scholarly journals Amorphous Al-Ti Powders Prepared by Mechanical Alloying and Consolidated by Electrical Resistance Sintering

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1140 ◽  
Author(s):  
Petr Urban ◽  
Fátima Ternero ◽  
Eduardo S. Caballero ◽  
Sooraj Nandyala ◽  
Juan Manuel Montes ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Alloying ◽  
Electrical Resistance ◽  
High Hardness ◽  
Scanning Calorimetry ◽  
Sintered Compact ◽  
Processing Times ◽  
Conventional Sintering ◽  
Long Time ◽  
Novel Processing

A novel processing method for amorphous Al50Ti50 alloy, obtained by mechanical alloying and subsequently consolidated by electrical resistance sintering, has been investigated. The characterisation of the powders and the confirmation of the presence of amorphous phase have been carried out by laser diffraction, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and transmission electron microscopy. The amorphous Al50Ti50 powders, milled for 75 h, have a high hardness and small plastic deformation capacity, not being possible to achieve green compacts for conventional sintering. Moreover, conventional sintering takes a long time, being not possible to avoid crystallisation. Amorphous powders have been consolidated by electrical resistance sintering. Electrically sintered compacts with different current intensities (7–8 kA) and processing times (0.8–1.6 s) show a porosity between 16.5 and 20%. The highest Vickers hardness of 662 HV is reached in the centre of an electrically sintered compact with 8 kA and 1.2 s from amorphous Al50Ti50 powder. The hardness results are compared with the values found in the literature.

scholarly journals Smart conductive inks

2008 ◽  
Vol 2 (4) ◽  
pp. 305-308
Author(s):  
Jose Rangel ◽  
◽  
Alicia del-Real ◽  
Victor Castano ◽  
◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Electrical Resistance ◽  
Automatic System ◽  
Ethyl Acrylate ◽  
Conductive Ink ◽  
Scanning Calorimetry ◽  
Acrylic Polymers ◽  
Pressure Sensitive ◽  
Scanning Electron

A novel conductive ink, suitable for employment in a pressure-sensitive automatic system, was prepared and characterized via scanning electron microscopy, FTIR and differential scanning calorimetry. The ink was obtained as a composite by mixing a solution of ethyl acrylate-methyl acrylate (50/50 ratio) copolymer and carbon black and graphite into a solvent standard for acrylic polymers. The ink average electrical resistance ranges from 40 ohms/cm to 150 ohms/cm.

Crystal structure, microstructure, and magnetic properties of the Fe2CrSi nanostructured Heusler alloy elaborated by the mechanical alloying method

2020 ◽  
Vol 111 (8) ◽  
pp. 681-687
Author(s):  
Fatiha Djaidi ◽  
Hanane Mechri ◽  
Mohammed Azzaz
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Magnetic Properties ◽  
Mechanical Alloying ◽  
Heusler Alloy ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Transmission Electron ◽  
Disordered Crystal ◽  
Microstructure And Magnetic Properties

Abstract The Fe2CrSi nanostructured Heusler alloy was prepared by mechanical alloying followed by heat treatment. The structure, microstructure, and magnetic properties of the samples were studied by the following analysis methods: X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectrometry, transmission electron microscopy, and a vibrating sample magnetometer. The a-Fe (Si, Cr) solid solution with a disordered body centered cubic (bcc) crystal structure was obtained after 24 h of milling. An example of the sample milled for 32 h with a disordered crystal structure a-Fe(Si, Cr) was chosen to investigate the transformation with temperature using differential scanning calorimetry. The effect of annealing temperatures on the structural, microstructural, and magnetic properties of the ordered Fe2CrSi Heusler phase for the sample milled for 32 h was investigated.

Solid State Amorphization of Ti60Si40 Alloy via Mechanical Alloying

2021 ◽  
Vol 876 ◽  
pp. 7-12
Author(s):  
Petr Urban ◽  
Fátima Ternero Fernández ◽  
Rosa M. Aranda Louvier ◽  
Raquel Astacio López ◽  
Jesus Cintas Físico
Keyword(s):  
Electron Microscopy ◽  
Particle Size ◽  
Mechanical Alloying ◽  
Amorphous Phase ◽  
Milling Time ◽  
X Ray Diffraction ◽  
Mechanically Alloyed ◽  
Scanning Calorimetry ◽  
Transmission Electron ◽  
Heating Up

The effect of milling time on the microstructure evolution and formation of amorphous phase of Ti60Si40 alloy produced by mechanical alloying (MA) has been investigated. Laser diffraction, Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) were employed to characterize the particle size, morphology and structure of mechanically alloyed Ti60Si40. When the milling time is increased to 20 h, the particle size decreases from 23.7 to 4.7 μm, the shape of the particles changes to spherical and the crystalline structure is transformed into an amorphous phase. The amorphous Ti60Si40 alloy is stable when heating up to 750oC. Above this temperature, the cold crystallization of the intermetallic compounds Ti5Si3 and/or Ti5Si4 begins.

Effect of Boron on the Amorphization of Fe-Si Alloys by Mechanical Alloying

2012 ◽  
Vol 730-732 ◽  
pp. 739-744 ◽  
Author(s):  
Petr Urban ◽  
Francisco Gomez Cuevas ◽  
Juan M. Montes ◽  
Jesus Cintas
Keyword(s):  
Electron Microscopy ◽  
Mechanical Alloying ◽  
Alloy System ◽  
High Energy ◽  
Milling Process ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Structural And Phase Transformations ◽  
Transmission Electron ◽  
Energy Ball

The amorphization process by mechanical alloying in the Fe-Si alloy system has been studied. High energy ball milling has been applied for alloys synthesis. X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to monitor the structural and phase transformations through the different stages of milling. The addition of amorphous boron in the milling process and the increase of the milling time were used to improve the formation of the amorphous phase. Heating the samples resulted in the crystallization of the synthesized amorphous alloys and the appearance of equilibrium intermetallic compounds.

scholarly journals Medium-frequency Electrical Resistance Sintering of Oxidized c.p. Iron Powder

2018 ◽  
Author(s):  
Juan Manuel Montes Martos ◽  
Francisco Gómez Cuevas ◽  
Fátima Ternero Fernández ◽  
Raquel Astacio López ◽  
Eduardo Sánchez Caballero ◽  
...  
Keyword(s):  
Electrical Resistance ◽  
Low Voltage ◽  
Electrical Current ◽  
Medium Frequency ◽  
Sintered Compact ◽  
Resistance Evolution ◽  
Degree Of Oxidation ◽  
Powder Mass ◽  
Conventional Sintering ◽  
High Degree

Commercially pure (c.p.) iron powders with a deliberate high degree of oxidation were consolidated by medium-frequency electrical resistance sintering (MF-ERS). This is a consolidation technique where pressure, and heat coming from a low-voltage and high-intensity electrical current, are simultaneously applied to a powder mass. In this work, the achieved densification rate is interpreted according to a qualitative microscopic model, based on the compacts global porosity and electrical resistance evolution. The effect of current intensity and sintering time on compacts was studied on the basis of micrographs revealing the porosity distribution inside the sintered compact. The microstructural characteristics of compacts consolidated by the traditional cold-press and furnace-sinter powder metallurgy route are compared with results of MF-ERS consolidation. The goodness of MF-ERS versus the problems of conventional sintering when working with oxidized powders is analyzed. The electrical consolidation allows to obtain higher densifications than the traditional route under non-reducing atmospheres.

Structural Characteristics and Electrochemical Properties of Mg-Ni-Cu-Y Alloy Synthesized by Mechanical Alloying

2005 ◽  
Vol 488-489 ◽  
pp. 689-692
Author(s):  
Li Min Wang ◽  
Xin Bo Zhang ◽  
Yao Ming Wu
Keyword(s):  
Electron Microscopy ◽  
Mechanical Alloying ◽  
Electrochemical Properties ◽  
Structural Characteristics ◽  
Powder Materials ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Nanocrystalline Phases ◽  
Scanning Electron

A powder material of Mg-Ni-Cu-Y was synthesized by mechanical alloying method. Considerable amounts of amorphous and nanocrystalline phases formed after a mixture of elemental powder with the overall composition of Mg78Ni9Cu11Y2 was mechanical alloyed for 200 h. The phase formed in the synthesized powder materials was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The electrochemical properties were examined with a solution of 6M KOH.

scholarly journals Mechanical Characterization of Conventional and Non-Conventional Sintering Methods of Commercial and Lab-Synthesized Y-TZP Zirconia for Dental Applications

2014 ◽  
Vol 87 ◽  
pp. 151-156
Author(s):  
Alvaro Presenda ◽  
María Dolores Salvador ◽  
Felipe Peñaranda-Foix ◽  
José Manuel Catalá ◽  
Amparo Borrell
Keyword(s):  
Mechanical Properties ◽  
Microwave Sintering ◽  
Ceramic Powder ◽  
Production Costs ◽  
Processing Times ◽  
Powder Sintering ◽  
Conventional Sintering ◽  
Novel Processing ◽  
Dental Applications

Ceramics for dental applications have become increasingly important in the last decades. Particularly, the introduction of yttria-stabilized zirconia tetragonal polycrystalline (Y-TZP) materials as an alternative to the manufacturing of dental implants and prosthesis has provided a powerful tool to meet the demands required for these replacements in terms of biocompatibility, toughness, hardness and optical properties. Several commercial Y-TZP materials are currently available on the market and strong efforts in research and development facilities are being carried out to improve processing of Y-TZP to fully consolidate odontological pieces. Novel processing methods for ceramic powder sintering, including Y-TZP, aim to reduce processing times and production costs significantly, while maintaining or even improving the resulting microstructure and mechanical properties of the material. One of these methods includes microwave sintering. The purpose of this study is to characterize and compare the resulting properties of Y-TZP materials after conventional sintering and the non-conventional method of microwave heating. In this work one commercial material and one laboratory-synthesized Y-TZP powder are considered. The results suggest that microwave sintering results, generally, in better mechanical properties of the material in terms of hardness and fracture toughness than conventional sintering.

Metallic Powders Amorphization by Mechanical Alloying and Subsequent Electrical Sintering

2008 ◽  
Vol 587-588 ◽  
pp. 375-379
Author(s):  
P. Urban ◽  
Francicso Gomez Cuevas ◽  
Juan M. Montes ◽  
José M. Gallardo
Keyword(s):  
Mechanical Alloying ◽  
Optical Microscopy ◽  
Microstructural Evolution ◽  
Electrical Resistance ◽  
High Hardness ◽  
High Energy ◽  
Milling Process ◽  
Cold Pressing ◽  
Green Strength ◽  
Powder Particles

Al-base and Fe-base powders have been amorphized by a high energy milling process in an Attritor miller. Microstructural evolution in powder particles has been analyzed by XRD, DSC, SEM and TEM. The conventional route of cold pressing and sintering applied to these powders does not result adequate to preserve their amorphous or nanometric character. An additional disadvantage of this route appears during the cold pressing stage, as a consequence of the insufficient green strength of the compacts, due to the high hardness of the milled powders. In order to avoid these difficulties a new consolidation technique, electrical resistance sintering (ERS), has been successfully employed. ERS consolidated compacts have been microstructurally characterized by optical microscopy and XRD, showing that compacts preserve their amorphous and/or nanometric character.

Electron microscopy of crystalline structure in thermotropic random copolymers

1991 ◽  
Vol 49 ◽  
pp. 1054-1055
Author(s):  
Afzana Anwer ◽  
S. Eilidh Bedford ◽  
Richard J. Spontak ◽  
Alan H. Windle
Keyword(s):  
Electron Microscopy ◽  
Crystalline Structure ◽  
Liquid Crystalline ◽  
Elevated Temperatures ◽  
Random Copolymers ◽  
Molecular Characteristics ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Identical Monomer ◽  
Periodic Layer

Random copolyesters composed of wholly aromatic monomers such as p-oxybenzoate (B) and 2,6-oxynaphthoate (N) are known to exhibit liquid crystalline characteristics at elevated temperatures and over a broad composition range. Previous studies employing techniques such as X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) have conclusively proven that these thermotropic copolymers can possess a significant crystalline fraction, depending on molecular characteristics and processing history, despite the fact that the copolymer chains possess random intramolecular sequencing. Consequently, the nature of the crystalline structure that develops when these materials are processed in their mesophases and subsequently annealed has recently received considerable attention. A model that has been consistent with all experimental observations involves the Non-Periodic Layer (NPL) crystallite, which occurs when identical monomer sequences enter into register between adjacent chains. The objective of this work is to employ electron microscopy to identify and characterize these crystallites.

A new tool for rapid development of electron microscopy negatives and micrographs: Initial impressions of the MOHR/PRO-8 processor

1992 ◽  
Vol 50 (2) ◽  
pp. 972-973
Author(s):  
James C. Long
Keyword(s):  
Electron Microscopy ◽  
Processing Time ◽  
Rapid Development ◽  
Processing Times ◽  
Initial Impressions ◽  
Transport Method

Over the years, many techniques and products have been developed to reduce the amount of time spent in a darkroom processing electron microscopy negatives and micrographs. One of the latest tools, effective in this effort, is the Mohr/Pro-8 film and rc paper processor.At the time of writing, a unit has been recently installed in the photographic facilities of the Electron Microscopy Center at Texas A&M University. It is being evaluated for use with TEM sheet film, SEM sheet film, 35mm roll film (B&W), and rc paper.Originally designed for use in the phototypesetting industry, this processor has only recently been introduced to the field of electron microscopy.The unit is a tabletop model, approximately 1.5 × 1.5 × 2.0 ft, and uses a roller transport method of processing. It has an adjustable processing time of 2 to 6.5 minutes, dry-to-dry. The installed unit has an extended processing switch, enabling processing times of 8 to 14 minutes to be selected.

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