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The nature of oxide phases at metal–oxide interfaces, i.e. of oxide layers in the proximity of a metal surface, is assessed by critically examining the available data in the literature. The data reveal a trend towards the formation of reduced oxide phases with lower oxidation states in the vicinity of the interface with a metal. The physical origin of these interface-stabilized oxide layers is discussed and the possible causes include strong metal–metal bonding, high oxygen affinity of the substrate metal, reduction of the interfacial strain, and the stability of two-dimensional oxide phases.

DCB means direct copper bonding and denotes a process in which copper and a ceramic material are directly bonded. Between the temperature of the metal's melting point and the eutectic temperature of the metal-oxygen, DCB depends on the eutectic compound to join the copper and the ceramic. We do some research to investigate the interface between the copper foils and Al₂O₃ ceramics; it is the key factor in influencing the performance of the DCB substrate. We also discuss how to get good microstructure of the DCB interface.

The potential applications of diamond in the field of electronics working under high power and high temperature (aeronautic, aerospace, etc.) require highly oriented films on heterosubstrates. This is the key motivation of the huge research efforts that have been carried out during the last ten years. Very significant progress has been accomplished and nowadays diamond films with misorientations close to 1.5° are elaborated on β-SiC monocrystals. Moreover, an excellent crystalline quality with polar and azimuthal misalignments lower than 0.6° is reported for diamond films grown on iridium buffer layers. Unfortunately, these films are still too defective for high power electronics applications. To achieve higher crystalline quality, further improvements of the deposition methods are needed. Nevertheless, a deeper knowledge of the elemental mechanisms occurring during the early stages of growth is also essential. The first part of this paper focuses on the state of the art of the different investigated ways towards heteroepitaxy. Secondly, the present knowledge of the early stages of diamond nucleation and growth on silicon substrates for both classical nucleation and bias-assisted nucleation (BEN) is reviewed. Finally, the remaining questions concerning the understanding of the nucleation processes are discussed.

The interface structure of Be/HR-1 stainless steel (SS) joint following diffusion bonding was investigated. Metallurgical observation, electron scanning microscopy, X-ray diffraction and scanning Auger microspectroscopy were performed for basic evaluation of bonded joints. There are intermetallic compounds such as Be₁₁Fe and Be₁₂Cr in the interface region of Be/SS joints, which drastically reduce the mechanical strength of the joints. Cu, Ag and Al barriers can block effective inter-diffusion of Be and HR-1 stainless steel, then forming brittle phases.

TiC/TiN-reinforced composite coatings were fabricated on the substrate of Ti–6Al–4V alloy using laser remelting. X-ray diffraction (XRD) was used to identify the phases in the laser-clad composite coating; the interface characterization of the dilution zone-clad zone (IDC) and the dilution zone-heat-affected zone (IDH) was observed with a scanning electron microscope (SEM). The results show that the microstructure of a cross-section has stratification characterization, and consists of the clad zone (CZ), the dilution zone (DZ), the diffusion layer (DL) and the heat-affected zone (HAZ). The layer-by-layer microstructure results from the boundary layer phenomenon of viscous melt-fluid and diffusion. The kind of reinforced particle has an effect on the interface morphology, microstructure and flow characterization of the melt-fluid. The phase constitution in the clad zone consists of (Cr–Ni–Fe), TiC, Ni₄B₃, Ti₂Ni, Cr₂B and M₂₃C₆ for TiC+NiCrBSi coating, and (Cr–Ni–Fe), TiN, NiB, Cr₂Ti and Ti₂Ni for TiN+NiCrBSi coating. The interfaces of the IDC in the NiCrBSi-clad layer is clear and clean; those of TiC+NiCrBSi and TiN+NiCrBSi are illegible. Ti–Ni phases with acicular microstructure link dilution zone and clad zone, and two kinds of phase with acicular microstructure, are similar in composition and shape.

The microscopic morphology and microstructure of Ti-N and Ti-Ni phase between the dilution zone and the clad zone in laser remelting NiCrBSi/TiN layer on a Ti-6Al-4V alloy were characterized using TEM and SEM. The experimental results showed that during laser irradiation heating, TiN particles were partially dissolved into the melted Ni-base alloy, and the dissolved Ti and N atoms were precipitated in the form of TiN, TiN_0.3. Ti exhibits height activity, it combines with Ni forming Ti₂Ni, TiNi matrix intermetallic during laser remelting, faults exist in the Ti₂Ni and TiNi phase, and crystal lattice of TiNi phase is superlattice. Lastly, the cause of the formation of the Ti-N and Ti-Ni phase is discussed.

The effect on the vibrational properties of nanostructures at the interface between two thin films is presented. The model used consists of the coupling of two semi-infinite plans A and B having three and two atomic layers, respectively. Theoretical calculations of localized phonon modes and vibrational field were carried out using the matching procedure. Close to the interface, the transversal translational symmetry is broken down inducing Raleigh-like branches. The polarization degeneracy of the ordered surface Raleigh mode in the longitudinal direction is lifted. The presence of acoustic and optical-like phonons is discussed in terms of the elastic constant forces. The density of states and the spectral densities are presented for sample atomic sites. A hyperfine resonance structure is obtained. It allows the analysis of the dynamical evolution from thin film A to thin film B.

Surface tension (γ, mN/m) of potassium halide salts with water and interfacial tension (IFT) (±0.01 mN/m) of benzene interfaces with water are reported at 298.15 K temperature. The 0.1, 0.5 and 1.0 mol kg^-1 potassium fluoride (KF), chloride (KCl), bromide (KBr) and potassium iodide (KI) solutions were studied. The KCl, KBr, KF and KI increased the surface tension by 5.2, 4.0, 3.1 and 3.0%, respectively, with salt–water interaction influence by anionic sizes. The surface tension of water from air–water to benzene–water interfaces is decreased by 51% due to the benzene–water mutual interaction with dipolar and π-conjugation. The KI, KF, KCl and KBr salts decrease the IFT by 63, 61, 61 and 56%, respectively, because of larger differences in sizes of the anions and the K⁺ with individual salt. The KI developed stronger interactions with an induced potential of a large sized I^- anion that held the water engaged and integrated the aqueous phase with higher interfacial tension. The dipolar and π-conjugation interaction model is proposed with biphasic systems.

Microstructural evolution and fracture behavior of zirconia (ZrO₂)-based thermal barrier coatings (TBCs) were investigated under thermal exposure. New ZrO₂ granule with 8 wt.% yttria (Y₂O₃) with a deformed hollow morphology was developed through a spray drying process and employed to prepare TBCs. The thermal exposure tests were conducted at 1210°C with a dwell time of 100 h till 800 h. The residual stress at the interface between top coat and thermally grown oxide (TGO) layer was measured using a nanoindentation technique before and after thermal exposure. Vertical cracks on the top coat were newly formed and interlamellar cracks at the interface were enhanced after the thermal exposure of 800 h. Especially, partial delamination was observed at the interface after the thermal exposure of 800 h in TBC samples tested. The microstructural evolution in the top coat could be defined through load–displacement curves, showing a higher load or a less displacement after the thermal exposure of 800 h. The stress state was strongly dependent on the TGO geometry, resulting in the compressive stresses at the "valleys" or the "troughs," and the tensile stresses at the "crests" or peak areas, in the ranges of -500 to -75 MPa and of +168 to + 24 MPa, respectively. These stress terms incorporated with resintering during thermal exposure affected the mechanical properties such as hardness and elastic modulus of the top coat.

We have studied the superconductivity of Pb ultra-thin films with thickness from 1 monolayer (ML) to 7 ML grown on Si(111) by molecular beam epitaxy. In situ low temperature scanning tunneling spectroscopy (STS) and angle-resolved photoemission spectroscopy (ARPES) measurements were performed on the films. It is suggested that the interface effect plays a critical role in enhancing the electron-phonon coupling, which consequently increases the superconducting transition temperature when a film reaches to the two-dimensional limit.

We prepared gradated nano-transient layers at different interfaces between deposited film and substrates by high-intensity pulsed ion beam (HIPIB) irradiation. The deposited film was (Al–Si) alloy and substrates were Ni and Ti, respectively. The gradated nano-transient layers at different interfaces were measured by Rutherford backscattering, its spectra were solved by SIMNRA code and then the microstructures of the gradated nano-transient layers at the interfaces of these two irradiated samples were obtained. The experimental results were analyzed by STEIPIB code. The formation of the gradated distribution of element contents in nano-transient layer at the interface can eliminate the abrupt changes of thermal and elastic characteristics at the interface. And, it can greatly reduce the mismatch of thermal expansion coefficients and Young's modulus at the interface between deposited film and substrate. Thus, after the formation of the gradated nano-transient layer, the adhesion at the interface between different materials can be enhanced and the level of thermal stresses can also be reduced in the case of thermal loading.

Intermetallic matrix composites reinforced with ceramic particles such as TiC have received increasing attention in recent years due to the combined potential of ceramics and intermetallics to give a desirable balance of properties. But an understanding of some experimental results presented elsewhere has remained elusive. In this communication, interface valence electron structure of TiC–NiAl composites was set up on the basis of Pauling's nature of the chemical bond, and valence electron density ρ of different atomic states TiC and NiAl composites in various planes was determined. From the viewpoint of biphase interface electron density continuing, the corresponding experimental phenomena are explained.

We report on the buckling morphologies and interfacial properties of silicon nitride films deposited on float glass substrates. The coexistence of straight-sided and telephone cord buckles can be observed in the silicon nitride films after annealing at a high temperature. The straight-sided structure is metastable and can spontaneously evolve into the telephone cord structure accompanied by the increase in the buckle width and height. The geometric parameters of various buckling structures (including the straight blister, telephone cord and their transition state) have been measured by optical microscopy and atomic force microscopy (AFM). The internal stress and interfacial adhesion of the films are evaluated and analyzed based on the continuum elastic theory. It is valid to measure the interfacial properties of thin films by simplifying the telephone cord buckle as a straight-sided structure. This measurement technique is suitable for all the film systems provided that the buckles can form in the film.

In this paper, we have electrodeposited copper on polypyrrole surface. Results show that at high applied cathodic potential ($>$$-$1.8V), copper electrodeposition occurs with difficulties. The amount of electrodeposited copper is low (1.32%) and it is limited by the low polypyrrole conductivity. At this potential, poor conductivity is caused by its insulating state. However, at an applied cathodic potential of $-$1.2V, the polypyrrole exhibits a relatively high conductivity and copper particles are electrodeposited with large amounts (12.44%) on polypyrrole/silicon system. At high applied cathodic potential, the SEM images show clearly dispersed grains of copper, but polypyrrole surface is less occupied. At an applied cathodic potential of $-$1.2V, the SEM image shows that polypyrrole surface is homogenously more occupied with copper. After copper deposition, the Cu/PPy/Si system is used to catalyze the hydrogen reaction. It was found that, once the deposited copper is present with considerable amounts, the proton reduction occurs easily. As for the polypyrrole conductivity, it was found that electrodeposited copper onto PPy/Si surface affect the total conductivity.

Facing the challenge of low energy density of conventional electric double layer supercapacitors, researchers have long been focusing on the development of novel pseudocapacitive electrode materials with higher energy densities. Since capacitive charge storage reaction mostly occurs on the interface of electrode and electrolyte, the interface chemistry determines the achievable power and energy densities of a supercapacitor. Consequently, understanding of surface–interface reaction mechanism is a key towards efficient design of high-performance supercapacitor electrode materials. In this paper, we have reviewed the recent advances in the understanding of surfaces–interfaces in the system of pseudocapacitive supercapacitors. With significant research advancements in the understanding of surface–interface of supercapacitors, novel colloidal electrode materials with improved surface–interface structures have been developed in our previous work, which have the potential to deliver both high energy and power densities. This review aims to provide an in-depth analysis on the surface–interface control approaches to improve the energy and power densities of supercapacitors.

The growth and stability of hafnium films on $n$-GaN(0001) surface with native oxide was investigated with X-ray and ultraviolet photoelectron spectroscopy (XPS, UPS). It is shown that hafnium creates a continuous and stable layer on GaN substrate. Thermal treatment at $850^{\circ }$C of Hf/GaN system causes decomposition of GaN and reaction of hafnium with atomic nitrogen from the substrate. XPS spectra demonstrate the reaction by a strong shift of the N 1s and Hf 4f lines. An attempt for bringing on the same reaction with molecular nitrogen under pressure of $1.2\times 10^{-6}$ mbar was not successful. UPS spectra show a metallic character of the hafnium adlayer in such instances.