Advanced Engineering Materials

Brief Introduction of Physical Vapour Deposition (PVD)? Physical vapour deposition  (PVD) is a thin-film coating process which produces coatings of pure metals, metallic alloys and ceramics with a thickness usually in the range 1 to 10µm. Physical vapour deposition, as its name implies, involves physically depositing atoms, ions or molecules of a coating species on to a substrate. There are three main types of PVD, all of which are undertaken in a chamber containing a controlled atmosphere at reduced pressure (0.1 to 1 N/m 2). All three techniques can be used for the direct deposition of a material or for 'reactive' use in which chemical reaction occurs in the vapour/plasma phase between atoms of the coating material and 'reactive' gases. 1. Thermal evaporation. Thermal evaporation uses the heating of a material to form a vapour which condenses on a substrate to form the coating. Heating is achieved by various methods including hot filament, electrical resistance...

Description of Tungsten Carbide Powder: Tungsten carbide powder  (WC) is the main raw material for the production of cemented carbide, chemical formula is  WC . Tungsten carbide powder is a black six square crystal, with metallic luster. Its hardness was similar to diamond, a good conductor of electricity and heat. The melting point is 2870 DEG, the boiling point is at a temperature of 6000 DEG , and the relative density is about 15.63 (18 DEG C). Tungsten carbide is insoluble in water, hydrochloric acid and sulfuric acid, soluble in mixed acid of nitric acid and hydrofluoric acid. The  pure tungsten carbide  is fragile, but the brittleness will reduce, if mixed with a small amount of titanium, cobalt and other metals. Processing as the tungsten carbide cutting tool, in order to improve the anti explosion capacity,  titanium carbide ,  tantalum carbide  is often added. Chemical stability of tungsten carbide. Applications of Tungsten Carbide Powde...

Rare earths  are crucial to the manufacture of many hi-tech products. Despite their name, most are abundant in nature but are hazardous to extract. Most "rare earth" elements have uses in several different fields. Neodymium This is used to make powerful magnets used in loudspeakers and computer hard drives to enable them to be smaller and more efficient. Magnets containing neodymium are also used in green technologies such as the manufacture of wind turbines and hybrid cars. Lanthanum This element is used in camera and telescope lenses. Compounds containing lanthanum are used extensively in carbon lighting applications, such as studio lighting and cinema projection. Cerium Used in catalytic converters in cars, enabling them to run at high temperatures and playing a crucial role in the chemical reactions in the converter. Lanthanum and cerium are also used in the process of refining crude oil. Yttrium Yttrium is used in the process of generating colour display...

What is magnetron sputtering? With magnetron sputtering, magnetic fields increase plasma density for a higher deposition rate and a more efficient process. While conventional cathode sputtering can deposit extremely thin films down to the atomic scale, it tends to be slow and most effective only with small  substrates . The bombardment of the substrate can also create overheating or damage to the object to be coated. Magnets (usually permanent magnets) behind the cathode confine electrons over the negatively charged target material, enhancing both the efficiency of the initial ionization process and allowing plasma to be generated at lower pressures. The lower pressure reduces both background gas incorporation in the growing film and energy losses in the sputtered atom through more gas collisions since electrons follow helical (spiral) paths around magnetic field lines. The longer paths mean a higher probability of ionizing collisions with gaseous neutrals near the target su...

Description of Tungsten Powder: Tungsten powder  is the main raw material for processing  Tungsten alloy .  Pure Tungsten powder  can be made into wire, rod, tube, plate and other processing materials and certain shape products. Tungsten powder mixed with other metal powder, can be made into all kinds of  Tungsten Carbide , such as Tungsten Cobalt alloy,  Tungsten Rhenium alloy ,  Tungsten Copper alloy  and high density Tungsten alloy. Applications of Tungsten Powder: Tungsten powder is widely used in the production of weight fillers, radiation shielding fillers and induction accelerators, etc.. The thin film surface of its polymer mixture is ideally suitable for radiation protection. The large particle size makes it an ideal heavy metal filler for injection-molding applications. The unique shape and the resulted high flow ability of the particles make it suitable for applications in metal spray industry. Another important application of T...

Before 1965 there was relatively little demand for rare earth elements. At that time, most of the world's supply was being produced from placer deposits in India and Brazil. In the 1950s, South Africa became the leading producer from rare earth bearing monazite deposits. At that time, the Mountain Pass Mine in California was producing minor amounts of rare earth oxides from a Precambrian carbonatite. Color Television Ignites Demand The demand for rare earth elements saw its first explosion in the mid-1960s, as the first color television sets were entering the market. Europium was the essential material for producing the color images. The Mountain Pass Mine began producing europium from bastnasite, which contained about 0.1% europium. This effort made the Mountain Pass Mine the largest rare earth producer in the world and placed the United States as the leading producer. China Enters the Market China began producing notable amounts of rare earth oxides in the early 1980s an...

When you try to evaporate  titanium evaporation material , your  tungsten boat  may break. Why would this happen? A material’s evaporation temperature is often regarded as that needed for the material’s equilibrium vapor pressure to be 1E-2 Torr. At that vapor pressure, the deposition rate on a substrate in a system of “normal” geometry is good or high. For titanium, that temperature is ~1,750C. Titanium has to melt and “wet” a boat or crucible in order for efficient evaporation to take place. At this temperature, titanium will be liquid and quickly alloy with a refractory boat, destroying its electrical and mechanical properties. The end result is the boat cracking and falling apart. Is there any other solution? A second option for thermal evaporation is to use a shielded tantalum crucible heater with a tall, intermetallic crucible. Thin films of titanium can be evaporated from intermetallic crucibles. However, film thickness may be limited to 500 angstroms, and the...