Atomizers, carbon coatings

Sundararajan, S., and Bhushan, B., Micro/Nanotribology of Ultra-thin Hard Amorphous Carbon Coatings Using Atomic Force/Friction Force Microscopy," Wear, Vol. 225-229, 1999, pp. 678-689. 

The most important information about the nanoparticles is the size, shape, and their distributions which crucially influence physical and chemical properties of nanoparticles. TEM is a powerful tool for the characterization of nanoparticles. TEM specimen is easily prepared by placing a drop of the solution of nanoparticles onto a carbon-coated copper microgrid, followed by natural evaporation of the solvent. Even with low magnification TEM one can distinguish the difference in contrast derived from the atomic weight and the lattice direction. Furthermore, selective area electron diffraction can provide information on the crystal structure of nanoparticles. 

In the present paper, the term DLC refers to amorphous, pure carbon coatings with diamond like properties while DLHC indicates the amorphous diamond-like hydrocarbon form. Both types contain a significant amount of sp carbon sites. There is little or no hydrogen present in the former type while the latter type contains 17 to 60 atomic percent of hydrogen. 

For instance, a dip-coating technique can be used to prepare GaN films from either [Ga(N3)3]o= or the base-stabilized species . A unique azide that contains no carbon or hydrogen is [Cl2GaN3]3. It can be used to form GaN under ultra high vacuum CVD conditions . A related derivative, monomeric Cl2GaN3-NMe3, has a higher vapor pressure and can be used to form pure GaN (1-2 atom % carbon and chlorine) more effectively ... 

Sundararajan, S. Bhushan, B. Micro/nanotiibology of ultra-thin hard amorphous carbon coatings using atomic force friction force microscopy. Wear 1999, 229, 678. 

Nicked circular PM2 DNA (0.02 mg/mL) was incubated in NaClOt (10 mM) with platinum compounds at 20 C in the dark for 8 d. After dialysis against NaClOt (10 mM) and platinum determination by atomic absorption spectrophotometry, the complexes were absorbed on carbon-coated copper grids and observed using a Philips 301 electron microscope. The average length of control DNA (Ldsa) and of platinum-DNA complexes (Ldna pO were determined from an observation of at least 60 molecules. 

Diazotetrazole (16) was obtained by dropwise addition of 2-pentyl nitrite to a solution of 5-amino-l//-tetrazole in a 4 1 mixture of tetrahydrofuran and aqueous hydrochloric acid. The diazonium chloride can be extracted into ether. Shevlin obtained the extremely explosive solid diazonium salt (16) by evaporation of that solution. He has recommended that not more than 0.75 mmol of diazonium salt be isolated at one time. An explosion during the diazotization of 5-aminotetrazole on a laboratory scale was described by Gray and coworkers. The structure 17 (equation 5) indicates clearly that this diazo compound may have the tendency to decompose into atomic carbon and three equivalents of dinitrogen—a reaction which is clearly highly exothermic. The decomposition of the tetrazole-5-diazonium chloride (16) has been studied by Shevlin by coating the salt on the walls of a 500 ml flask in the presence of two substrates, ethene and ethylene oxide. With ethene the products found after heating the flask to 80 °C are shown in equation 6, and with ethylene oxide in equation 7. The products correspond to those found with atomic carbon formed by completely different methods (see references cited by Shevlin). 

So, clean surfaces tend to restructure to satisfy the unbalanced atomic forces. When foreign atoms adsorb onto such surfaces, further reconstruction is possible. For example, the chemisorption of contaminant atoms can destroy the clean surface reconstructions described above. Alternatively, new structures may form, as when carbon is chemisorbed on nickel (100) surfaces. If such carbon-coated surfaces were brought together in an adhesion experiment, the carbon would have to diffuse out before full Ni-Ni adhesion could be attained. Such diffusion and restracturing effects could explain the observed changes of adhesion with time. Also, hysteresis in adhesion values could then be accounted for. 

Figure 3.3 Hydrogen/carbon atom ratio in hard carbon coatings as a function of depth into the film, as measured by elastic recoil detection. The different curves are for different film samples. ...

---