properties colour

Each of these properties may be beneficial or unwanted. The large size of aggregates, when compared to the primary particles, improves powder handling, but may deteriorate the optical properties (colour/opacity) of the final product or may require intensive dispersion when, e.g., used in polishing slurries. Sometimes just the presence or absence of aggregates is of interest, e.g., when evaluating the stability of colloidal suspensions. 

Optical properties Colour, clarity, refractive index The appearance of the object can be improved by educated choice of conservation material Epoxy adhesives can be chosen to have a matching refractive index to the substrate... 

We begin our discussion of nanocrystals in diis chapter widi die most challenging problem faced in die field die preparation and characterization of nanocrystals. These systems present challenging problems for inorganic and analytical chemists alike, and die success of any nanocrystal syndiesis plays a major role in die furdier quantitative study of nanocrystal properties. Next, we will address die unique size-dependent optical properties of bodi metal and semiconductor nanocrystals. Indeed, it is die striking size-dependent colours of nanocrystals diat first attracted... 

The striking size-dependent colours of many nanocrystal samples are one of tlieir most compelling features detailed studies of tlieir optical properties have been among tire most active research areas in nanocrystal science. Evidently, tire optical properties of bulk materials are substantially different from Arose of isolated atoms of tire... 

By the use of microstructured mixers, pigment and other particulate syntheses can be improved. In this way, finer particles with more uniform size distribution were yielded for the commercial azo pigment Yellow 12 (see Fig. 2) [11]. The particles formed in the microstructured mixer have better optical properties such as the glossiness or transparency at similar tinctorial power. Since the micro-mixer made pigments have more intense colour, lower contents of the costly raw material in the commercial dye products can now be employed which increases the profitability of the pigment manufacture. 

For certain AB cements, used in dentistry, optical properties are important for their overall acceptability as materials. The two particular properties of interest have been colour and translucency, both of which need to match natural tooth material as closely as possible if good aesthetics are to be developed (Wilson McLean, 1988). Of the AB cements currently used in dentistry, the glass-ionomer cement has the best aesthetics, since it has a... 

Evaluation of these optical properties may be done by simple observation this approach is useful clinically (Knibbs, Plant Pearson, 1986), since acceptability of the colour match to the surrounding tooth material can be readily seen without the need for instrumental measurement. On the other hand, for quantitative evaluation of optical properties, some kind of instrumental measurement is necessary, and the property usually evaluated is opacity. 

The first synthetic polymers to be used as paint varnishes were acrylic and vinylic resins. Poly(vinyl acetate) (PVAc), commercialized under the name Mowilith by Hoechst and Vinylite by Union Carbide, has been used in conservation as an adhesive since 1932 and in 1937 it was proposed as a picture varnish by Stout and Cross [63]. PVAc was soon rejected as a varnish because, despite its light stability and good solubility in organic solvents, it demonstrated poor optical properties in terms of colour saturation and the tendency to pick up dirt due to its low glass transition temperature. 

R. J. D. Tilley, Colour and the Optical Properties of Materials, Wiley, Chichester, 2000. 

In the case of paints and printing inks, the initial preparations will be in the semi-solid state because solvents are needed both in the process of dispersing the pigment in the paint or ink medium and for application purposes. These solvents dry out after the paint or ink is applied. When making coloured plastic articles, both heating and solvents may be used to aid dispersion in the plastic medium as part of the moulding process. However, from the viewpoint of the optical properties in all of these pigment uses, what is most important is that each of these media has a refractive index close to 1.5. 

BS 2782 Method 520A, Methods of testing plastics. Optical and colour properties, weathering. Determination of specular gloss, 1992. 

It is insoluble in water, microcrystallinc, and lilac in colour.1 Many of these derivatives of platinum containing organic bases have been obtained in optically active forms. Those containing 1-propylene-diamine will serve as examples. These are easily prepared, and as they are remarkably stable are easily examined for optical properties. The compounds are prepared by the interaction of cis-dichloro-l-propylenc-diamino-platinum, [Pt pnCl2], with the calculated quantity of the corresponding base, 1-propylcnediamine, ammonia, ethylenediamine, or trimethylenediamine. The liquid obtained is evaporated on a water-bath and precipitated with alcohol. The di-derivative of 1-propylene-diamine, [Pt pns]Cla, has rotation [a]o+46-37°, [M]r>+192-0°. 

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