Engineering topics

Holleck, G.

Publications and source records attributed to Holleck, G..

9 records

NASA NTRS1981

Common pressure vessel development for the nickel hydrogen technology

The design of a pressure vessel nickel hydrogen cell is described. The cell has the following key features: it eliminates electrolyte bridging; provides for independent electrolyte management for each unit stack; provides for independent oxygen management for each unit stack; has good heat dissipation; has a mechanically sound and practical interconnection; and has the maximum in common with state of the art individual pressure vessel technology.

Holleck, G.↗

NASA NTRS1978

Configuration analysis of nickel hydrogen cell

The significance of various stack configurations and components on the cycle life for nickel hydrogen cells for synchronous orbit used was evaluated. Failure modes of electrolyte management and 02 management were solved by modifications in the reservoir, the wick, and/or the stack configuration.

Holleck, G.↗

NASA NTRS1978

Silver hydrogen batteries

The feasibility of silver hydrogen batteries was investigated. Cell configurations and cell cycling were discussed. Energy density was found to be 65 to 100 watt hours per kilogram. Electrolyte management was considered critical to the cell's performance. Factors of electrolyte management which were particularly important were: (1) the nature of the separator system, and (2) the amount of electrolyte.

Holleck, G.↗

NASA NTRS1977

Self discharge of nickel-hydrogen cells

Values for the capacity loss with time, naturally on open circuit stand, and information regarding the minimum amount of circuit charge needed to keep the cell charged can be determined from the self-discharge behavior of nickel hydrogen cells. Furthermore, the rate of reaction between hydrogen and a charged nickel electrode is also open for nickel cadmium batteries. In a nickel hydrogen cell, the hydrogen is stored as pressurized gas and the cell stack with the charge that is oxidized nickel-hydroxide electrode is in direct contact with the hydrogen. Therefore, the rate of reaction can be measured easily and precisely by monitoring the charge, the change in hydrogen pressure with time. Measures made on twelve 15 ampere hour nickel hydrogen cells of different stack configurations built for COMSAT are discussed.

Holleck, G.↗

NASA NTRS1972

NiCd battery electrodes

The objective of this research program was to develop and evaluate electrodes for a negative limited nickel-cadmium cell and to prove its feasibility. The program consisted of three phases: (1) the development of cadmium electrodes with high hydrogen overvoltage characteristics, (2) the testing of positive and negative plates, and (3) the fabrication and testing of complete negative limited NiCd cells. The following electrode structures were manufactured and their physical and electrochemical characteristics were evaluated: (1) silver sinter-based Cd electrodes, (2) Teflon-bonded Cd electrodes, (3) electrodeposited Cd sponge, and (4) Cd-sinter structures. All cadmium electrode structures showed a sharp increase in potential at the end of charge, with the advent of hydrogen evolution occurring at approximately -1.3 V versus Hg/HgO. The hydrogen advent potentials on pure cadmium structures were 50 to 70 mV more cathodic than those of their silver-containing counterparts.

Holleck, G.↗

NASA NTRS1972

NiCd battery electrodes, C-150

Electrodes for a nongassing negative limited nickel-cadmium cell are discussed. The key element is the development of cadmium electrodes with high hydrogen overvoltage. For this, the following electrode structures were manufactured and their physical and electrochemical characteristics were evaluated: (1) silver-sinter-based Cd electrodes, (2) Teflon-bonded Cd electrodes, (3) electrodeposited Cd sponge, and (4) Cd-sinter structures.

Holleck, G.↗

NASA NTRS1971

NiCd battery electrodes, C-150

A research program to develop and evaluate electrodes for a nongassing negative limited nickel-cadmium cell is described. The concept of the negative limited cell and its implications on electrode structure are discussed. The key element is the development of a cadmium electrode with high hydrogen overvoltage. For this, Teflon-bonded Cd electrodes and silver-sinter based Gc electrodes were manufactured and in preliminary experiments their physical and electrochemical characteristics were evaluated. Hydrogen evolution on cadmium was found to occur approximately 100 mV more cathodic than on silver. Both electrode structures exhibit a fairly sharp potential rise at the end of the charging cycle and the advent of gas evolution occurs at potentials between -1.2 and -1.3 V versus a Hg/HgO reference electrode. These results are compared with conventional Ni-sinter based Cd electrodes.

Holleck, G.↗

NASA NTRS1971

Research on rechargeable oxygen electrodes

Studies were carried out on a number of factors which may influence the behavior of the platinum electrocatalyst of oxygen electrodes for use in rechargeable metal-oxygen batteries or hydrogen-oxygen fuel cells. The effects of pretreatments for various potentials and added ionic species, which could be present in such systems, were studied with reguard to: (1) the state of surface oxidation, (2) platinum dissolution, (3) the kinetics of oxygen evolution and reduction (including the role of hydrogen peroxide), and (4) changes in porous electrode structure. These studies were carried out on smooth platinum, platinized platinum, and Teflon-bonded platinum black electrodes in carefully purified electrolyte solutions. The main factors which appear to affect rechargeable oxygen electrode performance and life are: (1) the buildup of a refractory anodic layer on extended cycling, and (2) the dissolution of platinum.

Giner, J.↗

NASA NTRS1970

Research on rechargeable oxygen electrodes.

A research program is described which consisted of studying the effects of electrode cycling in very pure KOH solutions, with and without controlled additions of impurities, on oxide formation, oxygen evolution kinetics, oxygen reduction kinetics (including hydrogen peroxide formation), and changes in electrode structure. Bright platinum, platinized platinum, and Teflon-bonded platinum black electrodes were studied. Three main problem areas are identified: the buildup of a refractory anodic layer on prolonged cycling, which leads to a degradation of performance; the dissolution and subsequent deposition of dendritic platinum in the separator, leading to short-circuit ing and loss of electrocatalyst; and the disruptive effect of bubbling during gas evolution on charge. Each of these problem areas is analyzed, and remedial solutions are proposed.

Giner, J.↗