Journal articles: 'Hematite'

1

Alpochoritis, Georgios, Argiris Kolokithas Ntoukas, and Vasilios I. Georgakilas. "Hematene Nanoplatelets with Enhanced Visible Light Absorption; the Role of Aromatic Molecules." Molecules 29, no. 13 (June 29, 2024): 3115. http://dx.doi.org/10.3390/molecules29133115.

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Hematite has been considered an important candidate for the development of an efficient photoelectrocatalytic water-splitting system. One of the most serious obstacles that limits the efficiency of hematite is low absorption capacity in visible light. Herein, we report the production of hematene nanoplatelets from hematite ore with yields of up to 60%, using a low-cost, sustainable method that is based on the ultrasonic treatment of hematite ore in a water solution of a series of organic aromatic compounds. We show that the chemisorption of molecules with increased aromaticity on the surface of hematene resulted in the significant improvement of its visible light absorptivity, with an increase of up to 200%. As a result, using a water solution of terephthalaldehyde as a liquid medium, hematite ore was exfoliated to hematene nanoplatelets with a yield of 40% and remarkable stability in water. Due to this, hematene was easily drop-casted on glass forming homogenous thin films with strong absorptivity in the visible region.

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Kang, Myung Jong, Na Hyeon An, and Young Soo Kang. "Magnetic and Photochemical Properties of Cu Doped Hematite Nanocrystal." Materials Science Forum 893 (March 2017): 136–43. http://dx.doi.org/10.4028/www.scientific.net/msf.893.136.

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In this report, the magnetic and photochemical properties of Cu doped hematite nanocrystal was investigated intensively. The Cu doped hematite nanocrystals were prepared by hydrothermal method, changing the molar ratio of Cu precursors. The XRD and XPS techniques are used for revealing crystal and chemical state of Cu doped hematite nanocrystal. Raman spectroscopy was also used for confirming Cu atoms replacing Fe position in Cu doped hematite crystal. The UV-vis and UPS were used for assigning electronic band position for photocatalytic properties. Cu doped hematite showed the enhanced photocatalytic properties within photodegradation of methyl orange. Finally, by checking magnetic hysteresis loops of Cu doped hematites with VSM, it was revealed that the magnetic property of Cu doped hematite nanocrystal was increased after doping Cu into hematite nanocrystal, get the distortion of magnetic sub-lattices.

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Cabral, A. R., B. Lehmann, H. F. Galbiatti, and O. G. Rocha Filho. "Evidence for metre-scale variations in hematite composition within the Palaeoproterozoic Itabira Iron Formation, Minas Gerais, Brazil." Mineralogical Magazine 70, no. 5 (October 2006): 591–602. http://dx.doi.org/10.1180/0026461067050352.

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AbstractHematite is a mineral the chemical composition of which rarely differs significantly from stoichiometric Fe2O3. As such, little attention has been paid to the mineral chemistry of hematite in Precambrian iron formations, where hematite forms monomineralic high-grade orebodies. Electron microprobe analysis of hematite from two iron-ore deposits, Cauê (Itabira district) and Gongo Soco, in the Palaeoproterozoic Itabira Iron Formation, Quadrilátero Ferrífero of Minas Gerais, Brazil, has revealed distinct variations in chemical composition with respect to Ti and Cr. Hematite containing Ti and/or Cr is of very local occurrence in the itabirite unit and shows a spatial relationship to hematitic, palladiferous gold-bearing veins (known as ‘jacutinga’), occurring either within the veins (adjacent to, or included in, palladiferous gold grains) or in their vicinity. Where present, titaniferous hematite (to ∼1.3 wt.% TiO2) is lepidoblastic and defines a pervasive tectonic foliation (S1). In contrast, Ti-free, chromiferous hematite (to ∼6.4 wt.% Cr2O3) characteristically occurs as inclusions in palladiferous gold within S1-truncating ‘jacutinga’. Replacement of granoblastic, Ti-free, chromiferous martite with relicts of magnetite by lepidoblastic, Cr-depleted, titaniferous hematite proves that Cr and Ti were mobile during metamorphism. Chromium was ultimately fractionated into the hematite found in auriferous aggregates within cross-cutting ‘jacutinga’. A positive correlation between Cr and Pt in bulk-rock samples from the Itabira district suggests that Cr is a potential prospective guide for Au-Pd-Pt-bearing hematitic veins (‘jacutinga’).

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Su, Jinzhan, Jian Wang, Cong Liu, Bo Feng, Yubin Chen, and Liejin Guo. "On the role of metal atom doping in hematite for improved photoelectrochemical properties: a comparison study." RSC Advances 6, no. 104 (2016): 101745–51. http://dx.doi.org/10.1039/c6ra22895j.

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A systematic comparison study of various metal atoms doped hematites was performed to look into the effect of metal element doping on the photoelectrochemical (PEC) properties of hematite photoelectrodes.

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5

Gromadskaya, L. I., I. V. Romanova, O. A. Vyshnevskyi, and S. A. Kirillov. "Near-Stoichiometric Adsorption of Phosphate by Silica Gel Supported Nanosized Hematite." ISRN Inorganic Chemistry 2013 (July 16, 2013): 1–10. http://dx.doi.org/10.1155/2013/969746.

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Decreasing the size of oxide particles to nanoscale enables one to ensure maximal reaction rates and depths in the solid due to the enhancement of the specific surface area and the increase of the diffusion rate caused by shortening diffusion paths. For that reason, one may suggest that in the case of adsorption onto nanoparticles, the complete conversion of sorbents to stoichiometric compounds would become possible. Adsorption of phosphate ions onto nanosized hematite supported on silica gel surface has been studied. Modification of silica gel surface by hematite in the quantity of 0.62 and 1.25 mass% has been carried out by means of a citric acid aided method. The morphology of the samples obtained has been characterized using DTA, XRD, SEM, and low temperature desorption of nitrogen. It has been found in batch experiments that unlike natural and synthetic hematites, for which the limiting adsorption values do not exceed 14 mg/g, silica gel supported nanosized hematite adsorbs 400–2000 mg of the phosphate ions per gram, thus forming near-stoichiometric iron phosphates on the surface of the support. The degree of conversion of hematite to iron phosphates is greater in acidic media and at a lower surface coverage, when hematite crystallites are small and better accessible by adsorbate.

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Climo, Lawrence H. "Hematite." American Journal of Psychiatry 164, no. 4 (April 2007): 566–67. http://dx.doi.org/10.1176/ajp.2007.164.4.566.

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7

Torrent, J., U. Schwertmann, and V. Barron. "The reductive dissolution of synthetic goethite and hematite in dithionite." Clay Minerals 22, no. 3 (September 1987): 329–37. http://dx.doi.org/10.1180/claymin.1987.022.3.07.

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AbstractThe reductive dissolution by Na-dithionite of 28 synthetic goethites and 26 hematites having widely different crystal morphologies, specific surfaces and aluminium substitution levels has been investigated. For both minerals the initial dissolution rate per unit of surface area decreased with aluminium substitution. At similar aluminium substitution and specific surface, goethites and hematites showed similar dissolution rates. These results suggest that preferential, reductive dissolution of hematite in some natural environments, such as soils or sediments, might be due to the generally lower aluminium substitution of this mineral compared to goethite.

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8

Yoo, Jaemin, Dongkyu Lee, Jimo Lee, Taehyeong Kim, Hyungyu Jin, and Gunsu S. Yun. "Catalytic effect of laser-combined atmospheric pressure plasma in lowering the reduction temperature of hematite." RSC Advances 11, no. 56 (2021): 35489–93. http://dx.doi.org/10.1039/d1ra06858j.

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We report a novel method of controlling the oxidation state of hematite using microwave-driven atmospheric pressure plasma assisted by laser surface heating. The method lowers hematite's reduction temperature and accelerates the reduction speed.

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9

Secco, L., F. Nestola, A. Dal Negro, and L. Z. Reznitsky. "Crystal-chemical study of Rc natural oxides along the eskolaite – karelianite – hematite (Cr2O3–V2O3–Fe2O3) join." Mineralogical Magazine 72, no. 3 (June 2008): 785–92. http://dx.doi.org/10.1180/minmag.2008.072.3.785.

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AbstractSix natural crystals from the Sludyanka crystalline complex belonging to the eskolaite (Cr2O3)–karelianite (V2O3)–hematite (Fe2O3) solid solution were studied by means of X-ray diffraction and electron microprobe. The Fe3+-poor samples show a general increase in a and c cell parameters with increasing mean cationic radius (MCR), consistent with that shown by the synthetic crystals along the eskolaite–karelianite join. The Fe3+-richer sample deviates significantly from the behaviour shown by the Fe3+-poor ones, similar to synthetic and natural hematites; with increasing MCR, the a and c cell parameters increase linearly along the eskolaite-karelianite join. However, for the samples rich in Fe3+, from karelianite to hematite, a shows a slightly steeper slope whereas the c parameter decreases strongly. The octahedral distortion increases slightly as a function of MCR along the eskolaite-karelianite join, whereas it increases markedly for Fe3+-rich samples. The evolution of the octahedral edges and of the octahedral distortions as a function of MCR are responsible for the behaviour of the unit-cell parameters along the eskolaite-karelianite-hematite join.

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10

Liu, Xiaonan, Gang He, Jinshan Li, and Guangfu Yin. "The Synthesis and Mechanism of (001)-Orientated Hematite Nano Rings: A Combined Theoretical and Experimental Investigation." Nano 12, no. 09 (September 2017): 1750111. http://dx.doi.org/10.1142/s1793292017501119.

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In this study, we synthesized Hematite nano rings using hydrothermal treatment. The experimental results demonstrated that the (001)-orientated Hematite nano rings were produced in all of the obtained products. To determine the formation mechanism of the (001) orientation, the lowest three index crystal faces of Hematite, Hematite (001), Hematite (101), and Hematite (104), were investigated with the Cambridge Sequential Total Energy Package (CASTEP) within the Materials Studio software environment (MS5.5) using the density functional theory (DFT). Our theoretical results showed that Hematite (001), the Hematite crystal with the lowest surface energy, had the greatest Hematite nano ring growth. In addition, we present the growth process of the Hematite nano rings based on our experimental and theoretical results.

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11

Cvetkovic, Zeljko, and Pavle Tancic. "Mineralogical and crystallographic characteristics of bauxites from some Grebnik’s (Metohija, Serbia) ore deposits." Annales g?ologiques de la Peninsule balkanique 80, no. 1 (2019): 45–61. http://dx.doi.org/10.2298/gabp19010045c.

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Five typical bauxite samples from three ore deposits from the wider area of Grebnik Mt. (Metohija, Serbia) were examined with the optical microscopic, X-ray powder diffraction (XRPD) and chemical methods. The occurrences in bauxites were studied and described and the presence of major minerals was determined: diaspore, boehmite and hematite; minor minerals: quartz, goethite, rutile, kaolinite and hydro-hematite; as well as anatase, brookite, magnetite and chromite, which occur only sporadically. According to the quantity of main Al-bearers, three types of bauxite ore were recognized: diaspore, boehmite and boehmite-diaspore. Unit cell dimensions of major minerals were determined, mostly with values within reference data. However, all of the studied hematites have smaller a0 and V0 values, most probably due to the substitution of Fe3+ by Al3+. All samples are further classified as iron-rich and ferritic bauxites. It was found that there were changes in origin conditions between major Al-hydroxides minerals and hematite, as well as between the diaspore and boehmite. Determined chemical compositions put this raw material into high-quality raw materials for obtaining the electro corundum and alumina. The synthesis of the obtained data indicate that Grebnik?s bauxites have some unique characteristics, more or less different from most of the World?s known bauxite ore deposits.

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12

Pelevin, A. E. "Production of hematite concentrate from hematite-magnetite ore." Mining informational and analytical bulletin, no. 3-1 (March 20, 2020): 422–30. http://dx.doi.org/10.25018/0236-1493-2020-31-0-422-430.

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The main useful minerals in composition of hematite-magnetite ore are magnetite and hematite. Magnetite is extracted by wet magnetic separation in weak magnetic field with production of magnetite concentrate and nonmagnetic product. The nonmagnetic product is a feed of the processing circuit for hematite. It is difficult to produce concentrate with iron content of 58-60 mass % if hematite grains are smaller than 0.05 mm. For hematite concentrate production from finely disseminated hematite-magnetite ore, the magnetic-gravitation and magnetic- flotation circuits are designed. This article discusses the magnetic-gravitational separation circuit for hematite grains smaller than 0.05 mm. The first stage of this circuit is fine screening intended to remove large particles. The second stage is high-gradient magnetic separation. The high-gradient separator performance depends on the mineral composition of initial ore and on the rate of mineral dissociation. In finely disseminated hematite-magnetite ore, the associate minerals are mainly represented by quart and amphiboles. Magnetic properties of hematite and amphiboles are similar. For this reason, the high-gradient magnetic separation product contained hematite, amphiboles and quartz-magnetic accretions. The iron content of the magnetic product was 28.9 %. Thus, additional treatment is required, and separation by gravity is applicable in this case. The gravitational separation was carried out on centrifugal concentrator, jigging machine, spiral separator and sluice, and on concentration table. The best results are obtained on the concentration table. The iron content of the final concentrate was 62.3 %.

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13

Ismunandar, Nadya Nurdini, Moh Mualliful Ilmi, Evi Maryanti, and Grandprix Thomryes Marth Kadja. "Investigation on the Crystal Structures of Hematite Pigments at Different Sintering Temperatures." Key Engineering Materials 874 (January 2021): 20–27. http://dx.doi.org/10.4028/www.scientific.net/kem.874.20.

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Hematite is one of the most stable oxide phases and has been used as a rock-art pigment material in the prehistoric era. Hematite in the form of ochre has been widely used in rock art, burial rites, cosmetics, and decorations on pottery surfaces. Hematite has several hues, ranging from red to black. The variety of hues might arise due to the differences in physicochemical properties of hematite such as crystallinity, crystallite size, morphology, and electronic structure. The differences in physicochemical properties in hematite pigments might be originated from the differences in the pretreatment technique used before application. Herein, we have conducted a thorough study to investigate the evolution of the crystal structure of hematite under various temperatures. We aim to determine the temperature needed to change the hematite color and uncover the transformation of crystallographic properties as a function of sintering temperature. The hematite was synthesized using the precipitation method with Fe (NO3)3.6H2O as a precursor and ammonia (NH4OH) solution as a precipitating agent. The study of the hematite structural evolution was carried out by varying the sintering temperatures from 600 to 900 °C and analyzing the products after sintered using X-ray diffraction technique. The results showed that hematite hue was gradually darkened as the sintering temperature increased as a consequence of higher crystallinity and larger crystallite size of hematite crystal. This study confirms that the origin of color changes in hematite is due to the heating treatment of hematite material.

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Poorni, S., and K. A. Natarajan. "Biomediated Separation of Kaolinite and Hematite Using Bacillus subtilis." Advanced Materials Research 825 (October 2013): 223–26. http://dx.doi.org/10.4028/www.scientific.net/amr.825.223.

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Bacillus subtilis was used to demonstrate microbially induced selective flocculation to separate kaolinite and hematite. In neutral pH range of 7 - 8, 90 - 95% of hematite was selectively flocculated whereas 80 - 85% of kaolinite was dispersed using hematite - grown cells. Hematite- grown cells exhibited significant adsorption onto hematite than onto kaolinite, compared to unadapted cells. Kaolinite grown Bacillus subtilis secreted significant amounts of mineral specific proteins which conferred surface hydrophobicity whereas hematite-grown cells secreted more polysaccharides rendering hematite hydrophilic. Bacterial extracellular protein (EP) was isolated and the protein profiles of bacteria grown in the absence and presence of minerals were established.

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Chen, Yen-Hua, and Kuo-Jui Tu. "Thickness Dependent on Photocatalytic Activity of Hematite Thin Films." International Journal of Photoenergy 2012 (2012): 1–6. http://dx.doi.org/10.1155/2012/980595.

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Hematite (Fe2O3) thin films with different thicknesses are fabricated by the rf magnetron sputtering deposition. The effects of film thicknesses on the photocatalytic activity of hematite films have been investigated. Hematite films possess a polycrystalline hexagonal structure, and the band gap decreases with an increase of film thickness. Moreover, all hematite films exhibit good photocatalytic ability under visible-light irradiation; the photocatalytic activity of hematite films increases with the increasing film thickness. This is because the hematite film with a thicker thickness has a rougher surface, providing more reaction sites for photocatalysis. Another reason is a lower band gap of a hematite film would generate more electron-hole pairs under visible-light illumination to enhance photocatalytic efficiency. Experimental data are well fitted with Langmuir-Hinshelwood kinetic model. The photocatalytic rate constant of hematite films ranges from 0.052 to 0.068 min-1. This suggests that the hematite film is a superior photocatalyst under visible-light irradiation.

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Anand, RR, and RJ Gilkes. "Variations in the properties of iron oxides within individual specimens of lateritic duricrust." Soil Research 25, no. 3 (1987): 287. http://dx.doi.org/10.1071/sr9870287.

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The morphologically distinct materials in Darling Range lateritic duricrust (i.e. loose and cemented pisoliths, concretions, matrix, pisolith coatings and void coatings) exhibit goethite/(goethite + hematite) ratios ranging from 0.15 for individual pisoliths to 1.0 for void coatings. Mole % Al substitution ranged from 20 to 34% in goethite and from 2 to 15% in hematite. Goethite and hematite in pisoliths and concretions were mostly highly Al substituted. Al substitution in goethite was positively related (P < 0.01) to Al substitution in hematite. Al substitution in maghemite was less than 5%. Goethite crystals ranged in size from 130 to 260 A. Hematite crystals ranged from 140 to 520 A, and were systematically smaller in pisoliths. Crystal size of goethite and hematite decreased with increasing Al substitution. Hematite crystals were usually about 50% larger than goethite crystals in the same sample, and crystal sizes of goethite and hematite were positively correlated (P < 0.01). Goethite and hematite occurred as aggregates of subrounded platy crystals. Differences in the properties of goethite and hematite between morphologically distinct materials in single hand specimens are indicative of the complex history of these duricrusts.

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Han, Wenjie, Yimin Zhu, Zhichao Shuai, Jie Liu, and Yanjun Li. "Investigations on the Reverse Flotation of Quartz/Hematite Using Pullulan as a Novel Depressant." Metals 13, no. 3 (March 9, 2023): 550. http://dx.doi.org/10.3390/met13030550.

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The traditional hematite depressant starch has the disadvantages of poor solubility and high viscosity. In this study, a novel hematite depressant, pullulan, with better performance and flotation effect than starch was found. The structure, molecular weight and viscosity of pullulan were determined for its characterization. The results of flotation tests revealed that the flotation separation of hematite-quartz by pullulan was better than that of starch for hematite-quartz. The selective depression mechanism of pullulan on hematite was studied by contact angle measurement, zeta potential measurement, FT-IR analyses and XPS analyses. Overall, the weak adsorption of pullulan on quartz did not affect the adsorption of DOPA on the quartz surface. However, it was adsorbed strongly on hematite surface and hindered the adsorption of DOPA. This selective adsorption led to a much greater hydrophobicity of quartz than hematite in the reverse flotation, resulting in the separation of quartz and hematite. Pullulan was adsorbed by chemical bonding between its hydroxyl group and iron sites on the hematite surface. Thus, compared with starch, pullulan was easy to dissolve in water, had low viscosity and good flotation effect, so it was a better hematite depressant.

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Mazhanov, Oleh M., Valeriy D. Evtekhov, Oleh S. Demchenko, Volodymyr M. Voloshyn, and Yevhen M. Kulyk. "Mineralogical justification for potentiality of producing marketable hematite products." Journal of Geology, Geography and Geoecology 30, no. 2 (July 18, 2021): 334–43. http://dx.doi.org/10.15421/112130.

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Hematite quartzites are a product of weathering of magnetite quartzites, which make up the ferruginous horizons of deposits of the Precambrian banded-iron formation. They occur all over the planet. The largest deposits are found in the iron-producing areas and basins of Central Kazakhstan, the Kursk magnetic anomaly, the Karelian-Kola region, Western Australia, Southeastern India, Brazil, the United States, and Canada. The geological and mineralogical issues of hematite quartzites as raw materials for producing concentrate and sinter ore have been studied most deeply and comprehensively for the deposits of the Kryvyi Rih basin and Central Kazakhstan. However, when developing an effective scheme for producing high-quality metallurgical raw materials, the mineralogical features of hematite ores have been taken into account insufficiently. The aim of the authors of the present work was to study the localization, structure of deposits and mineral composition of hematite quartzites as raw materials for sinter ore and concentrate production. Data from geological observations and mineralogical studies were used as source material. Proven geological, mineralogical, petrochemical methods were used. In accordance with the obtained results, the hematite quartzites are composed of ore-forming (quartz, hematite) and secondary (relict and newly formed) minerals. The total content of the hematite and quartz exceeds 90 mass %. The peculiarity of Ushkatyn III deposit ores is the high content of manganese oxides. The depth of distribution of the weathering crust composed of hematite quartzites varies from 200 to 1000 m. The hematite quartzites’ bodies are characterized by a zonal structure. Their central parts are represented by martite-micaceous hematite, micaceous hematite- martite quartzites; intermediate ones by martite quartzites; peripheral parts – by dispersed hematite-martite, kaolinite-martite-dispersed hematite quartzites. The horizons differ in the quantitative ratio of these varieties. The quantitative ratio of mineral varieties of hematite quartzites, morphology of individuals and aggregates of ore-forming and secondary minerals, their chemical composition and physical properties must be taken into account when developing the optimal technology for the production of high-quality hematite concentrate.

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Cao, Wei, Zhaoxia Jiang, Congcong Gai, Vidal Barrón, José Torrent, Yi Zhong, and Qingsong Liu. "Re-Visiting the Quantification of Hematite by Diffuse Reflectance Spectroscopy." Minerals 12, no. 7 (July 11, 2022): 872. http://dx.doi.org/10.3390/min12070872.

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Hematite concentration is an important climatic proxy for environmental (climatic) studies of soils and sediments. However, the accurate quantification of naturally occurring hematite has always been a difficult question, especially for those areas with lower hematite concentrations. Diffuse reflectance spectroscopy (DRS) is an effective method for hematite identification and quantification with lower detection limits. In this study, we synthesized a set of samples with well-determined concentrations to explore the exact detectable range of hematite and propose the most effective transfer function between the DRS proxy and hematite concentration. In addition, natural sediments from Inland Asia and the Western Pacific Ocean were used to further test the feasibility of the new transfer function. Results show that the lowest DRS detection limit for hematite could reach ~0.00078%, but is affected by the natural matrix. We also find that the second derivative of the Kubelka–Munk (K–M) function is monotonically correlated with the hematite concentration (0.00078%–100%), but ambiguities exist for the first derivative. Therefore, the second derivative of the K–M function is highly suggested for the hematite quantification, especially when concentration exhibits a wide range of variations. This study provides important references for the application of hematite proxy and promotes the popularization and development of the DRS method.

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Li, Tong, Fei Shi, Yiting Ju, and Zezhou Ding. "Facet-Dependent Adsorption of Phosphate on Hematite Nanoparticles: Role of Singly Coordinated Hydroxyl." Water 15, no. 23 (November 23, 2023): 4070. http://dx.doi.org/10.3390/w15234070.

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Phosphorus is an essential nutrient for plant and animal growth, while excessive phosphorus discharges can cause eutrophication of water bodies, leading to deterioration of water quality and posing serious risks to biodiversity and human health. Hematite is abundant on the Earth’s surface and plays a key role in phosphorus cycle. In particular, hematite nanoparticles may adsorb organic or inorganic phosphorus, consequently affecting phosphorus fate and effects. Yet, how the intrinsic properties of hematite (e.g., crystal facet) affect its adsorption process of phosphorus remains unclear. Here, three hematite nanoparticles with different exposed crystal facets were controllably synthesized to investigate their adsorption of phosphate under different pH conditions. The results revealed that the efficiency of hematite for adsorbing the phosphate depends on the crystal facets of hematite in the order of {104} > {110} > {001}. The phosphate adsorption on the hematite surface involves inner-sphere complexation between the phosphate and surface hydroxyl groups of hematite. The facet-dependent adsorption affinity of phosphate to hematite is mainly determined by the content of singly coordinated hydroxyl groups of hematite. These findings are useful to evaluate the potential environmental risks of iron oxide nanoparticles as a medium to the biochemical cycle of P element.

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Li, Guang Qiang, Heng Hui Wang, Jian Yang, and Jiang Hua Ma. "Preparation of Iron Carbide from High Phosphorus Oolitic Hematite." Advanced Materials Research 881-883 (January 2014): 98–101. http://dx.doi.org/10.4028/www.scientific.net/amr.881-883.98.

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In order to find a new way to utilize the high phosphorus oolitic hematite ore as raw material for steelmaking, the reduction and carburization of high phosphorus oolitic hematite by the gas of CH4-H2were studied. High phosphorus oolitic hematite, reduction and carburization products were investigated by the means of XRD and scanning electron microscope. The SEM-EDS and XRD analysis show that the main compositions of this ore are hematite and quartz, main microstructure is oolitic cluster with the zonal distribution of hematite and apatite, and iron carbide can be prepared from high phosphorus oolitic hematite.

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Chaudhury, Swati, Chandrika Varadachari, and Kunal Ghosh. "Ab Initio Studies on Hematite Surface and the Adsorption of Phosphate." Journal of Theoretical Chemistry 2014 (September 28, 2014): 1–7. http://dx.doi.org/10.1155/2014/312921.

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This investigation explores the ab initio DFT method for understanding surface structure of hematite and the nature and energetics of phosphate adsorption. Using the full potential linearized plane wave method (FP-LAPW), we derived the structure and energies of various magnetic forms of hematite. The antiferromagnetic (AFM) form was observed to be the most stable. Hematite surfaces with Fe-termination, O-termination, or OH-termination were studied. The OH-terminated surface was the most stable. Stability of hematite surfaces follows the order OH-termination > Fe-termination > O-termination. Thus, surface reaction with hematite would occur with the OH at the surface and not with Fe atoms. The structure of phosphate adsorbed on hematite was derived. Bonding is through the H atom of the OH at the surface. An alternative mechanism of phosphate adsorption on hematite has been derived. Adsorption energy is high and suggests chemisorption rather than physisorption of phosphate on hematite.

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Wu, Xi Qing, Ping Wei Yang, Zheng Cheng, and Liang Dai. "Surface Magnetization of Hematite by Metal Ions." Advanced Materials Research 785-786 (September 2013): 1104–10. http://dx.doi.org/10.4028/www.scientific.net/amr.785-786.1104.

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In an open hematite pulp with Fe2+ or Fe3+, Mn2+ and Zn2+, the surface magnetization of mineral hematite was accomplished by mechanical stirring. The both systems of Fe2+ or Fe3+, Mn2+ and Zn2+ magnetized the hematite surface to improve the recovery of hematite by magnetic separation. In the presence of Fe2+, the recovery of hematite increased from 69.0% to 85.7% after magnetization when the pulp temperature was 65°C, the concentration of Fe2+ 1.8x10-2mol/L, the concentration of OH- 0.1mol/L, the stirring speed 400r/min and the reaction time 5min respectively, and the saturation magnetization of hematite also increased from 0.62emu/g to 1.07emu/g, while in the presence of Fe3+, Mn2+ and Zn2+ ions, the saturation magnetization increased to 0.79emu/g. So, the magnetization and the magnetic recovery of hematite in the case of Fe2+ is better than that of Fe3+, Mn2+ and Zn2+. The surface magnetization of hematite occurs due to the adsorption of ultra-fine particles with strong magnetism on the hematite surface in the form of aggregates in the case of Fe2+ while in the form of flakes in the case of Fe3+, Mn2+ and Zn2+.

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Liang, Bing, Li Bing Zhao, Miao Miao Han, Hao Zhang, Qing Feng Zhang, Wei Min Zheng, Wen Shuang Wu, and Ao Shu Meng. "The Influences and the Mechanism of Action of Sodium Hexametaphosphate during Micro Fine Particle of Lean Hematite Ore of Grinding Operation." Applied Mechanics and Materials 641-642 (September 2014): 469–73. http://dx.doi.org/10.4028/www.scientific.net/amm.641-642.469.

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In this paper, the effect of sodium hexametaphosphate on the hematite was studied and the mechanism was analyzed. The results indicated that under the condition of the optimal grinding medium, compared with the result without sodium hexametaphosphate added, with citric acid added at the mass of 0.30% of the hematite, the content of-0.074mm of grinding production was increased by 6.38%; physical adsorption and chemical adsorption which were on the surface of hematite produced by sodium hexametaphosphate can reduce viscosity of grinding pulp, change surface potential of the hematite, and reduce the hardness on the surface of the hematite. Therefore citric acid can improve the grinding efficiency of the hematite.

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Cai, Jiajia, Yinglei Liu, Song Li, Meiqi Gao, Dunwei Wang, and Gaowu Qin. "Orientation modulated charge transport in hematite for photoelectrochemical water splitting." Functional Materials Letters 09, no. 03 (June 2016): 1650047. http://dx.doi.org/10.1142/s1793604716500478.

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Hematite is currently considered one of the most promising photoanode materials for light-driven water splitting. The photoelectrochemical performance of hematite is limited by its low conductivity. In this work, we demonstrate that the conductivity of hematite films can be tuned by controlling the orientation of hematite crystals. By applying a high magnetic field (up to 10 T) during the drop-casting preparation, hematite films composed of single crystal particles show featured texture by promoting those particles alignment with (001) normal to the substrate. By enhancing the photocurrent densities with tuned hematite orientation, the current method provides an effective way for increasing the number of carriers that can reach the surface.

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Liang, Bing, Jin Rui Zhang, Miao Miao Han, and Li Bing Zhao. "The Influences and the Mechanism of Action of Grinding Aid Agent during Micro Fine Particle of Lean Hematite Ore of Grinding Operation." Applied Mechanics and Materials 580-583 (July 2014): 2545–49. http://dx.doi.org/10.4028/www.scientific.net/amm.580-583.2545.

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In this paper, the effect of citric acid on the hematite was studied and the mechanism was analyzed. The results indicated that under the condition of the optimal grinding medium, compared with the result without citric acid added, with citric acid added at the mass of 0.10% of the hematite, the content of-0.074mm of grinding production was increased by 7.11%; physical adsorption and chemical adsorption which were on the surface of hematite produced by citric acid can reduce viscosity of grinding pulp, change surface potential of the hematite, and reduce the hardness on the surface of the hematite. Therefore citric acid can improve the grinding efficiency of the hematite.

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Fu, Yue, Huizi Wang, Jiang Zhang, Jian Chen, Quanqi Shi, Chao Yue, Honglei Lin, et al. "Possible Formation Mechanism of Lunar Hematite." Magnetochemistry 9, no. 2 (January 28, 2023): 43. http://dx.doi.org/10.3390/magnetochemistry9020043.

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Hematite, a ferric mineral with diagnostic features in the visible and infrared spectral range, has recently been discovered in the polar regions of the Moon by the Chandrayaan-1 Moon Mineralogy Mapper (M3). The oxygen involving the oxidization process producing lunar hematite is supposed to originate from the Earth’s upper atmosphere, and hematite with different ages may have preserved information on the oxygen evolution of the Earth’s atmosphere in the past billions of years. The discovery of lunar hematite may provide insight into the understanding of the oxidation products on the Moon and other airless bodies. In this work, we analyze hematite abundance distribution in the lunar polar regions, showing that the content of hematite on the lunar surface increases with latitude, and is positively correlated with surface water abundance. We suggest that the latitude dependence of hematite is derived from the latitude dependence of water, which indicates that water may play an essential role in the formation of hematite. The correlation between hematite and the optical maturity parameter (OMAT) was analyzed and a significant positive correlation was observed, which suggests that the hematite in the polar regions is the result of gradual and persistent oxidation reactions. In addition, based on the analysis of oxygen particles in the Earth wind, it was found that O+ and O2+ are much more abundant, suggesting that low-energy O+ or O2+ ions escaping from the upper atmosphere of the Earth may play a crucial role in the formation of hematite in the lunar polar regions.

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Cavaliere-Jaricot, S., A. Brioude, and P. Miele. "Ultrathin Polycrystalline Hematite and Goethite−Hematite Core−Shell Nanorods." Langmuir 25, no. 5 (March 3, 2009): 2551–53. http://dx.doi.org/10.1021/la803172b.

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Doula, M., A. Ioannou, A. Dimirkou, and György Füleky. "APPLICATION OF A FOUR-LAYER MODEL TO DESCRIBE HEMATITE, KAOLINITE AND KAOLINITE-HEMATITE SYSTEM (K-H) SURFACES." Acta Agronomica Hungarica 48, no. 4 (January 1, 2001): 381–93. http://dx.doi.org/10.1556/aagr.48.2000.4.8.

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The surface charges on hematite, kaolinite and on kaolinite coated with hematite (kaolinite-hematite system) were measured and successfully described using the model (Four-Layer Model) developed by Bowden and co-workers (1977; 1980a; 1980b). The surface charge was also calculated theoretically, according to a computer program developed by Barrow (1987). Significant differences were pointed out for the surface properties of the three solids examined. Anion-specific adsorption was observed for hematite and kaolinite-hematite, and cation adsorption for kaolinite.

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Niu, Yakun, Yi Zhou, Ping Niu, Haiyan Shen, and Ying Ma. "Effects of Ti Doping on Hematite Photoanodes: More Surface States." Journal of Nanoscience and Nanotechnology 19, no. 6 (June 1, 2019): 3437–46. http://dx.doi.org/10.1166/jnn.2019.16091.

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Ti doped hematite photoanodes have been intensively investigated due to their excellent activity for photoelectrochemical water oxidation. However, little attention has been paid to the doping effect on the photocurrent onset potential of hematite and the underlying mechanism. In this paper, Ti doped hematite nanorod arrays were successfully prepared through a facile treatment of hematite with TiCl3 solution. The photocurrent of the Ti doped hematite photoanode increases by three times, and its onset potential shifts more positively as compared with that of the undoped one. Electrochemical analyses were employed to unravel the mechanism of anodic shift of the onset potential. Cyclic voltammograms and electrochemical impedance spectra confirmed that more surface states were formed in Ti doped hematite than the undoped one. As a result, lower activity towards oxygen evolution reaction (OER) and increased electron–hole recombination after light on/off in low potential region were observed in Ti doped hematite. It is concluded that these doping induced surface states may be a hindrance to charge transfer and the onset potential of Ti doped hematite shifts anodically.

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Peršić, Ana, Nina Popov, Ljerka Kratofil Krehula, and Stjepko Krehula. "The Influence of Different Hematite (α-Fe2O3) Particles on the Thermal, Optical, Mechanical, and Barrier Properties of LDPE/Hematite Composites." Materials 16, no. 2 (January 11, 2023): 706. http://dx.doi.org/10.3390/ma16020706.

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There is an increasing need to develop new polymer composites with improved properties compared to conventional pure polymer materials. This work aims to develop composites of low-density polyethylene (LDPE) and iron oxide hematite particles. For this purpose, different types of hematite particles with well-defined shapes and narrow size distributions were synthesized: HC2 sample with pseudocubic hematite particles of an average diameter of 1020 nm, HE1 sample with ellipsoidal hematite particles of an average diameter of 533 nm, and HS1 sample with spherical hematite particles of an average diameter of 168 nm. The mass fractions of hematite in the composites were 0.25%, 0.5%, and 1%. Prepared LDPE/hematite composites were characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), and diffuse reflectance ultraviolet-visible-near infrared (UV-Vis-NIR) spectroscopy. The mechanical and barrier properties were also studied. The obtained results showed that all prepared composites have improved properties compared to the pure LDPE, especially the composites with pseudocubic hematite particles of well-defined shapes. The results of this study indicate that LDPE/hematite composites can be promising materials for a wide range of applications, especially as packaging materials where improved thermal and mechanical properties as well as resistance to ultraviolet (UV) irradiation are required.

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Burdin, Dmitri A., Dmitri V. Chashin, Nikolai A. Ekonomov, Leonid Y. Fetisov, Vladimir L. Preobrazhensky, and Yuri K. Fetisov. "Low-Frequency Resonant Magnetoelectric Effects in Layered Heterostructures Antiferromagnet-Piezoelectric." Sensors 23, no. 13 (June 25, 2023): 5901. http://dx.doi.org/10.3390/s23135901.

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Magnetic field sensors using magnetoelectric (ME) effects in planar ferromagnetic-piezoelectric heterostructures convert a magnetic field into an output voltage. The parameters of ME sensors are determined by characteristics of the magnetic constituent. In this work, the low-frequency ME effects in heterostructures comprising a layer of antiferromagnetic hematite α-Fe2O3 crystal with easy-plane anisotropy and a piezoelectric layer are studied. The effects arise due to a combination of magnetostriction and piezoelectricity because of mechanical coupling of the layers. The field dependences of magnetization and magnetostriction of the hematite crystal are measured. The resonant ME effects in the hematite-piezopolymer and hematite-piezoceramic structures are studied. The strong coupling between magnetic and acoustic subsystems of hematite results in a tuning of the acoustic resonance frequency by the magnetic field. For the hematite layer, the frequency tuning was found to be ~37% with an increase in the bias field up to 600 Oe. For the hematite-PVDF heterostructure, the frequency tuning reached ~24% and the ME coefficient was 58 mV/(Oe∙cm). For the hematite-piezoceramic heterostructure, the frequency tuning was ~4.4% and the ME coefficient 4.8 V/(Oe∙cm). Efficient generation of the second voltage harmonic in the hematite-piezoceramic heterostructure was observed.

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Li, Jiawei, Bin Lü, Tianyuan Chen, Xin Liu, Jinmeng Tang, and Hui Yan. "A New Perspective on the Applicability of Diffuse Reflectance Spectroscopy for Determining the Hematite Content of Fe-Rich Soils in the Tropical Margins of China." Minerals 14, no. 3 (February 27, 2024): 242. http://dx.doi.org/10.3390/min14030242.

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Hematite and goethite are widely occurring chromogenic iron oxides in soils and sediments that are sensitive to climatic dry/wet shifts. However, only by accurately quantifying the content or ratio of hematite and goethite can they be applied reliably to palaeoclimate reconstruction. Compared to the Loess Plateau of China, hematite in the soils of southern China has not been sufficiently studied. We used diffuse reflectance spectroscopy (abbreviation DRS, including the first-derivative curves and the second-derivative curves of the Kubelka–Munk remission functions), combined with ignition at 950 °C, and X-ray fluorescence (XRF) to quantify the hematite content of four tropical-margin iron-rich soil profiles with different matrix compositions in the Leizhou Peninsula, China. We also examined the application of hematite quantification parameters in soils with different matrix compositions under the same climatic conditions. Our main findings are as follows: (i) DRS first-derivative curves can reflect the presence of goethite and hematite in soils, and their relative contents can be compared within the same profile. (ii) The second-derivative curve of the Kubelka–Munk remission functions can reflect the relative proportions of goethite and hematite and provide information about the degree of Al substitution. (iii) Combined with calibration equations, soil redness can reliably quantify the hematite content, but it is necessary to consider the effect of mucilage envelopes in the process of hematite formation. Additionally, we summarize various methods used for quantifying hematite, and the influence of soil matrix compositions, with the aim of providing a reference for hematite quantification elsewhere. We also propose a new indicator (ΔHmRed/HmRed) to help detect iron hydroxide/iron oxide changes in soils.

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Chen, Jiang An, Jun Liu, and Xian Ping Luo. "Study on Technological Mineralogy and the Experimental of Hematite in Fengyang Anhui." Advanced Materials Research 361-363 (October 2011): 283–87. http://dx.doi.org/10.4028/www.scientific.net/amr.361-363.283.

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The paper researched on hematite’s characteristic of process mineralogy in Fengyang Anhui province. The chemical compositions of the ore were analyzed. The species, components of the hematite are determined, and the grain size and embedded characteristic of the ore are statistical. Some suggestions are proposed to improve the recovery of Fe2O3 according to the result of the process mineralogy study.

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Truong Thi, Hien, Bich Vu Thi, Binh Phan Thi, Thuy Mai Thi Thanh, Tan Man Minh, Dai Nguyen Tien, Trang Tran Thi, Hien Chu Thi Thu, Tuan Chu Van, and Nguyet Nguyen Thi. "Sn doped Hematite Nanorods for High-Performance Photoelectrochemical Water Splitting." Vietnam Journal of Catalysis and Adsorption 10, no. 1S (October 15, 2021): 405–9. http://dx.doi.org/10.51316/jca.2021.129.

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Photoelectrochemical water splitting is of great attention due to its environmentally friendly generation of clean fuels. Hematite (α-Fe2O3) is considered a promising candidate due to its intrinsic properties for the high-performance photoelectrochemical electrode, such as favorable bandgap (2.0–2.2 eV), a suitable energy band position non-toxicity, low cost, and excellent chemical stability. Herein, we report about Sn-doped hematite nanorods and their implementation as photoanodes for photoelectrochemical water splitting. We provide the simple but efficient route to incorporate the Sn into the hematite without structural damage in the nanostructure and scrutinize the effect of Sn dopant on the photoelectrochemical activity of the hematite. Sn can be successfully incorporated into the hematite by the two-step heat treatment process, which reveals the enhanced photoelectrochemical responses compared with undoped hematite. We elaborate on the effect of Sn dopant in the hematite on the photoelectrochemical activities, thereby suggesting the optimum concentration of Sn dopant.

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Pariona, Nicolaza, M. Herrera-Trejo, J. Oliva, and A. I. Martinez. "Peroxidase-Like Activity of Ferrihydrite and Hematite Nanoparticles for the Degradation of Methylene Blue." Journal of Nanomaterials 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/3427809.

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The peroxidase-like catalytic properties of 2-line ferrihydrite (2LFh) and hematite nanoparticles (NPs) for the degradation of methylene blue (MB) were studied. It is highlighted that the hematite NPs were prepared from the transformation of the metastable 2LFh NPs. It was found that the 2LFh NPs exhibited poor crystallinity with an average size of 5 nm, while the hematite NPs exhibited high crystallinity with an average size ofca. 100 nm. It was found that the total degradation of MB occurred for hematite NPs, while only a maximum degradation of 69% was possible for the 2LFh NPs. The Michaelis–Menten parameters indicated that the hematite NPs present higher catalytic activity than the 2LFh NPs at basic pH. It was found that the ordered surface of the hematite NPs has a stronger effect for the degradation of MB than its low surface area. It was concluded that the crystal planes of the hematite NPs affect the catalytic process more significantly than the high surface area of 2LFh NPs.

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Carvalho, Danúbia Bordim de, Roberto da Costa Lima, Letícia dos Santos Aguilera, Ronaldo Sergio de Biasi, and André Ben-Hur da Silva Figueiredo. "Ballistic resistance and microwave absorbing properties of a composite made of aramid fabric impregnated with polyethylene glycol and hematite nanoparticles." OBSERVATÓRIO DE LA ECONOMÍA LATINOAMERICANA 22, no. 3 (March 13, 2024): e3739. http://dx.doi.org/10.55905/oelv22n3-111.

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The ballistic resistance and microwave absorption of a composite of aramid fabric impregnated with polyethylene glycol and hematite nanoparticles was investigated for different hematite concentrations between 0 and 17 wt%. Different damage and energy absorbing mechanisms during ballistic impact were identified: cone formation on the back face of the target, tensile failure of primary yarns and deformation of secondary yarns. In terms of energy absorption, the best results were achieved with 7 wt% hematite, while the smallest depth of penetration (DOP) was observed for a composite with 9 wt% hematite. A scanning electron microscope (SEM) image of the composite with 7% hematite after the ballistic test showed that the main energy absorption mechanism was deformation of secondary yarns. The microwave absorption was measured using the waveguide technique in the frequency range from 8 to 12 GHz. The results showed that the dielectric loss ɛ”/ɛ’ is maximum for a concentration of 3% hematite, while the magnetic loss µ”/µ’ is maximum for a concentration of 11 wt% hematite. A reasonable compromise between ballistic resistance and microwave absorption seems to be a composite with 7 wt% hematite.

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Braga de Oliveira, Flávia, Gilberto Álvares da Silva, and Leonardo Martins Graça. "Defining the hematite topotaxial crystal growth in magnetite–hematite phase transformation." Journal of Applied Crystallography 53, no. 4 (June 18, 2020): 896–903. http://dx.doi.org/10.1107/s1600576720006305.

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Magnetite and hematite iron oxides are minerals of great economic and scientific importance. The oxidation of magnetite to hematite is characterized as a topotaxial reaction in which the crystallographic orientations of the hematite crystals are determined by the orientation of the magnetite crystals. Thus, the transformation between these minerals is described by specific orientation relationships, called topotaxial relationships. This study presents electron-backscatter diffraction analyses conducted on natural octahedral crystals of magnetite partially transformed into hematite. Inverse pole figure maps and pole figures were used to establish the topotaxial relationships between these phases. Transformation matrices were also applied to Euler angles to assess the diffraction patterns obtained and confirm the identified relationships. A new orientation condition resulting from the magnetite–hematite transformation was characterized, defined by the parallelism between the octahedral planes {111} of magnetite and rhombohedral planes \{10\bar {1}1\} of hematite. Moreover, there was a coincidence between one of the octahedral planes of magnetite and the basal {0001} plane of hematite, and between dodecahedral planes {110} of magnetite and prismatic planes \{11\bar {2}0\} of hematite. All these three orientation conditions are necessary and define a growth model for hematite crystals from a magnetite crystal. A new topotaxial relationship is also proposed: (111)Mag || (0001)Hem and (\bar {1}\bar {1}1)_{\rm Mag} || (10\bar {1}1)_{\rm Hem}.

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He, Wang, Zhijun Yang, Jintao Hu, Ke Zhang, and Hongwei Li. "Color Origin of Red Beds within the Danxia Basin, Southern China." Minerals 13, no. 8 (August 9, 2023): 1054. http://dx.doi.org/10.3390/min13081054.

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Sedimentary facies color is an important paleoclimate indicator, but may be unreliable in thick continental red beds. The Danxia Formation is the landscape strata of the Danxia basin, and its color fluctuates between reddish-brown and reddish-purple vertically. This study examined the ferric oxides characteristics, distribution, and mineral composition of the Danxia Formation using a variety of analytical techniques, including optical microscopy, high-resolution scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and micro-Raman spectroscopy. The results indicate that the reddish-brown mineral is composed primarily of fine hematite with traces of goethite, while the reddish-purple mineral consists solely of fine hematite. These hematites exhibit a particle size range of submicron to micron and display various morphologies, including spherical, flake, and fibrous forms. Goethite particles are needle-shaped and often form star-shaped aggregates containing twins. Whole rock geochemical analysis reveals a strong positive correlation between iron and iron group elements, as well as phosphorus and rare earth elements. The findings suggest that the reddening of the Danxia Formation occurs during diagenesis, with fine hematite forming as a result of the alteration of iron-bearing detrital grains. In addition, vertical color variations in Danxia Formation are not attributable to the paleoclimate records, but rather the result of the differentiation of sediment sources. This study provides a novel viewpoint for examining the coloration of thick continental red beds in other regions.

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Liu, Shu Xian, Li Li Shen, and Jin Xia Zhang. "Process Mineralogy and Concentrating of Hematite-Limonite Ore in Southern China." Advanced Materials Research 201-203 (February 2011): 2749–52. http://dx.doi.org/10.4028/www.scientific.net/amr.201-203.2749.

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The grade of the crude hematite-limonite ore is 39.79%. The main metallic minerals are hematite-limonite. Hematite has disseminated structure distributed in the gangue. Limonite was inlayed as stars in hematite. Due to their fine dissemination and close association with gangue minerals, the hematite and limonite particles are hard to be fully liberated, bringing difficulty in their separation. Staged grinding-separation process consisting of high intensity magnetic separation and reverse floatation wag adopted in the beneficiation test on the regionally representative hematite—limonite ore resource. At a grind of 70.0% -200 mesh for the primary grinding and 98.7% -200 mesh for the secondary grinding, the final iron concentrate grade 58.26% and having an iron recovery of 8.33% can be achieved after reverse flotation process test on magnetic concentrate.

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Kim, Seong Hee, Woo Chun Lee, Hyen Goo Cho, and Soon-Oh Kim. "Characterization of Arsenic Adsorption onto Hematite." Journal of the Mineralogical Society of Korea 25, no. 4 (December 31, 2012): 197–210. http://dx.doi.org/10.9727/jmsk.2012.25.4.197.

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Dvoretskaya, A. N., L. G. Anikanova, and N. V. Dvoretskii. "Effect of the Precursor and Synthesis Mode on the Properties of Hematite for the Preparation of Promoted Iron Oxide Catalysts." Kataliz v promyshlennosti 22, no. 5 (September 27, 2022): 6–14. http://dx.doi.org/10.18412/1816-0387-2022-5-6-14.

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The fine crystal structure of hematite samples used to prepare potassium-promoted iron oxide dehydrogenation catalysts has been studied by X-ray diffraction and scanning electron microscopy. Samples of α-Fe2O3 were obtained under nonequilibrium conditions from several precursors under different thermolysis regimes. The most important characteristic of hematite, which determines the activity and selectivity of the catalyst based on it, is the fine crystal structure (TCS). The TCS of hematite determines the phase composition of the catalyst. The TCS of hematite is formed during the synthesis of hematite and is determined by the nature of the precursor, the temperature of sample synthesis, and the temperature gradient of the rate of removal of gaseous thermolysis products. The highest activity was demonstrated by a catalyst prepared on the basis of hematite with mosaic blocks of 70–90 nm, with a minimum concentration of SF due to half and quaternary dislocations. Such hematite was obtained by thermolysis of iron sulfate at 950 K under fluidized bed conditions and a low temperature gradient. Hematite from iron carbonate is not recommended for the synthesis of a catalyst due to the high concentration of low-temperature SF, which leads to the formation of catalytically inactive potassium β-polyferrite.

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Kratofil Krehula, Ljerka, Ana Peršić, Nina Popov, and Stjepko Krehula. "Polymer Composites of Low-Density Polyethylene (LDPE) with Elongated Hematite (α-Fe2O3) Particles of Different Shapes." Journal of Composites Science 8, no. 2 (February 11, 2024): 73. http://dx.doi.org/10.3390/jcs8020073.

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Due to the intensive search for new types of advanced polymer materials for targeted applications, this work offers insight into the properties of low-density polyethylene/hematite composites. The specific feature of this study lies in the use of elongated hematite particles of different shapes. Uniform ellipsoid-, peanut- and rod-shaped hematite particles were hydrothermally synthesized and incorporated into the polymer matrix of low-density polyethylene (LDPE). LDPE/hematite composites are prepared by melt mixing. Hematite particles are characterized by scanning electron microscopy (SEM) and powder X-ray diffraction (PXRD). The pure LDPE polymer and LDPE/hematite composites were studied by FT-IR and UV-Vis-NIR spectroscopy and by thermogravimetric analysis (TGA). The determination of the mechanical and barrier properties was also carried out. The obtained results indicate the influence of the elongated particles on the improvement of LDPE properties. An increase in thermal stability and UV-absorption was observed as well as the improvement of mechanical and barrier properties. The improvement of the composites’ properties in comparison to the pure LDPE is especially visible in the composites prepared with low content of hematite (0.25%). LDPE/hematite composites have promising characteristics for application as packaging materials with enhanced mechanical, thermal and barrier properties as well as UV-protective materials.

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Wu, Xi Qing, Liang Dai, Chuan Dai, Zheng Cheng, Long Sheng Yi, and Xiao Qi Liu. "Synergic Surface Magnetization of Siderite on Hematite." Advanced Materials Research 881-883 (January 2014): 1647–54. http://dx.doi.org/10.4028/www.scientific.net/amr.881-883.1647.

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The surface magnetization without adding any iron-containing substance as a magnetic seed is called self-magnetization. Tests show that temperature and pH of the slurry are two important factors in the self-magnetization of siderite and its synergic effect on hematite; that the self-magnetization took place on siderite but did not on hematite while a synergic effect of surface magnetization, i.e. the promotion of surface magnetization of hematite in the presence of siderite, appeared in the mineral mixtures or real iron ore containing hematite and siderite. The infrared spectra indicate that there is Fe3O4 generated on the surface of siderite in the process of self-magnetization; the measurement of VSM confirmed a significant change in magnetic hysteresis loops and increase of the saturated magnetization after hematite was magnetized by Fe2+ in the slurry; and SEM observed the adsorption of Fe3O4 species on the surface of hematite, which is generated originally from the siderite in an alkaline slurry, resulting in the synergic effect of siderite on hematite .

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45

Wan Ahmad, Wan Rosmaria, M. H. Mamat, A. S. Zoolfakar, Z. Khusaimi, A. S. Ismail, T. N. T. Yaakub, and M. Rusop. "Effect of substrate placement in schott vial to hematite properties." Bulletin of Electrical Engineering and Informatics 8, no. 1 (March 1, 2019): 58–64. http://dx.doi.org/10.11591/eei.v8i1.1391.

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In the present study, hematite (α-Fe2O3) nanostructures were deposited on fluorine doped tin oxide (FTO) coated glass substrate using sonicated immersion synthesis method. The effect of FTO glass substrate placement in Schott vial during immersion process was studied on the growth of the hematite nanostructure and its properties. XRD pattern has revealed seven diffraction peaks of α-Fe2O3 for both hematite nanostructures samples attributed to polycrystalline with rhombohedral lattice structure. The surface morphologies from FESEM have shown that the hematite nanostructures were grown uniformly in both samples with FTO conductive layer facing up and down. Hematite sample with FTO facing down exhibits a smaller size of nanorod, 26.7 nm average diameter, compared to the hematite sample that FTO face up with 53.8nm average diameter. Optical properties revealed higher transmittance in the sample with FTO facing down, probably due to smaller size of nanostructure. The optical band gap energy plotted and extrapolated at 2.50eV and 2.55eV for FTO face up and FTO face down hematite samples respectively, presenting the sample with FTO face up has a lower optical bandgap energy.

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Faustino, Lívia Marques, Belinda McFadzean, José Tadeu Gouvêa Junior, and Laurindo de Salles Leal Filho. "Bulk and Surface Characterization of Distinct Hematite Morphology: Implications for Wettability and Flotation Response." Minerals 14, no. 6 (June 14, 2024): 609. http://dx.doi.org/10.3390/min14060609.

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To understand why hematite of different genesis behave diversely in flotation systems, this study assesses the flotation response at pH 5 of bulk (morphology, texture, Crystal Preferential Orientation (CPO)) plus interfacial (surface area, zeta potential, immersion enthalpy, contact angle, induction time) characteristics of species formed under distinct metamorphic conditions: low-strain deformation (Hematite-1) versus high-strain deformation (Hematite-2). Hematite-2 (predominantly composed of specular and lamellar morphologies) shows (001) CPO and exhibits fewer Fe sites on its surface that undergo doubly coordinated Fe-OH when exposed to moisture. This results in a less reactive surface associated with a less ordered adsorbed water layer than Hematite-1, which is predominantly composed of granular and sinuous hematite. Those characteristics lead to a naturally hydrophobic behavior characterized by the exothermic energy below the Critical Immersion Enthalpy (−∆Himm < 200 mJ/m2), lower values of zeta potential due to attenuated dissociation of Fe-OH(surf), lower induction time (47 ms vs. 128 ms), higher contact angle (39° vs. 13°), and higher flotation recovery (21% vs. 12%) than Hematite-1.

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Wang, Rongming, Yaofeng Chen, Yunyi Fu, Han Zhang, and Christian Kisielowski. "Bicrystalline Hematite Nanowires." Journal of Physical Chemistry B 109, no. 25 (June 2005): 12245–49. http://dx.doi.org/10.1021/jp051197q.

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48

Inaba, Mika, Kenji Katayama, and Woon Yong Sohn. "Cooperative effects of surface and interface treatments in a hematite (α-Fe2O3) photo-anode on its photo-electrochemical performance." Sustainable Energy & Fuels 4, no. 5 (2020): 2174–83. http://dx.doi.org/10.1039/c9se01081e.

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To enhance the efficiency of the oxygen evolution reaction of hematite (α-Fe₂O₃), we engineered both the surface of the hematite nanorods and the FTO/hematite interface simultaneously with an optimal annealing condition.

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49

Dimirkou, A., A. Ioannou, and Ch Kalliannou. "Synthesis‐identification of hematite and bentonite ‐hematite (b‐h) system." Communications in Soil Science and Plant Analysis 27, no. 5-8 (March 1996): 1055–69. http://dx.doi.org/10.1080/00103629609369617.

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50

Dimirkou, A., A. Ioannou, and Ch Kalliannou. "Synthesis‐identification of hematite and kaolinite ‐hematite (k‐h) system." Communications in Soil Science and Plant Analysis 27, no. 5-8 (March 1996): 1091–106. http://dx.doi.org/10.1080/00103629609369619.

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Journal articles on the topic 'Hematite'

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