Current Search: Lipka, Stephen M. (x)
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- Title
- Carbon nano-fibers for electrochemical double-layer capacitors.
- Creator
- Cao, Xuejun., Florida Atlantic University, Lipka, Stephen M.
- Abstract/Description
-
A novel carbon nano-fiber was prepared using catalytic vapor phase growth. Electrochemical capacitors were assembled using these fibers. Physical analysis was conducted on the carbon nano-fibers and electrochemical analysis was performed on capacitors made from these carbon nano-fibers. Scanning electron microscopy revealed that the nano-fibers had diameters ranging from 20nm to 400nm. X-ray diffraction showed the nano-fibers were more ordered than some commercial carbon fibers. BET...
Show moreA novel carbon nano-fiber was prepared using catalytic vapor phase growth. Electrochemical capacitors were assembled using these fibers. Physical analysis was conducted on the carbon nano-fibers and electrochemical analysis was performed on capacitors made from these carbon nano-fibers. Scanning electron microscopy revealed that the nano-fibers had diameters ranging from 20nm to 400nm. X-ray diffraction showed the nano-fibers were more ordered than some commercial carbon fibers. BET adsorption yielded specific surface areas of the nano-fibers at around 400 m$\sp2$/g. Electrochemical studies including cyclic voltammetry and electrochemical impedance spectroscopy indicated that capacitors made from carbon nano-fibers were promising for practical use. Further modification/activation of the carbon nano-fibers was conducted and capacitors made from these materials were also evaluated.
Show less - Date Issued
- 1999
- PURL
- http://purl.flvc.org/fcla/dt/15622
- Subject Headings
- Capacitors, Electric double layer, Carbon fibers
- Format
- Document (PDF)
- Title
- Effect of fiber sterilization atmosphere on insertion of lithium into PAN-based carbon filter electrodes.
- Creator
- Braun, James Christian., Florida Atlantic University, Lipka, Stephen M.
- Abstract/Description
-
A novel electrode structure for Li-ion batteries was created by thermally treating nonwoven polyacrylonitrile (PAN) fabric in an inert atmosphere. Rapid carbonization of PAN fiber, stabilized in an inert atmosphere, produced a fused carbon fiber structure having a reversible specific capacity for lithium above 300 mAh/g; with charge reversibility between 95 and 100%. Chemical, structural and electrochemical analyses, including electrochemical impedance spectroscopy were performed on carbon...
Show moreA novel electrode structure for Li-ion batteries was created by thermally treating nonwoven polyacrylonitrile (PAN) fabric in an inert atmosphere. Rapid carbonization of PAN fiber, stabilized in an inert atmosphere, produced a fused carbon fiber structure having a reversible specific capacity for lithium above 300 mAh/g; with charge reversibility between 95 and 100%. Chemical, structural and electrochemical analyses, including electrochemical impedance spectroscopy were performed on carbon fiber electrodes. Scanning electron microscopy revealed grooves and striations on the surfaces of carbon fibers prepared from PAN precursors stabilized in oxygen; but could not resolve any surface features on the fused carbon fibers, prepared from PAN precursors stabilized in an inert atmosphere. The fused, porous carbon fibers are believed to contain a large fraction of carbon chains with relatively few carbon planes.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/15484
- Subject Headings
- Lithium cells, Electrodes, Carbon, Nonwoven fabrics
- Format
- Document (PDF)
- Title
- Electrochemical impedance spectroscopy to monitor degradation of carbon fiber reinforced polymer composites subjected to simulated ocean environment.
- Creator
- Ahmed, Mohammad Mesbahuddin., Florida Atlantic University, Lipka, Stephen M.
- Abstract/Description
-
This research evaluated the applicability of electrochemical impedance spectroscopy (EIS) as a non-destructive technique to predict and characterize the degradation of carbon fiber reinforced polymer (CFRP) composites exposed to aqueous environments at ambient and 6.2 $\pm$ 0.3 MPa. Changes in EIS data were related to water uptake into the composite material as a function of exposure time. Electrochemically induced damage (both anodic and cathodic) were also evaluated using impedance...
Show moreThis research evaluated the applicability of electrochemical impedance spectroscopy (EIS) as a non-destructive technique to predict and characterize the degradation of carbon fiber reinforced polymer (CFRP) composites exposed to aqueous environments at ambient and 6.2 $\pm$ 0.3 MPa. Changes in EIS data were related to water uptake into the composite material as a function of exposure time. Electrochemically induced damage (both anodic and cathodic) were also evaluated using impedance measurements. Three point flexure tests with concurrent EIS measurements were employed to study the effect of stresses on water uptake and mechanical degradation. Visual observation of the extent of damage (i.e., fiber-matrix debonding) was made using scanning electron microscopy (SEM) and correlated with EIS observation.
Show less - Date Issued
- 1993
- PURL
- http://purl.flvc.org/fcla/dt/14962
- Subject Headings
- Polymers--Deterioration, Composite materials--Environmental aspects, Carbon fibers, Polymeric composites, Spectrum analysis
- Format
- Document (PDF)
- Title
- Electrochemical behavior of carbon fiber cathode materials in organic electrolytes containing various lithium salts.
- Creator
- Durand, Severine Nathalie., Florida Atlantic University, Lipka, Stephen M.
- Abstract/Description
-
The intercalation of anions into carbon fiber from organic electrolytes containing lithium salts was studied. The reversible intercalation of anions into carbon could lead to the possible substitution of conventional metal oxide cathode materials in lithium-ion cells. EWC300 was selected as the most suitable carbon fiber material based on data from preliminary tests. Experiments were performed with LiClO4 in EC/DMC and LiPF6 in EC/DMC electrolytes. Slow scan cyclic voltammetry (0.1 mV/s) and...
Show moreThe intercalation of anions into carbon fiber from organic electrolytes containing lithium salts was studied. The reversible intercalation of anions into carbon could lead to the possible substitution of conventional metal oxide cathode materials in lithium-ion cells. EWC300 was selected as the most suitable carbon fiber material based on data from preliminary tests. Experiments were performed with LiClO4 in EC/DMC and LiPF6 in EC/DMC electrolytes. Slow scan cyclic voltammetry (0.1 mV/s) and galvanostatic charge/discharge experiments at various C rates were used. Intercalation of PF6- occurred by staging and was highly dependent on the current density. High current density (20 mA/g) was necessary to reach potentials over 5 V vs Li to achieve intercalation capacities over 80 mAh/g. Powder x-ray diffraction revealed that carbon fibers became less crystalline after anions were intercalated into their structure. Scanning electron microscopy showed longitudinal cracking on the carbon fibers after 120 cycles indicating dimensional instability.
Show less - Date Issued
- 1999
- PURL
- http://purl.flvc.org/fcla/dt/15624
- Subject Headings
- Anions, Carbon fibers, Lithium cells, Electrochemical analysis
- Format
- Document (PDF)
- Title
- Stress corrosion cracking susceptibility of engineering alloys in acidified seawater.
- Creator
- Campaignolle, Xavier., Florida Atlantic University, Lipka, Stephen M.
- Abstract/Description
-
Experiments were conducted to determine the stress corrosion cracking (SCC) susceptibility of various corrosion-resistant alloys which included: 17-4 PH, INCONEL 718 and A286. These alloys were studied for different aging (heat) treatments. Slow strain rate tests (extension rate = 4.7 x 10^-5 mm/s) were performed on each alloy in four different environments; including air and natural seawater acidified with reagent grade hydrochloric acid to a pH of 0.1, 1 and 3. During the experiments, the...
Show moreExperiments were conducted to determine the stress corrosion cracking (SCC) susceptibility of various corrosion-resistant alloys which included: 17-4 PH, INCONEL 718 and A286. These alloys were studied for different aging (heat) treatments. Slow strain rate tests (extension rate = 4.7 x 10^-5 mm/s) were performed on each alloy in four different environments; including air and natural seawater acidified with reagent grade hydrochloric acid to a pH of 0.1, 1 and 3. During the experiments, the load versus time and the open circuit potential were monitored. Various parameters such as time-to-failure, energy-to-failure, maximum or failure stress and reduction-in-area were calculated in order to determine SCC susceptibility. Fractography using SEM was conducted to confirm whether any SCC occurred and, if so, to identify its mode (intergranular or transgranular). Limited potentiodynamic studies were also completed to evaluate the passive behavior of these alloys. The results are discussed in terms of the SCC susceptibility and the nature of the cracking. An attempt was also made to correlate alloy microstructure, slow strain rate test parameters and passivation behavior with SCC susceptibility.
Show less - Date Issued
- 1991
- PURL
- http://purl.flvc.org/fcla/dt/14756
- Subject Headings
- Stress corrosion, Alloys--Stress corrosion, Metals--Stress corrosion
- Format
- Document (PDF)
- Title
- Characterization of nickel electrodes for secondary batteries by means of electrochemical impedance spectroscopy.
- Creator
- Nenov, Krassimir Petrov., Florida Atlantic University, Lipka, Stephen M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
An automated procedure for integrated cycling and electrochemical impedance spectroscopy (EIS) testing of nickel sinter individualized pressure vessel electrodes for secondary nickel/hydrogen batteries was developed. Nickel electrodes from three major U.S. manufacturers were cycled under various conditions. The condition of the electrodes was monitored using both EIS and traditional electrochemical methods. In order to establish relationships between the status of the electrodes and the...
Show moreAn automated procedure for integrated cycling and electrochemical impedance spectroscopy (EIS) testing of nickel sinter individualized pressure vessel electrodes for secondary nickel/hydrogen batteries was developed. Nickel electrodes from three major U.S. manufacturers were cycled under various conditions. The condition of the electrodes was monitored using both EIS and traditional electrochemical methods. In order to establish relationships between the status of the electrodes and the acquired impedance spectra, various cycling and electrode parameters were analyzed and compared with the EIS data. Nonlinear least squares (NLS) regression was used for analysis of the impedance data. An equivalent circuit was developed which produced good correlation with the impedance data at all states-of-charge and discharge rates. Problems with the experimental procedure which limit the validity of EIS testing were discussed.
Show less - Date Issued
- 1991
- PURL
- http://purl.flvc.org/fcla/dt/14777
- Subject Headings
- Impedance spectroscopy, Electrochemical analysis, Electric batteries--Electrodes
- Format
- Document (PDF)
- Title
- CVD synthesis of carbon nanotubes as active materials for electrochemical capacitors.
- Creator
- Merritt, Ryan Patrick., Florida Atlantic University, Lipka, Stephen M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Results are reported on a method to synthesize multi-wall carbon Nanotubes (MWNTs) using a liquid injection chemical vapor deposition (CVD) method centered around ferrocene as the catalyst precursor. These materials were specifically targeted as active materials for electrochemical double layer capacitors (EDLCs). A parameteric study was developed to optimize material synthesis based on growth parameters, characterize physical growth properties, and evaluate the performance of the MWNTs as...
Show moreResults are reported on a method to synthesize multi-wall carbon Nanotubes (MWNTs) using a liquid injection chemical vapor deposition (CVD) method centered around ferrocene as the catalyst precursor. These materials were specifically targeted as active materials for electrochemical double layer capacitors (EDLCs). A parameteric study was developed to optimize material synthesis based on growth parameters, characterize physical growth properties, and evaluate the performance of the MWNTs as electrodes in electrochemical capacitors. Physical data includes scanning electron micrographs (SEM), transmission electron micrographs (TEM), and x-ray powder diffraction (XRD). Electrochemical performance data is given based on cyclic voltammetry (CV) and impedance spectroscopy (EIS).
Show less - Date Issued
- 2003
- PURL
- http://purl.flvc.org/fcla/dt/13037
- Subject Headings
- Chemical vapor deposition, Electric double layer, Electrolytic capacitors, Nanotubes
- Format
- Document (PDF)
- Title
- Environmental cracking susceptibility of austenitic stainless steel alloys in acidified seawater.
- Creator
- Poulassichidis, Antonios N., Florida Atlantic University, Lipka, Stephen M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The stress corrosion cracking susceptibility of austenitic stainless steels SS304L, SS316L and SS904L was studied in an acidified seawater environment by slow strain rate testing at 24, 38 and 66$\sp\circ$C. Fractographic evidence of SCC susceptibility was obtained using scanning electron microscopy. The degree of susceptibility to SCC for each alloy in these environments is discussed based on the mechanical parameters, fractography and anodic polarization behavior. The results showed that...
Show moreThe stress corrosion cracking susceptibility of austenitic stainless steels SS304L, SS316L and SS904L was studied in an acidified seawater environment by slow strain rate testing at 24, 38 and 66$\sp\circ$C. Fractographic evidence of SCC susceptibility was obtained using scanning electron microscopy. The degree of susceptibility to SCC for each alloy in these environments is discussed based on the mechanical parameters, fractography and anodic polarization behavior. The results showed that SS904L performed better than SS304L and SS316L in the aforementioned environments.
Show less - Date Issued
- 1994
- PURL
- http://purl.flvc.org/fcla/dt/15071
- Subject Headings
- Stress corrosion, Seawater corrosion, Alloys--Stress corrosion
- Format
- Document (PDF)
- Title
- Lithium intercalation into PAN-based carbon fiber materials.
- Creator
- Nechev, Kamen S., Florida Atlantic University, Lipka, Stephen M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
High energy density PAN-based carbon fiber anode materials for lithium-ion type batteries were developed. Commercially available organic precursors were thermally converted to carbons. The effects of precursor material, carbonization temperature, heating ramp rate, soak time and gaseous atmosphere during the thermal treatment on the electrochemical performance of the carbon fibers were studied. In order to evaluate the electrochemical performance of the carbon fibers, test cells were assemble...
Show moreHigh energy density PAN-based carbon fiber anode materials for lithium-ion type batteries were developed. Commercially available organic precursors were thermally converted to carbons. The effects of precursor material, carbonization temperature, heating ramp rate, soak time and gaseous atmosphere during the thermal treatment on the electrochemical performance of the carbon fibers were studied. In order to evaluate the electrochemical performance of the carbon fibers, test cells were assemble using the carbon materials prepared in the laboratory and intercalation/deintercalation experiments were performed. The results indicated that the highest reversible capacity and lowest irreversible capacity loss was obtained for carbon fibers carbonized at 1100C at fast ramp rate of 26C/min. X-ray diffraction experiments revealed a relation between the capacity and the irreversible capacity loss on first cycle, and the size of the crystallites Lc. A phenomenological explanation for this behavior was developed. Using electrochemical impedance spectroscopy the diffusion coefficient of Li in the tested carbon fibers was calculated. In addition, the influence of electrolyte composition (solvent and salt) on the reversible and irreversible capacities as well as on the intercalation/deintercalation potential profile was investigated. An electrolyte containing 1M LiPF6 in EC:DEC:DMC (40:30:30 v/o) proved to be most suitable for these carbon fiber materials improving significantly their electrochemical performance. Finally, coin cells were assembled containing the carbon fiber material prepared in the laboratory. They were tested for reversible and irreversible capacity. The coin cells proved that the synthesized carbon anode materials possess high energy density and could be used in commercial applications.
Show less - Date Issued
- 1996
- PURL
- http://purl.flvc.org/fcla/dt/12471
- Subject Headings
- Lithium cells, Carbon fibers, Electric batteries
- Format
- Document (PDF)
- Title
- Fabrication and characterization of copper/molybdenum coatings on carbon fibers by electrodeposition.
- Creator
- Maucione, Luke J., Florida Atlantic University, Lipka, Stephen M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The codeposition of a smooth and uniform coating of copper and molybdenum was successfully achieved on T-650 carbon fiber. The effect of various plating parameters on the electrodeposition of copper and molybdenum such as plating bath chemistry, current density, and pulse frequency were studied. By adjusting the aforementioned variables, qualitative and quantitative analysis was conducted to evaluate the deposit smoothness, uniformity, and wetting characteristics. Qualitative analysis of the...
Show moreThe codeposition of a smooth and uniform coating of copper and molybdenum was successfully achieved on T-650 carbon fiber. The effect of various plating parameters on the electrodeposition of copper and molybdenum such as plating bath chemistry, current density, and pulse frequency were studied. By adjusting the aforementioned variables, qualitative and quantitative analysis was conducted to evaluate the deposit smoothness, uniformity, and wetting characteristics. Qualitative analysis of the deposits were made using scanning electron microscopy and energy dispersive spectroscopy. Quantitative analysis of the deposit coating was conducted using inductively coupled plasma chemical analysis, dewetting tests, X-ray diffraction, transmission electron microscopy, and auger electron spectroscopy. Based on the results, a plating line was designed and constructed for the continuous deposition of copper and molybdenum onto carbon fiber tows.
Show less - Date Issued
- 1995
- PURL
- http://purl.flvc.org/fcla/dt/15124
- Subject Headings
- Composite materials, Alloy plating, Metallic composites, Molybdenum alloys
- Format
- Document (PDF)
- Title
- Electrochemical double-layer capacitors utilizing low surface area graphite fibers.
- Creator
- Zawacki, David Isaiah., Florida Atlantic University, Lipka, Stephen M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Electrochemical double-layer capacitors were constructed using low surface area carbon fibers that are commercially available. The fibers were made from polyacrylonitrile (PAN) and pitch and vary from low (LC = 14A, d002 = 3.54A) to high (LC = 169A, d002 = 3.40A) crystallinity. High energy densities (up to 7.83 Wh/kg) were obtained by electrochemically intercalating HSO4- ions between the graphene planes of the carbon fibers. The intercalation process was strongly influenced by the...
Show moreElectrochemical double-layer capacitors were constructed using low surface area carbon fibers that are commercially available. The fibers were made from polyacrylonitrile (PAN) and pitch and vary from low (LC = 14A, d002 = 3.54A) to high (LC = 169A, d002 = 3.40A) crystallinity. High energy densities (up to 7.83 Wh/kg) were obtained by electrochemically intercalating HSO4- ions between the graphene planes of the carbon fibers. The intercalation process was strongly influenced by the crystallinity of the carbon fiber and by the precursors from which the fiber was manufactured. All the pitch fibers had a higher structural order and a higher carbon content than the PAN fibers. A total of 10 capacitors were constructed. Nine of these were constructed from fibers that were electrochemically activated and one was constructed from fiber as received. 38 w/o sulfuric acid was used as the electrolyte for each of these capacitors. Performance of the capacitors decreased as the structural order and carbon content of the fibers decreased.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/15427
- Subject Headings
- Capacitors, Electric double layer, Graphite fibers
- Format
- Document (PDF)
- Title
- Electrochemical intercalation of lithium-ion into carbon fibers prepared from synthetic cellulose precursor.
- Creator
- Kashauer, Robert Lewis., Florida Atlantic University, Lipka, Stephen M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
A number of fibrous carbon materials have been investigated as intercalation host materials. Commercially available rayon fiber (synthetic cellulose) based carbon fibers were synthesized for use as anode material in lithium-ion batteries. The effects of oxidation and carbonization temperature, heating ramp rate, soak time and gaseous atmosphere during thermal treatment on the electrochemical performance of the carbon fibers were studied. Intercalation/deintercalation experiments were...
Show moreA number of fibrous carbon materials have been investigated as intercalation host materials. Commercially available rayon fiber (synthetic cellulose) based carbon fibers were synthesized for use as anode material in lithium-ion batteries. The effects of oxidation and carbonization temperature, heating ramp rate, soak time and gaseous atmosphere during thermal treatment on the electrochemical performance of the carbon fibers were studied. Intercalation/deintercalation experiments were performed to evaluate the electrochemical performance of the carbon fibers. The highest reversible capacity and lowest irreversible capacity loss were obtained for carbon fibers carbonized at 1100C at a ramp rate of 10C/min held at soak times of 1 and 5 hours. Electrolyte containing 1M LiPF6 in 70/30 v/o EC:DMC proved to be most suitable for these carbon fiber materials. The influence of electrolyte composition (solvent and salt) on the reversible and irreversible capacities as well as on the intercalation/deintercalation potential profile were also studied.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/15452
- Subject Headings
- Carbon fibers, Lithium cells, Electrolytes
- Format
- Document (PDF)
- Title
- Electrochemical impedance spectroscopy of nickel-hydrogen and silver oxide-metal hydride secondary batteries.
- Creator
- Nechev, Kamen S., Florida Atlantic University, Lipka, Stephen M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Full nickel-hydrogen (Ni-H2) boilerplate batteries were cycled and impedance measurements were made at different states-of-charge (SOC), electrolyte concentrations and charge/discharge rates. Experiments were conducted on cells containing new and cycled (11,000 cycles) electrodes. Additionally, an EIS study of Ni-H2 flightweight IPV satellite cells was performed. A number of experiments were conducted on silver oxide-metal hydride batteries. The interest was focused on both negative and...
Show moreFull nickel-hydrogen (Ni-H2) boilerplate batteries were cycled and impedance measurements were made at different states-of-charge (SOC), electrolyte concentrations and charge/discharge rates. Experiments were conducted on cells containing new and cycled (11,000 cycles) electrodes. Additionally, an EIS study of Ni-H2 flightweight IPV satellite cells was performed. A number of experiments were conducted on silver oxide-metal hydride batteries. The interest was focused on both negative and positive electrodes and upon the system itself. This work was preliminary and aided in describing the general performance of the battery. For analysis, the data was fitted to an equivalent electrical circuit using the Nonlinear Least Squares Method (NLSM). The correlation between theoretical and empirical data was sufficiently good.
Show less - Date Issued
- 1993
- PURL
- http://purl.flvc.org/fcla/dt/14958
- Subject Headings
- Nickel-hydrogen batteries, Electrodes, Nickel, Impedance spectroscopy, Electrochemical analysis, Electric batteries--Electrodes
- Format
- Document (PDF)
- Title
- Effect of strain rate and temperature on the stress corrosion cracking tendency of engineering alloys in acidified seawater.
- Creator
- Kundalgurki, Srivatsa G., Florida Atlantic University, Lipka, Stephen M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The stress corrosion cracking (SCC) tendencies of several engineering alloys were studied in an acidified seawater environment as a function of applied strain rate and electrolyte temperature. The selected alloys included austenitic stainless steels 304L, 316L, 904L and A-286 (an iron-based superalloy at two heat treatments yielding ultimate tensile strengths of 130 and 200 ksi), Inconel 718 (220 ksi ultimate tensile strength) and Hastelloys C-22 and C-276. The slow strain rate test technique...
Show moreThe stress corrosion cracking (SCC) tendencies of several engineering alloys were studied in an acidified seawater environment as a function of applied strain rate and electrolyte temperature. The selected alloys included austenitic stainless steels 304L, 316L, 904L and A-286 (an iron-based superalloy at two heat treatments yielding ultimate tensile strengths of 130 and 200 ksi), Inconel 718 (220 ksi ultimate tensile strength) and Hastelloys C-22 and C-276. The slow strain rate test technique was used to evaluate the SCC strain rate dependency of each alloy at extension rates of 4.7 x 10^-6, 4.7 x 10^-4 and 4.7 x 10^-3 mm/sec. The effect of electrolyte temperature was evaluated at 38C and 60C at a single extension rate of 4.7 x 10^-5 mm/sec. Control specimens were tested in a laboratory air environment at an extension rate of 4.7 x 10^-5 mm/sec. Various mechanical parameters of the specimens tested in the corrosive medium were compared with those of control specimens to quantify the degree of cracking. Fractographic evidence of SCC was obtained using scanning electron microscopy (SEM). An attempt was made to correlate SCC tendency with the alloy's passivation kinetics and microstructure. Atmospheric exposure testing was performed in a simulated space shuttle launch pad environment for selected alloys.
Show less - Date Issued
- 1992
- PURL
- http://purl.flvc.org/fcla/dt/14853
- Subject Headings
- Alloys--Stress corrosion, Stress corrosion, Sea-water corrosion
- Format
- Document (PDF)