Metallic additives

EMI shielding compounds based on stainless steel fibres are supplied as masterbatch compounds that can be added at low levels, ensuring minimal effect 

Extremely thin-drawn filaments of stainless steel have been developed by Bekaert under the name Beki-Shield. meeting EMI and ESD specifications at very low loadings. Maximum effectiveness is reached at about 15% by weight. The mechanical and physical properties of the plastic are only minimally affected and 

In a plastics compound they create an electrically conductive network in the moulded part. The fibres are available as a continuous bundle and in chopped fibre form. The latter are bound with polymeric binders specific for various resins, forming concentrates of stainless steel fibres, designed for easy dispersion into the matrix. Dry blends or melt compounds with the fibre are also available worldwide. 

Work on metallic additives has been particularly to the fore in Japan. A process to produce very fine metal fibres has been developed at the Nippon Institute of Technology (NIT), Saitama, Japan, and has been commercialized in a joint venture with NV Bekaert, Belgium, under the name Bekinit KK. Described as coil shaving, it is faster and more versatile than traditional methods. Fibres of 20-100 pm in diameter can be produced from titanium, aluminium, nickel, copper, and stainless steel, which offer improved conductivity in plastics compounds. Filter media, heat-resistant fabrics, and motorcycle silencers are among other potential applications. 

% fibre Weight % fibre Volume resistivity (flcm) Performance (30-1000 MHz range of shielding)  

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Nelson, O.L., R.W. Krumm, R.S. Fein, D.D. Fuller, G.K. Rightmire and G.E, Ducker (1989), "A broad spectrum, non metallic additive for gasoline and diesel fuels performance in gasoline engines". SAE paper No. 89-0214, fnt. Congress, Detroit, MI. 

Metallic additions to the melt, usually in the form of copper sulfate, brighten the shade of certain dyes, such as the Bordeaux range made from phenazones and the greens made from the indophenols the metal forms a complex with the dye. However, copper-containing dyes cannot be appHed to material that requires vulcanization. 

Titanium is susceptible to pitting and crevice corrosion in aqueous chloride environments. The area of susceptibiUty for several alloys is shown in Figure 7 as a function of temperature and pH. The susceptibiUty depends on pH. The susceptibiUty temperature increases paraboHcaHy from 65°C as pH is increased from 2ero. After the incorporation of noble-metal additions such as in ASTM Grades 7 or 12, crevice corrosion attack is not observed above pH 2 until ca 270°C. Noble alloying elements shift the equiUbrium potential into the passive region where a protective film is formed and maintained. 

Misleading also is the idea that vinyl should be harmed from incinerators because it contains heavy-metal additives. This is an evolving issue. Most vinyl products do not contain heavy metals and vinyl is a small fraction in feed to incinerators. Reformulation to replace heavy metals is in progress but some use is likely to continue. Banning vinyl from incinerators does not eliminate this problem. Rather, regulations should specify that incinerator residues (ash) be disposed of appropriately. 

The metal fillers act as a reinforcing material that results in added strength and stiffness (126). They color the plastic gray for nickel, 2inc, stainless steel, and aluminum, and brown for copper. Metal additives are more expensive than carbon black or surface-active agents, but they get extensive use in EMI shielding appHcations. 

Similar reactions can be written for other metallic additives. At the negative electrode two more reactions can occur. Hydrogen evolution... 

Ductility Tests. The ductihty of plated metals differs considerably from the corresponding thermally cast metals. Additionally, ductihty which is an important property if parts are to be deformed after plating, varies with the chemical composition of the plating solution, as well as the operating conditions of a given plating process. Ductihty can also be important when plated parts are stressed in use. Some metal deposits have coefficients of... 

Volume 11 Metal-Support and Metal-Additive Effects in Catalysis. Proceedingsof an International Symposium, Ecully (Lyon), September 14-16,1982 edited by B. Imelik,C. Naccache, G. Coudurier, H. Praliaud, P. Meriaudeau,... 

Similar reactions are available for the other alkali metals. Metalation (metal-hydrogen exchange) and metal addition to alkenes provide further routes, e.g. 

Gniewek, J., Pezy, J., Baker, B. G. and Bockris, J. The Effect of Noble Metal Additions upon Corrosion An Auger Spectroscopic Study , Journal of the Electrochemical Society, 125, 17-23 (1978)... 

The addition of a small percentage of a noble metal to a base metal such as stainless steel or titanium can provide sites of low overvoltage for the cathodic reduction of dissolved oxygen or hydrogen ions. This permits larger currents and hence more positive potentials to be obtained at the anodic region, and promotes passivation under some circumstances . This effect has been demonstrated for stainless steels but has not been adopted in practice, since under other conditions the noble metal addition accelerates corrosion . 

Several metal additives were investigated to improve this nonuniform reaction. Figure 41 shows the cycle performance of several Li-Al alloy electrodes. It was found that Li-Al-Mn and Li-Al-Cr alloys had better rechargeability than Li-Al alloy in the Li-Al-Mn alloy, particularly no de-... 

Boggs, J.L. Prentice, K.J. Kraeutle J.E. Crump, The Role of the Scanning Electron Microscope in the Study of Solid Propellant Combustion , inavwepsceiiu ir h/zo yiyoy) do) u,u, Graber, F.C. Rauch A.J. Fanelli, Observation of Solid-Solid Polymorphic Transformation in 2,4,6-Trinitro Toluene , JPhChem 73, (10), 3514—15 (1969) 39) J.E. Crump, J.L. Prentice K.J. Kraeutle Role of Scanning Electron Microscopy in the Study of Solid Propellant Combustion. Part 11—Behavior of Metal Additives , NavWepsCentr TP-5142-PT-2 (1969) 40) J.A. Markham A.R. Cox, Applications... 

There arc stability problems with most of the metal additives other than aluminum, although... 

Effect of Metal Additives on Specific Impulse of Ammonium Perchlorate Propellants... 

R.C. Oliver et al, USDeptCom, Office Tech-Serv ..AD 265822,(1961) CA 60, 10466 (1969) Metal additives for solid proplnts formulas for calculating specific impulse and other proplnt performance parameters are given. A mathematical treatment of the free-energy minimization procedure for equilibrium compn calcns is provided. The treatment is extended to include ionized species and mixing of condensed phases. Sources and techniques for thermodynamic-property calcns are also discussed... 

When these metal additives are delivered to the furnace, in whatever form suitable, they become oxides. In this active form, they exert a catalytic effect on the fuel combustion process. 

Flames, either with or without metallic additives, are rich in ion-molecule reactions of both positive and negative ions. The use of flames as media in which these reactions may be studied over broad ranges of temperature and pressure is in its infancy. Most of the phenomena observed can be explained qualitatively, and some quantitative results have been obtained. 

Activation methods can be divided into two groups. Activation by addition of selected metals (a few wt%), mainly transition metals, e.g., fine powders of Fe, Ni, Co, Cr, Pt, Pd, etc. ", or chlorides of these metals when these are reducible to the metal by hydrogen during presintering. The mechanism of activation is not understood (surface tension, surface diffusion, etc.) but is related to the electronic structure of the metal additive. Activation by carbon is also effective. Alternatively, activation utilizes powders in a specially activated state, e.g., very fine (submicronic) powders. ... 

In relation to PVC additives, the study concluded that heavy metal additives are more likely to be released under acidogenic conditions (compared with plasticizers, for example, which are released mainly during the anaerobic and methanogenic phases of landfill development). With respect to landfill emissions, it was concluded that organotin compormds carmot be directly attributed to the presence of PVC in landfills. 

Beside complexation with transition-metals, PAM 4 exhibited unusual chemistry when treated with an alkali metal. Addition of four equivalents of lithium... 

Volume 11 Metal-Support and Metal-Additive Effects in Catalysis. Proceedings of an... 

Peters R, Fischer DF (2005) Preparation and diastereoselective ort/io-metalation of chiral ferrocenyl imidazolines remarkable influence of LDA as metalation additive. Org Lett 7 4137 140... 

Imellk, B. et al., eds. "Metal-Support and Metal Additive Effects In Catalysis" Elsevier Amsterdam, 1982, and references cited therein. 

V (2 ), Cr ( ), Zr (1 ), or Ta (1 ). The role of these promoters in the air cathode is unclear, and some have suggested that the active catalysts are alloys of the Ft with the transition metal (1,4) which form during heat-treatment of the oxide impregnated precursor. In the first section of this paper, we review the work from the Lawrence Berkeley Laboratory on the study of the mechanism of promotion of air cathode performance by these transition metal additives. 

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