Archive for July 2011
You are browsing the archives of 2011 July.
You are browsing the archives of 2011 July.
Here is what we are hearing:
NexTech has been awarded the International Organization for Standardization 9001:2008 certification for its Quality Management System. Recognizing the quality needs of its clients, NexTech has voluntarily registered with ISO to provide independent assessment of our quality processes.
Corning Incorporated has approved a capital expenditure plan of approximately $170 million to expand the Corning Shanghai Company Limited facility and to increase its capacity to manufacture emissions control substrates for light-duty (automotive) passenger vehicles. This expansion is expected to be complete and operational in the third quarter of 2013.
Unifrax LLC, the Niagara Falls, NY based manufacturer of ceramic fiber insulation products, announced today that it has entered into an agreement to acquire Super Saffil Limited and Saffil America Inc. from Dyson Group plc. Saffil develops, manufactures and sells innovative, high-temperature polycrystalline wool materials to a global customer base. It has two main business units: Saffil Automotive and Saffil Fiber. The Saffil business has a rich history based upon its high-performance Saffil High-Alumina Fiber and Ecoflex product lines. Saffil products are used in a wide variety of applications in both the industrial insulation and automotive emission control support mat markets.
Morgan Technical Ceramics is offering ceramic cores made with its proprietary P-52 material. Ceramic cores produced with P-52 exhibit greater dimensional accuracy while maintaining tight tolerances without distortion, making them ideal for use in investment casting of aerospace engine components. The material does not prematurely deform, which is critical, given the extremely high temperatures required for superalloy engine component production. The cores can be chemically dissolved after the casting has cooled, leaving the clean air passage replica needed in today’s efficient turbine engines.
Riedhammer will deliver a foam glass production plant consisting of two fast-firing tunnel kilns with belt conveyance, as well as the associated mixing and dosing technology for the production of foam glass gravel. Over the past 10 years Riedhammer GmbH has developed and supplied equipment for the production of foam glass.
Monday was a busy day at the Cements Division meeting, hosted by Vandy’s Department of Civil and Environmental Engineering, with lots of great presentations, a lively Della Roy Lecture by Karen Scrivener (I’ll write about this in another post) and a division meeting where new officers and award winners were announced.
The officers for 2011-2012 are:
Besides the talks presented, as I mentioned in an earlier post, Division leaders challenged the audience to launch a discussion on “Future Directions for Cementitious Materials.” The challenge to identify the most important areas of future research, advancements, education and multidisciplinary work seemed to be enthusiastically embraced by the crowd beginning with an hour group discussion to identify three or four topic areas, each of which would be fleshed-out during focused small-group meetings during the Monday and Tuesday lunch periods.
The initial discussion—in the large-group setting—fairly easily narrowed in on four potential strategic avenues of interest (the exact wording may be a little off here): 1) Multiscale modeling; 2) Hydration mechanisms (particularly in regard to supplementary cementitious materials); Best practices (particularly in regard to examining and comparing data sets, test beds and cases, building data repositories); and Sustainability (particularly in regard to the use of SCMs).
Each of these was then discussed in smaller groups over lunch, Monday, with the discussions to continue at lunch today. I was only around Monday, but it appeared that all of the groups were making progress and starting to layout some suggestions for plans that would be reported out. My understanding is that division leaders and other volunteers will attempt to gather these ideas and start developing some specific proposals for collaborative efforts, white papers and funding proposals, at least in time for next year’s meeting.
Speaking of the 2012 Cements Division meeting, the hope is to hold it in June in Austin, Texas.
As part of the meeting’s activities, the division announced the winner of its 2010 Stephen Brunauer Award for best cements paper published by ACerS during the previous year. The winning paper, First-Principles Study of Elastic Constants and Interlayer Interactions of Complex Hydrated Oxides: Case Study of Tobermorite and Jennite (doi:10.1111/j.1551-2916.2009.03199.x) appeared in JACerS and was written by Rouzbeh Shahsavari, Markus J. Buehler, Roland J.-M. Pellenq and Franz-Josef Ulm, who are connected with the Department of Civil and Environmental Engineering at MIT and the Centre Interdisciplinaire des Nanosciences at CNRS-Marseille Université (France).
One of the highlights of the meeting was the announcement that two members of ACerS’ Cements Division will be members of the Society’s class of Fellows for 2011. Kim Kurtis and Joe Biernacki will be inducted along with other new Fellows during ceremonies at the ACerS Annual Meeting and Awards Banquet on Oct. 17, 2011.
Finally, the meeting organizers recognized six poster presenters for the exceptional quality of their work:
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:O2-, traps O2- ions but has no charge carriers in the molten state because CaO and Al2O3 are stable, electrically insulating oxides.
By reacting C12A7:O2- 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:O2- 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.
Today I am at the Cements Division’s annual meeting being held at Vanderbilt University in Nashville, Tenn. The meeting, which began yesterday afternoon and runs through Tuesday, is held in conjunction with the Center for Advanced Cements-Based Materials.
I made it into Nashville late enough to miss the worst of the sweltering heat, but I still arrived in time to catch the well-attended poster session and reception. One quick observation is that there were quite a few posters on testing and characterization plus several groups looking at the use of various additives (e.g., TiO2) and reinforcement materials (e.g., carbon nanotubes).
Besides the 28 posters, the meetings has 41 talks organized into six different sessions, so the 105+ in attendance have plenty to choose from.
Tonight, the big event is the Della Roy Reception and Lecture (sponsored by Elsevier). The division is honoring the work Karen Scrivener of the Ecole Polytechnique Fédérale de Lausanne, Switzerland, who will be presenting, ”Modeling Hydration Kinetics of Cementitious Systems.”
All the above is pretty much standard meetings fare, but the Cements Division and ACBM have added an unusual twist today with the purpose of exploring the “Future Directions of Cementitious Materials.” The program chairs have organized a working lunch session today with followup sessions Tuesday to explore the following questions:
Those are some hefty questions, and when I spoke to the division leaders last night they acknowledged that even if consensus is elusive, just having these discussions will be a step forward and, it is hoped, will lead to some roadmaps, white papers and collaborative research opportunities. Organizers mention that they hope, for example, that the discussions lead to the development of new research need statements for submittal to the National Cooperative Highway Research Program.
Mathematics—the common language of science and engineering—often proves to be the doorway between disciplines. The common ground between a skyscraper, an airplane wing, and facial bones may not seem obvious until one realizes that from a structural perspective, they are all framework systems that must support and transmit loads within certain constraints. By breaking a structure into trusses, nodes, forces, etc., the mathematics transcends the application, and modeling principles can be applied broadly.
A story on the NSF website describes a study that demonstrates the use of topological optimization to “engineer” new faces when facial bones are destroyed by severe injury or disease. The standard surgical approach to craniofacial repair has been to take part of a larger bone from the patient and sculpt it to shape for implantation, an imperfect approach that may leave the patient improved but still significantly deformed.
“The middle of the face is the most complicated part of the human skeleton. What makes the reconstruction more complicated is the fact that the bones are small, delicate, highly specialized and located in a region highly susceptible to contamination by bacteria,” says Glaucio Paulino in the story. Paulino is program director of the mechanics of materials program at the NSF, professor of civil and environmental engineering at the University of Illinois, Urbana-Champaign and one of the PIs on the study.
Topological optimization takes into account limiting factors, such as available space, applied force, load and layout constraints. From the story, “Imagine a building grid in which you can determine where there should be material and where there shouldn’t. Moreover, you can express loads and supports that would affect certain parts of this block of material. Your final result is an optimized structure that fits your established constraints.”
In a PNAS paper (pdf) published in 2010, Paulino and his colleagues from Ohio State University’s School of Medicine demonstrated the feasibility of using the method to custom design a bone replacement for a massive facial injury. In the conclusions of the paper, they also note that the computational algorithms can be expanded to include other critical variables like oxygen levels, surgical flaps, aesthetics and even cost.
(This fascinating 40-second video shows the transformation of a block into a complex upper jaw prosthesis.)
This approach to designing the prosthetic’s structure dovetails very nicely with work already being done in the materials community on additive manufacturing and laser-based manufacturing fabrication of surgical implants.
At the Fraunhofer Institute in Germany, studies are showing that selective laser melting can be used to fabricate a porous polylactide-tricalcium phosphate composite that the body absorbs as natural bone grows into the scaffold. Structures have been assembled that can close openings of up to 25 cm. Selective laser melting is an additive manufacturing process that uses three dimensional CAD renderings to guide a laser beam through a powder bed to melt powders into a dense component.
The Roger Narayan group at the combined UNC-NC State biomedical engineering department is using two-photon polymerization to synthesize polymeric and zirconia shapes for medical applications. Two-photon polymerization uses laser radiation to initiate chemical reactions, polymerization and hardening of a material to build submicrometer structures.
There are commercial examples, too, of rapid prototyping fabrication of customized surgical implants. TMJ Concepts manufactures temporomandibular joint prostheses from titanium using computer numerical control machining based on patient CAT scans.