Aluminium chemical properties

GENERAL PROPERTIES OF THE CUPRO-ALUMINIUMS Chemical Properties. 

This example of aluminium illustrates the importance of the protective him, and hlms that are hard, dense and adherent will provide better protection than those that are loosely adherent or that are brittle and therefore crack and spall when the metal is subjected to stress. The ability of the metal to reform a protective him is highly important and metals like titanium and tantalum that are readily passivated are more resistant to erosion-corrosion than copper, brass, lead and some of the stainless steels. There is some evidence that the hardness of a metal is a signihcant factor in resistance to erosion-corrosion, but since alloying to increase hardness will also affect the chemical properties of the alloy it is difficult to separate these two factors. Thus althou copper is highly susceptible to impingement attack its resistance increases with increase in zinc content, with a corresponding increase in hardness. However, the increase in resistance to attack is due to the formation of a more protective him rather than to an increase in hardness. 

When controlled nitridation of surface layers is required, as for example in the modification of the chemical properties of the surface of a support, the atomic layer deposition (ALD) technique can be applied." This technique is based upon repeated separate saturating reactions of at least two different reactants with the surface, which leads to the controlled build-up of thin films via reaction of the second component with the chemisorbed residues of the first reactant. Aluminium nitride surfaces have been prepared on both alumina and silica supports by this method wherein reaction cycles of trimethylaluminium and ammonia have been performed with the respective supports, retaining their high surface areas." This method has been applied to the modification of the support composition for chromium catalysts supported on alumina." ... 

The most intriguing difference between the chemical properties of cyclopolysilanes and those of cycloalkanes is the ability of the former to form either anion or cation radicals upon one-electron reduction or oxidation, respectively. For example, the cyclic pentamer (Mc2Si)5 is reduced to the corresponding radical anion by sodium-potassium alloy in diethyl ether [see eqn (4.1) in Section 4.1.3], whereas the hexamer (Me2Si)6 is oxidised by aluminium trichloride in dichlor-omethane to the corresponding cation radical. In both cases the EPR spectra of the radical ions can be interpreted in terms of a-electron delocalisation over the entire polysilane ring (see Section 10.1.4.1). In this respect, the cyclosilanes resemble aromatic hydrocarbons rather than their aliphatic analogues. 

In table 11.6.3 some chemical properties of an aluminium oxide (trade name Biolox) are compared with those of some other metals. 

Nitric acid is a colourless liquid at room temperature and atmospheric pressure. It is soluble in water in all proportions and there is a release of heat of solution upon dilution. This solubility has tended to shape the process methods for commercial nitric acid manufacture. It is a strong acid that almost completely ionizes when in dilute solution. It is also a powerful oxidizing agent with the ability to passivate some metals such as iron and aluminium. A compilation of many of the physical and chemical properties of nitric acid is presented in Table A.1 of Appendix A. Arguably the most important physical property of nitric acid is its azeotropic point, this influences the techniques associated with strong acid production. The constant-boiling mixture occurs at 121.9°C, for a concentration of 68.4%(wt) acid at atmospheric pressure. 

In modern technical alloys, which almost all consist of a large number of components, the presence or absence of traces of some elements plays an extraordinarily great role in determining the mechanical properties. We have previously seen how it is just in the metals that such a great influence of traces can become manifest. The individual, typically chemical properties of the admixed elements usually play only a minor role in this (compare on the other hand de-oxidation of steel by aluminium or sodium). 

VH.16 BERYLLIUM, Be (At 9 01) Beryllium is a greyish-white, light but very hard, brittle metal. It dissolves readily in dilute acids. In its compounds beryllium is divalent, otherwise it resembles closely aluminium in chemical properties it also exhibits resemblances to the alkaline earth metals. The salts react acid in aqueous solution, and possess a sweet taste (hence the name glucinum formerly given to the element). Beryllium compounds are highly poisonous. 

The chemical properties of the early members of the series are similar to those of calcium but, with increasing atomic number, these give place to other properties more like those of aluminium. At the same time there is a progressive increase in the solubility of the potassium double sulphates. 

Section 1 considers the methods of synthesis and physico-chemical properties of new types of inorganic sorbents (complex carbon-mineral sorbents, co-precipitated hydroxides, functional polysiloxane sorbents, porous glasses with controlled porosity, colloidal silicas, aluminium oxyhydroxide colloids, apatites). These sorbents are widely used in scientific investigations, in chemical practice and are important from a technological point of view. The presented results provide additional possibilities for the preparation of inorganic sorbents possessing unique adsorption and catalytic properties. Moreover, Section 1 presents the possibilities of the computational studies on the design of synthetic materials for selective adsorption of different substances. 

Beryllium (Be, at. mass 9.012) forms cations Be ". In its chemical properties, beryllium resembles magnesium and aluminium. Beryllium hydroxide is precipitated at pH 6, and dissolves in alkali hydroxides. Freshly precipitated Be(OH)2 dissolves in NaaCOs solution to form a rather unstable carbonate complex. Beryllium also forms weak complexes with citrate, tartrate, and fluoride anions. Beryllium and its compounds are highly toxic. 

Scandium (Sc, at. mass 44.96) occurs in its compounds exclusively in the III oxidation state. Some of its chemical properties resemble those of the lanthanides and yttrium. Scandium hydroxide Sc(OH>3 precipitates at a pH as low as 4.8 and dissolves in alkaline medium in this respect scandium resembles aluminium. 

As for magnesium oxide, it should be mentioned that this drops out of the dependence for alkaline-earth oxides, because the chemical properties of magnesium are closer to those of aluminium than to the properties of other members of alkali-metal subgroup (it is the so-called diagonal periodicity). The dependence of oxide solubilities against their melting points exists for the... 

Some elements appear in more than one group because they have more than one important function. In addition, chemical properties overlap. The arrangement in Table 2.1a implies only that the elements in each group exhibit similar, rather than identical, behavior in soils. Table 2.1a does little to indicate the relative importance of the chemical elements. Certain elements dominate soil reactions because of their greater abundance, because of the rapidity of their reactions, or because they are a source of energy. For example, all transition metal ions and aluminium produce acid-... 

Discussion In some of the preceding experiments, the importance has been emphasized of studying the behavior of the hydroxides of the elements with acids, with sodium hydroxide, and with ammonium hydroxide, as showing the base- or acidforming properties of the elements, their ability to form complex or substituted compounds with ammonia, and the means of distinguishing compounds of one element from those of others. The following experiments on aluminium hydroxide are designed to show the chemical properties of this element in these same respects. 

Only at the end of the article were there a few words about Mendeleev s note. Boisbaudran admitted that he had read it with great interest since classification of simple substances interested him for a long time. He had never known about Mendeleev s prediction of eka-aluminium properties but it did not matter Boisbaudran believed that his discovery of gallium was facilitated by his own laws of spectral lines of elements with similar chemical properties. In his opinion, spectral analysis played a decisive role. And not a word that Mendeleev in his prediction of eka-aluminium also underlined the prominent role of spectral analysis in the discovery of the new element. According to Boisbaudran, Mendeleev s predictions had nothing to do with the discovery of gallium. 

In this paper Mendeleev made some bold and confident assertions. He had previously predicted the existence of two undiscovered elements analogous to aluminium and silicon and lying between zinc and arsenic. He now forecast the existence of a third, similar in properties to boron, and lying between calcium and titanium. He christened the three elements eka-aluminium, eka-silicon and eka-boron, and using the periodic law he made extremely detailed predictions of their physical and chemical properties. 

Plasma electrolytic oxidation (PEO) is an efficient method for production of functional ceramic surface layers on non-ferrous metals, such as aluminium, magnesium, zirconium and titanium alloys. During PEO process the electrochemical reaction of anodic oxidation on the metal surface is assisted by micro-discharge events to promote formation of thick, hard and well-adhered oxide ceramic surface layers with specific morphologies and phase compositions, exhibiting superior protective performance and other useful electro-physical and chemical properties. ... 

Moreover, some of the gases have chemical properties (corrosive, highly toxic, self-igniting) that require the use of special equipment on the compressed gas containers (i.e. remotely controlled, pneumatically operated cylinder valves, flow restrictors, metal-to-metal seal between cylinder valve and process lines). Containers for electronic gases are subject to special cleaning procedures to remove particles, organic impurities, deposits and corrosion products from their inner surface. Depending on the chemical properties of the respective product and the speciflc demands in the respective field of application, apart from the usual steel containers also inside polished containers of steel, stainless steel or aluminium are used. 

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