scholarly journals Disruption of an Alumina Layer During Sintering of Aluminium in Nitrogen

2017 ◽  
Vol 62 (2) ◽  
pp. 987-992 ◽  
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.

Intermetallic Effects on the Ductility of Sintered Aluminium

2008 ◽  
Vol 587-588 ◽  
pp. 380-384
Author(s):  
Jesus Cintas ◽  
José A. Rodríguez ◽  
Francicso Gomez Cuevas ◽  
José M. Gallardo
Keyword(s):  
Heat Treatment ◽  
Particle Size ◽  
Intermetallic Particle ◽  
Quantitative Metallography ◽  
Mechanically Alloyed ◽  
Aluminium Powder ◽  
Attrition Milling ◽  
Different Temperatures ◽  
Alloyed Aluminium ◽  
Milled Powders

Mechanically alloyed aluminium powder was prepared by attrition-milling for 10 hours in the presence of a wax. Milled powders were annealed in vacuum at different temperatures (500, 575, 600, 625 and 650°C). Compacts were consolidated starting from unannealed and from 600°Cannealed powders. Studies by SEM microfractography and quantitative metallography, to investigate the influence of Fe-Al intermetallics on compacts fracture, have been carried out. It is concluded that fracture takes place at regions where the area occupied by the intermetallics is high and intermetallics particles are big. Intermetallic particle size can be controlled by an appropriated heat treatment.

Vulcanization of Rubber. By Organic Peroxides or by Ammonium Persulphate

1930 ◽  
Vol 3 (2) ◽  
pp. 195-200 ◽  
Author(s):  
Iwan Ostromislensky
Keyword(s):  
Benzoyl Peroxide ◽  
Organic Peroxides ◽  
Ammonium Persulphate ◽  
Aluminium Powder ◽  
Metallic Oxides ◽  
Vulcanized Rubber ◽  
Viscous Mass ◽  
Metallic Aluminium ◽  
Short Time ◽  
Rubber Product

Abstract 1. Organic peroxides vulcanize rubber not only in the absence of sulphur but likewise without any foreign substances such as metallic oxides or accelerators of any kind. 2. Rubber vulcanized by means of an adequate amount of benzoyl peroxide (10 to 30 per cent.) gives a soft rubber product which does not differ in point of physical properties from products cured with sulphur, or rather with sulphur chloride. 3. The process of vulcanizing rubber with benzoyl Superoxide is completed in a relatively short time even at a fairly low temperature, sometimes even in two minutes at 119° C., corresponding to 13 pounds pressure. 4. Vulcanization of rubber by means of peroxides may lead to the formation of a soft, transparent and elastic product, which is almost entirely colorless. 5. The products in question vulcanized by means of various peroxides are gradually converted to a very sticky and viscous mass. 6. Sulphur protects the vulcanizates in question from such decomposition or oxidation. However, the products obtained in vulcanization of rubber with organic peroxides in the presence of sulphur are opaque. 7. As distinguished from sulphur, selenium, tellurium, their sulphides, metal oxides (in particular, lead oxide) as well as amines (aniline), tannic acid, and metallic aluminium powder not only do not protect the peroxide vulcanized rubber products from decomposition or oxidation but, on the contrary, they accelerate such processes quite considerably. 8. Benzoyl peroxide is the active vulcanizing agent in the process of heating rubber with a mixture of sulphur and benzoyl peroxide. 9. When rubber is subjected to the action of a mixture of some nitrobenzenes and benzoyl peroxides, vulcanization is effected exclusively by the nitrobenzenes, and the benzoyl peroxide remains altogether passive. 10. Ammonium persulphate vulcanizes rubber completely, resulting in a porous product which, generally speaking, is of small practical value.

Organorheniumhalogenide: Synthesen, Strukturen und Reaktivität gegenüber Alkinen / Organorhenium Halogenides: Synthesis, Structure and Reactivity upon Treatment with Alkynes

1988 ◽  
Vol 43 (11) ◽  
pp. 1391-1404 ◽  
Author(s):  
Wolfgang A. Herrmann ◽  
Roland A. Fischer ◽  
Josef K. Felixberger ◽  
Rocco A. Paciello ◽  
Pavlo Kiprof ◽  
...  
Keyword(s):  
Diffraction Study ◽  
Single Bond ◽  
X Ray Diffraction ◽  
Alkyl Aryl ◽  
X Ray ◽  
Aluminium Powder ◽  
Metal Metal ◽  
Related Derivative ◽  
Alkyne Complexes ◽  
Powder Forming

The organorhenium(V) complexes (η5-C5Me5)ReX4 (2a, X = Cl; 2b, X = Br; Me = CH3) undergo stepwise dehalogenation upon treatment with various reducing agents, e.g. with HgCl2-activated aluminium powder, forming the isolable ReIV and ReIII dimers [η5-C5Me5)ReCl3]2 (3a) and [η5-C5Me5)ReX2]2 (4a, X = Cl;4b, X = Br), respectively. The weak metal-metal single bond of 3a (307.4(0) pm; X-ray diffraction study) is disrupted upon reaction with alkynes yielding the ReIII derivatives (η5-C5Me5)ReCl2(η2-R1CCR2) (9a-e; R1, R2: alkyl, aryl) and novel rhenium(V)- allylidenyl complexes of type (η5-C5Me5)ReCl2[η1:η3-R1CC(Cl)CHR3] (10a-d; R1: alkyl. aryl; R3: H, alkyl). Reduction of 2a (Al/HgCl2) in the presence of alkynes gives a complex reaction mixture of 9a-c, 10a - c and bis(π-alkyne) complexes [(η5-C5Me5)ReCl(η2-R1CCR2)2] + [AlCl4]-(11a-c) (X-ray diffraction study of the related derivative [(η5-C5Me5)ReBr(η2-MeCCMe)2] + [SbF6]-).

Metal/Metal-Oxide Interfaces: How Metal Contacts Affect the Work Function and Band Structure of MoO3

2012 ◽  
Vol 23 (2) ◽  
pp. 215-226 ◽  
Author(s):  
Mark T. Greiner ◽  
Lily Chai ◽  
Michael G. Helander ◽  
Wing-Man Tang ◽  
Zheng-Hong Lu
Keyword(s):  
Band Structure ◽  
Metal Oxide ◽  
Work Function ◽  
Metal Contacts ◽  
Oxide Interfaces ◽  
Metal Metal

Influence of PCA Content on Mechanical Properties of Sintered MA Aluminium

2006 ◽  
Vol 514-516 ◽  
pp. 1279-1283 ◽  
Author(s):  
Jesus Cintas ◽  
Juan M. Montes ◽  
Francicso Gomez Cuevas ◽  
José M. Gallardo
Keyword(s):  
Control Agent ◽  
Dispersion Strengthening ◽  
Process Control Agent ◽  
Mechanically Alloyed ◽  
Aluminium Powder ◽  
Attrition Milling ◽  
Ultrafine Grained ◽  
Ultrafine Grained Materials ◽  
Alloyed Aluminium ◽  
Sintering Method

Aluminium powder has been mechanically milled using different amounts of process control agent (PCA). Mechanically alloyed aluminium powder (MA Al) was prepared by attrition milling in the presence of 1.5 and 3wt.% of an EBS wax. Milling was carried out in vacuum during 10 h. Milled powders were consolidated by a press-and-sintering method. This consolidation method is not usually employed with MA Al powders. The amount of dispersed carbides formed in the Al powder increases with the percentage of PCA. These carbides restrain Al grain growth during sintering, resulting in consolidated compacts with a grain size of about 550 nm. Thus, these PM materials can be considered ultrafine grained materials. Due to grain refinement and dispersion strengthening, the tensile strength of MA Al specimens is increased remarkably.

Analysis of metal-metal contacts in RF MEMS switches

2013 ◽  
Author(s):  
Steffen Kurth ◽  
Sven Voigt ◽  
Sven Haas ◽  
Andreas Bertz ◽  
Christian Kaufmann ◽  
...  
Keyword(s):  
Rf Mems ◽  
Metal Contacts ◽  
Mems Switches ◽  
Rf Mems Switches ◽  
Metal Metal

Effect of Die Temperature on Mechanical Properties of Hot Pressed P/M Parts

2010 ◽  
Vol 638-642 ◽  
pp. 1802-1810
Author(s):  
Abolfazl Babakhani ◽  
Ali Haerian
Keyword(s):  
Room Temperature ◽  
Strength Properties ◽  
Metal Contacts ◽  
Powder Morphology ◽  
Particle Spacing ◽  
Green Strength ◽  
Flow Problems ◽  
Metal Metal ◽  
Different Temperatures ◽  
Die Temperature

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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