P. Nash

Illinois Institute of Technology, Mechanical, Materials, and Aerospace Engineering, Faculty Member

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The Ni-Rh (Nickel-Rhodium) system

Bulletin of Alloy Phase Diagrams, 1984

Fabrication and Performance of a Lithium X-Ray Lens

AIP Conference Proceedings, 2007

Compound refractive lenses (CRLs) are arrays of concave lenses whose simple design and ease in im... more Compound refractive lenses (CRLs) are arrays of concave lenses whose simple design and ease in implementation and alignment make them an attractive optic to focus x-rays. Factors considered in designing CRLs include lens material, fabrication, and assembly. Lithium is a desirable material because it provides the largest index of refraction decrement per unit absorption length of any solid elements. Lithium is a difficult material to handle and fabricate because it is rather malleable and more importantly, it reacts with moisture, and to a lesser extent, with oxygen and nitrogen in air. It also tends to adhere to molds and dies. We report on the fabrication and performance of a parabolic lithium lens consisting of 32 lenslets. Lenslets are fabricated in a precision press using an indenter with a parabolic profile and a 100 µm tip radius. The indenter is made of stainless steel and is figured using a computer numerically controlled (CNC) machine. The lens is designed to have a 1.7 m focal length at 10 keV energy. In an experiment conducted at the Advanced Photon Source (APS), a 0.5 mm x 0.5 mm monochromatic undulator beam strikes the lens. A focal length of 1.71, a focal spot size of 24 µm x 34 µm, and a peak intensity gain of over 18 are obtained.

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Effect of Zn addition on thermoelectric properties of Zn/sub 4/Sb/sub 3/ synthesized by direct hot pressing

ICT 2005. 24th International Conference on Thermoelectrics, 2005., 2005

ABSTRACT Powder metallurgy was used to produce polycrystalline specimens of single phase &amp... more ABSTRACT Powder metallurgy was used to produce polycrystalline specimens of single phase &amp;epsi;-Zn4Sb3 and two-phase specimens of &amp;epsi;-Zn4Sb3 (majority phase) and Zn. The effect of excess Zn addition to the stoichiometry of Zn4Sb3 was investigated on the thermoelectric properties as well as mechanical properties in the alloy system. The room-temperature thermoelectric properties of our single phase Zn4Sb3 alloys are comparable to those reported by other researchers on samples prepared by hot pressing of ingot melted alloy powders. It is shown that the addition of Zn enhances the mechanical properties while sacrificing the thermoelectric properties.

Coarsening kinetics of solid and liquid silver particles in nickel

Materials Science and Technology, 1992

ABSTRACT

Deformation behavior of 4;Mo alloys

Acta Metallurgica, 1985

Five polycrystalline nickel-molybdenum single-phase alloys (up to 10 at. pct Mo) and pure nickel ... more Five polycrystalline nickel-molybdenum single-phase alloys (up to 10 at. pct Mo) and pure nickel (INCO 270) were tested in compression at two temperatures. The molybdenum solutes contribute not only an additive friction stress, but also a multiplicative effect on the strain-hardening rate. This multiplicative effect is interpreted in terms of an influence of mobile solutes on the dislocation/dislocation interaction strength. Solute mobility was evidenced by the occurrence of static strain aging and of a strain-rate sensitivity that has a negative contribution. The total rate sensitivity, however, remained positive and jerky flow was not observed. 18 references.

Microstructure and texture in hot-extruded NiAl

Scripta Metallurgica et Materialia, 1992

Secondary recrystallization and high temperature compressive properties of ODS MA NiAl

Scripta Materialia, 2002

A NiAl based oxide dispersion strengthened alloy has been produced by mechanical alloying and con... more A NiAl based oxide dispersion strengthened alloy has been produced by mechanical alloying and consolidated by hot extrusion. Thermo-mechanical treatments have been performed to induce secondary recrystallization (SRx). SRx leads to a pronounced grain coarsening without concurrent dispersoid coarsening, resulting in improved high temperature mechanical properties.

format_quoteResults from SRx processes were contrasted with as-consolidated and cast materials, emphasizing the unique properties of SRx MA NiAl.format_quote

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The Ge−Ni (Germanium-Nickel) system

Bulletin of Alloy Phase Diagrams, 1987

Experimental investigation and thermodynamic assessment of the Hf–Ge system

ASM Handbook, Vol. 3: Alloy Phase Diagrams

ASM Handbook. Vol. 3. Alloy Phase Diagrams. H Baker, H Okamoto ASM International, Materials Park,... more

The Al-Ni-Ti (Aluminum-Nickel-Titanium) System

Phase equilibria in the Ni- Ta-AI system

Metal Science, 1979

ABSTRACT

Origin of heterogeneous microstructure in mechanically alloyed NiAl

Scripta Materialia, 1996

format_quoteX-ray diffraction reveals only NiAl in the consolidated material, with significant changes in peak patterns indicating successful consolidation processes.format_quote

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Synthesis and properties of trialuminides with ultra-fine microstructures

Nanostructured Materials, 1992

Determination of residual Ni in mechanically alloyed NiAl

Metallurgical and Materials Transactions A, 1994

Mechanical alloying (MA) has become a promising technique to produce dispersion-strengthened (DS)... more Mechanical alloying (MA) has become a promising technique to produce dispersion-strengthened (DS) intermetallic alloys having a fine grain size which are difficult or impossible to produce by conventional casting techniques, t~,21 The MA process has been successfully applied to producing intermetallic compounds such as NiA1, Ni3AI, A13Zr, and TiA1. t3' 4' 51 In our work on DS NiA1, we have been producing NiA1 powder by MA and studying the effect of processing variables on powder characteristics. The powder characteristics have an influence on the consolidated microstructure and thus on the properties of the final product. During the study of the effects of processing time on alloying, it was observed that formation of NiAI from elemental powders occurred after 37 hours of MA. After 61 hours of MA, only X-ray diffraction peaks of NiA1 were observed, t41 Nevertheless, the powder was slightly magnetic, suggesting that some residual Ni, Ni solid solution, or Fe contamination was present. A set of experiments was made to determine the type of magnetic material and if there was a correlation between the amount of residual material and the particle size. Elemental powder blends of -200-mesh Ni and -325-mesh A1 were mechanically alloyed in a high-energy attritor mill for 70 hours under Ar atmosphere. The weight average particle size of asmilled powder sieved to -325 mesh, determined by a centrifugal sedimentation instrument, was typically from 3 to 6/xm. The chemical composition of the as-milled powder produced is shown in .

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Phase equilibria in the Ni-Al-Ti system at 1173 k

Metallurgical Transactions A, 1985

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Reinforcing copper matrix composites through molecular-level mixing of functionalized nanodiamond by co-deposition route

Materials Science and Engineering: A, 2008

This work reports a chemical method called "co-deposition route" for fabricating ND (nanodiamond)... more This work reports a chemical method called "co-deposition route" for fabricating ND (nanodiamond)/Cu composite at a molecular-level mixing. The main procedure of "co-deposition route" includes four steps. ND particles have been functionalized by HF acid before co-deposition. SEM, HRTEM (high-resolution transmission electron spectroscopy), XRD (X-ray diffraction), EDS (energy-dispersive spectrum analysis) and optical microscope were carried out to characterize the as-prepared composite powders and bulk composites. Results indicated that copper matrix composite with a homogeneous dispersion of functionalized ND particles can be prepared. The modification of ND particles was performed by HF (30 vol%) acid at 70 • C, and C F bond was successfully detected by XPS (X-ray photoelectron spectrum) and IR (Infrared spectroscopy). The properties of relative density, microhardness and electric conductivity of ND/Cu composites have been measured. With the comparison of conventional methods, it showed that the as-prepared ND/Cu composites with good combined performances have a promising future for industry application.

format_quoteStable ultradispersed ND suspension is crucial for co-deposition process, impacting the overall effectiveness of the composite fabrication.format_quote

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Creep in mechanically alloyed NiAl

Materials Science and Engineering: A, 1995

The creep behaviour of mechanically alloyed (MA) NiAl, consolidated by a hot extrusion or hot pre... more The creep behaviour of mechanically alloyed (MA) NiAl, consolidated by a hot extrusion or hot pressing, was examined. Hot extruded MA NiAl exhibited higher creep rates due to the development of a strong (110) texture along the extrusion direction, the presence of somewhat coarser oxides and the lower level of interstitial atoms. In general, minimum creep rates in MA NiAl were on average three orders of magnitude lower than those in their case counterparts. Improved creep resistance of MA NiAl is postulated to result from the presence of dispersoids and interstitial atoms and, to a limited extent, from its fine grain size. Taking into consideration the temperature and stress ranges in the present study, the measured values of the stress exponent and the activation energies for creep, and the occurrence of the threshold stress below which creep does not occur, one can conclude that creep in the MA NiAl materials is controlled by climb of dislocations over dispersoid.

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The Al-Hf-Ni system (Aluminum-Hafnium-Nickel)

Journal of Phase Equilibria, 1991

The Ag−Ni (Silver-Nickel) system

Journal of Phase Equilibria, 1987

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