Chemical and physical properties of presymptomatic and symptomatic aluminium hydroxide crystalline.
The chemical and physical properties of both the multisodium and mono-potassium aluminium hydroxides crystalline, previously isolated from the dialysate of dialysis patients affected by aluminium disease, have been investigated. The purity of the preparations used in the analysis was verified by X-ray powder diffraction, X-ray fluorescence, infrared and differential thermal analysis. Water content (wt.%) was determined as was the percentage content of different elements. Furthermore, the chemical properties, such as the acidity and alkalinity, the percentage content of aluminum, the cation exchange capacity, as well as the amount and the type of cations, mostly the crystalline sodium and potassium ions, were also determined. A surface analysis of the mineral particles was carried out by means of the measurement of a variety of physicochemical and elemental parameters. The surface properties were found to be closely related to the hydration state of the substance. Regarding the chemical properties, a mono-potassium sample exhibited a slightly acidic pH (3.7), a cation exchange capacity of 17.5 mequiv x H(2)O/100 g, as well as a content of sodium ions in the crystalline phase of 55.9%, whilst the sodium content was 32.2% in the amorphous fraction. The multisodium alumina sample had a very similar behavior, except for the higher alkalinity and less cations present in the amorphous fraction. According to the literature, amorphous aluminium hydroxide, formed by the slow precipitation of the alumina, is richer in potassium than the crystalline precipitate, whereas the latter is more acidic. Thus, the phenomenon of amorphization of the hydroxide and the precipitation of the crystalline phases during the early stages of the disease must be envisaged as a probable explanation of the similar chemical and physical properties of the two forms of the aluminium hydroxides.The Online Financial Aid Office is responsible for the advising and counseling of students applying for financial aid. This group prepares the students for their admissions interview. The office is responsible for processing and recording all applications.
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price tablet and mobile pdf Â· TravellerLevelB2teachersBook The book was launched at the Whistler Museum. have been long-standing collaborators, working on mezzotint engraving projects together.1. Field of the Invention
The invention relates generally to semiconductor processing, and more particularly to the fabrication of semiconductor devices.
2. Background of the Related Art
Semiconductor technology, especially microelectronics, has experienced extraordinary gains in the past quarter century. A major part of the progress is due to the use of aluminum and aluminum alloys for metallization, especially interconnection metallization. However, with this rapid progress, a major obstacle to further progress is reliability and quality, especially adhesion between the interconnection metallization and the passivation layer.
There are two basic categories of passivation layers used for integrated circuits: organic and inorganic. Organic passivation layers generally provide passivation against moisture and/or oxygen, and are typically made from photoresist or polyimide. Although these organic layers perform well for their intended purposes, they have several drawbacks including poor adhesion to metallic layers. This means that, after etching away the passivation layer, delamination occurs between the metallic layers and the passivation layer. As the dimensions for integrated circuits continue to shrink, it becomes increasingly difficult to fabricate a reliable structure, especially when the dimensions approach and sometimes exceed the critical dimensions of the materials used to fabricate the structure. The passivation of the underbump metallurgy (UBM) structure is particularly challenging because of the small critical dimensions and the high aspect ratio of the UBM.
While an inorganic passivation layer is typically amorphous, organic passivation layers are predominantly crystalline. This crystal orientation provides strength and adhesion. However, this inherent crystal orientation is incompatible with the orientation of the contact used to etch out the UBM. The etch used to etch the contact through the passivation layer is not anisotropic, which means that a portion of the etching proceeds through the organic passivation layer itself. This results in undercut (etching downward into the passivation layer) and undercut etching of the UBM. UBM undercut, in turn, results in a weakening of the UBM.
Consequently, a need exists for a passivation layer that can be deposited over a UBM structure without causing increased undercut