ChemInform Abstract: 2-PYRIDYLPHOSPHINES. II. LIGANDS FOR EXTREMELY SHORT METAL-METAL CONTACTS IN GOLD COMPLEXES

In conventional warm compaction, both powder and die are heated to a certain temperature during compaction. This is a technique for producing P/M compacts with higher green and sintered strength as compared to room temperature pressing. However, there is a certain limit to powder temperature due to flow problems at higher temperatures. Heating the die above this practical limit can further improve properties. In this work, the effect of die temperature on green and sintered properties of Astaloy CrM powder has been investigated. Here, the powder at 135 oC was fed to the die at different temperatures. Density and strength for samples in green and sintered conditions were evaluated for two compaction pressures of 500 and 650MPa and temperatures ranging from ranging from 135 to 165 oC. Comparison of samples compressed at room temperature showed marked improvement in density and strength properties. A 22% increase in density, as well as 40% increase in green strength was observed. Tensile and impact strengths were improved by about 10% and 20% respectively. SEM micrographs showed more rounded pores and hence reduced stress raising sites. The improvement in properties can be mainly attributed to changes in powder morphology and die wall lubrication due to migration of hot lubricant from interparticle space to die walls. The latter will reduce particle spacing and bring about more intimate metal-metal contacts as well as better lubrication on die walls.

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Disruption of an Alumina Layer During Sintering of Aluminium in Nitrogen

Archives of Metallurgy and Materials ◽

10.1515/amm-2017-0139 ◽

2017 ◽

Vol 62 (2) ◽

pp. 987-992 ◽

Cited By ~ 2

Author(s):

T. Pieczonka

Keyword(s):

Thermal Analyses ◽

Metal Contacts ◽

Alumina Layer ◽

Sintering Atmosphere ◽

Aluminium Powder ◽

Mechanical Disruption ◽

Chemically Induced ◽

Metal Metal ◽

Metallic Aluminium ◽

Alloyed Aluminium

AbstractAluminium oxide layer on aluminium particles cannot be avoided. However, to make the metal-metal contacts possible, this sintering barrier has to be overcome in some way, necessarily to form sintering necks and their development. It is postulated that the disruption of alumina layer under sintering conditions may originate physically and chemically. Additionally, to sinter successfully non alloyed aluminium powder in nitrogen, the operation of both types mechanism is required. It is to be noted that metallic aluminium surface has to be available to initiate reactions between aluminium and the sintering atmosphere, i.e. mechanical disruption of alumina film precedes the chemical reactions, and only then chemically induced mechanisms may develop. Dilatometry, gravimetric and differential thermal analyses, and microstructure investigations were used to study the sintering response of aluminium at 620°C in nitrogen, which is the only sintering atmosphere producing shrinkage.

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Electrical resistance behaviour of metal-metal contacts under normal dynamic loads

Wear ◽

10.1016/0043-1648(69)90427-x ◽

1969 ◽

Vol 13 (1) ◽

pp. 3-12 ◽

Cited By ~ 5

Author(s):

R.I.L. Howells ◽

S.D. Probert

Keyword(s):

Electrical Resistance ◽

Dynamic Loads ◽

Metal Contacts ◽

Metal Metal

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Extraction of thermal contact conductance of metal–metal contacts from scale-resolved direct numerical simulation

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2015.11.026 ◽

2016 ◽

Vol 94 ◽

pp. 164-173 ◽

Cited By ~ 12

Author(s):

Navni N. Verma ◽

Sandip Mazumder

Keyword(s):

Numerical Simulation ◽

Direct Numerical Simulation ◽

Thermal Contact ◽

Thermal Contact Conductance ◽

Metal Contacts ◽

Contact Conductance ◽

Metal Metal

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Crystal structure and chemistry of natural kutinaite from Černý Důl, Krkonoše, Czech Republic

Mineralogical Magazine ◽

10.1180/minmag.2015.079.5.06 ◽

2015 ◽

Vol 79 (5) ◽

pp. 1099-1109 ◽

Cited By ~ 1

Author(s):

Luca Bindi ◽

Emil Makovicky

Keyword(s):

Crystal Structure ◽

Czech Republic ◽

Metal Contacts ◽

X Ray Diffraction ◽

Space Group ◽

X Ray ◽

Cell Parameters ◽

Metal Metal ◽

Crystal Structure And Chemistry

AbstractWe have characterized the crystal structure of natural kutinaite, a rare mineral from the ores of Černý Důl, Czech Republic, by single-crystal X-ray diffraction and chemical analysis. We found that the structure of natural kutinaite is not identical to that of synthetic Cu14Ag6As7, previously reported to be cubic, space group Pm3m. Although topologically similar, the structure of natural kutinaite is indeed tetragonal, space group P4/mmm, with cell parameters: a = 11.789(2), c = 11.766(2) Å, V = 1635.5(4) Å3 and Z = 4. Electron microprobe analyses pointed to the (K,Tl)0.25Cu14Ag6As6.75 stoichiometry (Z = 4), or (K, Tl)Cu56Ag24As27 with Z = 16. The crystal structure of an untwinned crystal has been refined to R1 = 2.61%. It consists of clusters of eight edge-sharing tetrahedra of Cu, which alternate in a 3D chess-board manner with octahedral clusters of six Ag atoms. The latter are surrounded by triangularly coordinated copper in eight faces of a cuboctahedron. The last structure components are large cavities containing partly occupied (K,Tl) sites, coordinated by 18 Ag and As ligands. The structure is full of direct metal-metal contacts although As plays the role of anion, associating especially with copper.

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