Zinc oxide can be called a multifunctional material thanks to its unique physical and chemical properties. The first part of this paper presents the most important methods of preparation of ZnO divided into metallurgical and chemical methods.
Solidified Slag Gas metal arc welding GMAWalso known as metal inert gas or MIG welding, is a semi-automatic or automatic process that uses a continuous wire feed as an electrode and an inert or semi-inert gas mixture to protect the weld from contamination.
It is often used when quality welds are extremely important, such as in bicycleaircraft and naval applications. The arc is more concentrated than the GTAW arc, making transverse control more critical and thus generally restricting the technique to a mechanized process.
Because of its stable current, the method can be used on a wider range of material thicknesses than can the GTAW process and it is much faster. It can be applied to all of the same materials as GTAW except magnesium, and automated welding of stainless steel is one important application of the process.
A variation of the process is plasma cuttingan efficient steel cutting process.
This increases arc quality, since contaminants in the atmosphere are blocked by the flux. The slag that forms on the weld generally comes off by itself, and combined with the use of a continuous wire feed, the weld deposition rate is high.
Working conditions are much improved over other arc welding processes, since the flux hides the arc and almost no smoke is produced. The process is commonly used in industry, especially for large products and in the manufacture of welded pressure vessels. Oxy-fuel welding and cutting The most common gas welding process is oxyfuel welding,  also known as oxyacetylene welding.
It is one of the oldest and most versatile welding processes, but in recent years it has become less popular in industrial applications. It is still widely used for welding pipes and tubes, as well as repair work.
A similar process, generally called oxyfuel cutting, is used to cut metals. Resistance welding Resistance welding involves the generation of heat by passing current through the resistance caused by the contact between two or more metal surfaces.
Small pools of molten metal are formed at the weld area as high current —, A is passed through the metal. The advantages of the method include efficient energy uselimited workpiece deformation, high production rates, easy automation, and no required filler materials.
Weld strength is significantly lower than with other welding methods, making the process suitable for only certain applications. It is used extensively in the automotive industry—ordinary cars can have several thousand spot welds made by industrial robots.
A specialized process, called shot weldingcan be used to spot weld stainless steel. However, instead of pointed electrodes, wheel-shaped electrodes roll along and often feed the workpiece, making it possible to make long continuous welds. In the past, this process was used in the manufacture of beverage cans, but now its uses are more limited.
The two processes are quite similar, differing most notably in their source of power. Laser beam welding employs a highly focused laser beam, while electron beam welding is done in a vacuum and uses an electron beam.
Both have a very high energy density, making deep weld penetration possible and minimizing the size of the weld area. Both processes are extremely fast, and are easily automated, making them highly productive.
The primary disadvantages are their very high equipment costs though these are decreasing and a susceptibility to thermal cracking. Developments in this area include laser-hybrid weldingwhich uses principles from both laser beam welding and arc welding for even better weld properties, laser claddingand x-ray welding.
One of the most popular, ultrasonic weldingis used to connect thin sheets or wires made of metal or thermoplastic by vibrating them at high frequency and under high pressure. Welding metals with this process does not involve melting the materials; instead, the weld is formed by introducing mechanical vibrations horizontally under pressure.
When welding plastics, the materials should have similar melting temperatures, and the vibrations are introduced vertically. Ultrasonic welding is commonly used for making electrical connections out of aluminum or copper, and it is also a very common polymer welding process. The energy from the impact plasticizes the materials, forming a weld, even though only a limited amount of heat is generated.
The process is commonly used for welding dissimilar materials, such as the welding of aluminum with steel in ship hulls or compound plates.
Welding joint Common welding joint types — 1 Square butt joint, 2 V butt joint, 3 Lap joint, 4 T-joint Welds can be geometrically prepared in many different ways. The five basic types of weld joints are the butt joint, lap joint, corner joint, edge joint, and T-joint a variant of this last is the cruciform joint.
Other variations exist as well—for example, double-V preparation joints are characterized by the two pieces of material each tapering to a single center point at one-half their height. Single-U and double-U preparation joints are also fairly common—instead of having straight edges like the single-V and double-V preparation joints, they are curved, forming the shape of a U.
Lap joints are also commonly more than two pieces thick—depending on the process used and the thickness of the material, many pieces can be welded together in a lap joint geometry. Other welding methods, like shielded metal arc welding, are extremely versatile and can weld virtually any type of joint.
Some processes can also be used to make multipass welds, in which one weld is allowed to cool, and then another weld is performed on top of it. This allows for the welding of thick sections arranged in a single-V preparation joint, for example.Chemical Bonds Essay.
Chemical bonds are interactions of electrons between atoms. This is because chemical bonds allow atoms to become stable. There are three different types of chemical bonds, Ionic Bonds, Covalent Bonds, and Metallic Bonds. Ionic Bonds Essay The periodic table is a masterpiece of organized chemical information.
Ionic, covalent and metallic bonding are all various types of bonding found between atoms, Help.
Learn the art of brilliant essay writing with help from our teachers. Learn more. Ionic and Covalent Bonding Ionic and covalent bonding is involved when the atoms of an element chemically combine to make their outer.
There is another type of bonding and this is called metallic bonding, this type of bonding is the force of attraction.
Papers - Ionic and Covalent Bonding. My Account. Ionic and Covalent Bonding Essay. Ionic and Covalent Bonding Essay There is another type of bonding and this is called metallic bonding, Need Writing Help?
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APPENDIX – A Paper II-Modern poetry and General Essay Credits: 4 1 to 20 poems for Modern Poetry variation of atomic volume, atomic and ionic radii, ionization potential, electron affinity, electro.