Dilatometers

In the Audibert-Amu dilatometer test (91), a thin cylinder of compressed powdered coal contacting a steel piston is heated at a rate not over 5°C/min. The piston movement is used to calculate the percent dilation. 

Ausdehnungs-arbeit,/. work done in expanding, -koeflizient, m. expansion coefficient, -messer, m. dilatometer extensometer. -vermOgen, n. expansibility extensibility dilatability. -zahl, /. expansion coefficient, ausdenken, v.t. think out. devise, conceive, ausdeuten, v.t. interpret, explain, ausdorren, v.t. dry up, desiccate season (timber). 

Delmung, /, extension stretching elongation tension expansion dilation, delmungsfahig, a. extensible expansible, DelmungS kraft, /. = Dehnkraft. messer, m. extensometer dilatometer. -warme,/. heat of extension. zahl, /. coefficient of extension or expansion. 

I = complex impedance, B = conductivity bridge, C = capillary viscometer, P = pycnometer or dilatometer, V = volumetric glassware, I = instrument, U = method unknown... 

Figure 4. Thennal strain for a single-crystal Nio625Alo 3 5 alloy measured on cooling along three (lOO directions in a capacitance dilatometer. The inset shows in detail the data in the temperature range 100-250K (From reference 6)...

The specimen can be square or round to fit a dilatometer test tube in a free sliding manner. The length is governed by the sensitivity of dial gauge, the expected expansion, and the... 

Dilatometer Basically it is a pyrometer equipped with instruments to study density as a function of temperature and/or time. It can measure the thermal expansion or contraction of solids or liquids. They also study polymerization reactions it can measure the contraction in volume of unsaturated compounds. It basically is a technique in which a dimension of a material under negligible load is measured as a function of temperature while it is subjected to a controlled temperature program. 

Sample dilatometric data are given in Table 2-3. Figure 2-4 shows the variation of V, the dilatometer reading, with time, and the line represents the least-squares fit to Eq. f2-30). 

The only one that is not readily accessible by DTA is the expansion coefficient. It is determined by use of a thermal expansion apparatus, i.e.- a dilatometer. Methods and uses of thermal expansion will be described in a succeeding section. 

How does a dilatometer work to provide a means of measuring the rate of chain growth reactions From a practical perspective, what issues are likely to arise during this method of measurement ... 

The dilatometer readings (h) listed below are given in arbitrary units and are arranged in pairs taken at a fixed interval of 2 hr. They are related to the extent of reaction by h - h0... 

Time, t (min) Dilatometer reading at time t Dilatometer reading at time t + 2 hr... 

Note that k can be determined from the slope of a plot of the left side of equation B versus time and that this plot can be prepared without a knowledge of the dilatometer readings at times zero and infinity. The data are worked up below and plotted in Figure 3.8. 

Using the dilatometer technique, a small sample of powder (about 1 -2 grams) is heated at constant rate in the apparatus depicted schematically in Fig. 43. Dilatation of the sample is measured by a linear voltage transducer (LVDT) contraction of the sample indicates particle-particle surface flattening and defines the minimum softening point ox sintering temperature, Ts. In... 

Figure 43. Schematic diagram of a dilatometer. (From Tardos and Pfeffer, Powder Technology, 85 29-35, 1995, with kind permission from Elsevier Science S.A., P.O. Box 564, 1001 Lausanne, Switzerland.)...

The measurement of the linear expansion coefficient can be carried out by several methods (see Chapter 13), for example, by means of an interferometric dilatometer [77], a capacitance dilatometer [78] or a SQUID dilatometer [74]. The latter can achieve resolutions as small as 2 x l(T14m. 

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