La2O3对激光熔覆铁基合金层硬度及其分布的影响

通过扫描电镜(SEM)研究了稀土氧化物La2O3对铁基合金激光熔覆层组织形貌的影响，用纳米硬度探针测定了熔覆层与基体界面附近和搭接区的硬度和弹性模量，并用MT3型显微硬度计测试了多道熔覆层硬度的面分布．结果表明，稀土的加入细化了晶粒，减小了二次枝晶间距；近界面和搭接区的纳米硬度和弹性模量有不同程度的提高．硬度面分布测量结果表明，加入稀土后熔覆层的平均硬度(HV)约为500，比未加稀土的提高约50，本文还讨论了稀土作用的机理。     

Y2O3对Fe-Al-Si-B等离子熔覆层组织与性能的影响

采用等离子弧熔覆技术,在Q235基体钢板表面熔覆了一层Fe-Al-Si-B原位复合涂层,并通过在熔覆粉末中添加稀土氧化物Y2O3改善熔覆层的组织与性能。利用光学显微镜(OM) 、扫描电镜( SEM) 、X射线衍射仪( XRD)、显微硬度仪、摩擦磨损试验机对熔覆层的组织、相组成、显微硬度及磨损性能进行了分析。结果表明：Y2O3的加入净化了晶界,使得晶界处夹杂物均匀化,明显改善了晶界处夹杂物的形态,形成了致密均匀、无缺陷且显著细化的熔覆层组织。当稀土氧化物Y2O3含量为0.9%时,熔覆层的硬度达到510HV,耐磨性能达到最佳。     

Y2O3含量对激光熔覆层组织和性能的影响

利用OM、XRD和硬度计研究了Y2O3含量对熔覆层组织结构和硬度的影响.结果表明:熔覆层与基体之间实现了良好的冶金结合,当不含Y2O3时,熔覆层的基体相为α-Fe,其上分布着一些非晶相、金属间化合物,如Fe2B、Fe,C、FeSi等,组织粗大,平均硬度为660 HV0.2;当添加Y2O3后熔覆层中生成了少量的尖晶石类矿物质如FeFe2O4,晶粒明显细化.当w(Y2O3)=1.0%时,平均硬度为703 HV0.2,当加w(Y2O3)=2.0%时,平均硬度为768 HV0.2,当w(Y2O3)=3.0%时,平均硬度为743 HV0.2.     

纳米Y2O3-Co基合金激光熔覆复合涂层的分析

采用纳米Y2O3和Co基合金粉末,并利用激光表面熔覆技术和堆焊技术在Ni基合金基体上制备了纳米Y2O3-Co基合金复合涂层.运用扫描电镜(SEM)等测试方法,研究了复合涂层的显微组织和显微硬度,通过磨损试验和腐蚀试验分析了激光熔覆涂层和单一堆焊层的耐磨性和耐蚀性.结果表明,激光熔覆层显微组织由熔合区、细等轴状枝晶区及粗枝晶区构成;激光熔覆层的显微硬度由堆焊层的512.8 HV提高到868.9HV;激光熔覆层的耐磨性提高了51.2倍,40 min磨损量由堆焊层的25.6 mg降低到激光熔覆层的0.5 mg;激光熔覆层在10%HCl、10% HNO3和10% NaOH中的耐腐蚀性均比堆焊表面有明显改善.     

T10钢表面激光熔覆Ni/WC-La_2O_3性能研究

采用激光熔覆技术在T10钢表而激光熔覆Ni基合金,并研究了在Ni基合金中加入WC硬质相、纳米稀土氧化物La_2O_3后的性能和组织结构的变化情况.实验表明:激光熔覆层由熔覆层、结合区和热影响区组成,在合适的工艺条件下可得到结合性能良好的熔覆层.Ni60+30%WC熔覆层的硬度与未加入WC相比改变不大,但耐磨性却得到很大的提高;Ni60+1.0%La_2O_3熔覆层主要由树枝晶组成,在激光熔覆层中添加La_2O_3,起到细化枝晶的作用,同时激光熔覆层平均硬度比未加稀土的提高约150 HV0.1.     

Y2O3含量对激光熔覆0.3C-18Cr合金涂层组织和性能的影响

在3Cr14不锈钢基体上激光熔覆制备不同Y₂O₃含量的0.3C-18Cr复合涂层。采用金相显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射(XRD)、显微硬度仪等设备研究了不同Y₂O₃含量对熔覆层的微观结构、相组成及硬度的影响。结果表明,未添加Y₂O₃试样熔覆层有较多孔洞,熔覆层组织由晶内铁素体、晶界分布的上贝氏体及少量马氏体组成;加入在3Cr14不锈钢基体上激光熔覆制备不同Y2O3含量的0.3C-18Cr复合涂层。采用金相显微镜（OM）、扫描电子显微镜（SEM）、X射线衍射（XRD）、显微硬度仪等设备研究了不同Y2O3含量对熔覆层的微观结构、相组成及硬度的影响。结果表明,未添加Y2O3试样熔覆层有较多孔洞,熔覆层组织由晶内铁素体、晶界分布的上贝氏体及少量马氏体组成;加入Y2O3后熔覆层枝晶长度减小且数量减少,枝晶尖端钝化且径向粗化,长径比减小,同时熔覆层气孔减少,熔覆层得到净化;熔覆层组织由板条马氏体+晶界少量贝氏体构成;且随Y2O3含量增加,板条马氏体略有粗化,贝氏体数量明显减少,贝氏体碳化物的碳浓度增大,碳化物类型由低碳型碳化物向高碳型碳化物转变。加入Y2O3后,熔覆层显微硬度显著提高,添加2% Y2O3时熔覆层的硬化效果最佳,比未添加Y2O3时增加160 HV0.2。     

35CrMo钢表面激光熔覆Ni/WC-Y2O3熔覆层性能研究

研究对35CrMo钢表面激光熔覆Ni/WC-Y2O3合金,分析其工艺、熔覆层显微组织和综合性能,在Ni基合金中加入一定量WC硬质相、稀土氧化物Y2O3后,能对熔覆层组织的性能起到改善作用.分析试验数据表明:多种强化机制共同作用,使熔覆层的硬度和耐磨性能有显著提高;添加WC硬质相,熔覆层硬度变化不大,但耐磨性有很大程度提...     

等离子电弧熔覆Y2O3/钴基合金的组织结构及耐磨性能

应用光学显微镜、扫描电镜(SEM)、X射线衍射(XRD)、透射电镜(TEM)以及磨粒磨损试验,研究了质量分数为0.8%的Y2O3对等离子熔覆钴基合金组织结构和耐磨性能的影响.结果表明:没有添加Y2O3的钴基合金熔覆层主要是由面心立方的γ(Co)和六方结构的M2C3构成,并且在钴基固溶体中存在着许多堆垛层错:0.8%Y2O3的加入,并未改变熔覆层的相组成,未熔的Y2O3存在,提高了位于钴基固溶体中堆垛层错的密度和宽度;此外,由于Y2O3的加入,熔覆层的凝固组织发生了变化,由柱状晶转变为等轴晶;稀土氧化物Y2O3作为异质形核核心,细化了组织,改善了熔覆层组织的择优分布,从而提高了熔覆层的耐磨性能.     

纳米Y_2O_3弥散强化Ni基合金激光熔覆层

研究了纳米Y2O3对Ni基合金激光熔覆层显微组织、相结构和性能的影响。结果表明:加入纳米Y2O3 的Ni基激光熔覆层出现大量细小、无方向性生长的等轴晶;熔覆层主相为γ-Ni,此外还有Cr23C6、Ni4.6Si2B和 Ni17Y2等;加入1．5％纳米Y2O3的熔覆层显微硬度值大幅度提高,其耐磨性比纯Ni基提高5倍多,磨损机理由较为严重的粘着磨损转变为微动磨损。     

WC对Ni-Cr3C2激光熔覆层组织与性能的影响

研究了WC加入量对镍基碳化铬熔覆层显微组织、横截面微观硬度及熔覆层耐磨性的影响。结果表明,WC的加入使涂层组织中出现了弥散分布的白色相,白色相由白亮色的芯部及浅白色的环形相组成,白色相从熔覆层底部至表面呈先增后减的分布规律。弥散分布的白色相使熔覆层硬度提高,当WC加入量为2wt%时,涂层平均显微硬度约1096 HV,比未加WC的平均硬度(788 HV)高308 HV。WC的加入会增加材料的脆性,影响涂层使用寿命。当WC加入量为2wt%时,熔覆层硬度与脆性增加达到最佳匹配值,对提高材料耐磨性有利。     

Thermodynamics and phase diagrams in the binary systems Na2O-SiO2, Na2O-GeO2, Na2O-B2O3, Li2O-B2O3, CaO-B2O3, SrO-B2O3, and BaO-B2O3

We applied our model to the enthalpy of mixing data of the binary systems Na₂O-SiO₂, Na₂O-GeO₂, Na₂O-B₂O₃, Li₂O-B₂O₃, CaO-B₂O₃, SrO-B₂O₃, and BaO-B₂O₃. The most stable composition in the liquid, that is where the enthalpy of mixing is most negative, is with a metal-oxygen ratio of 4 to 3, for monovalent metals (Na and Li) and 3 to 4 for divalent metals (Ba and Ca) in liquid silicates or borates. The same applies to the CaO-SiO₂, CaO-Al₂O₃, PbO-B₂O₃, PbO-SiO₂, ZnO-B₂O₃, and ZnO-SiO₂ systems. The oxygen to metal ratio, its constant value in various types of systems, reflects and describes the structure of the liquid. Using the analyzed enthalpies of mixing data and the available phase diagrams, we calculated the enthalpies of formation of the various binary compounds. The results are in excellent agreement with data in the literature that were obtained from direct solid-solid calorimetry.     

Crystal structures and structural relationships of KFe2(SeO2OH)(SeO3)3 and SrCo2(SeO2OH)2(SeO3)2

The new phases KFe₂(SeO₂OH)(SeO₃)₃ and SrCo₂(SeO₂OH)₂(SeO₃)₂ have been synthesized under low-hydrothermal conditions and their structures were determined by single-crystal X-ray methods. Both compounds are monoclinic; KFe₂(SeO₂OH)(SeO₃)₃: space group P2, A = 9.983(4), B = 5.270(1), C = 10.614(4) Å, β = 97.42(2)°, V = 553.7 ų, Z = 2; SrCo₂(SeO₂OH)₂(SeO₃)₂: space group P2ln, A = 14.984(2), B = 5.286(1), C = 13.790(2) Å, β = 94.72(1)°, V = 1088.5 ų , Z = 4. The refinements converged to R-values of 2.9 and 3.6% respectively.

The atomic arrangement in KFe₂(SeO₂OH)(SeO₃)₃ and SrCo₂(SeO₂OH)₂(SeO₃)₂ is based on isolated MO₆ octahedra (M = Fe³⁺, Co²⁺), which are corner-linked via trigonal pyramidal selenite groups to a framework structure. Interstitials are occupied by potassium or strontium atoms in ten- or eight-coordination respectively, and by the lone-pair electrons of the Se⁴⁺ atoms. Both compounds are not isotypic but are closely related and may be interpreted as different distortions of an idealized structure type in space group P2/m, which was modelled for a theoretical compound SrFe₂(SeO₃)₄ by distance least squares refinement (program ).     

MoS2 coated with Al2O3 for Ni-MoS2/Al2O3 composite coatings by pulse electrodeposition

The MoS₂ powders were coated with Al₂O₃ (5 wt.%) through controlling hydrolysis of Al (NO₃)₃·9H₂O. MoS₂ powder coated with Al₂O₃ was written as MoS₂/Al₂O₃ hereinafter. MoS₂/Al₂O₃ powders were put into Ni plating electrolyte bath. Cetyltrimethylammonium bromide (CTAB) — the surfactant was also put into the bath. The experiment proves that MoS₂/Al₂O₃ particles were absorbed onto the Ni plate. The amount of MoS₂/Al₂O₃ deposited on Ni plate rises with the increasing concentration of MoS₂/Al₂O₃ in the bath. The microhardness, micro-surface, phase and the tribological property of the MoS₂/Al₂O₃ multi-plating coating were measured and analyzed. The performances of microhardness and wear resistance of the Ni-MoS₂/Al₂O₃ composite are better than those of Ni-MoS₂ composite.     

Processing and properties of ZrO2(3Y2O3)–Al2O3 nanocomposites

Nanocomposites of yttria-stabilized zirconia (YSZ), containing 20 and 40 wt% alumina, were prepared by a two-step process: (1) fine-particle aggregates of the constituent phases were melted and homogenized in a high enthalpy plasma, prior to rapid quenching in water to obtain metastable starting powders, and (2) the metastable powders were consolidated by hot isostatic pressing (HIP), under conditions designed to ensure the formation of nanocomposites by controlling the metastable-to-stable phase transformation during sintering. In both cases, the resulting nanocomposites had completely uniform structures, comprising 27 and 50 vol% of -Al₂O₃ in a tetragonal YSZ matrix phase. Measurements of hardness and indentation toughness were correlated with observed structures.     

NH4HF2 氟化Al2O3 制备无水AlF3 研究

采用热重-差热分析（TG-DTA）方法对不同NH₄HF₂/Al₂O₃质量比的Al₂O₃+NH₄HF₂混合物的热行为进行了分析,确定了DTA曲线的临界温度。进一步分析了各临界温度前后直接热处理所得产物的形貌和物相。结果表明,质量比对临界反应温度和反应过程没有影响。氟化反应在室温下以(NH₄)₃AlF₆的形成开始,在162.3~162.8 ℃时占主导地位,在180 ℃左右完成。进一步热处理后,(NH₄)₃AlF₆在249.8~250.1 ℃分解为NH₄AlF₄,在356.8~357.7 ℃分解为β-AlF₃;随后β-AlF₃在400~650 ℃向α-AlF₃转变。     

Mechanochemical synthesis of Al2O3-TiB2 nanocomposite powder from Al-TiO2-H3BO3 mixture

Alumina-titanium diboride nanocomposite (Al₂O₃-TiB₂) was produced using mixtures of titanium dioxide, acid boric and pure aluminum as raw materials via mechanochemical process. The phase transformation and structural characterization during mechanochemical process were utilized by X-ray diffractometry (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric analyses (TG-DTA) techniques. A thermodynamic appraisal showed that the reaction between TiO₂, B₂O₃ and Al is highly exothermic and should be self-sustaining. XRD analyses exhibited that the Al₂O₃-TiB₂ nanocomposite was formed after 1.5 h milling time. The results indicate that increasing milling time up to 40 h had no significant effect other than refining the crystallite size.     

La2/3Ca1/3MnO3∶Ag0.4与La2/3Ba1/3MnO3∶Ag0.4的制备及其性能研究

采用化学共沉淀法合成制备了Ag掺杂摩尔百分比为0.4的La2/3Ca1/3MnO3∶Ag0.4 (LCMO∶Ag0.4)、La2/3Ba1/3MnO3∶Ag0.4(LBMO∶Ag0.4)多晶复合材料,通过XRD和R-T分别对两种材料的结构和性能进行测试分析.实验结果表明:所得样品均为正交晶系钙钛矿结构;LCMO∶Ag0.4的金属-绝缘转变温度(Tp=280.2 K)比LBMO∶Ag0.4要高(Tp=256.8 K);LCMO:Ag0.4样品的电阻值比LBMO∶Ag0.4要小两个数量级;LCMO∶Ag0.4的TCR最大值为28％,要远远高于LBMO∶Ag0.4的TCR最大值(0.5％).     

Thermal cycle behavior of plasma sprayed La2O3, Y2O3 stabilized ZrO2 coatings

The effects of La₂O₃ addition on thermal conductivity, phase stability and thermal cycle life of Y₂O₃ stabilized ZrO₂ plasma sprayed coatings were investigated. Although low thermal conductivity as well as high resistance to sintering was achieved by La₂O₃ addition, it tended to also result in lower phase stability and thermal cycle life of the coatings. Optimization of the composition and structure of the coatings improved these properties, and the optimized coatings showed prolonged thermal cycle life.     

Critical thermodynamic evaluation and optimization of the MgO-Al2O3, CaO-MgO-Al2O3, and MgO-Al2O3-SiO2 Systems

A complete literature review, critical evaluation, and thermodynamic modeling of the phase diagrams and thermodynamic properties of all oxide phases in the MgO-Al₂O₃, CaO-MgO-Al₂O₃, and MgO-Al₂O₃-SiO₂ systems at 1 bar total pressure are presented. Optimized model equations for the thermodynamic properties of all phases are obtained that reproduce all available thermodynamic and phase equilibrium data within experimental error limits from 25 °C to above the liquidus temperatures at all compositions. The database of the model parameters can be used along with software for Gibbs energy minimization to calculate all thermodynamic properties and any type of phase diagram section. The modified quasichemical model was used for the liquid slag phase and sublattice models, based upon the compound energy formalism, were used for the spinel, pyroxene, and monoxide solid solutions. The use of physically reasonable models means that the models can be used to predict thermodynamic properties and phase equilibria in composition and temperature regions where data are not available.     

热电Bi2Te3/Bi2Se3纳米“弹簧”材料的电化学组装

为了探索制备具有高热电优值的一维纳米材料,采用脉冲电化学技术制备了一种热电Bi₂Te₃/Bi₂Se₃多层纳米线材料。对电沉积过程的监测结果表明,电沉积过程中体系电阻不断增大,随着电沉积的不断进行,体系电阻增大幅度越来越小。对电沉积产物进行退火处理,然后溶解掉模板,进行XRD测试,结果表明,所制备的产物是Bi₂Te₃/Bi₂Se₃,同时,有很多“卫星峰”出现在衍射图上,表明所制备的材料具有超晶格结构。运用FE-SEM、TEM对产物形貌进行分析,结果发现,所制备的材料是像“弹簧”一样形状的Bi₂Te₃/Bi₂Se₃多层纳米线。通过对脉冲时间的调节,可以实现对多层纳米线周期的调制。