New Horizons in Electrochemical Science and Technology (1986) / Chapter Skim
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5. Opportunities in Particular Technologies
5. Opportunities in Particular Technologies
Pages 41-94
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From page 41... ...
The current status and needs for research and technology development, along with some institutional issues, are examined for Batteries and fuel cells: Technical requirements are documented for advanced applications in ground-based vehicles, space and central electric utility systems, communication systems, medical applications, and weapons; associated research and development topics are summarized. · Biomedical science and health care: Electrochemical processes characteristic of living systems are reviewed, including such aspects as applications based on neuroscience, enzyme biocatalysis, adhesion and cell fusion, and electrophoresis.
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From page 42... ...
BATTERIES AND FUEL CELLS The current and emerging applications for batteries and fuel cells are numerous and highly varied (1-4~. These chemical sources of electrical energy are absolutely essential for life in today's world.
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From page 43... ...
Note that high specific power and high specific energy are offered by some of the new batteries. Emerging applications for fuel cells and batteries are oriented toward higher performance and longer life.
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From page 44... ...
A number of these medical applications will be fulfilled within the next several years. The performance capabilities required of batteries and fuel cells vary according to the type of application.
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From page 45... ...
An opportunity exists for the development of systems that have the capability of storing 5 to 10 times more energy per unit weight than the Pb-PbO2 cell. More specific barriers to meeting the goals include the high cost of electrocatalysts and some porous electrodes; the prevention of corrosion of active and passive cell components; instabilities of porous electrode structures under long-term cycling; loss of electrocatalytic activity with time and use; susceptibility of electrolytes to oxidation and/or reduction by electrode reactants; inadequate conductivity of electrolytes for high-performance applications; inadequate membranes and separators (low chemical stability and conductivity)
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From page 46... ...
TABLE 5-2 Performance Requirements~for Fuel Cells in Advanced Applications Specific Fuel Cell Power Efficiency Startup Cost Application (W/kg)
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· Electrocatalysis of the oxidation of logistic fuels (hydrocarbons' reformer gas, methanol, coal) Suppression of passive film formation ~ Advanced methods for the design and optimization of electrodes, cells, and electrochemical systems · Advanced methods for in situ study of electrochemical and chemical reactions in porous electrodes and immobilized electrolytes A plan for a more vigorous electrochemical R&D program (at a funding level at 2 to 3 times the present value)
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From page 48... ...
Such knowledge is also indispensable for developing ways of utilizing information about biological processes for industrial or medical applications (5~. The five examples that follow are illustrative but not inclusive of all areas where electrochemical phenomena represent an essential component.
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From page 49... ...
affect selectivity and sensitivity of ionic permeabilities of protein membranes, films, or lamina Improved film prototypes, such as conducting polymers involving polypeptides, which might represent improved hosts for electroactive protein insertion, as well as the characterization of a larger number and variety of such proteins in order to improve knowledge of structureactivity relationships, including the contribution of the protein to the permeability-regulating capabilities of the laden film or membrane · Better understanding of deterioration of ionic permeability, usually associated with unwanted protein adsorption, in order to to design synthetic systems that retain for practical periods their desired capabilities Cell Fusion Cell-to-cell fusion can be achieved with the aid of electrical stimulation (7-10~. Several techniques have been demonstrated in which an electric field is applied for a short duration to pointadhering (or agglutinated)
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From page 50... ...
Electrode surfaces that have been properly modified with bioreactive layers (enzyme, antibody, receptor) can provide access to the in vivo investigation of biologically significant materials.
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From page 51... ...
The industry that coating technology supports has multibillion-dollar annual sales and includes areas such as paints, enamels, electrodeposits, and conductive polymers. As a result of advances in the fields of surface modification, surface characterization, and adhesion, a revolution is occurring in coating technology.
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From page 52... ...
However, the development of surface modification techniques is introducing opportunities for covalent interaction and hence greatly improved adhesion (19~. For example, silanization may be used to form covalent interactions between surface hydroxyl groups and organic coating materials, as follows: R' R s' OH OH O ~ O ~ ~ + RR' Si(OCH3)
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From page 53... ...
~ · CH2 =0~ CH2 ~ 2 {> 2 3; Adhesion is due to van der Waals interaction with the surface, and, while polyparylene films exhibit excellent chemical stability, poor adhesion continues to be a major technological problem and limitation. Surface modification techniques, which result in covalent interaction between the polymer film and the surface, might greatly improve adhesion and hence render polyparylene films more protective.
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From page 54... ...
However, oxygen reduction electrocatalysis is still the principal limitation in alkaline and acid fuel cell performance, so that continued investment is required to bring electrochemical energy conversion into the general marketplace. Exciting possibilities exist in the use of conducting polymer coatings, because of the possibility of stereo- and product-selectivity and because the electronic properties of the coating can be controlled (at least in principle)
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From page 55... ...
The panel addressed three general topics: corrosion research and engineering, research on advanced materials, and dissemination of information. The first of these topics focuses on fundamental understanding of corrosion processes, on utilization of measurements and understanding in the engineering systems analysis of corroding systems, and on life prediction.
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From page 56... ...
Six central recommendations were identified on theory and modeling, experimental probes, lifetime prediction, investigation of advanced materials, multidisciplinary efforts, and education. · Theory and Modeling: Greater emphasis on modeling and theory is recommended for both elementary corrosion processes and their interactions in complex macroscopic systems.
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From page 57... ...
A major objective of corrosion science and engineering is to permit selection of materials giving corrosion resistance compatible with system design in specific service environments. Even for the simplest case, general corrosion of metals, present lifetime prediction strategies are qualitative or nonexistent because of the lack of (a)
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From page 58... ...
Codifying their knowledge for wider accessibility and utility will lead to improved corrosion resistant designs. · Corrosion Resistance of Advanced Materials: The corrosion behavior and limits of chemical stability of newly developed materials should be determined as an integral part of materials development in order to indicate where more detailed modeling and experimental efforts are warranted.
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From page 59... ...
Efforts should be made to include more laboratory experience in corrosion in conjunction with lecture courses at this level. ELECTROCHEMICAL SURFACE PROCESSING The use of electrochemical processes for modification of surface properties is growing in response to needs for new materials and more demanding process requirements (27-32~.
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From page 60... ...
The following are some of these new applications: New materials formed by alloy plating to produce thick amorphous materials having special properties of strength, hardness, magnetism, etc.; to contribute to corrosion resistance (high-rate deposition of stainless steel and of alloys that are solderable and paintable) ; to replace gold for electronic contacts; and to produce conducting polymer coatings formed in situ by electropolymerization Novel coatings formed by electrophoretic deposition of ceramics, glasses, conducting polymers, and high-temperature polymers Composite materials fabricated by codeposition of particulates (MoS2 in metal for lubrication, diamond or SiC in metal for wear resistance, etc.)
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From page 61... ...
Better understanding is needed of instability phenomena that lead to shape evolution, such as dendrites, surface roughness, anisotropic chemical and plasma etching, and patterning. Simulation of electrolytic cells Effective surface processing technology hinges on the ability to design and scale up processes in a predictive manner.
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From page 62... ...
The committee therefore recommends that a detailed assessment be made of scientific and technological opportunities and routes to their realization in the area of electrochemical surface processing. The following research areas hold high promise for advancing technological growth in the near term: · Electroplating under ultrapure conditions · Transport and reaction phenomena during high-speed processing · Invention of new processing conditions and discovery of new unique materials fabricated by electrochemical surface processing · Theory for electrocrystallization at solid-liquid interfaces MANUFACTURING AND WASTE UTILIZATION Metal and industrial mineral production is a major manufacturing activity in the United States.
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From page 63... ...
industrial production for the years shown (33~. Primary Metals Motor Vehicles Electronic Components Mining and Quarrying Industrial Chemicals Crude Petroleum and Gas % of Total /////////A \ ~/,//~/~/9 \\\\ ./~///A Gil\\\\\\\\\\]
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From page 64... ...
industry. Electrochemical reactions occupy an important position in mineral processing and are likely to maintain this key role for a long time.
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From page 65... ...
However, it seems apparent (at least in the case of aluminum extractive metallurgy) that technological development on existing processes that might offset the inherent advantage of the foreign producers is unlikely to be reduced to practice because of the high financial risk, high capital requirements, and the likelihood that foreign producers would restore their advantage by quickly adopting the new technology.
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From page 66... ...
In this case significant benefits can be derived for the domestic industry through electrochemical research aimed at lighter, corrosion-resistant, lower cost vehicles in the short time frame as well as fundamental understanding that identifies major breakthroughs for longer range competition. Electro-Organic Synthesis There are about 30 electro-organic synthesis processes thought to be in production and 100 additional ones that have been demonstrated to be feasible on bench scale.
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From page 67... ...
Although simple planar cell designs such as those used in chioralkali, aluminum, and magnesium production are still the industry workhorses, new cell designs are being developed based on the use of porous and fluid-bed electrodes. The invention and engineering development of three-dimensional porous electrodes having high reaction rates per unit volume have permitted vastly improved cell designs and have reduced capital costs enough to make some electrolytic processes competitive, even with rising energy costs.
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From page 68... ...
O lactobionate Herdom Poland 2 5-Dimethoxy- Furan dihydrofuran BASF Dimethyl sulfoxide Dimethyl sulfide Gianzatoff; AKZO; Petroles ~ Aquitaine Dodecenedicarboxylic Unknown acid Fluorinated carboxylic acids Fluorinated methanesulfonic acids Alkanoic acid fluorides Bis-fluoro-sulfonyl 3M methane Glyoxylic acid Oxalic acid Hexahydrocarbazole Tetrahydrocarbazole BASF Hexafluoropropylene Hexafluoropropylene Hoechst oxide Japan 3M; Dai Nippon Rhone Poulenc; Streetly Chemical; Japan
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From page 69... ...
ICERI Indian Central Electrochemical Research Institute *
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From page 70... ...
and are limited to a few feet of height, resulting in sprawling plants that cover many acres with relatively high costs in terms of land, foundations, buildings, and utilities. The present state of the art therefore constrains the use of electrolytic processing for extractive metallurgy to three broad categories-those products that can be made by no other known method with available containment materials, those with sufficiently high density or markup value to offset the required capital and power costs, and those processes where more than
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From page 71... ...
Inorganic Chemicals Chlorine, hydrogen, and ammonia may be coproduced from ammonium chloride using a beta-alumina diaphragm separating a sodium chloride-zinc chloride mixture on the anode side and an ammonium chloride-sodium chloride-zinc chloride mixture on the cathodic side, where ammonia and hydrogen are produced (38~. None of the thermochemical or hybrid cycles for hydrogen production are as economical as the electrolysis of water, which is still too costly for fuel cell application (39~.
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From page 72... ...
Burning hydrogen and chlorine for the chlorination of hydrocarbons may be carried out either in a HC1 aqueous cell or fused metal chloride cell, simultaneously producing electrical energy and marketable chemicals by the cell reaction. Nitric oxide may be electrogeneratively reduced in an electrochemical cell to generate by-product electricity while producing ammonia and eliminating a polluting effluent gas stream (42,43~.
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From page 73... ...
In electrodialysis, an alternating stack of cationic- and anionic-selective membranes is employed in an applied field to produce a concentrated waste stream along with cleaned product water. Gas-phase purification using electrochemistry has been limited mainly to flue gas desulfurization.
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From page 74... ...
Gas-phase electrochemical membrane transport is one of the techniques chosen by National Aeronautics and Space Administration or manned spacecraft CO2 control (51~. This technique, suggested by fuel cell development, has given rise to similar processes for SO2 removal from flue gas and H2O removal from coal gas (52~.
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From page 75... ...
Fuel cells may be developed for either auxiliary or primary power using methanol as the liquid fuel of choice, and in the distant future technology could evolve to synthesize hydrocarbon fuel on board.
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From page 76... ...
At a constant current density of 1000 A/m2, there is an order of magnitude higher investment allowed in reactors that can yield a good return for high-priced specialty chemicals over commodity chemicals commanding one-fifth the price. Since three-dimensional electrode reactor designs such as bipolar plates, trickle beds, and monopolar or bipolar packed or fluid beds cost only $400 to $1000 per square meter of active electrode surface, as compared to $2500 to $10,000 for more conventional planar designs, only the former can be used profitably in the production of low-cost commodity chemicals.
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From page 77... ...
Research Needs For implementation of the ideas suggested under the heading "Emerging Technologies," it will be necessary to carry out research focused on the following fundamental topics: · Study the fundamental factors at interfaces that control charge-transfer reactions, in order to develop new electrocatalysts Develop new electrochemical reactor designs that permit very high current densities by moving the electrolyte at high velocity between very close electrodes, taking advantage of the third dimension through bipolar plates and designing means for separating the anode and cathode products Develop new electrode materials and the modification of electrode surfaces by investigation of conductive polymers, organometallic conductors and semiconductors, and the phenomena of absorption and covalent attachment · Develop sensors using electrochemistry as well as new electroanalytical methods · Study electrocrystallization phenomena and electrode surface morphology when deposition and stripping are taking place · Determine kinetics and mechanisms of electrode reactions shown to be potentially useful (i.e., carbon monoxide and dioxide reduction, alkali metal deposition, solution redox reactions, and oxygen reduction) to permit the design of highly efficient electrolytic cells (55)
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From page 78... ...
, energy conversion and storage (separators for batteries and fuel cells) , food and biochemical processing (desalting and demineralization of food products, controlled release of drugs)
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From page 79... ...
Biomembranes are nature's supreme molecular organizers, and the development of membrane processes that mimic their behavior would have far-reaching implications in health care, chemical synthesis, and solar energy conversion. Along more general lines, there are several areas where fundamental scientific problems need to be addressed.
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From page 80... ...
Impediments to university-industry interaction may arise, however, since academics need access to membrane fabrication techniques whereas the industry, for proprietary reasons, is reluctant to part with such knowledge. The following research areas hold promise for advancing major technological growth: · Stable anion exchange membranes and low-cost cation exchange membranes · Basic transport studies at the molecular level aimed at molecular design of membranes · Invention of new membranes that contain active elements · Biocompatibility of membranes with living systems to permit affinity-discrimination, sensing, and molecular recognition
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From page 81... ...
experimentation, will surely expand in the near future. Processes for the Manufacture of Microcircuits The chemical, electrochemical, and photoelectrochemical etching processes by which microelectronic components are made are controlled by electrochemical potentials of surfaces in contact with electrolytes.
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From page 82... ...
The relevant fundamental areas of electrochemistry are ion transport in microcells; modeling of microcells of high aspect ratio; electrochemical leveling; electrochemical stability of metal-polymer interfaces; and humidity- and temperature-dependent transport of ions through polymers, ceramics, and glasses and at their interfaces with metals and with the atmosphere. Processes for the Manufacture of Lightwave Communication Devices Lightwave communication devices, such as integrated microlenses that focus light from light-emitting diodes onto the ends of optical fibers, are manufactured by photoelectrochemical etching of III-V semiconductors.
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From page 83... ...
Also unavailable are data on what ions are selectively trapped in the hydrated SiO2 surface, although it is this trapping that perturbs the operating characteristics of microcircuits. To avoid surface corrosion processes, the microelectronic industry takes three precautions: it avoids the use of solvents and reagents that may leave an ionic residue on the microcircuits; it encapsulates the integrated circuits; and it packages the microcircuits in plastic containers.
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From page 84... ...
If complexing functions like carboxylic acids are formed upon oxidation of the polymer or are intrinsically present, they complex the copper cations, causing both gradual dissolution of the metal and a change in the electrical properties of the dielectric. Because multilayer interconnecting networks are an important element of advanced chips and parallel processors, it is essential that an understanding of the corrosion processes that affect their reliability be developed.
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From page 85... ...
Their design requires. as · , .~ e , · · ~ seen In the previous section, ~n-depth understanding of the interracial electrochemistry between metals and dielectrics and of ion transport in channels of diminishing size that connect metal runners in different planes.
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From page 86... ...
Recent advances in microelectronic fabrication techniques, in development of modified electrode surfaces and ion-selective membranes, and in availability of new materials give promise for development of new electrochemical sensors. For both gas and liquid sensors, the possibility of much higher sensitivity exists.
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From page 87... ...
Key scientific challenges include the design of new molecules and substrates that possess the high transport selectivity required for new and improved sensors. The discovery and molecular characterization of new sensing elements will include surfaces modified with specific electrocatalysts and/or enzymes, ion-specific membranes, fast ionconducting ceramics and glasses, conducting polymers, and semiconductor materials.
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From page 88... ...
Fuel Cell Materials Technology in Vehicular Propulsion. National Materials Advisory Board, NMAB-411.
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From page 89... ...
Electric field mediated fusion and related electrical phenomena. Biochim.
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From page 90... ...
Oudar, eds. Fundamental Aspects of Corrosion Protection by Surface Modification.
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From page 91... ...
The electroreduction of nitric oxide on bulk platinum and acid solutions. Electrochim.
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From page 92... ...
H Electrogenerative reduction of nitric oxide for pollution abatement.
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From page 93... ...
B Proceedings of the Symposium on Membranes and Ionic and Electronic Conducting Polymers.
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From page 94... ...
Electrochemical sensors based on biological principles. Electrochim.
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