Phase, magnetism and thermal conductivity of glass ceramics from iron ore tailings

In order to develop the applications of ore tailings, the glass ceramics were prepared by using a conventional melting-quenching-sintering process. The phase component, microstructures, magnetic properties and thermal conductivities of the prepared glass ceramics were investigated by using X-ray diffractometer, scanning electron microscopy, vibrating sample magnetometer and thermophysical properties tester, respectively. The results show that orthorhombic olivine-type phase and triclinic sunstone-type phase formed when the glass was annealed at 700 oC, the concentration of olivine-type and sunstone-type phases decreased, the spinel-type cubic phase occurred and the amount increased when the annealing temperatures increased. The magnetic properties from the cubic spinel ferrites were detected in the glass ceramics, and the related saturation magnetization increased with the annealing temperature increasing. The porous glass ceramics with magnetic property showed much lower thermal conductivity, compared with the non-magnetic porous glass-ceramic and the dense glass-ceramics.

The B-site ordering in RFe_(0.5)Cr_(0.5)O_(3)ceramics and its effect on magnetic properties

To insight into the B-site ordering in RFe_(0.5)Cr_(0.5)O_(3)ceramics,a series of RFe_(0.5)Cr_(0.5)O_(3)ceramics(R=La,Y,Lu)were synthesized by the sol-gel method,and the structural and magnetic properties were systemically investigated.By using the Rietveld refinement of all samples,it is found that the structural distortion is increased as the R ionic radius decreases,leading to the weakened interactions between Fe/Cr ions.Moreover,the Fe and Cr are arranged in disorder in LaFe_(0.5)Cr_(0.5)O_(3),but partially ordered in YFe_(0.5)Cr_(0.5)O_(3)and LuFe_(0.5)Cr_(0.5)O_(3),showing an increasing trend of the proportion of ordered domains with the decrease of R ionic radius.Through fitting the temperature-dependent magnetizations,it is identified that the magnetization reversal(MR)in disorder LaFe_(0.5)Cr_(0.5)O_(3)is resulted from the competition between the moments of Cr and Fe sublattices.In the partially ordered YFe_(0.5)Cr_(0.5)O_(3)and LuFe_(0.5)Cr_(0.5)O_(3)ceramics,because of the presence of Fe-O-Cr networks in the ordered domains whose moment is antiparallel to that of Fe-O-Fe and Cr-O-Cr in the disordered domains,the compensation temperature T_(comp)of MR is increased by nearly 50 K.These results suggest that the changing of R-site ions could be used very effectively to modify the Fe-O-Cr ordering,apart from the structural distortion,which has a direct effect on the magnetic exchange interactions in RFe_(0.5)Cr_(0.5)O_(3)ceramics.Then at values of composition where ordered domains are expected to be larger in number as compared to disordered domains and with a weaker structural distortion,one can expect a higher transition temperature Tcomp,providing a different view for adjustment of the magnetic properties of RFe_(0.5)Cr_(0.5)O_(3)ceramics for practical applications.

Reaction behavior and non-isothermal kinetics of suspension magnetization roasting of limonite and siderite

In order to develop limonite and decrease CO_(2) emissions,siderite is proposed as a clean reductant for suspension magnetization roasting(SMR) of limonite.An iron concentrate(iron grade:65.92wt%,iron recovery:98.54wt%) was obtained by magnetic separation under the optimum SMR conditions:siderite dosage 40wt%,roasting temperature 700℃,roasting time 10 min.According to the magnetic analysis,SMR achieved the conversion of weak magnetic minerals to strong magnetic minerals,thus enabling the recovery of iron via magnetic separation.Based on the phase transformation analysis,during the SMR process,limonite was first dehydrated and converted to hematite,and then siderite decomposed to generate magnetite and CO,where CO reduced the freshly formed hematite to magnetite.The microstructure evolution analysis indicated that the magnetite particles were loose and porous with a destroyed structure,making them easier to be ground.The non-isothermal kinetic results show that the main reaction between limonite and siderite conformed to the two-dimension diffusion mechanism,suggesting that the diffusion of CO controlled the reaction.These results encourage the application of siderite as a reductant in SMR.

Fluidized magnetization roasting of refractory siderite-containing iron ore via preoxidation-low-temperature reduction

Magnetization roasting is one of the most effective way of utilizing low-grade refractory iron ore.However,the reduction roasting of siderite(FeCO3)generates weakly magnetic wüstite,thus reducing iron recovery via weak magnetic separation.We systematically studied and proposed the fluidized preoxidation-low-temperature reduction magnetization roasting process for siderite.We found that the maghemite generated during the air oxidation roasting of siderite would be further reduced into wüstite at 500 and 550℃due to the unstable intermediate product magnetite(Fe_(3)O_(4)).Stable magnetite can be obtained through maghemite reduction only at low temperature.The optimal fluidized magnetization roasting parameters included preoxidation at 610℃for 2.5 min,followed by reduction at 450℃for 5 min.For roasted ore,weak magnetic separation yielded an iron ore concentrate grade of 62.0wt%and an iron recovery rate of 88.36%.Compared with that of conventional direct reduction magnetization roasting,the iron recovery rate of weak magnetic separation had greatly improved by 34.33%.The proposed fluidized preoxidation-low-temperature reduction magnetization roasting process can realize the efficient magnetization roasting utilization of low-grade refractory siderite-containing iron ore without wüstite generation and is unlimited by the proportion of siderite and hematite in iron ore.

Chemico-viscous remanent magnetization in the oxidation of siderite and its implications in paleomagnetism

Studies have been done of the secondary chemico-viscous remanent magnetization (CVRM) produced in the oxidization and decomposition of high-purity crystal siderite specimens collected from Dalizi Deposit, Jilin Province, The CVRM intensity increases to a peak value at an annealing temperature of 490*^0 . The direction of CVRM is always parallel to the applied field , and no self- reversal behavior has been observed in the transformation of maghemite to hematite . It is suggested that the phase transition of magnetic minerals can make great contribution to secondary magnetization. Results of successive heating at low temperature indicate that the crystal mineral siderite is basically stable. Finally , the paleomagnetic significance of CVRM is discussed.

Phase evolution and room temperature ferroelectric and magnetic properties of Fe-doped BaTiO_3 ceramics

To make the ferroelectric BaTiO3 possess ferromagnetism simultaneously,magnetic Fe was doped into BaTiO3 ceramics at doping levels up to 10%(molar fraction).Both tetragonal and hexagonal phases coexisted in the Fe-doped BaTiO3 ceramics except at 1% doping level.X-ray diffraction analysis indicated that higher doping level of Fe,higher sintering temperature and longer sintering time promoted the formation of hexagonal phases in Fe-doped BaTiO3 ceramics.Ferroelectricity was observed in all samples at room temperature,but it was greatly depressed by Fe doping.Except at doping level of 1%,room-temperature ferromagnetism was observed in the BaTiO3 ceramics.The dependence of the saturation magnetization and coercivities of the Fe-doped BaTiO3 ceramics on doping level was systematically studied.Both the saturation magnetization and magnetic coercivities were found to be dependent on the doping level as well as the fraction of the hexagonal phase in the ceramics.

Influence of Composite Phosphate Inorganic Antibacterial Materials Containing Rare Earth on Activated Water Property of Ceramics

Antibacterial ceramic was prepared by doping enamel slurry with composite phosphate inorganic antibacterial materials containing rare earth (inorganic antibacterial additives), and then the mechanisms for activating water and improving seed germinative property were tested by nuclear magnetic resonance (NMR) and the method of testing oxygen dissolved in activated water. Results show that the half peak width of (()^(17)O-NMR) for tap water activated by the antibacterial ceramic drops from 115.36 to 99.15 Hz, and oxygen concentrations of activated water increase by 20%, germinate rate of horsebean and earthnut seeds increases by 12.5% and 7.5%, respectively. Therefore antibacterial ceramic doped enamel slurry with inorganic antibacterial additives containing rare earth can reduce the volume of clusters of water molecules, improve activation of tap water, and promote plant seeds germinate.

Influential Factors on Electromagnetic Properties of Selected 3D Reticulated Ceramics

3D reticulated ceramics (3DRCs) with the composition containing SrFe12O19-SiC-TiO2 were prepared by a replication process with polyurethane sponges as the template in ceramic slurry. The electrical conductivity, dielectric and magnetic parameters of 3D reticulated ceramics (3DRCs) were measured with changes in cell size of the sponges, contents in the slurry and sintering temperature in this paper. Discussions about the influential factors of those parameters were focused on their electrical conductivity. The experimental results indicated that the electrical conductivity of 3DRCs raised with the increase of cell size, SiC/SrO 6Fe2O3 with weight ratio and sintering temperature. X-ray diffractions and SEM were used to investigate the relationship between electrical conductivity and sintering temperature. Deoxidizing reactions of SrO 6Fe2O3 caused the increasing electrical conductivity. The real part of permittivity (ε') and imaginary part of permeability (μ') raised with the increase of electrical conductivity (σ). The imaginary part of permittivity (ε') has a maximum at 10o S/cm with the increase of a, and the real part of permeability (μ') changes slightly with the increase of a. When a is at the range of 10-4 S/cm to 10o S/cm (a semi conductive state), both the imagine part of permittivity and permeability raises with increasing a, therefore, the 3DRCs present their high electromagnetic loss properties.

Siderite pyrolysis in suspension roasting:An in-situ study on kinetics,phase transformation,and product properties

Siderite,as an abundant iron ore,has not been effectively utilized,with a low utilization rate.In this study,the in-situ kinetics and mechanism of siderite during suspension magnetization roasting(SMR)were investigated to improve the selective conversion of siderite to magnetite and CO,enriching the theoretical system of green SMR using siderite as a reductant.According to the gas products analyses,the peak value of the reaction rate increased with increasing temperature,and its curves presented the feature of an early peak and long tail.The mechanism function of the siderite pyrolysis was the contraction sphere model(R_(3)):f(α)=3(1−α)2/3;E_(α)was 46.4653 kJ/mol;A was 0.5938 s^(−1);the kinetics equation was k=0.5938exp[−46.4653/(RT)].The in-situ HT-XRD results indicated that siderite was converted into magnetite and wüstite that exhibited a good crystallinity in SMR under a N_(2) atmosphere.At 620℃,the saturation magnetization(M_(s)),remanence magnetization(Mr),and coercivity(Hc)of the product peaked at 53.63×10^(-3)A·m^(2)/g,10.23×10^(-3)A·m^(2)/g,and 12.40×10^(3)A/m,respectively.Meanwhile,the initial particles with a smooth surface were transformed into particles with a porous and loose structure in the roasting process,which would contribute to reducing the grinding cost.

Anomalous magnetic properties of an iron film system deposited on fracture surfaces of α-Al_2O_3 ceramics

An iron film percolation system is fabricated by vapour-phase deposition on fracture surfaces of α-Al2O3 ceramics. The zero-field-cooled （ZFC） and field-cooled （FC） magnetization measurement reveals that the magnetic phase of the film samples evolve from a high-temperature ferromagnetic state to a low-temperature spin-glass-like state, which is also demonstrated by the temperature-dependent ac susceptibility of the iron films. The temperature dependence of the exchange bias field He of the iron film exhibits a minimum peak around the temperature T=5 K, which is independent of the magnitude of the cooling field Hcf. However, for T 〉 10K, （1） He is always negative when Hcf=2kOe and （2） for Hcf= 20 kOe （1Oe≈80 A/m）, He changes from negative to positive values as T increases. Our experimental results show that the anomalous hysteresis properties mainly result from the oxide surfaces of the films with spin-glass-like phase.

Comparative Study of Dielectric and Magnetic Properties of Selected 3D Reticulated Ceramics and Their Same Composition Ceramic Disks

3-dimensional reticulated ceramics (3DRCs) and their same composition ceramic disks(SCCDs) were fabricated by sol-gel method, with the composition of SrO-6Fe203(30%), SiC(35%) and Ti02(35%), sintered at 1200C in N2. The dielectric and magnetic parameters of such 3DRCs and their SCCDs were measured respectively in a temperature range from room temperature to 800癈 and in a frequency range from 2.6 GHz to 18 GHz. The results showed that the dielectric and magnetic loss of 3DRCs were obviously larger than those of their SCCDs in a wide range of temperature and the whole range of measuring frequency. The increase of dielectric loss of SDRCs was much higher than that of magnetic loss compared to their SCCDs, which was found due to the 3D net structure extrinsic characteristics.

Comparison of Effects of MPTCP and PTCP Ceramics Implanted for the Treatment of Bone Defects in Rabbits

The magnetic porous tricalcium phosphate (MPTCP) and porous tricalcium phosphate (PTCP) ceramic cylinders were implanted into right and left bone defects of rabbits' radii in order to determine the utility of the MPTCP ceramics. Based on naked eye inspection, light and scanning electron microphotography, roentgenography,quantitative histological measurement of new bone formation and anti-break test for a period of 5 months. The results showed that the two kinds of ceramics were biocompatible with human tissue. MPTCP ceramics could induce more new bone formation than PTCP ceramics. Treatment of fractures with synthetic calcium phosphate ceramics and magnetic fields were discussed.

Dielectric and Magnetic Properties of (1-x)CaTiO3-xNi0.5Zn0.5Fe2O4 Composite Ceramics

（1-x）CaTiO3-xNi0.5Zn0.5Fe2O4（0 x 1.0） composite ceramics were synthesized by a conventional solid state reaction method.The phase formation,microstructure,and dielectric and magnetic properties were investigated by X-ray diffraction,scanning electron microscopy,precision impedance analysis,and vibrating sample magnetometry,respectively.The results indicate that the composite ceramics are composed of both perovskite phase Ca TiO3 and spinel phase Ni0.5Zn0.5Fe2O4.The maximal relative density for 0.5CaTiO3-xNi0.5Zn0.5Fe2O4 composite ceramics reaches 97.8%,as it has been sintered at the temperature of 1260 ℃ for 3 h.Dielectric constant and loss tangent of（1-x）CaTiO3-xNi0.5Zn0.5Fe2O4 composite ceramics show dispersion in the low frequency range.Their phase transition temperature of the dielectric constant shifts to lower temperatures with the increase of Ni0.5Zn0.5Fe2O4 content.This phenomenon is attributed to that the phase transition temperature of CaTiO3 is higher than that of Ni0.5Zn0.5Fe2O4.The saturation magnetization of （1-x）CaTiO3-xNi0.5Zn0.5Fe2O4 composite ceramics increases with the Ni0.5Zn0.5Fe2O4 ferrite content.

CERAMICS AS CANDIDATE STRUCTURAL MATERIALS FOR CRYOGENIC APPLICATIONS

The use of zirconia-based ceramic materials as smpport materidls for superconducting magnets and in cryopenic engineeriny generally has been considered. The relationship between compsition and mechanical properties at cryogenic temperature has also been investigated.

MAGNETIC AND MOSSBAUER STUDY OF ANCIENT YAOZHOU TANG TRICOLOR CERAMICS

Ⅰ. INTRODUCTIONThe valuable information about the ancient ceramics can be acquired from studying their structures, compositions and manufacture technology by modern scientific and technical method. It is an important field of the modern scientific and technological archaeology (STA), which is also called experimental archaeology and has a special significance for the "country of ceramics" .

Effect of Mn doping on the microstructure and magnetic properties of CuFeO2 ceramics

The effects of Mn doping on the microstructure and magnetic properties of CuFeO2 systems were studied using X-ray diffraction(XRD),X-ray photoelectron spectroscopy,scanning electron microscopy(SEM),and a physical property measurement method.The microstructure measurements demonstrated that the substitution of Mn for Fe can cause lattice distortion,promote grain growth,and change the valence state of Fe and Mn ions.Ceramic samples with doping content x=0.00−0.03 exhibited two successive magnetic transition temperature(TN)at TN1≈14 K and TN2≈10 K.TN decreased gradually with the Mn4+content,and TN2 was not observed in the x>0.05 samples within a temperature range of T=5−300 K.Magnetic hysteresis loops revealed that only anti-ferromagnetic behavior occurred in the low-doped samples(x=0.00−0.03),and the coexistence of ferromagnetism and anti-ferromagnetism was observed in the high-doped samples(x=0.05−0.10).Besides,the x=0.10 sample had a maximum magnetization of 5.98 emu/g.This study provides basic experimental data for investigating the relationship between the microstructure and magnetic properties of CuFeO2 systems.

某尾矿强磁选预富集产品的工艺矿物学研究及可选性分析

西南某多金属原生矿现场尾矿TFe品位13.88%,有害元素S含量为1.24%,主要脉石成分SiO2含量为40.82%,铁矿物主要以赤褐铁矿、菱铁矿及磁铁矿的形式存在,属复杂难选铁尾矿资源。为制定合理的二次资源综合回收工艺,从工艺矿物学角度出发,利用场发射扫描电镜(FESEM)、背散射电子成像(BSE)、X射线能谱分析(EDS)、矿物特征自动定量分析系统(AMICS)等多种检测手段,对现场强磁选预富集产品开展了矿物组成、铁矿物粒度分布、主要元素赋存状态、嵌布特征、解离特征以及热分解特性等系统的工艺矿物学研究。结果表明:采用预氧化—低温还原磁化焙烧—弱磁选选冶联合工艺,预富集产品经550℃预氧化7.5min后,在450℃、还原势R=0.6的条件下磁化焙烧7.5min,可获得作业产率90.84%、铁品位30.02%、磁化率95.05%的磁化焙烧产品;磁化焙烧产品再磨至-38μm占89.5%,经两段弱磁选铁,可获得作业产率28.94%、铁品位60.18%、铁作业回收率63.86%的铁精矿。研究结果可为后续开展合理的资源高效、综合回收试验提供理论支撑。

Mechanism of improved magnetizing roasting of siderite–hematite iron ore using a synergistic CO–H2 mixture

A fluidized-bed magnetizing roasting-magnetic separation process was selected to treat this type of material.Phase transformations and microstructural changes in the product resulting from magnetizing roasting under different reducing gases(CO,H2,CO+H2)were clarified by vibrating sample magnetometry,X-ray diffraction,scanning electron microscopy,and energy-dispersive X-ray spectroscopy.The results indicated that the conversion ratio and saturation magnetization of samples roasted in a mixed gas of CO and H2 were higher than those of samples produced under CO or H2 alone.This indicated that synergy of the combined CO and H2 gas had a positive effect on the fluidized-bed magnetizing roasting process.The mechanism and kinetics of the improved magnetizing roasting of a siderite-hematite iron ore mixture under this synergistic CO-H2 system were investigated under isothermal conditions.The results indicated that the apparent activation energies of the reactions of the iron oxides decreased from 37.7 and 17.9 to 15.9 kJ/moI when the roasting atmosphere was changed from pure H2 or CO to a gas mixture of CO and H2,respectively.The mixed CO-H2 gas promoted the conversion ratio of hematite and siderite to magnetite,thereby improving the conversion ratio in the fluidized-bed magnetizing roasting process.

Influence of A-site doping barium on structure,magnetic and microwave absorption properties of LaFeO_(3)ceramics powders

In this paper,the effect of Ba^(2+)ions A-site doping LaFeO_(3)on structure,magnetic properties and microwave absorption properties was investigated by the sol-gel method.According to the TEM and FullProf refinement results,the structure of LaFeO_(3)changes from orthogonal(SG:Pnma)to cubic(SG:Pm-3 m)when the Ba doping amount is x=0.4.The SEM image shows that the particles size tends to decrease with the increase of Ba content.The production of weak ferromagnetism indicates that Ba doping has a significant effect on the magnetic properties of LaFeO_(3).The Neel temperature(TN)decreases significantly with the increase of Ba doping amount.An appropriate amount of Ba doping can effectively increase the dielectric and magnetic loss of LaFeO_(3)ceramics powders.The increase permittivity(ε’andε″)may be attributed to the hopping of the electrons between the Fe^(3+)and Fe^(4+)ions with the Ba^(2+)ions doping.The minimum reflection loss(RL_(min))of La_(0.9)Ba_(0.1)FeO_(3)at 6.72 GHz reaches-30.04 dB,its effective bandwidth(RL≤-10 dB)is 2.1 GHz,and the matching thickness is only 3.2 mm.These results indicate that Ba doping can effectively control the microwave absorption properties of LaFeO_(3),especially in the Cband.

磁BAF工艺深度处理养猪废水生化尾水

为实现养猪废水生化尾水资源化,取荆州市某养猪企业污水处理站A~2O工艺出水,将其混凝预处理后分别送入以磁性陶粒、普通陶粒为填料构建的曝气生物滤池,探究磁场作用下装置去除污染物的效果以及磁场对微生物比耗氧速率、硝化速率的影响。实验结果表明,在m(污泥):m(高岭土):m(磁粉)=3:1:4,预热温度为300℃,焙烧温度为1 000℃条件下制备所得的磁性陶粒的机械性能最好;在相同条件下,磁场通过提高微生物比耗氧速率、硝化速率使得曝气生物滤池启动挂膜时间更短,且稳定阶段对污染物去除效果较普通曝气生物滤池更优;当陶粒充磁为2.8 mT,HRT为8 h,DO为4~5 mg/L时,系统运行最佳,对COD、NH_(4)^(+)-N的去除率可分别达76.1%、93.8%,出水中溶解性微生物副产物与类富里酸物质几乎消失,仅存少量分子结构复杂、化学性质较稳定的腐殖酸类物质,满足《污水综合排放标准》(GB 8978—1996)中一级标准。