Metal porous surface

Ducheyne, P., Radin, S., Heughebaert, M., and Heughebaert, J.C. (1990) Calcium phosphate coatings on metallic porous surfaces. The effect of structure and composition on the electrophoretic deposition, vacuum sintering, and in vitro dissolution behavior. Biomaterials, 11, 244- 254. 

Several types of aggregate-bed filters are available which provide in-depth filtration. Both gravel and particle-bed filters have been developed for removal of dry particulates but have not been used extensively. Filters have also been developed using a porous ceramic or porous metal filter surface. 

The next advance in total hip arthroplasty came with the development of various porous surface treatments which allow bone tissue to grow into the metal porous coating on the femoral stem of the hip implant and on the acetabular component of the total joint replacement. These developments arose because of patients who were not able to tolerate cemented implants because of allergies to the cement, methylmethacrylate. More youthflil patients are better served by a press-fit implant as well. Figure 12 shows the difference between textured and beaded surface-treated orthopedic prostheses. 

Film and foil adhesives based on internally plastici2ed copolymer adhesives have been suggested. For instance, vinyl acetate—ethylene or vinyl acetate—acrylate copolymers may be used for adhesion of films to porous surfaces. For metallic foil adhesion, copolymers containing carboxylate functionahty are suggested. 

Directed Oxidation of a Molten Metal. Directed oxidation of a molten metal or the Lanxide process (45,68,91) involves the reaction of a molten metal with a gaseous oxidant, eg, A1 with O2 in air, to form a porous three-dimensional oxide that grows outward from the metal/ceramic surface. The process proceeds via capillary action as the molten metal wicks into open pore channels in the oxide scale growth. Reinforced ceramic matrix composites can be formed by positioning inert filler materials, eg, fibers, whiskers, and/or particulates, in the path of the oxide scale growth. The resultant composite is comprised of both interconnected metal and ceramic. Typically 5—30 vol % metal remains after processing. The composite product maintains many of the desirable properties of a ceramic however, the presence of the metal serves to increase the fracture toughness of the composite. 

Surface preparation of the dental implant prior to implantation wiH have an effect on corrosion behavior, initial metal ion release, and interface tissue response (316). The titanium and titanium aHoy dental implants in present use have many forms to assist bone ingrowth attachment including cylinders with holes, screw threaded surfaces, porous surfaces, and other types of roughened surfaces. Methods used to produce porous surfaces iaclude arc plasma... 

The scale can also be removed by shot blasting using abrasive grits such as dry sand, less than I mm (p. This method is more suited for components not suited to the dip method and cast iron components, in which the acid may become trapped in the porous surfaces. For sheet-metal components and complicated shapes and crevices, the dip method alone is recommended. 

Many finishes exhibit low maintenance requirements (e.g. plasticzed metallic sheeting, epoxy coatings, continuous tiling systems, etc.). Others may be more maintenance intensive and may provide lower durability. However, selection must also consider the other operating parameters such as acoustic performance (which may mandate heavier mass or more porous-surfaced materials) or load-bearing capabilities, etc. 

Metal oxide surfaces become more hydrophilic with time of incubation with aqueous solutions probably due to penetration of water in a porous... 

Construction materials must be nonabsorbent and easily cleaned or decontaminated. Seamless flooring avoids cracks from which spilled chemicals can contribute a significant pollution burden to the laboratory air. Epoxy paint should be used for interior walls. Dropped ceilings should be made of nonabsorbent material such as enameled metal. Hoods and sinks should be fabricated of stainless steel. Wood or other porous surfaces must be avoided. 

Practical experience has been that the best places to look for such residues are surfaces that were either in contact with or in close proximity to the explosive before the explosion, and also that non-porous substrates such as metals tend to be better prospects than porous surfaces. Having located the seat of the explosion one can then think about where items bearing residues are likely to have been thrown, as well as identifying any items remaining in situ which could have acted as residue collectors. For example, if a small device has exploded inside a building then nearby... 

Smooth platinum, lead dioxide and graphite are anode materials commonly used in electrooxidation processes. All show large overpotentials for oxygen evolution in aqueous solution. Platinum coated titanium is available as an alternative to sheet platinum metal. Stable surfaces of lead dioxide are prepared by electrolytic oxidation of sheet lead in dilute sulphuric acid and can be used in the presence of sulphuric acid as electrolyte. Lead dioxide may also be electroplated onto titanium anodes from lead(Il) nitrate solution to form a non-porous layer which can then be used in other electrolyte solutions [21],... 

The application coverage of Metraxt will vary with surface porosity and operator efficiency. The coverage for porous surfaces is 100 ft /gal, and for nonporous surfaces it is 125 ft /gal. This material may be corrosive to some metal surfaces and painted surfaces. 

Last, but by no means least, reference should be made to the use of proteins in nano-fabrication [492]. One approach is illustrated by the fabrication of a 1-nm-thick metal film with 15-nm-diameters holes, periodically arranged on a triangular protein lattice [493]. Advantage was taken of the 10-nm-thick, uniformly porous surface (or S) layer of the crystalline protein obtained from the thermophilic bacterium Sulfolobus acidocaldarius. The protein was adsorbed from a dilute solution onto a molecularly smooth carbon-film surface, metal coated by evaporation, and ion milled to give spatial ordering of holes with the same nanometer periodicity as the protein lattice [493]. 

These last few decades many ceramic materials have been used as implants. This development will be discussed in the next paragraphs. As far as the present state of affairs is concerned, nature is still the best engineer. The ideal implant has not yet been found. Pure titanium is best tolerated by living tissue. However, increasingly often a porous surface layer is applied to the metal. In this way it is easier for the bone cells to attach themselves to the metal. In addition we now use materials which were thought to be unsuitable in the past. Improved surgical techniques and the development of antibiotics have been of vital importance here. 

We use wipe sampling to detect contaminants on non-porous surfaces, such as the surfaces of plastic or metal drums transformer casings various heavy equipment walls floors ceilings laboratory benches. Sampling with wipes allows transferring contaminants from a surface area of a known size onto the wipe material. The wipes are then analyzed, and the amounts of contaminants found on the wipe are related to the surface area. 

Coating of polymer surfaces with thicker metal layers (10-30 pm) is a much more complicated operation. Several pre-treatment steps are required first the polymer surface has to be modified in such a way that, by a chemical process, a layer of copper or nickel can be deposited. With ABS use is made of the circumstance that it is a two-phase system, consisting of a hard matrix in which rubber particles are dispersed. The rubber particles present at the surface, are etched away, leaving a rough, porous surface, which offers a good adhesion to the chemically deposited copper or nickel. Thereafter the application by electrolysis of further layers of other metals (e.g. chromium) is simple. Also for PP, PMMA and polyamides, methods have been developed for chemical deposition of the first metal layer. 

The method has been successfully used in detection of flaws in Al, Mg, Cu, brass, cast iron, stainless steels and titanium. This method can also be used in testing ceramics, plastics, rubber products, powdered metal products, as long as it is borne in mind that the method is limited to the detection of open discontinuities on the surface and limited to materials devoid of porous surfaces. 

Metals, glass and other impervious surfaces Porous surfaces... 

The hydroxy oxides, especially y boehmite, have excellent coalescing properties so they are particularly good for forming large support pellets and granules. They are also used as wash coats to provide porous surfaces for catalyst adhesion to non-porous materials such as metals and ceramics. 

Type D crude oils. These are non-toxic and do not penetrate porous surfaces and are black, heavy, semi-solid, tarry bitumen. They also contain traces of residual oils, heavy crude oils and lighter paraffin oils. Analysis of this type of crude oil for metals content, particularly toxic metals, is important because it is used for road surfacing, roofing, children s playgrounds and other uses that could have environmental concerns. 

---