This paper focus on the analysis of the interfaces of nanocomposite TiAlN/Mo multilayers by high-resolution transmission electron microscopy (HRTEM). These thin films were deposited by reactive magnetron sputtering, with modulation periods below 7 nm. The structural disorder at the interfaces was probed by the analysis of the X-ray diffraction data, and afterwards correlated with the TEM observations on the cross-sections of the TiAlN/Mo multilayers. For specific deposition conditions, these structures can be prepared with relatively planar interfaces, revealing layer-by-layer growth. For modulation periods below 3 nm the intermixing acts a major role in the degradation of the multilayer chemical modulation.

Strontium titanate (SrTiO3, ST) has a perovskite type structure that is cubic at room temperature, but transforms into a tetragonal one at 105K. At very low temperatures, ST exhibits an extremely large dielectric permittivity and piezoelectric and superconducting characteristics. ST finds applications in tunable microwave devices, due to a dependence of its dielectric response on the electric field and low microwave losses. ST electrical properties are strongly dependent on grain boundaries features and directly influenced by grain size distribution. It was found in our previous studies that a small variation in the stoichiometry of ST has a significant effect on the grain size of the sintered ceramic and related electrical properties: increased grain size and dielectric permittivity values have been reported for Ti excess compositions whereas Sr excess caused a decrease of grain size and of the dielectric permittivity. The tailoring of the dielectric properties by small non-stoichiometric variations in ST needs, however, a full understanding of its effects on the microstructure, phases structure and on the structure / composition of the grain boundaries.

Transition metal dichalcogenides (TMD) are widely used as self-lubricating material either as oil additive or directly as thin films. Magnetron sputtering is a deposition method allowing depositing such films with high density and adhesion. However, their spread use in practical applications is still hindered since their excellent sliding properties are deteriorated in the presence of humidity and under high contact pressures. MoSe2, one of the members of TMD family recently studied, has been co-sputtered with carbon in order to improve the mechanical and tribological properties when compared to pure MoSe2 films.

High dielectric constant important for functional electronic applications have been reported in the Sr1-1.5xYxTiO3 ceramic system with a maximum value for x = 0.01 coincident with the maximum grain size. This observation points to a possible correlation between the dielectric response and the microstructure of these ceramics. A solid solubility limit around x = 0.04 was reported recently by Fu et al., although the second phase was observed by X-ray diffraction only for x = 0.07. Therefore, the structure, microstructure and local composition of Sr1-1.5xYxTiO3 ceramics (x = 0 − 0.05) prepared by conventional mixed oxide method is investigated in this work by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy facilities.

The use of a high-brightness field-emission gun (FEG) in scanning electron microscopy (SEM) is a powerful technique to examine microstructures at very high spatial resolution down to nanometer level and has significantly enhanced our ability to solve challenging materials problems, allowing studies of nanoprecipitates.

Continuously miniaturization of electronic components using PCB's technology for the manufacturing of SDRAM's uses a solder ball attach process, producing a joint which robustness and electrical response are crucial factors to success. At present, near-eutectic Sn-Ag-Cu alloys are the leading candidates for Pb-free solders. According to Chun et al., the rapid formation of Cu-Sn intermetallic compounds at the interface affects the reliability of this solder joint and represents a major concern. In this study we characterize the interface of an attachment between the copper layer conductors of a memory and a solder ball which allows further bonding to printed circuit modules, see figure 1.a.

SiAlON ceramics have found applications in many different areas due to their excellent engineering properties such as high hardness, fracture toughness, good thermal shock and oxidation resistance. SiAlON exist mainly in two different polymorphs: a (MxSi12-(m+n)Al(m+n)OnN16-n; M: metal and rare earth cations, x≈0,35 and n≤1,35) and β (β-Si6-zAlzOzN8-z; 0≤z≤4). In general, stable alpha and beta phases separately as well as in combination of α and β are obtained by incorporation of metal and rare earth cations as sintering additives. The metal cations such as Li, Mg, Ca, Y, and most lanthanide cations with the exception of La, Ce, Pr and Eu are able to stabilise α-SiAlON structure. Ekstrom et al. 1991 found that cerium can not occupy interstitial sites in α-SiAlON structure due to the fact that ionic radius of Ce3+ (0.103 nm) is too large, whereas ionic radius of Ce4+ (0.080 nm) is too small to stabilise α-SiAlON structure. After this work, several studies carried out to incorporate cerium cations into α-SiAlON structure. It was shown that cerium cation alone can be incorporated into α-SiAlON if the samples are either fast cooled after sintering, or when the samples are spark plasma sintered. On the other hand, cerium can also be incorporated into the α-SiAlON structure when it is used as a sintering additive together with a smaller α-SiAlON stabiliser cation such as Yb or Ca. Similar results were observed in other multi-cation doped SiAlONS that non α-SiAlON stabiliser cations like Sr2+ (0.112 nm) and La3+ (0.106 nm) are able to stabilise α-SiAlON when used together with α-SiAlON stabiliser cations such as Ca or Yb. Although it was shown that cerium existed in mixed valance state at domain boundaries in Ce-doped and spark plasma sintered α-SiAlON, there is no work on the valance determination of cerium in sintered α-SiAlON which has no domain boundaries. Therefore, in this study; it was aimed to incorporate cerium into α-SiAlON structure by combining with Yb3+ and the determination of possible cerium valence states (Ce3+/Ce4+) in both α-SiAlON grains and secondary phases.

Piezoelectric and electrostrictive responses in poled and unpoled ferroelectric and relaxor ferroelectric compositions are of importance in transducers for converting electrical to mechanical impulses and vice-versa. Sensor applications make use of the very high piezoelectric constant dijk of the converse effect, which also permit efficient conversion of electrical to mechanical response. One of the most important families of materials for piezoelectric applications is Pb(Zr,Ti)O3(PZT). The most widely studied composition of PZT lies at the boundary between the tetragonal and rhombohedral phases, known as the morphotropic phase boundary (MPB) and exhibits greatly enhanced dielectric and piezoelectric properties in bulk and thin film. In modern electronic applications, pyroelectric detectors, piezoelectric microsensors, and micromechanical pumps require the integration of PZT films into a variety of device structures. To get sufficiently large piezoelectric strains for optimization of the performance and reliability of the device, thick films in the thickness range of 5–50 μm are desired. On the other hand burying the device components within the substrate is of utmost importance for miniaturization. In comparison to traditional surface mounted components embedded ones will free surface space for a higher functionality of the device, reduce solder points and increase device reliability. Additionally, to reduce the device costs the use of flexible copper foil as substrates is of particular interest. Its high conductivity and compatibility with printed circuit boards makes copper an attractive candidate substrate for embedded application. However, depositing PZT thick films on copper is not trivial, due to the conflict between the high temperature required to sinter PZT (∼1150°C) and low melting temperature of Cu (∼1050°C), in addition to the easy oxidation of Cu. As a consequence the preparation of PZT thick films on Cu involves a complex route to decrease the ceramic sintering temperature and to control the oxygen partial pressure. So far, no successful deposition of PZT thick films on copper foils was reported.

Recently, a new class of coatings based on oxynitrides has drawn much attention in the research field as well as in industrial applications, as shown by either the large numbers of recent publications on TM O N systems (TM—transition metal) such as Ti-O-N, Zr-O-N and Ta-O-N, or the development of Si O-N for opto-electronic devices. The properties of these coatings are related to the chemical composition and the structural arrangement. However, the knowledge about the structure of TM-O-N systems is very limited, especially how the structural arrangement of the non-metallic elements is in the lattices. To the best of our knowledge, only a few studies exist on the development of structural models for oxynitrides, based on XRD and/or XPS analysis, as e.g. Si-O-N and Ti-O-N, or on Mössbauer spectrometry for Fe-O-N. TEM was used scarcely for the characterization of TM-O-N coatings possibly due to the damage of the structure by the electron-irradiation as it is reported for Cr-O-N. This work is aimed at the crystallographic understanding of W-O-N sputtered films by using TEM and HR TEM techniques for complementing the information provided by XRD characterization.

The interest in titanium based intermetallics, such as Ti-Al alloys, for high temperatures applications has been increased in recent years mainly due to their high plastic deformation resistance, chemistry stability (oxidation and corrosion resistance) and creep and fatigue resistance at high temperatures. However, the industrial application of Ti-Al intermetallics is very limited so far, due to the lack of ductility and fracture toughness at room temperature with associated processing difficulties. To overcome this problem and to improve mechanical properties of Ti-Al intermetallics, a powder mixture with atomic composition of Ti52Al48 was synthesized by mechanical alloying (MA) and subsequently coated with a ductile element (aluminium), by d.c. magnetron sputtering. Later, in order to obtain a compacted material, as final step, the coated MA'ed powders were submitted to hot isostatic pressing (HIP), giving rise to a bulk material. The aim of the current work is to understand the influence of coating layer in mechanical alloyed (MA'ed) powders and the influence in bulk material properties.

When compared with conventional bare metal stents, such as 316L stainless steel, the introduction of drug-eluting stents can promote reduction in the incidence of in-stent restenosis. However, the chemical discrepancy between the metallic stent and the polymeric material that acts as the reservoir for the drug is responsible for some problems during the cardiovascular surgery. Besides the research work aiming at the development of new bulk alloys for stent production, focus as been also directed to the surface modification of these devices. However, the use of functional graded coatings (FGC), i.e., coatings with a gradient of chemical composition between the substrate and the outmost layer, has never been reported in devices for cardiovascular surgery.

Bioactive materials for potential medical application have inspired and stimulated new searches. It has been confirmed that bioactive glasses bond to living bone through an apatite layer that precipitates on their surface in physiological media. These glasses normally constituted by silica, where the silicon is the network former, induce apatite nucleation by the formation of Si-OH groups. The presence of OH groups seems to be of utmost importance in the bioactive behaviour of materials. It was revealed that even metals, such as pure titania gel can bond to bone, if previously subjected to alkali and heat treatments. In the present work a new composite with a Ca-P-Ti glass was synthesized and its in vitro bioactivity was studied in Kokubo's simulated body fluid. It is believed that the formation of Ti-OH groups on the glass can induce apatite precipitation on the composites surface.

The hardmetal composites are generally produced from powders of tungsten carbide (WC) and of metal elements, belonging to group 8-10 of the periodic table, which are mixed together by wet milling. News processes, alternatives to milling, have been developed, aiming a higher uniformity of the metallic binder distribution in WC based composites, together with other technological benefits. One of those methods consists of the sputter deposition of metal binder onto the WC powder leading to powder particles coated with the metallic elements. The particles coating showed to be chemically and morphologically very uniform and possesses a nanocrystalline structure and improved surface properties, such as powder's flowability, pressing behaviour, sinterability and thermal reactivity.

Nickel aluminides can be formed by thermal annealing of alternate layers of Ni and Al that react exothermically. These metals have medium/high energy of mixing and when in adiabatic conditions the reaction could become self-propagating. The first phase to form in Ni/Al reactions has been widely investigated, but there is no consensus regarding this subject. Depending on the overall chemical composition and modulation period of the multilayer, and on the processing history, the first phase to form could be NiAl3, NiAl and Ni2Al9.

The continuous miniaturization of the mechanical components and devices push to microfabrication techniques such as μPIM (micro-Powder Injection Moulding) and laser sintering, particularly DMLS (Direct Metal Laser Sintering).

Chromium dioxide (CrO2) has been extensively used in the magnetic recording industry. However, it is its ferromagnetic half-metallic nature that has more recently attracted much attention, primarily for the development of spintronic devices. CrO2 is the only stoichiometric binary oxide theoretically predicted to be fully spin polarized at the Fermi level. It presents a Curie temperature of ∼ 396 K, i.e. well above room temperature, and a magnetic moment of 2 mB per formula unit. However an antiferromagnetic native insulating layer of Cr2O3 is always present on the CrO2 surface which enhances the CrO2 magnetoresistance and might be used as a barrier in magnetic tunnel junctions.

Materials mechanical resistance is known to depend on the size of structural features, accordingly to the familiar HallPetch equation. For the nanometer range of grain sizes, this relationship breaks down and a change of the grain size exponent is needed to satisfy this dependency. Nevertheless, the superior strength of the nanocrystalline material relays on the small dimension of its grains. Characterization of the thermal stability of these materials becomes relevant since a large fraction of atoms are in the grain boundaries and, as a result, its structure posses a large excess of energy that promotes grain growth. Grain growth in nanocrystalline metals has been observed well below the temperatures needed to promote grain growth in coarse grained materials; in some cases, even at room temperature. From this perspective, the study of grain growth in nanocrystalline metals is crucial for the development of new nanocrystalline materials with outstanding mechanical properties. There are many studies that propose models to explain the mechanism of nucleation and growth of annealing twins in F.C.C. materials. In-situ TEM and SEM techniques are invaluable for understanding and characterizing dynamic microstructural changes like nucleation and growth of grains and twins. This is an important observation because twinning affects the properties of materials and so is essential to comprehend the mechanism of twin formation. Other advantage of the in-situ TEM technique is the study of grain growth in ultra fine film with a thickness in the range of 50 to 100 nm. With these techniques, the mechanisms and kinetics of grain growth in nanocrystalline thin films can be observed and studied in real time.

Ferroelectric films with a composition gradient have attracted much attention because of their large polarization offset present in the hysteresis loops. Lead Zirconate Titanate (PZT) films were deposited on Pt/TiO2/SiO2/Si substrates by Pulsed Laser Deposition (PLD) technique, using a Nd:YAG laser (Surelite) with a source pulse wavelength of 1064 nm and duration of 5-7 ns delivering an energy of 320 mJ per pulse and a laser fluence energy about 20 J/cm2. The film growth is performed in O2 atmosphere (0,40 mbar) while the substrate is heated at 600°C by a quartz lamp. Starting from ceramic targets based on PZT compositions and containing 5% mol. of excess of PbO to compensate the lead evaporation during heat treatment, three films with different compositions Zr/Ti 55/45, 65/35 and 92/8, and two types of complex structures were produced. These complex structures are in the case of the up-graded structure (UpG), with PZT (92/8) at the bottom, PZT (65/35) on middle and PZT (55/45) on the top, and for down-graded (DoG) one, that order is reversed.

The study of old mortars composition, using physical-chemical, mineralogical and microstructural characterization has an important role in the preservation of architectural heritage, allowing a deep knowledge about the materials used, construction techniques, possible repairs and degradation processes.

Ge NCs have attracted considerable attention because of their potential applications in nonvolatile memory and integrated optoelectronics. A number of groups have already proposed integrate flash memories based on Ge NCs embedded SiO2 matrix. Since Al2O3 presents a high dielectric constant comparatively to SiO2, it is a good candidate to replace silica in flash memory systems, and therefore improve their performances. Moreover, Al2O3 presents good mechanical properties, and supports high temperature, which leads it to be an ideal material for Si processing conditions. However, a few studies have been reported on Ge NCs embedded in Al2O3 matrix.