On Materials Science and Engineering in Energy

Solar tower concentrates light reflected from surrounding panels.  (Source: Paul Langrock/Zenit/Laif/Redux)

A thoroughly interesting report [1] has recently been published regarding the future of materials science and engineering in energy and related fields.  The report is available on-line here; and it is also summarized in the latest issue of the Journal of Minerals, Metals, and Materials (JOM) [2].  The report is written well and with the general public in mind; for the hobby scientist, it also helps convey a thought-provoking state-of-the-art in materials science and engineering.  To summarize the already-summarized article in JOM, the topics in the report - and subjects which will be in the forefront of future materials study - are:

Functional Surface Technology (or: making the surfaces of materials perform in new/different/improved ways).  This includes:

• Catalysts with high selectivity and conversion efficiency.  When catalysts aren't efficient, energy is wasted.
• Smart coating / lubricant systems for lightweight alloys.  Lighter alloys such as aluminum and magnesium tend to wear down relatively quickly. 
• Coatings to inhibit galvanic corrosion.  Corroded materials' performance rapidly degrades.
• Solar photovoltaic materials utilizing a broader spectrum of light.  Current solar panels only collect a fraction of the light energy available.
• Treatment processes to rebuild or enhance surfaces.  Materials' recycle-ability, re-use, and service life can all extended.
• High flux membranes for selective separation of atmospheric gases.  Capture of carbon dioxide emissions, for example, can be made more efficient and scalable to industrial levels.    

Higher-Performance Materials for Extreme Environments.  This includes:

• High-temperature, phase-stable alloys.  Long-term properties degrade in industrial systems which operate using high-temperature and chemically-aggressive conditions.
• Thermoelectric materials with high conversion efficiency.  Thermoelectric materials convert waste heat into electricity, and can help recapture lost energy.
• Lightweight, high-strength ductile materials.  Trade-offs typically exist: strength at the expense of ductility; light weight at the expense of strength; and so on.
• Irradiation-resistant structural alloys for nuclear applications.  Nuclear irradiation degrades the mechanical properties of many materials. 
• High-pressure hydrogen-resistant materials.  Storage and handling of hydrogen is not an easy task.
• Collaborative, comprehensive materials database.  Materials development can be sped and cost reduced.
• Predictive materials performance code.  Computer modeling of materials' mechanical properties will enable rapid, inexpensive, and iterative development.

Multi-Materials Integration in Energy Systems (or: composites to provide what the individual components can't).  This includes:

• Low-cost carbon fibers and composites manufacturing processes.  Carbon fiber products are too expensive to manufacture for widespread use.
• Joining process for assembling multi-material structures. Some material pairs are incompatible (i.e. structurally or chemically) and can not form suitable joints or be brought into contact.
• High energy density, low-cost battery cathodes.  Improved battery longevity, storage, and discharge will enable new alternative energy technologies.
• Low-cost fuel cell catalyst.  A current benchmark catalyst, Platinum, rare and expensive, is not ideal.
• Integrated computational materials engineering modeling package.  Initial composite design and proof-of-concept can be performed first through computation, saving development time and costs.

Sustainable Manufacturing of Materials.  This includes:

• Net-shape processing of structural metals.  Scrap and waste (e.g. from machining a block of steel into its final shape) can be reduced.
• Additive manufacturing of components and systems.  Energy-intensive production methods and industrial systems as a whole can be made more efficient.
• Low-cost processing and energy reduction technology for metals.  Lightweight metals such as aluminum, titanium, and magnesium can benefit greatly from improved processing methods.
• Separation of materials for recycling.  Major efficiency barriers surround the screening and sorting of mixed materials.  Carbon fiber recycling is also expensive.
• Real-time sensor technology for gases and molten metals.  Enhanced detection methods are needed for identifying damage during processing of high-performance and energy-intensive products. 

This report covers a lot of ground regarding sustainability of materials science and engineering in energy and related fields.  But it also presents a good overview of the diversity and breadth of the meaning or interpretation of sustainability - an important point that should be considered alongside the sustainability design itself.  

[1] Linking Transformational Materials and Processing for an Energy-Efficient and Low-Carbon Economy: Creating the Vision and Accelerating Realization - Opportunity Analysis for Materials Science and Engineering.  The Mining, Metals, and Materials Society (2011).  (Available On-Line.)
[2] L. Robinson.  Opportunity analysis for MSE - Report defines pathway to a more sustainable energy future.  JOM, Vol. 63 (Issue 2) (2011), pp. 30-33.

Materials Science in Seismic and Earthquake Engineering

Toronto's CN Tower was one of the first skyscrapers built with "mass dampers" for increased structural stability and earthquake resistance (Source).

A topic currently on the minds of many people, I thought in this post I'd take a look at material science in seismic and earthquake engineering.  In general, successful engineering for earthquakes, tsunamis, and other natural disasters requires intimate knowledge of the landscape, the likely magnitude and type of natural disaster, as well as the likely failure mechanism(s) of the building or structure.  In this regard, Japan has become one of the world leaders in earthquake engineering research, and possesses a full-scale "shaking table" at the Hyogo Earthquake Engineering Research Center [1].  The table is used to test and investigate failure modes of full-scale buildings and structures (see here for testing videos).  In order to engineer a building or structure so that it may withstand an earthquake and associated effects - for a given landscape, magnitude, and failure mechanism(s) - a number of solutions are being developed which combine architecture, civil engineering, and materials science.  (For a more general outline of these solutions, see Wikipedia.)

Springs and frequency "dampers" act to reduce the potentially catastrophic resonant coupling between external forces (e.g. from an earthquake) and the building or structure.  Because springs and dampers undergo cyclic loading, the materials used to make them must possess i) consistent cyclic mechanical properties such as high fatigue strength and low hysteresis, as well as ii) environmental stability, e.g. resistance to corrosion and embrittlement.  Friction pendulum bearings (FPBs) and metallic roller bearings operate cyclically like springs and dampers, but with the added complexity of contact dynamics.  In particular, the use of friction, which generates heat, further reduces the energy transferred to the building or structure.  In addition to high fatigue strength, low hysteresis (in some cases), and environmental stability, the materials designed for use in these bearings must also possess high wear resistance, high thermal stability, and resistance to spall formation. 

Other approaches make use of more fundamental and advanced material science concepts.  For example, Lead Rubber Bearings (LRBs) (developed in the 1970's [2]) are short blocks that consist of a core made of Lead surrounded by a rubber skin.  By utilizing strict lateral (shearing) deformation of these blocks, the building or structure above is effectively isolated from the ground below (see test video here from UCSD).  Lead is compliant (has low Young's modulus) and is very ductile, which translates to a large amount of energy that can be absorbed in the bearing during its deformation.  Lead also possesses a great deal of density (or inertia) to assist with mechanical damping.  Like the Lead component, the rubber is also compliant; but its higher elastic limit (strength) maintains the bearing shape and keeps the cyclic properties intact (i.e. low hysteresis).  The combination of these material properties in LRBs has lead to some significant improvements in seismic energy attenuation [2].

In contrast to LRBs, hysteretic dampers make specific use of materials' non-linear mechanical properties.  For example, viscous fluid dampers for structures are similar to automotive shock absorbers - they consist of a piston filled with a fluid that possesses non-linear viscosity (e.g. oil or honey, but not water).  Viscoelastic dampers behave similarly but consist of largely solid materials with visco-elastic (i.e. non-linear and hysteretic) mechanical properties.  These (or metallic dampers or yielding dampers) transform the non-linear deformation energy into an alternate form, such as heat, which can be dissipated.  A subset of metallic dampers are "superelastic" dampers made of shape-memory alloys.  Shape-memory alloys demonstrate complicated and temperature-sensitive mechanical behaviour - a thermal treatment will return a deformed piece to its shape before deformation - which has been utilized to further dissipate energy as part of a seismic damper, e.g. [3-5].

There is considerable and growing research and development in the area of materials with novel properties for seismic control and earthquake engineering - see reviews [3-5].  A great deal of this work has been done and is underway in Japan, among other earthquake-prone countries.  Engineering solutions will continue to address the diverse and unique landscapes, types and magnitudes of disaster, and failure mechanisms.  In general, however, and as I've written in the case of Haiti, the most appropriate engineering solutions must also consider geographical location, available resources, long-term outlook, and, of course, cost.

[1] Hyogo Earthquake Engineering Research Center.  Facility website: www.bosai.go.jp/hyogo/ehyogo/index.html.
[2] Robinson Seismic Ltd.  Company website: www.rslnz.com.
[3] S. Valliappan and K. Qi.  Review of seismic vibration control using 'smart materials'.  Structural Engineering and Mechanics, Vol. 11 (2001), pp. 617-636.
[4] P. Towashiraporn et al.  Passive control methods for seismic response modification.  Progress in Structural Engineering and Materials, Vol. 4 (2002), pp. 74-86. 
[5] Y.M. Parulekar and G.R. Reddy.  Passive response control systems for seismic response reduction: a state-of-the-art review.  International Journal of Structural Stability and Dynamics, Vol. 9 (2009), pp. 151-177.

Celebrating Engineering

March is National Engineering Month in Canada. (Image from University of Toronto.)

March is National Engineering Month (NEM), and there are a number of events happening across the country - both professionally and at Canada's academic institutions - to help celebrate the wide-ranging and far-spanning work done by engineers.  This year's NEM theme is "Designing the Future", which has a rich flexibility in interpretation but also includes concepts such as progress and sustainability in the discipline as a whole.  Besides learning more about the discipline and what engineers do at the official NEM site, here are a few sources for information:

First, Engineers Canada is the national organization that regulates the profession within the entire country.  This should be a first stop for high-level information, national programs, memberships, and projects.  On a more local scale, you can collect information specific to particular provinces - such as Professional Engineers Ontario, the Professional Engineers and Geoscientists of BC, or Engineers Nova Scotia.  There are also groups divided further by discipline, which are far too numerous to include here.  For a large list of the engineering societies which exist (both in Canada and internationally), the Wikipedia page is a good start.  Basically, there's a lot of information out there - so start Googling!

Second, academic institutions provide fun, simple, and interactive engineering demonstrations.  Designing an energy-absorption apparatus to enable the safe landing of an egg from a fall is one easy example; the design and operation of Rube Goldberg machines is another.  For example, as part of this year's NEM, the Engineering Students Societies Council of Ontario (ESSCO) put into motion the world's largest Rube Goldberg machine (constructed using the internet), which finished by lighting the CN Tower.  Watch the YouTube video here.

Universities also tend to showcase some of the more impressive and cutting-edge (not to mention concise) examples of engineering design, prototyping, and the progression from scientific and mathematical fundamentals to a working product.  Highlighted on the University of Toronto website, for example, are a number of the NEM events as well as stories that emphasize the "Designing the Future" theme in engineering disciplines.  Universities also display how discoveries in the laboratory have lead to significant commercialization opportunities.  For example, the Toronto-based engineering company Integran Technologies Inc. - co-founded by U of Toronto alumnus Dr. Gino Palumbo - has brought to fruition advancements made in the field of materials science, leading to significant and novel product developments for high-performance applications.  Not to be outdone, NEM events are also in focus this month at the University of Waterloo, University of Ottawa, Dalhousie University, or University of Alberta, among others.  Find an interactive event nearby to see the science at work and the progress behind the profession.

Also recently, there have been international events to help promote the engineering profession across the world.  Last October in the U.S., for example, the First USA Science & Engineering Festival was held in Washington D.C.  It was there that Dr. Chuck Vest - a former president of MIT and currently the president of the National Academy of Engineering (NAE) - was interviewed about the future of engineering as a career and profession (see video interview here):

"[W]e've done a miserable job of communicating the excitement and the importance and what engineers and what scientists really do ... One of the things that I think is important, is that the message gets out there that these great challenges that face humankind - in the United States and around the world - none of these things can be solved without engineering."

Dr. Vest also presents an interesting set of statistics: the percent of college graduates (both men and women) in the field of engineering is 21% in Asia, 13% in Europe, and 4.5% in the United States.  According to Dr. Vest, this problem can be rectified:

"Part of the mission of the National Academy of Engineering is to promote increases in the quality, the quantity, and the diversity of our engineering workforce; in my view it's absolutely essential for a good future for this country."   

Because Canada tends to be somewhere between the U.S. and Europe in engineering graduate percentages, communication and interaction is also critical here to help bridge gaps and build them anew to the new students and future generations of engineers.  Communication and interaction are also critical to maintain a fluent, open, and accessible scientific dialogue for those who are not engineers but who interact daily with engineering technology.  In this way, the sustainable practice of engineering design and its core principles can continue to be respected and upheld.

The Value of Mass in Material Products

Strength versus density for a range of materials.  Source: University of Cambridge.

For a great number of material products, their mass is inextricably linked to their attractiveness and commercial success.  Mass is also a key parameter targeted in the constant development of new materials, part of the mantra "Lighter, Faster, Stronger."  For example, steel has been progressively replaced with materials such as aluminum (~35% as dense), magnesium (~22% as dense), and in some cases polymer or carbon fiber (~10-15% as dense).

The value of weight reduction is an interesting topic of discussion; it is also a topic which will constantly evolve with the development of new markets, products, as well as new materials and their properties.  The latter point is of particular focus in materials science.  For example, aluminum alloys possess a wide range of strengths, depending primarily on a) particular element additions to the aluminum base, and b) amount of mechanical working introduced.  Improvements to either can enable aluminum alloys to be applied to new products, e.g. in which a minimum strength is required and minimum density increases the product value.

However, not all commercial products and markets value (or perceive) weight reduction equally.  As described by Ashby [1], exchange constants provide the value or 'utility' of a unit change in mass.  The perceived value of these constants can be determined by graphing cost versus mass for a range of products in a given market sector.  For example, Ashby [1] has performed an exchange constant analysis for bicycles; he found that the constants in this market range from $20/kg (plain steel) to $2,000/kg (carbon fiber).  On the other hand, engineering values of these constants can be determined based on engineering criteria.  In the transport systems sector, for example, the constants are "...derived from the value of the fuel saved or of the increased payload, evaluated over the life of the system."  Namely [1]:

• Family car: $1-2/kg;
• Truck: $5-20/kg;
• Civil aircraft: $100-500/kg
• Military aircraft: $500-1,000/kg
• Space vehicle: $3,000-$10,000/kg

In other words, it doesn't make a lot of engineering sense to produce family cars from extremely light-weight materials because weight savings aren't valued highly in that market.  (But based on the perceived value, there may be a small market for carbon fiber minivans.)

The comparison of product prices per unit weight between market sectors can also offer interesting insight into the value of mass.  From Ashby [1]:

• Buildings (car parks to high-tech buildings): ~$0.10-$2/kg;
• Packaging (paper to metal foil): ~$1-10/kg;
• Marine and Offshore (bridge to luxury yacht): ~$1-100/kg;
• Automotive (subcompact to Ferrari): ~$7-$300/kg;
• Appliances (refrigerator to portable computer): ~$9-$1,000/kg;
• Sports Equipment (skis to fly-fishing rod): ~$100-$10,000/kg;
• Aerospace (light plane to space craft): ~$200-$60,000/kg; and
• Biomedical (toothbrush to contact lens): ~$300-$100,000/kg

While there are a number of surprizes in this list - for example, that a toothbrush costs as much as a Ferrari on a weight basis - the range is a testament to the importance of market knowledge to materials engineering and weight-centric design.  As mentioned above, this list is ever-changing - responding to new markets, new materials, and new properties; but it is also closely linked with environmental changes such as volatility of materials, changes in consumer perception, and evolving political landscapes.  Because of the time required to get new materials to market, materials engineers and designers must therefore remain equally dynamic and flexible to meet the needs of consumers.

[1] M.F. Ashby.  Materials Selection in Mechanical Design, 4th Edition.  Butterworth-Heinemann (2010), pp. 208-210, 482-483.