Thermal expansion behaviour

On top of that, the valve body will be cooled down from outside in. So, the body will see the opposite thermal expansion behaviour than in process conditions where the cold will act inside out. Therefore, the thermal stresses that exist on the valve do not reflect the real conditions. 

V NMR has been used to study a series of solid solutions in the system ZrV2-xPxO some members of which show negative isotropic thermal expansion properties over a broad temperature range up to at least 950°C. This unique thermal expansion behaviour appears to be related to frustration in bending V-O-V (or P-O-P) angles away from 180° in a cooperative manner (Korthuis et al. 1995). 

These two methods of synthesis have led to the discovery that at compositions around x = 2, a monophase, polycrystalline NASION is very difficult to produce, even though it can be sintered to reasonable mass density ( >3.20 g/cm ) at relatively low temperatures (1100-1375°C). Unfortunately these materials contain a ZtOz second phase, possess poor mechanical strength with a low fracture toughness, have an anomalous thermal expansion behaviour, and are subject to chemical and phase instability during densification . 

The uniform anisotropic structure of a nematic LSCE is directly reflected in the thermal expansion behaviour. When heating the LSCE from the nematic state into the isotropic state a strong reduction of the sample length along the optical axis is observed (Eigure 9.8). This process directly indicates... 

Besides the highest thermomechanical stress build up due to the different thermal expansion behaviour, this system requires the largest temperature gradient over the compositional gradient for pressureless densification. 

The thermal expansion behaviour in the magnetically ordered regime is closely connected with the pressure dependence of the Curie temperature. Measurements of Tc as a function of pressure were made on Nd2Fe14B by Fukamichi et al. (1986) and for several other R2Fe14B compounds by Kamarad et al. (1987) and Nagata et al. (1987). These authors showed that the Curie temperature of these compounds decrease strongly with applied pressure. By contrast, Kamarad et al. found that the spin reorientation temperature remains unaffected under pressure. 

Sample sheets of 100 x 50 x 4 millimeter were prepared with the wet deposition technique. Two rectangular TMA samples and one circular TMA sample were machined from these sheets. The rectangular samples, 10 x 7 x 4 mm, were taken in the length (X) direction and in the width (Y) direction of the sample sheet. The circular sample, diameter 5 mm, was used to measure the l.e.c. in the Z direction. The samples, placed in a TMA 7, were measured from -20°C to 120°C with a heating rate of 2°C/minute. Subsequently, the sample was cooled with the same rate and heated again for the real measuring scan. The first heating scan was ment to remove the frozen-in stresses which influence the thermal expansion behaviour (see 3.1.2). 

Figure 1.21 Variation in the cubic lattice parameter of Cd(CN)2 guest) with temperature. The parent phase Cd(CN)2-CCl4 displays positive thermal expansion, whereas the apohost CdfCNji displays the most pronounced isotropic negative thermal expansion behaviour known. Reprinted with permission from A.E. Phillips, A.L. Goodwin, G.J. Haider, P.D. Southon and C.J. Kepert, Angew. Chem. Int. Ed., 47,1396. Copyright (2008) Wiley-VCH Verlag GmbH c Co...

T. Klug, V. Fleischer and R. Bruckner, Thermal Expansion Behaviour of Fibre-Reinforced DURAN Glass, Glastech. Ber. 66, 201-206 (1983). 

The thermal expansion behaviour of the hot gas ducting corresponded with the precalculated behaviour. The horizontal expansions were taken up by the bellows and the sliding supports located inside. Vertical expansions were accomodated by support springs. The welded lip seal flange joints maintained their helium tightness even after multiple pressure and temperature cycling. 

A series of phosphate ceramics of the formula A M2(P04)3 [A=Ca, Sr M = Ti, Zr, Hf and Sn] belonging to the calcium titanium phosphate family have been synthesised and their thermal expansion behaviour investigated. These compounds are candidate matrices for nuclear waste immobilization. The thermal expansivity and expansion anisotropy of the compotmds in the temperature range of 300 - 1273 K have been found to depend on the nature of the metal ions in the interstitial space and structural framework. The observed expansion behaviour has been explained in terms of the crystal chemistry of the compounds. 

The primaiy problem in Joining dissimilar materials is the difference in thermal expansion. When the Joint is used at any temperature other than the cure temperature of the adhesive, the adhesive will be stressed owing to the relative movements of the adherends. These stresses may become high enough to cause the joint to fail without external loads. It is possible to calculate these stresses analytically together with the stresses from the mechanical loading. Procedures for single-lap and double-lap Joints are presented in 5.3.5. When the members to be Joined have dissimilar thermal expansion behaviour, ductile adhesives are preferred. 

Korb G, Korab J, Groboth G, Thermal expansion behaviour of unidirectional carbon-fiber reinforced copper-matrix composites, Composites Part A-Appl Sci Manuf, 29(12), 1563-1567, 1998. 

Taylor MB, Barrera GD, Allan NL, Barron THK (1997) Free-energy derivatives and stracture optinuzation within quasiharmottic lattice dynamics. Phys Rev B 56 14380-14390 Tschaufeser P, Parker SC (1995) Thermal-expansion behaviour of zeohtes and ALPO(4)s. J Phys Chem 99 10609-10615... 

The thermal expansion of C/C composites is strongly influenced by the same parameters also responsible for the mechanical properties. The coefficients of thermal expansion as well as the linear thermal expansion are dependent on temperature, and differences occur between the data for thermal expansion behaviour of the graphite single crystal in the a, b direction and c direction ... 

Parallel to the fibre axis, the thermal expansion behaviour is controlled only by the thermal expansion of the C fibre, whereas the thermal expansion perpendicular to the fibre axis is dominated mainly by the carbonaceous matrix. In Fig. 14, the thermal expansion and the coefficient of thermal expansion of unidirectionally reinforced C/C composites parallel and perpendicular to the fibre axis is shown versus temperature. In Fig. 14a, curves are plotted of composites with polyimide as the matrix precursor with different final heat treatment temperatures of 1500°C, 2000 C, and 2700°C. Figure 14b illustrates, in comparison with the polyimide-based composites, the expansion behaviour of pitch-based composites reinforced with different types of graphitized C fibres. 

The influence of the different graphitized fibre types on the thermal expansion behaviour is not significant. 

No significant differences of the thermal expansion behaviour were observed for samples reinforced with the same type of C fibre, but different matrix precursors. Also, at low temperatures, the coefficient of thermal expansion is dominated by the fibres, a at liquid He temperature is nearly zero. The composites, reinforced with different fibre types, possess extremely different expansion behaviour. The coefficient of thermal expansion of the high-modulus... 

To examine the influence of other parameters on thermal expansion behaviour, the thermal expansion of 2-D carbon-cloth-reinforced C/C composites with different porosity was measured at low temperatures. The C/C composites were reinforced with 35 V/o 8-harness satin-carbon cloth (sigrafil GDS 8/30) and have porosites of 18 and 15 V/o, respectively. The matrix precursor was CT pitch, modified with elemental sulfur and heat treated to lOOO C. 

It must be pointed out that these measurements of the thermal expansion behaviour of C/C composites at low temperatures shall primarily demonstrate that it may be possible to tailor a high-performance material with a required thermal expansion behaviour for use as cryogenic material. For tailoring the required properties, there are a lot of parameters like those of C fibres the... 

Le Bozec Y, Kaang S, Hine P J and Ward I M (2000) The thermal-expansion behaviour of hot-compacted polypropylene and polyethylene composites, Compos Sci Technol 60 333-344. 

The thermal expansion behaviour of ultra high modulus polyethylene is very anisotropic. Transverse to the draw direction the thermal expansion coefficient is positive and comparable to that for isotropic polymer. In the draw direction the coefficient is negative and very small ( v 10" / ). For low molecular weight polymers the value... 

Ean, B., Yan, J., and Yan, X. (2011) The ionic conductivity, thermal expansion behaviour and chemical compatibility of hao.S4Sro.44Coo,2Fco.803 s as SOFC cathode material. Solid State Set, 13,... 

H.T. Smyth The role of transverse oxygen vibrations in thermal expansion behaviour of glasses and crystals , in Graham, M.G., Hagy, E.E. Thermal expansion (American Inst, of Physics, New York, 1971)... 

T. Sheu, W. O Brien, S. Rasmussen and T. Tien Mechanical properties and thermal expansion behaviour in leucite containing materials. J. Mater. Sei., 29, 125-28 (1994). 

Recently, Mori et al. [29] have observed a thermal expansion behaviour which exhibits some anomalous dependence on dopant concentration that is, there is a minimum in TEC around a dopant concentration of 0.1-0.2. The reported minimum TEC values are about 10 x 10 and 11 x 10 for Lao.8Cao.2MnOa and Lao.gSro.iMnOa, respectively. They also observed a... 

In some cases, thermal expansion (see Section 9.3.4) of rocks is also of interest. Thermal expansion behaviour is different for the rock-forming minerals this has significant effects on the structure of rocks and can result in structural damage (Somerton, 1992). 

The exact chemical composition of alkali alkaline earth sihcate glasses does not so much influence the maximum service temperature of these glasses. However, it will very much affect the thermal expansion behaviour of the final glass product. Figures 1.29 and 1.30 illustrate the effect of a changing chemical composition of the glass on the thermal expansion coefficient. 

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