Solid-state batteries with lithium metal anodes have the potential for higher energy density, longer lifetime, wider operating temperature, and increased safety. Although the bulk of the research has focused on improving transport kinetics and electrochemical stability of the materials and interfaces, there are also critical challenges that require investigation of the mechanics of materials. In batteries with solid-solid interfaces, mechanical contacts, and the development of stresses during operation of the solid-state batteries, become as critical as the electrochemical stability to keep steady charge transfer at these interfaces. This review will focus on stress and strain that result from normal and extended battery cycling and the associated mechanisms for stress relief, some of which lead to failure of these batteries.

Instrumented indentation performed at room temperature with a Berkovich and 10 μm radius sphere has been used to measure the stress exponent for creep before and after the strain burst observed in well-annealed, high-purity indium. Before the strain burst, the measured values are successfully rationalized using a new model based on stress directed diffusional flow along the interface between the indenter tip and test specimen. After the strain burst, the measured stress exponents are found to be representative of dislocation glide and climb assisted glide. These results are compared and contrasted to the previous experimental investigations and modeling efforts of Feng et al., Lucas et al., and Li et al. Collectively, the experimental observations and rationalization presented here provide significant new insight into the mechanisms of action that control the competition for stress relief in small, constrained volumes of crystalline metals subjected to high homologous temperatures.

Acid-detecting strips (A-D Strips (R)) available from the Image Permanence Institute (IPI) and third-party suppliers outside the USA were originally developed to detect volatile acids from deteriorating film stock made from cellulose acetate (CA) by using a five-step colour scale to represent acetic acid concentration. The strips are shown here to be sufficiently sensitive for the detection of acetic acid as a volatile organic compound (VOC) generated by degrading CA in objects in storage. In confined spaces, the local air concentration of VOCs can deviate significantly from background levels due to low air circulation and interaction with solid materials and can be explored by this means. The usefulness of placing a number of A-D Strips (R) with CA-based artworks stored in closed containers, instead of or during the deployment of SPME fibres to monitor the degradation of these plastics, is assessed critically. The useful level of indicative and semi-quantitative information they can offer in such practical situations is presented. It is proposed that an interpretation of acetic acid concentration on an eight-step colour scale of measurement of b* in CIELAB1976 colour space with a hand-held spectrophotometer, or visual comparison with the IPI-provided colour scale is more useful than a direct calculation of concentration, because placement around stored objects introduces significant measurement errors. This paper gives guidance on the limitations and benefits of using A-D Strips (R) as a low-cost passive monitoring tool for CA-based objects, whether visibly degraded or not. The guidance is also relevant for monitoring VOCs derived from wood-based crating materials used in museum storage areas, which also generate acetic acid.

Sc and Zr additions in Al matrix offer enormous potential for strengthening at elevated temperatures due to formation of coarsening resistant precipitates. The high-temperature properties of supersaturated Al-0.4Sc-0.4Zr at% alloy, produced via melt-spinning and extrusion, were studied in creep and elevated temperature compression. Given the larger amount of solute resulting from rapid solidification, the elevated temperature compressive strength of the supersaturated Al-0.4Sc-0.4Zr at% was significantly higher compared to dilute Al-0.06Sc-0.06Zr at%. The operating deformation mechanism at elevated temperatures in both alloys was dislocation climb, and the difference in threshold stress was assessed between Al-0.4Sc-0.4Zr at% and Al-0.06Sc-0.06Zr at%. The larger threshold stress in the supersaturated Al-0.4Sc-0.4Zr at% was attributed to the different microstructure due to the processing. The stress exponents and activation energies from the creep tests are consistent with the diffusion-controlled dislocation climb mechanism. The small grain size led to diffusional creep in the low stress regime in both alloys.

Al-Sc-Zr alloy contains precipitate Al(Sc,Zr) shows good coarsening resistance due to the small diffusivities of Sc and Zr. Two supersaturated Al-0.4Sc-0.4Zr at% alloys were produced using melt-spinning and following extrusion. The coarsening behavior of supersaturated Al-0.4Sc-0.4Zr at% alloys was investigated using scanning transmission electron microscopy (STEM). Accelerated coarsening was observed in the extruded melt-spun ribbon with larger precipitate size and higher precipitate volume fraction than in melt-spun ribbon. The accelerated effective diffusivity after extrusion was explicitly linked to the initially refined extruded microstructure. Precipitate volume fraction and chemical composition in both melt-spun ribbon and extruded rod during annealing were quantified with the help of STEM and energy-dispersive x-ray spectroscopy. Precipitate size and number density were predicted using Umantsev-Olson-Kuehman-Voorhees model for ternary alloys, and the predictions showed good agreement with experimental results by considering changes in diffusivity and precipitate volume fraction.

Nanoindentation and electron microscopy have been used to examine the length-scale-dependent stress relaxation mechanisms in well-annealed, high-purity indium at a homologous temperature of 0.69. The experimental methods, analysis, and observations serve as a stepping stone in identifying the stress relaxation mechanisms enabling the formation and growth of metallic dendrites originating at the buried interface between a metallic anode and a solid electrolyte separator. Indium’s load–displacement data are found to be very similar to that of high-purity lithium. Residual hardness impressions show two distinct surface morphologies. Based on these morphologies, the measured hardness, and the estimated pile-up volume, it is proposed that residual impressions exhibiting significant pile-up are the result of deformation dominated by interface diffusion. Alternatively, impressions with no significant pile-up are taken to be the result of shear-driven dislocation glide. An analytical model is presented to rationalize the pile-up profile using interface diffusion.

ABSTRACT Rapidly formed eutectic textures are observed in Fe silicides in a fulgurite from Michigan. The 14 cm-diameter fulgurite was formed in sandy glacial till in 2014 near Houghton Lake, Michigan. Spherical droplets of iron silicides up to ∼200 μm in diameter were found in the natural glass. Back-scattered electron images of some droplets show a eutectic intergrowth texture of two iron silicides with individual crystals up to ∼1 μm in maximum dimension. X-ray diffraction study showed the specimens to be an intergrowth of naquite (FeSi) and linzhiite (FeSi2) or naquite and xifengite (Fe5Si3). Droplets also contain minor native silicon, Fe-Ti silicides, and/or other Ti- rich phases which were discovered during TEM observations. It is important to note that the lower-temperature phase luobusaite (Fe3Si7) was not observed in any droplets, indicating rapid quenching of the fulgurite, consistent with a natural origin during a lightning strike as opposed to an artificial origin, e.g., resulting from a downed power line.

Under electrochemical cycling, stress intensification and relaxation within small volumes at the lithium/solidstate electrolyte (SSE) interface are thought to be critical factors contributing to mechanical failure of the SSE and subsequent short- circuiting of the device. Nanoindentation has been used to examine the diffusion-limited pressure lithium can support in the absence of active dislocation sources at high homologous temperatures. Based on the underlying physics of this deformation mechanism, a simple perturbation model coupling local current density, elastic stress, and diffusional creep relaxation is introduced. Combining this analysis with the indentation results, it is possible to describe a defect length scale which is too large for effective diffusional creep relaxation, but too small for efficient dislocation multiplication. In this instance, the properties of the SSE may become critical, and relevant indentation results of the SSE are described. The final outcome of the proposed analysis is a newly developed deformation mechanism map.

Nanoindentation experiments are performed at the vicinity of grain boundaries, in Fe–Si tricrystals, to illustrate the existence of a critical stress at which slip transmission occurs across grain boundaries. Such a critical stress can be considered as a grain boundary yield stress and can be quantified within the framework of conventional gradient plasticity theory, enhanced by introducing a new mechanically induced “interface energy” term. The present study takes a first step in trying to provide a physical interpretation for this “far from thermodynamic equilibrium” interface energy term by conducting nanoindentation tests in three Fe–3wt%Si tricrystals, each of which had three distinct types of grain boundary misorientations, namely 22.5°, 42.0° and 44.6°. By relating the experimentally measured grain boundary yield stress to the predictions of interfacial gradient plasticity, it is possible to determine the interface parameter (\( \xi \)), which provides a measure of the resistance to slip transmission for each grain boundary examined. In particular, microscopic arguments from standard dislocation theory reveal that \( \xi \) depends on both the grain interior properties and the grain boundary structure. The internal length is shown to depend on multiple characteristic lengths of the microstructure, while a new expression is deduced for relating the Hall-Petch slope to both the interface parameter and internal length.

The extrinsic indentation size effect (ISE) is utilized to analyze the depth-dependent hardness for Berkovich indentation of non-uniform dislocation distributions with one and two dimensional deformation gradients and is then extended to indentation results at grain boundaries. The role of the Berkovich pyramid orientation and placement relative to the grain boundary on extrinsic ISE is considered in terms of slip transmission at yield and plastic incompatibility during post-yield deformation. The results are interpreted using a local dislocation hardening mechanism originally proposed by Ashby, combined with the Hall–Petch equation. The Hall–Petch coefficient determined from the extrinsic ISE of the grain boundary is found to be consistent with the published values for pure Fe and mild steel. A simple, linear continuum strain gradient plasticity model is used to further analyze the results to include contributions from a non-uniform distribution in plastic strain and dislocation density.

Sn anodes for Na-ion batteries exhibit a promising initial capacity of 847 mAh g(-)1, which however, cannot be retained throughout continuous cycling due to the 420% volume changes that Sn experiences during sodiation. Previous experimental studies suggest that fracture does not occur in the submicron Sn particles during the formation of Na-Sn alloys; however, such colossal volume changes must result in microstructural damage. In the present work, the damage mechanisms during sodiation are isolated and accentuated by employing a Sn thick film of 0.5 mm as the anode. This simplified planar geometry allows to dispense with the influence of the binder and carbon additives that are required in porous electrodes. Post-mortem electron microscopy revealed new deformation mechanisms for anode materials, as multiple whiskers nucleated on the surface of the Sn, whereas pores formed within the Sn (over the Na-ion penetration distance) after electrochemical cycling. These mechanisms were in addition to the dry lake-bed fracture that was also observed. A comparative study on a Sn thin-film anode of 0.06 mm revealed the formation of fracture and pores after cycling, but no whiskers. The whiskers and pores observed in the thick Sn film anode may be more subtle at the nanoscale, and therefore have not been reported for submicron Sn particles in porous electrodes during sodiation.

Surface texturing of Si has attracted significant attention over the past decades as micro/nano patterns allow for preferred opto-electronic and electrochemical properties. Here a new fabrication method, based on etching in aqueous NaOH-polyethylene glycol solution is presented, which allows the formation of novel eight and twelve sided Si micropyramids. Particularly, the presence of NaOH resulted in the formation of four sided facets along intersecting {111} planes, while with continuous etching the high molar mass polyethylene glycol resulted in the formation of four additional facets identified to be (212) planes producing octagonal pyramids. Further etching of these octagonal pyramids lead to the formation of twelve-sided pyramids. Eight-faceted (octagonal) pyramids have been reported in the literature, but only through the use of photolithography, while twelve-faceted (dodecagonal) pyramids have not been observed for any type of crystal.

Nanoindentation experiments performed in high-purity vapor deposited lithium films at 31 °C reveal a strain rate and length scale dependence in the stress at which pop-in type events signal an abrupt transition from diffusion to dislocation-mediated flow. The stress level at which the transition to dislocation-mediated flow occurs varies with the strain rate and ranges from 88 to 208 times larger than the nominal yield strength of bulk, polycrystalline lithium. Variation in the indentation strain rate reveals the relationship between the stress required to initiate the transition and the length scale at which the transition occurs follows the power-law relation, hardness × depth^1.17 = 1.545 N/m^0.83, where the magnitude of the exponent and constant reflect the defect structure of the film. A rationalization of the transition is provided through direct comparisons between the measured cumulative distribution function (CDF) and the CDF hypothesized for the activation of a Frank-Read source.

Nanoindentation has been used to measure the elastic modulus of 5 and 18 μm thick high-purity vapor deposited polycrystalline lithium films at 31 °C. Over indentation depths ranging from 150 to 1100 nm, the modulus is found to vary with film thickness from 9.8 GPa ± 11.9% to 8.2 GPa ± 14.5%. These results are well within the range of lithium’s orientation dependent elastic modulus, which spans approximately 3.1 to 21.4 GPa. The measured values may also indicate (111) and (100) texture for the 5 and 18 μm thick films, respectively. The potential effects of pileup and surface contamination are found to be negligible if any at all. Small but discernible changes in damping capability near the free surface may provide insight into the subsurface defect structure and the potential for localized heating. Numerous experimental challenges are addressed and key metrics are used to validate the measured elastic modulus.

Instrumented indentation of a high purity Fe surface with unresolved surface deformation due to mechanical polishing is compared to the same grain surface annealed at increasing time and temperature. The differences in indentation size effect behavior with annealing are correlated with hardness and electron backscatter diffraction measurements as independent measures of surface layer deformation. It is found that the Nix Gao plot evolves from non-linear (bilinear) towards the predicted linear relationship as the surface deformation is removed. The experimental observations are rationalized by inclusion of a depth dependent, polishing induced forest dislocation density within the Nix-Gao model.

Both tin (Sn) and sulfur (S) can act as hosts for lithium-ions and, therefore, Sn/C and SnS/C nanocomposites, prepared by the solution method, have the potential to be used as anodes in next-generation Li-ion batteries. One of the key factors in the design of promising anodes is the ability of their microstructure to accommodate the Li-insertion and de-insertion; hence, in the present study, various carbon types were employed, and the metal volume fractions (S and Sn) were varied in order to determine the most promising microstructures. Particularly, the types of carbons, which were considered in this study, were artificial graphite (AG), mesocarbonmicrobeads (MCMB), and graphene (GC). To prepare Sn/graphene composites, the amount of Sn was made to vary between 10 wt.% and 20 wt.%. As for the SnS/C materials, the Sn and S ratios were 10 : 10 and 20 : 20, and the types of carbon used were MCMB and AG. X-ray diffraction showed that Sn and SnS phases develop within graphite, and scanning electron microscopy revealed that these phases disperse well in graphite. Furthermore, transmission electron microscopy allowed for a better observation of the nanometer dimensions of the particle size in all the samples.

The project investigated the local mechanical behavior of metal grain boundaries with and without the influence of a segregated alloy element, specifically in the Fe-C alloy system. Local deformation was carried out using nano-indentation with varying indentation-grain boundary geometry and strain rate. Stress relaxation under constant load and strain rate response to stress jumps were used to determine activation energy, activation volume and athermal stress as a function of grain boundary chemistry. The primary accomplishments of the project were (i) resolving the action of the proposed Ashby mechanism of grain boundary hardening from the action of the accepted Hall-Petch mechanism (ii) revealed the relationship between grain boundary chemistry, activation energy and athermal stress.

Merelaniite is a new mineral from the tanzanite gem mines near Merelani, Lelatema Mountains, Simanjiro District, Manyara Region, Tanzania. It occurs sporadically as metallic dark gray cylindrical whiskers that are typically tens of micrometers in diameter and up to a millimeter long, although a few whiskers up to 12 mm long have been observed. The most commonly associated minerals include zoisite (variety tanzanite), prehnite, stilbite, chabazite, tremolite, diopside, quartz, calcite, graphite, alabandite, and wurtzite. In reflected polarized light, polished sections of merelaniite are gray to white in color, show strong bireflectance and strong anisotropism with pale blue and orange-brown rotation tints. Electron microprobe analysis (n = 13), based on 15 anions per formula unit, gives the formula Mo4.33Pb4.00As0.10V0.86Sb0.43Bi0.33Mn0.05 W0.05Cu0.03(S14.70Se0.30)Σ15, ideally Mo4Pb4VSbS15. An arsenic-rich variety has also been documented. X-ray diffraction, electron diffraction, and high-resolution transmission electron microscopy show that merelaniite is a member of the cylindrite group, with alternating centered pseudo-tetragonal (Q) and pseudo-hexagonal (H) layers with respective PbS and MoS2 structure types. The Q and H layers are both triclinic with space group C1 or C 1 ¯ . The unit cell parameters for the Q layer are: a = 5.929(8) Å; b = 5.961(5) Å; c = 12.03(1) Å; α = 91.33(9); β = 90.88(5); γ = 91.79(4); V = 425(2) Å3; and Z = 4. For the H layer, a = 5.547(9) Å; b = 3.156(4) Å; c = 11.91(1) Å; α = 89.52(9); β = 92.13(5); γ = 90.18(4); V = 208(2) Å3; and Z = 2. Among naturally occurring minerals of the cylindrite homologous series, merelaniite represents the first Mo-essential member and the first case of triangular-prismatic coordination in the H layers. The strongest X-ray powder diffraction lines [d in Å (I/I0)] are 6.14 (30); 5.94 (60); 2.968 (25); 2.965 (100); 2.272 (40); 1.829 (30). The new mineral has been approved by the IMA CNMNC (2016-042) and is named after the locality of its discovery in honor of the local miners.

Acid-detector (A-D) strips were originally developed to assess the deterioration of acetate film stock, but they can also be used more generally within enclosures to detect volatile acidic pollution. A hand-held reflectance spectrophotometer was used to record the colour of individual strips in order to make consistent and reproducible readings. Calibration was carried out using the yellow-blue axis b*(D65) value in the CIELAB1976 system to measure the colour of A-D strips suspended in enclosed containers over solutions of acetic acid in combinations with glycerol to control the relative humidity (RH). A-D strips were found to be sensitive to changes in high RH (60–90%) but affected little by changes in lower RH or temperatures in the museum display and storage range. A-D strips can be used to establish the presence of volatile acids, record the indication of acid vapour concentration, explore conditions within a container, and to find sources of volatile acidity. They respond very quickly and several can be placed around an object. They therefore show promise for measuring slowly changing conditions, such as seasonal changes and the gradual accumulation of acidity in poorly ventilated containers and spaces. A-D strips proved useful in assessing air quality in storage and display enclosures. Examples and test results are presented. Well-sealed plywood transit frames and storage cases were found to be most polluted with volatile acids. Storage rooms with air filtration systems but filled with wooden objects had significantly reduced air quality.