Bulk Properties Of Metals Research Articles

Stig Hagström

Stig Hagström

Changes produced by a low-energy plasma in the surface layers and bulk properties of metals and alloys

Here we survey researches dealing with regularities and mechanisms for the bulk changes in properties in metals and alloys on surface treatment with low-energy plasmas. Descriptions are given of dislocations and dislocation-loop generation and of the formation of dislocation substructures. The dislocation density increases with irradiation time and as the distance from the surface decreases or as the yield point decreases. The effect is nonmonotonically dependent on the irradiation voltage and screening conditions. The types of dislocation structure formed are similar to those produced in plastic strain.

Surface and bulk properties of metals modelled with Sutton-Chen potentials

Surface and bulk properties of metals modelled with Sutton-Chen potentials

Fracture analysis of soldered wire by plasma ashing and SEM

The increasing demand for higher quality and reliability in the computer peripherals industry requires that the components function without premature materials failure. SEM has been found to be an indispensable technique for studies leading to improved materials and processes. Because of the variety of materials used, SEM specimen preparation requires continuing innovation.Low temperature oxygen plasma-ashing was found to be a convenient technique to remove organic resins and other hydrocarbons. A gaseous plasma, consisting of neutral, energized and ionized atoms, is created by sending oxygen through a high voltage electric field. The plasma readily reacts with the hydrocarbons forming gaseous carbonaceous by-products. The addition of argon to oxygen provides sputter-etching and a more effective resin removal. The temperature of the specimen rarely goes above 50°C and so it is called low temperature gas plasma. The plasma does not alter surfaces or bulk properties of metals and ceramics.

On the Fundamental Nature of Metal-Metal Adhesion

The cohesion of metals and their adhesion to other metals are complicated and poorly understood processes. Theories of adhesion have been judged by the use of indirect friction and wear data because of the scarcity of good experimental adhesion data. The adhesion of one metal to another appears to be a manifestation of the electronic configuration of the atoms involved because the cohesive nature of materials results from these atomic forces. Therefore, the atomic binding energies, the distribution of the atomic species in the surface layers, the surface structure, and the crystal lattice disregistration must be influential in metal-metal adhesion. Adhesion is a surface oriented process and, thus, the bulk properties of metals should have only secondary influences. Those metals having an electron deficiency in their outer atomic orbitals should adhere better than those metals which do not in order to minimize the total free energy and approach a more stable state. A correlation is shown between outer s or...

Metal Surfaces and Their Changes by Chemisorption

Two basic approaches to the solution of surface problems exist in both theoretical and experimental research on metals. In the first approach, the bulk properties of metals and changes caused by surface processes are studied and the interpretation is based on the nearly-free-electron model of the metal. This approach was successful in the explanation of bulk properties. However, because of the complexity and asymmetry of the system (crystal and gas molecule), one is usually forced to use oversimplified models, which sometimes fail in the elucidation of all the observed effects. Another approach is based on the assumption that the surface interaction (resulting in the formation of a quasichemical compound) concerns a limited number of participants (as in a chemical reaction). In the simplest case: gas particle and a surface atom. New experimental evidence (field-ion-emission microscopy, field-electron-emission microscopy, ion-neutralization spectroscopy) has been found supporting the idea that the properties of a surface atom in the moment of the interaction can be roughly approximated by the properties of an individual atom. The type of approach which should be used in a particular case depends both on the experimental method and on the problems in which we are interested.