“Mo Parts, made with 99.95% purity materials"
Mo Parts is a component used in varous products and industries from home appliances microwave oven to military radar, and its application range becomes enlarged as the increase of industrial usage of it.
Spot welding with the terminal of Center Lead, to support the upper part of Filament
Component to connect Ceramic and Upper End Shield, going across the inner diameter of Down End Shield
Supporting the lower part of Filament, unique shapes by welding with Side Lead, and essential component for cathode supporting
Microwave oven was developed in US at 1946. There was phenomenon it became warm when hands approached to the wave during experiment of radar, and this is the initial idea of Microwave oven. While oven bakes the food by elevating inner temperature, Microwave oven does it by using moisture contained in food.
Water molecule, structuring the most part of food, has polarity. Accordingly, the side of hydrogen ion shows relatively positive charge and the side of oxygen ion negative, respecti- vely. If molecule has polarity like this, the one side can bind to the opposite charged part of the other molecule. In this time, when microwave is transmitted to this bound molecules, the electrical vector of microwave is vibrated to make bound molecules rotate. In here, if the rotation is inhibited by other molecule, this bond will be broken. Microwave energy is entered into the molecule in this moment. After a wile, energy is emitted by re-binding molecules, and this energy make cook the food as an internal energy
Microwave is transmitted to food in various directions. This can be shown in the structure of Microwave oven. Microwave is reflected in vari- ous direction by the rotational plate of Microwave oven.
In general, it is said the principle of microwave oven is that the resonance is occurred from the same oscillation frequency of microwave and water molecule. However, the oscillation frequency of microwave is 2.45GHz, and significantly different from that of water, 9GHz in T =0℃. Then, if we adopt the microwave with the same resonance frequency of water molecule, it make faster absorption of energy, but why we do not use it? The solution for this may be explained with electromagnetic. The frequency of microwave is related to the penetration depth of it. Penetration depth means the depth that microwave can penetrate through the surface of food. The more frequency the lesser penetration depth rapidly. Therefore if the frequency of microwave is raised up to the frequency of water, it may cook faster but we cannot eat the surface of it.
Most of current commercial microwave ovens are manufacture by attaching the heat transfer equipment of oven or grill to microwave heating device. Microwave oven composed of heating source which emitting microwave, power source, control panel, cooling fan, and case. And it is also equipped the turn table for rotating foods for uniform distribution of microwave. Heating source is composed of special electrode vacuum tube of Magnetron. This is a device to generate the ultra high frequency (UHF), which concentrates on food through output antenna. Strong frequency emitted from microwave oven is harmful to human body, so it must not be leaked. For this reason, it is manufactured with safety device not for opening door during operation and also with metallic case.
There are two types of Magnetron that pulse Magnetron and continuous wave Magnetron. Pulse magnetron is mainly used in radar and continuous magnetron is used in each kind of heater and microwave medical instrument as well as Microwave oven. As the use of microwave in industry, the interest for continuous wave Magnetron becomes increase, and its application is to be various more and more.
Magnetron is structured with combining electric field and magnetic field, and generates 2.4GHz of microwave by spinning the electron under vacuum. Microwave oven, currently used in home, is separated to tungsten filament for emitting microwave (containing thorium) and cathode supporter which supporting this filament. Since filament and cathode supporter are operated in high temperature, it is used that the high purity Mo (Molybdenum) with high m.p under the vacuum condition. Though it may be a little changed the dimension and material by Magnetron manufacturer, but it commonly separated as follows.
They support the high frequency emitting filament in both sides of up and down that the Upper End Shield and Lower End Shield. Refer to the below homepage to see more detailed properties, dimension, and materials of Magnetron.
The 6th group elements of Cr-group in periodic table. The name is originated from the molybdenite of the ore MoS2. In ancient Greek, molybdos meant lead, especially, a galena out of lead ore was called to mo lybdenum, in latter, black lead and Molybdenite were included in this category of molybdenum. But when Swedish scientist K.W. Scheele found molybdenum at 1778, these were separated into other materials and Molybdenite has been called to as is
|Elementary Symbol||Mo||Electronegativity, Pauling||2.16|
|Atomic Number||42||State at RT||Solid, Metal|
|Atomic Weight||95.94||Melting Poin(℃)||2662±10|
|Oxidation States||2,3,4,5,6||Boiling Point(℃)||4800|
It exists relatively wide extents in the earth but its amount is not so much. Its Clarkes No. is 0.0013(the 42nd), contained in earth's crust as the same amount of lead, and main ore is Molybdenite. It is a biophile element, so it is always contained in animal and plant though it is little amount, as well as sea. Main producing center is US, occupies about 70% of the world production, and 2/3 of it are produced from Climax Mine of CO. It is also produced in Canada·Russia·Chile·China·Austrailia.
Reduced one is gray powder, and sintered or melted one is polished silver-white
metal. It has electric conductivity and ductility, and possible to casting and rolling. It
has been known the metal with high melting point together with tungsten, similar to
carbon in high temperature since its vapor pressure is low, and also possible to forg
ing. It has very strong mechanical power in all temperature from ultimately low to
high temperature through RT. Electronic conductivity is 34% of that of silver, and react
with oxygen, chloride, bromine, carbon, silicon, and iodine in high temperature. More over it composes the fluoride with fluorine in low temperature. Atomic value for chemical is 2, 3, 4, 5, and 6, and 6th is most stable out of them. It is not dissolved in hydrochloric acid and weak sulphuric acid but dissolved in strong sulphuric acid, nitric acid, and aqua regia, furthermore it vigorously dissolved in the mixture of hydrogen fluoride and sulphuric aacid.
Sintering is, a heat treatment to get the physical and mechanical properties required in powder compact by making chemical bonding composed by 1st binding strength between elements through heating compressed/uncompressed powder compact under the temperature below M.P of main metal element, which is only maintained by weak binding strength or contact. There are two sintering methods of liquid phase sinter ing and solid phase sintering. Solid phase sintering is a one to induce the binding between powder by heat treatment in temperature below m.p of powder, and liquid phase sintering indicates when one or more components form the liquid phase within sintering body in multi- elements system. It is produced by liquid phase sinter ing that the each kind of ceramic manufactures as well ultra hard metal, hard metal, and some of densely casting components. In this experiment, it has been studied about solid phase sintering.
Sintering of nickel powder, the initial contact point (in A) is extended for enlarging the contact surface (B and C) during heating material with 1100℃. (pore is contracted in reverse direction.) Powder particles are closely attached and the area of surface is decreased.
|Initial binding of particle.||The binding between particles are converted to chemical or metallic atomic binding by extrusion.|
|Growth of contact neck||The contact part which bound in 1st step is called to neck, and in this step, the contact surface is extended by the movement of elements around this neck.|
|Close of pore channel||This stage is to give the most change in spatial property of pore in sintering body. It creates isolated pore by closing pore channel which used to be connected between particles.|
|Globalization of pore||The globalization of pore is natural result from the growth of neck, and this is for the minimization of surface energy.|
|Contraction and termination of pore (Densification)||In this step, pore is disappeared or contracted by the movement of materials into the pore.|
|Coarsening of Pore||This is the final stage of sintering, forming larger pore by contracting or disappearing of small and isolated pores.|
The main driving force for the above sintering reaction is the decrease of free energy by the decrease of total surface area of powder compact in resulting from the growth of particle or the contraction of pore.