The residual stress and lattice-parameter depth profiles in a γ′-Fe4N1-x layer (6-μm thickness) grown on top of an α-Fe substrate were investigated using x-ray diffraction stress analysis at constant penetration depths. Three different reflections (220, 311, and 222) were recorded at six different penetration depths using three different wavelengths. At each penetration depth, x-ray diffraction stress analysis was performed on the basis of the sin2ψ method. As a result, the residual-stress depth profile was obtained from the measured lattice strains. The lattice spacings measured in the strain-free direction were used to determine the (strain-free) lattice-parameter depth profile. The nitrogen-concentration depth profile in the layer was calculated by applying a relationship between the (strain-free) γ′ lattice parameter and the nitrogen concentration. It was found that the strain-free lattice-parameter depth profile as derived from the 311 reflections is best compatible with nitrogen concentrations at the surface and at the γ′/α interface as predicted on the basis of local thermodynamic equilibrium. It could be shown that the 311 reflection is most suitable for the analysis of lattice-parameter and residual stress depth profiles because the corresponding x-ray elastic constants exhibit the least sensitivity to the type of and changes in grain interaction. The depth-dependence of the grain interaction could be revealed. It was found that the grain interaction changes from Voigt-type near the surface to Reuss-type at the layer/substrate interface.

Transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and x-ray diffraction (XRD) investigations were conducted on the hot-pressed Ti2SnC bulk ceramic. Microstructure features of bulk Ti2SnC ceramic were characterized by using TEM, and a needle-shaped β-Sn precipitation was observed inside Ti2SnC grains with the orientation relationship: (0001) Ti2SnC // (200) Sn and Ti2SnC // [001] Sn. With the combination of DSC and XRD analyses, the precipitation of metallic Sn was demonstrated to be a thermal stress-induced process during the cooling procedure. The reheating temperature, even as low as 400 °C, could trigger the precipitation of Sn from Ti2SnC, which indicated the low-temperature instability of Ti2SnC. A substoichiometry Ti2SnxC formed after depletion of Sn from ternary Ti2SnC phase. Under electron beam irradiation, metallic Sn was observed diffusing back into Ti2SnxC. Furthermore, a new Ti7SnC6 phase with the lattice constants of a = 0.32 and c = 4.1 nm was identified and added in the Ti-Sn-C ternary system.

The uniaxial compressive deformation of core/shell-type Cu/Ag nanoparticles and naked Cu nanoparticles were simulated by molecular dynamics, revealing the role of nanophase boundaries in the mechanical deformation. The simulations show that single type of partial dislocations glide across the entire slip planes of the Cu cores, resulting in elongated Cu cores compared with circular Cu cores of naked Cu nanoparticles. The phase boundary is the nucleation source of dislocations, and the ultrahigh atomic level stress of part atoms in the phase boundary can ensure the movement of the single type of dislocations under compressed.

This paper reports on the preparation and characterization of nickel ferrite (NiFe1.98O4) ceramics doped with Bi2O3 as sintering aid. Focus has been on the effects of concentration of Bi2O3 and sintering temperature on the densification, grain growth, dielectric, and magnetic properties of the NiFe1.98O4 ceramics, with an aim at developing magnetodielectric properties, with almost equal real permeability and permittivity, as well as sufficiently low magnetic and dielectric loss tangents, over 3 to 30 MHz (high frequency or HF band). X-ray diffraction results indicated that there is no obvious reaction between NiFe1.98O4 and Bi2O3, at Bi2O3 levels of up to 7 wt% and temperatures up to 1150 °C. The addition of Bi2O3 facilitated a liquid phase sintering mechanism for the densification of NiFe1.98O4 ceramics. The addition of Bi2O3 not only improved the densification but also promoted the grain growth of NiFe1.98O4 ceramics. To achieve sufficiently low dielectric loss tangent, the concentration of Bi2O3 should not be less than 5 wt%. The low dielectric loss tangents of the samples doped with high concentrations of Bi2O3 can be attributed to the full densification of the ceramics. Magnetic properties of the NiFe1.98O4 ceramics, as a function of sintering temperature and Bi2O3 concentration, can be qualitatively explained by the Globus model. Promising magnetodielectric properties have been obtained in the sample doped with 5% Bi2O3 and sintered at 1050 °C for 2 h. The sample has almost equal values of permeability and permittivity of ∼12, together with low dielectric and magnetic loss tangents, over 3 to 30 MHz. This material might be useful for the miniaturization of HF (3 to 30 MHz) antennas.

The aim of the investigation was to study the influence of indenter tip geometry on the conventionally obtained indentation modulus of enamel by nanoindentation. Indentation tests on bovine enamel using three different diamond pyramidal indenters with half face angles 65.27°, 45°, and 35.26° were conducted to evaluate the indentation modulus using the Oliver–Pharr method [W.C. Oliver and G.M. Pharr, J. Mater. Res.7, 1564 (1992)]. In addition, three different dehydration conditions were studied: wet under Hank's balanced salt solution, laboratory dried, and vacuum dehydrated. For the Berkovich indenter (65.27°) and 45° pyramidal indenters, there was only a small difference between indentation modulus values, whereas for the cube-corner indenter (35.26°) a ratio of 2.4 between laboratory dry and wet samples was found. A detailed evaluation, including indentation creep and recovery as well as pileup, resulted in a reduction of this latter ratio to 1.7. This still large difference was rationalized on the basis of the different deformation mechanisms generated by indenters of different face angles.

Molecular organization of self-assembled n-dimethyl-n-octadecyl-3-aminopropyltrimethoxysilychloride (DMOAP) layers on indium tin oxide (ITO) coated glass substrates was thoroughly investigated. The layer thickness for each deposition was determined by variable angle spectroscopic ellipsometry (VASE), while from static contact-angle measurements we deduced valuable information regarding the ordering of the molecular structures at the solid-air interface. In particular, the DMOAP thin film formation was studied for two different drying temperatures (85 °C and 120 °C). While at Tdrying = 85 °C we observed the formation of a molecular monolayer characterized by a close packed structure, at the higher temperature the DMOAP molecules “bend” at the substrate as they stack in relatively disordered clusters. A qualitative interpretation of this phenomenon is given, in good agreement both with the obtained experimental data and experimental investigation reported in the scientific literature. The observations regarding the DMOAP molecular level organization as a function of substrate temperature could bring essential information to the self assembly research community and also explain some important physical phenomena occurring at interfaces.

This work presents a simple electrochemical etching method to increase the surface roughness of copper indium disulphide (CIS) thin films using low concentration of hydrochloric acid. Film morphologies were investigated using scanning electron microscopy and atomic force microscopy. The structure of films was investigated using x-ray diffraction. A comparative study of optical properties of as-deposited and roughened CIS thin films by transmittance and reflectance experiments show a strong enhancement of absorbance for wavelengths between 600 and 900 nm.

The indentation stress is the key and fundamental parameter in indentation delamination tests, which are widely used in characterization of the interfacial fracture toughness (or adhesion) between a thin film and its substrate. The indentation stress was analyzed in the present work by using the finite element method for microwedge indenters of different wedge angles and with various other geometrical and mechanical parameters including the penetration depth, film thickness, delamination size, Young's modulus, and yield strength of the indented film. The analysis exhibited the stress field under an indentation load and the stress field after unloading caused by plastic deformation, which resulted in the loading indentation stress and the unloading indentation stress, respectively, expressed by empirical formula in terms of the indenter geometry, the indentation depth, and the film thickness and mechanical properties. The energy release rate was also calculated for the indentation-induced interfacial crack.

Co–B films were synthesized through the solvent evaporation-assisted chemical reduction method by using a mixed-surfactant solution containing Span 40 and (1S)-(+)-10-camphorsulfonic acid. With the characterization of x-ray diffraction, selected-area electron diffraction, x-ray photoelectron spectroscopy, scanning electron micrography, and transmission electron micrography, the resulting Co–B films were identified to be amorphous alloys with mesoporous structure. The synergistic effect of two kinds of surfactants is essential for the formation of mesoporous structure. During liquid-phase cinnamaldehyde hydrogenation to cinnamyl alcohol, the mesoporous Co–B amorphous alloy films exhibited a much higher activity and better selectivity than the solid Co–B nanoparticles prepared by direct reduction of cobalt ions with borohydride. The enhanced activity is attributed to both the mesoporous and the film structure, which provides more Co active sites for the adsorption and diffusion of reactant molecules. The improved selectivity may be related to the difference in surface curvature.

Nanometer-sized intermetallic Mg-Ni and Mg-Cu compound powders were prepared by a physical vapor deposition method (arc discharge) and characterized by means of x-ray diffraction and transmission electron microscopy. Based on an empirical specific heat equation, the effective heat of formation and its temperature dependence were calculated to explain phase formation in nanoscale powders of the binary Mg-Ni and Mg-Cu systems. It is shown that theoretic calculations are in good agreement with the experimental observations.

The aim of this work is to study the effect of Nb element doping on the microstructure and electrical properties of lead zirconate stannum titanate (PZST) ceramic and to improve phase transition properties of PZST. Nb-doped Pb(Zr,Sn,Ti)O3 ceramic samples were prepared by the conventional mixed oxide method. Phase transitions induced by temperature, pressure, and electric field were measured with electric dielectric permittivity, hydrostatic pressure, and hysteresis. The microstructure of the samples was observed by electron scanning microscope to discuss the effect of Nb doping on PZST ceramics. The experiment results indicated that the remnant polarization (Pr), dielectric constant, phase transition, and microstructure were strongly dependent on Nb doping content.

Bonding character, elastic mechanical parameters, ideal strengths, and atomistic shear deformation mechanisms of M3AlN (M = Zr and Hf) were studied by first-principles method. M3AlN exhibits layered chemical bonding character due to the alternately stacking of relatively soft Al–M and strong N–M covalent bonds. The second-order elastic constants and mechanical parameters of M3AlN were reported for the first time. The stress–strain relationships for different deformation modes were studied and the ideal shear and tensile strength were obtained. M3AlN ceramics are predicted to be “quasi-ductile” layered nitrides based on the low shear-modulus-to-bulk-modulus ratios, positive Cauchy pressure (c12–c44), and lower ideal shear strength compared to ideal tensile strength. Investigation of the atomistic shear deformation mechanism of Hf3AlN shows that stretching of soft Al–Hf bonds and relatively weak bridge N–Hf1 bonds dominate the shear deformation; while the rigid N–Hf2 bonds resist against the applied shear strain. Chemical bonding characteristics and shear deformation mechanism of M3AlN are similar with those of other “quasi-ductile” ceramics, such as MAX phases, LaPO4 monazite, and γ-Y2Si2O7. The results further suggest that M3AlN nitrides should be quasi-ductile and damage tolerant.

The effects of the catalysts on the evolution of in-plane stress during heating were studied for silica gel coatings prepared from alkoxide solutions. Tetramethylorthosilicate was hydrolyzed in the presence of nitric acid, acetic acid, and ammonia as catalysts. Gel films were deposited on Si(100) wafers by spin coating, and heated at a constant rate of 5 °C/min up to 500 °C. During heating, in situ measurement of the in-plane stress was conducted by measuring the radius of curvature of the substrate. In-plane, tensile stress increased up to 560 and 370 MPa in the films prepared with HNO3 and CH3COOH, respectively. However, the stress was much smaller at 30–40 MPa, which remained almost constant during heating, for the films prepared with NH3. The much smaller stress resulted from the much lower degrees of the progress of densification during heating, which was revealed in the changes in thickness and infrared absorption spectra during heating. The low degrees of the progress of densification were caused by the colloidal nature of the gel films.

Significant shifts of the frequency of the Raman spectra of the tangential mode of single walled carbon nanotubes (SWNTs) and fluorinated tubes (FSWNTs) in composites of polybutadiene (PB) were observed relative to the pristine SWNTs indicative of the interaction between the polymer and the SWNTs. Proton NMR line width measurements demonstrate partial suppression of polymer segmental motion for both types of nanotube composites and spin-lattice relaxation results indicate that short time-scale localized motions are also affected by SWNT inclusion, more so for FSWNTs. Hardness measurements as a function of wt% SWNTs and FSWNTs in the polymer show larger enhancements of hardness in the composite with the fluorinated tubes.

A novel route to organic-inorganic composites was described based on biomineralization of poly(ethylene glycol) (PEG)-based hydrogels. The 3-dimensional hydrogels were synthesized by radical crosslinking polymerization of poly(ethylene glycol fumarate) (PEGF) in the presence of ethylene glycol methacrylate phosphate (EGMP) as an apatite-nuclating monomer, acrylamide (AAm) as a composition-modulating comonomer, and potassium persulfate (PPS) as a radical initiator. We used the urea-mediated solution precipitation technique for biomineralization of hydrogels. The apatite grown on the surface and interior of the hydrogel was similar to biological apatites in the composition and crystalline structure. Powder x-ray diffraction (XRD) showed that the calcium phosphate crystalline platelets on hydrogels are preferentially aligned along the crystallographic c-axis direction. Inductively-coupled plasma mass spectroscopy (ICP-MS) analysis showed that the Ca/P molar ratio of apatites grown on the hydrogel template was found to be 1.60, which is identical to that of natural bones. In vitro cell experiments showed that the cell adhesion/proliferation on the mineralized hydrogel was more pronounced than on the pure polymer hydrogel.

In instrumented indentation tests for a thin film coating on a substrate (film/substrate composite), it is well known that the substrate-affected contact area estimated through conventional approximations includes significant uncertainties, leading to a crucial difficulty in determining the elastic modulus and the contact hardness. To overcome this difficulty, an instrumented indentation microscope that enables researchers to make an in situ determination of the contact area is applied to an elastoplastic film on substrates having various values of their elastic moduli. Using the indentation microscope, the substrate-affected indentation contact parameters including contact hardness of the film/substrate composites are determined directly as well as quantitatively without any undesirable assumptions and approximations associated with the contact area estimate. The effect of a stiffer substrate on the contact profile of impression is significant, switching the profile from sinking in to piling up during penetration, and resulting in the substrate-affected contact hardness being highly enhanced at deeper penetrations. Through the present experimental study, it is demonstrated how efficient that instrumented indentation microscopy is in determining the substrate-affected elastoplastic contact parameters of film/substrate composite systems.

Many clay-bearing sedimentary stones such as Portland Brownstone will swell when exposed to water, and this can generate damaging stresses as differential strains evolve during a wetting cycle. Current swelling inhibitors, consisting of α,ω-diaminoalkanes, can reduce swelling in Portland Brownstone up to 50%. In this study, through x-ray diffraction and swelling strain experiments, we demonstrate that the α,ω-diaminoalkanes inhibit swelling by substituting for interlayer cations and partially hydrophobicizing the interlayer, then rehydrating on subsequent wetting cycles. We also introduce the copper (II) ethylenediamine complex as a potential treatment for swelling inhibition.

The Rockwell indentation test was used to generate interface delamination in an EB-PVD thermal barrier coating (TBC) system that was thermally cycled between 300 °C and 1050 °C. Luminescence spectroscopy was applied to measure the thermally grown oxide (TGO) stresses in indentation-affected and perfectly bonded regions. Comparison between experimental stress mapping in bonded and delaminated regions by luminescence spectroscopy and finite element analysis was shown and the effect of delamination paths was presented. Zigzag delamination paths alternating between the top TBC-TGO interface and TGO-bond coat interface were shown to induce TGO stress releases and fluctuations in the delaminated region. Luminescence spectroscopy measurements successfully detect such behavior, making it possible to identify nondestructively the size of the delaminated region, the delamination crack front position, and the delamination paths in part.

YVO4: 10%RE3+ (RE = Eu, Sm, Dy, Er) nanophosphors have been synthesized by a facile modified hydrothermal technology to obtain the high purity. The key procedure for this hydrothermal process is the adding order of precursors, in which excess sodium vanadate should be added in the solution of rare earth nitrates. The microstructure (crystal phase, morphology, particle size) of these phosphors are characterized by x-ray powder diffraction, scanning electron microscope, and transmission electron microscope, which indicates that there are some cube-like crystals with tetragonal zircon structure and the average particle size is approximately 40 nm. The luminescent behaviors for the four rare earth ion-activated YVO4 nanophosphors have been studied, and, for YVO4: 10%Eu3+ nanophosphors in particular, it is found that a different hydrothermal process influences the phase composition, microstructure, and photoluminescence. This result suggests that the hydrothermal synthesis process (by adding sodium vanadate to the solution of rare earth nitrates) is favorable for YVO4 nanophosphor to obtain pure phase, small particle size, long luminescent lifetime, and high luminescence quantum efficiency.

A new method for measuring plastic properties of thin films deposited on a substrate is presented. Micrometric cylindrical specimens with the axis perpendicular to the film surface were prepared by milling out the surrounding material using the focused ion beam technique. Such specimens were deformed by means of a nanoindenter outfitted with a flat diamond tip. An equivalent to the macroscopic compressive curve was obtained. Elastic modulus and hardness of the film were then measured using a Berkovich tip. The precise knowledge of the gage length and the independent measurement of elastic properties enable the accurate determination of the stress–strain curve. As compared with the results published in the literature on the specimens with the same dimensions, the studied material deforms less heterogeneously, probably as a consequence of the symmetric crystallographic orientation of the specimens.