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Liquid Wall Prototype for Innovate:Integrate Exhibition from arbuckle industries on Vimeo.

This video features one example of the innovative architectural structural design opportunities emerging from the availability of ultra-high-performance concrete. This material, also known as ultra-high-strength concrete, provides improved strength, stiffness, ductility and durability compared to typical concrete. The UHPC used in this video is a product called Ductal, made by Lafarge North America.

The design for the curtain wall permits replacement of individual units and allows for the incorporation of passive solar heating panels.

For an good overview on UHPC (or UHSC), see this prophetic 1998 paper by Surendra P. Shah and W. Jason Weiss from the Center for Advanced Cement-Based Materials.

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Crystal structure of Mayenite (12CaO-7Al2O3). Credit: Paul Myers, CERAM Research Ltd. on AZoM

With the Cements Division meeting wrapping up in Nashville, Tenn. this week, an article in the July 1 issue of Science caught my eye. It pulls together an unusual gang: cement, iron smelting slag, crystal chemistry and quantum physics. The work shows how insulating, light-metal oxides can be transformed into electrical conductors at high temperatures, effectively becoming metallic cements.

Since the early 1800s chemists have known that solutions of alkali metals dissolved in polar solvents like water or ammonia have interesting properties. For example, dilute alkali-ammonia solutions are bright blue and exhibit electrolytic conductivity. Concentrated solutions are a striking golden-bronze and exhibit metallic conductivity. In ammonia, the alkali valence electrons are ionized quickly and released into the solution.

Nearly a century ago, Kraus described  (J. Am. Chem. Soc. 36 864 (1914)) the electrons, the charge carriers in the solution, as “the negative electron surrounded with an envelope of solvent molecules,” that is, the electron is surrounded by ammonia molecules. A few years later, Gibson and Argo (Phys. Rev. 7, 33 (1916)) named these surrounded electrons “solvated electrons.” (The subject of solvated ions came up in an earlier post on anomalous supercapacitance observations.)

Metal-amine solutions can be condensed ionic solids, known as electrides, in which the electrons are trapped in the compound’s structural cavities or channels. However, organic-based electrides, such as crown ethers, are not thermally stable.

Kim et. al., based in Japan, wondered whether a thermally stable electride material could be found, and in earlier research, were able to synthesize thermally stable inorganic electrides from calcium aluminate, 12CaO-7Al₂O₃ (or C12A7). This compound is known by geologists as mayenite and by cement chemists as one of the components in alumina cement. Mayenite is also a constituent of the slag produced by the iron smelting process. The electride compound, designated as C12A7:O^2-, traps O^2- ions but has no charge carriers in the molten state because CaO and Al₂O₃ are stable, electrically insulating oxides.

By reacting C12A7:O^2- with elemental titanium at high temperatures, an electride can by made that traps an electron instead on an ion (C12A7:e^-). The question the Kim team sought to answer is whether solvated electrons exist in the molten C12A7:e^- the same way solvated electrons exist in metal–ammonia solutions. (See Kim, et. al. in Science, Vol. 33, doi: 10.1126/science.1204394)

It turns out they do. During the reaction with titanium, electrons are trapped at the oxygen ion vacancies and coordinated-solvated-by calcium within the cage-like structure. Like the metal–ammonia solvated solutions, the C12A7 melt transforms from a transparent, insulating C12A7:O^2- melt to a colorful, electrically conducting C12A7:e^- melt.

When the concentration of solvated electrons in solution reaches high enough levels (~10²¹ electrons/cm³), the electrical conductivity becomes metallic. In a Perspectives article in the same issue of Science, Peter Edwards remarks, “This must surely be one of the most unusual and spectacular observations of the transition to the metallic state—turning liquid cement into liquid metal.” The metallic conductivity comes about by extensive delocalization of the solvated wave functions across the melt.

The Kim team took the experiment one step further and studied glasses made from C12A7:e^-. Using a wide range of tools like Raman spectroscopy optical absorption spectroscopy, electron spin resonance measurements and iodometry, the atomic structure of the glass was established. They found that the solvated electrons are frozen into the glass, but the majority of them adopt a two-electron, spin-paired state. That is, instead of overlapping wave functions, the electrons pair off to form peanut shaped bipolaron structures, and the result is amorphous, semiconductive oxide glass.

As Edwards says, Kim’s work “represents a material showing the ultimate confinement of a quantum particle—an electron “set” in cement.” Both Kim and Edwards suggest that the ability to tune electrical conductivity of melts, slags and glasses should lead to new applications for the light-metal oxide, semiconducting class of materials. Kim et al., expect there may be other inorganic compounds that can be electrides, and that this work will lead also to the study of elemental electride materials under high pressure.

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Tubohotel in village of Tepoztlan, Morelos, Mexico. Credit: Luis Gordoa/gordoafotografia; Tubohotel.

Via Gizmag, and originally from archdaily:

“The idea came when we built Cafe Five, where we saw the need to adapt an inexpensive room for users. In our search for solutions, we found Desparkhotel, the work of the architect Andreas Strauss in 2006, using recycled concrete pipes for hotel rooms. Our client decided to make a hotel with the same characteristics as the Desparkhotel on a ground that is located on the outskirts of Tepoztlan, with excellent panoramic views of the Sierra del Tepozteco. Located in a wooded setting of unusual features, the surrounding environment provides an unique natural environment and for our project.”

Rentals go for 500 pesos (about $43) per night.

Also, some great construction photos can be seen at T3Arc.

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Steel rebar embedded in concrete (left) and “nanorebar” made of carbon nanofibers. Credit: F. Sanchez, Vanderbilt University; ACerS Bulletin.

President Obama announced the launch of a Materials Genome Initiative during his speech at Carnegie Mellon University last week when he also announced the launch of the Advanced Manufacturing Partnership. (Read our report on the AMP announcement). The goal of the MGI, he said, is to “to help business develop, discover and deploy new materials twice as fast…”

Stating the obvious — This is great news for the materials science and engineering community.

The president did not say much more about the MGI than the above quote, but the White House released a white paper the same day, “Materials Genome Initiative for Global Competitiveness (pdf),” written by an ad hoc committee of the National Science and Technology Council (a Cabinet-level cross-agency entity). In the press release announcing the MGI white paper, the White House says “current “time-to-market” from discovery to deployment for new classes of materials is far too slow, given the range of urgent problems that advanced materials can help us solve.”

The white paper presents a vision for “how the development of advanced materials can be accelerated through advances in computational techniques, more effective use of standards, and enhanced data management.” Envisioned is a comprehensive collaboration among stakeholders, from theorists to R&D labs to manufacturers that will encompass academia, small and large businesses, professional societies and government.

In broad strokes, the paper addresses key issues like materials deployment and acceleration of the materials continuum by developing a materials innovation infrastructure, achieving national goals with advanced materials and preparing the next-generation workforce. A six-point action plan outlines activities that will be coordinated by DOD, DOE, NSF and NIST. The president has written $100M into his FY12 budget to launch the MGI (but it is not clear whether this is included in the $500 million AMP funding request for FY12).

Computational tools are expected to be used extensively to get around the time-consuming and repetitive experimentation that is inevitable but necessary to the development and testing of new materials. The authors of the white paper observe that researchers need to have access to large data sets for accurate simulation and modeling, and that there is no standardized mechanism for sharing algorithms, models or data at present.

Getting good data to feed into models is easy to say, hard to do.

In the March 2011 issue of the Bulletin, the article “A perspective on materials databases,” addresses the issue of data, noting the importance of easy access to reliable materials property data, but large volumes of data are hidden in widely dispersed or unavailable databases. The provenance of available data is often unknown, so the quality of conclusions drawn from such data is also unknown. Old data with well-known provenance still can prove to be insufficiently well-known. The example of 96 percent alumina is given. The composition of the remaining 4 percent can matter enormously, but is not always known. Often processing and preparation information that can affect properties is missing.

The NSF is working to resolve this dilemma by requiring its investigators to include a plan for data sharing in their proposals. The article’s authors admit that the cost of developing and maintaining a comprehensive data system is a formidable obstacle, one which the MGI should help mitigate.

There are plenty of examples of computational tools being used already for materials engineering. In the May 2010 issue of the Bulletin, the article “Atomic-scale computational modeling of cement and concrete,” describes the application of ab-initio and molecular dynamics methods to the engineering of the concrete and cement, materials that nearly everyone worldwide knows. Nanoscale engineering of skyscrapers!

The Chicago-based company, QuesTek - with the tagline “Materials by Design” - is an alloy development company that uses computational methods to expedite alloy development including the commercially available Ferrium line of alloys, one which is under consideration for a use as a helicopter gear by Bell Helicopter. QuesTek’s computational know-how is based on the industry-funded research of its founder, Greg Olson, professor at Northwestern University.

Not surprisingly, QuesTek has come out in strong support of the MGI.

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Electron micrographs of the cross-section of magnesium phosphate cement-cylinders. (a) MPC-cylinder without bacteria. (b) Macroporous structure within the inner section of freshly prepared MPC with embedded R. ruber bacteria. (c) Macroporous structure within the inner section of MPC with embedded R. ruber after 19 batch cycles. The arrows mark assemblies of R. ruber bacteria. Credit: Soltmann et al; Adv. Eng. Mat.

For some time, it has been common to use enzymes as a biocatalyst. When the enzymes required are difficult or expensive to extract, the utilization of microorganisms such as bacteria, yeast, or fungi is an alternative.

For many applications, the living cells are immobilized within a stable matrix system. This prevents the embedded cells against culture washout and protects them from external impact like shear forces, pH, or solvents. Besides commonly used natural polymers some porous inorganic matrices have become increasingly important for immobilizing living cells.

Results of former studies have shown that bacteria can be successfully embedded within a very hard concrete matrix and remained viable for a period of four months. This encouraged the R&D organization GMBU and the company InnoTERE (both Dresden, Germany) to investigate the immobilization of microorganisms in cements. The researchers examined the viability and biocatalytic applicability of the bacteria Rhodococcus ruber and the yeast Saccharomyces cerevisiae, in particular their dependence on preparation conditions.

For their investigations, they used magnesium phosphate cement, which can be easily prepared by mixing hard-burned tribasic magnesium phosphate powder and ammonium phosphate solution. Due to the stiffness of the cement matrix bioactive MPC could be very interesting for applications in bioremediation, in biotechnology as bulk material in large columns or reactive walls, or as bioactive cement plaster within sewers.

To evaluate the applicability of MPC for the immobilization of living microorganisms the researchers determined the glucose conversion using immobilized S. cerevisiae and the phenol degradation using immobilized R. ruber.

The results of the study, “Cements with embedded living microorganisms — a new class of biocatalytic composite materials for application in bioremediation, biotechnology” (doe:10.1002/adem.201080040) revealed that the bioactive composite material exhibits good mechanical and chemical stability. The embedded cells survived the embedding within the cement matrix even though the cements showed much slower glucose and phenol consumption in comparison to non-immobilized cells.

Limitations in mass-transfer probably cause the reduced activity of the embedded cells. To overcome such limitations further examinations especially to the size and pore structure are necessary. Nevertheless, combining a cement matrix with living microorganisms very promising biocomposite materials for application in biotechnology can be fabricated.

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