Search Results for spray drying

This article discusses the methods and procedures used to extract, purify, and synthesize tungsten carbide powder, metal, and other refractory carbide/nitride powders used in hard metal production. Selection of powders, additives, equipment, and processes for making ready-to-press hard metal powders is also discussed. The article also provides information on the emerging technologies for tungsten carbide synthesis and binders in hard metal production, such as cobalt, iron, and nickel.

This article discusses three types of powder-feeder systems that are commonly used throughout the thermal spray (TS) industry: gravity-based devices, rotating wheel devices, and fluidized-bed systems. It provides information on the various mechanical methods for producing powders, namely, crushing, milling, attriting, and machining. The article describes two prime methods of agglomeration. One method uses a binder by way of agglutination, while the other relies on a sintering operation. The article discusses the technology and principles of the processes that relate to thermal spraying, and offers an understanding for choosing particular feedstock materials that are classified based on the thermal spray process, material morphology, chemical nature of the material, and applications. Sieving, the most common method of separating powders into their size fractions, is also reviewed. The article also provides information on the topical areas and precautions to be undertaken to protect the operator from safety hazards.

The chemical process being catalyzed should have a high productivity within a specified reactor volume with high reaction rates for the desired reactions and low rates for undesired reaction pathways. This article reviews the general catalyst preparation procedures, namely, impregnation, ion exchange, and precipitation. Catalyst carriers are usually high-surface-area inorganic materials with complex pore structures, into which catalytic materials such as palladium, platinum, cobalt, chromium oxide, and vanadium pentoxide are deposited using these procedures. The article also provides information on catalyst powder processing.

This article explains how ceramic powders are made. It begins by briefly describing the raw materials used in structural clay products, whitewares, refractories, and advanced ceramics. It then examines various additives that promote uniformity at different stages of the process. After a description of the comminution process (wet and dry milling methods), it discusses batching and mixing operations and granulation methods. The article also deals with the effect of process variables and the steps involved in chemical synthesis, including preparation from solution and gas-phase reactions, filtration and washing, and powder recovery techniques. It concludes with a discussion on characterization, centering on size distribution analysis, specific surface area, density, porosity chemical composition, phase, and surface composition.

Significant expansion of thermal spray technology occurred with the invention of plasma spray, detonation gun, and high-velocity oxyfuel (HVOF) deposition technologies. This article provides a brief history of the major initiating inventions/developments of thermal spray processes. It provides information on feedstock materials developed for specific thermal spray processes.

This article provides an overview of the steps that are used in ceramics processing and related mechanical design considerations. It discusses various design approaches, such as the empirical design, the deterministic design, and the probabilistic design. The article presents a general process design flowchart for ceramic processing. Information on traditional ceramics and advanced ceramics is also provided. The article describes various ceramic forming processes, such as wet processing, plastic forming, dry processing, and machining. The factors for evaluating different ceramic forming processes are summarized in a table. The article discusses vitrification and sintering that generally pertain to ceramic firing and concludes with a discussion on firing process factors.

Painting is a generic term for the application of a thin organic coating to the surface of a material for decorative, protective, or functional purposes. This article provides a detailed account of the types and selection factors of paints and the various application methods, including conventional air atomized, airless, and electrostatic spray; roller coating; dip coating; flow coating; curtain coating; tumble coating; electrocoating; and powder coating. Surface preparation methods and prepaint treatments for coating systems are also discussed. The article includes information on quality control procedures, causes of paint film defects, cost calculation, and safety and environmental precautions. The composition and characteristics of organic coatings, coating system selection factors, the types of paints for structural steel, and the applications of paint on structural steel are also reviewed.

Thermal spray coatings, along with certain proprietary sealants, are widely used in the paper manufacturing industry for corrosion and wear resistance and to impart special surface characteristics. This article discusses the steps involved in the paper manufacturing process. Most modern papermaking machines are based on variations of the Fourdrinier machine. The article describes four operational sections of the machine: forming, press, drying, and calendar. It provides an overview of the machine components where thermal spray coatings are used, namely, digesters, blow tanks, suction roll, center press rolls, yankee dryer rolls, calendar rolls, doctor/scalping blades, and cutting equipment.

Environmental effects of ground and flight environments, including temperature extremes, damage by chemical fluids, moisture, and so forth, affect the durability of polymer-matrix composites. This article provides information on corrosion control methods in aircraft structures. It discusses the design considerations for sealants in joints. The article describes the common methods to seal aircraft structures: fay surface, fillet, butt joint, channel, brush, and form-in-place seals. It discusses the surface preparation and application method of primer and topcoat systems. Primer and paint application equipment as well as sealant application equipment are reviewed.

Two-component polyurea elastomeric coating/lining systems are the newest technology in the protective coating/lining industry and a wide variety of applications have been developed. These include coating/lining applications over concrete, geotextile membranes, various metals for corrosion and decorative areas, and some plastics. This article discusses the formulation basics of polyurea technology and compares the technology to that of polyurethane and polyurethane/polyurea systems. It addresses performance issues and describes application processing considerations and safety practices of polyurea coating/lining systems.

This article discusses the applications and use of salt spray (fog) testing used to test the resistance of aluminum alloys to exfoliation corrosion. There are two basic types of salt-spray/fog corrosion tests: static condition tests and cyclic condition tests. The article provides a discussion of these tests and indicates the significant differences in each type test used in the combination of weathering and corrosion testing procedures. It also provides information on the test specimen preparation for spray (fog) corrosion tests. Industry specific standards for test specimen procedures often reference the ASTM standards as a basis. The article includes various ASTM standards that describe several cleaning procedures used prior to testing. It describes the major components of a corrosion test chamber.

Ceramic-forming processes usually start with a powder which is then compacted into a porous shape, achieving maximum particle packing density with a high degree of uniformity. This article compares and contrasts several forming processes, including mechanical consolidation, dry pressing, cold isostatic pressing, slip casting, tape casting, roll compaction, extrusion, and injection molding. It describes the advantages, equipment and tooling, and material requirements of green machining, the machining of ceramics in an unfired state with the intent of producing parts as close to as possible to their final shape. The article also provides useful information on drying methods, shrinkage, and defects as well as the removal of organic processing aids such as dispersants, binders, plasticizers, and lubricants.

Corrosion problems and materials selection for emissions control equipment can be difficult because of varied corrosive compounds present and the severe environments encountered. This article discusses the selection of materials for construction of flue gas desulfurization systems. It addresses the problems associated with materials for incinerator off-gas treatment equipment. The off-gases can be classified according to their corrosiveness as: industrial chemical, hospital, municipal solid, and sewage sludge. The article provides information on the selection of materials for the three most common types of dust collection equipment used in bulk solids processing, namely, fabric filters, electrostatic precipitators, and wet scrubbers. It also discusses a wide variety of corrosion problems encountered in chemical and pharmaceutical industries.