Archive of Reports on IG meetings
Late 1986-1988
Contents This file gives access to reports
in:
- 1988
- 1987
- Autumn MeetingRothampstead 12th Nov
1987
- Workshop Clay minerals analysis "Brains
Trust",29th Jul 1987 - Rothampstead
- Spring Workshop, Practical XRD
(Chung),7th Apr 1987 - Heriot-Watt, Edinburgh
- Workshop Identification & the JCPDS
file, 9th Feb 1987 - GEC, Hirst Research Centre
- 1986
- Workshop Computer Problems,9 Oct 1987 -
Springfields
- Autumn Meeting Crystallography in
Industry, 6th Nov 1986 - British Rail, Derby
Page last updated by IG Web Editor 30 Jan 2001<
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The Powder Diffraction Course, held 4-6 November 1988 at the
Science & Engineering Council's Daresbury Laboratory,
Cheshire, was the first to be organised by the Industrial Group
of the British Crystallographic Association. Since it was formed
in 1983 the Group has arranged numerous one-day specialist
workshops, mainly for small groups of industrial
crystallographers who need an overview of a p
articular topic, or
wish to keep abreast of latest developments. These have covered a
diversity of topics, such as residual stress analysis, studies of
clay minerals, quantitative analysis, computer programs for PD
and the analysis of double-crystal rocking curves, but never
before had a three day PD course been attempted.
The Daresbury Laboratory, home of the UK dedicated synchrotron
radiation source, with an active powder diffraction group, was an
ideal venue. The course, which attracted
34 participants, was
sponsored by JCPDS-ICDD and conducted with characteristic
enthusiasm by its Principal Scientist, Ron Jenkins. The programme
was based on the well tried format for such courses, used
world-wide by the Joint Committee, except that particular
emphasis was placed on the use of the CD-ROM versions of the PDF
and the Crystal Data File which were introduced recently. In view
of the success of this first venture and the obvious demand for
tuition in basic powder diffraction, it is the G
roup's intention
to hold similar courses from time to time in the future. Details
of these will be published in 'Crystallography News'.
J. Ian Langford
(Co-ordinated by the Industrial Group)
This workshop took place at the BCA Spring meeting at the
University of Warwick and was chaired by the organising
co-ordinator Dr Jim Chisholm (Br
itish Museum, Natural History).
Over 100 people attended.
The first presentation was made by Eric Kelly (Electricity
Council Research Centre) who was responsible for the organisation
of the BCA Industrial Group round robin on computer programs for
lattice parameter calculation. Some interesting conclusions arose
concerning compiler options, data storage and use of appropriate
extrapolation functions. Different software was compared on the
same computer (at ECRC) and the same programs on dif
ferent
machines. The raw data circulated and all results are available
in a summary report obtainable from Eric.(Link to report)
Paper two was concerned with the accuracy and precision of
cubic unit cell lattice parameters and was given by Dermott Wood
(BP Research Centre). The materials examined were CeO2
- used for calibration, PSD assessment, comparison of
extrapolation functions and peak location methods, checking for
off-axis effects - and Ag for calibration and testing of a
high
temperature environmental chamber. Some interesting results were
shown relating to data collected with and without Soller slits,
and both the high temperature facility and the PSD gave good
results.
Dr Jim Chisholm (British Museum, Natural history) delivered
the third paper on matching measured to calculated lines and
least squares refinement on Debye-Scherrer powder photographs.
The concern was that the precision quoted after refinement was at
least a factor of 2 lower than in reali
ty. A possible explanation
was that "data massaging" occurs via the use of data that seems
to fit well and the use of unrealistically low tolerances.
Comments were made about large cell materials increasing the
problem and that the use of weightings might be appropriate.
The fourth paper was given by Dr Stephen Tarling (Birkbeck
College) on the subject of 'Dynamic Environmental/High
Temperature Powder Diffraction using a Laboratory System'. A
variety of examples were given concerning the us
e of a high
temperature attachment in conjunction with a PSD, ranging from
paint pigments, zeolites, drugs, cements and corrosion products
on Egyptian bolts. Some problems and their solutions were
highlighted as well as ideas for future improvements that would
be greatly beneficial.
The final presentation was made by Dr Mike Glazer (University
of Oxford) on 'Rietveld Refinement in Practice', and began with
an introduction to the technique. The process of Total Pattern
Fitting was described
for analysis of complete diffraction
spectre, and the need for very good quality/high resolution data
for 'ab initio' structure determination was emphasized. The basic
refinement strategy was outlined
and the use of well defined peak shapes was recommended -
either via good mathematical medals or simple (aberration-free)
experimental systems. Finally, the range of R-factors in usage as
a measure of the quality of the refinement were described.
Thanks are due to all contributors fo
r an interesting and
interactive session. Anyone requiring further information should
contact the authors themselves who will be only too glad to give
assistance, I am
sure.
Adrian Jones
Warwick University, 30 March 1988
The Industrial Group were delighted to welcome Dr. Bill
Parrish, one of the founder members of the American
Crystallographic Association,
as its opening speaker.
He was soon extolling the virtues of X-ray diffraction which
is undergoing a remarkable transformation as a result of the
discovery of the high temperature superconductor. XRD is the
single most powerful method used to determine the phases formed
in the high temperature superconductor and is now benefiting from
a wider exposure to materials scientists and solid state
chemists. In the history of the powder method, Dr. Parrish felt
that we were now in one of its most
finest hours because of the
recent advances made with the new source of radiation from the
synchrotron. He described the optics, instrumentation and methods
used with the synchrotron parallel beam, pointing out the
opportunities in angle and energy dispersive diffraction.
Glancing angle diffraction for thin film analysis was highlighted
using iron oxide thin films as examples. However, with 15,000
diffractometers throughout the world he made it clear that there
are not enough synchrotrons to meet th
e potential demand! Some of
the fundamental aspects of line profile analysis using
synchrotron radiation were described in detail, a2
elimination, increased resolution and the detection of features
obscured by long Lorentzian tails were covered. High peak to
background ratios were possible for all diffraction patterns
because of wavelength sensitivity. The fluorescence problem, for
instance, could be reduced by tuning the wavelength just beyond
the absorption edge. Dr. Parrish also commen
ted on some of the
less desirable effects associated with parallel beams from a
synchrotron source, particularly the intensity variation caused
by particle sizes greater than 10~m. He emphasised the need for
good specimen preparation and ended by gratefully acknowledging
his collaboration with Professor Hart.
The second paper by Dr. Lionel Clark from Shell Research was a
good example of the success of teamwork in studying the surface
structure of ZrO2 ceramics. ZrO2 is
stabilised into a tetragonal phase by the addition of MgO but
stress induced toughening causes a tetragonal to monoclinic
transformation. Interest lies in the mechanism behind this
transformation. XRD has been used successfully to assess the
effect of lubricants on the weight fraction and distribution of
the monoclinic phase in the surface. Cathodoluminescence and
Laser Raman spectroscopy have also proved valuable in
investigating the structure at grain boundaries. Lenticular
grains of the nominal
ly monoclinic phase within the tetragonal
matrix were observed in the TEM but the electron diffraction
pattern did not confirm a monoclinic phase. In conclusion Dr.
Clark felt that XRD had been the most successful technique
applied, commenting that sectioning of samples and beam heating
(in the TEM) may have introduced other problems.
Dr. Judith Milledge completed the first session of talks by
describing the way in which diffraction data from different
sources could be reconciled, acknowled
ging at the outset the
longstanding co-operation between the Statistical Science and
Crystallography departments at University College, London.
Various techniques have been devised for R factor refinements but
Dr. Milledge felt that it was admissible to restrict the input to
certain peaks, suggesting that data should be sampled and not
taken as a whole. In the iterative process of structure factor
least squares convergence different strategies had to be devised.
Silicate garnets were used as an exam
ple of the method of
selecting certain reflections and site occupation by magnesium
and calcium was equated to unit cell parameters. In theory one
reflection was all that was needed. Another example of the
monitoring of certain reflections only was in the study of
unstable crystals when there is a limited time to gather
information. Dr. Milledge convinced many crystallographers that,
in any data set, there was always the opportunity to be
selective.
Professor Mike Hart of the University of
Manchester presented
the first paper of the second session entitled "Synchrotron
Radiation - Does Industry Need It?", a topic dear to his heart,
although, as he said, a title that he himself might not have
used. It was after all rhetorical. He chose two topics to
illustrate the totally new opportunities that now exist with
synchrotron radiation at Daresbury, opportunities that, it was
stressed, are not possible in conventional laboratory
experiments. Special Laue patterns with 100 times as many spo
ts
as seen in laboratory experiments are available in a few seconds
and can be used to study silicon and silica thin films. Because
of the pulsed source of radiation in the storage ring, time
dependent studies of surface strains and temperature
distributions were also possible. The second illustrative aspect
of diffraction using synchrotron radiation was the total freedom
afforded to the experimentalist to optimise both wavelength and
geometry for specific purposes. At glancing incidence, the top 50
Angstroms of a surface could be analysed for Bragg peaks in
conjunction with a spectroscopic analysis of the fluorescent
radiation excited in the specimen. Wavelength variability could
be exploited by going close to the absorption edge for near
surface structural analysis and beyond the edge to study bulk
structure. X-ray energy just above the edge is used to excite
photoelectrons for EXAFS studies, in which the backscattering of
these electrons modifies the transmitted X-ray intensity. Fourier
tr
ansformation of the data to produce radial distribution
functions of atomic positions has been used in many studies, the
way in which water may leach radioactive materials from glass
structures being just one example chosen. Professor Hart ended
his talk by outlining the marketing aspects of industrial
collaboration in using the facilities at Daresbury, and left the
audience in no doubt about the answer to the question in the
title of his talk.
The session ended with an enthusiastic present
ation by Dr.
Paul Barnes of Birkbeck College on the use of intense radiation
sources for dynamic studies of phase transformations. Three
examples were chosen. The first was a study of polytypism in
silicon carbide crystals grown by G.E.C. Hirst Research Centre.
No single polytype could account for all the observed Laue
patterns but it was established that there were disordered
regions in the centre of the crystals and more ordered structures
in the outer cooler parts of the crystals. In the second
application of the technique, the distribution of aluminium and
silicon in ultramarine was determined. It was shown that there
was a random occupation of the tetrahedral sites by aluminium and
silicon in the synthetic ultramarine, unlike the ordered
structure in geologically mined samples. Finally in a very
interesting description of the curing of aerated concrete blocks
in autoclaves, Dr Barnes entertainingly provided a video film of
the industrial process. The morphology of growth was related to
n
eutron diffraction peaks; calcium hydroxide growth and free
water loss were also determined. The final phase, tobermorite,
was on display and has remarkable properties being extremely
light and a very good thermal and acoustic insulator.
All five speakers provided a very varied and informative
insight into the latest developments and applications in
crystallography in industry. The organisers and our hosts,
Warwick University are to be congratulated on a well thought out
and a well executed
programme.
P. A. TEMPEST.
Central Electricity Generating Board.
On Thursday, 19 February, the Industrial Group held its sixth
Specialist Symposium on the identification of unknown substances
by means of powder diffraction data. The venue was again the GEC
Hirst Research Centre, Wembley. The Group shares the concern of
the BCA Council about the inadequacy of crystallo
graphic
education and training, particularly with regard to the needs of
industrial organisations. Previous symposia have attempted to
remedy this situation in a small way, by inviting specialists in
various fields to review techniques and recent developments.
The latest symposium, however, was a new venture for the
Group: 17 crystallographers mainly from industrial laboratories,
including some with little experience of powder methods, learnt
about the routine use of the JCPDS Powder Diffra
ction File (PDF)
for identifying unknown materials.
The seminar was based on the PDF workbook, together with the
NBS-data subfile and its search manual. The material was supplied
to the Group by the JCPDS- International Centre for Diffraction
Data. A short introduction on the use and scope of the PDF and
the basic concepts of search/match procedures was followed by a
'tutorial' in which the participants tackled examples in the
workbook. For this I was assisted by John Harding (BR Derby) and
Steve Tarling (Birkbeck College). In the time available it was
only possible to cover manual searches of the file by means of
the alphabetical, Hanawalt and Fink indexes. It is intended to
hold an 'advanced' session on computer search/match methods in
due course and a symposium on the important topics of data
collection and evaluation and on the treatment of instrumental
and sample-induced errors is envisaged.
From our experience in conducting our first PDF workshop, it
is clear that the
Industrial Group can provide a valuable service
in training diffractionists in search/match methods and it is
likely that further short courses on the subject will be arranged
from time to time.
J. Ian Langford.
Autumn Meeting, 6th November 1986, British
Rail, Derby
The Autumn meeting of the B.C.A. Industrial Group was held on
November 6, 1986 at British Rail's Training School, Derby, our
hosts being British Rail Research Di
vision.
The Chairman of the morning session, Brian Bellamy (A.E.R.E.
Harwell), introduced Dr. Robert Sparrow who as Director of
Research of the Railway Technical Centre welcomed the delegates.
Dr. Sparrow then proceeded to give the first paper entitled 'The
role of the Research Division'. He gave a breakdown of the way in
which research at British Rail is funded and how it advances the
technological base essential for future business, while at the
same time helping to minimise costs and max
imise the effective
use of the Board's assets. He conclusively demonstrated these
points by showing how research into effective ballast packing and
track levelling had increased periods between maintenance and
significantly reduced costs.
The second paper given by Miss Kath Swift (Rolls Royce PLC)
was entitled "Residual Stress measurements in Aero Engine
Material'. She described how quantification of elastic stress and
plastic deformation generated during the manufacturing processes
of the
se high technology components, is leading to understanding
of service fatigue life, and how X-Ray Diffraction can be use to
monitor and control these surface stresses during production. The
results presented demonstrated how successful their hardware and
software modifications had been in analysing these residual
stresses.
The third paper entitled 'Quantitative Analysis of Thin Layer
Samples' was given by Cees Brandt (Philips I and E Division,
Almelo, The Netherlands). A concise review of t
he current
techniques available for infinitely thick polycrystalline samples
was presented, followed by a review of possible calculation
models, and methods of overcoming instrumental variations and
unknowns. Methods of applying these techniques to thin layer
samples where thickness and density of packing were two further
unknowns were described, and methods of overcoming these problems
were presented.
The last paper of the morning session was presented by Dr.
Pierre Graves (A.E.R.E. Harwe
ll) entitled Applications of Laser
Raman Microscopy, A Technique to complement X-Ray Diffraction.
The Harwell Laser Raman Microprobe (LRM) was described together
with an introduction into the field of Raman Spectroscopy. The
usefulness of the technique in conjunction with XRD and EPMA was
demonstrated using the results obtained from zirconia based
ceramics, oxide layers on stainless steel and silicon based
semiconductors.
The afternoon session chaired by Dr. Alun Bowen (R.A.E.
Farnborough)
opened with 'Aspects of the High Resolution Powder
Diffractometer on the Spallation Neutron Source at the Rutherford
Appleton Laboratory' presented by Dr. Bill David (Rutherford
Appleton Laboratory). The potential of the HRPD with a D d/d of 5 x 10-4 was
demonstrated by the structure determination of FeAsO4,
and subtle symmetry changes in NiO. Additional information on
strain distribution, sample homogeneity, anisotropic crystallite
size, could also
be obtained. Applications of the technique with
respect to time resolved kinematic experiments and multiphase
analysis were discussed.
In the second paper of the afternoon Dr. Jim Chisholm (British
Museum - Department of Mineralogy) described how using a
microcomputer he was now able to generate simulated powder
photographs directly comparable with actual photographs.
Intensity was indicated by the spacing of the spots making up the
line. The closer the spots the more black the line. It was
possible to select wavelengths, generate powder patterns of
mixtures and calculate powder patterns to test different
structural models. It was felt by a number of those present that
this program, based as it is on a microcomputer, could be a
valuable teaching aid.
The final paper of the day was given by Simon Clark (Birkbeck
College) entitled 'Time resolved X-Ray and Neutron Diffraction
Analysis of Hydrating Cements'. The chemical reactions in the
manufacture and use of cements were brief
ly outlined, followed by
a description of the time-resolved studies carried out at
Daresbury and the neutron source at ILL. The very promising data
is still being fully analysed.
Over seventy people attended this meeting and were rewarded
with well presented papers of a very high standard. The
organisers also are to be complimented on an excellent
meeting.
Derrick Hart
Plessey Research Caswell Ltd
COMPUTER PROGRAMS FOR POWDER DIFFRACTION PROBLEMS
A specialist interest workshop was held at Springfields
Nuclear Power Development Laboratories on 9 October. Twenty-seven
delegates attended. four of whom came from outside the U.K. The
equipment manufacturers Siemens and Philips were also
represented. This meeting was intended to enable everyone to
describe their work on
"crystallographic" computer programs and to contact others
with similar interests. The works
hop was also designed to see
whether not it is possible to sec up a directory of available
programs and start round robin tests to find the best program in
a particular field. however these undertakings require time and
money which is not forthcoming.
The meeting timetable was informally divided into subjects,
although the discussion varied over a wide range of topics within
these limits, which are listed below.
LATTICE PARAMETER CALCULATION AND REFINEMENT
There seem to b
e a number of such programs in use. Eric Kelly
(Electricity Council) agreed to co-ordinate a round robin test to
compare their results in the near future. Dr Ian Langford
(Birmingham University) pointed out chat small micros do not
offer sufficient numerical precision to produce reliable
results.
INDEXING POWDER PATTERNS
These are running on either minicomputers or mainframes, not
on micros. They have been summarised by R Shirley from the
University of Surrey.
PATTERN PR
EDICTION AND SIMULATION
Again programs are available from Philips and Siemens,
different ones are in use at Daresbury, Springfields and Harwell.
A program is also included as part of the Cambridge
Crystallographic Library. No good methods are available for
triclinic systems. Dissatisfaction was also expressed with the
JCPDS choice of alpha alumina as an intensity standard as small
changes in the atomic co-ordinates produce large variations in
the calculated peak intensities. Programs are al
so being used to
simulate peak profiles. Gaussian methods were generally thought
to be to unsatisfactory. This was discussed further when line
broadening was considered.
�
LINE BROADENING, CRYSTALLITE SIZE AND INELASTIC STRAIN
MEASUREMENTS
There is a considerable amount of activity in this area and it
would make an interesting topic for a BCA workshop.
Dr Ian Langford described the programs used at Birmingham
University for simulating peak profiles by Fourier an
d Rietveld
methods to enable the decomposition of overlapping peaks. Harwell
are using both Fourier methods and the program supplied by
Siemens for crystallite size measurement.. There was considerable
debate about
exactly how realistic peak profile simulations are.
A different method is in use at Springfields for crystallite
size and inelastic lattice strain measurements, using a program
which allows the crystallite shape to be simulated by the user.
Daresbury are also developing
line broadening programs. Most
other people appear to be using the programs supplied by Philips
and Siemens.
STRESS ANALYSIS AND PEAK LOCATION
Rolls-Royce have developed their own programs and equipment
for stress analysis. Harwell are also working on new methods. The
Siemens stress package is being used at Springfields. Most people
are using the Philips or Siemens programs for peak location. Both
programs tend to miss peeks in patterns containing reflections
with very different
breadths. ICI at Runcorn have their own
programs which can use a variety of search models.
SEARCH MATCH
The Siemens, Philips and Johnson-Vand search methods are in
use. Most of the problems encountered have been ascribed to the
original data quality. Programs are now emerging chat can be run
on micros. A standard D/I file format would be useful so that
data can be transferred between different search programs running
on the same system.
Quantitation, texture and the locat
ion of amorphous peaks were
also discussed.
IDEAS FOR THE FUTURE
Dr L Garcia de Viedma described the Nuclear Energy Agency
(NEA) database in France. This is a European organisation which
tests programs for nuclear industry and then makes the programs
available to anyone who is interested, It is funded by the EEC
but cannot buy or sell programs. Most of its present work is
concerned with nuclear safety. Although the NEA have never been
involved in X-ray diffraction before, they are
willing to
distribute any programs which are given to them. These programs
would then be described in their newsletter. Brian Bellamy agreed
to raise the matter with the BCA
Committee and to co-ordinate future action. The principal
problem here is that most people are not in a position to give
their programs away, now that they face much tighter budget
controls, nor are they able to offer software support.
FINALLY
The main achievement of the meeting was to put people in
touch
with others working in the same field. The testing of lattice
parameter programs was agreed and hopefully some will be sent to
the NEA database for distribution. At this point the BCA does not
have the funds to set up a central program library, however most
people felt that the first steps towards greater co-operation had
been made.
Judith Shackleton
A workshop on practical X-r
ay diffraction was held on 7th
April as part of the BCA Spring Meeting at Heriot-Watt
University, Edinburgh.
SAMPLE PREPARATION
Frank Chung (Sherwin-Williams Research Centre, Chicago) led
the discussion on this topic, beginning with a reminder that the
most expensive equipment and painstaking measurement can be set
at naught by poor sample preparation, as can the time and effort
spent on interpreting data. He then summarised briefly and
comprehensively the ways of detecting specim
en orientation
effects and the ideas which have been adopted to counter them.
Several participants then added variants, alternative materials
and practical hints of their own. The problem posed by small
samples was also covered but it may become intractable if there
is also preferred orientation.
Colin Dineen (GEC Hirst Research Centre) raised the difficulty
of mounting silicon wafers for X-ray topography without straining
them. Participants suggested various possibilities but it seems
imp
ossible to eliminate all strain at the supports.
PROGRAMS FOR LATTICE PARAMETER DETERMINATION
Eric Kelly (Electricity Council Research Centre) drew
attention to differences in the output cell dimensions from
different computer programs, arising from differences in computer
precision and in the corrections (if any) which are applied. A
round robin test of cell refinement programs is in progress [if
interested please contact Eric Kelly].
DISTANCE LEARNING VIDEO COURSE
Paul Barnes (Birkbeck College) gave delegates a preview of the
first of five video recordings intended for teaching with
accompanying workbook and tutorials. The introductory programme
deals with powder diffraction and included appearances by several
members of the Industrial Group extolling the practical value and
versatility of the technique. The next two programmes are to deal
with "finger printing" identification and with quantitative
powder diffraction. Possible topics for the final two prog
rammes
include indexing and Rietveld refinement, phase transformations
end chemical reactions, and neutron and synchrotron powder
diffraction. The series looks promising: it could do a lot to
spread the word about crystallography.
Around eighty people, including many from other groups of the
BCA, attended the workshop, which continued the lively and
friendly participation of earlier Industrial Group Workshops.
Jim Chisholm
British Mus
eum (Natural History)
The Autumn meeting of the BCA Industrial Group was held on
November 12th 1987 at the Rothamatead Experimental Station,
Harpenden, Harts. Over seventy delegates attended this meeting
representing a wide range of industrial, research establishments
and academic institutions. Seven papers were presented
illustrating a wide range of applications of X-ray diffraction
(and in one paper of IR spectroscop
y) to industrial problems.
Interestingly four papers originated from academic
institutions, two from research establishments and one directly
from industry. Illustrating, perhaps, the interest in industrial
research within academic institutions.
The first paper by Dr. Ian Wood, on home territory at
Rothamstead, gave an interesting review of crystallography at
Rothamstead starting some 50 years ago. he described
collaborative work with, for example, W.T. Astbury (plant
cellulose),
J.D. Bernal (viruses), W.H. Bragg (mineralogy of
soils and clay) and the more recent work of G. Brown (clay
minerals) and W.R. Truter (structure and activity). In addition
to the oral presentation Ian, with his colleagues, presented an
impressive display of posters. Sadly, we were told that the
future of crystallography at Rothamstead is bleak and that this
research is likely to cease early in 1988.
The second paper given by Dr. D.F. Barlow, Rugby Group PLC,
was entitled 'Some Applications
of X-Ray Diffraction in the
Cement Industry'. This paper contained a brief review of the
composition of the various cements and the problems associated
with application of XRD to their analysis. Dr. Barlow gave an
interesting account of the application of XRD to the
determination of glass content in hydrated cement containing CCBS
(ground granulated blast furnace slag) which is a replacement for
cement. This method has been introduced in BS6699.
Paper three entitled 'Time-Resolved Powder St
udies of Cement
and Ceramic Reactions with Neutron and Laboratory X-Ray Sources'
was a double act Elizabeth Polak and Gerda Mamott from the
Industrial Materials Group, Crystallography Department, Birkbeck
College. Elizabeth Polak described neutron diffraction
experiments on the structural changes in autoclaved lightweight
concrete caused by temperature and pressure changes. Gerda Mamott
described modifications to an X-ray diffractometer which enables
her to study the structural changes which occur o
n calcination of
zirconium hydroxide. These young ladies deserved the appreciation
they received from the floor for the delightful way in which they
presented their work.
Dr. Peter Knight from the AFRC Institute of Food Research,
Bristol, presented the fourth paper entitled 'Studies of Water
Retention in Meat by X·Ray Diffraction'. This was a superb
presentation of a somewhat unusual application of X-ray
diffraction. Dr. Knight discussed the nutritional value of the
water content an
d then described the construction of muscle and
how muscle contraction of about 5% results in 10% loss of water.
Some interesting results concerning post mortem shrinkage of beef
muscle with time were discussed and shown in the form of lattice
spacing vs time and intensity vs time curves.
The Autumn meeting usually contains a presentation on
alternative methods and this time it was the turn of Dr. Monica
Mendelssohn, Department of Geological Sciences, University
College London, who impresse
d with paper five and gave a very
lucid account of 'Applications of FTIR Spectroscopy'. This
involves the use of an FTIR spectrometer with an optical
microscope attachment and she described the application of the
technique to the characterisation of diamonds and to a number of
solid state reactions involving for example anthrone (electron
microscopy grid sample) and to single crystal IR spectra e.g.
anthracene, dianthracene and urea.
Paper six was presented by Professor J. Heizmann, Univers
ity
of Metz, and was entitled 'Pole Figure Measurement and Analysis
using a Curved Position Sensitive Detector'. Professor Heizmann's
obvious enthusiasm for his work showed clearly in his
presentation which concerned the considerable advantage in time,
accuracy and reduction in blind area problems when using the
120° C curved X-ray P.S.D.
compared with the conventional Schultz method to obtain
simultaneously the XRD data across the Debye Scherrer ring. The
advantages
were ably demonstrated with applications to copper
sheet and to single crystals of aluminium.
Finally, the seventh paper was presented by Dr. Ruth Fenn,
Portsmouth Polytechnic, who described some work carried out
during a short sabbatical at the materials Development Division,
Harwell Laboratory. Ruth's paper with the title 'Measurements of
Residual Stress in Carbon Fibre Composite Materials using X-Ray
Diffraction' was most eloquently presented and completely
eliminated the temptation to r
elax before the long journey home -
a clever move by the organisers. The work described involves the
insertion of metal particles (e.g. Al, Ni) between the fibres in
carbon fibre composites so that high angle reflections can be
used to determine strain due to thermal residual stresses in the
cured carbon fibre composites. The conversion of strain to stress
is then carried out by a calibration procedure. Some of the
results were unexpected in that they showed the presence of shear
strain in addition
to the compressive principal strains, this is
in conflict with theory which predicts no shear strain in a
unidirectional polymer - oh dear!
Thus concluded a very useful and enjoyable meeting.
Congratulations to the contributors; the organisers and to our
hosts.
Mike Boles
Plymouth Polytechnic
|
Industrial Group of the BCA