Carbon in its various forms, specifically nanocrystalline diamond, may become a key material for the manufacturing of micro- and nano-electromechanical (M/NEMS) devices in the twenty-first century. To utilize effectively these materials for M/NEMS applications, understanding of their microscopic structure and physical properties (mechanical properties, in particular) become indispensable. The microcrystalline and nanocrystalline diamond films were grown using hot-filament and microwave chemical vapor deposition techniques involving novel CH4/[TMB for boron doping and H2S for sulfur incorporation] in high hydrogen dilution chemistry. To investigate residual stress distribution and intermolecular forces at nanoscale, the films were characterized using Raman spectroscopy and atomic force microscopy in terms of topography, force curves, and force volume imaging. Traditional force curve measures the force felt by the tip as it approaches and retracts from a point on the sample surface, whereas force volume is an array of force curves over an extended range of sample area. Moreover, detailed microscale structural studies are able to demonstrate that the carbon bonding configuration (sp2 versus sp3 hybridization) and surface chemical termination in both the un-doped and doped diamond have a strong effect on nanoscale intermolecular forces. The preliminary information in the force volume measurement was decoupled from topographic data to offer new insights into the materials’ surface and mechanical properties of diamond films. These measurements are also complemented with scanning electron microscopy and x-ray diffraction to reveal their morphology and structure and frictional properties, albeit qualitative using lateral force microscopy mode. We present these comparative results and discuss their potential impact for electronic and electromechanical applications.

Zirconia oxynitride rare-earth-doped pigments were prepared by ammonolysis of the zirconium rare-earth oxides, previously synthesized using the citrate complexation/calcination route. Different coloration has been obtained, the intensity of which is a function of the nitrogen amount in the case of the oxynitrides; in the case of the oxides, both color and intensity depend on the doping amount of rare earth. The obtained phases, Zr(1−x)CexO2, Zr(1−x)RxO(2−x/2)□x/2, with R = Eu or Er and Zr(1−x)RxO(2−x/2−3/2y)Ny□x/2■y/2 (R = Ce, Eu, and Er), have been characterized by x-ray powder diffraction, scanning electron microscopy, and reflectance spectra data. These results show that the phases with minor rare-earth concentration adopt a baddeleyite-type structure, with a monoclinic symmetry, space group P21/c. By increasing the rare-earth doping, the obtained phases crystallize with the fluorite structure with tetragonal (P42/nmc) or cubic symmetry (Fm¯3m). On the other hand, the study of the magnetic properties of the oxides and oxynitrides indicate a paramagnetic behavior, and in the case of the cerium oxide, the nitridation process produces the reduction from Ce4+ to Ce3+. Diffuse reflectance data and CIE-LAB color coordinates suggest that these ceramics based on nitrogen containing zirconia are expected to be promising candidates as new ecological inorganic pigments.

High-quality epitaxial InN thin films grown on (0001) sapphire with GaN buffer were characterized using transmission electron microscopy. It was found that the GaN buffer layer exhibits the (0001) Ga polarity and the InN film has In-terminated polarity. At the InN/GaN interface, there exists a high density of misfit dislocation (MD) array. Perfect edge threading dislocations (TDs) with (1/3)〈1120〉 Burgers vectors are predominant defects that penetrate the GaN and InN layers. Pure screw and mixed TDs were also observed. Overall, the TD density decreases during film growth due to annihilation and fusion. The TD density in GaN is as high as ∼1.5 × 1011 cm−2, and it drops rapidly to ∼2.2 × 1010 cm−2 in InN films. Most half-loops in GaN are connected with MD segments at the InN/GaN interface to form loops, while some TD segments threaded the interface. Half-loops were also generated during the initial stages of InN growth.

Shearing behavior of Sn-37Pb, Sn-3Ag-0.5Cu, and Sn-3Ag-0.5Cu-8 in solder joints on tape ball grid array (TBGA) substrates were investigated with different shearing speeds from 7 μm/s to 700 μm/s and over a wide temperature range from −25 °C to 150 °C. Both shearing speed and testing temperature were found to have strong effects on the shearing strength and fracture mechanisms of the solder joints. At certain temperature, the shearing force increases sharply with the increase of shearing speed due to a small amount of grain boundary deformation and incomplete dislocation movement as well as more work hardening at a high strain rate. With a fixed speed, the shearing force decreases dramatically with the increase of shearing temperature as a result of a small amount of work hardening and more dynamic recovery, as well as a reduction in Young’s modulus at elevated temperatures. Two lead-free solder joints were much stronger than the tin-lead solder joints under any given shearing condition. At a low temperature of −25 °C, the tin-lead solder joints failed with a combination of intermetallic compounds (IMC) fracture and solder/IMC interface detachment, whereas both lead-free solder joints failed by IMC/Ni interfacial separation. From 25 °C to 150 °C, the fracture mode of all solder joints was complete ball cut through the bulk solder with a ductile rupture. The underlying mechanisms for different shearing performance are interpreted in relation to the properties of the interconnecting materials.

The valence band (VB) photoemission supported by ultraviolet–visible–near infrared spectroscopy techniques were used to determine the band gap values of polycrystalline Si and Ge single layers as well as of Si/Ge multilayer structures. The band gap values obtained from VB photoemission measurements for these structures were found to be much larger than their corresponding bulks and to match well with those determined from standard optical absorption measurements. In each case, the VB offset values were obtained by considering the corresponding VB maximum as a reference. The increase in band gap in case of thin single layers of Si and Ge with respect to bulks were interpreted in terms of quantum confinement effect, while in case of multilayer sample, the effect of various factors such as (i) intermixing leading to the formation of SiGe alloy, (ii) roughness at the interface, (iii) particle size, and (iv) strain seem to play an important role in the observed change in band gap.

The fracture of nanoporous methylsilsesquioxane thin-film glasses in moist air and aqueous solutions was investigated. We demonstrate the effects of controlled volume fractions of nanometer sized pores on the films resistance to fracture. Subcritical cracking accelerated by the presence of moisture, controlled pH, and hydrogen peroxide solutions is reported. Surprising changes in the near threshold growth rate behavior were observed for buffered solutions. We demonstrate that these changes are related to the unexpected diffusion of the aqueous solutions into the highly hydrophobic films. The presence of the solution changes the surface stress of the internal pore surfaces, which changes the stress state of the film. The change in film stress surrounding the crack alters the crack driving force and has profound effects on the resulting crack-growth threshold behavior.

Silicon carbide powders were synthesized by application of sol-gel processing. Fumed silica powder was used as the starting material for the silicon source, and phenolic resin was used for the carbon source. The effects of mixing ratio and difference between hydrophilic and hydrophobic types of fumed silica powders were investigated. The stirred mixtures of fumed silica powders and phenolic resin became apparent sol states owing to homogeneous distribution. SiC powders were formed derived from both the types of fumed silica powders after the gelation and pyrolysis up to 1800 °C. The hydrophilic silica powder was effective to synthesize more homogeneous SiC powders than the hydrophobic type. Single-phase SiC was obtained in the C/Si (molar ratio after pyrolysis at 1000 °C) range between 1.0 and 2.5, while free carbon was contained in the obtained powders of C/Si > 2.5. In contrast, formation of SiC was insufficient, and SiO2 was retained at ratios of C/Si < 1.0.

We recently observed that surfactant sodium dodecyl sulfate (SDS)-encased HiPco single-walled carbon nanotubes (SWNTs) respond optically to hydrogen peroxide (H2O2) in the near-infrared region. In this report, we demonstrate that SDS-encased SWNTs immobilized with glucose oxidase (GOx) can be used to optically detect an enzymatic reaction of glucose based on their H2O2 sensitivity as well as pH sensitivity. Only the enzymatic product H2O2 induces the SWNT near-infrared spectral changes in buffer solutions (pH = 6.0), but both H2O2 and gluconic acid products do this in unbuffered solutions. The SWNT optical response to glucose possesses sensitivity and selectivity similar to an electrochemical method using carbon nanotube nanoelectrode arrays. Our results suggest possible carbon nanotube-based optical tools for molecular recognition applications.

Bone is a composite material with hydroxyapatite mineral, collagen, and water as primary components. Water plays an important role in maintaining the mechanical integrity of the composite, but the manner in which water interacts within the collagen and mineral at ultrastructural length-scales is poorly understood. The current study examined changes in the mechanical properties of bone as a function of hydration state. Tissues were soaked in different solvents and solutions, with different polarities, to manipulate tissue hydration. Mineralized bone was characterized using nanoindentation creep tests for quantification of both the elastic and viscoelastic mechanical responses, which varied dramatically with tissue bathing solution. The results were considered within the context of solution physical chemistry. Selectively removing and then replacing water provided insights into the ultrastructure of the tissues via the corresponding changes in the experimentally determined mechanical responses.

Mechanical properties and micro-plastic deformation behavior of five bulk metallic glasses (BMGs) were studied by instrumented indentation. These materials included La60Al10Ni10Cu20, Mg65Cu25Gd10, Zr52.5Al10Ni10Cu15Be12.5, Cu60Zr20Hf10Ti10, and Ni60Nb37Sn3 alloys. Remarkable difference in deformation behavior was found in the load–displacement curves of nanoindentation and pileup morphologies around the indents. Serrated plastic deformation depended on the loading rate was found in Mg-, Zr-, and Cu-based BMGs. The subsurface plastic deformation zone of typical alloys was investigated through bonded interface technique using depth-sensing microindentation. Large and widely spaced shear bands were observed in Mg-based BMG. The effect of loading rate on the indentation deformation behaviors in different BMGs was elucidated by the change of shear band pattern.

A novel low-temperature (900 °C) chemical gelation method was developed to synthesize spherical and nonagglomerated Ce3+-doped yttrium aluminum oxide particles (YAG:Ce3+). This represents a process with a much lower processing temperature than current solid-state reaction processes (1400 °C). Characterization of the particles via x-ray diffraction and thermoanalytical methods showed that calcination at 900 °C for 2 h allowed direct crystallization from the amorphous phase, inferring that this process allows homogeneous mixing and increased precursor reactivity. Electron microscopy results showed that the spherical particles (∼100 to ∼3 μm) were the flocks of crystallites. The crystallite sizes (Rietveld refinement) grew linearly from 27 nm (900 °C) to 114 nm (1300 °C). The surface area decreased from 40 m2/g (900 °C) to 5 m2/g (1300 °C) because of the coagulating and growing of crystallites to bigger grains at 1300 °C. Single-crystal nanoparticles (around 100 nm) were obtained with this process and their atomic structures were revealed via high-resolution transmission electron microscopy.

A new europium-silicon-oxynitride compound EuSi2O2N2 was obtained by a reaction of Eu2O3, SiO2, and α–Si3N4 at 1300 °C under a nitrogen atmosphere. EuSi2O2N2 is indexed on a monoclinic unit cell with a = 13.151(5) Å, b =17.311(5) Å, c = 7.956(2) Å, β = 104.12(4)°, and V = 1756.56 Å3. EuSi2O2N2 shows a highly pure yellow color associated with a very steep drop in the reflection spectrum with an optical absorption edge at about 512 nm (2.43 eV). On the other hand, EuSi2O2N2 can be efficiently excited in the visible range 370–485 nm and shows a broad band emission peaking at about 568 nm corresponding to the Eu2+ 4f65d1 → 4f7 transition. EuSi2O2N2 shows paramagnetic Curie behavior with an experimental magnetic moment of 7.89(3) μB in accordance with 7 unpaired spins of Eu2+. Additionally, no magnetic ordering can be observed down to 5 K. The divalent nature of the Eu ions in EuSi2O2N2 is evident from both luminescence and magnetic properties.

A sol-gel technique was used to prepare Gd2Ti2O7:Eu3+-coated submicron silica spheres (SiO2@Gd2Ti2O7:Eu3+). The resulted SiO2@Gd2Ti2O7:Eu3+ core-shell particles were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive x-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL) spectra, as well as kinetic decays. The XRD results demonstrate that the Gd2Ti2O7:Eu3+ layers begin to crystallize on the SiO2 spheres after annealing at 800 °C and the crystallinity increases with raising the annealing temperature. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size ∼620 nm), non-agglomeration, and smooth surface. The thickness of the Gd2Ti2O7:Eu3+ shells on the SiO2 cores could be easily tailored by varying the number of deposition cycles (60 nm for four deposition cycles). Under the irradiation of 310 nm ultraviolet, the SiO2@Gd2Ti2O7:Eu3+ samples show strong emission of Eu3+. For the samples annealed from 600 to 800 °C, the emission is dominated by 613 nm red emission ascribed to 5D0–7F2 transition of Eu3+, while for those annealed from 900 to 1000 °C, the emission is dominated by 588 nm orange emission due to 5D0–7F1 transition of Eu3+. The PL intensity of Eu3+ increases with increasing the annealing temperature and the number of coating cycles.

The silver-copper oxide–based reactive air brazing technique was developed as a method of joining complex-shaped ceramic parts. To investigate the viability of this approach for high-temperature application, a series of air-brazed alumina joints were independently exposed to either oxidizing or reducing atmosphere at 800 °C for 100 h. Those samples that were thermally aged in air maintained good joint strength, similar to that of the original as-brazed samples. Microstructural analysis revealed no significant change in joint microstructure after long-term oxidation at elevated temperature, indicating excellent stability of the Ag–CuO-based filler metal in this environment. On the other hand, exposure of the air-brazed alumina joints to hydrogen under the same aging conditions resulted in a measurable decrease in joint strength. Scanning electron microscope analysis conducted on the fracture surfaces of the broken hydrogen-exposed specimens indicated that the source of joint failure was debonding along the interface between the filler metal and alumina substrate. This was due in large part to internal reduction of CuO precipitates within the filler metal to copper and accompanied by the simultaneous formation of porosity at these sites, both within the bulk of the joint as well as along the filler metal/substrate interfaces. Pore formation was noticeably present in filler metals prepared with a high concentration of copper oxide.

In this work, a novel substitutional solid solution (W0.8Al0.2)C was synthesized by mechanically activated high-temperature reaction. X-ray diffraction was used for phase identification during the whole reaction process. Environment scanning electronic microscopy–field emission gun and energy dispersive x-ray were used to investigate the microstructure and the quantitative material composition of the specimen. (W0.8Al0.2)C was found to crystallize in the WC-type, and the cell parameters were a = 2.907(1) Å and c = 2.837(1) Å. The hardness of (W0.8Al0.2)C was tested to be 19.3 ± 1 GPa, and the density was 13.19 ± 0.05 g cm−3.

The oxidation in air of NiAl(110) was investigated in the temperature range from 870 °C–1200 °C by in situ x-ray diffraction and transmission electron microscopy. Oxidation at 870 °C and 1 bar oxygen leads to the formation of an epitaxial layer of γ-alumina showing an R30° orientation relationship with respect to the underlying substrate. At oxidation temperatures between 950 °C and 1025 °C, we observed a coexistence of epitaxial γ- and polycrystalline δ-Al2O3. The α-Al2O3 starts to form at 1025 °C and the complete transformation of metastable phases to the stable α-alumina phase takes place at 1100 °C. The fcc-hcp martensitic-like transformation of the initial γ-Al2O3 to epitaxial α-Al2O3 was observed. X-ray diffraction and cross-section transmission electron microscopy proved the existence of a continuous epitaxial α-Al2O3 layer between the substrate and the polycrystalline oxide scale, having a thickness of about 150 nm. The relative orientation relationship between the epitaxial alumina and the underlying substrate was found to be NiAl(110) || α-Al2O3 (0001) and [110] NiAl || [1120].

The present work reports nitrogen doping of self-organized TiO2 nanotubular layers. Different thicknesses of the nanotubular layer architecture were formed by electrochemical anodization of Ti in different fluoride-containing electrolytes; tube lengths were 500 nm, 2.5 μm, and 6.1 μm. As-formed nanotube layers were annealed to an anatase structure and treated in ammonia environment at 550 °C to achieve nitrogen doping. The crystal structure, morphology, composition and photoresponse of the N-doped were characterized by scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and photoelectrochemical measurements. Results clearly show that successful N-doping of the TiO2 nanotubular layers can be achieved upon ammonia treatment. The magnitude of the photoresponse in ultraviolet and visible light is strongly dependent on the thicknesses of the layers. This effect is ascribed to recombination effects along the tube length.

Dimensional and finite element analyses were used to analyze the relationship between the mechanical properties and instrumented indentation response of materials. Results revealed the existence of a functional dependence of (engineering yield strength σE,y + engineering tensile strength σE,b)/Oliver & Pharr hardness on the ratio of reversible elastic work to total work obtained from an indentation test. The relationship links up the Oliver & Pharr hardness with the material strengths, although the Oliver & Pharr hardness may deviate from the true hardness when sinking in or piling up occurs. The functional relationship can further be used to estimate the sum σE,y + σE,b according to the data of an instrumented indentation test. The σE,y + σE,b value better reflects the strength of a material compared to the hardness value alone. The method was shown to be effective when applied to aluminum alloys. The relationship can further be used to estimate the fatigue limits, which are usually obtained from macroscopic fatigue tests in different modes.

The structure, composition, and mechanical response of Australian bamboo were investigated. The graded structure, composition, and mechanical properties were confirmed by depth profiles obtained using synchrotron radiation diffraction and Vickers indentation. The mechanical performance of bamboo was strongly dependent on age. Results indicated that young bamboo has a higher strength, elastic stiffness, and fracture toughness than its older counterpart does. In addition, the hardness of bamboo is both load dependent and time dependent as a result of an expanding interfacial damage zone and indentation creep, respectively. In addition to fiber debonding, crack deflection and crack-bridging are the major energy dissipative processes for imparting a high toughness in bamboo.

Experimental investigations by high-resolution transmission electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction show that during sputter-deposition of Ti–B–N films amorphous materials, e.g., TiB2 and BN, are found to precipitate at the grain boundaries, resulting in a decrease in grain size when the boron concentration or the amount of amorphous phase increases. To understand these experimental observations, we have used Monte Carlo simulations to investigate the effect of the amorphous phase precipitation on grain growth during film deposition. Our simulations demonstrate that the precipitation of amorphous phase at the grain boundaries can lower the grain growth exponent and thus leads to a low grain growth rate, particularly in the case of large amounts of amorphous phase. As a result, an exponential decay in grain size with the amount of amorphous phase can be observed in our simulations, which is in reasonably good agreement with the experimental results.