Around the instruments

Koala (Laue diffractometer)

The first report of a molecular structure determined by single-crystal neutron diffraction using KOALA has been published in Angewandte Chemie. Titled “Reduction of a Chelating Bis(NHC)Pd(II) Complex to [{μ‑bis(NHC)}₂Pd₂H]⁺: A Terminal Hydride in a Binuclear Pd(I) Species Formed Under Catalytically Relevant Conditions”, Angew. Chem. Int. Edit., 49(36), 6315-6318 (2010). The paper represents a large portion of the Master of Science project undertaken by Anung Riapanitra under the supervision of Dr Michael Gardiner, at the University of Tasmania.

Two neutron-diffraction studies for the complex as crystallized from each of two different solvents are reported and the terminal nature of the hydridic hydrogen bonded to the palladium atom is clearly evident in each compound. The structure determined from data collected on KOALA (the other data collection was completed on VIVALDI at the ILL) is crystallographically disordered in solvent-containing regions and the hydride is distributed equally across two clearly defined sites. This material undergoes an intriguing phase change at lower temperature and will be the subject of further investigation.

Platypus (reflectometer) & National Deuteration Facility

Mid-June saw our first experiment at OPAL using molecules purpose-synthesised in the Chemistry Laboratories of the National Deuteration Facility. Researchers from the Centre for Organic Photonics and Electronics (University of Queensland) conducted an experiment using the PLATYPUS time-of-flight neutron reflectometer to study the structure of layered thin-films for Organic Light Emitting Diodes (OLEDs).

OLEDs have attracted interest for their superior performance compared to current display technologies. While tuning the colour emission of such devices is critical for their commercial viability, enhancing the efficiency and performance is also vital. OLEDs are generally composed of several organic layers deposited one on top of the other.

Layered structure of a typical OLED device.

In these technologies the thin-film morphology and interfacial interactions between different molecular layers are key aspects for a successful device.

In order to investigate the molecular interactions in these devices, we deuterated specific compounds to provide neutron scattering contrast between the different organic layers. Deuterated molecules for both the hole-transport and the electron-transport layers were produced at the National Deuteration Facility. A dendrimer-like, hole-transport molecule was custom synthesised from a base cyclic amine aromatic compound, that was pre-deuterated to 85% in large quantities using a Parr reactor. The electron-transport molecule (also a complex aromatic compound) was amenable to direct deuteration (to 70%) in the Parr reactor, without the need to develop a complex organic synthesis protocol from constituent reagents.

Combined with an in-situ spectrophotometer on the PLATYPUS sample stage, the Queensland team were able to use neutron reflectivity data to correlate device properties with the film’s structure and thermal history following annealing.

Neutron reflectivity data from a multi-layer OLED device. The inset shows the refined scattering length density, with the region adjacent to the surface of the film comprised of deuterated molecules produced at the National Deuteration Facility.

Quokka (SANS)

The first user experiment with polarised neutrons on QUOKKA was completed in May. The figure below shows the polarised SANS signal from pearlitic steel as measured by Elliot Gilbert and Vladimir Luzin in a 6-T horizontal magnetic field at 200 K, after subtracting spin down (flipper off) from spin up (flipper on) scattering.

A polarised SANS signal from pearlitic steel in a 6-T horizontal field as recorded on QUOKKA.

Wombat (high-intensity powder diffractometer)

Klaus-Dieter Liss has re-joined the powder diffrection team to give user support on WOMBAT and ECHIDNA, after successful completion of an ANSTO Senior Research Fellowship: 'Modern Diffraction Methods project for the Investigation of Thermo-Mechanical Processes'. A major aim of the project was to develop in-situ time-resolved neutron measurements and to establish a texture measurement and evaluation facility, which is now available to users and is supported by the Institute.

Pole figure of structural nuclear material Zircaloy-4 after high-temperature heat treatment. (data evaluation: Saurabh Kabra)

Taipan (thermal three-axis spectrometer)

The beryllium blocks for the ARC-funded Molecular Spectroscopy option for our TAIPAN Thermal 3-Axis Spectrometer were recently inspected in the USA, and are currently being shipped to ANSTO. The polycrystalline beryllium acts as a low-energy filter to analyse the final neutron energy, after the scattering event at the sample. 

The 52 blocks of beryllium that make up the TAIPAN low-energy neutron filter.

Sika (cold three-axis spectrometer)

SIKA has achieved its first milestone, in that the essential parts of the primary shielding have recently been installed at the reactor face on beam CG-4. This includes adaptation to the reactor face, movable shielding wedges and motion-control components. The next step is the integration of the motion-control components into the instrument control software.

The SIKA installation team

12-T Vertical-Field Magnet

We have ordered a 12-T vertical-field magnet, similar to that available at the Berlin Neutron Scattering Centre (BENSC).

Also purchased from Oxford Instruments is a dilution-refrigerator insert which will enable users to attain sample temperatures down to 20 mK, either in conjunction with the magnet or within our standard ⁴He cryostats. Both items are expected to be available to users in late 2011.

Left: The Oxford Instruments dilution insert and; Centre and Right: The VM1 high-field symmetric magnet at BENSC.