Iron oxide

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Basic Information About the nature of the whole solution structure Introduction chemical reactions purpose other problems common reaction principle application Other Information About expand Edit this paragraph the basic information Chinese Name: black iron oxide [1] Chinese Synonyms: CI Pigment Black 11 ; iron oxide black; iron black; iron oxide black English name: CI Pigment Black 11 English Synonyms: 77499; iron oxide black CAS :12227-89-3; 58339-39-2; 65777-20-0; 65777-22 - 2 EINECS :235-442-5 Description Edit this paragraph iron oxide is an oxide of iron, its chemical formula is Fe3O4, relative molecular mass of 231.54 iron oxide is the only secondary school can be magnetized iron compounds. Iron oxide containing Fe2 + and Fe3 +, X-ray diffraction experiments show that the iron oxide has a trans-spinel structure, the crystal there has never been partial iron ions FeO2-. Iron oxide, also known as magnetic iron oxide, iron oxide black, magnets, magnets, magnet, natural mineral type is magnetite. Of iron in the iron oxide has two valence for trans-spinel structure, namely Fe Ⅲ [Fe Ⅲ Fe Ⅱ] O4. In addition, iron oxide, or conductor, because in magnetite as Fe2 + and Fe3 + in octahedral sites is essentially disordered arrangement, the electrons in the iron oxidation state between two rapidly shift, so tetroxide iron solid with excellent conductivity. Edit this paragraph the whole solution adopted here Introduction In a question and answer method to answer questions about the various iron oxide nature of the problem Q: Can you briefly explain the nature of Fe3O4 A: black Fe3O4 is a mixed valence iron oxide, mp 1597 ℃, density 5.17g/cm3, insoluble in water, soluble in acid, in nature in the form of magnetite occurs at room temperature when the magnet has a strong Asian sex with high conductivity. (Fe3O4 literature that has a melting point of 1538 ℃, insoluble in acid) Q: magnet with fire will lose their magnetism, Fe3O4 magnetic affected by temperature do? A: ferromagnetic and ferrimagnetic substances occurring in Curie temperature above the phase transition into two paramagnetic substances. The Curie temperature of Fe3O4 585 ℃ Q: What is the difference of these types of magnetic do? A: The magnetic material can be divided into five categories: (a) anti-magnetic (diamagnetic): the material of all electrons in the atomic or molecular orbital both tracks are paired, opposite spin, no permanent magnetic moment. (B) paramagnetic: atom or molecule has unpaired electrons exist, there is a permanent magnetic moment, but no interaction between the magnetic moment. (C) ferromagnetism: Each atom has several unpaired electrons, atomic magnetic moment larger and have a role to each other, so that the atomic magnetic moment parallel. (D) ferrimagnetic (ferrite): partial rendering adjacent atomic magnetic moments are not equal anti-parallel. (E) antiferromagnetic: above the Néel temperature was paramagnetic; below the Néel temperature, the magnetic moment between the magnetic moments of neighboring atoms present equal antiparallel.

variety of magnetic material inside the magnetic structure

Q: Only Fe3O4 iron oxide is paramagnetic do this? A: This is not correct, such as γ-Fe2O3 equally ferrimagnetic Unfortunately, at the secondary level, this substance has not been mentioned. Q: Why does Fe3O4 has a high electrical conductivity? A: Yes, the electrochemical properties of Fe3O4 unusual due to the electrons in the Fe2 + and Fe3 + transfer between

 

structure [key] Q: Our chemistry teacher said Fe3O4 can be seen as FeO · Fe2O3? A: The wording better describes the Fe3O4 containing Fe (II) and Fe (III). Disadvantages are that similar wording double salt chemical formula Fe3O4 easy for students to be mistaken for a mixture (or solid solution). Furthermore, this does not the real structure of the table name Fe3O4. Q: can also be seen as Fe (FeO2) 2, namely iron acid (III) iron (II)? (Or partial ferrous iron or iron ferrous sulfate acid) A: Fe3O4 is trans spinel structure belongs to cubic crystal system, the oxygen atom in the cubic close-packed structure, half of the Fe3 + occupy tetrahedral sites, Fe2 + and the other half Fe3 + occupy octahedral sites. Crystals and without FeO2-ions. Its real structure can be better expressed as Fe (III) [Fe (II) Fe (III)] O4 on iron oxide in iron valence [focus] Q: Fe3O4 in iron valence is how much? A: Fe3O4 in iron oxidation number of +2 and +3 formal oxidation number is positive eight thirds Q: valence oxidation numbers have anything to do with? What is apparent is the oxidation number? A: valence, including covalent, ionic valence, coordination number and oxidation number (oxidation state) several concepts. When the molecular electron sharing between the atoms is specified for a large part of electronegative atoms, each atom in the form of electric charge carried by the oxidation number of them are known. For Fe3O4,, oxidation number and ion valence synonymous. Valence ions in the ionic crystal or molecules, or in the molten salt solution, the charge ions. Performance (average) oxidation number can be directly determined by the chemical formula, a larger human factors. In contrast, covalent compound (actual) according to the oxidation number of the microstructure of the molecular judgment. Q: Why should introduce the concept of oxidation number of performance? A: introduction of the concept of apparent oxidation number of the oxidation-reduction reaction to determine, trim and more computationally easy and fast. Q: Why the mixed valence oxides Fe3O4 called mixed oxide instead? A: This is in order to avoid ambiguity. If the called mixed oxide mixture of oxides easily confused. Other issues Q: Fe3O4 is a mixture do? A: No, Fe3O4 is a pure substance. Its approximate composition is fixed, iron and oxygen atoms in the number ratio of about 3:4. (Due to the crystal defects, the atomic ratio is not the exact value, but usually negligible) Q: Why wire burning oxygen produces iron oxide? A: Usually the answer is more iron oxide standard molar Gibbs free energy of the size of the thermodynamic stability of Fe3O4 biggest draw, so the product is Fe3O4. However, using this method is not appropriate here. A better approach is the relatively high temperature by calculating generate three iron oxide into each reaction molar Gibbs free energy becomes the conclusion. Analysis of this in the literature. (Please note that when literature, ΔG = ΔH-TΔS not Gibbs-Helmholtz equation, do not confuse the two) Q: Since Fe3O4 thermodynamically most stable, why in the iron oxidation reaction at room temperature, the resulting rust main ingredient is Fe2O3 · ; χH2O it? Is not this usually the easiest to produce Fe2O3 do? A: Actually, this is not rigorous understanding. Iron will be in contact with air to form oxides on the surface of this case, the chemical composition of the oxide film itself is not uniform. If a low carbon steel can be covered with the oxide film into three: the metal contact is FeO, the side in contact with air is Fe2O3, the middle is Fe3O4. More precisely, perhaps are three saturated solid solution of oxides a mixture of iron oxide film surface. Meanwhile, the thickness of the oxide film is different depending on the oxidation of environmental conditions. At room temperature, dry air relatively pure iron oxide thickness of not more than 20 Å (1 Å = 0.1 nm), but in moist air significantly increased thickness of the oxide film can be seen on the surface rust. At this time deposition of a layered oxide, close to the metal side of the dense layer of amorphous water, close to the air side is thick porous hydrated layer fact, almost all of the solid surface actually exists on a different structure and composition inhomogeneities incompleteness, simply use the standard molar Gibbs free energy as the basis to judge is unreasonable. Q: Why does iron react with steam Fe3O4 and hydrogen? Hydrogen does not restore Fe3O4 do? A: two different reaction temperatures. Hydrogen at high temperatures can restore Fe3O4, at lower temperatures, steam iron, you can replace the hydrogen. The same reaction can be calculated using the molar Gibbs free energy conclusion. Q: How preparing Fe3O4? A: can be red hot steam iron through, FeO or partial oxidation of Fe2O3 is heated to above 1400 ℃ system. For Fe3O4 nanoparticles, there are chemical co-precipitation, sol - gel method and other preparation methods, described in detail below. Q: Fe3O4 Can dense iron oxide film formed on the surface? Have anti-corrosion effect you? A: Fe3O4 have anti-corrosion effects, such as iron and steel articles blue (also known as bluing and grilled blue) is the use of an alkaline oxidizing solution oxidation of the surface layer of the steel in blue-black or dark blue Fe3O4 films in order to increase corrosion resistance, gloss and aesthetic approach common chemical reaction (1) at high temperatures, easily oxidized into iron oxide. 4Fe3O4 + O2 = high = 6Fe2O3 (2) with a reducing agent at a high temperature under CO, Al, C and other reactions. 3Fe3O4 +8 Al = 4Al2O3 +9 Fe Fe3O4 +4 CO = High = 3Fe +4 CO2 (3) under heating conditions in the hydrogen reacts with a reducing agent. Fe3O4 +4 H2 = heat = 3Fe +4 H2O (4) nitrogen dioxide and the reaction of the hot iron iron oxide and nitrogen 2NO2 +3 Fe = heat = Fe3O4 + N2 (5) iron burning in oxygen generator iron oxide 2O2 +3 Fe = lit = Fe3O4 (6) and red-hot iron steam iron oxide reaction 4H2O +3 Fe = heat = Fe3O4 +4 H2 (7) and acid reaction Fe3O4 +8 HCl = 2FeCl3 + FeCl2 +4 H2O

wire burning in oxygen

edit this section uses iron oxide is a common magnetic materials. Specially pure iron oxide used as a tape recording of telecommunications equipment and raw materials. Natural magnetite iron materials. The system for primer and topcoat. It is very hard, can be used as an abrasive. Has been widely used in automotive braking areas, such as: brake pads, brake shoes and so on. Iron oxide welding material in the domestic field has been recognized for welding electrodes, welding wire production has just begun, the market prospect is very broad. Iron oxide pigments and polishes can be done. We can also pass certain chemical reactions, such as the use of sodium nitrite, etc., so that the steel surface of a layer of dense iron oxide, used to prevent or slow down the corrosion of steel, such as firearms, such as the surface of the blade blue, black. Commonly known as "grilled blue." Create special electrodes. Edit this section Other Information About four ferromagnetic iron oxide, if the formation of particle radius at the nanoscale level, known as magnetic iron oxide particles. Reaction principle in recent years, the literature on Fe3O4 nanoparticles prepared in large numbers, some of the new preparation process are also emerging. Preparation of Fe3O4 traditional methods include precipitation, hydrothermal (solvothermal) method, microemulsion, sol - gel method. Emerging prepared as microwave method, carbonyl precursor pyrolysis method, ultrasonic method, air oxidation, pyrolysis - reduction, polyol reduction method is becoming a hot research scholars. Fe3O4 in the relevant method of preparation, the new surface active agents, it has also exceeded preparation system. Surface active agents have not only limited SDS, PEG, CTAB, citric acid, oleic acid, etc., with NSOCMCS, polyacrylamide modifier have the coverage. Preparation systems have also appeared in ethanol - water system, n-propanol - water, propylene glycol - water system and so on. 1 Precipitation Precipitation simple process because of its low cost, high purity,nike soccer cleats 2013, uniform composition, suitable for mass production, the most common method for preparing nanoparticles. Meanwhile, the organic mixture was added to precipitate a dispersing agent or complexing agents can improve dispersion of the nanoparticles, nanoparticles easily overcome the shortcomings of agglomeration. Precipitation method are used coprecipitation, hydrolysis precipitation, ultrasonic precipitation method, an alcohol solution and the chelate salt decomposition method. (1) coprecipitation of precipitation in a solution containing a variety of cationic precipitant added, so that all ions completely precipitated. In order to obtain a uniform precipitation, usually contain a variety of cationic salt solution was slowly added to an excess of precipitant with stirring, so that all ions greatly exceeds the equilibrium concentration of sediment, as the proportion of each component simultaneously precipitates.

coprecipitation principle

The principle is Fe +2 Fe +8 OH → Fe3O4 +4 H2O. Specifically as right. When nanoparticles are prepared by precipitation, Fe, Fe molar ratio directly affects the crystal structure of the product; solution pH, ion concentration, reaction temperature, etc. affect the particle size. Preparation reflect conditions at the control structure of a single crystal, a uniform particle size precipitated nanoparticles facing major problems. Outside the precipitant was filtered, washed also must consider. Obtained by coprecipitation of iron oxide nanoparticles are mostly spherical structure, smaller particle size (5 ~ 10nm). However, as the reaction temperature is relatively low,Adidas AdiPure TF, the crystallinity of the obtained particles is relatively poor. Moreover, the nano-Fe3O4 particles prepared by precipitation in the washing, filtration and drying particles prone reunion, will affect the performance of Fe3O4. (2) hydrolysis precipitation precipitation method is the use of alkaline hydrolysis hydrolysis substance release OH, commonly used alkaline substances are urea, hexamethylene diamine, these substances slow release of OH, in the preparation of Fe3O4 particles generated when the beneficial nanoparticles of uniform particles, typically prepared by this method can 7nm to 39nm particle size distribution of the nanoparticles. (3) ultrasonic precipitation method in a solvent to produce ultrasound cavitation effect, resulting in cavitation bubbles collapse very short period of 10-11 seconds, the bubble generated in a high temperature of about 5000K. The series cavitation technology compared with conventional mixing mesoscopic easier to achieve uniform mixing, eliminating uneven local concentration, improve reaction speed, to stimulate the formation of new phases, but can also play on the reunion shearing, help small particles formation. The application of ultrasonic technology nature of the system has no special requirements, as long as the transmission of energy to the liquid medium. Vijayakumar.R, etc. with a high-intensity ultrasound radiation obtained from acetic acid aqueous ferric salt particle size of 10nm, with superparamagnetic Fe3O4 particles. (4) alkoxide solution of sodium acetate in water, the use of ionizing the reduction of the acetate generated in the autoclave to about 180 ℃ partial reduction of Fe Fe, Yonghui Deng sodium acetate, etc., FeCl3 and ethylene glycol is heated in the autoclave 200 ℃ 8h which was prepared with superparamagnetic Fe3O4 nanoparticles. (5) chelate of the Act principle of decomposition of metal ions with a suitable ligand stable complex formation temperature in a suitable temperature and pH values ​​complex is destroyed, re-release of metal ions in the solution OH ions and additional precipitation agent, oxidant to generate different valences insoluble metal oxide, hydroxide, salt, and other sediment, further treatment may have a certain size or shape of the nanoparticles. 2.1.2 hydrothermal (solvothermal) method hydrothermal (solvothermal) reaction in aqueous solution under high temperature and pressure (organic solvents) or steam and other fluids for chemical reactions carried out in general. Hydrothermal the past ten years developed a method for preparing nano-powder synthesis, this method prepared Fe3O4 small particle size, particle size is uniform, no high-temperature calcination pretreatment, and can achieve multivalent ions doped miscellaneous. However, due to hydrothermal method requires the use of high-temperature, high-pressure equipment, and thus the higher cost of this method, it is difficult to achieve large-scale production. Currently, Hydrothermal mostly Fe3O4 nanoparticles of inorganic iron salts (FeCl3 · 6H2O, FeCl2 · 4H2O, FeSO4) and organic iron (ferrocene Fe (C5 H5) 2) as a precursor to hydrazine, polyvinyl ethylene glycol, PVP, etc., as a surfactant, at less than 200 ℃ synthesized under alkaline solution conditions. Shouheng Sun particle size were prepared by hydrothermal method superparamagnetic Fe3O4 controllable particle. First, with Fe (acac) 3 was prepared in a particle size of 4nm Fe source of Fe3O4 particles with a particle size of 4nm and Fe3O4 particles of the seed crystal, by controlling the holding time of the particle size were prepared, respectively 6,8,12 , 16nm of Fe3O4 nanoparticles. Zhen Li et al reported the use of common FeCl3 · H2O replace expensive Fe (acac) 3 as a precursor prepared Fe3O4 nanoparticles. 2.1.3 Micro-emulsifying microemulsion method is the two immiscible solvents in the role of a surfactant to form an emulsion, which is the continuous medium amphiphilic molecules divided into the small space formed by the microreactor, wherein the reactants the solid phase reaction, as nucleation, crystal growth, coalescence, agglomeration of the micro-reactor processes are limited, so as to form a layer of the surfactant package and have a condensed structure and morphology of the nanoparticles. Preparation of nanometer microemulsion catalysts, with the necessary equipment is simple, mild experimental conditions, particle size control, etc., which is the other method can not be compared. Therefore, a nano-catalyst synthesis techniques of great concern. Currently, on the preparation of nano catalyst microemulsion method studies focus on the control of the particle size, with regard to the control of monodisperse particle research is still relatively small. 2.1.4 sol - gel method (sol-gel) of the method is the use of metal alkoxide hydrolysis and condensation reaction of a metal oxide or a metal hydroxide sol uniform, and concentrated to a transparent gel, the gel was dried heat-treated obtained after oxide ultrafine powder. Sol-gel method is that the metal alkoxide as a starting material resulting in high costs and a gel synthesis process cycle. Meanwhile, the application prepared by sol-gel particle size below 100nm nanoparticles also been reported. In addition, prepared by other methods such as microwave, carbonyl precursor pyrolysis method, ultrasonic method, air oxidation, pyrolysis - reduction method, the polyol reduction method has been reported in succession. Haiyan ice with FeSO4 solution was added aqueous ammonia solution is obtained in the microwave 8s black Fe3O4 nanoparticles. Alivasatos such a precursor carbonyl pyrolysis prepared a monodisperse γ-Fe2O3 nanoparticles, then the method of the preparation of monodisperse magnetic oxide nanoparticles has been widely used. Liu and using polyol reduction method using iron acetylacetonate and platinum acetylacetonate reduction of the liquid phase at high temperature reaction of a diameter of 3nm the FePt magnetic nanoparticles, the surface of the particles to render the active agent is monodisperse protection state. Meng Zhe, who pH = 10 at room temperature for about an environment induced by oxidation, air oxidation of Fe (OH) 2 suspension was successfully prepared by high purity, strong magnetic Fe3O4 ultrafine powders spherical distribution. Electrification and application of information technology in contemporary society, the magnetic material is widely used. Magnetic iron oxide as a versatile magnetic materials, in the treatment of tumors, microwave absorbing materials, catalyst carrier, cell separation, magnetic materials, magnetic fluid, medicine and other fields have a wide range of applications, this material is very There are prospects for development.