What is Tungsten?
Tungsten is an elementary metal which has found many uses in industry and our daily lives over the years. It's typically found in natural ores such as wolframite in mines all over the world. Tungsten is extremely heat resistant, having the highest melting point of all non-alloy metals in the world. This makes it perfect for jobs in high energy or high electricity environments. The filament in incandescent light bulbs are most commonly made from tungsten thanks to their ability to hold shape at such high temperatures. Though about as tough as steel when pure, when combined in a compound such as tungsten carbide, it's nearly indestructible. As a result it's used for drill heads in major mining and oil drilling as well as other high-stress work.

What are Tungsten Rings?
Tungsten rings are a decorative affectation which are becoming more popular with men throughout much of the world. Such rings are taking the place of class rings and wedding bands thanks to their durability. They should not be mistaken for being made from pure tungsten, as they're really tungsten carbide. This compound, once shined, will never dull, scratch, rust, or discolor. It's also completely hypo-allergenic. The reason for their popularity is as much an issue of symbolism as practicality. Gold wedding bands have a tendency to deform over time. One made from tungsten-carbide will not, giving the impression that the marriage union which the ring represents will endure as well.

How are Tungsten Rings Made?
Ground tungsten and carbon are poured into a metal die cube containing a ring mold. The mold is subjected to high pressure to push the powder together into a solid ring blank. The blank is then fired in an oxygen-powered furnace at temperatures exceeding 6,000 degrees Fahrenheit. Only at this obscenely high temperature will the blank's component elements intermingle and solidify as one. Once cooled, any burs or extra metal is removed with high-powered diamond edged saws. Diamond powdered files and sanders are then used to polish the ring until it shines. With this done the ring is ready to be worn. It should be noted that since such rings cannot be re-sized, each one must be constructed to order if it's to be a perfect fit.

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Background
Tungsten-filament bulbs, although the most widely used light source in the world, are inefficient, generating more heat than light. However, a new microscopic tungsten lattice developed at the Department of Energy’s Sandia National Laboratories has been shown to have the potential to redirect much of this wasted heat energy into visible light.

Increased Efficiency
This could raise the efficiency of an incandescent electric light bulb from 5% to greater than 60%. In doing so it would greatly reduce the world’s excess consumption of electrical power by inefficient lighting, and the accompanying environmental impact caused by CO2 emissions.

Fabrication of the New Lattices
The first step toward this goal, achieved at Sandia by Shawn Lin and Jim Fleming, was reported in Nature in May. The tungsten lattice device was built using an extension of well-known microelectro-mechanical systems technologies that themselves have been derived from mature semiconductor technologies. As a result, fabrication of such devices could be cheap and easy.

The tungsten structures, usually made out of silicon, consist of tiny bars fabricated to sit astride each other at regular pre-set distances and angles. Together, these form an artificial crystal. The spacing of the bars allows passage of only certain wavelengths of radiation they pass through but can also change direction as defects in the artificial crystal cause the light to follow the defect.

The Lattice’s Ability to Stop Other Frequencies
A further question considered by Lin and Fleming, with assistance from colleagues at Ames Laboratories in Iowa, was the tungsten lattice’s capability of ‘stopping’ other frequencies. If the crystals were built of tungsten, the metal could handle quite high temperatures and have a large and absolute photonic band gap in the visible range, where it is already known to emit light. But what would happen to the other, lower-wavelength radiation brought in by an electric current? Would the structure melt, or would the thermally excited tungsten atoms somehow prefer to reinforce emissions at higher wavelengths, such as in the visible frequency range?

Energy at the edge of the photonic band was observed to undergo an order-of-magnitude absorption increase energy was being preferentially absorbed into a selected frequency band. Meanwhile, periodic metal-air boundaries led to a large transmission enhancement. Experimental results show that a large photonic band gap for wavelengths from 8 to 20 microns proves ideally suited for suppressing broadband blackbody radiation in the infrared and has the potential to redirect thermal energy into the visible spectrum.

Results and Prospects
Lin and Fleming are delighted with the results, although the theory for the effect - re-partitioning energy between heat and visible light - remains unexplained. ‘It’s not theoretically predicted,’ says Fleming. ‘Possible explanations may involve variations in the speed of light as it propagates through such structures.’

Although the work was carried out with light in the mid-infrared range, no theoretical or practical difficulties are known to exist in downsizing the structure into the visible light range.

from www.azom.com

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Nanoparticles of tungsten carbide and tungsten carbide cobalt can enter cultured mammalian cells. These are the findings of a study conducted by researchers from the University of Dresden, the Leipzig-based Helmholtz Centre for Environmental Research and the Fraunhofer Institute for Ceramic Technologies and Systems in Dresden.

The results further show that pure tungsten carbide nanoparticles do not have cytotoxic effects. Only when the nanoparticles are mixed with a toxic substance, metallic cobalt in this case, are cytotoxic effects observed. The in vitro study, which was published in the renowned journal Environmental Health Perspectives, examined the effect of tungsten carbide and tungsten carbide cobalt nanoparticles with an aggregate size of 150 nanometres on cell lines of human lung, skin and intestinal cells and of primary cultures of rat brain cells.

Tungsten carbide is used primarily in the heavy metal industry for the manufacture of tools. The addition of cobalt increases its toughness and strength. During the manufacture process workers may be exposured. But until now, no scientific findings on the effects of nano-sized particles of the material have been available. Before nano-grained materials are used on a large scale, the risks to humans and the environment need to be investigated and taken into account.

The chemical and physical studies confirmed that both tungsten carbide and tungsten carbide cobalt particles are stabilised by albumin or serum in nutrient solutions. Adding albumin to the nutrient solutions makes it possible to carry out research in conditions that are very close to those found in exposed organisms. Using electron microscope methods it was possible to detect uptake of the particles by the cells under investigation.

Subsequent biological tests showed that tungsten carbide nanoparticles alone are not acutely toxic, whereas combinations of these particles with cobalt did have toxic effects at high particle concentrations. The toxicity of the WC-Co mixture was higher than that of similar concentrations of cobalt ions. It is not yet entirely clear why the combination of tungsten carbide and cobalt is more toxic. It is possible that nanoparticles act as a Trojan horse, i.e. they increase the cell's uptake of toxic cobalt ions. Further research is needed to clarify the effect of particle size and combination effects in order to draw conclusions about possible consequences for health risk assessments.

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The Democratic Republic of Congo (DRC) is a country rich in natural resources, including large deposits of tin, tantalum, and tungsten -- metals used to manufacture many of the electronics found in U.S. homes, such as laptops, cell phones, iPods and digital cameras.

U.S. and international electronics companies purchase significant quantities of these metals from the DRC, despite a ten-year civil war that has cost an estimated 5.4 million lives. Rebel groups perpetuating the country's conflict are funded by profits from mining activities, and by unwitting American consumers who purchase electronics using minerals sourced from mines in eastern DRC.

The Congo Conflict Minerals Act, recently introduced by Senators Sam Brownback (R-KS), Richard Durbin (D-IL) and Russ Feingold (D-WI), would require electronic companies such as Apple, Nokia and Nintendo, to report the exact location of mines in DRC from which they receive tin, tantalum and tungsten. This publicly available information would inform consumers whether the electronics they purchase originate from conflict zones in the DRC.

Passing the Congo Conflict Minerals Act, if accompanied by sufficient publicity, would likely have a significant impact on consumer (and eventually, corporate) behavior. As evident from the effective embargo on blood diamonds from Sierra Leone, many Americans and Europeans are conscientious consumers, sensitive to breaking the link between conflict and natural resources. U.S. and international companies also have reputational concerns. The SEC is a principal source of company information for potential investors.

Under this Act, all SEC-listed companies would be required to fully disclose the amount of money paid to foreign governments for oil, gas, and minerals in their required financial statements. Such transparency would allow companies to build solid reputations based on partnering with governments response to their citizens' needs and concerns. The Act would also mark an important step in ensuring sound revenue management, and fighting the corruption that hinders African countries from translating resource wealth into economic growth.

The pressing reality in eastern DRC, where on Monday Hillary Clinton met victims of one of the world's worst conflicts, underlines the urgency for precedent-setting U.S. action requiring companies to report on their financial flows into war-torn regions.

Despite a nine-year presence by the world's largest United Nations peacekeeping operation -- 18,422 personnel at an annual cost of $1.2 billion -- rebel forces in DRC continue to terrorize innocent citizens. Over one million women and children have become victims of sexual assault and rape in eastern DRC.

Lack of good governance in eastern DRC has played a significant role in allowing these atrocities to occur. Based on research by the World Resources Institute and our local partner organizations in Africa, we believe the Congo Conflict Minerals Act and the Extractive Industries Transparency Disclosure Act would provide a powerful platform for U.S. development assistance to work with governments to ensure revenues from natural resources contribute to economic growth and poverty reduction.

Ending the conflict in DRC is a long-standing and high-priority U.S. policy objective. In October 2006, then-President George Bush argued that the conflict constituted "an unusual and extraordinary threat" to our foreign policy. President Obama's administration has made its concern equally clear, hence the secretary of state's visit.

Strong Congressional support is needed now to prioritize and pass both the Congo Conflict Minerals Act and the Extractive Industries Transparency Disclosure Act. While iPods and cell phones are integral in our daily lives, our convenience should not be bought at great detriment to others.

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