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A novel electroformed nanocrystalline nickel cobalt alloy (n-NiCo) developed for sheet metal applications was investigated in terms of microstructure, as well as mechanical, thermal stability, and corrosion properties. The as-received material with a grain size of 18 ± 5 nm exhibited enhanced hardness compared with conventional polycrystalline NiCo mainly due to the Hall–Petch strengthening effect. Differential scanning calorimetry and annealing treatment results revealed that the n-NiCo was stable up to 200 °C for at least 1 h, and the onset of abnormal grain growth was observed when the material was annealed to 250 °C. While low-temperature annealing treatment was shown to increase the hardness of the material slightly, annealing at temperatures of 300 °C and above resulted in a reduction in hardness due to rapid normal grain growth. The n-NiCo sheet exhibited mixed Ni/Co anodic polarization behavior in environments of varying pH.

Electrodeposition is considered as a cost-effective fabrication method for metal-diamond heat sink materials. However, the formation of the metal-diamond interface has not been addressed in detail to date although controlling the interfacial microstructures is crucial. In this study, we electrodeposited copper-diamond composite materials and observed that 66 μm sized diamond particles decreased the thermal conductivity of copper whereas 420 μm sized diamond particles increased the thermal conductivity. The differential effective medium (DEM) model analysis showed that the thermal boundary conductance values at the electrodeposited copper matrix-diamond interface were 1.3 MW/m2K and 3.1 MW/m2K when the diamond particle sizes were 66 μm and 420 μm, respectively. This discrepancy was attributed to the microstructure of the copper matrix in the vicinity of diamond particles, which was caused by particle size dependent current density distribution. These results show that particle size in electrodeposited composite materials can strongly affect the microstructure of the metal matrix.

Copper matrix composite materials with diamond particles are considered to be among the leading candidates as the heat sink materials for future electronic devices. However, today, these materials are mostly produced by high temperature-high pressure (HTHP) processes, which can be very costly. In order to explore an economically more viable approach of producing copper-diamond composite materials, we used electrodeposition to synthesize such materials and measured their thermal conductivities. The maximum thermal conductivity observed was 454 W/mK at 68.2 vol % diamond. In an attempt to improve the thermal conductivity further, titanium carbide (TiC) coatings were implemented on the diamond particles. The TiC coated diamond particles embedded in the electrodeposited copper matrix improved the thermal conductivity to 557 W/mK at 34.7 vol % , which is ∼ 40 % higher than 400 W/mK for pure copper. This value is comparable to currently available commercial HTHP heat sink materials. These results show that there is a potential of using electrodeposition an alternative synthesis method for producing copper-diamond composite materials for thermal managements. However, the formation of the microstructure at different electrodeposition current densities suggests that a careful process optimization is required to obtain a void-free Cu matrix between the embedded diamond particles.

Copper coatings produced by additive manufacturing techniques often present complex microstructural heterogeneity. Reducing microstructural heterogeneity is critical for promoting uniform mechanical and corrosion behavior. The current study examines copper coatings at the closure weld zone of a prototype steel container designed to store used nuclear fuel. In this region, the copper coating is produced by two additive manufacturing processes: electrodeposition and cold spray. Microscopy analysis revealed a highly non-uniform microstructure in the as-processed state. After heat treatment at 350 °C for 1 h under inert conditions, this heterogeneity was significantly reduced resulting in favourable microstructural characteristics for the current application.

Cold-sprayed Cu coatings are known to have low ductility as the microstructure is composed of dynamically recrystallized fine grains, as well as larger crystals with high dislocation density. Annealing is typically employed to restore the ductility of the Cu coating to form larger crystals with low dislocation density; however, the influence of annealing on the microstructure and chemistry of the particle-particle interfaces (PPIs) have yet to be explored in great detail. Here, we report the structural evolution of PPI after annealing treatments. Nanoscale pores at the PPI can be effectively reduced by annealing and the trapped oxide films in the as-sprayed coatings break up and coarsen following classical interfacial phenomena. As a result, metallurgical bonding between particles increased significantly, contributing to the enhanced ductility of the cold-sprayed Cu coating.

A novel thin film anodized aluminum oxide templating process was developed and applied to make nanopores with anisotropic etching on crystalline silicon through reactive ion etching, with the purpose of enhancing the anti-reflection of silicon substrates. A unique two-step anodizing method was introduced to create high quality nano-channels and it was demonstrated that this process is superior over a one-step anodization approach. It was found that pore to pore distance and pore density can be tuned by changing the applied potential within a range of 10–80 V. Optical characterization of the nanopatterned silicon showed an average 10% reduction in reflection in the UV–Vis wavelength range.

Engineered non-wetting surfaces inspired by biological species are of interest in the industry due to their potential applications such as water repelling, self-cleaning, anti-icing, anti-corrosion, anti-fouling, and low fluid drag surfaces. However, the adoption of non-wetting surfaces in large scale industrial applications has been hampered by synthesis techniques that are not easily scalable and the limited long term stability and wear robustness of these surfaces in service. In this study, we demonstrate a simple, low cost, and scalable electrochemical technique to produce robust composite coatings with tunable non-wetting properties. The composite coatings are composed of an ultra-fine grain nickel matrix with embedded hydrophobic cerium oxide ceramic particles. Comprehensive characterization, including wetting property measurements, electron microscopy, focused ion beam analysis, hardness measurements, and abrasive wear testing were performed to establish the structure-property relationships for these materials. The grain refinement of the nickel matrix contributes to the high hardness of the composites. As a result of the bimodal CeO2 particle size, hierarchical roughness is present on the surface of the composite, leading to remarkable non-wetting properties, even after 720 m of abrasive wear.

Controlling the wetting property of ceramics, which is characterized by their water contact angles (WCAs), is of great interest because of their better thermal and chemical robustness compared with polymer materials. Among many ceramics, rare earth oxides (REOs) have attracted attention because of their high WCA (∼115°). Although several non-wetting mechanisms of REOs have been proposed thus far, the intrinsic mechanism has not been clarified yet due to the lack of information on crystallographic orientation–surface energy (SE)–WCA relationships. Here we report the WCA of (001), (110), and (111) oriented REO epitaxial films, which have different surface energies. We found that the WCA of fresh REO epitaxial film surfaces, which were prepared using a pulsed laser deposition technique, strongly depends on the crystallographic orientations, WCA(111) > WCA(110) > WCA(001), which reflects the differences in surface energy; SE(111) < SE(110) < SE(001). Moreover, we found that the WCA on REOs increases rapidly and converges to about 80° upon exposure to ambient air, regardless of the crystallographic orientation, likely due to surface adsorption of airborne carbon species. The present finding of ‘There is a strong correlation between the crystallographic orientation, wetting property and the surface energy’ is of great importance for the understanding of the wetting properties of ceramics.

Electrodeposited nanocrystalline and conventional polycrystalline NiFe alloys of similar iron content were investigated to understand the effect of grain size on the corrosion behaviour of these materials. Potentiodynamic polarization testing in 1 N H 2 SO 4 revealed similar active-passive-transpassive behaviour with negligible differences in the Tafel and transpassive regions regardless of grain size. It is shown that differences in the region of active dissolution are the result of strong contributions of sulfur impurities in the nanocrystalline electrodeposits rather than being due to grain size alone.

Commercialization of superhydrophobic surfaces remains rather limited due to the high costs of many fabrication processes and the poor understanding of the long term stability of their non-wetting properties. In this study, degradation of a recently developed superhydrophobic nanocrystalline Ni-PTFE composite made by electrodeposition was evaluated by a linear abrasion test on SiC abrasive media. For comparison, the same abrasion test was also conducted on a commercially available superhydrophobic spray-on treatment to benchmark the wear performance of the Ni-PTFE composite. Due to the microstructure of the Ni-PTFE composite coating, remarkable non-wetting properties were observed after extensive abrasive wear.

Previous research has shown that electrodeposited metal-diamond composite materials exhibit excellent mechanical properties, but their potential applications for thermal management in electronic devices have not been addressed. In contrast to common high temperature-high pressure (HTHP) methods, electrodeposition could offer a more economically viable route for making metal-diamond heat sink materials. In this study, nanocrystalline nickel-diamond composite materials were produced by electrodepositon. Using them as a prototype, the feasibility of using electrodeposited metal-diamond composite materials for heat sink applications was examined. The maximum thermal conductivity of nanocrystalline nickel-diamond composite was 200 W/mK at 61 vol% diamond, which is 2.6 times higher than 77 W/mK for pure nanocrystalline nickel. In addition, the thermal boundary conductance in the composite materials produced by electrodeposition was comparable to that previously reported for copper-diamond composite materials produced by the HTHP method. These results are a promising sign for producing electrodeposited metal-diamond composite materials with thermal conductivities high enough for heat management applications.

The current study details an experimental analysis that elucidates the relationship between the processing history, microstructural evolution, and bulk properties of cold-sprayed pure FCC copper coatings. Particular attention is paid to determining the effect of low temperature ex situ and in situ annealing (350 °C; 1 h) on the evolution of microstructure (i.e. grains and subgrains) and porosity, as well as the combined influence of these defects on the bulk properties (microhardness, and electrical conductivity) and fracture mechanics of cold-sprayed copper. SEM, TEM, in situ TEM, and fractography analysis together revealed that the inherently brittle nature of the cold-sprayed metals cannot be explained solely by their porosity or microstructure; their fracture mechanics is most likely governed by the coupling interaction between porosity and the nanocrystalline dynamically/static recrystallized (RX) grains adjacent to the pores. Under tensile loading, pores (0.5–20 µm) in the as-sprayed copper can easily act as crack tips which then propagate along the adjacent RX grains (∼100 nm), resulting in a brittle cleavage fracture. Although low-temperature annealing was not sufficient to remove the porosity, it was capable of promoting recovery and grain growth in these RX grains. The ductility of the region ahead of the crack tips was therefore enhanced to promote dimpling and potentially crack blunting. Consequently, this low-temperature annealing improved the tensile ductility of the cold-sprayed copper by 2 orders of magnitude (from ∼0.2% to ∼25% strain).

The effect of high temperature exposure on the water wetting properties of co-electrodeposited superhydrophobic nickel-polytetrafluoroethylene (Ni-PTFE) nanocomposite coating on copper substrates was studied. This was accomplished by comparing the performance with a commercial superhydrophobic spray treatment (CSHST). The Ni-PTFE and CSHST coatings were both subjected to heating at temperatures up to 400 °C. Results showed that the Ni-PTFE was able to maintain its superhydrophobicity throughout the entire temperature range, whereas the CSHST became more wettable at 300 °C. Furthermore, additional abrasive wear tests were conducted on both materials that were subjected to heating at 400 °C. The Ni-PTFE remained highly non-wettable even after 60 m of abrasion length on 800 grit silicon carbide paper, whereas the CSHST coating was hydrophilic after 15 m.

The formation of “mud-cracking” networks in coatings and thin films is a widely observed phenomenon, particularly in Cr-containing electrodeposited materials. Here we have documented and described aspects of mud-cracking specific to Cr-containing electrodeposited alloys made from trivalent Cr electrolytes. In addition to describing the different crack patterns observed in these materials and their relationship to the electroplating parameters, thickness, and composition of the coatings, we also investigated a never-before-reported phenomenon of post-deposition time-dependent cracking. Our analysis shows that cracks continue to form after the electroplating procedure has been completed, generally saturating 2 h after synthesis, but can continue for days afterwards. We theorize that the behaviour is related to the state of oxygen in these samples, which can sometimes reach beyond 30 at.%. It is believed that the breakdown of Cr-hydroxides and Cr-hydrides drives the increase in internal stresses that result in continued cracking. As a result, this time-dependent cracking phenomenon may impact the suitability of certain Cr-alloy electrodeposits in some applications.

Room temperature thermoelectrical transport was investigated on a series of thick (300 μm), fully-dense electrodeposited nanocrystalline Ni materials with grain sizes below 50 nm. Strong grain size effects were observed on both electrical resistivity and thermal conductivity. As grain size decreased from 47 to 28 nm, the nanocrystalline Ni exhibited an increase in electrical resistivity from 9.42 to 10.2 μΩ cm, and a reduction of thermal conductivity from 74.7 to 67.3 W/m-K, respectively. Analysis shows that for the nanocrystalline Ni, the change in the values of thermal conductivity and electrical resistivity is mainly due to grain boundary contributions with limited impurity effects. Furthermore, the thermoelectrical transport behavior agrees well with the Wiedemann–Franz law. The corresponding Lorenz numbers varied only in a narrow range from 2.30 × 10 −8 to 2.37 × 10 −8 W Ω/K 2 for the nanocrystalline Ni and were well within the experimentally measured value range of 2.12–2.44 × 10 −8 W Ω/K 2 for coarse-grained Ni reported in the literature.

Electrodeposited nanocrystalline NiFe alloys are compared to their polycrystalline, coarse-grained counterparts to understand the effects of grain size reduction on the passivation kinetics and the chemical structure of the passive film. The passive film formed in acidic sulfate environment was characterized using parallel angle-resolved XPS (PARXPS) to obtain non-destructive compositional depth profiles. The composition (Ni:Fe) of the passive film was insensitive to grain size; however, grain size reduction resulted in increased anodic activity producing thicker films that contained increased concentrations of higher oxide species.

In the design of used nuclear fuel containers for deep geological repositories, copper is considered to be a suitable and long-lived barrier for corrosion resistance. The microstructures of state-of-the-art copper materials used in this application produced through extrusion, a grain boundary engineered electrodeposition technique and cold spraying were studied via electron backscattered diffraction. Desirable microstructural characteristics for localized corrosion resistance of pure copper were compiled from the literature considering grain size, grain boundary character distribution, and crystallographic texture. The subject copper materials were found to have favourable microstructures for localized corrosion resistance, in particular, a high fraction of special grain boundaries, especially Σ3 twins, rendering them suitable for the given application.

Potentiodynamic polarization behaviour of electrodeposited nanocrystalline and conventional polycrystalline Ni-Fe alloys of similar compositions was investigated in neutral (pH 7) and alkaline (pH 10) 0.5 M Na2SO4 environments. In neutral solution, elevated current densities and delayed passivation were observed for all nanocrystalline materials, independent of composition. This behaviour was attributed to sulfur, present in the nanocrystalline materials as an impurity, more so than an effect of grain refinement. In alkaline solution, the effect of sulfur was exceeded by oxide film formation, and no significant difference in corrosion behaviour was observed as a function of grain size i.e. intercrystalline volume fraction.

Metallic foams show great potential as functional materials, due to their large surface area, low density, good gas permeability, and high strength-to-weight ratio. Owing to the inherent properties of Ni, including relatively high electrical conductivity, catalytic activity, and corrosion resistance, Ni foams are excellent candidate materials in energy applications such as electrodes for batteries and dye-sensitized solar cells, as well as current collectors in solid oxide fuel cells. In this study, we characterized Ni foams made by the freeze casting process using multi-scale morphological and structural characterization techniques, including X-ray computed tomography (XCT), scanning electron microscopy (SEM), and electron backscattered diffraction (EBSD) to study the structure of the Ni foams on the scale of several micrometers to a few millimeters. The multi-scale structural characterization results showed that the freeze casting method was successful in creating Ni foams with uniform directional pores, and the relative densities/solid area fraction and pore distribution of the Ni foams were uniform across different sample thicknesses, which can be fine-tuned by varying the concentration of NiO powder in the slurry during freeze casting.

The work hardening behavior of electrodeposited nanocrystalline nickel (29 and 19 nm) was investigated under multiaxial loading and compared with coarse-grained nickel. Plastic strain gradients were introduced into the materials using large Rockwell D hardness indentations, and measured through cross-sectional hardness profiles. The results showed that the coarse-grained material exhibited substantial hardening up to twice the hardness of the deformation-free area due to dislocation mediated deformation, while the nanocrystalline materials displayed small hardness variations along the strain gradient, indicative of considerably reduced dislocation interactions. Moreover, the grain structure analysis (cumulative volume fraction and size distribution) for the nanocrystalline materials suggested the operation of both dislocation mediated and grain boundary controlled deformation mechanisms, the latter becoming more significant with increasing cumulative sample volume of very small grains. The plastic deformation zone sizes under Rockwell indentation of the 29 nm Ni are similar to those conventional materials with reduced strain hardening. Microhardness-indentation size effects were negligible in both the nanocrystalline and coarse-grained materials.

The objective of the current research is to create multifunctional metal matrix composite coatings that are able to provide high strength as well as high water repellency by electrodeposition of nanocrystalline nickel matrix with embedded polytetrafluoroethylene (PTFE) particles. The study of the co-deposition process demonstrated that the amount of PTFE co-deposited is highly dependent on the concentration of PTFE particles in the electroplating bath. A very high fraction of co-deposited PTFE was achieved (69 vol.%) using a concentration of 30 g/L of PTFE particles in the plating bath. The contact angle of the surface greatly increased when the PTFE content increased over 50 vol.%. At 69 vol.% PTFE the coatings had a contact angle of 152°. Saccharin was added to the electroplating bath in an attempt to refine grain size. Using transmission electron microscopy, the average grain size of the nickel matrix without saccharin was determined to be 27 nm for the coating containing 69 vol.% PTFE. However, no nickel grain size reduction was observed when saccharin was added as it was found that the composite samples already had a very fine grain structure likely due to the use of cetyltrimethylammonium bromide (CTAB) as a PTFE particle dispersant. The addition of saccharin provided no additional hardening of the composite while the wetting angle was greatly decreased at concentrations greater than 0.1 g/L.

The rapid growth and early development period of the dual-scale surface topography was studied on the adaxial leaf surfaces of two aspen tree species with non-wetting leaves: the columnar European aspen (Populus tremula “Erecta”) and quaking aspen (Populus tremuloides). Particular attention was focused on the formation of micro- and nano-scale asperities on their cuticles, which was correlated with the development of superhydrophobic wetting behaviour. Measurements of the wetting properties (contact angle and tilt-angle) provided an indication of the degree of hydrophobicity of their cuticles. Scanning electron microscopy and optical profilometry micrographs were used to follow the growth and major morphological changes of micro-scale papillae and nano-scale epicuticular wax (ECW) crystals, which led to a significant improvement in non-wetting behaviour. Both species exhibited syntopism in the form of small and larger nano-scale ECW platelet morphologies. These findings provide additional support for earlier suggestions that due to fluctuations in leaf hydrophobicity throughout the growing season, canopy storage capacity may also vary considerably throughout this time period.

Room temperature tensile testing was performed on a coarse-grained polycrystalline Ni (32 μm), a nanocrystalline Ni (23 nm) and two nanocrystalline Ni–Fe (16 nm) electrodeposits at two strain rates of 10−1 and 10−2/s. Strain localizations and local temperature increases were simultaneously recorded during tensile testing. For all materials, higher loads or higher strain rate generally resulted in higher peak temperature with the highest temperatures recorded in the fracture regions. The maximum temperature for the nanocrystalline materials was just over 80 °C, which is significantly below the reported temperatures for the onset of thermally activated grain growth. Therefore, the previously reported grain growth observed on similar materials after tensile deformation is likely not thermally activated but a stress-induced phenomenon. Despite the wide grain range from 16 nm to 32 μm, all samples exhibited similar strain localization behavior. Local strain variations initiated in the early stage of macroscopic uniform deformation, subsequent necking and fracture took place in the region of initial strain localization. While the coarse-grained polycrystalline Ni exhibited little strain rate sensitivity, gradually increased strain rate sensitivity was observed for the 23 nm Ni and the two 16 nm Ni–Fe samples, suggesting that both dislocation-mediated and grain-boundary-controlled mechanisms were operative in the deformation of the nanocrystalline Ni and Ni–Fe samples.

Type 304L stainless steel (SS) samples were used to investigate the correlation between carbide precipitation and triple junction structure derived from crystallographic data obtained by the orientation imaging microscopy associated with electron backscattered diffraction. The samples were solution treated and annealed at different sensitization temperatures/time to introduce various degrees of carbide precipitation at the interface region, thus different degrees of selectivity toward triple junctions. Four models were used to characterize triple junction microstructures: (i) the I-line and U-line model, (ii) the coincident axial direction (CAD) model, (iii) the coincident site lattice (CSL)/grain boundary (GB) model and (iv) the plane matching (PM)/GB model. Among them, the I-line and U-line model is the most effective in identifying special triple junctions, i.e., those exhibiting the beneficial property of high resistance to carbide precipitation. The results showed that the percentage of special triple junctions (I-lines) immune to carbide precipitation, increased from 35 to 80%, as the precipitation became more selective toward triple junction structures due to the corresponding sensitization heat treatment conditions, whereas more than 80% of random triple junctions (U-lines) exhibited susceptibility to carbide precipitation regardless of the sensitization conditions.

Nanocrystalline Ni and Ni–Fe alloys produced by electrodeposition were characterized using high-resolution transmission electron microscopy (HR-TEM) and X-ray diffraction (XRD). The grain sizes for these materials spanned a range of about 81–10 nm. HR-TEM analysis on a series of images revealed the presence of local strains at both high-angle and low-angle grain boundaries and twin boundaries. In addition to this, stacking faults and twins of the growth type (growth faults) were observed in both the nanocrystalline Ni and Ni–Fe alloys. The growth fault density increased with increasing Fe concentration, which is consistent with a decrease in the stacking fault energy. The microstrain for the samples was determined from XRD pattern analysis based on line broadening. A general increasing microstrain trend with decreasing grain size was observed and considered to be related to the local strains observed at grain boundaries in the HR-TEM image analysis. With respect to grain size, the microstrain values for the nanocrystalline Ni–Fe samples were noticeably higher than some of the Ni samples. Further XRD pattern analysis was performed to determine the growth fault probabilities for each of the samples and analyze their influence on the microstrain. Increasing Fe was accompanied by an increase in growth fault probability, which was consistent with the HR-TEM image analysis. In addition to the effect of grain size, there is likely a contributing effect on microstrain-induced XRD line broadening due to the presence of growth faults.

The bulk specific heat of fully dense nanocrystalline Ni–P electrodeposits with essentially constant P content (about 4 at%) and varying average grain sizes from 6.9 to 28.9 nm was investigated using modulated differential scanning calorimetry. In the lower temperature range from room temperature to 120 °C, at which the as-deposited sample microstructure was thermally stable, the bulk specific heat varied only within ~2 % despite the substantial variation of interface volume fractions from 0.11 to 0.39 for this series of samples. Moreover, the measured bulk specific heat values of the Ni–P samples were all located within the reported specific heat value range for conventional polycrystalline Ni. Evidently, the contribution due to grain size-related interface excess free volume is negligible and the bulk specific heat for the materials can be characterized as a structure-insensitive property. In the elevated temperature range from 150 °C to the Curie temperature of 357 °C, the magnetic contribution to the specific heat was significantly influenced by the chemical environment of P in the Ni–P samples. When P atoms were in the form of supersaturated solution in the nickel matrix, a complete suppression of the characteristic λ peak of the magnetic contribution in the specific heat curves was observed for all materials. The λ peak re-appeared in the specific heat curve after the Ni–P sample underwent a transformation to a two-phase microstructure consisting of Ni and Ni3P grains. It can be concluded that at a given P content, paramagnetic phosphorus atoms in the form of solutes are more effective in reducing the magnetic contributions to the specific heat than the form of paramagnetic Ni3P second-phase particles for the nanocrystalline Ni–P alloy.

Corneal nano-nipple structures consisting of hexagonally arranged protrusions with diameters around 200 nm have long been known for their antireflection capability and have served as biological blueprint for solar cell, optical lens and other surface designs. However, little is known about the global arrangement of these nipples on the ommatidial surface and their growth during the eye development. This study provides new insights based on the analysis of nano-nipple arrangements on the mesoscale across entire ommatidia, which has never been done before. The most important feature in the nipple structures are topological 5- and 7-fold coordination defects, which align to form dislocations and interconnected networks of grain boundaries that divide the ommatidia into crystalline domains in different orientations. Furthermore, the domain size distribution might be log-normal and the domains demonstrate no preference in crystal orientation. Both observations suggest that the nipple growth process may be similar to the nucleation and growth mechanisms during the formation of other crystal structures. Our results are also consistent with the most recently proposed Turing-type reaction-diffusion process. In fact, we were able to produce the key structural characteristics of the nipple arrangements using Turing analysis from the nucleation to the final structure development.

In this review, we present an extensive summary of research on superhydrophobic electrodeposits reported in the literature over the past decade. As a synthesis technique, electrodeposition is a simple and scalable process to produce non-wetting metal surfaces. There are three main categories of superhydrophobic surfaces made by electrodeposition: (i) electrodeposits that are inherently non-wetting due to hierarchical roughness generated from the process; (ii) electrodeposits with plated surface roughness that are further modified with low surface energy material; (iii) composite electrodeposits with co-deposited inert and hydrophobic particles. A recently developed strategy to improve the durability during the application of superhydrophobic electrodeposits by controlling the microstructure of the metal matrix and the co-deposition of hydrophobic ceramic particles will also be addressed.

Here, we introduce a novel and inexpensive template-based structuring process to create superhydrophobic polymer surfaces adapted from the naturally occurring micro/nano structured surfaces found on the superhydrophobic leaves of the quaking aspen tree. Electroformed nanocrystalline nickel coupons were sandblasted and chemically etched to create a negative reproduction of the aspen leaf surface structure. These nanocrystalline nickel samples were then employed as re-useable templates and pressed against various polymers at elevated temperatures, transferring the desired superhydrophobic structure to their surfaces. This structuring process resulted in water contact angles above 150° and tilt angles below 5° for polyethylene, polypropylene and polytetrafluoroethylene samples. In addition, the effects of temperature, water drop size and surfactant concentration on these pressed polymer surfaces were investigated to assess potential application limitations for these surfaces.

Nanocrystalline metals are often produced in a state of stress which can adversely affect certain properties, e.g. corrosion resistance, wear, fatigue strength, etc. This stress is referred to as internal or “intrinsic” stress since it is not directly caused by applied loads. The structural causes of these stresses in nanocrystalline materials are not fully understood and are therefore an area of particular interest. The internal stresses of nanocrystalline Ni and Ni-16wt%Fe were measured and found to increase with the addition of iron. Characterization using HR-TEM revealed no signs of porosity, second phase particles, or a high density of dislocations. Both materials possessed well defined high-angle grain boundaries. The main structural difference between the two materials was found to be grain size and correspondingly, a decrease in grain size resulted in an increase in internal stress which supports the applicability of the coalescence theory. The current study also provides evidence to rule out the effect of voids (or porosity), dislocations, and second phases as possible causes of internal stress.

An analysis of grain-size dependent structure-sensitivity of various physical and mechanical properties of nickel is presented, covering the crystal size range from 10 nm to 10 μm. It is shown that the well established general trends regarding defect-sensitivity observed for conventional polycrystalline materials also apply to porosity-free nanomaterials with grain sizes less than 100 nm produced by the electrodeposition process.

Hardness and Young's modulus were measured by nanoindentation on a series of electrodeposited nanocrystalline nickel and nickel–iron alloys. Hardness values showed a transition from regular to inverse Hall–Petch behaviour, consistent with previous studies. There was no significant influence of grain size on the Young's modulus of nanocrystalline nickel and nickel–iron alloys with grain sizes greater than 20 nm. The Young's modulus values for nanocrystalline nickel and nickel–iron alloys for grain sizes less than 20 nm were slightly reduced when compared to their conventional (randomly oriented) polycrystalline counterparts. The observed trend with decreasing grain size was found to be consistent with composite model predictions that consider the influence of intercrystalline defects. However, there was some notable variability of the measured values when compared to the model predictions. Three theoretical relationships were used to characterise the anisotropic elastic behaviour of these materials. As a r...

While nanocrystalline materials hold promise for structural applications in which increased strength is beneficial, their adoption has been hindered by concerns over the achievable ductility, resulting largely from considerable data scatter in the literature. A statistically significant set of 147 electrodeposited nanocrystalline tensile specimens was used to investigate this topic, and it was found that while necking elongation obeys similar processing quality and geometrical dependencies as conventional engineering metals, the intrinsic ductility as measured by uniform plastic strain was unexpectedly independent of microstructure over the grain size range of 10–80 nm. This indicates that the underlying physical processes of grain boundary-mediated damage formation are strain-oriented phenomena that can be defined by a critical plastic strain regardless of the strength of the material as a whole.

Monolithic and multilayered iron electrodeposits were successfully synthesized by the pulse plating electrodeposition method. Electron microscopy and Vickers microhardness measurements were used to investigate the microstructure and mechanical properties of the iron electrodeposits produced. Two types of monolithic iron coatings were produced, one with a coarse grained, columnar structure and the other with an ultra-fine grained structure. Hall-Petch type grain size strengthening was observed in these monolithic coatings. Multilayered iron coatings composed of alternating layers of coarse grained and fine grained structures were also produced. The hardness value of the multilayered coatings falls between the hardness values for the two types of monolithic coatings produced. This study has demonstrated the possibility of applying a multilayered structure design to tailor the microstructure and mechanical properties of electrodeposited iron coatings.

The grain-size dependences of thermal conductivity and electrical resistivity of polycrystalline and nanocrystalline nickel were measured by the flash method and four-point probe method, respectively. Nanocrystalline nickel (grain size: 28 nm) was made by the pulsed-current electrodeposition process, while polycrystalline nickel (grain size: 57 μm) was the same material in fully annealed condition. Noticeable differences in thermal conductivity and electrical resistivity were observed for both materials. These results can be explained on the basis of the rapid increase in the intercrystalline grain boundary and triple junction volume fractions at very small grain sizes. The relationship between thermal conductivity and electrical resistivity of nanocrystalline nickel follows the classic Wiedemann-Franz law.

In this study, the surface structure of a self-cleaning, superhydrophobic leaf was examined using electron microscopy and optical methods, and its wetting properties were measured using a contact angle goniometer. Using the micro/nanostructural surface features of this leaf as a blueprint, an inexpensive surface structuring technique was developed by modifying the surface of nanocrystalline nickel to create a template. These templates were then pressed into softened polyethylene at elevated temperatures and pressures, thereby transferring the structured surface to the polymer samples. All templates and pressed polymers were characterized in the same manner as the leaves. This method increased the wetting angle for polyethylene from 96° to 151° and reduced the tilt angle from 38° to