http://en.wikipedia.org/wiki/Project_Habakkuk
I was surprised several years ago when delving into the literature to not find any references about addition of nanoparticles to ice, to study their impact on the mechanics of ice. In short, to make nanocomposites where the matrix is ice. So, with 2 high school students from IMSA, the Illinois Math and Science Academy, we set about (with their limited time for a bit of research) to try adding some nanoparticles to water and to freeze it. The students simply used their home freezers to do this, and their mechanics measurements were with a hammer and chisel...
Markus Buehler has commented on iMechanica about toughness in natural systems, as have others, for example:
P K Hansma, P J Turner,R S Ruoff, Optimized adhesives for strong lightweight, damage-resistant, nanocomposite materials: new insights from natural materials, Nanotechnology 18, (2007) 044026
This can be downloaded at http://bucky-central.mech.northwestern.edu/publications.html
#155.
So, with my high school student researchers I had suggested we try some biopolymers with extensive H-Bonding capacity, and then also graphene oxide, which is an individual layer of graphene but heavily oxidized so as to have -OH and epoxide and carboxylic acid groups on the basal plane and around the edges of each sheet. My group is well versed in making colloidal suspensions of graphene oxide in water (see publications link as mentioned above for various articles). So, there are both synthetic and natural nanoparticles that float around in low concentration in water. "Why not just freeze these colloidal dispersions", was, and is, my thought. It turns out that having a laboratory specially adapted for studies of the mechanics of ice is bound to be helpful. Such as exists at Dartmouth and surely other locations around the world.
Now, what really motivated my pondering experiments on the mechanics of ice as a function of the addition of nanoparticles with strong H-bonding capacity, was not really ice per se. But after some further reading, I realized that improving the mechanics of ice is not necessarily merely a pedestrian effort. Ice is deliberately made and used in some parts of the world for supporting trucks and so on. Phase separation even at very low concentrations of the nanoparticles could be a hurdle...formation of vitreous ice (amorphous ice) might be called for,
http://en.wikipedia.org/wiki/Amorphous_ice
What motivated my pondering such experiments on ice, was thinking about the realities of consumption, depletion, (and recycling, and sustainability). This will eventually bring us to discussing of whether experiments on ice can teach anything about how to make tough glass such as tough SiO2. But let us first take a short detour and discuss finite resources.
The doubling rate of an investment is calculated as 70/P, where P is the percentage rate of return. If you are earning 10%/yr, you double your money in 7 years. The same formula is used to assess the depletion rate of finite resources. Such as certain fossil fuels...and for a discussion of depletion of metals, for example, see: http://news.mongabay.com/2006/0126-yale.html One nice thing about silicon PVs is that while it is intelligent to minimize the use of silicon (for other reasons--it might be cheaper to have a very thin skin of the material versus a thick wafer of it, if the physics of the conversion to electricity is all happening in the thin skin), I am not hearing anyone say we have a shortage of Si or of SiO2 anytime soon. (There might be temporary shortages based on not having enough high quality Si made--I am not here referring to that.) So--it seems likely we could almost always (i.e., well into the future) be making large quantities of glass (in principle). So, why not use glass as a structural element? As everyone knows, it is typically too brittle. The Young's modulus of quartz of a particular grade from GE is 71 GPa. Remarkably the strength of glass fibers can be over 20 Gpa! But it does take special environments and special glass fibers for that to be the case. If there is some connection between the, say, fracture mechanics of ice and that of, say, silica, then perhaps studies on composites with frozen water as the matrix are relevant to future studies on composites with, say, silica as the matrix. Are there connections that actually tie in to the tetrahedral bonding of each which is fundamental to their structure? Does an order parameter based on chemical bonding (whether it be H-bonding or covalent bonding as for these two materials) play any role in the fracture mechanics? There might be mechanicians that could respond on this? Perhaps the energy scales are too disparate. H-bonds are 3-6 kcal/mole (roughly speaking) and covalent bonds are of course of order 100kcal/mole. Is there a Gene Stanley of solid mechanics who will tell me with a big smile that the mechanics is very similar in terms of universal behaviour, but that the magnitudes of the forces needed to induce mechanical changes in ice versus silica, are of course quite different? If there are ice researchers in the World that would like to collaborate, I can recycle my ideas from a few years back. There are a variety of interesting nanoparticles that disperse well in water and have good H-bonding capacity. Please contact me at r-ruoff@northwestern.edu if interested. What is needed is an ice lab where the right sorts of mechanics measurements can be made. And the ability to form amorphous ice and test it with methods such as nanoindentation may be relevant as well. Finally, I am not saying that Pykrete is a frozen water nanocomposite with a small percentage of filler! But there might be something to learn from it still, in terms of then working in the limit of small percentages of nanofiller...such as a nanofiller called cellulose.
