Lithium-aluminum-carbonate-hydroxide hydrate coatings on aluminum alloys: Composition, structure, and processing bath chemistry

1996 ◽  
Vol 11 (6) ◽  
pp. 1507-1513 ◽  
Author(s):  
C.A. Drewien ◽  
M. O. Eatough ◽  
D. R. Tallant ◽  
C. R. Hills ◽  
R. G. Buchheit
Keyword(s):  
Crystal Structure ◽  
Aluminum Alloys ◽  
Bulk Material ◽  
Lithium Carbonate ◽  
Lithium Aluminum ◽  
Nominal Composition ◽  
Al Alloy ◽  
Carbonate Hydroxide ◽  
Coating Formation ◽  
Composition Structure

A new corrosion resistant coating, being designed for possible replacement of chromate conversion coatings on aluminum alloys, was investigated for composition, structure, and solubility using a variety of techniques. The stoichiometry of the material, prepared by immersion of 1100 Al alloy into a lithium carbonate-lithium hydroxide solution, was approximately Li2Al4CO3(OH)12 · 3H2O. Processing time was shown to be dependent upon the bath pH, and consistent coating formation required supersaturation of the coating bath with aluminum. The exact crystal structure of this hydrotalcite material, hexagonal or monoclinic, was not determined. It was shown that both the bulk material and coatings with the same nominal composition and crystal structure could be formed by precipitation from an aluminum supersatured solution of lithium carbonate.

Copper enrichment on Al 2024 surface after de-oxidizing treatment

1993 ◽  
Vol 51 ◽  
pp. 860-861
Author(s):  
C. A. Drewien ◽  
R. G. Buchheit ◽  
K. R. Zavadil ◽  
T. E. Neil
Keyword(s):  
Aluminum Alloys ◽  
Salt Spray ◽  
Lithium Carbonate ◽  
Salt Spray Test ◽  
Lithium Aluminum ◽  
General Corrosion ◽  
Corrosion Properties ◽  
Carbonate Hydroxide ◽  
Processing Step ◽  
Aluminum Part

Coatings of lithium-aluminum-carbonate-hydroxide are being developed for corrosion protection of aluminum alloys against atmospheric and saline environments. Coating is performed by immersion of the aluminum part into a lithium carbonate-lithium hydroxide solution of pH=11.5. Before coating, the aluminum alloy is degreased in trichloroethylene, cleaned in a sodium carbonate-sodium silicate bath, and de-oxidized in nitric acid containing ammonium biflouride. Coating of most aluminum alloys is easily accomplished, and the coatings pass the ASTM B117 salt spray test. However, aluminum alloys that contain copper, specifically 2024-T3 and 7075-T6, yield coatings that fail the salt spray test, i.e. pitting and general corrosion is observed. Photographs of coatings after 168 hr salt spray exposure are shown in Figure 1 for Al 1100 and 2024-T3 alloys. A study has been undertaken to determine the influence of copper upon the corrosion properties of the coating.The surface of 2024-T3 was analyzed after each processing step in order to determine if copper enrichment at the specimen surface was occurring.

Analysis of Mixtures of Gamma Lithium Aluminate, Lithium Aluminum Carbonate Hydroxide Hydrate, and Lithium Carbonate

1997 ◽  
Vol 496 ◽  
Author(s):  
M. T. Nemeth ◽  
R. B. Ford ◽  
T. A. Taylor
Keyword(s):  
Ceramic Powder ◽  
Lithium Carbonate ◽  
Lithium Aluminum ◽  
Carbonate Content ◽  
Lithium Aluminate ◽  
Molten Carbonate ◽  
X Ray Diffraction ◽  
Carbonate Hydroxide ◽  
Molten Carbonate Fuel Cells ◽  
Hydroxide Hydrate

ABSTRACTLithium aluminate, LiA1O2is a ceramic powder which is used as the porous solid support for the electrolyte in molten carbonate fuel cells (MCFCs). It has previously been reported that gamma LiAlO2will convert to lithium aluminum carbonate hydroxide hydrate, Li2Al4(CO3)(OH)123H2O and Li2CO3when exposed to water vapor and carbon dioxide. We compare three techniques, weight gain, carbonate content and x-ray diffraction to measure the amount of conversion. The reaction may involve amorphous intermediates and no one technique by itself is satisfactory to study the conversion.

scholarly journals Investigation of Solvatomorphism and Its Photophysical Implications for Archetypal Trinuclear Au3(1-Methylimidazolate)3

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4404
Author(s):  
Shengyang Guan ◽  
David C. Mayer ◽  
Christian Jandl ◽  
Sebastian J. Weishäupl ◽  
Angela Casini ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Density Functional ◽  
Bulk Material ◽  
Variable Temperature ◽  
Active Phase ◽  
Solvent Free ◽  
X Ray Diffraction ◽  
X Ray ◽  
Aurophilic Interactions

A new solvatomorph of [Au3(1-Methylimidazolate)3] (Au3(MeIm)3)—the simplest congener of imidazolate-based Au(I) cyclic trinuclear complexes (CTCs)—has been identified and structurally characterized. Single-crystal X-ray diffraction revealed a dichloromethane solvate exhibiting remarkably short intermolecular Au⋯Au distances (3.2190(7) Å). This goes along with a dimer formation in the solid state, which is not observed in a previously reported solvent-free crystal structure. Hirshfeld analysis, in combination with density functional theory (DFT) calculations, indicates that the dimerization is generally driven by attractive aurophilic interactions, which are commonly associated with the luminescence properties of CTCs. Since Au3(MeIm)3 has previously been reported to be emissive in the solid-state, we conducted a thorough photophysical study combined with phase analysis by means of powder X-ray diffraction (PXRD), to correctly attribute the photophysically active phase of the bulk material. Interestingly, all investigated powder samples accessed via different preparation methods can be assigned to the pristine solvent-free crystal structure, showing no aurophilic interactions. Finally, the observed strong thermochromism of the solid-state material was investigated by means of variable-temperature PXRD, ruling out a significant phase transition being responsible for the drastic change of the emission properties (hypsochromic shift from 710 nm to 510 nm) when lowering the temperature down to 77 K.

An x-ray Fourier line shape analysis in cold-worked hexagonal magnesium base alloys

1990 ◽  
Vol 5 (10) ◽  
pp. 2120-2125 ◽  
Author(s):  
S. K. Chattopadhyay ◽  
S. K. Chatterjee ◽  
S. P. Sen Gupta
Keyword(s):  
Rare Earth ◽  
Line Shape ◽  
Cold Work ◽  
Domain Size ◽  
Pure Magnesium ◽  
Nominal Composition ◽  
Al Alloy ◽  
X Ray ◽  
Microstructural Parameters ◽  
Cold Worked

Detailed Fourier line shape analyses considering x-ray diffraction profiles from fault unaffected 10.0, 00.2, 11.0, 20.0, 11.2, and 00.4 reflections and fault affected 10.1, 10.2, 10.3, 20.1, 20.2, 10.4, and 20.3 reflections have been performed on three magnesium base hexagonal alloys used extensively in the aircraft industry. The first of the three alloys (Mg–Al–Mn, Alloy I) had the nominal composition in wt.% of Al-8.3, Mn-0.35, Si-0.2, Cu-0.12, Fe-0.2, and other 0.01; the second alloy (Mg–Zn–Mn, Alloy II) had the nominal composition in wt.% of Zn-4.0, Mn-0.15, Si-0.01, Cu-0.03, Fe-0.01, Zr-0.70, and rare earth elements-1.50; and the last of the alloys (Mg–Zn–Al, Alloy III) had the nominal composition in wt.% of Zn-4.3, Al-0.15, Mn-0.01, Si-0.03, Cu-0.01, Ni-0.005, Zr-0.6, and rare earth-1.4. The microstructural parameters determined in these analyses indicated the average domain size in alloys I, II, and III as 208 Å, 314 Å, and 400 Å, respectively. The deformation fault densities, α, in these alloy systems (∼54 ⊠ 10−3, 35 ⊠ 10−3, and 28 ⊠ 10−3, respectively, in alloys I, II, and III) were found to be appreciably high compared to the earlier work on pure magnesium (0.63 ⊠ 10−3). The deformation twin fault density, β, which was found to be negligible in pure magnesium (∼0.21 ⊠ 10−3), was found to be negative here, also indicating the negligible presence of twin faults in these alloys. These results establish that on cold work the solutes introduce deformation stacking faults in an appreciable quantity in magnesium which is not normally susceptible to faulting when in pure form. Of these three alloys, however, Alloy I (Mg–Al–Mn) was found to be the most prone to deformation faulting.

Fabrication and Characterization of Bulk Nanocrystalline Layer in Steel and Aluminum Alloys Formed by Shot Peening

2009 ◽  
Author(s):  
R. Waikar ◽  
Y. B. Guo ◽  
Keith A. Woodbury
Keyword(s):  
Aluminum Alloys ◽  
Shot Peening ◽  
Martensitic Steel ◽  
Bulk Material ◽  
Lower Surface ◽  
Martensitic Steels ◽  
Cross Sectional ◽  
Bulk Nanocrystalline ◽  
Nanocrystalline Layer

The formation of bulk nanocrystalline (NC) layers in AISI 1075 pearlitic and martensitic steels and aluminum alloys 6061-T6 and 7075 using air blast shot peening was studied. The cross-sectional microstructure of the samples showed a gradual reduction of the grain size near the surface. The NC layers were characterized using optical and scanning electron microscopy and nanohardness measurements. 2D surface topography of the top surface was also carried out. The roughness of the peened surfaces depends on sample hardness. The hardened AISI 1075 martensitic steel had lower surface roughness value. NC layers of 5 to 15 μm thickness were observed in the steels whereas the aluminum alloys 6061 and 7075 yielded NC layers up to 20 to 25 μm thick. The measured nanohardness in the NC layers confirmed the higher hardness of the NC layer compared with the bulk material.

scholarly journals Corrosion of the Welded Aluminium Alloy in 0.5 M NaCl Solution. Part 2: Coating Protection

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2177 ◽  
Author(s):  
Andrey Gnedenkov ◽  
Sergey Sinebryukhov ◽  
Dmitry Mashtalyar ◽  
Igor Vyaliy ◽  
Vladimir Egorkin ◽  
...  
Keyword(s):  
Aluminium Alloy ◽  
Welded Joint ◽  
Electrochemical Impedance ◽  
Corrosion Behaviour ◽  
Weld Interface ◽  
Open Circuit ◽  
Al Alloy ◽  
Protective Properties ◽  
Coating Formation ◽  
Electrode Technique

The high electrochemical activity of the aircraft 1579 aluminium alloy with a welded joint and the necessity of the coating formation to protect this material against corrosion as well as to increase the stability of the weld interface in the corrosive medium has been previously established. In this work, two suggested methods of protective coating formation based on plasma electrolytic oxidation (PEO) in tartrate-fluoride electrolyte significantly increased the protective properties of the welded joint area of the 1579 Al alloy. The electrochemical properties of the formed surface layers have been investigated using SVET (scanning vibrating electrode technique) and SIET (scanning ion-selective electrode technique), EIS (electrochemical impedance spectroscopy), OCP (open circuit potential), and PDP (potentiodynamic polarization) in 0.5 M NaCl. The less expressed character of the local electrochemical processes on the welded 1579 Al alloy with the composite coating in comparison with the base PEO-layer has been established. Polymer-containing coatings obtained using superdispersed polytetrafluoroethylene (SPTFE) treatment are characterized by the best possible protective properties and prevent the material from corrosion destruction. Single SPTFE treatment enables one to increase PEO-layer protection by 5.5 times. The results of this study indicate that SVET and SIET are promising to characterize and to compare corrosion behaviour of coated and uncoated samples with a welded joint in chloride-containing media.

scholarly journals The influence of multifunctional microalloyed ceramics microstructure on its capacity properties

2018 ◽  
Vol 15 (2) ◽  
pp. 187-199
Author(s):  
Jelena Purenovic ◽  
Nedeljko Ducic ◽  
Branko Matovic ◽  
Milovan Purenovic
Keyword(s):  
Crystal Structure ◽  
Dielectric Constant ◽  
Electrical Properties ◽  
Electrical Resistance ◽  
Ceramic Materials ◽  
Porous Ceramics ◽  
Electrophysical Properties ◽  
Microstructural Properties ◽  
Structure Morphology ◽  
Composition Structure

Modified porous alumo-silicate ceramics, alloyed with magnesium and microalloyed with aluminum, belongs to modern multifunctional ceramic materials. Microalloying has led to important changes in dielectric and electrical properties of ceramics, such as dielectric constant and electrical resistance. These changes are conditioned by the microstructural properties of modified porous ceramics. The obtained results have shown the unity of the influence of composition, structure, morphology and application of microalloyed multifunctional alumosilicate ceramics on electrophysical properties. Microstructural investigations have shown that this type of ceramics has an amorphous-crystal structure, which causes important changes in its electrical properties and affects its activity. Therefore the ceramics can be considered as an active dielectric. A correlation between microstructural properties and structurally sensitive, i.e. electrophysical properties of microalloyed multifunctional alumo-silicate ceramics, was confirmed.

Molybdate-Based Conversion Coatings for Aluminum Alloys Part I: Coating Formation

2013 ◽  
Vol 45 (28) ◽  
pp. 1-12 ◽  
Author(s):  
D. Rodriguez ◽  
R. Misra ◽  
D. Chidambaram
Keyword(s):  
Aluminum Alloys ◽  
Conversion Coatings ◽  
Coating Formation

Effect of Aluminum Concentration And Boron Dopant on Environmental Embriitlement In Feal Aluminides

1990 ◽  
Vol 213 ◽  
Author(s):  
C. T. Liu ◽  
E. P. George
Keyword(s):  
Aluminum Alloys ◽  
Grain Boundaries ◽  
Aluminum Concentration ◽  
Al Alloy ◽  
Test Environment ◽  
Environmental Embrittlement ◽  
Boron Doped ◽  
Weak Boundaries ◽  
Boron Dopant ◽  
Strong Segregation

ABSTRACTThe room-temperature tensile properties of FeAl aluminides were determined as functionsof aluminum concentration (35 to 43 at. % Al), test environment, and surface (oil) coating. The two lower aluminum alloys containing 35 and 36.5% Al are prone to severe environmental embrittlement, while the two higher aluminum alloys with 40 and 43% Al are much less sensitive to change in test environment and surface coating. The reason for the different behavior is that the grain boundaries are intrinsically weak in the higher aluminum alloys, and these weak boundaries dominate the low ductility and brittle fracture behavior of the 40 and 43% Al alloys. When boron is added to the 40% Al alloy as a grain-boundary strengthener, the environmental effect becomes prominent. In this case, the tensile ductility of the boron-doped alloy, just like that of the lower aluminum alloys, can be dramatically improved by control of test environment (e.g. dry oxygen vs air). Strong segregation of boron to the grain boundaries, with a segregation factor of 43, was revealed by Auger analyses.

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