US researchers have synthesised a chunk of diamond that would have Marilyn Monroe clones the world over coming to see it. The 1600 carat diamond is almost thirty centimetres long and about 1.5 millimetres thick and puts to shame even the fieriest of engagement rings. James Adair and Rajiv Singh of the Materials Science and Engineering Department at the University of Florida at Gainesville are just two of a growing band of researchers devising ways of creating artificial diamonds in the laboratory. They hope the techniques they develop will have applications in everything from the computer to the aerospace industries.
Diamond is still the hardest known material, despite theoretical predictions that certain carbon nitrides might be harder and as such has many applications in heavy industry as an abrasive and a coating for cutting tools. It also has a high thermal conductivity and if doped with the right additives is an excellent semiconductor.
These latter properties have opened up the possibility of using diamond as heat sinks and or instead of silicon as the next material for computer chips. The thermal properties would help keep the chips cool allowing microelectronics designers to cram more and more computing power on to a single chip.
Instead of the usual high temperature and pressure technique for making synthetic diamond, the researchers use chemical vapour deposition (CVD). In this method a hydrocarbon material is blasted to bits, usually in a hydrogen atmosphere, allowing active carbon species to condense like dew on a silicon substrate forming a crystalline layer.
Adair and Singh say that making the biggest synthetic diamond was not done just for fun. Taking slices from large diamond layers would make producing diamond semiconducting chips or heat sinks a far
more commercially viable process than having to make each from scratch.
Meanwhile, University of Bristol researchers, Mike Ashfold and Paul May and their colleagues have used chemical vapor deposition (CVD) to coat tungsten wires with a layer of diamond opening up another facet of diamond research. When they dissolve away the tungsten they are left with tough tubes of diamond.
According to May such materials in composite fibre form might be used to reinforce engine parts or support structures in aircraft without adding excess mass. Diamond's radar invisibility lends it ideally to military stealth applications.
It might be some years before our readers have to worry about hip replacement operations themselves but for the unfortunate people with bone wasting diseases or who are involved in accidents in which bones are damaged irreparably a nice heavy chunk of titanium alloy coated with ceramic and glue inserted as a surrogate body part is not the most satisfactory of options.
Chemists at the University of Nottingham are working with Russian scientists on a method for coating much lighter polymer materials with hydroxyapatite, the mineral that makes up the bulk of living bone.
Steve Howdle and his colleagues are using lasers to deposit the mineral on to test materials to create biocompatible surfaces that would be integrated into the surrounding tissue following transplant. They hope this would lead to minimal risk of rejection.