Thermal dilatometry analysis

This phase transformation is accompanied by a bone expansion, as indicated by the dilatometry analysis presented in Figure 16.2 (1260-1360 °C range) [28]. Traces of calcium oxide and magnesium oxide have been identified [11] in bone specimens (originating to different species) thermally treated at 1400 °C. They were not considered as products of hydroxyapatite decomposition, but reported as mineral phases. 

The procedures of measuring changes in some physical or mechanical property as a sample is heated, or alternatively as it is held at constant temperature, constitute the family of thermoanalytical methods of characterisation. A partial list of these procedures is differential thermal analysis, differential scanning calorimetry, dilatometry, thermogravimetry. A detailed overview of these and several related techniques is by Gallagher (1992). 

Shrinkage during sintering at high T can be determined experimentally by dilatometry, electrical conductivity, acoustic waves or thermal analysis . 

MSssbauer spectroscopy Electron spin resonance spectroscopy Colorimetry Thermoluminescence Thermal analysis differential thermal analysis, dilatometry... 

For materials generally, change in expansion (or density) by dilatometry was traditionally the most often used method for measuring Tg. Thermal properties, for example specific heat, are also widely used, particularly the methods of differential thermal analysis". A method for rubbers using DSC is being developed in ISO TC 45 as ISO 22768, but is not yet published. The inflection point on the heat input - temperature curve is usually obtained automatically by the analyser s software but, if obtained manually, is best found from the derivative of the curve. 

This monograph provides an introduction to scanning ther-moanalytical techniques such as differential thermal analysis (DTA), differential scanning calorimetry (DSC), dilatometry, and thermogravimetric analysis (TG). Elevated temperature pyrometry, as well as thermal conductivity/diffusivity and glass viscosity measurement techniques, described in later chapters, round out the topics related to thermal analysis. Ceramic materials are used predominantly as examples, yet the principles developed should be general to all materials. 

Changes in physical state may be observed from changes in thermodynamic quantities, which can be measured by calorimetric techniques, dilatometry, and thermal analysis. Spectroscopic methods are also available for the determination of changes in molecular mobility around transition temperatures. In addition to the changes in thermodynamic quantities and molecular mobility, a glass transition has significant effects on mechanical and dielectric properties. 

Another approach to anisotropic materials is to measure the bulk expansion of material using dilatometry (Fig. 6). The technique was used extensively to study initial rates of reaction for bulk styrene polymerization in the 1940s, an experiment which the author has used in his thermal analysis class on TMA. By immersing the sample in a fluid (normally silicon oil) or... 

While TMA is one of the older and simpler forms of thermal analysis, its importance is in no way diminished by its age. Advances in DSC technology and the appearance of dynamic mechanical analysis (DMA) as a common analytical tool have decreased the use of it for measuring glass transitions, but nothing else allows the measurement of CTE as readily as TMA. In addition, the ability to run standardized material test methods at elevated temperatures easily makes TMA a reasonable alternative to larger mechanical testers. As the electronic, biomedical, and aerospace industries continue to push the operating limits of polymers and their composites, this information will become even more important. During the last 5 years a major renewed interest in dilatometry and volumetric expansion has been seen. Other thermomechanical techniques will also likely be developed or modernized as new problems arise. 

Various techniques are available for the investigation of the solid state. These include microscopy (including hot-stage microscopy, HSM), infrared spectrophotometry (IRS), single-crystal X-ray and X-ray powder diffraction (XRPD), thermal analysis, and dilatometry. 

These methods are dilatometry [14], infrared spectroscopy [15], viscoelastic measurements [16-20], thermal analysis [17,21-34], nuclear magnetic relaxation in both broad-line NMR and pulsed NMR [17,35], and dielectric [36], piezoelectric [37], and acoustic [38] measurements. 

Recent work (7) has confirmed a previous observation of a fee phase (13) as the high temperature form of Pa the bcc form predicted (14) by extrapolating the variation of the expansion coefficients in the different lattice directions was never detected. Dilatometry and differential thermal analysis were used in an attempt to clear up controversy in the literature on the polymorphism of Am (15). There seem to be at least 3 different phases, the dhcp (" ot" ) phase stable up to about 650°C, a " 3 -phase" existing until 1050°C, followed by the high temperature form between 1050°C and the melting point. It is unknown which of the latter phases corresponds to the fee form observed. At variance with previous work, but according to recent results (16), the room temperature form of Cf is dhcp (not hep), and there are two different fee forms above 600 and 725°C, respectively, with different lattice parameters. 

Sample products measured directly or indirectly on 1R Smoke evolution measured with phoiodetecior Dilatometry not always employed. ETA-DTA is generally called emanation thermal analysis... 

Semi-empirical rules, which correlate the static glass transition temperature Ty from differential thermal analysis or dilatometry with the dynamic T(J taken from the tan 8 or E" peak, may be used with caution in analyzing two-phase systems with a dispersed rubbery phase. The dynamic Tg depends on the rubber phase volume, and it may be shifted further toward lower temperature for effectively crosslinked and grafted rubber particles because of dilatation. 

The crystal phases in the glass-ceramics were determined by XRD analysis. All instruments were precisely and identically set to ensure a high precision to obtain the integral peak area. The microstructure of the fresh fractured cross section of the glass-ceramics was observed by SEM. The thermal expansion coefficient (TEC) was calculated from room temperature to 500 °C at a heating rate of 5°C/min in the dilatometry analyser (NETZSCH, DIL402PC). The flexural strength was determined in a 3-point bend test at a constant strain ratio of 0.5mm/min. 

The kinetics of copolymerization or curing of epoxy resins with cyclic anhydrides initiated by tertiary amines was investigated by chemical analysis 52,65,73,74,90) differential scanning calorimetry isothermal methods electric methods , dynamic differential thermal analysis , IR spectroscopy dilatometry or viscometry Results of kinetic measurements and their interpretation differ most authors agree, however, that the copolymerization is of first order with respect to the tertiary amine. 

Figure 17. Processing of SiAlON ceramics by nitridation of PAIC precursors differential thermal analysis (DTA) and dilatometry of a monolithic amorphous sample obtained after pyrolysis in ammonia at 1000°C.

The dilatometric methods for detecting phase changes utilize volume changes in the same way as the calorimetric methods utilize thermal effects. Dilatometry is widely used in the analysis of melts and particularly of fats and waxes (Bailey, 1950 Swern, 1979). The techniques and equipment are usually quite simple. 

Koe, 1955Koel, 1955Koe2] Thermal analysis, dilatometry, magnetie property, microscopy and XRD Temperatures up to 1600°C, V contents < 60 mass%. 

Koel] Metallography, XRD, thermal analysis, dilatometry. Up to melting points, entire system ... 

Wev] Thermal analysis, optical microscopy. X-ray diffraction, dilatometry Fe-Ni-Cr2Ni-CrFe-Fe... 

Studying other systems, Noland et al (1971) presented data based on differential thermal analysis (DTA), thermomechanical analysis, and dilatometry to show that mechanical blends of poly(methyl methacrylate) and poly(ethyl acrylate) are compatible with poly(vinylidene fluoride)... 

To ensure optimum conditions for a direct comparison of DSA data with results obtained by other methods, devices were constructed to provide simultaneous measurement of additional parameters [11]. The equipment for simultaneous measurements by DSA, differential thermal analysis (DTA), thermogravimetry/differential thermogravimetry (TG/DTG) or dilatometry, available from Netzsch Ltd, Germany, ensures the optimal conditions for direct comparison of the results [12]. 

In contrast to DTA and thermogravimetry, diffusion structural analysis makes it possible to investigate processes that are not accompanied by thermal effects or mass changes. DSA permits, to examine consolidation, annealing of defects and sintering of powdered or geleous samples, which would be difficult to examine by means of dilatometry. 

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