A modified method for contact-induced adhesion on the elastic deformation contact between a rigid spherical indenter and a polydimethylsiloxane (PDMS) specimen is proposed in the present study. Adhesion due to van der Waals interactions was found to be minimal during loading processes. During the unloading process, the experimental load-displacement data revealed two-stage phenomena. The successive advancing contacts between the specimen and the indenter were considered to induce interfacial adhesion and resulted in elastic tension outside the Hertzian contact radius. A real-coded genetic algorithm (RGA) was applied to evaluate how adhesion energy varied with penetration depth.

We report our observations on the homoepitaxial diamond growth by microwave plasma chemical vapor deposition (MPCVD) experiments on Type Ib diamond substrates conducted by varying three independent variables. In a feed gas mixture of H2, N2, O2, and 13CH4, the amount of nitrogen was varied in the range of 0 to 4000 ppm, the amount of methane was varied from 2% CH4/H2 to 6% CH4/H2, and the substrate temperature was varied in the range of 850 to 1200 °C. We used isotopically enriched carbon-13 methane gas as the source of carbon in the plasma to clearly distinguish the grown diamond layer from the underlying substrate using Raman spectroscopy. The x-ray rocking curve measurements confirmed the homoepitaxial nature of the deposited layers with a slight increase in the full width at half-maximum for sample grown with the highest nitrogen content in the plasma. Optical and atomic force microscopy revealed dramatic changes in surface morphology with variation in each parameter. The nitrogen incorporation in carbon-13 diamond layers was monitored through photoluminescence spectroscopy of nitrogen–vacancy complexes. A twentyfold increase in diamond growth rate was clearly achieved in this multivariable study.

A high-conductivity and super-high-strength alloy, Cu-8.0Ni-1.8Si-0.6Sn-0.15Mg, has been developed. The processing conditions of the alloy have been investigated. The evolution of microstructure of the alloy on aging has been examined by transmission electron microscopy. The processing condition giving the highest hardness and good electrical conductivity is as follows: solution treatment at 970 °C for 4 h, cold rolling to 60% reduction, and aging at 500 °C for 30 min. The processed alloy has an average tensile strength of 1180 MPa, 0.2% proof strength of 795 MPa, elongation of 2.75%, and average electrical conductivity of 26.5% IACS. Orthorhombic Ni2Si precipitates are responsible for the age-hardening effect. The orientation relationship between the precipitates and the matrix is (110)m(211)p and. DO22 ordering together with spinodal decomposition also contributed to the hardening.

Highly sinterable La10Si6O27 and La10Si5.5M0.5O27 (M = Mg, and Al) nanopowders with apatite-type structure have been synthesized via a homogeneous precipitation method using diethylamine (DEA) as a precipitant. The synthetic approach using an organic precipitant with dispersant characteristics is advantageous in configuring weakly agglomerated nanopowders, leading to desirable sintering activity. X-ray diffraction powder patterns confirmed the single-phase crystalline lanthanum silicate of hexagonal apatite structure at 800 °C, which is a relatively lower calcination temperature compared to conventionally prepared samples. Transmission electron microscopy images revealed particles ∼30 nm in size with a high degree of crystallinity. A dense grain morphology was recognized from the scanning electron microscopy images of the polished surface of the pellets that were sintered at 1400 and 1500 °C for 10 h. This low-temperature sintering is significant because conventional powder processing requires a temperature above 1700 °C to obtain the same dense electrolyte. The doped-lanthanum silicate electrolyte prepared by the DEA process and sintered at 1500 °C for 10 h exhibited electrical conductivity comparable with samples prepared at much higher sintering temperature (>1700 °C).

This work investigates the coating of nano- to submicron-sized hollow nickel particles onto Al powders to optimize the thermal and combustion properties of Al-based energetic materials. Different wt% of hollow nickel particles coated onto Al particles was synthesized using an autocatalytic aqueous reduction method. X-ray diffraction results showed distinct crystalline Al and Ni phases indicating that a pure coating process was achieved. Homogeneous coating of hollow nickel particles onto individual Al particles was also reflected from the scanning electron microscope images. All the samples showed significant improvements in terms of their ignition and kinetics of combustion as compared to untreated Al. The most promising candidate produced was the 30wt%Ni–Al sample whereby the %complete combustion of Al exhibited the largest improvement. The hollow Ni-coated Al samples were also found to perform better than their physically mixed Ni–Al powder samples, as there is more intimate contact between the two components to hasten the overall combustion kinetics.

The use of magnetic elements within microelectronic devices are increasingly required in the fabrication of miniature magnetic structures with high energy densities. A synthesis technique is reported that yields Sb-doped CoPt nanoparticles possessing magnetic coercivities as high as 1671 kA/m and magnetic remanences of 295 kA/m, providing an energy product of 20 kJ/m2. Antimony doping was shown to influence the atomic ordering within the alloy sublattices, which allowed the tetragonalization temperature of the nanoparticle structure to be lowered by 200 °C to 400 °C, thereby reducing crystallite growth and sintering during annealing. The “as-synthesized” particles had average diameters of 4.5 nm, which rose to 25 nm on annealing at 600 °C. Synthesis of the doped CoPt particles with high-energy products together with control of particle size distributions in the range of 25 nm allows fabrication of micromagnetic structures by conventional microfabrication techniques such as spin coating and ink-jet printing.

A new method is proposed to determine the elastic modulus and residual stress of freestanding thin films based on nanoindentation techniques. The experimentally measured stiffness-displacement response is applied to a simple membrane model that assumes the film deformation is dominated by stretching as opposed to bending. Dimensional analysis is used to identify appropriate limitations of the proposed model. Experimental verification of the method is demonstrated for Al/0.5 wt% Cu films nominally 22 µm wide, 0.55 µm thick, and 150, 300, and 500 µm long. The estimated modulus for the four freestanding films match the value measured by electrostatic techniques to within 2%, and the residual stress to within 19.1%. The difference in residual stress can be completely accounted for by thermal expansion and a modest change in temperature of 3 °C. Numerous experimental pitfalls are identified and discussed. Collectively, these data and the technique used to generate them should help future investigators make more accurate and precise measurements of the mechanical properties of freestanding thin films using nanoindentation.

We investigated the reduction of TiO2 in the presence of Ni by nonequilibrium hydrogen gas, including low-temperature hydrogen plasma at 800 °C and supercooled monatomic hydrogen at 1000 °C. TiO2 was reduced to Ti2O3, which is not in equilibrium phase, by low-temperature hydrogen plasma. The results of x-ray diffraction and energy dispersive x-ray analysis in experiments at 1000 °C indicate that the thermodynamical reduction potential of supercooled monatomic hydrogen is almost the same as atmospheric hydrogen gas. However, the wide Ti3O5 layer formed only in the case of the reduction at 1000 °C by supercooled monatomic hydrogen. With these experimental facts, we speculate that the reduction mechanism by nonequilibrium hydrogen consists of two steps; the releasing energy process and the relaxation process. We can explain the difference of reduction products by nonequilibrium hydrogen gas on the assumption of the rate of the relaxation process between 800 and 1000 °C.

Microstructure features of five electrodeposited coppers with different grain sizes were systematically characterized by using transmission electron microscopy (TEM) observations and x-ray diffraction (XRD) analysis. Based on the experimental observations, two mechanisms for the grain refinement in electrodeposited copper were identified: (i) twin–twin intersection can directly create grains with large-angle boundaries as small as 10 nm and (ii) grains can also be refined via formation of dislocation cells, transformation of dislocation cell walls into sub-boundaries with small misorientations, and evolution of sub-boundaries into highly misoriented grain boundaries. Besides, dislocations are also effective to cut twin lamellas into pieces and make twin boundaries curved and round.

Single-phase nanocrystalline 4CaO·Al2O3·Fe2O3 powders were prepared directly from the combustion reaction using a new cost-effective, time-saving, and environmentally friendly version of solution combustion synthesis. Instead of a single fuel, a fuel mixture of urea and β-alanine was used. It was shown by x-ray diffraction, energy-dispersive x-ray analysis, thermogravimetric analysis, and optical microscopy that this new version of the solution combustion synthesis allows the maximization of the exothermic effect associated with the combustion reaction. On the other hand, it was shown that the traditional version of combustion synthesis involving the use of a single fuel, such as urea or β-alanine, does not ensure the formation of Ca4Al2Fe2O10 unless subsequent thermal treatments are applied. It was suggested that the occurrence of combustion reactions cannot be regarded only in terms of adiabatic temperature, as the kinetic aspects overrule the thermodynamic ones.

Instrumented indentation experiments on a Zr-based bulk metallic glass (BMG) in as-cast, shot-peened and structurally relaxed conditions were conducted to examine the dependence of plastic deformation on its structural state. Results show significant differences in hardness, H, with structural relaxation increasing it and shot peening markedly reducing it, and slightly changed morphology of shear bands around the indents. This effect is in contrast to uniaxial compressive yield strength, σy, which remains invariant with the change in the structural state of the alloys investigated. The plastic constraint factor, C = H/σy, of the relaxed BMG increases compared with that of the as-cast glass, indicating enhanced pressure sensitivity upon annealing. In contrast, C of the shot-peened layer was found to be similar to that observed in crystalline metals, indicating that severe plastic deformation could eliminate pressure sensitivity. Microscopic origins for this result, in terms of shear transformation zones and free volume, are discussed.

In this work, we report a new Mg-based glass-forming system of Mg–Ni–(Gd,Nd), which can be produced into glassy rods with maximum diameters of 2–5 mm by copper mold casting. The Mg75Ni15Gd10–xNdx(x = 0–10) BMGs simultaneously possess a high level of glass transition temperatures, high specific strength up to 2.75 × 105 Nm/kg, and enhanced malleability with plastic strains over 1%. In particular, the Mg75Ni15Gd5Nd5 BMG with the glass-forming ability (GFA) up to 5 mm, exhibited compressive yield strength over 900 MPa and plastic strain up to 50% without failure for the specimen with an aspect ratio of 0.5. The improved GFA and malleability for the Mg75Ni15Gd10–x Ndx(x = 0–10) BMGs were discussed, which exhibited their promising potentials for the application as lightweight engineering materials.

The effect of temperature on grinding-induced texture in tetragonal lead titanate (PT) has been investigated as a function of the magnitude of loading applied to the sample surface during grinding, using in situ x-ray diffraction (XRD) with an area detector. Compared to the ground PT under lower loading conditions (5 N), the ground PT under higher loading conditions (40 N) retains strong ferroelastic texture near the Curie temperature (TC) around 350 °C and undergoes smaller changes in lattice parameter or tetragonality versus temperature during in situ thermal cycling between room temperature and approximately 100 °C above the TC. Inhibited depoling of ground PT materials investigated by in situ texture measurements demonstrates the effects of residual stresses.

Despite active development over the past 15 years, contemporary nanoindentation methods still suffer serious drawbacks, particularly long thermal stabilization and thermal drift, which limit the duration of the measurements to only a short period of time. The presented work introduces a novel ultra nanoindentation method that uses loads from the μN range up to 50 mN, is capable of performing long-term stable measurements, and has negligible frame compliance. The method is based on a novel patented design, which uses an active top referencing system. Several materials were used to demonstrate the performance of the method. The measurements with hold at maximum load confirm extremely low levels of instrument thermal drift. The presented Ultra Nanoindentation Tester opens new possibilities for testing thin films and long-term testing, including creep of polymers at high resolution without the need of long thermal stabilization.

The in situ x-ray diffraction observations of the bainitic transformation were conducted by using the high-temperature x-ray diffraction technique. The volume fraction and carbon content of austenite depend on the transformation temperature. The d{110} value of bainitic ferrite decreases with increasing austempering temperature, which is related to the decrease of carbon concentration in bainitic ferrite. Asymmetry diffraction peaks are obtained for samples at the early stage of transformation at any austempering temperatures. This asymmetry diffraction peak after the formation of bainitic ferrite could be attributed to a heterogeneous distribution of carbon in different regions of austenite and show that two types of austenite with different carbon contents, low-carbon austenite (γLC) and the high-carbon austenite (γHC), exist during the transformation. The microstructure after cooling down to room temperature is presented to show the effectiveness of the x-ray diffraction analysis.

In this study, nucleation of dislocations in magnesium oxide (MgO) during nanoindentation with a spherical indenter is investigated. For flat and defect-free surfaces prepared by chemo/mechanical polishing, reversible load–displacement curves have been obtained for load as high as 300 mN, whereas on a cleaved MgO surface, pop-in and plastic deformation occur at 10 mN with the same indenter. Furthermore, these reversible curves deviate from the Hertz contact theory. Indented areas have then been characterized by atomic force microscopy and nanoetching. In some cases, few slip lines are observed for reversible indentation tests. However, the slip lines position indicate that the nucleation process of the corresponding dislocations is different from that involved during a pop-in phenomenon.

We report that various metallic glassy nanostructures including nanoridges, nanocones, nanowires, nanospheres, and nanoscale-striped patterns are spontaneously formed on the fracture surface of bulk metallic glasses at room temperature. A clear correlation between the dimensions of these nanostructures and the size of the plastic zone at the crack tip has been found, providing a way to control nanostructure sizes by controlling the plastic zone size intrinsically or extrinsically. This approach to forming metallic glassy nanostructures also has implications for understanding the deformation and fracture mechanisms of metallic glasses.

Dispersed crystalline copper particles were prepared by reacting aqueous dispersions of CuCl with ferrous citrate. We report that the Fe(II) citrate complex can reduce rapidly and completely cuprous chloride to metallic copper and propose a mechanism for the reaction observed. By changing the precipitation conditions, copper particles with sizes varying from 250 nm to 2.0 µm were obtained. The method described represents a simple and versatile approach for preparing copper powders for electronic applications.

One embodiment of YBa2Cu3O7-x (YBCO)-coated conductors consists of YBCO film grown using a metal-organic deposition (MOD) process on a buffer layer stack deposited on a Ni-W substrate. A possible alternative is to replace the multilayer buffer stack with a single layer of LaMnO3 (LMO) grown by MOD. A suitable temperature (T) – oxygen partial pressure (PO2) process-window to grow LMO films via MOD on Ni substrates has been identified. Untextured LMO was grown on pure Ni. However, we have not been able to grow phase-pure LMO films on either bare or Y2O3-coated, biaxially textured Ni-5W (at.%) due to the incongruent, overlapping requirements of having the PO2 low enough to not oxidize the Ni-5W substrate but high enough to convert the metal-organic precursors to LMO and the relatively high temperatures needed to form an epitaxial film in an MOD process. The main problem is that tungsten from the substrate reacts with cations in the overlying film forming tungstates when the films are processed in the T-PO2 window.

The current study shows that there is a preferred orientation relationship between Ag3Sn and Ag in reaction between molten Sn and Ag. Due to the preferred orientation relationship, the morphology of Ag3Sn grains formed on (001) Ag single crystal is different from those formed on (011), (358) single crystal Ag, and polycrystalline Ag Facet scallop-type Ag3Sn grains formed irregularly on (011), (358) single crystal Ag, and polycrystalline Ag; whereas the regular Ag3Sn grains with parallel edges grew on (001) Ag single crystal, and they were elongated along two perpendicular directions. The orientation relationship between Ag3Sn grains and (001) Ag single crystal was determined using electron backscattered diffraction. The preferential growth of regular Ag3Sn grains with parallel edges formed on (001) Ag single crystal can be attributed to their minimum misfit.