摘要:
The invention allows the fabrication of small, dense, highly polished spherical beads of hexagonal ferrites with selected compositions for use in nonreciprocal microwave and mm-wave devices as well as in microwave absorbent or reflective coatings, composites, and the like. A porous, generally spherical bead of hydrous iron oxide is made by a sol-gel process to form a substantially rigid bead having a generally fine crystallite size and correspondingly finely distributed internal porosity. The resulting gel bead is washed and hydrothermally reacted with a soluble alkaline earth salt (typically Ba or Sr) under conditions of elevated temperature and pressure to convert the bead into a mixed hydrous iron-alkaline earth oxide while retaining the generally spherical shape. This mixed oxide bead is then washed, dried, and calcined to produce the desired (BaFe12O19 or SrFe12O19) crystal structure. The calcined bead is then sintered to form a dense bead of the BaFe12O19 and SrFe12O19 phase suitable for polishing and incorporation into various microwave devices and components.
摘要:
Process for the preparation of iron oxide pigments from the waste acid resulting from the preparation of titanium dioxide by the sulfate process, characterized in that in a first stage a partial neutralization of the sulfuric acid contained in the waste acid is performed with compounds from the group comprising metallic iron and/or iron compounds, the sulfuric acid is optionally further neutralized with a further alkaline compound, the precipitate containing Ti, Al, Cr and V compounds is separated from the resultant reaction product and an iron oxide yellow pigment or iron oxide black pigment is precipitated from the resultant iron sulfate-containing solution by addition of alkaline compounds as well as an oxidizing agent, each pigment being able to be baked to form an iron oxide red pigment.
摘要:
The invention provides a process for the production of iron based pigments and anticorrosive additives from elemental iron comprising: a) reacting iron Fe° with ferric sulphate Fe2(SO4)3 and with sulfuric acid H2SO4 to produce ferrous sulphate FeSO4; b) oxidizing ferrous sulphate FeSO4 in a bacterial solution containing at 107 bactrial cells of thiobacillus ferrooxidans per 1 ml of solution under aerobic conditions to produce ferric oxide sulphate Fe2(SO4)3; c) reacting said ferric oxide sulphate Fe2(SO4)3 with water, to precipitate iron oxide monohydrate Fe2O3×H2O; and d) re-cycling the solution from step c, to step a, to utilize the sulphuric acid and a portion of the ferruos sulphate values therein.
摘要:
The present invention relates to a process for producing a yellow iron oxide pigments comprising the steps of I) mixing preprecipitated FeCl2 and an &agr;-FeOOH nucleus produced by the “alkali” process, II) oxidizing the suspension in a first oxidation step at 20 to 45° C. III) oxidizing the suspension in a first oxidation step at 55 to 85° C.