HjGMn衬板与高铬铸铁磨球配副的试验研究

本文论述了HjGMn衬板与高铬铸球在2.7×4m一级圈流磨上配副使用的试验过程,探讨了提高高锰钢材料耐磨性及使用寿命的相关技术途径。

Effects of high-energy ball milling oxide-doped and varistor ceramic powder on ZnO varistor

ZnO varistor ceramics doped with Bi2O3, Sb2O3, CO2O3, Cr2O3, and MnO2 were prepared separately by two high-energy ball milling processes： oxide-doped and varistor ceramic powder. A comparison in the electrical and microstructural properties of the samples obtained by both methods was made. The best results on these characteristics were achieved through the high-energy ball milling varistor ceramic powder route, obtaining a nonlinear coefficient of 57 and a breakdown field of 617 V/mm at a sintering temperature of 1000 ℃ for 3 h. The samples synthesized by this technique show not only high density value, 95% of the theoretical density, but also a homogeneous microstructure, which compete with those obtained by the high-energy ball milling oxide-doped powder route. With the advantage that the high-energy ball milling varistor ceramic powder route can refine grain, increase the driving force of sintering, accelerate the sintering process, and reduce the sintering temperature.

Influence of TiC catalyst on absorption/desorption behaviors and microstructures of sodium aluminum hydride

TiC-doped NaA1H4 complex hydrides were prepared by hydrogenation of ball-milled Nail/A1 mixture with x TiC powder （x = 0, 5%, 8%, 10%, mole fraction）. The effects of TiC catalyst content on the absorption/desorption behaviors of the samples were investigated. The results show that TiC can improve the hydriding/dehydriding kinetics of sodium aluminum hydride, the hydriding rate of the sample increases with increasing TiC content. It is found that the TiC-doped NaA1H4 composites have a relatively good cyclic stability. The composite doped with 10% TiC maintains steadily about 4.5% （mass fraction） hydrogen absorption capacity as against about 3.8% （mass fraction） hydrogen desorption capacity over 8 cycles. The particle sizes of the TiC-doped NaA1H4 composites can be reduced to 50-100 nm, which may play an important role in improving the hydriding/dehydriding kinetics.

Preparation and characterization of amorphous boron powder with high activity

The amorphous boron powders with high activity were prepared by the high-energy ball milling-combustion synthesis method. The effects of the milling rate and milling time on the crystallinity, microscopic morphology and reactivity of amorphous boron powder were studied. The results show that the crystallinity of amorphous nano-boron powder is only 22.5%, and its purity reaches 92.86%. The high-energy ball milling can significantly refine boron powder particle sizes, whose average particle sizes are smaller than 50 nm, and specific surface areas are of up to 70.03 m2/g. When the transmission electron beam irradiates the samples, they rapidly melt. It can be seen that the monomer amorphous boron size is less than 30 nm from the specimen melting traces, which indicates that the samples have high reactivity.

Electrochemical properties of nanocrystalline and amorphous Mg-Y-Ni alloys applied to Ni-MH battery

The as-cast Mg2Ni-type Mg20–xYxNi10 (x=0, 1, 2, 3 and 4) electrode alloys were prepared by vacuum induction melting. Subsequently, the as-cast alloys were mechanically milled in a planetary-type ball mill. The analyses of scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) reveal that nanocrystalline and amorphous structure can be obtained by mechanical milling, and the amount of amorphous phase increases with milling time prolonging. The electrochemical measurements show that the discharge capacity of Y0 alloy increases with milling time prolonging, while that of the Y-substituted alloys has a maximum value in the same condition. The cycle stabilities of the alloys decrease with milling time prolonging. The effect of milling time on the electrochemical kinetics of the alloys is related to Y content. Whenx=0, the high rate discharge ability, diffusion coefficient of hydrogen atom, limiting current density and charge transfer rate all increase with milling time prolonging, but the results are exactly opposite whenx=3.

Hydrogen storage performances of as-milled REMg_(11)Ni(RE=Y, Sm) alloys catalyzed by MoS_2

To compare the hydrogen storage performances of as-milled REMg11Ni-5MoS2(mass fraction)(RE=Y,Sm)alloys,which were catalyzed by MoS2,the corresponding alloys were prepared.The hydrogen storage performaces of these alloys were measured by various methods,such as XRD,TEM,automatic Sievert apparatus,TG and DSC.The results reveal that both of the as-milled alloys exhibit a nanocrystalline and amorphous structure.The RE=Y alloy shows a larger hydrogen absorption capacity,faster hydriding rate,lower initial hydrogen desorption temperature,superior hydrogen desorption property,and lower hydrogen desorption activation energy,which is thought to be the reason of its better hydrogen storage kinetics,as compared with RE=Sm alloy.

Effect of ball milling time on microstructures and mechanical properties of mechanically-alloyed iron-based materials

The microstructures and mechanical properties of an iron-based alloy (Fe-13Cr-3W-0.4Ti-0.25Y-0.30O) prepared by mechanical alloying were investigated with scanning electron microscope,optical microscope,X-ray diffractometer and hardness tester.The results show that the particle size does not decrease with milling time because serious welding occurs at 144 h.The density of the alloy sintered at 1 523 K is affected by the particle size of the powder.Finer particles lead to a high sintered density,while the bulk density by using particles milled for 144 h is as low as 70%.In the microstructures of the annealed alloy,large elongated particles and fine equiaxed grains can be detected.The elongated particle zone has a higher microhardness than the equiaxed grain area in the annealed alloys due to the larger residual strain and higher density of the precipitated phase.

Effect of ball-milling parameter on mechanical and damping properties of sintered Mg-Zr alloy

Effects of ball-milling parameter on structures and properties of sintered Mg-l.5Zr （mass fraction, %） alloy were researched by metallographic analysis, mechanical properties tests and DMA technology. The results indicate that with 310 r/min rotation speed, the microstructure of the sintered alloy is greatly refined, and Zr-phase distributes uniformly. The micro-hardness, bending strength and damping capacities are the greatest under 310 r/min rotation speed. The damping peak of sintered Mg-l.5Zr alloy increases with increasing frequency under the testing conditions. The relaxation time meets the Arrhenius relationship, and shows the characteristics of relaxation damping.

Nondestructive evaluation of mechanical properties of nanostructured Al-Cu alloy at room and elevated temperatures

The influence of processing variables on the mechanical properties of a nanostructured Al-10 wt.%Cu alloy was investigated.Stress-strain microprobe®system(SSM)and its automated ball indentation®(ABI®)test were used for evaluating the mechanical properties of this alloy.The tests were conducted at 21℃ on the bulk samples that were mechanically alloyed for 6 h at two ball-to-powder mass ratios(BPR)of 30:1 and 90:1.Furthermore,the tests were conducted at 200 and 400℃ on the samples that were processed at BPR of 90:1.Increasing BPR resulted in raising the final indentation load from(316±26)to(631±9)N and reducing the final indentation depth from 111 to 103μm.Regarding the samples that were processed at BPR of 90:1,increasing the test temperature from 21 to 400℃ resulted in decreasing the final load from(631±9)to(125±1)N and increasing the final depth from 103 to(116±1)μm.The sample processed at BPR of 90:1 and tested at 21℃ revealed the highest strength and the least deformability while the sample processed at BPR of 90:1 and tested at 400℃ exhibited the lowest strength and the greatest deformability,as compared to all samples under study.

Mechanical properties of Cu matrix composite fabricated by extrusion process

Carbon nanotube （CNT）was applied in various fields for itssuperior electrical, mechanical and thermal characteristics. After composites were fabricated by extrusion processusing ball-milledCu-CNT powders, mechanicalpropertiesofCu-CNT composites according to CNT fraction were reviewed. CNT （1%, 5% and 10%）,Cu （d=100 nm）, zirconia balls （90 g） and ethanol （20mL） were mixed and dispersed for5h at a speed of 500 r/minusing a planetary ball mill. A billet （d=50 mm, length=100 mm） was made with Cu, and the composite powderswerefilled up into billet using the uni-axial press. In the extrusion process, after the billet was heated at 880℃for1h, specimens were produced in the shape of a round bar using the billet by applying a load of 200 t. The composite powdersweremeasured for particle size byparticlesize distributionequipment. Then the specimen surface fabricated by extrusion was observed by SEM. Mechanicalpropertiesmeasured by the indentation equipment increased with increasing CNT content. The yield strength, tensile strength and hardness of theCu–CNTs composites canbeobviously improved.

Studies of Structure, Microstructure and Magnetic Properties of Fe70Si20Cr10 Nanocrystalline Alloy

Nanostructured Fe70Si20Cr10 alloy was produced by high energy planetary ball milling, starting from elemental powders. The structural, microstructural and magnetic properties of the milled powders were characterized by X-ray diffraction, scanning electron microscopy, vibrating sample magnetometer and 57Fe M6ssbauer. After 5 h of milling, it is observed the formation of a bcc solid solutions ~t-Fe （Si, Cr）. Its grain size decreases with increasing milling time attaining 20 nm after 15 h of milling time. Analysis of M6ssbauer spectra shows an increasing broad magnetic component when the milling time increases. Its mean hyperfme field is about 25.5 T at 15 h of milling. M-H hysteresis loop curves reveal a room temperature ferromagnetic behaviour with a saturation magnetisation reaching 143 emu/g after 15 hours of milling, which is 20% lower than that of bulk iron; i.e., 1800 emu/g, due to effect of alloying elements after the formation of ct-Fe （Si, Cr） solid solution.

Size Reduction of Hydrophobically Modified Starch on Beads Mill： Effect of Dispersing Medium and Milling Time

The primary interest to this study was to investigate the effect of milling parameters on the size of hydrophobically modified starch particles, aiming to produce small, uniformly sized modified starch microspheres. Octie, a commercial product originated from cornstarch modified using Octenyl Succinate Anhydride （OSA）, was dispersed （3 wt%） using different media （water or ethanol） and subsequently wet-milled using a beads mill with zirconium beads at a rotation of 6,000 rpm up to 30 min. It was found that milling Octie in water dispersion for 3 min resulted in the smallest mean particle size （2.04 i 0.91 ktm）, compared to unmilled modified starch granules （15.2 ~ 6.0 lam）. Granular size and morphology changed considerably with further milling. For instance, very dense clusters with variable particle sizes （20.6 ~ 10.0 lam） were obtained after 30 min milling. As depicted by Scanning Electronic Microscopy, a large number of particles were apparently flattened during the milling process rather than broken, forming aggregates. Ultimately, within the range of experimental conditions tested, production of sub-micron modified starch particles was not possible.

Defective MoS_2 electrocatalyst for highly efficient hydrogen evolution through a simple ball-milling method

Molybdenum disulfide（MoS2） has attracted extensive attention as an alternative to replace noble electrocatalysts in the hydrogen evolution reaction（HER）. Here, we highlight an efficient and straightforward ball milling method,using nanoscale Cu powders as reductant to reduce MoS2 engineering S-vacancies into MoS2 surfaces, to fabricate a defectrich MoS2material（DR-MoS2）. The micron-sized DR-MoS2 catalysts exhibit significantly enhanced catalytic activity for HER with an overpotential（at 10 mA cm^-2） of 176 m V in acidic media and 189 m V in basic media, surpassing most of Mo-based catalysts previously reported, especially in basic solution. Meanwhile stability tests confirm the outstanding durability of DR-MoS2 catalysts in both acid and basic electrolytes. This work not only opens a new pathway to implant defects to MoS2, but also provides low-cost alternative for efficient electrocatalytic production of hydrogen in both alkaline and acidic environments.