In MatSciEng: New Materials in Health and Safety

The MSDS diamond, including flammability, health, reactivity, and protective equipment information.

Despite best efforts and intentions, design and engineering for the lifetime of materials are sometimes incomplete.  In those cases, new materials can be introduced to refine and supplement the old materials or correct them entirely.  When health and safety are at risk, such new materials become the focus of international research and development effort.  In this post I've written about some new work and on-going investigation surrounding new materials in health and safety.

Nuclear Waste Storage in Clay 

A great deal of work is constantly on-going to study and monitor the safe storage of radioactive isotopes.  Care of ScienceDaily, Reich et al from the Gutenberg University Mainz have found that, in addition to other natural materials, natural clay materials can be used as storage for nuclear waste.  More specifically, it has shown that Opalinus Clay (a "Jurassic claystone" or weak mudstone) has the ability to sorb radioactive Plutonium (Pu) and Neptunium (Np) of select oxidation states from aqueous solutions.  For example, Neptunium, "...hardly diffuses through the clay, and even after a month is still almost where it started."  Longer investigations are always required when studying nuclear waste storage; for example, the radioactive half-life for Neptunium is 2.14 million years.

Replacement Coatings of Hexavalent Chromium (Cr)

Chromium metal exists most most commonly in the hexavalent oxidation state.  Hexavalent chromium is also a known human carcinogen via inhalation.  As a result, there is a great deal of motivation to find a replacement metal with similar properties, mechanical and otherwise.  However, the most common forms of hexavalent chrome are coatings - either in the electrolytic hard chrome (EHC) or decorative form - which possess a unique set of properties not easily replaced.  While some solutions do exist as partial replacements, a great deal of work is still on-going in aerospace, defense, and commercial markets to find a complete replacement for hexavalent chrome.   

Nanofiber Materials to Detect Chemical Hazards 

In a recent issue of the journal Advanced Materials [1] (also at ScienceDaily), Kelly et al have used porous Silicon (Si) filters as templates for the fabrication of carbon nanofibers.  These nanofibers have been demonstrated as sensors for hazardous chemical compounds.  More specifically, the nanofibers act as sensors for organic vapours which can cause neurological harm upon inhalation.  In application, such nanofibers can add supplementary information on whether activated charcoal air filters have expired or otherwise ceased to provide protection.

Composite Materials Extract Contaminants from Drinking Water 

Also over at ScienceDaily, a new composite 'multiphase' material has demonstrated the ability to extract radioactive and hazardous impurities - namely, radioactive iodide and arsenic - from drinking water.  Engineered by Drs. Pawlak and Venditti from NCSU, the material is made from natural and biodegradable material components hemicellulose and chitosan.  In addition, the internal structure of the 'multiphase' material is a foam, which possesses an increased surface area which likely helps increase the extraction efficiency.

Replacement of Cadmium (Cd) Metal Coatings

Similar to the work done to replace hexavalent Chromium, Cadmium (Cd) metal is also a target for replacement.  Cadmium is applied to a wide range of steel parts requiring corrosion protection, ranging from simple nuts and bolts to high-performance aircraft and defense components.  However, Cadmium itself is a toxic metal which can be released from the parts to the environment when in use.  Like Chromium, Cadmium has a unique set of material properties such as lubricity and contact resistance, as well as good corrosion resistance.  However, also like Chromium, complete Cadmium replacement still requires work as suitable material replacements have not been developed to adoptable levels.  Groups such as the Joint Cadmium Alternatives Team (JCAT) continue to drive study in this area.   

Nano-Materials can Detect and Neutralize Explosives 

Returning to ScienceDaily, work done by Prof. Apblett at the Oklahoma State University has focused on chemical-based sensing of explosives.  Apblett et al have sprayed thin coatings of catalytic Molybdenum (Mo) oxide nano-particles on various surfaces; in the presence of hydrogen peroxide-based explosives, the coatings undergo subsequent changes in colour and conductivity, both of which can be measured.  Adding additional spray, which reacts with the peroxide vapour, the coating can also disarm the explosive.  Additional studies performed by Apblett et al on Molybdenum oxides include sorbants for toxic metals, heavy metals, and radionuclides [2,3].

[1] T.L. Kelly et al. Carbon and carbon/silicon composites templated in rugate filters for the adsorption and detection of organic vapors.  Advanced Materials, Vol. 23 (2011), pp. 1776-1781.
[2] M. Chehbouni and A.W. Apblett. Molybdenum-oxide based sorbants for toxic metals.  Ceramic Transactions, Vol. 176 (2006), pp. 15-23.
[3] B.P. Kiran et al. Selective absorption of heavy metals and radionuclides from water in a direct-to-ceramic process.  Ceramic Transactions, Vol. 143 (2003), pp. 385-394.