Friday, July 27, 2012

Scientists at KU & TUHH Jointly Fabricate World's Lightest Carbon Material 'Aerographite'

A network of porous carbon tubes that is three-dimensionally interwoven at nano and micro level — this is the lightest material in the world. It weighs only 0.2 milligrams per cubic centimeter, and is therefore 75 times lighter than Styrofoam, but it is very strong nevertheless. Scientists of Kiel University (KU) and Hamburg University of Technology (TUHH) have named their joint creation "Aerographite". The scientific results were published as the title story in the scientific journal "Advanced Materials".

The properties

It is jet-black, remains stable, is electrically conductive, ductile and non-transparent. With these unique properties and it's very low density the carbon-made material "Aerographite" clearly outperforms all similar materials. "Our work is causing great discussions in the scientific community. Aerographite weights four times less than world-record-holder up to now", says Matthias Mecklenburg, co-author and Ph.D. student at the TUHH. The hitherto lightest material of the world, a nickel material that was presented to the public about six months ago, is also constructed of tiny tubes. Only, nickel has a higher atomic mass than carbon. "Also, we are able to produce tubes with porous walls. That makes them extremely light", adds Arnim Schuchard, co-author and Ph.D. student at Kiel University. Professor Lorenz Kienle and Dr. Andriy Lotnyk were able to decode the material's atomic structure with the aid of a transmission electron microscope (TEM).
Despite of its low weight Aerographite is highly resilient. While lightweight materials normally withstand compression but not tension, Aerographite features both: an excellent compression and tension load. It is able to be compressed up to 95 percent and be pulled back to its original form without any damage, says professor Rainer Adelung of Kiel University. "Up to a certain point the Aerographite will become even more solid and therefore stronger than before", he points out. Other materials become weaker and less stable when exposed to such stress. "Also, the newly constructed material absorbs light rays almost completely. One could say it creates the blackest black", acknowledges Hamburg's Professor Karl Schulte.

The construction

"Think of the Aerographite as an ivy-web, which winds itself around a tree. And then take away the tree", Adelung describes the construction process. The "tree" is a so-called sacrificial template, a means to an end. The Kiel-team, consisting of Arnim Schuchardt, Rainer Adelung, Yogendra Mishra and Sören Kaps, used a zinc oxide in powder form. By heating this up to 900 degrees Celsius, it was transformed into a crystalline form.
From this material, the scientists from Kiel made a kind of pill. In it, the zinc-oxide formed micro and nano structures, so called tetrapods. These interweave and construct a stable entity of particles that form the porous pill. In that way, the tetrapods produce the network that is the basis for Aerographite.
In a next step, the pill is positioned into the reactor for chemical vapor deposition at TUHH and heated up to 760 degrees Celsius. "In a streaming gas atmosphere that is enriched with carbon, the zinc oxide is being equipped with a graphite coating of only a few atomic layers. This forms the tanged-web structures of the Aerographite. Simultaneously, hydrogen is introduced. It reacts with the oxygen in the zinc oxide and results in the emission of steam and zinc gas", continues Schulte. The remains are the characteristic interwoven, tube-like carbon structure. TUHH-scientist Mecklenburg: "The faster we get the zinc out, the more porous the tube's wall gets and the lighter is the material. There is considerable scope." Schuchard adds: "The great thing is that we are able to affect the characteristics of the Aerographite; the template form and the separation process are constantly being adjusted in Kiel and Hamburg."

The application

Due to its unique material characteristics, Aerographite could fit onto the electrodes of Li-ion batteries. In that case, only a minimal amount of battery electrolyte would be necessary, which then would lead to an important reduction in the battery's weight. This purpose was sketched by the authors in a recently published article. Areas of application for these small batteries might be electronic cars or e-bikes. Thus, the material contributes to the development of green means of transportation.
According to the scientists, further areas of application could be the electrical conductivity of synthetic materials. Non-conductive plastic could be transformed, without causing it to gain weight. Statics, which occur to most people daily, could hence be avoided.
The number of further possible areas of application for the lightest material in the world is limitless. After officially acknowledging Aerographite, scientists of various research areas were bursting with ideas. One possibility might be the use in electronics for aviation and satellites because they have to endure high amounts of vibration. Also, the material might be a promising aid in water purification. It might act as an adsorbent for persistent water pollutants for it could oxidize or decompose and remove these. Here, scientists would benefit from Aerographite's advantages namely mechanical stability, electronic conductivity and a large surface. Another possibility might be the purification of ambient air for incubators or ventilation.

Wednesday, July 25, 2012

FDA Bans Use of BPA in Baby Bottles & Sippy Cups on ACC's Appeal

The Food and Drug Administration (FDA) recently announced in the Federal Register that it has revised the regulation of bisphenol-A (BPA) in baby bottles and sippy cups, bringing certainty to the marketplace that BPA is no longer in these products. The request to revise the rule was made by the American Chemistry Council (ACC) in October of 2011, in an effort to clarify for consumers that BPA is no longer used to manufacture these products and will not be used in these products in the future.

"Although governments around the world continue to support the safety of BPA in food contact materials, confusion about whether BPA is used in baby bottles and sippy cups had become an unnecessary distraction to consumers, legislators and state regulators," said Steven G. Hentges, Ph.D., of the Polycarbonate/BPA Global Group of ACC. "FDA action on this request now provides certainty that BPA is not used to make the baby bottles and sippy cups on store shelves, either today or in the future."

BPA is one of the most thoroughly tested chemicals in commerce today. The consensus of government agencies across the world is that BPA is safe for use in food-contact materials, including those intended for infants and toddlers.
State legislative and regulatory actions across the country had contributed to confusion about whether baby bottles and sippy cups sold in the United States contain BPA. In fact, manufacturers of baby bottles and sippy cups announced several years ago that due to consumer preference they had stopped using BPA in these products.

Sunday, July 15, 2012

White Rot Fungus Boosts Ethanol Production from Cellulosic Plants, Find Researchers

Scientists are reporting new evidence that a white rot fungus shows promise in the search for a way to use waste corn stalks, cobs and leaves — rather than corn itself — to produce ethanol to extend supplies of gasoline. Their study on using the fungus to break down the tough cellulose and related material in this so-called "corn stover" to free up sugars for ethanol fermentation appears in the ACS' journal Industrial & Engineering Chemistry Research.

Yebo Li and colleagues explain that corn ethanol supplies are facing a crunch because corn is critical for animal feed and food. They note that the need for new sources of ethanol has shifted attention to using stover, which is the most abundant agricultural residue in the U.S., estimated at 170-256 million tons per year. The challenge is to find a way to break down tough cellulose material in cobs, stalks and leaves — so that sugars inside can be fermented to ethanol. Previous studies indicated that the microbe Ceriporiopsis subvermispora, known as a white rot fungus, showed promise for breaking down the tough plant material prior to treatment with enzymes to release the sugars. To advance that knowledge, they evaluated how well the fungus broke down the different parts of corn stover and improved the sugar yield.
Treating stover with the white rot fungus for one month enabled them to extract up to 30 percent more sugar from the leaves and 50 percent more from the stalks and cobs. Because corn leaves are useful for controlling soil erosion when left in the field, harvesting only the cobs and stalks for ethanol production may make the most sense in terms of sustainable agriculture, the report suggests.

Thursday, July 12, 2012

CO2 Polymers - Novel Options for Plastic Industry - A Challenge to Sustainable Chemistry

The world's largest conference on "CO2 as Feedstock for Chemistry and Polymers" (Haus der Technik Essen, 10-11 October 2012) covers an incredibly wide range of uses for CO2, developing a vision for a sustainable carbon dioxide economy.
Carbon dioxide (CO2) emissions, the end product of burning fossil fuels or biomass, are largely responsible for the greenhouse effect and thus for climate change. A reduction in CO2 emissions are therefore at the very top of the international political agenda. Trials are running in parallel to explore underground sequestration of CO2 from power stations, thereby removing it from the atmosphere.
It would at first sight seem paradoxical to wish to use energy-poor, inert CO2 molecules. Considerable research and development efforts in recent years have led to new and innovative CO2-recycling technologies and a vision of a CO2 economy. CO2 recycling has quickly become a hot topic for the future for every large company in the chemicals and plastics sector. Wirtschaftswoche reports that even Novel prize winners George Olah and Joseph Stiglitz have recognized the gas as a future fuel and raw material of the chemical industry.
In the last three years, the US Department of Energy and the German Ministry for Research (BMBF) have each provided some €100 million for research into new uses for CO2. These investments are already bearing fruit. Evonik, BASF and Bayer Material Science are working hard on CO2 polymers. Siemens and BASF demonstrated the first applications in household appliances such as fridge compartments and vacuum cleaner casings at the ACHEMA fair in Frankfurt in June 2012. The automobile and aircraft industries are working on fuels that depend on neither from oil nor biomass, but are instead derived from solar and wind power — and CO2. These are also early days for a new chemical sector: recycling — the cascade use of CO2 as a raw material for the chemical industry. Now new chemical and electrochemical reactions must be discovered and further technologies developed (e.g. the efficient separation and purification of CO2 from the emission flow) to turn the climate killer into a renewable resource.
Alessandra Quadrelli from Lyons University sees CO2 as one of the most important raw materials for the chemical industry in the future. According to her calculations, innovative chemical uses of CO2 could achieve up to 10% of the global reduction in greenhouse gases that is required.

CO2 polymers — new options for the plastic industry

The main new CO2 polymer is polypropylene carbonate (PPC), which were first developed 40 years ago by Inoue, but is only now coming into its own. PPC is 43% CO2 by mass, biodegradable, shows high temperature stability, high elasticity and transparency, and a memory effect. These characteristics open up a wide range of applications for PPC, including countless uses as packing film and foams, dispersions and softeners for brittle plastics. The North American companies Novomer and Empower Materials, the Norwegian firm Norner and SK Innovation from South Korea is some of those working to develop and produce PPC. Bayer Material Science exhibited polyurethane blocks at ACHEMA, which were made from CO2 polyols. CO2 replaces some of the mineral oil use. Industrial manufacturing of foams for mattresses and insulating materials for fridges and buildings are due to start in 2015.

PPC as a softener for bioplastics

Many bio-based plastics, e.g. PLA and PHA, are originally too brittle and can therefore only be used in conjunction with additives for many uses. Now a new option is available. They can cover an extended range of material characteristics through combinations of PPC with PLA or PHA. This keeps the material biodegradable and translucent, and it can be processed without any trouble using normal machinery. The vacuum cleaner casings that Bosch Siemens Household Appliances (BSH) displayed at ACHEMA are predominantly made of BASF's PPC and PHA and are intended as a substitute for the bulk plastic ABS. The first internal lifecycle analysis studies demonstrate the material's clear advantages. PPC/PLA combinations were used in fridge compartments.

Fuel from wind power, solar power and CO2

An outside energy source is required if CO2 is to be used as fuel. The major option here is to use surplus wind and solar power, which frequently occurs in Germany. Storage is a central concern with the expansion of renewable energy. If the surplus electricity is used to produce hydrogen (H2) from water, this can then be converted into various fuels in conjunction with CO2. The first reaction is that of H2 with CO2 to form methane (CH4), which can then fed into the gas network. Further chemical processes lead to methanol, petrol, diesel and kerosene. The high temperature steam electrolysis that is being optimized in the BMBF project now achieves a 70% efficiency level (electricity to hydrogen).
In 2011 a consortium of businesses in Iceland began building the first commercial plant, which will produce 5 million liters of methanol per year from CO2. That would cover 2.5% of Iceland's fuel needs.

CO2 as growth substrate for algae and bacteria

However, the world's largest use of CO2 takes every day right in front of our eyes. With the help of photosynthesis (and with the action of sunlight), plants convert carbon dioxide into sugar, which they then use to produce all the important bio-molecules. This can also be commercially exploited: in large-scale reactors algae are gassed with carbon dioxide from power stations and then produce biomass.
Some bacteria can also use CO2. The metabolism of these so-called acetogenic bacteria enables them to use CO2 along with a carbon monoxide/hydrogen mixture (synthesis gas) as a growth substrate and as a basis for producing various products such as acetone, butanol and ethanol. A joint project between RWE and biotech company Brain was able to isolate numerous strains of bacteria in power station chimneys that could serve this purpose. Changes through molecular engineering to the bacteria can also lead to products other than the normal end products — for example the acrylic acids needed to produce PMMA (a polymer better known as plexiglass) and the biopolymer PHB. Synthetic biology methods should even allow for the production of customized bacteria in future for optimal CO2 efficiency. Evonik in particular is working on the production of various chemicals, while the New Zealand firm LanzaTech is developing aircraft fuel and specialty chemicals based on butanol derived from CO2 fermentation.