Uwe Erb - Academia.edu (original) (raw)

Papers by Uwe Erb

Journal of Materials Chemistry A, 2018

Understanding the wettability of rare earth oxide ceramics from crystallographic orientation–surf... more Understanding the wettability of rare earth oxide ceramics from crystallographic orientation–surface energy relationships.

Nanomaterials, 2018

The effect of high temperature exposure on the water wetting properties of co-electrodeposited su... more 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.

Microscopy and Microanalysis, 2019

Nuclear power supplies about 10% of the global electricity generation with approximately 450 nucl... more Nuclear power supplies about 10% of the global electricity generation with approximately 450 nuclear reactors globally [1]. Nuclear energy offers many benefits including stable electricity generation and low carbon output; however, one of the biggest challenges of nuclear power is the management of the radioactive fuel waste it generates. Canada's Nuclear Waste Management Organization (NWMO) has proposed a deep geological repository (DGR) solution where used Canada Deuterium Uranium (CANDU) fuel bundles are stored in a used fuel container (UFC), which is then placed at a reference depth of 500 m underground in a geologically stable rock formation and surrounded by bentonite clay. The UFC is made of a steel core for structural support with a 3 mm Cu coating on the surface for corrosion protection (Figure 1a). The Cu coating is applied onto the partially assembled UFC with a cylindrical body and two hemispherical heads by electrodeposition (ED). Used fuel bundles are placed into the body of the UFC and the container head is bonded to the main body using a hybrid laser arc welding technique to close the UFC. The exposed area of the steel around the weld zone is then coated with Cu by a cold spray (CS) technique. Finally, the CS-Cu coating around the weld zone is annealed to restore the ductility of the CS-Cu. Since the Cu coatings on the container are processed by two different methods, varying microstructures are expected in different regions of the UFC. In this study, extensive microstructural characterizations were performed using various electron microscopy techniques to ultimately develop a better understanding of the structure-mechanical and corrosion behaviour of these Cu coatings.

Public reporting burden for the collection of information is estimated to average 1 hour per resp... more Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.

Materials, 2016

In this review, we present an extensive summary of research on superhydrophobic electrodeposits r... more 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.

Scientific reports, Jun 22, 2016

Corneal nano-nipple structures consisting of hexagonally arranged protrusions with diameters arou... more 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 gr...

Le Journal de Physique Colloques, 1988

Materials Science Forum, 2012

Magnetic properties of nanocrystalline Ni and Ni-Fe alloys produced by electrodeposition have bee... more Magnetic properties of nanocrystalline Ni and Ni-Fe alloys produced by electrodeposition have been studied at 2K and at 298K. Ni and Ni-15%Fe alloy deposits show nano-grain structure with the average grain size of 23 nm and 12 nm, respectively. Both materials exhibit soft magnetic properties. Nanocrystalline Ni at 2K shows saturation magnetization, coercive force, and remanent magnetization of 57 emu/gr, 101 Oe, and 16 emu/gr respectively. Nanocrystalline Ni-15%Fe alloy exhibits superior soft magnetic properties than Ni with corresponding saturation magnetization, coercive force, and remanent magnetization at 2K of 96 emu/gr, 6 Oe, and 4 emu/gr respectively. The magnetic properties and their dependence upon temperature data are interpreted in terms of the Herzer random anisotropy model for nanocrystalline materials.

Physical Review B, 1999

Nanocrystalline materials have a proportion of atoms at grain boundaries that can be as high as 5... more Nanocrystalline materials have a proportion of atoms at grain boundaries that can be as high as 50% and are thus expected to have properties quite different from those of bulk or large-grained polycrystalline materials. In this article, we study the influence of the presence of grain boundaries on thermal expansion, mean-square amplitudes of vibration ͑MSAV's͒, and hydrogen diffusion using classical molecular-dynamics simulations with embedded-atom-method potentials, for the particular case of the special ͓100͔ ⌺ϭ5, 13, and 17 twist grain boundaries. We find that in the presence of grain boundaries, thermal expansion increases only slightly while both hydrogen diffusion and MSAV's are enhanced significantly, in accord with neutron-diffraction measurements. The presence of pores, or voids, likewise, seem to have very little effect on thermal expansion. The diffusion of hydrogen is found to proceed mainly in the plane of the grain boundaries, where the electron density is lowest. ͓S0163-1829͑99͒05438-7͔

Scripta Metallurgica et Materialia, 1992

A process for repairing degraded sections of metal tubes, such as heat exchanger tubes, by in sit... more A process for repairing degraded sections of metal tubes, such as heat exchanger tubes, by in situ electroforming utilizes a probe containing an electrode. The probe is mov able through the tube to the site of degradation and is sealed in place, thereby creating an electrochemical cell. Electro lyte flows from a reservoir through the cell and a structural layer of metal is deposited on the tube using a pulsed direct current and a duty cycle of 10-60%. The metal layer so formed possesses an ultrafine grain size preferably with a highly twinned microcrystalline structure giving the layer 5,527.

Scripta Materialia, 2002

A late stage of abnormal grain growth, having unusual planar abnormal growth interfaces, is obser... more A late stage of abnormal grain growth, having unusual planar abnormal growth interfaces, is observed during the isothermal annealing of electrodeposited nanocrystalline Ni and Ni-Fe alloys. This communication presents observations of grain embedding and the presence of a wetting, sulfur-rich second phase at the abnormal growth interface and suggests a growth mechanism.

Scripta Materialia, 2006

ABSTRACT Higher frequencies of low Σ boundaries, satisfying the Palumbo–Aust criterion, resulted ... more ABSTRACT Higher frequencies of low Σ boundaries, satisfying the Palumbo–Aust criterion, resulted in greater resistance to boron segregation and carbide formation at grain boundaries in alloy 304. Also, boron desegregated from grain boundaries and became incorporated into isolated grain boundary carbides, thereby providing a discontinuous path for impurity segregation.

Nanostructured Materials, 1993

The effects of grain size and phosphorous content on the corrosion characteristics of nanocrystal... more The effects of grain size and phosphorous content on the corrosion characteristics of nanocrystalline NiP alloys tested in 0.1M H2S04 by anodic polarization is evaluated and compared with the corrosion behavior of amorphous NiP and high purity conventional polycrystalline Ni. It is found that in contrast to conventional polycrystalline nickel neither nanocrystalline (grain sizes 22.6 and8.4 nm) nor amorphous NiP passivate during potentiodynamic polarization. The electrochemical response and corrosion morphologies observed for the different materials are discussed in terms of their microstructural differences.

Nanostructured Materials, 1997

Degradation of nuclear steam generator tubing via outside surface initiated-corrosion,-stress cor... more Degradation of nuclear steam generator tubing via outside surface initiated-corrosion,-stress corrosion cracking, and-fatigue, often leads to costly forced outages and system de-rating (ie tube plugging). A commonly applied approach to system rehabilitation has been to repair ...

Philosophical Magazine, 2006

ABSTRACT Electrodeposited nanocrystalline Co offers a relatively unique opportunity to study the ... more ABSTRACT Electrodeposited nanocrystalline Co offers a relatively unique opportunity to study the interaction of two fundamentally different elementary solid state reactions: grain growth and ε (HCP) to α (FCC) allotropic phase transformation. Samples were isothermally annealed at temperatures above and below the equilibrium transformation temperature (Tεα = 695 K) and quenched to ambient for subsequent characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Isothermal annealing above 695 K resulted in concurrent grain growth and ε to α transformation. Unexpectedly, however, simultaneous grain growth and ε to α transformation also occurred during isothermal annealing at temperatures as low as 573 K, i.e. 122 K below the expected equilibrium Tεα. It was observed that non-equilibrium α-Co formed within a matrix of nanocrystalline ε-Co via abnormal grain growth, and is therefore fundamentally different from the ε to α transformation typically observed in conventional polycrystalline Co.

Philosophical Magazine Letters, 1988

The existence of cusps in the interfacial energy against misorientation curve has been studied fo... more The existence of cusps in the interfacial energy against misorientation curve has been studied for Ag/Si(l00) and Ag/Si(111) interfaces using the modified sphere-plate technique. The following preferred orientations were obtained: Ag(100)//Si(100) with Ag[011]//Si[011], and Ag(111)//Si(111) with Ag[110]//Si[114]. These are the same preferred orientation relationships previously found in studies of thin-film growth and appear to be due to low interfacial energies.

Acta Materialia, 1997

The grain growth kinetics of nanocrystalline nickel electrodeposits was studied by transmission e... more The grain growth kinetics of nanocrystalline nickel electrodeposits was studied by transmission electron microscopy and differential scanning calorimetry at different heating rates. It was found that, upon annealing, the nanocrystals in the nickel electrodeposits appeared to grow abnormally and released about 415.7 k 3.5 Jjmol of heat. The mechanism of the abnormal grain growth was attributed to the subgrain coalescence. The method for determination of the grain growth activation energy as well as all the other kinetic parameters in the Johnson-MehlPAvrami equation was proposed based on an isokinetic analysis. This method is applicable to general types of transformation process governed by a single activation energy under the isokinetic condition. The activation energy for the grain growth of nanocrystalline nickel electrodeposits was found to be about 131.5 kJ/mol using this method. The difference between the present method and the Kissinger and Ozawa method was addressed in terms of their physical backgrounds. % 1997 Acta Metallurgica Inc.

Acta Metallurgica et Materialia, 1995

ABSTRACT The possibility of a dislocation mechanism in the deformation process of nanocrystalline... more ABSTRACT The possibility of a dislocation mechanism in the deformation process of nanocrystalline materials is reviewed and analyzed. The present theoretical calculation, by taking the anisotropic characteristic of crystallographic symmetry and different choices of critical shear strength into account, results in a reasonable limit in grain size for applying dislocation pile-up theory to nanocrystalline materials. The deviation from the Hall—Petch relationship is rationalized in terms of a small number dislocation pile-up mechanism. A composite model is proposed to evaluate the strength of nanocrystalline materials. It is shown that this model can be used for interpreting the various cases observed in Hall—Petch studies. An analytical expression for assessing the creep rate of nanocrystalline materials by a diffusion mechanism, including triple line diffusion, is derived. It is predicted that the creep rate due to triple line diffusion will exhibit a stronger grain size dependence than that due to grain boundary diffusion.