WorldWideScience

Sample records for high-coercivity sintered ndfeb

  1. High coercivity, anisotropic, heavy rare earth-free Nd-Fe-B by Flash Spark Plasma Sintering.

    Science.gov (United States)

    Castle, Elinor; Sheridan, Richard; Zhou, Wei; Grasso, Salvatore; Walton, Allan; Reece, Michael J

    2017-09-11

    In the drive to reduce the critical Heavy Rare Earth (HRE) content of magnets for green technologies, HRE-free Nd-Fe-B has become an attractive option. HRE is added to Nd-Fe-B to enhance the high temperature performance of the magnets. To produce similar high temperature properties without HRE, a crystallographically textured nanoscale grain structure is ideal; and this conventionally requires expensive "die upset" processing routes. Here, a Flash Spark Plasma Sintering (FSPS) process has been applied to a Dy-free Nd30.0Fe61.8Co5.8Ga0.6Al0.1B0.9 melt spun powder (MQU-F, neo Magnequench). Rapid sinter-forging of a green compact to near theoretical density was achieved during the 10 s process, and therefore represents a quick and efficient means of producing die-upset Nd-Fe-B material. The microstructure of the FSPS samples was investigated by SEM and TEM imaging, and the observations were used to guide the optimisation of the process. The most optimal sample is compared directly to commercially die-upset forged (MQIII-F) material made from the same MQU-F powder. It is shown that the grain size of the FSPS material is halved in comparison to the MQIII-F material, leading to a 14% increase in coercivity (1438 kA m(-1)) and matched remanence (1.16 T) giving a BHmax of 230 kJ m(-3).

  2. Corrosion resistance of sintered NdFeB coated with SiC/Al bilayer thin films by magnetron sputtering

    Science.gov (United States)

    Huang, Yiqin; Li, Heqin; Zuo, Min; Tao, Lei; Wang, Wei; Zhang, Jing; Tang, Qiong; Bai, Peiwen

    2016-07-01

    The poor corrosion resistance of sintered NdFeB imposes a great challenge in industrial applications. In this work, the SiC/Al bilayer thin films with the thickness of 510 nm were deposited on sintered NdFeB by magnetron sputtering to improve the corrosion resistance. A 100 nm Al buffer film was used to reduce the internal stress between SiC and NdFeB and improve the surface roughness of the SiC thin film. The morphologies and structures of SiC/Al bilayer thin films and SiC monolayer film were investigated with FESEM, AFM and X-ray diffraction. The corrosion behaviors of sintered NdFeB coated with SiC monolayer film and SiC/Al bilayer thin films were analyzed by polarization curves. The magnetic properties were measured with an ultra-high coercivity permanent magnet pulse tester. The results show that the surface of SiC/Al bilayer thin films is more compact and uniform than that of SiC monolayer film. The corrosion current densities of SiC/Al bilayer films coated on NdFeB in acid, alkali and salt solutions are much lower than that of SiC monolayer film. The SiC/Al bilayer thin films have little influence to the magnetic properties of NdFeB.

  3. History of Sintered NdFeB Magnets(Continued)

    Institute of Scientific and Technical Information of China (English)

    LUO Yang

    2007-01-01

    @@ 2. Output of sintered NdFeB magnets increased rapidly at the beginning of 21st century Annual output growth rate of magnets in China kept 25.2% from 1995-2000, and in Japan, USA and Europe was 26.2%,10% and 10.3% respectively.

  4. Grain Growth Behavior in Sintered Nd-Fe-B Magnets

    Institute of Scientific and Technical Information of China (English)

    Liu Xianglian; Zhou Shouzeng

    2007-01-01

    The Nd2Fe14B grain growth behavior in sintered Nd-Fe-B magnets was quantitatively described. The effects of sintering temperature and time, and alloy powder size and its distribution on grain growth process were analyzed. Hence, possible grain growth mechanisms in these magnets were qualitatively discussed. The Nd2Fe14B grain growth proceeded at quite a high rate in the initial 0~1 h of sintering and from then onwards the grain growth rate decreased. A large average particle size or a wide particle size distribution of initial alloy powders was found to remarkably accelerate the grain growth process and even result in the occurrence of abnormal grain growth. On the basis of experimental results, two grain growth mechanisms were considered to operate during sintering of Nd-Fe-B magnets, that is, dissolution and re-precipitation of Nd2Fe14B particles, and Nd2Fe14B particle growth by coalescence. It was believed that Nd2Fe14B particle growth by coalescence not only produced a large average grain size and a wide grain size distribution, but also was the fundamental reason for the formation of abnormally large grains in the microstructure of sintered Nd-Fe-B magnets.

  5. Rapid sintering of anisotropic, nanograined Nd-Fe-B by flash-spark plasma sintering

    Science.gov (United States)

    Castle, Elinor; Sheridan, Richard; Grasso, Salvatore; Walton, Allan; Reece, Mike

    2016-11-01

    A Spark Plasma Sintering (SPS) furnace was used to Flash-Sinter (FS) Nd-Fe-Dy-Co-B-Ga melt spun permanent magnetic material. During the 10 s "Flash" process (heating rate 2660 K min-1), sample sintering (to theoretical density) and deformation (54% height reduction) occurred. This produced texturing and significant magnetic anisotropy, comparable to conventional die-upset magnets; yet with much greater coercivities (>1600 kA m-1) due to the nanoscale characteristics of the plate-like sintered grains. These preliminary results suggest that Flash-SPS could provide a new processing route for the mass production of highly anisotropic, nanocrystalline magnetic materials with high coercivity.

  6. Corrosion behaviors of NdFeB magnets prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    Tao Li; Ming Yue; Aizhi Sun; Baoqin Qiu; Yaofu Xiao; Jiuxing Zhang

    2004-01-01

    The spark plasma sintering (SPS) technique was introduced into the field of NdFeB preparation due to its own advantages.High property NdFeB magnets with fine grains were prepared by SPS method. The corrosion behaviors of SPS NdFeB were studied by electrochemical measurements and 92% RH hyther tests at 353 K. The results were compared with those of the traditional sintered NdFeB magnets. It shows that both the SPS NdFeB and the traditional sintered NdFeB have good corrosion resistance in alkaline environment due to surface passivation; while, the fine grain microstructure of SPS NdFeB results in a more homogeneous phase composition distribution and thus reduces the electrochemical inhomogenity between the ferromagnetic phase and the Nd-rich intergranular phase in the magnet. Therefore, the SPS NdFeB exhibits better corrosion resistance than the traditional sintered NdFeB in neutral and weak acidic environment.

  7. HDDR法制备NdFeB永磁体的高矫顽力研究%Study on the Mechanism of the High Coercivity of NdFeB Magnets Prepared by HDDR Method

    Institute of Scientific and Technical Information of China (English)

    张朋越; 泮敏翔; 朱津津; 葛洪良; 孙浩; 金一彪

    2011-01-01

    , especially for the coercivity which is reduced by 1496 kA/m from 295 to 448 K.The coercivity mechanism of the NdFeB magnets prepared by HDDR method was analyzed by studying the behavior of Hc(T)/Ms(T) versus HminN (T)/Ms(T) (Kronmilller-plot).The results of Kronmiiller-plot sbow that nucleation is the dominating mechanism for the magnetization reversal in these samples.Micromagnetic parameters ak of 1.39 and Neff of 1.75 are responsible for the high coercivity of magnetic alloys.

  8. Heat treatment process of new NdFeB magnet prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    李涛; 岳明; 张久兴; 王公平; 肖耀福; 王润

    2003-01-01

    In recent years, spark plasma sintering technique(SPS) has been a focus in the field of material preparation due to its advantages. SPS technique is first introduced for preparation of high quality NdFeB magnets. The effects of heat treatment process on the magnetic properties of SPS NdFeB magnet were investigated. Meanwhile, the effects of heat treatment process on the microstructure, tropism and dimensional precision of the SPS NdFeB magnets were also studied. The high quality NdFeB magnets with fine grains were prepared under proper heat treatment process. The results show that the magnetic properties of SPS NdFeB can be further improved through proper heat treatment process. Meanwhile, the experiment also demonstrates that it is feasible to prepare near-net-shape NdFeB magnets with fine grains and high magnetic property by spark plasma sintering.

  9. Multilayer ceramic coating for impeding corrosion of sintered NdFeB magnets

    Institute of Scientific and Technical Information of China (English)

    A.Ali; A.Ahmad; K.M.Deen

    2009-01-01

    Sintered NdFeB magnets have complex microstructure that makes them susceptible to corrosion in active environments.The current paper evaluated the anticorrosion characteristics of multilayer titanium nitride ceramic coating applied through cathodic arc physical vapour deposition(CAPVD) for protection of sintered NdFeB permanent magnets.The performance of ceramic coating was compared to the electrodeposited nickel coating having a copper interlayer.Electrochemical impedance spectroscopy(EIS) and cyclic polar...

  10. Electrochemical Corrosion Behavior of Nd-Fe-B Sintered Magnets in Different Acid Solutions

    Institute of Scientific and Technical Information of China (English)

    Zheng Jingwu; Jiang Liqiang; Chen Qiaoling

    2006-01-01

    Electrochemical corrosion behavior of Nd-Fe-B sintered magnets in nitric acid, hydrochloric acid, sulfuric acid, phosphate acid and in oxalic acid was studied.Potentiodynamic polarization curves and immersion time dependence of corrosion rates of Nd-Fe-B sintered magnets in different acid solutions were tested.Microstructures of corroded Nd-Fe-B sintered magnets were investigated by means of SEM and AFM.The results indicate that in strong acid solutions of similar hydrogen ion concentration, the corrosion current increases in the order of HCl>H2SO4>HNO3 solution and Nd-Fe-B sintered magnets are passivated in phosphate acid and oxalic acid.Within 25 min, the corrosion rates of Nd-Fe-B sintered magnets in H2SO4 and H3PO4 solutions show a declining trend with immersion time, while in HNO3 and HCl solutions the corrosion rates are rising.And in H2C2O4 solution, weight of the magnets increases.The brim of Nd-Fe-B sintered magnets is corroded rather seriously and the size of the magnets changed greatly in nitric acid.The surfaces of the corroded magnets in the above mentioned acid solutions are all coarse.

  11. Specification Requirement for Thermal Stability of Sintered NdFeB Materials for Electrical Machines

    Institute of Scientific and Technical Information of China (English)

    Lin Yan; Jiang Daiwei; Chen Lixiang; Chen Hailing; Bi Haitao; Tang Renyuan

    2004-01-01

    Based on IEC standards and Chinese national standards of sintered NdFeB materials, in the paper the hightemperature, room-temperature properties and thermal stability of about one hundred samples of NdFeB materials for electrical machines were measured and analyzed.These materials are produced by ten representative manufactories in China.Combined with the analysis results, the paper points out that the magnetic properties of sintered NdFeB materials for electrical machines should meet not only the specific values in standards, such as Br, (BH)max ,HcJ ,but also the requirement of temperature coefficients a (Br) , a (HcJ).

  12. Magnetic properties of sintered high energy sm-co and nd-fe-b magnets

    Directory of Open Access Journals (Sweden)

    Talijan Nadežda M.

    2006-01-01

    Full Text Available Magnetic properties of permanent magnetic materials based on intermetallic compounds of Sm-Co and Nd-Fe-B are in direct dependence on the microstructure. In the first part of this paper, having in mind the importance of the regime of sintering and heat treatment to obtain the optimal magnetic structure, yet another approach in defining the most adequate technological parameters of the sintering process for applied heat treatment conditions was made. The goal of these investigations was to use the correlation that exists between sintering conditions (temperature and time and intensity of the diffraction peak of the (111 plane of the SmCo5 phase to optimize. In the second part a brief overview of high energy magnetic materials based on Nd-Fe-B is presented with special emphasis to the current research and development of high remanent nanocomposite magnetic materials based on Nd-Fe-B alloys with a reduced Nd content. Part of experimental results gained during research of the sintering process of SmCo5 magnetic materials were realized and published earlier. The scientific meeting devoted to the 60th anniversary of Frankel’s theory of sintering was an opportunity to show once more the importance and role of sintering in optimization of the magnetic microstructure of sintered Sm Co5 magnetic materials.

  13. Impulse Magnetization of Nd-Fe-B Sintered Magnets for Sensors.

    Science.gov (United States)

    Przybylski, Marek; Kapelski, Dariusz; Ślusarek, Barbara; Wiak, Sławomir

    2016-04-21

    Magnetization of large Nd-Fe-B sintered permanent magnets is still challenging. This type of permanent magnet is electrically conductive, so impulse magnetization causes a flow of eddy currents which prevent magnetization of the whole volume of the magnet. The paper deals with the impulse magnetization of sintered Nd-Fe-B permanent magnets and shows a method for the determination of suitable parameters for the supply system. The necessary magnetic field strength for magnetization of the magnet to saturation was determined. The optimal magnetizing fixture supply voltage for magnetization to saturation was determined from simulations in PSpice software, finite element analyses in Maxwell 15 and measurements. Measurements of magnetic induction on the surface of the Nd-Fe-B magnet are also presented to ensure that a magnet with 70 mm diameter and 20 mm in height is fully saturated.

  14. Impulse Magnetization of Nd-Fe-B Sintered Magnets for Sensors

    Directory of Open Access Journals (Sweden)

    Marek Przybylski

    2016-04-01

    Full Text Available Magnetization of large Nd-Fe-B sintered permanent magnets is still challenging. This type of permanent magnet is electrically conductive, so impulse magnetization causes a flow of eddy currents which prevent magnetization of the whole volume of the magnet. The paper deals with the impulse magnetization of sintered Nd-Fe-B permanent magnets and shows a method for the determination of suitable parameters for the supply system. The necessary magnetic field strength for magnetization of the magnet to saturation was determined. The optimal magnetizing fixture supply voltage for magnetization to saturation was determined from simulations in PSpice software, finite element analyses in Maxwell 15 and measurements. Measurements of magnetic induction on the surface of the Nd-Fe-B magnet are also presented to ensure that a magnet with 70 mm diameter and 20 mm in height is fully saturated.

  15. Statistical model of magnetization reversal in Nd-Fe-B sintered magnets

    Institute of Scientific and Technical Information of China (English)

    WANG Huijie; ZHU Minggang; LI Wei; ZHANG Xin

    2006-01-01

    Statistical model of magnetization reversal was used to simulate the magnetization reversal behavior in the sintered Nd-Fe-B magnets with double grain-size distributions due to the abnormal grain growth (AGG). The magnetic properties and mechanical properties due to the formation of AGG grains in Nd-Fe-B sintered magnets were tested. The results show that the magnetic properties, especially the rectangularity were severely deteriorated after the formation of the AGG grains and a step was shown on the demagnetization curve, and the occurrence of AGG mayaccount for the poor rectangularity and existence of the step on demagnetization curve according to the statistical model of magnetization reversal. The fracture toughness and bending strength are lowered because of the stress concentration in the AGG grains. The SEM images show that the formation of AGG grains is caused by the solid sintering due to the absence of RE-rich phase. Statistical model of magnetization reversal can qualitative by explain the dependence of the magnetization reversal behavior on the grain size in the Nd-Fe-B sintered magnets.

  16. The Effect of Nano-TiC Addition on Sintered Nd-Fe-B Permanent Magnets

    DEFF Research Database (Denmark)

    Mural, Zorjana; Kollo, Lauri; Xia, Manlong

    2017-01-01

    This paper addresses the effect of nano-TiC addition on sintered Nd-Fe-B permanent magnets. TiC nanoparticles were added to sintered Nd-Fe-B magnets with a specific aim to improve the Curie temperature and thermal stability. A standard powder metallurgy route was adopted to prepare the magnets. I...... for such magnets showed an improved shape and VSM analysis a coercivity value of 1188 kA/m, a remanence value of 0.96 T and a maximum energy product of 132 kJ/m3. The maximum working point and the Curie temperature of the developed magnets were 373 K and 623 K respectively....

  17. Factors Affecting the Squareness of Hysteresis Loops of Sintered NdFeB Magnets

    Institute of Scientific and Technical Information of China (English)

    Wang Zhanyong; Wang Xianying; Jin Minglin

    2007-01-01

    Investigation into the magnets with different squareness of hysteresis loop (SHL) reveals that the microstructure of sintered NdFeB magnets has great effects on the SHL of the magnets. The abnormal grain growth deteriorates the SHL seriously. The shape of the grain and the grain boundary affect the intensity of demagnetization field, and consequently on the SHL. The added elements have effects on the phase structures and distributions in the magnets, which influences the uniform of demagnetization field.

  18. Technique for recovering rare-earth metals from spent sintered Nd-Fe-B magnets without external heating

    Directory of Open Access Journals (Sweden)

    Ryo Sasai

    2016-06-01

    Full Text Available To selectively recover rare-earth metals with higher purity from spent sintered Nd-Fe-B magnets without external heating, we investigated the mechano-chemical treatment of spent sintered Nd-Fe-B magnet powder with a reaction solution of HCl and (COOH2 at room temperature. The results of various experiments showed that the mechano-chemical treatment with HCl and (COOH2 is very effective for recovering the rare-earth metals contained in spent sintered Nd-Fe-B magnet powder; the recovery rate and purity of the rare-earth metals were 95.3 and 95.0 mass%, respectively, under optimal conditions ([HCl] = 0.2 mol/dm3 and [(COOH2] = 0.25 mol/dm3.

  19. Effect of Annealing on the Magnetism of the Sintered NdFeB Magnet

    Institute of Scientific and Technical Information of China (English)

    ZHENG Hua-jun; HUANG Jian-guo; MA Chun-an

    2004-01-01

    This paper deals with the effect of annealing on the magnetism of the sintered NdFeB magnet with a composition of Nd30B5.1Dy1.2A10.6Nb0.7Fe62.4. Microstructural investigations of the grain size and grain boundaries with SEM were carried out. Microstructural investigations showed the presence of some Nd-rich phase in grain boundaries and main phase.The results of magnetic properties analysis shows that this non-magnetic Nd-rich phase, produced in annealing process,can increase or decrease the magnetism of the sintered NdFeB-type permanent magnet. Appropriate amount of Nd-rich phase will strengthen the pinning field and elevated the coercive force of magnet, but too many these non-magnetism phases in Nd2Fe14B main phase will decrease it. When the sintered NdFeB magnet was annealed at 3Pa and 492℃ for an hour the coercive force would raise from 915.6kA/m to 1164.8kA/m, and the (BH)max from 277.7kJ/m to 349.5kJ/m. However, annealing at a non-optimized temperature at 542℃, microstructure changes in some main phase will leading the decrease of properties.

  20. Magnetic Microstructure of Sintered Nd-Fe-B Magnets Made from Casting Strips

    Institute of Scientific and Technical Information of China (English)

    FANG Yi-Kun; ZHU Ming-Gang; GUO Yong-Quan; LI Wei; HAN Bao-Shan

    2004-01-01

    @@ The magnetic microstructures of two Dy-Al substituted sintered Nd-FeB magnets with the different nominal compositions of Nd12.2Dy0.6Fes0.4Al0. 7B6 (at. %) (composition-A, C-A) and Nd13.7Dy0.6Fe78.8Al0.7B6.2 (at. %)(composition-B, C-B) prepared by strip casting technique have been revealed by using a magnetic force microscope.

  1. The Studies of Composite Electroless Plating Process on Sintering Ndfeb Permanent Magnet

    Institute of Scientific and Technical Information of China (English)

    HU Jian-wen; MA Jing; YAN Dong-qing; GAO Qing; MENG Yong-qiang

    2004-01-01

    A reasonable pre-treatment and an ultrasonic pre-plating Cu film were applied for sintering NdFeB permanent magnet. The samples were then plated in neutral bath (PH=7) for 40min and in acidic bath (PH=4.8~5.1) for 2h. A composite electroless plating with different phosphor content was obtained. The results show that the composite plating coatings are dense and have a strong bond with the substrate, which contribute to the excellent corrosion resistance of the plating coating.

  2. The Studies of Composite Electroless Plating Process on Sintering Ndfeb Permanent Magnet

    Institute of Scientific and Technical Information of China (English)

    HUJian-wen; MAJing; YANDong-qing; GAOQing; MENGYong-qiang

    2004-01-01

    A reasonable pre-treatment and an ultrasonic pre-plating Cu film were applied for sintering NdFeB permanent magnet. The samples were then plated in neutral bath (PH=7) for 40rnin and in acidic bath (PH=4.8-5.1) for 2h. A composite electroless plating with different phosphor content was obtained. The results show that the composite plating coatings are dense and have a strong bond with the substrate, which contribute to the excellent corrosion resistance of the plating coating.

  3. Preparation Technology and Performances of Zn-Cr Coating on Sintered NdFeB Permanent Magnet

    Institute of Scientific and Technical Information of China (English)

    Yu Shengxue; Chen Ling

    2006-01-01

    Zn-Cr coating was prepared on the surface of sintered NdFeB permanent magnet samples and preparation parameters were established.The anticorrosive property of Zn-Cr coating on NdFeB was studied by whole-immersion test in NaCl solution and compared with that of zinc plating and nickel plating on NdFeB.Open-circuit potential and self-corrosion current of NdFeB samples with and without Zn-Cr coating were measured.The micro-morphology and composition of Zn-Cr coating were analyzed through SEM, XPS, EDS and XRD.The effect of Zn-Cr coating on magnetic property of NdFeB magnet was also investigated.It is exposed that Zn-Cr coating is anodic type coating for NdFeB magnet, and provided substrate electrochemical protection, barrier protection and passivation protection.The anticorrosion property of NdFeB magnet is obviously enhanced by Zn-Cr coating while the magnet property of NdFeB magnet changed little.

  4. Recycling of waste Nd-Fe-B sintered magnets by doping with dysprosium hydride nanoparticles

    Institute of Scientific and Technical Information of China (English)

    刘卫强; 李超; ZAKOTNIK Miha; 岳明; 张东涛; 黄秀莲

    2015-01-01

    Recycling of waste sintered Nd-Fe-B permanent magnets by doping DyH3 nanoparticles was investigated. The effect of the DyH3 nanoparticles on the microstructure and magnetic properties of the recycled magnets was studied. As the DyH3 nanoparticles additive increased, the coercivity of recycled magnet increased gradually. The recycled magnets with DyH3 nanoparticle content be-tween 0.0 wt.% and 1.0 wt.% maintained the remanence (Br), but, with higher additions, theBr began to decrease rapidly. The best recycled magnet produced contained 1.0 wt.% of DyH3 nanoparticles when compared to the properties of the starting waste sintering magnet. TheHcj,Br and (BH)max values of 101.7%, 95.4%, and 88.58%, respectively, were recovered.

  5. Magnetic Properties of Nd-Fe-B Sintered Magnet Powders Recovered by Yb Metal Vapor Sorption

    Institute of Scientific and Technical Information of China (English)

    Horikawa T; Itoh M; Suzuki Shunji; Machida K

    2004-01-01

    Fine ground powders of Nd-Fe-B sintered magnet bulks(particle size=46~125 μm in diameter) were coated and alloyed with Yb metal by sorbing them. A significant recovery of the decreased magnetic properties of the ground powders(remanence Br=~0.95 T, coercivity Hcj =~227 kA·m-1 and maximum energy product(BH)max=~48.8 kJ·m-3) was observed in accordance with increasing temperature up to 800 ℃. The sorbing temperature and time for Yb metal vapor were optimized and after heating at 800 ℃ for 90 min and annealing subsequently at 610 ℃ for 60 min, the Br, Hcj and(BH)max values were increased to be 0.98 T, 712 kA·m-1 and 173 kJ·m-3, respectively. From the microstructural characterizations of resulting samples by using X-ray diffraction(XRD), scanning electron microscopy(SEM), and electron probe X-ray microanalyzer(EPMA), it is found that the sorbed Yb metal uniformly covers the surface and diffuses to the Nd-rich grain boundary of fine ground powders of Nd-Fe-B sintered magnet bulks forming a(Nd,Yb)Fe2 phase.

  6. Relationship between controllable preparation and microstructure of NdFeB sintered magnets

    Institute of Scientific and Technical Information of China (English)

    李岩峰; 朱明刚; 李安华; 冯海波; 黄书林; 李卫; 杜安; 齐岩

    2014-01-01

    The double hard magnetic phase magnets with nominal compositions of Nd30-xDyxFe69B1 (x=2, and 4) (wt.%) were pre-pared. The magnetic properties of the magnets were measured with a NIM-2000H hysteresigraph. The crystalline structures of the magnets were identified by X-ray diffraction (XRD). The Rietveld refinement was carried out using the FULLPROF software. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses were carried out in order to investigate the microstructure of the magnets. It showed that the magnets consisted mainly of Nd2Fe14B phase, and some Nd-rich phase. Two types of matrix-phase grains in dark grey and light grey were found in the magnets with x=2 and 4. The Dy content was obviously dif-ferent in the two types of grains, which proved that the double hard magnetic phases (Dy-rich and Dy-lean phases) coexisted in the magnet. It revealed that the Nd-rich phases in junction regions had fcc structure, with the unit cell parameter of about 0.52-0.56 nm. The weak superlattice spots were found in the SAD patterns of the junction Nd-rich phases with large scale. The double hard mag-netic phase structure seemed to improve the magnetic properties of NdFeB magnets with high coercivity, while decrease the con-sumption of Dy element, compared with the single alloy magnet.

  7. Thermomagnetic treatment effects on microstructure in Nd-Fe-B type sintered magnets

    Science.gov (United States)

    PaigeSmith, Catherine

    Optimizing the microstructure of sintered Nd-Fe-B type magnets has become increasingly important. Sintered magnets are key components to the growing industry of alternative energy, particularly wind turbines and electric car generators. With rising costs and limited supply of rare earth elements, special attention has been dedicated to improving magnetic properties of these magnets through processing rather than compositional modifications. The magnetic property needing the most improvement in Nd-Fe-B type sintered magnets is coercivity. Coercivity dictates the performance of magnets at temperatures still below the demagnetizing threshold temperature. It has been shown that annealing sintered magnets in a magnetic field can enhance coercivity when compared to conventional post-sinter annealing in the absence of a magnetic field. However, little is known about the microstructural changes that occur in sintered magnets as a result of these thermo-magnetic treatments. This work presents themicrostructural characterization of Dy-free and Dy-containing sintered magnets that have undergone annealing in a magnetic field of 9T. Microstructural characterization techniques were used to identify phases, analyze the texture of phases identified, and to study intergranular phases. Microstructural findings were then used to propose a solidification scheme during annealing and connect such findings to magnetic property results, as well as to make suggestions for optimizing the manufacturing process. In addition to the magnetic phase, phases identified in the Dy-free and Dy-containing Nd-Fe-B sintered magnets consisted of Nb-rich precipitates, Nd-rich phases, and phases from the Nd-Fe-Cu ternary system. Nd-Fe-Cu phases included alpha-Nd, NdCu, and the tau (Nd6Fe13Cu). The Nd-rich phases were specifically identified to be NdOx precipitates in an alpha-Nd matrix, and contained an orientation relationship described by (0001)alpha-Nd||(111)NdOx and [112¯0]alpha-Nd||[1¯10]NdO x. This

  8. Production of NdFeB powders by HDDR from sintered magnets; Obtencao de pos de NdFeB por HDDR a partir de imas sinterizados

    Energy Technology Data Exchange (ETDEWEB)

    Janasi, S.R.; Rodrigues, D.; Landgraf, F.J.G. [Instituto de Pesquisas Tecnologicas (IPT), Sao Paulo, SP (Brazil). Lab. de Metalurgia e Materiais Ceramicos; Silva, B.F.A. da; Takiishi, H [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Campos, M.F. de [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil)

    2010-07-01

    The production of NdFeB powders by the HDDR process from metallic alloys has been widely investigated. Different HD and DR conditions have been used to induce anisotropy and to improve the intrinsic coercivity of the obtained powders. The purpose of this study is to apply the HDDR process in the reprocessing of NdFeB sintered magnet scraps. There were investigated different processing conditions as temperature and time of desorption and recombination (DR). The results of X ray diffraction show the formation of the magnetic phase Nd{sub 2}Fe{sub 14}B in all the investigated conditions. Magnetic measurements by vibrating sample magnetometer indicate that powders with intrinsic coercivity up to 790 kA/m were obtained. (author)

  9. Effect of optimal aging treatment on magnetic performance and mechanical properties of sintered Nd-Fe-B permanent magnets

    Institute of Scientific and Technical Information of China (English)

    DING Xia; DING Kai-hong; CUI Sheng-li; SUN Yong-cong; LI Mu-sen

    2016-01-01

    The magnetic performance and mechanical properties including hardness, brittleness, fracture toughness and strength characteristics of the as-sintered and the optimal aged Nd-Fe-B magnets were examined in this work. A new method of Vickers hardness indentation combined with acoustic emission was used to test the brittleness of the magnets.The results show that the magnetic properties of the magnets could be improved through aging treatment, especially the intrinsic coercive force. But it is accompanied by a decrease of strength and fracture toughness. Theoretical calculation confirms that acoustic emission energy accumulated count value could be used to characterize the material brittleness. The bending fracture morphologies of the as-sintered and the optimal aged NdFeB magnets were investigated with the emphasis on the relationship between mechanical properties and microstructure using a field emission scanning electron microscopy (FE-SEM). The research results indicate that the intergranular fracture is the primary fracture mechanism for both as-sintered and optimal aged NdFeB magnets. Aging treatment changes the morphology and distribution of the Nd-rich phases, reducing the sliding resistance between Nd2Fe14B main crystal grains and lowers the grain boundary strength, which is the main reason for the strength and fracture toughness decrease of the aged Nd-Fe-B magnets.

  10. Recycle for Sludge Scrap of Nd-Fe-B Sintered Magnet as Isotropic Bonded Magnet

    Institute of Scientific and Technical Information of China (English)

    Masahiro Itoh; Masahiro Masuda; Shunji Suzuki; Ken-ichi Machida

    2004-01-01

    The reduction diffusion method was performed for the sludge scrap of Nd-Fe-B sintered magnets with adding Ca metal to recover the oxidized Nd-Fe-B phase. After washing the resultant powders to remove Ca metal component, the powders obtained were recycled as an isotropic magnetic powder by the melt spinning method. The magnetic properties of powders as recycled were inferior, especially for the coercivity value, due to the deletion of rare earth metals during the washing process. The adjustment of metal composition, i.e., the addition of Nd metal, at the melt spinning process improved the magnetic properties to be Br=~0.75 T, Hcj=~0.93 mA·m-1, and(BH)max=~91 kJ·m-3. The magnetic properties of the bonded magnets prepared from the composition-adjusted powders were Br=~0.66 T, Hcj=~0.92 mA·m-1, and(BH)max=~70 kJ·m-3, which are approximately comparable to the commercially available MQPB boned one(Br=~0.73 T, Hcj=~0.79 mA·m-1, and(BH)max=~86 kJ·m-3).

  11. Enhanced magnetic properties in Nd-Fe-B magnets prepared by spark plasma sintering via die-upsetting process

    Institute of Scientific and Technical Information of China (English)

    HU Zhihua; CHU Linhua; LI Jun; LIU Ying

    2011-01-01

    The magnetic properties and microstructure of Nd-Fe-B magnets prepared by spark plasma sintering with different die-upsetting processes were investigated.The results showed that the optimum magnetic properties of die-upset Nd-Fe-B magnets were obtained at 680 ℃ when the die-upset level was 60%,and the degree of magnetic alignment was 0.84.The microstructures showed that the coarse grains occurred predominantly within certain areas,and abnormal grain growth was not observed within the major areas of well-aligned grains.There existed many small spherical grains,which stacked together and were not aligned during die upsetting when the deformation temperature was 650 ℃.These small spherical grains grew up,and were aligned when the deformation temperature increased from 650 to 680 ℃,which could improve the crystallographic alignment of die-upset Nd-Fe-B magnets.

  12. Development of Sintered NdFeB Magnet Industry in China (Continued)

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Ⅳ. Intensive competition in NdFeB industry 2. Competition features of NdFeB industry Competition in NdFeB industry will be fierce in the future affected by tight supply and high price level of raw materials.

  13. Micromagnetic simulation of the orientation dependence of grain boundary properties on the coercivity of Nd-Fe-B sintered magnets

    Science.gov (United States)

    Fujisaki, Jun; Furuya, Atsushi; Uehara, Yuji; Shimizu, Koichi; Ataka, Tadashi; Tanaka, Tomohiro; Oshima, Hirotaka; Ohkubo, Tadakatsu; Hirosawa, Satoshi; Hono, Kazuhiro

    2016-05-01

    This paper is focused on the micromagnetic simulation study about the orientation dependence of grain boundary properties on the coercivity of polycrystalline Nd-Fe-B sintered magnets. A multigrain object with a large number of meshes is introduced to analyze such anisotropic grain boundaries and the simulation is performed by combining the finite element method and the parallel computing. When the grain boundary phase parallel to the c-plane is less ferromagnetic the process of the magnetization reversal changes and the coercivity of the multigrain object increases. The simulations with various magnetic properties of the grain boundary phases are executed to search for the way to enhance the coercivity of polycrystalline Nd-Fe-B sintered magnets.

  14. Design and fabrication of sintered Nd-Fe-B magnets with a low temperature coefficient of intrinsic coercivity

    Directory of Open Access Journals (Sweden)

    Cui X.G.

    2009-01-01

    Full Text Available To decrease the temperature coefficients of sintered Nd-Fe-B magnets, the influencing factors on temperature coefficients, especially the reversible temperature coefficient β of intrinsic coercivity Hcj, were analyzed. The results showed that the absolute value of β decreased with increasing Hcj and also the ratio of microstructure parameter c to Neff, indicating that the increase of magnetocrystalline anisotropy field HA and c/Neff can effectively decrease the absolute value of β. On the basis of this analysis, a sintered Nd-Fe-B magnet with a low temperature coefficient of Hcj was fabricated through composition design, and the value of β was only -0.385%/ºC in the temperature interval of 20-150ºC.

  15. Effect of additions of zinc stearate on the properties of sintered Nd-Fe-B magnets

    Science.gov (United States)

    Popov, A. G.; Gerasimov, E. G.; Terent'ev, P. B.; Gaviko, V. S.; Shunyaev, K. Yu.; Mikhailova, T. L.; Vas'kovskii, V. O.; Kulesh, N. A.

    2013-04-01

    Zinc stearate additions have been used to increase the remanence of sintered Nd-Fe-B magnets produced by the powder metallurgy without powder pressing. Zinc stearate acts as an internal lubricant, i.e., it decreases the friction forces between the particles and favors an increase in the degree of texture of the powders, which is induced by the magnetic field. It is shown that the density and the magnetic hysteresis characteristics of sintered magnets produced using additions of 0.15 wt % zinc stearate exceeds the corresponding values obtained for magnets produced without this addition at a filling density of powders in containers of more than 2.9 and 3.0 g/cm3 in dry and wet states, respectively. Using additions of zinc stearate in the amount of 0.15% with respect to the weight of the powder, magnets with a density of 7.55 g/cm3, B r = 14.02 kG, H c = 7.91 kOe, and ( BH)max = 46.1 MG Oe have been produced.

  16. The influence of carbon and oxygen on the magnetic characteristics of press-less sintered NdFeB magnets

    DEFF Research Database (Denmark)

    Xia, Manlong; Abrahamsen, Asger Bech; Bahl, Christian

    2017-01-01

    and oxygen content in the magnets produced from wet ball milling of strip cast flakes was found to be of the order 104 ppm and 4·104 ppm respectively, which resulted in soft magnetic behavior. However using jet milling the carbon and oxygen concentration were decreased by an order of magnitude resulting......The Pressless Process (PLP) was adopted to manufacture NdFeB sintered magnets, where the investigations on carbon and oxygen residues from heptane milling liquid media and graphite crucibles used for sintering were quantified to evaluate the influence on the magnetic characteristics. The carbon...

  17. THE EFFECT OF Mo ADDITION ON COERCIVITY OF NdFeB SINTERED MAGNET PREPARED BY BLENDING METHOD

    Institute of Scientific and Technical Information of China (English)

    J.Q.Zhou; M.G. Zhang

    2005-01-01

    Alloy modification, accompanying with proper heat treatment, is commonly used to improve the thermal stability of NdFeB magnet. Traditional alloy modification is performed through melting process with alloy elements to form the multi-alloy. In doing so, these alloy elements not only are introduced into the inter-granular boundaries, but partly into the main phase, thus decreasing to some extent the magnetism of the main phase. In this paper, the blending method is used to prepare the Nd22Fe71B/Mo sintered magnet, and its magnetic properties and microstructures are investigated. The results show that by adding 1.5% (mass fraction) Mo, the intrinsic coercivity Hc of the magnet reaches the maximum value of 1719.36KA/m, while continually increasing the amount of Mo has a less effect on iHc Microstructures analysis indicates that Mo-free Nd-Fe-B magnet has not uniform grains in size, while that with Mo element has uniform grains in size and smooth grain boundaries. Experiments show that after the NdFeB magnet is sintered at 1273K and annealed at 873K, the added Mo element could prevent the equilibrium transformation between the main phase and Nd-rich phase, thus resulting in the precipitation of fine second main phase (Nd2Fe14-xMoxB) from the main phase boundaries, preventing the nucleation and expansion of anti-magnetic domain, and enhancing the coercivity.

  18. Effects of orientation and interaction of grains on coercivity for sintered NdFeB magnets

    Institute of Scientific and Technical Information of China (English)

    高汝伟; 李卫; 张建成; 吴良学; 喻晓军

    1999-01-01

    The coercivity of NdFeB magnets is determined by the coercivity of individual grains and the interaction between the grains composed of the magnets. The coercivity of individual grains and the intergrain interaction depend on the degree of the grain alignment. "tanθ type" Ganssian function is applied to describing the degree of the grain alignment. According to different coercivity mechanisms, there are different formula on the coercivity and the angular dependence of coercivity. The interaction between grains can be classified as the long-range magnetostatic interaction and the exchange-coupling interaction of neighboring grains. For the sintered magnet, the grain size is large and the grain boundaries are mostly separated by the non-magnetic phase. So, the long-range magnetostatic interaction is much stronger than the exchange coupling interaction and it makes the coercivity of the magnet composed of misaligned grains be bigger than that of the magnet composed of ideally aligned grains. The effects o

  19. Origin of (105) Reflection of X-Ray Diffraction and Quantitative Evaluation of Alignment Degree for Sintered Nd-Fe-B Magnets

    Institute of Scientific and Technical Information of China (English)

    HE Ye-Qing; ZHOU Shou-Zeng; ZHANG Zhen-Rong; HAN Bao-Shan

    2001-01-01

    A new method for quantitatively evaluating the alignment degree ofsintered Nd-FeB magnets by x-ray diffraction spectra has been proposed. It has been experimentally revealed that the strong (105) reflection existing in almost all x-ray diffraction spectra of sintered Nd-FeB magnets stems from the misalignment grains whose easy axes are at an angle of 15.5° with respect to the orientated direction of the magnet.

  20. Effect of FeGa{sub 3} powder addition on the magnetic properties of NdFeB sintered magnets

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, T.S.; Kim, Y.B.; Jeung, W.Y.

    1999-09-01

    NdFeB sintered magnets with the addition of various amounts of FeGa{sub 3} powder were prepared by blending during the ball milling process. The magnetic properties and microstructure of the NdFeB magnets were studied. It was found that the addition of 0.1--0.2 wt.% FeGa{sub 3} powder increases the coercivity of the magnets without reducing the remanence. The improvement in coercivity by the addition of FeGa{sub 3} powder may be related to the formation of a Nd{sub 6}Fe{sub 14{minus}x}Ga{sub x} (x {approx{underscore}equal} 1) intergranular phase in the magnets.

  1. Corrosion properties of aluminium coatings deposited on sintered NdFeB by ion-beam-assisted deposition

    Science.gov (United States)

    Mao, Shoudong; Yang, Hengxiu; Li, Jinlong; Huang, Feng; Song, Zhenlun

    2011-04-01

    Pure Al coatings were deposited by direct current (DC) magnetron sputtering to protect sintered NdFeB magnets. The effects of Ar+ ion-beam-assisted deposition (IBAD) on the structure and the corrosion behaviour of Al coatings were investigated. The Al coating prepared by DC magnetron sputtering with IBAD (IBAD-Al-coating) had fewer voids than the coating without IBAD (Al-coating). The corrosion behaviour of the Al-coated NdFeB specimens was investigated by potentiodynamic polarisation, a neutral salt spray (NSS) test, and electrochemical impedance spectroscopy (EIS). The pitting corrosion of the Al coatings always began at the voids of the grain boundaries. Bombardment by the Ar+ ion-beams effectively improved the corrosion resistance of the IBAD-Al-coating.

  2. Regeneration of waste sintered Nd-Fe-B magnets to fabricate anisotropic bonded magnets

    Institute of Scientific and Technical Information of China (English)

    李现涛; 岳明; 刘卫强; 张东涛; 左铁镛

    2015-01-01

    The waste sintered Nd-Fe-B magnets were regenerated as magnetic powders via manually crushing (MC) or hydrogen de-crepitation (HD) to fabricate anisotropic bonded magnets. Effect of size distribution on the magnetic properties of the regenerated magnetic MC and HD powders was investigated. For the MC powders, as the particle size decreased, the remanence (Br) increased first, and then decreased again, while the coercivity (Hci) dropped monotonically. The powders with particle size in the range of 200–450μm possessed the best magnetic properties ofBr of 1.22 T andHci of 875.6 kA/m. The corresponding bonded magnet exhibited magnetic properties ofBr of 0.838 T,Hci of 940.9 kA/m, and (BH)max of 91.4 kJ/m3, respectively. On the other hand, the HD powders with particle size range of 200-450μm bore the best magnetic properties ofBr of 1.24 T andHci of 860.4 kA/m. Compared with magnetic proper-ties of the waste magnet, the powders retained 93.9% ofBr and 70.0% ofHci, respectively. The bonded magnet produced from HD powders possessedBr of 0.9 T,Hci of 841.4 kA/m, and (BH)max of 111.6 kJ/m3, indicating its good potential in practical applications.

  3. Corrosion Resistance of Sintered NdFeB Permanent Magnet With Ni-P/TiO2 Composite Film

    Institute of Scientific and Technical Information of China (English)

    SONG Lai-zhou; YANG Zhi-yong

    2009-01-01

    The Ni-P/TiO2 composite film on sintered NdFeB permanent magnet was investigated by X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM), and energy dispersive X-ray spectrometer (EDX).The corrosion resistance of Ni-P/TiO2 film coated on NdFeB magnet, in 0. 5 mol/L NaCl solution, was studied by potentiodynamic polarization, salt spray test and electrochemical impedance spectroscopy (EIS) techniques. The selfcorrosion current density (icorr) and the polarization resistance (Rp) of Ni-P/TiO2 film are 0. 22 μA/cm2 (about 14% of that of Ni-P coating), and 120 kΩ·cm2 (about 2 times of that of Ni-P coating), respectively. The anti-salt spray time of Ni-P/TiO2 film is about 2.5 times of that of the Ni-P coating. The results indicate that Ni-P/TiO2 film has a better corrosion resistance than Ni-P coating, and the composite film increases the corrosion resistance of NdFeB magnet markedly.

  4. Electrophoretic deposition of graphene oxide as a corrosion inhibitor for sintered NdFeB

    Science.gov (United States)

    He, Wenting; Zhu, Liqun; Chen, Haining; Nan, Haiyang; Li, Weiping; Liu, Huicong; Wang, Yan

    2013-08-01

    Graphene oxide (GO) was deposited uniformly on the surface of permanent magnet material NdFeB by electrophoretic deposition (EPD). Electrophoretic deposited graphene oxide (EPD-GO) coating was reduced partially after EPD process, owing to the removal of oxygen functional groups. And EPD-GO coating showed excellent adhesion to the NdFeB matrix. According to the results of electrochemical tests, the decrease in corrosion current density and the positive shift in corrosion potential have both demonstrated that EPD-GO coating served as a corrosion inhibitor, protecting NdFeB from NaCl aqueous solution.

  5. Development of Sintered NdFeB Magnet Industry in China

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Rare earth performance materials grow rapidly in recent years with technical progress in electronic information, autos and manufacturing industries. As the fastest developing functional materials, NdFeB magnets have become the main force that pushes the development of whole rare earth industry.Applications of NdFeB magnets have been extended to many high tech fields with the continuous technique innovation in production process and improvement of product performances. Relying on abundant RE resources and lower labor cost, China has become the largest producer and also the biggest consumer of NdFeB magnets.

  6. The influence of carbon and oxygen on the magnetic characteristics of press-less sintered NdFeB magnets

    Science.gov (United States)

    Xia, M.; Abrahamsen, A. B.; Bahl, C. R. H.; Veluri, B.; Søegaard, A. I.; Bøjsøe, P.; Millot, S.

    2017-01-01

    The Pressless Process (PLP) was adopted to manufacture NdFeB sintered magnets, where the investigations on carbon and oxygen residues from heptane milling liquid media and graphite crucibles used for sintering were quantified to evaluate the influence on the magnetic characteristics. The carbon and oxygen content in the magnets produced from wet ball milling of strip cast flakes was found to be of the order 104 ppm and 4·104 ppm respectively, which resulted in soft magnetic behavior. However using jet milling the carbon and oxygen concentration were decreased by an order of magnitude resulting in coercivity of up to 829 kA/m. Thus the influence of the carbon from the graphite crucibles is small.

  7. Effect of Stabilization Heat Treatment on Time-Dependent Polarization Losses in Sintered Nd-Fe-B Permanent Magnets

    Directory of Open Access Journals (Sweden)

    Tuominen S.

    2013-01-01

    Full Text Available Some companies in the motor and generator industry utilizing sintered NdFeB magnets have adopted pre-ageing heat treatment in order to improve the stability of the magnets. The parameters of this stabilization heat treatment are based mainly on assumptions rather than on any published research results. In this work, the effects of pre-ageing treatment on the time-dependent polarization losses of two different types of commercial sintered NdFeB magnets were studied. The material showing the squarer J(H curve did not benefit from the pre-ageing treatment, since it seems to be stable under a certain critical temperature. In contrast, a stabilizing effect was observed in the material showing rounder J(H curve. After the stabilization heat treatment, the polarization of the magnets was found to be at lower level, but unchanged over a certain period of time. The length of this period depends on the temperature and the duration of the pre-ageing treatment. In addition, our analysis reveals that the stabilization heat treatment performed in an open circuit condition does not stabilize the magnet uniformly.

  8. Effects of terbium sulfide addition on magnetic properties, microstructure and thermal stability of sintered Nd-Fe-B magnets

    Science.gov (United States)

    Xiang-Bin, Li; Shuo, Liu; Xue-Jing, Cao; Bei-Bei, Zhou; Ling, Chen; A-Ru, Yan; Gao-Lin, Yan

    2016-07-01

    To increase coercivity and thermal stability of sintered Nd-Fe-B magnets for high-temperature applications, a novel terbium sulfide powder is added into (Pr0.25Nd0.75)30.6Cu0.15FebalB1 (wt.%) basic magnets. The effects of the addition of terbium sulfide on magnetic properties, microstructure, and thermal stability of sintered Nd-Fe-B magnets are investigated. The experimental results show that by adding 3 wt.% Tb2S3, the coercivity of the magnet is remarkably increased by about 54% without a considerable reduction in remanence and maximum energy product. By means of the electron probe microanalyzer (EPMA) technology, it is observed that Tb is mainly present in the outer region of 2:14:1 matrix grains and forms a well-developed Tb-shell phase, resulting in enhancement of H A, which accounts for the coercivity enhancement. Moreover, compared with Tb2S3-free magnets, the reversible temperature coefficients of remanence (α) and coercivity (β) and the irreversible flux loss of magnetic flow (h irr) values of Tb2S3-added magnets are improved, indicating that the thermal stability of the magnets is also effectively improved. Project supported by the Science Funds from the Ministry of Science and Technology, China (Grant Nos. 2014DFB50130 and 2011CB612304) and the National Natural Science Foundation of China (Grant Nos. 51172168 and 51072139).

  9. Grain boundary engineering in sintered Nd-Fe-B permanent magnets for efficient utilization of heavy rare earth elements

    Energy Technology Data Exchange (ETDEWEB)

    Loewe, Konrad

    2016-10-18

    The first part of the thesis investigates the diffusion of rare-earth (RE) elements in commercial sintered Nd-Fe-B based permanent magnets. A strong temperature dependence of the diffusion distance and resulting change in magnetic properties were found. A maximum increase in coercivity of ∼+350 kA/m using a Dy diffusion source occurred at the optimum annealing temperature of 900 C. After annealing for 6 h at this temperature, a Dy diffusion distance of about 4 mm has been observed with a scanning Hall probe. Consequently, the maximum thickness of grain boundary diffusion processed magnets with homogeneous properties is also only a few mm. The microstructural changes in the magnets after diffusion were investigated by electron microscopy coupled with electron probe microanalysis. It was found that the diffusion of Dy into sintered Nd-Fe-B permanent magnets occurs along the grain boundary phases, which is in accordance with previous studies. A partial melting of the Nd-Fe-B grains during the annealing process lead to the formation of so - called (Nd,Dy)-Fe-B shells at the outer part of the grains. These shells are μm thick at the immediate surface of the magnet and become thinner with increasing diffusion distance towards the center of the bulk. With scanning transmission electron microscopy coupled with electron probe analysis a Dy content of about 1 at.% was found in a shell located about 1.5 mm away from the surface of the magnet. The evaluation of diffusion speeds of Dy and other RE (Tb, Ce, Gd) in Nd-Fe-B magnets showed that Tb diffuses significantly faster than Dy, and Ce slightly slower than Dy, which is attributed to differences in the respective phase diagrams. The addition of Gd to the grain boundaries has an adverse effect on coercivity. Exemplary of the heavy rare earth element Tb, the nano - scale elemental distribution around the grain boundaries after the diffusion process was visualized with high resolution scanning transmission electron microscopy

  10. Development of Sintered NdFeB Magnet Industry in China (Continued)

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    @@ Ⅲ. Changes in NdFeB industry pattern With the development of China economy, many oversea companies have shifted the resource-intensive,energy-consumption and labor-intensive industries to China due to lack of predominance of resources and production cost in the competition with China.

  11. Relation between Nd{sub 2}Fe{sub 14}B grain alignment and coercive force decrease ratio in NdFeB sintered magnets

    Energy Technology Data Exchange (ETDEWEB)

    Matsuura, Yutaka, E-mail: Yutaka_Matsuura@hitachi-metals.co.jp [Hitachi Metals Ltd., NEOMAX Division, 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka 618-0013 (Japan); Hoshijima, Jun; Ishii, Rintaro [Hitachi Metals Ltd., NEOMAX Division, 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka 618-0013 (Japan)

    2013-06-15

    It was found that the coercive force of NdFeB sintered magnets decreases as the Nd{sub 2}Fe{sub 14}B grain alignment improves. Because of this phenomenon, studies looked at the relation between this alignment and the coercive force decrease ratio. In experiments, it was expected that the coercive force of perfectly aligned magnet reached 0.7 of coercive force in istotropically aligned magnet. When it is postulated that the coercive force is determined by the Stoner–Wohlfarth model, coercive force increases as the alignment improves and it becomes difficult to explain our experimental data. On the other hand, when the coercive force is determined by magnetic domain wall motion, the coercive force decreases as the alignment improves and the coercive force of the perfectly aligned magnet reaches 1/√(2) of the isotropically aligned magnet. This tendency and value was very close to our data. It strongly suggests that the coercive force of NdFeB sintered magnets is determined by the domain wall motion. - Highlights: ► Coercive force of NdFeB sintered magnets decreases as grains alignment improves. ► Coercive force decrease ratio reaches −30% at the perfect aligned magnet. ►These experimental results are different from the Stoner–Wohlfarth model. ► The magnetic domain wall motion could explain this coercive force decrease ratio.

  12. Effect Of DyMn Alloy-Powder Addition On Microstructure And Magnetic Properties Of NdFeB Sintered Magnets

    Directory of Open Access Journals (Sweden)

    Lee M.-W.

    2015-06-01

    Full Text Available Micostructural change and corresponding effect on coercivity of a NdFeB sintered magnet mixed with small amount of DyMn powder was investigated. In the sintered magnet mixed with the DyMn alloy-powder Dy-rich shell was formed at outer layer of the main grains, while Mn was mostly concentrated at Nd-rich triple junction phase (TJP, lowering melting temperature of the Nd-rich phase that eventually improved the microstructural characteristics of the gain boundary phase. The coercivity of a magnet increased more than 3.5 kOe by the mixing of the DyMn alloy-powder.

  13. Effect of microstructure changes on magnetic properties of spark plasma sintered Nd-Fe-B powders

    Directory of Open Access Journals (Sweden)

    Michalski B.

    2013-01-01

    Full Text Available In this study the SPS method was applied for low RE content (8,5% at. and high RE content (13,5 % at. MQ powders. The powders were sintered in a wide range of temperature, for 5 min., under pressure of 35 MPa. The low RE content grade, densified reluctantly and gained the density close to the theoretical value only for 850 °C. The coercivity decreased gradually with increasing sintering temperature. On the other hand, the densification of the higher RE content grade powder occurred much easier and the coercivity, close to the theoretical value, was achieved already at 650 °C. The coercivity of this material also decreased with increasing sintering temperature. Microstructural studies revealed that the SPS sintering process leads to partial decomposition of the Nd2Fe14B phase. The proportion of the RE-rich and iron phases increases parallel to the increasing sintering temperature. On the basis of the current results one can conclude that fabrication of high density MQ powders based magnets by the SPS method is possible, however the powders having higher RE content should be used for this purpose and the sintering temperature as low as possible, related to density, should be kept.

  14. Microstructural investigation of Nd-rich phase in sintered Nd-Fe-B magnets through electron microscopy

    Institute of Scientific and Technical Information of China (English)

    付新; 韩小磊; 杜志伟; 冯海波; 李岩峰

    2013-01-01

    The distribution, morphologies and structures of intergranular Nd-rich phase in sintered Nd-Fe-B magnets were studied through electron microscopy. Backscattered electron (BSE) imaging revealed that Nd-rich particles with various morphologies and sizes were randomly distributed at the grain boundaries and the triple junctions of the tetragonal Nd2Fe14B matrix. Through selected area electron diffraction (SAED) analysis under a systematic tilting condition, most intergranular Nd-rich phase particles, with sizes ranging from hundreds of nanometres to several micrometres, were identified as face-centred cubic (FCC) structure. Such particles possessed several approximate orientation relationships with their adjacent Nd2Fe14B matrix grains, such as (002)Nd2Fe14B//(200)FCC_Nd-rich [120] Nd2Fe14B//[001]FCC_Nd-rich, (002)Nd2Fe14B//( 220 )FCC_Nd-rich [110] Nd2Fe14B//[112]FCC_Nd-rich, as well as (011)Nd2Fe14B//(131)FCC_Nd-rich [111] Nd2Fe14B//[114]FCC_Nd-rich, which could be attributed to minimising interfacial energy. The combination of high-resolution electron microscopy with energy-dispersive X-ray spectroscopy revealed the internal inhomogeneous nature of Nd-rich phases. The large lattice distortion and nanoscale-ordered structures within a single Nd-rich grain were observed.

  15. Study of sintered Nd-Fe-B magnet with high performance of Hcj (kOe + (BHmax (MGOe > 75

    Directory of Open Access Journals (Sweden)

    Bo-Ping Hu

    2013-04-01

    Full Text Available We have developed a Nd-Fe-B sintered magnet of extremely high performance. The intrinsic coercivity Hcj is as high as 35.2 kOe (2803kA/m together with the maximum energy product (BHmax of 40.4 MGOe (321.6kJ/m3. These values result in Hcj (kOe + (BHmax (MGOe > 75. Between 293 K (20ºC and 473 K (200ºC, the temperature coefficients of remanence and intrinsic coercivity are αBr = −0.122 %/°C and αHcj = −0.403%/°C, respectively. A maximum operating temperature of 503 K (230ºC is obtained when permeance coefficient Pc = −B/H = 2. Grain boundary diffusion (GBD technique on magnet surface has been developed to increase Hcj by 3.6 kOe without significantly decrease of Br and (BHmax. The intrinsic coercivity of the GBD treated magnet Hcj(C has a linear relationship with that of the untreated magnet Hcj(B between 200 K and 473 K (in unit of kOe: Hcj(C = 1.03Hcj(B + 2.38. The enhancement of Hcj by GBD treatment has contributions not only from the improvement of microstructure but also from the increase of Ha in the grain surface layer. It is also found that GBD treatment brings no deterioration in corrosion resistance of untreated magnet.

  16. Effect of titania particles on the microstructure and properties of the epoxy resin coatings on sintered NdFeB permanent magnets

    Energy Technology Data Exchange (ETDEWEB)

    Xu, J.L., E-mail: jlxu@nchu.edu.cn; Huang, Z.X.; Luo, J.M.; Zhong, Z.C., E-mail: zzhong.2006@yahoo.com.cn

    2014-04-15

    The nanometer titania particles enhanced epoxy resin composite coatings were prepared on the sintered NdFeB permanent magnets by cathodic electrophoretic deposition. The effects of titania particle concentrations on the microstructure and properties of the epoxy coatings were investigated by surface and cross-sectional morphologies observation, surface roughness and microhardness measurement, H{sub 2}SO{sub 4} solution immersion test, neutral salt spray test and magnetic properties measurement. The results showed that the thickness of epoxy coatings with and without the titania particles addition was about 40 μm. The titania particles could be uniformly dispersed and embedded in the epoxy matrix if the titania particles concentration was lower than 40 g/l. With increasing titania particle concentrations, the number of the particles embedded in the epoxy matrix increased and the surface roughness and microhardness of the composite coatings increased. At the same time, the weight loss of the coated samples immersed in H{sub 2}SO{sub 4} solution decreased and the neutral salt spray time of the coated samples prolonged. It could be concluded that the titania particles did not change the thickness of the epoxy coatings and did not deteriorate the magnetic properties of NdFeB substrates, but could greatly improve the microhardness and corrosion resistance of the epoxy coatings. - Highlights: • The titania particles enhanced epoxy resin coatings were prepared on sintered NdFeB by cathodic electrophoretic deposition. • The titania particles could be uniformly dispersed and embedded in the epoxy resin matrix. • With increasing titania concentrations, the surface roughness and the microhardness of composite coatings increased. • The addition of titania particles greatly improved the corrosion resistance of the epoxy coatings. • The composition coatings did not deteriorate the magnetic properties of NdFeB substrates.

  17. Laboratory scale fabrication of Nd-Fe-B sintered magnets; Fabricacao de imas sinterizados de Nd-Fe-B em escala piloto

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Daniel; Beneduce Neto, Flavio; Landgraf, Fernando Jose Gomes; Neiva, Augusto Camara; Romero, Sergio; Missell, Frank Patrick

    1992-12-31

    Results are presented on magnetic properties of Nd-Fe-B sauntered magnets produced from 1 kg of alloy caste in vacuum induction furnace. The fabrication viability of these magnets, with properties similar to the commercial magnets, and the influence of particle size in the energy product, through the effect on the H{sub k} field, is confirmed 12 refs., 7 figs., 1 tab.

  18. Preparation and characterization of amorphous SiO2 coatings deposited by mirco-arc oxidation on sintered NdFeB permanent magnets

    Science.gov (United States)

    Xu, J. L.; Xiao, Q. F.; Mei, D. D.; Zhong, Z. C.; Tong, Y. X.; Zheng, Y. F.; Li, L.

    2017-03-01

    Amorphous SiO2 coatings were prepared on sintered NdFeB magnets by micro-arc oxidation (MAO) in silicate solution. The surface and cross-sectional morphologies, element and phase composition, corrosion resistance and magnetic properties of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), potentiodynamic polarization test and physical properties measurements system (PPMS). The results showed that the surface morphologies of the coatings exhibited the "coral reef" like structure, different from the typical MAO porous structure. With increasing the voltages, the thickness of the coatings increased from 12.72 to 19.90 μm, the content of Si element increased, while the contents of Fe, Nd and P elements decreased. The coatings were mainly composed of amorphous SiO2 and a few amorphous Fe2O3 and Nd2O3. The amorphous SiO2 coatings presented excellent thermal shock resistance, while the thermal shock resistance decreased with increasing the voltages. The corrosion resistance of the coatings increased with increasing the voltages, and it could be enhanced by one order of magnitude compared to the uncoated NdFeB magnets. The MAO coatings slightly decreased the magnetic properties of the NdFeB samples in different degrees.

  19. Normal and abnormal grain growth in fine-grained Nd-Fe-B sintered magnets prepared from He jet milled powders

    Science.gov (United States)

    Bittner, F.; Woodcock, T. G.; Schultz, L.; Schwöbel, C.; Gutfleisch, O.; Zickler, G. A.; Fidler, J.; Üstüner, K.; Katter, M.

    2017-03-01

    Fine-grained, heavy rare earth free Nd-Fe-B sintered magnets were prepared from He jet milled powders with an average particle size of 1.5 μm by low temperature sintering at 920 °C or 980 °C. A coercivity of >1600 kA/m was achieved for an average grain size of 1.68 μm. Transmission electron microscopy showed that the distribution and composition of intergranular and grain boundary junction phases was similar to that in conventionally processed magnets. Microstructural analysis on different length scales revealed the occurrence of abnormal grain growth, which is unexpected for sintering temperatures below 1000 °C. A larger area fraction of abnormal grains was observed in the sample sintered at 920 °C compared to that sintered at 980 °C. Microtexture investigation showed a better crystallographic alignment of the abnormal grains compared to the fine-grained matrix, which is explained by a size dependent alignment of the powder particles during magnetic field alignment prior to sintering. Slightly larger particles in the initial powder show a better alignment and will act as nucleation sites for abnormal grain growth. Magneto-optical Kerr investigations confirmed the lower switching field of the abnormal grains compared to the fine-grained matrix. The demagnetisation curve of the sample sintered at 920 °C showed reduced rectangularity and this was attributed to a cooperative effect of the larger fraction of abnormal grains with low switching field and, as a minor effect, a reduced degree of crystallographic texture in this sample compared to the material sintered at 980 °C, which did not show the reduced rectangularity of the demagnetisation curve.

  20. Effect of titania particles on the microstructure and properties of the epoxy resin coatings on sintered NdFeB permanent magnets

    Science.gov (United States)

    Xu, J. L.; Huang, Z. X.; Luo, J. M.; Zhong, Z. C.

    2014-04-01

    The nanometer titania particles enhanced epoxy resin composite coatings were prepared on the sintered NdFeB permanent magnets by cathodic electrophoretic deposition. The effects of titania particle concentrations on the microstructure and properties of the epoxy coatings were investigated by surface and cross-sectional morphologies observation, surface roughness and microhardness measurement, H2SO4 solution immersion test, neutral salt spray test and magnetic properties measurement. The results showed that the thickness of epoxy coatings with and without the titania particles addition was about 40 μm. The titania particles could be uniformly dispersed and embedded in the epoxy matrix if the titania particles concentration was lower than 40 g/l. With increasing titania particle concentrations, the number of the particles embedded in the epoxy matrix increased and the surface roughness and microhardness of the composite coatings increased. At the same time, the weight loss of the coated samples immersed in H2SO4 solution decreased and the neutral salt spray time of the coated samples prolonged. It could be concluded that the titania particles did not change the thickness of the epoxy coatings and did not deteriorate the magnetic properties of NdFeB substrates, but could greatly improve the microhardness and corrosion resistance of the epoxy coatings.

  1. Improvement of the thermal stability of sintered Nd-Fe-B magnets by intergranular addition of Dy{sub 82.3}Co{sub 17.7}

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaofeng; Guo, Shuai; Yan, Changjiang; Cai, Lingwen; Chen, Renjie; Yan, Aru, E-mail: aruyan@nimte.ac.cn [Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang (China); Lee, Don [University of Dayton, Dayton, Ohio 45469 (United States)

    2014-05-07

    In this study, microstructure and magnetic properties of sintered Nd-Fe-B magnets with addition of Dy{sub 82.3}Co{sub 17.7} (wt. %) were investigated. By adding a small amount of Dy{sub 82.3}Co{sub 17.7}, the coercivity is improved greatly, and the irreversible loss is decreased sharply. The increase of Curie temperature suggests that Co atoms have entered into the 2:14:1 main phase. Microstructural analysis indicates that a well-developed core-shell structure was formed in the magnets with the addition of Dy{sub 82.3}Co{sub 17.7}. The improvement of magnetic properties can be attributed to the microstructural modification and the intrinsic properties' improvement.

  2. Effect of sintering conditions on the magnetic and microstructural properties of Nd-Fe-B sintered magnets doped with DyF(3) powders.

    Science.gov (United States)

    Park, Song-E; Kim, Tae-Hoon; Lee, Seong-Rae; Namkung, Seok; Jang, Tae-Suk

    2012-04-01

    The microstructural and magnetic property changes of DyF(3)-doped (Nd(26.06), Dy(6.51))-Fe(bal) -B(0.97)-M(2.39) (wt. %) (M = Cu, Al, Co, and Nb) sintered magnets as functions of the sintering conditions were studied. The sintering conditions for the optimum core-shell microstructure were determined. When the magnets were sintered at 1050 °C for 4 h, a coercivity of 35.1 kOe was obtained without sacrificing the remanence. When the magnets were doped with DyF(3), the formation of the RE-rich phase (Nd-Dy-O) was effectively suppressed and, hence, saving the Dy. In addition, the formation of a cubic-NdOF triple-junction phase (TJP) improves the interface uniformity and enhances the coercivity.

  3. Improving sintered NdFeB permanent magnets by powder compaction in a 9 T superconducting solenoid

    Science.gov (United States)

    Mulcahy, T. M.; Hull, J. R.; Rozendaal, E.; Wise, J. H.; Turner, L. R.

    2003-05-01

    Commercial-grade magnet powder (Magnequench UG) was axial die pressed in the 76.2 mm warm bore of a 9 T superconducting solenoid. Otherwise, processing was performed as part of normal factory operations. This pressing was done to improve the alignment of the anisotropic single-crystal particles of the compact and, thus, the remanent magnetization of the sintered cylindrical permanent magnets (12.7 mm diameter). Although the press was operated in batch mode for this proof-of-concept study, its design enables automated production. Improvements of up to 8% in magnetization and 16% in energy products were obtained, as the alignment field H was increased above the 2 T maximum field of electromagnets used in industry. The greatest improvements were obtained for magnets with the smallest length-to-diameter ratios, L/D<0.5. The production of quality magnets in this near-final-shape size range is currently being pursued by industry to eliminate expensive machining steps. To understand the potential for 2-8 T alignment fields to overcome the distortions created in the otherwise uniform field by the self-field of short compacts, electromagnetic code (Opera) calculations were made. A simple material model was used to predict the distortions. The trends in the predicted field-line inclinations, with L/D and H, compare to trends in the improvement of the magnetic properties.

  4. High coercivity remanence in baked clay materials used in archeomagnetism

    Science.gov (United States)

    McIntosh, Gregg; Kovacheva, Mary; Catanzariti, Gianluca; Donadini, Fabio; Lopez, Maria Luisa Osete

    2011-02-01

    A study of the high coercivity remanence in archeological baked clays has been carried out. More than 150 specimens from 46 sites across Europe have been analyzed, selected on the basis of the presence of a fraction of their natural remanence that was resistant to alternating field demagnetization to 100 mT. The study was based on the stability of isothermal remanence to alternating field and thermal demagnetization and its variation on cooling to liquid nitrogen temperature. Results indicate that the high coercivity remanence may be carried by magnetite, hematite, and in isolated cases partially oxidized magnetite and goethite. In addition, a high coercivity, thermally stable, low unblocking temperature phase has been identified. The unblocking temperatures of both the isothermal remanence and the alternating field resistant natural remanence exhibit similar unblocking temperatures, suggesting that the same phases carry both signals. The high coercivity, low unblocking temperature phase contributes to the natural remanence, sometimes carrying a stable direction and behaving ideally during palaeointensity experiments and sometimes not. An unambiguous mineralogical identification of this phase is lacking, although likely candidates include hemoilmentite, related to clay source lithology, and substituted hematite or magnetic ferri-cristabolite, both possible products of thermal transformation of iron-bearing clays.

  5. High coercivity in nanostructured Co-ferrite thin films

    Indian Academy of Sciences (India)

    J H Yin; B H Liu; J Ding; Y C Wang

    2006-11-01

    Three methods including sol–gel, rf sputtering and pulsed laser deposition (PLD) have been used for the fabrication of high coercivity Co-ferrite thin films with a nanocrystalline structure. The PLD method is demonstrated to be a possible tool to achieve Co-ferrite films with high coercivity and small grain size at low deposition temperature. High coercivity, over 10 kOe, has been successfully achieved in Co-ferrite films with a thickness of ∼ 100 nm deposited using PLD with a substrate temperature at 550°C. The Co-ferrite films prepared by PLD at over 300°C on different substrates including amorphous glass, quartz and silicon exhibits an obvious (111) textured structure and possesses perpendicular anisotropy. Our study has also shown that the high coercivity is related with a large residual strain, which may induce an additional magnetic anisotropy (stress anisotropy) and at the same time serve as pinning centres, which can restrict the domain wall movement and therefore, increase the coercivity.

  6. Magnetic properties of Nd-Fe-B magnets sintered using granulated powders by spray drying method. 3; Spray zoryufun wo mochiita Nd-Fe-B shoketsu jishaku no jiki tokusei. 3

    Energy Technology Data Exchange (ETDEWEB)

    Kishimoto, Y. [Sumitomo Metal Industries Ltd., Osaka (Japan); Yamashita, O. [Sumitomo Special Metals Co. Ltd., Osaka (Japan)

    1997-08-15

    Using two kinds of polymers with different tensile strengths and plasticizer as binders for the spray drying method of Nd2Fe14B rare earth system alloy powder, the relation between binder composition and powder characteristics or sintered magnet characteristics was studied. The binder polymers with high tensile strength improved the binding strength between alloy powders, and formed the secondary grain powder with a flowability superior in granulation. An increase in residual carbon was controlled to 200-300ppm by decarbonization at 673K for 0.5h. Reduction of an oxygen content in granulated powders was important for improving magnet characteristics. Magnet characteristics of sintered bodies were largely dependent on the amount of added plasticizer. The higher flexibility of binders due to addition of more amount of plasticizer reduced the binding strength between alloy powders and slightly reduced the flowability, however, improved magnet characteristics. The binder composed of PVA of 0.2wt% and plasticizer (glycerine) of 0.09wt% was most suitable. 4 refs., 7 figs., 1 tab.

  7. Formation of FePt Nanoparticles Having High Coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Rutledge, R.D. [Vanderbilt University; MorrisIII, William H [Vanderbilt University; Wellons, M.S. [Vanderbilt University; Gai, Zheng [ORNL; Shen, Jian [ORNL; Bentley, James [ORNL; Wittig, J. E. [Vanderbilt University; Lukehart, C.M. [Vanderbilt University

    2006-01-01

    Ultrasonication of toluene solutions of the heteropolynuclear cluster complex, Pt{sub 3}Fe{sub 3}(CO){sub 15}, in the presence of oleic acid and oleylamine affords surface-capped fcc FePt nanoparticles having an average diameter of ca. 2 nm. Self-assembled arrays of these nanoparticles on oxidized Si wafers undergo a fcc-to-fct phase transition at 775 C to form ferromagnetic FePt nanocrystals ca. 5.8 nm in diameter well dispersed on the Si wafer surface. Room-temperature coercivity measurements of these annealed FePt nanoparticles confirm a high coercivity of ca. 22.3 kOe. Such high coercivity for fct FePt nanoparticles might result from use of a heterpolynuclear complex as a single-source precursor of Fe and Pt neutral atoms or from use of ultrasonication to form fcc FePt nanoparticles under conditions of exceptionally rapid heating. Experiments to determine the critical experimental conditions required to achieve such high room-temperature coercivities in ferromagnetic nanoparticles are underway.

  8. Very high coercivity magnetic stripes produced by particle rotation

    Energy Technology Data Exchange (ETDEWEB)

    Naylor, R.B.

    1992-12-01

    This paper describes a current research program at Sandia National Laboratories whereby magnetic stripes are produced through the use of a new particle rotation technology. This new process allows the stripes to be produced in bulk and then held in a latent state so that they may be encoded at a later date. Since particle rotation is less dependent on the type of magnetic particle used, very high coercivity particles could provide a way to increase both magnetic tamper-resistance and accidental erasure protection. This research was initially funded by the Department of Energy, Office of Safeguard and Security as a portion of their Science and Technology Base Development, Advanced Security Concepts program. Current program funding is being provided by Sandia National Laboratories as part of their Laboratory Directed Research and Development program.

  9. Nb含量对烧结NdFeB永磁体磁性能及显微结构的影响%INVESTIGATIONS ON THE MAGNETIC PROPERTIES AND MICROSTRUCTURES OF SINTERED NdFeB MAGNETS WITH DIFFERENT Nb ADDITIONS

    Institute of Scientific and Technical Information of China (English)

    成问好; 李卫; 李传健

    2001-01-01

    对Nd33.0Fe65.9-xNbxB1.1(wt%,x=0,0.3,0.6,1.0,1.5,2.0)系列烧结永磁体的磁性能、组织形貌以及磁性能与组织形貌间的关系进行了系统研究.研究发现,不含Nb的NdFeB磁体晶粒的大小、形状差异非常大.这种结构使NdFeB磁体的磁性能恶化.添加一定量的Nb元素后,磁体的组织结构变得均匀一致.当Nb含量小于1.0时磁体矫顽力、剩磁、磁能积均比相应不含Nb的磁体高.其原因是Nb使NdFeB磁体的晶粒变得均匀一致,密度提高.Nb对NdFeB磁体的绝大部分磁性能的影响均与Nb使NdFeB磁体的晶粒得到均匀化有关.%The magnetic properties and microstructures of a series of sintered magnets Nd33.0Fe65.9-xNbxB1.1(wt%,x=0,0.3,0.6,1.0,1.5,2.0) as well as their relations were investigated in detail. It was found that the grain size of NdFeB magnet without Nb addition was quiet different from each other and the shape of the grains was very irregular, which led to the deterioration of the magnetic properties. The microstructures of the magnets with proper Nb addition became homogeneous and the final size of the grain after annealing was very fine, and, correspondingly, the density of the final magnet was increased to a higher level. Magnetic measurements showed that the coercivity iHc, magnetic remanence Br and energy product (BH)max of the magnet with Nb additions below 1.0wt% were generally higher than those of their Nb-free counterparts. The effect of Nb on the magnetic properties originated mainly from the homogenization of the microstructure due to Nb addition.

  10. 放电等离子烧结-热变形各向异性Nd-Fe-B磁体的微观组织及磁性能%Microstructure and magnetic properties of anisotropic Nd-Fe-B magnets prepared by spark plasma sintering and hot deformation

    Institute of Scientific and Technical Information of China (English)

    李小强; 李力; 胡可; 陈志成; 屈盛官; 杨超

    2014-01-01

    Bulk anisotropic Nd-Fe-B magnets were prepared from hydrogen-disproportionation-desorption-recombination (HDDR) powders via spark plasma sintering (SPS) and subsequent hot deformation. The influence of sintering temperature on the structure and magnetic properties of the spark plasma sintered Nd-Fe-B magnets were studied. The remanence Br, intrinsic coercivity Hcj, and the maximum energy product (BH)max, of sintered Nd-Fe-B magnets first increase and then decrease with the increase of sintering temperature,TSPS, from 650 °C to 900 °C. The optimal magnetic properties can be obtained whenTSPS is 800 °C. The Nd-Fe-B magnet sinter treated at 800 °C was subjected to further hot deformation. Compared with the starting HDDR powders or the SPS treated magnets, the hot-deformed magnets present more obvious anisotropy and possess much better magnetic properties due to the goodc-axis texture formed in the deformation process. The anisotropic magnet deformed at 800 °C with 50% compression ratio has a microstructure consisting of well aligned and platelet-shaped Nd2Fe14B grains without abnormal grain growth and exhibits excellent magnetic properties parallel to the pressing axis.%采用放电等离子烧结及后续热变形技术制备各向异性Nd-Fe-B磁体,研究烧结温度对放电等离子烧结Nd-Fe-B磁体微观组织和磁性能的影响。随着烧结温度在650~900°C范围内的升高,烧结态Nd-Fe-B磁体的剩磁、内禀矫顽力及最大磁能积呈现先升后降的趋势。在800°C下烧结所获得磁体的磁性能最佳。随后,对800°C烧结后具有最佳磁性能的磁体采用放电等离子烧结技术进行后续热变形处理。与初始吸氢-歧化-脱氢-再复合粉末和烧结态磁体相比,热变形磁体拥有更显著的各向异性和更好的磁性能。当热变形温度为800°C且压缩比为50%时,热变形磁体中的Nd2Fe14B晶粒呈扁平片状且不发生异常长大;磁体沿热压方向具有最佳的磁

  11. Temperature stability and microstructure of ultra-high intrinsic coercivity Nd-Fe-B magnets

    Institute of Scientific and Technical Information of China (English)

    HU Zhihua; CHENG Xinghua; ZHU Minggang; LI Wei; LIAN Fazeng

    2008-01-01

    The variations of intrinsic coercivity and remanence of sintered Nd-Fe-B magnets with ultra-high intrinsic coercivity were investigated.The results showed that the intrinsic coercivity and remanence declined simultaneously with increasing temperature,but the squareness of the magnets has hardly been changed.The temperature coefficients of remanence (α) and coercivity (β) for the magnets were calculated by two different methods,and the variations of the temperature coefficients and the microstructure of sintered Nd-Fe-B magnets were analyzed.The temperature coefficients of remanence (α) and coercivity (β) for the sintered magnets are very small,and the existence of free microstructure is necessary to obtain sintered Nd-Fe-B magnets with ultra-high intrinsic coercivity.

  12. High coercivity through texture formation in SmCo5/Co multilayers

    Science.gov (United States)

    Sastry, P. U.; Mishra, P. K.; Krishnan, M.; Chowdhury, P.; Ravikumar, G.

    2013-02-01

    We have shown that high coercivity in SmCo5/Co multilayer exchange spring magnet can be obtained on silicon substrates as well. This is achieved by annealing the as-grown sample at an optimum temperature that favors texture formation. This compares well with multilayers grown on MgO substrates and post-annealed at the same temperature.

  13. Changes in domain structures of NdFeB permanent magnet after magnetization and temperature treatment%NdFeB磁体磁化及温度处理后磁畴结构的变化

    Institute of Scientific and Technical Information of China (English)

    陈杰; 张明; 徐光亮; 向海蓉; 王敬东

    2012-01-01

    We studied the phase components and magnetic domain structure of sintered NdFeB permanent magnet after magnetization and high-temperature treatment using magnetic force microscopy (MFM) and X-ray diffraction (XRD) as well as high-coercivity Co-Cr magnetic probe, made an analysis of the effect of magnetization and heat treatment on the phase components and magnetic domain structures. It is found that magnetization and high-temperature treatment result in no changes in the phase components, but obvious changes occurs in the magnetic domain structure ; open-circuit magnetic flux loss may attribute to the change of magnetic domain structures.%采用磁力显微镜(Magnetic force microscopy,MFM)和X射线衍射(XRD)研究了烧结NdFeB磁体磁化及125℃高温处理后的磁畴结构,分析了磁化及温度处理对磁体物相成分及磁畴结构的影响.结果发现,磁化及高温处理后磁体的相结构没有发生变化,而磁畴结构却发生明显变化;开路磁通的变化是磁畴结构变化引起的.

  14. Metal Injection Molding (MIM of NdFeB Magnets

    Directory of Open Access Journals (Sweden)

    Hartwig T.

    2014-07-01

    Full Text Available Due to the increased and unstable prices for Rare Earth elements there are activities to develop alternative hard magnetic materials. Reducing the amount of material necessary to produce complex sintered NdFeB magnets can also help to reduce some of the supply problem. Metal Injection Molding (MIM is able to produce near net shape parts and can reduce the amount of finishing to achieve final geometry. Although MIM of NdFeB has been patented and published fairly soon after the development of the NdFeB magnets there has never been an industrial production. This could be due to the fact that MIM was very young at that time and hardly developed. Thus, the feasibility of the process needs to be revaluated. This paper presents results of our work on determining the process parameters influencing the magnetic properties of the sintered magnets as well as the shrinkage during processing. The role of binder and powder loading on the alignment of the particles as well as on the carbon and oxygen contamination was examined.

  15. Influence of dysprosium substitution on magnetic and mechanical properties of high intrinsic coercivity Nd-Fe-B magnets prepared by double-alloy powder mixed method

    Institute of Scientific and Technical Information of China (English)

    胡志华; 瞿海锦; 马冬威; 罗成; 王会杰

    2016-01-01

    The double-alloy powder mixed method is very proper for developing new small-mass products by changing the composi-tion of sintered Nd-Fe-B magnets, and there is little research on this aspect. The variation on magnetic and mechanical properties of high intrinsic coercivity Nd-Fe-B magnets prepared by double-alloy powder mixed method was discussed, which is a method blend-ing two-type main phase alloy powders with different components. The results showed that the intrinsic coercivity and density of sin-tered Nd-Fe-B magnets increased gradually with the increase in Dy content, and the double-alloy powder mixed method could obtain high intrinsic coercivity Nd-Fe-B magnets with good crystallographic alignment and microstructure. The bending strength of sintered Nd-Fe-B magnets declined, and the Rockwell hardness of sintered Nd-Fe-B magnets first declined, and then increased with the in-crease in Dy content. The microstructure showed that there existed the phenomenon that the Dy element diffused into main phase dur-ing sintering process, and the distribution of Dy content in main phase had some variation in homogeneity as a result of incomplete reaction between the double-alloy powder types.

  16. Mechanochemical synthesis of Nd2Fe14B alloy with high coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Pal, A; Gabay, A; Hadjipanayis, GC

    2012-12-05

    High coercivity nanocrystalline Nd2Fe14B particles were synthesized by mechanochemical processing involving the reduction of Nd2O3 with Ca in presence of Fe-B and Fe. The as-milled powder shows amorphous structure and subsequent heat treatment results in formation of nanocrystalline Nd2Fe14B. The resulting powder does not only consist of Nd2Fe14B but also some Nd-rich phase. The optimally heat treated sample exhibits coercivity of more than 12 kOe. (C) 2012 Elsevier B.V. All rights reserved.

  17. Corrosion and protection of NdFeB type magnets

    Science.gov (United States)

    Cavalloti, P.; Bozzini, B.; Cecchini, R.; Bava, G. F.; Davies, H. A.; Hoggarth, C.

    1992-02-01

    A general mechanism for the corrosion behaviour of NdFeB magnets is presented, related to the magnet heterogeneity with the presence of different phases. Cathodic control is outlined. An electrochemical method to assess the corrosion resistance of magnets, with and without coatings, is proposed; it is based on the study of the transient voltage at the magnet surface after a second cathodic current pulse in a suitable aggressive solution and its dependence on the amount of cathodic current circulating. Suitable pretreatments have been tried and interesting results obtained with passivation pretreatments, giving phosphorous Nd at grain boundaries. Coatings if sintered and plastic magnets have been tried using several methods. Good results are obtained with Zn-Co layers on sintered magnets and a sol-gel glass on powders for plastic magnets. Improved ACS (Autocatalytic Chemical Deposition) Ni=P coatings have been realized, with an alkaline brass flash plating to start ACD deposition.

  18. SiO{sub 2} modified Co-ferrite with high coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Ding, J. E-mail: masdingj@nus.edu.sg; Gong, H.; Melaka, R.; Wang, S.; Shi, Y.; Chen, Y.J.; Phuc, N.X

    2001-05-01

    Magnetic and Moessbauer measurements have shown that 1-2 wt% of SiO{sub 2} were solved in the CoFe{sub 2}O{sub 4} structure after mechanical milling and subsequent heat treatment. Coercivity values up to 3.5 kOe were measured for CoFe{sub 2}O{sub 4}/SiO{sub 2} powders. High coercivities were also achieved in SiO{sub 2} doped Co-ferrite thin films prepared by sputtering technique. The Co-ferrite thin film deposited on silicon wafer using a 5 wt%-SiO{sub 2}/Co-ferrite target possessed a coercivity of 7.4 kOe, which is the highest value in Co-ferrite and spinel materials according to our knowledge.

  19. Highly coercive cobalt ferrite nanoparticles-CuTl-1223 superconductor composites

    Energy Technology Data Exchange (ETDEWEB)

    Jabbar, Abdul; Qasim, Irfan; Khan, Shahid A.; Nadeem, K.; Waqee-ur-Rehman, M.; Mumtaz, M., E-mail: mmumtaz75@yahoo.com; Zeb, F.

    2015-03-01

    We explored the effects of highly coercive cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles addition on structural, morphological, and superconducting properties of Cu{sub 0.5}Tl{sub 0.5}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10-δ} (CuTl-1223) matrix. Series of (CoFe{sub 2}O{sub 4}){sub x}/CuTl-1223 (x=0 ∼2.0 wt%) composites samples were synthesized and were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) absorption spectroscopy, and dc-resistivity versus temperature measurements. The magnetic behavior of CoFe{sub 2}O{sub 4} nanoparticles was determined by MH-loops with the help of superconducting quantum interference device (SQUID). MH-loops analysis showed that these nanoparticles exhibit high saturation magnetization (86 emu/g) and high coercivity (3350 Oe) at 50 K. The tetragonal structure of host CuTl-1223 superconducting matrix was not altered after the addition of CoFe{sub 2}O{sub 4} nanoparticles, which gave us a clue that these nanoparticles had occupied the inter-granular sites (grain-boundaries) and had filled the pores. The increase of mass density with increasing content of these nanoparticles in composites can also be an evidence of filling up the voids in the matrix. The resistivity versus temperature measurements showed an increase in zero resistivity critical {T_c(0)}, which could be most probably due to improvement of weak-links by the addition of these nanoparticles. But the addition of these nanoparticles beyond an optimum level caused the agglomeration and produced additional stresses in material and suppressed the superconductivity. - Highlights: • T{sub c}(0) increased with increasing CoFe{sub 2}O{sub 4} nanoparticles up to x=1.5. • CoFe{sub 2}O{sub 4} nanoparticles addition has not affected the structure of CuTl-1223. • Addition of CoFe{sub 2}O{sub 4} nanoparticles has improved inter-grains weak links. • Non-monotonic variation of ρ{sub (300} {sub K)} (Ω-cm) is due to

  20. High coercivity in Fe-Nb-B-Dy bulk nanocrystalline magnets

    Energy Technology Data Exchange (ETDEWEB)

    Ziolkowski, Grzegorz; Chrobak, Artur; Klimontko, Joanna [Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007, Katowice (Poland); Chrobak, Dariusz; Rak, Jan [Institute of Materials Science, University of Silesia, 75 Pulku Piechoty 1, 41-500, Chorzow (Poland); Zivotsky, Ondrej; Hendrych, Ales [Department of Physics, VSB-TU Ostrava, Ostrava (Czech Republic)

    2016-11-15

    The paper refers to structural and magnetic properties of the (Fe{sub 80}Nb{sub 6}B{sub 14}){sub 1-x}Dy{sub x} (x = 0.08, 0.10, 0.12, 0.16) bulk nanocrystalline alloys prepared by making use of the vacuum suction casting technique. The samples are in a form of rods with different diameters d = 1.5, 1, and 0.5 mm. The phase structure was investigated by XRD technique and reveals an occurrence of magnetically hard Dy{sub 2}Fe{sub 14}B as well as other relatively soft Dy-Fe, Fe-B, and Fe phases dependently on the Dy content. The alloys show hard magnetic properties with high coercive field up to 5.5 T (for x = 0.12 and d = 0.5 mm). The observed magnetic hardening effect with the increase of cooling rate (decrease of sample diameter d) can be attributed to a formation of ultra-hard magnetic objects as well as increasing role of low dimensional microstructure. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. High coercivity in mechanically milled ThMn12-type Nd-Fe-Mo nitrides

    Science.gov (United States)

    Zhang, Xiao-dong; Cheng, Ben-pei; Yang, Ying-chang

    2000-12-01

    Starting from carefully homogenized Nd10Fe90-yMoy (y=12, 10, 7) alloys and by appropriate mechanical milling, the as-milled microstructure consisting of a nanoscale mixture of severely distorted 1:12 phase and substitutional α-Fe-based solid solution was obtained. This kind of as-milled microstructure was thought to have a critical effect on the formation of iron-free nanocrystalline 1:12 phase during subsequent annealing. Upon nitrogenation, the sample of Nd10Fe78Mo12Nx exhibited a record-high coercivity of 13.1 kOe at 293 K. Measurements of initial magnetization curve and a family of demagnetization curves engendered under different maximum applied fields Hm were carried out, and the results revealed the domain-wall pinning at grain boundaries as the coercivity mechanism. A low Mo-content sample of Nd10Fe83Mo7Nx with iHc˜5.8 kOe, Br˜6.8 kG, and (BH)max˜7.0 MG Oe was made by optimizing the preparation conditions.

  2. Magnetic properties and thermal stability of anisotropic bonded Nd-Fe-B magnets by warm compaction

    Institute of Scientific and Technical Information of China (English)

    TAO Siwu; LU Xin; TIAN Jianjun; QU Xuanhui; Y. Honkura; H. Mitaraib; K. Noguchi

    2009-01-01

    Anisotropic bonded magnets were prepared by warm compaction using anisotropic Nd-Fe-B powder. The forming process, magnetic properties, and temperature stability were studied. The results indicate that the optimal temperature of the process, which was decided by the viscosity of the binders, was 110℃. With increasing pressure, the density of the magnets increased. When the pressure was above 700 MPa, the powder particles were destroyed and the magnetic properties decreased. The magnetic properties of the anisotropic bonded magnets were as follows: remanence Br = 0.98 T, intrinsic coercivity iHc=1361 kA/m, and maximum energy product BHmax = 166 kJ/m3. The magnets had excellent thermal stability because of the high coercivity and good squareness of demagnetization curves. The flux density of the magnets was 35% higher than that of isotropic bonded Nd-Fe-B magnets at 120℃ for 1000 h. The flux density of the bonded magnets showed little change with regard to temperature.

  3. Thermal effect on magnetic parameters of high-coercivity cobalt ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Chagas, E. F., E-mail: efchagas@fisica.ufmt.br; Ponce, A. S.; Prado, R. J.; Silva, G. M. [Instituto de Física, Universidade Federal de Mato Grosso, 78060-900 Cuiabá-MT (Brazil); Bettini, J. [Laboratório Nacional de Nanotecnologia, Centro Nacional de Pesquisa em Energia e Materiais, 13083-970 Campinas (Brazil); Baggio-Saitovitch, E. [Centro Brasileiro de Pesquisas Físicas, Rua Xavier Sigaud 150 Urca. Rio de Janeiro (Brazil)

    2014-07-21

    We prepared very high-coercivity cobalt ferrite nanoparticles synthesized by a combustion method and using short-time high-energy mechanical milling to increase strain and the structural defects density. The coercivity (H{sub C}) of the milled sample reached 3.75 kOe—a value almost five times higher than that obtained for the non-milled material (0.76 kOe). To investigate the effect of the temperature on the magnetic behavior of the milled sample, we performed a thermal treatment on the milled sample at 300, 400, and 600 °C for 30 and 180 min. We analyzed the changes in the magnetic behavior of the nanoparticles due to the thermal treatment using the hysteresis curves, Williamson-Hall analysis, and transmission electron microscopy. The thermal treatment at 600 °C causes decreases in the microstructural strain and density of structural defects resulting in a significant decrease in H{sub C}. Furthermore, this thermal treatment increases the size of the nanoparticles and, as a consequence, there is a substantial increase in the saturation magnetization (M{sub S}). The H{sub C} of the samples treated at 600 °C for 30 and 180 min were 2.24 and 1.93 kOe, respectively, and the M{sub S} of these same samples increased from 57 emu/g to 66 and 70 emu/g, respectively. The H{sub C} and the M{sub S} are less affected by the thermal treatment at 300 and 400 °C.

  4. Growth, structural and magnetic properties of high coercivity Co/Pt multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Weller, D.; Folks, L.; Best, M.; Fullerton, E.EwqTerris, B.D.; Kusinski, G.J.; Krishnan, K.M.; Thomas, G.

    2000-11-01

    Co/Pt multilayer films ([Co (tCo nm)/Pt(1 nm)]10, 0.2 < tCo < 2 nm) with perpendicular magnetic anisotropy and room temperature coercivity Hc = 12-15 kOe are fabricated using electron beam evaporation at elevated growth temperatures onto Si(001)/SiNx(40nm)/Pt(20nm) substrate/seed structures. Hysteresis and magnetic force microscopy (MFM) studies indicate changes in the magnetization reversal mechanism along with a sharp increase in coercivity for growth temperatures higher TG {approx} 230 - 250 degrees C. Films grown at TG < 230 degrees C (tCo = 0.2 - 0.4 nm) show large micrometer size magnetic domains and rectangular hysteresis loops indicating magnetization reversal dominated by rapid domain wall motion throughout the film following nucleation at Hn {approx} Hc. Films grown at TG > 250 degrees C show fine-grained MFM features on the sub-100 nm length scale and hysteresis studies indicate reversal dominated by localized switching of small clusters. The hysteresis curves for the highest coercivity films are sheared with a hysteresis slope alpha=4(pi)dM/dH|Hc approximately equal 1.5, which is close to the ideal value for completely decoupled grains of alpha =1. High resolution cross-sectional TEM with elemental analysis shows columnar grains extending throughout the multilayer stack. Sharp Co/Pt interfaces are found from TEM and grazing incidence X-ray diffraction. At higher TG, Co depletion and structural defects at the grain boundaries provide a mechanism for exchange decoupling of adjacent grains, which may result in the high coercivities observed. Anisotropy and magnetization values are estimated as Ku {approx} 8x106 erg/cc and MS {approx} 450 emu/cc (per total volume), hence Hk = 2Ku/MS {approx} 17.5 kOe for the highest coercivity Hc {approx} 15 kOe films.

  5. Application of bonded NdFeB magnet for C-Band circulator component

    Science.gov (United States)

    Kristiantoro, T.; Idayanti, N.; Sudrajat, N.; Septiani, A.; Dedi

    2016-11-01

    In this paper bonded NdFeB permanent magnets of the crashed-ribbon type were made as an alternative for circulator magnet to improve their magnetic performance. The fabrication process is also easier than the sintered NdFeB because there had no shrinkage of product (such as sintered barium ferrite magnet), with the others advantages as follows; large freeness of product shapes, high precision of dimension and good corrosion resistance. The dimension of the samples was measured to calculate its bulk densities and the magnetic properties were characterized by Permagraph to obtain values such as; Remanence induction (Br) in kG, Coercivity value (Hcj) in kOe, the Maximum energy product (BH max) in MGOe. Whereas the surface magnetic field strength (B) was observed by the Gauss-meter. The bonded NdFeB permanent magnets revealed 6.39 kG of Br, 6.974 kOe of Hcj and 7.13 MGOe of BHmax. The circulator performance was measured using Vector Network Analyzer (VNA). The optimum values of the circulator measurement at a frequency of 5 GHz show a VSWR value of 1.062 and insertion loss of -0.463 dB. The bonded magnet could be used as component of permanent magnets on the circulator that working on C-Band at a frequency range of 4 GHz - 8 GHz.

  6. High-Coercivity Iron Oxide Based Nanocomposites - Particle Shape and Magnetic Structure by Synchrotron and Neutron Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Vejpravova, Jana Poltierova; Prokleska, Jan; Vales, Vaclav; Danis, Stanislav; Mantlikova, Alice; Holy, Vaclav [Charles University Prague, Faculty of Mathematics and Physics, Department of Condensed Matter Physics, Ke Karlovu 5, 121 16 - Prague 2 (Czech Republic); Brazda, Petr [Institute of Inorganic Chemistry, Academy of Sciences of the CR, 250 68 - Rez (Czech Republic); Doyle, Stephen [Synchrotron Light Source ANKA, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany); Ritter, Clemens [Institute Laue Langevin, 6 rue Jules Horowitz, F-38042 - Grenoble Cedex 9 (France); Kitazawa, H [National Institute for Materials Science, Quantum Beam Center, Neutron Scattering Group, 1-2-2 Sengen, Tsukuba-shi, Ibaraki 305-0047 (Japan); Niznansky, D, E-mail: vejpravova@seznam.cz [Charles University Prague, Faculty of Science, Department of Inorganic Chemistry, Hlavova 2, 121 16 - Prague 2 (Czech Republic)

    2011-03-15

    We report on advanced investigation of structure and magnetism of high-coercivity Fe{sub 2-x}Al{sub x}O{sub 3}/SiO{sub 2} (x = 0 - 0.75) nanocrystals obtained by a smart sol-gel route. The substitution of Fe by Al originates suppression of the high-to-low coercivity crossover at 120 K typical for the {epsilon}-Fe{sub 2}O{sub 3} phase. Our neutron scattering experiment revealed, that the high-coercivity collinear magnetic structure of the {epsilon}-Fe{sub 2}O{sub 3} persists in the Al-doped nanocrystals down to low temperatures, while an incommensurate magnetic structure develops in the low-coercivity phase in the undoped {epsilon}-Fe{sub 2}O{sub 3} only. The size and shape of the nanocrystals was obtained by advanced profile analysis of the high-quality S-PXRD data.

  7. High-coercivity CoFe2O4 thin films on Si substrates by sol-gel

    Science.gov (United States)

    Tang, Xianwu; Jin, Linghua; Wei, Renhuai; Zhu, Xiaoguang; Yang, Jie; Dai, Jianming; Song, Wenhai; Zhu, Xuebin; Sun, Yuping

    2017-01-01

    CoFe2O4 (CFO) thin films with high coercivity HC are desirable in applications. The difficulty in achieving large-area CFO thin films with high coercivity by sol-gel has hindered the development of CFO thin films. Herein, polycrystalline CFO thin films with the room temperature out-of-plane and in-plane coercivity HC respectively reached ~5.9 and 3.6 kOe has been achieved on the silicon substrate by sol-gel. The room-temperature maximum magnetic energy product (BH)max and remanence ratio Mr/Ms are of 1.66 MG Oe and 0.58 respectively, which are also the largest values amongst the CFO thin films prepared by solution methods. At the same time, annealing temperature and thickness effects on the HC, (BH)max and Mr/Ms of the derived CFO thin films have been investigated. It is observed that grain size and residual tensile strain in the derived films play an important role in the variations of HC and Mr/Ms. These results will provide an effective route for fabricating larger-area high-coercivity CFO thin films with low-cost by sol-gel on silicon wafers.

  8. TEM observation of sintered permanent magnetic strontium ferrite

    Institute of Scientific and Technical Information of China (English)

    YU Hongya; LIU Zhengyi; ZENG Dechang

    2006-01-01

    Sintered permanent magnetic strontium ferrites were studied using transmission electron microscopy to investigate the microstructure morphology and its correlation with the magnetic properties. The present study shows that the microstructure of sintered permanent magnetic strontium ferrites is an important parameter in determining their magnetic properties. The microstructure morphology in low-performance ferrite magnet is obviously different from high-performance one. Themagnetic properties of sintered permanent strontium ferrite depend strongly on the orientation degree of strong magnetic crystals. The presence of ferric oxidephase in ferrite magnet can deteriorate the magnetic properties. Moreover, proper quantities of crystal defects are beneficial to high coercive force due to the fixing of magnetic domain.

  9. Structure and Properties of Nd-Fe-B Alloy Subjected to HDDR Process

    Directory of Open Access Journals (Sweden)

    Szymański M.

    2016-03-01

    Full Text Available In this paper the Hydrogenation, Disproportionation, Desorption and Recombination (HDDR route was tested, for the Nd-Fe-B master alloy, as a prospective procedure for recycling of sintered scrap neodymium magnets. The HDDR method is based on the hydrogen induced reversal phase transformation of Nd-Fe-B alloy: Nd2Fe14B + (2±x H2 = 2NdH2±x + Fe2B + 12Fe. Microstructural observations (SEM, phase constitution studies (XRD and measurement of magnetic properties (VSM were done to investigate the HDDR transformation progress. It was observed that disproportionation reaction starts at the grain boundaries, where the Nd-rich phase is located. Average grain size was reduced and coercive material was produced as a result of the HDDR process. Obtained results are similar to literature data.

  10. Sintering in Laser Sintering

    Science.gov (United States)

    Bourell, David L.

    2016-03-01

    Laser sintering is a popular additive manufacturing technology, particularly for service parts. Invented by C. Deckard in the mid-1980s, the approach of using a laser to densify a powder bed selectively has been extensively researched and has been applied to metals, ceramics, polymers and composites. In the traditional powder-metallurgical sense, sintering involves solid-state atomic transport resulting in neck formation and eventual densification in a powder mass. The use of the term "sintering" as a descriptive term for the powder-bed additive manufacturing process has been problematical to the technical community, because the predominant densification mechanism has been shown for most applications to be melting and reflow. The term has perpetuated as a name for the additive manufacturing process, at least for polymers. The technical term "sintering" is accurately associated with laser sintering insofar as powder pre-processing and part post-processing are concerned. It may also be used to describe formation of "part cake". This paper describes the circumstances surrounding the coining of the term, "laser sintering" and provides some examples of how sintering is used in pre- and post-processing.

  11. 3-D laser confocal microscopy study of the oxidation of NdFeB magnets in atmospheric conditions

    Science.gov (United States)

    Meakin, J. P.; Speight, J. D.; Sheridan, R. S.; Bradshaw, A.; Harris, I. R.; Williams, A. J.; Walton, A.

    2016-08-01

    Neodymium iron boron (NdFeB) magnets are used in a number of important applications, such as generators in gearless wind turbines, motors in electric vehicles and electronic goods (e.g.- computer hard disk drives, HDD). Hydrogen can be used as a processing gas to separate and recycle scrap sintered Nd-Fe-B magnets from end-of-life products to form a powder suitable for recycling. However, the magnets are likely to have been exposed to atmospheric conditions prior to processing, and any oxidation could lead to activation problems for the hydrogen decrepitation reaction. Many previous studies on the oxidation of NdFeB magnets have been performed at elevated temperatures; however, few studies have been formed under atmospheric conditions. In this paper a combination of 3-D laser confocal microscopy and Raman spectroscopy have been used to assess the composition, morphology and rate of oxidation/corrosion on scrap sintered NdFeB magnets. Confocal microscopy has been employed to measure the growth of surface reaction products at room temperature, immediately after exposure to air. The results showed that there was a significant height increase at the triple junctions of the Nd-rich grain boundaries. Using Raman spectroscopy, the product was shown to consist of Nd2O3 and formed only on the Nd-rich triple junctions. The diffusion coefficient of the triple junction reaction product growth at 20 °C was determined to be approximately 4 × 10-13 cm2/sec. This value is several orders of magnitude larger than values derived from the diffusion controlled oxide growth observations at elevated temperatures in the literature. This indicates that the growth of the room temperature oxidation products are likely defect enhanced processes at the NdFeB triple junctions.

  12. 3-D laser confocal microscopy study of the oxidation of NdFeB magnets in atmospheric conditions

    Energy Technology Data Exchange (ETDEWEB)

    Meakin, J.P., E-mail: jxm764@bham.ac.uk; Speight, J.D.; Sheridan, R.S.; Bradshaw, A.; Harris, I.R.; Williams, A.J.; Walton, A.

    2016-08-15

    Highlights: • Room temperature atmospheric oxidation behaviour of sintered NdFeB. • 3D laser confocal microscopy measurement of oxide phase growth. • Significant height increase of oxide phase only observed at triple points. • Raman spectroscopy identified oxide phase to be Nd{sub 2}O{sub 3}. • Diffusion coefficient determined to be 4 × 10{sup −13} cm{sup 2}/s. - Abstract: Neodymium iron boron (NdFeB) magnets are used in a number of important applications, such as generators in gearless wind turbines, motors in electric vehicles and electronic goods (e.g.— computer hard disk drives, HDD). Hydrogen can be used as a processing gas to separate and recycle scrap sintered Nd-Fe-B magnets from end-of-life products to form a powder suitable for recycling. However, the magnets are likely to have been exposed to atmospheric conditions prior to processing, and any oxidation could lead to activation problems for the hydrogen decrepitation reaction. Many previous studies on the oxidation of NdFeB magnets have been performed at elevated temperatures; however, few studies have been formed under atmospheric conditions. In this paper a combination of 3-D laser confocal microscopy and Raman spectroscopy have been used to assess the composition, morphology and rate of oxidation/corrosion on scrap sintered NdFeB magnets. Confocal microscopy has been employed to measure the growth of surface reaction products at room temperature, immediately after exposure to air. The results showed that there was a significant height increase at the triple junctions of the Nd-rich grain boundaries. Using Raman spectroscopy, the product was shown to consist of Nd{sub 2}O{sub 3} and formed only on the Nd-rich triple junctions. The diffusion coefficient of the triple junction reaction product growth at 20 °C was determined to be approximately 4 × 10{sup −13} cm{sup 2}/sec. This value is several orders of magnitude larger than values derived from the diffusion controlled oxide growth

  13. Synthesis of High Coercivity Core–Shell Nanorods Based on Nickel and Cobalt and Their Magnetic Properties

    Directory of Open Access Journals (Sweden)

    Shaijumon MM

    2009-01-01

    Full Text Available Abstract Hybrid magnetic nanostructures with high coercivity have immense application potential in various fields. Nickel (Ni electrodeposited inside Cobalt (Co nanotubes (a new system named Ni @ Co nanorods were fabricated using a two-step potentiostatic electrodeposition method. Ni @ Co nanorods were crystalline, and they have an average diameter of 150 nm and length of ~15 μm. The X-ray diffraction studies revealed the existence of two separate phases corresponding to Ni and Co. Ni @ Co nanorods exhibited a very high longitudinal coercivity. The general mobility-assisted growth mechanism proposed for the growth of one-dimensional nanostructures inside nano porous alumina during potentiostatic electrodeposition is found to be valid in this case too.

  14. Pembuatan Bonded Anisotropi Magnet NdFeB dan Karakterisasinya

    OpenAIRE

    Nuraini, Siti

    2015-01-01

    Research on fabrications of bonded magnets NdFeB type MQA-37-16 with polivynil chloride binder has been done. The purpose of this study the effect of field strength and orientation on the physical and magnetic properties in the manufacture of bonded magnets NdFeB. Preparation process by dry mixing powder magnets NdFeB and polivynil chloride binder bi using Shaker Mill. For each sample takes 4 grams total mass of bonded magnet NdFeB. Printing is done isotropic and anisotropy using a magnetic f...

  15. High coercivity sized controlled cobalt–gold core–shell nano-crystals prepared by reverse microemulsion

    Energy Technology Data Exchange (ETDEWEB)

    Bahmanrokh, Ghazaleh, E-mail: ghazalehbahmanrokh@yahoo.com [Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Hashim, Mansor [Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Soltani, Nayereh [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Ismail, Ismayadi [Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Vaziri, Parisa [Department of Medical Physics and Biomedical Engineering, Shahid Beheshti University of Medical Sciences, Tehran (Iran, Islamic Republic of); Navaseri, Manizheh; Erfani, Maryam [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Kanagesan, Samikannu [Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia)

    2013-10-15

    Graphical abstract: - Highlights: • Calculating the crystallinity percentage and percentage of phases presented in Co–Au core–shell nanoparticles. • Magnetic properties of four groups nanogarin: 5, 10, 15, 20 nm. • Single domain ferromagnetic materials with high coercivity at room temperature. • Intrinsic blocking temperature measured in zero field cooled-warmed (ZFC-W). - Abstract: Size-controlled cobalt–gold core–shell nanoparticles were synthesized via the reverse-micelle microemulsion method. In order to control the size of the nanoparticles, the nucleation and growth process were performed within a confined space by adjusting the water to surfactant ratio of reverse micelles solution during synthesis. The crystallinity percentage and percentage of phases presented in Co–Au core–shell nanoparticles were calculated using X-ray diffraction data. The results from transmission electron microscopy provide direct evidence for core–shell structure nanomaterials. Magnetic properties of the samples were investigated using a vibrating sample magnetometer. The as-prepared samples showed significant coercivity at room temperature. The intrinsic blocking temperature was experimentally deduced from zero-field-cooled warmed (ZFC-W) curves by a simple method without employing an external magnetic field. The B-field dependence temperature data of Co–Au nanoparticles exhibited an intrinsic blocking temperature at 45 K. Annealing these samples at 400 °C caused an increase in particle size, crystallinity percentage and further enhanced their magnetic properties.

  16. High coercivity microcrystalline Nd-rich Nd-Fe-Co-Al-B bulk magnets prepared by direct copper mold casting

    Science.gov (United States)

    Zhao, L. Z.; Hong, Y.; Fang, X. G.; Qiu, Z. G.; Zhong, X. C.; Gao, X. S.; Liu, Z. W.

    2016-06-01

    High coercivity Nd25Fe40Co20Al15-xBx (x=7-15) hard magnets were prepared by a simple process of injection casting. Different from many previous investigations on nanocomposite compositions, the magnets in this work contain hard magnetic Nd2(FeCoAl)14B, Nd-rich, and Nd1+ε(FeCo)4B4 phases. The magnetic properties, phase evolution, and microstructure of the as-cast and annealed magnets were investigated. As the boron content increased from 7 to 11 at%, the intrinsic coercivity Hcj of the as-cast magnet increased from 816 to 1140 kA/m. The magnets annealed at 750 °C have shown more regular and smaller grains than the as-cast alloys, especially for the x=11 alloy. The high intrinsic coercivities for the annealed alloys with x=8~11 result from the presence of small-sized grains in the microstructure. The highest Hcj of 1427 kA/m was obtained for the heat treated alloy with x=10. This work provides an alternative approach for preparing fully dense Nd-rich bulk hard magnets with relatively good properties.

  17. Inducing magnetic anisotropy and optimized microstructure in rapidly solidified Nd-Fe-B based magnets by thermal gradient, magnetic field and hot deformation

    Science.gov (United States)

    Zhao, L. Z.; Li, W.; Wu, X. H.; Hussain, M.; Liu, Z. W.; Zhang, G. Q.; Greneche, J. M.

    2016-10-01

    Direct preparation of Nd-Fe-B alloys by rapid solidification of copper mold casting is a very simple and low cost process for mini-magnets, but these magnets are generally magnetically isotropic. In this work, high coercivity Nd24Co20Fe41B11Al4 rods were produced by injection casting. To induce magnetic anisotropy, temperature gradient, assisted magnetic field, and hot deformation (HD) procedures were employed. As-cast samples showed non-uniform microstructure due to the melt convection. The thermal gradient during solidification led to the formation of radially distributed acicular hard magnetic grains, which gives the magnetic anisotropy. The growth of the oriented grains was confirmed by phase field simulation. A magnetic field up to 1 T applied along the casting direction could not induce significant magnetic anisotropy, but it improved the magnetic properties by reducing the non-uniformity and forming a uniform microstructure. The annealed alloys exhibited high intrinsic coercivity but disappeared anisotropy. HD was demonstrated to be a good approach for inducing magnetic anisotropy and enhanced coercivity by deforming and refining the grains. This work provides an alternative approach for preparing fully dense Nd-rich anisotropic bulk Nd-Fe-B magnets.

  18. Ultrathin SmCo5 nanoflakes with high-coercivity prepared by solid particle (NaCl) and surfactant co-assisted ball milling

    Science.gov (United States)

    Zuo, Wen-Liang; Zhao, Xin; Zhao, Tong-Yun; Hu, Feng-Xia; Sun, Ji-Rong; Shen, Bao-Gen

    2016-05-01

    The ultrathin SmCo5 nanoflakes with average thickness smaller than 50 nm are prepared by a novel method of solid particle (NaCl) and surfactant co-assisted ball milling. The as-prepared nanoflakes exhibit a narrower thickness distribution of 10–50 nm and high coercivity of 23 kOe. The possible formation mechanism of nanoflakes are proposed. Temperature dependence of demagnetization curves indicate that the magnetization reversal may be controlled by both nucleation and pinning. The results of X-ray powder diffraction and magnetic measurement for aligned SmCo5 nanoflakes resin composite indicate that the nanoflakes have a high texture degree. The ultrathin thickness and high coercivity are beneficial for preparing the high performance soft/hard coupling magnets and nanocomposite magnets.

  19. Preparation of Nd–Fe–B sintered magnets from HDDR-processed powder

    Energy Technology Data Exchange (ETDEWEB)

    Takagi, Kenta, E-mail: k-takagi@aist.go.jp [Green Innovative Magnetic Materials Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya 463-8560 (Japan); Akada, Misaho [Magnetic Materials R& D Center, Research Associations of Magnetic Materials for High-Efficiency Motors (MagHEM), Nagoya 463-8560 (Japan); Soda, Rikio; Ozaki, Kimihiro [Green Innovative Magnetic Materials Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya 463-8560 (Japan)

    2015-11-01

    The electric-current sintering technique was used to fully densify hydrogenation–disproportionation–desorption–recombination (HDDR)-processed Nd–Fe–B powder at temperatures below the grain growth temperature in order to produce high-coercive bulk magnets. However, the sintered magnets exhibited anomalous coercivity reduction that depended on sintered density. Reheating examination of the sintered magnets revealed that the reduced coercivity was increased in proportion to the heating temperature, resulting in complete recovery of coercivity. As a result, the combination of electric-current sintering and post-annealing produced sintered magnets with a coercivity of 15 kOe. Scanning and transmission electron microscopy revealed no evidence that associated the anomalous coercivity reduction and recovery with grain boundary morphology. On the other hand, various HDDR powders with different particle sizes were sintered, and finer powders yielded lower coercivity after sintering, implying that the anomalous coercivity reduction was associated with particle surface oxides of the raw powder. - Highlights: • We conduct a sintering of HDDR-processed Nd–Fe–B powder without coercivity reduction. • Rapid current sintering allows densification of this powder without grain growth. • However, the sintered magnets show an anomalous coercivity reduction phenomenon. • It is found that post-annealing completely recovers the reduced coercivity. • The anomalous coercivity reduction would be due to surface oxide of the raw powder.

  20. NdFeB Residue to Be Recycled

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ NdFeB is a permanent magnetic material with excellent performances. It is widely used in electronics and communications. Around 30% of rare earth elements (among which 90% is Nd, others are Tb and Dy) and 2-3% of Co element are contained in the material. NdFeB plays an important role in the development of our society and our economy.

  1. Use of paired, bonded NdFeB magnets in redox magnetohydrodynamics.

    Science.gov (United States)

    Arumugam, Prabhu U; Clark, Emily A; Fritsch, Ingrid

    2005-02-15

    Bonded neodymium-iron-boron (NdFeB) permanent magnets in a paired configuration were successfully used to control mass transport in redox-based, magnetohydrodynamics (MHD). Control of fluid flow based on magnetic fields has potential for use in portable lab-on-a-chip (LOAC) and analytical devices. Bonded magnets, composed of magnetic powder and organic binder materials, are less expensive and easier to fabricate and pattern than electromagnets and sintered permanent magnets, which have been previously used in MHD studies on electrochemical systems. The ability to pattern bonded magnets near and around the electrodes is expected to allow for better control over the magnetic field distribution and solution flow. Current was generated at an 800-microm-radius platinum disk electrode in a solution of 0.06 M nitrobenzene and 0.5 M tetra-n-butylammonium hexafluorophosphate in acetonitrile. Increases in limiting current in the presence of the magnetic field, which indicate enhancement in mass transport, for sintered (210+/-14%, N = 4, where B(r) = 1.23 T and magnetic field strength is 0.55 T) and bonded (94+/-8%, N = 4, where B(r) = 0.41 T and magnetic field strength is 0.20 T) magnets, were similar to those obtained using an electromagnet with the same magnetic flux densities. The magnetic field strength and not the magnet type is important in controlling fluid flow, which is encouraging for integration of bonded permanent magnets into LOAC devices.

  2. The impact of processing parameters on the properties of Zn-bonded Nd-Fe-B magnets

    Science.gov (United States)

    Kelhar, Luka; Zavašnik, Janez; McGuiness, Paul; Kobe, Spomenka

    2016-12-01

    We report on the effect of loading factor and pressure on the density and the magnetic properties of Zn-bonded Nd-Fe-B magnets produced by pulsed-electric-current sintering (PECS). The idea behind this study is to fabricate bonded magnets with a metallic binder in order for the bonded magnet to operate at temperatures higher than 180 °C: the current upper-limit for polymer-bonded magnets. These composites are made of hard-magnetic powder in the form of melt-spun ribbons bonded with the low-melting-point metal Zn. The binder additions were varied from 10 to 30 wt%, and pressures of 50 and 500 MPa were applied. The high-pressure mode with 20 wt% Zn resulted in a 24% increase of Jr, compared to the low-pressure mode. The magnetic measurements revealed a maximum remanence of 0.64 T for 10 wt% Zn, while the coercivity is largely unaffected by the processing conditions. The density of the composites was up to 7.0 g/cm3, corresponding to 94% of the theoretical density. Compared to commercial polymer-bonded magnets, the Zn-bonded counterparts exhibit a slightly lower Jr, but the coercivity is retained. We show that there is a minor diffusion of Zn into the Nd-Fe-B, forming a 1 μm thin transition layer, but it does not harm the magnetic properties. These metal-bonded Nd-Fe-B magnets are ideal for use in high-temperature automotive applications like under-the-hood sensors and other magnet-based devices that are close to the engine.

  3. ASPECTS REGARDING MECHANICAL PROCESSING OF STEELS FOR MAGNETS, NDFEB BASED

    Directory of Open Access Journals (Sweden)

    MELANIA TĂMAŞ

    2015-05-01

    Full Text Available This paper presents experimental research concerning the behavior on cutting by turning of steels for magnets NdFeB based. In this context, cutting by rough turning of steels magnet neodymium and boron ferrite based were performed. Turning processing with the values of the cutting parameters recommended by European Union and Sandvik Coromant company rules, taking into account the chemical composition of the processed material and cutting tool were performed. The tables have been drawn up with different values of the cutting parameters. By comparing these data it can be concluded that steels for permanent magnets, NdFeB based have acceptable behavior, the process by rough turning. A full assessment of the optimization of the cutting by turning process of steels for permanent magnet, NdFeB base will result from subsequent experimental research that will take into account the wear of cutting tools and quality (roughness of processed surface.

  4. Synthesis, morphology and microstructure of pomegranate-like hematite ({alpha}-Fe{sub 2}O{sub 3}) superstructure with high coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Tadic, Marin, E-mail: marint@vinca.rs [Condensed Matter Physics Laboratory, Vinca Institute, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia); Citakovic, Nada [Military Academy, Generala Pavla Jurisica Sturma 33, University of Belgrade, 11000 Belgrade (Serbia); Panjan, Matjaz [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Stanojevic, Boban [Vinca Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade, University of Belgrade (Serbia); Markovic, Dragana [Condensed Matter Physics Laboratory, Vinca Institute, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia); Jovanovic, Dorde [Center for Solid State Physics and New Materials, Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia); Spasojevic, Vojislav [Condensed Matter Physics Laboratory, Vinca Institute, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia)

    2012-12-05

    Highlights: Black-Right-Pointing-Pointer We found superior magnetic properties of the hematite ({alpha}-Fe{sub 2}O{sub 3}). Black-Right-Pointing-Pointer TEM and HRTEM images show a pomegranate-like superstructure. Black-Right-Pointing-Pointer Magnetic measurements display high coercivity H{sub C} = 4350 Oe at the room temperature. - Abstract: We found novel and superior magnetic properties of the hematite ({alpha}-Fe{sub 2}O{sub 3}) that originate from an internal microstructure of particles and strong inter-particle interactions between nanocrystal sub-units. The hematite particles were synthesized by thermal decomposition of iron (III) nitrate without any template or surfactant. The purity, size, crystallinity, morphology, microstructure and magnetic features of the as-prepared particles were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), Raman spectroscopy (RS) and SQUID magnetometry. An XRD study reveals a pure phase of {alpha}-Fe{sub 2}O{sub 3} whereas TEM shows {alpha}-Fe{sub 2}O{sub 3} spheres with a diameter of about 150 nm. RS also shows high quality and purity of the sample. Moreover, TEM and HRTEM images show a pomegranate-like superstructure and evidence that the spherical particles are composed of individual well-crystallized nanoparticle sub-units (self-assembled nanoparticles) with a size of about 20 nm. Magnetic measurements display hysteretic behavior at the room temperature with remanent magnetization M{sub r} = 0.731 emu/g, saturation magnetization M{sub S} = 6.83 emu/g and coercivity H{sub C} = 4350 Oe, as well as the Morin transition at T{sub M} = 261 K. These results and comparison with those in the literature reveal that the sample has extremely high coercivity. The magnetic properties of the sample are discussed in relation to morphology, internal microstructure, surface

  5. Enhanced method of magnetic powder alignment for production of PLP Nd-Fe-B magnets

    Science.gov (United States)

    Popov, A. G.; Golovnia, O. A.; Protasov, A. V.

    2017-04-01

    It is demonstrated how the high degree of powder alignment in PLP magnets can be achieved by loading the powder into a container placed in a magnetic field of moderate strength. The strip-cast alloy with a composition of 30.00 Nd, 1.95 Dy, 66.42 Fe, 0.99 B, 0.54 Co, 0.1 Ga (wt%) was subjected to hydrogen decrepitation and then milled in a vibratory mill in toluene to an average particle size of 2.9 μm determined by the FSSS method. The powder was compacted in the magnetic field of 0.2 - 1.2 T to the filling density 2.6 - 3.2×103 kg/m3. It is shown that loading the powder into a container placed in a magnetic field enhances the degree of powder alignment in sintered Nd-Fe-B magnets produced from non-pressed powder. At the filling density less than 3.2×103 kg/m3, the density of magnets is high but insufficient, because of the formation of magnetostatic chains of particles, which impedes the powder compaction. The simulation by the discrete-element method qualitatively proves that the magnetostatic interaction of the chains of particles that are formed in the course of loading in the magnetic field stimulates a decrease in the density of the sintered magnets and its non-uniform distribution over the sample. As a result of the optimization of the parameters of the alignment and compaction of the powder loaded in a magnetic field, PLP magnets with Br ≥1.34 T, Нc ≥950 kA/m, (BH)max ≥340 kJ/m3, and the degree of alignment exceeding 96% were produced.

  6. Formation of submicron-sized SrFe{sub 12-x}Al{sub x}O{sub 19} with very high coercivity

    Energy Technology Data Exchange (ETDEWEB)

    Kazin, P.E. [Chemistry Department, Moscow State University, 119991 Moscow (Russian Federation); Trusov, L.A. [Department of Materials Science, Moscow State University, 119991 Moscow (Russian Federation)], E-mail: doz.trusov@gmail.com; Zaitsev, D.D. [Department of Materials Science, Moscow State University, 119991 Moscow (Russian Federation); Tretyakov, Yu.D. [Chemistry Department, Moscow State University, 119991 Moscow (Russian Federation); Department of Materials Science, Moscow State University, 119991 Moscow (Russian Federation); Jansen, M. [Max-Planck-Institut fuer Festkoerperforschung, D-70569 Stuttgart (Germany)

    2008-03-15

    Submicron-sized SrFe{sub 12-x}Al{sub x}O{sub 19} (x=1.3) was formed in glass-ceramic matrix using controlled thermocrystallization of the SrO-Fe{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3} glass and the hexaferrite powder was obtained by removing the matrix phases. The samples were characterized by X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray (EDX) analysis and magnetization measurements. The glass-ceramic material exhibits very high coercivity value up to 10.18 kOe which approaches a theoretically estimated maximum value for the compound. The hexaferrite powder consists of well faceted single crystals, which adopt the shape of a truncated hexagonal bipyramid. The powder saturation magnetization value is close to the theoretically estimated one for bulk material. Crystal structure of the powder was refined by Rietveld method and distribution of Al atoms on Fe sites was determined. Al atoms occupy 41% of 2a sites, 14% of 12k sites and 5% of 4e(1/2) sites, while 4f sites are not affected.

  7. Fundamentals of Sintering Dolomite

    Institute of Scientific and Technical Information of China (English)

    LIMaoqiang

    1996-01-01

    The difficulties in sintering of dolomite rise form the low mutual diffusibilites of Ca2+ in MgO and Mg2+ in CaO ,and from unique pore and agglomerate structures formed after calcination of dolomite.These microstructures in decompsoed dolomite play a great role in inhibition of densification during sintering.The measures ,which can destroy these stuctures,such as hydration or isostatic pressing after calcination of dolomite,result in increasing the sintered density and reducting the sintering temperature,Addition of ome oxide such as Fe2O3,ater the sintering mechanism from solid state sintering to liquid phase sintering,therefore,dense dolomite ody can be obtained at relatively low sintering temperature,Com-minution of dolomite before its calcination can lower the sintering temperature and enhance the sinterd ensity due to increasing both the quantity and homogeneity of Fe2O3 in dolomite.

  8. Magnetic Behavior of Sintered NdFeB Magnets on a Long-Term Timescale

    Directory of Open Access Journals (Sweden)

    Minna Haavisto

    2014-01-01

    Full Text Available Stable polarization of permanent magnets over the lifetime of the application is an important aspect in electrical machine design. Specification of the long-term stability of magnet material is difficult, since knowledge of the phenomenon is incomplete. To be able to optimize magnet material selection, the long-term magnetic behavior of the material must also be understood. This study shows that material with a very square JH curve is stable until a certain critical operating temperature is reached. Major losses are detected as the critical temperature is exceeded. Material with a rounder JH curve does not show a well-defined critical temperature, but increasing losses over a large temperature range. The critical temperature of a material is also dependent on the field conditions. Results differ whether the tests are performed in an open or closed magnetic circuit. In open-circuit tests, the opposing field is not homogeneously distributed throughout the volume of the magnet and thus the long-term behavior is different than that in closed-circuit conditions. Open-circuit tests seem to give bigger losses than closed-circuit tests in cases where the permeance coefficient of the open-circuit sample is considered to be the average permeance coefficient, calculated according to the dimensions of the magnet.

  9. Hydrogen Decrepitation Press-Less Process Recycling of NdFeB sintered magnets

    DEFF Research Database (Denmark)

    Xia, Manlong; Abrahamsen, Asger Bech; Bahl, Christian

    2017-01-01

    in a graphite mold. Coercivities up to 534 kA/m were obtained in porous samples based on powder size d 100 μm. Adding a ball milling step resulted in full density isotropic magnets for d > 100 μm. The coercivity reached Hci = 957 kA/m being 86 % of the original N48M material without addition of rare earth...

  10. Environmental control on the occurrence of high-coercivity magnetic minerals and formation of iron sulfides in a 640 ka sediment sequence from Lake Ohrid (Balkans)

    Science.gov (United States)

    Just, Janna; Nowaczyk, Norbert R.; Sagnotti, Leonardo; Francke, Alexander; Vogel, Hendrik; Lacey, Jack H.; Wagner, Bernd

    2016-04-01

    The bulk magnetic mineral record from Lake Ohrid, spanning the past 637 kyr, reflects large-scale shifts in hydrological conditions, and, superimposed, a strong signal of environmental conditions on glacial-interglacial and millennial timescales. A shift in the formation of early diagenetic ferrimagnetic iron sulfides to siderites is observed around 320 ka. This change is probably associated with variable availability of sulfide in the pore water. We propose that sulfate concentrations were significantly higher before ˜ 320 ka, due to either a higher sulfate flux or lower dilution of lake sulfate due to a smaller water volume. Diagenetic iron minerals appear more abundant during glacials, which are generally characterized by higher Fe / Ca ratios in the sediments. While in the lower part of the core the ferrimagnetic sulfide signal overprints the primary detrital magnetic signal, the upper part of the core is dominated by variable proportions of high- to low-coercivity iron oxides. Glacial sediments are characterized by high concentration of high-coercivity magnetic minerals (hematite, goethite), which relate to enhanced erosion of soils that had formed during preceding interglacials. Superimposed on the glacial-interglacial behavior are millennial-scale oscillations in the magnetic mineral composition that parallel variations in summer insolation. Like the processes on glacial-interglacial timescales, low summer insolation and a retreat in vegetation resulted in enhanced erosion of soil material. Our study highlights that rock-magnetic studies, in concert with geochemical and sedimentological investigations, provide a multi-level contribution to environmental reconstructions, since the magnetic properties can mirror both environmental conditions on land and intra-lake processes.

  11. Preparation of YCo{sub 5}, PrCo{sub 5} and SmCo{sub 5} anisotropic high-coercivity powders via mechanochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Gabay, A.M., E-mail: gabay@udel.edu [Department of Physics and Astronomy, University of Delaware, 217 Sharp Lab, Newark, DE 19716 (United States); Hu, X.C. [Department of Materials Science and Engineering, University of Delaware, Newark, DE 19716 (United States); Hadjipanayis, G.C. [Department of Physics and Astronomy, University of Delaware, 217 Sharp Lab, Newark, DE 19716 (United States)

    2014-11-15

    Polydispersed RCo{sub 5} powders consisting mostly of single crystal particles with an average size ranging from 280 nm to 400 nm have been prepared mechanochemically for R=Y, Pr, Pr–Sm and Sm. The synthesis included (i) mechanical activation of a mixture of rare earth oxides, Co, Ca and CaO, (ii) short annealing and (iii) separation of the RCo{sub 5} particles through a multi-step washing process. The highest room-temperature coercivities of the oriented YCo{sub 5}, PrCo{sub 5} and SmCo{sub 5} powders were 20.6, 19.1 and 41.5 kOe, respectively. This improvement compared to traditionally ground powders is attributed to a lower density of crystalline defects. An investigation of a broad, 1050–1320 K, range of the synthesis temperatures revealed nearly universal evolution of crystalline anisotropy of the particles and their remanent magnetization, significant variations in the particle growth rate—with growth of the YCo{sub 5} particles being the most sluggish—and, surprisingly, no correlation between the average size of the particles and their coercivity. These findings extend the practical limits associated with hard magnetic materials and demonstrate that the hard magnetic properties of the mechanochemically synthesized YCo{sub 5} and PrCo{sub 5} powders are similar to those of traditionally prepared SmCo{sub 5}. - Highlights: • Mechanochemistry yields RCo{sub 5} single crystals few hundred nanometers in size. • Coercivity of powders is 2–5 times larger than the one attainable through milling. • The high coercivity is attributed to a lower density of crystalline defects.

  12. Effect of Copper and Titanium Addition on Microstructures and Magnetic Properties of Sintered Nd22Fe71B7 Magnets

    Institute of Scientific and Technical Information of China (English)

    宋晓平; 杨森; 王献辉; 孙占波; 孙军

    2001-01-01

    Alloying elements Cu and Ti were added to the intergranular regions of sintered NdFeB magnets and their effects on microstructure and magnetic properties were investigated. The results show that small amounts of Cu/Ti additives can enhance the coercivity greatly and have little effect on the remanence of the magnets, while Ti content is less than 1.2%. The improvement of the coercivity can be attributed to the segregation of Cu and Ti on the surface of main phase, which inhibits the growth of main phase grains during sintering. At the same time, segregation of Cu and Ti can also prevent the magnetic coupling of Nd2Fe14B grains to a certain degree and impede effectively the propagation of reversed domain walls through the magnetic phase grains. As the Ti content increased above 1.2% a strip-like Ti-rich phase appears in the intergranular region, resulting in the dramatic reduction of the remanence of Nd-Fe-B magnets. Compared with the single alloying method, the combined alloying of intergranular regions is more efficient to modify the properties of NdFeB magnets.

  13. Thermal aging of melt-spun NdFeB magnetic powder in hydrogen

    Science.gov (United States)

    Pinkerton, Frederick E.; Balogh, Michael P.; Ellison, Nicole; Foto, Aldo; Sechan, Martin; Tessema, Misle M.; Thompson, Margarita P.

    2016-11-01

    High energy product neodymium-iron-boron (NdFeB) magnets are the premier candidate for demanding electrified vehicle traction motor applications. Injection molded (IM) or compression molded (CM) magnets made using NdFeB powders are promising routes to improve motor efficiency, cost, and manufacturability. However, IM and CM NdFeB magnets are susceptible to substantial thermal aging losses at motor operating temperatures when exposed to the automatic transmission fluid (ATF) used as a lubricant and cooling medium. The intrinsic coercivity Hci of NdFeB IM and CM magnets degrades by as much as 18% when aged for 1000 h in ATF at 150 °C, compared to a 3% loss when aged in air. Here we report aging studies of rapidly quenched NdFeB powder in air, ATF, and H2 gas. Expansion of the NdFeB crystal lattice in both ATF and H2 identified hydrogen dissociated from the ATF during aging and diffused into the primary NdFeB phase as the probable cause of the coercivity loss of IM and CM magnets.

  14. Protection of NdFeB magnets by corrosion resistance phytic acid conversion film

    Science.gov (United States)

    Nan, Haiyang; Zhu, Liqun; Liu, Huicong; Li, Weiping

    2015-11-01

    Phytic acid conversion film was prepared on NdFeB magnets by dipping the NdFeB into phytic acid solution. The morphology, composition, structure and corrosion resistance of the film were systematically investigated. The results showed that the phytic acid film was effective in improving the corrosion resistance of NdFeB magnets. XRD, TEM and FT-IR analyses revealed that the film was amorphous and had a strong peak of phosphate radical (PO43-). The formation mechanism of the film was also explored by XPS and the potential of zero charge (Epzc) measurement at the solution-metal interface.

  15. Methods of flash sintering

    Energy Technology Data Exchange (ETDEWEB)

    Raj, Rishi; Cologna, Marco; Francis, John S.

    2016-05-10

    This disclosure provides methods of flash sintering and compositions created by these methods. Methods for sintering multilayered bodies are provided in which a sintered body is produced in less than one minute. In one aspect, each layer is of a different composition, and may be constituted wholly from a ceramic or from a combination of ceramic and metallic particles. When the body includes a layer of an anode composition, a layer of an electrolyte composition and a layer of a cathode composition, the sintered body can be used to produce a solid oxide fuel cell.

  16. Influence of NdFeB Fillers on Tensile and Electromagnetic Properties of Natural Rubber

    Directory of Open Access Journals (Sweden)

    Puripat LERTSURAWAT

    2009-06-01

    Full Text Available Tensile and electromagnetic properties of hard magnetic natural rubber composites were studied. In a fabrication stage, neodymium-iron-boron (NdFeB magnets were recycled from electronic wastes, broken and then ball-milled for 1 - 3 h. The NdFeB powder was then incorporated into natural rubber (NR by a 2-roll mill technique. Since the NdFeB powder behaved as a non-reinforced filler, thus, it inhibited cross-linking and stress-induced recrystallization. Therefore, the cure time and the tensile strength of the NdFeB-NR composites were reduced compared to the control sample without magnetic fillers. The addition of NdFeB fillers improved the electrical permittivity of NR and the magnetic moment in NdFeB-NR composites could be measured by a fluxmeter.

  17. Magnetic microstructure and coercivity mechanism of high performance Nd-Fe-B magnets

    Institute of Scientific and Technical Information of China (English)

    ZHU Minggang; LIU Xingmin; FANG Yikun; LI Zhengbang; LI Wei

    2006-01-01

    Magnetic microstructure of high performance Nd-Fe-B magnets was investigated by using magnetic force microscopy. The correlation between magnetic microstructure and coercivity for high performance Nd-Fe-B magnets was studied. It is found that the magnets with different coercivity mechanism take on different microstructures and magnetism. Moreover, the magnetic microstructures of high performance permanent magnets can be explained by the starting field theory model.

  18. Thermal aging of melt-spun NdFeB magnetic powder in hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Pinkerton, Frederick E., E-mail: frederick.e.pinkerton@gm.com [Chemical and Materials Systems Laboratory, General Motors Research and Development Center, Warren, MI 48092 (United States); Balogh, Michael P.; Ellison, Nicole [Chemical and Materials Systems Laboratory, General Motors Research and Development Center, Warren, MI 48092 (United States); Foto, Aldo [Element Materials Technology Wixom, Inc (United States); Sechan, Martin; Tessema, Misle M.; Thompson, Margarita P. [Powertrain Materials/Fluids/AMPPD Engineering and Labs, GFL VE/PT Materials Engineering, General Motors LLC, Pontiac, MI 48340 (United States)

    2016-11-01

    High energy product neodymium-iron-boron (NdFeB) magnets are the premier candidate for demanding electrified vehicle traction motor applications. Injection molded (IM) or compression molded (CM) magnets made using NdFeB powders are promising routes to improve motor efficiency, cost, and manufacturability. However, IM and CM NdFeB magnets are susceptible to substantial thermal aging losses at motor operating temperatures when exposed to the automatic transmission fluid (ATF) used as a lubricant and cooling medium. The intrinsic coercivity H{sub ci} of NdFeB IM and CM magnets degrades by as much as 18% when aged for 1000 h in ATF at 150 °C, compared to a 3% loss when aged in air. Here we report aging studies of rapidly quenched NdFeB powder in air, ATF, and H{sub 2} gas. Expansion of the NdFeB crystal lattice in both ATF and H{sub 2} identified hydrogen dissociated from the ATF during aging and diffused into the primary NdFeB phase as the probable cause of the coercivity loss of IM and CM magnets. - Highlights: • Injection molded NdFeB magnets age rapidly in automatic transmission fluid (ATF). • Coercivity loss is not due to direct chemical reaction between ATF and the powder. • Chemical reaction with the binder does not play a major role in aging. • Hydrogen dissociates from ATF and diffuses into Nd{sub 2}Fe{sub 14}B, reducing coercivity.

  19. Structure and magnetic properties of bulk nanocrystalline Nd-Fe-B permanent magnets prepared by hot pressing and hot deformation

    Institute of Scientific and Technical Information of China (English)

    SONG Jie; YUE Ming; ZUO Jianhua; ZHANG Zirui; LIU Weiqiang; ZHANG Dongtao; ZHANG Jiuxing

    2013-01-01

    Structure and magnetic properties were studied for bulk nanocrystalline Nd-Fe-B permanent magnets that were prepared at 650 ℃ for 3 min under 300 MPa using the SPS-3.20-MK-V sintering machine and the hot pressed magnets were then submitted to hot deformation with height reduction of 50%,60%,70%,80%,and 85%.Effects of height reduction (HR) and deformation temperature on the structure and magnetic properties of the magnets were investigated.The crystal structure was evaluated by means of X-ray diffraction (XRD) and the microstructure was observed by transmission electron microscopy (TEM).The magnetic properties of the magnets were investigated by vibrating sample magnetometer (VSM).As the height reduction increased,the remanence (Br) of the magnets increased first,peaks at 1.3 T with HR=60%,then decreased again,and the coercivity (Hci) of the magnets decreased monotonically.On the other hand,as the deformation temperature increased,the Br of the magnets increased first,peaks at 1.36 T with HR=60%,then decreased again,and the Hci of the magnets decreased monotonically.Under optimal conditions,the hot deformed magnet possessed excellent magnetic properties as Br=l.36 T,Hci=1143 kA/m,and (BH)max=370 kJ/m3,suggesting the good potential of the magnets in practical applications.

  20. A method for sintering

    DEFF Research Database (Denmark)

    2012-01-01

    The present invention provides a method for sintering, comprising in the following order the steps of: providing a body in the green state or in the pre-sintered state on a support; providing a load on at least one spacer on the support such that the load is located above said body in the green...

  1. Fast Neutron Damage Studies on NdFeB Materials

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, S.; Spencer, J.; Wolf, Z.; /SLAC; Baldwin, A.; Pellett, D.; Boussoufi, M.; /UC, Davis

    2005-05-17

    Many materials and electronics need to be tested for the radiation environment expected at linear colliders (LC) since both accelerator and detectors will be subjected to large fluences of hadrons, leptons and {gamma}'s over the life of the facility [1]. While the linacs will be superconducting, there are still many uses for NdFeB in the damping rings, injection and extraction lines and final focus. Our understanding of the situation for rare earth, permanent magnet materials was presented at PAC03 [2]. Our first measurements of fast neutron, stepped doses at the UC Davis McClellan Nuclear Reactor Center (UCD MNRC) were presented at EPAC04 [3]. We have extended the doses, included other manufacturer's samples, and measured induced radioactivities which are discussed in detail.

  2. Fast Neutron Damage Studies on NdFeB Materials

    CERN Document Server

    Spencer, James; Baldwin, A; Boussoufi, Moe; Pellet, David; Volk, James T; Wolf, Zachary

    2005-01-01

    Many materials and electronics need to be tested for the radiation environment expected at linear colliders (LC) where the accelerator and detectors will be subjected to large fluences of hadrons, leptons and gammas over the life of the facility. Although the linacs will be superconducting, there are still many potential uses for NdFeB in the damping rings, injection and extraction lines and final focus. Our understanding of the radiation damage situation for rare earth permanent magnet materials was presented at PAC2003 and our first measurements of fast neutron, stepped doses at the UC Davis McClellan Nuclear Reactor Center (UCD MNRC) were presented at EPAC2004 where the damage appeared proportional to the distances between the effective operating points and Hc. Here we have extended those doses and included more commercial samples together with the induced radioactivities associated with their respective dopants. Hall probe data for the external induction distributions are compared with vector magnetizatio...

  3. Sintered Superhard Materials

    Science.gov (United States)

    Wentorf, R. H.; Devries, R. C.; Bundy, F. P.

    1980-05-01

    Diamond or cubic boron nitride particles can be sintered into strong masses at high temperatures and very high pressures at which these crystalline forms are stable. Most of the desirable physical properties of the sintered masses, such as hardness and thermal conductivity, approach those of large single crystals; their resistance to wear and catastrophic splitting is superior. The sintered masses are produced on a commercial scale and are increasingly used as cutting tools on hard or abrasive materials, as wire-drawing dies, in rock drills, and in special high-pressure apparatus.

  4. Corrosion of rapidly solidified neodymium-iron-boron (Nd-Fe-B) permanent magnets and protection via sacrificial zinc coatings

    Energy Technology Data Exchange (ETDEWEB)

    Attanasio, S.A. [Massachusetts Inst. of Tech., Cambridge (United States). Dept. of Materials Science and Engineering; Latanision, R.M. [Massachusetts Inst. of Tech., Cambridge (United States). Dept. of Materials Science and Engineering

    1995-07-15

    Rapidly solidified Nd-Fe-B alloys were found to corrode actively at open circuit in aerated Na{sub 2}SO{sub 4} and NaCl at 30 C and 80 C. Estimated penetration rates (greater than 27 mil year{sup -1}) indicate the need for corrosion control methods.The use of sacrificial zinc coatings in controlling the corrosion of Nd-Fe-B alloys may have previously been overlooked because of two potential limitations: incomplete protection and hydrogen damage. The electrochemical activity of Nd may prevent zinc from providing complete sacrificial protection to Nd-Fe-B at breaks in the coating, and cracking could occur when hydrogen production is galvanically stimulated on Nd-Fe-B at breaks in the coating.This study focuses on the evaluation of the protection conferred to Nd-Fe-B when a Zn/Nd-Fe-B galvanic couple is formed due to coating penetration. Quantitative solution analysis was used to demonstrate that the dissolution of Nd, Fe and B is essentially prevented by the galvanic coupling of Nd-Fe-B to zinc in NaCl at 25 C. Galvanic coupling to zinc also reduces the rate of environmentally assisted cracking of Nd-Fe-B. Sacrificial zinc coatings appear to be a viable, cost-effective corrosion control method for Nd-Fe-B, and the limitations described above should not preclude their use in this application. (orig.)

  5. Microstructure and Magnetic Properties of NdFeB Films through Nd Surface Diffusion Process

    Directory of Open Access Journals (Sweden)

    Wenfeng Liu

    2017-01-01

    Full Text Available Ta/Nd/NdFeB/Nd/Ta films were deposited by magnetron sputtering on Si (100 substrates and subsequently annealed for 30 min at 923 K in vacuum. It was found that the microstructure and magnetic properties of Ta/Nd/NdFeB/Nd/Ta films strongly depend on the NdFeB layer thickness. With NdFeB layer thickness increasing, both the grain size and the strain firstly reduce and then increase. When NdFeB layer thickness is 750 nm, the strain reaches the minimum value. Meanwhile, both the in-plane and perpendicular coercivities firstly drastically increase and then slowly decrease with NdFeB layer thickness increasing. The highest in-plane and perpendicular coercivities can be obtained at NdFeB layer thickness of 750 nm, which are 21.2 kOe and 19.5 kOe, respectively. In addition, the high remanence ratio (remanent magnetization/saturation magnetization of 0.87 can also be achieved in Ta/Nd/NdFeB (750 nm/Nd/Ta film.

  6. Analysis of thermal demagnetization behavior of Nd–Fe–B sintered magnets using magnetic domain observation

    Directory of Open Access Journals (Sweden)

    Masaaki Takezawa

    2016-05-01

    Full Text Available We used magnetic domain observation to statistically observe the thermal demagnetization behavior of Nd–Fe–B sintered magnets at elevated temperatures up to 150 °C. Simultaneous magnetization reversal in a hundred adjacent grains occurred at 90 °C because of the magnetic interaction among the grains beyond grain boundaries in the Dysprosium (Dy-free low-coercivity magnet. Conversely, simultaneous magnetization reversal in a hundred grains did not occur in the Dy-added high-coercivity magnets, and the demagnetizing ratio steadily increased with temperature. Furthermore, the addition of Dy induced high thermal stability by eliminating the simultaneous thermal demagnetization, which was caused by the magnetic interaction among the grains.

  7. Sintering Theory and Practice

    Science.gov (United States)

    German, Randall M.

    1996-01-01

    Although sintering is an essential process in the manufacture of ceramics and certain metals, as well as several other industrial operations, until now, no single book has treated both the background theory and the practical application of this complex and often delicate procedure. In Sintering Theory and Practice, leading researcher and materials engineer Randall M. German presents a comprehensive treatment of this subject that will be of great use to manufacturers and scientists alike. This practical guide to sintering considers the fact that while the bonding process improves strength and other engineering properties of the compacted material, inappropriate methods of control may lead to cracking, distortion, and other defects. It provides a working knowledge of sintering, and shows how to avoid problems while accounting for variables such as particle size, maximum temperature, time at that temperature, and other problems that may cause changes in processing. The book describes the fundamental atomic events that govern the transformation from particles to solid, covers all forms of the sintering process, and provides a summary of many actual production cycles. Building from the ground up, it begins with definitions and progresses to measurement techniques, easing the transition, especially for students, into advanced topics such as single-phase solid-state sintering, microstructure changes, the complications of mixed particles, and pressure-assisted sintering. German draws on some six thousand references to provide a coherent and lucid treatment of the subject, making scientific principles and practical applications accessible to both students and professionals. In the process, he also points out and avoids the pitfalls found in various competing theories, concepts, and mathematical disputes within the field. A unique opportunity to discover what sintering is all about--both in theory and in practice What is sintering? We see the end product of this thermal

  8. Investigation Procedure of Magnetic Performances of NdFeB Permanent Magnets

    DEFF Research Database (Denmark)

    Calin, Marius-Daniel; Helerea, Elena; Ritchie, Ewen

    2011-01-01

    The permanent magnet applications based on carbon steel magnets, hard ferrites and AlNiCo magnets classes are renewed with new classes of advanced magnetic materials based on rare earth elements, the Sm-Co and NdFeB types. Performance increase of the hard magnetic materials and their use...... in specific applications impose also great advances in the field of magnetic measurement. New researches need to be validated in order to investigate the NdFeB permanent magnets performances, including their stability under different thermal operational regimes. In this paper a specific investigation...... procedure of magnetic performances of NdFeB permanent magnets in correlation with the range of operating temperature is proposed based on modern hysteresisgraph method and impulse magnetization technique....

  9. Net Shape 3D Printed NdFeB Permanent Magnet

    CERN Document Server

    Jacimovic, J; Herrmann, L G; Greuter, F; Genta, J; Calvo, M; Tomse, T; Simon, R A

    2016-01-01

    For two decades, NdFeB based magnets have been a critical component in a range of electrical devices engaged in energy production and conversion. The magnet shape and the internal microstructure of the selected NdFeB grade govern their efficiency and size. However, stricter requirements on device efficiency call for better performing magnets preferably with novel functionality not achievable today. Here we use 3D metal printing by Selective Laser Melting to fabricate dense net shape permanent magnets based on NdFeB that exhibit high magnetic performance. Evidence is provided that the internal microstructure, not achievable by traditional manufacturing means, is the origin of the solid magnetic properties. The freedom in magnet body shape and size that ranges from the millimeter to tens of centimeter scale opens up a design freedom that could be a catalyzer for the next generation of electrical devices.

  10. Direct Iron Coating onto Nd-Fe-B Powder by Thermal Decomposition of Iron Pentacarbonyl

    Energy Technology Data Exchange (ETDEWEB)

    Yamamuro, S; Okano, M; Tanaka, T [Department of Materials Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan); Sumiyama, K [Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Nozawa, N; Nishiuchi, T; Hirosawa, S [Magnetic Materials Research Laboratory, NEOMAX Company, Hitachi Metals, Ltd., Osaka 618-0013 (Japan); Ohkubo, T, E-mail: yamamuro@eng.ehime-u.ac.jp [Magnetic Materials Center, National Institute for Materials Science, Tsukuba 305-0047 (Japan)

    2011-01-01

    Iron-coated Nd-Fe-B composite powder was prepared by thermal decomposition of iron pentacarbonyl in an inert organic solvent in the presence of alkylamine. Though this method is based on a modified solution-phase process to synthesize highly size-controlled iron nanoparticles, it is in turn featured by a suppressed formation of iron nanoparticles to achieve an efficient iron coating solely onto the surfaces of rare-earth magnet powder. The Nd-Fe-B magnetic powder was successfully coated by iron shells whose thicknesses were of the order of submicrometer to micrometer, being tuneable by the amount of initially loaded iron pentacarbonyl in a reaction flask. The amount of the coated iron reached to more than 10 wt.% of the initial Nd-Fe-B magnetic powder, which is practically sufficient to fabricate Nd-Fe-B/{alpha}-Fe nanocomposite permanent magnets.

  11. Effective anisotropy and coercivity in nanocrystalline single-phase NdFeB permanent magnetic material

    Institute of Scientific and Technical Information of China (English)

    韩广兵; 高汝伟; 冯维存; 刘汉强; 王标; 张鹏; 陈伟; 李卫; 郭永权

    2003-01-01

    The effect of exchange-coupling interaction on the effective anisotropy and its varying tendency in nanocrystalline single-phase NdFeB permanent magnetic material have been investigated. The results show that the exchange-coupling interaction between grains makes the effective anisotropy of material, Keff, decrease with the reduction of grain size. The variation of Keff is basically the same as that of coercivity. The decrease in effective anisotropy is the main reason of the reduction of coercivity for nanocrystalline single-phase NdFeB permanent magnetic material. In order to get high anisotropy and coercivity in nanocrystalline single-phase NdFeB permanent material, the grain size should be larger than 35 nm.

  12. Examination and Research of the Surface Topography of Ultrasonic Vibration Honing Nd-Fe-B

    Institute of Scientific and Technical Information of China (English)

    Xi-jing ZHU; Zhi-meng LU; Jian-qing WANG; Quan CHENG

    2010-01-01

    The mechanism of ultrasonic vibration honing Nd-Fe-B has been briefly elaborated after the introduction of the strategic significanoe of processing Nd-Fe-B.Based on the formation principle of Scanning Electrvnic NTicroscope (SFM),and at the exarrnination with the aid of SEM to the ultrasonic vibration honing Nd-Fe-B materials superficial microscopic topography,the paper discusses the new processing mechanism according to the SFM examination picture.The research indicates that as a result of supersonic high frequency vibration,the path of the abrasion extends at the same time,and the supersonic cavitation effect fonts the intense shock-wave,impacting Nd-Fe-B material's internal surface,providing the supersonic energy for the superficial abrasive dust's elimination,which directly explain tat the honing processing efficiency is entranced,and the processing surface rwghness is high.

  13. Designing a Virtual laboratory for Simulating to Production of Nanocomposite NdFeB Magnets

    Directory of Open Access Journals (Sweden)

    Musa Faruk Çakir

    2014-02-01

    Full Text Available The talent figure for a permanent magnet is the multiplication of the maximum energy (BHmax. Less volume magnet is required for the production of magnet flux density if the BHmax value is higher. Mathematical functions are obtained from the data related to resiudal flux density, magnetic coercitivy, permanent magnet flux product capability, Curie temperature and density which were obtained as a result of the studies on different NdFeB alloys in the laboratory. Besides this, mathematical functions of NdFeB hard magnet’s resiudal flux density are obtained by adding elements. In this study, a virtual laboratory for producing nanocompositedNdFeB magnet has been designed. The virtual laboratory software has been used to simulate NdFeB hard magnets for industrial utilities.

  14. Multiple magnetic scattering in small-angle neutron scattering of Nd-Fe-B nanocrystalline magnet.

    Science.gov (United States)

    Ueno, Tetsuro; Saito, Kotaro; Yano, Masao; Ito, Masaaki; Shoji, Tetsuya; Sakuma, Noritsugu; Kato, Akira; Manabe, Akira; Hashimoto, Ai; Gilbert, Elliot P; Keiderling, Uwe; Ono, Kanta

    2016-06-20

    We have investigated the influence of multiple scattering on the magnetic small-angle neutron scattering (SANS) from a Nd-Fe-B nanocrystalline magnet. We performed sample-thickness- and neutron-wavelength-dependent SANS measurements, and observed the scattering vector dependence of the multiple magnetic scattering. It is revealed that significant multiple scattering exists in the magnetic scattering rather than the nuclear scattering of Nd-Fe-B nanocrystalline magnet. It is considered that the mean free path of the neutrons for magnetic scattering is rather short in Nd-Fe-B magnets. We analysed the SANS data by the phenomenological magnetic correlation model considering the magnetic microstructures and obtained the microstructural parameters.

  15. Assessment of corrosion resistance of Nd-Fe-B magnets by silanization for orthodontic applications

    Science.gov (United States)

    Fabiano, F.; Celegato, F.; Giordano, A.; Borsellino, C.; Bonaccorsi, L.; Calabrese, L.; Tiberto, P.; Cordasco, G.; Matarese, G.; Fabiano, V.; Azzerboni, B.

    2014-02-01

    Nd-Fe-B permanent magnets are characterised by excellent magnetic properties. However, being extremely vulnerable to the attack of both climate and corrosive environments, their applications are limited. This paper describes how, at different thicknesses of N-propyl-trimetoxy-silane, the coating affects the magnetic force of nickel plated magnets. We also investigate if the corrosion resistance of silanized Nd-Fe-B magnets increases in mildly corrosive environments by immersing them in a synthetic saliva solution. It was found that the silanization treatment does not affect the strength of the magnetic force and provide an enhancement of the corrosion resistance of the substrate.

  16. Dipolar energy of Nd-Fe-B nanocrystalline magnets in magnetization reversal process

    Science.gov (United States)

    Ohtori, Hiroyuki; Iwano, Kaoru; Mitsumata, Chiharu; Yano, Masao; Kato, Akira; Shoji, Tetsuya; Manabe, Akira; Ono, Kanta

    2014-05-01

    We analyzed the dipolar energy of Nd-Fe-B nanocrystalline magnets in magnetization reversal process through visualizing magnetic dipolar interaction. We obtained magnetization distribution images experimentally by using scanning transmission X-ray microscopy (STXM). The magnetic dipolar interaction was calculated by the interaction between the magnetization at each point and those at the other points on the STXM image. We showed the dipolar energy in the nanocrystalline Nd-Fe-B magnets and compared it with the exchange energy at various applied fields. Our results indicated the significance of the dipolar energy in magnetization reversal process.

  17. Sintering of calcium phosphate bioceramics.

    Science.gov (United States)

    Champion, E

    2013-04-01

    Calcium phosphate ceramics have become of prime importance for biological applications in the field of bone tissue engineering. This paper reviews the sintering behaviour of these bioceramics. Conventional pressureless sintering of hydroxyapatite, Ca10(PO4)6(OH)2, a reference compound, has been extensively studied. Its physico-chemistry is detailed. It can be seen as a competition between two thermally activated phenomena that proceed by solid-state diffusion of matter: densification and grain growth. Usually, the objective is to promote the first and prevent the second. Literature data are analysed from sintering maps (i.e. grain growth vs. densification). Sintering trajectories of hydroxyapatite produced by conventional pressureless sintering and non-conventional techniques, including two-step sintering, liquid phase sintering, hot pressing, hot isostatic pressing, ultrahigh pressure, microwave and spark plasma sintering, are presented. Whatever the sintering technique may be, grain growth occurs mainly during the last step of sintering, when the relative bulk density reaches 95% of the maximum value. Though often considered very advantageous, most assisted sintering techniques do not appear very superior to conventional pressureless sintering. Sintering of tricalcium phosphate or biphasic calcium phosphates is also discussed. The chemical composition of calcium phosphate influences the behaviour. Similarly, ionic substitutions in hydroxyapatite or in tricalcium phosphate create lattice defects that modify the sintering rate. Depending on their nature, they can either accelerate or slow down the sintering rate. The thermal stability of compounds at the sintering temperature must also be taken into account. Controlled atmospheres may be required to prevent thermal decomposition, and flash sintering techniques, which allow consolidation at low temperature, can be helpful.

  18. SinterHab

    Science.gov (United States)

    Rousek, Tomáš; Eriksson, Katarina; Doule, Ondřej

    2012-05-01

    This project describes a design study for a core module on a Lunar South Pole outpost, constructed by 3D printing technology with the use of in-situ resources and equipped with a bio-regenerative life support system. The module would be a hybrid of deployable (CLASS II) and in-situ built (CLASS III) structures. It would combine deployable membrane structures and pre-integrated rigid elements with a sintered regolith shell for enhanced radiation and micrometeorite shielding. The closed loop ecological system would support a sustainable presence on the Moon with particular focus on research activities. The core module accommodates from four to eight people, and provides laboratories as a test bed for development of new lunar technologies directly in the environment where they will be used. SinterHab also includes an experimental garden for development of new bio-regenerative life support system elements. The project explores these various concepts from an architectural point-of-view particularly, as they constitute the building, construction and interior elements. The construction method for SinterHab is based on 3D printing by sintering of the lunar regolith. Sinterator robotics 3D printing technology proposed by NASA JPL enables construction of future generations of large lunar settlements with little imported material and the use of solar energy. The regolith is processed, placed and sintered by the Sinterator robotics system which combines the NASA ATHLETE and the Chariot remotely controlled rovers. Microwave sintering creates a rigid structure in the form of walls, vaults and other architectural elements. The interior is coated with a layer of inflatable membranes inspired by the TransHab project. The life-support system is mainly bio-regenerative and several parts of the system are intrinsically multifunctional and serve more than one purpose. The plants for food production are also an efficient part of atmosphere revitalization and water treatment. Moreover

  19. Flash sintering of ceramic materials

    OpenAIRE

    Dancer, C. E. J.

    2016-01-01

    During flash sintering, ceramic materials can sinter to high density in a matter of seconds while subjected to electric field and elevated temperature. This process, which occurs at lower furnace temperatures and in shorter times than both conventional ceramic sintering and field-assisted methods such as spark plasma sintering, has the potential to radically reduce the power consumption required for the densification of ceramic materials. This paper reviews the experimental work on flash sint...

  20. Reduction in Flux Loss of an Nd-Fe-B Bonded Ring Magnet for an SPM Motor

    OpenAIRE

    Yanai, Takeshi; Horita, Satoshi; Nakano, Masaki; Tsutsumi, Shinichi; Fukunaga, Hirotoshi

    2014-01-01

    We have previously proposed a simulation method of an initial flux loss in permanent magnets using finite element method, and confirmed that predicted flux loss of an Nd-Fe-B boned ring magnet showed good agreement with measured flux loss. In this paper, we applied our proposed method to an Nd-Fe-B boned ring magnet in an SPM motor. We modeled a rotor composed of an Nd-Fe-B bonded ring magnet and a soft magnetic core made from silicon steels, and carried out the simulations for magnetizing pr...

  1. Production of Nd-Fe-B alloys by mechanical alloying; Mechanical alloying ni yoru Nd-Fe-B gokin no sakusei

    Energy Technology Data Exchange (ETDEWEB)

    Saito, T. [Chiba Inst. of Tech., Narashino (Japan)

    1998-07-01

    Nb-Fe-B system magnet known as a high performance permanent magnet is produced by powder metallurgy and quench solidification methods. At present, although for a magnetic powder for Nd-Fe-B magnet an isotropic powder coarsely crashed after conducting heat treatment to and Nd-Fe-B amorphous thin belt produced by melt-spin method, research and development on an anisotropic magnetic powder are being propagated earnestly for magnetic powder with high magnetic property alternating with this. For a new producing method of magnetic powder alternating with the melt spin method, manufacturing methods using mechanical alloying method and using hydrogen storing feature of the Nd-Fe-B alloy called HDDR method are studied. In this study, mechanical alloying of mixed powders of Nd, Fe and B was conducted under hydrogen or nitrogen atmosphere to investigate the reaction to atmospheric gas such as hydrogen, nitrogen and so forth. And, by conducting the obtained powders to vacuum treatment, it was also investigated if Nd2Fe14B ferromagnetic phase formed or not. 9 refs., 6 figs.

  2. Material Flow Analysis of NdFeB magnets for Denmark: A comprehensive waste flow sampling and analysis approach

    DEFF Research Database (Denmark)

    Habib, Komal; Schibye, Peter Klausen; Vestbø, Andreas Peter

    2014-01-01

    Neodymium-iron-boron (NdFeB) magnets have become highly desirable for modern hi-tech applications. These magnets, in general, contain two key Rare Earth Elements (REEs) i.e. neodymium (Nd) and dysprosium (Dy), which are responsible for the very high strength of these magnets allowing for consider......Neodymium-iron-boron (NdFeB) magnets have become highly desirable for modern hi-tech applications. These magnets, in general, contain two key Rare Earth Elements (REEs) i.e. neodymium (Nd) and dysprosium (Dy), which are responsible for the very high strength of these magnets allowing...... of stocks and flows of NdFeB magnets in Denmark. A novel element of this study is the value added to the traditionally practiced MFAs at national and/or global level by complementing them with a comprehensive sampling and elemental analysis of NdFeB magnets, taken out from a sample of 157 different products...

  3. Effect of pretreating technologies on the adhesive strength and anticorrosion property of Zn coated NdFeB specimens

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Pengjie [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Earth-Panda Advance Magnetic Material Co. Ltd., Hefei (China); Anhui Province Key Laboratory of Rare Earth Permanent Magnet Materials, Hefei (China); State Key Laboratory of Rare Earth Permanent Magnet Materials (Earth-Panda Advance Magnetic Material Co., Ltd.), Hefei (China); Xu, Guangqing, E-mail: gqxu1979@hfut.edu.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Liu, Jiaqin [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Yi, Xiaofei [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Earth-Panda Advance Magnetic Material Co. Ltd., Hefei (China); Anhui Province Key Laboratory of Rare Earth Permanent Magnet Materials, Hefei (China); State Key Laboratory of Rare Earth Permanent Magnet Materials (Earth-Panda Advance Magnetic Material Co., Ltd.), Hefei (China); Wu, Yucheng, E-mail: ycwu@hfut.edu.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Chen, JingWu [Earth-Panda Advance Magnetic Material Co. Ltd., Hefei (China); Anhui Province Key Laboratory of Rare Earth Permanent Magnet Materials, Hefei (China); State Key Laboratory of Rare Earth Permanent Magnet Materials (Earth-Panda Advance Magnetic Material Co., Ltd.), Hefei (China)

    2016-02-15

    Graphical abstract: Zn coated NdFeB specimens pretreated with different technologies possess different adhesive strengths and anticorrosion properties. And the combined technology of sandblasting and pickling (5 s) achieves the best comprehensive performance. - Highlights: • Zn coated NdFeB specimens are achieved with different pretreating technologies. • Combined technology possesses the highest adhesive strength. • Combined technology possesses excellent anticorrosion property. - Abstract: Zinc coated NdFeB specimens were prepared with different pretreating technologies, such as polishing, pickling (50 s), sandblasting and combined technology of sandblasting and pickling (5 s). Morphologies of the NdFeB substrates pretreated with different technologies were observed with a scanning electron microscope equipped with an energy dispersive spectrometer and an atomic force microscope. The tensile test was performed to measure the adhesive strength between Zn coating and NdFeB substrate. The self-corrosion behavior of the NdFeB specimen was characterized by potentiodynamic polarization curve. The anticorrosion properties of Zn coated NdFeB specimens were characterized by neutral salt spray tests. The pretreating technologies possess obvious impact on the adhesive strength and anticorrosion property of Zn coated NdFeB specimens. Combined pretreating technology of sandblasting and pickling (5 s) achieves the highest adhesive strength (25.56 MPa) and excellent anticorrosion property (average corrosion current density of 21 μA/cm{sup 2}) in the four pretreating technologies. The impacting mechanisms of the pretreating technology on the adhesive strength and anticorrosion properties are deeply discussed.

  4. Future directions in sintering research

    Directory of Open Access Journals (Sweden)

    Upadhyaya G.S.

    2011-01-01

    Full Text Available From time to time, the gap between sintering science and technology is being attempted to be bridged, but there are still a number of unresolved issues in sintering. So far, only thermal energy was considered for accomplishing sintering of a powder compact. However, other sources of energy may be treated exclusively or in combination with others to achieve densification. The main goal is to tailor the material properties during sintering through microstructural modifications. But in doing so, the very chemical nature of the material subjected to sintering needs to be considered. It is at this stage that the role of electronic structure comes into picture. The present paper reviews this aspect and proposes how the studies on nano-crystalline materials are able to validate the very basic electronic processes occurring during sintering.

  5. Flash sintering of ceramic materials

    Science.gov (United States)

    Dancer, C. E. J.

    2016-10-01

    During flash sintering, ceramic materials can sinter to high density in a matter of seconds while subjected to electric field and elevated temperature. This process, which occurs at lower furnace temperatures and in shorter times than both conventional ceramic sintering and field-assisted methods such as spark plasma sintering, has the potential to radically reduce the power consumption required for the densification of ceramic materials. This paper reviews the experimental work on flash sintering methods carried out to date, and compares the properties of the materials obtained to those produced by conventional sintering. The flash sintering process is described for oxides of zirconium, yttrium, aluminium, tin, zinc, and titanium; silicon and boron carbide, zirconium diboride, materials for solid oxide fuel applications, ferroelectric materials, and composite materials. While experimental observations have been made on a wide range of materials, understanding of the underlying mechanisms responsible for the onset and latter stages of flash sintering is still elusive. Elements of the proposed theories to explain the observed behaviour include extensive Joule heating throughout the material causing thermal runaway, arrested by the current limitation in the power supply, and the formation of defect avalanches which rapidly and dramatically increase the sample conductivity. Undoubtedly, the flash sintering process is affected by the electric field strength, furnace temperature and current density limit, but also by microstructural features such as the presence of second phase particles or dopants and the particle size in the starting material. While further experimental work and modelling is still required to attain a full understanding capable of predicting the success of the flash sintering process in different materials, the technique non-etheless holds great potential for exceptional control of the ceramic sintering process.

  6. Some Character of Application of Nd-Fe-B Permanent Magnet

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The character of application of Nd-Fe-B permanent magnet is characterized in an irreversible loss of magnetic flux in the various environment conditions. According to the size of permanent magnet in the various environment conditions the irreversible loss of the permanent magnets is very different. Therefore, the irreversible loss and the application method according to the size of permanent magnets and the intervals in the magnetic system are discussed.

  7. Effects of Fe fine powders doping on hot deformed NdFeB magnets

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Min, E-mail: linm@nimte.ac.cn [Ningbo Institute of Material Technology & Engineering Chinese Academy of Science, Ningbo 315201 (China); Wang, Huijie [Ningbo Jinji Strong Magnetic Material Company, Ningbo 315041 (China); Zheng, Jingwu [Zhejiang University of Technology, Hangzhou 310014 (China); Yan, Aru [Ningbo Institute of Material Technology & Engineering Chinese Academy of Science, Ningbo 315201 (China)

    2015-04-01

    The composite NdFeB magnets with blending melt-spun flakes and Fe fine powders were prepared by the hot-pressed and hot-deformed route. Characterizations of the hot-deformed NdFeB magnets affected by the doped Fe powders were tested. The doped Fe powders decrease the hot-deformed pressure when the strain is between 15 and 50%. XRD patterns show that the doped Fe powders have little influence on the c-axis alignment of hot-deformed NdFeB magnets in the press direction. The B{sub r} and the (BH){sub max} get improved when the doped Fe powders are less than 3 wt%. The doped Fe of hot-deformed NdFeB magnets exists in the elongated state and the spherical state surrounded by the Nd-rich phase. With the Fe fraction increasing, the potential of magnet moves to the positive direction and the diameter of the Nyquist arc becomes larger, which indicate that the corrosion resistance improved effectively. The bending strength was enhanced by the elongated α-Fe phase embedded in the matrix 2:14:1 phase. - Highlights: • The doped Fe powders have little influence on the c-axis alignment of magnets. • The elongated Fe powders are more than the spherical Fe powders in the magnets. • The corrosion resistance is improved effectively with the increasing Fe fraction. • The bending strength is enhanced by the elongated α-Fe phase embedded in the matrix.

  8. Study on Characteristics of Crystal Growth of NdFeB Cast Alloys

    Institute of Scientific and Technical Information of China (English)

    李波; 郭炳麟; 王东玲; 刘涛; 喻晓军

    2004-01-01

    The characteristic of crystal growth of NdFeB cast alloys was studied.It is found that the crystal growth orientation of conventional ingots is along or .As the cooling rate increases,the crystallization orientation changes from a axis to c axis,along which the grain is easy to be magnetized.Meanwhile,by analyzing the change of crystallization orientation,the influence on the property of magnets was discussed.

  9. Modification of the Interface Nanostructure and Magnetic Properties in Nd-Fe-B Thin Films.

    Science.gov (United States)

    Koike, Kunihiro; Kusano, Takanao; Ogawa, Daisuke; Kobayashi, Keisuke; Kato, Hiroaki; Oogane, Mikihiko; Miyazaki, Takamichi; Ando, Yasuo; Itakura, Masaru

    2016-12-01

    The effects of Nd2Fe14B grain size and Nd coating on the coercivity in sputter-deposited Nd-Fe-B/Nd thin films have been investigated in order to gain an insight into the coercivity mechanism of Nd-Fe-B magnets. Highly textured Nd2Fe14B particles were grown successfully on the MgO(100) single-crystal substrate with the Mo underlayer. As the Nd-Fe-B layer thickness t NFB was decreased from 70 to 5 nm, the coercivity H c increased gradually from 6.5 to 16 kOe. By depositing the Nd overlayer onto these films and post-annealing at 500 °C, the H c value further increased from 17.5 kOe (t NFB=70 nm) to 26.2 kOe (t NFB=5 nm). The amount of H c increase by the combination of the Nd coating and post-annealing was about 10 kOe irrespective of the t NFB value. These results therefore suggest an independence of size and interface effects on the coercivity of Nd-Fe-B magnets.

  10. Investigation of Optimal Megnetic Properties in NdFeB Magnets by Artificial Neural Network

    Institute of Scientific and Technical Information of China (English)

    Lian Lixian; Liu Ying; Hu Wang; Hou Tinghong; Gao Shengji; Tu Mingjing

    2004-01-01

    In order to study the effect of alloy component on magnetic properties of NdFeB magnets, the experiment schemes are carried out by the uniform design theory, and the relationship between the component and the magnetic properties is established by artificial neural network(ANN) predicting model.The element contents of alloys are optimized by the ANN model.Meanwhile, the influences of mono-factor or multi-factor interaction on alloy magnetic properties are respectively discussed according to the curves ploted by ANN model.Simulation result shows that the predicted and measured results are in good agreement.The relative error is every low, the error is not more than 1.68% for remanence Br, 1.56% for maximal energy product (BH)m, and 7.73% for coercivity Hcj.Hcj can be obviously improved and Br can be reduced by increasing Nd or Zr content.Co and B have advantageous effects on increasing Br and disadvantageous effects on increasing Hcj.Influence of alloying elements on Hcj and Br are inverse, and the interaction among the alloying elements play an important role in the magnetic properties of NdFeB magnets.The ANN prediction model presents a new approach to investigate the nonlinear relationship between the component and the magnetic properties of NdFeB alloys.

  11. Magnetostrictions and Magnetic Properties of Nd-Fe-B and SrFe12019

    Institute of Scientific and Technical Information of China (English)

    CHEN Hai-Ying; ZHANG Yan; YANG Yun-Bo; CHEN Xue-Gang; LIU Shun-Quan; WANG Chang-Sheng; YANG Ying-Chang; YANG Jin-Bo

    2011-01-01

    The magnetostrictions of polycrystalline Nd-Fe-B and Sr-ferrite at different temperatures are reinvestigated using a strain gauge rotating-sample method.It is found that the magnetostriction λs of Nd-Fe-B is +52× 10-6,and that of Sr-ferrite is -25×10-6 under a magnetic field of 8 T at room temperature.The maximum energy product (BH)max of the Nd-Fe-B magnet is improved when the powders are magnetically aligned perpendicular to the pressing direction,whereas that of the Sr-ferrite magnet is better when the powders are aligned parallel to the pressing direction.These experimental results suggest that the magnetostriction can generate compressive strain anisotropy resulting from the inverse effect of the magnetostriction.Thus,the magnetization of materials with a negative coefficient of magnetostriction are easier to be aligned normal to the stress direction,while for the materials with a positive coefficient of magnetostriction,the magnetization is easier to be aligned along the stress direction. Therefore,the magnetostriction anisotropy can be used to improve the alignment of the magnetic powders as well as the performance of the magnets.

  12. Binder Jetting: A Novel NdFeB Bonded Magnet Fabrication Process

    Science.gov (United States)

    Paranthaman, M. Parans; Shafer, Christopher S.; Elliott, Amy M.; Siddel, Derek H.; McGuire, Michael A.; Springfield, Robert M.; Martin, Josh; Fredette, Robert; Ormerod, John

    2016-07-01

    The goal of this research is to fabricate near-net-shape isotropic (Nd)2Fe14B-based (NdFeB) bonded magnets using a three dimensional printing process to compete with conventional injection molding techniques used for bonded magnets. Additive manufacturing minimizes the waste of critical materials and allows for the creation of complex shapes and sizes. The binder jetting process works similarly to an inkjet printer. A print-head passes over a bed of NdFeB powder and deposits a polymer binding agent to bind the layer of particles together. The bound powder is then coated with another layer of powder, building the desired shape in successive layers of bonded powder. Upon completion, the green part and surrounding powders are placed in an oven at temperatures between 100°C and 150°C for 4-6 h to cure the binder. After curing, the excess powder can be brushed away to reveal the completed "green" part. Green magnet parts were then infiltrated with a clear urethane resin to achieve the measured density of the magnet of 3.47 g/cm3 close to 46% relative to the NdFeB single crystal density of 7.6 g/cm3. Magnetic measurements indicate that there is no degradation in the magnetic properties. This study provides a new pathway for preparing near-net-shape bonded magnets for various magnetic applications.

  13. Physical and magnetic properties, microstructure of bonded magnet NdFeB prepared by using synthesis rubber

    Science.gov (United States)

    Suprapedi; Sardjono, P.; Muljadi

    2016-11-01

    The magnet permanent has been made by using NdFeB (NQP-B) powder with purity 99.90% and polymer rubber with purity 90%. This research was done to determine the effect of the polymer (rubber) composition as binder in the manufacture of bonded magnet NdFeB on physical properties, microstructure and magnetic properties. Bonded magnets are magnet material made from a mixture of magnetic powder as a filler and the polymer as a matrix material or as binder to bind the magnetic particles. The NdFeB (NQP-B) powder fractions of bonded magnets NdFeB investigated were as follows: a) 97 wt.% of NdFeB (NQP-B) and 3 wt.% of rubber,b) 95wt.% of NdFeB (NQP-B) and 5 wt.% of rubber, c) 93 wt.% of NdFeB (NQP-B) and 7 wt.% of rubber, d) 91 wt.% of NdFeB (NQP-B) and 9 wt.% of rubber. Both raw materials were mixed by using mixer until homogen with total weight about 16 g for each sample, then added 0.3 ml of catalyst and mixed again and put in dies mould and compacted at pressure 30 MPa, then dried for 2 hours at room temperature. The dried samples was characterized such as: bulk density measurement and magnetic properties by using BH-curve permeagraph. The bulk density values of the sample bonded NdFeB magnets using the binder 3% wt. and 5% wt. rubber are respectively 4,70 g/cm3 and 4.88 g/cm3. The result from BH- curve shows that the highest value of remanence (Br = 5.12 kGauss) is at sample with 3% wt. of rubber, but sample with 5% wt. of rubber has lowest value of remanance (Br = 4.40 kGauss). Based on the observation of the SEM photograph shown that the rubber material has been successfully covered the whole surface of the grain and fill some of the voids that are in the grain boundary.

  14. Material flow analysis of NdFeB magnets for Denmark: a comprehensive waste flow sampling and analysis approach.

    Science.gov (United States)

    Habib, Komal; Schibye, Peter Klausen; Vestbø, Andreas Peter; Dall, Ole; Wenzel, Henrik

    2014-10-21

    Neodymium-iron-boron (NdFeB) magnets have become highly desirable for modern hi-tech applications. These magnets, in general, contain two key rare earth elements (REEs), i.e., neodymium (Nd) and dysprosium (Dy), which are responsible for the very high strength of these magnets, allowing for considerable size and weight reduction in modern applications. This study aims to explore the current and future potential of a secondary supply of neodymium and dysprosium from recycling of NdFeB magnets. For this purpose, material flow analysis (MFA) has been carried out to perform the detailed mapping of stocks and flows of NdFeB magnets in Denmark. A novel element of this study is the value added to the traditionally practiced MFAs at national and/or global levels by complementing them with a comprehensive sampling and elemental analysis of NdFeB magnets, taken out from a sample of 157 different products representing 18 various product types. The results show that the current amount of neodymium and dysprosium in NdFeB magnets present in the Danish waste stream is only 3 and 0.2 Mg, respectively. However, this number is estimated to increase to 175 Mg of neodymium and 11.4 Mg of dysprosium by 2035. Nevertheless, efficient recovery of these elements from a very diverse electronic waste stream remains a logistic and economic challenge.

  15. Models of current sintering

    Science.gov (United States)

    Angst, Sebastian; Engelke, Lukas; Winterer, Markus; Wolf, Dietrich E.

    2017-06-01

    Densification of (semi-)conducting particle agglomerates with the help of an electrical current is much faster and more energy efficient than traditional thermal sintering or powder compression. Therefore, this method becomes more and more common among experimentalists, engineers, and in industry. The mechanisms at work at the particle scale are highly complex because of the mutual feedback between current and pore structure. This paper extends previous modelling approaches in order to study mixtures of particles of two different materials. In addition to the delivery of Joule heat throughout the sample, especially in current bottlenecks, thermoelectric effects must be taken into account. They lead to segregation or spatial correlations in the particle arrangement. Various model extensions are possible and will be discussed.

  16. Biomass for iron ore sintering

    Energy Technology Data Exchange (ETDEWEB)

    Zandi, M.; Martinez-Pacheco, M.; Fray, T.A.T. [Corus Research Development & Technology, Rotherham (United Kingdom)

    2010-11-15

    Within an integrated steelworks, iron ore sinter making is an energy intensive process. In recent years, biomass is becoming an attractive alternative source of energy to traditional fossil fuels such as coal. In this study, commercially available biomass materials suited to sinter making have been identified as an alternative source of fuel to coke breeze. Olive residues, sunflower husk pellets, almond shells, hazelnut shells and Bagasse pellets have been characterised and prepared for sintering. A laboratory sinter pot has been employed for studying sintering behaviour of biomass material. On average, the calorific values of selected biomass materials, on a dry basis, are about 65% of dry coke breeze. It was found that less of this energy would be available in sinter making due to the evaporation of some of the volatile matter ahead of the flame front. At a replacement rate of 25%, the crushed sunflower husk pellets showed the closest thermal profile to that of coke breeze alone in the size range of -0.8 to +0.6 mm. A specification of less than 1 mm has been recommended for the studied biomass materials when co-firing biomass with coke breeze for iron ore sintering.

  17. Sinterability and microstructure evolution during sintering of ferrous powder mixtures

    Directory of Open Access Journals (Sweden)

    Kétner Bendo Demétrio

    2013-01-01

    Full Text Available The present work is focused on ferrous powder metallurgy and presents some results of a development of a suitable masteralloy for use as an additive to iron powder for the production of sintered steels. The masteralloy was produced by melting a powder mixture containing approximately Fe + 20% Ni + 20% Mn + 20% Si + 1% C (wt%, in order to obtain a cast billet that was converted into fine powder by crushing and milling. It was observed presence of SiC in the masteralloy after melting that is undesirable in the alloy. Si element should be introduced by using ferrosilicon. Sintered alloys with distinct contents of alloying elements were prepared by mixing the masteralloy powder to plain iron powder. Samples were produced by die compaction of the powder mixtures and sintering at 1200 °C in a differential dilatometer in order to record their linear dimensional behaviour during heating up and isothermal sintering, aiming at studying the sinterability of the compacts. Microstructure development during sintering was studied by SEM, XRD and microprobe analyses.

  18. Mechanisms of Flash Sintering in Cubic Zirconia

    OpenAIRE

    Downs, John Axel

    2013-01-01

    The recently discovered flash sintering technique has shown that the application of a sufficiently large dc electric field (E-field) to a ceramic during sintering can cause sintering at temperatures several hundred degrees below conventional temperatures with sintering rates that allow for sintering in seconds rather than hours. This technique has already been demonstrated in wide range of ceramic materials including ionic conductors, electronic conductors, semi-conductors and insulators. Th...

  19. A route for recycling Nd from Nd-Fe-B magnets using Cu melts

    Energy Technology Data Exchange (ETDEWEB)

    Moore, Martina; Gebert, Annett, E-mail: a.gebert@ifw-dresden.de; Stoica, Mihai; Uhlemann, Margitta; Löser, Wolfgang

    2015-10-25

    Phase evolutions in Nd-Fe-B magnet/Cu systems have been explored with regard to Nd recycling. It was demonstrated that large scale phase separation into a ferromagnetic Fe(B)-rich ingot core with α-Fe main phase and a non-magnetic (Cu,Nd)-rich ingot rim takes place upon arc melting with Cu fractions ≥ 21.5 wt.-%. The re-solidification of the Nd{sub 2}Fe{sub 14}B magnet main phase is suppressed. The rim consists of the Cu{sub 2}Nd main phase and CuNd/Cu{sub 4}Nd minority phases in which Al traces from the magnetic material are gathered. Induction melting of such Nd-Fe-B/Cu mixtures can support the separation of these phase regions with very sharp boundaries. Main features of liquid phase separation and microstructure evolution have been interpreted on the basis of Nd-Fe-Cu phase diagram data. The key advantage with respect to Nd recycling from Nd-Fe-B permanent magnet scrap is the substantial accumulation of Nd in the (Cu,Nd)-rich region of the phase separated solidified specimen, which can be easily detached from the Fe-rich part by mechanical-magnetic treatments. Such portions contained up to ∼44 wt.-% Nd (25 at.-%) in first lab-scale experiments. Nd recovery from the (Cu,Nd)-rich fractions is possible by exploiting the large chemical property differences between the reactive rare earths elements and Cu. - Highlights: • phase evolution analysis in Nd-Fe-B magnet/Cu systems with regard to Nd recycling. • Cu ≥ 21 wt.-%, large scale phase separation- Fe(B)-rich ingot core, (Cu,Nd)-rich rim. • high Nd content (∼44 wt.-%) of (Cu,Nd)-rich region, mechanical-magnetic treatments.

  20. Magnetic properties of ND Rich Melt-Spun ND-FE-B alloy

    Directory of Open Access Journals (Sweden)

    Grujić Aleksandar

    2005-01-01

    Full Text Available As a part of these experimental investigations of melt-spun Nd-Fe-B alloy with Nd rich content in relation to Nd2Fe14B prepared by rapid quenching process for optimally selected cooling rate and heat treatment, the influence of the chosen chemical composition on magnetic properties was observed. The results of X-ray diffraction, Mössbauer spectroscopy phase analysis and magnetic measurement of investigated melt-spun Nd14.5Fe78.5B7 alloy are presented to bring some new information concerning the relation between their structure and magnetic properties.

  1. Study of Technology of Stripping Nickel Coating on NdFeB Permanent Magnet

    Institute of Scientific and Technical Information of China (English)

    Rao Houzeng; Li Guohua; Jiang Longfa; Lin Guanjie

    2004-01-01

    The influences of category and density of reagents, temperature and the value of pH in the solution of stripping the nickel coating on NdFeB permanent magnet on the stripping result were studied systematically.The practical formular contains mainly the oxidant m-O2NC6H4SO3Na, the complex reagent ( NaOOCCH2 ) 2N( CH2 ) 2N( CH2COOH)2,the reagent of retarding corrosion KF and the calatyze RL-3 was obtained.

  2. Micromagnetic Simulation of Demagnetization Curves for Single-Phase Nanocrystalline Nd-Fe-B Magnet

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The demangetization curves for the nanocrystalline Nd-Fe-B magnets of the stoichiometric com position were calculated by using the finite element technique of micromagnetism, The curve, especially iHc become smaller with increase of N. The most small iHc from a series of the curves along different field directions is closer to that for N=∞. iHc increases with increase of L. and are close or some what smaller than that the experimental values should be.

  3. Temperature stability and fracture toughness of Nd-Fe-B magnets

    Institute of Scientific and Technical Information of China (English)

    LI Ying; QI Yuxuan; LI Xiumei

    2006-01-01

    Temperature stability and toughness of magnets are very important properties especially for application in motor. In this paper, it is found that temperature stability and toughness of magnets are improved when Fe is substituted with Co andheavy rare earth is substituted for Nd in part and suitable rich B grain-boundary phase is added. In addition, heavy rare earth substitution decreases the remanence temperature coefficient greatly, but has a little effect on Curie temperature of the magnets, which is beneficial to Nd-Fe-B magnets for the application in motor.

  4. Magnetic and structural properties of spark plasma sintered nanocrystalline NdFeB-powders

    Energy Technology Data Exchange (ETDEWEB)

    Wuest, H., E-mail: holger.wuest@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Bommer, L., E-mail: lars.bommer@de.bosch.com [Robert Bosch GmbH, Postfach 10 60 50, 70049 Stuttgart (Germany); Weissgaerber, T., E-mail: thomas.weissgaerber@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Branch Lab Dresden, Winterbergstraße 28, 01277 Dresden (Germany); Kieback, B., E-mail: bernd.kieback@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Branch Lab Dresden, Winterbergstraße 28, 01277 Dresden (Germany); Technische Universität Dresden, Institute for Materials Science, Helmholtzstraße 7, 01069 Dresden (Germany)

    2015-10-15

    Near-stoichiometric NdFeB melt-spun ribbons have been subjected to spark plasma sintering varying the process temperature T{sub SPS} and pressure p{sub SPS} between 600 and 800 °C and 50–300 MPa, respectively. Produced bulk magnets were analyzed regarding microstructure and magnetic properties. For all samples the intrinsic coercivity H{sub c,J} gradually decreases with increasing sintering temperature and pressure, while residual induction B{sub r} increases simultaneously with sample density. Densities close to the theoretical limit were achieved for p{sub SPS}≥90 MPa and T{sub SPS}≥650 °C. With increasing T{sub SPS} precipitations of Nd-rich and Fe-rich phases have been observed as a result of a decomposition of the hard magnetic Nd{sub 2}Fe{sub 14}B phase. Under optimum sintering conditions of p{sub SPS}=300 MPa and T{sub SPS}=650 °C high-density bulk magnets with H{sub c,J}=652 kA/m, B{sub r}=0.86 T and (BH){sub max}=106 kJ/m{sup 3} have been produced. - Highlights: • Consolidation close to the theoretical density for p{sub SPS}≥90 MPa and T{sub SPS}≥650 °C. • Highest (BH){sub max} of 106 kJ/m{sup 3} for p{sub SPS}=300 MPa and T{sub SPS}=650 °C with 98% theo. • H{sub c,J} gradually decreases with increasing T{sub SPS}, while B{sub r} increases simultaneously with. • With increasing T{sub SPS}, Nd- and Fe-rich precipitations are observed. • Reduction in t{sub SPS} is economic but does not increase (BH){sub max} significantly.

  5. Magnetic domain structures of precipitation-hardened SmCo 2:17-type sintered magnets: Heat treatment effect

    Institute of Scientific and Technical Information of China (English)

    Li Xiu-Mei; Fang Yi-Kun; Guo Zhao-Hui; Liu Tao; Guo Yong-Quan; Li Wei; Han Bao-Shan

    2008-01-01

    The typical magnetic domains of Sm(CobalFe0.25Cu0.07Zr0.02)7.4 magnets quenched through various heat-treatment steps have been revealed by using magnetic force microscopy (MFM). For the specimens in which the nominal c-axis is perpendicular to the imaging plane, the domain configurations change from plate-like for the as-sintered mag-net to corrugation and spike-like for the homogenized one, and then to a coarse and finally to a finer domain structure when isothermally aged at 830℃ and then annealed at 400℃. However, only plate-like domains can be detected on the surfaces with the nominal c-axis parallel to the imaging plane. The finer domain (so-called interaction domain) is a characteristic magnetic domain pattern of the Sm-Co 2:17-type magnets with high coercivities. Domain walls in a zigzag shape are revealed by means of MFM in final bulk Sm-Co 2:17-type sintered magnets.

  6. Mechanical characteristics of microwave sintered silicon carbide

    Indian Academy of Sciences (India)

    S Mandal; A Seal; S K Dalui; A K Dey; S Ghatak; A K Mukhopadhyay

    2001-04-01

    The present work deals with the sintering of SiC with a low melting additive by microwave technique. The mechanical characteristics of the products were compared with that of conventionally sintered products. The failure stress of the microwave sintered products, in biaxial flexure, was superior to that of the products made by conventional sintering route in ambient condition. In firing of products by conventionally sintered process, SiC grain gets oxidized producing SiO2 (∼ 32 wt%) and deteriorates the quality of the product substantially. Partially sintered silicon carbide by such a method is a useful material for a varieties of applications ranging from kiln furniture to membrane material.

  7. Effect of mechanical attrition on microstructure and properties of electro-deposition coatings on NdFeB

    Institute of Scientific and Technical Information of China (English)

    董雪亮; 王德仁; 曾阳庆

    2014-01-01

    Surface mechanical attrition treatment (SMAT) was developed to synthesize nanostructure coatings on alloy surface. The SMAT action was applied in the process of Ni and Cu electroplating coatings on NdFeB substrates in this paper. The role of me-chanical attrition during barrel plating on the microstructure, mechanical and corrosion resistant properties of the coatings was exam-ined. The scanning electron microscopy (SEM) observation showed that the mechanical attrition could refine grain size, markedly smooth the coating surface and obviously decrease the number of pore in the coatings. The continuous collisions of glass balls onto the NdFeB samples could induce more beneficial nucleation defects on the coating, which was helpful for increasing nucleation sites and the nucleation rate. The mechanical attrition could also restrain the heterogeneous growth of the coating grain tips due to the abra-sive action of stainless steel balls. The Tafel polarization curve experimental results indicated that SMAT process could enhance the corrosion resistance of coatings on NdFeB. The scratching test revealed that the binding force between coating and NdFeB substrate could be improved dramatically with SMAT process.

  8. Isotropic and anisotropic nanocrystalline NdFeB bulk magnets prepared by binder-free high-velocity compaction technique

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Xiangxing [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Liu, Zhongwu, E-mail: zwliu@scut.edu.cn [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Yu, Hongya [School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640 (China); Xiao, Zhiyu [School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640 (China); Zhang, Guoqing [Science and Technology on Advanced High Temperature Structural Materials Laboratory, Beijing Institute of Aeronautical Materials, Beijing 100095 (China)

    2015-09-15

    NdFeB powders were consolidated into nanocrystalline bulk magnets by a near-net-shape process of high-velocity compaction (HVC) at room temperature with no binder employed. The nanostructure can be maintained after compaction. The compacted magnets with relatively high density can inherit the coercivity of the starting powders. The mechanical strength of the HVCed magnet after heat treatment is comparable to that of the conventional bonded NdFeB magnets. The anisotropic magnet has also been prepared by hot deformation using HVCed magnet as the precursor. The remanence value along the pressing direction increased from 0.64 to 0.95 T and maximum energy product (BH){sub max} increased from 65 to 120 kJ/m{sup 3} after hot deformation. The processing–structure–properties relationships for both isotropic and anisotropic magnets are discussed. - Highlights: • HVC is a feasible binder-free approach for preparing NdFeB magnets. • The compacted magnets can inherit the coercivity of the starting powders. • The magnets post heat treatment have compression strength higher than bonded magnets. • The approach of HVC is a potential pre-process for anisotropic NdFeB bulk magnets.

  9. Big Area Additive Manufacturing of High Performance Bonded NdFeB Magnets

    Science.gov (United States)

    Li, Ling; Tirado, Angelica; Nlebedim, I. C.; Rios, Orlando; Post, Brian; Kunc, Vlastimil; Lowden, R. R.; Lara-Curzio, Edgar; Fredette, Robert; Ormerod, John; Lograsso, Thomas A.; Paranthaman, M. Parans

    2016-10-01

    Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic properties are: intrinsic coercivity Hci = 688.4 kA/m, remanence Br = 0.51 T, and energy product (BH)max = 43.49 kJ/m3 (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. The present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials.

  10. Effect of microstructure on the coercivity of HDDR Nd-Fe-B permanent magnetic alloy

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The effect of the grain boundary microstructure on the anisotropy and coercivity was investigated in an HDDR Nd-Fe-B permanent magnetic alloy. Considering the special microstructure of its magnetic powder grain, an anisotropic theoretical model influenced simultaneously by the structure defect at the grain boundary and the exchange coupling interaction was put forward. The variations of the structure defect factors based on the nucleation and pinning mechanism with 2r0/lex (where r0 and lex are the defect thickness and the length of exchange coupling, respec-tively) were calculated. The results show that the coercivity mechanism of an HDDR Nd-Fe-B permanent magnetic alloy is greatly related to its microstructure defect at the grain boundary. For a fixed lex, when 2r0/lex < 1.67, the coercivity is controlled by the pinning mechanism; when 2r0/lex > 1.67, it is determined by the nucleation mechanism. The coercivity reaches the maximum when 2r0/lex = 1.67. The calcula-tion result is consistent well with the experimental result given by Morimoto et al.

  11. Study of Nd-Fe-B alloys with nonstoichiometric Nd content in optimal magnetic state

    Directory of Open Access Journals (Sweden)

    Ćosović V.

    2009-01-01

    Full Text Available Characterization of two rapid-quenched Nd-Fe-B alloys with nonstoichiometric Nd content in the optimized magnetic state was carried out using the X-ray diffractometry (XRD, 57Fe Mössbauer spectroscopic phase analysis (MS, electron microscopy (TEM, high resolution TEM (HREM and Superconducting Quantum Interference Device (SQUID magnetometer. The experimental results demonstrate the fundamental difference in the structure and magnetic properties of the two investigated alloys in the optimized magnetic state. The Nd-Fe-B alloy with the reduced Nd content (Nd4.5Fe77B18.5 was found to have the nanocomposite structure of Fe3B/Nd2Fe14B and partly α-Fe/Nd2Fe14B, with mean grain size below 30 nm. On the other side, the overstoichiometric Nd14Fe79B7 alloy has almost a monophase structure with the dominant content of the hard magnetic phase Nd2Fe14B (up to 95 wt. % and a mean crystallite size about 60 nm, as determined by XRD and TEM analysis. The results of magnetic measurements on SQUID magnetometer also suggest the nanocomposite structure of the Nd-low alloy and nanocrystalline decoupled structure of the Nd-rich alloy after the optimal heat treatment.

  12. Big Area Additive Manufacturing of High Performance Bonded NdFeB Magnets.

    Science.gov (United States)

    Li, Ling; Tirado, Angelica; Nlebedim, I C; Rios, Orlando; Post, Brian; Kunc, Vlastimil; Lowden, R R; Lara-Curzio, Edgar; Fredette, Robert; Ormerod, John; Lograsso, Thomas A; Paranthaman, M Parans

    2016-10-31

    Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm(3), and the room temperature magnetic properties are: intrinsic coercivity Hci = 688.4 kA/m, remanence Br = 0.51 T, and energy product (BH)max = 43.49 kJ/m(3) (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. The present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials.

  13. Big Area Additive Manufacturing of High Performance Bonded NdFeB Magnets

    Science.gov (United States)

    Li, Ling; Tirado, Angelica; Nlebedim, I. C.; Rios, Orlando; Post, Brian; Kunc, Vlastimil; Lowden, R. R.; Lara-Curzio, Edgar; Fredette, Robert; Ormerod, John; Lograsso, Thomas A.; Paranthaman, M. Parans

    2016-01-01

    Additive manufacturing allows for the production of complex parts with minimum material waste, offering an effective technique for fabricating permanent magnets which frequently involve critical rare earth elements. In this report, we demonstrate a novel method - Big Area Additive Manufacturing (BAAM) - to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic properties are: intrinsic coercivity Hci = 688.4 kA/m, remanence Br = 0.51 T, and energy product (BH)max = 43.49 kJ/m3 (5.47 MGOe). In addition, tensile tests performed on four dog-bone shaped specimens yielded an average ultimate tensile strength of 6.60 MPa and an average failure strain of 4.18%. Scanning electron microscopy images of the fracture surfaces indicate that the failure is primarily related to the debonding of the magnetic particles from the polymer binder. The present method significantly simplifies manufacturing of near-net-shape bonded magnets, enables efficient use of rare earth elements thus contributing towards enriching the supply of critical materials. PMID:27796339

  14. Melting and Sintering of Ashes

    DEFF Research Database (Denmark)

    Hansen, Lone Aslaug

    1997-01-01

    The thesis contains an experimental study of the fusion and sintering of ashes collected during straw and coal/straw co-firing.A laboratory technique for quantitative determination of ash fusion has been developed based on Simultaneous Thermal Analysis (STA). By means of this method the fraction...... of melt in the investigated ashes has been determined as a function of temperature. Ash fusion results have been correlated to the chemical and mineralogical composition of the ashes, to results from a standard ash fusion test and to results from sintering experiments. Furthermore, the ash fusion results......-firing, the model only had a qualitative agreement with the measured ash deposit formation rates.Sintering measurements were carried out by means of compression strength testing of ash pellets. This method showed to not be applicable for the salt rich fly ash derived from straw combustion. For the fly ashes...

  15. Recycling of mill scale in sintering process

    Directory of Open Access Journals (Sweden)

    El-Hussiny N.A.

    2011-01-01

    Full Text Available This investigation deals with the effect of replacing some amount of Baharia high barite iron ore concentrate by mill scale waste which was characterized by high iron oxide content on the parameters of the sintering process., and investigation the effect of different amount of coke breeze added on sintering process parameters when using 5% mill scale waste with 95% iron ore concentrate. The results of this work show that, replacement of iron ore concentrate with mill scale increases the amount of ready made sinter, sinter strength and productivity of the sinter machine and productivity at blast furnace yard. Also, the increase of coke breeze leads to an increase the ready made sinter and productivity of the sintering machine at blast furnace yard. The productivity of the sintering machine after 5% decreased slightly due to the decrease of vertical velocity.

  16. Microstructure and magnetic properties of backward extruded NdFeB ring magnets by the CAPA process

    Science.gov (United States)

    Kim, Hyoung-Tae; Kim, Yoon-Bae

    2004-06-01

    The inhomogeneity in microstructure and magnetic properties of a ring magnet prepared by backward extrusion with a current-applied pressure-assisted process has been investigated. The initial part (top part) of a ring magnet prepared by back extrusion shows a high coercivity which is comparable to the raw powder. It exhibits isotropic characteristics along the three orthogonal directions probably due to small deformation. The last part (bottom part) of the ring magnet has a a low coercivity with large grains because high current flows through the pressurized punches during the whole deformation process as to increase the temperature and grain growth. The middle part is under an appropriate deformation with short time exposure at high temperature, therefore it maintains a relatively high remanent polarization with high coercivity.

  17. Alternative sintering methods compared to conventional thermal sintering for inkjet printed silver nanoparticle ink

    Energy Technology Data Exchange (ETDEWEB)

    Niittynen, Juha, E-mail: juha.niittynen@tut.fi [Department of Electronics and Communications Engineering, Tampere University of Technology, Korkeakoulunkatu 3, 33720 Tampere (Finland); Abbel, Robert [Holst Centre, High Tech Campus 31, 5656 AE Eindhoven (Netherlands); Mäntysalo, Matti [Department of Electronics and Communications Engineering, Tampere University of Technology, Korkeakoulunkatu 3, 33720 Tampere (Finland); Perelaer, Jolke; Schubert, Ulrich S. [Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich-Schiller-University Jena, Humboldtstrasse 10, D-07743 Jena (Germany); Jena Center for Soft Matter (JCSM), Friedrich-Schiller-University Jena, Humboldtstrasse 10, D-07743 Jena (Germany); Lupo, Donald [Department of Electronics and Communications Engineering, Tampere University of Technology, Korkeakoulunkatu 3, 33720 Tampere (Finland)

    2014-04-01

    In this contribution several alternative sintering methods are compared to traditional thermal sintering as high temperature and long process time of thermal sintering are increasing the costs of inkjet-printing and preventing the use of this technology in large scale manufacturing. Alternative sintering techniques are evaluated based on the electrical and mechanical performance they enable on inkjet-printed structures as well as their potential feasibility for large scale manufacturing. Photonic sintering was identified as the most promising alternative to thermal sintering. - Highlights: • Comparison of alternative sintering techniques for large-scale electronics manufacturing • Laser, plasma and photonic sintering of nanoparticle silver ink tested • Electrical and mechanical properties of sintered inks tested • Microstructure analysis used to explain the different electrical and mechanical properties • Photonic sintering identified as the most promising alternative technique.

  18. Modeling the microstructural evolution during constrained sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Pryds, Nini

    A mesoscale numerical model able to simulate solid state constrained sintering is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element method for calculating stresses. The sintering behavior of a sample constrained by a rigid substrate ...

  19. Dislocation generation during early stage sintering.

    Science.gov (United States)

    Sheehan, J. E.; Lenel, F. V.; Ansell, G. S.

    1973-01-01

    Discussion of the effects of capillarity-induced stresses on dislocations during early stage sintering. A special version of Hirth's (1963) theoretical calculation procedures modified to describe dislocation nucleation on planes meeting the sintering body's neck surface obliquely is shown to predict plastic flow at stress levels know to exist between micron size metal particles in the early stages of sintering.

  20. Master Sintering Surface: A practical approach to its construction and utilization for Spark Plasma Sintering prediction

    Directory of Open Access Journals (Sweden)

    Pouchly V.

    2012-01-01

    Full Text Available The sintering is a complex thermally activated process, thus any prediction of sintering behaviour is very welcome not only for industrial purposes. Presented paper shows the possibility of densification prediction based on concept of Master Sintering Surface (MSS for pressure assisted Spark Plasma Sintering (SPS. User friendly software for evaluation of the MSS is presented. The concept was used for densification prediction of alumina ceramics sintered by SPS.

  1. Modeling the microstructural evolution during constrained sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Tikare, V.

    to the stress field as well as the FE calculation of the stress field from the microstructural evolution is discussed. The sintering behavior of two powder compacts constrained by a rigid substrate is simulated and compared to free sintering of the same samples. Constrained sintering result in a larger number......A numerical model able to simulate solid state constrained sintering of a powder compact is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element (FE) method for calculating stresses on a microstructural level. The microstructural response...

  2. Modeling the microstructural evolution during constrained sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Pryds, Nini

    2014-01-01

    as well as the FEM calculation of the stress field from the microstructural evolution is discussed. The sintering behavior of a sample constrained by a rigid substrate is simulated. The constrained sintering result in a larger number of pores near the substrate, as well as anisotropic sintering shrinkage......A numerical model able to simulate solid state constrained sintering is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element model (FEM) for calculating stresses on a microstructural level. The microstructural response to the local stress...

  3. Modeling the Microstructural Evolution During Constrained Sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Pryds, Nini

    2015-01-01

    as well as the FEM calculation of the stress field from the microstructural evolution is discussed. The sintering behavior of a sample constrained by a rigid substrate is simulated. The constrained sintering results in a larger number of pores near the substrate, as well as anisotropic sintering shrinkage......A numerical model able to simulate solid-state constrained sintering is presented. The model couples an existing kinetic Monte Carlo model for free sintering with a finite element model (FEM) for calculating stresses on a microstructural level. The microstructural response to the local stress...

  4. Microwave fast sintering of submicrometer alumina

    Directory of Open Access Journals (Sweden)

    Romualdo Rodrigues Menezes

    2010-09-01

    Full Text Available Commercially available alumina powder with high-purity submicrometer particle size and narrow particle size distribution was fully densified by a microwave hybrid fast firing technique. The alumina compacts were surrounded by susceptor material, which helped the heating of the samples, and sintered in a microwave oven at a frequency of 2.45 GHz and a power level of 1.8 kW. The sintered samples reached densities of 99% in sintering cycles of 30 to 40 minutes, a much shorter time than conventional sintering processes. The sintered samples showed uniform microstructures with powder particle size/average grain size rations higher than 1:2.

  5. Gravitational Role in Liquid Phase Sintering

    Science.gov (United States)

    Upadhyaya, Anish; Iacocca, Ronald G.; German, Randall M.

    1998-01-01

    To comprehensively understand the gravitational effects on the evolution of both the microstructure and the macrostructure during liquid phase sintering, W-Ni-Fe alloys with W content varying from 35 to 98 wt.% were sintered in microgravity. Compositions that slump during ground-based sintering also distort when sintered under microgravity. In ground-based sintering, low solid content alloys distort with a typical elephant-foot profile, while in microgravity, the compacts tend to spheroidize. This study shows that microstructural segregation occurs in both ground-based as well as microgravity sintering. In ground-based experiments, because of the density difference between the solid and the liquid phase, the solid content increases from top to the bottom of the sample. In microgravity, the solid content increases from periphery to the center of the samples. This study also shows that the pores during microgravity sintering act as a stable phase and attain anomalous shapes.

  6. Micromagnetic simulations on the grain shape effect in Nd-Fe-B magnets

    Science.gov (United States)

    Yi, Min; Gutfleisch, Oliver; Xu, Bai-Xiang

    2016-07-01

    Micromagnetic simulations were performed to study the effect of grain shape and defect layer in Nd-Fe-B magnets. It was found that the coercivity can be increased by a factor of ˜2 by changing the grain shape from the triangular prism to the spheroid. Both the anisotropy field contribution and the shape contribution to the coercivity, and thus also the final coercivity, were found to decrease in the order: spheroid > circular prism > hexagonal prism > square prism > triangular prism. Sputtered columnar grains and hot-deformed platelet grains with a constant volume were also considered. Results show that the coercivity initially increases with the aspect ratio and then nearly saturates above the ratio of ˜4. Simulations of multigrain ensembles showed that depending on the grain shape, compared to the case of single grain, a further decrease of ˜10%-45% in the coercivity is induced by magnetostatic coupling.

  7. Electron holography on remanent magnetization distribution of melt-spun Nd-Fe-B magnets.

    Science.gov (United States)

    Park, Young-Gil; Shindo, Daisuke

    2004-01-01

    Microstructures and magnetic domain structures of melt-spun Nd-Fe-B permanent magnets were investigated in detail by analytical electron microscopy and electron holography. While the crystal orientation of matrix Nd2Fe14B grains was analyzed by nanobeam electron diffraction, precipitates of a few tens of nanometers at grain boundaries were identified to be alpha-Fe by energy-dispersive X-ray spectroscopy. The detailed magnetization distribution in Nd2Fe14B grains and at their boundaries was visualized by electron holography. Ex situ experimentation with an electromagnet revealed that the domain walls in the demagnetized state and remanent states were pinned at grain boundaries, and Fe precipitates at the grain boundary were situated at the center of the closure domain.

  8. Magnetic force microscope study on anisotropic NdFeB permanent magnets

    Institute of Scientific and Technical Information of China (English)

    刘薇; 蒋建华; 吴建生; 李刚

    2003-01-01

    NdFeB permanent magnets prepared by powder metallurgy were investigated using magnetic force microscopy(MFM).The excellent MFM images of sample along the surfaces parallel and perpendicular to the alignment axis were collected respectively.The results show the necessity of annealing procedure in the preparation of the samples to remove the polishing surface stress and to illustrate the real magnetic domain structure,so that the much information about both the magnetic structure and the topographic microstructure is obtained.The hard MFM tip is verified to be effective for this material especially for the sample with the examined surface parallel to alignment axis.By analyzing these well-captured magnetic force images,magnetic domains and alignment degree as well as thetopographic information such as grain size and the nonmagnetic phases at the grain boundaries were demonstrated.

  9. Studies on in situ magnetic alignment of bonded anisotropic Nd-Fe-B alloy powders

    Science.gov (United States)

    Nlebedim, I. C.; Ucar, Huseyin; Hatter, Christine B.; McCallum, R. W.; McCall, Scott K.; Kramer, M. J.; Paranthaman, M. Parans

    2017-01-01

    Considerations for achieving high degree of alignment in polymer bonded permanent magnets are presented via the results of a study on in situ magnetic alignment of anisotropic Nd-Fe-B magnet powders. Contributions from effect of the alignment temperature, alignment magnetic field and the properties of the polymer on the hard magnetic properties of the bonded magnet were considered. The thermo-rheological properties of the polymer and the response of the magnet powders to the applied magnetic field indicate that hard magnetic properties were optimized at an alignment temperature just above the melting temperature of the EVA co-polymer. This agrees with an observed correlation between the change in magnetization due to improved magnetic alignment of the anisotropic powders and the change in viscosity of the binder. Manufacturing cost can be minimized by identifying optimum alignment temperatures and magnetic field strengths.

  10. Influence of dynamic crystallization on exchange-coupled NdFeB nanocrystalline permanent magnets

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ran; LIU Ying; MA Yilong; ZHANG Longfeng; XU Jianchuan; GAO Shengji

    2006-01-01

    Dynamic crystallization was introduced to improve the magnetic properties of NdFeB nanocrystalline permanent magnets by optimizing microstructure. The microstructure was studied by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It has been determined that, compared with the conventional heat treatment, dynamic crystallization can shorten the crystallization time. Moreover, dynamic crystallization can refine grains, enhance the exchange-coupled interaction among grains, and promote the magnetic properties. As a result, the optimal magnetic properties of Nd10.5(FeCoZr)83.4B6.1(Br=0.685T, Hci =732 kA·m -1 , Hcb =429 kA·m-1 ,( BH )m=75 kJ·m -3 ) are obtained after dynamic crystallization heat treatment at 700 ℃ for 10 min.

  11. Cathode electrophoretic technology for bonded NdFeB permanent magnet

    Institute of Scientific and Technical Information of China (English)

    CHEN Gang; YANG Xiao-lin; GAO Dan-ying; NI Jian-sen; XU Hui; ZHOU Bang-xin

    2006-01-01

    The bonded NdFeB permanent magnet was painted by cathode electrophoretic technology. The effect of technological parameters on the thickness of the layer was researched. The optimum voltage, time, electrophoresis temperature, area-ratio and spacing between cathode and anode are 220-250 V, 2-3 min, 25-32 ℃, 7-10 cm and (2-4)∶1, respectively. After treated under optimum conditions, the excellent corrosion resistance of the bonded magnet is achieved, with temperature and humidity resistant time of 468 h, brine-fast resistant time of 48 h. The cathode electrophoretic technology and treating process were successfully applied to produce bonded magnets with mass capacity of tens of million pieces per year.

  12. INTER-GRAIN EXCHANGE INTERACTION FOR SINGLE-PHASE NANOCRYSTALLINE Nd-Fe-B MAGNETS

    Institute of Scientific and Technical Information of China (English)

    WANG XUE-FENG; JIN HAN-MIN; ZHAO SU-FEN; YAN YU

    2001-01-01

    The demagnetization curve as a function of intensity of the inter-grain exchange interaction was calculated for single-phase nanocrystalline Nd-Fe-B magnets by use of the finite-element technique of micromagnetics. Also,the strength of the exchange interaction was estimated as a function of the Nd content x for the nanocrystalline NdxFe94-xB6 magnets by comparing the above result with the experimental relation between iHc and x for the magnets. We found that the inter-grain exchange interaction decreases with the increase of x, are≈70% and≈60% of the inter-grain exchange interaction for x=15.5(p0 iHc ≈2.0T) and x=19(p0 iHc ≈2.3T), respectively.

  13. Hydrogen Absorption and Release Behavior in Hydrogen Decrepitation Process of Nd-Fe-B Alloys

    Institute of Scientific and Technical Information of China (English)

    陈晓东; 姜忠良; 陈秀云; 石大立; 杨昌平; 朱静

    2003-01-01

    The behavior of hydrogen absorption and release in hydrogen decrepitation (HD) process of Nd-Fe-B alloys were investigated. The results reveal that the reactivity and the amount of hydrogen absorption in HD process are related to the surface activity of the alloy so that the fresh and active surface has a higher efficiency. The presence of Nd-rich phase at the grain boundary is an essential factor of the HD activity of the alloy at room temperature. On degassing, hydrogen is released from the HD powder continuously with increasing temperature. And the residual hydrogen is as low as 0.0015% at 1073 K, which shows that the hydrogen is almost exhaused. It is feasible to remove the hydrogen from the HD powder by heating treatment at the temperature of 523~723 K for 1 h prior to the magnetic field forming in order to decrease the harmful effect of hydrogen on the easy axis alignment of HD magnet.

  14. Improvement of the Sintered Surface and Bulk of the Product Via Differentiating Laser Sintering (Melting) Modes

    Science.gov (United States)

    Saprykina, N. A.; Saprykin, A. A.; Arkhipova, D. A.; Borovikov, I. F.

    2016-08-01

    Selective laser sintering (melting) enables using metal powdered materials to manufacture products of any geometrical complexity, requiring no preliminary costs to prepare processing equipment. However, quality of the sintered surface is often inadequate as against the product manufactured traditionally. Manufacturing a high quality product requires solution of such vital task as prediction of the sintered surface roughness. The authors address to the effect of laser sintering modes on roughness of the surface, sintered of copper powdered material PMS-l (IIMC-1). The dependence of roughness of the surface layer sintered of copper powder material PMS-l upon sintering process conditions is expressed mathematically. The authors suggest differentiating sintering modes to improve the sintered surface and the bulk of the product and dividing them into rough, semi-finishing, and finishing ones.

  15. Solidification process in melt spun Nd-Fe-B type magnets

    Energy Technology Data Exchange (ETDEWEB)

    Li, Changping [Iowa State Univ., Ames, IA (United States)

    1998-02-23

    A generalized solidification model has been developed based on a systematic investigation on the microstructure of melt spun Nd-Fe-B alloys. Melt spinning was conducted on initial stoichiometric and TiC added Nd2Fe14B (2-14-1) compositions to produce under, optimally and over quenched microstructures. Microstructural characterization was carried out by TEM, SEM, Optical microscopy, XRD, DTA, VSM and DC SQUID techniques. By taking the dendritic breakup during recalescence into consideration, this generalized model has successfully explained the solidification process of the melt spun Nd-Fe-B alloys. Challenging the conventional homogeneous nucleation models, the new model explains the fine and uniform equiaxed 2-14-1 microstructure in optimally quenched ribbons as a result of the breakup of the 2-14-1 dendrites which nucleate heterogeneously from the wheel surface and grow dendritically across the ribbon thickness due to the recalescence. Besides this dendritic breakup feature, the under quenched microstructure is further featured with another growth front starting with the primary solidification of Fe phase near the free side, which results in a coarsely grained microstructure with Fe dendritic inclusions and overall variation in microstructure across the ribbon thickness. In addition, because a epitaxy exists between the Fe phase and the 2-14-1, the so-formed coarse 2-14-1 grains may be textured. C-axis texturing was observed in under quenched ribbons. As a constraint to solidification models in this system, the cause and characteristics of this phenomenon has been studied in detail to test the authors proposed model, and agreement has been found. An extension has also been made to understand the solidification process when TiC is added, which suggests that Ti and C slow down the growth front of both Fe and 2-14-1 phase.

  16. Application of positron lifetime spectroscopy to the study of material processing of Nd-Fe-B permanent magnets

    Energy Technology Data Exchange (ETDEWEB)

    Nishiuchi, T., E-mail: Takeshi_Nishiuchi@hitachi-metals.co.j [Magnetic Materials Research Laboratory, NEOMAX Company, Hitachi Metals Ltd., 2-15-17 Egawa, Shimamoto, Osaka 618-0013 (Japan); Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan); Sakashita, S.; Hirosawa, S. [Magnetic Materials Research Laboratory, NEOMAX Company, Hitachi Metals Ltd., 2-15-17 Egawa, Shimamoto, Osaka 618-0013 (Japan); Nakamura, M.; Kakimoto, M.; Kawabayashi, T.; Mizuno, M.; Araki, H. [Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan); Shirai, Y. [Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan)

    2010-05-15

    A positron lifetime spectroscopy was applied to a series of samples of Nd-Fe-B based alloys prepared by hydrogenation-disproportionation-desorption-recombination (HDDR) process with various desorption-recombination (DR) times and the results were compared to the results of cross-sectional observation with scanning electron microscopy (SEM). From these studies, it is strongly suggested that microstructural changes, which causes the sudden onset of coercivity during DR stage progress abruptly in a relatively short period of time. Positron lifetime spectroscopy can detect the microstructural changes during DR treatment and furthermore, it is suggested that positron annihilation site is directly related to the region which determines the coercivity of the HDDR-processed Nd-Fe-B alloys.

  17. First-Principles Study of the Role of Cu in Improving the Coercivity of Nd-Fe-B Permanent Magnets

    Science.gov (United States)

    Tatetsu, Y.; Tsuneyuki, S.; Gohda, Y.

    2016-12-01

    We study the magnetic and electronic properties of Cu-doped Nd2 Fe14 B /NdOx systems with first-principles calculations in order to understand the roles of Cu in improving the coercivity of Nd-Fe-B permanent magnets. By analyzing the formation energies of several model systems, we find that Cu prefers to be at the interface. We conclude that the Cu addition to Nd-Fe-B magnets is a practical way of not only increasing the anisotropy of Nd atoms at the interface but also of lessening the magnetic coupling between the Nd and Fe atoms. Particularly, substituting Fe at the interface of the main phase with Cu works effectively in terms of improving the magnetic anisotropy in Nd atoms. This may explain the coercivity improvements reported recently.

  18. Influence of AC external magnetic field on guidance force relaxation between HTS bulk and NdFeB guideway

    Science.gov (United States)

    Zhang, Longcai; Wang, Suyu; Wang, Jiasu; Zheng, Jun

    2007-12-01

    Superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the HTS bulks are always exposed to time-varying external magnetic field, which is generated by the inhomogeneous surface magnetic field of the NdFeB guideway. So it is required to study whether the guidance force of the bulks is influenced by the inhomogeneity. In this paper, we studied the characteristics of the guidance force relaxation between the HTS bulk and the NdFeB guideway by an experiment in which AC external magnetic field generated by an electromagnet was used to simulate the time-varying external magnetic field caused by the inhomogeneity of the guideway. From the experiment results, it was found that the guidance force was decreased with the application of the AC external magnetic field, and the decay increased with the amplitude and was almost independent of the frequency.

  19. Investigation of the coercivity mechanism for Nd-Fe-B based magnets prepared by a new technique of strip casting

    Institute of Scientific and Technical Information of China (English)

    LI Bo; HU Jifan; WANG Dongling; GUO Binglin; WANG Xinlin

    2004-01-01

    The coercivity mechanism of Nd-Fe-B based magnets prepared by a new technique of strip casting was investigated. Different from the traditional magnets, α-Fe phases are difficult to be found in Nd-Fe-B magnets prepared by strip casting. Meanwhile, the rich-Nd phases occur not only near the grain boundaries of main phases, but also within the main-phase grains. Investigation on the magnetizing field dependence of the coercivity for the (Nd0.935Dy0.065)14.5Fe79.4B6.1magnet and the temperature dependence of the coercivity for the Nd14.5Fe79.4B6.1magnet have been done. Results show that coercivities for strip casting magnets are controlled by the nucleation mechanism.

  20. CRADA/NFE-15-05761 Report: Additive Manufacturing of Isotropic NdFeB Bonded Permanent Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Paranthaman, M Parans [ORNL

    2016-07-18

    The technical objective of this technical collaboration phase I proposal is to fabricate net shape isotropic NdFeB bonded magnets utilizing additive manufacturing technologies at the ORNL MDF. The goal is to form complex shapes of thermoplastic and/or thermoset bonded magnets without expensive tooling and with minimal wasted material. Two additive manufacturing methods; the binder jet process; and big area additive manufacturing (BAAM) were used. Binder jetting produced magnets with the measured density of the magnet of 3.47 g/cm3, close to 46% relative to the NdFeB single crystal density of 7.6 g/cm3 were demonstrated. Magnetic measurements indicate that there is no degradation in the magnetic properties. In addition, BAAM was used to fabricate isotropic near-net-shape NdFeB bonded magnets with magnetic and mechanical properties comparable or better than those of traditional injection molded magnets. The starting polymer magnet composite pellets consist of 65 vol% isotropic NdFeB powder and 35 vol% polyamide (Nylon-12). The density of the final BAAM magnet product reached 4.8 g/cm3, and the room temperature magnetic properties are: Intrinsic coercivity Hci = 8.65 kOe, Remanence Br = 5.07 kG, and energy product (BH)max = 5.47 MGOe (43.50 kJ/m3). This study provides a new pathway for preparing near-net shape bonded magnets for various magnetic applications.

  1. Microwave sintering of ceramic materials

    Science.gov (United States)

    Karayannis, V. G.

    2016-11-01

    In the present study, the potential of microwave irradiation as an innovative energy- efficient alternative to conventional heating technologies in ceramic manufacturing is reviewed, addressing the advantages/disadvantages, while also commenting on future applications of possible commercial interest. Ceramic materials have been extensively studied and used due to several advantages they exhibit. Sintering ceramics using microwave radiation, a novel technology widely employed in various fields, can be an efficient, economic and environmentally-friendlier approach, to improve the consolidation efficiency and reduce the processing cycle-time, in order to attain substantial energy and cost savings. Microwave sintering provides efficient internal heating, as energy is supplied directly and penetrates the material. Since energy transfer occurs at a molecular level, heat is generated throughout the material, thus avoiding significant temperature gradients between the surface and the interior, which are frequently encountered at high heating rates upon conventional sintering. Thus, rapid, volumetric and uniform heating of various raw materials and secondary resources for ceramic production is possible, with limited grain coarsening, leading to accelerated densification, and uniform and fine-grained microstructures, with enhanced mechanical performance. This is particularly important for manufacturing large-size ceramic products of quality, and also for specialty ceramic materials such as bioceramics and electroceramics. Critical parameters for the process optimization, including the electromagnetic field distribution, microwave-material interaction, heat transfer mechanisms and material transformations, should be taken into consideration.

  2. The epoxy resin variation effect on microstructure and physical properties to improve bonded NdFeB flux magnetic density

    Science.gov (United States)

    Rusnaeni, N.; Sarjono, Priyo; Muljadi; Noer, Nasrudin

    2016-11-01

    NdFeB magnets have been fabricated from a mixture of powder NdFeB (MPQ-B+) and epoxy resins (ER) with a variation of 0% wt, 2% wt, 4% wt and 6% wt. The pellets samples were made by pressing 4 tons of the mixture powder at room temperature before curing at 100°C for 1 hour. The SEM-EDX results showed the microstructure with ER were evenly smeared the NdFeB magnetic particles due to higher percent C and lower transition metals value. Sample with 2% wt epoxy resin was able to achieve the highest density of 5.35 g/cm3 and the highest magnetic flux of 2121 Gauss. The magnetic properties characterization using the permagraph indicates that the sample pellets with 2% wt epoxy resin has a value of remanence (Br) = 4.92 kG, coercivity (Hc) = 7.76 kOe, and energy product (Bhmax) = 4.58 MGOe. Despite low remanence value in the pellet samples, the resistance to demagnetization value was still acceptable.

  3. Decay Characteristics of Levitation Force of YBCO Bulk Exposed to AC Magnetic Field above NdFeB Guideway

    Science.gov (United States)

    Liu, Minxian; Lu, Yiyun; Wang, Suyu; Ma, Guangtong

    2011-04-01

    The superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the nonuniformity of the magnetic field along the movement direction above the NdFeB guideway is inevitable due to the assembly error and inhomogeneity of the material property of the NdFeB magnet. So it is required to study the characteristics of levitation force of the bulks affected by the non-uniform applied magnetic fields along the moving direction. In this paper, we will study the characteristics of the levitation force relaxation between the HTS bulk and the NdFeB guideway by an experiment in which AC external magnetic field generated by an electromagnet is used to simulate the time-varying external magnetic field caused by the inhomogeneity of the guideway. From the experimental results, it has found that the levitation force is decreasing with the application of the AC external magnetic field, and the decay increasing with the amplitude of the applied magnetic field and is almost independent of the frequency.

  4. Test of Cu base alloy Huadong sintering model

    Institute of Scientific and Technical Information of China (English)

    丁华东; 方宁象; 遇元宏

    2001-01-01

    Through modular pressing and sintering, the Cu-C powder metallurgy samples were made and the process was investigated. The results show that there exist expanding mechanism and shrinking mechanism in sintering process, and whether the sintering body is shrinking or expanding depends on the interacting between the two mechanisms, and the HD sintering model is in keeping with the actual sintering process.

  5. Characteristics of vacuum sintered stainless steels

    OpenAIRE

    Z. Brytan; L.A. Dobrzański; M. Actis Grande; Rosso, M.

    2009-01-01

    Purpose: In the present study duplex stainless steels were sintered in vacuum. using rapid cooling form the mixture of prealloyed and alloying element powders The purpose of this paper was to describe the obtained microstructures after sintering as well as the main mechanical properties of sintered stainless steels.Design/methodology/approach: In presented work duplex stainless steels were obtained through powder metallurgy starting from austenitic 316L or ferritic 410L prealloyed stainless s...

  6. Development of Sintered Iron Driving Bands

    Directory of Open Access Journals (Sweden)

    R. P. Khanna

    1974-07-01

    Full Text Available The present investigation reports some detailed studies carried out on the development testing and proving of sintered Iron Driving Bands. Sintering studies on two different types of iron powders together with a few Fe-Cu compositions have been made and based on the results there of, parameters for development iron driving bands have been standardised. The results obtained clearly demonstrate that substitution of copper by sintered iron is highly practicable alternative.

  7. Application of Optimal Sinter Burden Design

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The application of the optimal sinter burden design in the sinter shop of No.1 Iron-making Plant in Tangshan Iron & Steel Corp was reported. By using burden calculation and simulating production under different situations, it is demonstrated that the technology can provide the relevant information in product quality and cost etc. for decision-makers. The technology has been used to guide production of the Sinter Shop since 2000, and a remarkable achievement has been obtained.

  8. Flash Sintering of Alumina-based Ceramics

    OpenAIRE

    Biesuz, Mattia

    2017-01-01

    Flash sintering is an electrical field-assisted consolidation technology and represents a very novel technique for producing ceramic materials, which allows to decrease sensibly both processing temperature and time. Starting from 2010, when flash sintering was discovered, different ceramic materials with a wide range of electrical properties have been successfully densified. Up to date, the research on flash sintering has been mainly focused on ionic and electronic conductors and on semicondu...

  9. Sintering of Ceramic Materials Under Electric Field

    OpenAIRE

    Naik , Kiran Suresh

    2014-01-01

    The remarkable discovery of flash sintering came across during the early work of Cologna et al. and emerged as an attractive technique in the field of ceramic processing. In this technique the applied electric field initiates the “flash” event, while the densification is controlled by the current density set. Sintering occurs in less than 5 s at a threshold temperature for a given applied field. The objective of this thesis is to analyse the phenomena of flash sintering with different cer...

  10. Characteristics of vacuum sintered stainless steels

    Directory of Open Access Journals (Sweden)

    Z. Brytan

    2009-04-01

    Full Text Available Purpose: In the present study duplex stainless steels were sintered in vacuum. using rapid cooling form the mixture of prealloyed and alloying element powders The purpose of this paper was to describe the obtained microstructures after sintering as well as the main mechanical properties of sintered stainless steels.Design/methodology/approach: In presented work duplex stainless steels were obtained through powder metallurgy starting from austenitic 316L or ferritic 410L prealloyed stainless steels powders by controlled addition of alloying elements powder. Prepared mixes were sintered in a vacuum furnace in 1250°C for 1h. After sintering rapid cooling (6°C/s using nitrogen under pressure was applied. Sintered compositions were subjected to structural examinations by scanning and optical microscopy and EDS analysis as well as X-ray analysis. Mechanical properties were studied through tensile tests and Charpy impact test.Findings: It was demonstrated that austenitic-ferritic microstructures with regular arrangement of both phases and absence of precipitates can be obtained with properly designed powder mix composition as well as sintering cycle with rapid cooling rate. Obtained sintered duplex stainless steels shows good mechanical properties which depends on phases ratio in the microstructure and elements partitioning (Cr/Ni between phases.Research limitations/implications: Basing on alloys characteristics applied cooling rate and powder mix composition seems to be a good compromise to obtain balanced sintered duplex stainless steel microstructures.Practical implications: Mechanical properties of obtained sintered duplex stainless steels structures are rather promising, especially with the aim of extending their field of possible applications.Originality/value: The utilization of vacuum sintering process with rapid cooling after sintering combined with use of elemental powders added to a stainless steel base powder shows its advantages in terms

  11. Influence of Pressure in Flash Sintering Technique

    Science.gov (United States)

    Pcheliakov, D. A.; Yurlova, M. S.; Grigoryev, E. G.; Olevsky, E. A.

    An innovative pressure-assisted flash-sintering technique has been developed to investigate the effect of pressure applied on microstructure and the sintering behavior of titanium dioxide. There are numerous applications for titanium dioxide in ceramics including microeletronics, glass ceramics, refractive materials, structural ceramics and titanium-containing ceramic materials and chemical intermediates. The traditional sintering of titanium dioxide usually requires several hours at over 1200 °C. The conducted research indicates that titanium dioxide can be sintered to full density in only a few seconds at 800-1000 °C, when subjected to a DC electrical field at a certain temperature moment.

  12. Huadong sintering model about expansion and shrinkage

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The whole sintering course from the beginning of heating to the end of heat preservation stage was studied by taking into account the influence of pressing. It was found that there exist expanding mechanism and shrinking mechanism in the sintering process, and the expanding mechanism is always acting before the shrinking mechanism. Whether the sintering body shrinks or expands depends on the interaction between the two mechanisms. And according to this, the Huadong sintering model in account of expansion and shrinkage mechanism was given.

  13. Chemometric study of the sinter mixtures used in sinter plants in Poland

    Directory of Open Access Journals (Sweden)

    A. Smoliński

    2015-01-01

    Full Text Available The main goal of the study was the analysis of chemical parameters of sinter mixtures used in sinter plants in Poland. For this purpose the chemometric method was used, in this case hierarchical clustering analysis. This method allowed to examine the similarities and differences between the studied sinter mixtures.

  14. Harmful admixtures assessment in sinter mixtures used in iron ore sinter plants in Poland

    Directory of Open Access Journals (Sweden)

    J. Korol

    2014-10-01

    Full Text Available In this study composition of sinter mixtures used in Polish sinter plants were established. Seven sinter mixtures composition were examined, based on iron-bearing materials, admixtures and fuels. Contents of harmful admixtures were examined according to three kinds of environmental impacts: emissions of SOx, heavy metals, polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDDs/PCDFs.

  15. Alternative sintering methods compared to conventional thermal sintering for inkjet printed silver nanoparticle ink

    NARCIS (Netherlands)

    Niittynen, J.; Abbel, R.; Mäntysalo, M.; Perelaer, J.; Schubert, U.S.; Lupo, D.

    2014-01-01

    In this contribution several alternative sintering methods are compared to traditional thermal sintering as high temperature and long process time of thermal sintering are increasing the costs of inkjet-printing and preventing the use of this technology in large scale manufacturing. Alternative sint

  16. Effect of sinter layer porosity distribution on flow and temperature fields in a sinter cooler

    Institute of Scientific and Technical Information of China (English)

    Jik-chang Leong; Kai-wun Jin; Jia-shyan Shiau; Tzer-ming Jeng; Chang-hsien Tai

    2009-01-01

    When sinters are filled into the sinter cooler from the sintering machine, it is commonly seen that, due to segregation ef-fects, sinters of larger size usually accumulate closer to the inner wall of the sinter cooler, whereas those of smaller size are to the outer wall. This nonuniform distribution of sinters has led to uneven cooling effect throughout the cooler. This causes the sinters leaving the cooler at a large temperature difference. This undesired temperature difference leads to the deformation and even the de-struction of the conveyors. The computational fluid dynamics (CFD) technique was used in the present work to investigate the heat and fluid flow phenomena within the sinter cooler corresponding to the different distribution of sinter layer porosity, which was highly dependent on the arrangement and orientation of sinters within the sinter cooler. It is confirmed that a high mass flow rate within the sinter layer causes a low temperature region and vice versa. The flow fields for vertically reducing porosity distribution and random distribution are almost identical indicating the relative insignificance of convective heat transfer mechanism.

  17. Kinetics mechanism of microwave sintering in ceramic materials

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Based on the traditional sintering model incorporating the characteristic of microwave sintering, the ionic conductance diffusion mechanism in microwave sintering was studied. A flat-ball model was presented to describe the kinetics process in microwave sintering, and was applied to the sintering process of TZP and ZrO2-Al2O3 ceramics. The results indicate that the shrinkage rate of materials in microwave sintering is proportional to t2/3 and r-4/3, respectively, where t is the sintering time and r is the particle radius. Whereas, the shrinkage rate of materials in conventional sintering is proportional to sintering time t2/5. Our model suggests that microwave sintering is faster than conventional sintering, which shows a good agreement with the experimental observation in sintering process of TZP and ZrO2-Al2O3.

  18. 脉冲磁场技术在高矫顽力稀土永磁测量领域的应用%Application of pulsed field technique to magnetic property measurements of rare earth based hard magnetic materials with high coercivity

    Institute of Scientific and Technical Information of China (English)

    林安利; 贺建; 张跃; John Dudding

    2009-01-01

    An inherent problem was introduced when measuring the magnetic properties of high coercivity hard magnetic materials with an existent static BH tracer (hysteresisograph) and the reason why the problem happens was discussed. To deal with the problem a pulsed field magnetometer (PFM) system based on the f-2f method, which could generates 8756kA·m~(-1) magnetic field, was designed and applied to measure the whole hysteresis loop of high coercivity hard magnetic materials. The technical advantages, structure and eddy current effect correction of the system were also introduced. It can be approved, from a large quantity of measurement results, that the long term repeatability of the system is very good. The deviation of magnetic properties, i.e. remanence B_r, intrinsic coercivity H_(cJ), magnetic flux density coercivity H_(cB), and maximum energy product (BH)_(max), measured with a PFM compared with that measured with a national standard static BH tracer is within 1% for low coercivity hard magnets. For high coercivity hard magnets the system could measure the whole hysteresis loop and solve the high coercivity problem that a static BH tracer could not avoid.%简述了超高矫顽力永磁体测量现状,分析了静态磁滞回线仪在测量高矫顽力永磁体时存在的问题及其原因.为解决此问题,采用"f-2f"原理建立了基于脉冲磁场技术的高矫顽力永磁测量装置,该装置能产生最高8756kA·m~(-1)的测量磁场,能够测量高矫顽力永磁体的整个磁滞回线.阐述了该脉冲磁场测量装置的优势、组成结构以及涡流修正方法.经过实验验证,该系统具有良好的测量重复性.与国家永磁标准测量装置的对比结果显示:在低矫顽力范围内两者剩磁Br、内禀矫顽力H_(cJ)、磁感应强度矫顽力H_(cB)和最大磁能积(BH)_(max)四个参数的测量偏差在1%以内;在高矫顽力范围,该装置解决了静态磁滞回线仪测量曲线变形的问题.

  19. SELF SINTERING OF RADIOACTIVE WASTES

    Science.gov (United States)

    McVay, T.N.; Johnson, J.R.; Struxness, E.G.; Morgan, K.Z.

    1959-12-29

    A method is described for disposal of radioactive liquid waste materials. The wastes are mixed with clays and fluxes to form a ceramic slip and disposed in a thermally insulated container in a layer. The temperature of the layer rises due to conversion of the energy of radioactivity to heat boillng off the liquid to fomn a dry mass. The dry mass is then covered with thermal insulation, and the mass is self-sintered into a leach-resistant ceramic cake by further conversion of the energy of radioactivity to heat.

  20. Some features of sintering of tungsten powders

    Directory of Open Access Journals (Sweden)

    Andreiev Igor Viktorovich

    2016-01-01

    Full Text Available A method of activating the sintering process for tungsten powders using a closed reaction space and hydrogen, steam-saturated water was observed. This sintering process is allowed to activate super coarse-grained (1000μm tungsten powder sat relatively low temperatures (1000-1200°C.

  1. Method of sintering materials with microwave radiation

    Science.gov (United States)

    Kimrey, Jr., Harold D.; Holcombe, Jr., Cressie E.; Dykes, Norman L.

    1994-01-01

    A method of sintering ceramic materials following: A compacted article comprising inorganic particles coated with carbon is provided, the carbon providing improved microwave coupling. The compacted article is then heated by microwave radiation to a temperature and for a period of time sufficient to sinter the compacted article.

  2. The master sintering curve for pressure-less sintering of TiO2

    Directory of Open Access Journals (Sweden)

    Li D.

    2007-01-01

    Full Text Available A Master Sintering Curve (MSC for rutile TiO2 was constructed for Pressure-less sintering using constant heating rate dilatometry data based on the combined-stage sintering model. Construction of the master sintering curve is described and the validation is proved with rutile TiO2 under different thermal histories. The concept of master sintering can be used to predict the sintering shrinkage and final density and calculate the activation energy, and a value of 105 KJ/mol for TiO2 was obtained. With one temperature dependent parameter determined experimentally, it became possible to describe accurately the densification behavior of TiO2 from the initial to final stages of sintering. .

  3. The Influence of Sintering Temperature of Reactive Sintered (Ti, MoC-Ni Cermets

    Directory of Open Access Journals (Sweden)

    Marek Jõeleht

    2015-09-01

    Full Text Available Titanium-molybdenum carbide nickel cermets ((Ti, MoC-Ni were produced using high energy milling and reactive sintering process. Compared to conventional TiC-NiMo cermet sintering the parameters for reactive sintered cermets vary since additional processes are present such as carbide synthesis. Therefore, it is essential to acquire information about the suitable sintering regime for reactive sintered cermets. One of the key parameters is the final sintering temperature when the liquid binder Ni forms the final matrix and vacancies inside the material are removed. The influence of the final sintering temperature is analyzed by scanning electron microscopy. Mechanical properties of the material are characterized by transverse rupture strength, hardness and fracture toughness.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7179

  4. Equivalent Resistance in Pulse Electric Current Sintering

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The sintering resistance for conductive TiB2 and non-conductive Al2O3 as well as empty die during pulse current sintering were investigated in this paper.Equivalent resistances were measured by current and valtage during sintering the conductive and non-conductive materials in the same conditions.It is found that the current paths for conductive are different from those for non-conductive materials.For non-conductive materials,sintering resistances are influenced by powder sizes and heating rates,which indicates that pulse current has some interaction with non-conductive powders.For conductive TiB2,sintering resistances are influenced by heating rates and ball-milling time,which indicates the effect of powders activated by spark.

  5. Solar furnace sintering of ceramic materials

    Energy Technology Data Exchange (ETDEWEB)

    Zhilinska, N.; Zalite, I.; Korb, G.; Angerer, P.; Rodriguez, J.; Martinez, D.

    2004-07-01

    This paper reports on the current status of application of solar furnace for sintering of TiCN, TiO2 and Al2O3 nano powders with the specific surface area of 30-50 m''2/g and average particle size of 30-50 nm. The powders have been prepared by the plasma chemical synthesis and other methods. This work relates to innovative methods of sintering in the solar furnace at Plataforma Solar de Almeria and the Spark Plasma Sintering (SPS). The influence of sintering temperature, sintering time and heating rate on the densification behaviour of the nanopowders was investigated. The results were compared with the data obtained using commercial powders. (Author) 4 refs.

  6. Fabrication of ultrafine Nd-Fe-B powder by a modified reduction-diffusion process

    Institute of Scientific and Technical Information of China (English)

    JANG T.S.; LEE D.H.; YU J.H.; CHOI C.J.; SEO W.S.; LEE Y.H.

    2006-01-01

    In order to obtain ultrafine Nd-Fe-B powder, a spray-dried precursor was treated by reduction-diffusion (R/D) process.And, unlike the conventional R/D process, calcium reduction that is a crucial step for the formation of Nd2Fe14B was performed without conglomerating the precursor with Ca powder.By adopting this modified process, it is possible to synthesize the hard magnetic Nd2Fe14B at the reaction temperature as low as 850 ℃.The average size of Nd2Fe14B particles that are uniformly distributed in the optimally treated powder was < <1 μm.Most Nd2Fe14B particles were enclosed with thin layers of Nd-rich phase.Typical magnetic properties of such powder without eliminating impurity CaO were iHc=~5.9 kOe, Br=~5.5 kG, and (BH)max=~6 MGOe.

  7. ANISOTROPIC CHARACTERISTICS OF DEMAGNETIZATION CURVE FOR NANOCRYSTALLINE Nd-Fe-B MAGNET CALCULATED BY MICROMAGNETICS

    Institute of Scientific and Technical Information of China (English)

    金汉民; 王学凤; 赵素芬; 闫羽

    2001-01-01

    The demagnetization curves for nanocrystalline Nd-Fe-B magnets of a stoichiometric composition were calculated by making use of the finite element technique of micromagnetics. The curve, especially iHc, varies in a wide range with the direction of applied field if the grain number N is taken to be small. With the increase of N, the range becomes smaller and the average of iHc decreases and approaches a limit iHc(N = ∞). iHc for finite N is larger than, or at least equal to, iHc(N= o∞). Jr/Js is weakly affected by N and the field direction. Jr/Js(N = oo) decreases with the increase of grain size L. These are larger than the experimental values for the Nd-rich Nd2.33Fe14B1.06Si0.21 magnets by ~0.05. iHc(N = ∞) increases with the increase of L, and is close to or somewhat smaller than the experimental values of the Nd-rich magnet, as would be expected. In contrast, the curve calculated for the non-interacting grain system (Stoner-Wohlfarth model) of N 30 depends neither on the field direction nor on N.

  8. High-performance nanocrystalline NdFeB magnets by CAPA process

    Science.gov (United States)

    Kim, H. T.; Kim, Y. B.; Jeon, J. W.; Jang, I. H.; Kapustin, G. A.; Kim, H. S.

    2006-09-01

    The anisotropic NdFeB magnets were prepared from the melt-spun isotropic powders by CAPA process. The precursor isotropic magnet shows the uniform magnetic properties according to the overall position in the magnet. In the case of the anisotropic magnet, the outer position shows higher remanence and energy product compared to the center position. The magnetic properties of the anisotropic magnet obtained from Nd 14Fe 80B 6 powders are B=15 kG, iH=4.1 kOe and BH=36 MG Oe. In the case of addition of Zn to Nd 14Fe 80B 6 powders, the energy product increased because of the improved coercivity. The magnetic properties of the Zn-added magnet are B=14.5 kG, iH=9.7 kOe and BH=52 MG Oe. The Zn addition is effective to depress Nd 2Fe 14B grain growth of the interparticle regions during plastic deformation.

  9. High-performance nanocrystalline NdFeB magnets by CAPA process

    Energy Technology Data Exchange (ETDEWEB)

    Kim, H.T. [Tesla Co., Ltd., 340-1 Songsan-Ri, Yanggam-Myeon, Hwasung City, Gyeonggi-Do, 445-396 (Korea, Republic of)]. E-mail: htkim@gotesla.com; Kim, Y.B. [Korea Research Institute Standards and Sciences, 305-600, Daejeon (Korea, Republic of); Jeon, J.W. [Chonbuk National University, 756-356, Jeonju (Korea, Republic of); Jang, I.H. [Tesla Co., Ltd., 340-1 Songsan-Ri, Yanggam-Myeon, Hwasung City, Gyeonggi-Do, 445-396 (Korea, Republic of); Kapustin, G.A. [RRC Kurchatov Institute, Moscow, 123182 (Russian Federation); Kim, H.S. [Chonbuk National University, 756-356, Jeonju (Korea, Republic of)

    2006-09-15

    The anisotropic NdFeB magnets were prepared from the melt-spun isotropic powders by CAPA process. The precursor isotropic magnet shows the uniform magnetic properties according to the overall position in the magnet. In the case of the anisotropic magnet, the outer position shows higher remanence and energy product compared to the center position. The magnetic properties of the anisotropic magnet obtained from Nd{sub 14}Fe{sub 80}B{sub 6} powders are B{sub r}=15kG, {sub i}H{sub c}=4.1kOe and BH{sub max}=36MGOe. In the case of addition of Zn to Nd{sub 14}Fe{sub 80}B{sub 6} powders, the energy product increased because of the improved coercivity. The magnetic properties of the Zn-added magnet are B{sub r}=14.5kG, {sub i}H{sub c}=9.7kOe and BH{sub max}=52MGOe. The Zn addition is effective to depress Nd{sub 2}Fe{sub 14}B grain growth of the interparticle regions during plastic deformation.

  10. Microstructure of explosively compacted Nd-Fe-B magnet by TEM

    Institute of Scientific and Technical Information of China (English)

    AO Qi; LIU Wei; CAO Li-jun; WU Jian-sheng

    2005-01-01

    The microstructure of an explosively compacted Nd-Fe-B permanent magnet(Nd-Fe-B) was investigated by means of TEM and XRD. It is shown that there are three kinds of phases: Nd2 Fe14 B matrix phase, O-rich phases and Nd-rich phase with different structures and compositions in the magnet. The hard magnetic phase Nd2 Fe14 B is tetragonal, which lattice parameters are determined to be a=0. 88 nm and c= 1.22 nm. The O-rich phase locates at the grain boundaries and the triple junctions has fcc structure whose lattice parameter is a=0. 559 nm. A dislocation is observed in this phase. It is also found that a large number of the block-shaped Nd-rich phases with hcp structure are embedded in the Nd2 Fe14B matrix or at grain boundary. Their lattice parameters are determined to be a=0. 395 nm and c=0.628 nm.

  11. Research of warm compaction technology on nylon bonded Nd-Fe-B magnets

    Institute of Scientific and Technical Information of China (English)

    Xiuhai ZHANG; Weihao XIONG; Dameng YE; Jun QU; Zhenhua YAO

    2009-01-01

    Warm compaction and room temperature compaction were applied to prepare bonded Nd-Fe-B magnets. The results indicated that the density of magnet was determined by the compaction pressure and warm compaction temperature, whereas, the ther-mosetting temperature could hardly affect the density of magnet. The mechanical properties of magnets were the best when the thermosetting temperature was 200 ℃.The Br, Hcb, and (BH)max of warm compaction magnet were higher than those of room compaction. When the warm compaction temperature and thermosetting tem-perature were invariable, the density of magnet increased with the increase of com-paction pressure, which resulted in the increase of Br, Hob, and (BH)max of magnet and the decrease of Hcj of magnet. When the warm compaction temperature and compaction pressure were invariable, the magnetic properties of magnets decreased with the increase of thermosetting temperature. The magnetic properties of warm compaction molding magnets were better than those of injection molding magnets.

  12. Modeling of magnetic hystereses in soft MREs filled with NdFeB particles

    Science.gov (United States)

    Kalina, K. A.; Brummund, J.; Metsch, P.; Kästner, M.; Borin, D. Yu; Linke, J. M.; Odenbach, S.

    2017-10-01

    Herein, we investigate the structure-property relationships of soft magnetorheological elastomers (MREs) filled with remanently magnetizable particles. The study is motivated from experimental results which indicate a large difference between the magnetization loops of soft MREs filled with NdFeB particles and the loops of such particles embedded in a comparatively stiff matrix, e.g. an epoxy resin. We present a microscale model for MREs based on a general continuum formulation of the magnetomechanical boundary value problem which is valid for finite strains. In particular, we develop an energetically consistent constitutive model for the hysteretic magnetization behavior of the magnetically hard particles. The microstructure is discretized and the problem is solved numerically in terms of a coupled nonlinear finite element approach. Since the local magnetic and mechanical fields are resolved explicitly inside the heterogeneous microstructure of the MRE, our model also accounts for interactions of particles close to each other. In order to connect the microscopic fields to effective macroscopic quantities of the MRE, a suitable computational homogenization scheme is used. Based on this modeling approach, it is demonstrated that the observable macroscopic behavior of the considered MREs results from the rotation of the embedded particles. Furthermore, the performed numerical simulations indicate that the reversion of the sample’s magnetization occurs due to a combination of particle rotations and internal domain conversion processes. All of our simulation results obtained for such materials are in a good qualitative agreement with the experiments.

  13. Influence of bath PH value on microstructure and corrosion resistance of phosphate chemical conversion coating on sintered Nd-Fe-B permanent magnets

    Science.gov (United States)

    Ding, Xia; Xue, Long-fei; Wang, Xiu-chun; Ding, Kai-hong; Cui, Sheng-li; Sun, Yong-cong; Li, Mu-sen

    2016-10-01

    The effect of bath PH value on formation, microstructure and corrosion resistance of the phosphate chemical conversion (PCC) coatings as well as the effect on the magnetic property of the magnets is investigated in this paper. The results show that the coating mass and thickness increase with the decrease of the bath PH value. Scanning electron microscopy observation demonstrates that the PCC coatings are in a blocky structure with different grain size. Transmission electron microscope and X-ray diffractometer tests reveal the coatings are polycomponent and are mainly composed of neodymium phosphate hydrate and praseodymium phosphate hydrate. The electrochemical analysis and static immersion corrosion test show the corrosion resistance of the PCC coatings prepared at bath PH value of 0.52 is worst. Afterwards the corrosion resistance increases first and then decreases with the increasing of the bath PH values. The magnetic properties of all the samples with PCC treatment are decreased. The biggest loss is occurred when the bath PH value is 0.52. Taken together, the optimum PH range of 1.00-1.50 for the phosphate solution has been determined.

  14. 烧结Nd-Fe-B永磁体酸性化学镀Ni-P%Acidic electroless Ni-P plating on sintered Nd-Fe-B magnet

    Institute of Scientific and Technical Information of China (English)

    谷燕; 刘贵昌; 刘阳

    2005-01-01

    经除油、酸洗、封孔、活化、闪镀后,在Nd-Fe-B永磁体上进行常规化学镀Ni-P合金.测试了不同施镀时间下Ni-P镀层的性能.X射线与扫描电镜图显示该Ni-P镀层光亮、致密,为非晶态结构,其磷含量为12.1%. 采用极化曲线测量了Nd-Fe-B永磁体及Ni-P镀层的腐蚀电位、腐蚀电流密度和腐蚀速率,并对其进行了海水浸泡实验.结果表明,Ni-P镀层的自腐蚀电位较Nd-Fe-B大大提高,且封孔能提高镀层的耐蚀性;该镀层能明显提高Nd-Fe-B永磁体的耐腐蚀能力,且随镀层厚度增加,耐蚀性增加.

  15. The Fracture Toughness of Sintered NdFeB Permanent Magnet%烧结NdFeB永磁合金的断裂韧性

    Institute of Scientific and Technical Information of China (English)

    刘薇; 曹力军; 吴建生

    2005-01-01

    用Zwick万能实验机测量了烧结NdFeB永磁合金样品的三点弯曲强度、断裂韧性KIC及弹性模量E.在三点弯曲试验中测得塑变功为0,而断裂功与最大消耗功相等,表明烧结NdFeB合金具有极大的缺口敏感性.缺口敏感的脆性材料用单边切口粱法(SENB)测量KIC时要求较高的抛光精度,以消除表面划痕的影响,比较而言,压痕法测量KIC简便迅速.但由于所用NdFeB合金为烧结复相材料,其微观结构的不均匀性使实验数据较为分散.本研究借助Palmqvist裂纹系统半椭圆裂纹模型Hv-KIC的计算公式,采用开微缺口的单边缺口粱试样的KIC和压痕硬度及系列压痕裂纹参数,经回归分析确定了该公式中的经验常数,使之能够较为准确地表征烧结NdFeB永磁合金的断裂韧性.

  16. High magnetostriction parameters for low-temperature sintered cobalt ferrite obtained by two-stage sintering

    Energy Technology Data Exchange (ETDEWEB)

    Khaja Mohaideen, K.; Joy, P.A., E-mail: pa.joy@ncl.res.in

    2014-12-15

    From the studies on the magnetostriction characteristics of two-stage sintered polycrystalline CoFe{sub 2}O{sub 4} made from nanocrystalline powders, it is found that two-stage sintering at low temperatures is very effective for enhancing the density and for attaining higher magnetostriction coefficient. Magnetostriction coefficient and strain derivative are further enhanced by magnetic field annealing and relatively larger enhancement in the magnetostriction parameters is obtained for the samples sintered at lower temperatures, after magnetic annealing, despite the fact that samples sintered at higher temperatures show larger magnetostriction coefficients before annealing. A high magnetostriction coefficient of ∼380 ppm is obtained after field annealing for the sample sintered at 1100 °C, below a magnetic field of 400 kA/m, which is the highest value so far reported at low magnetic fields for sintered polycrystalline cobalt ferrite. - Highlights: • Effect of two-stage sintering on the magnetostriction characteristics of CoFe{sub 2}O{sub 4} is studied. • Two-stage sintering is very effective for enhancing the density and the magnetostriction parameters. • Higher magnetostriction for samples sintered at low temperatures and after magnetic field annealing. • Highest reported magnetostriction of 380 ppm at low fields after two-stage, low-temperature sintering.

  17. EXPERIMENTAL STUDIES FOR DEVELOPMENT HIGH-POWER AUDIO SPEAKER DEVICES PERFORMANCE USING PERMANENT NdFeB MAGNETS SPECIAL TECHNOLOGY

    Directory of Open Access Journals (Sweden)

    Constantin D. STĂNESCU

    2013-05-01

    Full Text Available In this paper the authors shows the research made for improving high-power audio speaker devices performance using permanent NdFeB magnets special technology. Magnetic losses inside these audio devices are due to mechanical system frictions and to thermal effect of Joules eddy currents. In this regard, by special technology, were made conical surfaces at top plate and center pin. Analysing results obtained by modelling the magnetic circuit finite element method using electronic software package,was measured increase efficiency by over 10 %, from 1,136T to13T.

  18. First-principles calculation of crystal field parameters of Dy ions substituted for Nd in Nd-Fe-B magnets

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, S; Moriya, H; Tsuchiura, H; Sakuma, A [Department of Applied Physics, Tohoku University, Sendai 980-8579 (Japan); Divis, M [Department of Condensed Matter, Charles University, FMF, Prague (Czech Republic); Novak, P, E-mail: tanaka@olive.apph.tohoku.ac.jp [Institute of Physics of ASCR, Cukrovarnicka 10, 162 53 Prague 6 (Czech Republic)

    2011-01-01

    We study the electronic structures of crystalline Nd{sub 2}Fe{sub 14}B, Dy{sub 2}Fe{sub 14}B and Dy-doped Nd-Fe-B, and estimate the crystal field parameter A{sup 0}{sub 2}(r{sup 2}) of the rare earth ions of these systems based on the first principles calculations. We find that the crystal field of the Dy ions is appreciably insensitive to its crystallographic location than that of Nd ions.

  19. Sintering of ultra high molecular weight polyethylene

    Indian Academy of Sciences (India)

    Sangeeta Hambir; J P Jog

    2000-06-01

    Ultra high molecular weight polyethylene (UHMWPE) is a high performance polymer having low coefficient of friction, good abrasion resistance, good chemical resistance etc. It is used in shipbuilding, textile industries and also in biomedical applications. UHMWPE is processed by powder processing technique because of its high melt viscosity at the processing temperature. Powder processing technique involves compaction of polymeric powder under pressure and sintering of the preforms at temperature above its melting point. In this study, we report our results on compaction and sintering behaviour of two grades of UHMWPE with reference to the powder morphology, sintering temperatures and strength development.

  20. Magnetic properties, microstructure and corrosion behavior of (Pr,nd)12.6Fe81.3B6.1-type sintered magnets doped with (Pr,nd)30Fe62Ga8

    Science.gov (United States)

    Ni, Junjie; Zhang, Zhenyu; Liu, Ying; Jia, Zhengfeng; Huang, Baoxu; Yin, Yibin

    2016-10-01

    NdFeB sintered magnets with (Pr,Nd)30Fe62Ga8 were prepared by a binary powder blending method and their magnetic properties, microstructure and corrosion behavior were investigated. Addition of 3 wt% (Pr,Nd)30Fe62Ga8 was found to be the most effective for improving (BH)max and iHc of the magnets. The increase in both magnetic parameters was related to the alteration in microstructure. However, in other samples the occurrence of micropore and the aggregation of intergranular phases harmed the magnetic properties. Such disadvantageous microstructure features also caused higher corrosion current density, thus decreasing the corrosion resistance of the sample with higher additive content. In addition, the Ga-containing intergranular phases that are more stable than the (Pr,Nd)-rich phase formed in the additive doped magnets, leading to better corrosion resistance of the 3 wt% additives doped sample in comparison with the contrastive sample.

  1. A comparative study of conventionally sintered and microwave sintered nickel zinc ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Rani, Rekha [Electroceramics Research Lab, GVM Girls College, Sonepat-131001, India and School of Physics and Materials Science, Thapar University, Patiala-147004 (India); Juneja, J. K. [Department of Physics, Hindu College, Sonepat-131001 (India); Raina, K. K. [School of Physics and Materials Science, Thapar University, Patiala-147004 (India); Kotnala, R. K. [National Physical Laboratory, New Delhi -110012 (India); Prakash, Chandra, E-mail: cprakash2014@gmail.com [Solid State Physics Laboratory, Timarpur, Delhi - 110054 (India)

    2014-04-24

    For the present work, nickel zinc ferrite having compositional formula Ni{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4} was synthesized by conventional solid state method and sintered in conventional and microwave furnaces. Pellets were sintered with very short soaking time of 10 min at 1150 °C in microwave furnace whereas 4 hrs of soaking time was selected for conventional sintering at 1200 °C. Phase formation was confirmed by X-ray diffraction analysis technique. Scanning electron micrographs were taken for microstructural study. Dielectric properties were studied as a function of temperature. To study magnetic behavior, M-H hysteresis loops were recorded for both samples. It is observed that microwave sintered sample could obtain comparable properties to the conventionally sintered one in lesser soaking time at lower sintering temperature.

  2. Cellular uptake of magnetite nanoparticles enhanced by NdFeB magnets in staggered arrangement

    Science.gov (United States)

    Lu, Yi-Ching; Chang, Fan-Yu; Tu, Shu-Ju; Chen, Jyh-Ping; Ma, Yunn-Hwa

    2017-04-01

    Magnetic force may greatly enhance uptake of magnetic nanoparticles (MNPs) by cultured cells; however, the effects of non-uniformity of magnetic field/ magnetic gradient on MNP internalization in culture has not been elucidated. Cellular uptake of polyacrylic acid coated-MNP by LN229 cells was measured with cylindrical NdFeB magnets arranged in a staggered pattern. The magnetic field generated by placing a magnet underneath (H-field) elicited a homogenous distribution of MNPs on the cells in culture; whereas the field without magnet underneath (L-field) resulted in MNP distribution along the edge of the wells. Cell-associated MNP (MNPcell) appeared to be magnetic field- and concentration-dependent. In H-field, MNPcell reached plateau within one hour of exposure to MNP with only one-min application of the magnetic force in the beginning of incubation; continuous presence of the magnet for 2 h did not further increase MNPcell, suggesting that magnetic force-induced uptake may be primarily contributed to enhanced MNP sedimentation. Although MNP distribution was much inhomogeneous in L-field, averaged MNPcell in the L-field may reach as high as 80% of that in H-field during 1-6 h incubation, suggesting high capacity of MNP internalization. In addition, no significant difference was observed in MNPcell analyzed by flow cytometry with the application of H-field of staggered plate vs. filled magnet plate. Therefore, biological variation may dominate MNP internalization even under relatively uniformed magnetic field; whereas non-uniformed magnetic field may serve as a model for tumor targeting with MNPs in vivo.

  3. Sintering of B{sub 4}C by pressureless liquid phase sintering

    Energy Technology Data Exchange (ETDEWEB)

    Rocha, Rosa Maria da; Melo, Francisco Cristovao Lourenco de, E-mail: rosarocha@iae.cta.br, E-mail: frapi@iae.cta.br [Instituto de Aeronautica e Espaco (IAE/CTA/IAE), Sao Jose dos Campos, SP (Brazil). Comando-Geral de Tecnologia Aeroespacial. Divisao de Materiais

    2009-07-01

    The effect of three different sintering additive systems on densification of boron carbide powder was investigated. The sintering additives were Al{sub 2}O{sub 3}:Y{sub 2}O{sub 3}, AlN:Y{sub 2}O{sub 3} and BN:Y{sub 2}O{sub 3} compositions. Powder mixtures were prepared with 10 vol% of sintering aids following conventional powder technology processes. Samples were sintered by pressureless sintering at 2050 deg C/30min in argon atmosphere. Sintered samples were compared to a sintered B{sub 4}C without sintering additive. Samples were characterized by XRD to analyze the crystalline phases after sintering and SEM to observe the microstructure and the second phase distribution. YB{sub 4} and YB{sub 2}C{sub 2} were identified in all samples, indicating a reaction between Y{sub 2}O{sub 3}, B{sub 4}C and B{sub 2}O{sub 3} present at the B{sub 4}C particle surface. The best densification result was achieved with Al{sub 2}O{sub 3}:Y{sub 2}O{sub 3} additive system, showing 92.0 % of theoretical density, low porosity and 15.2 % of linear shrinkage. But this sample showed the highest weight loss. (author)

  4. Sintering of nano crystalline silicon carbide doping with aluminium nitride

    Indian Academy of Sciences (India)

    M S Datta; A K Bandyopadhyay; B Chaudhuri

    2002-04-01

    Sinterable silicon carbide powders were prepared by attrition milling and chemical processing of an acheson type -SiC. Pressureless sintering of these powders was achieved by addition of aluminium nitride together with carbon. Nearly 99% sintered density was obtained. The mechanism of sintering was studied by scanning electron microscopy and transmission electron microscopy. This study shows that the mechanism is a solid sintering process.

  5. Ultrafast-Contactless Flash Sintering using Plasma Electrodes

    OpenAIRE

    Theo Saunders; Salvatore Grasso; Reece, Michael J.

    2016-01-01

    This paper presents a novel derivative of flash sintering, in which contactless flash sintering (CFS) is achieved using plasma electrodes. In this setup, electrical contact with the sample to be sintered is made by two arc plasma electrodes, one on either side, allowing current to pass through the sample. This opens up the possibility of continuous throughput flash sintering. Preheating, a usual precondition for flash sintering, is provided by the arc electrodes which heat the sample to 1400 ...

  6. Progress of Sintering Technology in Handan Iron and Steel Company

    Institute of Scientific and Technical Information of China (English)

    LIU Zheng-ping; WANG Yi-fang; WU Jin-bo

    2004-01-01

    As one of the biggest iron and steel companies in China, Handan Iron and Steel Co has made a substantial progress in the sintering process. The mini-pellet sintering technology has been successfully applied based on lab investigation and industrial trials. Equipment enlargement was realized through replacing small sintering strands with the construction of huge sintering machine with a grate area of 400 m2. The productivity, iron content and the metallurgical properties of sintering process have been improved.

  7. SINTERED REFRACTORY TUNGSTEN ALLOYS. Gesinterte hochschmelzende wolframlegierungen

    Energy Technology Data Exchange (ETDEWEB)

    Kieffer, R.; Sedlatschek, K.; Braun, H.

    1971-12-15

    Dependence of the melting point of the refractory metals on their positions in the periodic system - alloys of tungsten with other refractory metals - sintering of the alloys - processing of the alloys - technological properties.

  8. Nox reduction in the sintering process

    Institute of Scientific and Technical Information of China (English)

    Yan-guang Chen; Zhan-cheng Guo; Zhi Wang; Gen-sheng Feng

    2009-01-01

    A new process, NOx reduction with recycling flue gas and modifying coke breeze, was proposed. The effects of modified coke breeze and recycled flue gas on NOx reduction were investigated by sinter pot tests. The results show that the NOx reduction rate is over 10wt% in the sintering of modified coke breeze, the effects of the additives on NOx reduction are: CeO2CaOK2CO3.The NOx reduction rate increases with the amount of recycled flue gas, and is 22.35wt% in the sintering with recycling 30vo1% of the flue gas. When 30vo1% of the flue gas is recycled into the sintering of CeO2, CaO, and K2CO3 modified coke breeze, the NOx reduc-tion rates are 36.10wt%, 32.56wt%, and 32.17wt%, respectively.

  9. Sintering of magnesia: effect of additives

    Indian Academy of Sciences (India)

    Satyananda Behera; Ritwik Sarkar

    2015-10-01

    Effect of different additives, namely Cr2O3, Fe2O3 and TiO2, up to 2 wt% was studied on the sintering and microstructural developments of the chemically pure magnesia using the pressureless sintering technique between 1500 and 1600° C. Sintering was evaluated by per cent densification and microstructural developments were studied by electron microscopy and elemental distribution of the additives in the sintered products was also investigated for their distribution in the matrix. Cr2O3 and TiO2 were found to deteriorate the densification associated with grain growth. Fe2O3 was found to improve the densification and well-compacted grain distribution was observed in the microstructure.

  10. Magnetic texture of Nd2Fe14B solidified in the surface layer of anisotropic sintered-magnets

    Institute of Scientific and Technical Information of China (English)

    PAN Jing; LIU Xincai; TU Fenghua

    2006-01-01

    The arrangements of the easy magnetization axis [001] of columnar Nd2Fe14B crystals in the laser scanned layer on anisotropic sintered Nd15Fe77B8 magnets were investigated by XRD and the Bitter method. The results show that the common effects of both the heat flux and the substrate magnetization orientation constrain the columnar Nd2Fe14B solidified from the laser melting pool to form the c -axis texture orientated with the same direction as that of the substrate, when the geometric relationship between the heat flux in the laser scanning layer and c -axis texture orientation of the substrate is perpendicular to each other, and if the laser scanning velocity is no less than 25 mm·min-1 . The c -axes of columnar Nd2Fe14B crystals are no longer randomly distributed in the plane normal to their preferential growing direction as they are randomly done in both ingots cooled by water-cooling copper mould and directionally solidified Nd-Fe-B rods.

  11. Increased Efficiency of a Permanent Magnet Synchronous Generator through Optimization of NdFeB Magnet Arrays

    Science.gov (United States)

    Khazdozian, Helena; Hadimani, Ravi; Jiles, David

    2014-03-01

    The United States is currently dependent on fossil fuels for the majority of its energy needs, which has many negative consequences such as climate change. Wind turbines present a viable alternative, with the highest energy return on investment among even fossil fuel generation. Traditional commercial wind turbines use an induction generator for energy conversion. However, induction generators require a gearbox to increase the rotational speed of the drive shaft. These gearboxes increase the overall cost of the wind turbine and account for about 35 percent of reported wind turbine failures. Direct drive permanent magnet synchronous generators (PMSGs) offer an alternative to induction generators which eliminate the need for a gearbox. Yet, PMSGs can be more expensive than induction generators at large power output due to their size and weight. To increase the efficiency of PMSGs, the geometry and configuration of NdFeB permanent magnets were investigated using finite element techniques. The optimized design of the PMSG increases flux density and minimizes cogging torque with NdFeB permanent magnets of a reduced volume. These factors serve to increase the efficiency and reduce the overall cost of the PMSG. This work is supported by a National Science Foundation IGERT fellowship and the Barbara and James Palmer Endowment at the Department of Electrical and Computer Engineering of Iowa State University.

  12. Investigation of chemical composition and crystal structure in sintered Ce15Nd15FebalB1 magnet

    Directory of Open Access Journals (Sweden)

    Shu-lin Huang

    2014-10-01

    Full Text Available The substitution of cerium, a more abundant rare-earth element, for sintered Nd-Fe-B magnets has drawn intense interest. In the present work, nominal composition of Ce15Nd15FebalB1 (wt. %, with cerium constitutes increased to 50% of the total rare-earth content, was used. And Ce-free Nd30FebalB1 (wt. % was prepared by the same preparation process as comparison. The microstructure of the sintered magnets has been investigated by means of X-ray diffraction and transmission electron microscope. The results show that there are three kinds of RE-rich phases in the same magnet, i.e., fcc-(Ce,NdOx (a=0.547nm, hcp-(Ce,Nd2O3 (a=0.386nm, c=0.604nm and bcc-(Ce,Nd2O3 (a=1.113nm. Ors of (140(Ce,Nd2Fe14B// (1-21bcc-(Ce,Nd2O3(∼3°, [001](Ce,Nd2Fe14B// [-214]bcc-(Ce,Nd2O3; (01-1(Ce,Nd2Fe14B// (101fcc- (Ce,NdOx(∼2°, [101](Ce,Nd2Fe14B// [12-1]fcc-(Ce,NdOx were found through selected area electron diffraction (SAED analysis. According to the analysis, it can be concluded that cerium has partly substituted for neodymium by occupying the corresponding atom sites in the Ce15Nd15FebalB1 magnet, without changing the crystal configuration.

  13. Analysis of Laser Sintering Technology

    Directory of Open Access Journals (Sweden)

    Vladislav Markovič

    2014-02-01

    Full Text Available The new, high-tech development and customization is one ofthe most important factors in promoting the country‘s economicgrowth indicators. The economic downturn in the industryrequires technology and equipment using a minimumof raw materials and providing maximum performance. Thisstatement perfectly describes the innovative, forward-looking,cost-effective laser powder sintering (SLS technology. Here,thanks to the latest engineering achievements, product surfacesare modified and improved, they gain new characteristics. SLSis viable in automobile, engineering, construction, aerospace,aircraft, printing, medical and other areas.In order to create a product which meets the standards andtechnical documentation it is necessary to use and ensure highquality of raw materials, high-end equipment, qualified personnel,the working environment with proper climatic conditions, ergonomics,etc. But all of these, the quality of the product becomesthe decisive indicators meaningless if know how to properly selectthe laser processing operation. Scanning speed, beam power,pulse frequency, protective gases, powder layer thickness – allof them are the physical and mechanical characteristics of thechange in a small range changes the quality of the product of thefuture, the field of application and performance characteristics.

  14. Spark Plasma Sintering of Ultracapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Hill, Curtis W. [CK Technologies, Camirillo, CA (United States); Boatner, Lynn A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Tucker, Dennis [NASA Johnson Space Center, Houston, TX (United States); Kolopus, James A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cheng, Zhongyang [Auburn Univ., AL (United States)

    2016-01-01

    A solid-state ultracapacitor module to replace standard electrochemical batteries would achieve major performance gains and mass/volume reduction. This report summarizes a project to evaluate an alternative sintering process to produce a solid-state ultracapacitor to overcome the limitations of both the electrochemical batteries presently in use on spacecraft and of currently available electrochemical ultracapacitors. It will provide a robust energy storage device with higher reliability, wider working temperature range, longer lifetime, and less weight and volume than electrochemical batteries. As modern electronics decrease in size, more efficient and robust remote power is needed. Current state-of-the-art rechargeable batteries cannot be rapidly charged, contain harmful chemicals, and suffer from early wear-out mechanisms. Solid-state ultracapacitors are recyclable energy storage devices that offer the promise of higher power and a greater number of charge/discharge cycles than current rechargeable batteries. In addition, the theoretical energy density when compared to current electrochemical batteries indicates that a significant weight savings is possible. This is a project to develop a very high density solid-state ultracapacitor with giant permittivity and acceptable dielectric loss to overcome the energy-density barrier such that it will be a suitable replacement for batteries.

  15. Residual stresses in a co-sintered SOC half-cell during post-sintering cooling

    DEFF Research Database (Denmark)

    Charlas, Benoit; Chatzichristodoulou, Christodoulos; Brodersen, Karen

    2014-01-01

    . This methodology is however not valid for more layers, as several configurations of residual stresses in the layers can result in the same curvature. Therefore the development of residual stresses of co-sintered multilayer cells during the cooling after sintering is here studied by a finite element model...

  16. Iridate compound produces extraordinarily high coercive magnetic field

    Science.gov (United States)

    Zapf, Vivien; Topping, Craig; Kim, Jae-Wook; Mun, Eun-Deok; Goddard, Paul; Ghannadzadeh, Saman; Luo, Xuan; Cheong, Sang-Wook; Singleton, John

    2014-03-01

    We present a data on an iridate compound that shows an extraordinarily large magnetic hysteresis loop. The coercive magnetic field exceeds 40 Tesla in single-crystal samples. The hysteresis coexists with a linear background, and the total remanent magnetization is about half a Bohr magneton. We will discuss the emergence of these properties from the interplay of spin-orbit coupling, magnetic exchange and possible frustration. The single crystalline material exhibits a magnetic hysteresis loop for one orientation of the magnetic field and a smooth linear increase in the magnetization with field for the other. Measurements were conducted in 65 T short-pulse magnets and the 60 Tesla shaped-pulse magnet at the National High Magnetic Field Lab in Los Alamos. We do not observe any dependence of the magnetic hysteresis on magnetic field sweep rate. Compounds containing Ir4 + have attracted attention recently due to strong spin-orbit coupling that competes with crystal-electric field and exchange interactions. This competition can result in non-Hund's-rule ground states with unusual properties.

  17. τ-MnAl with high coercivity and saturation magnetization

    Directory of Open Access Journals (Sweden)

    J. Z. Wei

    2014-12-01

    Full Text Available In this paper, high purity τ-Mn54Al46 and Mn54−xAl46Cxalloys were successfully prepared using conventional arc-melting, melt-spinning, and heat treatment process. The magnetic and the structural properties were examined using x-ray diffraction (XRD, powder neutron diffraction and magnetic measurements. A room temperature saturation magnetization of 650.5 kAm-1, coercivity of 0.5 T, and a maximum energy product of (BHmax = 24.7 kJm-3 were achieved for the pure Mn54Al46 powders without carbon doping. The carbon substituted Mn54−xAl46Cx, however, reveals a lower Curie temperature but similar saturation magnetization as compared to the carbon-free sample. The electronic structure of MnAl shows that the Mn atom possesses a magnetic moment of 2.454 μB which results from strong hybridization between Mn-Al and Mn-Mn. We also investigated the volume and c/a ratio dependence of the magnetic moments of Mn and Al. The results indicate that an increase in the intra-atomic exchange splitting due to the cell volume expansion, leads to a large magnetic moment for the Mn atom. The Mn magnetic moment can reach a value of 2.9 μB at a volume expansion rate of ΔV/V ≈ 20%.

  18. Design and performance of electromagnetic machines based on Nd-Fe-B magnets

    Science.gov (United States)

    Hanitsch, R.

    1991-10-01

    The application of rare-earth permanent magnets - replacing wound coils - in electrical devices is advantageous concerning performance and cost. The benefits are: increased efficiency, reduced time constant, smaller volume and weight, and cost effective production. These magnets have mainly been installed in high-precision small-size motors such as brushless dc motors, stepping motors and coreless motors. Motors of these types are used in computer peripherals and portable electronic products. Because of improvements in the materials rare-earth magnets are now also used for automotive applications and industrial drives. In addition to sintered materials bonded materials are also used for motor and actuator designs.

  19. Design and development of expert system for controlling sintering process

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The general structure of expert system for controlling sintering process has been proposed. It includes knowledge base, inference engine, data acquisition system, learning system, knowledge base management system, explanation system and so on. The control functions consist of sintering chemical composition control centered on basicity and sintering process state control centered on permeability. The adaptive prediction of sintering chemical composition, the control strategy centered on basicity, the control strategy centered on permeability, the judgement of permeability and the prediction of burn through point were studied. The software of system, which includes about 1000 expert rules, was successfully applied in off-line control of sintering process in a sintering plant.

  20. Calcium Hex aluminate reaction sintering by Spark Plasma Sintering; Sinterizacion reactiva de Hexaluminato de Calcio mediante Spark Plasma Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Iglesia, P. G. de la; Garcia-Moreno, O.; Torrecillas, R.; Menendez, J. L.

    2012-11-01

    Calcium hex aluminate (CaAl{sub 1}2O{sub 1}9) is the most alumina-rich intermediate compound of the CaO-Al{sub 2}O{sub 3} system. The formation of this aluminate is produced by the reaction between calcium oxide and alumina with the consequent formation of intermediates compounds with lower alumina content with increasing temperature (CaAl{sub 2}O{sub 4}, CaAl4O{sub 7}). In this study we studied the variation of sintering parameters for obtaining dense and pure calcium hex aluminate by reaction sintering by Spark Plasma Sintering (SPS). A mixing of Al{sub 2}O{sub 3} and CaCO{sub 3} were used as reactive. Final densities close to the theoretical and phase transformation over 93% were achieved by this method. (Author) 22 refs.

  1. Investigation of sintering kinetics of magnesium titanate

    Directory of Open Access Journals (Sweden)

    Petrović V.V.

    2013-01-01

    Full Text Available Obtaining new materials including sintered electronic materials using different procedures is the consequence of long complex and expensive experimental work. However, the dynamics of expansive development of electronic devices requires fast development of new materials, especially sintered oxide materials. The recent rapid development of electronics is among other things due to development and improvement of new components based on titanate ceramics. Research in this work has included an experimental study of the synthesis of dielectric ceramics in the system MgCO3 - TiO2. Starting powders were mechanically activated by milling in a high energy planetary mill for different times. Samples were prepared for isothermal sintering at 1100ºC by dual pressing of powders into cylindrical samples in a hydraulic press.

  2. Titanium processing using selective laser sintering

    Science.gov (United States)

    Harlan, Nicole Renee

    1999-11-01

    A materials development workstation specifically designed to test high temperature metal and metal-matrix composites for direct selective laser sintering (SLS) was constructed. Using the workstation, a titanium-aluminum alloy was sintered into single layer coupons to demonstrate the feasibility of producing titanium components using direct SLS. A combination of low temperature indirect SLS and colloidal infiltration was used to create "partially-stabilized" zirconia molds for titanium casting. The base material, stabilized zirconia mixed with a copolymer, was laser sintered into the desired mold geometry. The copolymer was pyrolyzed and replaced by a zirconia precursor. The flexural strength and surface roughness of the SLS-produced casting molds were sufficient for titanium casting trials. A laser-scanned human femur was used as the basis for a mold design and technology demonstration. Titanium castings produced from SLS molds exhibited typical as-cast microstructures and an average surface roughness (Ra) of 8 mum.

  3. Fabrication of 200 mm Diameter Sintering Body of Skutterudite Thermoelectric Material by Spark Plasma Sintering

    Science.gov (United States)

    Tomida, T.; Sumiyoshi, A.; Nie, G.; Ochi, T.; Suzuki, S.; Kikuchi, M.; Mukaiyama, K.; Guo, J. Q.

    2016-11-01

    Filled skutterudite is a promising material for thermoelectric power generation because its ZT value is relatively high. However, mass production of high-performance thermoelectric materials remains a challenge. This study focused on the sintering process of thermoelectric materials. Large-diameter n-type (Yb or La, Ca, Al, Ga, In)0.8(Co, Fe)4Sb12 skutterudite sintering bodies with a small thickness were successfully produced by the spark plasma sintering (SPS) method. When direct current flows through the thermoelectric sintering body during the SPS pulse, the Peltier effect causes a temperature difference within the sintering body. To eliminate the Peltier effect, an electrical insulating material was inserted between the punch (electrode) and the sintering body. In this way, an n-type La-filled skutterudite sample with a diameter of 200 mm, thickness of 21 mm, and weight of 5 kg was successfully produced. The thermoelectric properties and microstructures of the sample were almost the same throughout the whole sintering body, and the dimensionless figure of merit reached 1.0 at 773 K.

  4. A novel method combining additive manufacturing and alloy infiltration for NdFeB bonded magnet fabrication

    Science.gov (United States)

    Li, Ling; Tirado, Angelica; Conner, B. S.; Chi, Miaofang; Elliott, Amy M.; Rios, Orlando; Zhou, Haidong; Paranthaman, M. Parans

    2017-09-01

    In this paper, binder jetting additive manufacturing technique is employed to fabricate NdFeB isotropic bonded magnets, followed by an infiltration process with low-melting point eutectic alloys [i.e., Nd3Cu0.25Co0.75 (NdCuCo) and Pr3Cu0.25Co0.75 (PrCuCo)]. Densification and mechanical strength improvement are achieved for the as-printed porous part. Meanwhile, the intrinsic coercivity Hci is enhanced from 732 to 1345 kA/m and 1233 kA/m after diffusion of NdCuCo and PrCuCo, respectively. This study presents a novel method for fabricating complex-shaped bonded magnets with promising mechanical and magnetic properties.

  5. Effect of bonding process on the properties of isotropic epoxy resin-bonded Nd-Fe-B magnets

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xiuhai; XIONG Weihao

    2009-01-01

    Bonded NdFeB magnets were prepared by compression molding. The effect of preparation technology on their magnetic and mechanical properties was studied through the analysis of density, Br Hcj, (BH)max, bending strength, and compressive strength of the bonded magnets. The results showed that the magnetic properties decreased with increasing binder content, whereas the mechanical properties increased. Brand (BH)max increased with rising pressure, whereas Hcj decreased. For a fixed mass fraction of the binder, the optimal pressure was 620 MPa and the best thermosetting temperature was 160℃. These conditions made the bonded magnets have the optimal mechanical properties. Scanning electron microscopy (SEM) analyses of the fracture surfaces indicated that the epoxy resin bonded magnets exhibited brittle behavior.

  6. Improved room-temperature-selectivity between Nd and Fe in Nd recovery from Nd-Fe-B magnet

    Energy Technology Data Exchange (ETDEWEB)

    Kataoka, Y.; Kitagawa, J., E-mail: j-kitagawa@fit.ac.jp [Department of Electrical Engineering, Faculty of Engineering, Fukuoka Institute of Technology, 3-30-1 Wajiro-higashi, Higashi-ku, Fukuoka 811-0295 (Japan); Ono, T.; Tsubota, M. [Physonit Inc., 6-10 Minami-Horikawa, Kaita Aki, Hiroshima 736-0044 (Japan)

    2015-11-15

    The sustainable society requires the recycling of rare metals. Rare earth Nd is one of rare metals, accompanying huge consumption especially in Nd-Fe-B magnets. Although the wet process using acid is in practical use in the in-plant recycle of sludge, higher selectivity between Nd and Fe at room temperature is desired. We have proposed a pretreatment of corrosion before the dissolution into HCl and the oxalic acid precipitation. The corrosion produces γ-FeOOH and a Nd hydroxide, which have high selectivity for HCl solution at room temperature. Nd can be recovered as Mn{sub 2}O{sub 3}-type Nd{sub 2}O{sub 3}. The estimated recovery-ratio of Nd reaches to 97%.

  7. Improved room-temperature-selectivity between Nd and Fe in Nd recovery from Nd-Fe-B magnet

    Directory of Open Access Journals (Sweden)

    Y. Kataoka

    2015-11-01

    Full Text Available The sustainable society requires the recycling of rare metals. Rare earth Nd is one of rare metals, accompanying huge consumption especially in Nd-Fe-B magnets. Although the wet process using acid is in practical use in the in-plant recycle of sludge, higher selectivity between Nd and Fe at room temperature is desired. We have proposed a pretreatment of corrosion before the dissolution into HCl and the oxalic acid precipitation. The corrosion produces γ-FeOOH and a Nd hydroxide, which have high selectivity for HCl solution at room temperature. Nd can be recovered as Mn2O3-type Nd2O3. The estimated recovery-ratio of Nd reaches to 97%.

  8. A comparative thermomagnetic study of melt-spun Nd-Fe-B alloys with different Nd content

    Directory of Open Access Journals (Sweden)

    Grujić A.

    2009-01-01

    Full Text Available Changes in the phase composition and magnetic properties of three types of commercial Nd-Fe-B alloys with different Nd content - low (10-12 wt%, near stoichiometric (21-25 wt% and rich (26-29 wt% caused by thermomagnetic analysis (TM were observed in regard to optimal magnetic state. Phase compositions of investigated alloys before and after TM measurement up to 800°C were compared using 57Fe Mössbauer spectroscopy and X-Ray analysis. The TM measurements decompose all three materials and the main products of decomposition process α-Fe and Fe2B phase. Observed changes in structure and phase composition had direct influence on magnetic properties. Loss of magnetic properties induced by thermal decomposition is clearly illustrated on corresponding SQUID hysteresis loops.

  9. Hydrogen Embrittlement Processes and Al/Al2O3 Hydrogen Resistance Coatings of NdFeB Magnets

    Institute of Scientific and Technical Information of China (English)

    张万里; 彭斌; 蒋洪川; 张文旭; 杨仕清

    2004-01-01

    After analyzing the phenomena and processes of hydrogen embrittlement of NdFeB permanent magnets,RF magnetron sputtering was used to fabricate Al thin films and then oxidized to form the Al/Al2O3 composite films on the magnets as the hydrogen resistance coatings.SEM and EDS were used to examine the morphology and composition respectively.Hydrogen resistance performance was tested by exposing the magnets in 10 MPa hydrogen gas at room temperature.The results show that the magnets with 8 μm Al/Al2O3 coatings can withstand hydrogen of 10 MPa for 65 min without being embrittled into powder.The samples with and without hydrogen resistance coatings have almost the same magnetic properties.

  10. New sintering process adjusts magnetic value of ferrite cores

    Science.gov (United States)

    Vinal, A. W.

    1964-01-01

    A two-phase sintering technique based on time and temperature permits reversible control of the coercive threshold of sintered ferrite cores. Threshold coercivity may be controlled over a substantial range of values by selective control of the cooling rate.

  11. effects of sintering temperature on the density and porosity of ...

    African Journals Online (AJOL)

    2013-03-01

    Mar 1, 2013 ... turing. 2. Sintering Mechanism. Sintering occurs by atomic diffusion processes that are stimulated by high .... of the experiments was repeated three times. 3.2. ... test revealed the variation of porosity across the mi- crostructure ...

  12. Numerical Simulation of Upsetting a Cubic Sintered Iron Powder Compact

    Institute of Scientific and Technical Information of China (English)

    Wei XIA; Puqing CHEN; Zhaoyao ZHOU; Weibin ZHAO; Yuanyuan LI

    2003-01-01

    This paper establishes a mechanical model for sintered powder metal material and simulates the material behavior.Powder metal specimens were compacted, sintered and upset. Relative density and contour of the specimen were measured. The force displacement

  13. Phase characterisation in spark plasma sintered TiPt alloy

    CSIR Research Space (South Africa)

    Chikosha, S

    2011-12-01

    Full Text Available The conclusions drawn from this presentation are that Spark Plasma Sintering (SPS) of equiatomic BE TiPt powder produces fully sintered specimens, with incomplete homogenisation. There is a need for improved furnace atmosphere control so...

  14. Plasma Nitriding of Low Alloy Sintered Steels

    Institute of Scientific and Technical Information of China (English)

    Shiva Mansoorzadeh; Fakhreddin Ashrafizadeh; Xiao-Ying Li; Tom Bell

    2004-01-01

    Fe-3Cr-0.5Mo-0.3C and Fe-3Cr-1.4Mn-0.5Mo-0.367C sintered alloys were plasma nitrided at different temperatures. Characterization was performed by microhardness measurement, optical microscopy, SEM and XRD. Both materials had similar nitriding case properties. 1.4% manganese did not change the as-sintered microstructure considerably.It was observed that monophase compound layer, γ, formed with increasing temperature. Compound layer thickness increased with increasing temperature while nitriding depth increased up to a level and then decreased. Core softening was more pronounced at higher temperature owing to cementite coarsening.

  15. Properties of oxide-hydroxide sintered ceramics

    Science.gov (United States)

    Levkov, R. V.; Kulkov, S. N.

    2017-02-01

    In this paper the study of porous ceramics obtained from aluminum hydroxide with gibbsite modification is presented. It was shown that aluminum hydroxide may be used for pore formation and pore volume in the sintered ceramics can be controlled by varying the aluminum hydroxide concentration and sintering temperature. It was shown that compressive strength of alumina ceramics increases by 40 times with decreasing the pore volume from 65 to 15%. Based on these results one can conclude that the obtained structure is very close to inorganic bone matrix and can be used as promising material for bone implants production.

  16. Mechanical characterization of microwave sintered zinc oxide

    Indian Academy of Sciences (India)

    A K Mukhopadhyay; M Ray Chaudhuri; A Seal; S K Dalui; M Banerjee; K K Phani

    2001-04-01

    The mechanical characterization of microwave sintered zinc oxide disks is reported. The microwave sintering was done with a specially designed applicator placed in a domestic microwave oven operating at a frequency of 2.45 GHz to a maximum power output of 800 Watt. These samples with a wide variation of density and hence, of open pore volume percentage, were characterized in terms of its elastic modulus determination by ultrasonic time of flight measurement using a 15 MHz transducer. In addition, the load dependence of the microhardness was examined for the range of loads 0.1–20 N. Finally, the fracture toughness data (IC) was obtained using the indentation technique.

  17. Coercivity enhancement of hot-deformed Nd-Fe-B magnets by the eutectic grain boundary diffusion process

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lihua [Elements Strategy Initiative Center for Magnetic Materials, National Institute of Materials Science, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Science, University of Tsukuba, Tsukuba 305-8577 (Japan); Sepehri-Amin, H.; Ohkubo, T. [Elements Strategy Initiative Center for Magnetic Materials, National Institute of Materials Science, Tsukuba 305-0047 (Japan); Yano, M.; Kato, A.; Shoji, T. [Toyota Motor Corporation, Advanced Material Engineering Div., Susono 410-1193 (Japan); Hono, K., E-mail: kazuhiro.hono@nims.go.jp [Elements Strategy Initiative Center for Magnetic Materials, National Institute of Materials Science, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Science, University of Tsukuba, Tsukuba 305-8577 (Japan)

    2016-05-05

    Nd-M (M = Al, Cu, Ga, Zn, Mn) alloys with compositions close to eutectic points were investigated as diffusion sources for the grain boundary diffusion process to hot-deformed Nd-Fe-B magnets. Coercivity enhancement was observed for most of the alloys. Among them, the sample processed with Nd{sub 90}Al{sub 10} exhibited the highest coercivity of 2.5 T at room temperature. However, the sample processed with Nd{sub 70}Cu{sub 30} exhibited the highest coercivity of 0.7 T at 200 {sup °}C. Microstructural observations using scanning transmission electron microscope (STEM) showed that nonferromagnetic Nd-rich intergranular phase envelops the Nd{sub 2}Fe{sub 14}B grains after the diffusion process. Abnormal grain growth and the dissolution of Al into the Nd{sub 2}Fe{sub 14}B grains were observed in the sample processed with Nd{sub 90}Al{sub 10}, which explains its inferior thermal stability of coercivity compared to the sample processed with Nd{sub 70}Cu{sub 30}. The coercivity enhancement and poor thermal stability of the coercivity of the Nd{sub 90}Al{sub 10} diffusion-processed sample are discussed based on microstructure studies by transmission electron microscopy. - Highlights: • Coercivity of hot-deformed Nd-Fe-B magnets is enhanced by the infiltration of various R-TM eutectic alloys. • The sample infiltrated with Nd{sub 90}Al{sub 10} shows the highest coercivity of 2.5 T at room temperature. • At 200 °C, Nd{sub 70}Cu{sub 30} diffusion-processed sample possesses the highest coercivity of 0.7 T.

  18. Nanocompositional Electron Microscopic Analysis and Role of Grain Boundary Phase of Isotropically Oriented Nd-Fe-B Magnets

    Directory of Open Access Journals (Sweden)

    Gregor A. Zickler

    2017-01-01

    Full Text Available Nanoanalytical TEM characterization in combination with finite element micromagnetic modelling clarifies the impact of the grain misalignment and grain boundary nanocomposition on the coercive field and gives guidelines how to improve coercivity in Nd-Fe-B based magnets. The nanoprobe electron energy loss spectroscopy measurements obtained an asymmetric composition profile of the Fe-content across the grain boundary phase in isotropically oriented melt-spun magnets and showed an enrichment of iron up to 60 at% in the Nd-containing grain boundaries close to Nd2Fe14B grain surfaces parallel to the c-axis and a reduced iron content up to 35% close to grain surfaces perpendicular to the c-axis. The numerical micromagnetic simulations on isotropically oriented magnets using realistic model structures from the TEM results reveal a complex magnetization reversal starting at the grain boundary phase and show that the coercive field increases compared to directly coupled grains with no grain boundary phase independently of the grain boundary thickness. This behaviour is contrary to the one in aligned anisotropic magnets, where the coercive field decreases compared to directly coupled grains with an increasing grain boundary thickness, if Js value is > 0.2 T, and the magnetization reversal and expansion of reversed magnetic domains primarily start as Bloch domain wall at grain boundaries at the prismatic planes parallel to the c-axis and secondly as Néel domain wall at the basal planes perpendicular to the c-axis. In summary our study shows an increase of coercive field in isotropically oriented Nd-Fe-B magnets for GB layer thickness > 5 nm and an average Js value of the GB layer < 0.8 T compared to the magnet with perfectly aligned grains.

  19. Improving NASICON Sinterability through Crystallization under High Frequency Electrical Fields

    Directory of Open Access Journals (Sweden)

    Ilya eLisenker

    2016-03-01

    Full Text Available The effect of high frequency (HF electric fields on the crystallization and sintering rates of a lithium aluminum germanium phosphate (LAGP ion conducting ceramic was investigated. LAGP with the nominal composition Li1.5Al0.5Ge1.5(PO43 was crystallized and sintered, both conventionally and under effect of electrical field. Electrical field application, of 300V/cm at 1MHz, produced up to a 40% improvement in sintering rate of LAGP that was crystallized and sintered under the HF field. Heat sink effect of the electrodes appears to arrest thermal runaway and subsequent flash behavior. Sintered pellets were characterized using XRD, SEM, TEM and EIS to compare conventionally and field sintered processes. The as-sintered structure appears largely unaffected by the field as the sintering curves tend to converge beyond initial stages of sintering. Differences in densities and microstructure after 1 hour of sintering were minor with measured sintering strains of 31% vs. 26% with and without field, respectively . Ionic conductivity of the sintered pellets was evaluated and no deterioration due to the use of HF field was noted, though capacitance of grain boundaries due to secondary phases was significantly increased.

  20. Accuracy analysis of the part made by selected laser sintering

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    The effects of different factors, including the precision of selected laser sintering (SLS) equipment, sintering temperature, sintered thickness of individual layer and laser scanning route, on the SLS part accuracy have been analyzed and studied. Some measures are suggested in order to improve the part accuracy made by SLS.

  1. The attenuation of the levitation force of HTS bulk exposed to AC magnetic field on the above NdFeB guideway

    Science.gov (United States)

    Liu, Minxian; Wang, Yan

    2012-01-01

    In the present High Temperature Superconducting (HTS) maglev vehicle system, the air gaps between the adjacent permanent magnets make the magnetic fields above the NdFeB guideway non-uniform. So it is required to study the characteristics of levitation force of the HTS bulk affected by the non-uniform applied magnetic fields along the moving direction. In this paper, we have studied the characteristics of the levitation force relaxation by an experiment in which AC magnetic field generated by an electromagnet is used to simulate the time-varying magnetic field caused by the inhomogeneity of the NdFeB guideway. From the experiment results, it is found that the levitation force is attenuated with the application of the AC field, and the attenuation is increased with the amplitude of the AC field, but the attenuation is almost independent of the frequency the AC magnetic field.

  2. Estimation of the activation energy of sintering in KNN ceramics using master sintering theory

    Science.gov (United States)

    Singh, Rajan; Patro, P. K.; Kulkarni, Ajit R.; Harendranath, C. S.

    2014-04-01

    The master sintering curve (MSC) of K0.5Na0.5NbO3 (KNN) ceramics was constructed using constant heating rate dilatometry data based on the combined stage sintering model. The linear shrinkage was recorded using three heating rates 5 °C, 7 °C and 11 °C/ min. The obtained results suggest that in MSC, the sintered density is a unique function of the integral of a temperature function over time and it is independent of the sintering history. The MSC theory can be applied to predict shrinkage and final density. Also, it can be used to design a reproducible process to fabricate ceramics with required density.

  3. Sintering behavior of LZSA glass-ceramics

    Directory of Open Access Journals (Sweden)

    Oscar Rubem Klegues Montedo

    2009-06-01

    Full Text Available The LZSA glass-ceramic system (Li2O-ZrO2-SiO2-Al2O 3 shows interesting properties, such as good chemical resistance, low thermal expansion, high abrasion resistance, and a low dielectric constant. However, in order to obtain a high performance material for specific applications, the sintering behavior must be better understood so that the porosity may be reduced and other properties improved. In this context, a sintering investigation for a specific LZSA glass-ceramic system composition was carried out. A 18.8Li2O-8.3ZrO2-64.2SiO2-8.7Al 2O3 glass was prepared by melting the solids, quenching the melt in water, and grinding the resulting solid in order to obtain a powder (3.68 μm average particle diameter. Subsequently, the glass powder was characterized (chemical analysis and determination of thermal properties and the sintering behavior was investigated using optical non-contact dilatometry measurements. The results showed that the crystallization process strongly reduced the sintering in the temperature interval from 785 to 940 °C, and a maximum thermal shrinkage of 15.4% was obtained with operating conditions of 1020 °C and 180 minutes.

  4. Multistep sintering to synthesize fast lithium garnets

    Science.gov (United States)

    Xu, Biyi; Duan, Huanan; Xia, Wenhao; Guo, Yiping; Kang, Hongmei; Li, Hua; Liu, Hezhou

    2016-01-01

    A multistep sintering schedule is developed to synthesize Li7La3Zr2O12 (LLZO) doped with 0.2 mol% Al3+. The effect of sintering steps on phase, relative density and ionic conductivity of Al-doped LLZO has been evaluated using powder X-Ray diffraction (XRD), scanning electron microscopy (SEM), 27Al magic spinning nuclear magnetic resonance (NMR) spectroscopy and electrochemical impedance spectroscopy (EIS). The results show that by holding the sample at 900 °C for 6 h, the mixture of tetragonal and cubic garnet phases are obtained; by continuously holding at 1100 °C for 6 h, the tetragonal phase completely transforms into cubic phase; by holding at 1200 °C, the relative density increases without decomposition of the cubic phase. The Al-LLZO pellets after multistep sintering exhibit cubic phase, relative density of 94.25% and ionic conductivity of 4.5 × 10-4 S cm-1 at room temperature. Based on the observation, a sintering model is proposed and discussed.

  5. Sintering of silicon nitride ceramics with magnesium silicon nitride and yttrium oxide as sintering aids

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, J; Xu, J Y [Shanghai Institute of Technology, Shanghai 200235 (China); Peng, G H [Guangxi Normal University, Guilin 541004, Guangxi (China); Zhuang, H R; Li, W L; Xu, S Y [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Mao, Y J, E-mail: guojianjiang@sit.edu.cn [Shanghai University, Shanghai 200444 (China)

    2011-10-29

    Silicon nitride (Si{sub 3}N{sub 4}) ceramics had been produced through pressureless sintering and hot-pressing sintering with MgSiN{sub 2}-Y{sub 2}O{sub 3} or only MgSiN{sub 2} as sintering aids. The influences of the amount of MgSiN{sub 2} and Y{sub 2}O{sub 3} and sintering methods on the properties of Si{sub 3}N{sub 4} ceramics were investigated. The results show that the bend strength of Si{sub 3}N{sub 4} ceramic fabricated through pressureless sintering at 1820 deg. C for 4 h with 5.6 wt.% MgSiN{sub 2}-15.8 wt.% Y{sub 2}O{sub 3} as sintering additive could achieve 839 MPa. However, the bend strength of Si{sub 3}N{sub 4} ceramic produced by hot-pressing sintering at 1750 deg. C for 1 h under uniaxial pressure of 20 MPa with 4.76 wt.% MgSiN{sub 2} was 1149 MPa. The thermal conductivity of the Si{sub 3}N{sub 4} ceramic 2 3 4 could reach to 129 W{center_dot}m{sup -1{center_dot}}K{sup 1}. The present work demonstrated that MgSiN{sub 2} aids and hot-pressing sintering were effective to improve the thermal conductivity of Si{sub 3}N{sub 4} ceramic.

  6. TiO2 doped UO2 fuels sintered by spark plasma sintering

    Science.gov (United States)

    Yao, Tiankai; Scott, Spencer M.; Xin, Guoqing; Lian, Jie

    2016-02-01

    UO2 fuels doped with oxide additives Cr2O3 and TiO2 display larger grain size, improving fission product retention capability and thus accident tolerance. Spark plasma sintering (SPS) was applied to consolidate TiO2-doped UO2 fuel pellets with 0.5 wt % dopant concentration, above its solubility, in order to induce eutectic phase formation and promote sintering kinetics. The grain size can reach 80 μm by sintering at 1700 °C for 20 min, and liquid U-Ti-O eutectic phase occurs at the triple junction of grain boundaries and significantly improves grain growth during sintering. The oxide additive also impedes the reduction of the initial hyperstoichiometric fuel powders to more stoichiometric fuel pellets upon SPS process. Thermal-mechanical properties of the sintered doped fuel pellets including thermal conductivity and hardness are measured and compared with undoped fuel pellets. The enlarged grain size (80 μm) and densification within short sintering duration highlight the immense possibility of SPS in fabricating large grained UO2 fuel pellets to improve fuel performance.

  7. Evaluation of the effects of aging in synthetic saliva solution of both commercial and silanized Nd-Fe-B magnets for dental application

    Science.gov (United States)

    Fabiano, F.; Puliafito, V.; Calabrese, L.; Borsellino, C.; Bonaccorsi, L. M.; Giordano, A.; Fabiano, V.; Cordasco, G.

    2016-04-01

    Neodymium-iron-boron magnets are able to ensure a magnetic flux with high maximum energy product also at miniaturized size. In the past, due to their marked corrosion in saliva they were unsuccessfully implemented in orthodontic systems. Thereby, we propose a multi-layered organic-inorganic coating able to supply anticorrosion resistance, wear resistance and durability to the whole assembly. We evaluated the influence on the magnetic force of commercial nickel plated and silanized Nd-Fe-B during aging time in synthetic Fusayama saliva. Two magnets based-micromagnetic simulations were performed in order to analyze the magnetic field generated which is linked to the magnetic force. Our key results underline that the proposed hybrid coating does not affect the magnetic force of Nd-Fe-B magnets, moreover, preventing corrosion degradation in aggressive solution. Thus the limiting aspects avoiding the use of Nd-Fe-B magnets for orthodontic and prosthodontic applications can be overcome by using silane agents as surface coating.

  8. Manufacturing of Injection-Molded NdFeB Magnet with (BH)max111 kJ · m-3

    Institute of Scientific and Technical Information of China (English)

    Duan Bohua; Qu Xuanhui; Xu Zhengzhou; Guo Shibo; Qin Mingli

    2004-01-01

    The bonded NdFeB magnets prepared by injection molding meet with the development tendency of the magnet in small volume, light weight and high performance ,and have a good prospect.In this paper, a modified nylonbased binder was developed for powder injection molding of NdFeB bonded magnets.The effects of pretreatment of NdFeB anisotropic magnetic powder produced with HDDR processing on the anti-oxidation behaviors of powder and the final magnetic properties of the molded bonded magnets were studied.The optimal powder loading of 65 vol% was achieved with the modified binder.It was found that the properties of the bonded magnets were mainly affected by the powder surface pretreatment and the intensity of the applied alignment magnetic field during injection molding for a certain powder.Bonded magnets with remanence of 0.820 T, intrinsic coercivity of 1140.3 kA· m-1 and maximum energy product of 111 kJ · m-3 were produced with the optimal processing.

  9. Laser sintering of conductive carbon paste on plastic substrate

    Science.gov (United States)

    Kinzel, Edward C.; Kelkar, Rohan; Xu, Xianfan

    2010-02-01

    This work investigates fabrication of functional conductive carbon paste onto a plastic substrate using a laser. The method allows simultaneous sintering, patterning, and functionalization of the carbon paste. Experiments are carried out to optimize the laser processing parameters. It is shown that sheet resistance values obtained by laser sintering are close to the one specified by the manufacturer using conventional sintering method. Additionally, a heat transfer analysis using numerical methods is conducted to understand the relationship between the temperature during sintering and the sheet resistance values of sintered carbon wires. The process developed in this work has the potential of producing carbon-based electronic components on low cost plastic substrates.

  10. Sintering studies on iron-carbon-copper compacts

    Directory of Open Access Journals (Sweden)

    Perianayagam Philomen-D-Anand Raj

    2016-01-01

    Full Text Available Sintered Iron-Carbon-Copper parts are among the most widely used powder metallurgy product in automobile. In this paper, studies have been carried out to find out the sintering characteristics of iron-carbon-copper compacts when sintered in nitrogen atmosphere. The effects of various processing parameters on the sintering characteristics were studied. The various processing parameters considered were compaction pressure, green density and sintering temperature. The sintering characteristics determined were sintered density, porosity, dimensional change, micro hardness and radial crush strength. The results obtained have been discussed on the basis of micro structural observations. The characteristics of SEM fractography were also used to determine the mechanism of fracture. The fracture energy is strongly dependent on density of the compact.

  11. Spark plasma sintering of hydrothermally synthesized bismuth ferrite

    Directory of Open Access Journals (Sweden)

    Zorica Branković

    2016-12-01

    Full Text Available Bismuth ferrite, BiFeO3 (BFO, powder was synthesized by hydrothermal method from Bi(NO33·5 H2O and Fe(NO33·9 H2O as precursors. The synthesized powder was further sintered using spark plasma sintering (SPS. The sintering conditions were optimized in order to achieve high density, minimal amount of secondary phases and improved ferroelectric and magnetic properties. The optimal structure and properties were achieved after spark plasma sintering at 630 °C for 20 min, under uniaxial pressure of 90 MPa. The composition, microstructure, ferroelectric and magnetic properties of the SPS samples were characterized and compared to those of conventionally sintered ceramics obtained from the same powder. Although the samples sintered using conventional method showed slightly lower amount of secondary phases, the spark plasma sintered samples exhibited favourable microstructure and better ferroelectric properties.

  12. Structure and Magnetic Properties of Sm2Fe17Nx Sintering Magnets Prepared by Spark Plasma Sintering

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Bulk Sm2Fe17Nx sintering magnet was fabricated by spark plasma sintering(SPS) technique. The effects of sintering pressure and sintering temperature on the magnetic properties of the Sm2Fe17Nx magnet were investigated. As a result, the density of the magnet is obviously improved with the increase of sintering pressure, but the coercivity drops since Sm2Fe17Nx has decomposed into SmN, α-Fe and N2. When sintering temperature was only above 200 ℃ under 1 GPa sintering pressure, the coercivity even begins to decrease, which indicates that high pressure promotes the decomposition of the Sm2Fe17Nx at lower temperature. The decomposition is also proved by the decrease of nitrogen and increase of α-Fe in the magnets.

  13. NdFeB Magnets Aligned in a 9-T Superconducting Solenoid (asterisk)

    Science.gov (United States)

    Mulcahy, T. M.; Hull, J. R.

    2002-08-01

    Commercial-grade magnet powder (Magnequench UG) was uniaxial die-pressed into cylindrical compacts, while being aligned in the 1-T to 8-T DC field of a superconducting solenoid at Argonne National Laboratory. Then, the compacts were added to normal Magnequench UG production batches for sintering and annealing. The variations in magnet properties for different strengths of alignment fields are reported for 15.88-mm (5/8-in.) diameter compacts made with length-to-diameter (L/D) ratios in the range 3 0.25 and L 1. The best magnets were produced when the powder-filled die was inserted into the active field of the solenoid and then pressed. Improvements in the residual flux density of 8% and in the energy product of 16% were achieved by increasing the alignment field beyond the typical 2-T capabilities of electromagnets. The most improvement was achieved for the compacts with the smallest L/D ratio. The ability to make very strong magnets with small L/D, where self-demagnetization effects during alignment are greatest, would benefit most the production of near-final-shape magnets. Compaction of the magnet powder using a horizontal die and a continuously active superconducting solenoid was not a problem. Although the press was operated in the batch mode for this proof-of-concept study, its design is intended to enable automated production.

  14. Reheating of zinc-titanate sintered specimens

    Directory of Open Access Journals (Sweden)

    Labus N.

    2015-01-01

    Full Text Available The scope of this work was observing dimensional and heat transfer changes in ZnTiO3 samples during heating in nitrogen and air atmosphere. Interactions of bulk specimens with gaseous surrounding induce microstructure changes during heating. Sintered ZnTiO3 nanopowder samples were submitted to subsequent heating. Dilatation curves and thermogravimetric with simultaneous differential thermal analysis TGA/DTA curves were recorded. Reheating was performed in air and nitrogen atmospheres. Reheated samples obtained at different characteristic temperatures in air were analyzed by X-ray diffraction (XRD. Microstructures obtained by scanning electron microscopy (SEM of reheated sintered samples are presented and compared. Reheating in a different atmosphere induced different microstructures. The goal was indicating possible causes leading to the microstructure changes. [Projekat Ministarstva nauke Republike Srbije, br. OI172057 i br. III45014

  15. Thermal conductivity of sintered lithium orthosilicate compacts

    Science.gov (United States)

    Löbbecke, Birgit; Knitter, Regina; Rohde, Magnus; Reimann, Jörg

    2009-04-01

    The design of solid breeder blankets is strongly affected by the low values of thermal conductivity and density of ceramic breeder pebble beds. A significant rise of both quantities would enhance the thermal performance and lead to an increased tritium breeding ratio. In order to improve these quantities pretreated lithium orthosilicate pebble material was dry pressed and subsequently sintered. The thermal conductivity of cylindrical pellets was determined by the heat pulse method using a laser flash device. A pebble bed characteristic sample was also investigated in order to check the measurement accuracy in comparison with previous results. Furthermore, two samples of low density cellular ceramics were also prepared by infiltration of polymer foams with a ceramic slurry. The thermal conductivity results show that the values are affected both by the particle size and the sample density. Thermal conductivity values of higher than 2 W/m K were obtained using large particles and sintering at 1000 °C.

  16. Microwave sintered nanocomposite electrodes for solid oxide fuel cells.

    Science.gov (United States)

    Raza, Rizwan; Zhu, Bin

    2011-06-01

    Microwave sintering is a very interesting subject, which provides an alternative method to overcome problems faced with conventional sintering. This process is very efficient and only requires a few minutes. In this paper, nanocomposite electrodes (Cu0.15Ni0.85-GDC) were sintered at 700 degrees C for 10 mins in a single mode 2.45 GHz microwave oven by the solid state reaction method. The composition influence and the sintering methods on the as-obtained powder were characterized by XRD, SEM and TEM. It was observed that excellent sintering took place. Excellent fuel cell performance was achieved with microwave sintering compared tosamples sintered using conventional sintering. Electrochemical analysis was carried out using AC Impedance technique. This paper reports a new approach to develop a microwave sintered based nanocomposite material, which is more efficient on time and energy. This method can gain significant economical benefits compared to conventional sintered materials for applications in low temperature solid oxide fuel cells (LTSOFC).

  17. Sintering Behavior, Microstructure, and Mechanical Properties: A Comparison among Pressureless Sintered Ultra-Refractory Carbides

    Directory of Open Access Journals (Sweden)

    Laura Silvestroni

    2010-01-01

    Full Text Available Nearly fully dense carbides of zirconium, hafnium, and tantalum were obtained by pressureless sintering at 1950°C with the addition of 5–20 vol% of MoSi2. Increasing the amount of sintering aid, the final density increased too, thanks to the formation of small amounts of liquid phase constituted by M-Mo-Si-O-C, where M is either Zr, Hf, or Ta. The matrices of the composites obtained with the standard procedure showed faceted squared grains; when an ultrasonication step was introduced in the powder treatment, the grains were more rounded and no exaggerated grains growth occurred. Other secondary phases observed in the microstructure were SiC and mixed silicides of the transition metals. Among the three carbides prepared by pressurless sintering, TaC-based composites had the highest mechanical properties at room temperature (strength 590 MPa, Young's modulus 480 GPa, toughness 3.8 MPa·m1/2. HfC-based materials showed the highest sinterability (in terms of final density versus amount of sintering aid and the highest high-temperature strength (300 MPa at 1500  °C.

  18. Microwave sintering versus conventional sintering of NiCuZn ferrites. Part I: Densification evolution

    Science.gov (United States)

    Zhu, Jianhua; Ouyang, Chenxin; Xiao, Shumin; Gao, Yongyi

    2016-06-01

    This work reports the recent study on the microwave sintering (MS) versus conventional sintering (CS) of NiCuZn ferrites, with particular interests in the densification evolution. NiCuZn ferrite powders were synthesized through the solid state reaction route. Densification behaviors of ferrite samples under the two types of thermal sources were monitored in real-time. Meanwhile, the influences of additives (1 wt% BSZ glass or 1 wt% Bi2O3) on the densifications were also investigated. Both constant heating rate (CHR) and master sintering curve (MSC) models were used to evaluate the sintering activation energy (Q). Results demonstrated that the microwave-enhanced diffusion mainly occurs at the intermediate sintering stage. The Q-value estimated by MSC method agreed well with that from CHR method. With the influence of microwave electromagnetic field, the activation energy of NiCuZn ferrites was decreased by roughly 100-150 kJ/mol. In addition, doping a small amount of additives could improve densification degree and reduce the minimal energy to activate diffusion mechanisms.

  19. Spark plasma sintering and spark plasma joining of refractory ceramics

    Science.gov (United States)

    Hoefer, Jeffrey Andrew

    Consolidation of refractory ceramics such as boron carbide (B4C) and silicon carbide (SiC) by conventional sintering techniques (pressure-less sintering, hot pressing, hot isostatic pressing etc.) can prove challenging due to the high temperatures required for sintering. Typically sintering additives are used in order to decrease sintering temperature, but at the sacrifice of purity. Typically B4C requires sintering temperatures above 2000°C without the use of additives, while SiC is generally considered not sinterable without additives, and requires temperatures above 2000°C even with additives. Spark Plasma Sintering (SPS) has emerged as a technology that can reduce the sintering temperature considerably compared to more conventional techniques. The simultaneous application of pressure, heat, and current can reduce sintering temperatures without the use of sintering aids to 1600°C and 2000°C for boron carbide and silicon carbide respectively. One shortcoming of SPS, however, is the difficulty in producing complex shapes. Therefore, for carbide materials such as B4C and SiC, which are difficult to machine, the ability to produce complex shapes is worthy of investigation. One means of creating complex shapes is by joining simple shapes. Joining of monolithic ceramics, in particular SiC, has been achieved, however in all cases an intermediate joining material is used (Ti foil, Silica Powder etc.). Joining of materials using SPS, or as it is called, Spark Plasma Joining, can eliminate the need for an intermediate joining material, producing a high purity and high strength joint. This study investigates SPS of 3 different B4C Powders, as well as SPS joining of simple shape monolithic SiC. Sintering parameters such as temperature, pressure, time, and heating rate are all considered. Influence of sintering parameters on density, grain size, mechanical strength, and joint quality is investigated in detail.

  20. The dimensional accuracy of the sintered billets

    Directory of Open Access Journals (Sweden)

    Чингиз Ариф оглы Алиев

    2016-01-01

    Full Text Available The article presents the results of assessing the impact of the behaviour stability of the components included in the compositions and process parameters of their production, on the dimensional accuracy of workpieces. It was found that by increasing the amount of oxide in the composition is greater compaction of the sintered billet in the process of heat treatment. This also increases the density of all components of the composition

  1. Plasma Synthesis and Sintering of Advanced Ceramics

    Science.gov (United States)

    1990-09-15

    glow discharge, corona discharge, RF or microwave discharge, etc.) and the electron concentration in the plasma are important. The efficiency of... corona discharge, and the low pressure capacitively or inductively coupled RF discharge. It is probable that a low pressure microwave discharge would also...Rhodes, "Agglomerate and Particle Size Effects on Sintering Yttria- Stabilized Zirconia ", J. Am. Ceram. Soc., 64 [1] 19-22 (1981). 4. T. S. Yeh and M

  2. Sintering of titanium alloy by powder metallurgy

    Energy Technology Data Exchange (ETDEWEB)

    Cosme, C.R.M. [Universidade de Brasilia (UnB), DF (Brazil); Henriques, V.A.R.; Cairo, C.A.A.; Taddei, E.B. [Centro Tecnico Aeroespacial (CTA), Sao Jose dos Campos, SP (Brazil)

    2009-07-01

    Full text: Titanium alloys are suitable for biomaterial applications, considering its biocompatibility and low elastic modulus compared to steel. Bone resorption in this case can be reduced by load sharing between the implant and natural bone.Starting powders were obtained by hydride method, carried out under positive hydrogen pressure at 500 deg C for titanium and 800 deg C for Nb, Zr and Ta powders. After reaching the nominal temperature, the material was held for 3h, with subsequent cooling to room temperature and milling of the friable hydride. Samples were produce by mixing of initial metallic powders followed by and cold isostatic pressing. Subsequent densification by sintering was performed at temperature range between 900 and 1700 deg C. Characterization was carried out with scanning electron microscopy, X-ray diffractometry and microhardness measurements. Microstructural examinations revealed higher amount of &⧣946;-phase for higher sintering temperature and dissolution of Ta and NB particles. In vitro tests revealed low cytotoxicity of sintered samples. (author)

  3. Ceramic components manufacturing by selective laser sintering

    Science.gov (United States)

    Bertrand, Ph.; Bayle, F.; Combe, C.; Goeuriot, P.; Smurov, I.

    2007-12-01

    In the present paper, technology of selective laser sintering/melting is applied to manufacture net shaped objects from pure yttria-zirconia powders. Experiments are carried out on Phenix Systems PM100 machine with 50 W fibre laser. Powder is spread by a roller over the surface of 100 mm diameter alumina cylinder. Design of experiments is applied to identify influent process parameters (powder characteristics, powder layering and laser manufacturing strategy) to obtain high-quality ceramic components (density and micro-structure). The influence of the yttria-zirconia particle size and morphology onto powder layering process is analysed. The influence of the powder layer thickness on laser sintering/melting is studied for different laser beam velocity V ( V = 1250-2000 mm/s), defocalisation (-6 to 12 mm), distance between two neighbour melted lines (so-called "vectors") (20-40 μm), vector length and temperature in the furnace. The powder bed density before laser sintering/melting also has significant influence on the manufactured samples density. Different manufacturing strategies are applied and compared: (a) different laser beam scanning paths to fill the sliced surfaces of the manufactured object, (b) variation of vector length (c) different strategies of powder layering, (d) temperature in the furnace and (e) post heat treatment in conventional furnace. Performance and limitations of different strategies are analysed applying the following criteria: geometrical accuracy of the manufactured samples, porosity. The process stability is proved by fabrication of 1 cm 3 volume cube.

  4. Basic characteristics of Australian iron ore concentrate and its effects on sinter properties during the high-limonite sintering process

    Science.gov (United States)

    Liu, Dong-hui; Liu, Hao; Zhang, Jian-liang; Liu, Zheng-jian; Xue, Xun; Wang, Guang-wei; Kang, Qing-feng

    2017-09-01

    The basic characteristics of Australian iron ore concentrate (Ore-A) and its effects on sinter properties during a high-limonite sintering process were studied using micro-sinter and sinter pot methods. The results show that the Ore-A exhibits good granulation properties, strong liquid flow capability, high bonding phase strength and crystal strength, but poor assimilability. With increasing Ore-A ratio, the tumbler index and the reduction index (RI) of the sinter first increase and then decrease, whereas the softening interval (Δ T) and the softening start temperature ( T 10%) of the sinter exhibit the opposite behavior; the reduction degradation index (RDI+3.15) of the sinter increases linearly, but the sinter yield exhibits no obvious effects. With increasing Ore-A ratio, the distribution and crystallization of the minerals are improved, the main bonding phase first changes from silico-ferrite of calcium and aluminum (SFCA) to kirschsteinite, silicate, and SFCA and then transforms to 2CaO·SiO2 and SFCA. Given the utilization of Ore-A and the improvement of the sinter properties, the Ore-A ratio in the high-limonite sintering process is suggested to be controlled at approximately 6wt%.

  5. Sintering of Multilayered Porous Structures: Part I-Constitutive Models

    DEFF Research Database (Denmark)

    Olevsky, Eugene; Tadesse Molla, Tesfaye; Frandsen, Henrik Lund;

    2013-01-01

    of all input parameters necessary for modeling sintering of bilayers using experimental techniques similar to optical dilatometry applied to each individual layer and to a symmetric trilayered porous structure based on the two-layer materials utilized in the bilayered system. Examples of sintering......Theoretical analyses of shrinkage and distortion kinetics during sintering of bilayered porous structures are carried out. The developed modeling framework is based on the continuum theory of sintering; it enables the direct assessment of the cofiring process outcomes and of the impact of process...... controlling parameters. The derived “master sintering curve”-type solutions are capable of describing and optimizing the generic sintering shrinkage and distortion kinetics for various material systems. The approach utilizes the material-specific parameters, which define the relative kinetics of layer...

  6. Sintering of transparent Nd:YAG ceramics in oxygen atmosphere

    Institute of Scientific and Technical Information of China (English)

    HUANG Yihua; JIANG Dongliang; ZHANG Jingxian; LIN Qingling; HUANG Zhengren

    2013-01-01

    Yttrium aluminum garnet (YAG) transparent ceramics were fabricated by sintering at oxygen atmosphere.Tetraethyl orthosilicate (TEOS) was added as the sintering additive to control the grain growth and densification.Pores were eliminated clearly at temperature lower than 1700 ℃,while grain size was around 3 μm.The in-line transmittance was 80% at 1064 nm when samples vere sintered at 1710 ℃.The effect of TEOS was studied in oxygen atmosphere sintering for Nd:YAG transparent ceramics.At higher temperature like 1710 ℃,the grain growth mechanism was solute drag,while at 1630 and 1550 ℃ the grain growth was controlled by liquid phase sintering mechanism.And 0.5 wt.% TEOS was the best adding content for Nd:YAG sintered in oxygen atmosphere.

  7. Selective laser sintering mechanism of polymer-coated molybdenum powder

    Institute of Scientific and Technical Information of China (English)

    BAI Pei-kang; WANG Wen-feng

    2007-01-01

    A type of polymer-coated molybdenum powder used in selective laser sintering technology was prepared by coating polymer on molybdenum particles and frozen grinding techniques, with the maximum particle diameter of 71 μm. The laser sintering experiments of polymer-coated molybdenum powder were conducted by using the self-developed selective laser sintering machine (HLRP-350I). The method of microscopic analysis was used to investigate the dynamic laser sintering process of polymer-coated molybdenum powder. Based on the study, the laser sintering mechanisms of polymer-coated molybdenum powder were presented. It is found that the mechanism is viscous flow when the laser sintering temperature is between 100 ℃ and 160 ℃, which can be described by a two-sphere model; and the mechanism is melting /solidification when the temperature is above 160 ℃.

  8. Influence of Segmentation of Ring-Shaped NdFeB Magnets with Parallel Magnetization on Cylindrical Actuators

    Directory of Open Access Journals (Sweden)

    Paulo Roberto Eckert

    2014-07-01

    Full Text Available This work analyses the effects of segmentation followed by parallel magnetization of ring-shaped NdFeB permanent magnets used in slotless cylindrical linear actuators. The main purpose of the work is to evaluate the effects of that segmentation on the performance of the actuator and to present a general overview of the influence of parallel magnetization by varying the number of segments and comparing the results with ideal radially magnetized rings. The analysis is first performed by modelling mathematically the radial and circumferential components of magnetization for both radial and parallel magnetizations, followed by an analysis carried out by means of the 3D finite element method. Results obtained from the models are validated by measuring radial and tangential components of magnetic flux distribution in the air gap on a prototype which employs magnet rings with eight segments each with parallel magnetization. The axial force produced by the actuator was also measured and compared with the results obtained from numerical models. Although this analysis focused on a specific topology of cylindrical actuator, the observed effects on the topology could be extended to others in which surface-mounted permanent magnets are employed, including rotating electrical machines.

  9. Influence of segmentation of ring-shaped NdFeB magnets with parallel magnetization on cylindrical actuators.

    Science.gov (United States)

    Eckert, Paulo Roberto; Goltz, Evandro Claiton; Flores Filho, Aly Ferreira

    2014-07-21

    This work analyses the effects of segmentation followed by parallel magnetization of ring-shaped NdFeB permanent magnets used in slotless cylindrical linear actuators. The main purpose of the work is to evaluate the effects of that segmentation on the performance of the actuator and to present a general overview of the influence of parallel magnetization by varying the number of segments and comparing the results with ideal radially magnetized rings. The analysis is first performed by modelling mathematically the radial and circumferential components of magnetization for both radial and parallel magnetizations, followed by an analysis carried out by means of the 3D finite element method. Results obtained from the models are validated by measuring radial and tangential components of magnetic flux distribution in the air gap on a prototype which employs magnet rings with eight segments each with parallel magnetization. The axial force produced by the actuator was also measured and compared with the results obtained from numerical models. Although this analysis focused on a specific topology of cylindrical actuator, the observed effects on the topology could be extended to others in which surface-mounted permanent magnets are employed, including rotating electrical machines.

  10. Influence of Segmentation of Ring-Shaped NdFeB Magnets with Parallel Magnetization on Cylindrical Actuators

    Science.gov (United States)

    Eckert, Paulo Roberto; Goltz, Evandro Claiton; Filho, Aly Ferreira Flores

    2014-01-01

    This work analyses the effects of segmentation followed by parallel magnetization of ring-shaped NdFeB permanent magnets used in slotless cylindrical linear actuators. The main purpose of the work is to evaluate the effects of that segmentation on the performance of the actuator and to present a general overview of the influence of parallel magnetization by varying the number of segments and comparing the results with ideal radially magnetized rings. The analysis is first performed by modelling mathematically the radial and circumferential components of magnetization for both radial and parallel magnetizations, followed by an analysis carried out by means of the 3D finite element method. Results obtained from the models are validated by measuring radial and tangential components of magnetic flux distribution in the air gap on a prototype which employs magnet rings with eight segments each with parallel magnetization. The axial force produced by the actuator was also measured and compared with the results obtained from numerical models. Although this analysis focused on a specific topology of cylindrical actuator, the observed effects on the topology could be extended to others in which surface-mounted permanent magnets are employed, including rotating electrical machines. PMID:25051032

  11. Microwave sintering of nano size powder β-TCP bioceramics

    Directory of Open Access Journals (Sweden)

    Mirhadi B.

    2014-01-01

    Full Text Available A nano sized beta tricalcium phosphate (β-TCP powder was conventional sintered (CS and microwave sintered (MW, in order to obtain dense β-TCP ceramics. In this work the effect of microwave sintering conditions on the microstructure, phase composition and mechanical properties of materials based on tricalcium phosphate (TCP was investigated by SEM (scanning electron microscopyand XRD(X-ray diffraction and then compared with conventional sintered samples. Nano-size β-TCP powders with average grain size of 80 nm were prepared by the wet chemical precipitation method with calcium nitrate and diammonium hydrogen phosphate as calcium and phosphorus precursors, respectively. The precipitation process employed was also found to be suitable for the production of submicrometre β-TCP powder in situ. The β-TCP samples microwave (MW sintered for 15 min at 1100°C, with average grain size of 3μm, showed better densification, higher density and certainly higher hardness than samples conventionally sintered for 2 h at the same temperature. By comparing sintered and MW sintered β-TCP samples, it was concluded that MW sintered β-TCP samples have superior mechanical properties.

  12. Microwave Sintering of Silver Nanoink for Radio Frequency Applications.

    Science.gov (United States)

    Kim, Kwang-Seok; Park, Bum-Geun; Jung, Kwang-Ho; Kim, Jong-Woong; Jeong, Myung Yung; Jung, Seung-Boo

    2015-03-01

    Microwave sintering is a promising method for low-temperature processes, as it provides advantages such as uniform, fast, and volumetric heating. In this study, we investigated the electrical characteristics of inkjet-printed silver (Ag) circuits sintered by microwaves. The microstructural evolutions of inkjet-printed Ag circuits sintered at various temperatures for different durations were observed with a field emission scanning electron microscope. The electrical properties of the inkjet-printed Ag circuits were analysed by electrical resistivity measurements and radio frequency properties including scattering-parameters in the frequency range of 20 MHz to 20 GHz. The experimental results show that the signal losses of the Ag circuits sintered by microwave heating were lower than those sintered by conventional heating as microwave heating led to granular films which were nearly fully sintered without pores on the surfaces. When the inkjet-printed Ag circuits were sintered by microwaves at 300 °C for 4 min, their electrical resistivity was 5.1 µΩ cm, which is 3.2 times larger than that of bulk Ag. Furthermore, microwave sintering at 150 °C for 4 min achieved much lower signal losses (1.1 dB at 20 GHz) than conventional sintering under the same conditions.

  13. Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics

    Directory of Open Access Journals (Sweden)

    Barbara Malič

    2015-12-01

    Full Text Available The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient, lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining phase-pure materials with a high density and a uniform, fine-grained microstructure is a major challenge. For this reason the present paper reviews the different methods for consolidating KNN ceramics. The difficulties involved in the solid-state synthesis of KNN powder, i.e., obtaining phase purity, the stoichiometry of the perovskite phase, and the chemical homogeneity, are discussed. The solid-state sintering of stoichiometric KNN is characterized by poor densification and an extremely narrow sintering-temperature range, which is close to the solidus temperature. A study of the initial sintering stage revealed that coarsening of the microstructure without densification contributes to a reduction of the driving force for sintering. The influences of the (K + Na/Nb molar ratio, the presence of a liquid phase, chemical modifications (doping, complex solid solutions and different atmospheres (i.e., defect chemistry on the sintering are discussed. Special sintering techniques, such as pressure-assisted sintering and spark-plasma sintering, can be effective methods for enhancing the density of KNN ceramics. The sintering behavior of KNN is compared to that of a representative piezoelectric lead zirconate titanate (PZT.

  14. Properties, structure and machnining capabilities sintered corundum abrasives

    Directory of Open Access Journals (Sweden)

    Cz.J. Niżankowski

    2010-07-01

    Full Text Available The diversity of sintered corundum abrasives used in both bonded and in the embankment of abrasive tools currently poses substantialproblems for their choice of technology to specific tasks. Therefore performed a comparative study of ownership structures and capacitiesof elected representatives machnining sintered corundum abrasives of different generations, and this is normal sintered alumina,submicrocrystalline alumina sintered and nanocrystalline alumina sintered. Were studied some properties of a set of abrasive particles,physicochemical properties and structural and mechanical and technological properties. The studies used the method of microscopicmeasurement to determine the shape of abrasive particles, the pycnometer to determine the density of abrasive, a spectrometer todetermine the chemical composition of the magnetic analyzer for determining the magnetic fraction, scanning electron microscope toanalysis of abrasive grains and a special position to designate the machining capacity abrasive grains. The results showed a significantincrease in machining capacity sintered corundum abrasives with increasing degree of fragmentation of the crystallites sintered corundum abrasives and distinctive bands in the emerging microchip. The originality of the development provides a comparative summary ofproperties of sintered corundum abrasives of different generations and functions obtained by the author making the change in value indexof machininhcapacity grit from cutting speeds for different generations of sintered corundum.

  15. Laser sintering of thick-film conductors for microelectronic applications

    Science.gov (United States)

    Kinzel, Edward C.; Sigmarsson, Hjalti H.; Xu, Xianfan; Chappell, William J.

    2007-03-01

    This paper investigates fabrication of functional thick metal films using simultaneous laser sintering and patterning along with the fundamental physical phenomena that govern the laser sintering process. The effects of the processing parameters on the quality of the fabricated components are investigated through a heat transfer analysis. We show that our process has potentials for metallization of microelectronics directly onto substrates whose melting temperatures are much lower than the temperature needed for sintering, which is only possible by properly controlling the temperature field during laser sintering. Optimum properties of the fabricated components are obtained when certain thermal conditions are produced during laser heating.

  16. Flash light sintering of nickel nanoparticles for printed electronics

    Energy Technology Data Exchange (ETDEWEB)

    Park, Sung-Hyeon [School of Mechanical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Kim, Hak-Sung, E-mail: kima@hanyang.ac.kr [School of Mechanical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Institute of Nano Science and Technology, Hanyang University, Seoul 133-79 (Korea, Republic of)

    2014-01-01

    In this paper, a sintering process for nickel nanoparticles using flash light irradiation was investigated for multilayer ceramic capacitors, magnetic devices and printed electronics. The existence of a small amount of 10 nm size nanoparticles in the ink significantly improved the flash light absorption and induced the melting and sintering of the nanoparticles. Due to this phenomenon, uniform diameter nickel nanoparticles (50 nm) could not be sintered, while the nickel nanoparticles with varying diameters (5–500 nm) were sintered by flash light irradiation. In order to acquire high electrical conductivity in the sintered nickel nanoparticles, several flash light sintering parameters such as light energy and pulsed light patterns were optimized. Also, the nickel nano-ink was optimized by changing the weight fractions of organic binder in the ink. - Highlights: • Nickel nanoparticle was sintered by flash light irradiation technique. • The existence of 10 nm size nanoparticles improved the flash light absorption. • The melting temperature of the 10 nm size nanoparticles is significantly decreased. • The only nickel nanoparticles with varying diameters (5–500 nm) were sintered. • Several sintering parameters were optimized for conductivity of nickel nanoparticle.

  17. Interpretation of Frenkel’s theory of sintering considering evolution of activated pores: III. Determination of equilibrium sintering time

    Directory of Open Access Journals (Sweden)

    Yu C.L.

    2015-01-01

    Full Text Available In this article, the Frenkel’s theory of liquid-phase sintering was interpreted regarding pores as the activated volume. The mathematical model established by Nikolić et al. was used to infer the equilibrium sintering time at varied sintering temperatures during the isothermal sintering of codierite glass by Giess et al. Through the calculation, the equilibrium time at 800ºC, 820ºC, 840ºC and 860ºC is inferred to be 7014.42mins, 1569.65mins, 368.92mins and 114.61mins, respectively. The equilibrium time decreases as the temperature increases. And the theoretical value is in good accordance with the experimental results. Thus, the model established by Nikolić et al. can be applied successfully to predict the equilibrium sintering time of the cordierite glass at varied temperatures during isothermal sintering.

  18. Effect of sintering aids on boron carbide sintering; Efeito de aditivos na sinterizacao de carbeto de boro

    Energy Technology Data Exchange (ETDEWEB)

    Melo, Francisco Cristovao Lourenco de; Silva, Cosme Roberto Moreira da [Centro Tecnico Aeroespacial, Sao Jose dos Campos, SP (Brazil). Inst. de Atividades Espaciais; Bressiani, Jose Carlos [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)

    1995-12-31

    The special physical characteristics of boron carbide (B{sub 4} C) allow its use in a wide range of application in engineering design. Despite of this, the densification during sintering step became the main drawback of the development of ceramics components. The present work deals with the role of sintering aids on the densification of boron carbide ceramics produced through pressureless and hot-pressing sintering. The applied sintering aids were, C+B{sub 2} O{sub 3}+ Al{sub 2} O{sub 3}, Ni and/or Ti. Dilatometry was used to assist hot-pressing and, C+B{sub 2} O{sub 3} + Al{sub 2} O{sub 3} were the sintering aids. In the both cases the sintering temperature was lowered to 2200 K and 2073 K, pressureless and hot pressing respectively. The results of hardness of about 35 GPa and densification of 99% theoretical density for hot-pressed material show the effectiveness of these sintering aids. So far as the obtained data from this work is concerned we may believe that is possible to produce boron carbide ceramics components with both high density and hardness with lower cost by lowering sintering temperatures, that is, 200 K for pressureless sintering and 350 K for hot-pressing. (author) 13 refs., 1 fig., 5 tabs.

  19. The effect of sintering pressure on the microstructure and properties of a nanocrystalline magnesium alloy in spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ka Ram; Kim, Hye Sung; Kwon, Soon Hong; Hwang, Dae Youn [Pusan National University, Miryang (Korea, Republic of)

    2014-11-15

    Many studies have shown that particle boundaries in spark plasma sintering (SPS) can be easily removed by using a combination of sintering temperature and pressure. We already reported that a degassing treatment prior to sintering by SPS was a critical step to remove particle-particle boundaries effectively and to obtain a magnesium alloy having high strength and high ductility. In this study, the microstructural evolution and the mechanical properties of nanocrystalline Mg-6%Al alloys were investigated to determine the effect of sintering pressure combined with an appropriate degassing treatment.

  20. The Effect of Grinding and Roasting Conditions on the Selective Leaching of Nd and Dy from NdFeB Magnet Scraps

    Directory of Open Access Journals (Sweden)

    Ho-Sung Yoon

    2015-07-01

    Full Text Available The pretreatment processes consisting of grinding followed by roasting were investigated to improve the selective leaching of Nd and Dy from neodymium-iron-boron (NdFeB magnet scraps. The peaks of Nd(OH3 and Fe were observed in XRD results after grinding with NaOH as the amount of water addition increased to 5 cm3. These results indicate that the components of Nd and Fe in NdFeB magnet could be changed successfully into Nd(OH3 and Fe, respectively. In the roasting tests using the ground product, with increasing roasting temperature to 500 °C, the peaks of Nd(OH3 and Fe disappeared while those of Nd2O3 and Fe2O3 were shown. The peaks of NdFeO3 in the sample roasted at 600 °C were observed in the XRD pattern. Consequently, 94.2%, 93.1%, 1.0% of Nd, Dy, Fe were leached at 400 rpm and 90 °C in 1 kmol·m−3 acetic acid solution with 1% pulp density using a sample prepared under the following conditions: 15 in stoichiometric molar ratio of NaOH:Nd, 550 rpm in rotational grinding speed, 5 cm3 in water addition, 30 min in grinding time, 400 °C and 2 h in roasting temperature and time. The results indicate that the selective leaching of Nd and Dy from NdFeB magnet could be achieved successfully by grinding and then roasting treatments.

  1. Unburned carbon behavior in sintered coal fly-ash bulk material by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Hasezaki, K.; Nakashita, A.; Kaneko, G.Y.; Kakuda, H. [Shimane University, Shimane (Japan). Dept. of Material Science

    2007-12-15

    Coal fly-ash bulk materials were prepared by spark plasma sintering (SPS). The as-received coal fly ash produced by Misumi Power Station (The Chugoku Flectric Power Co., Inc.), had an average particle size of 19 {mu}m and contained about 2% carbon from unburned coal. The sintering temperature was 1000{sup o}C for 10 min. The mass density of the sintered compact was 2.4 x 10{sup 3} kg/m{sup 3}. After three-point flexural testing of the compact, the average flexural strength and Young's modulus were 25.6 MPa and 23.0 GPa, respectively. From the flexural strength, the Weibull modulus was found to be m = 6.13, indicating that the compact was a typical ceramics. Fractographic examination indicated that in all specimens the fracture origin was located on the bottom surface and was not an intrinsic flaw. Vickers indentation test showed that the fracture toughness was 0.61 MPa.m{sup 0.5} and the calculated critical flaw size, c{sub 0}, was 0.18 mm. This c{sub 0} value was larger than that of the voids and unburned carbon on the fracture surface. It is noteworthy that the mechanical strength of the sintered compact was not affected by the voids and unburned carbon.

  2. Spray freeze granulation of submicron alumina and its sintering behavior via spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Liu Wei

    2015-01-01

    Full Text Available Spray freeze granulation is an improved method based on spray granulation, solving many limitations of spray granulation. In this work, spray freeze granulation of submicron alumina is performed to explore the possibility of industrial-scale production of dense alumina via spark plasma sintering. Powder pretreatment such as sedimentation and the selection of granules with the appropriate size are employed for the maximum use of the high qualified as-prepared granules and granule sliding, which would provide a guidance for the industrial-scale production. Debound granules were densified via SPS and the corresponding sintering behaviors such as the recorded shrinkage and shrinkage rate were discussed. The comparison of sintering behaviors between granulated and as-received powder are conducted to identify the role of spray freeze granulation in sinterability for dense alumina. The Vickers hardness (Hv and the fracture toughness (KIC of the freeze granulated body are higher than the corresponding properties of the as-received body due to the more homogenous microstructure with little agglomeration in the particle packing after freeze granulation.

  3. Ceramic components manufacturing by selective laser sintering

    Energy Technology Data Exchange (ETDEWEB)

    Bertrand, Ph.; Bayle, F.; Combe, C. [Ecole Nationale d' Ingenieurs de Saint-Etienne (ENISE), DIPI Laboratory, 58 rue Jean Parot, 42023 Saint-Etienne Cedex 2 (France); Goeuriot, P. [Ecole Nationale Superieure des Mines de Saint-Etienne (ENSMSE), Centre SMS 158, Cours Fauriel, 42023 Saint-Etienne Cedex 2 (France); Smurov, I. [Ecole Nationale d' Ingenieurs de Saint-Etienne (ENISE), DIPI Laboratory, 58 rue Jean Parot, 42023 Saint-Etienne Cedex 2 (France)], E-mail: smurov@enise.fr

    2007-12-15

    In the present paper, technology of selective laser sintering/melting is applied to manufacture net shaped objects from pure yttria-zirconia powders. Experiments are carried out on Phenix Systems PM100 machine with 50 W fibre laser. Powder is spread by a roller over the surface of 100 mm diameter alumina cylinder. Design of experiments is applied to identify influent process parameters (powder characteristics, powder layering and laser manufacturing strategy) to obtain high-quality ceramic components (density and micro-structure). The influence of the yttria-zirconia particle size and morphology onto powder layering process is analysed. The influence of the powder layer thickness on laser sintering/melting is studied for different laser beam velocity V (V = 1250-2000 mm/s), defocalisation (-6 to 12 mm), distance between two neighbour melted lines (so-called 'vectors') (20-40 {mu}m), vector length and temperature in the furnace. The powder bed density before laser sintering/melting also has significant influence on the manufactured samples density. Different manufacturing strategies are applied and compared: (a) different laser beam scanning paths to fill the sliced surfaces of the manufactured object, (b) variation of vector length (c) different strategies of powder layering, (d) temperature in the furnace and (e) post heat treatment in conventional furnace. Performance and limitations of different strategies are analysed applying the following criteria: geometrical accuracy of the manufactured samples, porosity. The process stability is proved by fabrication of 1 cm{sup 3} volume cube.

  4. Selective laser sintering in biomedical engineering.

    Science.gov (United States)

    Mazzoli, Alida

    2013-03-01

    Selective laser sintering (SLS) is a solid freeform fabrication technique, developed by Carl Deckard for his master's thesis at the University of Texas, patented in 1989. SLS manufacturing is a technique that produces physical models through a selective solidification of a variety of fine powders. SLS technology is getting a great amount of attention in the clinical field. In this paper the characteristics features of SLS and the materials that have been developed for are reviewed together with a discussion on the principles of the above-mentioned manufacturing technique. The applications of SLS in tissue engineering, and at-large in the biomedical field, are reviewed and discussed.

  5. Computer Modeling of Direct Metal Laser Sintering

    Science.gov (United States)

    Cross, Matthew

    2014-01-01

    A computational approach to modeling direct metal laser sintering (DMLS) additive manufacturing process is presented. The primary application of the model is for determining the temperature history of parts fabricated using DMLS to evaluate residual stresses found in finished pieces and to assess manufacturing process strategies to reduce part slumping. The model utilizes MSC SINDA as a heat transfer solver with imbedded FORTRAN computer code to direct laser motion, apply laser heating as a boundary condition, and simulate the addition of metal powder layers during part fabrication. Model results are compared to available data collected during in situ DMLS part manufacture.

  6. Microwave Combustion and Sintering Without Isostatic Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Ebadian, M.A.; Monroe, N.D.H.

    1998-10-20

    This investigation involves a study of the influence of key processing parameters on the heating of materials using microwave energy. Selective and localized heating characteristics of microwaves will be utilized in the sintering of ceramics without hydrostatic pressure. In addition, combustion synthesis will be studied for the production of powders, carbides, and nitrides by combining two or more solids or a solid and a gas to form new materials. The insight gained from the interaction of microwaves with various materials will be utilized in the mobilization and subsequent redeposition of uranium.

  7. Sintering of nickel steam reforming catalysts

    DEFF Research Database (Denmark)

    Sehested, Jens; Larsen, Niels Wessel; Falsig, Hanne;

    2014-01-01

    . In this paper, particle migration and coalescence in nickel steam reforming catalysts is studied. Density functional theory calculations indicate that Ni-OH dominate nickel transport at nickel surfaces in the presence of steam and hydrogen as Ni-OH has the lowest combined energies of formation and diffusion...... compared to other potential nickel transport species. The relation between experimental catalyst sintering data and the effective mass diffusion constant for Ni-OH is established by numerical modelling of the particle migration and coalescence process. Using this relation, the effective mass diffusion...

  8. Ultrahigh coercivity and core-shell microstructure achieved in oriented Nd-Fe-B thin films diffusion-processed with Dy-based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Tongbo; Zhou, Xiaoqian; Yu, Dedong; Fu, Yanqing; Cui, Weibin [Northeastern University, Key Laboratory of Electromagnetic Processing of Materials (EPM), Ministry of Education, Shenyang (China); Northeastern University, Department of Physics and Chemistry of Materials, School of Materials Science and Engineering, Shenyang (China); Li, Guojian; Wang, Qiang [Northeastern University, Key Laboratory of Electromagnetic Processing of Materials (EPM), Ministry of Education, Shenyang (China)

    2017-01-15

    Ultrahigh ambient coercivities of ∝4 T were achieved in Nd-Fe-B benchmark thin film with coercivity of 1.06 T by diffusion-processing with Dy, Dy{sub 70}Cu{sub 30} and Dy{sub 80}Ag{sub 20} alloy layer. High texture and good squareness were obtained. In triple-junction regions, Dy element was found to be immiscible with Nd element. Microstructure observation indicated the typical gradient elementary distribution. Unambiguous core/shell microstructure was characterized by transition electron microscopy. Due to the enhanced ambient coercivity, the coercivity temperature stability was also substantially increased. (orig.)

  9. Ultrahigh coercivity and core-shell microstructure achieved in oriented Nd-Fe-B thin films diffusion-processed with Dy-based alloys

    Science.gov (United States)

    Zhang, Tongbo; Zhou, Xiaoqian; Yu, Dedong; Fu, Yanqing; Li, Guojian; Cui, Weibin; Wang, Qiang

    2017-01-01

    Ultrahigh ambient coercivities of 4 T were achieved in Nd-Fe-B benchmark thin film with coercivity of 1.06 T by diffusion-processing with Dy, Dy70Cu30 and Dy80Ag20 alloy layer. High texture and good squareness were obtained. In triple-junction regions, Dy element was found to be immiscible with Nd element. Microstructure observation indicated the typical gradient elementary distribution. Unambiguous core/shell microstructure was characterized by transition electron microscopy. Due to the enhanced ambient coercivity, the coercivity temperature stability was also substantially increased.

  10. Monitoring Sintering Burn-Through Point Using Infrared Thermography

    Directory of Open Access Journals (Sweden)

    Francisco G. Bulnes

    2013-08-01

    Full Text Available Sintering is a complex industrial process that applies heat to fine particles of iron ore and other materials to produce sinter, a solidified porous material used in blast furnaces. The sintering process needs to be carefully adjusted, so that the combustion zone reaches the bottom of the material just before the discharge end. This is known as the burnthrough point. Many different parameters need to be finely tuned, including the speed and the quantities of the materials mixed. However, in order to achieve good results, sintering control requires precise feedback to adjust these parameters. This work presents a sensor to monitor the sintering burn-through point based on infrared thermography. The proposed procedure is based on the acquisition of infrared images at the end of the sintering process. At this position, infrared images contain the cross-section temperatures of the mixture. The objective of this work is to process this information to extract relevant features about the sintering process. The proposed procedure is based on four steps: key frame detection, region of interest detection, segmentation and feature extraction. The results indicate that the proposed procedure is very robust and reliable, providing features that can be used effectively to control the sintering process.

  11. Monitoring Sintering Burn-Through Point Using Infrared Thermography

    Science.gov (United States)

    Usamentiaga, Rubén; Molleda, Julio; Garcia, Daniel F.; Bulnes, Francisco G.

    2013-01-01

    Sintering is a complex industrial process that applies heat to fine particles of iron ore and other materials to produce sinter, a solidified porous material used in blast furnaces. The sintering process needs to be carefully adjusted, so that the combustion zone reaches the bottom of the material just before the discharge end. This is known as the burn-through point. Many different parameters need to be finely tuned, including the speed and the quantities of the materials mixed. However, in order to achieve good results, sintering control requires precise feedback to adjust these parameters. This work presents a sensor to monitor the sintering burn-through point based on infrared thermography. The proposed procedure is based on the acquisition of infrared images at the end of the sintering process. At this position, infrared images contain the cross-section temperatures of the mixture. The objective of this work is to process this information to extract relevant features about the sintering process. The proposed procedure is based on four steps: key frame detection, region of interest detection, segmentation and feature extraction. The results indicate that the proposed procedure is very robust and reliable, providing features that can be used effectively to control the sintering process. PMID:23939585

  12. Sintering Properties and Optimal Blending Schemes of Iron Ores

    Institute of Scientific and Technical Information of China (English)

    Dauter0liveira; WUSheng—li; DAIYu—ming; XUJian; CHEN Hong

    2012-01-01

    In order to obtain good sintering performance, it is important to understand sintering properties of iron ores. Sintering properties including chemical composition, granulation and high-temperature behaviors of ores from China, Brazil and Australia. Furthermore, several indices were defined to evaluate sintering properties of iron ores. The results show that: for chemical composition, Brazilian ores present high TFe, low SiOz, and low Alz03 con- tent. For granulation, particle diameter ratio of Brazilian ores are high; particle intermediate fraction of Chinese con- centrates are low; and average particle size and clay type index of Australian ores are high. For high-temperature properties, ores from China, Brazil and Australia present different characteristics. Ores from different origins should be mixed together to obtain good high-temperature properties. According to the analysis of each ore's sintering prop- erties, an ore blending scheme (Chinese concentrates 20 ~-1- Brazilian ores 400//oo -k Australian ores 40 ~) was sugges- ted. Moreover, sinter pot test using blending mix was performed, and the results indicated that the ore blending scheme led to good sintering performance and sinter quality.

  13. The sintering behavior of close-packed spheres

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Tikare, V.; Frandsen, Henrik Lund

    2012-01-01

    The sintering behavior of close-packed spheres is investigated using a numerical model. The investigated systems are the body-centered cubic (bcc), face-centered cubic (fcc) and hexagonal close-packed spheres (hcp). The sintering behavior is found to be ideal, with no grain growth until full dens...

  14. Field assisted hot pressing of sintering Inconel 718 MIM samples

    Science.gov (United States)

    Dugauguez, Olivier; Torralba, Jose Manuel; Barriere, Thierry; Gelin, Jean-Claude

    2016-10-01

    In this investigation on samples obtained by Metal Injection Molding (MIM), the conventional way of sintering in a furnace will be compared to Field Assisted Hot pressing (FAHP) sintering. The difficulty of this method is to be able to control the shrinkage of the sample and so its shape. It has yet not been investigated with a super alloy powder and so, the effects of a high sintering rate. By accelerating the sintering kinetics, the thermal behavior may be modified. Hence, the behavior of the Inconel 718 sintered by FAHP has been investigated. The sintered samples were all injected from a feedstock composed of a fine particle Inconel powder and a binder principally composed of Cellulose Acetate Butyrate CAB and Poly-Ethylene Glycol PEG. The effects of the two methods on the microstructure and the mechanical properties are then compared. There was no difference in distribution of pores between the conventional sintering and the FAHP sintering but a finer grain size showed better hardness.

  15. Sintering as a process of transport of activated volume

    Directory of Open Access Journals (Sweden)

    Nikolić Nataša S.

    2002-01-01

    Full Text Available Starting with the fact that sintering is the consequence of the process of transport of activated volume, it has been shown how the kinetics of the sintering process can be defined. The activated volume was in principle defined as a parameter which describes a system’s deffectivity on an atomic level.

  16. Phase transformations during sintering of mechanically alloyed TiPt

    CSIR Research Space (South Africa)

    Nxumalo, S

    2010-10-01

    Full Text Available A TiPt alloy was produced by mechanically alloying the desired quantities of titanium and platinum. The resultant TiPt alloy powder was cold pressed to produce green bodies. Several sintering conditions were used to sinter this alloy...

  17. Direct metal laser sintering: a digitised metal casting technology.

    Science.gov (United States)

    Venkatesh, K Vijay; Nandini, V Vidyashree

    2013-12-01

    Dental technology is undergoing advancements at a fast pace and technology is being imported from various other fields. One such imported technology is direct metal laser sintering technology for casting metal crowns. This article will discuss the process of laser sintering for making metal crowns and fixed partial dentures with a understanding of their pros and cons.

  18. Direct Metal Laser Sintering: A Digitised Metal Casting Technology

    OpenAIRE

    Venkatesh, K. Vijay; Nandini, V Vidyashree

    2013-01-01

    Dental technology is undergoing advancements at a fast pace and technology is being imported from various other fields. One such imported technology is direct metal laser sintering technology for casting metal crowns. This article will discuss the process of laser sintering for making metal crowns and fixed partial dentures with a understanding of their pros and cons.

  19. Direct Metal Laser Sintering: A Digitised Metal Casting Technology

    OpenAIRE

    Venkatesh, K. Vijay; Nandini, V Vidyashree

    2013-01-01

    Dental technology is undergoing advancements at a fast pace and technology is being imported from various other fields. One such imported technology is direct metal laser sintering technology for casting metal crowns. This article will discuss the process of laser sintering for making metal crowns and fixed partial dentures with a understanding of their pros and cons.

  20. Monitoring sintering burn-through point using infrared thermography.

    Science.gov (United States)

    Usamentiaga, Rubén; Molleda, Julio; Garcia, Daniel F; Bulnes, Francisco G

    2013-08-09

    Sintering is a complex industrial process that applies heat to fine particles of iron ore and other materials to produce sinter, a solidified porous material used in blast furnaces. The sintering process needs to be carefully adjusted, so that the combustion zone reaches the bottom of the material just before the discharge end. This is known as the burn-through point. Many different parameters need to be finely tuned, including the speed and the quantities of the materials mixed. However, in order to achieve good results, sintering control requires precise feedback to adjust these parameters. This work presents a sensor to monitor the sintering burn-through point based on infrared thermography. The proposed procedure is based on the acquisition of infrared images at the end of the sintering process. At this position, infrared images contain the cross-section temperatures of the mixture. The objective of this work is to process this information to extract relevant features about the sintering process. The proposed procedure is based on four steps: key frame detection, region of interest detection, segmentation and feature extraction. The results indicate that the proposed procedure is very robust and reliable, providing features that can be used effectively to control the sintering process.

  1. Corrosion behaviour of sintered duplex stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Utrilla, M. Victoria; Urena, Alejandro; Otero, Enrique; Munez, Claudio Jose [Escuela Superior de Ciencias Experimentales y Tecnologia, Universidad Rey Juan Carlos, C/ Tulipan s/n, 28933 Mostoles, Madrid (Spain)

    2004-07-01

    Duplex austenite-ferrite stainless steels were prepared by mixing austenitic (316L) and ferritic (434L) atomized powders. Although different 316L/434L ratios were prepared, present work centred its study on 50% ferrite - 50% austenite sintered steel. The powders were mixed and pressed at 700 MPa and sintered at 1250 deg. C for 30 min in vacuum. The cooling rate was 5 deg. C/min. Solution treatment was carried out to homogenize the microstructure at 1100 deg. C during 20 min. A microstructural study of the material in solution was performed, evaluating the microstructure, proportion and shape of porosity, and ferrite percentage. This last was measured by two methods, quantitative metallography and Fischer ferrito-metry. The materials were heat treated in the range of 700 to 1000 deg. C, for 10, 30 and 60 min and water quenched, to study the microstructural changes and the influence on the intergranular corrosion resistance. The method used to evaluate the sensitization to the intergranular corrosion was the electrochemical potentio-kinetic reactivation procedure (EPR). The test solution was 0.5 M H{sub 2}SO{sub 4} + 0,01 M KSCN at 30 deg. C. The criterion used to evaluate the sensitization was the ratio between the maximum reactivation density (Ir) and the maximum activation density (Ia). The results of the electrochemical tests were discussed in relation with the microstructures observed at the different heat treatments. (authors)

  2. Synthesis and sintering of ceramic nanocomposites with high mixed conductivity

    Directory of Open Access Journals (Sweden)

    Zyryanov V.V.

    2005-01-01

    Full Text Available Metastable solid solutions of complex oxides with fluorite and perovskite structures are obtained by mechanosynthesis. Dense ceramics on the base of these metastable phases was obtained by thermal sintering of nanopowders due to kinetic stabilization. Different degrees of a chemical interaction (interdiffusion are observed during sintering of "perovskite+fluorite" and "perovskite+perovskite" composites. It is shown, that optimization of the composition, mixing conditions of individual phases and their sintering, preparation of ceramic composites with mixed conductivity for use in catalytic membrane reactors is possible. Unusual behavior of complex perovskites and fluorites is discovered during sintering, enabling determination of an optimum sintering temperature and time for which a qualitative explanation is given. It is established that rearrangement of fine crystalline particles as a whole plays a key role in shrinkage.

  3. The Emergence of Quantitative Sintering Theory from 1945 to 1955

    Science.gov (United States)

    German, Randall M.

    2017-04-01

    Particles flow and pack under stress, allowing shaping of the particles into target engineering geometries. Subsequently, in a process termed sintering, the particles are heated to induce bonding that results in a strong solid. Although first practiced 26,000 years ago, sintering was largely unexplained until recent times. Sintering science moved from an empirical and largely qualitative notion into a quantitative theory over a relatively short time period following World War II. That conceptual transition took place just as commercial applications for sintered materials underwent significant growth. This article highlights the key changes in sintering concepts that occurred in the 1945-1955 time period. This time span starts with the first quantitative neck growth model from Frenkel and ends with the quantitative shrinkage model from Kingery and Berg that includes several transport mechanisms.

  4. Microstructure evolution during pressureless sintering of bulk oxide ceramics

    Directory of Open Access Journals (Sweden)

    Karel Maca

    2009-06-01

    Full Text Available The author’s experience concerning the infl uence of the choice of different pressureless heating schedules on the fi nal microstructure of oxide ceramic materials is summarized in the paper. Alumina, ceria, strontium titanate, as well as tetragonal (3 mol% Y2O3 and cubic (8 mol% Y2O3 zirconia were cold isostatically pressed or injection moulded and pressureless sintered with different heating schedules – namely with Constant-Rate of Heating with different dwell temperatures (CRH, with Rate-Controlled Sintering (RCS and with Two-Step Sintering (TSS. It was examined whether some of these three sintering schedules, with the same fi nal density achieved, can lead to a decrease of the grain size of sintered ceramics. The results showed that only TSS (and only for selected materials brought significant decrease of the grain size.

  5. Sintered silver joints via controlled topography of electronic packaging subcomponents

    Science.gov (United States)

    Wereszczak, Andrew A.

    2014-09-02

    Disclosed are sintered silver bonded electronic package subcomponents and methods for making the same. Embodiments of the sintered silver bonded EPSs include topography modification of one or more metal surfaces of semiconductor devices bonded together by the sintered silver joint. The sintered silver bonded EPSs include a first semiconductor device having a first metal surface, the first metal surface having a modified topography that has been chemically etched, grit blasted, uniaxial ground and/or grid sliced connected to a second semiconductor device which may also include a first metal surface with a modified topography, a silver plating layer on the first metal surface of the first semiconductor device and a silver plating layer on the first metal surface of the second semiconductor device and a sintered silver joint between the silver plating layers of the first and second semiconductor devices which bonds the first semiconductor device to the second semiconductor device.

  6. A Combined Statistical-Microstructural Model for Simulation of Sintering

    Energy Technology Data Exchange (ETDEWEB)

    BRAGINSKY,MICHAEL V.; DEHOFF,ROBERT T.; OLEVSKY,EUGENE A.; TIKARE,VEENA

    1999-10-22

    Sintering theory has been developed either as the application of complex diffusion mechanisms to a simple geometry or as the deformation and shrinkage of a continuum body. They present a model that can treat in detail both the evolution of microstructure and the sintering mechanisms, on the mesoscale, so that constitutive equations with detail microstructural information can be generated. The model is capable of simulating vacancy diffusion by grain boundary diffusion, annihilation of vacancies at grain boundaries resulting in densification, and coarsening of the microstructural features. In this paper, they review the stereological theory of sintering and its application to microstructural evolution and the diffusion mechanism, which lead to sintering. They then demonstrate how these stereological concepts and diffusion mechanisms were incorporated into a kinetic Monte Carlo model to simulate sintering. Finally, they discuss the limitations of this model.

  7. Powder metallurgy: Solid and liquid phase sintering of copper

    Science.gov (United States)

    Sheldon, Rex; Weiser, Martin W.

    1993-01-01

    Basic powder metallurgy (P/M) principles and techniques are presented in this laboratory experiment. A copper based system is used since it is relatively easy to work with and is commercially important. In addition to standard solid state sintering, small quantities of low melting metals such as tin, zinc, lead, and aluminum can be added to demonstrate liquid phase sintering and alloy formation. The Taguchi Method of experimental design was used to study the effect of particle size, pressing force, sintering temperature, and sintering time. These parameters can be easily changed to incorporate liquid phase sintering effects and some guidelines for such substitutions are presented. The experiment is typically carried out over a period of three weeks.

  8. The Emergence of Quantitative Sintering Theory from 1945 to 1955

    Science.gov (United States)

    German, Randall M.

    2017-01-01

    Particles flow and pack under stress, allowing shaping of the particles into target engineering geometries. Subsequently, in a process termed sintering, the particles are heated to induce bonding that results in a strong solid. Although first practiced 26,000 years ago, sintering was largely unexplained until recent times. Sintering science moved from an empirical and largely qualitative notion into a quantitative theory over a relatively short time period following World War II. That conceptual transition took place just as commercial applications for sintered materials underwent significant growth. This article highlights the key changes in sintering concepts that occurred in the 1945-1955 time period. This time span starts with the first quantitative neck growth model from Frenkel and ends with the quantitative shrinkage model from Kingery and Berg that includes several transport mechanisms.

  9. Intense pulsed light sintering of copper nanoink for printed electronics

    Science.gov (United States)

    Kim, Hak-Sung; Dhage, Sanjay R.; Shim, Dong-Eun; Hahn, H. Thomas

    2009-12-01

    An intense pulsed light (IPL) from a xenon flash lamp was used to sinter copper nanoink printed on low-temperature polymer substrates at room temperature in ambient condition. The IPL can sinter the copper nanoink without damaging the polymer substrates in extremely short time (2 ms). The microstructure of the sintered copper film was investigated using X-ray powder diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), X-ray micro tomography, and atomic force microscopy (AFM). The sintered copper film has a grainy structure with neck-like junctions. The resulting resistivity was 5 μΩ cm of electrical resistivity which is only 3 times as high as that of bulk copper. The IPL sintering technique allows copper nanoparticles to be used in inkjet printing on low-temperature substrates such as polymers in ambient conditions.

  10. Sintering unalloyed titanium in DC electrical abnormal glow discharge

    Directory of Open Access Journals (Sweden)

    Allan Seeber

    2010-03-01

    Full Text Available Powder metallurgy is widely used in the manufacture of components that have complex geometry. The good dimensional control, reduction in manufacturing steps and operating costs which has favored the use of this technique for manufacturing of titanium alloys components. However, the high affinity of this material with oxygen hinders strongly the sintering process. For this, the sintering associated with plasma technology can be considered an alternative technique for the processing of this material. The strict control of sintering atmosphere performed at low pressures and the reactive species present in the plasma environment can help to improve the sintering of this material. The results presented in this paper show a good correlation between the parameters used for the compaction of the samples and the microstructure develop during the plasma sintering of samples. The microstructure of the plasma assisted samples is also affected by the particular configuration used in the plasma reactor.

  11. Ash chemistry and sintering, verification of the mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Hupa, M.; Skrifvars, B.J.; Backman, R.; Lauren, T.; Uusikartano, T.; Malm, H.; Stenstroem, P.; Vesterkvist, M. [Aabo Akademi, Turku (Finland). Combustion Chemistry Research Group

    1997-10-01

    In this project four sintering mechanisms have been studied, i.e., partial melting with a viscous liquid, partial melting with a non-viscous liquid, chemical reaction sintering and solid state sintering. The work has aimed at improving the understanding of ash sintering mechanisms and quantifying their role in combustion and gasification. The work has been oriented in particular on the understanding of biomass ash behavior. The work has not directly focused on any specific technical application. However, results can also be applied on other fuels such as brown coal, petroleum coke, black liquor and different types of wastes (PDF, RDF, MSW). During 1996 the work has focused on identifying bed agglomeration mechanisms and analysing bed agglomerates in both full scale and lab scale FB reactors, as well as comparing how well the compression strength based sintering test can predict bed agglomeration in an FB furnace. (orig.)

  12. Intense pulsed light sintering of copper nanoink for printed electronics

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hak-Sung; Dhage, Sanjay R.; Shim, Dong-Eun [University of California, Mechanical and Aerospace Engineering Department, Los Angeles, CA (United States); Hahn, H.T. [University of California, Mechanical and Aerospace Engineering Department, Los Angeles, CA (United States); University of California, Material Science and Engineering Department, California NanoSystems Institute, Los Angeles, CA (United States)

    2009-12-15

    An intense pulsed light (IPL) from a xenon flash lamp was used to sinter copper nanoink printed on low-temperature polymer substrates at room temperature in ambient condition. The IPL can sinter the copper nanoink without damaging the polymer substrates in extremely short time (2 ms). The microstructure of the sintered copper film was investigated using X-ray powder diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), X-ray micro tomography, and atomic force microscopy (AFM). The sintered copper film has a grainy structure with neck-like junctions. The resulting resistivity was 5{mu}{omega} cm of electrical resistivity which is only 3 times as high as that of bulk copper. The IPL sintering technique allows copper nanoparticles to be used in inkjet printing on low-temperature substrates such as polymers in ambient conditions. (orig.)

  13. Effect of Nb and Cu on the crystallization behavior of under-stoichiometric Nd-Fe-B alloys

    Science.gov (United States)

    Salazar, D.; Martín-Cid, A.; Madugundo, R.; Garitaonandia, J. S.; Barandiaran, J. M.; Hadjipanayis, G. C.

    2017-01-01

    In this work, we present a complete study of the influence of Nb and Cu addition on the crystallization behavior of Nd-lean Nd-Fe-B melt-spun alloys. Alloys with compositions Nd10-x-y Fe84B6Nb x Cu y (x  =  1, y  =  0 and x  =  0.5, y  =  0.5) were melt-spun at different wheel speeds (15-40 m s-1) to obtain samples in amorphous, highly disordered and nanocrystalline structures. The crystallization process, induced by different heat treatments, was studied by means of differential thermal analysis and x-ray powder thermodiffraction. Magnetic properties of as-made and heat-treated ribbons were measured by magnetometry. The as-made amorphous samples showed a crystallization to the 2:14:1 hard magnetic phase at T 1 ~ 350 °C. Doping with Nb results in an increase of T 1, and addition of Cu lowers T 1. This behavior is explained in terms of an inhibition of grain growth by Nb and a nucleation enhancement by Cu additions. During the crystallization process, a secondary phase (identified as a bcc-Fe-rich phase) is formed. The amount of such a phase increases with the annealing temperature. Coercivity increases upon annealing reaching maxima at 700-750 °C. This can be explained in terms of competition between the two phases formed: the 2:14:1 hard phase and the soft bcc-Fe-rich phase. The highest coercivity of the Nd-lean samples is observed when the microstructure is appropriate and both phases are exchange-coupled.

  14. Higher d.c. resistivity of Li–Zn–Cd ferrites prepared by microwave sintering compared with conventional sintering

    Indian Academy of Sciences (India)

    Mamata Maisnam; Sumitra Phanjoubam

    2014-10-01

    Cd2+-substituted Li–Zn ferrites having the general formula Li$^{+}_{0.4–x/2}$Zn$^{2+}_{0.2}$Cd$^{2+}_{x}$Fe$^{3+}_{2.4–x/2}$O$^{2-}_{4}$ where x = 0.02, 0.03 and 0.04 have been prepared by both microwave sintering and conventional sintering. In the former case, sintering was done at 1050 °C for 25 min, whereas in the latter case sintering was done at 1050 °C for 6 h. The various structural properties, microstructures and d.c. resistivity of the samples prepared by the two techniques were compared. The study showed higher d.c. resistivity and higher activation energies in the samples prepared by microwave sintering. The mechanisms pertaining to the results are discussed.

  15. The attenuation of the levitation force of HTS bulk exposed to AC magnetic field on the above NdFeB guideway

    Energy Technology Data Exchange (ETDEWEB)

    Liu Minxian, E-mail: liukey_sjtu@263.net [School of Computer Science and Technology, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Wang Yan [Luoyang Institute of Science and Technology, Luoyang, Henan 471023 (China)

    2012-01-15

    The characteristic of the levitation force relaxation was studied by experiment. The levitation force is attenuated with the application of the AC external magnetic field. The decay increases with the amplitude of the A external magnetic field. The decay is almost independent of the frequency of AC field. In the present High Temperature Superconducting (HTS) maglev vehicle system, the air gaps between the adjacent permanent magnets make the magnetic fields above the NdFeB guideway non-uniform. So it is required to study the characteristics of levitation force of the HTS bulk affected by the non-uniform applied magnetic fields along the moving direction. In this paper, we have studied the characteristics of the levitation force relaxation by an experiment in which AC magnetic field generated by an electromagnet is used to simulate the time-varying magnetic field caused by the inhomogeneity of the NdFeB guideway. From the experiment results, it is found that the levitation force is attenuated with the application of the AC field, and the attenuation is increased with the amplitude of the AC field, but the attenuation is almost independent of the frequency the AC magnetic field.

  16. Synthesis of functionally graded materials via electrophoretic deposition and sintering

    Science.gov (United States)

    Wang, Xuan

    In this research, both the experiments and the modeling aspects of the net-shape fabrication of Functionally Graded Materials (FGM) by Electrophoretic Deposition (EPD) and consecutive sintering have been investigated. In order to obtain FGMs with desired final shape and properties, the issues regarding the shape evolution during sintering, the optimization of initial properties and composition profiles, and the fabrication of green components by EPD have been analyzed. In order to fabricate FGMs by the proposed technological sequence (EPD with the following sintering), the initial shape has to be optimized prior to sintering. In this research, the formulations to simulate sintering of an FGM were developed based on the continuum theory of sintering. A finite element sintering-modeling subroutine has been created and linked to the commercial finite element package ABAQUS. The shape changes of FGM disks during sintering were simulated. In order to obtain the desired final shape after sintering, an inverse modeling methodology was developed to optimize the initial shape. In order to fabricate the optimized initial shape of a green FGM specimen determined by the inverse continuum modeling of sintering, EPD of a number of FGMs was investigated. The FGM green specimens made of Al2O 3 and ZrO2 with the initial shape predicted by the inverse modeling, were deposited using self-designed equipments. The acetone-based suspension with n-butylamine as a particle-charging additive was used. The comparison of the shape between the sintered and the green FGM indicated that the developed experimental-theoretical methodology provided a reliable solution for near net shaping of complex 3-D FGM components. Other applications of EPD, such as in electronic packaging materials and zeolites, were also investigated. In order to fabricate functionally graded materials based on aligned porous structures, unidirectional freezing followed by freeze-drying and sintering has been investigated

  17. In-situ grown silica sinters in Icelandic geothermal areas.

    Science.gov (United States)

    Tobler, Dominique J; Stefánsson, Andri; Benning, Liane G

    2008-12-01

    Field in-situ sinter growth studies have been carried out in five geochemically very different Icelandic geothermal areas with the aim to quantify the effects of water chemistry, (e.g. silica content (250 to 695 p.p.m. SiO(2)), salinity (meteoric to seawater), pH (7.5 to 10)), temperature (42-96 degrees C) and microbial abundance (prevalence, density) on the growth rates, textures and structures of sinters forming within and around geothermal waters. At each location, sinter growth was monitored over time periods between 30 min and 25 months using glass slides that acted as precipitation substrates from which sinter growth rates were derived. In geothermal areas like Svartsengi and Reykjanes, subaqueous sinters developed rapidly with growth rates of 10 and 304 kg year(-1 )m(-2), respectively, and this was attributed primarily to the near neutral pH, high salinity and medium to high silica content within these geothermal waters. The porous and homogeneous precipitates that formed at these sites were dominated by aggregates of amorphous silica and they contained few if any microorganisms. At Hveragerdi and Geysir, the geothermal waters were characterized by slightly alkaline pH, low salinity and moderate silica contents, resulting in substantially lower rates of sinter growth (0.2-1.4 kg year(-1 )m(-2)). At these sites sinter formation was restricted to the vicinity of the air-water interface (AWI) where evaporation and condensation processes predominated, with sinter textures being governed by the formation of dense and heterogeneous crusts with well-defined spicules and silica terraces. In contrast, the subaqueous sinters at these sites were characterized by extensive biofilms, which, with time, became fully silicified and thus well preserved within the sinter edifices. Finally, at Krafla, the geothermal waters exhibited high sinter growth rates (19.5 kg year(-1 )m(-2)) despite being considerably undersaturated with respect to amorphous silica. However, the bulk of

  18. Synthesis and Sintering of Mg2Si Thermoelectric Generator by Spark Plasma Sintering

    Institute of Scientific and Technical Information of China (English)

    YANG Meijun; ZHANG Lianmeng; SHEN Qiang

    2008-01-01

    Raw Mg,Si powder were used to fabricate Mg2Si bulk thermoelectric generator by spark plasma sintering (SPS).The optimum parameters to synthesize pure Mg2Si powder were found to be 823 K,0 MPa,10 min with excessive content of 10wt% Mg from the stoichiometric Mg2Si.Mg2Si bulk was synthesized and densified simultaneously at low temperature (823 K) and high pressure (higher than 100 MPa) from the raw powder,but Mg,Si could not react completely,and the sample was not very dense with some microcracks on the surface.Then,Mg,Si powder reacted at 823 K,0 MPa,10 min in SPS chamber to form Mg2Si green compact,again sintered by SPS at 1023 K,20 MPa,5 min.The fabricated sample only contained MgESi phase with fully relative density.

  19. FEM Optimisation of Spark Plasma Sintering Furnace

    CERN Document Server

    Kellari, Demetrios Vasili

    2013-01-01

    Coupled electro-thermal FEM analysis has been carried out on a sintering furnace used to produce new materials for LHC collimators. The analysis showed there exist margins for improvement of the current process and equipment through minor changes. To optimise the design of the furnace several design changes have been proposed including: optimization of material selection using copper cooling plates, control of convection in cooling plates by lowering the water flow rate, modifying the electrode shape using unsymmetrical electrodes and upgrading the thermal shielding to make use of multilayer graphite shields. The results show that we have a significant improvement in temperature gradient on the plate, from 453 to 258 °C and a reduction in power requirement from 62 to 44 kW.

  20. Research on sintering process of YSZ electrolyte

    Institute of Scientific and Technical Information of China (English)

    HAN Minfang; TANG Xiuling; PENG Suping

    2006-01-01

    Yttria stabilized zirconia (YSZ) has widely been used as electrolyte in solid oxide fuel cell (SOFC).The microstructure of YSZ related to the fabrication process was discussed in the paper.With YSZ nano-powders about 40-100 nm as raw material, the YSZ adobe was manufactured by tape calendering process.The named three-step sintering process was performed at 1000 ℃ for 2 h, then raised the temperature with normal rate and as soon as up to 1400 ℃, the furnace was controlled at 1250-1300 ℃ for 10-20 h.The high dense YSZs with the relative density of 96%-99% were obtained; the grain size of YSZ could be reduced to 0.5-3 μm.The above result is benefited to co-fired in the electrode-supported SOFCs.

  1. Effect of YSZ sintering temperature on mixed potential sensor performance

    Energy Technology Data Exchange (ETDEWEB)

    Sekhar, Praveen K [Los Alamos National Laboratory; Brosha, Eric L [Los Alamos National Laboratory; Rangachary, Mukundan [Los Alamos National Laboratory; Garzon, Fernando H [Los Alamos National Laboratory; Nelson, Mark A [Los Alamos National Laboratory; Toracco, Dennis [Los Alamos National Laboratory

    2009-01-01

    In this article, the influence of Yttria-Stabilized Zirconia (YSZ) sintering temperature on a Pt/YSZ/La{sub 0.8}Sr{sub 0.2}CrO{sub 3} mixed potential sensor performance is reported. The sintering temperature of YSZ was varied from 1000 to 1200 C. Mercury porosity measurements were performed to estimate the porosity and tortuosity of the YSZ sample as a function of sintering temperature. Further, the surface area of YSZ was computed by the BET method. After YSZ characterization, the unbiased and biased sensor response was recorded. The 1000 C sintered YSZ sample was taken as the reference for comparison purposes. Experimental results indicated a 30% reduction in porosity for the 1200 C sintered YSZ sample, accounting for a 14-fold increase in the sensor response rise time. In addition, for the same sample, a 13-fold increase in sensitivity was observed upon exposure to propylene (100 ppm), associated with a 76% reduction in surface area. The slow response time of the sensor with YSZ sintered at higher temperatures has been attributed to higher tortuosity (delay in gas permeation to the three phase interface). Whereas, reduced heterogeneous catalysis induced by lower surface area accounts for the rise in sensitivity levels. The optimum YSZ sintering temperature was found to lie between 1100 and 1150 C.

  2. Removable partial denture alloys processed by laser-sintering technique.

    Science.gov (United States)

    Alageel, Omar; Abdallah, Mohamed-Nur; Alsheghri, Ammar; Song, Jun; Caron, Eric; Tamimi, Faleh

    2017-05-31

    Removable partial dentures (RPDs) are traditionally made using a casting technique. New additive manufacturing processes based on laser sintering has been developed for quick fabrication of RPDs metal frameworks at low cost. The objective of this study was to characterize the mechanical, physical, and biocompatibility properties of RPD cobalt-chromium (Co-Cr) alloys produced by two laser-sintering systems and compare them to those prepared using traditional casting methods. The laser-sintered Co-Cr alloys were processed by the selective laser-sintering method (SLS) and the direct metal laser-sintering (DMLS) method using the Phenix system (L-1) and EOS system (L-2), respectively. L-1 and L-2 techniques were 8 and 3.5 times more precise than the casting (CC) technique (p laser-sintered and cast alloys were biocompatible. In conclusion, laser-sintered alloys are more precise and present better mechanical and fatigue properties than cast alloys for RPDs. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2017. © 2017 Wiley Periodicals, Inc.

  3. Evaluation of effect of surface treatment on corrosion resistance of Nd-Fe-B magnets; Avaliacao do efeito de tratamentos superficiais na resistencia a corrosao de magnetos de Nd-Fe-B

    Energy Technology Data Exchange (ETDEWEB)

    Martins, Emerson Alves

    2009-07-01

    Nd-Fe-B magnets produced by powder metallurgy are highly susceptible to corrosion due to their complex microstructure and intrinsic porosity due to their fabrication process. Moreover, these magnets have excellent magnetic properties and find many applications. In the nuclear area, permanent magnets based on rare earth transition-iron-boron (Ne-Fe-B) are used in the manufacture of magnetic media (magnetic levitation) for ultra-centrifuges used for isotopic enrichment of uranium employed in nuclear reactors. In dentistry these types of magnets are used to fix total and partial prostheses on implants; in orthodontics to correct dental malocclusion and make moves; in buco-maxillo-facial surgery for setting facial prostheses of large defects of the face. In electronic equipment, they are used in scales, locks, electric motors and particularly in the manufacturing of hard drives of computers. The objective of this study is to evaluate the corrosion resistance of the magnet tested and surface treatments that could replace chromating that generates toxic residues and present high cost of processing waste with treatments that are environmentally friendly. The evaluation of the corrosion resistance was carried out through the analysis potentiodynamic polarization curves, electrochemical impedance spectroscopy, monitoring of corrosion potential as a function of test time and scanning electron microscopy to try to correlate the magnet microstructure with its corrosion resistance. The results show that these magnets are highly susceptible to corrosion that occurs preferentially in the Nd-rich phase, located in the boundaries of the magnetic matrix phase ({psi}). Treatment with silane, cerium, sam, Cr 6{sup +}, tricationic phosphate followed by bath of chromium trioxide and in NaH{sup 2}PO{sup 4} solution for 24 hours followed by bath of zinc sulphate did not improve the corrosion resistance of the magnet. Among the treatments used, immersion in NaH{sup 2}PO{sup 4} solution for

  4. Microwave sintering of biogenic hydroxyapatite ceramics for reconstructive surgery

    Directory of Open Access Journals (Sweden)

    Hanna Tovstonoh

    2014-03-01

    Full Text Available Ceramics based on biogenic hydroxyapatite have been produced via a microwave sintering at 1000 °C for 5, 10, 15, 20 and 30 min. It was shown that all of the ceramics studied exhibit volumetric shrinkage (2.3–4.6 %, which increases with increasing sintering time at maximum temperature. It was established that the total porosity did not depend on sintering time at 1000 °C and was equal to 38–40 %. Moreover, in all of the materials an open porosity dominated. The ultimate compression strength was in the range 35–40 MPa.

  5. LOW TEMPERATURE SINTERING OF ALUMINA BIOCERAMIC UNDER NORMAL PRESSURE

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Superfine alumina powder with high purity (mean particle size is less than 0. 35μm) were used as main starting material for sintering alumina ceramic. A multiple additive MgO-ZrO2 (Y2O3) was homogeneously added into the batch by the chemical coprecipitation method. Sintering of alumina bioceramic at low tempera ture (<1600C) was achieved resulting in a dense and high strength alumina ceramic with the bending strength up to 382 MPa and an improved fracture toughness. Mechanism that the multiple additives promote the sintering of alumina ceramic is discussed on the base of XRD and SEM analysis.

  6. Fracture in sintered Sm-Co permanent magnetic materials

    Institute of Scientific and Technical Information of China (English)

    LI; Anhua(李安华); DONG; Shengzhi(董生智); LI; Wei(李卫)

    2003-01-01

    The bending strength and fracture toughness of sintered Sm-Co permanent magnetic materials are measured. A scanning electron microscope equipped with an energy dispersive X-ray analysis system is employed to investigate the bending fractography. The fracture behavior and micromechanism are discussed. The fracture behavior of sintered Sm-Co permanent magnetic materials exhibits cleavage fracture. Some Sm-rich impurities are found in fracture plane, suggesting that the Sm-rich impurities help reduce the cleavage brittleness of sintered Sm-Co permanent magnetic materials. The possible methods for improving the strength and toughness are also proposed.

  7. Spark Plasma Sintering of Fuel Cermets for Nuclear Reactor Applications

    Energy Technology Data Exchange (ETDEWEB)

    Yang Zhong; Robert C. O' Brien; Steven D. Howe; Nathan D. Jerred; Kristopher Schwinn; Laura Sudderth; Joshua Hundley

    2011-11-01

    The feasibility of the fabrication of tungsten based nuclear fuel cermets via Spark Plasma Sintering (SPS) is investigated in this work. CeO2 is used to simulate fuel loadings of UO2 or Mixed-Oxide (MOX) fuels within tungsten-based cermets due to the similar properties of these materials. This study shows that after a short time sintering, greater than 90 % density can be achieved, which is suitable to possess good strength as well as the ability to contain fission products. The mechanical properties and the densities of the samples are also investigated as functions of the applied pressures during the sintering.

  8. Low temperature spark plasma sintering of YIG powders

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Garcia, L. [Department of Nanostructured Materials, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Suarez, M., E-mail: m.suarez@cinn.e [Department of Nanostructured Materials, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Fundacion ITMA, Parque Tecnologico de Asturias, 33428, Llanera (Spain); Menendez, J.L. [Department of Nanostructured Materials, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain)

    2010-07-16

    A transition from a low to a high spin state in the magnetization saturation between 1000 and 1100 {sup o}C calcination temperature is observed in YIG powders prepared by oxides mixture. Spark plasma sintering of these powders between 900 and 950 {sup o}C leads to dense samples with minimal formation of YFeO{sub 3}, opening the way to co-sintering of YIG with metals or metallic alloys. The optical properties depend on the sintering stage: low (high) density samples show poor (bulk) optical absorption.

  9. Electrical discharge machining studies on reactive sintered FeAl

    Indian Academy of Sciences (India)

    A K Khanra; S Patra; M M Godkhindi

    2006-06-01

    Electrical discharge machining (EDM) studies on reactive sintered FeAl were carried out with different process parameters. The metal removal rate and tool removal rate were found to increase with the applied pulse on-time. The surface roughness of machined surface also changed with the applied pulse on-time. XRD analysis of machined surface of sintered FeAl showed the formation of Fe3C phase during the EDM process. The debris analysis was used to identify the material removal mechanism occurring during the EDM of sintered FeAl.

  10. Substrate-facilitated nanoparticle sintering and component interconnection procedure.

    Science.gov (United States)

    Allen, Mark; Leppäniemi, Jaakko; Vilkman, Marja; Alastalo, Ari; Mattila, Tomi

    2010-11-26

    Room temperature substrate-facilitated sintering of nanoparticles is demonstrated using commercially available silver nanoparticle ink and inkjet printing substrates. The sintering mechanism is based on the chemical removal of the nanoparticle stabilizing ligand and is shown to provide conductivity above one-fourth that of bulk silver. A novel approach to attach discrete components to printed conductors is presented, where the sintered silver provides the metallic interconnects with good electrical and mechanical properties. A process for printing and chip-on-demand assembly is suggested.

  11. Combined macro-meso scale modeling of sintering. Part I: Continuum approach

    Energy Technology Data Exchange (ETDEWEB)

    OLEVSKY,EUGENE A.; TIKARE,VEENA

    2000-05-23

    An integrated approach, including a continuum theory of sintering and mesostructure evolution analysis, is used for the solution of the problem of bi-layered structure sintering. Two types of bi-layered structures are considered: layers of the same material different by initial porosity, and layers of two different materials. The effective sintering stress and the normalized bulk modulus for the bi-layer powder sintering are derived based on mesoscale simulations. The combined effect of the layers' porosity and differences in sintering rate on shrinkage and warpage is studied for both sintering on a rigid substrate and free sintering.

  12. Sintering activation of 316L powder using a liquid phase forming powder

    Directory of Open Access Journals (Sweden)

    Nattaya Tosangthum

    2010-03-01

    Full Text Available It was found that the addition of a liquid forming powder (up to 6 wt.% of a gas-atomized tin powder to 316L powdercould activate the sintering process. Sintering activation could be observed by an increase of the sintered density and selected mechanical properties. When optimized tin powder content was used, shorter sintering time and lower sintering temperaturecould produce sintered 316L+tin materials with excellent mechanical properties. Electron dispersive spectroscopy analyses across 316L-tin-316L grains indicated that Ni transportation during the sintering process was enhanced by the presence of liquid tin.

  13. Effect of sintering parameters on warm compacted iron-based material

    Institute of Scientific and Technical Information of China (English)

    李元元; 肖志瑜; 倪东惠; 夏伟; 陈维平

    2003-01-01

    Iron-based powder metallurgy material was prepared by warm compaction at 125℃ using a compacting pressure of 700 Mpa.Sintering temperature ranging from 1100℃ to 1300℃ and sintering time ranging from 40min to 80 min were used to study the effects of sintering parameters on the compacts.Die wall lubrication polytetrafluoroethylene(PTFE)emulsion was also applied in combination with warm compaction in hope to increase the compact density and the mechanical properties of the sintered material.Green and sintered density,spring back effect and sinter shrinkage were measured.Mechanical properties of both as-sinter and heat treated samples were also measured.Results show that mechanical properties of the sintered compacts increase with the increase of sintering temperature and sintering time.Sample prepared by die wall lubricated warm compaction always shows higher density and mechanical properties.

  14. Sintering process and grain growth of Mn-Zn ferrite nanoparticles

    Institute of Scientific and Technical Information of China (English)

    WANG Xin; CUI Yinfang; WANG Yongming; HAO Shunli; LIU Chunjing

    2006-01-01

    The density, microstructure and magnetic properties of non-doped Mn-Zn ferrite nanoparticles sintered compacts were investigated. The compacts of non-doped Mn-Zn ferrite nanoparticles were sintered by segmented-sintering process at lower sintering temperature. The density of sintered samples was measured by Archimedes method, and the phase composition and microstructure were examined by XRD and SEM. The sintered Mn-Zn ferrite magnetic measurements were carried out with Vibrating Sample. The results show that the density of sintered compacts increases with the rising of sintering temperature, achieving 4.8245 g·cm-3 when sintered at 900 ℃, which is the optimal density of Mn-Zn functional ferrite needed and from the fractured surface of sintered samples, it can be seen that the grain grows well with small grain size and homogeneous distribution.

  15. Master sintering curves for UO{sub 2} and UO{sub 2}–SiC composite processed by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Zhichao [Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611 (United States); Subhash, Ghatu, E-mail: subhash@ufl.edu [Mechanical and Aerospace Engineering, University of Florida, Gainesville, FL 32611 (United States); Tulenko, James S. [Materials Science and Engineering, University of Florida, Gainesville, FL 32611 (United States)

    2014-11-15

    Highlights: • Constructed master sintering curves for spark plasma sintering (SPS) of nuclear fuels. • Characterized sinterability of UO{sub 2} and UO{sub 2}–SiC powder compacts during SPS. • Determined activation energies for sintering of UO{sub 2} and UO{sub 2}–SiC composites by SPS. - Abstract: Master sintering curve (MSC) theory has been applied successfully to UO{sub 2} and UO{sub 2}–SiC composite ceramics processed using spark plasma sintering (SPS). By applying the constant heating rate method, where the powder compact was heated at a constant rate to a specified maximum temperature and then cooled naturally, the apparent activation energies for sintering have been determined to be 140 kJ/mol for UO{sub 2} and 420 kJ/mol for UO{sub 2}–SiC composite. The ability of the derived MSCs to control and predict final density in the sintered compact was demonstrated by additional experimental runs using the isothermal heating method, in which the powder is held for a specified time at the maximum sintering temperature. It is shown that the master sintering curve is an effective tool to characterize the densification and sinterability behavior of a given nuclear powder compact during spark plasma sintering. The reason for significantly lower activation energy in SPS processed UO{sub 2} pellets compared to conventional sintering has been rationalized on the basis of field activation in SPS process.

  16. Plutonium Immobilization Project Binder Burnout and Sintering Studies (Milestone 6.6a)

    Energy Technology Data Exchange (ETDEWEB)

    Chandler, G.

    1999-10-28

    The Plutonium Immobilization Team has developed an integrated test program to understand and optimize the controlling variables for the sintering step of the plutonium immobilization process. Sintering is the key process step that controls the product minerology. It is expected that the sintering will be the limiting process step that controls the throughput of the production line. The goal of the current sintering test program is to better understand factors that affect the sintering process.

  17. Chemical state mapping of heterogeneous reduction of iron ore sinter

    Science.gov (United States)

    Kimura, M.; Takeichi, Y.; Murao, R.; Obayashi, I.; Hiraoka, Y.; Liu, Y.

    2017-06-01

    Iron ore sinter constitutes the major component of the iron-bearing burden in blast furnaces, and its reduction mechanism is one of the keys to improving the productivity of ironmaking. Iron ore sinter is composed of multiple iron oxide phases and calcium ferrites (CFs), and their heterogeneous reduction was investigated in terms of changes in iron chemical state: FeIII, FeII, and Fe0 were examined macroscopically by 2D X-ray absorption and microscopically by 3D transmission X-ray microscopy (TXM). It was shown that the reduction starts at iron oxide grains rather than at calcium ferrite (CF) grains, especially those located near micropores. The heterogeneous reduction causes crack formation and deteriorates the mechanical strength of the sinter. These results help us to understand the fundamental aspects of heterogeneous reduction schemes in iron ore sinter.

  18. Modeling Macroscopic Shape Distortions during Sintering of Multi-layers

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye

    Ceramic multi-layered composites are being used as components in various technologies ranging from electronics to energy conversion devices. Thus, different architectures of multi-layers involving ceramic materials are often required to be produced by powder processing, followed by sintering...... evolutions during co-firing of bi-layers. Optimizations of the co-firing process by controlling the initial geometry of the sample and structural characteristics are also suggested. Furthermore, the multi-scale model has also shown the expected behavior of shape distortions for different bi-layers systems...... involving layers with the same and different sinterabilities. Based on the experimental and simulation results, the following conclusions are reached: during sintering of planar multi-layers, understanding of the effect of gravity on the camber evolution can be used in optimizing the co-sintering process so...

  19. Supersolidus Liquid Phase Sintering Modeling of Inconel 718 Superalloy

    Science.gov (United States)

    Levasseur, David; Brochu, Mathieu

    2016-02-01

    Powder metallurgy of Inconel 718 superalloy is advantageous as a near-net shape process for complex parts to reduce the buy-to-fly ratio and machining cost. However, sintering Inconel 718 requires the assistance of supersolidus liquid formation to achieve near full density and involves the risk of distortion at high temperatures. The present work is focused on modeling the onset of sintering and distortion as a function of temperature, grain size, and part geometry for Inconel 718. Using experimental sintering results and data available in the literature, the supersolidus liquid phase sintering of Inconel 718 was modeled. The model was used to define a processing window where part distortion would be avoided.

  20. Processing of bulk Al7075 alloy by spark plasma sintering

    Science.gov (United States)

    Málek, P.; Molnárová, O.; Cinert, J.; Lukáč, F.; Chráska, T.

    2017-02-01

    The main advantages of powder metallurgy processing route are the possibility to produce near-net-shape compacts and to minimize the finish machining and material loss. The main problem in particle consolidation process is to suppress porosity, to remove oxide layers, and to retain the microstructure of powder materials. Spark plasma sintering (SPS) combines concurrent uniaxial pressure and direct heating by a pulsed DC current. Sintering occurs at relatively low temperatures for a short time and does not influence significantly the microstructure in the interiors of original powder particles. The efficiency of SPS in producing compacts with low porosity might be dependent on the distribution of particle size in original powder material. The gas atomized Al7075 powder was sieved to several charges and then sintered by SPS. Microstructure of sintered compacts was studied by light and scanning electron microscopy. The phase composition was investigated using X-ray diffraction. The mechanical behaviour was tested by bending tests.

  1. Liquid Phase Sintering of Highly Alloyed Stainless Steel

    DEFF Research Database (Denmark)

    Mathiesen, Troels

    1996-01-01

    Liquid phase sintering of stainless steel is usually applied to improve corrosion resistance by obtaining a material without an open pore system. The dense structure normally also give a higher strength when compared to conventional sintered steel. Liquid phase sintrering based on addition...... of boride to AISI 316L type steels have previously been studied, but were found to be sensitive to intergranular corrosion due to formation of intermetallic phases rich in chromium and molybdenum. In order to improve this system further, new investigations have focused on the use of higher alloyed stainless...... steel as base material. The stainless base powders were added different amounts and types of boride and sintered in hydrogen at different temperatures and times in a laboratory furnace. During sintering the outlet gas was analyzed and subsequently related to the obtained microstructure. Thermodynamic...

  2. Journal of EEA, Vol. 30, 2013 SAND SINTERING PROBLEM ON ...

    African Journals Online (AJOL)

    dell

    SAND SINTERING PROBLEM ON BRONZE CASTINGS. Asmamaw Tegegne* ... required to improve the quality of casting with regard to .... property in service and certain amount of zinc for .... a result of which huge finance is required. As seen.

  3. Factors influencing particle agglomeration during solid-state sintering

    Institute of Scientific and Technical Information of China (English)

    Chao Wang; Shao-Hua Chen

    2012-01-01

    Discrete element method (DEM) is used to study the factors affecting agglomeration in three-dimensional copper particle systems during solid-state sintering.A new parameter is proposed to characterize agglomeration.The effects of a series of factors are studied,including particle size,size distribution,inter-particle tangential viscosity,temperature,initial density and initial distribution of particles on agglomeration.We find that the systems with smaller particles,broader particle size distribution,smaller viscosity,higher sintering temperature and smaller initial density have stronger particle agglomeration and different distributions of particles induce different agglomerations.This study should be very useful for understanding the phenomenon of agglomeration and the micro-structural evolution during sintering and guiding sintering routes to avoid detrimental agglomeration.

  4. Pressureless sintering behavior of injection molded alumina ceramics

    Directory of Open Access Journals (Sweden)

    Liu W.

    2014-01-01

    Full Text Available The pressureless sintering behaviors of two widely used submicron alumina (MgOdoped and undoped with different solid loadings produced by injection molding have been studied systematically. Regardless of the sinterability of different powders depending on their inherent properties, solid loading plays a critical role on the sintering behavior of injection molded alumina, which greatly determines the densification and grain size, and leads to its full densification at low temperatures. As compared to the MgO-doped alumina powder, the undoped specimens exhibit a higher sinterability for its smaller particle size and larger surface area. While full densification could be achieved for MgO-doped powders with only a lower solid loading, due to the fact that MgO addition can reduce the detrimental effect of the large pore space on the pore-boundary separation.

  5. Modeling sintering of multilayers under influence of gravity

    DEFF Research Database (Denmark)

    Frandsen, Henrik Lund; Olevsky, Eugene; Tadesse Molla, Tesfaye

    2013-01-01

    , which describes the combined effect of sintering and gravity of thin multilayers, is derived and later compared with experimental results. It allows for consideration of both uniaxial and biaxial stress states. The model is based on the Skorohod-Olevsky viscous sintering framework, the classical...... laminate theory and the elastic-viscoelastic correspondence principle. The modeling approach is then applied to illustrate the effect of gravity during sintering of thin layers of cerium gadolinium oxide (CGO), and it is found to be significant. © 2012 The American Ceramic Society.......There is a tendency for multiple functional ceramic layers used in various applications to have increasing surface areas and decreasing thicknesses. Sintering samples with such geometry is challenging, as differential shrinkage of the layers causes undesired distortions. In this work, a model...

  6. Onset conditions for flash sintering of UO2

    Science.gov (United States)

    Raftery, Alicia M.; Pereira da Silva, João Gustavo; Byler, Darrin D.; Andersson, David A.; Uberuaga, Blas P.; Stanek, Christopher R.; McClellan, Kenneth J.

    2017-09-01

    In this work, flash sintering was demonstrated on stoichiometric and non-stoichiometric uranium dioxide pellets at temperatures ranging from room temperature (26 °C) up to 600 °C . The onset conditions for flash sintering were determined for three stoichiometries (UO2.00, UO2.08, and UO2.16) and analyzed against an established thermal runaway model. The presence of excess oxygen was found to enhance the flash sintering onset behavior of uranium dioxide, lowering the field required to flash and shortening the time required for a flash to occur. The results from this study highlight the effect of stoichiometry on the flash sintering behavior of uranium dioxide and will serve as the foundation for future studies on this material.

  7. A constitutive model for sintering of granulated ceramic powders

    Science.gov (United States)

    Shinagawa, K.; Hirashima, Y.

    1998-05-01

    Sintering behavior of granulated powder is investigated to develop a constitutive model for deformation analysis of ceramic powder compacts during sintering. Spray-dried alumina is compacted by CIPing (cold isostatic pressing) and sintered at various temperatures. Shrinkage and the change in grain size of the compacts during sintering are revealed in relation to the inhomogeneous microstructure consisting of fractured and unfractured granules as a consequence of the compaction. A constitutive model for the ceramic powder compacts having the internal structure is presented; The difference in grain growth in dense and sparse regions of the compacts is taken into consideration to the model. The results calculated by the model show good agreement with that obtained by experiment.

  8. Large magnetocaloric effect in sintered ferromagnetic EuS

    Science.gov (United States)

    Matsumoto, Koichi; Li, Liang; Hirai, Shinji; Nakamura, Eiji; Murayama, Daiki; Ura, Yutaro; Abe, Satoshi

    2016-10-01

    We present magnetocaloric effect measurements of the ferromagnetic semiconductor EuS in the vicinity of its ordering temperature. Single phase EuS powder was synthesized by CS2 gas sulfurization of Eu2O3. A sintered compact with relative density over 95% was prepared by pulsed electric current sintering of the powder. Temperature and magnetic field dependence of the magnetization and specific heat were characteristic of a paramagnetic to ferromagnetic second order phase transition. The entropy change induced by an external magnetic field and the specific heat were both close to those of a single crystal. We obtained an entropy-temperature (S-T) diagram of the EuS sintered compact. Carnot cycle liquefaction of hydrogen using EuS was compared with several other materials, with results indicating that sintered EuS is an excellent magnetic refrigerant for hydrogen liquefaction.

  9. Characterization Of The Graded Microstructure In Powder Sintered Porous Titanium

    Directory of Open Access Journals (Sweden)

    Oak J.-J.

    2015-06-01

    Full Text Available The proposed sintering process produce porosity and functional graded microstructure in the sinterd titanium powders. Titanium powders with different micro sizes were sintered at the proposed temperature region at 1200 and 1300°C for 2h. The apatite-forming on the graded microstructure is observed by immersion test in Hanks balanced salt soluion at 37°C. Sintering condition of titanium powders is estimated by thermogravitmetry-differential thermal analysis (TG-DTA. The synthersied surface structures and apatite-forming ability were characterized by a field emission scanning electron microscopy (FE-SEM observation and energy dispersive X-ray spectroscopy (EDS analysis. As results, these graded microstructure of sintered porous titanium powders reveals apatite-forming ability as osseointegration by calcification in Hanks balanced salt soluion(HBSS at 37°C.

  10. The effect of manganese oxide on the sinterability of hydroxyapatite

    Directory of Open Access Journals (Sweden)

    S. Ramesh et al

    2007-01-01

    Full Text Available The sinterability of manganese oxide (MnO2 doped hydroxyapatite (HA ranging from 0.05 to 1 wt% was investigated. Green samples were prepared and sintered in air at temperatures ranging from 1000 to 1400 °C. Sintered bodies were characterized to determine the phase stability, grain size, bulk density, hardness, fracture toughness and Young's modulus. XRD analysis revealed that the HA phase stability was not disrupted throughout the sintering regime employed. In general, samples containing less than 0.5 wt% MnO2 and when sintered at lower temperatures exhibited higher mechanical properties than the undoped HA. The study revealed that all the MnO2-doped HA achieved >99% relative density when sintered at 1100–1250 °C as compared to the undoped HA which could only attained highest value of 98.9% at 1150 °C. The addition of 0.05 wt% MnO2 was found to be most beneficial as the samples exhibited the highest hardness of 7.58 GPa and fracture toughness of 1.65 MPam1/2 as compared to 5.72 GPa and 1.22 MPam1/2 for the undoped HA when sintered at 1000 °C. Additionally, it was found that the MnO2-doped samples attained E values above 110 GPa when sintered at temperature as low as 1000 °C if compared to 1050 °C for the undoped HA.

  11. Low temperature sintering of fluorapatite glass-ceramics.

    Science.gov (United States)

    Denry, Isabelle; Holloway, Julie A

    2014-02-01

    Fluorapatite glass-ceramics have been shown to be excellent candidates as scaffold materials for bone grafts, however, scaffold production by sintering is hindered by concurrent crystallization of the glass. Objective, our goal was to investigate the effect of Ca/Al ratio on the sintering behavior of Nb-doped fluorapatite-based glasses in the SiO2-Al2O3-P2O5-MgO-Na2O-K2O-CaO-CaF2 system. Methods, glass compositions with Ca/Al ratio of 1 (A), 2 (B), 4 (C) and 19 (D) were prepared by twice melting at 1525°C for 3h. Glasses were either cast as cylindrical ingots or ground into powders. Disk-shaped specimens were prepared by either sectioning from the ingots or powder-compacting in a mold, followed by heat treatment at temperatures ranging between 700 and 1050°C for 1h. The density was measured on both sintered specimens and heat treated discs as controls. The degree of sintering was determined from these measurements. Results and Significance XRD showed that fluorapatite crystallized in all glass-ceramics. A high degree of sintering was achieved at 775°C for glass-ceramic D (98.99±0.04%), and 900°C for glass-ceramic C (91.31±0.10). Glass-ceramics A or B were only partially sintered at 1000°C (63.6±0.8% and 74.1±1.5%, respectively). SEM revealed a unique microstructure of micron-sized spherulitic fluorapatite crystals in glass-ceramics C and D. Increasing the Ca/Al ratio promoted low temperature sintering of fluorapatite glass-ceramics, which are traditionally difficult to sinter.

  12. Properties of Bulk Sintered Silver As a Function of Porosity

    Energy Technology Data Exchange (ETDEWEB)

    Wereszczak, Andrew A [ORNL; Vuono, Daniel J [ORNL; Wang, Hsin [ORNL; Ferber, Mattison K [ORNL; Liang, Zhenxian [ORNL

    2012-06-01

    This report summarizes a study where various properties of bulk-sintered silver were investigated over a range of porosity. This work was conducted within the National Transportation Research Center's Power Device Packaging project that is part of the DOE Vehicle Technologies Advanced Power Electronics and Electric Motors Program. Sintered silver, as an interconnect material in power electronics, inherently has porosity in its produced structure because of the way it is made. Therefore, interest existed in this study to examine if that porosity affected electrical properties, thermal properties, and mechanical properties because any dependencies could affect the intended function (e.g., thermal transfer, mechanical stress relief, etc.) or reliability of that interconnect layer and alter how its performance is modeled. Disks of bulk-sintered silver were fabricated using different starting silver pastes and different sintering conditions to promote different amounts of porosity. Test coupons were harvested out of the disks to measure electrical resistivity and electrical conductivity, thermal conductivity, coefficient of thermal expansion, elastic modulus, Poisson's ratio, and yield stress. The authors fully recognize that the microstructure of processed bulk silver coupons may indeed not be identical to the microstructure produced in thin (20-50 microns) layers of sintered silver. However, measuring these same properties with such a thin actual structure is very difficult, requires very specialized specimen preparation and unique testing instrumentation, is expensive, and has experimental shortfalls of its own, so the authors concluded that the herein measured responses using processed bulk sintered silver coupons would be sufficient to determine acceptable values of those properties. Almost all the investigated properties of bulk sintered silver changed with porosity content within a range of 3-38% porosity. Electrical resistivity, electrical conductivity

  13. Ash chemistry and sintering, verification of the mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Hupa, M.; Skrifvars, B.J. [Aabo Akademi, Turku (Finland)

    1996-12-01

    In this project four sintering mechanisms have been studied, i.e., partial melting with a viscous liquid, partial melting with a non-viscous liquid, chemical reaction sintering and solid state sintering. The work has aimed at improving the understanding of ash sintering mechanisms and quantifying their role in combustion and gasification. The work has been oriented in particular on the understanding of biomass ash behavior. The work has not directly focused on any specific technical application. However, results can also be applied on other fuels such as brown coal, petroleum coke, black liquor and different types of wastes (PDF, RDF, MSW). In one part of study the melting behavior was calculated for ten biomass ashes and compared with lab measurements of sintering tendencies. The comparison showed that the T{sub 15} temperatures, i.e. those temperatures at which the ashes contained 15 % molten phase, correlated fairly well with the temperature at which the sintering measurements detected sintering. This suggests that partial melting can be predicted fairly accurate for some ashes already with the today existing thermodynamic calculation routines. In some cases, however the melting calculations did not correlate with the detected sintering temperatures. In a second part detailed measurements on ash behavior was conducted both in a semi full scale CFB and a lab scale FBC. Ashes and deposits were collected and analyzed in several different ways. These analyses show that the ash chemistry shifts radically when the fuel is shifted. Fuels with silicate based ashes behaved totally different than those with an oxide or salt based ash. The chemistry was also affected by fuel blending. The ultimate goal has been to be able to predict the ash thermal behavior during biomass thermal conversion, using the fuel and ash elemental analyses and a few operational key parameters as the only input data. This goal has not yet today been achieved. (author)

  14. Alloy element redistribution during sintering of powder metallurgy steels

    OpenAIRE

    Tahir, Abdul Malik

    2014-01-01

    Homogenization of alloying elements is desired during sintering of powder metallurgy components. The redistribution processes such as penetration of liquid phase into the interparticle/grain boundaries of solid particles and subsequent solid-state  diffusion of alloy element(s) in the base powder, are important for the effective homogenization of alloy element(s) during liquid phase sintering of the mixed powders. The aim of this study is to increase the understanding of alloy element redistr...

  15. Liquid-phase sintering of Al with addition of Ti

    Directory of Open Access Journals (Sweden)

    Romanov G.N.

    2006-01-01

    Full Text Available Samples made from aluminium-titanium elemental powder blend with titanium contents ranging from 5 to 20 at. % were prepared by die pressing and subsequent sintering under vacuum in a dilatometer quartz tube at 700, 800 and 900 °C. Dilatometric and heating curves of sintering were analysed and discussed in connection with X-ray data and results from microstructural investigations. .

  16. A study of the method of making dental prosthetic appliances by sintered titanium alloys: effect of copper powder content on properties of sintered titanium alloy.

    Science.gov (United States)

    Oda, Y; Nakanishi, K; Sumii, T

    1990-02-01

    The effects of added copper powder to the properties of the sintered titanium alloys were investigated by measuring the compressive strength and densities of the green and sintered compacts, the thermal expansion curves and dimensional changes in the sintered compacts, and the accuracy of the crown-type restorations. The compressive strengths of green compacts ranged from 55 to 75 MPa. The expansion of green compacts increased with increased copper content. The sintered density was lower than the green density. The compressive yield strength of sintered compacts ranged from 260 MPa to 410 MPa. The sintered compacts expanded from 0.35% to 1.03% and the expansion increased with increased copper content. The dimensional accuracy of crown-type restorations showed the same dimensional change tendencies as did the sintered compacts. These results showed that the fit and the strength of sintered titanium alloy restorations could be improved.

  17. Atmospheric emission of polychlorinated naphthalenes from iron ore sintering processes.

    Science.gov (United States)

    Liu, Guorui; Zheng, Minghui; Du, Bing; Nie, Zhiqiang; Zhang, Bing; Liu, Wenbin; Li, Cheng; Hu, Jicheng

    2012-10-01

    Iron ore sintering processes constitute significant sources of dioxins, and studies have confirmed a close correlation between polychlorinated naphthalenes (PCNs) and dioxin formation. Thus, iron ore sintering processes are thought to be a potential source of PCNs, although intensive investigations on PCN emissions from sintering processes have not been carried out. Therefore, the aim of the present study was to qualify and quantify PCN emissions from nine sintering plants operating on different industrial scales. PCN concentrations ranged from 3 to 983 ng m(-3) (0.4-23.3 pg TEQ(PCN) m(-3)) and emission factors ranged from 14 to 1749 μg t(-1) (0.5-41.5 ng TEQ(PCN) t(-1)), with a geometric mean of 84 μg t(-1) (2.1 ng TEQ(PCN) t(-1)). The estimated annual emission of PCNs from sintering processes in China was 1390 mg TEQ(PCN). These figures will assist in the development of a PCN emissions inventory. Regarding emission characteristics, PCNs mainly comprised low-chlorinated homologs. The ratios of several characteristic PCN congeners were also measured and compared with those from other sources. Taken together, these results may provide useful information for identifying the sources of PCNs produced by iron ore sintering processes. Copyright © 2012 Elsevier Ltd. All rights reserved.

  18. Enhanced Sintering of Boron Carbide-Silicon Composites by Silicon

    Science.gov (United States)

    Zeng, Xiaojun; Liu, Weiliang

    2016-09-01

    Boron carbide (B4C)-silicon (Si) composites have been prepared by aqueous tape casting, laminating, and spark plasma sintering (SPS). The influences of silicon (Si) content on the phases, microstructure, sintering properties, and mechanical properties of the obtained B4C-Si composites are studied. The results indicate that the addition of Si powder can act as a sintering aid and contribute to the sintering densification. The addition of Si powder can also act as a second phase and contribute to the toughening for composites. The relative density of B4C-Si composites samples with adding 10 wt.% Si powder prepared by SPS at 1600 °C and 50 MPa for 8 min is up to 98.3%. The bending strength, fracture toughness, and Vickers hardness of the sintered samples are 518.5 MPa, 5.87 MPa m1/2, and 38.9 GPa, respectively. The testing temperature-dependent high-temperature bending strength and fracture toughness can reach a maximum value at 1350 °C. The B4C-Si composites prepared at 1600, 1650, and 1700 °C have good high-temperature mechanical properties. This paper provides a facile low-temperature sintering route for B4C ceramics with improved properties.

  19. Fabrication of Carbon Nanotube - Chromium Carbide Composite Through Laser Sintering

    Science.gov (United States)

    Liu, Ze; Gao, Yibo; Liang, Fei; Wu, Benxin; Gou, Jihua; Detrois, Martin; Tin, Sammy; Yin, Ming; Nash, Philip; Tang, Xiaoduan; Wang, Xinwei

    2016-03-01

    Ceramics often have high hardness and strength, and good wear and corrosion resistance, and hence have many important applications, which, however, are often limited by their poor fracture toughness. Carbon nanotubes (CNTs) may enhance ceramic fracture toughness, but hot pressing (which is one typical approach of fabricating CNT-ceramic composites) is difficult to apply for applications that require localized heat input, such as fabricating composites as surface coatings. Laser beam may realize localized material sintering with little thermal effect on the surrounding regions. However, for the typical ceramics for hard coating applications (as listed in Ref.[1]), previous work on laser sintering of CNT-ceramic composites with mechanical property characterizations has been very limited. In this paper, research work has been reported on the fabrication and characterization of CNT-ceramic composites through laser sintering of mixtures of CNTs and chromium carbide powders. Under the studied conditions, it has been found that laser-sintered composites have a much higher hardness than that for plasma-sprayed composites reported in the literature. It has also been found that the composites obtained by laser sintering of CNTs and chromium carbide powder mixtures have a fracture toughness that is ~23 % higher than the material obtained by laser sintering of chromium carbide powders without CNTs.

  20. Method to Determine Maximum Allowable Sinterable Silver Interconnect Size

    Energy Technology Data Exchange (ETDEWEB)

    Wereszczak, A. A.; Modugno, M. C.; Waters, S. B.; DeVoto, D. J.; Paret, P. P.

    2016-05-01

    The use of sintered-silver for large-area interconnection is attractive for some large-area bonding applications in power electronics such as the bonding of metal-clad, electrically-insulating substrates to heat sinks. Arrays of different pad sizes and pad shapes have been considered for such large area bonding; however, rather than arbitrarily choosing their size, it is desirable to use the largest size possible where the onset of interconnect delamination does not occur. If that is achieved, then sintered-silver's high thermal and electrical conductivities can be fully taken advantage of. Toward achieving this, a simple and inexpensive proof test is described to identify the largest achievable interconnect size with sinterable silver. The method's objective is to purposely initiate failure or delamination. Copper and invar (a ferrous-nickel alloy whose coefficient of thermal expansion (CTE) is similar to that of silicon or silicon carbide) disks were used in this study and sinterable silver was used to bond them. As a consequence of the method's execution, delamination occurred in some samples during cooling from the 250 degrees C sintering temperature to room temperature and bonding temperature and from thermal cycling in others. These occurrences and their interpretations highlight the method's utility, and the herein described results are used to speculate how sintered-silver bonding will work with other material combinations.

  1. Sintering of Soft Magnetic Material under Microwave Magnetic Field

    Directory of Open Access Journals (Sweden)

    Sadatsugu Takayama

    2012-01-01

    Full Text Available We have developed a simple process for sintering of soft magnetization materials using microwave sintering. The saturated magnetization (Ms of sintered magnetite was 85.6 emu/g, which was as high as 95% of magnetite before heating (90.4 emu/g. On the other hand, the averaged remanence (Mr and coercivity (Hc of the magnetite after heating were 0.17 emu/g and 1.12 Oe under measuring limit of SQUID, respectively. For the sintering process of soft magnetic materials, magnetic fields of microwave have been performed in nitrogen atmosphere. Therefore, a microwave single-mode system operating at a frequency of 2.45 GHz and with a maximum power level of 1.5 kW was used. We can sinter the good soft magnetic material in microwave magnetic field. The sample shrank to 82% theoretical density (TD from 45%TD of green body. The sintered sample was observed the microstructure by TEM and the crystal size was estimated the approximate average size is 10 nm.

  2. Mesoporous Silica Nanoparticles under Sintering Conditions: A Quantitative Study.

    Science.gov (United States)

    Silencieux, Fanny; Bouchoucha, Meryem; Mercier, Olivier; Turgeon, Stéphane; Chevallier, Pascale; Kleitz, Freddy; Fortin, Marc-André

    2015-12-01

    Thin films made of mesoporous silica nanoparticles (MSNs) are finding new applications in catalysis, optics, as well as in biomedicine. The fabrication of MSNs thin films requires a precise control over the deposition and sintering of MSNs on flat substrates. In this study, MSNs of narrow size distribution (150 nm) are synthesized, and then assembled onto flat silicon substrates, by means of a dip-coating process. Using concentrated MSN colloidal solutions (19.5 mg mL(-1) SiO2), withdrawal speed of 0.01 mm s(-1), and well-controlled atmospheric conditions (ambient temperature, ∼ 70% of relative humidity), monolayers are assembled under well-structured compact patterns. The thin films are sintered up to 900 °C, and the evolution of the MSNs size distributions are compared to those of their pore volumes and densities. Particle size distributions of the sintered thin films were precisely fitted using a model specifically developed for asymmetric particle size distributions. With increasing temperature, there is first evidence of intraparticle reorganization/relaxation followed by intraparticle sintering followed by interparticle sintering. This study is the first to quantify the impact of sintering on MSNs assembled as thin films.

  3. Ultrafast-Contactless Flash Sintering using Plasma Electrodes

    Science.gov (United States)

    Saunders, Theo; Grasso, Salvatore; Reece, Michael J.

    2016-06-01

    This paper presents a novel derivative of flash sintering, in which contactless flash sintering (CFS) is achieved using plasma electrodes. In this setup, electrical contact with the sample to be sintered is made by two arc plasma electrodes, one on either side, allowing current to pass through the sample. This opens up the possibility of continuous throughput flash sintering. Preheating, a usual precondition for flash sintering, is provided by the arc electrodes which heat the sample to 1400 °C. The best results were produced with pre-compacted samples (bars 1.8 mm thick) of pure B4C (discharge time 2s, current 4A) and SiC:B4C 50 wt% (3s at 6A), which were fully consolidated under a heating rate approaching 20000 °C/min. For the composite a cylindrical volume of 14 mm3 was sintered to full density with limited grain growth.

  4. SINTERING EFFECTS ON THE DENSIFICATION OF NANOCRYSTALLINE HYDROXYAPATITE

    Directory of Open Access Journals (Sweden)

    M. Amiriyan

    2011-06-01

    Full Text Available The effects of sintering profiles on the densification behaviour of synthesized nanocrystalline hydroxyapatite (HA powder were investigated in terms of phase stability and mechanical properties. A wet chemical precipitation method was successfully employed to synthesize a high purity and single phase HA powder. Green HA compacts were prepared and subjected to sintering in air atmosphere over a temperature range of 700° C to 1300° C. In this study two different holding times were compared, i.e. 1 minute versus the standard 120 minutes. The results revealed that the 1 minute holding time sintering profile was indeed effective in producing a HA body with high density of 98% theoretical when sintered at 1200° C. High mechanical properties such as fracture toughness of 1.41 MPa.m1/2 and hardness of 9.5 GPa were also measured for HA samples sintered under this profile. Additionally, XRD analysis indicated that decomposition of the HA phase during sintering at high temperatures was suppressed.

  5. Enhanced Sintering of Boron Carbide-Silicon Composites by Silicon

    Science.gov (United States)

    Zeng, Xiaojun; Liu, Weiliang

    2016-11-01

    Boron carbide (B4C)-silicon (Si) composites have been prepared by aqueous tape casting, laminating, and spark plasma sintering (SPS). The influences of silicon (Si) content on the phases, microstructure, sintering properties, and mechanical properties of the obtained B4C-Si composites are studied. The results indicate that the addition of Si powder can act as a sintering aid and contribute to the sintering densification. The addition of Si powder can also act as a second phase and contribute to the toughening for composites. The relative density of B4C-Si composites samples with adding 10 wt.% Si powder prepared by SPS at 1600 °C and 50 MPa for 8 min is up to 98.3%. The bending strength, fracture toughness, and Vickers hardness of the sintered samples are 518.5 MPa, 5.87 MPa m1/2, and 38.9 GPa, respectively. The testing temperature-dependent high-temperature bending strength and fracture toughness can reach a maximum value at 1350 °C. The B4C-Si composites prepared at 1600, 1650, and 1700 °C have good high-temperature mechanical properties. This paper provides a facile low-temperature sintering route for B4C ceramics with improved properties.

  6. Improvement of Thermal Stability of Nd-Tb-Fe-Co-B Sintered Magnets by Additions of Pr, Ho, Al, and Cu

    Directory of Open Access Journals (Sweden)

    A. A. Lukin

    2012-01-01

    Full Text Available The present work investigates the influence of Pr, Al, Cu, B and Ho which were introduced into the Co-containing sintered magnets of Nd-Dy-Tb-Fe-Co-B type on the magnetic parameters (α, Hci, Br, BHmax⁡. The effect of heat treatment parameters on magnetic properties was also studied. It was revealed that the essential alloying of NdFeB magnets by such elements as Dy, Tb, Ho, Co as well as by boron-forming elements, for example, by titanium, may lead to reducing of F-phase quantity, and, as a consequence, to decreasing of magnetic parameters. It was also shown that additional doping of such alloys by Pr, B, Al and Cu leads to a significant increase of the quantity of F-phase in magnets as well as solubility of the Dy, Tb, Ho and Co in it. This promotes the increase of magnetic parameters. It was possible to attain the following properties for the magnets (Nd0,15Pr0,35Tb0,25Ho0,2515(Fe0,71Co0,29bal ⋅ Al0,9Cu0,1B8,5 (at. % after optimal thermal treatment {1175 K (3,6–7,2 ks with slow (12–16 ks cooling to 675 K and subsequently remaining at T=775 K for 3,6 ks—hardening}: Br=0,88 T, Hci=1760 kA/m, BHmax⁡=144 kJ/m3, α<|0,01|%/K in the temperature interval 223–323 K.

  7. Effect of sintering on the relative density of Cr-coated diamond/Cu composites prepared by spark plasma sintering

    Institute of Scientific and Technical Information of China (English)

    Wei Cui; Hui Xu; Jian-hao Chen; Shu-bin Ren; Xin-bo He; Xuan-hui Qu

    2016-01-01

    Cr-coated diamond/Cu composites were prepared by spark plasma sintering. The effects of sintering pressure, sintering tempera-ture, sintering duration, and Cu powder particle size on the relative density and thermal conductivity of the composites were investigated in this paper. The influence of these parameters on the properties and microstructures of the composites was also discussed. The results show that the relative density of Cr-coated diamond/Cu reaches ~100% when the composite is gradually compressed to 30 MPa during the heating process. The densification temperature increases from 880 to 915°C when the diamond content is increased from 45vol% to 60vol%. The densification temperature does not increase further when the content reaches 65vol%. Cu powder particles in larger size are beneficial for in-creasing the relative density of the composite.

  8. Chemically produced tungsten-praseodymium oxide composite sintered by spark plasma sintering

    Science.gov (United States)

    Ding, Xiao-Yu; Luo, Lai-Ma; Lu, Ze-Long; Luo, Guang-Nan; Zhu, Xiao-Yong; Cheng, Ji-Gui; Wu, Yu-Cheng

    2014-11-01

    Pr2O3 doped W composite were synthesized by a novel wet chemical method and spark plasma sintering. The grain size, relative density and the Vicker hardness HV0.2 of Pr2O3/W samples were 4 μm, 98.3% and 377.2, respectively. The tensile strength values of Pr2O3/W were higher than those of pure W. As the temperature rises from 25 °C to 800 °C, the conductivity of pure W and W-1 wt% Pr2O3 composites decreased with the same trend, was above 150 W/m K.

  9. Sintering behaviour of spinel–alumina composites

    Indian Academy of Sciences (India)

    Soumen Pal; A K Bandyopadhyay; P G Pal; S Mukherjee; B N Samaddar

    2009-04-01

    Study of alumina–magnesia binary phase diagram reveals that around 40–50 wt% alumina dissolves in spinel (MgAl2O4) at 1600°C. Solid solubility of alumina in spinel decreases rapidly with decreasing temperature, which causes exsolution of alumina from spinel phase. Previous work of one of the authors revealed that the exsolution of alumina makes some interlocking structures in between alumina and spinel phases. In the present investigation, refractory grade calcined alumina and spinel powder were used to make different batch compositions. Green pellets, formed at a pressure of 1550 kg cm-2 were fired at different temperatures of 1500°, 1550° and 1600°C for 2 h soaking time. Bulk density, percent apparent porosity, firing shrinkage etc were measured at each temperature. Sintering results were analysed to understand the mechanism of spinel–alumina interactions. SEM study of present samples does not reveal the distinct precipitation of needle shaped -alumina from spinel, but has some effect on densification process of spinel–alumina composites. Microstructural differences between present and previous work suggest an ample scope of further work in spinel–alumina composites.

  10. Polymer powders for selective laser sintering (SLS)

    Science.gov (United States)

    Schmid, Manfred; Amado, Antonio; Wegener, Konrad

    2015-05-01

    Selective Laser Sintering (SLS) is close to be accepted as a production technique (Additive Manufacturing). However, one problem limiting employment of SLS for additive manufacturing in a wide-ranging industrial scope is the narrow variety of applicable polymers. The commonly applied SLS powder to date is polyamide 12 (PA 12). PA 12 or ccompounds of PA 12 (dry blends) are approximately 90 % of complete industrial consumption. The remaining small quantity is distributed on polyamide 11 (PA11) and some other `exotic' polymers (TPU, PEBA, P(E)EK). Industry is awaiting commodity polymers like polypropylene (PP) or polyethylene (PE) crucial to open new market segments. But several approaches launching those polymers failed. But what are the reasons for the difficulties in developing new SLS powders? The contribution is to answer this and highlights the combination of intrinsic and extrinsic polymer properties necessary to generate a polymer powder promising for SLS application. Particle shape, powder distribution, thermal, rheological and optical requirements must be considered and only a particularly controlled property combination leads to successful SLS implementation. Thermal behavior, particle shape and -distribution is discussed in detail, although the other properties can't be disregarded for providing new commercially successful SLS powder finally.

  11. Microwave combustion and sintering without isostatic pressure

    Energy Technology Data Exchange (ETDEWEB)

    Ebadian, M.A.

    1998-01-01

    In recent years interest has grown rapidly in the application of microwave energy to the processing of ceramics, composites, polymers, and other materials. Advances in the understanding of microwave/materials interactions will facilitate the production of new ceramic materials with superior mechanical properties. One application of particular interest is the use of microwave energy for the mobilization of uranium for subsequent redeposition. Phase III (FY98) will focus on the microwave assisted chemical vapor infiltration tests for mobilization and redeposition of radioactive species in the mixed sludge waste. Uranium hexachloride and uranium (IV) borohydride are volatile compounds for which the chemical vapor infiltration procedure might be developed for the separation of uranium. Microwave heating characterized by an inverse temperature profile within a preformed ceramic matrix will be utilized for CVI using a carrier gas. Matrix deposition is expected to commence from the inside of the sample where the highest temperature is present. The preform matrix materials, which include aluminosilicate based ceramics and silicon carbide based ceramics, are all amenable to extreme volume reduction, densification, and vitrification. Important parameters of microwave sintering such as frequency, power requirement, soaking temperature, and holding time will be investigated to optimize process conditions for the volatilization of uranyl species using a reactive carrier gas in a microwave chamber.

  12. Investigation of Coercivity Mechanism for Nd-Fe-B Magnets Prepared by Combination of Strip-Casting with Hydrogen Decrepitation Techniques

    Institute of Scientific and Technical Information of China (English)

    李波; 胡季帆; 王东玲; 郭炳麟; 王新林

    2003-01-01

    The coercivity mechanism of Nd-Fe-B magnets prepared by combination of strip-casting with hydrogen decrepitation techniques was investigated. The microstructure of (Nd0.935Dy0.065)14.5Fe79.4B6.1 magnet was observed. The average grain size is about 6~12 μm. The magnetizing field dependence of the hardmagnetic properties for the (Nd0.935Dy0.065)14.5Fe79.4B6.1 and the temperature dependence of the coercivity for the Nd14.5Fe79.4B6.1 were investigated. Results show that the coercivity for magnets prepared by the combination of strip-casting with hydrogen decrepitation techniques is controlled by the nucleation mechanism.

  13. Influence of maglev force relaxation on the forces of bulk HTSC subjected to different lateral displacements above the NdFeB guideway

    Science.gov (United States)

    Qin, Yujie; Hou, Xiaojing

    2011-02-01

    This paper studied the influence of maglev force relaxation on the force (both levitation and guidance forces) of bulk high-temperature superconductor (HTSC) subjected to different lateral displacements above a NdFeB guideway. Firstly, the maglev forces relaxation property of bulk HTSC above the permanent-magnet guideway (PMG) was studied experimentally, then the levitation and guidance forces were measured by SCML-2 measurement system synchronously at different lateral displacements, some times later(after relaxation), the forces were measured again as the same way. Compared to the two measured results, it was found that the change of the levitation force was larger compared to the case without relaxation, while the change of the guidance force was smaller. In addition, the rate of change of levitation force and guidance force was different for different maximum lateral displacements. This work provided a scientific analysis for the practical application of the bulk HTS.

  14. The effect of Nd-Cu diffusion during hot pressing and hot deformation on the coercivity and the deformation ability of Nd-Fe-B HDDR magnets

    Science.gov (United States)

    Wang, Haihang; Chen, Renjie; Yin, Wenzong; Zhu, Mingyuan; Tang, Xu; Wang, Zexuan; Jin, Chaoxiang; Ju, Jinyun; Lee, Don; Yan, Aru

    2017-09-01

    HDDR processed Nd-Fe-B powders blended with Nd-Cu powders were hot-pressed and then hot-deformed to obtain fully dense, anisotropic magnets. The microstructure evolution in hot-pressed and hot-deformed HDDR magnets was studied to illustrate the impact of Nd-Cu diffusion on coercivity and deformation ability. It was found that the coercivity and the deformation ability were improved significantly by Nd-Cu addition. The coercivity of hot-deformed magnets was increased from 3.81 kOe to 13.01 kOe after 2 wt% Nd-Cu additions and the annealing at 900 °C for 2 h. Scanning electron microscopy and transmission electron microscopy observations revealed that the variation in coercivity was attributed to the diffusion of Nd-Cu along the grain boundaries during hot pressing and hot deformation.

  15. Composition-dependent magnetic properties of melt-spun La or/and Ce substituted nanocomposite NdFeB alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, M.; Zhao, L.Z.; Zhang, C.; Jiao, D.L.; Zhong, X.C.; Liu, Z.W.

    2016-02-15

    Aiming at high-performance low-cost NdFeB magnets, the magnetic properties and microstructure for melt spun nanocrystalline (Nd{sub 1−x}M{sub x}){sub 10}Fe{sub 84}B{sub 6} (M=La, Ce, or La{sub 0.5}Ce{sub 0.5}; x=0–0.7) alloys were investigated. Relatively, LaCe-substituted alloys show high values of the remanent magnetization M{sub r}, the maximum energy product (BH){sub max} and the coercivity H{sub c}, up to 114 emu/g (1.07 T), 147 kJ/m{sup 3} and 471 kA/m, respectively, at x=0.1. The unusual increase in coercivity for the alloys with 10% La or 10% La{sub 0.5}Ce{sub 0.5} substitution is possibly attributed to the phase segregation in alloys with certain La or LaCe contents. The reduced Curie temperature and spin-reorientation temperature were obtained for La, Ce or LaCe substituted alloys. Transmission electron microscope analysis has revealed that a fine and uniform distributed grain structure leads to remanence enhancement for La{sub 0.5}Ce{sub 0.5} substituted alloys. The present results indicate that partially substituting Nd by La or/and Ce cannot only effectively reduce the cost of nanocrystalline NdFeB based magnetic powders but also can maintain a relatively good combination of magnetic properties.

  16. Effects of additive elements (Cu, Zr, Al) on morphological and magnetic properties of NdFeB thin films with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Y.G. [Research Institute of Magnetic Materials, Lanzhou University, Lanzhou 730000 (China); Li, R.S. [Research Institute of Magnetic Materials, Lanzhou University, Lanzhou 730000 (China); Yang, Z. [Research Institute of Magnetic Materials, Lanzhou University, Lanzhou 730000 (China)]. E-mail: yangz@lzu.edu.cn; Matsumoto, M. [Department of Information Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan); Morisako, A. [Department of Information Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan); Takei, S. [Department of Information Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553 (Japan)

    2005-03-25

    Cu, Zr, Al were doped into the NdFeB thin films to improve the morphological and magnetic properties of the films. Distinct results have been observed due to the different nature of these additives (such as atomic radius and chemical affinity, etc.). The morphological and magnetic properties of the films could be improved selectively according to the additive element. Grains in the Cu-doped film significantly grew and became strip-like. Both Zr and Al addition effectively reduced the grain size. But Zr addition led to a large grain size distribution while Al addition produced more uniformly sized grains in the film. The perpendicular coercivities of NdFeB films could be enhanced by doping a certain amount of the additive element. Addition of 1.0 at.% Cu or 3.8 at.% Zr increased the perpendicular coercivity H {sub cperpendicular} up to 487 or 565 kA/m from 382 kA/m, respectively. On the other hand, addition of 5.0 at.% Al could effectively moderate H {sub cperpendicular} to 279 kA/m while remained a high perpendicular remanent magnetization ratio S{sub perpendicular} around 0.9. Magnetization reversal mechanisms of the doped samples were also discussed according to the angular dependence of the coercivity H {sub c}({theta}) and M-H loop shapes. It was suggested that magnetization reversal of Cu-doped sample was initiated by domain wall motion and ended by domain wall pinning. Most of the grains in the Zr-doped sample were inversely magnetized by magnetization coherent rotation, but the rest were demagnetized by magnetization incoherent switching. In the Al-doped sample, magnetization reversal was proceeded mainly by magnetization incoherent rotation.

  17. Study on sintering process and characteristic of nanosized soft magnetic MnZn ferrite powders

    Institute of Scientific and Technical Information of China (English)

    WANG Yongming; WANG Xin; JIANG Yanfei; HAO Shunli; LIU Chunjing

    2006-01-01

    The effect of sintering process (especially the sintering temperature) on the magnetic property and microstructure of sintered sample of nanosized soft magnetic MnZn ferrite powder was investigated. The sintered sample of MnZn ferrite was prepared by both traditional pressing and cool isostatic pressing on MnZn ferrite nanoparticals. The sintering process of which was segmented. Thedensity, microstructure and phase composition of sintered sample were analyzed by Archimedes'law, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The grain growth and densification in sintering process of MnZn ferrite were investigated. The magnetic property was measured by vibrating sample magnetometer (VSM) and Nim2000 magnetic material testing system. The results show that the better sintering temperature is 850 ℃, at which the better magnetic property and microstructure of sintered compact were obtained.

  18. Tailored Net-Shape Powder Composites by Spark Plasma Sintering

    Science.gov (United States)

    Khaleghi, Evan Aryan

    This dissertation investigates the ability to produce net-shape and tailored composites in spark plasma sintering (SPS), with an analysis of how grain growth, densification, and mechanical properties are affected. Using alumina and four progressively anisotropic dies, we studied the impact of specimen shape on densification. We found specimen shape had an impact on overall densification, but no impact on localized properties. We expected areas of the specimen to densify differently, or have higher grain growth, based on current anisotropy in the specimen during sintering, and preliminary results indicated this, but further investigation showed this did not occur. Overall average grain size and porosity decreased as shape complexity increased. In Fe-V-C steel, we mechanical alloyed two rapidly solidified powders, and used spark sintering to retain the properties imparted during the rapid solidification. We noticed VC grains being produced during densification, which improved the final properties. We conducted spark plasma extrusion (SPE) of aluminum to understand the effect on microstructure. We found, through an analysis of the grain structure, that SPE did have a grain deformation potential, and grain size was severely decreased compared to conventional sintering. Dynamic recrystallization did not occur, due to the reduced temperatures we were able to extrude with SPS. Finally, we examined whether there were particular sintering conditions for SPS that reduced the complexity of the grain growth and porosity relationship to one similar to conventional sintering, of the form G = k G0 ε -1/. We found that although a reasonable case could be made for free sintering, as found in the literature, for hot-pressing and SPS the conditions required go against the common knowledge in grain growth and densification kinetics. We were able to fit our data very well to the model, but the correlated results do not make physical sense.

  19. Dry Sintered Metal Coating of Halloysite Nanotubes

    Directory of Open Access Journals (Sweden)

    James C. Nicholson

    2016-09-01

    Full Text Available Halloysite nanotubes (HNTs are a naturally-occurring aluminosilicate whose dimensions measure microns in length and tens of nanometers in diameter. Bonding defects between the alumina and silica lead to net negative and positive charges on the exterior and interior lumen, respectively. HNTs have been shown to enhance the material properties of polymer matrices and enable the sustained release of loaded chemicals, drugs, and growth factors. Due to the net charges, these nanotubes can also be readily coated in layered-depositions using the HNT exterior lumen’s net negative charge as the basis for assembly. These coatings are primarily done through wet chemical processes, the majority of which are limited in their use of desired chemicals, due to the polarity of the halloysite. Furthermore, this restriction in the type of chemicals used often requires the use of more toxic chemicals in place of greener options, and typically necessitates the use of a significantly longer chemical process to achieve the desired coating. In this study, we show that HNTs can be coated with metal acetylacetonates—compounds primarily employed in the synthesis of nanoparticles, as metal catalysts, and as NMR shift reagents—through a dry sintering process. This method was capable of thermally decaying the metal acetylacetonate, resulting in a free positively-charged metal ion that readily bonded to the negatively-charged HNT exterior, resulting in metallic coatings forming on the HNT surface. Our coating method may enable greater deposition of coated material onto these nanotubes as required for a desired application. Furthermore, the use of chemical processes using toxic chemicals is not required, thus eliminating exposure to toxic chemicals and costs associated with the disposal of the resultant chemical waste.

  20. Effects of Mineral Composition and Microstructure on Crack Resistance of Sintered Ore

    Institute of Scientific and Technical Information of China (English)

    YING Zi-wei; JIANG Mao-fa; XU Li-xian

    2006-01-01

    Vickers indentation test was used to study the effects of mineral composition and microstructure on crack resistance of sintered ore, and the initiation and propagation of cracks in different minerals contained in sintered ore were examined. The results indicate that the microstructure of calcium ferrites is a major factor influencing crack resistance of sintered ore. Finer grain size of calcium ferrite will lead to higher cracking threshold and better crack resistance of sintered ore. The formation of calcium ferrite with fine grain size during sintering process is favorable for crack resistance of sintered ore.

  1. Liquid Phase Sintering (LPS) and Dielectric Constant of α-Silicon Nitride Ceramic

    Institute of Scientific and Technical Information of China (English)

    CHEN Changlian; CHEN Fei; SHEN Qiang; ZHANG Lianmeng; YAN Faqiang

    2006-01-01

    The spark plasma sintering (SPS) was applied to prepare α-Si3N4 ceramics of different densities with magnesia, silicon dioxide, alumina as the sintering aids. The mechanism of liquid phase sintering (LPS) was discussed and the factors influencing the density of the prepared samples were analyzed. The dielectric constant of sintered samples was tested. The experimental results show that the density can be controlled from 2.48 g/cm3 to 3.09 g/cm3 while the content of the sintering aids and the sintering temperature alter and the dielectric constant is closely dependent on the density of obtained samples.

  2. 添加Dy2O3对烧结NdFeB磁体微观结构的影响%Effects of Dy2O3 Addition on Microstructure of Sintered NdFeB Magnets

    Institute of Scientific and Technical Information of China (English)

    王占勇

    2007-01-01

    研究了NdFeB粉末中添加1wt%Dy2O3粉末对烧结NdFeB磁体微观结构的影响,研究发现,在烧结过程中,Dy2O3中的Dy与Nd2Fe14B中的Nd发生了置换反应,Dy进入Nd2Fe14B相,形成了(Nd,Dy)2Fe14B相,提高了磁体的矫顽力.

  3. Microstructures in Transition Zone of a Laser Remelting/Solidificaiton Pool of Sintered Nd-Fe-B Magnets%粉末烧结钕铁硼激光熔凝过渡区组织的研究

    Institute of Scientific and Technical Information of China (English)

    潘晶; 刘新才

    2004-01-01

    对粉末烧结Nd15Fe77B8永磁体表面激光熔凝池中过渡区的组织进行了研究. 结果表明, 过渡区由初生相α-Fe和富Nd的Nd2Fe14B两相组成.离激光熔凝池与基体的分界面越远, α-Fe二次枝晶间距越小, 而Nd2Fe14B以胞状液固界面向上推进的速度逐步加快, 最后越过了先析出的α-Fe, 导致在过渡区结束时α-Fe相不再出现.当粉末烧结Nd15Fe77B8磁体易磁化轴的取向为z轴时, 过渡区的α-Fe体积百分数最大; Nd2Fe14B以与z轴夹角30°~50°的方向生长, 直到进入胞状区, 其生长方向才逐步调整到与z轴基本平行.当磁体易磁化轴取向为随机分布时, 过渡区α-Fe的体积分数最小; 过渡区Nd2Fe14B选择在基体内易磁化轴在XOY面内的等轴晶Nd2Fe14B上生长. 当磁体的易磁化轴取向分别为x或y轴时, 过渡区Nd2Fe14B直接在基体的Nd2Fe14B上生长, 并在过渡区结束前后, 1个过渡区Nd2Fe14B上平均分化出3个胞状区Nd2Fe14B柱状晶.

  4. Pretreatment Tecnology of Electroplating on Sintered NdFeB Permanent Magnet for Plating%烧结型NdFeB永磁体的镀前处理工艺

    Institute of Scientific and Technical Information of China (English)

    周琦

    2001-01-01

    对NdFeB永磁体材料的不同前处理工艺流程和工艺规范进行实验,并对不同前处理工艺的镀层结合力和耐蚀性进行测定.结果表明,经打磨、封孔、抛光、化学除油、除锈、活化等前处理的试片可直接电镀,经划痕试验和锉刀试验,镀层与基体的结合力良好,并经盐雾试验检测其耐蚀性优良.

  5. 前处理对烧结钕铁硼化学镀镍结合力的影响%EFFECT OF PRETREATMENT ON ADHESION OF ELECTROLESS PLATED Ni-P COATINGS ON SINTERED Nd-Fe-B PERMANENT MAGNET

    Institute of Scientific and Technical Information of China (English)

    孙臣; 张伟; 严川伟

    2009-01-01

    主要研究了酸洗和超声波清洗前处理工艺对化学镀镍结合力的影响.扫描电镜(SEM)结果表明:随着硝酸浓度的增加,烧结钕铁硼酸洗后表面越来越粗糙.其中,硝酸(65%)浓度为20~40 mL/L时,酸洗不能完全去除烧结钕铁硼表面的氧化膜;硝酸(65%)浓度为80~100 ml/L时,不仅将钕铁硼表面的氧化物和富钕相腐蚀掉,而且腐蚀钕铁硼内部的富钕相,使钕铁硼表面粉化.酸洗后,烧结钕铁硼表面粘有大量脱落的主相的晶粒,使用超声波可以有效地去除这些晶粒,消除钕铁硼和镀层之间的夹层.万能实验拉伸机实验结果表明:当硝酸(65%)浓度为60ml/L,酸洗时间40s,并结合超声波清洗时,得到了化学镀镍层结合力最好,结合力大于28 MPa.

  6. Low sintering temperature glass waste forms for sequestering radioactive iodine

    Science.gov (United States)

    Nenoff, Tina M.; Krumhansl, James L.; Garino, Terry J.; Ockwig, Nathan W.

    2012-09-11

    Materials and methods of making low-sintering-temperature glass waste forms that sequester radioactive iodine in a strong and durable structure. First, the iodine is captured by an adsorbant, which forms an iodine-loaded material, e.g., AgI, AgI-zeolite, AgI-mordenite, Ag-silica aerogel, ZnI.sub.2, CuI, or Bi.sub.5O.sub.7I. Next, particles of the iodine-loaded material are mixed with powdered frits of low-sintering-temperature glasses (comprising various oxides of Si, B, Bi, Pb, and Zn), and then sintered at a relatively low temperature, ranging from 425.degree. C. to 550.degree. C. The sintering converts the mixed powders into a solid block of a glassy waste form, having low iodine leaching rates. The vitrified glassy waste form can contain as much as 60 wt % AgI. A preferred glass, having a sintering temperature of 500.degree. C. (below the silver iodide sublimation temperature of 500.degree. C.) was identified that contains oxides of boron, bismuth, and zinc, while containing essentially no lead or silicon.

  7. Toward Interpreting Failure in Sintered-Silver Interconnection Systems

    Energy Technology Data Exchange (ETDEWEB)

    Wereszczak, Andrew A [ORNL; Waters, Shirley B [ORNL

    2016-01-01

    The mechanical strength and subsequent reliability of a sintered-silver interconnection system is a function of numerous independent parameters. That system is still undergoing process development. Most of those parameters (e.g., choice of plating) are arguably and unfortunately taken for granted and are independent of the silver s cohesive strength. To explore such effects, shear strength testing and failure analyses were completed on a simple, mock sintered-silver interconnection system consisting of bonding two DBC ceramic substrates. Silver and gold platings were part of the test matrix, as was pre-drying strategies, and the consideration of stencil-printing vs. screen-printing. Shear strength of sintered-silver interconnect systems was found to be was insensitive to the choice of plating, drying practice, and printing method provided careful and consistent processing of the sintered-silver are practiced. But if the service stress in sintered silver interconnect systems is anticipated to exceed ~ 60 MPa, then the system will likely fail.

  8. Study of hydroxyapatite behaviour during sintering of 316L steel

    Directory of Open Access Journals (Sweden)

    A. Szewczyk-Nykiel

    2010-07-01

    Full Text Available 316L stainless steel – hydroxyapatite composite biomaterials with different hydroxyapatite weight fraction in the composite wereinvestigated. Hydroxyapatite (HAp – Ca10(PO46(OH2 is well known biomaterial. HAp reveals excellent chemical and biological affinitywith bony tissues. On the other hand hydroxyapatite shows low mechanical properties. The combination of very good biocompatibility of hydroxyapatite and high mechanical properties of stainless steel seems to be a good solution. In presented research natural originhydroxyapatite and 316L austenitic stainless steel were used. In this work, metal-ceramics composites were fabricated by the powdermetallurgy technology (involving pressing and sintering process. Sintering was carried out at 1250oC in hydrogen atmosphere. Thedensity, porosity and hardness were investigated. Metallographic microscope and SEM were carried out in order to investigate themicrostructure. The horizontal NETZSCH DIL 402E dilatometer was used to evaluate the dimensional changes and phenomena occurringduring sintering. The research displayed that physical properties of sintered 316L-HAp composites decrease with increase ofhydroxyapatite content. Microstructure of investigated composites consists of austenitic and probably inclusions of hydroxyapatite andheterogeneous eutectic occurring on the grain boundaries. It was shown that amount of hydroxyapatite in the powder mixtures influencethe dimensional changes occurring during sintering.

  9. Effects of flux concentrations and sintering temperature on dental porcelain

    Science.gov (United States)

    Ghose, Polash; Gafur, Md. Abdul; Das, Sujan Kumar; Ranjan Chakraborty, Shyamal; Mohsin, Md.; Deb, Arun Kumar; Rakibul Qadir, Md.

    2014-02-01

    In this study, samples of dental porcelain bodies have been made by using the materials collected from selected deposits employing different mixing proportions of clay, quartz and feldspar. Dental porcelain ceramics have been successfully fabricated by using the sintering technique together with some Na2CO3 additive. The dental porcelain powder has been pressed into pellets at first and subsequently sintered at 700, 800, 900, 1000 and 1100 °C for 2 h. The physical and mechanical properties of the prepared samples have been investigated. The sintering behavior of the fired samples has been evaluated by bulk density, linear shrinkage, water absorption and apparent porosity measurements. This study includes the evaluation of the Vickers's microhardness by microhardness tester. Phase analysis and microstructural study have been performed by XRD and optical microscope respectively. Optical properties have been investigated using UV-visible spectroscopy. Influence of firing conditions on leucite formation, densification and microstructural development of the sintered samples has been investigated. It has been found that the choice of sintering temperature is one of the key factors in controlling leucite crystallization in dental porcelain ceramics. It has also been found that the flux concentration of material and the effect of temperature on preparation of dental porcelain contribute to the firing shrinkage and hardness, which has been found to increase with the increase of treatment temperature.

  10. Leaching of metals from fresh and sintered red mud.

    Science.gov (United States)

    Ghosh, Indrani; Guha, Saumyen; Balasubramaniam, R; Kumar, A V Ramesh

    2011-01-30

    The disposal of red mud, a solid waste generated during the extraction of alumina from bauxite, is one of the major problems faced by the aluminum industry. Proper disposal followed by its utilization, for example as bricks, can provide a satisfactory solution to this problem. Pollution potential of red mud and its finished product, due to metals leaching out from them under certain environmental conditions, need to be studied. Sintering of red mud was performed in a resistance type vertical tube furnace to simulate the brick-making conditions in lab-scale. Leachability of metals in red mud and the sintered product was evaluated by performing sequential extraction experiments on both. The metals studied were the 'macro metals' iron and aluminum and the 'trace metals' copper and chromium. The total extractabilities of all the metals estimated by the microwave digestion of red mud samples decreased due to sintering. The leachability in sequential extraction of the macro metals iron and aluminum, on the other hand, increased due to sintering in all phases of sequential extraction. However, the effect of sintering on the leachability of the trace metals by sequential extraction was different for copper and chromium in different fractions of sequential extraction.

  11. Sintering of Titanium in Vacuum by Microwave Radiation

    Science.gov (United States)

    Luo, S. D.; Yan, M.; Schaffer, G. B.; Qian, M.

    2011-08-01

    The effectiveness of microwave (MW) sintering has been demonstrated on many ceramic systems, a number of metallic systems, and metal-ceramic composites, but remains ambiguous for Ti powder materials. This work presents a detailed comparative study of MW and conventional sintering of Ti powder compacts in vacuum. It is shown that MW radiation is effective in heating Ti powder compacts with the assistance of MW susceptors; it delivered an average heating rate of 34 K/min (34 °C/min), compared to 4 K/min (4 °C/min) by conventional vacuum heating in an alumina-tube furnace. Microwave radiation resulted in similar densification with well-developed sinter bonds. However, MW-sintered samples showed higher bulk hardness, a harder surface shell, and coarser grains. The difference in hardness is attributed to the difference in the oxygen content, supported by X-ray photoelectron spectroscopy analyses. The mechanisms of MW heating for metal powder compacts are discussed in the context of the sintering of Ti powder materials and attributed to three combined effects. These include heat radiation from the MW susceptors at low temperatures, enhanced MW absorption due to the transformation of the TiO2 film on each Ti powder particle to oxygen-deficient Ti oxides, which are MW absorbers; and the volumetric heating of Ti powder particles by eddy currents.

  12. Laser Ceramics Sintering by Millimeter-Wave Heating

    Science.gov (United States)

    Egorov, S. V.; Bykov, Yu. V.; Eremeev, A. G.; Sorokin, A. A.

    2014-01-01

    Prospects for using microwave radiation to sinter optically transparent ceramics are stipulated by the absence of the heaters and screens contaminating the sintered material and the presence of the inverse temperature distribution in the product, which allows one to fabricate maximum-density ceramics. In this work, we present the results of studying the process of producing optically transparent Yb:YAG and Yb:(LaY)2O3 ceramics when the samples are sintered in the chamber of a gyrotron complex operated at a frequency of 24 GHz. The various-composition samples were manufactured by compaction of a mixture of commercially available powders (Yb:YAG ceramics) and the powders prepared by the self-propagating high-temperature synthesis (Yb:(LaY)2O3 ceramics). The sintering temperatures were varied in the interval 1700-1900°C, the sintering time was varied from 2 to 20 h, and the residual-air pressure in the working chamber was 10 Pa. Lasing was obtained for the samples of both compositions.

  13. Granulation of coke breeze fine for using in the sintering process

    Directory of Open Access Journals (Sweden)

    Mohamed F.M.

    2010-01-01

    Full Text Available Coke breeze is the main fuel used in the sintering process. The value of -3+1 mm. represents the most favorable particle size for coke breeze in the sintering process. About 20% of total coke fines (-0.5 mm are produced during different steps of preparation. Introducing these fines during the sintering process proves to be very harmful for different operating parameters. Thus ,this study aims at investigating the production of granules resulting from these fines using molasses as organic binder and its application in sintering of an iron ore. The results showed that the granules having the highest mechanical properties were obtained with 14.5 wt % molasses addition. The sintering experiments were performed by using coke breeze in different shapes (-3+1 mm in size, coke breeze without sieving and coke breeze granules -3+1 mm. The reduction experiments, microscopic structure and X-ray analysis for the produced sinter were carried out. The results revealed that, all sinter properties (such as shatter test, productivity of sinter machine and blast furnace, reduction time and chemical composition for produced sinter by using coke breeze with size -3+1 mm and coke breeze granules were almost the same. The iron ore sinter which was produced by using coke breeze without sieving yielded low productivity for both sinter machine and blast furnace. Furthermore, using coke breeze without sieving in sintering of an iron ore decreases the vertical velocity of sinter machine and increases the reduction time.

  14. Characterization of mechanically milled and spark plasma sintered Al2124-CNT nanocomposites

    Directory of Open Access Journals (Sweden)

    Saheb N.

    2015-01-01

    Full Text Available In the present work, ball milling and spark plasma sintering were used to develop Al2124-CNT nanocomposites. The effect of milling time on the grain size and lattice strain of the ball milled Al2124 alloy powder and the effect of sintering time and temperature on the grain size of the matrix in spark plasma sintered Al2124 alloy and CNT-reinforced Al2124 nanocomposites were investigated. The density and hardness of the developed materials were evaluated as functions of the sintering parameters. It was found that ball milling not only reduced the particle size of the Al2124 powder but also decreased the grain size of the α-aluminum phase to 50 nm and increased its lattice strain. A milling time of 6 hours was found to be the optimum time to reach a nanostructured α-aluminum matrix. The grain size of the α-aluminum phase in the sintered samples increased with increasing sintering temperature and time to reach maximum values at a sintering temperature of 500°C and a sintering time of 20 minutes. Although sintering led to grain growth, the grain size of the α-aluminium matrix remained in the nanometer range and did not exceed 150 nm. The relative density and hardness of the sintered samples increased with increasing sintering temperature and time to reach maximum values at a sintering temperature of 500°C and a sintering time of 20 minutes.

  15. Residual stresses in a co-sintered SOC half-cell during post-sintering cooling

    DEFF Research Database (Denmark)

    Charlas, Benoit; Chatzichristodoulou, Christodoulos; Brodersen, Karen;

    2014-01-01

    Due to the thermal expansion mismatch between the layers of a Solid Oxide Cell, residual stresses (thermal stresses) develop during the cooling after sintering. Residual stresses can induce cell curvature for asymmetric cells but more importantly they also result in more fragile cells. Depending...... on the loading conditions, the additional stress needed to break the cells can indeed be smaller due to the initial thermo-mechanical stress state. The residual stresses can for a bilayer cell be approximated by estimating the temperature at which elastic stresses start to build up during the cooling, i.......e. the reference temperature (Tref) or the strain difference based on the curvature. This approximation gives good results for bilayers with a defined cooling temperature profile, where the curvature of the bilayer defines a unique balance between the two unknown residual stress states in the two layers...

  16. Selective autocatalytic reduction of NO from sintering flue gas by the hot sintered ore in the presence of NH3.

    Science.gov (United States)

    Chen, Wangsheng; Luo, Jing; Qin, Linbo; Han, Jun

    2015-12-01

    In this paper, the selective autocatalytic reduction of NO by NH3 combined with multi-metal oxides in the hot sintered ore was studied, and the catalytic activity of the hot sintered ore was investigated as a function of temperature, NH3/NO ratio, O2 content, H2O and SO2. The experimental results indicated that the hot sintered ore, when combined with NH3, had a maximum denitration efficiency of 37.67% at 450 °C, 3000 h(-1) gas hourly space velocity (GHSV) and a NH3/NO ratio of 0.4/1. Additionally, it was found that O2 played an important role in removing NOx. However, high O2 content had a negative effect on NO reduction. H2O was found to promote the denitration efficiency in the absence of SO2, while SO2 inhibited the catalytic activity of the sintered ore. In the presence of H2O and SO2, the catalytic activity of the sintered ore was dramatically suppressed.

  17. The sintering of uranium carbide and of uranium-plutonium carbide, and the role of nickel as a sintering additive

    Science.gov (United States)

    Pickles, S.; Yates, G.; Bramman, J. I.; Finlayson, Moira B.

    1980-04-01

    A comparison of the experimentally determined sintering kinetics for uranium and uranium-plutonium carbides of different stoichiometries with calculations for various theoretical models has been used to indicate probable sintering mechanisms. A bulk diffusion model with activation energies approximating to those for chemical diffusion under a concentration gradient is thought to apply. Ceramography has been used to study the influence of changes in composition and sintering atmosphere on grain size and microstructure, with the conclusion that grain growth is impeded by the presence of a grain-boundary second phase. The role of nickel as a sintering aid has also been investigated using, in addition to the above techniques, electron microprobe analysis and X-ray diffraction for chemical identification of phases. It is concluded that the first stage of sintering is one of particle rearrangement in a binary metallic liquid phase (U-Ni), followed by a solution-precipitation process. On prolonged annealing ternary U-C-Ni phases are produced, dominated by the composition U 2NiC 3.

  18. Nano pores evolution in hydroxyapatite microsphere during spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Lin C.

    2011-01-01

    Full Text Available Micron-spherical granules of hydroxyapatite (HAp nanoparticles were prepared by powder granulation methods. Through subsequent sintering, porous HAp microspheres with tailored pore and grain framework structures were obtained. Detailed microstructure investigation by SEM and TEM revealed the correlation of the pore structure and the necking strength with the sintering profiles that determine the coalescence features of the nanoparticles. The partially sintered porous HAp microspheres containing more than 50% porosity consisting of pores and grains both in nano-scale are active in inducing the precipitation of HAp in simulated body fluid. The nano-porous HAp microspheres with an extensive surface and interconnecting pores thus demonstrate the potential of stimulating the formation of collagen and bone and the integration with the newly formed bones during physiological bone remodeling.

  19. Karakteristik Distribusi Temperatur Build Part pada Proses Pressureless Indirect Sintering

    Directory of Open Access Journals (Sweden)

    Susilo Adi Widyanto

    2011-01-01

    Full Text Available Curling phenomenon on rapid prototyping (RP product is an actual problem which has not been solved clearly, also on MMD-Is product. Previous experiment showed, it was caused dominantly by un-uniformity of temperature distribution in build part system when sintering was executed. Differ to the sintering process in the common commercial RP process, sintering process in MMD-Is is conducted in supporting powder media. The research is aimed to observe the effect of supporting powder materials, particle size and configuration of heater system on temperature distribution of the build part. Temperature distribution was measured by immersing thermocouples into supporting powder in vertical and horizontal formation. The experimental results show that the un-uniformity of the build part temperature is caused by secondary heating phenomenon by piston material at base position.

  20. Final flotation waste kinetics of sintering at different heating regimes

    Directory of Open Access Journals (Sweden)

    Cocić Mira

    2016-01-01

    Full Text Available In the copper extraction, especially during the process of flotation enrichment and the pyrometallurgical processing, the waste materials that represent huge polluters of environment are being generated. In order to examine the application of Final flotation waste (FFW in the manufacturing of new materials from the glass-ceramic group phase and mineral composition were examined as well as thermal properties. FFW kinetics of sintering has been tested at different dyamics (1°C/min, 29°C/min and 43°C/min, in order to find the optimum conditions for sintering with a minimum amount of energy and time consumption. The samples were examined using: X-ray diffraction, X-ray fluorescence analysis, SEM (Scanning Electron Microscopy and thermal microscopy. The best results for the production of glass ceramic materials were obtained during the sintering at heating regime of 29°C/min. [Projekat Ministarstva nauke Republike Srbije, br. 176010

  1. Microstructure of pre-sintered permanent magnetic strontium ferrite powder

    Institute of Scientific and Technical Information of China (English)

    YU Hongya; LIU Zhengyi; ZENG Dechang

    2006-01-01

    The microstructure and characteristics of pre-sintered strontium ferrite powderwere investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The present study shows that the pre-sintered strontium ferrite powder is provided with a certain particle size distribution, which results in high-density magnets. The strontium ferrite particle has a laminar hexagonal structure with a size similar to ferrite single domain. Ferric oxidephase due to an incomplete solid phase reaction in the first sintering is discovered, which will deteriorate the magnetic properties of ferrite magnet. In addition, the waste ferrite magnets with needle shape arranging along C axis in good order into the powders are found, which have no negative effects on finished product quality.

  2. Synthesis and Sintering Character of Nanophase Calcium-deficient Apatite

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Nanophase calcium-deficient hydroxyapatite( CDHA ) with a Ca/P ratio about 1.5 synthesized by chemical wet method was sintered at different temperatures, and then its chemical composition, phase structure and morphology were analyzed with methods of FT- IR spectroscopy, X- ray diffraction (XRD) and field emission scanning microscopy (FESEM), respectively. Results shaw that when the sintering temperature is below 500 ℃ ,apatite crystal keeps a stable size with a diameter of 12-26 nm and a length of 30-66 nm. After being sintered at600 ℃ for 2 h, apatite crystal grows much larger with a diameter of 25-40 nm and a length of 75-100 nm. At the temperature of 700-800 ℃, this powder decomposes into Ca3 ( PO4 )2 - The crystal size of the Ca3 ( PO4 )2surpasses 200 nm in diameter and length. NH4+ ion can be removed at terrperature beyond 300 ℃ .

  3. INTERNAL FINISHING OF CYLINDRICAL PIPES USING SINTERED MAGNETIC ABRASIVES

    Directory of Open Access Journals (Sweden)

    PALWINDER SINGH

    2011-07-01

    Full Text Available An internal magnetic abrasive finishing (MAF process was proposed to produce highly finished inner surfaces of workpieces used in critical applications. The process principle and the finishing characteristics of magnetic abrasive finishing of cylindrical pipes using sintered magnetic abrasives are described in this research work. Thesintered magnetic abrasive is a mixture of Al2O3 abrasive and ferromagnetic particles. The Al2O3 based sintered magnetic abrasives have been developed in sintering machine. The surface roughness measurements resulting from finishing experiments demonstrate the effects of the abrasive behavior on the surface modifications. Thesurface finish was analysed in terms of percent improvement in surface finish (PISF. Also surface finish was analysed using Response Surface Methodology (RSM. The obtained maximum PISF was 95% and minimum surface roughness was 0.05 μm Ra. To further study the improvement in surface finish, the surface was microscopically examined using X-Ray Diffraction (XRD.

  4. Microstructure and properties of sintered mullite developed from Indian bauxite

    Indian Academy of Sciences (India)

    H S Tripathi; A Ghosh; M K Halder; B Mukherjee; H S Maiti

    2012-08-01

    Dense mullite aggregates with 72% Al2O3 have been synthesized by reaction sintering of two varieties of Indian bauxite and silica sol. The bauxites used are of inferior grade with different levels of accessory impurities such as Fe2O3, TiO2, CaO. The phase and microstructure development of sintered samples were investigated by XRD and SEM. It was found that morphology of the sintered grain is very much dependent on the impurity level. Mullite formed from bauxite-1 with low impurity is mostly equiaxed, whereas mullite developed from bauxite 2 with higher impurity particularly CaO is needle shaped. Presence of CaO in bauxite was found to be more detrimental than TiO2 and Fe2O3.

  5. Direct laser sintered WC-10Co/Cu nanocomposites

    Science.gov (United States)

    Gu, Dongdong; Shen, Yifu

    2008-04-01

    In the present work, the direct metal laser sintering (DMLS) process was used to prepare the WC-Co/Cu nanocomposites in bulk form. The WC reinforcing nanoparticles were added in the form of WC-10 wt.% Co composite powder. The microstructural features and mechanical properties of the laser-sintered sample were characterized by X-ray diffraction (XRD), atomic force microscope (AFM), scanning electron microscope (SEM), energy dispersive X-ray spectroscope (EDX), and nanoindentation tester. It showed that the original nanometric nature of the WC reinforcing particulates was well retained without appreciable grain growth after laser processing. A homogeneous distribution of the WC reinforcing nanoparticles with a coherent particulate/matrix interfacial bonding was obtained in the laser-sintered structure. The 94.3% dense nanocomposites have a dynamic nanohardness of 3.47 GPa and a reduced elastic modulus of 613.42 GPa.

  6. Determination of residual stresses in sintered ceramics. A hypoelastic model

    Energy Technology Data Exchange (ETDEWEB)

    Taheri, F. (Advanced Materials Engineering Centre, Halifax, NS (Canada)); Murphy, J.G. (General Compiste Technology, Halifax, NS (Canada))

    1991-04-01

    The ceramic firing cycles necessary for sintering often produce high thermal gradients. Such thermal cycles, especially in materials with low thermal conductivity, can cause different densification rates. The result of such mechanical nonuniformity is the formation of residual stress patterns in the materials. The magnitude of these stresses is sufficient to cause microcracks to occur. In this study, a practical and versatile methodology used in evaluating the residual stresses resulting from mechanical nonuniformity in slip cast ceramics will be discussed. The analysis uses the commercial finite element program ABAQUS in conjunction with a hypoelastic material constitutive model. The qualitative results obtained from the preliminary finite element method (FEM) investigations illustrate that this numerical methodology can be used to emulate the sintering mechanism, and estimate the residual stresses caused by sintering processes. (orig.).

  7. Spark plasma sintering of Mn-Al-C hard magnets.

    Science.gov (United States)

    Pasko, A; LoBue, M; Fazakas, E; Varga, L K; Mazaleyrat, F

    2014-02-12

    Structural and magnetic characterization of isotropic Mn-Al-C bulk samples obtained by spark plasma sintering (SPS) is reported. This technique, to the best of our knowledge, has not been used for preparation of Mn-Al-based permanent magnets previously. Transformation from the parent -phase to the ferromagnetic τ-phase occurred on heating in the process of sintering. The phase constitution of the melt-spun precursors and consolidated samples was determined by x-ray diffraction. Magnetic hysteresis loops were recorded using a vibrating sample magnetometer. The compositional dependence of the coercivity, magnetization and density of the sintered materials is analysed. To combine good magnetic properties with proper densification, further optimization of the production parameters is necessary.

  8. Reactive Sintering of Bimodal WC-Co Hardmetals

    Directory of Open Access Journals (Sweden)

    Marek Tarraste

    2015-09-01

    Full Text Available Bimodal WC-Co hardmetals were produced using novel technology - reactive sintering. Milled and activated tungsten and graphite powders were mixed with commercial coarse grained WC-Co powder and then sintered. The microstructure of produced materials was free of defects and consisted of evenly distributed coarse and fine tungsten carbide grains in cobalt binder. The microstructure, hardness and fracture toughness of reactive sintered bimodal WC-Co hardmetals is exhibited. Developed bimodal hardmetal has perspective for demanding wear applications for its increased combined hardness and toughness. Compared to coarse material there is only slight decrease in fracture toughness (K1c is 14.7 for coarse grained and 14.4 for bimodal, hardness is increased from 1290 to 1350 HV units.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7511

  9. Evaluation of benefits resulting from innovation of input raw materials dosing process in sintering

    Directory of Open Access Journals (Sweden)

    P. Besta

    2012-10-01

    Full Text Available Production of blast furnace sinter is among the processes with the highest energy and material requirements. Fuel consumption is especially significant cost item here. The presence of grate sintered in charge, i.e. return sinter from 12 to 22 mm in size, can have fundamental impact on the technical and economic indicators of the sintering process. Grate sinter can be used as a foundation layer under the sintering mixture, to increase air permeability of charge and to improve the gas-dynamic conditions. The article analyzes the impact of grate sinter on the sintering process, based on an analysis of the acquired production indicators within the scope of the research in question.

  10. Fe-Mo-B Enhanced Sintering of P/M 316L Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    YANG Xia; GUO Shi-ju

    2008-01-01

    Liquid-phase enhanced sintering of powder metallurgy (P/M) 316L stainless steel by addition of sintering aids was studied. 2%-8% of pre-alloyed Fe-Mo-B powder with two different particle sizes was added as sintering aids, and the specimens were sintered in vacuum at 1 200-1 350 ℃. The results show that the fine Fe-Mo-B powder (5-10 μm) has stronger activated effect. The sintered density increases with the increase in sintering aid content or sintering temperature. Warm compaction has a better effect on the control of dimensional precision of compacts. The prealloyed Fe-Mo-B powder deviated from Mo2FeB2 component can also be sintering aid of P/M 316L stainless steel.

  11. Investigation of Sintering Technology for Composite of Stainless Steel and Partially Stabilized Zirconia

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The sintering technology for mixed powdered extrusion rods of different proportions of stainless steel to magnesiapartially stabilized zirconia (PSZ) was investigated. The effects of some sintering parameters including holdingtime, atmosphere and protective gas pressure on shrinkage, relative density, microstructure, micro-Vickers hardnessand compression strength of sintered samples were mainly researched. The experimental results are as follows: (1)The shrinkage and the relative density of the sintered samples decrease as increasing stainless steel content in thecomposite, except for the case containing 90 percent of stainless steel; (2) The porosity in PSZ matrix rises asincreasing the stainless steel content in the composite; (3) Longer sintering holding time, higher sintering vacuumand gas-pressure sintering process not only enhance the relative density, but also improve microstructure of composite;(4) Micro-Vickers hardness of PSZ matrix decreases as increasing stainless steel content, while that of stainless steelparticles in sintered samples varies unnoticeably.

  12. Thermal Properties of Silver Nanoparticle Sintering Bonding Paste for High-Power LED Packaging

    Directory of Open Access Journals (Sweden)

    Ping Zhang

    2016-01-01

    Full Text Available This paper describes the preparation of low-temperature sintered nanosilver paste with inverse microemulsion method with Span-80/Triton X-100 as the mixed-surfactant and analyzes the influence of different sintering parameters (temperature, pressure on the shear properties of low-temperature sintering of nanosilver. Experimental results show that the shear strength of the low-temperature sintering of nanosilver increases as the temperature and pressure increase. But there are many pores and relative fewer cracks on the sintering layer after low-temperature sintered. The test thermal resistance of low-temperature sintered nanosilver paste is 0.795 K/W which is greater than SAC305 weld layer with a T3ster thermal analyzer. The adhesive performance and the heat dispersion of low-temperature sintered nanosilver paste need to be further researched and improved.

  13. Low-temperature sintering process for UO2 pellets in partially-oxidative atmosphere

    Institute of Scientific and Technical Information of China (English)

    YANG Xiao-dong; GAO Jia-cheng; WANG Yong; CHANG Xin

    2008-01-01

    Low-temperature sintering(LTS) experiments of UO2 pellets and their results were reported. Moreover, a routine process of LTS for UO2 pellets was primarily established. Being sintered at 1 400 ℃ for 3 h in a partially-oxidative atmosphere, the relative density of the pellet can be up to around 94%. Pellets with such a high density are of benefit for following-up reduction-sintering processes. Orthogonal test indicates that the importance of factors affecting the density decreases in the sequence of partial-oxidative sintering temperature and time, reduction-sintering time and temperature, and sintering atmosphere. It is found that it is helpful to introducing a small amount of water vapor into the sintering atmosphere during the latter stage. It is believed that it is the key factor to raise the O/U ratio of original powder in order to improve the properties of the low-temperature sintered pellets.

  14. Effect of cerium on the corrosion behaviour of sintered (Nd,Ce)FeB magnet

    Science.gov (United States)

    Yang, Lijing; Bi, Mengxue; Jiang, Jianjun; Ding, Xuefeng; Zhu, Minggang; Li, Wei; Lv, Zhongshan; Song, Zhenlun

    2017-06-01

    For the balanced consumption of rare-earth elements, cerium (Ce) was partially used for NdFeB magnets instead of Nd. The corrosion behaviour of the (Nd,Ce)FeB magnet with different Ce contents in 3.5% NaCl solution was investigated by SEM, XRD, EDS and electrochemical tests. After immersion, the weight loss was calculated and the magnetic properties of the samples were measured. Results showed that Ce affected the corrosion of the (Nd,Ce)FeB magnet. Compared with the NdFeB magnet without Ce but of the same grade as the magnetic energy product, (Nd,Ce)FeB magnet showed better corrosion resistance. With increased Ce content, the corrosion resistances and magnetic properties of (Nd,Ce)FeB magnets were investigated.

  15. Sintering of Catalytic Nanoparticles: Particle Migration or Ostwald Ripening?

    DEFF Research Database (Denmark)

    Hansen, Thomas Willum; DeLaRiva, Andrew T.; Challa, Sivakumar R.

    2013-01-01

    Metal nanoparticles contain the active sites in heterogeneous catalysts, which are important for many industrial applications including the production of clean fuels, chemicals and pharmaceuticals, and the cleanup of exhaust from automobiles and stationary power plants. Sintering, or thermal...... review recent evidence obtained via in situ methods to determine the relative importance of PMC and OR in each of these phases of catalyst sintering. The evidence suggests that, in phase I, OR is responsible for the rapid loss of activity that occurs when particles are very small. Surprisingly, very...

  16. In situ Transmission Electron Microscopy of catalyst sintering

    DEFF Research Database (Denmark)

    DeLaRiva, Andrew T.; Hansen, Thomas Willum; Challa, Sivakumar R.

    2013-01-01

    Recent advancements in the field of electron microscopy, such as aberration correctors, have now been integrated into Environmental Transmission Electron Microscopes (TEMs), making it possible to study the behavior of supported metal catalysts under operating conditions at atomic resolution. Here......, we focus on in situ electron microscopy studies of catalysts that shed light on the mechanistic aspects of catalyst sintering. Catalyst sintering is an important mechanism for activity loss, especially for catalysts that operate at elevated temperatures. Literature from the past decade is reviewed...

  17. Structural Evolution of Silicon Carbide Nanopowders during the Sintering Process

    Directory of Open Access Journals (Sweden)

    Galina Volkova

    2014-01-01

    Full Text Available Processes of sintering of silicon carbide nanopowder were investigated. Values of density (ρ=3.17 g/cm3 and strength (σ=450 MPa were obtained. Within the theory of dispersed systems, the temperature evolution of the materials structure was considered. The relationship between sintering temperature, characteristics of crystal structure and physical properties, in particular, density, and strength of aforementioned ceramics was established. It was concluded that it is necessary to suppress the anomalous diffusion at temperatures above 2080°C.

  18. Pressureless sintering of translucent MgO ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Chen Dianying [Department of Chemical, Materials and Biomolecular Engineering, Institute of Materials Science, University of Connecticut, Storrs, CT 06269 (United States); Jordan, Eric H. [Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269 (United States)], E-mail: jordan@engr.uconn.edu; Gell, Maurice [Department of Chemical, Materials and Biomolecular Engineering, Institute of Materials Science, University of Connecticut, Storrs, CT 06269 (United States)

    2008-10-15

    MgO nanocrystalline powders were synthesized via a wet precipitation process. X-ray diffraction analysis of the heat-treated precursor powders shows that a crystalline MgO phase forms at {approx}500 deg. C. Translucent MgO ceramics were prepared by pressureless sintering the nanocrystalline MgO powders at 1400 deg. C for 2 h under ambient atmosphere. The as-sintered MgO ceramics have a relative density of 98.1% with an average hardness of 6.8 GPa. Scanning electron microscope characterization revealed that the translucent MgO ceramics have an average grain size of {approx}6 {mu}m.

  19. Preparation of Porous Mullite Composite by Microwave Sintering

    Institute of Scientific and Technical Information of China (English)

    FAN Bingbing; ZHANG Rui; SUN Bing; LI Xuqin; LI Chunguang

    2012-01-01

    Microwave sintering method was carried out to prepare porous mullite composite.An insulation structure based on hybrid heating mode was well designed with the wall of mullite and the aided heaters of SiC.The obtained samples were characterized by XRD analysis,apparent porosity detection,and bending strength measurement.SEM was used to observe the microstructure of the sample.It is found that the porous mullite composite could be prepared through the microwave sintering within 2 h at relatively low temperatures around 1000 ℃.The lasted samples show comparatively superior properties to the products prepared by conventional processing.

  20. Microstructure of Spark Plasma-Sintered Silicon Nitride Ceramics

    Science.gov (United States)

    Lukianova, O. A.; Novikov, V. Yu.; Parkhomenko, A. A.; Sirota, V. V.; Krasilnikov, V. V.

    2017-04-01

    The microstructure and phase composition of the high-content Al2O3-Y2O3-doped spark plasma-sintered silicon nitride were investigated. Fully dense silicon nitride ceramics with a typical α-Si3N4 equiaxed structure with average grain size from 200 to 530 nm, high elastic modulus of 288 GPa, and high hardness of 2038 HV were spark plasma sintered (SPSed) at 1550 °C. Silicon nitride with elongated β-Si3N4 grains, higher hardness of 1800 HV, density of 3.25 g/cm3, and Young's modulus 300 GPa SPSed at 1650 °C was also reviewed.

  1. Thermal Properties of Silver Nanoparticle Sintering Bonding Paste for High-Power LED Packaging

    OpenAIRE

    Ping Zhang; Rongzhuan Wei; Jianhua Zeng; Miao Cai; Jing Xiao; Daoguo Yang

    2016-01-01

    This paper describes the preparation of low-temperature sintered nanosilver paste with inverse microemulsion method with Span-80/Triton X-100 as the mixed-surfactant and analyzes the influence of different sintering parameters (temperature, pressure) on the shear properties of low-temperature sintering of nanosilver. Experimental results show that the shear strength of the low-temperature sintering of nanosilver increases as the temperature and pressure increase. But there are many pores and ...

  2. Flash (Ultra-Rapid) Spark-Plasma Sintering of Silicon Carbide

    OpenAIRE

    Eugene A. Olevsky; Stephen M. Rolfing; Maximenko, Andrey L.

    2016-01-01

    A new ultra-rapid process of flash spark plasma sintering is developed. The idea of flash spark plasma sintering (or flash hot pressing - FHP) stems from the conducted theoretical analysis of the role of thermal runaway phenomena for material processing by flash sintering. The major purpose of the present study is to theoretically analyze the thermal runaway nature of flash sintering and to experimentally address the challenge of uncontrollable thermal conditions by the stabilization of the f...

  3. Mechanical properties and microstructural evolution of alumina-zirconia nanocomposites by microwave sintering

    OpenAIRE

    Benavente Martínez, Rut; Salvador Moya, Mª Dolores; Penaranda-Foix, Felipe L.; Pallone, Eliria; Borrell Tomás, María Amparo

    2014-01-01

    Microwave sintering has emerged in recent years as a novel method for sintering a variety of materials that have shown significant advantages against conventional sintering procedures. This work involved an investigation of microwave hybrid fast firing of alumina–zirconia nanocomposites using commercial alumina powder and monoclinic nanometric zirconia. The suspensions were prepared separately in order to obtain 5, 10 and 15 vol% of ZrO2 in the alumina matrix. The samples were sinter...

  4. Microwave and conventional sintering of premixed and prealloyed Cu-12Sn bronze

    Directory of Open Access Journals (Sweden)

    Sethi G.

    2003-01-01

    Full Text Available The aim of the present investigation is to study the sintering behavior of the Cu-12Sn bronze system in both, a microwave furnace as well as a conventional furnace. The powders prepared by premixed and prealloyed routes were sintered in the range of solid state, transient and supersolidus liquid phase sintering conditions. The comparative analysis is based on the sintered density, densification parameter, hardness, macrostructures and microstructures of the samples.

  5. NdFeB磁体表面镀铝膜层退镀液配方的研究%Study on formulation of stripping solution for aluminum coating on surface of NdFeB magnet

    Institute of Scientific and Technical Information of China (English)

    陈梓赫; 代明江; 胡芳; 林松盛; 侯惠君

    2015-01-01

    A highly efficient and stable solution for stripping aluminum coating from the surface of NdFeB magnet was developed based on NaOH as corrosion agent with auxiliary salt, surfactant, coordination agent, and corrosion inhibitor. The content of aluminum coating on surface of NdFeB and the weight loss of substrate were used as performance evaluation indexes. The optimal stripping process was determined by orthogonal test as follows: NaOH 10 g/L, Na2CO330 g/L, sodium dodecyl benzene sulfonate 6 g/L, EDTA-2Na 4 g/L, and hexamethylenetetramine 4 g/L. A 12-µm thick aluminum coating on surface of NdFeB substrate can be stripped completely by using the optimized stripping solution at room temperature for 3 min. After stripping, the remanence, coercive force, and maximum magnetic energy product of the substrate are changed only by 1.27%, 1.25%, and 0.47%, respectively. The stripping shows less damage to magnetic properties. The mechanism of stripping aluminum coating on NdFeB surface was discussed.%用 NaOH 作腐蚀剂,添加辅助盐、表面活性剂、配位剂和缓蚀剂,研制了一种高效稳定的 NdFeB 表面镀铝膜退镀液。以NdFeB试样表面的铝含量和基体失重量作为性能评定指标,通过正交试验确定了优化的退镀液配方为:NaOH 10 g/L,Na2CO330 g/L,十二烷基苯磺酸钠6 g/L,EDTA-2Na 4 g/L,六次甲基四胺4 g/L。优化的退镀液在室温条件下退镀3 min,即可把NdFeB基体上约12μm厚的铝膜退除干净,而且退镀后基体的剩磁、矫顽力和最大磁能积仅分别变化1.27%、1.25%和0.47%,磁性能损伤较小。探讨了NdFeB表面镀铝膜层的退镀机理。

  6. Application of fine-grained coke breeze fractions in the process of iron ore sintering

    Directory of Open Access Journals (Sweden)

    M. Niesler

    2014-01-01

    Full Text Available The testing cycle, described in the paper, included fine-grained coke breeze granulation tests and iron concentrate sintering tests with the use of selected granulate samples. The use of granulated coke breeze in the sintering process results in a higher process efficiency, shorter sintering duration and fuel saving.

  7. Fabrication of High Strength and Ductile Stainless Steel Fiber Felts by Sintering

    Science.gov (United States)

    Wang, J. Z.; Tang, H. P.; Qian, M.; Li, A. J.; Ma, J.; Xu, Z. G.; Li, C. L.; Liu, Y.; Wang, Y.

    2016-03-01

    Stainless steel fiber felts are important porous stainless steel products for a variety of industry applications. A systematic study of the sintering of 28- µm stainless steel fibers has been conducted for the first time, assisted with synchrotron radiation experiments to understand the evolution of the sintered joints. The critical sintering conditions for the formation of bamboo-like grain structures in the fiber ligaments were identified. The evolution of the number density of the sintered joints and the average sintered neck radius during sintering was assessed based on synchrotron radiation experiments. The optimum sintering condition for the fabrication of high strength and ductile 28- µm-diameter stainless steel fiber felts was determined to be sintering at 1000°C for 900 s. Sintering under this optimum condition increased the tensile strength of the as-sintered stainless steel fiber felts by 50% compared to conventional sintering (1200°C for 7200 s), in addition to much reduced sintering cycle and energy consumption.

  8. Fuel cell life improved by metallic sinter activation after electrode assembly welding

    Science.gov (United States)

    Taylor, W. A.

    1967-01-01

    Technique improves the service life of fuel cell electrodes. The welding is done before the metallic sinter is activated by depositing finely divided metal within the sinter structure from a solution with corrosion inhibiting ions. The activator solution flows through the porous sinter while attached to the backup plate.

  9. Preparation and mechanism of the sintered bricks produced from Yellow River silt and red mud.

    Science.gov (United States)

    He, Hongtao; Yue, Qinyan; Su, Yuan; Gao, Baoyu; Gao, Yue; Wang, Jingzhou; Yu, Hui

    2012-02-15

    The preparation, characteristics and mechanisms of sintered bricks manufactured by Yellow River silt and red mud were studied. The sintering shrinkage, weight loss on ignition, water absorption and compressive strength were tested to determine the optimum preparation condition. Sintering mechanisms were discussed through linear regression analysis. Crystalline components of raw materials and bricks were analyzed by X-ray diffraction. Leaching toxicity of raw materials and bricks were measured according to sulphuric acid and nitric acid method. Radiation safety of the sintered bricks was characterized by calculating internal exposure index and external exposure index. The results showed that at the chosen best parameters (red mud content of 40%, sintering temperature of 1050°C and sintering time of 2h), the best characteristics of sintered bricks could be obtained. The weight loss on ignition of sintered bricks was principally caused by the removal of absorbed water and crystal water. The sintering shrinkage of sintered bricks mainly depended on sodium compounds and iron compounds of red mud. The sintering process made some components of raw materials transform into other crystals having better thermostability. Besides, the leaching toxicity and radioactivity index of sintered bricks produced under the optimum condition were all below standards.

  10. Process for the production of metal nitride sintered bodies and resultant silicon nitride and aluminum nitride sintered bodies

    Science.gov (United States)

    Yajima, S.; Omori, M.; Hayashi, J.; Kayano, H.; Hamano, M.

    1983-01-01

    A process for the manufacture of metal nitride sintered bodies, in particular, a process in which a mixture of metal nitrite powders is shaped and heated together with a binding agent is described. Of the metal nitrides Si3N4 and AIN were used especially frequently because of their excellent properties at high temperatures. The goal is to produce a process for metal nitride sintered bodies with high strength, high corrosion resistance, thermal shock resistance, thermal shock resistance, and avoidance of previously known faults.

  11. Design of Controlled Release Non-erodible Polymeric Matrix Tablet Using Microwave Oven-assisted Sintering Technique.

    Science.gov (United States)

    Patel, Dm; Patel, Bk; Patel, Ha; Patel, Cn

    2011-07-01

    The objective of the present study was to evaluate the effect of sintering condition on matrix formation and subsequent drug release from polymer matrix tablet for controlled release. The present study highlights the use of a microwave oven for the sintering process in order to achieve more uniform heat distribution with reduction in time required for sintering. We could achieve effective sintering within 8 min which is very less compared to conventional hot air oven sintering. The tablets containing the drug (propranolol hydrochloride) and sintering polymer (eudragit S-100) were prepared and kept in a microwave oven at 540 watt, 720 watt and 900 watt power for different time periods for sintering. The sintered tablets were evaluated for various tablet characteristics including dissolution study. Tablets sintered at 900 watt power for 8 min gave better dissolution profile compared to others. We conclude that microwave oven sintering is better than conventional hot air oven sintering process in preparation of controlled release tablets.

  12. Sintering of wax for controlling release from pellets.

    Science.gov (United States)

    Singh, Reena; Poddar, S S; Chivate, Amit

    2007-09-14

    The purpose of the present study was to investigate incorporation of hydrophobic (ie, waxy) material into pellets using a thermal sintering technique and to evaluate the pellets in vitro for controlled release. Pellets prepared by extrusion-spheronization technology were formulated with a water-soluble drug, microcrystalline cellulose, and carnauba wax. Powdered carnauba wax (4%-20%) prepared by grinding or by emulsification was studied with an attempt to retard the drug release. The inclusion of ground or emulsified carnauba wax did not sustain the release of theophylline for more than 3 hours. Matrix pellets of theophylline prepared with various concentrations of carnauba wax were sintered thermally at various times and temperatures. In vitro drug release profiles indicated an increase in drug release retardation with increasing carnauba wax concentration. Pellets prepared with ground wax showed a higher standard deviation than did those prepared with emulsified wax. There was incomplete release at the end of 12 hours for pellets prepared with 20% ground or emulsified wax. The sintering temperature and duration were optimized to allow for a sustained release lasting at least 12 hours. The optimized temperature and duration were found to be 100 degrees C and 140 seconds, respectively. The sintered pellets had a higher hydrophobicity than did the unsintered pellets. Scanning electron micrographs indicated that the carnauba wax moved internally, thereby increasing the surface area of wax within the pellets.

  13. tribological study of a bronze obtained by sintering proceeds

    African Journals Online (AJOL)

    F. Keraghel, K. Loucif, M. P. Delplanck

    2017-01-01

    Jan 1, 2017 ... behavior of materials. ... a Cu 8% Sn bronze pressure sintered self-lubricating mode fo ... in temperature, which usually accelerates the wear of the parts. ... We must add that for loads and high speeds, the curves do not tend ...

  14. Self-healing of damaged particulate materials through sintering

    NARCIS (Netherlands)

    Luding, S.; Suiker, A.S.J.

    2008-01-01

    Particulate materials loaded under uniaxial compression and tension are studied using the discrete element method. Self-healing of the damaged samples is activated through sintering, a process that effectively increases the contact adhesion (i.e. the tensile strength) between particles. The initial

  15. Modeling constrained sintering of bi-layered tubular structures

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye; Kothanda Ramachandran, Dhavanesan; Ni, De Wei;

    2015-01-01

    . Furthermore, the model is validated using densification results from sintering of bi-layered tubular ceramic oxygen membrane based on porous MgO and Ce0.9Gd0.1O1.95-d layers. Model input parameters, such as the shrinkage kinetics and viscous parameters are obtained experimentally using optical dilatometry...

  16. Pulse plasma sintering of a tungsten/steel divertor module

    Energy Technology Data Exchange (ETDEWEB)

    Kruszewski, Mirosław J., E-mail: m.kruszewski@inmat.pw.edu.pl; Ciupiński, Łukasz; Rosiński, Marcin; Michalski, Andrzej; Kurzydłowski, Krzysztof J.

    2013-10-15

    Highlights: • W/WL10 and WL10/steel joints were fabricated via pulse plasma sintering. • Fe interlayer successfully compensated thermal stresses at the WL10/steel joint. • Maximum temperature of a single stage sintering of the module was established. • Better accuracy in machining of W and WL10 elements is needed. -- Abstract: The paper presents the preliminary evaluation of the potential of a pulse plasma sintering (PPS) technique for the fabrication of a He-cooled modular divertor with a multiple-jet cooling module. In this work the W and WL10 elements were directly bonded by PPS. Examination of the microstructure revealed some minor defects at the interface, but the overall quality of the joint was good with no cracks or delamination being detected. To reduce the thermal stress gradient a thin transition layer of iron was used at the WL10/steel interface. In addition an attempt was made to fabricate the complete module by a single sintering process. The microstructures of the fabricated modules were examined and the findings were reported.

  17. Hydraulic and acoustic investigation of sintered glass beads

    Science.gov (United States)

    Gueven, Ibrahim; Luding, Stefan; Steeb, Holger

    2013-06-01

    In the present contribution, we are focussing on the hydraulical and acoustical charcterization of sintered glass beads. For the experiments sintered mono-and weakly polydisperse glass bead samples were applied. Depending on the particle size, degree of particle dispersion and sample treatment during the sintering process, the produced cylindircal samples exhibit different hydraulic and acoustic properties. The more general focus of our research lies on the physical behaviour of oil-water emulsions in porous media by means of combined electromagnetic and acoustic wave propagation. For this purpose, a hydraulic multi-task measuring cell was developed. This cell allows carrying out simple hydraulic permeability and challenging ultrasound experiments in porous materials saturated with Pickering emulsions. In the first phase of our experiments, hydraulical and acoustical measurements of cylindrical sintered glass bead samples were performed in order to determine their intrinsic permeabilities and effective ultrasound velocities. The intrinsic permeability ks, a coupling parameter between the solid matrix and the pore fluid, has a huge influence on wave propagation in fluid-saturated porous media. For the assessment of permeabilities, particle size distributions and porosities of the investigated glass beads were determined.

  18. Sintering and foaming of barium silicate glass powder compacts

    Science.gov (United States)

    Mueller, Ralf; Reinsch, Stefan; Agea-Blanco, Boris

    2016-10-01

    The manufacture of sintered glasses and glass-ceramics, glass matrix composites and glass-bounded ceramics or pastes is often affected by gas bubble formation. Against this background, we studied sintering and foaming of barium silicate glass powders used as SOFC sealants using different powder milling procedures. Sintering was measured by means of heating microscopy backed up by XPD, DTA, Vacuum Hot Extraction (VHE) and optical and electron microscopy. Foaming increased significantly as milling progressed. For moderately milled glass powders, subsequent storage in air could also promote foaming. Although the powder compacts were uniaxially pressed and sintered in air, the milling atmosphere sig¬ni¬ficantly affected foaming. The strength of this effect increased in the order Ar ? N2 encapsulated CO2, even for powders milled in Ar and N2. Results of this study thus indicate that foaming is caused by carbonaceous species trapped on the glass powder surface. Foaming could be substantially reduced by milling in water and 10 wt% HCl.

  19. Binding Mechanisms in Selective Laser Sintering and Selective Laser Melting

    NARCIS (Netherlands)

    Kruth, J.-P.; Mercelis, P.; Van Vaerenbergh, J.; Froyen, L.; Rombouts, M.

    2005-01-01

    Purpose – This paper provides an overview of the different binding mechanisms in selective laser sintering (SLS) and selective laser melting (SLM), thus improving the understanding of these processes. Design/methodology/approach – A classification of SLS/SLM processes was developed, based on the bin

  20. Diffusion of silver during sintering in high permittivity COG dielectrics

    NARCIS (Netherlands)

    Mikkenie, R.; Groen, W.A.; Drift, R. van der

    2010-01-01

    To achieve cost reduction in multi-layer ceramic capacitors and actuators, which use a silver-palladium alloy as internal electrode, the trend is to use alloys with the highest silver content possible. This requires ceramic materials which must be sintered at a relative low temperature. Goal is to a

  1. New developments in laser sintering of diamond cutting disks

    NARCIS (Netherlands)

    Kovalenko, V.; Golovko, L.; Meijer, J.; Anyakin, M.

    2007-01-01

    The analysis of techniques and problems in the fabrication of cutting tools based on super hard composites results in a solution by the application of lasers. The results of systematic study of diamond composites sintering with laser radiation are discussed. A mathematical modeling of the heat

  2. Strain in the mesoscale kinetic Monte Carlo model for sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Tikare, V.

    2014-01-01

    Shrinkage strains measured from microstructural simulations using the mesoscale kinetic Monte Carlo (kMC) model for solid state sintering are discussed. This model represents the microstructure using digitized discrete sites that are either grain or pore sites. The algorithm used to simulate...

  3. Sintering and foaming of barium silicate glass powder compacts

    Directory of Open Access Journals (Sweden)

    Ralf Mueller

    2016-10-01

    Full Text Available The manufacture of sintered glasses and glass-ceramics, glass matrix composites and glass-bounded ceramics or pastes is often affected by gas bubble formation. Against this background, we studied sintering and foaming of barium silicate glass powders used as SOFC sealants using different powder milling procedures. Sintering was measured by means of heating microscopy backed up by XPD, DTA, Vacuum Hot Extraction (VHE and optical and electron microscopy. Foaming increased significantly as milling progressed. For moderately milled glass powders, subsequent storage in air could also promote foaming. Although the powder compacts were uniaxially pressed and sintered in air, the milling atmosphere sig¬ni¬ficantly affected foaming. The strength of this effect increased in the order Ar  N2 < air < CO2. Conformingly, VHE studies revealed that the pores of foamed samples predominantly encapsulated CO2, even for powders milled in Ar and N2. Results of this study thus indicate that foaming is caused by carbonaceous species trapped on the glass powder surface. Foaming could be substantially reduced by milling in water and 10 wt% HCl.

  4. Multilayer tape cast SOFC – Effect of anode sintering temperature

    DEFF Research Database (Denmark)

    Hauch, Anne; Birkl, Christoph; Brodersen, Karen;

    2012-01-01

    large “temperature-window”. To increase our understanding of the MTC process, obtained microstructures and the resulting electrochemical performance of these SOFC, we here report a study of MTC based cells. The half-cells have been produced and co-sintered at 5 different temperatures from 1255 °C...

  5. Sintering Reaction of Pseudoleucite Syenite: Thermodynamic Analysis and Process Evaluation

    Science.gov (United States)

    TAN, Danjun; MA, Hongwen; LI, Ge; LIU, Hao; ZOU, Dan

    On the basis of comprehensive analysis of the modal composition of a pseudoleucite syenite ore sample, collected from the Zijin Hill of Lin County, Shanxi Province, thermodynamic analysis of the pseudoleucite syenite sintering process with sodium carbonate as the additive was carried out. It indicated that when the pseudoleucite syenite was sintered at 760-880°C for 1.0-1.5 h, with sodium carbonate as the additive. The decomposition rate of minerals in the pseudoleucite syenite could reach 97.1%. The thermodynamic calculation shows that it needs to consume Na 2CO 3, i.e., 0.65 t treating per ton pseudoleucite syenite ore and approximately 95% of Na 2CO 3 could be recycled. This process consumes heat energy (2.29-2.48)×10 -6 kJ, corresponding to standard coal 190.97-206.82 kg as the thermal efficiency was 40% and CO 2 emission was 0.77-0.81 t. Compared with the Russian limestone-sintering technique, the natural mineral resources and energy consumptions and greenhouse gas emissions of the soda-sintering technique were reduced by 65%, 63%, and 65%, respectively. It is, therefore, feasible that the procedure suggested in this article could be industrialized providing both economic benefit and environmental conservation.

  6. New Developments in Laser Sintering of Diamond Cutting Disks

    NARCIS (Netherlands)

    Kovalenko, V.; Golovko, L.; Meijer, J.; Anyakin, M.

    2007-01-01

    The analysis of techniques and problems in the fabrication of cutting tools based on super hard composites results in a solution by the application of lasers. The results of systematic study of diamond composites sintering with laser radiation are discussed. A mathematical modeling of the heat trans

  7. KINETICS OF DENSIFICATION PROCESSES OF POWDER MATERIALS UNDER ELECTROPULSE SINTERING

    NARCIS (Netherlands)

    Grigoryev, E. G.

    2009-01-01

    The process of electropulse sintering of ferrous and high-speed steel powder materials by powerful pulse current and external pressure was investigated. Formation of high density and high strength structure of ferrous and highspeed steel powder materials was analyzed and optimal process parameters w

  8. Diffusion of silver during sintering in high permittivity COG dielectrics

    NARCIS (Netherlands)

    Mikkenie, R.; Groen, W.A.; Drift, R. van der

    2010-01-01

    To achieve cost reduction in multi-layer ceramic capacitors and actuators, which use a silver-palladium alloy as internal electrode, the trend is to use alloys with the highest silver content possible. This requires ceramic materials which must be sintered at a relative low temperature. Goal is to

  9. Thermal conductivity evaluation of initial stage sintering phenomena

    Science.gov (United States)

    Schlaefer, Constance Elaine

    The onset of sinter bonding and concomitant handling strength is a critical period in the processing of powder metallurgy materials. Mechanical characterization of this evolution during predensification sintering is difficult, due to the fragile nature of the materials. Thermal properties such as thermal diffusivity and thermal conductivity also evolve during the onset of sinter bonding. This research investigates the potential for assessing mechanical strength through thermal diffusivity evaluation, using the non-contact technique of laser flash analysis. Thermal conductivity and transverse rupture strength were evaluated for a nickel powder system in three different formats: injection-molded, low-density die-compacted, and high-density die-compacted. Measurements focused on post-sintering strength and thermal conductivity evolution from 20 to 700°C for the first two formats. In situ strength was evaluated for the high-density die-compacted material. Thermal conductivity was demonstrated to be a linear function of neck diameter, versus a function of the neck area as anticipated. Strength evaluation confirmed previous research that strength is a function of the neck area. Based on both properties' dependence on neck size, an integrated relationship was constructed, allowing mechanical strength to be directly predicted from thermal conductivity measurement for the given system.

  10. Microstructural aspects and wear behavior of sinter hardened distaloy HP

    Energy Technology Data Exchange (ETDEWEB)

    Sheikhi Moghaddam, K.; Ghambari, M.; Farhangi, H. [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran (Iran, Islamic Republic of); Solimanjad, N.; Bergmark, A. [Hoeganaes AB, Bruksgatan, Hoeganaes (Sweden); Khorsand, H. [K.N. Toosi University, Tehran (Iran, Islamic Republic of)

    2011-11-15

    Effect of cooling rate during sinter hardening on the microstructure and wear behavior of sintered steel grade Distaloy HP has been studied. Wear performances are closely related to macro and micro hardness of the materials. Dry sliding wear tests have been conducted using a reciprocating pin on flat wear testing machine under normal loads of 25, 35 and 45N and at a constant speed of 0.3 m/s. The samples were sinter hardened at different cooling rates 0.5-3 C/s in order to investigate the influence of microstructure and hardness on wear behavior. It has been shown that, sintering process and cooling rate change the microstructure and hence the hardness and wear behavior of the material. The best wear resistance was detected at a cooling rate of 3 C/s. At this cooling rate the material had an almost martensitic microstructure and the wear rate was some how independent of the applied load. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Novel sintered ceramic materials incorporated with EAF carbon steel slag

    Science.gov (United States)

    Karayannis, V.; Ntampegliotis, K.; Lamprakopoulos, S.; Papapolymerou, G.; Spiliotis, X.

    2017-01-01

    In the present research, novel sintered clay-based ceramic materials containing electric arc furnace carbon steel slag (EAFC) as a useful admixture were developed and characterized. The environmentally safe management of steel industry waste by-products and their valorization as secondary resources into value-added materials towards circular economy have attracted much attention in the last years. EAF Carbon steel slag in particular, is generated during the manufacture of carbon steel. It is a solid residue mainly composed of rich-in- Fe, Ca and Si compounds. The experimental results show that the beneficial incorporation of lower percentages of EAFC up to 6%wt. into ceramics sintered at 950 °C is attained without significant variations in sintering behavior and physico-mechanical properties. Further heating up to 1100 °C strongly enhances the densification of the ceramic microstructures, thus reducing the porosity and strengthening their mechanical performance. On the other side, in terms of thermal insulation behavior as well as energy consumption savings and production cost alleviation, the optimum sintering temperature appears to be 950 °C.

  12. Cu salt ink formulation for printed electronics using photonic sintering.

    Science.gov (United States)

    Araki, Teppei; Sugahara, Tohru; Jiu, Jinting; Nagao, Shijo; Nogi, Masaya; Koga, Hirotaka; Uchida, Hiroshi; Shinozaki, Kenji; Suganuma, Katsuaki

    2013-09-03

    We formulate copper salt (copper formate/acetate/oleate) precursor inks for photonic sintering using high-intensity pulsed light (HIPL) based on the ink's light absorption ability. The inks can be developed through controllable crystal field splitting states (i.e., the ligand weights and their coordination around the metal centers). The inks' light absorption properties are extremely sensitive to the carbon chain lengths of the ligands, and the ink colors can drastically change. From the relationship between the ratios of C/Cu and the required sintering energies, it is possible to ascertain that the integral absorbance coefficients are strongly correlated with the photonic sintering behavior. These results suggest that the ink absorbance properties are the most important factors in photosintering. The wires formed by sintered copper formate complex ink via the HIPL method showed good electronic conduction, achieving a low resistivity of 5.6 × 10(-5) Ω cm. However, the resistivity of the wires increased with increasing contains carbon chain length of the inks, suggesting that large amounts of residual carbon have negative effects on both the wire's surface morphology and the electrical conductivity. We find in this study that high light absorptivity and low carbon inks would lead to a lower environmental load in future by reducing both energy usage and carbon oxide gas emissions.

  13. Corrosion resistance properties of sintered duplex stainless steel

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2006-09-01

    Full Text Available Purpose: of this paper was to examine the corrosion resistance of duplex stainless steels using electrochemical methods in 1M NaCl solution. The influence of powder mixes preparation and cooling cycle after sintering on corrosion properties was evaluated.Design/methodology/approach: In presented study duplex stainless steels were obtained through powder metallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements, such as Cr, Ni, Mo and Cu. In the studies behind the preparation of mixes, Schaeffler’s diagram was taken into consideration. Prepared mixes have been compacted at 800 MPa and sintered in a vacuum furnace with argon backfilling at 1260°C for 1 h. After sintering two different cooling cycles were applied: rapid cooling with an average cooling rate of 245 °C/min and slow cooling of 5 °C/min in argon atmosphere. Produced duplex stainless steels have been studied by scanning and optical microscopy and EDS chemical analysis of microstructure components. Corrosion properties have been studied through electrochemical methods in 1M NaCl water solutionFindings: According to achieved results, it was affirmed that applied sintering method as well as powder mixes preparation allows for manufacturing the sintered duplex steels with good corrosion properties which depends on austenite/ferrite ratio in the microstructure and elements partitioning between phases. Corrosion resistance of sintered stainless steels is strictly connected with the density and the pore morphology present in the microstructure too. The highest resistance to pitting corrosion in 1M NaCl solution was achieved for composition with approximate balance of ferrite and austenite in the microstructure.Research limitations/implications: According to the powders characteristic, the applied fast cooling rate seems to be a good compromise for corrosion properties and microstructures, nevertheless further tests should be carried out in

  14. Permeability, drying, and sintering of pressure filtered ceramic nanopowders

    Science.gov (United States)

    Sweeney, Sean M.

    2002-01-01

    Three aspects of nanocrystalline ceramic body formation are examined in this work: permeability, drying stress, and sintering behavior. The permeabilities of nanocrystalline 3 mol% yttria-stabilized zirconia (3Y-TZP), silica, and boehmite powder compacts are measured during their formation by constant rate pressure filtration. The classic Carman-Kozeny equation with no account for the effect of adsorbed water often overestimates by a factor of 2 or more the measured permeabilities, with increasing deviation with decreasing permeability. A permeability equation from the literature and one derived here, both taking into account the effect of adsorbed water, show significant improvement over the classic Carman-Kozeny equation for predicting measured permeabilities. The equation derived here allows straightforward predictions to be made of how permeability will change as the critical point of drying (when shrinkage stops) is approached. An approximate expression for the maximum tensile stress occurring in an elastic finite cylinder during drying from all sides is derived. Numerical calculations of the exact state of stress during drying show that for cylinder length-to-diameter ratios up to 2/3, the present expression is more accurate than equations from the literature for an infinite plate and an infinite cylinder. For cylinders with length-to-diameter ratios greater than 2/3, numerical calculations show an equation from the literature for the drying stress in an infinite cylinder to be more accurate. To test the validity of the present expression, the drying rates above which fracture occurs are determined for disk-shaped samples of pressure filtered nanocrystalline 3Y-TZP, boehmite, and silica powders. These maximum safe drying rates are used with the present expression to calculate the maximum drying stresses that can be sustained without fracture, and these stresses are compared to diametral compression-measured strengths of similar samples dried to the critical

  15. Oxidation Protection of Uranium Nitride Fuel using Liquid Phase Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Paul A. Lessing

    2012-03-01

    Two methods are proposed to increase the oxidation resistance of uranium nitride (UN) nuclear fuel. These paths are: (1) Addition of USi{sub x} (e.g. U3Si2) to UN nitride powder, followed by liquid phase sintering, and (2) 'alloying' UN nitride with various compounds (followed by densification via Spark Plasma Sintering or Liquid Phase Sintering) that will greatly increase oxidation resistance. The advantages (high thermal conductivity, very high melting point, and high density) of nitride fuel have long been recognized. The sodium cooled BR-10 reactor in Russia operated for 18 years on uranium nitride fuel (UN was used as the driver fuel for two core loads). However, the potential advantages (large power up-grade, increased cycle lengths, possible high burn-ups) as a Light Water Reactor (LWR) fuel are offset by uranium nitride's extremely low oxidation resistance (UN powders oxidize in air and UN pellets decompose in hot water). Innovative research is proposed to solve this problem and thereby provide an accident tolerant LWR fuel that would resist water leaks and high temperature steam oxidation/spalling during an accident. It is proposed that we investigate two methods to increase the oxidation resistance of UN: (1) Addition of USi{sub x} (e.g. U{sub 3}Si{sub 2}) to UN nitride powder, followed by liquid phase sintering, and (2) 'alloying' UN nitride with compounds (followed by densification via Spark Plasma Sintering) that will greatly increase oxidation resistance.

  16. On the Mechanism of Microwave Flash Sintering of Ceramics

    Directory of Open Access Journals (Sweden)

    Yury V. Bykov

    2016-08-01

    Full Text Available The results of a study of ultra-rapid (flash sintering of oxide ceramic materials under microwave heating with high absorbed power per unit volume of material (10–500 W/cm3 are presented. Ceramic samples of various compositions—Al2O3; Y2O3; MgAl2O4; and Yb(LaO2O3—were sintered using a 24 GHz gyrotron system to a density above 0.98–0.99 of the theoretical value in 0.5–5 min without isothermal hold. An analysis of the experimental data (microwave power; heating and cooling rates along with microstructure characterization provided an insight into the mechanism of flash sintering. Flash sintering occurs when the processing conditions—including the temperature of the sample; the properties of thermal insulation; and the intensity of microwave radiation—facilitate the development of thermal runaway due to an Arrhenius-type dependency of the material’s effective conductivity on temperature. The proper control over the thermal runaway effect is provided by fast regulation of the microwave power. The elevated concentration of defects and impurities in the boundary regions of the grains leads to localized preferential absorption of microwave radiation and results in grain boundary softening/pre-melting. The rapid densification of the granular medium with a reduced viscosity of the grain boundary phase occurs via rotation and sliding of the grains which accommodate their shape due to fast diffusion mass transport through the (quasi-liquid phase. The same mechanism based on a thermal runaway under volumetric heating can be relevant for the effect of flash sintering of various oxide ceramics under a dc/ac voltage applied to the sample.

  17. Microstructural characterisation of sintered soft magnetic nanocomposite materials

    Directory of Open Access Journals (Sweden)

    J. Konieczny

    2013-11-01

    Full Text Available Purpose: The main aim of this work is to investigate microstructure of of sintered soft magnetic nanocomposite materials produced by sintering axially on one side in the ambient atmosphere. Design/methodology/approach: Microstructure observations of 20 mm diameter sintered roller by light microscopy OLYMPUS, scanning electron microscopy OPTON DSM-940 and ZEISS SUPRA 35, and transmission electron microscopy JEOL 3010. The X-ray tests were realized with the use of the XRD 7 SEIFERT-FPM diffractometer equipped with the lamp of the cobalt anode of 35 kV voltage and 30 mA filament current was used. The nanocrystalline ferromagnetic powders were manufactured by high-energy ball milling (8000 SPEX CertiPrep Mixer/Mill of metallic glasses ribbons in as state. The hot pressing process was made on machine “Degussa”. Findings: The analysis of the results enabled determination of the hot pressing parameters on structure of obtained stampings. This is typical of an dispersion strengthened case. Research limitations/implications: For the sintered roller obtained from metallic Co-based amorphous ribbons, further mechanical and magnetic examinations are planed. Practical implications: Conducted research shows that applied technology of sintered roller production allows to obtain good microstructural characteristics. Structure analysis of die stampings of powdered amorphous metallic ribbons is helpful to prepare this material by laboratory methods. Feature an alternative to commercial alloys and composite materials are the amorphous and nanocrystalline metal amorphous ribbons obtained by melt spinning technique and make it possible to obtain the new composite materials with best magnetic properties, which dimensions and shape can be freely formed. Originality/value: The paper presents influence of hot pressing parameters process of metallic powdered ribbons Co77Si11.5B11.5 on structure of obtained die stampings.

  18. Progress on grain growth dynamics in sintering of nano-powders

    Institute of Scientific and Technical Information of China (English)

    LIU Chunjing; WANG Xin; JIANG Yanfei; WANG Yongming; HAO Shunli

    2006-01-01

    Nanostructured materials, characterized by an ultrafine grain size, have stimulated much research interest by virtue of their unusual mechanical, electrical, optical, and magnetic properties. In this paper, the sintering process of nano-powders were reviewed, to which sintering of the traditional materials compared. The microstructural development, i.e., grain growth and densification during sintering as well as the mechanism of crystal surface diffusion and boundary migration were analyzed, and the dynamic models on sintering process were summarized by the relationship of grain growth and pores size, interface diffusion, densification rate, and sintering temperature. Finally, the research tendency of this major on the basis of above models was discussed.

  19. Advances in Thermal Modeling of Selective Laser Sintering of Metal Powders

    CERN Document Server

    Xiao, Bin

    2016-01-01

    Selective laser sintering (SLS) of single component metal powders is a rapid prototyping technology in which a high-energy laser beam scans, melts, shrinks and consolidates metal powders with single component. For better understanding physical mechanisms during laser sintering of single-component metal particles, a temperature transforming model with the consideration of shrinkage and convective flows is introduced to analyze the thermal/fluid behaviors in selective laser sintering of single powder layer. The model is also applied to investigate the sintering of powders on top of existing sintered layers under single- multiple-line scanning manners according to the practical manufacturing processes.

  20. A phenomenological analysis of sintering kinetics from the viewpoint of activated volume

    Directory of Open Access Journals (Sweden)

    Nikolić M.V.

    2005-01-01

    Full Text Available The sintering kinetics of real systems has been viewed as a process of transport of activated volume. Activated volume is a parameter that can be used to describe mass transport during the sintering process. It defines the movement of point defects and dislocations during the sintering process. A phenomenological equation has been defined using this parameter, which can be applied to analyze kinetics of the sintering process. It has been applied to analyze the sintering process of several disperse systems. Values obtained for parameters of the equation have also been analyzed.