The first high-resolution transmission electron microscope (HR-TEM) with atomic resolution to be employed on the continent is critical to South Africa’s research and development (R&D), says Dr Tracy Bromfield, R&D manager for applied research at Sasol Technology.

“This technology sends a strong message that the country wants to be competitive on a global nanotechnology and R&D scale,” she adds.

Bromfield explains that, for South Africa, this is a strategic intervention by the National Research Foundation (NRF), the Department of Science and Technology (DST), the Department of Higher Education and Training (DHET), the Nelson Mandela Metropolitan University (NMMU) and Sasol, which shows that an investment is being made in South Africa by government and industry in nanotechnology and towards attracting business into the country.

The atomic resolution HR-TEM is one of four new microscopes in a R120-million teaching and research facility housed at NMMU, in Port Elizabeth.

The HR-TEM also allows for nanoresearch that has previously been out of reach to academics, universities and many companies in the country, owing to the challenges involved in accessing high-resolution instruments such as this internationally.

The aberration-corrected HR-TEM technology is also in line with governments nanotechnology programmes.

The HR-TEM uses beams of electrons to create an image of a specimen. A focussed beam of electrons passes through the sample and interacts with it. The electrons are diffracted and these diffraction patterns can be transformed to produce an image of the structure of the material.

Previously HR-TEMs had a resolution of over 1Å (10–10 m). The diameter of an atom is less than 1Å. Although these instruments were, and still are, useful in determining the crystalline structure of many materials, they were not capable of resolving individual atoms.

Some instruments were created with higher resolution, such as 1Å, by increasing the excitation voltage of the electron beams to high values, from 200 kiloelectron volts to greater than one mega- electron volt.

However, a more efficient way of improving resolution is to reduce the so-called aberrations in the image caused by lenses. In aberration-corrected HR-TEMs, spheri- cal aberrations in the image, or in the probe, caused by the lenses of the instrument, can now be eliminated by installing specially designed electromagnetic lenses. This makes atomic resolution possible.

The instrument installed by supplier of analytical and electron optical instruments JEOL, at NMMU, is the first to have both image and probe aberration correctors. This allows either aberration-corrected HR transmission electron microscopy or scanning transmission electron microscopy to be performed.

Electron tomography can produce three-dimensional (3D) images of objects on the nano- metre scale. A series of two- dimensional images of an object taken at different angles can be measured by systematically tilting the sample in the beam. A 3D reconstruction can then be computed.

Modern electron microscopes can also be used for chemical analysis. The chemical composition of the samples can now be measured at an atomic level by analysing the energy loss of some electrons as these pass through the sample.

Elemental maps of the material can also be made at nanometre resolution, and lower.

Academics from NMMU and other universities and industrial research scientists from Sasol and other companies will make use of the HR-TEM in a number of broad applications.

Sasol will mainly use the equipment for materials such as catalysts. The performance of catalysts is determined by the atomic structure of the active sites on the surface of the material. “An aberration-corrected HR-TEM will allow us to see and to analyse these structures for the first time in South Africa,” says Bromfield.

University Collaboration Initiative

The atomic resolution HR-TEM was launched at NMMU in early October. Sasol chose to coinvest in the Centre for HR-TEM at the university because it already has the expertise to operate the technology.

NMMU Professor Jan Neethling and his group have led the country in the fundamental understanding of the HR-TEM for materials science research. However, they had a 15-year-old microscope and he and his group members had to go abroad to use state-of-the-art microscopes for their research.

Neethling pioneered the Centre for HR-TEM at the university and has the expertise to train others in the use of these techniques.

The contribution of Sasol to the centre was part of its University Collaboration Programme, which has been running for six years. “We are thrilled that Sasol is part of this centre and its one-of-a-kind technology. More importantly, the development of skilled operators and researchers for Sasol and South Africa will be significant,” says Bromfield.

When Sasol embarked on its University Collaboration Programme, it specifically considered the competences and the level of expertise that each university could offer.

The programme is being used to develop research capacity in specific areas at local universities and to train postgraduates to potentially be employed at Sasol and in the local chemicals industry. We realised that we needed to provide for the future in terms of access to skills in the science and engineering disciplines, says Bromfield.

Further, for postgraduates to develop adequate skills, they require access to up-to-date equipment and top academics, so a critical mass of researchers needs to be retained at local universities.

Postgraduate students are able to undertake projects that are technically relevant and are exposed to the types of advanced techniques expected at Sasol.

Bromfield states that this programme will not only benefit the petrochemicals group, but will also advance South Africa’s petrochemicals industry.

Sasol Technology believes there has been a lot of value generated from the university programme over the past six years. “We are optimistic that there will be lasting benefits from this programme and that, in whatever form, funding and investment in local universities is something that must continue in key focus areas,” says Bromfield.

She adds that the programme is being continuously reviewed, but there are certainly a number of established groups and students that have graduated and felt the benefits that have come with it. “We will consider continuing this programme in some form at the end of its ten-year run, since we believe that the benefits for Sasol and the country require a long-term view to be taken around building and maintaining relevant research capacity.”

Sasol Microscope Unit

Meanwhile, Sasol is looking to expand its own microscope unit in South Africa.

“These will be very high-end – and some will also be aberration-corrected, which is important because it enables one to operate at high resolution,” Bromfield explains.

Sasol Technology R&D is currently constructing state-of-the-art laboratories for materials science research at its headquarters in Sasolburg. These include a suite of laboratories for four electron microscopes.

“The facility is similar to the one opened at NMMU in that it can accommodate two scanning electron microscopes (SEMs) and two aberration-corrected HR-TEM instruments,” Bromfield notes.

The expected completion date is May 2012.

Sasol currently has two Carl Zeiss SEMs, an Ultra 55 HR-field emission gun- (FEG-) SEM and a Lanthanum Hexaboride EVO series SEM.

The first HR-TEM, a Tecnai Osiris 200 kV FEG scanning transmission electron microscope (STEM), from supplier of electron micro- scopes and other scientific apparatus FEI, has been ordered and will be delivered in May 2012, upon completion of the laboratories.

Sasol will make regular and frequent use of the facility at NMMU to train its current and future electron microscopists, and to make use of the new aberration-corrected 200 kV JEM atomic resolution HR-FEG-STEM. This will support research projects. Sasol also plans to build business cases for the acquisition of its own aberration-corrected HR-TEM in future.

Bromfield believes the rest of Africa will probably follow sometime in the future, but it helps if there is an operating unit for people to become excited about.

She notes that, despite all the funding and access to resources available to Sasol and NMMU, there will always be a short supply of equipment and skills.

However, none of the work being done in the University Collaboration Programme would have been possible through Sasol’s efforts alone. “We are very gratified by the fact that the universities have stepped up the mark and invested in their own facilities. Some have taken bold steps and made big leaps of faith to set up expen- sive, high-end facilities,” Bromfield says.

She adds that the DST, the NRF and the DHET have coinvested with the participating universities in many of these facilities, creating a partnership that has contributed to the success of the Sasol university collaboration initiative.

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