A hybrid with uniaxial negative thermal expansion behaviour: the synergistic role of organic and inorganic components

2014 ◽  
Vol 50 (95) ◽  
pp. 14960-14963 ◽  
Author(s):  
Kai-Yao Wang ◽  
Mei-Ling Feng ◽  
Liu-Jiang Zhou ◽  
Jian-Rong Li ◽  
Xing-Hui Qi ◽  
...  

Through the study on a new Mn2(api)Sb2S5compound, we propose a strategy for designing a novel hybrid with uniaxial NTE behaviour based on the synergistic role of organic and inorganic components.

1998 ◽  
Vol 547 ◽  
Author(s):  
D. A. Woodcock ◽  
P. Lightfoot ◽  
R. I. Smith

AbstractWe present new detailed structural data versus temperature on the Nasicon structured material NbTi(PO4)3 obtained from powder neutron diffraction studies. This material shows a significant volume contraction over the range 20°C < T < 700°C. αa varies between –4.34 and -0.11 × 10-6°C-1 and αc between 0.08 and 3.07 × 10-6°C-1 over this range. This behaviour contrasts with the case of NaTi2(PO4)3 (NaTP) which shows a positive volume expansion. The difference in this behaviour can be explained by the presence of filled MI sites in NaTP which are vacant in the case of NbTP.


2018 ◽  
Author(s):  
Adam Sapnik ◽  
Harry Geddes ◽  
Emily Reynolds ◽  
Hamish Yeung ◽  
Andrew Goodwin

<div>We study the structural and thermomechanical effects</div><div>of cation substitution in the compositional family of</div><div>metal–organic frameworks Zn1􀀀xCdx(mIm)2 (HmIm = 2-</div><div>methylimidazole). We find complete miscibility for all</div><div>compositions x, with evidence of inhomogeneous distributions of Cd and Zn that in turn affect framework aperture characteristics. Using variable-temperature X-ray powder diffraction measurements, we show that Cd substitution drives a threefold reduction in the magnitude of thermal expansion behaviour. We interpret this effect in terms of an increased density of negative thermal expansion modes in the more flexible Cd-rich frameworks.</div>


2018 ◽  
Author(s):  
Adam Sapnik ◽  
Harry Geddes ◽  
Emily Reynolds ◽  
Hamish Yeung ◽  
Andrew Goodwin

<div>We study the structural and thermomechanical effects</div><div>of cation substitution in the compositional family of</div><div>metal–organic frameworks Zn1􀀀xCdx(mIm)2 (HmIm = 2-</div><div>methylimidazole). We find complete miscibility for all</div><div>compositions x, with evidence of inhomogeneous distributions of Cd and Zn that in turn affect framework aperture characteristics. Using variable-temperature X-ray powder diffraction measurements, we show that Cd substitution drives a threefold reduction in the magnitude of thermal expansion behaviour. We interpret this effect in terms of an increased density of negative thermal expansion modes in the more flexible Cd-rich frameworks.</div>


2017 ◽  
Vol 53 (5) ◽  
pp. 861-864 ◽  
Author(s):  
Himanshu Aggarwal ◽  
Raj Kumar Das ◽  
Emile R. Engel ◽  
Leonard J. Barbour

A five-fold interpenetrated MOF has the highest uniaxial negative thermal expansion coefficient reported for any interpenetrated MOF to date. Upon dehydration, the framework shows considerable change in the magnitudes of the thermal expansion coefficients.


1981 ◽  
Vol 6 ◽  
Author(s):  
J.R. Mclaren ◽  
R.W. Davidge ◽  
I. Titchell ◽  
K. Sincock ◽  
A. Bromley

ABSTRACTHeating to temperatures up to 500°C, gives a reduction in Young's modulus and increase in permeability of granitic rocks and it is likely that a major reason is grain boundary cracking. The cracking of grain boundary facets in polycrystalline multiphase materials showing anisotropic thermal expansion behaviour is controlled by several microstructural factors in addition to the intrinsic thermal and elastic properties. Of specific interest are the relative orientations of the two grains meeting at the facet, and the size of the facet; these factors thus introduce two statistical aspects to the problem and these are introduced to give quantitative data on crack density versus temperature. The theory is compared with experimental measurements of Young's modulus and permeability for various rocks as a function of temperature. There is good qualitative agreement, and the additional (mainly microstructural) data required for a quantitative comparison are defined.


1991 ◽  
Vol 126 (1) ◽  
pp. K43-K47 ◽  
Author(s):  
J. Bak-Misiuk ◽  
J. Köhler ◽  
U. Pietsch

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