Ball milling of stainless steel scrap chips to produce nanocrystalline powder

Nanocrystalline stainless steel powder was produced by ball milling of austenitic stainless steel scrap chips. The structural and morphological changes of samples during ball milling and after subsequent heat treatment were investigated by X-ray diffractometery, scanning electron microscopy and microhardness measurements. During ball milling the austenite in as-received chips partially transformed to the martensite phase with nanoscale size grains of ∼15 nm. This structure exhibited high microhardness value of about 850 Hv which is much higher than that for original samples. The deformation-induced martensite partially transformed to austenite after annealing at 700 °C for 1 h reducing the hardness of powder particles.     

Reactive ball milling to produce nanocrystalline ZnO

Ball milling of zinc powders in oxygen atmosphere leads to nanocrystalline ZnO. The average grain size has a value of 9 nm. The zinc oxidation proceeds gradually. It is compared with the combustion oxidation reactions of metals (Zr, Ti, Fe and Sn) reported previously. We propose a new parameter ΔH/C_p(metal) instead of simplified adiabatic temperature to judge if the mechanochemical oxidation of a particular metal happens via gradual or combustion reaction.     

Hydrothermal processings to produce magnetic particulates

α-Fe₂O₃, γ-Fe₂O₃ , and α-FeOOH powders were used as starting materials to prepare barium hexaferrite hydrothermally. Since strontium hexaferrite and lanthanum-doped calcium hexaferrite have coercivities similar to that of barium ferrite, the hydrothermal synthesis of strontium hexaferrite and lanthanum-doped calcium hexaferrite were also explored. The reaction products obtained with the various starting materials are described. Electron micrographs showed that α-Fe₂O₃, γ-Fe₂O₃, or α-FeOOH dissolved in the solution first, and then barium hexaferrite nucleated and grew from the solution     

Glasses as engineering materials: A review

Glass products have applications in design engineering, and they can solve many special problems. These materials can work in situations in which plastics and metals would fail and need to be part of designer’s repertoire. In some situations, by using these materials, some difficult problems would be solved. This paper contains a number of chapters as follows: a brief about ceramics family, a short history of glass, a brief about physics and the technology of glass fabrication, recently developed glasses with special destinations, testing methods and news about glass parts processing (grinding, waterjet processing, laser cutting, nanoimprint lithography, etc.). The last chapter of this review paper contain some strategic lines of glass usage in industry and estimations about the future of glass development.     

制备Co-P纳米粒子的新方法及其表征

采用化学镀技术制备了金属Co -P纳米粒子 ,元素分析表明 ,其成分为Co :95 6%、P :4 31%。由X -射线衍射确认晶相为六方密排Co。对其形状和大小进行了透射电镜和激光散射分析。确认Co -P纳米粒子为球形 ,平均粒径为 37 0nm。在正已烷中存在软团聚 ,团聚平均尺寸约 65 0nm。     

Electromagnetism as a means for understanding materials mechanics phenomena in magnetic materials

Electromagnetic properties are an interesting means for monitoring a variety of materials' mechanical properties in ferro‐ and paramagnetic materials non‐destructively. Those properties include uni‐ und multi‐axial stress states as well as plasticity and fatigue damage and can be measured at macro‐ as well as at microscopic scales, depending on what measurement equipment will be used. The article describes the general electromagnetic phenomena to be considered as well as the equipment to be used before presenting a variety of different experimental results from which the materials mechanical properties mentioned above can be directly derived being an ideal means for monitoring the health of any magnetic metallic structure.     

A critical review of magnetic recording materials

A review of the methods of preparation and the relevant properties of materials which the authors consider suitable for incorporation in conventional magnetic recording surfaces such as tapes, disks, drums, strips, and cards is provided. This field is presently dominated by one material, gamma ferric oxide in fine particle form, and so it is not surprising that this material is discussed at greater length than its potential rivals. The reasons for this dominance are considered and found to be 1) the ability of gamma ferric oxide recording surfaces to perform adequately in the recording systems which have been developed so far, i.e., the magnetic properties of the oxide have apparently not been the limiting factors in the performance of recording systems; 2) the relative cheapness of the particles; 3) the existence of suitable binder systems of proven durability; and 4) the need for compatibility with existing recording devices.     

Ball milling of barium ferrite in air and vacuum

The effects of prolonged milling in air and vacuum on BaFe₁₂O₁₉ ionic crystal structure and particles morphology have been analysed. X-ray diffraction, scanning electron microscopy and thermal analysis experiments show that for vacuum-milled material the ordered structure transforms progressively into a stable disordered nanocrystalline phase. For air-milled samples, apart from structural transformation, chemical decomposition was found.     

Superparamagnetism and other magnetic features in granular materials: a review on ideal and real systems

An overview on magnetic of nanostructured magnetic materials is presented, with particular emphasis on the basic features displayed by granular nanomagnetic solids. Besides a review of the basic concepts and experimental techniques, the role of structural disorder (mainly the distribution of grain sizes), interparticle magnetic interactions and surface effects are also discussed with some detail. Recent results, models and trends on the area are also discussed.     

制备C0-P纳米粒子的新方法及其表征

采用化学镀技术制备了金属Co-P纳米粒子,元素分析表明,其成分为Co95.6%、P4.31%.由X-射线衍射确认晶相为六方密排Co.对其形状和大小进行了透射电镜和激光散射分析.确认Co-P纳米粒子为球形,平均粒径为37.0nm.在正已烷中存在软团聚,团聚平均尺寸约65.0nm.     

A review and new perspectives for the magnetocaloric effect: New materials and local heating and cooling inside the human body

Nowadays, the magnetocaloric effect (MCE) is considered to be one of the most important fundamental thermodynamic effects to be employed in various technological applications. At present researchers focus mainly on environmentally-friendly magnetic materials and their applications in heating, refrigeration and magnetic energy conversion technologies. However, one must also pay attention to the increasing number of medical applications of the MCE, as e.g. controllable delivery and release of drugs and biomedical substances to defined locations in the human body, and applications of magnetic hyperthermia (cancer treatment). The first method demands local cooling of thermo-sensitive polymers in the body and the second induces local heating by a magnetic mechanism. In the first part of this article the recent progress in magnetocalorics (mainly on materials) is reviewed and the possibilities to increase the effect, e.g. by studying the interactions of magnetic and structural subsystems of magnetic materials in the vicinity of magnetic phase transitions and critical points, are outlined. To determine such and other important phenomena in the MCE, dynamic measurements have been developed. In the second part of the article the applications of the MCE in new methods, developed for applications in medical fields, as briefly mentioned above, are introduced and discussed. It is clear that a comprehensive overview on all important developments cannot be given here. Therefore, only the most important works are cited with a focus on important developments of Russian research. We ask those authors, who have contributed to the MCE and stay unmentioned in this review article, for their understanding.     

Xylitol-assisted ball milling of graphite to prepare long-cycle and high-capacity graphene nanosheet as lithium-ion anode materials

Journal of Materials Science - A simple and effective xylitol-assisted mechanochemical stripping method has been used to peel graphite into graphene nanosheets (GNSs). Using xylitol as a ball...     

Strong static magnetic field processing of metallic materials: A review

Metallic materials processing in an imposed strong static magnetic field (SSMF) has attracted widely attention in the last decade since a magnetic field of 10 T or higher becomes easily attainable. Fundamentals including magnetic energy, magnetic anisotropy and magnetic forces influence significantly the research and development of this technology by means of both scientific and engineering paths. The ability to control metallic materials processing depends crucially on the understanding of the fundamentals and subsequently the engineering of the strong magnetic field effects. This review provides a critical examination of different SSMF effects together with the fundamentals that can be used in liquid/solid metal controlling and the subsequent metallic materials preparation. These effects are discussed by integrating them into different technologies or experimental results and accompanied by theoretical considerations of the fundamentals. Comprehensive comparisons are then carried out for each series of SSMF effects. It is aiming to provide an overview of the recent progress in SSMF processing of metallic materials.     

The magnetic metrology of materials—A review

This paper gives a survey of the present state and new aspects of the measurement techniques for the characteristics of magnetic materials (except for recording materials) with several examples. Particular attention is paid to the aspects of reproducibility and traceability to SI units, and to the current trend of quality assurance and standardization.     

A review on Mn based materials for magnetic refrigeration: Structure and properties

Magnetic refrigeration employing magnetically ordered materials is a relatively novel technique, differing in some respects from magnetic cooling by means of adiabatic demagnetization of paramagnetic substances. Magnetic refrigeration has been known for more than a century and is based on the magnetocaloric effect. It has received new impetus recently because it has several advantages over vapor-compression refrigeration. In the last few years the magnetic and magnetocaloric properties of a large number of intermetallic compounds were investigated, in which the magnetic moments are carried by atoms of 3d transition elements. In the present paper we will focus on intermetallic compounds in which one of the components is Mn. The results obtained on several groups of such intermetallic compounds will be reviewed. By far the most promising materials of this group of intermetallics are compounds of the type MnFeP_1−xAs_x. Although it is understood that these compounds are probably nontoxic, the presence of As atoms in them might form a mental barrier to exploit these materials on a commercial basis. Special attention will therefore be paid to efforts attempting to substitute other elements for As in MnFeP_1−xAs_x with the proviso that the favorable magnetocaloric properties be retained.     

The structural and magnetic properties of Fe-Si and Fe-C solid solutions as a function of milling times

We have studied the formation of metal-metalloid alloys for Fe-Si and Fe-C as a function of milling times. These alloys were produced using mechanical alloying. The effect of milling time on local structural changes of Fe-Si and Fe-C has been investigated by means of Mössbauer spectrometry, EXAFS study and XRD. Saturation magnetization was also measured by VSM. XRD pattern from mechanically alloyed Fe-Si and Fe-C powders indicates the formation of solid solution. The different variation of lattice parameters could be analysed from the different substitution of Si and C atoms into the Fe structure. The Mössbauer spectrum showed typical sextets in the 1 h milled sample corresponding to alpha-Fe spectrum. Increasing the milling time, the sextets became broader due to appearance of disordered Fe atoms in both solid solutions. The hyperfine field distributions were decreased as increasing milling time, which is similar trend with magnetization distribution.     

Hydrocarbon decomposition in alumina membrane: an effective way to produce carbon nanotubes bundles

Carbon nanotubes were synthesised within the pores of an alumina membrane. The membrane had 200 nm diameter pores and 60 microm thickness, and ethylene was used as carbon source. Membrane dissolution by HF results in a bundle of parallel open tubes, aligned without macroscopic defects. The external diameter of the tubes is uniform and there is no evidence of any amorphous carbon. Wall thickness control was obtained by varying the reaction time, length by the thickness of alumina membrane, and external tube diameter by the membrane pore size. Scanning (SEM) and transmission (TEM) electron microscopy, atomic force microscopy (AFM), X-ray diffraction, thermogravimetric analysis (TG) and surface area evaluation by nitrogen adsorption were used for the characterization of membrane and nanotubes.