پوشش های آلومینیمی : شرح و سنجش

Aluminum Coatings: Description and Testing 
پوشش های آلومینیمی : شرح و سنجش

ABSTRACT

Pure aluminum, the 3xxx, 5xxx, and most 6xxx series alloys, are sufficiently resistant to be used in industrial atmospheres and waters without any protective coatings. Coatings are recommended for the higher strength 6xxx alloys, such as alloy 6013, and for all 2xxx and 7xxx alloys. The thickness of the natural oxide passive film can be increased by a factor of 10 by prefilming in hot water and by a factor of 1000 or more by anodizing in sulfuric acid. Different options for mechanical and chemical surface preparation are available depending on choice of coating, appearance, and/or performance. Weak organic acids and their derivatives form insoluble salts and rely on the adsorption of the hydrophobic anions to provide a thin barrier layer. Chelating inhibitors create a thin tenacious passive layer (up to 20 nm). Aluminum alloys are protected by more active metals or by cathodic protection. Corrosion can be prevented or reduced by cladding. Some joint-sealing compounds that contain suitable soluble inhibitors are particularly recommended. Aluminum can be protected by electroless or conventional plating. Aluminum and aluminum alloys in the active state act as a sacrificial anode in the form of plate or as a powder coating. Conversion layers can be created through physical vapor deposition, cathodic magnetron sputtering, high-energy ion beams, and laser ablation. Electrochemical anodization, plasma ablation, and chromate conversion coatings are frequently considered. There are thermoplastic coatings and converted coatings that are applied during or after processing and include principally three types of paints: epoxy, polyurethane, and moisture coatings. Corrosion monitoring is currently carried out by electrochemical impedance spectroscopy methods and electrochemical noise measurements.

آلومینات­ ها Aluminates

Aluminates

آلومینات­ ها

ABSTRACT

Aluminates form in binary systems with alkali, alkaline earth or rare-earth oxides and share the high melting point and resistance to chemical attack of the pure Al2O3 end-member. This means that these ceramics have a variety of applications as cements, castable ceramics, bioceramics, and electroceramics. Calcium aluminate cements are used for example in specialist applications as diverse as lining sewers and as dental restoratives. Ceramics in aluminate systems are usually formed from cubic crystal systems and this includes spinel and garnet. Rare earth aluminate garnets include the phase YAG (yttrium aluminium garnet), which is an important laser host when doped with Nd(III) and more recently Yb(III). Associated applications include applications as scintillators and phosphors. Aluminate glasses are transparent in the infrared region and these too have specialist applications, although the glass-forming ability is poor. Recently, rare earth aluminate glasses have been developed commercially in optical applications as alternatives to sapphire for use in, for example, infrared windows. Aluminates are refractory materials and their synthesis often simply involves solidstate growth of mixtures of purified oxides. Alternative synthesis routes are also used in specialist applications, for example in production of materials with controlled porosity and these invariably involve sol–gel methods. For glasses, one notable, commercially important method of production is container-less synthesis, which is necessary because of the non-Arrhenius (fragile) viscosity of aluminate liquids.

آلومینا Alumina

Alumina

آلومینا

ABSTRACT

The uses, processing, structure, and properties of alumina are summarized in this article. Various polymorphs of alumina and its phase relations with other oxides are described. The following properties are discussed: mechanical, thermal, thermodynamic, electrical, diffusional, chemical, and optical. Quantitative values for these properties are given in tables. The usefulness of alumina results from its high strength, melting temperature, abrasion resistance, optical transparency, and electrical resistivity. Traditional uses of alumina because of these properties are furnace components, cutting tools, bearings, and gem stones; more recent applications include catalyst substrates, tubes for arc lamps, and laser hosts. Possible new uses of alumina are in electronic circuits, optical components, and biomaterials. Alumina fibers for composites and optics must be pure, defect free, and cheap.

مروری بر مزایا و محدودیت های HPT

Advantages and limitations of HPT: a review

مروری بر مزایا و محدودیت های HPT

ABSTRACT

The improvements in the design of the HPT tools lead to a well defined torsiondeformation and permits, therefore, a comparison with other SPD-techniques. The design of thetools, the advantages and disadvantages of HPT, as well as the limitation in the sample size are discussed.For a long time torsion has been frequently used to determine the stress strain behaviour at large strains. In free torsion, the geometrical changes are usually very small. The fracture strain is significantly larger than in tensile experiments due to the vanishing macroscopic hydrostatic tension component of the stress. By applying an additional hydrostatic compression stress, the fracture strain can be further enhanced and can be increased to infinity at very high hydrostatic compression stresses.High pressure torsion, HPT, is a realisation of such a torsion experiment [1-3]. One can distinguish between constrained and unconstrained version.

مطالعه ه­ای تئوری بر روی بازدارنده­ های خوردگی مس در اسید نیتریک

A theoretical study on the inhibition efficiencies of some quinoxalines as corrosion inhibitors of copper in nitric acid

مطالعه ه­ای تئوری بر روی بازده­ های بازدارندگی چند مورد از کوین­اگزالات­ ها به عنوان بازدارنده­ های خوردگی مس در اسید نیتریک

ABSTRACT

Quantum chemical calculations based on DFT method were performed on three quinoxalines compounds namely ethyl 2-(4-(2-ethoxy-2-oxoethyl)-2-p-tolylquinoxalin-1(4H)-yl)acetate (Q1), 1-[4-acetyl-2-(4-chlorophenyl)quinoxalin-1(4H)-yl]acetone (Q2) and 2-(4-methylphenyl)-1,4- dihydroquinoxaline (Q3), used as corrosion inhibitors for copper in nitric acid media to determine the relationship between the molecular structure of quinoxalines and inhibition efficiency. Quantum chemical parameters such as the highest occupied molecular orbital energy (EHOMO), the lowest unoccupied molecular orbital energy (ELUMO), energy gap (DE), dipole moment (l), electronegativity (v), electron affinity (A), global hardness (g), softness (r), ionization potential (I), the fraction of electrons transferred (DN), and the total energy (TE), were calculated. The theoretically obtained results were found to be consistent with the experimental data reported.

یک بازدارنده خوردگی جدید برای محافظت مس

A new corrosion inhibitor for copper protection

یک بازدارنده خوردگی جدید برای محافظت مس

ABSTRACT

Methyl 3-((2-mercaptophenyl)imino)butanoate (MMPB) was synthesized as inhibitor compound for copper protection. The molecule was designed with azole, thiol functional groups and carboxylate tail group. The inhibition efficiency was examined in acidic chloride media, by means of various electrochemical and spectroscopy techniques. Electrochemical study results showed that high efficiency of MMPB was mainly related with its capability of complex formation with Cu(I) at the surface. The thiol group also improves the adsorptive interaction with the surface, as the carboxylate groups provide extra intermolecular attraction.

مطالعه امکان­پذیری فرآیند ریخته­ گری تحت­ فشار در خلأ

A feasibility study of the partial squeeze and vacuum die casting process

مطالعه امکان­پذیری فرآیند ریخته­ گری تحت­ فشار در خلأ و انقباض جزئی

ABSTRACT

A feasibility study of the partial squeeze and vacuum die casting process was performed to make defect-free casting products with excellent mechanical properties. The trial die casting process in this study was industrially implemented for producing a reaction shaft support made of a hyper eutectic Al±15%Si alloy. To combine the squeezing and vacuum effect, the plunger injection system was designed and attached to a chill vent type vacuum machinery system. The combination of the vacuum effect before injection and the squeezing effect after injection resulted in excellent defect-free die casting products. The uniform distribution of ®ne acicular eutectic and proeutectic silicon obtained from the trial process also provided excellent mechanical properties.

 

بازدارنده های جدید برای خوردگی مس

New inhibitors for copper corrosion

بازدارنده های جدید برای خوردگی مس

ABSTRACT

The study of the effectiveness of several potential copper corrosion inhibitors in acidic media was studied. The investigated thiazole derivative functional groups contain heterocyclic atoms such as nitrogen, sulfur, and oxygen. Thiazole derivatives, 5-benzylidene- 2,4-dioxotetrahydro-1,3-thiazole (BDT) 5-(4′-isopropylbenzylidene)-2,4-dioxotetrahydro- 1,3-thiazole (IPBDT), 5-(3′-thenylidene)-2,4-dioxotetrahydro-1,3-thiazole (TDT), and 5-(3′,4′-dimetoxybenzylidene)-2,4-dioxotetrahydro-1,3-thiazole (MBDT) were tested for copper corrosion inhibition properties. The electrolyte solution was 0.1 M Na2SO4. In situ information on corrosion and inhibition processes can be obtained using different techniques. Electrochemical measurements (EIS), in situ scanning probe microscopy (SPM), in addition to quartz crystal microbalance (QCM) measurements were applied. Those methods are very useful owing to their high sensitivity and resolution. Dynamic STM and AFM measurements on Cu(111) single-crystal electrode with and without the addition of some inhibitors were performed. The presence of the isopropyl group in the case of IPBDT produced far better protection against copper corrosion in acidic sulfate-containing media than the rest of the derivatives.

مرکپتوبنزواکسازول بعنوان بازدارنده ی خوردگی مس در محیط کلریدی

: Mercaptobenzimidazole as a copper corrosion inhibitor
 Long-term immersion, 3D-profilometry, and electrochemistry

مرکپتوبنزواکسازول بعنوان بازدارنده ی خوردگی مس در محیط کلریدی: الکتروشیمی، پروفیل سنجی سه بعدی، آنالیز سطحی XPS

ABSTRACT

The high corrosion inhibition effectiveness of 2-mercaptobenzimidazole (MBIH) in 3 wt.% aqueous NaCl solution is reported using long term immersion tests, 3D-profilometry, electrochemical impedance spectroscopy, and potentiodynamic curve measurements. The high corrosion inhibition performance was proven after 180 days of immersion. The impedance spectra were characterized by two time constants relating to charge transfer and finite layer thickness or semi-infinite diffusion of copper ions through the surface layer, therefore Cu corrosion in solution containing MBIH follows kinetic-controlled and diffusion- controlled processes. Moreover, it is shown that MBIH is a mixed-type inhibitor.

 

پوشش های هوشمند خود تمیز شونده جهت حفاظت از اکسیداسیون

Smart self-cleaning coatings for corrosion protection

پوشش های هوشمند خود تمیز شونده جهت حفاظت از اکسیداسیون

ABSTRACT

Self-cleaning surfaces have attracted signifi cant attention in recent years for their potential in both fundamental research and practical applications. Under the scope of self-cleaning smart coatings, this chapter explores the principal features of materials that can be used as protective coatings with an emphasis on the photocatalytic materials that have been developed to date. The chapter also highlights the importance of using titanium dioxide (TiO 2 ) as a semiconductor material in industrial applications since it can act as a photoanode for metal cathodic protection.