Iron phosphates structure

Several other iron phosphate structures have been described. The phase Li3Fe2(P04)3 has been stud-... 

In the development of a reactive non-chrome post-treatment, a variety of phenolic resins were synthesized and commercial phenolic resins evaluated. It was found that phenol-formaldehyde resins, creso1-forma1dehyd e condensates, ortho-novo 1 ak resins, and phenol-formaldehyde emulsions gave positive results when employed as post-treatments over zinc and iron phosphate conversion coatings. The above materials all possessed drawbacks. The materials in general have poor water solubility at low concentrations used in post-treatment applications and had to be dried and baked in place in order to obtain good performance. The best results were obtained with poly-4-vinylphenol and derivatives thereof as shown in the following structure (8,9,10)... 

The quality observed with "Mannich" derivatives of polyvinylphenol is affected by the concentration, time of treatment, temperature, pH, and whether or not a final deionized water rinse is used. The results shown in Tables I-III below represent evaluations conducted for poly-[methy1(2-hydroxyethy1)amino]methyl-4-vinylphenol, as shown in Structure I. Post-treatments based on polyvinylphenols overcome deficiencies observed with previous chrome-free rinses, since these systems are reactive and a final water rinse actually improves performance as is illustrated in Table I where the new non-chrome system is evaluated on Bonderite 1000, an iron phosphate conversion coating, as a function of concentration with and without a final water rinse. It is also... 

The "Mannich" adduct synthesized from the condensation of formaldehyde, 2-(methylamino)ethanol and poly-4-vinylphenol as shown in Structure I, has been evaluated as a function of molecular weight versus corrosion resistance as measured by salt spray and humidity tests on Bonderite 1000, an iron phosphate conversion coating. The molecular weight of the polymer was varied from approximately = 2,900 to 60,000. The corrosion resistance results were essentially equivalent over the molecular weight range evaluated. 

Ferritin, found in plants, animals, and some bacteria, serves as a reserve of iron for iron-proteins, such as those of respiration, photosynthesis, and DNA synthesis, as well as providing a safe site for detoxification of excess iron. The structure of ferritin, unique among proteins, is a protein coat of multiple, highly conserved polypeptides around a core of hydrous ferric oxide with variable amounts of phosphate. 

Badyal, Y., Karabulut, M. et al. 1999. The effect of uranium on the structure of iron phosphate glasses. Materials Research Society Symposium Proceedings, 556, 297—304. 

Bonding operations frequently require the mechanical or chemical removal of loose oxide layers from iron and steel surfaces before adhesives are applied. To guard against slow reaction with environmental moisture after the bond has formed, iron and steel surfaces are often phosphated prior to bonding. This process converts the relatively reactive iron atoms to a more passive, chemically stable form that is coated with zinc or iron phosphate crystals. Such coatings are applied in an effort to convert a reactive and largely unknown surface to a relatively inert one whose structure and properties are reasonably well understood. 

We now examine a few select examples of three-dimensional metal phosphate structures. A novel iron phosphate, [(C4N3H16)(C4N3H15)] [Fe5F4(H2P04)(HP04)3(P04)3]H20, was prepared recently by employing hydro-thermal methods in the presence of diethylenetriamine (DETA) [29]. The three-dimensional structure can be considered as made from layers along... 

As mentioned above, the iron phosphate-oxalate layers in this material are cross-linked by the (out-of-plane) oxalate units as in most of the phosphate-oxalates. It is interesting that similar dual functionality has also been observed in the zinc oxalate described earlier. The zinc oxalate also contains both the inplane and out-of-plane oxalate linkages to create three-dimensional connectivity, and possessing channels [45]. In Fig. 7.38, we show the structure of this material to illustrate the presence of the oxalates within the layers as well as a bridge between the layers. This dual functionality of the oxalate units, in the Zn oxalate, gives rise to an elliptical aperture made by the linkages between 10 Zn and 10 oxalate units within the same plane, with the other oxalate unit... 

The products of such reactions depend upon the pressure, temperature, pH, phosphate, and cation concentrations, and may be difficult to predict or rationalize. For example, the equation (3) produces an acid phosphate and a phosphate hydroxide. Microporous aluminophosphates and related phases (see Section 5.1.2) are prepared in hydrothermal bombs using hydrated cations or molecular templates such as organic amines or ammonium cations to direct the porous framework. Many new structures with metal phosphate chains, layers, or three-dimensional networks have been prepared hydrothermally in recent years, for example, templated vanadium phosphates and iron phosphates. ... 

As established in the previous chapter (section 6.17), the anhydrous iron phosphate has a relatively simple crystal structure, however, poor crystallinity of the powder results in broad peaks where full widths at half maximum vary from 0.2 to 0.5° when Mo Ka radiation is employed. Therefore, the resolution of the diffraction data is quite low, as was illustrated in Figure 6.33. There are only 6 atoms in the asymmetric unit but Rietveld refinement of the model is complicated by the inadequate quality of the diffraction data. The model, derived from a suspected analogy with the hydrated FeP04 2H20, cannot be completed based solely on the powder diffraction data due to problems with the experiment. Thus, Rietveld refinement considered in this section starts from the model improved by... 

Rakovan J, Reeder RJ, Rlzinga EJ, Cherniak DJ, Tail CD, Morris DE (in press) Structural characterization of U(VI) in apatite by X-ray absorption spectroscopy. Environ Sci Techn Robinson, MT (1983) Computer simulation of collision cascades in monazite. Phys Rev B 27 5347-5359 Reis ST, Martinelli IR (1999) Cs iimnobilization by sintered lead iron phosphate glasses. J Non-Ciystalhne Solids. 247 241-247... 

Padhi A, Nanjundaswamy K, Masquelier C, Okada S, Goodenough J (1997) Effect of structure on the Fe /Fe redox couple in iron phosphates. J Electrochtan Soc... 

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