Achievements of ISIS neutron science 1996-2000

Highlights in ISIS science 1996-2000.

Local structure in water

Whilst we may think of a liquid water as having no internal structure, in fact there are short-range correlations between molecules which play an important part in determining water’s unique properties.  Neutron diffraction has been shown to be a powerful tool for elucidating this local structure.

AK Soper et al., J. Chem. Phys. 106 (1997) 247; AK Soper, Chem. Phys. 258 (2000) 121.

Protein absorption at interfaces

Protein absorption at interfaces is important in a wide variety of biological processes.  Neutron reflectivity offers the opportunity of measuring not only adsorbed protein amounts, but the surface/interfacial structure of the adsorbed protein at a level of resolution not obtainable by other techniques.  For example, the technique has been used to study the structure of layers of lysozyme, a protein found in egg whites  adsorbed at the silica-water interface.
TJ Su et al., Langmuir 14 (1998) 438.

Flow dynamics of entangled polymers

Small angle neutron scattering (SANS) can enable detailed models to be built up to describe the flow dynamics of entangled polymers, important for process engineering.  In combination with deuterium labelling, high-quality polymer synthesis, rheology and theoretical studies, SANS data have provide new insights into the melt dynamics of monodisperse entangled polymers of H-shaped architecture.

TCB McLeish et al., Macromolecules 32 (1999) 6734.

Origins of magnetoresistance

Some substances, known magnetoresistive materials, show very large changes in their electrical resistance when a magnetic field is applied to them. This property makes them useful for, for example, computer hard drives. In 1994 a new class of such materials was found which exhibit this property particularly strongly – the colossal magnetoresistive manganites. ISIS neutrons have been used to explore the magnetic properties of these materials, providing new insights to aid our understanding of how they work.

TG Perring et al., Phys. Rev. Lett. 78 (1997) 3197.

Magnetic properties of heavy fermions

Heavy fermion materials are so-called because the electrons which can carry charge within them look like they are much heavier than normal electrons. They have a variety of interesting properties, including, in some cases, showing superconductivity or unusual magnetic behaviour. The magnetic properties of one particular heavy fermion have been explored using ISIS neutrons and provide a test fundamental theories of magnetism.

A Schroder et al., Nature 407 (2000) 351.

Structure of polymer-polymer interfaces

Polymer-polymer interfaces play an important role in polymer blends and surface wetting. Characterisation at a microscopic level is necessary to understand their behaviour. Neutron reflectometry provides a poweful tool for studying such interface structure.

M Sferrazza et al., Phys. Rev. Lett. 78 (1997) 3693; M Sferrazza et al., Phys. Rev. Lett. 81 (1998) 5173.

Properties of magnetic thin films

Magnetic materials with very different geometries from standard, bulk magnets are now commonly being employed in, for example, data storage devices. Neutron reflectometry can be used to study the domain distribution in thin-film magnetic multilayers, providing information that is not readily available through other techniques.

S. Langridge et al., Phys. Rev. Lett. 85 (2000) 4964.

Catalyst poisoning by methyl groups

Neutron scattering has been used to understand the deactivation of palladium catalysts used for industrial applications. Other techniques were unable to reveal why the catalysts had stopped working. But inelastic neutron scattering revealed the presence of methyl groups on the catalyst surface which were causing catalyst poisoning. This was a new catalyst deactivation mechanism, with the discovery helping to solve a real-life problem and being relevant to other catalyst systems.

P. Albers et al., J. Chem. Soc. Chem. Comm. (1999) 1619-1620.

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