Current Science Activities in Thermodynamics and
and Concretes are such a fundamental part of the infrastructure
that it is tempting to overlook the complex and fascinating chemistry
involved in their production and use. MTDATA is well suited to
modelling their behaviour as long as thermodynamic databases are
available for the various liquid and crystalline phases present. One
example relates to Portand cements where the database developed at NPL
for a very wide range of oxide systems has been used for the
calculation of phase equilibria in order to understand aspects of their
processing and production. For further information click here.
database had been used previously to model the potential interaction
between the core of a nuclear reactor and the concrete containment in a
simulation of the chemistry associated with core meltdown. For further
information click here.
More recent work has been
concerned with the development and testing of
thermodynamic models for calcium silicate hydrate (C-S-H) gels. The
engineered component of a low and intermediate level nuclear waste
repository in the United Kingdom will almost certainly consist
primarily of ordinary Portland cement (OPC) based materials. OPC
provides a chemical barrier by its ability to buffer the pH to be
higher than about 12 as it dissolves in a percolating groundwater. A
high pH in a repository is desirable because it helps to minimize the
solubility of many radionuclides, metal corrosion and microbial
activity. Reliable models are required in order to assess the likely
performance of the chemical barrier and to make predictions beyond the
spatial and temporal limits imposed by experiment and observation.The
ability of the model to predict the thermodynamic and phase behaviour
of C-S-H gels in different aqueous environments, from room temperature
up to 85 °C, has been demonstrated by means of a comparison
between calculations and measured solubility data, such as pH and
calcium and silicon concentrations in solution. For further information
has participated actively in the development of a thermodynamic
database for lead free solders as part of the COST531
European Action. Version 3.0 of the database has just been
released to participants. As a result of the scientific work carried
out under COST531 two volumes are being published, the first being an Atlas of Phase Diagrams for
Lead-Free Soldering by A T Dinsdale, A Watson, A Kroupa, J
Vrestal, A Zemanova and J Vizdal, and the second being a Handbook of
properties of Lead-Free Solders and Joints by C Schmetterer, H Ipser
and J Pearce. The COST531 thermodynamic database is now available for
as a SOLDERS database with the major software platforms for the
calculation of phase diagrams. For the scope of the database, please
For further information please contact Alan Dinsdale.
is also participating in the development of the thermodynamic database
for a new European COST Action concerned with High Temperature Lead
Free Solders (MP0602,
HISOLD). The aim of this Action is to increase the basic
understanding of alloys that can be used as Pb-free alternatives to
high temperatures currently exempt from legislation. Such materials
would have application in for example aerospace and automotive
has also been collaborating with Loughborough University in the use of
thermodynamic data for solders in modelling the reactions at the
interface between solders and substrates. This has resulted in the
development of a computational interface between MTDATA and MATLAB/
COMSOL Multiphysics to provide a methodology for sophisticated combined
thermodynamic / kinetic modelling. For further information click here.
liquids form potentially the basis of a new industrial technology that
could revolutionalise chemical processing as well as impact on many
other industries. NPL is supporting effective adoption of this
innovative technology by developing and improving physical property
characterisation in the context of measurement and modelling of the
thermodynamic properties of phase equilibria of ionic liquids.
is developing a comprehensive thermodynamic database for oxide systems.
Together with MTDATA it can be used to give an in-depth understanding
of materials and process optimisation problems faced by industry,
involving interactions between different types of material, such as
slags, mattes, ceramics, glasses, cements and minerals as well as gases
and aqueous solutions. The project is support by a number of industrial
Data for elements
maintenance of standard reference data for the elements has, for a
number of years, been an important part of NPL activities. This is
carried out in close collaboration with other members of SGTE. The
initial outcome of this work was a publication of data for 78 elements
in their condensed phases in CALPHAD (A T Dinsdale, CALPHAD, 1991,
15(4), 317-425). This source has since become widely adopted in the
international community as the basis for the critical assessment of
thermodynamic data for a wide range of materials.
so-called unary database has been updated continously and is available
in version 4.4. A new publication
is being prepared to represent the contents of this database.
work is underway to make use of a "two-state" model to represent the
properties of the liquid phase below the melting point. This is being
tested out on a number of metals and will be the subject of a
presentation at the forthcoming conference "Thermodynamics of Alloys"
to be held in Krakow in June 2008.
compliation of data for the molar volumes and expansivities of the
elements is also in preparation.
General database development
manages the main Solution Database on behalf of SGTE.
the last thirty years or so the availability of exerimental equipment
to measure thermodynamic properties and the number of people to use
such equipment have declined dramatically. This period has also seen a
dramatic increase in the speed and power of computers, and the
development of quantum mechanical software to undertake ab-initio
calculations. This means that, in principle, the gaps left from the
reduction in experimental capability can start to be filled. NPL is
currently involved in attempting to validate these techniques against
the best available experimental and critically assessed thermodynamic
data for gaseous and condensed phases. NPL is aiming to work with
existing users of such software and software developers to identify and
understand any glaring discrepancies.
for the calculation of thermodynamic properties of gas phase
species from molecular constants, although used widely in developing
data for standard publications such as JANAF and TCRAS, are not readily
available. NPL is developing such software and has just released a free
standalone version for sympathetic use. In the future this capability
will be include within MTDATA Studio. Please click here for screenshots of the
software and further information.
thermodynamic properties of Ni base superalloys
is currently involved in various projects which require the development
of a thermodynamic database
for Ni base superalloys. The main vehicle for this is in support of the
development of a capability at
NPL to measure accurately temperatures and enthalpies of transitions
for high temperature materials using
a single pan technique. The database development also supports a
Technology Strategy Board project "Improved Modelling of Material
Properties for Advanced Power Plant" which has the ultimate aim of
developing new improved materials and
increase the utilisation of power plant through a better understanding
of degradation mechanisms. This will
be achieved through integration of various material modelling
techniques from nano scale through to macro scale. This work also feeds
IMPRESS European FP6 project concerned with the development
of new intermetallic alloys for industrial applications such as gas
turbine blades and hydrogen fuel cells. Ultimately the thermodynamic
will be available commercially in conjunction with MTDATA and the Virtual Measurement System.
thermodynamic properties of Mg alloys
support of a related project on measuring thermophysical properties
for lightweight alloys, NPL is also
developing a thermodynamic database for Mg alloys.
Computational Fluid Dynamics
is currently investigating methods of linking software for the
calculation of materials chemistry (such as MTDATA) to third party CFD (Computational
Fluid Dynamics) packages in order to study systems where
are significant temperature and concentration gradients.
Molecular Dynamics, in principle,
provides a mechanism for calculating thermodynamic properties from
field data. NPL is looking into methods where this could be applicable
in order to provide data where
experimental data are lacking or difficult to obtain eg developing
equations of state for real gases or measurement
of the enthalpies of mixing in ionic melts.
Heat Transfer with Phase Changes
is currently involved in linking MTDATA to another NPL software package
Thermol 3D to provide a powerful system of capable of modelling
transient heat transfer.