Vacuum deposition, aluminium


Optical Properties. The index of refraction and extinction coefficient of vacuum-deposited aluminum films have been reported (8,9) as have the total reflectance at various wavelengths and emissivity at various temperatures (10). Emissivity increases significantly as the thickness of the oxide film on aluminum increases and can be 70—80% for oxide films of 100 nm.  [c.94]

Thin films of photochromic glass containing silver haUde have been produced by simultaneous vacuum deposition of siUcon monoxide, lead siUcate, aluminum chloride, copper (I) chloride, and silver haUdes (9). Again, heat treatment (120°C for several hours) after vacuum deposition results in the formation of photochromic silver haUde crystaUites. Photochemical darkening and thermal fade rates are much slower than those of the standard dispersed systems.  [c.162]

Amorphous (vitreous) selenium, vacuum-deposited on an aluminum substrate such as a dmm or a plate, was the first photoconductor commercially used in xerography (6). It is highly photosensitive, but only to blue light (2). Its light absorption falls off rather rapidly above 550 nm. Because of the lack of photoresponse in the red or near infrared regions, selenium photoreceptors caimot be used in laser printers having He—Ne lasers (632.8 nm), or soHd-state lasers (680—830 nm).  [c.130]

Sprayed, vacuum-deposited and plated coatings can be applied to most metals and to many non-metals, e.g. vacuum deposition is applied to many substrates including plastics spray application can be used for coating fabric, plastic and paper. Hot dipping and other diffusion processes are dependent on the nature of the substrate for the properties of the coating. Most commercial applications of aluminium coatings are on iron and steel with smaller quantities applied to aluminium alloys and plastics.  [c.465]

Vacuum-deposited and electroplated coatings are pure metal with no chemical bond to the underlying surface. The properties will be those of pure aluminium. The presence of lacquer, in the case of vacuum-deposited coatings will, however, afford resistance to the passage of electricity and limit the maximum temperature of use.  [c.470]

Vacuum Deposited Coatings Aluminium coatings have been strongly considered as a replacement for cadmium in the protection of high-tensile steel  [c.477]

Metallization layers are generally deposited either by CVD or by physical vapor deposition methods such as evaporation (qv) or sputtering. In recent years sputter deposition has become the predominant technique for aluminum metallization. Energetic ions are used to bombard a target such as soHd aluminum to release atoms that subsequentiy condense on the desired substrate surface. The quaUty of the deposited layers depends on the cleanliness and efficiency of the vacuum systems used in the process. The mass deposited per unit area can be calculated using the cosine law of deposition  [c.348]

Costing with Aluminum. The numerous methods of applying aluminum coatings include continuous and batch hot dipping, pack diffusion, slurry processes, thermal spraying, and cladding, as well as vacuum, chemical, and ion-vapor deposition. Regardless of method, the essential factor for successful coating is proper preparation of the steel surface. The iron oxide scale, as well as adsorbed moisture and gas, must be removed.  [c.131]

The vaporization rate from a hot surface into a vacuum, ie, free surface vaporization rate, depends on the temperature and the equiUbrium vapor pressure of the material at that temperature. For thermal evaporation, a reasonable deposition rate can be obtained only if the free surface vaporization rate is fairly high and an equiUbrium vapor pressure of ca 1 Pa (10 ton) is arbitrarily considered as the value necessary to provide a useful deposition rate. Materials having vapor pressure above the soHd are described as subliming materials. Examples are Cr and C. Materials having vapor pressure above the hquid are described as evaporating materials. Many materials, such as titanium, can be deposited by either sublimation or evaporation, depending on the temperature of the source. For some materials, such as aluminum and tin, the temperature of the molten material must be significantly greater than the melting point in order to have a significant vaporization rate. For alloys, the thermal vaporization rate of each constituent is proportional to the relative vapor pressures (Raoult s law). Therefore during vaporization, the higher vapor pressure material vaporizes more rapidly and the vaporization source is progressively enriched in the lower vapor pressure material as evaporation progresses.  [c.516]

There are several vacuum processes such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), sputtering, and anodic vacuum arc deposition. Materials other than metals, ie, tetraethylorthosiHcate, silane, and titanium aluminum nitride, can also be appHed.  [c.313]

The metal-insulator-metal sandwich is known as a tunnel junction, and its preparation is all-important. The standard junction consists of an aluminum strip ca. 60-80 nm thick and 0.5-1.0 mm wide deposited in a very good vacuum on to scrupulously clean glass or ceramic the surface of the strip is then oxidized either thermally or by glow discharge. The resulting oxide layer is extremely uniform and approximately 3 nm thick. Introduction of adsorbed molecules on to the oxide layer, or "doping , as it is called, is then effected either by immersion in a solution then spinning to remove excess fluid, or by coating from the gas phase. The final stage in preparation is deposition of the second metal (invariably lead) of the sandwich this deposition is performed in a second vacuum system (i. e. not that used for aluminum deposition), the final thickness of lead being approximately 300 nm, and the width of the lead strip being the same as that of the aluminum strip. The reason for using lead is that all lETS measurements are conducted at liquid helium temperature,  [c.85]

Other matrix materials include metals that can be made to flow around an in-place fiber system by diffusion bonding or by heating and vacuum infiltration. Common examples include aluminum, titanium, and nickel-chromium alloys. Ceramic-matrix composite materials can be cast from a molten slurry around stirred-in fibers with random orientation or with preferred flow-direction orientation because of stirring or some other manner of introducing the ceramic. Alternatively, ceramic matrix material can be vapor deposited around a collection of already in-place fibers. Finally, carbon matrix material can be vapor deposited on an already in-place fiber system. Alternatively, liquid material can be infiltrated around in-place fibers and then carbonized in place by heating to high temperature. The process involving liquid infiltration and carbonization must be repeated many times because carbonizing the liquid results in decreased volume of the matrix. Until the voids can no longer be filled (they become disconnected as densification continues), the potential matrix strength and stiffness have not been achieved.  [c.6]

Other matrix materials include metals that can be made to flow around an in-place fiber system by diffusion bonding or by heating and vacuum infiltration. Common examples include aluminum, titanium, and nickel-chromium alloys. Ceramic-matrix composite materials can be cast from a molten slurry around stirred-in fibers with random orientation or with preferred flow-direction orientation because of stirring or some other manner of introducing the ceramic. Alternatively, ceramic matrix material can be vapor deposited around a collection of already in-place fibers. Finally, carbon matrix material can be vapor deposited on an already in-place fiber system. Alternatively, liquid material can be infiltrated around in-place fibers and then carbonized in place by heating to high temperature. The process involving liquid infiltration and carbonization must be repeated many times because carbonizing the liquid results in decreased volume of the matrix. Until the voids can no longer be filled (they become disconnected as densification continues), the potential matrix strength and stiffness have not been achieved.  [c.6]

Every computer needs a long-term memory store as well as an evanescent (RAM) store. Things have come a long way since punched paper tapes were used, before World War II. The history of magnetic recording during the past century is surveyed by Livingston (1998). The workhorse of longterm memory storage is the hard disc, in which a minute horseshoe electromagnet is made (by exploiting aerodynamic lift) to float just micrometres (now, a fraction of a micrometre) above a polished ferromagnetic thin film vacuum-deposited on a polished hard non-magnetic substrate such as an Al-Mg alloy, with a thin carbon surface layer to provide wear resistance in case the read/write head accidentally touches the surface. According to the above-mentioned overview, densities of 30 megabytes per cm" were current in 1994, but increasing rapidly year by year, with (at that time) a cost of 1/ megabyte and data-writing rates of 9 megabytes per second. The first hard-disc drive was introduced by IBM in 1956... the RAMAC, or Random Access Method of Accounting and Control. It incorporated 50 aluminium discs 60 cm in diameter, and the device, capable of storing 5 million characters (which today would occupy less than a square centimetre), weighed nearly a ton and occupied the same floor space as two modern refrigerators. This information comes from a survey of future trends in hard-disc design, (Toigo 2000) this article also claims that the magnetic coating of RAMAC was derived from the primer used to paint the Golden Gate Bridge in San Francisco.  [c.287]

Methods available for coating other metals with aluminium include spraying spray aluminising (heat-treated sprayed coatings) hot dipping Calorising (diffusion or cementation) vacuum deposition electroplating electrophoretic deposition chemical deposition (gas or vapour plating) cladding or mechanical bonding casting.  [c.465]

Vacuum deposition of high-purity aluminium has been used as a bright finish of a decorative nature on domestic items and some car accessories, as well as special items for space missions where opacity to solar radiation was required. Continuous deposition on plastic strip at speeds up to 450m/min has been achieved.  [c.476]

Air is widely used as the feed gas for commercial ozone generators. The air feed gas to the ozone generator should be dry and free of foreign matter. EHtered ambient air is drawn into the plant by vacuum, blower, or compressor. The pressure of the treated air can vary from sub atmospheric to >400 kPa kPa (4 atm). Since compression heats the air, cooling is necessary. The air is filtered again to remove oH droplets that can foul the desiccant dryers and interfere with ozone generation. Any hydrocarbons in the air can be removed with activated carbon. Moisture is removed by desiccant-drying or a combination of refrigerant- and desiccant-drying. Desiccant-drying is accompHshed by using molecular sieves (qv), sHica gel, or activated alumina, aH of which are capable of regeneration. Liquid water droplets in refrigerant-dried air should be removed by filtration prior to contacting the desiccant dryers. A final filtration is necessary to remove desiccant dust particles down to 1 p.m. The efficiency of ozone generation decreases with increasing moisture content in the air (95). At high dew points, nitrous and nitric acids are deposited within the ozone generator, decreasing performance and substantiaHy increasing the maintenance frequency. The air feed to the ozone generator should have a dew point of at least —60° C, corresponding to a moisture content of <20 ppmv some systems, however, operate at a dew point of —80° C. A sensor should be placed in the air stream entering the generator that can shut the system off and sound an alarm if the dew point increases above the desired level. In high pressure systems, the pressure of the compressed air prior to entering the ozone generator is reduced by means of a pressure-reducing valve. The pressure employed depends on the ozone generator type and can vary from 100 to 240 kPa (0—20 psig). The pressure of the ozone generator feed should be maintained at a constant level to avoid affecting power draw and apphed voltage.  [c.498]

Thin Film. In the thin-film approach, raw material usage is generally more than two orders of magnitude less and patterning is more direct. In some thin-film approaches, certain individual layers may be only 50 atoms thick, which means that large-area uniformity of coating is the key to success. These coatings must be both optically and electrically uniform over areas the si2e of about a square meter. The technical decisions ate complex and may be ordered as follows (/) What substrate is to be coated The principal choices are glass, steel, ceramic, or plastic. (2) What materials are to be deposited The principal semiconductor options are amorphous and polysilicon, cadmium teUuride, copper indium diselenide, and alloys of these basic options. The most significant conductor options are silver, nickel, aluminum, tin oxide, 2inc oxide, indium oxide, and some alloys of these choices. (3) What deposition process is to be utilhed The options are vacuum evaporation, sputtering, glow discharge, chemical vapor deposition (CVD), electroplating, spraying, and screen printing. (4) How are the layers to be patterned These options include screen printing, laser scribing, mechanical scribing, and photoUthographicaHy defined wet etching.  [c.471]

Xerography. Photocopiers and laser printers, using the xerographic principle of operation (see Electrophotography), are a primary apphcation for selenium and selenium-based alloys. A large number of such machines use selenium in the dmm or belt photoconductor, which is the critical component for both the image generation and image development functions. The selenium is typically deposited on the metal belt or aluminum dmm used in these machines, as a 50-p.m vitreous layer, using a process which involves the thermal evaporation of high purity grades of selenium under vacuum. Early copiers used pure selenium coatings, but these have been almost totally replaced by alloys using additions of arsenic, chlorine, and tellurium in order to improve the lifetime of the dmms, to modify their photoconductive or spectral response, and to improve their resistance to abrasion. As a result of these changes, some types of selenium-based photocopiers and printers can operate at very fast speeds and defiver hundreds of thousands of pages of output before the dmm or belt needs to be replaced. Used selenium dmms or belts are returned to the suppfier for recycling. In the lower speed, lower cost, desktop digital copier, selenium has been largely replaced by organic-based photoconductors.  [c.336]


See pages that mention the term Vacuum deposition, aluminium : [c.750]    [c.467]   
Corrosion, Volume 2 (2000) -- [ c.13 , c.20 ]