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The world’s carbon dioxide emissions have escalated 38 percent since 1992, climbing from 6.1 billion tons in 1992 to 8.5 billion tons last year, according to DOE’s Carbon Dioxide Information Analysis Center, located at Oak Ridge National Labs. In 1992, the United States headed the list of the world’s top five CO₂ emitters. The rest of the list included (in order of CO₂ emissions) China, Russia, Japan and India, reports CDIAC’s Gregg Marland. “The source of emissions has shifted dramatically,” Marland now says, noting that increased manufacturing and rising energy demands in developing countries - particularly in China and India - have caused the list to be reordered since 1992. According to Marland, China moved to the top of the list in 2006, dropping the U.S. to second place. He says India surpassed Japan for fourth place in 2002 and, by the end of 2008, is expected to take over third place from Russia. This leaves the Soviets in fourth place, with Japan trailing at number five. Unfortunately, the CO₂ emissions race is one competition no nation wants to win.

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We posted about this novel use of carbon nanotubes as audio speakers on Monday, but today we have a video of the real deal, courtesy of the American Chemical Society. The first part of the video shows the transparency of such a speaker. The second part is an illustration of the way the CNTs create the sound by going through rapid heating-cooling cycles instead of vibrations. The third part shows how the sound quality is unaffected by stretching. Finally, the video shows a CNT speaker sewn onto a small, waving flag.

Federal scientists working at PNNL today unveiled results of research that appear to show that carbon dioxide can be permanently stored in deep underground basalt formations with little or no threats to safety. A PNNL news release states that facility staff

“have discovered key factors that show water-saturated liquid CO2, under conditions mimicking deep geologic settings, will plug cracks within the rock that otherwise might allow the hazardous greenhouse gas to escape. . . . [W]ater-saturated liquid CO2 - CO2 gas in a supercritical phase - showed similar or even greater reactivity than observed for CO2-saturated water. The swift chemical reaction detected on metal and oxide surfaces, as well as the silicate surfaces found in basalt rock.”

Pete McGrail, the chief researcher on this project, said more work needs to be done to extend the findings beyond basalt, especially in model development for reactions in the liquid or supercritical CO2 phase: “Although these initial experiments focused on basalt, the principles are not unique to basalts and would apply generally to other reservoir systems and caprocks,” McGrail said. Pilot injection projects are apprently being planned as a followup to this study.

What’s transparent, stretchable, nearly weightless, flexible enough to be sown onto a shirt and plugs into your iPod? Maybe, soon, this may describe one of the best and most durable audio speakers you’ll ever own. A group of Chinese researchers have discovered that, by zapping an audio-frequency current through a carbon nanotube thin film, it can be made into a wispy-thin high-performance loudspeaker that emits sound in a wide-frequency range, operates without moving parts or magnets. Moreover, the phenomenon’s discoverers say the CTN loudspeaker can be bent into numerous shapes, mounted onto a variety of rigid and flexible insulating surfaces – including clothes – and, since it doesn’t vibrate, can even operate when torn, worn or partially damaged. Details of the CTN loudspeakers have been reported in the Oct. 29 online edition of Nano Letters published by The American Chemical Society by KaiLi Jiang and Shoushan Fan, professors at Tsinghua University in Beijing, and their colleagues at Beijing Normal University. The researchers explain how they drew out a thin film from CTN arrays and, then, tested the thin film for acoustic properties. Finding that the nanotube speaker emitted sound, they wondered if it did so in a manner similar to conventional speakers. Testing it with a laser vibrometer, they learned it did not. The CTN thin film did not vibrate. “We attributed this to the thermoacoustic effect,” Jiang says in a Nov. 2 interview with Nanowerk, an online nanotechnology news vehicle. “The alternating current periodically heated the CNT thin films, resulting in a temperature oscillation. The temperature oscillation excites the pressure oscillation in the surrounding air, resulting in sound generation.” Elaborating on this effect, via Newscientist.com, Shoushan Fan explains that when the team passed an alternating current through their CNT thin-film speaker, the film quickly switched back and forth between room temperature and 80°C. These swift temperature changes resulted in pressure oscillations in the air next to the thin-film. Fan reports the team found these thermally-induced pressure oscillations responsible for the sound emitted by the thin-film speaker. He notes that, when fully stretched, the nanotube speaker became transparent, causing the team to envision attaching it to the front of an LCD screen in place of standard speakers. Some of the more “exotic uses” they dreamed up for the speaker, he says, included the possibility stitching it into clothing to create a kind of “singing and speaking jacket.” Despite its many pluses, Jiang says the CNT loudspeaker has one negative – its output frequency doubles that of its input . This makes “the human voice sound strange when a commercial bipolar audio amplifier is used to drive the CNT thin-film loudspeaker,” he reveals in Nano Letters. He describes how this can be solved in a relatively simple manner, however, by adding a direct current bias I0 to the alternating current. Additional challenges will undoubtedly be encountered on the road to commercialization. At present, the researchers say they will focus on developing the CNT thin-film speakers into real products. But production of the material is relatively easy and should be inexpensive:

“One superaligned CNT array grown on a 4 in. silicon wafer can be totally converted to a continuous CNT thin film up to 10 cm wide and 60 m long, which can be further made into approximately 500 loudspeakers with a size of 10 cm by 10 cm! [The speakers] can be tailored into many shapes and mounted on a variety of insulating surfaces, such as room walls, ceilings, pillars, windows, flags, and clothes without area limitations. Furthermore, CNT thin films can also be made into small area devices, such as earphones and buzzers.”

Complete finding and several videos are published online.

VT’s Center for Energy Harvesting Materials and Systems is hosting its 4th Annual Energy Harvesting Workshop Jan 28-29 in Blacksburg, VA. Energy harvesting refers to efforts to tap unused power from industrial machines, human activity, vehicles, vibrating structures and various other environment sources. Workshop organizers say the events bring together leading industries, national labs, defense agencies and NASA. This year, the meeting will focus on:

• Energy harvesting using piezoelectric, inductive, photovoltaic and thermoelectric devices
• Micro Batteries
• Structural health monitoring

What’s “structural health monitoring,” you ask, a new twist from life insurance companies? Nope. SHM is an emerging area of R&D that is centered on the development and use of sensing systems to track the health of structures such as bridges, buildings, dams, tunnels, pipelines, platforms or ships. Sounds interesting! The American Ceramics Society and its Electronics Division have endorsed the workshop. Complete information and registration is available online.