脉冲磁场退火对纳米晶复合Nd8.5Fe77Co5Zr2.7Ga0.6B6.2永磁合金磁性能的影响

对快淬Nd8.5Fe77Co5Zr2.7Ga0.6B6.2合金,采用脉冲磁场下热处理的方法制备纳米晶复合永磁材料,研究脉冲磁退火对合金的晶化过程、相组成、交换耦合作用以及磁性能的影响,结果表明,同常规退火相比,脉冲磁退火降低了合金的最佳退火温度,改善了合金的微结构,从而增强了软、硬磁性晶粒间的交换耦合作用,明显提高了合金的磁性能,经670℃脉冲磁退火后合金具有最佳的磁性能,即iHc=586kA/m,Jr=1.01T,(BH)max=138kJ/m3,最大磁能积比常规退火工艺条件下提高了15%。     

热处理工艺对块体纳米晶Fe3B/Nd2Fe14B复合磁体性能的影响

采用放电等离子烧结技术(Spark Plasma Sintering,简称SPS技术)将快淬Nd4.5Fe77B18.5薄带制备成块状纳米晶复合磁体.着重研究了热处理工艺对磁体密度、微观结构和磁性能的影响.结果表明,通过直接烧结得到的磁体具有超细纳米晶结构,合适的热处理可以消除残余非晶,得到较好的晶体结构和磁性能.但过高的热处理温度和较长的保温时间的增大会造成晶粒长大,结果导致磁性能的恶化.在最佳热处理条件下得到的磁体的磁性能为Br=1.014T,JHc=237.21 kA/m,(BH)max=61.85 kJ/m3.     

溅射制备Ni-Mn-Ga磁性形状记忆合金薄膜的组织结构研究

采用磁控溅射法制备Ni-Mn-Ga磁性形状记忆合金薄膜,并将制备薄膜在不同的温度下进行真空热处理.研究了不同工艺条件下制备薄膜的结构、形貌和磁性.结果表明:采用磁控溅射在单晶Si基底上溅射Ni-Mn-Ga磁性形状记忆合金薄膜,主要为沿基底法线方向的柱状晶结构,随着热处理温度提高,薄膜晶化程度提高,沉积在Cu基底上的薄膜磁性优于沉积在Si基底上薄膜的磁性.     

热处理时间对NiFe薄膜性能的影响

用磁控溅射法制备了厚度２０－２００ｎｍ的ＮｉＦｅ合金薄膜。研究了热处理时间（及温度）对ＮｉＦｅ薄膜的电阻（电阻率）、各向异性磁电阻比和软磁性能的影响。在一定温度下，经适当时间的热处理可以减小ＮｉＦｅ薄膜的电阻、增大其各和中异性磁电阻比，从而制备出性能较好（各向异性磁电阻比较大、温度稳定性较好）的薄膜磁性材料。     

Fe_(40)Ni_(38)Mo_4B_(18)非晶态合金的退火脆性研究

本文研究了Fe_(40)Ni_(38)Mo_4B_(16)非晶态合金的退火脆性规律;讨论了制备时的冷却速度、薄带厚度、薄带表面质量及热处理工艺等因素对退火脆性的影响及其原因。测量了在脆化温度和脆化时间以内磁场退火样品的直流磁特性,并与其最佳磁特性进行了比较;探讨了在保证样品不脆的前提下,通过改变磁场退火的退火温度和磁场大小,使合金的磁性能接近最佳磁性能的可能性     

磁场退火制备FePt/Ag垂直磁化薄膜

采用磁控溅射法在自然氧化的单晶Si（100）基底上制备了（FePL／Ag）10多层薄膜,并在10kA／m磁场中进行了不同温度的真空热处理,研究了磁场作用下,不同热处理温度对FePt薄膜有序化转变及磁性能的影响。X射线衍射研究表明,在磁场作用下通过多层膜设计可以比较容易获得垂直生长的易磁化轴;选择适当的热处理温度、降低多层膜中每层膜厚可以制备出晶粒尺寸细小均匀的FePL／Ag垂直磁化薄膜,适用于高密度垂直磁记录介质材料。     

热处理对放电等离子烧结NdFeB永磁材料的影响

采用放电等离子烧结技术(spark plasma sintering,简称SPS)制备了高性能新型NdFeB永磁材料.研究了热处理工艺对SPS NdFeB磁体的组织和性能影响,采用扫描电镜、B-H回线仪研究磁体的显微组织和磁性能.结果表明,不同烧结温度的SPS烧结体对不同温度的热处理表现出同样的规律性,最佳热处理温度为1050℃.SPS NdFeB磁体的热处理过程,富稀土相成分和结构发生改变.在优化工艺条件下制备出最佳性能为Br=1.351T,Hci=674.4kA·m-1,BHm=360.4 kJ·m-3的新型SPS NdFeB磁体.     

晶化热处理条件对Nd2(FeCo)14B/α-Fe纳米复合材料磁性能的影响

用熔体快淬和晶化处理的方法制备了Nd2(FeCo)14B／α-Fe纳米复合材料。研究了晶化热处理温度和时间对材料磁性能的影响。结果表明Nd2Fe35.5Co2B4.5纳米复合材料的磁性能随热处理条件而变化．较高温度短时间比较低温度长时间热处理样品的磁性能稍好一些，并对其机理进行了研究。     

核壳型磁载TiO2/CoFe2O4光催化剂的制备与性能研究

纳米TiO2是一种高效的光催化剂,为了解决TiO2纳米颗粒从悬浮体系中分离回收难的问题,可将其包覆于磁性微球之外,借助于磁场的作用实现快速有效地分离.以尖晶石型CoFe2O4为磁核,制备了核壳型纳米磁性TiO2/CoFe2O4光催化剂,通过水浴恒温条件、热处理温度的改变,以及工艺的调整优化了催化剂的制备工艺.采用XRD和TEM分析了催化剂的结构与形貌.研究发现,水浴90℃恒温2h、600℃热处理后的TiO2/CoFe2O4在降解TNT时表现出了较高的催化活性.表明合适的反应时间和热处理温度是影响催化剂活性的关键因素.     

稳恒强磁场热处理对钴铁氧体结构和磁性能的影响

在强磁场下对钴铁氧体纳米粉末压块进行了热处理,分析讨论了热处理温度和磁感应强度对钴铁氧体的结构和磁性能的影响.结果表明,强磁场退火有利于钴铁氧体结晶度的提高和磁性能的增强,在居里点附近550℃下磁场处理作用效果最强,磁场强度越大,作用效果越明显.     

静电纺丝法制备的Co0.6Ni0.3Cu0.1Fe2O4和Co0.6Ni0.3Zn0.1Fe2O4纳米纤维的结构及磁性能

采用静电纺丝技术制备出表面光滑、直径均匀的Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4/PVP和Co_(0.6)Ni_(0.3)Zn_(0.1)Fe_2O_4/PVP纳米纤维前驱丝,经500~900℃煅烧后得到Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4和Co_(0.6)Ni_(0.3)Zn_(0.1)Fe_2O_4纳米纤维。用TG-DSC、XRD、SEM及VSM现代测试分析手段对Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4和Co_(0.6)Ni_(0.3)Zn_(0.1)Fe_2O_4纳米纤维的结构、形貌及磁学性能进行测试表征。结果表明:在空气气氛中经500~900℃煅烧后可得到纯尖晶石相、结晶度良好的纳米纤维或短纤维;当温度为700℃时,Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4和Co_(0.6)Ni_(0.3)Zn_(0.1)Fe_2O_4纳米纤维的形貌细长而光滑且直径相对均匀,大约为80nm;此时Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4纳米纤维则保有较高的剩磁比(M_r/M_s)及矫顽力,分别为0.56和1 088.87Oe。在500℃、600℃、700℃、800℃、900℃煅烧后,Co_(0.6)Ni_(0.3)Zn_(0.1)Fe_2O_4纳米纤维的饱和磁化强度分别比Co_(0.6)Ni_(0.3)Cu_(0.1)Fe_2O_4纳米纤维增大了14.5%、7%、16%、10.7%、8%,而矫顽力则分别降低了38%、51%、50%、46%、46.7%。两种纳米纤维的饱和磁化强度及矫顽力存在差异,为CoNi铁氧体在电磁方面的应用提供了很好的参考。     

反应物量对燃烧合成Ni-Zn铁氧体粉的影响

为探讨燃烧合成法制备Ni0.4Zn0.6Fe2O4粉末工业化放大合成的可行性,研究不同反应物量对燃烧合成制备的Ni0.4Zn0.6Fe2O4粉体及烧结后产物的物相、微观形貌及磁性能的影响,对终产物进行XRD、SEM和EDS分析,对样品经行磁性能测试.结果表明:Fe-Fe2O3-Zn O-Ni O体系燃烧合成过程是以扩散-溶解-析出机制进行的,燃烧反应在非平衡条件下进行,燃烧产物的主要物相为Ni-Zn铁氧体,其中存在Zn O及一些铁的氧化物的杂质,产物经热处理后物相全部转变为尖晶石结构;随着反应物量的增加,产物颗粒尺寸增大,均匀度增加,反应物量的增加对产物的磁性能影响不大;随着反应物量的增加,饱和磁化强度逐渐增加,矫顽力基本不变,反应物量为1 500 g时制备的产品磁性能最佳,具有较高的饱和磁化强度Ms=63.72 emu/g和较低的矫顽力Hc=15.61 Oe.     

纳米Fe3O4/聚苯胺复合粒子的制备及其在交变磁场下的发热性能

用水解沉淀法合成了纳米Fe₃O₄粒子,并在其悬浮液中原位包覆聚苯胺,制备出纳米Fe₃O₄/聚苯胺复合粒子。研究了两种纳米粒子在交变磁场下的发热性能,对它们在定向集热治疗肿瘤中的应用前景进行了评价。纳米Fe₃O₄粒子的粒径为10~30nm,表面包覆聚苯胺后,复合粒子的粒径为30~50nm。纳米Fe₃O₄粒子的比饱和磁化强度为50.05Am2/kg,矫顽力为10.9kA/m;纳米Fe₃O₄/聚苯胺复合粒子的比饱和磁化强度为26.34Am2/kg,矫顽力为0。在10mg/mL的生理盐水悬浮液中,在外加交变磁场作用30min后,纳米Fe₃O₄粒子悬浮液的温度为63.6℃,纳米Fe₃O₄/聚苯胺悬浮液的温度为52.4℃,二者均达到了医学上定向集热治疗肿瘤用热籽的发热要求,是很有应用前景的医用纳米材料。      

参杂尖晶石型镍基铁氧体的磁性能与介电性能

采用溶胶-凝胶法制备了立方晶系尖晶石型镍基铁氧体微粉Ni0.5M0.5Fe2O4（M=Zn、Mn、Cu）,采用X射线衍射仪、扫描电子显微镜、振动样品磁强计和矢量网络分析仪对粉末的结构、形貌、磁性以及电磁性能进行了表征,结果表明,三种粉末在室温下具有超顺磁性,其饱和磁化强度MS分别为76．0、59．4和54．4emu·g-1。在2—11GHz范围内,Ni0.5M0.5Fe2O4的电磁损耗角正切值tgδ随频率的增大而逐渐减小;Ni0.5M0.5Fe2O4和 Ni0.5M0.5Fe2O4的tgδ随频率的增大先增大后减小。     

Magnetic and catalytic properties of Cu0.5Zn0.5Fe2O4 nanocrystallite powders

Cu0.5Zn0.5Fe2O4 nanocrystallite powders (average size 13 nm) were synthesized from Cu-Zn spent catalyst (fertilizers) industries and ferrous sulfate wastes formed during iron and steel making. Cu-Zn catalyst (22.4% Cu and 26.4% Zn) was chemically treated with sulfuric acid at temperature 80 degrees C for 1 hr for the complete dissolving of copper and zinc into sulfate solution, then the produced solution was mixed with stoichiometric ratio of ferrous sulfate and the mixture was chemically precipitated as hydroxides followed by hydrothermal processing. The parameters affecting the magnetic properties and crystallite size of the produced ferrites powder e.g., temperature, time, and pH were systemically studied. X-ray diffraction analysis was used in order to determine the average crystallite size and phase identifications of the produced powder. The magnetic properties were studied by vibrating sample magnetometry. The results showed that the average crystallite size of the powder decreased for the ferrites powder formed at 150 degrees C and then increased by increasing the temperature to 200 degrees C. Interestingly, the saturation magnetization (Bs), remanent magnetization (Br) and coercive force (Hc) were 25.03 emu/g, 0.71 emu/g, and 4.83 Oe, respectively at hydrothermal temperature 150 degrees C for 24 hr and changed to 16.38 emu/g, 0.3864 emu/g, and 5.2 Oe at 150 degrees C and 72 hr. The produced nanoferrite powders are used for studying the catalytic activity of CO conversion to CO2 at different temperatures, pH and times. The maximum conversion (82%) is obtained at temperature 150 degrees C for 24 hrs and pH 12.     

Synthesis of highly stable graphite-encapsulated metal (Fe, Co, and Ni) nanoparticles

Graphite-encapsulated metal magnetic nanoparticles have been attracted for biological applications because of their high magnetization of the encapsulated particles. However, most of the synthetic methods have limitations in terms of scalability and economics because of the demanding synthetic conditions and low yields. Here, we show that well-controlled graphite-encapsulated metal (Fe, Co, and Ni) nanoparticles can be synthesized by a hydrothermal method, simply by mixing metal source with sucrose as a carbon source. The saturation magnetization (Ms) values of Fe/C, Co/C, and Ni/C were 86.6, 43.8, and 113.1?emu/g, respectively. The Fe/C and Ni/C showed higher Ms values than bulk Fe₃O₄ (75.5?emu/g). The graphite-encapsulated metal nanoparticles showed good stability against acid and base environments.     

Preparation and structural characterization of vulcanized natural rubber nanocomposites containing nickel-zinc ferrite nanopowders

Single-phase polycrystalline mixed nickel-zinc ferrites belonging to Ni0.5Zn0.5Fe2O4 were prepared on a nanometric scale (mean crystallite size equal to 14.7 nm) by chemical synthesis named the modified poliol method. Ferrite nanopowder was then incorporated into a natural rubber matrix producing nanocomposites. The samples were investigated by means of infrared spectroscopy, X-ray diffraction, scanning electron microscopy and magnetic measurements. The obtained results suggest that the base concentration of nickel-zinc ferrite nanoparticles inside the polymer matrix volume greatly influences the magnetic properties of nanocomposites. A small quantity of nanoparticles, less than 10 phr, in the nanocomposite is sufficient to produce a small alteration in the semi-crystallinity of nanocomposites observed by X-ray diffraction analysis and it produces a flexible magnetic composite material with a saturation magnetization, a coercivity field and an initial magnetic permeability equal to 3.08 emu/g, 99.22 Oe and 9.42 x 10(-5) respectively.     

过渡金属(Mn2+、Ni2+、Fe3+、Cu2+)掺杂ZnO基稀磁半导体的制备及性质

利用溶液腐蚀法制备了Mn2+、Ni2+、Fe3+、Cu2+离子掺杂的ZnO基稀磁半导体。XRD表明掺杂后的ZnO仍然保持单一的纤锌矿结构,没有任何杂质相产生。由紫外-可见光反射谱可知掺杂后吸收边发生了红移。掺杂前ZnO的带隙为3.20eV,对样品分别掺入Mn、Ni、Fe和Cu后的带隙分别为3.19eV、3.15eV、3.08eV和3.17eV。掺杂后样品的室温PL谱除了紫外发射峰外,对于Mn掺杂的样品还在蓝光区域出现了2个分别位于424nm和443nm的发射峰,Fe掺杂的样品出现了一个位于468nm的微弱发射峰,Cu掺杂的样品出现了位于469nm及535nm的很宽的发射峰。室温磁滞回线显示掺杂后样品有明显的铁磁性,掺入Mn、Ni、Fe和Cu样品的剩余磁化强度(Ms)分别为0.3902×10-3emu/cm3、0.454emu/cm3、0.372emu/cm3和0.962×10-3emu/cm3,矫顽力分别为47Oe、115.92Oe、99.33Oe和23Oe。经分析室温铁磁性来源于缺陷调制的Mn2+-Mn2+长程铁磁交换相互作用。     

Preparation of α-Fe_2O_3 Nanodisks by Blocking the Growth of (001) Plane

Based on the difference of hydroxy group configuration on different planes of α-Fe2O3 nanoparticles, using the special adsorption and coordination of phosphate on the (001) plane of α-Fe2O3, well-crystallized and well dispersed α-Fe2O3 nanodisks with diameter of 150–200 nm and thickness of 40–80 nm were synthesized via a hydrothermal method. The magnetic properties of synthesized nanodisks were investigated. It was found that the nanodisks possessed a saturation magnetization (Ms) of 0.38 emu/g, a remanent ...     

纳米MnFe2O4·Fe3O4固溶体的制备及其电磁性能研究

二乙酰二茂铁苯二甲酰腙聚合物在DMSO中与氯化锰反应合成二乙酰二茂铁二甲酰腙-Mn配位聚合物(PFZMn),高温(400、600及1200℃)热解制得MnFe2O4.Fe3O4固溶体;采用XRD、TEM、超导量子强磁计(SQUID),高频、微波下(0.1～1.8GHz)对固溶体进行表征。结果表明1200℃热解所得的固溶体为纳米强磁体,它在5及300K的饱和磁化强度(Ms)、剩磁(Mr)及矫顽力(Hc)分别为62.80及49.30emu/g;5.13及3.15emu/g和305及268Oe。而在0.1～1.8GHz有较高的电磁参数(1GHz时,),及较低的电磁损耗(1GHz下,μr′=6×10-3,εr′=2.5×10-2)。