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Journal ArticleDOI

Electroless nickel-phosphorus coating on Ti and Al elemental powders

31 Jul 2001-Scripta Materialia (Elsevier BV)-Vol. 45, Iss: 2, pp 183-189
About: This article is published in Scripta Materialia.The article was published on 2001-07-31. It has received 32 citations till now. The article focuses on the topics: Electroless nickel & Metal powder.
Citations
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Journal ArticleDOI
TL;DR: In this paper, the formation of TiAl (γ) and Ti3Al (α 2) phases were confirmed by x-ray diffraction after milling for 75h in case of graphite addition and 100h for carbon addition in the intermetallic matrix.
Abstract: In the present work, TiAl-based intermetallic matrix composite with second phase reinforcement as Ni-P-coated carbon and graphite powders were synthesized by mechanical alloying route. Graphite powder (20–30 µm) and elemental carbon powders (1–5 µm) were coated with Ni-P by the electroless coating technique, which was added to the elemental powder mixtures of Ti-48Al-1%Cr -1%Nb with 1% composition of either of the two. The powder mixtures were subjected to mechanical alloying at 300 rpm up to 250 h using toluene as a process control agent. The samples were collected after 25 h duration and characterized. The formation of TiAl (γ) and Ti3Al (α 2) phases are confirmed by x-ray diffraction. The formations of these phases were found after milling for 75 h in case of graphite addition and 100 h in case of carbon addition in the intermetallic matrix. The mechanically alloyed samples milled for different extents of time were examined by a field emission scanning electron microscope (FESEM) and energy dispersive ...

6 citations


Cites background from "Electroless nickel-phosphorus coati..."

  • ...The phosphorus addition can enhance the oxidation resistance of titanium aluminides by reducing the number of vacant lattice sites for oxygen (Ramaseshan et al. 2001)....

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Journal ArticleDOI
TL;DR: In this paper, a review of Ni-based composite powder (NCP) is presented, focusing on the application of NCP in electrocatalysis, functional coating, and energy field.

6 citations

Proceedings ArticleDOI
04 Jan 2010
TL;DR: In this paper, a fine nickel-coated aluminum powder and reference uncoated aluminium powder with a similar particle size distribution are compared for a fine Ni-coating aluminum powder.
Abstract: Oxidation, ignition, and combustion processes are studied and compared for a fine nickelcoated aluminum powder and reference uncoated aluminum powder with a similar particle size distribution. Oxidation is studied by thermogravimetry in argon-oxygen mixtures. Ignition processes are studied for powders coated on an electrically heated metal filament. Combustion is characterized in constant volume explosion tests. Both ignition and combustion experiments were performed in air. Thermogravimetric measurements showed selective oxidation of Ni at low temperatures, where oxidation of Al remains undetected. At higher temperatures, oxidation for both, nickel-coated and uncoated powders occurs in a characteristic stepwise process with individual oxidation steps associated with polymorphic phase changes in the growing alumina layer and with growth of individual alumina polymorphs. The activation energies for individual oxidation steps appear to be unaffected by the Ni coating; however the oxidation occurs somewhat faster for the coated powder, indicating an increase in the pre-exponential coefficients in Arrhenius formulations describing respective oxidation processes. Ignition kinetics for both coated and uncoated powders are similar, however, ignition is more readily detected and appears to be more violent for the coated powders. Finally, powder combustion experiments showed substantially reduced ignition delays and somewhat increased overall burn rates for the coated powders.

4 citations

Journal ArticleDOI
TL;DR: In this paper, a novel hydrothermal coating process was developed to deposit nickel compound over octahedral α-Fe 2 O 3 particles of narrow size distribution (0.2-0.3 μm) by treating aqueous dispersions of the preformed cores at elevated temperatures in Ni(NO 3 ) 2 /CH 3 COONa solutions.

4 citations

Journal ArticleDOI
TL;DR: In this article, microstructures and mechanical properties of spark plasma sintered (SPS) Al 2 O 3 -Co composites were investigated depending on the sintering temperatures (900-1200°C) and cobalt contents (0∼12mass%).
Abstract: Microstructures and mechanical properties of spark plasma sintered (SPS) Al 2 O 3 -Co composites were investigated depending on the sintering temperatures (900-1200°C) and cobalt contents (0∼12mass%) The material properties of relative density and fracture toughness increased as the sintering temperature and Co content (up to 12mass%Co) increased In the SPSed Al 2 O 3 -Co composite sintered at 1200°C, maximum values of relative density and fracture toughness about 993% and 81 MPam 1/2 , respectively were obtained The fracture morphology of SPSed Al 2 O 3 -12mass%Co composite showed a semi-brittle fracture mode due to the homogeneous dispersion of fine-sized Co particles

4 citations

References
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01 Jan 1985
TL;DR: In this article, the authors describe the behavior of grain boundaries in a two-dimensional model ordered alloy and the effects of elastic anisotropy on the anomalious yield behavior of cubic ordered alloys.
Abstract: This book contains over 50 selections. Some of the titles are: Order-disorder behavior of grain boundaries in a two-dimensional model ordered alloy; Dislocation reactions at grain boundaries in Ll/sub 2/ ordered alloys; Creep cavitation in a nickel aluminide; Effects of elastic anisotropy on the anomalious yield behavior of cubic ordered alloys; and Processing technology for nickel aluminides.

2,123 citations

Book
Ian M. Watt1
30 Jun 1985
TL;DR: The electron microscopy with light and electrons (EM) family as discussed by the authors is a family of microscopy techniques that use electron microscopes for high-vacuity measurements. But the electron microscope family is not suitable for the analysis of high-voltage measurements.
Abstract: 1. Microscopy with light and electrons 2. The electron microscope family 3. Rudiments of specimen preparation and interpretation of micrographs 4. Specialised techniques in electron microscopy 5. Examples of the use of electron microscopy Appendix 1: Production and measurement of high vacua Appendix 2: Vacuum deposition of thin metallic and carbon films for electron microscopy Appendix 3: X-ray generation and analysis Appendix 4: Electron sources for electron microscopes.

170 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of Cr additions to y-base alloys have been investigated, using bulk materials consolidated from rapid solidification-processed ribbons, and it was concluded that the ductilization effect of Cr in duplex alloys is partially due to the tendency of Cr to occupy Al lattice sites.
Abstract: The effects of Cr additions to y-base alloys have been investigated, using bulk materials consolidated from rapid solidification-processed ribbons. The composition ranges studied were 0 to 4 at. pet Cr and 44 to 54 at. pet Al. It was found that Cr additions do not affect the deformation behavior of single-phase γ alloys. However, they significantly enhance the plasticity of Al-lean duplex alloys which contain grains of single-phase γ and grains of lamellar γ/α2. Other Cr effects on microstructure, phase stability, site occupancy, and deformation sub-structures were characterized and correlated to the observed mechanical behavior. It was concluded that the ductilization effect of Cr in duplex alloys is partially due to the tendency of Cr to occupy Al lattice sites. Ductilization is also partially due to the ability of Cr to modify the Al partitioning and, therefore, the thermal stability of transformed α2 laths.

158 citations

Journal ArticleDOI
TL;DR: In this article, the ternary alloys of arc-melted, nearequiatomic TiAl alloys containing boron additions are analyzed and compared with those of binary Ti-Al and Ti-B alloys processed in a similar fashion.
Abstract: Solidification microstructures of arc-melted, near-equiatomic TiAl alloys containing boron additions are analyzed and compared with those of binary Ti-Al and Ti-B alloys processed in a similar fashion. With the exception of the boride phase, the matrix of the ternary alloy consists of the same α2 (DO19) and γ (Ll0) intermetallic phases found in the binary Ti-50 at. pct Al alloy. On the other hand, the boride phase, which is TiB (B27) in the binary Ti-B alloys, changes to TiB2 (C32) with the addition of Al. The solidification path of the ternary alloys starts with the formation of primary α (A3) for an alloy lean in boron (∼1 at. pct) and with primary TiB2 for a higher boron concentration (∼5 at. pct). In both cases, the system follows the liquidus surface down to a monovariant line, where both α and TiB2 are solidified concurrently. In the final stage, the α phase gives way to γ, presumably by a peritectic-type reaction similar to the one in the binary Ti-Al system. Upon cooling, the α dendrites order to α2 and later decompose to a lath structure consisting of alternating layers of γ and α2.

109 citations