The four-point bend (4PB) test is an industry standard in assessment of adhesion in thin films. Obtaining crack propagation along the desired interface plays a cardinal role in the success of this test. Crack penetration and deflection at a bimaterial interface has been extensively studied in the past. Most general results are based on asymptotic analyses involving the interface between two semi-infinite media. The results of these analyses cannot be directly used in case of the 4PB test since the boundary conditions and finite size effects in actual test specimen geometry are not accounted for. The purpose of this paper is twofold: first to develop a simple methodology to understand the preferred failure mode in a 4PB test and gain insight into the factors governing its success; second to examine the extent to which the results can be reconciled with those reported previously based on analysis of a crack in two semi-infinite media bonded together at the interface.

Tellurium nanotubes and nanorods were synthesized by physical vapor deposition (PVD) in an induction furnace for reaction times between 25 and 35 min. The growth morphologies depended on the reaction times and the atmosphere in the induction furnace. Nanotubes grew only under argon atmosphere (1 mbar). Under vacuum, tellurium blades and nanorods were observed. Of particular interest are the dense carpets of nanorods observed on polycrystalline aluminum. PVD experiences in a conventional high vacuum coating system did not lead to the formation of nanotubes nor nanorods. The interesting electrical properties of tellurium and tellurium compounds combined with the observed growth morphologies are promising for the fabrication of nanoscale functional devices.

Cartilage repair is an ongoing challenge in orthopaedic research. Both biological and mechanical properties are needed for full functional characterization of a tissue replacement. However, assessment of cartilage repair tissue has relied primarily on histological markers because mechanical properties are difficult to measure in small tissue regions. Nanoindentation is a technique that is specialized for measuring local mechanical properties in small specimens. In this study, nanoindentation was used to measure the mechanical properties of cartilage repair tissue following microfracture treatment of chondral defects in three rabbit knees. The mechanical properties were then correlated with histology findings from the same tissue samples. Nanoindentation provided complementary information to histology. In particular, the nanoindentation results showed that the mechanical properties of the repair tissue were inferior to the control tissue properties, even though some tissue regions were histologically similar to the control tissue.

This study used nanoindentation coupled with stressed overlayers to evaluate the effect of titanium interlayers on the interfacial fracture energy of platinum films on SiO2 substrates. Interfacial fracture energy was calculated three ways: from platinum buckles that formed spontaneously upon deposition of the film, from buckles that formed upon deposition of a stressed tungsten overlayer, and from blisters triggered by indentation of a platinum film with a tungsten stressed overlayer. The calculated values for the interfacial fracture energy of the Pt-SiO2 interface were 0.2 and 0.5 J/m2 for indentation blisters and spontaneous buckles, respectively. The effect of a titanium interlayer on adhesion was examined using a tungsten stressed overlayer coupled with nanoindentation. The addition of a titanium layer improved the adhesion of the platinum film on SiO2 from 0.2 to 1.0 J/m2.

Room-temperature epitaxy of AlN thin films on sapphire (0001) substrates was achieved by pulsed laser deposition using an epitaxial NiO ultrathin buffer layer (approximately 6 nm thick). Four-circle x-ray diffraction analysis indicates a double heteroepitaxial structure of AlN (0001)/NiO(111)/sapphire (0001) with the epitaxial relationship of AlN [10-10] ‖ NiO [11-2] ‖ sapphire [11-20]. The surface morphology of room-temperature grown AlN thin films was found to be atomically smooth and nanostepped, reflecting the surface of the ultrasmooth sapphire substrate with 0.2-nm-high steps.

Nano-grained phosphors of Eu3+-doped MgGa2O4 crystallites were prepared by sol-gel technique. The characterization and optical properties of luminescent MgGa2O4:Eu3+ powders have been investigated. The dried sol-gel powders were calcined in air at different temperature from 600 to 1000 °C for 5 h. The x-ray diffraction profiles showed that the MgGa2O4:Eu3+ powders began to crystallize around 600 °C and formed stable MgGa2O4 phase in the temperature range of 600–900 °C. The transmission electron microscopy morphology observations revealed that the fired powders exhibit small grain size less than 20 nm. In the PL studies, under ultraviolet (394 nm) excitation, the calcined powders emitted bright red luminescence (615 nm, 5D0→7F2), and the powders fired at 900 °C were found to have the maximum photoluminescence intensity. The quenching concentration of Eu3+ in MgGa2O4 crystallites was also indicated to be about 5∼6 mol%.

Interfacial oxygen diffusion from high-permittivity gate dielectrics (ZrO2 and HfO2) into Si substrates in ultra-large-scale integrated circuits must be suppressed to prevent the formation of interfacial layers between the gate dielectrics and the Si substrates. Oxygen diffusion was analyzed by using a molecular dynamics technique that includes many-body interactions and charge transfer between different elements. The analysis results showed that the addition of Ti is effective in suppressing interfacial oxygen diffusion. The results also showed that the diffusion at the ZrO2/Si(111) and HfO2/Si(111) interfaces is much more suppressed than the diffusion at the ZrO2/Si(001) and HfO2/Si(001) interfaces.

Molecular dynamics simulations of intergranular films (IGFs) containing Si, O, N, and Ca in contact with three different types of surface terminations of Si3N4 were performed using a multi-body interatomic potential. IGFs with the same Ca concentration (12 mol% CaO) but different nitrogen concentrations [N/(N + O) = 0, 15, 30, and 50%] were studied. In all 12 IGFs, Ca ions did not compete with the first adsorbed layer of Si at the IGF/basal crystal interface, but did so at the IGF/prism crystal interface. The simulations show the epitaxial adsorption of Si, O, and N from the IGF onto the basal and prism crystal surfaces. While more adsorbed N was expected as nitrogen concentration increases, there was a significantly larger amount of N adsorbed to the basal surface than to the prism surface. It was found that Ca ions sit closer to the prism surface than the basal surface but move closer to the crystal at both surfaces with increasing nitrogen concentration, although the effect was more pronounced at the basal interface. With the increase of nitrogen concentration, the percentage of two-coordinated oxygen remained about the same, but there was a change in the type of defect oxygen present. In all the simulations, the central position of the first peak in the Si–O pair distribution fixation (PDF) ranges from 1.63 to 1.65 Å, and that of Si–N PDF ranges from 1.71 to 1.73 Å, both consistent with experimental findings. Furthermore, the first peak of both the Si–O and Si-N PDF shifts to larger values as the nitrogen concentration increases, indicating the elongation of the Si–O and Si–N bond in the IGF with the increase of nitrogen concentration. Elongation of both the Si–N and Si–O bonds could lead to weakening of the IGF as nitrogen concentration increases, although competing changes in bonding of the O complicate the effect of N addition on the strength of the IGF.

The microstructure and composition of aluminum oxide films, formed by a two-step anodization process in various electrolytes at 100 V then subject to an intermediate heat treatment (500 °C, 2 min), were investigated. The anodization electrolytes used included ammonium adipate electrolyte, phosphoric acid electrolyte, ammonium dihydrogen phosphate electrolyte, and their mixtures. The cross-section morphologies, crystal structure, and chemical composition of aluminum anodic oxides were examined by transmission electron microscopy. X-ray photoelectron spectroscopy was carried out to study the surface chemical state of the anodic films. The corresponding capacitances and retention voltages of these oxide films were also explored. The results indicated that amorphous-to-crystalline transformation of the oxide, primarily in films formed in ammonium adipate electrolyte, was induced by the heat treatment. Electron diffraction analyses further revealed the oxide films consisted of two distinct zones, which included an inner amorphous layer and an outer layer containing crystalline γ′-Al2O3. This study found that the phosphorous species in either the primary or the re-anodization electrolytes had a potential to cause changes of Al and O distributions within the oxides. The oxide film primarily anodized in ammonium adipate and re-anodized in phosphoric acid had the highest capacitance due to its high degree of crystallinity and thinness compared to oxides formed in other electrolytes. The presence of phosphorus, from the primary anodization electrolytes, in the oxides could inhibit the formation of crystalline γ′-Al2O3 and, consequently, decrease the capacitances of the anodic films. At the same time, the retention voltage and hydration resistance of these oxide films were improved.

A new approach to the contact to coated elastic materials is presented. A relatively simple numerical algorithm based on an exact integral formulation of the elastic contact of an axisymmetric indenter to a coated substrate is detailed. It provides contact force and penetration as a function of the contact radius. Computations were carried out for substrate to layer moduli ratios ranging from 10−2 to 102 and various indenter shapes. Computed equivalent moduli showed good agreement with the Gao model for mismatch ratios ranging from 0.5 to 2. Beyond this range, substantial effects of inhomogeneous strain distribution are evidenced. An empirical function is proposed to fit the equivalent modulus. More importantly, if the indenter is not flat-ended, the simple relation between contact radius and penetration valid for homogeneous substrates breaks down. If neglected, this phenomenon leads to significant errors in the evaluation of the contact radius in depth-sensing indentation on coated substrates with large elastic modulus mismatch.

Undoped and manganese-doped zinc gallate powders and thin films have been synthesized via the hydrothermal route from aqueous solutions at a pH between 9.5 and 12.5. The chemical composition and the crystal size of the synthesized powder have been studied as a function of pH, temperature, and the composition of the precursor solution, such as the type of hydroxide used and the zinc, gallium, and lithium content. Specimens have been analyzed by x-ray diffraction, scanning and transmission electron microscopy, energy-dispersive x-ray spectroscopy, thermogravimetry, and inductively coupled plasma atomic emission spectroscopy. It is shown that crystallite size and chemical composition strongly depend on the solubility of the gallium species within the solution, which appears to determine the number of ZnGa2O4 nuclei per unit volume. Crystals of a few micrometers in size can be synthesized from solutions where Ga is very soluble (e.g., pH ≥ 11), whereas when Ga is not very soluble, the synthesis product is nanocrystalline. Thermogravimetric studies indicate that a considerable amount of OH− is incorporated at the oxygen sites (every 5th to 10th site). Hydrothermal growth of heteroepitaxial zinc gallate thin films has been carried out on (111) MgAl2O4 and (00.1) LiNbO3 substrates. Heteroepitaxy is based on a coincident pattern of oxygen sites in the two structures; that is, (111)ZGO ∥ (111)MAO and (111)ZGO ∥ (00.6)LNO for the out-of plane orientation and (1¯10)ZGO ∥ (1¯10)MAO and (1¯10)ZGO ∥ (1¯10)LNO for the in-plane orientation, respectively. The thin films cover the substrate completely and consist of oriented grains of up to several hundred nanometers in size. In general, the films are twinned with two variants (in separate grains) that are related by a 60° rotation around [111]. This twinning can only be suppressed at high pH and high temperature and only on the MgAl2O4 substrates.

Intermetallic compound (IMC) spalling from electroless Ni-P film was investigated with lead-free solders in terms of solder-deposition methods (electroplating, solder paste, and thin foil), P content in the Ni-P film (4.6, 9, and 13 wt% P), and solder thickness (120 versus .200 μm). The reaction of Ni-P with Sn3.5Ag paste easily led to IMC spalling after 2-min reflow at 250 °C while IMCs adhered to the Ni-P layer after 10-min reflow with electroplated Sn or Sn3.5Ag. It has been shown that not only the solder composition but also the deposition method is important for IMC spalling from the Ni-P layer. The spalling increased with P content as well as with solder volume. Ni3Sn4 intermetallics formed as a needle-shaped morphology at an early stage and changed into a chunk-shape. Needle-shaped compounds exhibited a higher propensity for spalling than chunk-shaped compounds because many channels among the needle-shaped IMCs facilitated Sn penetration. A reaction between the penetrated Sn and the Ni3P layer formed a Ni3SnP layer and Ni3Sn4 IMCs spalled off the Ni3SnP surface. Dewetting of solder from the Ni3SnP layer, however, did not occur even after spalling of most IMCs.

The goal of this study was to demonstrate that a relationship exists between surface stress and pitting corrosion. The surface stress field generated by polishing was first calculated using a thermomechanical model and a finite element code. Pitting corrosion tests performed at the microscale along the austenite/ferrite interface using the electrochemical microcell technique were then analyzed considering the microstructure, and the residual surface stress field calculated numerically under the microcapillary. Mechanical criteria are proposed leading to an enhancement of pitting corrosion of duplex steels.

The formation enthalpies for alkali rare-earth compounds of the type K3RE(PO4)2 where RE = Sc, Y, Lu, Er, Ho, Dy, Gd, Nd, or Ce and for A3Lu(PO4)2 compounds with A = K, Rb, or Cs were determined using high-temperature oxide-melt solution calorimetry. Structural phase transitions were observed and characterized using differential scanning calorimetry and high-temperature x-ray diffraction. The formation enthalpy of the K3RE(PO4)2 phases from oxides becomes more exothermic with increasing rare-earth radius for the K3RE(PO4)2 series and with increasing alkali radius for the A3Lu(PO4)2 compounds. The K3RE(PO4)2 phases are stable with respect to anhydrous K3PO4 and REPO4. The monoclinic K3RE(PO4)2 compounds undergo a reversible phase transition to a hexagonal (glaserite-type) structure with a phase transition temperature that increases from −99 to 1197 °C with increasing RE ionic radius going from Lu to Ce.

Advancements in nanotechnology for material processing via combustion synthesis have spurred the development of superalloys that provide improved protective properties. Nanoscale reactant particles offer unique thermal properties and increased homogeneity that improve the microstructural features and macroscopic properties of the synthesized product. In this study nanoscale molybdenum trioxide (MoO3) particles were added to micron scale nickel (Ni) and aluminum (Al). The goal was to incorporate a nanoscale additive within the reactant matrix that would produce a superalloy by generating excessively high heating rates and creating controlled quantities of Al2O3 (a strengthening agent) within the microstructure of the alloy. Ignition and flame propagation were examined using a CO2 laser and imaging diagnostics that include a copper-vapor laser coupled with a high-speed camera. Product microstructure was examined using micro-x-ray diffraction analysis and scanning electron microscopy. Abrasion testing was performed to evaluate the wear resistance properties of the superalloy. Results show that adding MoO3 increases the flame temperature, results in greater ignition sensitivity, produces a more homogeneous microstructure, and increases the overall wear resistance of the product.

Li-doped NiO epitaxial films with high electrical conductivity and atomically flat stepped surfaces were fabricated by a combined technique of pulsed laser deposition and subsequent annealing. It was determined that subsequently annealing at temperatures as low as 600 °C significantly decreased electrical conductivity due to Li evaporation when the film surface was not protected from Li evaporation. To suppress Li evaporation, a yttria-stabilized-zironia plate was used to cover the film surface, which raised the annealing temperature up to 1300 °C while maintaining a high Li concentration and electrical conductivity. Thermally annealing at this temperature also improved crystal quality and formed epitaxial films with atomically flat stepped surfaces. The films were single crystalline at least in observation areas, 10 μm × 10 μm. A reasonably large Hall mobility approximately 0.05 cm2/Vs similar to that reported for bulk single-crystal NiO and a visible-light transmission in excess of 75% were obtained on 120-nm-thick films. Although annealing at higher temperatures such as 1400 °C can further improve the structural and optical properties, the Li concentration in the films was decreased to <3% of the as-deposited film.

Yb3+-doped single-crystal Ca3Y2(BO3)4 with dimension φ20 × 55 mm was grown by the Czochralski method. The structure of it was determined by x-ray diffraction. It belongs to the orthorhombic system, space group Pnma, with the following parameters: a= 7.1690(4), b = 15.4758(8), c = 8.5587(6) Å, V = 949.55(10)Å3, Mr = 537.51, Z = 2, Dc = 3.8 g/cm3, (MoKa) = 0.71073 Å, F(000) = 508, μ = 6.927 mm-1, final R = 0.0670, and wR = 0.1542 for 2975 independent reflections. The structure of Yb:Ca3Y2(BO3)4 is made up of three set of M-oxygen distorted polyhedrons, and three set of BO3 planar triangles. Ca2+ and Y3+ ions occupy three M sites statistically. Yb3+ ions substitute Y3+ ions to enter these three lattices. The adsorption and emission spectra were measured. It exhibits a broad absorption band ranging from 850 to 1000 nm in the absorption spectrum, which is well matched with the emission wavelength of a laser diode. A broad emission spectrum ranging from 927.95 to 1102.7 nm was observed under the excitation of 895 nm.

The tensile fracture behavior for solid-state-annealed eutectic SnPb and lead-free solder flip chip bumps was examined. The annealing temperatures were in the range of 125–170 °C for 500 h. Prior to solid state annealing, the eutectic Sn–37Pb (SnPb) and Sn–0.7Cu (SnCu) solders showed fracture through the bulk solder. Brittle interfacial fracture occurred in the Sn–3.5Ag (SnAg) solder. After solid-state annealing, the fracture behavior changed dramatically. For eutectic SnPb solder, the fracture modes gradually changed from cohesive solder failure to interfacial fracture with increasing annealing temperature. The fracture mode of the SnCu solder showed greater change than the SnPb and SnCu solders. After annealing at 125 °C, the SnAg solder had a ductile taffy pull fracture, but an increase in temperature resulted in brittle interfacial fracture again. The SnCu solder maintained the same ductile taffy pull mode up to170 °C annealing, independent of the under bump metallization (UBM) type. Microstructure analysis showed that the interfacial fracture of the SnPb and SnAg solder bumps was ascribed to Pb-rich layer formation and Ag embrittlement at the interface, respectively. The bulk solder fracture of SnAg annealed at 125 °C appeared to be a transient phenomenon due to the abrupt breakdown of the hard lamella structure. The eutectic SnCu solder bumps had no significant change in the interfacial structure, except for interfacial intermetallic growth.

We studied the effects of the sintering temperature and applied pressure on Nd–Fe–B bulk nanocomposite magnets produced by the spark plasma sintering (SPS) method. Amorphous Nd4Fe77.5B18.5 melt-spun ribbons were successfully consolidated into bulk form by the SPS method. When sintered at 873 K under applied pressures between 30 and 70 MPa, the bulk materials consisted of nanocomposite materials with a soft magnetic Fe3B phase and hard magnetic Nd2Fe14B phase. The density and magnetic properties of the bulk materials sintered at 873 K were strongly dependent on the applied pressure during sintering. Bulk Nd4Fe77.5B18.5 nanocomposite magnets sintered at 873 K under an applied pressure of 70 MPa showed a high remanence of 9.3 kG with a high coercivity of 2.5 kOe.

Heat treatment of γ-Ni(Al)/γ′-Ni3Al multilayer thin films demonstrates that multilayer hardness correlates with the magnitude of biaxial stress in alternating layers. Films with a columnar grain morphology and (001) texture were fabricated over a range of volume fraction and bilayer thickness via direct current magnetron sputtering onto NaCl (001) substrates at 623 K. The films were removed from substrates, heat-treated at either 673 K or 1073 K in argon, and then mounted for nanoindentation and x-ray diffraction. The biaxial stress state in each phase was furnished from x-ray diffraction measurement of (002) interplanar spacings. The 673 K treatment increases the magnitude of alternating biaxial stress state by 70 to 100% and increases hardness by 25 to 100%, depending on bilayer thickness. In contrast, the 1073 K heat treatment decreases the stress magnitude by 70% and decreases hardness by 50%. The results suggest that the yield strength of these thin films is controlled, in part, by the magnitude of internal stress. Further, thermal treatments are demonstrated to be an effective means to manipulate internal stress.