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For the first time, experimental data on the high-temperature interaction of liquid Mg with pure Ag are presented. The study was performed by the sessile drop method and capillary purification procedure. The test was carried out under isothermal conditions at 720 °C in a protective atmosphere of Ar + 5 wt.% H2. The solidified couple was subjected to detailed microstructural observations by scanning electron microscopy (SEM) coupled with energy-dispersive x-ray spectroscopy (EDS). Under the used conditions, immediately after contact with the Ag substrate, liquid Mg drop showed a good wetting (θ0 ~ 65°) followed by fast spreading over the substrate in subsecond time to form the final contact angle of θf ~ 31°.SEM/EDS analysis showed that θf is apparent because of a deep crater (200 μm) formed in the substrate under the drop by the dissolution of Ag in liquid Mg. SEM/EDS observations of complex structural transformations in the Mg/Ag couple due to high-temperature contact and subsequent cooling are in good agreement with the Ag-Mg phase diagram. Besides substrate dissolution, the interaction between liquid Mg and solid Ag at 720 °C is accompanied with the alloying of the Mg drop with Ag and the formation of a continuous layer of the β-AgMg phase at the Mg/Ag interface. During cooling, the chemical composition of the Mg(Ag) drop continuously changes, and this process is followed by the formation of the β-AgMg phase by secondary precipitation from Ag-saturated liquid, a partial transformation of the β-AgMg to ε′-Ag17Mg54 phase by peritectic reaction, followed by the solid-state transformation of the ε′-phase to the ε-AgMg3 phase, and finally, the solidification of residual liquid in the form of the two-phase eutectic mixture of AgMg4 + (Mg). The results obtained suggest that a very good wetting and fast spreading observed experimentally for the Mg/Ag couple is caused by high reactivity between liquid Mg and Ag substrate leading to the combined effect of two reactive wetting mechanisms, i.e. through dissolutive wetting and wetting through the formation of the interfacial reaction product (β-phase).

Steam oxidation test was carried out at 800 °C for 2000 h on nine plasma sprayed coatings on gamma-prime (γ’) strengthened Haynes® 282® Ni-based alloy. The lowest oxidation kinetics and extensive reduction in internal oxidation process was observed in the sample coated with nano CeO2 with no bond coat. This is due to the oxygen deficiency in CeOx that facilitates the inward movement of oxygen arising from the presence of Ce3+ oxidation state and ensures the quick formation of protective, impermeable and adherent layer of Cr2O3.

The phase diagram of the ternary Gd-Ti-Zr system has been investigated. The phase equilibria behave as a pseudo-binary Gd-(Ti, Zr) system with the solid state been characterized by the coexistence of elemental Gd and (Ti, Zr) solid solution phase with low solubility ( 20 Ti 40 Zr 40 , Gd 40 Ti 20 Zr 40 and Gd 40 Ti 50 Zr 10 by in situ high energy synchrotron X-ray diffraction at elevated temperatures. Based on the experimental data a thermodynamic description of the ternary Gd-Ti-Zr system is derived.

Lead-free alloys containing various amounts of zinc (4.5%, 9%, 13%) and constant copper addition (1%) were discussed. The results of microstructure examinations carried out by light microscopy (qualitative and quantitative) and by SEM were presented. In the light microscopy, a combinatorial method was used for the quantitative evaluation of microstructure. In general, this method is based on the phase quanta theory according to which every microstructure can be treated as an arrangement of phases/structural components in the matrix material. Based on this method, selected geometrical parameters of the alloy microstructure were determined. SEM examinations were based on chemical analyses carried out in microregions by EDS technique. The aim of the analyses was to identify the intermetallic phases/compounds occurring in the examined alloys. In fatigue testing, a modified low cycle fatigue test method (MLCF) was used. Its undeniable advantage is the fact that each time, using one sample only, several mechanical parameters can be estimated. As a result of structure examinations, the effect of alloying elements on the formation of intermetallic phases and compounds identified in the examined lead-free alloys was determined. In turn, the results of mechanical tests showed the effect of intermetallic phases identified in the examined alloys on their fatigue life. Some concepts and advantages of the use of the combinatorial and MLCF methods in materials research were also presented.

The knowledge of thermophysical properties of liquid Co-Si alloys is a key requirement for manufacturing of composite materials by infiltration method. Despite this need, the experimental and predicted property data of the Co-Si system are scarce and often inconsistent between the various sources. In the present work the mixing behaviour of Co-Si melts has been analysed through the study of the concentration dependence of various thermodynamic, surface (surface tension and surface composition) and structural properties (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) in the framework of the Compound Formation Model (CFM) and Quasi Chemical Approximation for regular solutions (QCA). In addition, the surface tension of the Co22·5Si77.5 (in at%) eutectic alloy, that is proposed to be used as the infiltrant, has been measured by the pendant drop method at temperatures ranging from 1593 to 1773 K. The results obtained were discussed with respect to both, temperature and concentration, and subsequently compared with the model predictions and literature data.

To develop an optimised manufacturing method of fly ash-reinforced metal matrix composites, the preliminary tests were performed on the cenospheres selected from fly ash (FACS) with halloysite nanotubes (HNTs) addition. The preform made out of FACS with and without the addition of HNT (with 5 and 10 wt.%) has been infiltrated by the pure aluminium (Al) via adapted gas pressure infiltration process. This paper reveals the influence of HNT addition on the microstructure (analysis was done by computed tomography and scanning electron microscopy combined with energy-dispersive x-ray spectroscopy), thermal properties (thermal expansion coefficient, thermal conductivity and specific heat) and the mechanical properties (hardness and compression test) of manufactured composites. The analysis of structure-property relationships for Al/FACS-HNT composites produced shows that the addition of 5 wt.% of HNT to FACS preform contributes to receiving of the best mechanical and structural properties of investigated composites.

Compact Cu matrix composites reinforced with graphene were prepared by thermochemical processes and cold isostatic pressing. Thermophysical properties were investigated using laser flash analysis, differential scanning calorimetry, and dilatometry. From the results of the measurements, it follows that within the entire investigated temperature range, both the thermal diffusivity and the calculated values therefrom of the thermal conductivity of copper-graphene composites change according to the temperature changes. Above 500 °C, abnormal decrease of the thermal diffusivity was registered for sample prepared from pure copper powder. In this case, the elevated temperature of test could cause sintering of copper particles, which were not coated by graphene. The as-received composites had higher thermal diffusivity and the thermal conductivity at the room temperature in comparison to the material obtained by standard pressing of pure copper powder. However, the production methods of some samples could cause their partial sintering. Based on the study, it could not be concluded that graphene only has impacts on the thermophysical properties.

Wettability of glass-like carbon substrate (Cglc) by molten Al-10 wt.% Sr alloy (AlSr10) has been examined by a sessile drop method at 700-800 °C for 120 min under vacuum. Non-contact heating to the test temperature combined with the removal of oxide film from the alloy drop was done using capillary purification procedure by squeezing the liquid alloy from a capillary. The influence of the type of capillary on wetting behavior of AlSr10/Cglc couples was noticed. Molten AlSr10 alloy does not wet Cglc at about 700 °C forming the contact angles of 111° with graphite capillary and 141° with alumina capillary. At 800 °C with alumina capillary, non-wetting-to-wetting transition takes place resulting in a final contact angle of 70°. After testing at 800 °C, the AlSr10/Cglc interface was revealed at the test temperature directly in the vacuum chamber by the drop suction procedure. Structural characterization of the interfaces by scanning and transmission electron microscopy combined with energy-dispersive x-ray spectroscopy and by scanning probe microscopy combined with Auger electron spectrometry did not show any new phases formed with Sr. It suggests that the dominant role in wettability improvement by alloying Al with 10 wt.% Sr was related with significant lowering of the surface tension of liquid metal and adsorption of Sr at the interface.

AMADEUS es un proyecto europeo que investiga materiales y dispositivos de estado sólidopara almacenar energía a muy alta temperatura. Usando aleados de silicio como materialesde cambio de fase se alcanzan calores latentes superiores a 1000 kWh/m3, propiciando laobtención de altísimas densidades energéticas. Dichos aleados suponen temperaturas dealmacenamiento por encima de los 1000 ºC, muy por encima de las de los sistemas actualesde acumulación térmica. El artículo describe las actividades del proyecto y sus primerosresultados, explicando los principales retos de este nuevo sistema que combina laacumulación de energía en forma de calor en silicio fundido con dispositivos de estado sólidotermiónicos y termofotovoltaicos para la posterior conversión en electricidad.

AMADEUS es un proyecto europeo que investiga materiales y dispositivos de estado sólido para almacenar energía a muy alta temperatura. Usando aleados de silicio como materiales de cambio de fase se alcanzan calores latentes superiores a 1000 kWh/m3, propiciando la obtención de altísimas densidades energéticas. Dichos aleados suponen temperaturas de almacenamiento por encima de los 1000 ºC, muy por encima de las de los sistemas actuales de acumulación térmica. El artículo describe las actividades del proyecto y sus primeros resultados, explicando los principales retos de este nuevo sistema que combina la acumulación de energía en forma de calor en silicio fundido con dispositivos de estado sólido termiónicos y termofotovoltaicos para la posterior conversión en electricidad. AMADEUS is a H2020 project that researches on materials and solid-state devices for very high temperature energy storage and conversion. By exploring silicon-based alloys as new phase change materials (PCMs), latent heat higher than 1000 kWh/m3 is achievable, which implies a very high energy density. In addition, silicon-based PCMs lead to storage temperatures well beyond 1000 ºC, well beyond that of current state-of-the-art thermal energy storage (TES). This paper describes the project R&D activities and first results, and comments on challenges towards a new kind of systems combining latent heat energy storage in molten silicon with thermionic and thermophotovoltaic solid state heat-to-power conversion.

Poster presented at13th Conference on Calorimetry and Thermal Analysis (CCTA 13), Zakopane, Poland, 2-6 September, 2018.

Combination of extreme service conditions and complex thermomechanical loadings, e.g., in electronics or power industry, requires using advanced materials with unique properties. Dissipation of heat generated during the operation of high-power electronic elements is crucial from the point of view of their efficiency. Good cooling conditions can be guaranteed, for instance, with materials of very high thermal conductivity and low thermal expansion coefficient, and by designing the heat dissipation system in an accurate manner. Conventional materials such as silver, copper, or their alloys, often fail to meet such severe requirements. This paper discusses the results of investigations connected with Cu-C (multiwall carbon nanotubes (MWNTs), graphene nanopowder (GNP), or thermally reduced graphene oxide (RGO)) composites, produced using the spark plasma sintering technique. The obtained composites are characterized by uniform distribution of a carbon phase and high relative density. Compared with pure copper, developed materials are characterized by similar thermal conductivity and much lower values of thermal expansion coefficient. The most promising materials to use as heat dissipation elements seems to be copper-based composites reinforced by carbon nanotubes (CNTs) and GNP.

Preparation and characterization of CVD-TiN-coated carbon fibers for applications in metal matrix composites (MMC) are promising materials for lightweight applications. So far the application has been hindered by a lack wettability of carbon fibers by aluminum alloys and detrimental reactions like aluminum carbide (Al4C3) formation. Protective coatings prepared by chemical vapor deposition (CVD) could be a suitable way to overcome these problems. In this work carbon fiber based 3D-textile preforms were coated with titanium nitride (TiN). Coating thickness, homogeneity, layer structure and composition were determined. Furthermore oxidation resistance and tensile strength of coated fibers were investigated. The wettability by molten aluminum combined with an interface analysis is examined on TiN-coated graphite substrates. Finally the quality of MMC parts prepared by gas pressure infiltration (GPI) method are evaluated. The CVD process was performed with a gas mixture of TiCl4, N2 and H2. A homogeneous coating was achieved at moderate deposition temperatures in the range from 800° to 850°C and by proper adjustment of further process parameters as TiCl4 concentration and total pressure. A very thin TiN layer with a thickness between 30 nm and 35 nm improves the oxidation resistance and results in a moderate decrease of the tensile strength from 3.9 GPa to 2.2 GPa. TiN improves the wettability and acts as a protective coating. However because of the long infiltration time in the GPI process, interface reactions occur. SEM investigations of TiN coated 3D-textile preforms infiltrated with AlSi9Cu3 alloy (226D) showa completely dense composite with a strong reduction of the Al4C3 formation. TiN offers a good protective effect if the contact time with the melt is not too long.

Poster presented at13th Conference on Calorimetry and Thermal Analysis (CCTA 13), Zakopane, Poland, 2-6 September, 2018

The ionic contamination on printed circuit boards (PCB) having different surface finishes was examined using ionograph. The study was performed at the RT on three types of PCBs covered with: (i) hot air solder leveling (HASL LF), (ii) electroless nickel immersion gold (ENIG), and (iii) organic surface protectant (OSP), all on Cu substrates, as well as two types of fluxes, namely EF2202 and RF800. In the group of boards without soldered components, the lowest average value of contamination was for the ENIG 18 µm surface (0.01 μg NaCl/cm2). Boards with soldered components were more contaminated (from 0.29 μg NaCl/cm2 for the HASL LF 18 µm surface). After spraying boards with fluxing agents, the values of contaminants were the highest. The influence of phosphorus content in Ni-P layer of ENIG finish on ionic contamination was examined. In the group of PCBs with Au coating, the smallest amount of surface contaminants (0.32 μg NaCl/cm2) was for Ni-2-5%P layer. PCBs with Ni-11%P layer were higher contaminated (0.47 μg NaCl/cm2), and another with Ni-8%P layer had 0.81 μg NaCl/cm2. PCBs without Au coating, had the lowest contamination (0.48 μg NaCl/cm2) at phosphorous content equal 11%P. Higher contamination (0.67 μg NaCl/cm2) was at 2-5%P, up to 1.98 μg NaCl/cm2 for 8% of P. Boards with Au finish have lower value of contamination than identical boards without Au layer thus contributing to better reliability of electronic assemblies, since its failures due to current leakage and corrosion can be caused by contaminants.

The microstructure and chemistry of the interface between SAC305 solder and electroless Ni–P coating (ENIG) was examined using scanning and transmission electron microscope equipped with an energy dispersive X-ray spectrometer. Four layers have been distinguished after 5 min of interaction at 503 K. There were: NiP-amorphous layer corresponding to Ni–P coating, Ni12P5 and Ni2SnP. The discontinuous Ni2SnP layer at SAC/ENIG interface was composed of fine crystalline particles. The last layer was formed mainly of (Ni,Cu)3Sn4 with some amount of (Cu,Ni)6Sn5 and Ag4Sn phases. The voids observed in the NiP-amorphous layer after processing can be considered as the potential source of the “black pad” failure.

The solderability of the SAC305 alloy in contact with printed circuit boards (PCB) having different surface finishes was examined using the wetting balance method. The study was performed at a temperature of 260 °C on three types of PCBs covered with (1) hot air solder leveling (HASL LF), (2) electroless nickel immersion gold (ENIG), and (3) organic surface protectant (OSP), organic finish, all on Cu substrates and two types of fluxes (EF2202 and RF800). The results showed that the PCB substrate surface finish has a strong effect on the value of both the wetting time t 0 and the contact angle θ. The shortest wetting time was noted for the OSP finish (t 0 = 0.6 s with EF2202 flux and t 0 = 0.98 s with RF800 flux), while the ENIG finish showed the longest wetting time (t 0 = 1.36 s with EF2202 flux and t 0 = 1.55 s with RF800 flux). The θ values calculated from the wetting balance tests were as follows: the lowest θ of 45° was formed on HASL LF (EF2202 flux), the highest θ of 63° was noted on the OSP finish, while on the ENIG finish, it was 58° (EF2202 flux). After the solderability tests, the interface characterization of cross-sectional samples was performed by means of scanning electron microscopy coupled with energy dispersive spectroscopy.

The mechanism of liquid–liquid phase separation and factors determining the solid-state microstructure of monotectic alloys are discussed. The effect of the cooling rate on the phase-separated morphology is shown in examples of Al–In, Al–Pb, Ni–Nb–Y and Zr–Gd–Co–Al alloys solidified by different techniques. A remarkable improvement of the microstructure for the Al91Pb9 hypermonotectic alloy cast with TiB2 particles, which catalyze the phase separation, is demonstrated.

The research was undertaken to establish mechanical properties of as-cast and heat-treated Sn-Zn-based alloys of binary and ternary systems as candidates for lead (Pb)-free solder materials for high-temperature applications. The heat treatment of as-cast alloys was made under different combinations of processing parameters (168 h/50 °C, 42 h/80 °C, and 24 h/110 °C). The systematic study of structure-property relationships in Sn-Zn, Sn-Zn-Ag, and Sn-Zn-Cu alloys containing the same amount of Zn (4.5, 9, 13.5 wt.%) and 1 wt.% of either Ag or Cu was conducted to identify the effects of chemical composition and heat treatment processing parameters on the alloy microstructure and mechanical behavior. Structural characterization was made using optical microscopy and scanning electron microscopy techniques coupled with EDS analysis. Mechanical properties (initial Young’s modulus E, ultimate tensile strength UTS, elastic limit R 0.05, yield point R 0.2, elongation A 5, and necking Z) were determined by means of static tensile tests. All the examined Sn-Zn-based alloys have attractive combination of mechanical characteristics, especially tensile strength, having values higher than that of common leaded solders and their substitutes of Pb-free SAC family. The results obtained demonstrate that the Sn-Zn-based alloys present competitive Pb-free solder candidates for high-temperature applications.

The wetting behavior of liquid Ni and NiW10 on MgO(1 0 0) single crystals was examined by the sessile drop method at 1773 K in flowing Ar. A special procedure was used for in situ opening of the Ni/MgO and NiW10/MgO interfaces directly during wettability test at high temperature. Scanning probe microscopy revealed evidence of strong surface modification of MgO(1 0 0) during wettability tests that was found to be affected by metal evaporation, the chemistry of the liquid metal and the primary oxide film.

The microstructure studies of the reaction product region (RPR) obtained due to the interaction between the liquid aluminium and polycrystalline zinc oxide substrate at 1273 K has been studied. The RPR extended over the oxide substrate and showed a typical C4 (co-continuous-ceramic-composites) structure composed of two interpenetrating phases. The scanning electron microscopy studies revealed that the large crystals of alumina were surrounded by an Al(Zn) metallic phase. Moreover, the transmission electron microscopy investigation showed the presence of a thin (~250 nm) layer next to the ZnO. The chemical analysis accompanied by the selected area electron diffraction patterns indicated in both cases the same stoichiometric aluminium oxide but of different crystallographic structure, i.e., large crystals had α-Al2O3 structure while the layer was identified as metastable δ-Al2O3. The results were compared to those reported for interaction between liquid aluminium and monocrystalline ZnO.

The systematic microstructure and thermodynamic studies of the reactions between liquid aluminum and dense polycrystalline yttria (Y2O3) substrates at 1,273 K are reported in this article. The microstructure observations showed the presence of three reaction product zones extending ~1 mm into the oxide substrate of typical C4 (Co-Continuous-Ceramic-Composites) structure. The first zone starting from the drop side was composed of fine crystalline precipitates of the Al5Y3O12 (YAG) phase dispersed in the Al3Y matrix. The second zone was built of larger AlYO3 (YAP) crystals. The third zone formed elongated oxide precipitates (YAP) surrounded by the Al2Y intermetallic channels. The thermodynamic calculation indicated that, depending on the amount of the yttrium dissolved in aluminum, the YAG (up to 5 at.% Y), YAP (5–13 at.% Y), or Al2Y for higher content of yttrium might form at 1,273 K, while the Al3Y phase might appear during cooling.

The model presented in this paper considers heat transfer, gas diffusion and simultaneous growth of solid and gas fractions in an ordered porosity ingot. Special attention is paid to the gas pore nucleation. The diffusion boundary layer ahead of the solid/liquid interface is analysed with respect to the diffusion process and structure formation, both controlled by external gas pressure, solidification velocity and gas fluxes between solid, liquid and pores. The relationships between processing parameters and structure characteristics are described. How the porosity structure is affected by the size of gas nuclei and the number of nucleation sites on the solid/melt interface is analysed.

The development of a free form bulk Nickel reinforced Alumina matrix nano composites using Air Plasma Spray and laser processing has been presented. The process consumes less time and requires further minimal machining and therefore is cost effective. The relative differences in using APS over laser processing in development of bulk metal-ceramic nanocomposites have been discussed. The process intricacies involved during processing such as material specific mandrel selection, plasma-particle interaction are highlighted. Electroless coating has been used to uniformly disperse Nickel in alumina matrix as a source material. The electroless Ni coated alumina particles are subjected to both laser processing and Air Plasma Spraying with optimized parameters. Consolidation by laser processing could not be achieved as the laser beam was reflective to Nickel. On the other hand, APS Ni-alumina nanocomposite with a cylindrical shape of 1.2" OD x 1" ID x 1.5" length has been fabricated with minimum or no surface defects. HRTEM pictures revealed the nanostructure retention thereby corroborating the fact that bulk nanostructures can be made using Air Plasma Spray. XRD analysis confirmed the phase transformation from alpha alumina to gamma alumina and oxidation of Ni to NiO. Subsequent reduction of NiO to metallic nickel using hydrogen atmosphere has also been demonstrated. Mechanical properties such as, hardness (1025 HV) and fracture toughness (5 MPa m1/2) for the nanocomposite are presented herein.

The development of a free form bulk Nickel reinforced Alumina matrix nano composites using Air Plasma Spray and laser processing has been presented. The process consumes less time and requires further minimal machining and therefore is cost effective. The relative differences in using APS over laser processing in development of bulk metal-ceramic nanocomposites have been discussed. The process intricacies involved during processing such as material specific mandrel selection, plasma-particle interaction are highlighted. Electroless coating has been used to uniformly disperse Nickel in alumina matrix as a source material. The electroless Ni coated alumina particles are subjected to both laser processing and Air Plasma Spraying with optimized parameters. Consolidation by laser processing could not be achieved as the laser beam was reflective to Nickel. On the other hand, APS Ni–alumina nanocomposite with a cylindrical shape of 1.2″ OD × 1″ ID × 1.5″ length has been fabricated with minimum or no surface defects. HRTEM pictures revealed the nanostructure retention thereby corroborating the fact that bulk nanostructures can be made using Air Plasma Spray. XRD analysis confirmed the phase transformation from alpha alumina to gamma alumina and oxidation of Ni to NiO. Subsequent reduction of NiO to metallic nickel using hydrogen atmosphere has also been demonstrated. Mechanical properties such as, hardness (1025 HV) and fracture toughness (5 MPa m1/2) for the nanocomposite are presented herein.

The relationship between wetting behavior, interface structure and mechanical properties of solder/substrate couples has been studied on example of Sn-alloys and Cu substrates. The sessile drop method was used to investigate the solder wetting and spreading on polished Cu substrates in vacuum at a temperature of 503 K. The sessile drop samples after solidification were bisected perpendicularly to the substrate at the mid-plane of the contact circle. The first half of each sample was used for structural characterization of interfaces and evaluation of their mechanical properties by improved push-off shear test. The second half was used for investigation of the effect of thermocycling on structural stability and corresponding mechanical behavior of model solder/Cu joints. A comparison with the results obtained on standard solder joints has shown the usefulness of the improved push-off shear test performed directly on solidified sessile drop samples as an express test for evaluation of technological and mechanical compatibility of solder/substrate couples, particularly at the first stage of solder candidate selection.

The structure and chemistry of interfaces formed between molten Al or Al–6Ti alloy and dense carbon material (vitreous carbon or carbon fibres) under different processing parameters were investigated by transmission electron microscopy (TEM). Alloying Al with Ti was found to improve the chemical compatibility in the Al/C system by forming TiC instead of undesirable Al 4 C 3 if processing conditions (e.g. in squeeze casting process) assure kinetic compatibility in the system.

The thermal fatigue resistance of AlSi alloys and discontinuously reinforced Al-matrix composites containing graphite, silicon carbide, and fly ash particulates, and short alumina (Saffil) fibers was characterized by measuring the total length of microcracks on gravity-cast and squeeze-cast test specimens as a function of number of thermal cycles (1000–5000 cycles, 270 K amplitude). In each thermal cycle, the test specimens were heated and stabilized in air at 375 °C, water quenched, and air stabilized. In all specimens, the total crack length on a specified region increased with increasing number of thermal cycles. Whereas among monolithic alloys, squeeze-cast Al-12SiCuNiMg alloy exhibited better resistance to thermal cracking than Al-25Si and Al-20SiNi alloys, among the composites, squeeze-cast Al-alumina and Al-fly ash composites exhibited the best thermal fatigue resistance. The theoretical estimates of the thermal fatigue resistance of these composites are consistent with the experimental observations.

Sedimentation is an important phenomenon in metal matrix composite production. To enlarge the potential for controlling this process an adequate mathematical description should be used. There are many reasons due to which multiparticle movement cannot be described in the same manner as single particle movement. Several well-known formulae are used to calculate parameters of multiparticle sedimentation. Each formula provides more or less precision compared to experimental results. In this paper, the nature of particle movement is discussed on the basis of sedimentation experiments carried out with water–SiC suspension. A new formula for viscosity, which takes into account the movement of many particles and provides quite good coincidence of measured and calculated values for parameters of sedimentation, is proposed.

The present study investigates the effect of deposition temperature (ambient and liquid N 2 temperatures) and sputtering power on the mechanical and chemical properties of magnetron sputtered Ti 3 Al thin films on 316 stainless steel substrates. Film structure and morphology are investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Films deposited at liquid N 2 temperature showed a dense nanocrystalline structure, whereas ambient temperature deposited films showed voids and discontinuities in their columnar grain morphology as evident from TEM analysis. A detailed analysis of the surface chemistry of DC-magnetron sputtered thin films is performed using X-ray photoelectron spectroscopy (XPS). Glancing angle XPS studies are carried out to study the chemistry at a few layers beneath the surface and monitor changes in thin film stoichiometry. Surface oxides are always present in the films and are more prominent in ambient temperature deposition. Higher power leads to an enhanced metallic Ti 3 Al component as detected from XPS Al(2p) and Ti(2p) lines. Films deposited at liquid N 2 temperature are nanocrystalline and stoichiometric (Ti/Al∼3:1) and showed improved hardness than those deposited at ambient temperatures under similar sputtering conditions and constant film thickness. The hardness of the films increases with increased sputtering power at ambient temperature deposition.

The chemical and physical interaction of liquid metal surfaces with various substrates is an important, largely unexplored aspect of technology, with implications in composite science and catalysis. In the present case, we have employed X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES), in conjugation with sessile drop wettability tests, to examine the interfacial properties and surface chemistry of the systems formed by adding liquid drops of select Al–Ti alloys to graphite substrates. A variety of different chemical states was revealed in the XPS results, suggesting the formation of separate regions composed of elemental metals, alloys and carbides. Many of the specific features detected appear to depend on the various treatment properties, e.g. the temperature, bulk alloy composition, size and shape of the alloy drop and time of interaction. The surface analyses were also supported by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies. The combined results suggest the induction of a strong reaction between titanium and carbon, resulting in an improvement in the wettability of the alloy with the graphite substrate and a corresponding structure transformation from the (LAl–Ti+Al3Ti) state to the (LAl–Ti+TiC) semi-liquid state. © 1998 Kluwer Academic Publishers

The phase equilibria of the binary Nd–Zr system have been investigated by combining the gas levitation technique with in situ high energy synchrotron X-ray diffraction at elevated temperatures. The Nd–Zr system is of a eutectic type. From the diffraction data the liquidus line was experimentally determined between 1300 and 1800 K. At T =1274±10 K the eutectic reaction L↔ bcc -Nd+ bcc -Zr is evident. The eutectic composition x =7±2 at% Zr is determined from the analysis of the microstructure of cast alloys in accordance with the in situ diffraction data. Based on the experimental data the Nd–Zr phase diagram is presented and a self-consistent thermodynamic description is given.