A thin film composed of an ion-exchangeable layered oxide HxTi(2-x/4)⃞x/4O4 (HTiO) (where the open square, ⃞, is vacancy) is studied as an electrode material. The thin film prepared on an indium tin oxide substrate functions as an electrode for the redox reaction of Ru(bpy)32+/Ru(bpy)33+ without noticeable degradation. Lack of reaction in the presence of Fe(CN)64−/Fe(CN)63− indicates that reaction on this electrode occurs in the interlayers between titanate sheets. A Ru(bpy)32+-intercalated form of the electrode generates photocurrent under visible light irradiation.

Electron beam physical-vapor-deposited Y2O3-stabilized ZrO2 thermal barrier coating (TBC) samples were indented from room temperature to 900 °C using an instrumented high-temperature vacuum displacement-sensitive indenter. Hardness and elastic modulus were determined from the load–displacement curves recorded during indentation. Both the hardness and the elastic modulus of the TBCs were much lower than those of dense ceramics of a similar composition; this is attributed to the increased compliance that results from the porous columnar microstructure of the TBCs. In addition, the TBCs showed an unusual absence of elastic recovery at the residual indents compared to the dense ceramics.

A detailed study of the size, distribution, and morphology of oxide particles in as-sprayed deposited 5083 Al synthesized by reactive atomization and deposition was reported. The results indicated that the oxides exhibit thin-plate morphology and are distributed at prior droplet boundaries, grain boundaries, and grain interiors with a dimensional scale on the order of tenths of micrometers up to a few micrometers. The mechanisms involved in the formation of the observed oxide distribution were analyzed in detail.

The effects of heat treatments on strength and electrical conductivity after 100 h in air up to 1500 °C were evaluated on hot-pressed Si3N4–35 vol% MoSi2 composite. The long-term oxidation involves microstructural changes at the material surface and subsurface, such as the formation of oxide scales and of a multilayered microstructure. At T ⩾ 1200 °C, a glassy silicate phase is formed, which embeds cristobalite grains and highly textured Y2Si2O7 crystals. At the same time, MoSi2, assisted by oxygen, reacts with Si3N4 forming Mo5Si3, Si2N2O, and SiO2. The decrease of the room temperature flexural strength reached about 25% in the samples exposed at 1000 °C for 100 h, compared to the as-produced materials. On the contrary, after treatments at higher temperatures, the strength decrease is lower at 1500 °C, the residual strength is 836 ± 62 MPa with a strength decrease of about 8%. The surface oxide scale is an insulator and, consequently, the electrical resistivity of the composite rises from 10-3 to 107–109 Ωcm.

Fluorinated mesoporous organosilicate films were synthesized by sol-gel spin-coating on a quartz substrate using (heptadecafluorodecyl)trimethoxysilane, tetramethylorthosilicate, and n-cetyltrimethylammonium chloride as the fluoro-precursor, silica source, and supramolecular template, respectively. The photochromism efficiency of photochromic dyes (spiropyran) increases in the order non-porous < hexagonal mesoporous < fluorinated mesoporous organosilicate films. The relatively high efficiency of the photochromism of spiropyran in fluorinated mesoporous organosilicate films suggests that such films are promising materials for applications as optical shutters and light modulators.

The frictional behavior of rocks in the laboratory is reasonably well described by rate- and state-variable friction laws, which reproduce a rich variety of natural phenomena when used in models of earthquakes. Despite the widespread adoption of the rate and state formalism in earthquake mechanics, the physical mechanisms that occur at microscopic contacting asperities on the sliding surface, which give rise to the observed rate and state effects, are still poorly understood. In an attempt to identify these underlying mechanisms, a series of nanoindentation experiments on quartz, an abundant mineral in the earth’s crust, was conducted. These experiments demonstrate the utility of using continuous stiffness measurements as a means of obtaining reliable indentation creep data on hard materials like quartz at room temperature. The projected area of indentation in quartz increases linearly with the logarithm of the time of indentation, in agreement with the increase in real area of contact with log time inferred from slide-hold-slide friction experiments on quartz rocks. However, the increase in fractional area with time in the indentation tests was larger than that inferred from friction experiments by a factor of 1.7. Differences between the rates of fractional area increase in the two tests may indicate that the increase in contact area during the hold portion of slide-hold-slide tests was modulated by slip that occurs during reloading after the hold, as was observed for other materials. The nanoindentation results suggest that the increase in frictional strength (i.e., the increase of state in the rate- and state-variable friction laws) during slide-hold-slide friction experiments was caused by creep of the highly stressed asperity contacts.

Unloading rate and maximum load have been previously shown to affect the response of silicon to sharp indentation, but no such study exists for spherical indentation. In this work, a statistical analysis of over 1900 indentations made with a 13.5-μm radius spherical indenter on a single-crystal silicon wafer over a range of loads (25–700 mN) and loading/unloading rates (1–30 mN/s) is presented. The location of “pop-in” and “pop-out” events, most likely due to pressure-induced phase transformations, is noted, as well as pressures at which they occur. Multiple occurrences of pop-in and pop-out events are reported. Raman micro-spectroscopy shows a higher intensity of metastable silicon phases at some depth under the surface of the residual impression, where the highest shear stresses are present. A stability range for Si-II is demonstrated and compared with previous results for Berkovich indentation.

Using transmission electron microscopy, we studied aluminum-containing intergranular phases and secondary-phase particles at triple-junctions in SiC (hot-pressed with aluminum, boron, and carbon additions). This study of statistical high-resolution electron microscopy of intergranular films indicated that a large fraction of the vitreous intergranular films (in the as-hot-pressed SiC) crystallized during post-annealing in argon above 1000 °C. However, brief heating to 1900 °C indeed re-melted 25% of the crystallized intergranular films. The structural transitions were reflected in the statistical width distributions of the amorphous grain-boundary layers. At triple-junctions, Al2O3, Al2OC-SiC solid solution, and mullite phases were newly identified. These phases, together with others reported before, are represented in a quaternary phase diagram for 1900 °C. It is proposed that a SiC-Al2OC liquid domain should be included in this phase diagram.

Ta2O5–xEr2O3 (TE) films were produced by a sol-gel method and a dip-coating technique with heat treatment at 600–1000 °C. Their powders were also prepared from the same sol. The Er3+ fluorescence property of the TE films containing various contents of Er3+ was measured as a function of the heat-treatment temperature. In crystallized films, the Er3+ fluorescence was observed because water-related residues (Ta–OH and H2O) and carbon-related residues (–CH3, –CH2–, –(C ⁼ O)–, and C≡C–H) were removed from the films. It is shown from infrared absorption spectroscopy that Ta–O− and Ta ⁼ O structures dissolve the Er3+ ions selectively and play a role in dispersing the Er3+. The strongest Er3+ fluorescence is observed in the TE film with 2 mol% of Er2O3 because of its highest ability to disperse the Er3+ ions.

Ceramics with III-IV pyrochlore compositions, A3+2B4+2O7 (A = Y and rare earth elements; B = Ti, Zr, Sn, or Hf), show a wide range of responses to ion-beam irradiation. To evaluate the role of the B-site cations on the radiation stability ofthe pyrochlore structure-type, Gd2Sn2O7 and Gd2Hf2O7 have been irradiated by1 MeV Kr+. The results are discussed in terms of the ionic size and type ofbonding of Sn4+ and Hf4+ and compared to previous results for titanate andzirconate pyrochlores. Gd2Sn2O7 is sensitive to ion beam–induced amorphizationwith a critical amorphization dose of approximately 3.4 displacements per atom(dpa) (2.62 × 1015 ions/cm2) at room temperature and a critical amorphization temperature of approximately 350 K. Gd2Hf2O7 does not become amorphous at adose of approximately 4.54 displacement per [lattice] atom (3.13 × 1015 ions/cm2) at room temperature, but instead is transformed to a disordered fluorite structure upon ion-beam irradiation. Although the radius ratio of the A- to B-site cations provides a general indication of the type of radiation response of different pyrochlore compositions, the results for Gd2Sn2O7 emphasize the importance of bond type, particularly the covalency of the 〈Sn–O〉 bond in determining the radiation response.

We used Raman spectroscopy to characterize indentations on silicon. We focused our attention on the strain field around several indentations made on an (001) oriented silicon wafer with loads ranging from 100 mN to 10 N. Micro-Raman spectroscopy was used for the analysis of the indentation strain field. By multiplying the frequency shift of the optical phonon of silicon by the distance from the center of the fingerprint to the point under investigation, we were able to determine the strained zone extension accurately with the boundary between the strained area and the unperturbed area, which becomes clearly visible. This method allowed us to propose an equation valid over a large range of loads (0.1–10 N), which allowed us to estimate the size of the strained zone. We show that even in the absence of visible defects, the strain field extended to a region relatively far from the imprint in between cracks. The analysis of the radial and lateral cracks gives information where the proposed equations are valid.

The effects of conversion parameters on transport properties of YBa2Cu3O7-δ (YBCO) films on rolling assisted biaxially textured substrates (RABiTS) in the BaF2 ex situ process were investigated for total pressures Ptotal between 0.1 and 1.3 atm, water vapor pressures PH2O between approximately 7 and 70 Torr and processing temperatures TS between 700 and 790 °C. For this study, a 0.3-μm-thick Y–BaF2–Cu–O precursor film was deposited on a 1-cm-wide Ni=3 at.% W RABiTS with a buffer layer architecture of CeO2/YSZ/Y2O3/Ni deposited in single passes in various reel-to-reel systems for each layer. Under the conditions of Ptotal = 0.1 atm, TS = 740 °C and PO2 approximately 150 mTorr, JC > 2 MA/cm2 was obtained at 77 K and self field for PH2O ≤ 20 Torr. At higher PH2O (=70 Torr), however, the maximum attainable JC decreased. In addition, the JC at these higher PH2O dropped rapidly with increased dwell time. The highest JC, 2.5 MA/cm2, was achieved at 730 °C with Ptotal = 0.1 atm and PH2O approximately 7 Torr. Finally, the variation of IC with wet conversion time was performed at each processing temperature.

In the title of this paper (and also in several places in the text), the chemical notation for the orthorhombic semiconducting iron disilicide is given incorrectly. In the whole paper, the chemical formula “β-FeSi2.5” should be replaced by the formula “β-FeSi2”.

The influence of stress on the elastic modulus E and hardness H in soda-lime glass was studied in the Vickers residual stress field by nanoindentation. The Oliver–Pharr method of analysis first gave higher values of E and H, but after correcting for the pileup contact areas around the nanoindents, results consistent with literature values were obtained at regions in the stress field where the stresses were either low or close to zero. Determination of the pileup contact areas was made possible by the use of the atomic force microscope, which has facility for generating cross-section images of the indents. The elastic modulus was found to decrease with stress, which is explained with reference to the influence of applied stresses on the Si–O–Si bond angle. The hardness on the other hand did not depend on the stresses except in the region very close to the edge of the Vickers indent where the stresses are high.

Recent experiments with the National Institute of Standards and Technology (NIST) Electrostatic Force Balance (EFB) have achieved agreement between an electrostatic force and a gravitational force of 10−5 N to within a few hundred pN/μN. This result suggests that a force derived from measurements of length, capacitance, and voltage provides a viable small force standard consistent with the Système International d’Unités. In this paper, we have measured the force sensitivity of a piezoresistive microcantilever by directly probing the NIST EFB. These measurements were linear and repeatable at a relative standard uncertainty of 0.8%. We then used the calibrated cantilever as a secondary force standard to transfer the unit of force to an optical lever–based sensor mounted in an atomic force microscope. This experiment was perhaps the first ever force calibration of an atomic force microscope to preserve an unbroken traceability chain to appropriate national standards. We estimate the relative standard uncertainty of the force sensitivity at 5%, but caution that a simple model of the contact mechanics suggests errors may arise due to friction.

After this article appeared in the January 2004 issue of Journal of Materials Research, the authors noticed that Fig. 6(b) was incorrect. The correct figure is shown below.

Using continuous wafer-curvature measurements, stress generation was monitored as nickel thin films reacted with silicon substrates to form Ni2Si during isothermal anneals. A large compressive force developed during the reaction, but gradually relaxed after the reaction was complete. From a model for reactive film formation, a lower limit for the instantaneous stress associated with compound formation was found to be −2.00 ± 0.75 GPa. This instantaneous stress can be explained by a volumetric strain of 1.65 ± 0.62%, which is much smaller than the theoretical volume expansion of 62% in this system. These results suggest that significant inelastic deformation occurs during silicide formation. It was also found that diffusive creep relaxes the growth stress after the reaction. The observed instantaneous stress indicates that the energy of deformation associated with the reaction is of the same order as the energy that drives it, suggesting that stress generation and stress relaxation can play a significant role in the kinetics of reactive film formation.

The nanostructure, stoichiometry and sensing performance of SnO2 films grown by pulsed laser deposition (PLD) have been shown to be highly sensitive to the deposition conditions. In particular, PLD deposition under vacuum is known to produce films that are composed of both a polycrystalline SnO2 phase and an amorphous SnO phase, for deposition temperatures in the 20–600 °C range. The presence of such an amorphous SnO phase in the films greatly limits their practical use as gas-sensing devices.

This article was originally published in [J. Mater. Res. 19, 707 (2004)] and was incorrectly printed. The correct version appears below.