铁精粉品位水分在线快速分析仪的研制

文章介绍了一种以单片机为核心,采用铁精粉品位能够引起电感线圈电感值变化的原理研制的快速在线铁精粉品位水分分析仪。该仪表成本低、性能稳定,满足了小型矿山企业铁精粉生产过程在线检测控制的要求。     

分布式多通道挥发性有机物在线监测系统测试方法的研究

分布式多通道挥发性有机物在线监测系统是监测工业园区、产线、厂界及无组织排放VOCs的有效手段，但目前国内缺乏对其检测的依据。本文结合国内实际情况，研究具有针对性的专用测试方法，并对其计量特性进行测试评价。实验证明：该系统结果一致性好，可作为评价监测系统的方法依据。     

配碳量对中低品位磷矿真空碳热还原的影响

通过FactSage理论计算与实验相结合的方法研究了配碳量对中低品位磷矿真空碳热还原的影响。理论计算表明:在保持温度和压强不变的条件下,增加配碳量,还原矿样的失重率不断增加,气相中磷单质的质量随之增加,PO、PO_2的质量不断减小。当配碳量达到14%时,磷的收得率达到99.91%。实验结果表明:还原矿样的失重率与磷的收得率随着矿样中配碳量的增加而逐渐增加。理论计算与实验结果较吻合。     

铁磁流体互易性磁致旋光效应的传输特性及数值模拟

对水基铁磁流体在外加磁场作用下的磁致旋光效应的传输特性进行实验和数值模拟研究.在构建铁磁流体纵向磁光效应测试平台的基础上,对铁磁流体在恒定磁场、单个脉冲磁场以及连续方渡脉冲磁场作用下的磁致旋光效应进行了研究.结果表明,铁磁流体对偏振光振动方向的旋转与纵向调制磁场的方向无关;铁磁流体对于快脉冲磁场的响应是一个双指数弛豫过...     

光纤光栅水准仪在建筑物远程实时监测中的应用

随着现代测试技术正趋于向在线、动态、实时的监测与控制,基于传统的机电测试技术的监测方法,很难实现远程实时动态监测。以河北大学电信楼为背景,采用光纤光栅水准仪对建筑物整体沉降情况进行监测。在监测过程中通过压路机对建筑物施加动力荷载,获得建筑物的动力特性和动力响应规律。监测结果表明:光纤光栅静力水准仪可以用于建筑物的动力特性监测同时又可以实现远程在线监测,其监测结果对类似工程具有很大的指导意义。     

甘肃某低品位铁矿选矿试验

本文主要针对甘肃某低品位磁铁矿的性质,通过磁选条件试验确定采用干式预选-三段阶段磨矿-五段阶段磁选的工艺流程,使TFe品位为22.15%的低品位单一磁铁矿获得TFe品位为63.04%、回收率为47.91%的较好技术指标的选矿试验研究。     

铁磁/反铁磁双层膜中的磁化性质与界面微结构

采用Monte Carlo模拟方法,通过反铁磁层中非磁性掺杂方式调节铁磁层与反铁磁层界面微结构,讨论了其界面微结构对体系的磁滞回线的不对称性、交换偏置场及矫顽场的影响.模拟结果显示:在同一掺杂浓度下,体系的磁滞回线的不对称性及交换偏置场强烈地依赖于掺杂方式,但矫顽场几乎不受影响,其相应的温度特性亦依赖于掺杂方式.它表明铁磁/反铁磁双层膜体系中的磁滞回线的不对称性以及交换偏置场与其界面微结构密切相关,同时实验上人们可通过界面微结构的改变获得交换偏置场大、矫顽场小且热稳定性好的自旋阀结构.     

发动机连杆组件振动特性的实验研究

本文利用振动信号分析处理技术,以实验测试的方法在四冲程发动机上研究了连杆组件及有关部件的振动特性.文章着重探讨了连杆组件在非正常状态下工作时振动特性的变化规律.由此得出的有关信息可用于连杆组件的故障诊断及状态监测.     

NiO/CoFe双层膜的交换机制研究

通过改变制备NiO薄膜的氩气压和衬底材料,研究了NiO的结构、表面粗糙度对NiO/CoFe双层膜交换耦合场Hex的影响.实验表明完全自旋未补偿面与交换耦合场的产生没有直接联系,但交换耦合场Hex与界面状况密切相关.增大NiO的表面粗糙度会使交换耦合场Hex减小.应用随机场理论在考虑了实际界面存在的粗造度、杂质和缺陷等实际情况下,正确地预测了交换耦合场的数量级,而且对交换耦合场与铁磁层厚度tFM、反铁磁层厚度tAFM以及交换耦合场的温度特性等实验结果做出了合理解释.并应用随机场模型对反铁磁/铁磁双层膜中铁磁层矫顽力Hc与铁磁层厚度tFM的关系进行了定量计算,发现矫顽力Hc与铁磁层厚度1/tFM成正比,这一结果表明理论计算与我们的实验数据符合得很好.     

航空制造领域温湿度计在线校准的探讨

本文针对航空制造领域温湿度计在线计量测试需求,进行了深入调研.分析和梳理不同品牌温湿度箱及温湿度计的设备特性、校准方法及其对应的自动控制手段.最终,提出了可行的在线自动校准实施方案,对工程推广及应用具有直接效益.     

Preparation of iron boride-silica core-shell nanoparticles with soft ferromagnetic properties

A one-pot aqueous chemical synthesis for silica-passivated ferromagnetic nanoparticles is presented. The average size of these particles is 84 ± 20?nm. The x-ray and electron diffraction experiments revealed that the nanoparticles are mainly composed of polycrystalline iron boride. The broad x-ray diffraction peak leads to an average crystallite size of 1.8?nm, which is much smaller than the overall size of the particles, and is consistent with the polycrystalline nature of the samples. M?ssbauer spectroscopy and magnetization experiments were used to establish the room temperature magnetic properties as well as the chemical nature of the particles. Fe(2)B dominates the composition of the nanoparticles, having a hyperfine field broadly distributed in the 10-33?T range. Alpha iron, the second ferromagnetic material identified in the particles, amounts to 4.6% of the composition. Finally, a paramagnetic phase accounting for approximately 14.6% of the material of the particles was also detected. These nanoparticles contain a core with soft ferromagnetic properties surrounded by a passivating silica layer, and are suitable for magnetically targeted drug delivery and electromagnetic induction heating applications.     

Mineralogical reconstruction of Titanium-Vanadium hematite and magnetic separation mechanism of titanium and iron minerals

In this paper, magnetization roasting - low-intensity magnetic separation was performed on a pre-concentration concentrate obtained from an Australian hematite containing titanium and vanadium to realize the separation of titanium and vanadium. The results showed that an iron concentrate with TFe (total iron) grade of 58.71%, iron recovery of 86.72% and V₂O₅ grade of 1.00%, V₂O₅ recovery of 93.97% could be obtained under the optimum roasting conditions (roasting temperature of 580 °C, total gas-flow rate of 1.44 m³/h, CO concentrate of 30%, roasting time of 20 min), meanwhile the iron tailings (i.e., TiO₂ concentrate) with TiO₂ grade of 43.76%, TiO₂ recovery of 63.42% was obtained. XRD analysis, phase iron chemical analysis, and magnetic analysis were conducted on the raw sample and the roasted products. The results showed that after magnetization roasting, the hematite and limonite in raw sample were transformed into magnetite with strong magnetism, and the vanadium hematite of hexagonal system was transformed into vanadium magnetite of equiaxed system. As the weakly magnetic ilmenite does not participate in the reaction during reduction roasting, the separation of ilmenite and vanadium can be easily achieved via magnetic separation.     

An efficient method for decoration of the multiwalled carbon nanotubes with nearly monodispersed magnetite nanoparticles

A one-pot method has been developed to prepare magnetite nanoparticles decorated carbon nanotubes (CNTs) by thermal decomposition of iron chloride on CNTs templates in diethylene glycol. The morphological and structural characterizations indicate that magnetite nanoparticles are coated on the surfaces of the CNTs to form CNT-based nanocomposites. The density of magnetite nanoparticles on CNTs could be easily tuned by adjusting the weight ratio of iron chloride to CNTs. Magnetic measurements showed that the nanocomposites are superparamagnetic at room temperature and the magnetic properties of the samples can also be tuned by adjusting preparing conditions. The nanocomposites can be readily dispersed in water to form a stable solution and can be manipulated using an external magnetic field. As-synthesized nanocomposites may have potential applications in target–drug delivery, detection and separations, and in clinical diagnosis.     

Magnetic properties of encapsulated nanoparticles in nitrogen-doped multiwalled cabon nanotubes embedded in SiOx matrices

We report the production, characterization, thermal transformations (400-1000 degrees C), and magnetic properties of nanoparticles encapsulated in nitrogen-doped multiwall carbon nanotubes (CNx-MWNT), which were embedded in silicon oxide (SiOx) matrices via sol-gel techniques. The vapor chemical deposition (CVD) method with ferrocene-benzelamine mixtures was used to synthesize Fe and Fe3C nanoparticles inside CNx-MWNTs. Composites consisting of CNx-MWNTs (filler) and SiOx (matrix) were fabricated and thermally treated to different temperatures and exposure times (t). All samples were characterized using scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), thermogravimetic analysis (TGA), and magnetometry (vibrating sample). We found that upon thermal treatment, the ferromagnetic nanoparticles modify their morphology, composition and aspect ratio, thus resulting in drastic changes in the magnetic and structural properties. In particular, as produced encapsulated nanoparticles mainly consisting of Fe and Fe3C phases were thermally modified into magnetite (Fe3O4). We have also observed that the hysteresis loops are very sensitive to the thermal treatment of the sample. Thus we can control the magnetic properties of the samples using thermal treatments.     

Oriented growth of magnetite along the carbon nanotubes via covalently bonded method in a simple solvothermal system

A new type of CNTs/magnetite hybrid material was prepared via covalently bonded method in a simple solvothermal system using FeCl₃ as iron source, ethylene glycol as the reducing agent, and 4-aminophenoxyphthalonitrile-grafted CNTs as templates. The magnetite nanoparticles, with the diameters of 70-80 nm, were self-assembled along the CNTs. The FTIR, UV-vis and DSC revealed that a stable covalent bond between nitriles group and iron ion promoted the oriented growth of magnetite nanoparticles along the CNTs, resulting in good dispersibility and solution storage stability. The magnetic properties measurements indicated that a higher saturated magnetization (70.7 emu g⁻¹) existed in the CNTs/magnetite hybrid material, which further enhanced the electromagnetic properties. The magnetic loss was caused mainly by natural resonance, which is in good agreement with the Kittel equation results. The novel electromagnetic hybrid material is believed to have potential applications in the microwave absorbing performances.     

Bi-layered polymer–magnetite core/shell particles: synthesis and characterization

Polymer magnetic core particles receive growing attention due to these materials owing magnetic properties which are widely used in different applications. The prepared composite particles are characterized with different properties namely: a magnetic core, a hydrophobic first shell, and finally an external second hydrophilic shell. The present study describes a method for the preparation of bi-layered polymer magnetic core particles (diameter range is 50–150 nm). This method comprises several steps including the precipitation of the magnetic iron oxide, coating the magnetite with oleic acid, attaching the first polymer shell by miniemulsion polymerization and finally introducing hydrophilic surface properties by condensation polymerization. The first step is the formation of magnetite nanoparticles within a co-precipitation process using oleic acid as the stabilizing agent for magnetite. The second step is the encapsulation of magnetite into polyvinylbenzyl chloride particles by miniemulsion polymerization to form a magnetic core with a hydrophobic polymer shell. The hydrophobic shell is desired to protect magnetite nanoparticles against chemical attack. The third step is the coating of magnetic core hydrophobic polymer shell composites with a hydrophilic layer of polyethylene glycol by condensation polymerization. Regarding the miniemulsion polymerization the influence of the amount of water, the mixing intensity and the surfactant concentration were studied with respect to the formation of particles which can be further used in chemical engineering applications. The resulting magnetic polymer nanoparticles were characterized by particle size measurement, chemical stability, iron content, TEM, SEM, and IR.     

Reduction and characterizations of iron particles: influence of reduction parameters

Iron particles have some applications as electromagnetic devices in magnetic recording and data storage technology due to their small sizes and high data storage capacity. The devices can be advanced by improving the properties of existing materials according to the production parameters. Thus, the influences of reduction parameters on the properties of iron particles were studied. The iron particles were reduced from superparamagnetic iron oxide nanoparticles by altering reduction parameters under hydrogen atmosphere at high (400 °C) temperature. The structural analysis of the films was carried out using the X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) techniques. The XRD data revealed that the crystal textures changed for the particles reduced at each parameter. And, the crystal structure turns from the cubic spinel structure of magnetite and body centered cubic (bcc) structure of iron to the bcc iron as the reduction time increases from 15 to 240 min. Then, the similar structure change can be seen for the samples reduced at increasing hydrogen flow rates. The HRTEM studies revealed that the surface morphology of the films strongly depend on the flow rate. Finally, magnetite peaks weaken and then disappear as the precursor mass decreases to the lowest value. The average crystallite sizes were found to be consistent with changing crystal structure. Furthermore, the magnetic characteristics studied by a vibrating sample magnetometer were observed to be affected by the parameters. Besides, magnetic differences may arise from the variation of crystal structure and crystal sizes caused by individual reduction parameters of reduction time, hydrogen flow rate and precursor mass.     

Method for estimation of magnetic viscosity of ferromagnetics

A method providing quantitative estimation of the degree of magnetic viscosity of ferromagnetic materials by measurement of the phase of the signal from the measuring coil at field excitation by a sinusoidal signal in longitudinally extended samples with constant cross section is described. It is demonstrated that, in estimation of magnetic viscosity, it is necessary to take into account the sample size and shape, as well as the frequency of measurement. Additional information obtained by determination of the decrement of the signal from the measuring coil can be used together with the magnetic viscosity for determination of steel grade. Corresponding plots are presented.     

Structure analysis on Ni and V co-doped zinc oxide prepared by solid state reactions

Powder samples of ZnO co-doped with Ni and V have been grown by standard solid state reaction technique with varying concentrations 2, 4 and 6 %. The grown samples were found to be dilute magnetic in nature along with semiconducting property. The structure of the grown material was solved using powder X-ray diffraction refinements and the electronic structure of the material was determined by maximum entropy method. Magnetic properties of the samples were studied using vibrating sample magnetometry and the samples exhibited ferromagnetic characteristics at room temperature. Inductively coupled-atomic emission spectroscopy was employed to identify the elemental composition of the grown samples. Direct band gap of the material was calculated using UV–vis studies.     

Magnetite Nanoparticles in Fullerite C60 Powder

Data are presented on the resonance and magnetic properties of Fe–fullerene nanomaterials prepared by heating a mixture of C₆₀ fullerene and iron(III) acetylacetonate. The starting-mixture composition is shown to have a significant effect on the particle size and properties of the resulting magnetite and the magnetic properties of the material. The influence of chemical treatment on the properties of the material is analyzed.