The Physical Properties Of Ferrite Nanomaterials And Preparation Of Ordered Porous Alumina Template

As a new kind of materials, ferrite nano-materials take on unique properties, which are different from other ordinary materials, including physical, chemical, electromagnetic properties, and have been widely applied in recording medium, information storage, magneto-optical devices and microwave absorption materials. Ferrite nano-materials are widely applied, which have great value in all kinds of national economic fields, and have developed into several tens of billions of dollars industries, and become an important substantial backbone driving world economy and society development, and their preparation and magnetic properties have become one of the important focuses in domestic and international study.In recent years, with the development of science and technology, ferrite nano-materials have been more widely applied meanwhile more and more performance demanding requirements are need. In order to improve the performances of ferrite, the majority of studies are based on synthesis and doping different element, which directly decide the performance of ferrite, because the component and structure are dependent on preparation process. In this dissertation, the hexangular M type strontium ferrite and nano-crystal Ni-Zn ferrite were successfully synthesized by microwave-assisted sol-gel method and ceramic technique, respectively. XRD, IR, SEM and VSM were used to investigate the variety regularity of synthetic materials in terms of structure,phase transformation,particle size and magnetic properties. The main study content and innovations in the paper include the following aspects:(1) The study on magnetic properties of permanent ferriteThe synthetic processes of nano-crystal strontium ferrite prepared by microwave-assisted sol-gel method were systemically studied, and the as-prepared samples were annealed by two steps method, and the influence of calcining heat on magnetic property were also studied. The phase,morphology and magnetic properties of the as-synthesized samples were characterized by XRD,SEM and VSM. The results show that:the as-prepared nano-crystal strontium ferrites take on a single hexagonal magneto-plumbite structure; the magnetization curve has very obvious wasp waist and high coercivity, and the sample take on representative ferrous magnetic property; with the temperature increasing, saturation magnetization of samples increase slightly and coercivity decrease, which very benefits to the application of strontium ferrite in high-density magnetic recording materials; the average grain size of the hexagonal strontium ferrite synthesized by annealing at 1100℃for 5h is about 100-150nm.(2) The physical properties study of soft ferriteNano-crystal Ni-Zn ferrites with doping Ni were prepared by ceramic technique, sintering at 900℃for 2h, and the influences of doping Ni on the physical properties of nano-crystal Ni-Zn ferrite were studied also. The as-synthesized samples were characterized by XRD,IR,SEM and VSM. The results show that:the as-synthesized Ni-Zn ferrite take on spinel structure; The absorption peak around 577.76cm-1 and 418.86cm-1 is the characteristic stretching vibration of octahedron and tetrahedron in Ni-Zn ferrite, furthermore when x=0.6, the characteristic absorption peak is stronger than that when x=0.4; magnetization curves of samples take on thin, the saturation magnetization is high, according with that of bulk materials; the as-prepared Ni-Zn ferrite nano-particles take on quasi-spherical type, the grain size is about 80-100nm, and the size of particles is generally uniform, which is very different from the amorphous nano-powders prepared by majority of other scholars using other means calcining at abouve1000℃.(3)The preparation of ordered porous alumina templateAccording to two step electrochemical anodization method, ordered porous alumina membranes of highly regular structure were prepared on the surface of high purity aluminum. The holes of as-prepared aluminum oxide membranes distribute very regularly. The holes arrange parallel, their diameter and density are respectively 40nm and 5×1010个/cm2, the aperture arrange densely in terms of hexagon, the center distance among holes is about 60nm, the axes of holes are vertical to the their surface. At last, the formation mechanism of ordered porous alumina template is also investigated.