Permanent ferrite magnet materials are extensively employed due to their exceptional magnetic properties and cost-effectiveness.The fast development in electromobile and household appliance industries contributes to a...Permanent ferrite magnet materials are extensively employed due to their exceptional magnetic properties and cost-effectiveness.The fast development in electromobile and household appliance industries contributes to a new progress in permanent ferrite materials.This paper reviews the deveolpement and progress of permanent ferrite magnet industry in recent years.The emergence of new raw material,the advancement of perparation methods and manufacturing techniques,and the potential applications of permanent ferrite materials are introduced and discussed.Specifically,nanocrystallization plays a crucial role in achieving high performance at a low cost and reducing reliance on rare earth resources,and therefore it could be a promising development trendency.展开更多
Hydrothermal method was used to synthesize nanoscale particles of MnZn ferrites. The crystallites were characterized by XRD, TEM and SEM. The effects of the reaction time, temperature and additives on the product were...Hydrothermal method was used to synthesize nanoscale particles of MnZn ferrites. The crystallites were characterized by XRD, TEM and SEM. The effects of the reaction time, temperature and additives on the product were investigated. Crystallization process would be carried out above 160 ℃ for 5 h or more, higher temperature can reduce the reaction time. Additives were used to remove impurities such as Fe 2O 3, ZnMnO 3.10～15 nm pure slightly agglomerated MnZn ferrite crystallites with a narrow grain size distribution were obtained.展开更多
Hard and brittle materials such as ferrite, optical glass and ceramics have been widely used in many fields because of their good characteristics and still gain more attentions. However, it is difficult to machine and...Hard and brittle materials such as ferrite, optical glass and ceramics have been widely used in many fields because of their good characteristics and still gain more attentions. However, it is difficult to machine and get good surface quality. Some parts made of these materials have large machining allowances and need to be produced with large batch, but the machining efficiency is very low with usual grinding method. So it is of great importance to research the high efficiency grinding technology of hard and brittle materials. Electrolytic in-process dressing (ELID) grinding is a new grinding technology which has been adopted to the ultra-precision machining of hard and brittle materials. With the function of in-process dressing of metal bond diamond and CBN wheel, ELID grinding has the ability to keep the sharpness of the wheel surface and is widely used in fine abrasive grinding, but it also has the potentialities to high efficiency grinding. In this paper, the mechanism of ELID grinding and its grinding performance are analyzed, then the cast iron bond diamond wheels and ELID grinding device are used on a surface grinder to research the feasibility of ELID grinding to high efficiency grinding. To make comparison, the garnet ferrite (YAG) work piece has been machined in plunge grinding both by ELID grinding and by the resin bond diamond wheel. The grinding force and surface quality are tested and analyzed. It has been found that the grinding force of the cast iron bond diamond wheel with ELID grinding is apparently smaller than that of the resin bond diamond wheel. Under the same conditions, it is about 2/5～3/5 as the force using the resin bond diamond wheel. So with the same grinder and machining conditions, ELID grinding can machine work piece with greater depth of cut. Because of the smaller grinding force, it is also beneficial to avoid the edge collapse of the work piece and keep the integrity of the grinding surface. This experiment shows that the grinding efficiency can be highly improved and the surface quality be ensured by applying ELID grinding technology and adopting large grinding depth. The results indicate that the ELID grinding technology can be effectively used in the high efficiency machining of garnet ferrite and other hard and brittle materials.展开更多
In order to investigate the effect of additives and nano-particle on the surface tensions of lithium bromide(Li Br) aqueous solution/ammonia, many experiments were carried out based on Wilhelmy plate method. Firstly, ...In order to investigate the effect of additives and nano-particle on the surface tensions of lithium bromide(Li Br) aqueous solution/ammonia, many experiments were carried out based on Wilhelmy plate method. Firstly, the surface tension of Li Br aqueous solution with 1-octanol was measured and then the comparison between the measured results and previous experimental results was given to verify the measuring accuracy. Some new additives, such as cationic surfactants cetyltrimethyl ammonium chloride(CTAC), and cetyltrimethyl ammonium bromide(CTAB) were chosen in the experiments. The experimental results show that CTAC and CTAB can obviously reduce the surface tension of Li Br aqueous solution/ammonia. In addition, it is found that nano-particles cannot remarkably decrease the surface tension of Li Br aqueous solution/ammonia. However, the mixed addition of additives and nano-particles can remarkably affect the surface tension of Li Br aqueous solution/ammonia. That is to say, additives play more important role in reducing the surface tension of Li Br aqueous solution/ammonia. But nano-particles may enhance the heat transfer in the absorption refrigeration process.展开更多
The dissolution property of high-ferrite gibbsitic bauxite and the effect of ferrite content on the dissolution kinetics of gibbsitic bauxites in sodium hydroxide solution under atmospheric pressure from 50 to 90 ...The dissolution property of high-ferrite gibbsitic bauxite and the effect of ferrite content on the dissolution kinetics of gibbsitic bauxites in sodium hydroxide solution under atmospheric pressure from 50 to 90 °C were systematically investigated.The dissolution property of high-ferrite gibbsitic bauxite is increased by increasing the dissolution temperature and the Na OH concentration or decreasing the particle size of bauxite,which is easy to dissolve under atmospheric pressure.The kinetic equations of gibbsitic bauxites with different ferrite contents during the dissolution process at different temperatures for different times were established,and the corresponding activation energies were calculated.The ferrite in the gibbsitic bauxite reduces the dissolution speed and increases the activation energy of dissolution,the diffusion process of which is the rate-controlling step.展开更多
The effect of additive RCOONa on the formation of MnZn ferrite homogeneous coprecipitation precursor was studied in this paper. The action of additive in the MnZn ferrite hydrothermal crystallization process was inves...The effect of additive RCOONa on the formation of MnZn ferrite homogeneous coprecipitation precursor was studied in this paper. The action of additive in the MnZn ferrite hydrothermal crystallization process was investigated according to crystal field theory and crystal growth unit theory. And the growth unit formation process was presented and its structure was illustrated. The results show that the precursor of MnZn ferrite is a colloidal mixture composed of Zn(OH) 2, Fe(OH) 2, Mn(OH) 2, MnO(OH) , MnO 2· x H 2O and so on, and dissolves in solution in the form of hydroxyl coordination tetrahedron and octahedron such as Zn(OH) 2- 4, Fe(OH) 2- 4, Fe(OH) 4- 6,Fe(OH) - 4, Fe(OH) 3- 6,Mn(OH) 2- 4,Mn(OH) 3- 6 etc., and the growth unit is formed by combination of the coordination polyhedra subsequently in the hydrothermal precess. The additive is beneficial to the formation of homogeneous precursor and has dispersive effect on the aggregation of the crystal growth unit by forming associate with hydrogen bond, which is beneficial to the synthesis of the pure product with a tiny size and a narrow size distribution.展开更多
It is generally known that the large formation amount of calcium ferrite is favorable for the iron ore sintering. The effects of sintering temperature and O2 content of inlet gas on the calcium ferrite formation chara...It is generally known that the large formation amount of calcium ferrite is favorable for the iron ore sintering. The effects of sintering temperature and O2 content of inlet gas on the calcium ferrite formation characteristic of typical iron ores, including hematite, limonite, specularite and magnetite, were investigated. And the effect of O2 content on the microstructure of the roasted briquettes was also studied in detail. The results show the amount of calcium ferrite initially increases then decreases with the increase of the sintering temperature. The temperature of maximum calcium ferrite generation amount is determined as follows： for hematite and limonite it is 1275 ~C, whereas for specularite and magnetite, 1250℃. The maximum contents of calcium ferrite for hematite, limonite, specularite and magnetite under the optimal sintering temperature are 73%, 82%, 67% and 63%, respectively. Increasing O2 content of the airflow is advantageous to the formation of calcium ferrite. Relatively, the effect of O2 content on the calcium ferrite formation of magnetite is the most pronounced, while O2 content of inlet gas has little effect on the calcium ferrite formation of limonite.展开更多
An analytical method for the determination of 26 impurity elements （such as Li, Be, Na, Mg, Al, Si, P, S, K, Ca, Sc, Ti, V, Cr, Co, Ni, Ga, Ge, Y, Nb, Mo, Ag, Cd, Sb, W and Pb） in MnZn ferrite powder by direct curre...An analytical method for the determination of 26 impurity elements （such as Li, Be, Na, Mg, Al, Si, P, S, K, Ca, Sc, Ti, V, Cr, Co, Ni, Ga, Ge, Y, Nb, Mo, Ag, Cd, Sb, W and Pb） in MnZn ferrite powder by direct current glow discharge mass spectrometry （GD-MS） was established. MnZn ferrite powder was mixed with copper powder, used as a conductor, and pressed. The effects of MnZn ferrite powder preparation conditions and glow discharge parameters for the sensitivity and stability of signal analysis were investigated. By determining the choice of isotope and the application of the mass resolutions of 4000 （MR, medium resolution） and 10000 （HR, high resolution）, mass spectral interference was eliminated. The contents of impurity elements in MnZn ferrite powder was calculated by subtraction after normalizing the total signal of Mn, Zn, Fe, O and Cu. The results showed that the detection limit of 26 kinds of impurity elements was between 0.002 and 0.57 μg/g, and the relative standard deviation （RSD） was between 3.33% and 32.35%. The accuracy of this method was verified by the ICP-MS. The method was simple and practical, which is applied to the determination of impurity elements in MnZn ferrite powder.展开更多
Ni-W-P composite coatings reinforced by Ce O2 and Si O2 nano-particles on the surface of common carbon steels, were prepared by double pulse electrodeposition. The crystallization course was characterized by phase str...Ni-W-P composite coatings reinforced by Ce O2 and Si O2 nano-particles on the surface of common carbon steels, were prepared by double pulse electrodeposition. The crystallization course was characterized by phase structures, crystallinity, grain sizes and microstructures. The results indicate that as-deposited composite coating is amorphous. Whereas it turns into the crystalline structure with 98.25% crystallinity, and Ni3 P, Ni2 P and Ni5P2 alloy phases precipitate from structures at 400 °C. Thereafter, Ni2 P and Ni5P2 metastable alloy phases turn into Ni3 P stable alloy phase at 500 °C. The crystallization course of the composite coating has finished when being heat-treated at 700 °C. The average sizes of Ni grains increase with the rise of heat treatment temperature from400 °C to 700 °C. Ce O2 and Si O2 nano-particles deposited into Ni-W-P alloys can delay the crystallization course and habit the growth of alloy phases.展开更多
Ferroplasma thermophilum,a sort of extreme acidophilic archaea,which can synthesize intracellular cobalt ferrite nanocrystals,is investigated in this study.The nanocrystals were analyzed with ultrathin sections and tr...Ferroplasma thermophilum,a sort of extreme acidophilic archaea,which can synthesize intracellular cobalt ferrite nanocrystals,is investigated in this study.The nanocrystals were analyzed with ultrathin sections and transmission electron microscope,with the size of 20−60 nm,the number of more than 30 in each cell at average,which indicated that F.thermophilum can synthesize intracellular nanocrystals and also belongs to high-yield nanocrystals-producing strain.Intriguingly,the nanocrystals contain ferrite and cobalt characterized by EDS X-ray analysis,suggesting that both cobalt and ferrite are potentially contributed to the formation of nanocrystals.Moreover,under the different energy source culture conditions of FeSO4 and CuFeS2,the size and the morphology of the nanocrystals are different.It was also found that the higher initial Fe availability leads to an induced synthesis of larger nanocrystals and the lower oxidation-reduction potential(ORP)leads to an induced effect on the synthesis of nanocrystals with abnormal unhomogeneous size,which suggested that the higher initial Fe availability and the lower oxidation-reduction potential lead to a higher uptake efficiency of iron ions of F.thermophilum by iron and ORP gradient culture.展开更多
MnZn ferrite nanoscale particles were synthesized by hydrothermal method. The effects of amount of addition La3+ on the products were discussed. The product was characterized by X-ray diffraction （XRD） and transmiss...MnZn ferrite nanoscale particles were synthesized by hydrothermal method. The effects of amount of addition La3+ on the products were discussed. The product was characterized by X-ray diffraction （XRD） and transmission electron microscope （TEM）. The results show that the sample with 0.2% La3+（mass fraction） or without La3+ has only spinel phase, but the sample with mass fraction of La3+ exceeding 0.4% posses second phase besides the spinel one; and the nano-MnZn ferrites change from cube to hexagon when the mass fractions of La3+ is up to （1.2%.） TEM image of the sample with 1.2% La3+ indicates that the homogeneous hexagonal crystal is obtained and the particles are larger than those of undoped; the addition of La3+ has great influence on the crystallization of hydrothermal process and can change the shape of particles and improve their growth. The saturation magnetization of the sample with 1.2% La3+ (2.64 A·m2·kg-1) is lower than that of undoped (17.54 (A·m2·kg-1)) and it behaves superparamagnetically.展开更多
Nanometer Ni0.5Zn0.5Fe2O4 powders with spinel phase were prepared by the hydrothermal method using purified FeSO4 solution from sodium jarosite＇s slag as materials. The results show that the spinel phase of Ni0.5Zn0....Nanometer Ni0.5Zn0.5Fe2O4 powders with spinel phase were prepared by the hydrothermal method using purified FeSO4 solution from sodium jarosite＇s slag as materials. The results show that the spinel phase of Ni0.5Zn0.5Fe2O4 powders begins to form at a relatively low temperature （130 ℃） and a shorter holding time （1 h） when pH=8. The crystallization kinetics equation at 200℃ is ln[-ln（1-x）] =-0.78＋0.951n t. The growth activation energy of Ni0.5Zn0.5Fe2O4 grains is 41.6 kJ/moL in hydrothermal synthesis process. With the increase of sintering temperature, the density and diameter shrinkage of ferrite circulus increase, whereas its pores decrease. The results of magnetic measurements show that saturation magnetic flux density Bs increases and the coercivity Hc decreases with the increase of their sintering temperature. Magnetic parameters of all the investigated samples satisfy the character demand of high Bs, low Br and low Hc of soft magnetic ferrite materials.展开更多
An inductively coupled plasma mass spectrometry(ICP-MS) method was developed for the determination of Na, Mg, Al,K, Ca, Ti, Cr, Co, Ni, Cu, Ga, As, Mo, Ag, Cd and Pb in MnZn ferrites. The sample was digested by HNO3+H...An inductively coupled plasma mass spectrometry(ICP-MS) method was developed for the determination of Na, Mg, Al,K, Ca, Ti, Cr, Co, Ni, Cu, Ga, As, Mo, Ag, Cd and Pb in MnZn ferrites. The sample was digested by HNO3+HCl with microwave digestion followed by dilution with ultrapure water, then the above 16 impurity elements in the solution were analyzed directly by ICP-MS. The impurity elements were introduced by the helium gas or hydrogen gas into the octopole reaction system(ORS) to eliminate the polyatomic interferences caused by the high salty matrixes. The matrix effect was minimized through matrix matching,and Be, Y and Rh were used as internal standard elements. The working parameters of the instrument were optimized. The results show that the method has good precision and high accuracy. The detection limits for the investigated elements are in the range of0.9-37.5 ng/L, the relative standard deviation of each element is within 1.1%-4.8%, and the recovery of each element is 90%-108%.展开更多
The effect of non-magnetic Al^3＋ ion doping on the magnetic properties of MnFe2-2x Al2xO4 （0 ≤x≤ 0.4） spinel ferrites was studied using Moessbauer spectroscopy measurements at room temperature. From the Moessbaue...The effect of non-magnetic Al^3＋ ion doping on the magnetic properties of MnFe2-2x Al2xO4 （0 ≤x≤ 0.4） spinel ferrites was studied using Moessbauer spectroscopy measurements at room temperature. From the Moessbauer study, it is observed that the ：esolved hyperfine sextets are due to the distribution of Fe ions on the two sublattices of the spinel ferrites. The value of the isomer shift obtained from the fitting of the Moessbauer spectra indicates that Fe ions are in ＋3 state. A paramagnetic doublet is observed at ：iegree of inversion x=0.4, superimposed on the hyperfine sextets, indicating that the super-exchange interaction A-B decreases due to ：he dilution of sublattice by Al^3＋ ions. The hyperfine magnetic field decreases at both interstitial sites of tetrahedral （A） and 3ctahedral （B） with the increase in Al concentration.展开更多
The complex impedance spectroscopy and surface morphology of Mn1+xFe2-2xTixO4(0≤x≤0.5) system,prepared using a conventional solid state reaction technique,were investigated.The impedance spectroscopy measurements we...The complex impedance spectroscopy and surface morphology of Mn1+xFe2-2xTixO4(0≤x≤0.5) system,prepared using a conventional solid state reaction technique,were investigated.The impedance spectroscopy measurements were carried out at room temperature in the frequency range of 42-5 MHz.The electrical processes in the samples were modeled in the form of an equivalent circuit made up of a combination of two parallel RC circuits attributed to grain and grain boundaries.The DC conductivity obtained by extrapolation of AC data using impedance spectroscopy and four-probe method increases at 10% doping of Ti ions.The energy-dispersive X-ray(EDX) pattern confirmed the homogeneous mixing of the Mn,Fe,Ti and O atoms in pure and doped ferrite samples.展开更多
Rutile phase exhibits higher refractive index and h id ing power, good chemical stability, and is becoming a candidate material for the high-temperature separation and catalysis applications. The thermodynamically sta...Rutile phase exhibits higher refractive index and h id ing power, good chemical stability, and is becoming a candidate material for the high-temperature separation and catalysis applications. The thermodynamically stable feature of rutile among the three polymorphs of TiO 2 usually hinders ob taining nano-sized rutile phase by a conventional calcining way. However, acid peptization of amorphous TiO 2 is favorable to the formation of rutile phase. I n this work, well-crystallized and well-dispersed rod-like rutile particles w ith specific surface areas of 49.1 and 35.0 m 2/g were prepared by hydrothermal ly treating the acid peptized TiO 2 amorphous sols at relatively low temperatur es of 200 ℃ or 240 ℃, respectively. The formation of non-touching rutile part icles is attributed to high long-range electrostatic forces between particles i n the presence of the high concentration of the peptizer. The acid peptization w ould easily break the ≡Ti-O-Ti≡ bonds to form ≡Ti-OH or HO-Ti-OH species depending on the amount of acid, and create conditions for the formation of rut ile nuclei after structural rearrangements.展开更多
Monodispersed manganese ferrite （MnFe2O4） nanocrystals could be successfully synthesized in large quantities via a facile synthetic technique based on the pyrolysis of organometallic compound precursor, in which oct...Monodispersed manganese ferrite （MnFe2O4） nanocrystals could be successfully synthesized in large quantities via a facile synthetic technique based on the pyrolysis of organometallic compound precursor, in which octadecene was used as solvent, and oleic acid and oleylamine were used as capping ligands. MnFe204 nanocrystals were obtained with size in a tunable range of 4- 15 nm and their morphologies could be tuned from spherical to triangle-shaped by varying the surfactants. The phase structure, morphology, and size of the products were characterized in detail by X-ray diffraction （XRD） and transmission electron microscopy （TEM）. Magnetic properties of MnFe2O4 nanocrystals with different morphologies were measured using a superconducting quantum interference device （SQUID）. Both monodisperse MnFe204 nanocrystals with spherical and triangle-shapes are superparamagnetic at room temperature while ferromagnetic at 2 K. The pyrolysis method may provide an effective route to synthesize other spinel ferrites or metal oxides nanocrystals.展开更多
The flow stress of ferrite/pearlite steel under uni-axial tension was simulated with finite element method (FEM) by applying commercial software MARC/MENTAT. Flow stress curves of ferrite/pearlite steels were calculat...The flow stress of ferrite/pearlite steel under uni-axial tension was simulated with finite element method (FEM) by applying commercial software MARC/MENTAT. Flow stress curves of ferrite/pearlite steels were calculated based on unit cell model. The effects of volume fraction, distribution and the aspect ratio of pearlite on tensile properties have been investigated.展开更多
The hexagonal BaNd x Fe12?x O19(x=0.1?1.0) fine powders with M-type structure were synthesized by sol-gel auto-combustion high-temperature synthesis method. The structure of powders, gels’ combustion and magnetic pro...The hexagonal BaNd x Fe12?x O19(x=0.1?1.0) fine powders with M-type structure were synthesized by sol-gel auto-combustion high-temperature synthesis method. The structure of powders, gels’ combustion and magnetic properties of powders were respectively studied by means of X-ray diffractometer (XRD), differential thermal analysis-thermogravimetric analysis (DTA-TG) and vibrating sample magnetometer (VSM). The powders before and after combustion and calcination at 450–850 °C with different mole ratio of Nd to Ba (0.1–1.0) were compared in terms of XRD. In addition, the effects of different synthesis conditions on magnetic properties of powders were also discussed. The results show that at pH 7.0 or so, mole ratio of citrate to nitrate (1–3) and calcination temperature of 850 °C for 1 h, M-type BaNd x Fe12?x O19(x=0.1?1.0) fine powders can be obtained, and the coercive force reaches 436880 A·m?1 at x=1, which is far greater than that of barium permanent ferrite (BaFe12O19).展开更多
基金Project(1053320222852)supported by the Graduate Student Innovation Program of Central South University,China。
文摘Permanent ferrite magnet materials are extensively employed due to their exceptional magnetic properties and cost-effectiveness.The fast development in electromobile and household appliance industries contributes to a new progress in permanent ferrite materials.This paper reviews the deveolpement and progress of permanent ferrite magnet industry in recent years.The emergence of new raw material,the advancement of perparation methods and manufacturing techniques,and the potential applications of permanent ferrite materials are introduced and discussed.Specifically,nanocrystallization plays a crucial role in achieving high performance at a low cost and reducing reliance on rare earth resources,and therefore it could be a promising development trendency.
文摘Hydrothermal method was used to synthesize nanoscale particles of MnZn ferrites. The crystallites were characterized by XRD, TEM and SEM. The effects of the reaction time, temperature and additives on the product were investigated. Crystallization process would be carried out above 160 ℃ for 5 h or more, higher temperature can reduce the reaction time. Additives were used to remove impurities such as Fe 2O 3, ZnMnO 3.10～15 nm pure slightly agglomerated MnZn ferrite crystallites with a narrow grain size distribution were obtained.
文摘Hard and brittle materials such as ferrite, optical glass and ceramics have been widely used in many fields because of their good characteristics and still gain more attentions. However, it is difficult to machine and get good surface quality. Some parts made of these materials have large machining allowances and need to be produced with large batch, but the machining efficiency is very low with usual grinding method. So it is of great importance to research the high efficiency grinding technology of hard and brittle materials. Electrolytic in-process dressing (ELID) grinding is a new grinding technology which has been adopted to the ultra-precision machining of hard and brittle materials. With the function of in-process dressing of metal bond diamond and CBN wheel, ELID grinding has the ability to keep the sharpness of the wheel surface and is widely used in fine abrasive grinding, but it also has the potentialities to high efficiency grinding. In this paper, the mechanism of ELID grinding and its grinding performance are analyzed, then the cast iron bond diamond wheels and ELID grinding device are used on a surface grinder to research the feasibility of ELID grinding to high efficiency grinding. To make comparison, the garnet ferrite (YAG) work piece has been machined in plunge grinding both by ELID grinding and by the resin bond diamond wheel. The grinding force and surface quality are tested and analyzed. It has been found that the grinding force of the cast iron bond diamond wheel with ELID grinding is apparently smaller than that of the resin bond diamond wheel. Under the same conditions, it is about 2/5～3/5 as the force using the resin bond diamond wheel. So with the same grinder and machining conditions, ELID grinding can machine work piece with greater depth of cut. Because of the smaller grinding force, it is also beneficial to avoid the edge collapse of the work piece and keep the integrity of the grinding surface. This experiment shows that the grinding efficiency can be highly improved and the surface quality be ensured by applying ELID grinding technology and adopting large grinding depth. The results indicate that the ELID grinding technology can be effectively used in the high efficiency machining of garnet ferrite and other hard and brittle materials.
基金Project(51206033)supported by the National Natural Science Foundation of ChinaProjects(2011M500652,2013T60354)supported by the China Postdoctoral Science FoundationProject(2011LBH-Z11139)supported by the Heilongjiang Postdoctoral Science Foundation,China
文摘In order to investigate the effect of additives and nano-particle on the surface tensions of lithium bromide(Li Br) aqueous solution/ammonia, many experiments were carried out based on Wilhelmy plate method. Firstly, the surface tension of Li Br aqueous solution with 1-octanol was measured and then the comparison between the measured results and previous experimental results was given to verify the measuring accuracy. Some new additives, such as cationic surfactants cetyltrimethyl ammonium chloride(CTAC), and cetyltrimethyl ammonium bromide(CTAB) were chosen in the experiments. The experimental results show that CTAC and CTAB can obviously reduce the surface tension of Li Br aqueous solution/ammonia. In addition, it is found that nano-particles cannot remarkably decrease the surface tension of Li Br aqueous solution/ammonia. However, the mixed addition of additives and nano-particles can remarkably affect the surface tension of Li Br aqueous solution/ammonia. That is to say, additives play more important role in reducing the surface tension of Li Br aqueous solution/ammonia. But nano-particles may enhance the heat transfer in the absorption refrigeration process.
基金Projects(51104041,51174054,51374065)supported by the National Natural Science Foundation of ChinaProject(N130402010)supported by the Fundamental Research Funds for the Central Universities of China
文摘The dissolution property of high-ferrite gibbsitic bauxite and the effect of ferrite content on the dissolution kinetics of gibbsitic bauxites in sodium hydroxide solution under atmospheric pressure from 50 to 90 °C were systematically investigated.The dissolution property of high-ferrite gibbsitic bauxite is increased by increasing the dissolution temperature and the Na OH concentration or decreasing the particle size of bauxite,which is easy to dissolve under atmospheric pressure.The kinetic equations of gibbsitic bauxites with different ferrite contents during the dissolution process at different temperatures for different times were established,and the corresponding activation energies were calculated.The ferrite in the gibbsitic bauxite reduces the dissolution speed and increases the activation energy of dissolution,the diffusion process of which is the rate-controlling step.
文摘The effect of additive RCOONa on the formation of MnZn ferrite homogeneous coprecipitation precursor was studied in this paper. The action of additive in the MnZn ferrite hydrothermal crystallization process was investigated according to crystal field theory and crystal growth unit theory. And the growth unit formation process was presented and its structure was illustrated. The results show that the precursor of MnZn ferrite is a colloidal mixture composed of Zn(OH) 2, Fe(OH) 2, Mn(OH) 2, MnO(OH) , MnO 2· x H 2O and so on, and dissolves in solution in the form of hydroxyl coordination tetrahedron and octahedron such as Zn(OH) 2- 4, Fe(OH) 2- 4, Fe(OH) 4- 6,Fe(OH) - 4, Fe(OH) 3- 6,Mn(OH) 2- 4,Mn(OH) 3- 6 etc., and the growth unit is formed by combination of the coordination polyhedra subsequently in the hydrothermal precess. The additive is beneficial to the formation of homogeneous precursor and has dispersive effect on the aggregation of the crystal growth unit by forming associate with hydrogen bond, which is beneficial to the synthesis of the pure product with a tiny size and a narrow size distribution.
基金Project(2013JSJJ028)supported by the Key Programs of Science and Technology from Hunan Province,China
文摘It is generally known that the large formation amount of calcium ferrite is favorable for the iron ore sintering. The effects of sintering temperature and O2 content of inlet gas on the calcium ferrite formation characteristic of typical iron ores, including hematite, limonite, specularite and magnetite, were investigated. And the effect of O2 content on the microstructure of the roasted briquettes was also studied in detail. The results show the amount of calcium ferrite initially increases then decreases with the increase of the sintering temperature. The temperature of maximum calcium ferrite generation amount is determined as follows： for hematite and limonite it is 1275 ~C, whereas for specularite and magnetite, 1250℃. The maximum contents of calcium ferrite for hematite, limonite, specularite and magnetite under the optimal sintering temperature are 73%, 82%, 67% and 63%, respectively. Increasing O2 content of the airflow is advantageous to the formation of calcium ferrite. Relatively, the effect of O2 content on the calcium ferrite formation of magnetite is the most pronounced, while O2 content of inlet gas has little effect on the calcium ferrite formation of limonite.
基金Project(21275162)supported by the National Natural Science Foundation of ChinaProject(KJZH14217)supported by the Achievement Transfer Program of Institutions of Higher Education in Chongqing,ChinaProject(KJ1601224)supported by the Scientific and Technological Research Program of Chongqing Municipal Education Commission,China
文摘An analytical method for the determination of 26 impurity elements （such as Li, Be, Na, Mg, Al, Si, P, S, K, Ca, Sc, Ti, V, Cr, Co, Ni, Ga, Ge, Y, Nb, Mo, Ag, Cd, Sb, W and Pb） in MnZn ferrite powder by direct current glow discharge mass spectrometry （GD-MS） was established. MnZn ferrite powder was mixed with copper powder, used as a conductor, and pressed. The effects of MnZn ferrite powder preparation conditions and glow discharge parameters for the sensitivity and stability of signal analysis were investigated. By determining the choice of isotope and the application of the mass resolutions of 4000 （MR, medium resolution） and 10000 （HR, high resolution）, mass spectral interference was eliminated. The contents of impurity elements in MnZn ferrite powder was calculated by subtraction after normalizing the total signal of Mn, Zn, Fe, O and Cu. The results showed that the detection limit of 26 kinds of impurity elements was between 0.002 and 0.57 μg/g, and the relative standard deviation （RSD） was between 3.33% and 32.35%. The accuracy of this method was verified by the ICP-MS. The method was simple and practical, which is applied to the determination of impurity elements in MnZn ferrite powder.
基金Project(20806035)supported by the National Natural Science Foundation of ChinaProject(2009CI026)supported by the Back-up Personnel Foundation of Academic and Technology Leaders of Yunnan Province,ChinaProject(KKZ6200927001)supported by the Opening Fund of Key Laboratory of Inorganic Coating Materials,Chinese Academy of Sciences
文摘Ni-W-P composite coatings reinforced by Ce O2 and Si O2 nano-particles on the surface of common carbon steels, were prepared by double pulse electrodeposition. The crystallization course was characterized by phase structures, crystallinity, grain sizes and microstructures. The results indicate that as-deposited composite coating is amorphous. Whereas it turns into the crystalline structure with 98.25% crystallinity, and Ni3 P, Ni2 P and Ni5P2 alloy phases precipitate from structures at 400 °C. Thereafter, Ni2 P and Ni5P2 metastable alloy phases turn into Ni3 P stable alloy phase at 500 °C. The crystallization course of the composite coating has finished when being heat-treated at 700 °C. The average sizes of Ni grains increase with the rise of heat treatment temperature from400 °C to 700 °C. Ce O2 and Si O2 nano-particles deposited into Ni-W-P alloys can delay the crystallization course and habit the growth of alloy phases.
基金Project(2018JJ1041)supported by the Natural Science Foundation of Hunan,ChinaProjects(51774332,51934009,U1932129)supported by the National Natural Science Foundation of China。
文摘Ferroplasma thermophilum,a sort of extreme acidophilic archaea,which can synthesize intracellular cobalt ferrite nanocrystals,is investigated in this study.The nanocrystals were analyzed with ultrathin sections and transmission electron microscope,with the size of 20−60 nm,the number of more than 30 in each cell at average,which indicated that F.thermophilum can synthesize intracellular nanocrystals and also belongs to high-yield nanocrystals-producing strain.Intriguingly,the nanocrystals contain ferrite and cobalt characterized by EDS X-ray analysis,suggesting that both cobalt and ferrite are potentially contributed to the formation of nanocrystals.Moreover,under the different energy source culture conditions of FeSO4 and CuFeS2,the size and the morphology of the nanocrystals are different.It was also found that the higher initial Fe availability leads to an induced synthesis of larger nanocrystals and the lower oxidation-reduction potential(ORP)leads to an induced effect on the synthesis of nanocrystals with abnormal unhomogeneous size,which suggested that the higher initial Fe availability and the lower oxidation-reduction potential lead to a higher uptake efficiency of iron ions of F.thermophilum by iron and ORP gradient culture.
文摘MnZn ferrite nanoscale particles were synthesized by hydrothermal method. The effects of amount of addition La3+ on the products were discussed. The product was characterized by X-ray diffraction （XRD） and transmission electron microscope （TEM）. The results show that the sample with 0.2% La3+（mass fraction） or without La3+ has only spinel phase, but the sample with mass fraction of La3+ exceeding 0.4% posses second phase besides the spinel one; and the nano-MnZn ferrites change from cube to hexagon when the mass fractions of La3+ is up to （1.2%.） TEM image of the sample with 1.2% La3+ indicates that the homogeneous hexagonal crystal is obtained and the particles are larger than those of undoped; the addition of La3+ has great influence on the crystallization of hydrothermal process and can change the shape of particles and improve their growth. The saturation magnetization of the sample with 1.2% La3+ (2.64 A·m2·kg-1) is lower than that of undoped (17.54 (A·m2·kg-1)) and it behaves superparamagnetically.
基金Project(50204001) supported by the National Natural Science Foundation of China
文摘Nanometer Ni0.5Zn0.5Fe2O4 powders with spinel phase were prepared by the hydrothermal method using purified FeSO4 solution from sodium jarosite＇s slag as materials. The results show that the spinel phase of Ni0.5Zn0.5Fe2O4 powders begins to form at a relatively low temperature （130 ℃） and a shorter holding time （1 h） when pH=8. The crystallization kinetics equation at 200℃ is ln[-ln（1-x）] =-0.78＋0.951n t. The growth activation energy of Ni0.5Zn0.5Fe2O4 grains is 41.6 kJ/moL in hydrothermal synthesis process. With the increase of sintering temperature, the density and diameter shrinkage of ferrite circulus increase, whereas its pores decrease. The results of magnetic measurements show that saturation magnetic flux density Bs increases and the coercivity Hc decreases with the increase of their sintering temperature. Magnetic parameters of all the investigated samples satisfy the character demand of high Bs, low Br and low Hc of soft magnetic ferrite materials.
基金Project(21271187)supported by the National Natural Science Foundation of ChinaProject(cstc2013jcyj A10088)supported by the Chongqing Natural Science Foundation,China+1 种基金Projects(2013FJ3093,2013SK3268)supported by the Science and Technology Project of Hunan Province,ChinaProject(KJZH14217)supported by Achievement Transfer Education in Chongqing,China
文摘An inductively coupled plasma mass spectrometry(ICP-MS) method was developed for the determination of Na, Mg, Al,K, Ca, Ti, Cr, Co, Ni, Cu, Ga, As, Mo, Ag, Cd and Pb in MnZn ferrites. The sample was digested by HNO3+HCl with microwave digestion followed by dilution with ultrapure water, then the above 16 impurity elements in the solution were analyzed directly by ICP-MS. The impurity elements were introduced by the helium gas or hydrogen gas into the octopole reaction system(ORS) to eliminate the polyatomic interferences caused by the high salty matrixes. The matrix effect was minimized through matrix matching,and Be, Y and Rh were used as internal standard elements. The working parameters of the instrument were optimized. The results show that the method has good precision and high accuracy. The detection limits for the investigated elements are in the range of0.9-37.5 ng/L, the relative standard deviation of each element is within 1.1%-4.8%, and the recovery of each element is 90%-108%.
基金Project supported by the Second Stage of Brain Korea 21 ProjectProject(RTI04-01-03) supported by the Regional Technology Innovation Program of the Ministry of Knowledge Economy (MKE),Korea
文摘The effect of non-magnetic Al^3＋ ion doping on the magnetic properties of MnFe2-2x Al2xO4 （0 ≤x≤ 0.4） spinel ferrites was studied using Moessbauer spectroscopy measurements at room temperature. From the Moessbauer study, it is observed that the ：esolved hyperfine sextets are due to the distribution of Fe ions on the two sublattices of the spinel ferrites. The value of the isomer shift obtained from the fitting of the Moessbauer spectra indicates that Fe ions are in ＋3 state. A paramagnetic doublet is observed at ：iegree of inversion x=0.4, superimposed on the hyperfine sextets, indicating that the super-exchange interaction A-B decreases due to ：he dilution of sublattice by Al^3＋ ions. The hyperfine magnetic field decreases at both interstitial sites of tetrahedral （A） and 3ctahedral （B） with the increase in Al concentration.
基金Project supported by the Second Stage of Brain Korea 21 ProjectProject(RTI04-01-03) supported by the Regional Technology Innovation Program of the Ministry of Knowledge Economy (MKE),Korea
文摘The complex impedance spectroscopy and surface morphology of Mn1+xFe2-2xTixO4(0≤x≤0.5) system,prepared using a conventional solid state reaction technique,were investigated.The impedance spectroscopy measurements were carried out at room temperature in the frequency range of 42-5 MHz.The electrical processes in the samples were modeled in the form of an equivalent circuit made up of a combination of two parallel RC circuits attributed to grain and grain boundaries.The DC conductivity obtained by extrapolation of AC data using impedance spectroscopy and four-probe method increases at 10% doping of Ti ions.The energy-dispersive X-ray(EDX) pattern confirmed the homogeneous mixing of the Mn,Fe,Ti and O atoms in pure and doped ferrite samples.
文摘Rutile phase exhibits higher refractive index and h id ing power, good chemical stability, and is becoming a candidate material for the high-temperature separation and catalysis applications. The thermodynamically stable feature of rutile among the three polymorphs of TiO 2 usually hinders ob taining nano-sized rutile phase by a conventional calcining way. However, acid peptization of amorphous TiO 2 is favorable to the formation of rutile phase. I n this work, well-crystallized and well-dispersed rod-like rutile particles w ith specific surface areas of 49.1 and 35.0 m 2/g were prepared by hydrothermal ly treating the acid peptized TiO 2 amorphous sols at relatively low temperatur es of 200 ℃ or 240 ℃, respectively. The formation of non-touching rutile part icles is attributed to high long-range electrostatic forces between particles i n the presence of the high concentration of the peptizer. The acid peptization w ould easily break the ≡Ti-O-Ti≡ bonds to form ≡Ti-OH or HO-Ti-OH species depending on the amount of acid, and create conditions for the formation of rut ile nuclei after structural rearrangements.
基金Project(2010QZZD008) supported by the Prospect Key Projects of Fundamental Research Funds for the Central UniversitiesProject(2007FJ3008) supported by the Hunan Provincial Key Science and Technology Program of China
文摘Monodispersed manganese ferrite （MnFe2O4） nanocrystals could be successfully synthesized in large quantities via a facile synthetic technique based on the pyrolysis of organometallic compound precursor, in which octadecene was used as solvent, and oleic acid and oleylamine were used as capping ligands. MnFe204 nanocrystals were obtained with size in a tunable range of 4- 15 nm and their morphologies could be tuned from spherical to triangle-shaped by varying the surfactants. The phase structure, morphology, and size of the products were characterized in detail by X-ray diffraction （XRD） and transmission electron microscopy （TEM）. Magnetic properties of MnFe2O4 nanocrystals with different morphologies were measured using a superconducting quantum interference device （SQUID）. Both monodisperse MnFe204 nanocrystals with spherical and triangle-shapes are superparamagnetic at room temperature while ferromagnetic at 2 K. The pyrolysis method may provide an effective route to synthesize other spinel ferrites or metal oxides nanocrystals.
文摘The flow stress of ferrite/pearlite steel under uni-axial tension was simulated with finite element method (FEM) by applying commercial software MARC/MENTAT. Flow stress curves of ferrite/pearlite steels were calculated based on unit cell model. The effects of volume fraction, distribution and the aspect ratio of pearlite on tensile properties have been investigated.
文摘The hexagonal BaNd x Fe12?x O19(x=0.1?1.0) fine powders with M-type structure were synthesized by sol-gel auto-combustion high-temperature synthesis method. The structure of powders, gels’ combustion and magnetic properties of powders were respectively studied by means of X-ray diffractometer (XRD), differential thermal analysis-thermogravimetric analysis (DTA-TG) and vibrating sample magnetometer (VSM). The powders before and after combustion and calcination at 450–850 °C with different mole ratio of Nd to Ba (0.1–1.0) were compared in terms of XRD. In addition, the effects of different synthesis conditions on magnetic properties of powders were also discussed. The results show that at pH 7.0 or so, mole ratio of citrate to nitrate (1–3) and calcination temperature of 850 °C for 1 h, M-type BaNd x Fe12?x O19(x=0.1?1.0) fine powders can be obtained, and the coercive force reaches 436880 A·m?1 at x=1, which is far greater than that of barium permanent ferrite (BaFe12O19).
