TiN Nanocrystals Research Articles

Mechanical Properties of Nanocomposite TiN/Si3N4 Films Synthesized by Ion Beam Assisted Deposition (IBAD)

Nanocomposite coatings of TiN/Si3N4 have been prepared by ion beam assisted deposition (IBAD): simultaneous sputtering of Ti and Si targets and film bombardment by N2+ ions at 1000 eV. The Si/Ti ratio in the film varies from 0 to 0.9. The coatings are composed of amorphous Si3N4 and TiN nanocrystals with grain size of several nanometers. Such nanocomposites exhibit improved mechanical properties in comparison with TiN or Si3N4 deposited under the same conditions. The nanoindentation hardness of TiN/Si3N4 film at the Si/Ti ratio of 0.3 reaches a maximum of 42 GPa, compared with 22 GPa for TiN and 18 GPa for Si3N4. The wear resistance of AISI 52100 steel coated with these nanocomposite coatings is increased about three times.

Microstructural study of the initiation and formation of immersion tin coating on copper

The initiation and growth of immersion tin coating from hydrochloric acid based and methanesulphonic acid based baths on the inner surface of copper tube was studied by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The formation of immersion tin coating crystallites from hydrochloric acid based bath occurs semi-coherently with copper substrate. Tin crystallites grow actively both in vertical and horizontal directions yielding an equiaxial grain structure. The immersion tin deposition from methanesulphonic acid based bath proceeds by the formation of tin nanocrystals. These nanocrystals transform into columnar grains during the grain growth process. Differences in the coating formation characteristics between studied baths are reflected to the microstructural details and properties of coatings, such as surface morphology, porosity and adhesion.

Characterization of Nanocomposite Coatings in the System Ti-B-N by Analytical Electron Microscopy and X-Ray Photoelectron Spectroscopy

Superhard nanocomposite coatings of different composition in the quasi-binary system TiN-TiB2 were deposited onto stainless steel sheets by means of unbalanced DC magnetron cosputtering using segmented TiN/TiB2 targets. The chemistry and microstructure of a TiB0.6N0.7 coating was investigated using X-ray and electron diffraction, photoelectron spectroscopy, energy-filtering transmission electron microscopy, and electron energy-loss spectrometry. High resolution elemental mapping of the elements Ti, B, N, and O with energy-filtering TEM reveals a homogeneous distribution on the nanometer scale. X-Ray and electron diffraction exhibit only TiN crystallites of nanometer size, but no information on the boron-rich phase. The near-edge fine structures of the BK and NK ionization edges in the EELS spectra of the Ti-B-N coatings were used to derive information on the phases by comparing the edges with those of reference compounds. It was found that the TiN nanocrystals occur together with TiO x particles; the grains are embedded in a strongly disordered or quasi-amorphous matrix consisting mainly of TiB2 particles and, near the steel substrate, also boron oxide (B203).

Reactively sputtered Ti–B–N nanocomposite films: correlation between structure and optical properties

Ti–B–N nanocomposite coatings were deposited on silicon, glass and steel substrates by DC magnetron sputtering of a TiB 2 target in various Ar–N 2 reactive mixtures. In this report, some optical properties of the films were investigated in connection with their structure. At low nitrogen flow rate, coatings contain nanocrystals of titanium diboride. On the other hand, at high nitrogen flow rate, only titanium nitride nanocrystals are detected by grazing angle X-ray diffraction. Whatever the nitrogen flow rate, Fourier-transform infrared spectroscopy shows the occurrence of an amorphous boron nitride phase. Moreover, the number of BN bonds continuously increases with the nitrogen flow rate, even if the boron and nitrogen concentrations in the film become nearly constant. Colour measurements show a progressive decrease of the coating brilliance vs. the nitrogen flow rate. Thus, Ti–B–N nanocomposite coatings are suitable for decorative applications. The UV-visible transmittance of Ti–B–N coatings increases with the nitrogen flow rate due to an increase in the number of BN bonds. Finally, the shape of the transmittance curve for a Ti–B–N coating is similar to that of a TiN coating, as soon as TiN nanocrystals are detected in Ti–B–N coatings.

Composition, nanostructure and origin of the ultrahardness in nc-TiN/a-Si 3N 4/a- and nc-TiSi 2 nanocomposites with HV=80 to ≥105 GPa

Multiphase nanocomposite coatings (3–20 μm thick) consisting of nanocrystalline TiN, amorphous Si 3N 4, and amorphous and nanocrystalline TiSi 2, nc-TiN/a-SiN x /a- and nc-TiSi 2 were deposited on steel substrates by means of plasma CVD. The load-independent Vickers microhardness from 80 to >105 GPa was measured by the load–depth sensing technique for applied loads between 30 and 200 mN and verified by measuring the size of the remaining plastic indentation using SEM. The results of a complex analysis provide a consistent picture of the nature of the grain boundaries which determines the hardness in the whole range of silicon content between approximately 3 and 22 at.%. At a high discharge current density of ≥2.5 mA/cm 2 the a-Si 3N 4 forms the grain boundaries and the nanocomposites are superhard (40–50 GPa) as we reported earlier. At a lower current density of ≤1 mA/cm 2 a mixture of TiSi 2 and Si 3N 4 is formed. With increasing Si-content the amount of a-TiSi 2 in the grain boundaries of the TiN nanocrystals increases, and above 10 at.% of Si approximately 3 nm small TiSi 2 nanocrystals precipitate. The hardness depends critically and in a complex way on the Si 3N 4 content and the TiSi 2/Si 3N 4 ratio. The ultrahardness 1 In order to differentiate we suggest to use the term ‘superhard’ as usual for coatings with hardness of ≥40 GPa and the term ‘ultrahard’ for those with hardness exceeding 80 GPa, i.e. in the range of diamond or more. 1 of ≥80 GPa is achieved when the surface of the TiN nanocrystals is covered with approximately one monolayer of Si 3N 4. Under these conditions the ultrahardness of 80–100 GPa depends on the amount of a- and nc-TiSi 2.

AFM and XPS study of nitrided TiO2 and SiO2–TiO2 sol–gel derived films

Sol-gel derived SiO2, TiO2, xSiO2−(100−x)TiO2 (where x=10, 20, 40, 50, 60, 80 mol%) films on silicon substrates were nitrided by ammonia treatment at 1200°C. The structural transformations occur in silica–titania films as a result of ammonolysis. These transformations were studied by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). XPS spectra of nitrided films showed that Ti atoms are bonding to nitrogen as well as to oxygen. The shape of the Ti(2p) spectra are changed after nitridation and after deconvolution of at least three components, related to oxide, oxynitride and nitride can be detected. AFM was used to study the nanoscale morphologies of the coatings. AFM observations revealed that all nitrided films containing more than 40mol% TiO2 are almost completely covered by TiN nano-crystals that increase in size with TiO2 content. Oxide and oxynitride phases are responsible for the bonding between the TiN nano-crystals and the silicon substrate.

Superhard nanocrystalline composite materials: The TiN/Si3N4 system

Thin films of novel superhard composite materials consisting of TiN nanocrystals in an amorphous Si3N4 matrix have been prepared by means of plasma chemical vapor deposition. The films show a high Vickers hardness of 5000 kg/mm2 and elastic modulus of ≳500 GPa, and they are resistant against oxidation in air up to ≥800 °C. The theoretical background of these unusual properties are briefly discussed and practical rules suggested according to which similar properties should be expected for composites of other ternary systems.

Fundamental properties of lead and tin nanocrystals in a dielectric matrix

A careful inspection of the temperature evolution of Pb and Sn nanoparticles encased in a SiOx(x, 1) matrix was carried out by means of optical reflectivity and dark field electron microscopy measurements. A strong decrease of the melting temperature with size and the presence of an hysteresis cycle, which clearly separates melting and solidification temperatures, are evidenced. It is shown that an appreciable tailoring of the properties of the effective medium can be obtained.