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NaOCl aq is used as a cleansing and non-specific deproteinizing agent in endodontic treatment, as a component of new chemomechanical caries treatment, and is under study for its alterations of dentin bonding characteristics. We sought to determine the microstructural and nanomechanical changes with such treatments and to test if NaOCl aq removed dentin collagen without microstructural or nanomechanical alteration of underlying mineralized dentin. Polished human dentin disks were prepared with a double reference technique that allowed changes to be determined following 10% citric acid etching for 15 s and subsequent treatment of the etched and unetched portions of the sample with 6.5% NaOCl aq , using atomic force microscopy (AFM) (Nanoscope III, Digital Instruments, Santa Barbara, CA). Images and measurements were made at intervals up to 1800 s. A Triboscope (Hysitron, Minneapolis, MN) on the AFM was used to measure nanohardness and the reduced elastic modulus. The double reference method allowed measurements immediately following etching and at intervals during deproteinization. Etching caused deep peritubular dentin removal and a small depth change of hydrated intertubular dentin as mineral was removed and left a remnant collagen matrix. NaOCl aq removed collagen over time, during which individual fibrils could be resolved; the underlying mineralized dentin was left with a unique porous surface containing numerous channels that are not normally observed in etched or fractured dentin. This could provide an attractive bonding substrate because of the increased surface area and high mineral content, if toughness is not reduced too much. Nanomechanical measurements showed that the reduced elastic modulus and hardness were 75% of original values after removal of the exposed collagen. Current dentin bonding systems rely on hybrid layer formation in which hydrophilic primers/polymers penetrate the opened collagen matrix exposed by etching. However some research suggests that preventing hybrid layer formation by deproteinization, in some cases, can give good bonding, and as shown here, alters the substrate microstructure. There are significant changes as indicated by ANOVA in the reduced elastic modulus that require further study to determine if these changes might affect clinical efficacy.

Epitaxial silicon carbide films are grown on Si(100) and Si(111) substrates at surface temperatures between 950 and 1250 K via c60 precursors. Films have been grown up to thicknesses greater than 1 μm. The growth rate of the SiC film is not limited by the surface reaction rate of C60 with silicon at these temperatures, rather by the arrival rate of the reactants Si (by diffusion) or C60. This results in rapid film growth. Films have been characterized by low energy electron diffraction, X-ray diffraction, and Auger depth profiling. X-ray diffraction suggests the growth of β-SiC in the temperature range investigated. Auger depth profiling shows the film is stoichiometric. Selective crystalline silicon carbide growth is achieved on patterned silicon-silicon oxide samples.

The interaction of C60 with aluminum was investigated using Auger electron spectroscopy (AES), temperature programmed desorption (TPD), photoluminescence and soft X-ray photoelectron spectroscopy. The interaction of C70 with aluminum was also probed with soft X-ray photoelectron spectroscopy. The bonding of C60 and C70 to the aluminum surface is strong such that after multilayer desorption at 570 and 620 K, respectively, a monolayer coverage of the fullerene remains intact, as seen in the valence band spectra, on the surface to 700 K. Above surface temperatures of 700 K the continued presence of a C60 photoluminescence signal and the decline in the surface carbon concentration suggests that the C60 dissolves into the aluminum bulk. The chemical shift in the binding energy of the Al 2p electrons also indicates strong interaction between C60 and aluminum. Multilayer and monolayer coverages of C60 on aluminum passivated the surface such that exposures of 340 L of water at room temperature led to no oxidation of the surface. Multilayer coverages of C60 on aluminum were protective against oxidation at ambient conditions.

The reaction of Cl2 with polycrystalline β-silicon carbide was studied by the modulated molecular beam-mass spectrometric detection method. The temperature range was 300–1000 K and beam intensities between 1016 and 1017/cm2 s were employed. The sole silicon-bearing gaseous product was SiCl4, which was produced with a maximum reaction probability of 5 × 10-4 at 740 K. At higher temperatures, the reaction probability dropped precipitously, probably because of decomposition of Si-Cl surface intermediates prior to further reaction to produce the SiCl4 etch product. The CCl4 reaction product was also observed, but with a reaction probability ∼4 times lower than that of SiCl4. Buildup of an ash of unreacted carbon on the surface was demonstrated by scanning Auger microscopy. Ion bombardment during reaction had little effect on increasing product yields.

The reaction of molecular chlorine with polycrystalline molybdenum was studied by the modulated molecular beam mass spectrometry technique. Between 300 and 900 K, MoCl2 was produced with a reaction probability of about 10−3 on a chlorine-covered surface. At higher temperatures, the chlorine coverage decreased because of three direct reactions on the substrate metal: recombination to form Cl2; direct desorption of atomic chlorine; and a second reaction channel to produce MoCl2. Chlorine chemisorbed on the metal surface acquired sufficient mobility to move away from the spot illuminated by the incident molecular beam. By 1500 K, the only major processes remaining were chemisorption of incident Cl2 with near-unity sticking probability followed by rapid desorption of atomic chlorine. A kinetic model of the reaction, including all of the component elementary steps, was developed and compared to the data.