Archive of Reports on Past meetings

• 1998 Annual meeting in St Andrews, Pharmacy meeting
• 1997 Annual meeting in Leeds, Pharmacy meeting and diffraction at high temperatures
• 1996
  • Sessions at BCA 96 Annual Meeting in Cambridge
  • 7 Nov 96 Crystallography in Industry
  • Industrial Award for 96
• 1995
  • Industrial Award 1995 Winner
  • Autumn Meeting 95 Roz Schwarz
  • Instrument Sensitivity Round Robin Dave Taylor
  • Residual Stress Measurement
  • Sessions at BCA Spring meeting Cardiff March 95

Industrial Award 1995 Winner

At the November 1995 meeting of the Industrial Group, the Chairman, Dr. David Dyson(left in picture), presented the award, a Beevers model of Kaolinite to Peter Salt of ECC (o n the right in picture). Peter started his career at Rothamstead Experimental Station, where he worked on a soil survey of England and Wales. In 1968 he moved to ECC at St. Austell, where he became responsible for the analytical section, and developed automated XRD and its application to clay minerals analysis. He also worked on Occupational Health matters, particularly studies of crystalline silica, and standardisation of dust analysis, with reference to the international standard MDHS51/2.

Obituary Peter Salt

Instrument Sensitivity Round Robin

The Industrial Group of the BCA are co-ordinating the UK implementation of an international round robin exercise on Powder Diffraction Sensitivity for the International Centre for Diffraction Data (ICDD). The measurements are based on the NIST standard SRM 1976 Alumina plate a number of which will be cir culated around participants who do not have their own. Both Philips and Siemens have donated standards suitable for their sample holders.

Participants will be required to run a series of 22 scans with varying settings of tube current, voltage, step size, slit size and count times. The data produced will be submitted as plots and raw data (either hardcopy or PC readable files on floppy discs) to the UK co-ordinator.

Each participant will be given a user number to ensure anonymity a nd on completion will be provided with a summary of the data obtained from all participants and their individual user number. This will allow comparison of the performance of their equipment against the range of other participants. It will provide a useful basis for ongoing performance tests to check instrumentation and satisfy the instrument performance criteria of accreditation.

The round robin will be launched at the Industrial Group Autumn meeting on 3/11/95. For further information or a registration form contact the UK co-ordinator - Dave Taylor at:-

 

Tel 01695 54303    Fax 01695 54596  E-mail [email protected] 

D J Taylor 

Pilkington Technology Centre 

Hall Lane 

Lathom 

Ormskirk 

Lancs 

L40 5UF 

BCA Industrial Group Autumn Meeting 1995

The theme of the Autumn Meeting held on the 2nd of November 1995 at the British Steel Swinden Techn ology Centre in Rotherham was the analysis of small samples by XRD. It was attended by about 45 members and non-members. David Naylor welcomed the meeting to British Steel and introduced the company and its markets. Thanks to the process and product development carried out at its three technical centres, British Steel has remained a major player in the automotive and construction industries.

David Dyson (British Steel, Swinden Technology Centre) then gave the meeting an historical overview of the scope of XRD in steel-making, recalling the good (?) old days of pumping down the tube with fingers crossed on a Monday. He surveyed the major uses of the technique in quantitative analysis and texture work and gave a glimpse of the future by showing some electron back scatter patterns which could give pole figures for individual grains of a sample.

Gordon Cressey (Department of Mineralogy, Natural History Museum) reported work with a 120 degree curved position sensitive detector of new anode design. He processed his results using a method by which component patterns are successively stripped from the sample pattern and quantified. Rapid data acquisition gave usable patterns in 3 seconds from conventional sized samples and, hot from the diffractometer, work with a sample holder only two weeks old showed that when using more conventional counting times equally good results could be obtained from a sample size of 0.072 cubic mm.

Kees Brandt (Philips Analytical X-R ay, Almelo) continued the small sample theme with a consideration of intensity correction factor calculations needed when sample mounts such as obliquely cut single crystals of silicon or quartz are used. For these small sample holders, which show no interfering lines, the traditional method of correcting using the intensity of a line from the mounting plate cannot be used and instead the intensity ratio of two lines of the sample itself must be corrected using the intensity ratio found in an infini tely thick sample. Some advantages and disadvantages of reporting the results as concentrations or mass loadings were discussed.

The major advantages gained by using synchrotron radiation were exploited in work presented by Professor Watson Fuller (Keele University) which looked at structural variation in polymers under industrial processing conditions. Changes in orientation and crystallinity during drawing have been observed on a 40 microsecond time scale. Synchrotron radiation can be collimated to give a spatial resolution as fine as 2 microns or utilised for simultaneous wide angle and small angle scattering (WAXS and SAXS) and an example was presented of each technique.

After an excellent lunch and wine courtesy of Rigaku, the BCA Industrial Group Award, a model of the kaolinite structure, was presented to Peter Salt in appreciation of a distinguished career in diffractometry. For over twenty years Peter has been a leader in the development of quantitative XRD in the fields of clay mineral analysis and crystalline silica determination and this award paid tribute to his depth of knowledge and experience. After thanking the Group for the honour, Peter then concentrated on the vital area of the errors in quantitative diffractometry. He focused on the importance of understanding particle statistics illustrated by the decrease in relative standard deviation obtained as the particle size decreases. However he also reminded us that the X-ray amorphous layer on the surface of particles is estimated to be approximately 0.03 micron thick and must form a considerable part of the volume of a 0.5 micron particle. Consequently very small particles lower the XRD analysis figure. He summarised by saying that the main sources of error in XRD are quite well known but that improving accuracy is much more difficult.

Angelika Iberl (Siemens, Karlsruhe) suggested some different approaches to the study of small samples. She discussed the use of a graded multilayer as a primary monochromator which can give a considerable gain in intensity especially with transmission geometry and capillary mounts. Using a HiStar 2D position sensitive detector, a point focused beam and cross coupled mirrors more of the Debye-Sherrer rings can be observed which is useful for example in forensic work.

David Taylor (Pilkingtons, Omskirk) introduced an international Round Robin initiated by Ron Jenkins of the ICDD. The measurements are based on the NIST standard SRM 1976 a lumina plate which can be borrowed by participants who do not have their own and should give the participants a better understanding of the accuracy of their own instrumentation. This exercise has already been carried out in the USA, Holland and Australia.

For the final paper Steve Norval (ICI, Wilton) continued the validation theme by presenting the meeting with some ideas on how, over and above the requirements of legislation, XRD users can ascertain that their instruments are worki ng the way they should. The basic instrument and also any add-ons, including software, could be tested using reference materials or procedures provided by the manufacturer. Specification of the results that should be obtained under given conditions for line positions, intensities and widths or for software line profile analysis would give the user reassurance and make fault finding easier.

The meeting concluded with thanks to British Steel for the use of their excellent facilities at the Swinden Technology Centre and to David Dyson and David Naylor for hosting the session with the able assistance of Justin Carpenter and Richard Hughes. Ros Schwarz.
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Under the European VAMAS standards scheme, money to coordinate a four year programme to provide guidelines and to identify standards for residual stress measurement by neutron diffraction has been made available.

The object of the programme is to produce a draft that will form the basis for the Standards Bodies to produce an international standard for this type of measurement. The programme is academically based, in collaboration with the European neutron facilities; however input from all interested parties is welcome.

The current plan is for the academic bodies and neutron facilities to hold a planning meeting in Grenoble in early January 1996 to ide ntify which facilities will be involved, the scope of the work and the timetable the project will work to. It is then intended that the national facilities (in the UK this will be the ISIS spallation source at the Rutherford Appleton Laboratory) will consult interested parties within their own countries. The first meeting of this type could be expected in mid-1996.

The working party is chaired by Professor G Webster of Imperial College, and he has requested that the BCA Industrial Group co nsider forming an industrially based view of the programme, how any recommendations might be implemented and how effective any standards might be.

Although neutron diffraction is not carried out by many industrial concerns, it is closely allied with X-Ray measurement of residual stress. The development of procedures and standards is thus of interest to workers in both fields. If anyone has any views on the subject, would like information as it arises or, hopefully, would like to con tribute to an industrial input to the programme, please contact :
Colin Small, Rolls Royce Plc, P O Box 31, Derby, DE24 8BJ
tel: 01332 240210 fax: 01332 240327
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Spring Meeting - University of Wales - Cardiff

The Joint Spring meeting of the BCA - BACG was held at the University of Wales, Cardiff on March 27 - 31st 1995, during which the Industrial Group of the BCA offered a va ried insight into the diverse problems encountered within Industry. Jo Jutson and Craig Adam of the Industrial Group of the BCA brought together a range of lecturers to offer papers on two broad subject areas, Novel Materials & Applications, and Rietveld Analysis in Industry. The latter set of papers was designed to complement the IG workshop held last autumn in London. A recurring theme throughout the day was not only the extraordinarily wide range of problems susceptible to XRD analysis, but also the need for high standards of data acquisition and the use of secondary techniques to support the conclusions drawn from XRD.

The plenary lecture (Chairman David Dyson) was presented by Ron Jenkins who offered a fascinating insight into the work of the ICDD. Ron noted that more progress has been made in powder diffraction in the last five years than the previous fifty in terms of new materials and techniques, with 70,000 compounds on file and additions running at 2, 000 per annum. Of the latter, approximately 1,500 are inorganic and 500 organic, with data being culled from literature references (of 5,000 inspected each year only 1,000 are found to be acceptable for inclusion), direct contributions to the ICDD (about 200 p.a.) and data generated by the Grants in Aid (800 or so). The Grants in Aid scheme was detailed, with interesting data showing that a swing from an American to a European bias in terms of numbers of participants has occurred over the last few y ears. The importance of this scheme to the continued health of the ICDD database was clearly made. Some idea of the problems of editorial control was presented - a diversity of measuring systems from Debye Scherrer cameras, goniometers through to synchrotron sources to Rietveld derived data coupled with changing database formats results in a wide matrix of possible data sets. Choosing the correct (or most acceptable) format for the future is not trivial, given that the existing database must remain accessible or be re-run (a daunting task!) The possibility of filing the raw data sets is under discussion, but the existing database which has taken 60 years to produce might require 15 - 20 years to recreate and this presents quite a logistical problem.

Following the plenary lecture, the morning session on Novel Materials and Applications was started by Tom Ryan of Philips with a demonstration of the analysis of sub-nanometre films. Using a sealed tube generator with an open Eulerian crad le, three film examples were presented. The first, using an omega - fixed 2theta scan demonstrated the epitaxial growth of a 0.4nm Au film on Cu. Despite count rates as low as 25cps, very usable traces were obtained. A second example, layers of 0.5 - 40nm Pd on MgO, gave not only the mixed orientation of the Pd, but also evidence of secondary nucleation, confirmed by TEM analysis. The final example was of a sandwich structure - 8nm of Ni/Fe between 3nms of Ta. Grain size and orientation were obtaine d. The use of standard instrumentation and its ability to analyse such thin films was made evident.

Frank Buragzy of Siemens offered a interesting approach to the analysis of thin films and irregular objects by the use of the "Gobel" mirror - a graded multilayer parabolic reflector which can be manufactured to yield either parallel beam or focused optics. A marked increase in reflectivity ( 80% vs 25% for standard systems ) and the parallel beam give enhanced signal to noise and the abilit y to examine rough surfaces. Thus the patina on a 3rd century South Arabian brass camel could be analysed directly without damage to the sample. The edge of yoghurt pot demonstrated the ability to analyse a small area of a low absorbing "awkwardly shaped" sample. The possibility of using two cross-coupled mirrors to achieve a point focus system for high resolution XRD was also presented.

Colin Small of Rolls Royce then presented an insight into jet engine technology. The higher the operatin g temperature within an engine, the better the efficiency but with 8tons of air passing through a jet engine each minute, temperatures of up to 2,000degC, and up to 50kg of sand per minute on take off from a desert airfield, analysis of temperature regimes within the engine is vital. Modelling is used, but is necessarily limited; thermocouples and pyrometers cannot be used, so recourse is made to thermochromic paints which reveal the temperatures components have reached. Colin presented a study of " reverse engineering" - the analysis of a thermochromic paint whose precise nature was not known. XRD played a vital role not only in identifying the components, but also in detailed studies of the interaction of the separated components at differing temperatures. With the data derived from XRD, TGA, DSC and GC/MS, not only was the formulation determined, but also clues as to the route forward for higher temperature paints.

Chris Pygall of Alcan rounded up the morning session with a detaile d presentation of zirconium sulphate chemistry. Not only used as hydrocarbon isomerisation catalysts, these phases are important intermediates in Zr compound formation. The importance of XRD in identifying the various compounds and the role of Rietveld analysis was presented.

The afternoon session (chaired by Craig Adam) started with an overview of the Rietveld method by Andy Fitch. Using this technique, the ability to refine powder patterns with extensive Bragg peak overlaps was introduced , making accessible structural information from a wide range of materials for which single crystals were not available, or for examination of crystal phases under realistic working conditions. Originally formulated for neutron diffraction it was rapidly extended to time of flight instruments, synchrotrons and conventional XRD systems. The choice of technique enables a wide range of problems to be solved: Fullerenes by Time of Flight experiments; Olivine structure by XRD; the structure of benzene/hex afluorobenzene by synchrotron were some of the examples quoted. The capabilities of modern Rietveld programmes include multi-phase analysis, molecular geometry restraints; temperature factor constraints, etc, resulting in the ability to handle complex structural refinements. The accuracy of the initial model is, however of paramount importance, and the latest development of simultaneous fitting to more than one data set takes advantage of the complementary nature of the differing radiation sources.< /p>

Paul Attfield next presented the concept of resonant powder (anomalous scattering) XRD to elucidate the differing valence states of absorbing elements, and to refine disordered structures. The ability to contrast elements with similar atomic numbers was illustrated by the refinement of the Fe/Ni oxoborate system, and a variety of complex superconductive materials were refined using XRD and neutron data simultaneously, taking advantage of the high selectivity of this methodology.

A real-time video presentation was next given by David Bates of British Gas, showing the use of the DBWS program, together with the CERIUS molecular modelling package. The application to ceramics and drill-core samples was demonstrated.

Tony Bell next presented the results of refinements of Leucite structures ( KAlSi2O6 ) where both framework and extra-framework cationic substitution has occurred. Using the Rietveld technique and data derived from high resolution synchrotron XRD powder studi es, electron diffraction, Mossbauer spectroscopy and MAS NMR ( all used to produce a valid initial model ), the structures of a wide range of compounds were derived. The use of analogues as a starting point in the refinement was highlighted.

Finally Steve Andrews of ICI presented a cautionary tale. Rietveld analysis has been used to investigate the structure of poly(ether-ether-ketone) and poly(ether-ketone), using crystalline oligomers as analogues of the final polymers. The low symmetry a nd unit cell shape (one long and two similar short axes) results in complex overlapping patterns. Very good fits were obtained for the 7 ring oligomers and this model was applied to the polymers. However a recent re-appraisal based on high resolution synchrotron XRD data of the polymers has shown that the in-chain bond angles, and axial angles of rotation differ very slightly between the polymers and oligomers. The need for data of the highest quality and from as many differing sources was stressed, in order to ensure that the starting model is the best possible.

The meeting closed with Craig Adam offering thanks to all the presenters and the BCA organisers.

Bruce Fox.