Hematite Powder Research Articles

Preparation of microsized hematite powder from ferrous sulfate via microwave calcination

The preparation of microsized hematite powder from ferrous sulfate using microwave calcination was investigated based on the TG/DTG curves. The decomposition of industrial ferrous sulfate under air atmosphere was divided into three stages, and a ferrous sulfate sample added with 15% Fe2O3 could strongly absorb microwave energy. Therefore, preparing hematite powder from ferrous sulfate using microwave calcination was feasible. Hematite was obtained under the following optimized conditions: calcination temperature, 850 °C; microwave power, 650 W; and sample amount, 40 g. The obtained hematite satisfied the first-grade quality requirements. The total ferrum value was more than 58%, and the total sulfur and phosphorus contents were less than 0.5% and 0.2%, respectively. X-ray powder diffraction and scanning electron microscopy were used to characterize the structure and morphology of microsized hematite powder. The particles were non-spherical in shape, and the average particle size distribution was 10.45 μm. This work provides new potential applications for waste ferrous sulfate.

The effect of Fe2+ state in electrical property variations of Sn‐doped hematite powders

AbstractThe structural, electrical, and chemical properties of Sn‐doped Fe2O3 powders were investigated. Various quantities of Sn‐doped Fe2O3 powders were synthesized using solid‐state reactions. Rietveld analysis for the powders that were doped below 2% revealed a phase‐pure Sn‐doped Fe2O3 structure (i.e., identical to Fe2O3 structure). Alternatively, the analysis for the powders that were doped more than 3% exhibited secondary phase. The unit cell volume and electrical conductivity of the phase‐pure samples increased with an increase in the doping concentration. X‐ray photoelectron spectroscopy measurements showed an increased Fe2+ state with the increase in Sn doping concentration. Therefore, the improved electrical conductivity and unit cell volume with the increase in doping concentration of the phase‐pure powders might be related to the increased Fe2+ state.

Desilication of hematite, goethite and iron powder seeded low alumina to caustic liquors

Even though many studies have been carried out aimed at the development of methodologies for the inhibition of scale formation during the Bayer process there is still limited understanding of the underlying desilication processes and kinetics, in particular for the high solids density environment of single-stream heat exchangers. Our objective was to gain insight into the relative desilication due to nucleation and/or growth, and the kinetics of scale formation in the presence of typical solid phases. We have chosen a caustic aluminosilicate liquor composition in which both aluminate concentration and A/C are less than for heat exchanger feed liquor and hence aluminosilicate supersaturation is increased. These concentration conditions were chosen to investigate the early stage of scale formation in single-stream Bayer plant heat exchangers by increasing the component of aluminosilicate bulk precipitate upon seeding and decreasing the relative degree of scaling. The precipitation of aluminosilicate phases from this liquor at 140 and 180°C seeded with hematite, goethite and iron powder crystals was investigated. Upon seeding rapid desilication took place with significant suppression of scale formation on steel coupon surfaces as compared to unseeded experiments. Seeding with hematite resulted in the most rapid reduction in aluminosilicate supersaturation. Additionally, the presence of hematite, in contrast to the other seed types, appears to promote the transformation of sodalite to cancrinite. Precipitation was found to occur predominantly via heterogeneous nucleation during the 240min reaction time. The results of this study suggest that a seeding strategy, especially using hematite, may be effective in reducing scale formation on mild steel process equipment in a single-stream Bayer heat exchanger process environment.

The reduction kinetics of hematite particles in H2 and CO atmospheres

The reduction characteristics of hematite particles (i.e., Fe2O3) in H2 and CO atmospheres were experimentally investigated using isothermal thermo-gravimetric analysis (TGA). The mean diameter of the hematite powder (dP,m) was about 0.74μm. A mixture of pure hydrogen (H2) and carbon monoxide (CO) gases was used as a reductant at a fixed flow rate of 0.1lpm. Nitrogen (N2) was used as a diluent gas to control the mole fraction of the reductive mixture. The temperature for hematite particle reduction in the TGA (TR) was varied from 550 to 1300°C. Experimental results showed an increase in the reduction rate of iron oxide particles with an increase in the reductant mole fraction and surrounding temperature. The reduced particles displayed a sticking behavior at TR=1050 and 1300°C. The phenomenon of particle swelling was observed in a CO atmosphere. The global activation energy of the iron oxide particles was measured as 43.5kJ/mol for a H2 atmosphere and 2.3kJ/mol for a CO atmosphere at TR=800–1300°C.

Improvement of magnetization of submicron-sized high coercivity Sm2Fe17N3 powder by using hydrothermally synthesized sintering-tolerant cubic hematite

We investigated the cause of forming of aggregates which decreases magnetization of a submicron-sized Sm2Fe17N3 powder. The aggregation was considered to be caused through sintering and growth of α-Fe particles in a hydrogen reduction treatment. We newly synthesized cubic hematite powder which has tolerance for the sintering of particles in a hydrogen reduction treatment. The aggregation of submicron-sized Sm2Fe17N3 particles was significantly reduced by using the cubic hematite as a precursor, and the magnetization was improved without decreasing the high coercivity.

Chromium-substituted hematite powder as a catalytic material for photochemical and electrochemical water oxidation

The catalytic properties of Fe2O3 for electrochemical water oxidation are promoted by Cr(iii) substitution for Fe(iii). The substitution improves charge transfer to the reactant from the oxide inside, estimated by impedance measurement.

Characterization and sorption properties of γ-AlOOH/α-Fe2O3 composite powders prepared via hydrothermal method

Properties of boehmite and hematite powders formed under hydrothermal conditions are well known. However, a synergistic effect is expected when the γ-AlOOH/α-Fe2O3 composite powders are obtained under the same conditions. Hence, it should be possible to improve the properties (including adsorption) as compared to these of pure γ-AlOOH and α-Fe2O3. The γ-AlOOH/α-Fe2O3 composite powders were synthesized by hydrothermal method using metal nitrate solutions and urea as precursors. The influence of the [Al3+]:[Fe3+] ratio on the phase composition, textural properties, morphology, and thermal effects of composites was investigated. The γ-AlOOH/α-Fe2O3 composite powders had a smaller particle size and showed higher specific surface area and sorption capacity as compared to these of pure γ-AlOOH and α-Fe2O3. The sample prepared by using a solution with [Al3+]:[Fe3+] = 1 showed the highest specific surface area (98.1 m2/g) and adsorption capacity (4.17 mg/g) in the removal of Cr(VI) from aqueous solutions. Sorption experiments showed that the mean free adsorption energy is below 8 kJ/mol for all samples, indicating the adsorption process as the physical in nature and suggesting the possibility of Cr(VI) desorption and adsorbent regeneration.

Well-Dispersed α-Fe2O3 Particles for Lead-Free Red Overglaze Enamels through Hydrothermal Treatment.

The traditional Japanese overglaze ceramic, akae porcelain, typically known for Kakiemon-style wares, has been prized around the world for over 400 years. The red color of akae porcelain provides an attractive contrast to white porcelain. In recent years, because the use of leaded frit in making akae has been restricted by law owing to the effects of lead on human health and the environment, lead-free glass frit mixtures for overglaze ceramic wares have been developed in various porcelain production areas throughout Japan. However, current lead-free frit for red overglaze enamels produces a color that is duller than that of conventional leaded frit. Therefore, the development of red pigments that are suitable for use with lead-free frit is strongly desired. In this study, we used a hydrothermal process to prepare nanosized iron oxide and oxyhydroxide powders, which showed good particle dispersion in molten lead-free frit. The precursor paste was prepared by reacting iron nitrate with ammonium hydrogen carbonate and heated in a sealed vessel at 80–150 °C. The sample powder prepared at 90 °C was almost monophasic α-Fe2O3 (hematite) and exhibited the brightest red color (highest L*, a*, and b* values). This powder featured primary particles of ∼15 nm in diameter that aggregated to form secondary spherical particles of ∼100 nm in diameter. This powder was mixed with lead-free frit and applied as a red paint to a porcelain test piece. The resultant akae showed a bright red color with high L*, a*, and b* values that exceeded the values of akae prepared using conventional hematite powder. Microscopic analysis revealed that the hematite particles were well dispersed in the resultant glass layer, indicating that the hematite powders have good dispersibility in molten frit.

Controlling the Color of Lead-Free Red Overglaze Enamels and a Process for Preparing High-Quality Red Paints.

Akae porcelain, an artistic Japanese traditional overglaze ceramic typically known for Kakiemon-style ware, has fascinated porcelain lovers around the world for over 400 years because of the graceful red color displayed by akae that matches so well with white porcelain bodies. In this work, we clarified the factors that control the color of akae and those that are conventionally controlled by artisans based on empirical experience. Inspired by a recent particle-design method, we also developed a practical facile process to prepare red paints that yields high-quality akae. Various akae samples were prepared from a combination of lead-free alkali borosilicate glass frits with different particle sizes and hematite powders with differing dispersibilities. Polarized light microscopy, scanning electron microscopy, and transmission electron microscopy analyses indicate that considering only the dispersibility of hematite powders is not sufficient, but the frit-particle size must be controlled to obtain high-quality akae with a high reflectance value for ≥580 nm visible light. In addition, we developed a process for preparing high-quality red paints that uses a large-particle frit powder and a strongly aggregated-hematite powder, both of which are easily obtainable. The red paint composed of frit, hematite, and the solvent is mixed until the paint is drying. By adding more solvent and repeating this process three times, we obtained high-quality akae with a higher reflectance value than for the akae prepared from a frit with submicron-sized particles and weakly aggregated-hematite powder. On the basis of transmission electron microscopic observations, we consider the red paint to consist of a core/shell-like composite structure of frit and hematite, forming a three-dimensional network in the akae glass layer. The good dispersibility of these particles leads to high-quality akae.

Effect of Various Fillers on Mechanical Properties of Glass Fiber Reinforced Polymer Composites: A Review

Filler materials are the inert materials which are used in glass fiber reinforced polymer (GFRP) composites for modifying the chemical and physical properties of the matrix polymers to reduce material costs, to improve processability, to improve product performance or to simply act as extenders or matrix diluents. Some of the commonly used fillers are carbon black, calcium carbonate, clay, alumina tri-hydrate, magnesium hydroxide, bone powder, coconut powder, hematite powder, TiO2, SiO2,ZnS, graphite, etc. Effect of these fillers on mechanical properties like tensile strength, flexural strength, inter laminar shear strength (ILSS), tensile modulus, impact strength, hardness were tested by various methods experimentally. Some of the authors also discussed the effect of filler size on the above mechanical properties. KeywordsFillers, glass fiber reinforced polymer composites (GFRP), Mechanical properties Introduction Filler materials are generally the inert materials which are used in composite materials to reduce material costs, to improve mechanical properties to some extent, in some cases to improve processability and to improve product performance. Two or more materials with different material properties are combined together they will form a composite material. Fibers when embedded with weaker matrix materials comprise of strong load carrying capacity.The fibers in the composite materials will improve the mechanical properties such as tensile strength, flexural strength, impact strength, stiffness and matrix will transfer stresses between the reinforcing fibers. Fiber reinforced polymer composites are also called as fibrous composites because they consists of fibers as the reinforcing materials. The applications of composite materials are in automotive, marine, aerospace, etc. because of having properties such as high specific strength and stiffness. The types of composite materials are metal matrix composites, ceramic matrix composites and polymer matrix composites. When the matrix material is taken as ceramic it is called as ceramic matrix composite. The properties of ceramic matrix composites are better toughness, high strength, hardness, high temperature properties and better wear resistance.When the polymer resin is used as a matrix material then it is called as polymer matrix composite. These materials are having properties such as low density, good thermal and electrical insulator, ease of fabrication and low cost. The properties of polymer matrix composites mainly depend upon types of reinforcement that is particles and fibers, the type of polymer used and interface which is used between them. Polymers are classified into thermoplastics and thermosets. Thermoplastic materials are reversible and reshaped by

Characterization of cosmetic sticks at Xiaohe Cemetery in early Bronze Age Xinjiang, China.

Cosmetics have been studied for a long time in the society and culture research, and its consumption is regarded as a cultural symbol of human society. This paper focuses on the analysis of the red cosmetic sticks, found in Xiaohe Cemetery (1980–1450BC), Xinjiang, China. The structure of the red cosmetic sticks was disclosed by SR-μCT scanning (Synchrotron Radiation Micro-computed Tomography), while the chemical components were characterized by FTIR (Fourier Transform Infrared Spectroscopy), Raman Spectroscopy and Proteomics. The results suggested that the cosmetic sticks were made from the cattle heart and covered with a layer of hematite powders as the pigment. Given the numerous red painted relics in Xiaohe Cemetery, this kind of cosmetic sticks might be used as a primitive form of crayon for makeup and painting. The usage of cattle hearts as cosmetic sticks is firstly reported up to our knowledge, which not only reveals the varied utilizations of cattle in Xiaohe Cemetery but also shows the distinctive religious function. Furthermore, these red cosmetic sticks were usually buried with women, implying that the woman may be the painter and play a special role in religious activities.

Hematite nanopowder obtained from waste: Iron-removal sludge

X-ray diffraction and Fourier-transform IR spectroscopy techniques were employed to confirm that heavy-tonnage iron-removal sludge wastes could be successfully used to synthesize hematite nanopowder (HM NP) with an average particle size of 42nm. The sizes of the HM NP particles were confirmed from the TEM images. The hematite particles mostly exhibit elongated irregular oval shapes and their sizes vary within 18–74nm, with a dominant fraction at 42–46nm. The obtained HM NPs were characterized by a saturation magnetization of ~1.5emu/g and a remanent magnetization of ~0.9emu/g. Low-temperature nitrogen adsorption measurements showed that the obtained powder had a large specific surface area (S=14m2/g) and well-developed mesoporosity (average pore size, 17.2nm). A comparison of the obtained results to data from other researchers suggests that this hematite powder has high potential for use in the preparation of sorbents for water purification.

Role of catalytic agents and processing parameters in the graphitization process of a carbon-based refractory binder

The chemical resistance and thermo-mechanical properties of carbon-containing refractories are highly dependent on the presence of carbonaceous phases with structures similar to graphite ones. However, most of the thermosetting resins (used as binders) are classified as non-graphitizing carbon sources. Consequently, there is a high degree interest in finding alternative routes to induce an effective graphitization of such polymeric components at temperatures and conditions similar to the ones that refractories are submitted to in service. This research evaluates the effect of different catalytic agents (ferrocene, hematite and nano-Fe2O3 powder) and some processing parameters (i.e., temperature, dwell time, heating rate, amount of cross-linking additive) on the graphitization process of a novolak resin. X-ray diffraction, SEM/EDS and thermogravimetric analyses were carried out to identify the phase and microstructural evolution of the prepared compositions. According to the attained results, carbon graphitization was observed after firing the samples at 1000°C and 1400°C for 5h under a reducing atmosphere. The addition of ferrocene (>2wt%) favored the generation of a higher amount of iron oxide particles in the microstructure at 1400°C and led to a more effective graphitization, whereas the greater tendency for nano-Fe2O3 powder to agglomerate during the initial samples’ mixing step inhibited carbon crystallization. Regarding the effect of the processing parameters, the use of a heating rate of 3°C/min and dwell time of 5h at the maximum temperature of 1400°C, led to the generation of a maximum amount of graphitic carbon, 33.1%, in the composition with novolak resin +3wt% ferrocene.

Detection of an Anomalous Magnetic Transition in Hematite by Means of Derivative Microwave Absorption

We have investigated the derivative microwave power absorption (dP/dH) at X-band (8.8–9.8 GHz) in the hematite (a-Fe2O3) powders, for the 180-280 K temperature range. Two microwave absorption techniques are mainly used: the magnetically modulated microwave absorption spectroscopy (MAMMAS) and the extended field microwave absorption (EFMA). MAMMAS response showed distinctive features associated with the Morin transition at T Mo = 260 K, and below T Mo, a weak ferromagnetism is also observed. Additionally, EFMA technique is used to give further knowledge on this material, where this technique shows a change in microwave absorption dynamics in the vicinity of 200 K and it is associated with an anomalous magnetic transition, different to the Morin transition, and which is also confirmed by means of magnetic measurements and the low-field microwave absorption (LFMA).

Gas phase condensation of superparamagnetic iron oxide-silica nanoparticles--control of the intraparticle phase distribution.

Spherical, softly agglomerated and superparamagnetic nanoparticles (NPs) consisting of maghemite (γ-Fe2O3) and amorphous silica (SiO2) were prepared by CO2 laser co-vaporization (CoLAVA) of hematite powder (α-Fe2O3) and quartz sand (SiO2). The α-Fe2O3 portion of the homogeneous starting mixtures was gradually increased (15 mass%-95 mass%). It was found that (i) with increasing iron oxide content the NPs' morphology changes from a nanoscale SiO2 matrix with multiple γ-Fe2O3 inclusions to Janus NPs consisting of a γ-Fe2O3 and a SiO2 hemisphere to γ-Fe2O3 NPs each carrying one small SiO2 lens on its surface, (ii) the multiple γ-Fe2O3 inclusions accumulate at the NPs' inner surfaces, and (iii) all composite NPs are covered by a thin layer of amorphous SiO2. These morphological characteristics are attributed to (i) the phase segregation of iron oxide and silica within the condensed Fe2O3-SiO2 droplets, (ii) the temperature gradient within these droplets which arises during rapid cooling in the CoLAVA process, and (iii) the significantly lower surface energy of silica when compared to iron oxide. The proposed growth mechanism of these Fe2O3-SiO2 composite NPs during gas phase condensation can be transferred to other systems comprising a glass-network former and another component that is insoluble in the regarding glass. Thus, our model will facilitate the development of novel functional composite NPs for applications in biomedicine, optics, electronics, or catalysis.

Influence of mechanical activation time, annealing, and Fe/O ratio on Fe3O4/Fe composites formation from Fe2O3 and Fe powders mixture

Commercially, iron (α-Fe) and hematite (α-Fe2O3) powders were used for the synthesis of composite powders of Fe2O3/Fe type by mechanical milling. Several ratios of Fe2O3/Fe were chosen for the composite synthesis; the atomic percent of oxygen in the starting mixtures ranged from 21 to 46 %. The Fe2O3/Fe composite samples with various Fe/O ratios were milled for different milling times. The milled composite samples were subjected to the heat treatments in argon up to 900 °C. During the heat treatment at temperatures that do not exceed 550 °C, Fe3O4/Fe composite particles are formed by the reaction between the Fe2O3 and Fe. Further increase of the heat treatment up to 700 °C leads to the reaction of the Fe3O4/Fe composite component phases, resulting thus in the formation of FeO/Fe composite. The heat treatment up to 900 °C of the Fe2O3/Fe leads to the formation of a composite of FeO/Fe3O4/Fe independent of the milling time and Fe2O3/Fe ratios. The onset temperatures of the Fe3O4 and FeO formations decrease upon increasing the milling time. Another important aspect is that, in the case of the same milling time but with a large amount of iron into the composite powder the formations temperatures of Fe3O4 and FeO are also decreasing. The influence of the mechanical activation time, heat treatment temperature, and Fe/O ratio on the formation of the (Fe3O4, FeO)/Fe composite from Fe2O3+Fe precursor mixtures was studied by differential scanning calorimetry and X-ray diffraction techniques.

Properties and sintering behaviour of fine spherical iron powders produced by new hydrogen reduction process

The most important use of fine spherical iron powders is for metal injection moulding (MIM). For many applications, the high costs of powder based on the carbonyl or atomising production route are a limiting factors. An alternative two-step hydrogen reduction process using a granulated hematite powder, which is a recycling product from steelmaking, has been developed to produce <25 µm spherical powder. The morphology and properties of the powder have been found to depend strongly on the second temperature step of the reduction process. A further important step is enclosed powder processing by milling and sieving to remove agglomerates. The powder properties and sintering behaviour as a function of heat treatment and processing parameters are reported and discussed.

Preparation of Crystalline Hematite from Bauxite

A novel of hydrothermal stripping technique is developed to synthesize nano-particles of ferric oxide from iron-loaded organic phase by ammonia. The iron-loaded organic phase was prepared by extracting simulated bauxite hydrochloric acid leaching liquors with N235 and then the iron is stripped by heating the organic phase up to 180°C to precipitate as ferric oxide. XRD patterns exhibits that the ferric oxide is composed of α-Fe2O3 and TEM images reveals that the particles of crystalline hematite powders are homogenous with quasi-spherical fine crystallites and its primary particles are about 150 nm. This process is a proof of concept for the removal and precipitation of iron from bauxite hydrochloric acid leaching liquors.

Iron oxide nanotube layer fabricated with electrostatic anodization for heterogeneous Fenton like reaction

Iron oxide nanotubes (INT) were fabricated with potentiostatic anodization of zero valent iron foil in 1M Na2SO4 containing 0.5wt% NH4F electrolyte, holding the potential at 20, 40, and 60V for 20min, respectively. Field emission scanning electron microscopy and X-ray diffractometry were used to evaluate the morphology and crystalline structure of the INT film. The potential of 40V for 20min was observed to be optimal to produce an optimal catalytic film. Cyanide dissolved in water was degraded through the Fenton-like reaction using the INT film with hydrogen peroxide (H2O2). In case of INT-40V in the presence of H2O2 3%, the first-order rate constant was found to be 1.7×10−2min−1, and 1.2×10−2min−1 with commercial hematite powder. Degradation of cyanide was much less with only H2O2. Therefore, this process proposed in this work can be an excellent alternative to traditional catalysts for Fenton-like reaction.

Direct Electrochemical Reduction of Hematite Pellets in Alkaline Solutions

Our previous studies on the electrowinning of iron from hematite particles suspended in sodium hydroxide solutions demonstrated that iron was produced through a direct solid phase electrochemical reduction of the oxide particles. This suggests that the electro-deoxidation of a hematite powder pellet by the FFC type process should be possible in aqueous solutions at a low temperature. We investigated the electrochemical reduction of a solid hematite pellet cathode manufactured by conventional mechanical pressing followed by sintering process in concentrated sodium hydroxide solutions using a nickel inert anode at 110 °C. The experimental results indicated that hematite was reduced to iron metal. Propagation of the reduction reaction front through the oxide phase occurred at a high speed, and the rate-determining step was the diffusion of the oxygen ion through the shrinking cores of the oxide particle.