Superconductivity is a property displayed by certain materials at very low temperatures. Metals and their alloys have been known to be superconductive (ex. Tin, aluminum) other materials that have also been found to be superconductive are ceramics which contain copper and oxygen atoms. Superconductors have a special property which is that they can conduct electricity without resistance which means that energy is not lost. Once in motion, energy can flow through a closed loop of superconductive material forever.
However, at higher temperatures and with different superconductor systems, the BCS theory has consequently became insufficient to fully explain electron behavior. The Type 1 category of superconductors is basically made up of pure metals that normally show conductivity at room temperature. They require really cold temperatures to slow down molecular vibrations enough to facilitate unrestrained electron flow in agreement to the BCS theory. BCS theory suggests that electrons team up in cooper pairs in order to help each other overcome molecular obstacles. Type 1 superconductors were discovered first and require the coldest temperatures to become superconductive.
It involves the joining of metals without fusion or filler metals. Since FSW is essentially solid state, high quality weld is obtained, characterized with absence of solidification cracking, porosity, oxidation and other defects typical to traditional fusion welding. The peak temperature in the FSW process is generally of the order of about 80% that of the liquidus temperature of the material being welded. The joint produced in this process is asymmetric about the weld line, as the material in a highly plastic state flows differently at the two sides of the welded joint. Owing to the velocity difference between the rotating tool and the stationary work piece, the mechanical interaction produces heat by means of frictional work and material plastic deformation.
The purpose of this paper is to examine the materials, properties, and theory of superconductivity, a quantum phenomenon that occurs when a material is brought below a critical temperature and will conduct electricity without any resistance, the nearest model in nature to perpetual motion. According to Ecks (1990), Once current is applied to a superconducting material the current will continue in a closed lope without ever losing intensity. (Ecks, 1990) Superconductive materials can greatly vary in mechanics and materials. They are separated into Type 1 and Type 2 superconductors. All superconductors display the unique ability to repel magnetic fields, known as the Meissner effect.
On the other hand, the active magnetic refrigeration cycle is similar to the ADR cycle, but heat addition and rejection occurs at a constant magnetic field rather than at constant temperature. Isothermal heat rejection and addition is impractical to implement since the applied magnetic field must be modulated to match the temperature with the heat rejection rate , 188.8.131.52. Some Theoretical Background for the (AMRR)
A metal in this state has very unique magnetic properties that are unlike those at normal temperatures. A superconductor is often referred to as the perfect diamagnetic. Diamagnetic, ideally, are a class of materials that do not conserve magnetic flux, but expel it. A superconductor is classified as a perfect diamagnetic because by all measurable standards the magnetic flux within the material is zero. Electrons have a wave-like nature so an electron moving through a metal can be represented by a plane wave progressing in the same direction.
Conductors, like copper and other metals, have very low resistance, and superconductors, comprised of certain metals such as mercury and ceramics such as lanthanum-barium-copper-oxide, have no resistance. Resistance is an obstacle in the flow of electricity. Superconductors also have strong diamagnetism. In other words, they are repelled by magnetic fields. Due to these special characteristics of superconductors, no electrical energy is lost while flowing and since magnetic levitation above a superconductor is possible.
1.1 PRELUDE: The phenomenon of ferromagnetism is associated only with the solid state of matter; like iron, nickel, cobalt and some rare earth metals and their alloys. Thus, up to now, there is no intrinsic homogeneous fluid having ferromagnetic properties; although, theories admit the possibility of ferromagnetism in the liquid state, and suggest that there is no inherent reason why they should not exist [1-3,5]. Ferromagnetism occurs when paramagnetic ions in a solid lock together in such a way that their spins all point (on the average) in the same direction . At a certain temperature this locking breaks down and ferromagnetic materials become paramagnetic. This transition temperature is called the Curie point (TC), which is invariably well below the melting point of the corresponding material [1,8,12].
This usually only happens with heavy elements though. They are so heavy that the concentration of them on earth is so small that it has no effect on us. When you hear of Uranium being radioactive, this is what they are talking about. This is what is picked up by a Geiger counter. Now we can’t just let that type of fission happen and expect there is be a substantial energy output.
Missing Figures The purpose of this paper is to describe and explain the properties of ferrofluids. Imagine the applications of a liquid substance that can be controlled at a distance by a magnetic force. To create such a liquid is not as simple as liquefying a magnetic solid. Magnetic solids lose their magnetic properties at the temperature above the Curie temperature of the substance. At that temperature thermal energy overwhelms the tendency of the electrons to align in regions of similar spins.