The "Diamond Age"

First came the Stone age, followed by the Bronze age, which yeilded to the Iron Age (AKA "Industrial Age"). Enter the Diamond age, with the ability to create not only nano-sized diamonds of high purity, but assemble materials atom by atom.


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Important Forces

Thermal:

Vibration in CO2 Molecule


Important forces in nanoworld

 Hydrogen bonding between molecules and silicon surface

Hydrogen bonds have about a tenth of the strength of an average covalent bond, and are being constantly broken and reformed in liquid water. If you liken the covalent bond between the oxygen and hydrogen to a stable marriage, the hydrogen bond has "just good friends" status. On the same scale, van der Waals attractions represent mere passing acquaintances!

 

Van der Waals (London) forces between molecules

Intermolecular attractions are attractions between one molecule and a neighboring molecule. All molecules experience intermolecular attractions, although in some cases those attractions are very weak. Attractions are electrical in nature. In a symmetrical molecule like hydrogen, however, there doesn't seem to be any electrical distortion to produce positive or negative parts. But that's only true on average. But the electrons are mobile, and at any one instant they might find themselves towards one end of the molecule, making that end delta "-". The other end will be temporarily short of electrons and so becomes delta "+". An instant later the electrons may well have moved up to the other end, reversing the polarity of the molecule. Imagine a molecule which has a temporary polarity being approached by one which happens to be entirely non-polar just at that moment. As the right hand molecule approaches, its electrons will tend to be attracted by the slightly positive end of the left hand one.

This sets up an induced dipole in the approaching molecule, which is orientated in such a way that the + end of one is attracted to the - end of the other.An instant later the electrons in the left hand molecule may well have moved up the other end. In doing so, they will repel the electrons in the right hand one. There is no reason why this has to be restricted to two molecules. As long as the molecules are close together this synchronized movement of the electrons can occur over huge numbers of molecules.


Quantum Mechanics

Matrix mechanics
In 1925 W. Heisenberg introduced matrix mechanics. His work was based on the correspondence principle of Bohr, which can be formulated as follows: In the limit of the quantum numbers approaching infinity the result of quantum theory should agree with that of the classical theory.

Heisenberg’s greatest contribution was uncertainty principal, which made knowing both position and momentum of an election was impossible. There was a trade-off, in which one could be certain about its position or momentum, which related to the act of observing changes the system.

Wave mechanics
In 1926 E. Schrödinger introduced the equation obeyed by the de Broglie waves, and he demonstrated that the quantization conditions emerge from the solution of the eigenvalue problem for his wave equation. He applied his equation to the hydrogen atom and he found that both the quantization of angular momentum and the quantization of energy emerge from his equation. The Schrödinger equation  describes the behavior of quantum particles by means of waves and thereby reconciles, in a consistent manner, the wave / particle duality.


Respecting the Forces of Nature

Those so called "weak forces" (as seen in the left column) make materials at nano-sizes behave quite differently than our macro dimension. Combine the increased effect of thermal vibration and the so-called “weak” forces in the dimension, self assembly becomes possible as the necessary parts are vibrated until the achieve the correct position, or the jostling of the parts breaks up the wrong positions and forces the parts to try again and again until the get it “right.” Add quantium mechanics and you have a very alien word to what we are accustomed to living in.

In my RET-NANO course at Drexel University I’m working with Patricia Reddington (Valenzuela) on research improving the characteristics of lithium ion batteries so that a “super” lithium battery is produced. The “super” would imply faster charge (and discharge rates), increased storage of energy and vastly improved cycling from the current 5,000 to ~100,000 times. Using nano technology changing not the efficient lithium canode, but the anode (graphite). Currently the cathode, graphite, is not a nano material, and degrades rather quickly by the stress imposed by in the charging & discharging process. Other issues a result of intercalation of the graphite with lithium ions during the charging process, is the slow charge (and discharge) rate imposed by the relatively long distances involved with moving ions into the 2 dimensional planes of the graphite anode.

Lithium-ion batteries are popular because they have a number of important advantages over competing technologies

  • They're generally much lighter than other types of rechargeable batteries of the same size. The electrodes of a lithium-ion battery are made of lightweight lithium and carbon. Lithium is also a highly reactive element, meaning that a lot of energy can be stored in its atomic bonds. This translates into a very high energy density for lithium-ion batteries.
  • Here is a way to get a perspective on the energy density. A typical lithium-ion battery can store 150 watt-hours of electricity in 1 kilogram of battery. A NiMH (nickel-metal hydride) battery pack can store perhaps 100 watt-hours per kilogram, although 60 to 70 watt-hours might be more typical. A lead-acid battery can store only 25 watt-hours per kilogram. Using lead-acid technology, it takes 6 kilograms to store the same amount of energy that a 1 kilogram lithium-ion battery can handle. That's a huge difference [Source: Everything2.com].
  • They hold their charge. A lithium-ion battery pack loses only about 5 percent of its charge per month, compared to a 20 percent loss per month for NiMH batteries.
  • They have no memory effect, which means that you do not have to completely discharge them before recharging, as with some other battery chemistries.
  • Lithium-ion batteries can handle hundreds of charge/discharge cycles.

That is not to say that lithium-ion batteries are flawless. They have a few disadvantages as well:

  • They start degrading as soon as they leave the factory. They will only last two or three years from the date of manufacture whether you use them or not.
  • They are extremely sensitive to high temperatures. Heat causes lithium-ion battery packs to degrade much faster than they normally would.
  • If you completely discharge a lithium-ion battery, it is ruined.
  • A lithium-ion battery pack must have an on-board computer to manage the battery. This makes them even more expensive than they already are.
  • There is a small chance that, if a lithium-ion battery pack fails, it will burst into flames.[i]

The study of lithium diffusion in carbon materials is of great interest in both theoretical and practical aspects. During recent two decades this process was studied mainly in connection with the development of lithium ion batteries. Such batteries have negative electrodes based on graphite and other carbon materials.[iii]

In Dr. Yury Gogotsi.’s nanotecnology lab I am working with carbon nanotubes, filled with nano sized (~5NM) silicon particles using capillary action. Sonification is used to disperse the silicon particles into a solution. However, much like trying to put a camel through the eye of a needle, the origonal silicon particles must be reduced in size.

This requires hydrofluoric acid (HF) and nitric acid (HNO3) sometimes diluted with deionized water (to slow the reaction enough so that there is time to stop it as the 5 nm size is attained). The first samples of silicon particles we “nano-sized” with our solutions was 0.003 grams of Silicon, later we tried 0.006. HF will clear of a layer of SiO2. HNO3 then oxidizes the next layer of Si and HF the clears that layer of SIO2. One could compare this process to that of pealing and onion, layer bye layer. Again sonification is used to keep the silicon suspended in solution, while this size reduction proceeds.

When the correctly sized silicon particles are produced, photoluminescence is clearly seen under 254 nm ultra violet, the range in color can be from red to green. To slow desired reaction one the particle size is correct methanol is added. The particles are filtered out of solution using a ceramic filter holding a polyvinylidene fluoride (PVDF) membrane filter, and washing of the silicon continued until the pH was neutral.
Since silicon is very reactive in air (with oxygen, forming SIO2), it needed to be stabilized. For this we used 1-octadecene and ultra-violet cabinets, leading to the photoinitiated hydrosilylation of the silicon; some of the 1-octadecene reacted with the 4 hydrogen atoms on the silicon (like carbon, silicon has a valence of four). Part of the octadecene molicllure removed the hydrogen atoms, the rest of the organic C-H chain, then bonded with the silicon. The excess 1-octadecene molecules were removed in a vacuum oven at 90 degrees celcius.


This product was then dispersed in toluene (which was not degassed and remained saturated with dissolved oxygen), and was capped to prevent evaporation, and also  subjected to UV radiation. This time we wanted dissolved oxygen in the mixture, as the oxygen would then insert itself into between the silicon and the organic chain forming a secure double bond.

[i] How Stuff Works (accessed 7/21/2008) http://electronics.howstuffworks.com/lithium-ion-battery.htm

 

 


  

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