Many researchers have focused on the behavior of fiber-reinforced concrete(FRC)in the construction of various defensive structures to resist against impact forces resulting from explosions and projectiles.However,the ...Many researchers have focused on the behavior of fiber-reinforced concrete(FRC)in the construction of various defensive structures to resist against impact forces resulting from explosions and projectiles.However,the lack of sufficient research regarding the resistance of functionally graded fiber-reinforced concrete against projectile impacts has resulted in a limited understanding of the performance of this concrete type,which is necessary for the design and construction of structures requiring great resistance against external threats.Here,the performance of functionally graded fiber-reinforced concrete against projectile impacts was investigated experimentally using a(two-stage light)gas gun and a drop weight testing machine.For this objective,12 mix designs,with which 35 cylindrical specimens and 30 slab specimens were made,were prepared,and the main variables were the magnetite aggregate vol%(55%)replacing natural coarse aggregate,steel fiber vol%,and steel fiber type(3D and 5D).The fibers were added at six vol%of 0%,0.5%,0.75%,1%,1.25%,and 1.5%in 10 specimen series(three identical specimens per each series)with dimensions of 40×40×7.5 cm and functional grading(three layers),and the manufactured specimens were subjected to the drop weight impact and projectile penetration tests by the drop weight testing machine and gas gun,respectively,to assess their performance.Parameters under study included the compressive strength,destruction level,and penetration depth.The experimental results demonstrate that using the magnetite aggregate instead of the natural coarse aggregate elevated the compressive strength of the concrete by 61%.In the tests by the drop weight machine,it was observed that by increasing the total vol%of the fibers,especially by increasing the fiber content in the outer layers(impact surface),the cracking resistance and energy absorption increased by around 100%.Note that the fiber geometry had little effect on the energy absorption in the drop weight test.Investigating the optimum specimens showed that using 3D steel fibers at a total fiber content of 1 vol%,consisting of a layered grading of 1.5 vol%,0 vol%,and 1.5 vol%,improved the penetration depth by 76%and lowered the destruction level by 85%.In addition,incorporating the 5D steel fibers at a total fiber content of 1 vol%,consisting of the layered fiber contents of 1.5%,0%,and 1.5%,improved the projectile penetration depth by 50%and lowered the damage level by 61%compared with the case of using the 3D fibers.展开更多
Compared with natural magnetite concentrate, artificial magnetite with more lattice defects and higher activity tends to be oxidized. And the artificial magnetite pellet at the temperature of 400℃ has the oxidation d...Compared with natural magnetite concentrate, artificial magnetite with more lattice defects and higher activity tends to be oxidized. And the artificial magnetite pellet at the temperature of 400℃ has the oxidation degree approaching to natural magnetite concentrate pellet fired at 1000℃. Besides, two kinds of pellets displayed quite different roasting characteristics. When preheated at the same temperature for the same period of time, natural magnetite concentrate pellet and artificial magnetite concentrate pellet need to be roasted at the temperature of 1100℃ and 1250℃, respectively, for 25 min to reach the compressive strength of 3000 N per pellet. When roasted at the same temperature of 1200℃, natural magnetite pellet and artificial magnetite pellet need to be roasted for 15 min and 30 min, respectively, to reach the compressive strength over 3000 N per pellet. It can be seen from the test that artificial magnetite pellet has a faster oxidation, resulting in the high porosity in the produced pellet, and it requires a roasting process at higher temperature for a longer time to reach the desired compressive strength for industrial production.展开更多
The effect of sinter basicity on softening-melting behaviors of mixed burden made from chromium-bearing vanadium-titanium magnetite(Cr-V-Ti magnetite) was investigated and the function mechanism was simultaneously ana...The effect of sinter basicity on softening-melting behaviors of mixed burden made from chromium-bearing vanadium-titanium magnetite(Cr-V-Ti magnetite) was investigated and the function mechanism was simultaneously analyzed.The results show that with increasing sinter basicity from 1.71 to 2.36,the softening interval tends to increase from 149.3 ℃ to 181.7 ℃while the melting interval tends to decrease from 178.0 ℃ to 136.7 ℃.The location of cohesive zone moves downwards firstly and then ascends slightly,but the cohesive zone becomes thinner.The softening-melting characteristic value becomes small,which indicates that the permeability of burden column is improved.The dripping ratio of mixed burden tends to increase firstly and then decrease,which comes to the highest value of 74.50%when the sinter basicity is 2.13.The content and the recovery of V and Cr in dripping iron are all increased.The generation amount of components with high melting point in slag becomes little with the increase of sinter basicity,which could improve the permeability of mixed burden.Taking softening-melting behaviors of mixed burden and recovery of valuable elements into account,the proper sinter basicity is no less than 2.13 for smelting mixed burden made from Cr-V-Ti magnetite in blast furnace.展开更多
Proper utilization of the FeSO4·7H2O waste slag generated from TiO2 industry is an urgent need, and Fe3O4 particles are currently being widely used in the wastewater flocculation field. In this work, magnetite wa...Proper utilization of the FeSO4·7H2O waste slag generated from TiO2 industry is an urgent need, and Fe3O4 particles are currently being widely used in the wastewater flocculation field. In this work, magnetite was recovered from ferrous sulphate by a novel co-precipitation method with calcium hydroxide as the precipitant. Under optimum conditions, the obtained spherical magnetite particles are well crystallized with a Fe304 purity of 88.78%, but apt to aggregate with a median particle size of 1.83 μm. Magnetic measurement reveals the obtained Fe304 particles are soft magnetic with a saturation magnetization of 81.73 A-m2/kg. In addition, a highly crystallized gypsum co-product is obtained in blocky or irregular shape. Predictably, this study would provide additional opportunities for future application of low-cost Fe3O4 particles in water treatment field.展开更多
Modified humic acid (MHA) binder based on lignite humic substances is a novel sort of promising organic binder for iron ore pellets.Humic acid (HA) is one of the main ingredients of MHA binder.Pure HA was firstly isol...Modified humic acid (MHA) binder based on lignite humic substances is a novel sort of promising organic binder for iron ore pellets.Humic acid (HA) is one of the main ingredients of MHA binder.Pure HA was firstly isolated from lignite and then adsorption of HA onto magnetite particle surface was investigated.The final results indicate that the adsorption of HA onto magnetite surface accords with Langmuir model well,and it is evidently influenced by the initial HA concentration and solution pH value.Adsorption depends on chemical interaction at pH values above the PZC (the pH where the Zeta potentials of minerals are zero) of magnetite,while electrostatic attraction and chemical interaction both contribute to the adsorption at pH values below the PZC.展开更多
Magnetite is a kind of iron ore that is difficult to carburize.In order to improve the carburizing performance of magnetite pellet,pre-oxidation treatment was carried out,and the oxidation,reduction and carburization ...Magnetite is a kind of iron ore that is difficult to carburize.In order to improve the carburizing performance of magnetite pellet,pre-oxidation treatment was carried out,and the oxidation,reduction and carburization behaviors of magnetite pellet were investigated in this study.The magnetite pellet was oxidized in the air and carburized in CO-CO_(2)-H_(2) gas mixtures,the oxidation,reduction and carburization behaviors were demonstrated by detecting phase change,microstructure,carburizing index via thermogravimetry,X-ray diffraction(XRD),infrared carbon-sulfur analyzer,and scanning electron microscope(SEM).The results show that the dense magnetite particles inside pellet are oxidized to porous hematite particles,and the Fe_(3)O_(4) transforms to Fe_(2)O_(3) with high lattice defect concentration during the pre-oxidation process.Then the porous hematite particles and newly formed Fe_(2)O_(3) significantly promote the reduction efficiency.Porous metallic iron particles are produced in the reduction process.Finally,both high reduction efficiency and the porous structure of metallic iron particles dramatically enhance the carburization efficiency of pellet.High preoxidation temperature favors to the carburization of magnetite pellet.However,the carburized index decreases due to the recrystallization of iron oxide when the temperature extends to 1000℃.The optimum pre-oxidation temperature for magnetite pellet carburization is 900℃.展开更多
The effects of basicity and temperature on the reduction process of Hongge high-chromium vanadium-titanium magnetite(HCVTM)sinter were investigated in this work.The main characterization methods of X-ray fluorescence(...The effects of basicity and temperature on the reduction process of Hongge high-chromium vanadium-titanium magnetite(HCVTM)sinter were investigated in this work.The main characterization methods of X-ray fluorescence(XRF),X-ray diffraction(XRD),scanning electron microscope(SEM),and metallographic microscope were employed in this study.In this work,the reduction of HCVTM sinter with different temperature and basicity were experimented.The Fe,FeO,and TiO in reductive samples increase with increasing basicity and temperatures.The increase of basicity and temperature is favorable to the reduction of HCVTM sinter.The Fe phase has out-migration tendency to the surface of sinter while the perovskite and silicate phases have in-migration tendency to the inside of sinter.The reduction degradation index(RDI)decreases while the reduction index(RI)increases with increasing basicity.The RI increases from 67.14%to 82.09%with increasing temperature from 1073 K to 1373 K.展开更多
In this study,the effects of drying temperature,hot airflow speed and diameter of green pellet on drying rate of artificial magnetite pellet were deeply investigated to clarify the drying characteristics of artificial...In this study,the effects of drying temperature,hot airflow speed and diameter of green pellet on drying rate of artificial magnetite pellet were deeply investigated to clarify the drying characteristics of artificial magnetite green pellet.The results show that the drying process of artificial magnetite green pellet has three stages,accelerated drying stage,constant drying stage and decelerated drying stage.And drying temperature and hot airflow speed both have significant reciprocal effects on moisture ratio and drying rate of green pellet during the drying process.However,the diameter of green pellet has little effect on drying process of green pellet.Then the drying fitting models of Correction Henderson and Pabis,Lewis,Correction Page(III),Wang and Singh are used to describe the drying kinetics of artificial magnetite green pellet.The fitting results indicate that the drying process of artificial magnetite pellet can be described by Correction Page(III)model accurately.Finally,the contrast experiments demonstrate that the fitting model can well describe the actual drying process.展开更多
The pulsed power is a potential means for energy saving and presents an alternative to the conventional mechanical communication for minerals.The effect of magnetic pulse treatment on grindability of a magnetite ore w...The pulsed power is a potential means for energy saving and presents an alternative to the conventional mechanical communication for minerals.The effect of magnetic pulse treatment on grindability of a magnetite ore was investigated by grindability tests.The results of the investigation show that the pulsed treatment has little effect on the particle size distribution of the magnetite ore.Significant micro-cracks or fractures are not found by SEM analysis in magnetic pulse treated sample.Magnetic separation of magnetic pulse treated and untreated magnetite ore indicates that iron recovery increases from 81.3% in the untreated sample to 87.7% in the magnetic pulse treated sample,and the corresponding iron grade increases from 42.1% to 44.4%.The results demonstrate that the magnetic pulse treatment does not significantly weaken the mineral grain boundaries or facilitate the liberation of minerals,but is beneficial to magnetic separation.展开更多
Grinding is one of the most costly operations in the mechanical breaking and mining.Determination of the breakage characteristics and preconditioning is important to increase the grinding efficiency.Investigations of ...Grinding is one of the most costly operations in the mechanical breaking and mining.Determination of the breakage characteristics and preconditioning is important to increase the grinding efficiency.Investigations of the seismic,mechanical and breakage properties of iron oxides are very important parameters for investigating the rock fragmentation by blasting and comminution processes in iron ore mines.In this paper,at first,geomechanical and seismic properties of the oxide ores(magnetite and hematite)in the Chadormalu iron ore mine were studied.The results showed that the percentage of magnetite has a direct relationship with uniaxial compressive strength,tensile strength and P and S wave’s velocities and has an inverse relationship with Poisson ratio and porosity.Moreover,to study breakage and preconditioning characteristics in the iron ores,two samples with different magnetite percents were blasted by detonation cord.The results showed that with higher percentage of magnetite,the number of fractures induced by blasting increased.Bond work index and magnetite percent were investigated in the 430 blasts in the mine.This investigation not only confirmed the small scale blasting results,but also showed that increasing the magnetite percent up to 50%noticeably reduces Bond work index and energy consumption in the grinding process.Also,the relationship between muck pile fragmentation and magnetite percentage were studied for several blasts that had the same blast pattern parameters and similar geology conditions.These results also confirmed precedents conclusions regarding magnetite percent and preconditioning relationship.展开更多
In nature, iron cations in magnetite are usually isomorphically substituted by divalent (Co, Ni, Zn, Cu, Mn, etc.), trivalent (Al, V, Cr, etc.) and tetravalent (Ti) cations while maintaining the spinel structure. Some...In nature, iron cations in magnetite are usually isomorphically substituted by divalent (Co, Ni, Zn, Cu, Mn, etc.), trivalent (Al, V, Cr, etc.) and tetravalent (Ti) cations while maintaining the spinel structure. Some of the substituting cations, e.g. Cr3+, V3+ and Mn2+, improve the catalytic activity of magnetite in heterogeneous Fenton reaction through the enhancement of hydroxyl radical OH production and the pollutant adsorption.展开更多
The iron-oxide system can be used as a marker of oxidized and reduced conditions in closed systems. However, natural rocks with iron-oxide minerals also exhibit such reactions, although the natural system is typically...The iron-oxide system can be used as a marker of oxidized and reduced conditions in closed systems. However, natural rocks with iron-oxide minerals also exhibit such reactions, although the natural system is typically open. To understand the behaviour of this natural system, they were investigated the similarities, in terms of crystallographic textures, between the microstructures of two systems: natural open system and synthetic closed system of iron-oxide phase transformation.展开更多
There has recently been a fundamental need to develop high efficiency microwave absorbers to reduce electro-magnet-ic pollution.It is often very difficult to obtain superior absorption with only one material,so we hav...There has recently been a fundamental need to develop high efficiency microwave absorbers to reduce electro-magnet-ic pollution.It is often very difficult to obtain superior absorption with only one material,so we have explored composites using fillers of activated carbon derived from biological material(oleaster seeds)and resin(apricot tree gum)with Fe_(3)O_(4) in a paraffin wax matrix to improve the dielectric properties and achieve a high specific surface area.A 1 mm thick layer of a Fe_(3)O_(4)+resin(FEOR),with the magnetic nanoparticles anchored to the gum,resulted in a reflection loss of−71.09 dB.We compared this with the results for composites using a filler of Fe_(3)O_(4)+activated carbon,and one with a three-component filler of Fe_(3)O_(4)+activated carbon+resin which had a very porous structure that had a direct effect on the surface polarization.However,the FEOR sample had near-ideal im-pedance matching,close to 1,which resulted in high absorption performance.In addition,the presence of defects improves mi-crowave attenuation by dipole polarization and charge carrier trapping.This work suggests the use of new types of biomaterials to in-crease microwave absorption.展开更多
Mineral compositions and microstructures of fluorine bearing magnetite concentrate and vanadium titanomagnetite concentrate are studied. The results show that a boride and a catalytic oxidation agent have great effect...Mineral compositions and microstructures of fluorine bearing magnetite concentrate and vanadium titanomagnetite concentrate are studied. The results show that a boride and a catalytic oxidation agent have great effects on ameliorating the mineral compositions and microstructures of these sinters, and the catalytic agent is more effective. Comparing these two kinds of ores, the performance of fluorine bearing magnetite concentrate is better. Addition of 0.01% catalyst into fluorine bearing magnetite concentrate can increase calcium ferrite content from 15% 20% up to 34% 39%, and its microstructure changes from large cavities and thin framework into intermediate cavities and thick framework, and the microcracks disappear.展开更多
Qara-aghaj and Skandian as hard rock titanium deposit and Kahnooj one as a placer deposit were investigated from applied mineralogical point of view. The mineralogical studies were carried out using XRD, XRF, optical ...Qara-aghaj and Skandian as hard rock titanium deposit and Kahnooj one as a placer deposit were investigated from applied mineralogical point of view. The mineralogical studies were carried out using XRD, XRF, optical microscopy, scanning electron microscopy and microprobe analysis. These studies indicated that ilmenite and magnetite are main valuable minerals in the studied ores. Pyroxene, olivine and plagioclase are the main gangue minerals in Qara-aghaj ore while chlorite and plagioclase are the major gangue minerals in Skandian ore. Plagioclase, clinopyroxene, amphibole, feldspate and some quartz are the important gangue minerals in kahnooj deposit. In all three ores ilmenite is mainly in the form of ilmenite grains but some lamellae of ilmenite with thickness between 0.1 to 20 μm have been occurred as exsolution textures inside magnetite grains, where the magnetite here can be referred to as ilmenomagnetite. In the hard rock ores some fine ilmenites have been disseminated in silicate minerals. The liberation degree of granular ilmenite was determined 150, 140 and 200 μm for Qara-aghaj, Skandian and Kahnooj, respectively. So, only the granular form of ilmenite is recoverable by physical methods. Some sphene and rutile as titanium containing minerals were observed mainly inside ilmenite phase in kahnooj ore. Some fine rutile was also found inside Skandian ilmenite while there were not any other titanium minerals inside Qara-aghaj ilmenite. Apatite is another valuable mineral which was found only in Qara-aghaj ore. Using SEM and microprobe analysis it was found that there are different amounts of exsolved fine lamellae of hematite inside ilmenite in Qara-aghaj and Kahnooj ores while it was not observed in Sckandian one. The average contents of TiO2 in the lattice of Qara-aghaj, Skandian and Kahnooj ilmenite were determined 51.13, 50.9% and 52.02%, respectively. FeO content of ilmenite lattice for all three samples is clearly lower than the theoretical content. This is due to the substitution of Mg and Mn for some Fe2+ ions in the ilmenite lattice. V2O3 content of magnetite lattice is up to 1%. So, magnetite can be a suitable source for production of vanadium as a by-product in all three deposits.展开更多
The separation of iron oxide from banded hematite jasper(BHJ) assaying 47.8% Fe, 25.6% Si O2 and 2.30%Al2O3 using selective magnetic coating was studied. Characterization studies of the low grade ore indicate that bes...The separation of iron oxide from banded hematite jasper(BHJ) assaying 47.8% Fe, 25.6% Si O2 and 2.30%Al2O3 using selective magnetic coating was studied. Characterization studies of the low grade ore indicate that besides hematite and goethite,jasper, a microcrystalline form of quartzite, is the major impurity associated with this ore. Beneficiation by conventional magnetic separation technique could yield a magnetic concentrate containing 60.8% Fe with 51% Fe recovery. In order to enhance the recovery of the iron oxide minerals, fine magnetite, colloidal magnetite and oleate colloidal magnetite were used as the coating material. When subjected to magnetic separation, the coated ore produces an iron concentrate containing 60.2% Fe with an enhanced recovery of56%. The AFM studies indicate that the coagulation of hematite particles with the oleate colloidal magnetite facilitates the higher recovery of iron particles from the low grade BHJ iron ore under appropriate conditions.展开更多
Large scaled uniform and size-controllable magnetic submicroparticles(MSPs) were synthesized via solvothermal method with ferric chloride as iron source and sodium acetate as trapping agent. The influence of Fe^(3+) a...Large scaled uniform and size-controllable magnetic submicroparticles(MSPs) were synthesized via solvothermal method with ferric chloride as iron source and sodium acetate as trapping agent. The influence of Fe^(3+) and Na Ac contents on the size distribution of MSPs was investigated. The structural and morphological properties of the synthesized particles were studied by scanning electron microscopy(SEM), X-ray power diffraction(XRD) and vibrating sample magnetometer(VSM). The well-dispersed MSPs with size of 100-1000 nm were obtained by simply adjusting the contents of Fe^(3+) and NaA c. In addition, the hemolysis and cytotoxicity of Fe_3O_4 MSPs, and their ability to case arrest in cell life-cycles were studied. The results indicate that larger size could lead to lower hemolysis. From MTT(3-(4,5-dimethylthuazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, the interactions between MSPs and adhesive mouse fibroblast cell line(L929) were probed. Larger size of Fe_3O_4 MSPs demonstrates lower cell viability following an exposure to the cells.展开更多
The northern section of the UAE is bordered by the Gulf of Oman’s northern extension (East Coast) and Arabian Gulf’s Eastern extension (northern West Coast). Unlike the rest, the coastline of this section is more or...The northern section of the UAE is bordered by the Gulf of Oman’s northern extension (East Coast) and Arabian Gulf’s Eastern extension (northern West Coast). Unlike the rest, the coastline of this section is more or less faced by mountainous areas of various rock types. The beach sands a long this coastline at both sides (East and northern-West) signify some heavy minerals concentration of an important consideration.展开更多
Automated core scanning technologies for mineralogical characterisation of diamond core, drill chips pulps is now an established technique, particularly in the Australian iron ore industry, for mineral analysis in exp...Automated core scanning technologies for mineralogical characterisation of diamond core, drill chips pulps is now an established technique, particularly in the Australian iron ore industry, for mineral analysis in exploration and mining. Application of reflectance spectroscopy over the 400–2500 nm, visible to near-infrared wavelength range, has been used to characterise the iron ore oxide mineralogy of bedded iron deposit (BID) derived iron ores in India (Thangavelu et al., 2011) and Brazil (da Costa et al., 2009), and used to define the ore and gangue (e.g., clay) mineralogy in ironstone or channel iron deposits (CID) in the Pilbara region of Western Australia (e.g., Haest et al., 2012).展开更多
文摘Many researchers have focused on the behavior of fiber-reinforced concrete(FRC)in the construction of various defensive structures to resist against impact forces resulting from explosions and projectiles.However,the lack of sufficient research regarding the resistance of functionally graded fiber-reinforced concrete against projectile impacts has resulted in a limited understanding of the performance of this concrete type,which is necessary for the design and construction of structures requiring great resistance against external threats.Here,the performance of functionally graded fiber-reinforced concrete against projectile impacts was investigated experimentally using a(two-stage light)gas gun and a drop weight testing machine.For this objective,12 mix designs,with which 35 cylindrical specimens and 30 slab specimens were made,were prepared,and the main variables were the magnetite aggregate vol%(55%)replacing natural coarse aggregate,steel fiber vol%,and steel fiber type(3D and 5D).The fibers were added at six vol%of 0%,0.5%,0.75%,1%,1.25%,and 1.5%in 10 specimen series(three identical specimens per each series)with dimensions of 40×40×7.5 cm and functional grading(three layers),and the manufactured specimens were subjected to the drop weight impact and projectile penetration tests by the drop weight testing machine and gas gun,respectively,to assess their performance.Parameters under study included the compressive strength,destruction level,and penetration depth.The experimental results demonstrate that using the magnetite aggregate instead of the natural coarse aggregate elevated the compressive strength of the concrete by 61%.In the tests by the drop weight machine,it was observed that by increasing the total vol%of the fibers,especially by increasing the fiber content in the outer layers(impact surface),the cracking resistance and energy absorption increased by around 100%.Note that the fiber geometry had little effect on the energy absorption in the drop weight test.Investigating the optimum specimens showed that using 3D steel fibers at a total fiber content of 1 vol%,consisting of a layered grading of 1.5 vol%,0 vol%,and 1.5 vol%,improved the penetration depth by 76%and lowered the destruction level by 85%.In addition,incorporating the 5D steel fibers at a total fiber content of 1 vol%,consisting of the layered fiber contents of 1.5%,0%,and 1.5%,improved the projectile penetration depth by 50%and lowered the damage level by 61%compared with the case of using the 3D fibers.
基金Project(51474161)supported by the National Natural Science Foundation of China
文摘Compared with natural magnetite concentrate, artificial magnetite with more lattice defects and higher activity tends to be oxidized. And the artificial magnetite pellet at the temperature of 400℃ has the oxidation degree approaching to natural magnetite concentrate pellet fired at 1000℃. Besides, two kinds of pellets displayed quite different roasting characteristics. When preheated at the same temperature for the same period of time, natural magnetite concentrate pellet and artificial magnetite concentrate pellet need to be roasted at the temperature of 1100℃ and 1250℃, respectively, for 25 min to reach the compressive strength of 3000 N per pellet. When roasted at the same temperature of 1200℃, natural magnetite pellet and artificial magnetite pellet need to be roasted for 15 min and 30 min, respectively, to reach the compressive strength over 3000 N per pellet. It can be seen from the test that artificial magnetite pellet has a faster oxidation, resulting in the high porosity in the produced pellet, and it requires a roasting process at higher temperature for a longer time to reach the desired compressive strength for industrial production.
基金Project(51574067)supported by the National Natural Science Fundation of ChinaProjects(2012AA062302,2012AA062304)supported by the National High Technology Research and Development Program of ChinaProject(N110202001)supported by the Fundamental Research Funds for the Central Universities of China
文摘The effect of sinter basicity on softening-melting behaviors of mixed burden made from chromium-bearing vanadium-titanium magnetite(Cr-V-Ti magnetite) was investigated and the function mechanism was simultaneously analyzed.The results show that with increasing sinter basicity from 1.71 to 2.36,the softening interval tends to increase from 149.3 ℃ to 181.7 ℃while the melting interval tends to decrease from 178.0 ℃ to 136.7 ℃.The location of cohesive zone moves downwards firstly and then ascends slightly,but the cohesive zone becomes thinner.The softening-melting characteristic value becomes small,which indicates that the permeability of burden column is improved.The dripping ratio of mixed burden tends to increase firstly and then decrease,which comes to the highest value of 74.50%when the sinter basicity is 2.13.The content and the recovery of V and Cr in dripping iron are all increased.The generation amount of components with high melting point in slag becomes little with the increase of sinter basicity,which could improve the permeability of mixed burden.Taking softening-melting behaviors of mixed burden and recovery of valuable elements into account,the proper sinter basicity is no less than 2.13 for smelting mixed burden made from Cr-V-Ti magnetite in blast furnace.
基金Project(2013A090100013)supported by the Special Project on the Integration of Industry,Education and Research of Guangdong Province,ChinaProject(201407300993)supported by the High-Tech Research and Development Program of Xinjiang Uygur Autonomous Region,China
文摘Proper utilization of the FeSO4·7H2O waste slag generated from TiO2 industry is an urgent need, and Fe3O4 particles are currently being widely used in the wastewater flocculation field. In this work, magnetite was recovered from ferrous sulphate by a novel co-precipitation method with calcium hydroxide as the precipitant. Under optimum conditions, the obtained spherical magnetite particles are well crystallized with a Fe304 purity of 88.78%, but apt to aggregate with a median particle size of 1.83 μm. Magnetic measurement reveals the obtained Fe304 particles are soft magnetic with a saturation magnetization of 81.73 A-m2/kg. In addition, a highly crystallized gypsum co-product is obtained in blocky or irregular shape. Predictably, this study would provide additional opportunities for future application of low-cost Fe3O4 particles in water treatment field.
基金Project(50804059) supported by the National Natural Science Foundation of ChinaProject(50725416) supported by the National Natural Science Funds for Distinguished Young Scholars of China
文摘Modified humic acid (MHA) binder based on lignite humic substances is a novel sort of promising organic binder for iron ore pellets.Humic acid (HA) is one of the main ingredients of MHA binder.Pure HA was firstly isolated from lignite and then adsorption of HA onto magnetite particle surface was investigated.The final results indicate that the adsorption of HA onto magnetite surface accords with Langmuir model well,and it is evidently influenced by the initial HA concentration and solution pH value.Adsorption depends on chemical interaction at pH values above the PZC (the pH where the Zeta potentials of minerals are zero) of magnetite,while electrostatic attraction and chemical interaction both contribute to the adsorption at pH values below the PZC.
基金Project(U1960104)supported by the National Natural Science Foundation of ChinaProject(LYU Ya-nan)supported by the Jiangsu Colleges and Universities Qing Lan Project,China。
文摘Magnetite is a kind of iron ore that is difficult to carburize.In order to improve the carburizing performance of magnetite pellet,pre-oxidation treatment was carried out,and the oxidation,reduction and carburization behaviors of magnetite pellet were investigated in this study.The magnetite pellet was oxidized in the air and carburized in CO-CO_(2)-H_(2) gas mixtures,the oxidation,reduction and carburization behaviors were demonstrated by detecting phase change,microstructure,carburizing index via thermogravimetry,X-ray diffraction(XRD),infrared carbon-sulfur analyzer,and scanning electron microscope(SEM).The results show that the dense magnetite particles inside pellet are oxidized to porous hematite particles,and the Fe_(3)O_(4) transforms to Fe_(2)O_(3) with high lattice defect concentration during the pre-oxidation process.Then the porous hematite particles and newly formed Fe_(2)O_(3) significantly promote the reduction efficiency.Porous metallic iron particles are produced in the reduction process.Finally,both high reduction efficiency and the porous structure of metallic iron particles dramatically enhance the carburization efficiency of pellet.High preoxidation temperature favors to the carburization of magnetite pellet.However,the carburized index decreases due to the recrystallization of iron oxide when the temperature extends to 1000℃.The optimum pre-oxidation temperature for magnetite pellet carburization is 900℃.
基金Project(2013CB632603)supported by the National Basic Research Program of ChinaProject(2015BAB19B02)supported by the National Key Technology R&D Program of ChinaProjects(51674084,51174051,51574082)supported by National Natural Science Foundation of China
文摘The effects of basicity and temperature on the reduction process of Hongge high-chromium vanadium-titanium magnetite(HCVTM)sinter were investigated in this work.The main characterization methods of X-ray fluorescence(XRF),X-ray diffraction(XRD),scanning electron microscope(SEM),and metallographic microscope were employed in this study.In this work,the reduction of HCVTM sinter with different temperature and basicity were experimented.The Fe,FeO,and TiO in reductive samples increase with increasing basicity and temperatures.The increase of basicity and temperature is favorable to the reduction of HCVTM sinter.The Fe phase has out-migration tendency to the surface of sinter while the perovskite and silicate phases have in-migration tendency to the inside of sinter.The reduction degradation index(RDI)decreases while the reduction index(RI)increases with increasing basicity.The RI increases from 67.14%to 82.09%with increasing temperature from 1073 K to 1373 K.
基金Projects(51974204,51474161)supported by the National Natural Science Foundation of China。
文摘In this study,the effects of drying temperature,hot airflow speed and diameter of green pellet on drying rate of artificial magnetite pellet were deeply investigated to clarify the drying characteristics of artificial magnetite green pellet.The results show that the drying process of artificial magnetite green pellet has three stages,accelerated drying stage,constant drying stage and decelerated drying stage.And drying temperature and hot airflow speed both have significant reciprocal effects on moisture ratio and drying rate of green pellet during the drying process.However,the diameter of green pellet has little effect on drying process of green pellet.Then the drying fitting models of Correction Henderson and Pabis,Lewis,Correction Page(III),Wang and Singh are used to describe the drying kinetics of artificial magnetite green pellet.The fitting results indicate that the drying process of artificial magnetite pellet can be described by Correction Page(III)model accurately.Finally,the contrast experiments demonstrate that the fitting model can well describe the actual drying process.
基金Projects(N140108001,N150106003)supported by the Fundamental Research Funds for National University of China
文摘The pulsed power is a potential means for energy saving and presents an alternative to the conventional mechanical communication for minerals.The effect of magnetic pulse treatment on grindability of a magnetite ore was investigated by grindability tests.The results of the investigation show that the pulsed treatment has little effect on the particle size distribution of the magnetite ore.Significant micro-cracks or fractures are not found by SEM analysis in magnetic pulse treated sample.Magnetic separation of magnetic pulse treated and untreated magnetite ore indicates that iron recovery increases from 81.3% in the untreated sample to 87.7% in the magnetic pulse treated sample,and the corresponding iron grade increases from 42.1% to 44.4%.The results demonstrate that the magnetic pulse treatment does not significantly weaken the mineral grain boundaries or facilitate the liberation of minerals,but is beneficial to magnetic separation.
文摘Grinding is one of the most costly operations in the mechanical breaking and mining.Determination of the breakage characteristics and preconditioning is important to increase the grinding efficiency.Investigations of the seismic,mechanical and breakage properties of iron oxides are very important parameters for investigating the rock fragmentation by blasting and comminution processes in iron ore mines.In this paper,at first,geomechanical and seismic properties of the oxide ores(magnetite and hematite)in the Chadormalu iron ore mine were studied.The results showed that the percentage of magnetite has a direct relationship with uniaxial compressive strength,tensile strength and P and S wave’s velocities and has an inverse relationship with Poisson ratio and porosity.Moreover,to study breakage and preconditioning characteristics in the iron ores,two samples with different magnetite percents were blasted by detonation cord.The results showed that with higher percentage of magnetite,the number of fractures induced by blasting increased.Bond work index and magnetite percent were investigated in the 430 blasts in the mine.This investigation not only confirmed the small scale blasting results,but also showed that increasing the magnetite percent up to 50%noticeably reduces Bond work index and energy consumption in the grinding process.Also,the relationship between muck pile fragmentation and magnetite percentage were studied for several blasts that had the same blast pattern parameters and similar geology conditions.These results also confirmed precedents conclusions regarding magnetite percent and preconditioning relationship.
文摘In nature, iron cations in magnetite are usually isomorphically substituted by divalent (Co, Ni, Zn, Cu, Mn, etc.), trivalent (Al, V, Cr, etc.) and tetravalent (Ti) cations while maintaining the spinel structure. Some of the substituting cations, e.g. Cr3+, V3+ and Mn2+, improve the catalytic activity of magnetite in heterogeneous Fenton reaction through the enhancement of hydroxyl radical OH production and the pollutant adsorption.
文摘The iron-oxide system can be used as a marker of oxidized and reduced conditions in closed systems. However, natural rocks with iron-oxide minerals also exhibit such reactions, although the natural system is typically open. To understand the behaviour of this natural system, they were investigated the similarities, in terms of crystallographic textures, between the microstructures of two systems: natural open system and synthetic closed system of iron-oxide phase transformation.
基金funding from Stiftelsen Olle Engkvist Byggmastare(214-0346 and 217-0014)the Swedish Research Council(202103675)。
文摘There has recently been a fundamental need to develop high efficiency microwave absorbers to reduce electro-magnet-ic pollution.It is often very difficult to obtain superior absorption with only one material,so we have explored composites using fillers of activated carbon derived from biological material(oleaster seeds)and resin(apricot tree gum)with Fe_(3)O_(4) in a paraffin wax matrix to improve the dielectric properties and achieve a high specific surface area.A 1 mm thick layer of a Fe_(3)O_(4)+resin(FEOR),with the magnetic nanoparticles anchored to the gum,resulted in a reflection loss of−71.09 dB.We compared this with the results for composites using a filler of Fe_(3)O_(4)+activated carbon,and one with a three-component filler of Fe_(3)O_(4)+activated carbon+resin which had a very porous structure that had a direct effect on the surface polarization.However,the FEOR sample had near-ideal im-pedance matching,close to 1,which resulted in high absorption performance.In addition,the presence of defects improves mi-crowave attenuation by dipole polarization and charge carrier trapping.This work suggests the use of new types of biomaterials to in-crease microwave absorption.
文摘Mineral compositions and microstructures of fluorine bearing magnetite concentrate and vanadium titanomagnetite concentrate are studied. The results show that a boride and a catalytic oxidation agent have great effects on ameliorating the mineral compositions and microstructures of these sinters, and the catalytic agent is more effective. Comparing these two kinds of ores, the performance of fluorine bearing magnetite concentrate is better. Addition of 0.01% catalyst into fluorine bearing magnetite concentrate can increase calcium ferrite content from 15% 20% up to 34% 39%, and its microstructure changes from large cavities and thin framework into intermediate cavities and thick framework, and the microcracks disappear.
文摘Qara-aghaj and Skandian as hard rock titanium deposit and Kahnooj one as a placer deposit were investigated from applied mineralogical point of view. The mineralogical studies were carried out using XRD, XRF, optical microscopy, scanning electron microscopy and microprobe analysis. These studies indicated that ilmenite and magnetite are main valuable minerals in the studied ores. Pyroxene, olivine and plagioclase are the main gangue minerals in Qara-aghaj ore while chlorite and plagioclase are the major gangue minerals in Skandian ore. Plagioclase, clinopyroxene, amphibole, feldspate and some quartz are the important gangue minerals in kahnooj deposit. In all three ores ilmenite is mainly in the form of ilmenite grains but some lamellae of ilmenite with thickness between 0.1 to 20 μm have been occurred as exsolution textures inside magnetite grains, where the magnetite here can be referred to as ilmenomagnetite. In the hard rock ores some fine ilmenites have been disseminated in silicate minerals. The liberation degree of granular ilmenite was determined 150, 140 and 200 μm for Qara-aghaj, Skandian and Kahnooj, respectively. So, only the granular form of ilmenite is recoverable by physical methods. Some sphene and rutile as titanium containing minerals were observed mainly inside ilmenite phase in kahnooj ore. Some fine rutile was also found inside Skandian ilmenite while there were not any other titanium minerals inside Qara-aghaj ilmenite. Apatite is another valuable mineral which was found only in Qara-aghaj ore. Using SEM and microprobe analysis it was found that there are different amounts of exsolved fine lamellae of hematite inside ilmenite in Qara-aghaj and Kahnooj ores while it was not observed in Sckandian one. The average contents of TiO2 in the lattice of Qara-aghaj, Skandian and Kahnooj ilmenite were determined 51.13, 50.9% and 52.02%, respectively. FeO content of ilmenite lattice for all three samples is clearly lower than the theoretical content. This is due to the substitution of Mg and Mn for some Fe2+ ions in the ilmenite lattice. V2O3 content of magnetite lattice is up to 1%. So, magnetite can be a suitable source for production of vanadium as a by-product in all three deposits.
文摘The separation of iron oxide from banded hematite jasper(BHJ) assaying 47.8% Fe, 25.6% Si O2 and 2.30%Al2O3 using selective magnetic coating was studied. Characterization studies of the low grade ore indicate that besides hematite and goethite,jasper, a microcrystalline form of quartzite, is the major impurity associated with this ore. Beneficiation by conventional magnetic separation technique could yield a magnetic concentrate containing 60.8% Fe with 51% Fe recovery. In order to enhance the recovery of the iron oxide minerals, fine magnetite, colloidal magnetite and oleate colloidal magnetite were used as the coating material. When subjected to magnetic separation, the coated ore produces an iron concentrate containing 60.2% Fe with an enhanced recovery of56%. The AFM studies indicate that the coagulation of hematite particles with the oleate colloidal magnetite facilitates the higher recovery of iron particles from the low grade BHJ iron ore under appropriate conditions.
基金Project(2013DFA5129)supported by the International Science and Technology Cooperation Program of China
文摘Large scaled uniform and size-controllable magnetic submicroparticles(MSPs) were synthesized via solvothermal method with ferric chloride as iron source and sodium acetate as trapping agent. The influence of Fe^(3+) and Na Ac contents on the size distribution of MSPs was investigated. The structural and morphological properties of the synthesized particles were studied by scanning electron microscopy(SEM), X-ray power diffraction(XRD) and vibrating sample magnetometer(VSM). The well-dispersed MSPs with size of 100-1000 nm were obtained by simply adjusting the contents of Fe^(3+) and NaA c. In addition, the hemolysis and cytotoxicity of Fe_3O_4 MSPs, and their ability to case arrest in cell life-cycles were studied. The results indicate that larger size could lead to lower hemolysis. From MTT(3-(4,5-dimethylthuazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, the interactions between MSPs and adhesive mouse fibroblast cell line(L929) were probed. Larger size of Fe_3O_4 MSPs demonstrates lower cell viability following an exposure to the cells.
文摘The northern section of the UAE is bordered by the Gulf of Oman’s northern extension (East Coast) and Arabian Gulf’s Eastern extension (northern West Coast). Unlike the rest, the coastline of this section is more or less faced by mountainous areas of various rock types. The beach sands a long this coastline at both sides (East and northern-West) signify some heavy minerals concentration of an important consideration.
文摘Automated core scanning technologies for mineralogical characterisation of diamond core, drill chips pulps is now an established technique, particularly in the Australian iron ore industry, for mineral analysis in exploration and mining. Application of reflectance spectroscopy over the 400–2500 nm, visible to near-infrared wavelength range, has been used to characterise the iron ore oxide mineralogy of bedded iron deposit (BID) derived iron ores in India (Thangavelu et al., 2011) and Brazil (da Costa et al., 2009), and used to define the ore and gangue (e.g., clay) mineralogy in ironstone or channel iron deposits (CID) in the Pilbara region of Western Australia (e.g., Haest et al., 2012).
