Analysis of Microstructure Evolution and Mechanical Properties during Compression of Open-Cell Ni-Foams with Hollow Struts Using Micro-CT and FEM

Based on electron backscatter diffraction (EBSD), hollow structures of Ni foam struts fabricated by electroplating on a chemically removable template were observed. Three-dimensional (3D) pore structures of Ni foams were also obtained using X-ray computed tomography (CT), and microstructural features such as porosity, pore size and strut thickness were statistically quantified. Evolution of microstructure and mechanical properties during ex situ compression of open-cell Ni-foams was investigated based on X-ray CT, and experimental results were compared with predictions by the finite element method (FEM). 3D microstructures obtained by X-ray CT revealed that the stress drop started with the buckling of struts at the center of the Ni-foams. The flow stress increased after the buckling of the struts spreads to most of the regions. For effective simulation of the compressive deformation and determination of the microstructural evolution, small domains of interest were selected from the entire set of observed 3D microstructures based on X-ray CT, and struts of Ni foams with a hollow structure were simplified with relevant thin-solid struts. Numerical 3D modeling comprehensively disclosed that compression caused the transverse buckling of the struts, with the bending and buckling of struts thus reducing the stress. Thickness variation of the struts causes a change in the porosity of Ni-foams without a change in pore shape or connectivity. The overall range of strut thickness was from 59 to 133 μm, and the range of porosity values was from 80% to 93.7%. A stress drop was predicted with a decrease in the strut thickness or an increase in the porosity, as measured experimentally. It was also found that the stress drop contributed to an increase in the calculated energy absorption efficiency.

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Characterisation of Intermetallic Phases in Multicomponent Al-Si Casting Alloys for Engineering Applications

Materials Science Forum ◽

10.4028/www.scientific.net/msf.519-521.359 ◽

2006 ◽

Vol 519-521 ◽

pp. 359-364 ◽

Cited By ~ 18

Author(s):

C.L. Chen ◽

G.D. West ◽

Rachel C. Thomson

Keyword(s):

Mechanical Properties ◽

Electron Backscatter Diffraction ◽

Physical And Mechanical Properties ◽

Alloy System ◽

Intermetallic Phases ◽

Design Strategies ◽

Engineering Applications ◽

X Ray ◽

Casting Alloys ◽

Backscatter Diffraction

Multicomponent Al-Si based casting alloys are used for a variety of engineering applications. The presence of additional elements in the Al-Si alloy system allows many complex intermetallic phases to form, which make characterisation non-trivial due to the fact that some of the phases have either similar crystal structures or only subtle changes in their chemistries. A combination of electron backscatter diffraction (EBSD) and energy dispersive X-ray analysis (EDX) have therefore been used for discrimination between the various phases. It is shown that this is a powerful technique for microstructure characterisation and provides detailed information which can be related to microstructure evolution during initial casting and subsequent heat treatment. The mechanical properties of different intermetallic phases have been investigated as a function of temperature using the nanoindentation technique. In particular, the hardness and modulus of a number of phases have been established for a range of alloy compositions. Physical properties of some of the intermetallic phases are also discussed. Phase identity, composition, physical and mechanical properties are set in context to inform alloy design strategies.

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Development of Sustainable and Eco-Friendly Materials from Termite Hill Soil Stabilized with Cement for Low-Cost Housing in Chad

Buildings ◽

10.3390/buildings11030086 ◽

2021 ◽

Vol 11 (3) ◽

pp. 86

Author(s):

Assia Aboubakar Mahamat ◽

Numfor Linda Bih ◽

Olugbenga Ayeni ◽

Peter Azikiwe Onwualu ◽

Holmer Savastano ◽

...

Keyword(s):

Electron Microscopy ◽

Mechanical Properties ◽

Fracture Toughness ◽

Scanning Electron Microscopy ◽

Low Cost ◽

Sub Saharan Africa ◽

Ex Situ ◽

Termite Mound ◽

X Ray ◽

Scanning Electron

This paper explores the effects of cement stabilization (5, 10, 15 and 20 wt%) on the structural and mechanical properties (compressive/flexural strengths and fracture toughness) of abandoned termite mound soil. The crystal structures and crystallinity of the constituents were determined using X-ray diffraction (XRD), while the microstructure was characterized via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The functional groups were also identified using Fourier transform infra-red spectroscopy (FTIR). The compressive/flexural strengths of the stabilized and un-stabilized termite mound soil were also studied after curing for 7, 14 and 28 days. The fracture toughness mechanism was analyzed with the aid of the R-curve method. Additionally, the underlying deformation and cracking mechanisms are elucidated via in-situ/ex-situ optical and scanning electron microscopy. The stabilized termite mound soil displayed the highest mechanical properties of 13.91 MPa, 10.25 MPa and 3.52 kPa·m1/2 for compressive strength, flexural strength and fracture toughness, respectively. Besides displaying good mechanical properties and being locally available at no cost, renewable and an eco-friendly material, the termite mound soil will contribute to lowering the cost of housing in Sub-Saharan Africa, particularly in Chad.

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Determination of Quantity and Localization of Liquid in the Semi-Solid State Using both 3D X-Ray Microtomography and 2D Techniques for Steel Thixoforming

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.192-193.191 ◽

2012 ◽

Vol 192-193 ◽

pp. 191-196

Author(s):

Guo Chao Gu ◽

Raphaël Pesci ◽

Eric Becker ◽

Laurent Langlois ◽

Régis Bigot

Keyword(s):

Mechanical Properties ◽

High Temperature ◽

Solid State ◽

Room Temperature ◽

Great Influence ◽

Ex Situ ◽

X Ray ◽

Semi Solid

The distribution of liquid at the semi solid state is one of the most important parameters for steel thixoforging. It has a great influence on the viscosity of the material, on the flows and finally on the final shape and mechanical properties of the thixoforged parts. Both ex situ and in situ 3D X-ray microtomography characterizations have been carried out to determine the quantity and localization of liquid at high temperature of M2 steel slugs. Microtomography was first performed ex situ at room temperature on samples heated and quenched from semi-solid state. The specimens were also scanned in situ directly at high temperature. The obtained results have been compared to 2D observations using EDS technique in SEM on heated and quenched specimens. They showed a good correlation making both approaches very efficient for the study of the liquid zones at the semi-solid state

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Phase Transformations in Ti-7w/oMo-3w/oMe Alloy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100052584 ◽

1974 ◽

Vol 32 ◽

pp. 514-515

Author(s):

S. Fujishiro

Keyword(s):

Electron Microscopy ◽

Mechanical Properties ◽

Transmission Electron Microscopy ◽

Tensile Strength ◽

Mechanical Processing ◽

Ray Method ◽

X Ray ◽

Transmission Electron ◽

Water Quench ◽

Alpha Beta

The mechanical properties of three titanium alloys (Ti-7Mo-3Al, Ti-7Mo- 3Cu and Ti-7Mo-3Ta) were evaluated as function of: 1) Solutionizing in the beta field and aging, 2) Thermal Mechanical Processing in the beta field and aging, 3) Solutionizing in the alpha + beta field and aging. The samples were isothermally aged in the temperature range 300° to 700*C for 4 to 24 hours, followed by a water quench. Transmission electron microscopy and X-ray method were used to identify the phase formed. All three alloys solutionized at 1050°C (beta field) transformed to martensitic alpha (alpha prime) upon being water quenched. Despite this heavily strained alpha prime, which is characterized by microtwins the tensile strength of the as-quenched alloys is relatively low and the elongation is as high as 30%.

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Macroprobe Mode for the Study of Segregation in Steels

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100134909 ◽

1990 ◽

Vol 48 (2) ◽

pp. 260-261

Author(s):

Auclair Gilles ◽

Benoit Danièle

Keyword(s):

Mechanical Properties ◽

Spatial Distribution ◽

High Performance ◽

Volume Fraction ◽

Sheet Steel ◽

Acquisition Time ◽

Chemical Information ◽

X Ray ◽

Accurate Quantitative Analysis ◽

Optical Micrographs

During these last 10 years, high performance correction procedures have been developed for classical EPMA, and it is nowadays possible to obtain accurate quantitative analysis even for soft X-ray radiations. It is also possible to perform EPMA by adapting this accurate quantitative procedures to unusual applications such as the measurement of the segregation on wide areas in as-cast and sheet steel products.The main objection for analysis of segregation in steel by means of a line-scan mode is that it requires a very heavy sampling plan to make sure that the most significant points are analyzed. Moreover only local chemical information is obtained whereas mechanical properties are also dependant on the volume fraction and the spatial distribution of highly segregated zones. For these reasons we have chosen to systematically acquire X-ray calibrated mappings which give pictures similar to optical micrographs. Although mapping requires lengthy acquisition time there is a corresponding increase in the information given by image anlysis.

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Interfacial properties of GaSb/InAs superlattices

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100149969 ◽

1993 ◽

Vol 51 ◽

pp. 826-827

Author(s):

M. E. Twigg ◽

B. R. Bennett ◽

J. R. Waterman ◽

J. L. Davis ◽

B. V. Shanabrook ◽

...

Keyword(s):

Gaas Substrate ◽

Molecular Beam ◽

Infrared Detector ◽

Interfacial Properties ◽

Ex Situ ◽

X Ray Diffraction ◽

Absorption Coefficients ◽

X Ray ◽

Short Period ◽

High Optical Absorption

Recently, the GaSb/InAs superlattice system has received renewed attention. The interest stems from a model demonstrating that short period Ga1-xInxSb/InAs superlattices will have both a band gap less than 100 meV and high optical absorption coefficients, principal requirements for infrared detector applications. Because this superlattice system contains two species of cations and anions, it is possible to prepare either InSb-like or GaAs-like interfaces. As such, the system presents a unique opportunity to examine interfacial properties.We used molecular beam epitaxy (MBE) to prepare an extensive set of GaSb/InAs superlattices grown on an GaSb buffer, which, in turn had been grown on a (100) GaAs substrate. Through appropriate shutter sequences, the interfaces were directed to assume either an InSb-like or GaAs-like character. These superlattices were then studied with a variety of ex-situ probes such as x-ray diffraction and Raman spectroscopy. These probes confirmed that, indeed, predominantly InSb-like and GaAs-like interfaces had been achieved.

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Mechanical properties of FeAlSi powders prepared by mechanical alloying from different initial feedstock materials

Matériaux & Techniques ◽

10.1051/mattech/2018063 ◽

2019 ◽

Vol 107 (2) ◽

pp. 207 ◽

Cited By ~ 2

Author(s):

Jaroslav Čech ◽

Petr Haušild ◽

Miroslav Karlík ◽

Veronika Kadlecová ◽

Jiří Čapek ◽

...

Keyword(s):

Mechanical Properties ◽

Mechanical Alloying ◽

Young’S Modulus ◽

Milling Time ◽

Young's Modulus ◽

Element Model ◽

X Ray Diffraction ◽

X Ray ◽

Powder Particles ◽

Complete Homogenization

FeAl20Si20 (wt.%) powders prepared by mechanical alloying from different initial feedstock materials (Fe, Al, Si, FeAl27) were investigated in this study. Scanning electron microscopy, X-ray diffraction and nanoindentation techniques were used to analyze microstructure, phase composition and mechanical properties (hardness and Young’s modulus). Finite element model was developed to account for the decrease in measured values of mechanical properties of powder particles with increasing penetration depth caused by surrounding soft resin used for embedding powder particles. Progressive homogenization of the powders’ microstructure and an increase of hardness and Young’s modulus with milling time were observed and the time for complete homogenization was estimated.

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CO2 Reduction to Propanol by Copper Foams: A Pre- and Post-Catalysis Study

10.26434/chemrxiv.12022623.v1 ◽

2020 ◽

Author(s):

Jennifer A. Rudd ◽

Ewa Kazimierska ◽

Louise B. Hamdy ◽

Odin Bain ◽

Sunyhik Ahn ◽

...

Keyword(s):

Carbon Dioxide ◽

Photoelectron Spectroscopy ◽

Carbon Capture ◽

Surface Composition ◽

Co2 Reduction ◽

Structural Rearrangement ◽

Copper Electrode ◽

Ex Situ ◽

X Ray ◽

Copper Electrodes

The utilization of carbon dioxide is a major incentive for the growing field of carbon capture. Carbon dioxide could be an abundant building block to generate higher value products. Herein, we describe the use of porous copper electrodes to catalyze the reduction of carbon dioxide into higher value products such as ethylene, ethanol and, notably, propanol. For n-propanol production, faradaic efficiencies reach 4.93% at -0.83 V vs RHE, with a geometric partial current density of -1.85 mA/cm2. We have documented the performance of the catalyst in both pristine and urea-modified foams pre- and post-electrolysis. Before electrolysis, the copper electrode consisted of a mixture of cuboctahedra and dendrites. After 35-minute electrolysis, the cuboctahedra and dendrites have undergone structural rearrangement. Changes in the interaction of urea with the catalyst surface have also been observed. These transformations were characterized ex-situ using scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. We found that alterations in the morphology, crystallinity, and surface composition of the catalyst led to the deactivation of the copper foams.

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Atomic Layer Deposition of LiF and Lithium Ion Conducting (AlF3)(LiF)x Alloys Using Trimethylaluminum, Lithium Hexamethyldisilazide and Hydrogen Fluoride

10.26434/chemrxiv.5459653 ◽

2017 ◽

Author(s):

Younghee Lee ◽

Daniela M. Piper ◽

Andrew S. Cavanagh ◽

Matthias J. Young ◽

Se-Hee Lee ◽

...

Keyword(s):

Lithium Ion ◽

Atomic Layer ◽

Mass Gain ◽

Alloy Film ◽

Ex Situ ◽

X Ray ◽

Layer Deposition ◽

Ion Conducting ◽

Good Agreement

<div>Atomic layer deposition (ALD) of LiF and lithium ion conducting (AlF3)(LiF)x alloys was developed using trimethylaluminum, lithium hexamethyldisilazide (LiHMDS) and hydrogen fluoride derived from HF-pyridine solution. ALD of LiF was studied using in situ quartz crystal microbalance (QCM) and in situ quadrupole mass spectrometer (QMS) at reaction temperatures between 125°C and 250°C. A mass gain per cycle of 12 ng/(cm2 cycle) was obtained from QCM measurements at 150°C and decreased at higher temperatures. QMS detected FSi(CH3)3 as a reaction byproduct instead of HMDS at 150°C. LiF ALD showed self-limiting behavior. Ex situ measurements using X-ray reflectivity (XRR) and spectroscopic ellipsometry (SE) showed a growth rate of 0.5-0.6 Å/cycle, in good agreement with the in situ QCM measurements.</div><div>ALD of lithium ion conducting (AlF3)(LiF)x alloys was also demonstrated using in situ QCM and in situ QMS at reaction temperatures at 150°C A mass gain per sequence of 22 ng/(cm2 cycle) was obtained from QCM measurements at 150°C. Ex situ measurements using XRR and SE showed a linear growth rate of 0.9 Å/sequence, in good agreement with the in situ QCM measurements. Stoichiometry between AlF3 and LiF by QCM experiment was calculated to 1:2.8. XPS showed LiF film consist of lithium and fluorine. XPS also showed (AlF3)(LiF)x alloy consists of aluminum, lithium and fluorine. Carbon, oxygen, and nitrogen impurities were both below the detection limit of XPS. Grazing incidence X-ray diffraction (GIXRD) observed that LiF and (AlF3)(LiF)x alloy film have crystalline structures. Inductively coupled plasma mass spectrometry (ICP-MS) and ionic chromatography revealed atomic ratio of Li:F=1:1.1 and Al:Li:F=1:2.7: 5.4 for (AlF3)(LiF)x alloy film. These atomic ratios were consistent with the calculation from QCM experiments. Finally, lithium ion conductivity (AlF3)(LiF)x alloy film was measured as σ = 7.5 × 10-6 S/cm.</div>

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Stable and Metastable Phase Equilibria Involving the Cu6Sn5 Intermetallic

Journal of Electronic Materials ◽

10.1007/s11664-021-09067-4 ◽

2021 ◽

Author(s):

A. Leineweber ◽

M. Löffler ◽

S. Martin

Keyword(s):

Phase Equilibria ◽

Electron Backscatter Diffraction ◽

Metastable Phase ◽

Stable Phase ◽

X Ray Diffraction ◽

X Ray ◽

Heat Treated ◽

Ordered Phases ◽

Backscatter Diffraction ◽

Kinetics Of

Abstract Cu6Sn5 intermetallic occurs in the form of differently ordered phases η, η′ and η′′. In solder joints, this intermetallic can undergo changes in composition and the state of order without or while interacting with excess Cu and excess Sn in the system, potentially giving rise to detrimental changes in the mechanical properties of the solder. In order to study such processes in fundamental detail and to get more detailed information about the metastable and stable phase equilibria, model alloys consisting of Cu3Sn + Cu6Sn5 as well as Cu6Sn5 + Sn-rich melt were heat treated. Powder x-ray diffraction and scanning electron microscopy supplemented by electron backscatter diffraction were used to investigate the structural and microstructural changes. It was shown that Sn-poor η can increase its Sn content by Cu3Sn precipitation at grain boundaries or by uptake of Sn from the Sn-rich melt. From the kinetics of the former process at 513 K and the grain size of the η phase, we obtained an interdiffusion coefficient in η of (3 ± 1) × 10−16 m2 s−1. Comparison of this value with literature data implies that this value reflects pure volume (inter)diffusion, while Cu6Sn5 growth at low temperature is typically strongly influenced by grain-boundary diffusion. These investigations also confirm that η′′ forming below a composition-dependent transus temperature gradually enriches in Sn content, confirming that Sn-poor η′′ is metastable against decomposition into Cu3Sn and more Sn-rich η or (at lower temperatures) η′. Graphic Abstract

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