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Jason Derek Giallonardo

A thesis submitted in conformity with the requirements

for the degree of Doctor of Philosophy

Department of Materials Science and Engineering

University of Toronto

© Copyright by Jason Derek Giallonardo (2013)




Jason Derek Giallonardo Doctor of Philosophy Materials Science and Engineering University of Toronto ABSTRACT This research work presents the first comprehensive study on nanocrystalline materials produced in bulk quantities using a novel continuous electrodeposition process. A series of nanocrystalline Ni and Ni-Fe alloy continuous foils were produced and an intensive investigation into their structure and various properties was carried out. High-resolution transmission electron microscopy (HR-TEM) revealed the presence of local strain at high and low angle, and twin boundaries. The cause for these local strains was explained based on the interpretation of non-equilibrium grain boundary structures that result when conditions of compatibility are not satisfied. HR-TEM also revealed the presence of twin faults of the growth type, or “growth faults”, which increased in density with the addition of Fe. This observation was found to be consistent with a corresponding increase in the growth fault probabilities determined quantitatively using X-ray diffraction (XRD) pattern analysis.

Hardness and Young’s modulus were measured by nanoindentation. Hardness followed the regular Hall-Petch behaviour down to a grain size of 20 nm after which an ii inverse trend was observed. Young’s modulus was slightly reduced at grain sizes less than 20 nm and found to be affected by texture. Microstrain based on XRD line broadening was measured for these materials and found to increase primarily with a decrease in grain size or an increase in intercrystal defect density (i.e., grain boundaries and triple junctions). This microstrain is associated with the local strains observed at grain boundaries in the HR-TEM image analysis. A contribution to microstrain from the presence of growth faults in the nanocrystalline Ni-Fe alloys was also noted. The macrostresses for these materials were determined from strain measurements using a two-dimensional XRD technique. At grain sizes less than 20 nm, there was a sharp increase in compressive macrostresses which was also owed to the corresponding increase in intercrystal defects or interfaces in the solid.

–  –  –

Firstly, I would like to express my sincere gratitude to Professor Uwe Erb. His mentorship through learning, dialog, and challenge over the course of this research was exceptional. I’d like to especially thank Dr. Gino Palumbo, a distinguished individual in this field of scientific research and in the industry, who with no reservation opened the door and introduced me to the world of materials science and engineering. It was an honour to have Professor Emeritus Karl T. Aust’s involvement in this work since its inception. His inspiring support and encouragement over the course of my studies is truly appreciated. The guidance and support of my supervisory committee members, Professors Zhirui Wang, Doug D.

Perovic, Nazir P. Kherani, and Glenn D. Hibbard are gratefully acknowledged. I would like to also acknowledge the past and present members of the Nanomaterials Research Group for the many insightful discussions and technical assistance, in particular, Dr. Yijian Zhou and Dr. Gordana Avramovic-Cingara. The technical expertise and assistance of Sal Boccia is also very much appreciated. Many thanks are owed to my co-workers at Integran Technologies, Inc. including: Francisco (Paco) Gonzalez, Jon McCrea, Iain Brooks, Peter Lin, Nandakumar Nagarajan, Andy Robertson, Dave Limoges, and Konstantinos (Gus) Panagiotopoulos. I would also like to thank my family and friends for their enduring support over the course of this long journey. Finally, I am indebted to my wife, Luciana, and our daughter, Ilaria. Their lasting patience over these trying years was instrumental in making this dream of mine a reality.

–  –  –

Table 2.1.

Main-sources and sub-sources of Type I stresses [Macherauch and Kloos (1986)].

Table 3.1.

Parameter working ranges for jet polishing using the Struers Tenupol-3.

Table 4.1.

Summary of materials produced for this study with deposit Fe, S, and C concentrations.

Table 4.2.

Summary of grain sizes determined by TEM image analysis.

Table 4.3.

Calculation of the position and relative intensities of Ni diffraction lines.

Table 4.4.

Summary of lattice parameter calculations using the interplanar spacing derived from the (111) and (200) diffraction lines.

Table 4.5.

Orientation indices for the four principal crystallographic directions of the nanocrystalline Ni and Ni-Fe samples.

Table 4.6.

Summary of grain size estimations using the Scherrer formula for the (111) and (200) broadened lines.

Table 4.7.

Growth fault probabilities for the series of nanocrystalline Ni and Ni-Fe alloys.

Table 4.8.

Total enthalpy, H total, the peak temperature, Tp, and Curie temperature, Tc, for the samples, and respective Fe concentration and grain size values.

Table 4.9.

Calculated excess interfacial enthalpy and grain boundary energy for the nanocrystalline Ni samples. Also shown are the values from Turi (1997).

Table 5.1.

Characterization, hardness, and Young’s modulus data.

Table 5.2.

Elastic stiffnesses ( cij ) for single crystal Ni and Ni-Fe alloys (in units of 1011 N/m2).

Table 6.1.

Microstrain values for the series of nanocrystalline Ni and Ni-Fe alloys.

Table 6.2.

Summary of macrostress measurements using 2D-XRD.

–  –  –

Figure 2.1.

Electrochemical processing of nanocrystalline metals and alloys: (1) plating cell, (2) electrolyte, (3) anode, (4) ammeter, (5) power source, (6) cathode, (7) transistored switch, (8) wave generator, (9) oscilloscope, and (10) constant temperature bath [Erb et al. (1995)].

Figure 2.2.

Cross-sectional structure of (a) conventional and (b) nanocrystalline electrodeposits [Erb et al. (2007)].

Figure 2.3.

Schematic diagram of a two-dimensional structure of nanocrystalline materials [Gleiter (1989)].

Figure 2.4.

(a) Tetrakaidecahedral grains, (b) effect of grain size on calculated volume fractions of intercrystal regions, grain boundaries and triple junctions, assuming a grain boundary thickness of 1 nm [Palumbo et al. (1990)].

Figure 2.5.

Hardness as a function of d 1 / 2 for as-prepared nanocrystalline Ni electrodeposits [El-Sherik et al. (1992)].

Figure 2.6.

Effect of Fe concentration on the grain size of electrodeposited nanocrystalline Ni-Fe alloys [Cheung et al. (1995)].

Figure 2.7.

Microhardness of electrodeposited nanocrystalline and conventional polycrystalline Ni-Fe alloys as a function of Fe concentration [Cheung et al. (1995)].

Figure 2.8.

Hall-Petch plot for electrodeposited nanocrystalline Ni-Fe alloys showing transition from regular to inverse Hall-Petch behaviour [Cheung et al. (1995)].

Figure 2.9.

Compilation of normalized Young’s modulus Em / E0, where E is the measured Young’s modulus value and E0 is the published value for the polycrystalline counterpart, as a function of grain size [Zhou et al. (2003b)].

Figure 2.10.

Comparison between the Young’s modulus and the interfacial component volume fractions [Zhou et al. (2003a)].

Figure 2.11.

Power difference ( P ), increment in electrical resistivity (  ), and hardness (VHN) for specimens of polycrystalline Ni deformed in torsion and heated at 6o/min [Clarebrough et al. (1955)].

Figure 2.12.

Anisothermal anneal curve (DSC) of a 10 nm electrodeposited Ni sample at a heating rate of 10 oC/min [Klement et al. (1995a)].

–  –  –

Figure 2.14.

Effect of uniform and non-uniform strains (left side of the figure) on diffraction peak position and width (right side of the figure). (a) Shows the unstrained sample, (b) shows uniform strain, and (c) shows non-uniform strain within the volume samples by the xray beam [Cullity and Stock (2001)].

Figure 2.15.

Polycrystalline thin film before and after the point of crystallite coalescence [Nix and Clemens (1999)].

Figure 2.16.

Types of stacking faults: (a) normal fcc sequence, (b) deformation or intrinsic stacking fault, (c) extrinsic stacking fault, and (d) twin or growth stacking fault [Wagner (1957)].

Figure 3.1.

Cross-sectional schematic view of the drum plating apparatus (1) filled with an electrolyte (2). A rotating cathode in the shape of a drum (3) is electrically connected to a power supply (4). The drum is rotated by an electric motor (not shown) with a belt drive having a variable speed control. The anode (5) is conforming, as shown, and is also connected to the power supply (4). The foil (6) that is electrodeposited on the drum is pulled from the surface emerging from the electrolyte [Palumbo et al. (2005)].

Figure 3.2.

Schematic representation of a section through an indentation identifying the parameters used in the analysis [Oliver and Pharr (1992)].

Figure 3.3.

A schematic representation of load versus indenter displacement data. Pmax is the peak indentation load; hmax is the indenter displacement at peak load; h f is the final depth of contact impression after unloading; and S is the initial unloading stiffness [Oliver and Pharr (1992)].

Figure 3.4.

Schematic of the strain measurement based on the Bragg law. N is the plane normal direction and when there is a strain the d-spacing is not in equilibrium and thus there is a strain,  n, in the plane normal direction [He (2009)].

Figure 3.5.

An illustration of the difference between conventional and 2D X-ray diffraction [He (2009)].

Figure 3.6.

An illustration of the diffraction cone due to stresses [He (2009)].

Figure 3.7.

(a) Stress components on a volume element [He (2009)], and (b) the stress tensor.

Figure 4.1.

Fe-Ni binary alloy phase diagram [Scott (1992)].

–  –  –

Figure 4.3.

S concentration in the nanocrystalline Ni deposit vs. the Nanovate™ A24 concentration in the electrolyte used to produce nanocrystalline Ni samples no. 1-5.

Figure 4.4.

Plot of Fe concentration in the deposit vs. FeSO4·5H2O in the electrolyte used to produce nanocrystalline Ni-Fe samples no. 2, 6, 7, 8 and 9.

Figure 4.5.

SEM image (60,000X) of sample no. 1 (Ni) showing faceting.

Figure 4.6.

SEM image (60,000X) of sample no. 5 (Ni).

Figure 4.7.

SEM image (60,000X) of sample no. 9 (Ni-32wt.%Fe).

Figure 4.8.

TEM images of sample no. 5 (Ni, 23 nm): (a) BF image, (b) DF image, (c) SAD pattern, and (d) grain size distribution.

Figure 4.9.

TEM images of sample no. 7 (Ni-16wt.%Fe, 12 nm): (a) BF image, (b) DF image, (c) SAD pattern, and (d) grain size distribution.

Figure 4.10.

Cumulative volume fraction vs. grain size for the nanocrystalline Ni and Ni-Fe samples produced for this study. The sample no.’s are labeled at the top of each distribution curve.

Figure 4.11.

Plot of grain size vs. Nanovate™ A24 concentration in the electrolyte used to produce the nanocrystalline Ni samples no. 1-5.

Figure 4.12.

Plot of grain size vs. Fe concentration in the deposit for nanocrystalline Ni-Fe samples no. 6-9.

Figure 4.13.

HR-TEM image of sample no. 5 (Ni, 23 nm).

Figure 4.14.

HR-TEM image of sample no. 7 (Ni-16wt.%Fe, 12 nm).

Figure 4.15.

HR-TEM image of sample no. 9 (Ni-32wt%Fe, 10 nm).

Figure 4.16.

HR-TEM image of a triple junction in sample no. 5 (Ni, 23 nm). To the right of the image are the FFT patterns for grains A, B, and C corresponding to zone axes [001], [112], and [011], respectively.

–  –  –

Figure 4.18.

HR-TEM image of a low angle grain boundary from sample no. 7 (Niwt.%Fe, 12 nm) having a 13o angle of misorientation with grain A and B both having a [011] zone axis.

Figure 4.19.

FFT of grain A and grain B from Fig. 4.18 both having a [011] zone axis and showing a slight rotation with respect to each other.

Figure 4.20.

IFFT image of Fig. 4.18 showing the accommodation of dislocations (marked by the arrows) at the low angle grain boundary.

Figure 4.21.

HR-TEM image of two twin boundaries from sample no. 5 (Ni, 23 nm). Inset is the indexed FFT pattern and the zone axis is [011].

Figure 4.22.

IFFT of Fig. 4.21 showing dislocations (marked by the arrows) at the twin boundary necessary to compensate for the misalignment of the lattices.

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