高温镍基合金电渣重熔过程中的Al、Ti成分控制

电渣重熔过程中Al和Ti的氧化导致电渣锭轴向成分不均匀,从而对电渣锭的耐腐蚀性能和力学性能产生不利影响。为了控制电渣铸锭中Al和Ti含量的均匀性,需要明确高温电渣重熔过程中Al和Ti含量的变化,并通过优化渣体系比例和冶炼条件来减少合金中Al和Ti的氧化。在现有文献的基础上,以CaF₂-CaO-Al₂O₃-MgO-TiO₂这一低氟渣系和Incoloy825合金为例,综述了电渣重熔过程中Al和Ti元素控制的研究现状。应用离子与分子共存理论（IMCT）,结合FactSage软件,总结了渣的热力学和动力学研究方法。讨论了温度和渣成分对合金中平衡Al、Ti含量的影响。基于膜渗透理论,提出了预测合金中Al和Ti含量的动力学模型,得到了电渣过程中Al和Ti含量随时间变化的数学方程式以及渣-金属反应速率的限制方法。确定电渣重熔Incoloy825合金时TiO₂的最佳添加量约为10％。用IMCT和FactSage对渣-金平衡实验结果进行了比较和分析。FactSage计算结果比IMCT计算结果更准确。TiO₂含量越高,计算结果与实验结果之间的偏差越小。     

物理-化学耦合活化法制煤基活性炭

以神府3#煤为原料,氢氧化钾为化学活化剂,水蒸气为物理活化剂,探讨了物理-化学耦合活化法制备煤基活性炭的工艺条件和耦合活化机理,考察了氢氧化钾与煤的浸渍比、活化温度及总活化时间对活性炭性能的影响.结果表明,当活化温度为700 ℃,碱渍比为0.5,活化时间为60 min时,活性炭的性能较好,碘吸附值为837 mg/g,亚甲基蓝吸附值为409 mg/g, BET比表面积943 m2/g,总孔容积达0.31 cm3/g,煤副产氢气约58 mmol/g.     

煤与大豆分离蛋白的接枝改性研究

研究了神府煤与大豆分离蛋白的接枝聚合反应 .考察了反应温度、反应时间、引发剂用量和 p H值等因素对接枝反应的影响 .通过凯氏定氮法对接枝产物氮含量的测定发现 ,接枝煤的氮含量较原煤提高了 1 .75倍 ;TG,DTG,DSC分析发现接枝煤较未接枝样在 2 4 0℃出现了明显的变化 ;红外光谱谱图中也增加了酰氨基的伸缩振动吸收峰及游离的 NH2 的弯曲振动吸收峰 .证明了在硝酸铈铵的作用下 ,煤可以与大豆蛋白发生接枝聚合     

Structural and magnetic characterizations of Co2MnO4 doped with Cr,Mn, Fe and Cu

The structural and magnetic properties of Co_2-xM_xMnO₄ (M= Cr, Mn, Fe and Cu) samples are investigated. Element substitution does not change the cubic lattice structure within a range of concentrations. There is a structural transition from cubic to tetragonal with the excessive addition of Mn atoms. The site preference of transition metal atoms influences the interatomic interactions in the oxide system. The interatomic interactions of Co₂MnO₄ and CoMn₂O₄ samples are analyzed though ZFC/FC curves, the transition temperatures of which are attributed to the combined effect of magnetic interactions in different sublattices. The magnetic structure is restructured by atomic substitution and site preference, resulting in the compositional dependence of magnetic properties.     

Al-5Ti-1B晶粒细化剂对V-Al氢分离合金显微组织和硬度的影响

在纯V中分别添加质量分数5%的Al和5%Al-5Ti-1B(ATB)中间合金(晶粒细化剂)电弧熔炼形成V-5Al和V-5ATB合金铸锭。利用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)、透射电镜(TEM)和显微硬度仪等测试手段分析晶粒细化前后V-Al合金的显微组织和硬度变化。结果表明:V-5ATB合金组织中析出长针状第二相TiB使晶粒尺寸明显减小,相比V-5Al合金,V-5ATB合金由于固溶、细晶和硬质TiB第二相等强化效应导致硬度提高。     

Slater–Pauling behavior and half-metallicity in Heusler alloys Mn2CuZ (Z = Ge and Sb)

The Slater–Pauling behavior and half-metallic properties of full-Heusler alloys Mn₂CuZ (Z = Ge and Sb) have been studied by first-principles calculations. It is found that the total spin moment (M_t) and the number of valence electrons (Z_t) follow a Slater–Pauling rule of M_t = Z_t ? 28 rather than M_t = Z_t ? 24 in normal Heusler alloys. Mn₂CuSb is predicted to be a half-metal at equilibrium lattice constant and Mn₂CuGe is also half-metallic with a small expansion of the lattice. Mn₂CuGe and Mn₂CuSb are both ferrimagnets with total spin moment of +0.97μ_B/f.u. and +2.00μ_B/f.u., respectively. Considering Mn₂CuGe and Mn₂CuSb have 29 and 30 valence electrons, the S-P curve of M_t = Z_t ? 28 works quite well. This different S-P rule is strongly related to the low-lying Cu states and the weak hybridization between the d states of Cu and Mn.     

宁东直流大地回线转金属回线转换失败原因分析与改进建议

在我国高压直流输电投入实际运行以来,在大地回线转金属回线过程中,多次发生由于金属回线转换开关(MRTB)并联的吸能避雷器损坏而导致转换失败的事件,迫切需要精确反应开关动作机理的研究手段。通过对宁东直流输电系统现场大地回线转金属回线转换成功的与失败的录波波形对比分析,得出转换失败前后的系统电气特征。采用宁东直流实际的主回路设备参数和控制保护功能,建立起以直流电磁暂态程序(EMTDC)为基础的详细模型,再现了开关转换和故障过程的暂态现象。不仅验证避雷器由于四柱并联,长期运行操作使每个柱特性变化不一致,较小阻抗单柱承受较大的能量而损坏,而且,通过对转换失败之后逆变站金属回线接地保护动作闭锁直流系统事件进行分析,得出由于逆变站金属回线接地保护软件策略缺陷,导致保护动作闭锁直流系统。根据分析结果,对宁东直流大地转金属回线过程提出改进建议,同时对后续直流工程的MRTB并联避雷器的成套设计提出建议。     

Magnetic and anomalous transport properties in Fe2MnAl

This study investigated the magnetism and anomalous transport properties of the melt-spun ribbon Fe₂MnAl alloy. It is found that the alloy exhibits ferromagnetic order with the Curie temperature of ∼150 K, followed by another magnetic transition at T_R ∼ 51 K. It is suggested there is antiferromagnetism pinning effect on the ferromagnetic matrix at the temperature below T_R. A steep rise of the resistance below T_R has been observed, which can be understood in terms of antiferromagnetic scattering. An appearance of the resistance maximum near the Curie temperature and the negative temperature dependence of the resistance above Curie temperature are associated with the magnetic phase transition from ferromagnetism to paramagnetism. A negative magnetoresistance at low temperature arising from inhomogeneous magnetic scattering is reported.     

Effect of Co addition on martensitic phase transformation and magnetic properties of Mn50Ni40-xIn10Cox polycrystalline alloys

This study investigated the use of Co to enhance the magnetic driving force for inducing the martensitic transformation of Mn₅₀Ni_40-xIn₁₀Co_x alloys. These alloys present a martensitic transformation from a Hg₂CuTi-type austenite to a body centered tetragonal martensite, with a large lattice distortion of 15.7% elongation along the c direction and 8.2% contraction along a and b directions. The martensitic transformation temperatures, transformation enthalpy and entropy changes decreased with increasing the Co content in these alloys. The maximum magnetization of the austenite increased significantly, whereas that of the martensite changed much less prominently with increasing the Co substitution for Ni, leading to increase of the magnetic driving force for the transformation. The magnetization increase of the austenite is found to be due to (i) formation of ferromagnetically coupled Mn–Mn due to new atomic configuration in off-stoichiometric composition, (ii) magnetic moment contribution of Co and (iii) widening of the temperature window for magnetization of the austenite by lowering the temperature of the martensitic transformation. These findings clarify the effect of Co addition on martensitic transformation and magnetic properties in Mn-rich ferromagnetic shape memory alloys, and provide useful understanding for alloy design for magnetoactuation applications.     

带横缝拱坝的非线性地震响应

本文运用非线性有限元方法研究了具有横向建筑缝的拱坝在地震作用下的响应，模拟了横向建筑缝的连续，张开，闭合，相对滑移等多种受力状态，并给出了算例。