Whisker treatment

Tia, as well as some other metals, can undergo a phenomenon where tiny metal filaments, called whiskers, form randomly on parts used ia electrical apphcafions. In low voltage, miniature circuitry, whiskers can cause short circuits. Alloys having 2% lead minimum or 0.5% bismuth or heat treatments are said to overcome the problem. A specification for electroplated fin coafings is available (133). 

The following is an example of a box plot of seizure data by treatment at each of three visits. This first example is created with the traditional PROC GPLOT. This box plot has boxes that span the interquartile range and whiskers that extend to the maximum and minimum values. Also, a connecting line joins the median values for each treatment. 

Surface treatments of carbon fibers can in general be classified into oxidative and non-oxidative treatments. Oxidative treatments are further divided into dry oxidation in the presence of gases, plasma etching and wet oxidation the last of which is carried out chemically or electrolytically. Deposition of more active forms of carbon, such as the highly effective whiskerization, plasma polymerization and grafting of polymers are among the non-oxidative treatments of carbon fiber surfaces. 

The tensile strength of materials is dependent on the treatment and form of the material. Thus, the tensile strength of isotropic bulk nylon-6,6 is less than that of anisotropic oriented nylon-6,6 fiber. Inorganics and metals also form fibers and whiskers with varying tensile strengths (Table 14.1). Fibers are generally less crystalline and larger than whiskers. 

Graphitization of the PPN whiskers. High-temperature heat treatment of the whisker revealed that PPN was also a typical graphitizing material (doo2 = 3 357 X for HTT = 2800 C), the graphitization... 

In general, both cordierite and metallic monoliths are unsuitable as catalytic supports. To process a monolith into an active monolithic catalyst, a layer of porous catalytic support must be deposited on the walls between channels. y-Alumina appeared to be the most effective support for automotive catalysts. The alumina layer is deposited by sol-gel technique (so called washcoating). Adherence of 7-alumina to cordierite is relatively strong. However, to form the stable 7-alumina layer on a metallic surface, we need to use an appropriate alloy that is appropriately processed before the layer is deposited. Stainless steel containing chromium, aluminum, and yttrium subjected to thermal treatment under oxidizing conditions meets requirements of automotive converters. Aluminum in the steel is oxidized to form 7-alumina needles (whiskers) protruding above the metal... 

Aluminium titanate (tielite, Al2Ti05) has excellent thermal shock resistance but poor mechanical strength which can, however, be improved by reinforcing with whiskers of a related phase such as potassium hollandite (K2Al2Ti60i6). Such composites can be formed by thermal decomposition of sol-gel precursors, reaction sintering of the two phases or by thermal treatment of an appropriate glass-ceramic material. Al MS NMR has been used to study the co-formation of these two phases during thermal treatment, and indicates that hollandite crystallises as whiskers within the tielite matrix (Kohn and Jansen 1998). 

The bulk chemistries, surface chemistries, and morphologies of silicon carbide whiskers vary widely depending on the type of process used, the stage of the process development, and the postsynthesis treatments practiced by the producer. The synthesis of the whiskers as described earlier is... 

It is not only the blend morphology which is affected by filler presence filler orientation might be affected by its surface treatment, as was observed in the works on PC/ABS blends containing aluminum borate whisker. When the whisker surface was treated with epoxy silane, its reaction to flow in injection and compression molding processes changed, resulting in a different orientation even though all other parameters of process and composition were the same. ... 

The coating of metallic monolith, which was more problematic than for ceramics, has been extensively studied and improved. Zwinkels et have shown that special treatment of metallic alloy generates an alumina whisker-covered surface. Those alumina whiskers act as an anchor and facilitate the stable washcoating with ceramics. 

Some imperfections arise from dislocations at the interface of microcrystalline domains along the microfibril length. These imperfections were exploited to advantage by treatment of the sample with acid to produce nanocrystals called whiskers, having the same diameter as the starting mierofibrils but of much shorter lengfli. 

Ultrasonic treatments [70] have the potential to change the morphology of the formed whiskers. When hydrolysis is carried out under ultrasonic treatment, a combination of both sulfuric and hydrochloric acids during the hydrolysis appears to generate spherical cellulose nanocrystals instead of rod like nanocrystal which are the typical morphology of whiskers. These spherical cellulose nanocrystals show better thermal stability mainly because they possess fewer sulfate groups on their surfaces [71]. 

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