A small amount of industrial production involves wet chemical processes, which start with aqueous solutions of zinc salts, from which zinc carbonate or zinc hydroxide is precipitated. The solid precipitate is then calcined at temperatures around 800 °C.
Wet chemical process
Zinc oxide
Zinc oxide | Wet chemical process
It is a process that starts with aqueous solutions of zinc salts, from which zinc carbonate or zinc hydroxide is precipitated. A small amount of industrial production involves wet chemical processes, which start with aqueous solutions of zinc salts, from which zinc carbonate or zinc hydroxide is precipitated A small amount of industrial production involves wet chemical processes, which start with aqueous solutions of zinc salts, from which zinc carbonate or zinc hydroxide is precipitated. A small amount of industrial production involves wet chemical processes, which start with aqueous solutions of zinc salts, from which zinc carbonate or zinc hydroxide is precipitated.
describe in general terms the structure of ionic solids such as nacl
user
Ions typically pack into extremely regular crystalline structures, in an arrangement that minimizes the lattice energy.
assistant
what can you tell me about their boiling point?
user
Boiling points exhibit similar trends to melting points in terms of the size of ions and strength of other interactions. When vapourized, the ions are still not freed of one another.
assistant
can you name any compounds?
user
Ammonium acetate, zinc oxide, aluminum hydroxide,  aluminium oxide and lead(II) oxide.
assistant
what are the uses of the aforesaid initial one?
user
It is also used as a diuretic.
assistant
what can you tell me about its production?
user
Ammonium acetate is produced by the neutralization of acetic acid with ammonium carbonate or by saturating glacial acetic acid with ammonia.
assistant
what are the applications of the second one?
user
It is used for making plastics, ceramics, glass, cement, rubber, lubricants, paints, ointments, adhesive, sealants, concrete manufacturing, pigments, foods, batteries, ferrites, fire retardants, etc.
assistant
how is it used in the ceramic industry?
user
It is used in ceramic glaze and frit compositions.
assistant
can you name the medicines in which they are used?
user
Calamine lotion, zinc oxide eugenol and others.
assistant
what are its mechanical properties?
user
It is a relatively soft material with approximate hardness of 4.5 on the Mohs scale. Also its elastic constants are smaller than those of relevant III-V semiconductors.
assistant
what is wet chemical process?
user
A small amount of industrial production involves wet chemical processes, which start with aqueous solutions of zinc salts, from which zinc carbonate or zinc hydroxide is precipitated. The solid precipitate is then calcined at temperatures around 800 °C.
Zinc oxide | Wet chemical process
The process consists of treating zinc containing material, in which zinc can be in the form zinc oxide, zinc silicate, zinc ferrite, zinc sulphide together with a carbon containing reductant/fuel, within a rotary kiln at 1000 °C to 1500 °C. The kiln feed material comprising zinc 'waste', fluxes and reductant (coke) is typically pelletized before addition to the kiln. The chemical process involves the reduction of zinc compounds to elemental zinc (boiling point 907 °C) which volatalises, which oxidises in the vapour phase to zinc oxide. The zinc oxide is collected from the kiln outlet exhaust by filters/electrostatic precipitators/settling chambers etc.
Waelz process | History and description
In the indirect or French process, metallic zinc is melted in a graphite crucible and vaporized at temperatures above 907 °C (typically around 1000 °C). Zinc vapor reacts with the oxygen in the air to give ZnO, accompanied by a drop in its temperature and bright luminescence. Zinc oxide particles are transported into a cooling duct and collected in a bag house. This indirect method was popularized by LeClaire (France) in 1844 and therefore is commonly known as the French process. Its product normally consists of agglomerated zinc oxide particles with an average size of 0.1 to a few micrometers.
Zinc oxide | Indirect process
Wet chemical etching consists in selective removal of material by dipping a substrate into a solution that dissolves it. The chemical nature of this etching process provides a good selectivity, which means the etching rate of the target material is considerably higher than the mask material if selected carefully.
Microelectromechanical systems | Wet etching
The large reaction surface area of the dust material input as well as not having an inner Zn-cycle and not requiring pretreatment processes has proven the effectiveness and efficiency of the RecoDust process. A typical RecoDust process will often require temperatures from 1600-1650 °C with a dry, pourable, and well-defined grain sized raw material input of approximately 300 kg/h. In one experiment, 94% of chlorine, 93% of fluorine and 92% of lead was eliminated from the steel mill dust with a 97% recovery of zinc.
Flash reactor | Treatment of steel mill dust to recover zinc
The direct or American process starts with diverse contaminated zinc composites, such as zinc ores or smelter by-products. The zinc precursors are reduced (carbothermal reduction) by heating with a source of carbon such as anthracite to produce zinc vapor, which is then oxidized as in the indirect process. Because of the lower purity of the source material, the final product is also of lower quality in the direct process as compared to the indirect one.
Zinc oxide | Direct process
The wet process consists of mixing, heating, extruding and additive removal steps. The polymer resins are first mixed with, paraffin oil, antioxidant and other additives. The mixture is heated to produce a homogenous solution. The heated solution is pushed through a sheet die to make a gel-like film. The additives are then removed with a volatile solvent to form the microporous result. The wet process is suitable for both crystalline and amorphous polymers. Wet process separators often use ultrahigh-molecular-weight polyethylene. The use of these polymers enables the batteries with favorable mechanical properties, while shutting it down when it becomes too hot.
Separator (electricity) | Wet process
After neutralizing and rinsing, the remaining resist is removed and the sheet of parts is cleaned and dried.
Photochemical machining | Process
Thus, CCVD technique is a true vapor deposition process for making thin film coatings. The CCVD coating process has the ability to deposit thin films in the open atmosphere using inexpensive precursor chemicals in solution leading to continuous, production-line manufacturing. It does not require post-deposition treatment e.g., annealing. The throughput potential is high. Coatings can be deposited at substantial temperatures, for example, alpha-alumna was deposited on Ni-20Cr at temperatures between 1050 and 1125 C. A 1999 review article summarizes the various oxide coatings that had been deposited to date, which included Al2O3, Cr2O3, SiO2, CeO2, some spinel oxides (MgAl2O4, NiAl2O4), and yttria stabilized zirconia (YSZ).
Combustion chemical vapor deposition | Principles and procedure
Typical process steps are the following: I. Preparation of silicon substrate (layer 1) II. CVD of SiO, pad/buffer oxide (layer 2) III. CVD of SiN, nitride mask (layer 3) IV. Etching of nitride layer (layer 3) and silicon oxide layer (layer 2) V. Thermal growth of silicon oxide (structure 4) VI. Further growth of thermal silicon oxide (structure 4) VII. Removal of nitride mask (layer 3) There are 4 basic layers/structures:
LOCOS | Process
These conditions allow for the following chemical reaction to occur: The zinc vapour and carbon dioxide pass to a vacuum condenser, where zinc is recovered by bubbling through a molten zinc bath. Over 95% of the zinc vapour leaving the retort is condensed to liquid zinc. The carbon dioxide is regenerated with carbon, and the carbon monoxide is recycled back to the retort furnace.
Zinc smelting | St. Joseph Mineral Company (electrothermic) process
The concentration of the product acid depends on the HO/SO ratio in the catalytically converted gases and on the condensation temperature. The combustion gases are cooled to the converter inlet temperature of about 420–440 °C. To process these wet gases in a conventional cold-gas contact process (DCDA) plant would necessitate cooling and drying of the gas to remove all moisture. Therefore, the WSA process is in many cases a more cost-efficient way of producing sulfuric acid.
Wet sulfuric acid process | Spent acid regeneration and production of sulfuric acid
A photo mask, composed of silicon nitride, is patterned on the top of this sacrificial oxide. A second layer is added to the wafer to create a planar surface. After that, the silicon is thermally oxidized, so the oxide grows in regions where there is no Si3N4 and the growth is between 0.5 and 1.0 μm thick. Since the oxidizing species such as water or oxygen are unable to diffuse through the mask, the nitride prevents the oxidation. Next, the etching process is used to etch the wafer and leave a small amount of oxide in the active areas. In the end, CMP is used to polish the SiO overburden with an oxide on the active area.
Chemical-mechanical polishing | Application
Thermal oxidation of silicon is usually performed at a temperature between 800 and 1200 °C, resulting in so called High Temperature Oxide layer (HTO). It may use either water vapor (usually UHP steam) or molecular oxygen as the oxidant; it is consequently called either "wet" or "dry" oxidation. The reaction is one of the following: The oxidizing ambient may also contain several percent of hydrochloric acid (HCl). The chlorine removes metal ions that may occur in the oxide. Thermal oxide incorporates silicon consumed from the substrate and oxygen supplied from the ambient. Thus, it grows both down into the wafer and up out of it.
Thermal oxidation | The chemical reaction
Wet chemistry is a form of analytical chemistry that uses classical methods such as observation to analyze materials. It is called wet chemistry since most analyzing is done in the liquid phase. Wet chemistry is also called bench chemistry since many tests are performed at lab benches.
Wet chemistry | Introduction
The manual performance of wet chemistry mostly occurs in schools.
Wet chemistry | History
In etching, a liquid ("wet") or plasma ("dry") chemical agent removes the uppermost layer of the substrate in the areas that are not protected by photoresist. In semiconductor fabrication, dry etching techniques are generally used, as they can be made anisotropic, in order to avoid significant undercutting of the photoresist pattern. This is essential when the width of the features to be defined is similar to or less than the thickness of the material being etched (i.e. when the aspect ratio approaches unity). Wet etch processes are generally isotropic in nature, which is often indispensable for microelectromechanical systems, where suspended structures must be "released" from the underlying layer.
Photolithography | Etching
Wet processing engineering is one of the major streams in textile engineering refers to textile chemical processing engineering and applied science. The other three streams in textile engineering are yarn manufacturing engineering, fabric manufacturing engineering, and garments manufacturing engineering. The processes of this stream are involved or carried out in an aqueous stage and thus it is called a wet process which usually covers pretreatment, dyeing, printing, and finishing. The wet process is usually done on the manufactured assembly of interlacing fibers, filaments, and/or yarns having a substantial surface (planar) area in relation to its thickness, and adequate mechanical strength to give it a cohesive structure.
Wet processing engineering | Introduction
Industries where WSA process plants are installed:
Wet sulfuric acid process | Industrial applications
Each of a number of steps consists of two sieve tray columns. One column is maintained at 30°C and is called the "cold tower" and the other at 130°C and is called the "hot tower". The enrichment process is based on the difference in separation between 30°C and 130°C. The process of interest is the equilibrium reaction, At 30°C, the equilibrium constant K = 2.33, while at 130°C, K = 1.82. This difference is exploited for enriching deuterium in heavy water.
Girdler sulfide process | The process
Nanoparticles of certain materials can be created by "wet" chemical processes, in which solutions of suitable compounds are mixed or otherwise treated to form an insoluble precipitate of the desired material. The size of the particles of the latter is adjusted by choosing the concentration of the reagents and the temperature of the solutions, and through the addition of suitable inert agents that affect the viscosity and diffusion rate of the liquid. With different parameters, the same general process may yield other nanoscale structures of the same material, such as aerogels and other porous networks. The nanoparticles formed by this method are then separated from the solvent and soluble byproducts of the reaction by a combination of evaporation, sedimentation, centrifugation, washing, and filtration.
Nanoparticle | Wet chemistry
Metal Assisted Chemical Etching (also known as MACE) is the process of wet chemical etching of semiconductors (mainly silicon) with the use of a metal catalyst, usually deposited on the surface of a semiconductor in the form of a thin film. Both noble metals such as gold, platinum, palladium, and silver and base metals such as iron, nickel, and copper can act as a catalyst in the process.
Metal assisted chemical etching | Introduction
The acid and metal reaction also generates hydrogen gas in the form of tiny bubbles that adhere to the surface of the metal. These prevent the acid from reaching the metal surface and slow down the reaction. To overcome this, sodium nitrite is frequently added to act as an oxidizing agent that reacts with the hydrogen to form water. This chemistry is known as a nitrate accelerated solution. Hydrogen is prevented from forming a passivating layer on the surface by the oxidant additive. The following is a typical phosphating procedure:
Phosphate conversion coating | Process
Enzymes are applied in the desizing process if starch is used as sizing materials. Carboxymethyl cellulose (CMC) and Poly vinyl alcohol (PVA) are often used as sizing materials.
Wet processing engineering | Desizing
The thermochemical two-step water splitting process uses redox systems: For the first endothermic step concentrating solar power is used in which zinc oxide is thermally dissociated at into zinc and oxygen. In the second non-solar exothermic step zinc reacts at with water and produces hydrogen and zinc oxide. The temperature level is realized by using a solar power tower and a set of heliostats to collect the solar thermal energy.
Zinc–zinc oxide cycle | Process description
Wet oxidation is preferred to dry oxidation for growing thick oxides, because of the higher growth rate. However, fast oxidation leaves more dangling bonds at the silicon interface, which produce quantum states for electrons and allow current to leak along the interface. (This is called a "dirty" interface.) Wet oxidation also yields a lower-density oxide, with lower dielectric strength. The long time required to grow a thick oxide in dry oxidation makes this process impractical. Thick oxides are usually grown with a long wet oxidation bracketed by short dry ones (a "dry-wet-dry" cycle). The beginning and ending dry oxidations produce films of high-quality oxide at the outer and inner surfaces of the oxide layer, respectively.
Thermal oxidation | Oxide quality
Wet electrons, which occur on the surface of metal oxides, are a transition state for electrons between the solid and liquid states of matter. Wet electrons are attracted to positively charged hydroxide ions which form on oxide surfaces in the presence of atmospheric moisture. These electrons in turn affect the interaction of other materials with the oxide. Hydrogen atoms on water or hydroxide (OH) can be involved in hydrogen bonds or be dangling. Wet electrons are primarily stabilized by the dangling atoms on OH, which is more acidic than water, but the dangling atoms on water also contribute to the stabilization.
Wet electrons | Introduction
The process is akin to following the lowest elevation path between valleys with a mountain between them. The minimum energy necessary to change an electron from the solid to the liquid state corresponds to going through the wet electron state. Wet electrons are a transition state (saddle point) between electrons in the liquid and solid states.
Wet electrons | Introduction
It resulted in three scholarly papers: the first presenting a thermal model of material removal on the cathode, the second presenting a thermal model for the erosion occurring on the anode and the third introducing a model describing the plasma channel formed during the passage of the discharge current through the dielectric liquid. Validation of these models is supported by experimental data provided by AGIE. These models give the most authoritative support for the claim that EDM is a thermal process, removing material from the two electrodes because of melting or vaporization, along with pressure dynamics established in the spark-gap by the collapsing of the plasma channel.
Electrical discharge machining | Material removal mechanism
The process of metalorganic vapour phase epitaxy (MOCVD) entails pyrolysis of volatile organometallic compounds to give semiconductors, hard coatings, and other applicable materials. The reactions entail thermal degradation of precursors, with deposition of the inorganic component and release of the hydrocarbons as gaseous waste. Since it is an atom-by-atom deposition, these atoms organize themselves into crystals to form the bulk semiconductor. Silicon chips are produced by the pyrolysis of silane: Gallium arsenide, another semiconductor, forms upon co-pyrolysis of trimethylgallium and arsine.
Pyrolysis | Semiconductors
By weight, most of the world's zinc oxide is manufactured via French process.
Zinc oxide | Indirect process
Demasking is the process of clearing the part of etchant and maskant. Etchant is generally removed with a wash of clear, cold water. A de-oxidizing bath may also be required in the common case that the etching process left a film of oxide on the surface of the material. Various methods may be used to remove the maskant, the most common being hand removal using scraping tools. This is frequently time-consuming and laborious, and for large-scale processes may be automated. 2% Nital is common etchant for plain carbon steels.
Chemical milling | Demasking
The Waelz process is a method of recovering zinc and other relatively low boiling point metals from metallurgical waste (typically EAF flue dust) and other recycled materials using a rotary kiln (waelz kiln). The zinc enriched product is referred to as waelz oxide, and the reduced zinc by product as waelz slag.
Waelz process | Introduction
Zinc is a soft metal (MH 2.5) with poor mechanical properties. It has a crystalline structure (BCN 6+6) that is slightly distorted from the ideal. Many zinc compounds are markedly covalent in character. The oxide and hydroxide of zinc in its preferred oxidation state of +2, namely ZnO and Zn(OH), are amphoteric; it forms anionic zincates in strongly basic solutions. Zinc forms Zintl phases such as LiZn, NaZn and BaZn. Highly purified zinc, at room temperature, is ductile. It reacts with moist air to form a thin layer of carbonate that prevents further corrosion. Cadmium is a soft, ductile metal (MH 2.0) that undergoes substantial deformation, under load, at room temperature.
Post-transition metal | Group 12
Oxidation and impurities in the metal films affect the diffusion reactions by reducing the diffusion rates. Therefore, clean deposition practices and bonding with oxide removal and re-oxidation prevention steps are applied. The oxide layer removal can be realized by various oxide etch chemistry methods. Dry etching processes, i.e. formic acid vapor cleaning, are preferred based on the minimization of the immersion in fluids and the resulting etching of the passivation or the adhesion layer. Using the CMP process, which is especially for Cu and Al required, creates a planarized surface with micro roughness around several nanometer and enables the achievement of void-free diffusion bonds.
Thermocompression bonding | Pre-conditioning
The wetting layer is epitaxially grown on a surface using molecular beam epitaxy (MBE). The temperatures required for wetting layer growth typically range from 400-500 degrees Celsius. When a material "A" is deposited on a surface of a lattice-mismatched material "B", the first atomic layer of material "A" often adopts the lattice constant of "B". This mono-layer of material "A" is called the wetting layer. When the thickness of layer "A" increases further, it becomes energetically unfavorable for material "A" to keep the lattice constant of "B". Due to the high strain of layer "A", additional atoms group together once a certain critical thickness of layer "A" is reached.
Wetting layer | Process
Wet etching of GaAs industrially uses an oxidizing agent such as hydrogen peroxide or bromine water, and the same strategy has been described in a patent relating to processing scrap components containing GaAs where the is complexed with a hydroxamic acid ("HA"), for example: This reaction produces arsenic acid.
Gallium arsenide | Etching
Shallow trench isolation (STI), a process used to fabricate semiconductor devices, is a technique used to enhance the isolation between devices and active areas. Moreover, STI has a higher degree of planarity making it essential in photolithographic applications, depth of focus budget by decreasing minimum line width. To planarize shallow trenches, a common method should be used such as the combination of resist etching-back (REB) and chemical mechanical polishing (CMP). This process comes in a sequence pattern as follows. First, the isolation trench pattern is transferred to the silicon wafer. Oxide is deposited on the wafer in the shape of trenches.
Chemical-mechanical polishing | Application
Another technique involves the consecutive spraying of the molten metal onto a chemical vapor deposition surface. However, the layers do not fuse together as desired and this causes oxides to be contained in the structure and pores to form around the structure. Manufacturing companies take an interest in the resultant products because of their near-net shaping capabilities.
Splat quenching | Procedure
The WSA process can also be used for production of sulfuric acid from sulfur burning or for regeneration of the spent acid from e.g. alkylation plants. Wet catalysis processes differ from other contact sulfuric acid processes in that the feed gas contains excess moisture when it comes into contact with the catalyst. The sulfur trioxide formed by catalytic oxidation of the sulfur dioxide reacts instantly with the moisture to produce sulfuric acid in the vapour phase to an extent determined by the temperature. Liquid acid is subsequently formed by condensation of the sulfuric acid vapour and not by absorption of the sulfur trioxide in concentrated sulfuric acid, as is the case in contact processes based on dry gases.
Wet sulfuric acid process | Spent acid regeneration and production of sulfuric acid
The energy released by the above-mentioned reactions is used for steam production. Approximately 2–3 ton high-pressure steam per ton of acid produced.
Wet sulfuric acid process | The process
Chemical Vapor Deposition (CVD) is a technique that produces materials by depositing solid films. It has been a very attractive process because it is chemically selective process, the material produced is high-quality and high-performing, and the thickness of the film can be easily controlled. McElwee-White has studied the various complexities of CVD on tungsten nitride and carbonitride films (WNC films), exploring tungsten nitrido complexes as precursors and analyzing the effect of ligand structure on the reaction. She has also expanded her research scope to the metallization of organic thin films. For the process of metallization of organic thin films, normal thermal CVD processes which require high temperatures usually destroy organic films.
Lisa McElwee-White | Chemical Vapor Deposition
Typical for an inorganic polymer, Zn(CN) is insoluble in most solvents. The solid dissolves in, or more precisely, is degraded by, aqueous solutions of basic ligands such as hydroxide, ammonia, and additional cyanide to give anionic complexes.
Zinc cyanide | Chemical properties
If the oxide layer has not been sufficiently thinned and/or the desired degree of planarity has not been achieved during this process, then (theoretically) the wafer can be repolished, but in a practical sense this is unattractive in production and is to be avoided if at all possible. If the oxide thickness is too thin or too non-uniform, then the wafer must be reworked, an even less attractive process and one that is likely to fail. Obviously, this method is time-consuming and costly since technicians have to be more attentive while performing this process.
Chemical-mechanical polishing | Limitations
Before the age of theoretical and computational chemistry, wet chemistry was the predominant form of scientific discovery in the chemical field. This is why it is sometimes referred to as classic chemistry or classical chemistry. Scientists would continuously develop techniques to improve the accuracy of wet chemistry. Later on, instruments were developed to conduct research impossible for wet chemistry. Over time, this became a separate branch of analytical chemistry called instrumental analysis. Because of the high volume of wet chemistry that must be done in today's society and new quality control requirements, many wet chemistry methods have been automated and computerized for streamlined analysis.
Wet chemistry | History
Crease-resist finishing of cotton includes the following steps: The catalyst allows the reaction to be carried out 130-180 degree temperature range usually employed in the textile industry and within the usual curing time (within 3 minutes, maximum).
Wet processing engineering | Crease resistance
Zinc oxide nanoparticles are nanoparticles of zinc oxide (ZnO) that have diameters less than 100 nanometers. They have a large surface area relative to their size and high catalytic activity. The exact physical and chemical properties of zinc oxide nanoparticles depend on the different ways they are synthesized. Some possible ways to produce ZnO nano-particles are laser ablation, hydrothermal methods, electrochemical depositions, sol–gel method, chemical vapor deposition, thermal decomposition, combustion methods, ultrasound, microwave-assisted combustion method, two-step mechanochemical–thermal synthesis, anodization, co-precipitation, electrophoretic deposition, and precipitation processes using solution concentration, pH, and washing medium. ZnO is a wide-bandgap semiconductor with an energy gap of 3.37 eV at room temperature.
Zinc oxide nanoparticle | Introduction
O + O → OO + O
Surface properties of transition metal oxides | Gas-phase photocatalysis
Thin films have been produced by chemical vapour deposition of Bis(bis(trimethylsilyl)amido]zinc with ammonia gas onto silica or ZnO coated alumina at 275 to 410 °C. The crystal structure is anti-isomorphous with Manganese(III) oxide. (bixbyite). The heat of formation is c. per mol. It is a semiconductor with a reported bandgap of c. 3.2eV, however, a thin zinc nitride film prepared by electrolysis of molten salt mixture containing LiN with a zinc electrode showed a band-gap of 1.01 eV.
Zinc nitride | Chemical properties
Remove contaminants as far forward in the system as practical and cost effective. Steady state flow in the makeup and primary sections to avoid TOC and conductivity spikes (NO start/stop operation). Recirculate excess flow upstream. Minimize the use of chemicals following the reverse osmosis units.
Ultrapure water | Key UPW design criteria for semiconductor fabrication
Since 2010, a flash-reactor pilot plant was successfully operating at the Montanuniversität in Leoben, Austria. Known as the RecoDust process, such a setup was designed to recover zinc from the dust collected in steel operations. Whilst tests have proven the functionality of this process, further research and implementation of this process in industry was halted due to the steel industry's uncertain economic outlook. Nonetheless, research has shown a great potential for the use of the FR in recovering zinc from steel mill dust as it provides a strong oxidizing and reducing condition in the reaction vessel, with no waste materials produced.
Flash reactor | Treatment of steel mill dust to recover zinc
It was not commonly used in semiconductor processing for many years, but has seen a resurgence with more widespread use of chemical-mechanical polishing techniques.
Thin film | Chemical deposition
anatase-rutile interfaces), noble-metal nanoparticles, silicon nanowires and substitutional cation doping. The ultimate goal of photocatalyst design is to facilitate reactions between the excited electrons with oxidants to produce reduced products, and/or reactions between the generated holes with reductants to produce oxidized products. Due to the generation of positive holes and electrons, oxidation-reduction reactions take place at the surface of semiconductors. In one mechanism of the oxidative reaction, the positive holes react with the moisture present on the surface and produce a hydroxyl radical. The reaction starts by photo-induced exciton generation in the metal oxide surface (MO stands for metal oxide):
Photocatalysis | Heterogeneous photocatalysis
The transport process entails the addition small amount of a transport agent, e.g., iodine, which generates a volatile intermediate species that migrates (transports). The ampoule is then placed in an oven with two temperature zones. Chemical vapour deposition is a method that is widely employed for the preparation of coatings and semiconductors from molecular precursors.
Solid-state chemistry | Gas reactions
Molecular zinc(II) hydride, ZnH, was recently identified as a volatile product of the acidified reduction of zinc ions with sodium borohydride. This reaction is similar to the acidified reduction with lithium aluminium hydride, however a greater fraction of the generated zinc(II) hydride is in the molecular form. This can be attributed to a slower reaction rate, which prevents a polymerising concentration of building over the progression of the reaction. This follows earlier experiments in direct synthesis from the elements. The reaction of excited zinc atoms with molecular hydrogen in the gas phase was studied by Breckenridge "et al" using laserpump-probe techniques.
Zinc hydride | Molecular form
The wet sulfuric acid process (WSA process) is one of the key gas desulfurization processes on the market today. Since the Danish catalyst company Haldor Topsoe introduced and patented this technology in the late 1980s, it has been recognised as an efficient process for recovering sulfur from various process gases in the form of commercial quality sulfuric acid (HSO), with simultaneous production of high pressure steam. The WSA process is applied in all industries where removal of sulfur is an issue. The wet catalysis process is especially suited for processing one or more sulfur containing streams such as.:
Wet sulfuric acid process | Introduction
By efficient conversion of hydrophobic polymers into hydrophilic polymer nano-dots (Pdots), polymer-water interfacial contact is therefore increased, which results in significantly improved photocatalytic performance of these materials.
Photocatalytic water splitting | Aluminum‐based metal–organic frameworks (MOF)
These oxides are usually present on zinc surfaces, but do not protect them from wet storage stain because they are only loosely adherent to the surface and any moisture can attack the oxides from underneath. Also, chlorides and sulfates accelerate the formation of corrosion.
Wet storage stain | Chemistry
CC-HOD requires that water be heated only modestly above ambient temperature, catalytic carbon and scrap metal. If aluminium is submerged in a tank with the catalytic carbon. Pure Hydrogen gas is formed when the water reaches a temperature of about . Oxygen remains in the tank where it bonds with the aluminium to form aluminium hydroxide: Al + H²O + CC = CC + Al(OH)³ + H²
CC-HOD | Process
Depending on the process, areas of the photoresist that are exposed to the light either harden or soften, and then the softer areas are washed away using a solvent. The result is a duplication of the pattern from the mask onto the surface of the wafer. Chemical processing is then used on the pattern to give it the desired electrical qualities. This entire process is repeated several times to build up the complete IC design. Each step uses a different design on the mask. The features are measured in microns, so any previous design already deposited has to be precisely aligned with the new mask that will be applied.
Micralign | Background
ZnO is a relatively soft material with approximate hardness of 4.5 on the Mohs scale. Its elastic constants are smaller than those of relevant III-V semiconductors, such as GaN. The high heat capacity and heat conductivity, low thermal expansion and high melting temperature of ZnO are beneficial for ceramics. The E2 optical phonon in ZnO exhibits an unusually long lifetime of 133 ps at 10 K. Among the tetrahedrally bonded semiconductors, it has been stated that ZnO has the highest piezoelectric tensor, or at least one comparable to that of GaN and AlN. This property makes it a technologically important material for many piezoelectrical applications, which require a large electromechanical coupling.
Zinc oxide | Mechanical properties
The process uses an abrasive and corrosive chemical slurry (commonly a colloid) in conjunction with a polishing pad and retaining ring, typically of a greater diameter than the wafer. The pad and wafer are pressed together by a dynamic polishing head and held in place by a plastic retaining ring. The dynamic polishing head is rotated with different axes of rotation (i.e., not concentric). This removes material and tends to even out any irregular topography, making the wafer flat or planar. This may be necessary to set up the wafer for the formation of additional circuit elements. For example, CMP can bring the entire surface within the depth of field of a photolithography system, or selectively remove material based on its position.
Chemical-mechanical polishing | Description
Preparation and scouring are prerequisites to most of the other finishing processes. At this stage even the most naturally white cotton fibers are yellowish, and bleaching, the next process, is required. The three main processes involved in the scouring are saponification, emulsification and detergency. The main chemical reagent used in the cotton scouring is sodium hydroxide which converts saponifiable fats and oils into soaps, dissolves mineral matter and converts pectose and pectin into their soluble salts.
Wet processing engineering | Scouring
Both the crucible and socket must be cooled. This is typically done by water circulation. In the case of ingots, molten liquid can form on its surface, which can be kept constant by vertical displacement of the ingot. The evaporation rate may be on the order of 10 g/(cm·s).
Electron-beam physical vapor deposition | Thin-film deposition process
Generally, these pads are made from porous polymeric materials with a pore size between 30-50 μm, and because they are consumed in the process, they must be regularly reconditioned. In most cases the pads are very much proprietary, and are usually referred to by their trademark names rather than their chemical or other properties.
Chemical-mechanical polishing | Physical action
Dry etching refers to the removal of material, typically a masked pattern of semiconductor material, by exposing the material to a bombardment of ions (usually a plasma of reactive gases such as fluorocarbons, oxygen, chlorine, boron trichloride; sometimes with addition of nitrogen, argon, helium and other gases) that dislodge portions of the material from the exposed surface. A common type of dry etching is reactive-ion etching. Unlike with many (but not all, see isotropic etching) of the wet chemical etchants used in wet etching, the dry etching process typically etches directionally or anisotropically.
Dry etching | Introduction
Both the plate and the carrier are then rotated and the carrier is kept oscillating; this can be better seen in the top view of Figure 2. A downward pressure/down force is applied to the carrier, pushing it against the pad; typically the down force is an average force, but local pressure is needed for the removal mechanisms. Down force depends on the contact area which, in turn, is dependent on the structures of both the wafer and the pad. Typically the pads have a roughness of 50 μm; contact is made by asperities (which typically are the high points on the wafer) and, as a result, the contact area is only a fraction of the wafer area.
Chemical-mechanical polishing | Physical action
The process involves submerging the metal part into a phosphoric acid solution whose key ingredient is often zinc or manganese, with varying additional amounts of nitrates, chlorates, and copper. In one of the many processes that have been developed, the solution is heated to a temperature of for a period ranging between 5 and 45 minutes. A stream of small hydrogen bubbles is emitted from the metal part as the process takes place; when the bubbling stops, the process is complete. In addition to this particular processing temperature, there have also been various similar Parkerizing processes developed and patented that permit using either lower temperatures (for energy efficiency) or higher temperatures (for faster processing).
Parkerizing | Application
The strength of metal oxide adhesion effectively determines the wetting of the metal-oxide interface. The strength of this adhesion is important, for instance, in production of light bulbs and fiber-matrix composites that depend on the optimization of wetting to create metal-ceramic interfaces. The strength of adhesion also determines the extent of dispersion on catalytically active metal. Metal oxide adhesion is important for applications such as complementary metal oxide semiconductor devices. These devices make possible the high packing densities of modern integrated circuits.
Metal oxide adhesion | Introduction
The diagram shows a ceramic crucible with a steel cylinder suspended within. Both cathode (C) and anode (A) are made of iron or nickel. The temperature is cooler at the bottom and hotter at the top so that the sodium hydroxide is solid in the neck (B) and liquid in the body of the vessel. Sodium metal forms at the cathode but is less dense than the fused sodium hydroxide electrolyte. Wire gauze (G) confines the sodium metal to accumulating at the top of the collection device (P). The cathode reaction is The anode reaction is Despite the elevated temperature, some of the water produced remains dissolved in the electrolyte.
Castner process | Process details
These methods are known as vapor-solid (VS) processes due to their reactants states. VS processes can create a variety of ZnO nanostructures but their morphology and properties are highly dependent on the reactants and reaction conditions such as the temperature and vapor partial pressures. Vapor deposition processes can also use catalysts to assist the growth of nanostructures. These are known as vapor-liquid-solid (VLS) processes, and use a catalytic liquid alloy phase as an extra step in nanostructure synthesis to accelerate growth. The liquid alloy, which includes zinc, is attached to nucleated seeds made usually of gold or silica. The alloy absorbs the oxygen vapor and saturates, facilitating a chemical reaction between zinc and oxygen.
ZnO nanostructures | Chemical vapor deposition (CVD)
Each reaction can be applied individually or sequentially as dictated by the characteristics of the stream to be treated. The process consist of three main sections: An absorber (gas washing section), a bioreactor (sulfide oxidation and regeneration of washing liquid) and Sulfur handling section as shown in the figure below: The washing step uses a dilute alkaline solution to remove hydrogen sulfide (HS) from the sour gas according to: The loaded washing liquid is transported to a bioreactor where a biocatalyst oxidises the aqueous NaHS to elemental sulfur with about 95% selectivity according to: Combined reaction equation: The regenerated washing liquid is sent back to the washing column.
Shell–Paques process | Process chemistry
Chemical deposition techniques include chemical vapor deposition (CVD), in which a stream of source gas reacts on the substrate to grow the material desired. This can be further divided into categories depending on the details of the technique, for example LPCVD (low-pressure chemical vapor deposition) and PECVD (plasma-enhanced chemical vapor deposition). Oxide films can also be grown by the technique of thermal oxidation, in which the (typically silicon) wafer is exposed to oxygen and/or steam, to grow a thin surface layer of silicon dioxide.
Microelectromechanical systems | Chemical deposition
Before about 1990 CMP was viewed as too "dirty" to be included in high-precision fabrication processes, since abrasion tends to create particles and the abrasives themselves are not without impurities. Since that time, the integrated circuit industry has moved from aluminum to copper conductors. This required the development of an "additive patterning" process, which relies on the unique abilities of CMP to remove material in a planar and uniform fashion and to stop repeatably at the interface between copper and oxide insulating layers (see Copper interconnects for details). Adoption of this process has made CMP processing much more widespread. In addition to aluminum and copper, CMP processes have been developed for polishing tungsten, silicon dioxide, and (recently) carbon nanotubes.
Chemical-mechanical polishing | Usage in semiconductor fabrication
Wet chemistry commonly uses laboratory glassware such as beakers and graduated cylinders to prevent materials from being contaminated or interfered with by unintended sources. Gasoline, Bunsen burners, and crucibles may also be used to evaporate and isolate substances in their dry forms. Wet chemistry is not performed with any advanced instruments since most automatically scan substances. Although, simple instruments such as scales are used to measure the weight of a substance before and after a change occurs. Many high school and college laboratories teach students basic wet chemistry methods.
Wet chemistry | Materials
The liquid resin has a density of 0.97 and reacts into a solid with a density of 1.03 which constitutes a volumetric shrinkage of 6%. Since most parts are panels, most of the shrinkage will happen in the Z-axis (thickness). This makes the parts self-demoulding as they do not have a good contact with the core side of the tool [The core side is the side which will be the back side of the part. The front side of the part is called the matrix side]. A reacting system is always governed by temperature - in any form. This means that the temperature of the liquid components has a strong influence on the reactivity.
Polydicyclopentadiene | Process Considerations
Using the dry-air blast, production yields increased by as much as 20%. After its inception, this process was described as one of the "greatest achievements in modern metallurgical chemistry" by members of the Perkin Medal committee.
James Gayley | Career
Cationization of cotton Dyeing Finishing (textiles)
Wet processing engineering | See also
Wet nanotechnology (also known as wet nanotech) involves working up to large masses from small ones. Wet nanotechnology requires water in which the process occurs. The process also involves chemists and biologists trying to reach larger scales by putting together individual molecules. While Eric Drexler put forth the idea of nano-assemblers working dry, wet nanotech appears to be the likely first area in which something like a nano-assembler may achieve economic results. Pharmaceuticals and bioscience are central features of most nanotech start-ups. Richard A.L. Jones calls nanotechnology that steals bits of natural nanotechnology and puts them in a synthetic structure "biokleptic nanotechnology".
Wet nanotechnology | Introduction
A sheet made for saturating would have none of those chemical ingredients. The unsized saturating cotton fibre paper prepared for vulcanized fibre would be passed through a vat containing a zinc chloride solution.
Vulcanized fibre | Process
The dry process involves extruding, annealing and stretching steps. The final porosity depends on the morphology of the precursor film and the specifics of each step. The extruding step is generally carried out at a temperature higher than the melting point of the polymer resin. This is because the resins are melted to shape them into a uniaxially-oriented tubular film, called a precursor film. The structure and orientation of the precursor film depends on the processing conditions and the resin's characteristics. In the annealing process, the precursor is annealed at a temperature slightly lower than the polymer's melting point. The purpose of this step is to improve the crystalline structure.
Separator (electricity) | Dry process
Due to the relatively high reaction temperature (approx. 340 °C), the average molecular weight of the product is so low that no liquid product phase occurs under reaction conditions. The catalyst particles moving around in the reactor are small (particle diameter 100 µm) and carbon deposition on the catalyst does not disturb reactor operation. Thus a low catalyst porosity with small pore diameters as obtained from fused magnetite (plus promoters) after reduction with hydrogen is appropriate. For maximising the overall gasoline yield, C and C alkenes have been oligomerized at Sasol. However, recovering the olefins for use as chemicals in, e.g., polymerization processes is advantageous today.
Fischer–Tropsch process | Iron
The Institute for Chemical-Physical Processes (IPCF) is part of the Department of Materials and Devices of the Italian Research Council.
Institute for Chemical-Physical Processes | Introduction
When the reaction conditions are chosen to allow this reaction to occur in the gas phase throughout the tube volume, in contrast to earlier techniques where the reaction occurred only on the glass surface, this technique is called "modified chemical vapor deposition (MCVD)". The oxide particles then agglomerate to form large particle chains, which subsequently deposit on the walls of the tube as soot. The deposition is due to the large difference in temperature between the gas core and the wall causing the gas to push the particles outward (this is known as thermophoresis). The torch is then traversed up and down the length of the tube to deposit the material evenly.
Optical fiber | Preform
Chemical milling is normally performed in a series of five steps: cleaning, masking, scribing, etching, and demasking. Video of chemical milling process Learn more about the video
Chemical milling | Process
Wet storage stain is a white, crumbly, and porous substance that is a mixture of three chemical compounds: 2ZnCO·3Zn(OH), ZnO, and β-Zn(OH). Underneath the white coating is usually a dark gray surface. The corrosion product is very voluminous; it is approximately 100 times greater in volume than the zinc consumed. Because of this the corrosion is not usually detrimental to the usability of the item, unless the zinc surface is only a thin coating, such as zinc electroplating. Wet storage stain only occurs in situations where there is a lack of oxygen or carbon dioxide, because it usually forms zinc oxide and zinc hydroxide in open air environments.
Wet storage stain | Chemistry
The process typically takes place between 900 and 1100 °C, with an anode (typically carbon) and a cathode (oxide being reduced) in a bath of molten CaCl. Depending on the nature of the oxide it will exist at a particular potential relative to the anode, which is dependent on the quantity of CaO present in CaCl. The cathode is then polarised to a more negative voltages versus the anode. This is simply achieved by imposing a voltage between the anode and cathode. When polarised to more negative voltages the oxide releases oxygen ions into the CaCl salt, which exists as CaO.
FFC Cambridge process | Process
The wet chemical synthesis of thiolate-protected gold clusters is achieved by the reduction of gold(III) salt solutions, using a mild reducing agent in the presence of thiol compounds. This method starts with gold ions and synthesizes larger particles from them, therefore this type of synthesis can be regarded as a "bottom-up approach" in nanotechnology to the synthesis of nanoparticles. The reduction process depends on the equilibrium between different oxidation states of the gold and the oxidized or reduced forms of the reducing agent, or thiols. Gold(I)-thiolate polymers have been identified as important in the initial steps of the reaction. Several synthesis recipes exist that are similar to the Brust synthesis of colloidal gold, however the mechanism is not yet fully understood.
Thiolate-protected gold cluster | Wet chemical synthesis
Sherardising is a process of galvanization of ferrous metal surfaces, also called vapour galvanising and dry galvanizing. The process is named after British metallurgist Sherard Osborn Cowper-Coles (son of naval inventor Cowper Phipps Coles) who invented and patented the method c. 1900. This process involves heating the steel parts up to c. 500 °C in a closed rotating drum that contains metallic zinc dust and possibly an inert filler, such as sand. At temperatures above 300 °C, zinc evaporates and diffuses into the steel substrate forming diffusion bonded Zn-Fe-phases. Sherardising is ideal for small parts and parts that require coating of inner surfaces, such as batches of small items.
Sherardising | Introduction
There are two basic categories of etching processes: wet etching and dry etching. In the former, the material is dissolved when immersed in a chemical solution. In the latter, the material is sputtered or dissolved using reactive ions or a vapor phase etchant.
Microelectromechanical systems | Etching processes
Kiln size is typically long / internal diameter, with a rotation speed of around 1 rpm. The recovered dust ("Waelz oxide") is enriched in zinc oxide and is a feed product for zinc smelters, the zinc reduced by-product is known as "Waelz slag". Sub-optimal features of the process are high energy consumption, and lack of iron recovery (and iron rich slag). The process also captures other low boiling metals in the "waelz oxide" including lead, cadmium and silver. Halogen compounds are also present in the product oxide.
Waelz process | History and description
P-glass softens and reflows at temperatures above 1000 °C. This process requires a phosphorus concentration of at least 6%, but concentrations above 8% can corrode aluminium. Phosphorus is deposited from phosphine gas and oxygen:
Chemical vapor deposition | Silicon dioxide
Zeolite -- Zinc -- Zinnwaldite -- Zircon -- Zirconium -- Zone melting --
Index of chemical engineering articles | Z
There are also several pyrometallurgical processes that reduce zinc oxide using carbon, then distil the metallic zinc from the resulting mix in an atmosphere of carbon monoxide. The major downfall of any of the pyrometallurgical process is that it is only 98% pure; a standard composition is 1.3% lead, 0.2% cadmium, 0.03% iron, and 98.5% zinc. This may be pure enough for galvanization, but not enough for die casting alloys, which requires special high-grade zinc (99.995% pure). In order to reach this purity the zinc must be refined. The four types of commercial pyrometallurgical processes are the "St. Joseph Minerals Corporation's" (electrothermic) process, the "blast furnace" process, the "New Jersey Zinc continuous vertical-retort" process, and the "Belgian-type horizontal retort" process.
Zinc smelting | Pyrometallurgical processes
Sendzimir process (named after Tadeusz Sendzimir) is used to galvanize a steel strip by using a small amount of aluminum in the zinc bath and producing a coating with essentially no iron-zinc alloy. The process guarantees high resistance and durability characteristics. About 75% of hydrogen was needed in the original Sendzimir process but all the newer nonoxidizing methods of degreasing require only 7–15%. The rolling of hot steel slabs using a Sendzimir mill requires a much smaller operational area than a continuous hot strip mill. This milling process is not recommended for heavy duty running surfaces such as crane rail
Sendzimir process | Introduction
Silicon dioxide (usually called simply "oxide" in the semiconductor industry) may be deposited by several different processes. Common source gases include silane and oxygen, dichlorosilane (SiClH) and nitrous oxide (NO), or tetraethylorthosilicate (TEOS; Si(OCH)). The reactions are as follows: The choice of source gas depends on the thermal stability of the substrate; for instance, aluminium is sensitive to high temperature. Silane deposits between 300 and 500 °C, dichlorosilane at around 900 °C, and TEOS between 650 and 750 °C, resulting in a layer of "low- temperature oxide" (LTO). However, silane produces a lower-quality oxide than the other methods (lower dielectric strength, for instance), and it deposits nonconformally.
Chemical vapor deposition | Silicon dioxide
A chemical process is a series of unit operations used to produce a material in large quantities. In the chemical industry, chemical engineers will use the following to define or illustrate a process:
Process (engineering) | Chemical engineering
Wet nanotechnology is a form of wet engineering as opposed to dry engineering. There are different fields that deal with those two types of engineering. Biologists, from the point of view of nanotechnology, deal with wet engineering. They study processes that happen in life, and for the most part those processes take place in aqueous environments. Our bodies are made up mostly of water. Electrical and mechanical engineers are on the other side of the line in dry engineering. They are involved with processes and manufacturing that does not occur in aqueous environments. For the most part, wet engineering deals with “soft” materials that allow for flexibility which is vital at the nanoscale in biological manufacturing.
Wet nanotechnology | “Wet” vs. “Dry”
Water gas is compressed to 20 bar and pumped into the Linde-Frank-Caro reactor. A water column removes most of the carbon dioxide and sulfur. Tubes with caustic soda then remove the remaining carbon dioxide, sulphur, and water from the gas stream. The gas enters a chamber and is cooled to −190 °C, resulting in the condensation of most of the gas to a liquid. The remaining gas is pumped to the next vessel where the nitrogen is liquefied by cooling to −205 °C, resulting in hydrogen gas as an end product.
Linde–Frank–Caro process | Process description
In the first stage, carbon precipitates into ε-carbon (FeC). In the second stage, occurring between and , the retained austenite transforms into a form of lower-bainite containing ε-carbon rather than cementite (archaically referred to as "troostite"). The third stage occurs at and higher. In the third stage, ε-carbon precipitates into cementite, and the carbon content in the martensite decreases. If tempered at higher temperatures, between and , or for longer amounts of time, the martensite may become fully ferritic and the cementite may become coarser or spheroidize. In spheroidized steel, the cementite network breaks apart and recedes into rods or spherical shaped globules, and the steel becomes softer than annealed steel; nearly as soft as pure iron, making it very easy to form or machine.
Tempering (metallurgy) | Physical processes