球磨诱发AlN陶瓷微观结构的演变

通过球磨可以极大地细化AlN陶瓷的晶粒尺寸,透射电镜（TEM）观察的结果表明,经过40h的球磨后,晶粒尺寸由原始的40μm减小到30-200nm,高分辨电镜（HREM）观察表明,球磨过程中在大晶粒内形成了高密度的位错和很高的微应变,晶粒细化是一个通过位错产生,运行和重排蛤使大晶粒分解为亚晶粒的塑性变形过程,在晶粒细化的同时,在磨球的剧烈作用下,AlN颗粒表面层晶格发生重畸变,甚至失去其固有结构特征。     

基于径向基函数神经网络的铣刀磨损监控技术的研究

提出一种基于径向基函数神经网络的铣刀磨损监控方法,径向基函数神经网络的输出是刀具磨损的具体值,这样有利于对刀具磨损进行各种实时补偿。实验表明,利用径向基函数神经网络进行状态识别可对小型立铣刀的磨损进行监控,能够取得良好的效果,同时证明RBF网络的训练速度优于BP网络。     

圆周铣削参数多目标模糊优化建模

金属切削加工参数优化问题本质上是一个模糊问题。分析了圆周铣削传统优化模型的缺点 ,建立了圆周铣削参数多目标模糊优化模型 ,并根据模糊集合原理 ,将其转化为一个传统的单目标约束优化问题 ,从而可用任一非线性规划求解器进行求解。算例表明 ,模糊优化解具有优越性。     

宏程序在垫块零件铣削加工中的应用

宏程序是通过循环语句和变量的控制实现规则曲面的加工,它具有修改方便,易读性好,程序段短等优点,在实际生产中占有一席之地。垫块零件是企业中急需的备件,采用合理的宏程序对垫块零件进行加工,可以提高加工效率,也可以为相关技术人员提供参考。     

磁场下球磨处理各向异性纳米级Sm2Co17磁粉的制备与分析

2∶17型SmCo稀土永磁合金以良好的温度特性和较高的磁性能已成为不可或缺的高温永磁器件,通过球磨工艺,利用有机试剂庚烷和油酸对2∶17型Sm(CobalFe0.07Cu0.088Zr0.025)7.5磁粉表面包覆预处理,并在磁场强度为1.5T的外磁场下,对该磁粉进行细磨0.5～20h,制备得到厚度为20～100nm、具有各向异性能的纳米级磁片,其对应的磁性能(BH)m为127.36kJ/m3。     

MoO3 nanoparticles distributed uniformly in carbon matrix for supercapacitor applications

A highly uniform nanocomposite of MoO₃ and carbon with a weight ratio of 1:1 is prepared by employing a simple procedure of ball milling. Such composite as electrochemical pseudocapacitor materials for potential energy storage applications exhibits a high specific capacitance of ~ 179 F/g at a charge and discharge current density of 50 mA/g with excellent cycling ability over 1000 cycles. Compared with the capacitance of pure milled graphite (~ 22 F/g) and MoO₃ (< 10 F/g), an enhanced electrochemical performance of the composite with a weight ratio of 1:1 is attributed to its unique structure, in which MoO₃ nanoparticles (with a size range of 1-180 nm) are uniformly dispersed in an electrically conductive carbon host.     

高分散多壁碳纳米管增强铝基复合材料的制备(英文)

采用机械合金化技术制备高分散多壁碳纳米管(MWCNTs)-铝(Al)复合材料。将纯度99%的铝粉和质量分数2%的MWCNTs经超声和水平球磨处理使Al颗粒与MWCNTs间产生机械键合力。场发射SEM观察表明,MWCNTs分散在Al薄片的表面,随球磨时间的不同,颗粒大小和形貌各异。采用加压烧结手段将混合粉末加工成块体材料,其微观硬度测试表明,加入MWCNTs后Al基体的机械性能得到提高。     

MgH2–Nb2O5 investigated by in situ synchrotron X-ray diffraction

In situ real time synchrotron radiation powder X-ray diffraction (SR-PXD) experiments are utilized to study changes in the crystalline compounds under dynamic hydrogenation and dehydrogenation reactions of MgH₂ ball milled with 8 mol% Nb₂O₅. The ball milling conditions were systematically varied to prepare three samples with different reactivity. Up to eight full cycles of hydrogen release and uptake were investigated for each sample, which reveal that Nb₂O₅ reacts with Mg forming a ternary oxide, Mg_xNb_1−xO. The PXD data for the ternary oxide is similar to that observed for the isostructural compounds MgO and NbO although shifted to lower Bragg diffraction angles revealing an expansion of the unit cell. Rietveld refinements suggest that Mg_xNb_1−xO has a limiting composition of x ∼ 0.6 after eight cycles of hydrogen release and uptake. At elevated temperatures Nb(II) is reduced to metallic Nb(0) and extracted from the ternary oxide and forms in a reaction with Mg. This work suggests that a ternary solid solution Mg_xNb_1−xO is the active material responsible for the prolific kinetic properties for the additive Nb₂O₅. Mg_0.6Nb_0.4O has a ∼4.6% larger unit cell volume as compared to the binary oxides, MgO and NbO, which may lead to formation of cracks and hydrogen diffusion pathways in dense magnesium oxide surface layers.     

Hydrogen sorption in MgH2-based composites: The role of Ni and LiBH4 additives

In the present work we investigate the hydrogen sorption properties of composites in the MgH₂–Ni, MgH₂–Ni–LiH and MgH₂–Ni–LiBH₄ systems and analyze why Ni addition improve hydrogen sorption rates while LiBH₄ enhance the hydrogen storage capacity. Although all composites with Ni addition showed significantly improved hydrogen storage kinetics compared with the pure MgH₂, the fastest hydrogen sorption kinetics is obtained for Ni-doped MgH₂. The formation of Mg₂Ni/Mg₂NiH₄ in Ni-doped MgH₂ composite and its microstructure allows to uptake 5.0 wt% of hydrogen in 25 s and to release it in 8 min at 275 °C. In the MgH₂–Ni–LiBH₄ composite, decomposition of LiBH₄ occurs during the first dehydriding leading to the formation of diborane, which has a Ni catalyst poison effect via the formation of a passivating boron layer. A combination of FTIR, XRD and volumetric measurements demonstrate that the formation of MgNi₃B₂ in the MgH₂–Ni–LiBH₄ composite happens in the subsequent hydriding cycle from the reaction between Mg₂Ni/Mg₂NiH₄ and B. Activation energy analysis demonstrates that the presence of Ni particles has a catalytic effect in MgH₂–Ni and MgH₂–Ni–LiH systems, but it is practically nullified by the addition of LiBH₄. The beneficial role of LiBH₄ on the hydrogen storage capacity of the MgH₂–Ni–LiBH₄ composite is discussed.     

Fe73.5Cu1Nb3-xTixSi13.5B9 (x=0, 1, 2, 3)合金粉的结构与磁性

将Fe73.5Cu1Nb3-xTixSi13.5B9(x=0,1,2,3)合金快淬带进行高能球磨制成粉末样品,在550℃真空退火1h,研究了磁粉的相结构及磁性。结果表明,随球磨时间延长,不添加Ti的Fe73.5Cu1Nb3Si13.5B9合金中析出晶化相的晶格常数增大。添加Ti的Fe73.5Cu1Nb3-xTixSi13.5B9(x=0,1,2,3)合金在球磨60h后再退火,可以得到单一α-Fe(Si)软磁相,且随Ti含量增大,析出晶化相的晶格常数减小,饱和磁化强度增大、矫顽力降低。