Using tabulated thermodynamic data, a comprehensive investigation of the thermo-dynamic stability of binary oxides in contact with silicon at 1000 K was conducted. Reactions between silicon and each binary oxide at 1000 K, including those involving ternary phases, were considered. Sufficient data exist to conclude that all binary oxides except the following are thermodynamically unstable in contact with silicon at 1000 K: Li2O, most of the alkaline earth oxides (BeO, MgO, CaO, and SrO), the column IIIB oxides (Sc2O3, Y2O3, and Re2O3, where Re is a rare earth), ThO2, UO2, ZrO2, HfO2, and Al2O3. Of these remaining oxides, sufficient data exist to conclude that BeO, MgO, and ZrO2 are thermodynamically stable in contact with silicon at 1000 K. Our results are consistent with reported investigations of silicon/binary oxide interfaces and identify candidate materials for future investigations.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400010384

Thermodynamic stability of binary oxides in contact With silicon

During the past two decades, diamond-like carbon (DLC) films have attracted an overwhelming interest from both industry and the research community. These films offer a wide range of exceptional physical, mechanical, biomedical and tribological properties that make them scientifically very fascinating and commercially essential for numerous industrial applications. Mechanically, certain DLC films are extremely hard (as hard as 90 GPa) and resilient, while tribologically they provide some of the lowest known friction and wear coefficients. Their optical and electrical properties are also extraordinary and can be tailored to meet the specific requirements of a given application. Because of their excellent chemical inertness, these films are resistant to corrosive and/or oxidative attacks in acidic and saline media. The combination of such a wide range of outstanding properties in one material is rather uncommon, so DLC can be very useful in meeting the multifunctional application needs of advanced mechanical systems. In fact, these films are now used in numerous industrial applications, including razor blades, magnetic hard discs, critical engine parts, mechanical face seals, scratch-resistant glasses, invasive and implantable medical devices and microelectromechanical systems. DLC films are primarily made of carbon atoms that are extracted or derived from carbon-containing sources, such as solid carbon targets and liquid and gaseous forms of hydrocarbons and fullerenes. Depending on the type of carbon source being used during the film deposition, the type of bonds (i.e. sp 1 ,s p 2 ,s p 3 ) that hold carbon atoms together in DLC may vary a great deal and can affect their mechanical, electrical, optical and tribological properties. Recent systematic studies of DLC films have confirmed that the presence or absence of certain elemental species, such as hydrogen, nitrogen, sulfur, silicon, tungsten, titanium and fluorine, in their microstructure can also play significant roles in their properties. The main goal of this review paper is to highlight the most recent developments in the synthesis, characterization and application of DLC films. We will also discuss the progress made in understanding the fundamental mechanisms that control their very unique friction and wear behaviours. Novel design concepts and the principles of superlubricity in DLC films are also presented. (Some figures in this article are in colour only in the electronic version)

https://iopscience.iop.org/article/10.1088/0022-3727/39/18/R01/pdf

Tribology of diamond-like carbon films: recent progress and future prospects

Diamond-like carbon (DLC) films combine several excellent properties like high hardness, low friction coefficients and chemical inertness. The DLC coating material can be further classified in two main groups, the hydrogenated amorphous carbon (a-C:H, ta-C:H) and the hydrogen free amorphous carbon (a-C, ta-C). By adding other elements like metals (a-C:H:Me) or non-metal elements like silicon, oxygen, fluorine or others (a-C:H:X), several modifications of the properties can be adjusted according to application requirements. First reports on hard amorphous carbon films were published in the 1950s and about 20 years later there began worldwide intensive research activities on DLC. In the following years the number of publications increased continuously and the importance for industrial applications became more and more evident. Several deposition techniques were applied to prepare a-C:H, ta-C, metal containing a-C:H:Me and non-metal containing a-C:H:X coatings. In parallel the structure and deposition mechanisms of DLC coatings were extensively studied. An essential obstacle for a broad industrial application was the high compressive stress level in a-C:H films causing delamination and limiting the film thicknesses. With metal based intermediate layer systems most adhesion problems could be solved satisfactorily and thus from the mid-1990s the pre-conditions for a broad application especially in the automotive industry were given. With modified a-C:H:X and a-C:X coatings a considerable friction reduction or surface energy adjustments could be achieved.

History of diamond-like carbon films — From first experiments to worldwide applications

An overview on the tribological behavior of diamond-like carbon in technical and medical applications

Microstructure evolution in tungsten during low-energy helium ion irradiation

A series of tungsten-containing diamond-like carbon (Me-DLC) coatings have been produced by unbalanced magnetron sputtering using a Hauzer HTC-1000 production PVD system. Sputtering from WC targets has been used to form W-C:H coatings. The metal to carbon ratio has been varied to study changes in the metal carbide formation and distribution within the amorphous hydrocarbons (a-C:H) matrix. The difference in the formation of the metal carbide is then linked to changes in the mechanical and tribological properties of the coatings. Detailed high-resolution cross-section TEM has been carried out to analyze the microstructure of the coatings. By changing the amount of a-C:H in the W-C:H coatings, the coefficient of friction could be varied between 0.129 and 0.312. The hardness was found to vary between 8 and 27.5 GPa by using different acetylene gas flows. It was observed that all coatings did have a pronounced multilayered structure.

/pdf/investigation-on-the-formation-of-tungsten-carbide-in-23dvuki5cx.pdf

Investigation on the formation of tungsten carbide in tungsten-containing diamond like carbon coatings

A comparison is made between various models which predict the ability to form an amorphous phase with a relatively high crystallization temperature by rapid quenching or vapour deposition. These models are compared with recent experimental information. It is demonstrated that the effect of atomic size alone is not sufficient to describe the range of formation of amorphous phases. The crystal structure of the constituent elements must also be taken into account. The structural stability is correlated with the average number of valence electrons per atom Z . Easy amorphous phase formation is expected for those values of Z where structural stability is at a minimum. The comparison with experimental results suggests that the relative weight of the structural stability is different for 3d, 4d and 5d transition metal series.

On the composition range of amorphous binary transition metal alloys

Metal containing diamond-like carbon (Me-DLC) coatings are widely applied in industrial applications. Normally, the coatings are produced with small inclusions of carbide forming elements like the 3d, 4d or 5d metals, or Si or B. The small carbide islands have sizes of approximately 2–20 nm. The effect of the nano inclusions is a reduction of internal compressive stress, a lowering of Young's modulus, a lower hardness, and a higher coefficient of friction as compared to pure diamond-like carbon (DLC). The contents of metallic elements are typically between 10 and 20 at.%; for B containing diamond-like carbon a higher percentage is observed (up to 50% B). In this work the effect of replacing the nano inclusions by a stack of extremely thin carbide layers, separated by carbon layers, is tested. Properties like adhesion, hardness, E-modulus, fatigue resistance, coefficient of friction and wear resistance were studied. Furthermore, detailed high resolution TEM was performed to observe the effects of layer integrity. The results show a clear difference in wear and fatigue behavior when the multilayer structure was altered. Short periods within the multilayer structure of W-C:H promotes the wear resistance, while long periods promote the fatigue resistance.

Properties and characterization of multilayers of carbides and diamond-like carbon

Boron carbide coatings are well-known for extreme hardness and excellent wear resistance. In this paper a d.c. magnetron sputter process for the deposition of boron carbide coatings is described. It is shown that by adding small amounts of a hydrocarbon reactive gas (in this case acetylene) the coefficient of friction can be reduced from 0.8 down to 0.2. Results from a laboratory scale deposition device are successfully transferred to an industrial batch coater. The coating adhesion is well enhanced by a titanium interlayer. From the analysis of the chemical composition and from hardness values it is concluded that a structural modification is responsible for the improvement of sliding behaviour. It is suggested that the introduction of additional bondings reduces the brittleness of boron carbide. Furthermore, a comparison with metal-containing amorphous carbon coatings (Me-DLC) reveals several similarities.

Improving tribological properties of sputtered boron carbide coatings by process modifications

https://pure.rug.nl/ws/files/14691824/1985JNuclMatervdKolk.pdf

G.J. van der Kolk

Papers

Investigation on the formation of tungsten carbide in tungsten-containing diamond like carbon coatings

On the composition range of amorphous binary transition metal alloys

Properties and characterization of multilayers of carbides and diamond-like carbon

Improving tribological properties of sputtered boron carbide coatings by process modifications

Binding of helium to metallic impurities in tungsten - experiments and computer-simulations