Archive of Reports on IG meetings
1988-1989

• 1989
  • Autumn Meeting
  • Workshop on Special environments7-Dec-89, Birkbeck College
  • Workshop Line broadening I, ICI Runcorn
  • Spring Meeting, EXAFS, micro-ionics, microtexture U of Oxford
• 1988
  • Autumn Meeting ICI, Runcorn
  • Workshop

1989 Autumn Meeting

The most recent of the Group's one-day 'Crystallography in industry' meetings was held on November 2 1989 at the Technology and Environmental Centre of National Power at Leatherhead. (As yet, the venue is better known by the long-established name of CERL, Leatherhead - the new title being a side-effect of the impending privatisation of the electricity supply industry.) The arrangement for the meeting was co-ordinated by Mrs Phyllis Dolbear, whose team Is to be c ongratulated for their smoothly organised occasion.

The day's first paper war presented by Dr J E Chisholm of the Mineralogy Department of the British Museum (Natural History). Jim revealed the history of the museum and the place of the Mineralogy Department within it. The museum's mineral collection exceeds 300,000 specimens and increases by about 1000 specimens each year; In addition there are thousands of rock, ocean bottom deposit and meteorite samples. Debye-Scherrer photographs are u sed for identification and archive purposes; over 30,000 films are in the catalogue and collaborative work with University College is in hand to digitise the film so that the data can be made more widely available. In addition, the staff of the mineralogy department have extensive research Interests in a variety of geological and mineralogical topics.

In a paper on The Structure of n-Alkanes, Dr A R Gerson (Strathclyde University) explained work, carried out with her co-worker at Strathclyd e and Daresbury on the crystal structures of C₁₈ to C₂₈ n-alkanes, which make up some three percent of diesel engine fuel. The topic is of much interest as part of research directed at elimination of the problem caused by fuel waxing at low ambient temperature. The high resolution achievable with synchrotron radiation was employed to reveal that odd carbon-numbered alkanes in this range had orthorhombic cells, C₁₈H₃₈, C₂₀H₄₂ and C₂₂H₄₈ had triclinic cells whilst C₂₈H₅₀ had a monoclinic cell. The unit cells of C₂₄H₅₀ and C₂₆H₅₄ were shown to be monoclinic with two molecules per unit cell. Dr W I F David (Rutherford Appleton Laboratory) described several applications of neutron diffraction techniques, in particular a study of failure mechanisms in "Duracell" batteries. The high flux available permitted the in-situ study of chemical reactions yi elding conclusive indication of intercalation of hydrogen into manganese dioxide and the growth of impurity phases associated with battery failure. It is expected that such experiments will become routine as a diagnostic tool. Some applications of X-ray Topography of Semiconductors were described by Dr P J Halfpenny (University of Strathclyde), illustrating the nature and mechanisms of introduction of process-induced defects in semiconductor silicon. Peter stressed the ways in which different defect types interact during device processing.

For economic reasons, Fe-8Mn alloys are attractive as replacements for Fe-Ni alloys in cryogenic applications. However, Fe-Mn alloys are susceptible to temper embrittlement. Dr M D Bramhall (Sheffield City polytechnic) described work on these alloys, involving xrd and Mossbaur spectroscopy, in which tempering in (a + g ) region of the phase diagram produced reverted austenite (g ) structure in the lath martenite (a¹) structure, giving a significant improvement in toughness. The importance of specimen preparation was stressed - light grinding followed by electopolishing having proved to be the appropriate route.

The final paper of a very full day was presented by Ranko Yrcelj (Birkbeck College) who described a CASE project to study variations in the physical properties of metallic glass, during changes to the crystal line counterparts. Two particular areas had been investigated - the identification of the crystalline components and the kinetics of the reactions occurring during crystallisation. It is interesting to note that apart from Jim Chisholm's "special interest" paper all the day's presentations were made by speakers who work in Laboratories which are not owned by industrial companies. Nevertheless the work described was clearly industrial in nature - an indication of the way in which the industrial Group 's meetings surmount conventional boundaries between disciplines.

Eric H Kelly.

BCA Spring Meeting 1989, Oxford.

Although the annual BCA. Easter meeting is often associated with a spell of bad weather (the rains of Bristol and the cold winds of York) this is the first meeting which will be associated with an unseasonal flurry of snow - perha ps not industrial crystals unless you work at a ski resort - but a strong crystal theme nevertheless.

The first session was chaired by our outgoing outgoing chairman Brian Bellamy (outgoing in both character and office), who didn't even need to detail transatlantic air schedules for us to appreciate the minor adjustment to the running order to allow our first speaker to catch an early flight to the U.S.A.

Thus Dr. David Dingly from Bristol University spoke first on 'Microdiffracti on in the scanning electron microscope for phase identification and on-line orientation measurement. The initial description of a method which could work on small and far from perfect samples, using a stationary probe, at small additional cost and covering a very large angle was mouth watering.

He also gave a number of well illustrated examples or both the phase identification and orientation aspects. Stainless steel got a careful look at 2000 A spatial resolution and a most interesting exa mple of NiCl₂ growing epitaxially on NiS₂ was shown; it had been perhaps a disappointment to David that he had not discovered a new phase of NiS₂, but there was compensation in the fact that XRF had not been able to detect the chloride phase. Although a piece of film and some string and sealing wax seem to be all that is needed to start, the new high gain T.V. cameras have enabled impressive on-line measurements to be realised; for instance the fixing of a crystal or ientation well inside a minute. These Kikuchi line patterns have led to a new notation for the pole figures and we had a taste of Frank-Rodrigues space using bees as a excellent model for the axes. David finished by detailing two new mineral structures, one cubic and one monoclinic. His proselytising style was captivating and he was last seen carrying a suitcase and a pair of snow-shoes out through the registration area.

Professor Geoff Alien from the Central Electricity Generating Board, Berkeley Nuclear Laboratories presented the next talk on 'Interfaces in nuclear materials'. Geoff covered two particular aspects that have been studied using an impressive battery of methods the acronymic index of which was mind blowing (I'm still not sure about ESIMXRPES!). This seemed to be second only in range to the number of phases from UO₂ to U₃O₈, and yet the work on oxygen cluster geometry has allowed Geoff to rationalise two entire series of these oxides in a most satisfying scheme. The beautiful pictures of the structures helped us visualise this and appreciate how increasing insight does (sometimes?) lead to an elegant overview. The second topic was that of carbon deposition; particularly that which appears patchily as an unwanted insulating layer where the gas coolant from a reactor core passes over metal surfaces. A large number of spinels have been studied and examples of the Mn/Fe Cr₂0₄ studied by high angle XRD were most in teresting. Carbon contents have been quantified using a windowless detector and Geoff's final story detailed the studies of preferential growth on faces of magnetite crystals, the source of which had taken ten years to find.

Although Professor Richard Joyner is now based at Liverpool University he was previously working with B.P. and his talk on 'Industrial applications of x-ray absorption spectroscopy' covered both incarnations. He started with a didactic section on the techniques of EXAFS and XANES and his re-interpretation of the initials (e.g. Extremely eXpensive And Frustrating Spectroscopy) of the teenage techniques will be well remembered. Thus he outlined the physics of these absorption techniques which are poor for structure determination but excellent for probing local structure, for liquids as well as solids. Although experimentally conceptually simple there is the small matter of a synchrotron for good results and Richard is pleased with the Daresbury SRS facility and went on to outline two examples. The environment of Ni in heavy crude oils was probed, making use of a number of standards with square planar Ni and most of the oils showed a porphyrinic Ni environment. The rhodium based gas catalyst studied by EXAFS were probed in situ in a high temperature environmental chamber and most exciting results for range of gaseous composition were presented showing that in the industrial CO/H₂ mixture the Rh takes on a quite metallic looking environment but with a n expanded Rh-Rh distance compared to the metal. This is in stark contrast to both the H only and CO only atmospheres and provided an excellent example of the advantage of studying industrial materials in their working environments.

After the break it seemed appropriate that our new chairman Dr. Alun Bowen took over and his first speaker was Professor Josh Thomas who had come over from the University of Uppsala to talk on 'From structure to industrial applications in micro-ionics'. Althoug h the ionic conduction of Na beta-alumina has been known for some 22 years we still do not have electric cars with solid electrolyte batteries. However this has not discouraged, Josh from probing the structure - particularly the distribution of the mobile ions. Unfortunately the space group of the host alumina lattice imposes symmetry restrictions on the ion positions and thus simulation techniques have been brought to bear. The distribution of sodium at various temperatures has been explored to rev eal some of the secrets of ion conduction and the substitution of other ions shows counter-intuitive differences. The exploitable features of 2-D conduction and high exchangeability lead to a number of applications and Josh not only looked at current ideas but was brave enough to look into his micro-ionic crystal ball. Thus from optical wave guides, submarine communication (a euphemism for detection?) and lasing we were taken into a world of a tunable micro-laser, optical memory, phosphors and humid ity sensors.

The last talk of the session was from Dr. Mike Barry of ICI Chemicals and Polymers in Runcorn whose subject 'Consolidation and coalescence of Latex dispersions studied by small angle scattering' was the result of a most successful co-operation with Salford University. Polymer Latex materials account for some 20% of the world's polymer production and there are, inevitably, a range of compromises to be optimised - in this case a cost-flexibility- thermal stability-barrier surface to be explored. A range of polymers between vinyl chlorides and acrylates called Haloflex which are used in many coating applications from primers on blast clean steel to anti-fouling coatings have been studied. Small angle scattering using the SRS was used to investigate the size and geometry of the particles in suspension. Using Bessel functions the analysis of monodisperse systems has been effective, but the use of a coating material on the particles giving a core plus shell model has proved mor e of a challenge. The Guinier approximation (which is valid for Monodisperse and dilute dispersions) does not apply and the Porod region is more suitable for a Haloflex which has around 50% solids. At ILL, a cunning use of contrast matching using D₂O has helped reveal details of the system and the studies on sphere size, and coalescence proved to be much more exciting than watching paint dry! The four-region scheme that Mike proposed, from the initial formation of monolayers to the final coalescence of particles across surfactant bilayers was confirmed using reflectivity measurements.

In this Industrial Group Session we were treated clear views of complicated systems through the insight of sophisticated techniques, careful analyses and well prepared speakers.

Stephen Tarling, Birkbeck College.

1988 Autumn Meeting, ICI Runcorn

This year's Autumn meeting of the BCA Industrial Group was hosted by ICI C hemicals & Polymers Ltd at Runcorn in Cheshire, on November 3rd, 1988. For the second year in succession attendance was good (77 delegates in all) and the Group was especially pleased to have the BCA president Prof. Michael Woolfson in attendance. Alun Bowen (RAE, Farnborough) acted as chairman in the absence of Brian Bellamy who was unable to attend through illness.

The opening paper, traditionally by a representative of the host establishment, was given by Dr. Steve Fletcher. Steve d escribed briefly the activities of the different industrial sites of ICI Ltd, going on to talk in more detail about the uses of powder diffraction at Runcorn. An interesting historical aside was the fact that 'polythene' was first manufactured (and characterised by XRD) at Runcorn in 1936. Powder diffraction was currently used for the examination of fibres, thin films and catalysts. Information such as crystallinity and chain conformation was obtainable from fibre diffraction patterns whilst crystal lite size and strain in catalyst particles were useful parameters in determining the activity and age of these materials.

The second talk entitled "Use of combined databases in a PC/CD-ROM environment" was given by Dr. Ron Jenkins of the International Centre for Diffraction Data, U.S.A. Ron described the three main databases which are commercially available from JCPDS. PDF-2 which contains full card images, PDF-1 which holds d's, I's, name and subfile designation, and CDF which contains re duced cell parameters, space group, calc. density, chemical class, formula end name, and journal references. The same data format was used in each database so the same search routines could be used. A fourth database currently under construction is PDF-3 which holds fully digitised powder patterns. CD-ROM was the best medium for these large databases and the simplest, cheapest system was an IBM 'XT' or 'AT' or clone with a 20Mb hard disk and a 500Mb CD-ROM. On a semi-serious note, Ron said that the J CPDS were considering adding a 'jargon' file to the databases in order to cope with Versions of the English language as used in the USA, the UK, and at a pinch, that used in Australia!

The third talk concerned developments in powder diffraction at the SRS, Daresbury. Dr. Bob Cernik spoke about progress in a variety of experiments conducted at stations 9.1 and 9.3. The introduction of a water-cooled Si monochromator designed by Mike Hart had successfully overcome alignment and intensity prob lems with a 2-circle diffractometer. Good, high resolution data were collected using a multiple foil c6llimator in the diffracted beam. Changes in software were expected to improve peak-fitting routines for patterns with narrow (0.030) peak widths. Diesel fuels at low temperatures form waxy plate-like crystals and to date five different forms had been indexed. EDXRD had been used to examine the crystallinity of these waxy crystals as a function of temperature and it had also been useful in following the hydration process of tricalcium silicate in Portland cement.

Jo Jutson of the CEGB's Berkeley Nuclear Laboratories provided the last talk before lunch. Carbon deposition on stainless steel components of AGR's is a problem which causes reduced heat transfer. Spinel oxide composition on the steel surfaces is known to influence this deposition so oxides of the type (Mn, Cr, Fe & Ni) formed on the reactor components were synthesised in CO₂ or CO₂/CO atmospheres an d characterised by XRD and EDXRD. These spinels were then formed into ceramic disks and exposed in a heated, gas-filled cell capsule to gamma rays, in order to simulate reactor conditions. It was found that Fe-Ni spinels deposited amorphous carbon, magnetite surfaces with Ni particles produced carbon filaments, and Fe-Mn spinels deposited both types.

Professor Mike Hart of the University of Manchester opened the afternoon session with a thought-provoking talk on the use of high energy X-ra y diffraction. Mike described double crystal diffraction experiments with 140-160kev X-rays. Low absorption, the absence of extinction and the high Q values (20-30A^-1) obtainable were some of the advantages over conventional Cu radiation. These advantages were of use to the semiconductor industry in which measurement of rocking curves or mosaic spreads of Si or Ge crystals had previously been restricted to thin (<lmm) specimens. Thicker specimens had always required a neutron source. R ocking curves of thick Si crystals had now been measured at 0.2 sec. arc with 140 kev X-rays. Mike concluded by promising even better prospects with synchrotron radiation in this energy range as it would have a brightness some 10,000 times greater at 150kev.

The sixth talk was a contribution by Dr. Tony Bell of UKAEA, Springfields on Ruthenia in simulated vitrified nuclear waste. RuO₂ has low solubility in the product glass and had previously been thought to remain unchanged duri ng the vitrification process. However, determination of cell constants of pure RuO₂ (a = 4.490, c = 3.105A), RuO₂ in glass with waste oxides (a = 4.497, c = 3.082A), and RuO₂ in glass with no waste oxides (a = 4.493, c = 3.103A) showed otherwise. Use of EPMA revealed that Fe and Mg had been absorbed in the RuO₂ Lattice whilst Scanning Electron Microscopy showed differences in the shape and size of the crystallites in pure RuO₂ and those in the g lass. XRD also indicated strain in the needle-like glass-bound RuO₂ while pure RuO₂ was strain-free and had cubic morphology.

Jamshed Anwar of Birkbeck College presented the seventh talk of the day entitled "Kinetics of phase transformations in drugs". The kinetics of polymorphic transformations of the drug sulphathiazole had been studied using powder diffraction and DSC. The main objective was to achieve high accuracy in determining the fraction transformed (a (t,T)) and fortunately this was made easier in the quantitative calculations as the four polymorphs have the same linear absorption coefficient. Full diffraction pattern profile fitting was used, taking into account changes in the unit cells of the different phases occurring at elevated temperatures. The synchrotron source (station 9.7 with EDXRD) at Daresbury had been used for some of the work, enabling 1/20 sec. time resolution during phase transformation.

The final talk on "Glancing angle EXAFS on condensed interfaces" was given by Dr. Kevin Roberts of Strathclyde University. Considerable interest had been shown in the application of X-ray surface sensitive techniques to the characterization of "real" surfaces using X-ray reflectivity and EXAFS at glancing angles. For example, corrosion on the surface of stainless steel blocks could be monitored by observing the near edge structure (XANES) of bulk steel when the fingerprint of steel transformed first into that of magnetite and then hematite with the passage of time. Surface oxides on Gallium arsenide wafers had been studied using EXAFS at the absorption edges of Ga and As. Radial distribution functions showed a 20% increase in Ga-O distances, a 120% increase in As-O distance and a 25% decrease in As-Os distances ie. a net loss of As at the surface.

The meeting was closed at 3.45 pm with thanks from the chairman to all the speakers and especial thanks to Steve Fletcher and his colleagues at the ICI Heath Site Conference Centre for the excellent organization and hospitality. Enraf-Nonius Ltd were also thanked for their generosity in providing the conference folders and of course the liquid refreshment at lunch time.