what does every1 think of this in relation to our super bugs?
From the Chief Executive
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- New ways of seeing with X-rays
- Making tougher bucket liners for the mining industry
Know your Materials
- Metallic glass
- The foam that killed a shuttle
- The fine art of stripping
Future Materials People
- A life-long love affair with materials - Dr Vladimir Golovanevskiy
- Exploring Materials with ANU
- Eureka for materials engineering journalism
A student at the Australian National University holds up specimens of bulk metallic glass, a new wonder material.
Know you Materials Metallic glass
In the last decade a new class of wonder materials called metallic glasses have begun to emerge from materials labs around the world. They exhibit properties of incredible strength and elasticity, and are promoted as a true wonder material.
Conventional metals have a crystalline structure in which the atoms are lined up in neat, orderly arrays; the bulk of these standard metals typically consists of small regions of aligned atoms, called grains, and the boundaries between them. Within metallic glass, however, atoms are packed together in a somewhat random fashion, similar to that of a liquid. Research indicates that the prized physical properties of metallic glasses (also known as amorphous metal) arise in large part from their lack of grain boundaries, which can serve as points of weakness.
Unlike conventional metals, which are usually cooled slowly until they fully solidify, metallic glasses must be cooled very rapidly and very uniformly to freeze their random atomic pattern in place before crystallisation occurs due to the nucleation and growth of crystal grains. When this phenomenon were first being explored, some 40 years ago, the only way to extract heat fast enough to maintain the metal's random state was to keep the material very thin. It was produced by splat cooling in which droplets of molten metal were quickly frozen on a cold surface. Continuous amorphous metal ribbons less than 0.1 millimeter thick could also be formed at a cooling rate of 1 millionįC per second. The ribbons were wear-resistant and possessed interesting magnetic properties but the high fabrication cost meant it never found any commercial application.
Over the past decade, methods have been developed to produce metallic glasses in bulk based on mixes of zirconium, magnesium, aluminum, and iron. Early approaches to bulk fabrication were mostly empirical in nature, but researchers gradually began to understand that the correct choice of elemental constituents would lead to amorphous metals amenable to cooling rates as slow as 1 - 100įC per second. These slower cooling rates mean that large parts can be fabricated. Furthermore, many of these metallic glasses remain stable against crystallisation when heated to temperatures somewhat above their glass-transition temperatures.
One of the general guiding principles to designing alloys that form bulk metallic glasses is to pick elements with dramatic differences in size, which leads to a complicated structure that crystallises less easily. A beryllium atom, for example, is much smaller than a zirconium atom. One common mix of these new bulk metallic glasses is two-thirds zirconium, one-fifth beryllium, and the remainder split among copper, titanium, and nickel.
These new bulk metallic glasses exhibit high strength-to-weight ratios and hardness, extreme springiness and rebound characteristics, and good acoustic-dampening properties. They're being considered for a range of applications including golf-club heads, amour piercing ammunition casings and surgical prosthetics.
Unfortunately, the Achilles heel of this wonder material is that it has an extremely low resistance to crack-initiation-the propagation of a crack once it has formed. When it fails, it fails catastrophically. To fill this hole a range of strengthening materials are being considered to add to bulk metallic glasses (BMG), and one technique being investigated is rods of BMG reinforced with tungsten wire.
*********** also good other links listed in post BUT about health life 1 i think it was called - to me really wreaks of CDC behind it to convince us of otherwise acceptable explanation so we'll leave it all be for their sake.especially when they put in red capital letters seperate from rest of infon that he personally rang cdc & spoke with an absolute professional in this field and they completley 100% exactly confirmed his theory to be true ---i don't think so!!!!!!!!
y wouldn't the world have been enlightened to this on the news and us crazies put in our place straight away in relation to our suspicions- little too convienient & i bet they wouldn't tell you the name of this cdc worker ever!!!!!