A molecular dynamics study of Fe50-XMXAl50 ternary alloy (M=Ag, Pt, Pd)

ABSTRACTIron aluminide intermetallic alloys are of great importance in many industries due to their excellent oxidation resistance, low cost, low density, resistance to corrosion and good ductility at room temperature. However, these alloys suffer limited room temperature ductility above 873 K. In this paper, a molecular dynamics-based LAMMPS-EAM was used to model Fe50-XMXAl doped systems with either Ag, Pt or Pd. The lattice side preferences of the dopant were deduced from their energy landscape, and Fe sub-lattices showed promising properties. It was found that the addition of Ag, Pt and Pd enhances the stability of Fe50-XMXAl composition. More importantly, Ag and Pd doped systems gave comparable transition temperatures to experimental findings of 1273 K and 1073 K, respectively. Their thermodynamic and the mechanical stability trends showed promising properties for industrial applications, displaying stability at a high temperature below 1300 K.

Download Full-text

ALCHEMI of B2-Ordered Fe50Al45Me5 alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100165203 ◽

1996 ◽

Vol 54 ◽

pp. 548-549

Author(s):

Ian M. Anderson

Keyword(s):

Room Temperature ◽

Iron Aluminide ◽

Low Density ◽

Intermetallic Alloys ◽

Practical Applications ◽

Alloying Additions ◽

Site Distribution ◽

Good Corrosion Resistance ◽

Room Temperature Ductility ◽

The Matrix

B2-ordered iron aluminide intermetallic alloys exhibit a combination of attractive properties such as low density and good corrosion resistance. However, the practical applications of these alloys are limited by their poor fracture toughness and low room temperature ductility. One current strategy for overcoming these undesirable properties is to attempt to modify the basic chemistry of the materials with alloying additions. These changes in the chemistry of the material cannot be fully understood without a knowledge of the site-distribution of the alloying elements. In this paper, the site-distributions of a series of 3d-transition metal alloying additions in B2-ordered iron aluminides are studied with ALCHEMI.A series of seven alloys of stoichiometry Fe50AL45Me5, with Me = {Ti, V, Cr, Mn, Co, Ni, Cu}, were prepared with identical heating cycles. Microalloying additions of 0.2% B and 0.1% Zr were also incorporated to strengthen the grain boundaries, but these alloying additions have little influence on the matrix chemistry and are incidental to this study.

Download Full-text

Longevity of Raw and Lyophilized Crude Urease Extracts

Sustainable Chemistry ◽

10.3390/suschem2020018 ◽

2021 ◽

Vol 2 (2) ◽

pp. 325-334

Author(s):

Neda Javadi ◽

Hamed Khodadadi Tirkolaei ◽

Nasser Hamdan ◽

Edward Kavazanjian

Keyword(s):

Crude Extract ◽

Room Temperature ◽

Low Cost ◽

Extraction Process ◽

Crude Extracts ◽

Simple Extraction ◽

Commercial Applications ◽

Stable Source ◽

The Stability ◽

The Cost

The stability (longevity of activity) of three crude urease extracts was evaluated in a laboratory study as part of an effort to reduce the cost of urease for applications that do not require high purity enzyme. A low-cost, stable source of urease will greatly facilitate engineering applications of urease such as biocementation of soil. Inexpensive crude extracts of urease have been shown to be effective at hydrolyzing urea for carbonate precipitation. However, some studies have suggested that the activity of a crude extract may decrease with time, limiting the potential for its mass production for commercial applications. The stability of crude urease extracts shown to be effective for biocementation was studied. The crude extracts were obtained from jack beans via a simple extraction process, stored at room temperature and at 4 ℃, and periodically tested to evaluate their stability. To facilitate storage and transportation of the extracted enzyme, the longevity of the enzyme following freeze drying (lyophilization) to reduce the crude extract to a powder and subsequent re-hydration into an aqueous solution was evaluated. In an attempt to improve the shelf life of the lyophilized extract, dextran and sucrose were added during lyophilization. The stability of purified commercial urease following rehydration was also investigated. Results of the laboratory tests showed that the lyophilized crude extract maintained its activity during storage more effectively than either the crude extract solution or the rehydrated commercial urease. While incorporating 2% dextran (w/v) prior to lyophilization of the crude extract increased the overall enzymatic activity, it did not enhance the stability of the urease during storage.

Download Full-text

Phase Stability, Microstructure and Mechanical Properties in the Multi-Phse Alloys Based on the L12-Ni3(Al,Be)

MRS Proceedings ◽

10.1557/proc-364-855 ◽

1994 ◽

Vol 364 ◽

Author(s):

Takahiro Matsuo ◽

Hideki Hosoda ◽

Seiji Miura ◽

Yoshinao Mishima

Keyword(s):

Mechanical Properties ◽

Thermal Analysis ◽

Room Temperature ◽

Vertical Section ◽

Intermetallic Alloys ◽

Primary Solidification Phase ◽

Four Point Bending ◽

Room Temperature Ductility ◽

Three Phase ◽

Multi Phase

AbstractIntermetallic alloys based on the Ll2 Ni3(Al,Be) phase in the ternary Ni-Al-Bc system are prepared so that the alloys are multi-phase with the B2 intermetallic compound NiBe and a Ni primary solid solution denoted as (Ni). Such three-phase alloys, Ni-16 to 20 at%Al-10 at%Be, exhibit good room temperature ductility as measured by four-point bending. In order to examine the phase stabilities and relations among constituent phases, a vertical section of the ternary system is constructed at a constant 10 at%Bc mainly by differential thermal analysis. It is found that improvement in room temperature ductility can be achieved by the formation of a fine mixture of constituent phases during invariant reactions during solidification, which is further enhanced by the co-existence of the Ll2 phase formed as the primary solidification phase.

Download Full-text

Development of a Stable TiO2Nanocomposite Self-Cleaning Coating for Outdoor Applications

Advances in Materials Science and Engineering ◽

10.1155/2016/7958152 ◽

2016 ◽

Vol 2016 ◽

pp. 1-8 ◽

Cited By ~ 5

Author(s):

F. Madidi ◽

G. Momen ◽

M. Farzaneh

Keyword(s):

Mechanical Stability ◽

Low Cost ◽

Spray Coating ◽

Dielectric Behavior ◽

Superhydrophobic Coatings ◽

Angle Measurements ◽

Coating Method ◽

Specific Frequency ◽

Self Cleaning ◽

The Stability

A convenient and low-cost approach for the elaboration of a stable superhydrophobic coating is reported, involving the use of TiO2nanoparticles via the spray coating method. This method can be used for preparing self-cleaning superhydrophobic coatings on large areas for different kinds of substrates. The synergistic effect of the micro/nanobinary scale roughness was produced by a multilayer RTV SR/TiO2composite. The influence of the nanofiller concentration in a specific frequency range (40 Hz to 2 MHz) on the dielectric behavior was analyzed as well. It was found that the real relative permittivity (εr′) increases as the nanofiller concentration increases. Superhydrophobic behavior is analyzed by contact angle measurements, scanning electron microscopy (SEM), and profilometer. The stability of the developed coating also has been evaluated in terms of immersion in various aqueous solutions, heating, adhesion, and exposure to UV irradiation, and the results showed good stability against these factors. The coating retained its superhydrophobicity after several days of immersion in solutions of different pH levels (2, 4, 6, and 12) and different conductivities. In addition, they also exhibited exceptional stability against UV radiation and heating, as well as good mechanical stability.

Download Full-text

Effect of compositional modification on ductility of B2 phase in Ti–Al–Nb intermetallic alloy

Journal of Materials Research ◽

10.1557/jmr.2002.0378 ◽

2002 ◽

Vol 17 (10) ◽

pp. 2611-2614 ◽

Cited By ~ 1

Author(s):

Feng Tang ◽

Masuo Hagiwara

Keyword(s):

Room Temperature ◽

Single Phase ◽

Phase State ◽

Intermetallic Alloy ◽

Chemical Compositions ◽

Intermetallic Alloys ◽

Two Phase ◽

Room Temperature Ductility ◽

Single Phase State ◽

B2 Phase

Room-temperature ductility of two Ti–Al–Nb intermetallic alloys with close chemical compositions was investigated by tensile testing. The two alloys' ductilities in the B2 single-phase state were significantly different, which indicated that the ductility of B2 phase state was sensitive to the chemical composition. The alloy with more ductile B2 phase exhibited higher ductility in O + B2 two-phase state.

Download Full-text

HAT-field: a very cheap, robust and quantitative point-of-care serological test for Covid-19.

10.1101/2022.01.14.22268980 ◽

2022 ◽

Author(s):

Etienne Joly ◽

Agnes Maurel Ribes

Keyword(s):

Room Temperature ◽

Serological Test ◽

Point Of Care ◽

Low Cost ◽

Single Step ◽

Test Protocol ◽

Laboratory Equipment ◽

Human Red Blood Cells ◽

The Stability ◽

Disposable Equipment

We have recently described a very simple and cheap serological test called HAT to detect antibodies directed against the RBD of the SARS-Cov-2 virus. HAT is based on hemagglutination, triggered by a single reagent (IH4-RBD) comprised of the viral RBD domain fused to a nanobody specific for glycophorin, which is expressed at very high levels at the surface of human red blood cells (RBCs). One of the main initial goals of this study was to devise a test protocol that would be sensitive and reliable, yet require no specialized laboratory equipment such as adjustable pipets, so that it could be performed in the most remote corners of the world by people with minimal levels of training. Because antibody levels against the viral RBD have been found to correlate closely with sero-neutralisation titers, and thus with protection against reinfection, it has become obvious during the course of this study that making this test reliably quantitative would be a further significant advantage. We have found that, in PBN, a buffer which contains BSA and sodium azide, IH4-RBD is stable for over 6 months at room temperature, and that PBN also improves HAT performance compared to using straight PBS. We also show that performing HAT at either 4°C, room temperature or 37°C has minimal influence on the results, and that quantitative evaluation of the levels of antibodies directed against the SARS-CoV-2 RBD can be achieved in a single step using titration of the IH4-RBD reagent. The HAT-field protocol described here requires only very simple disposable equipment and a few microliters of whole blood, such as can be obtained by finger prick. Because it is based on a single soluble reagent, the test can be adapted very simply and rapidly to detect antibodies against variants of the SARS-CoV-2, or conceivably against different pathogens. HAT-field appears well suited to provide quantitative assessments of the serological protection of populations as well as individuals, and given its very low cost, the stability of the IH4-RBD reagent in the adapted buffer, and the simplicity of the procedure, could be deployed pretty much anywhere, including in the poorest countries and the most remote corners of the globe.

Download Full-text

Stability and Relaxation of Point Defects in amorphous silicon

MRS Proceedings ◽

10.1557/proc-279-189 ◽

1992 ◽

Vol 279 ◽

Author(s):

Raymond Lutz ◽

Laurent J. Lewis

Keyword(s):

Molecular Dynamics ◽

Low Temperature ◽

Amorphous Silicon ◽

Point Defects ◽

Room Temperature ◽

Empirical Potential ◽

The Stability

ABSTRACTWe have used molecular-dynamics to investigate the stability and relaxation of point defects — vacancies and interstitials — in a model of amorphous silicon, with the interactions between atoms described by the Stillinger-Weber empirical potential. The annihila-tion of point defects has been proposed as an important mechanism by which relaxation proceeds in amorphous silicon. Starting with a Wooten-Winer-Weaire model of a-Si, we “manually” create vacancies in the structure by removing a number of randomly-selected four-fold coordinated atoms. The system is then allowed to relax. Our calculations reveal unambiguously that, of a number of vacancies introduced in the model at low temperature, roughly a third are stable; these anneal out upon heating at room temperature. The vacancies seem, in most cases, to consist of a relatively large empty volume bounded by four atoms of which at least one is undercoordinated. Our study of interstitials seems to indicate that they diffuse through a “jump-and-bump” process, eventually annihilating when a large enough, properly coordinated, vacant volume is encountered.

Download Full-text

Matrix design of a novel ductile cast iron modified by W and Al: A comparison between thermodynamic modeling and experimental data

Metallurgical and Materials Engineering ◽

10.30544/449 ◽

2020 ◽

Vol 26 (1) ◽

pp. 15-29

Author(s):

Gülşah Aktaş Çelik ◽

Maria-Ioanna T. Tzini ◽

Şeyda Polat ◽

Şaban Hakan Atapek ◽

Gregory N. Haidemenopoulos

Keyword(s):

Cast Iron ◽

High Temperature ◽

Room Temperature ◽

Elevated Temperatures ◽

Mechanical Stability ◽

Low Cost ◽

Equilibrium Temperature ◽

Ductile Cast Iron ◽

Thermal Expansivity ◽

Thermodynamic Calculations

In high-temperature applications of ferrous materials, as in the case of exhaust manifolds, high thermal and mechanical stability are required. Stainless steels and Ni-resist alloys having austenitic matrices are good candidates to meet these requirements at elevated temperatures; however, they are expensive materials and present difficulties in casting. Ferritic ductile cast irons, like the commercial SiMo alloy, are comparatively cheaper materials with better castability but they cannot be used above approximately 800 °C. Thus, to meet the requirements with low-cost materials having improved high-temperature properties, new alloys must be developed by ferrite forming elements having the potential to increase equilibrium temperature. In this study, initially, a novel ductile cast iron matrix was designed using 1 W and 0-4 Al wt.-% and their phases stable at room temperature, transformation temperatures, solidification sequences and thermal expansivity values were determined using thermodynamic calculations with Thermo-Calc software. Computational studies revealed that (i) designed alloy matrices had graphite and M6C type carbides embedded in a ferritic matrix at room temperature as expected, (ii) A1 temperature increased as aluminum content increased. The obtained values were all above that of commercial SiMo alloy, (iii) the detrimental effect of increased aluminum addition on graphite content, and thermal expansivity was observed. Secondly, microstructural and thermal characterizations of cast alloys were performed for validation – the obtained data were in good agreement with the thermodynamic calculations.

Download Full-text

Design and Development of the Stability Test System for Gas Sensor Array Based on ARM

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.798-799.553 ◽

2013 ◽

Vol 798-799 ◽

pp. 553-556

Author(s):

Tao Zhou ◽

Qing Zhou

Keyword(s):

Gas Sensor ◽

Gas Sensors ◽

Sensor Array ◽

Low Cost ◽

Industrial Applications ◽

Test System ◽

Stability Test ◽

Stability Parameters ◽

Gas Sensor Array ◽

The Stability

In order to eliminate or minimize the early instability of gas sensors, the aging process is needed. After aging,it is necessary to test stability parameters of gas sensors in a certain batch of the sensors for massive production. In this work, a system for the stability test of gas sensor array has been designed and developed both in hardware and software based ARM. Measurements demonstrate the quality and flexibility of it. It is low cost, excellent cost performance. The stability test system now works well in industrial applications and meets the need of industrial mass-production.

Download Full-text