Al含量对Al_2O_3/Al金属陶瓷性能影响研究

金属陶瓷既保持了陶瓷材料优异特性,又具备金属材料优势,是一种重要的新型工程材料。本文利用粉末冶金方法制备氧化铝-铝金属陶瓷材料,研究其致密化机理,为制备高性能金属陶瓷材料提供参考。研究表明,随着Al含量的降低,金属陶瓷材料的致密度逐渐降低。在扫描电镜图片中,颗粒呈连续分布且较大的为金属Al颗粒,颗粒呈不连续分布较细小的为Al2O3颗粒。随着Al含量的降低,金属陶瓷材料的晶界数量逐渐增多。随着Al含量由75%(质量分数,下同)减至25%时,硬度依次下降,Al含量高,易熔融相多,Al2O3粉末相对少,Al能较好较充分的将Al2O3粉末包裹住,且致密化效果好,故样品整体有较高的硬度。随着Al含量的降低,样品的导电性逐渐变差。     

添加球磨铁碳粉对Fe-2Cu-0.8C材料性能的影响

本文采用不同工艺制备球磨铁碳粉,并以球磨铁碳粉替代石墨粉与铁粉、铜粉混合,配制Fe-2Cu-0.8C材料,研究添加球磨粉的球磨时间和球磨粉成分对材料性能的影响,并与元素粉配料的Fe-2Cu-0.8C材料进行对比。结果表明,与添加其他球磨时间粉末的材料相比,添加球磨12 h粉末配制的材料,粉末的流动性好,试样的密度、强度和硬度相对较高。添加不同碳含量球磨粉末的材料,粉末的流动性和试样的密度与添加的球磨粉碳含量关系不大,试样的强度和硬度随碳含量增加有所降低。与元素粉配料的材料相比,添加球磨12 h粉末配制的材料强度和硬度提高近30%。     

添加钕对Mg2Ni储氢合金的结构和电极性能的影响

利用两步法制备了一系列添加Nd的三元Mg2-xNdxNi合金。XRD分析证实，当x=0．05，0．1时，制得的三元Mg2-xNdxNi合金均为Mg2Ni单相合金；三元Mg18Nd0．2Ni(x=0．2，0．3)合金为三相合金，三相分别为Mg2Ni，NdNi，NdMgNi4。模拟电池测试结果表明，同Mg2Ni合金相比，球磨10h的三元Mg1．8Nd0．2Ni合金和Mg17Nd03Ni合金电极的放电容量提高明显，且Mg17Nd03Ni合金电极的循环性能有明显改善。这极有可能与合金中NdMgNi4相的存在以及球磨形成的微结构有关。     

金属-Al2O3陶瓷基复合材料的研究与发展前景

Al2O3陶瓷是一种很重要的抗氧化、抗腐蚀的高温结构陶瓷材料.但由于其烧结活性低,难以烧结致密,脆性大,而在应用上受到限制.在Al2O3陶瓷中引入延性金属第二相和采用纳米材料可大大提高烧结活性,不仅起到金属增韧的效果,而且也可使陶瓷具有一定的导电、导热性,从而扩大其在微电子行业中的应用.本文综述了国内外近几年来对纳米金属-Al2O3陶瓷的研究发展现状,指出了其应用前景.     

金属添加方式对NiFe基/NiFe2O4金属陶瓷微观组织的影响

采用粉末冶金法制备了2种金属陶瓷,通过X射线衍射和扫描电镜(SEM)分析发现金属相添加方式(尤其是Al的添加方式)对陶瓷的结构和组成有较大的影响,当Al以单质形式加入时,它会改变原有尖晶石的成分,形成新的尖晶石,同时,还会导致各金属元素的局部分布不均匀现象;合金化后Al的扩散得到了较好的控制,并没有改变原有陶瓷成分.2种金属陶瓷中的陶瓷相在高温烧结中都存在不稳定性,出现了离解现象.金属含量不同,金属陶瓷中陶瓷相和金属相的烧结机理也不同.     

添加剂对Cr2O3—Al系SHS反应的影响

研究了添加ＣｒＯ３－Ａｌ、Ｆｅ２Ｏ３－Ａｌ＋ＭｇＯ及Ｔｉ－Ｃ的Ｃｒ２Ｏ３－Ａｌ系的燃烧特性。实验发现，添加ＣｒＯ３－Ａｌ、Ｆｅ２Ｏ３－Ａｌ＋ＭｇＯ时，自蔓燃反应易于引发；体系中混入Ｔｉ－Ｃ添加剂对反应引发不利，但在用纯Ｔｉ－Ｃ作引火剂情况下可以引发。随着ＣｒＯ３－Ａｌ添加量的增加，燃烧温度升高，但添加量大于２０％时，燃烧温度反而下降。燃烧温度随Ｆｅ２Ｏ３－Ａｌ＋ＭｇＯ添加量的增加而升高。Ｔｉ－Ｃ添加量的增大对燃烧温度影响不大。燃烧速度随以上添加剂量的增大而增大     

Cr_3C_2和Ni对TiC基金属陶瓷组织性能的影响

主要研究Cr3C2和Ni在不同配比下烧结成TiC基金属陶瓷,利用洛氏硬度计测试硬度,利用扫描电镜进行显微形貌观察,利用能谱仪进行元素分布分析以及利用XRD衍射仪进行物相分析.研究表明,Ni作为粘结相分布在TiC基体的边缘,不同Cr3C2和Ni含量影响TiC基金属陶瓷组织形貌和性能的原因是由于不同新相的生成.     

金属-Al2O3陶瓷基复合材料的研究现状及应用前景

Al2O3陶瓷是一种重要的抗氧化、抗腐蚀的高温结构陶瓷材料.但由于其烧结活性低,难以烧结致密,脆性大,在应用上受到限制.在Al2O3陶瓷中引入延性金属第二相和采用纳米材料可大大提高其烧结活性,不仅能使金属增韧,而且也能使陶瓷具有一定的导电、导热性,从而扩大了它在微电子行业中的应用.在此,作者综述了国内外近几年来对纳米金属-Al2O3陶瓷的研究现状,指出了其应用前景.     

添加氧化锆对硬质合金组织和性能的影响

研究了添加不同质量分数的非稳定态钇氧化锆ZrO2（摩尔分数为3%Y2O3）对硬质合金组织和性能的影响,并对金相组织和性能的理化检测结果进行了分析研究.结果表明：在烧结体中,通过控制添加的非稳定态钇氧化锆ZrO2（3%Y2O3）重量比例可以使硬质合金的组织稳定,在不降低硬度的前提下,使硬质合金的抗弯强度得到提高.     

High temperature thermodynamic properties of the chromium carbides Cr7C3 and Cr3C2 determined using a galvanic cell technique

The standard free energies of formation of Cr₇C₃ and Cr₃C₂ have been obtained from emf measurements on the following galvanic cells with BaF₂-BaC₂ solid solutions as the electrolyte: Cr,Cr₂₃C₆∣BaF-BaC₂∣Cr₂₃C₆,Cr₇C₃ (920 to 1250 K) (A) Cr₂₃C₆, Cr₇C₃ ∣BaF₂-BaC₂∣W, WC (900 to 1200 K) (B) WC, W∣BaF₂-BaC₂∣Cr₃C₂, Cr₇C₃ (973 to 1173 K) (C) Combining the results of this study with a previous work¹⁵ and those of Kulkarniet al. and Dawsonet al., the following equations for ΔG _f ^ℴ of Cr₇C₃ and Cr₃C₂ have been determined: from cell (A): ΔG _Cr7C3 ^o (±2300) = −155410(±173) − 35.8(±0.1)T joules; from cell (B): ΔG _Cr7C3 ^o (±2000) = −155585(±385) − 35.8(±0.4)T joules for the reaction 7Cr + 3C = Cr₇C₃; from cell (C): ΔG _Cr3C2 ^o , (±1200) = −92860(±210) − 19.4(±0.2)T joules for the reaction 3Cr + 2C = Cr₃C₂.     

Calculation and evaluation of the gibbs energies of formation of Cr3C2, Cr7C3, and Cr23C6

A thermodynamic analysis of chemical composition data for a series of iron alloys containing chromium and carbon has been completed. These data were obtained from literature compilations for alloys equilibrated for extended times at 700 °C under neutral atmospheres. The results of this analysis, when supplemented with thermochemical data from the literature, permitted the calculation of the standard Gibbs energies of formation for the chromium carbides Cr₇C₃ and Cr₂₃C₆ over the range 600 to 1000 °C. These standard Gibbs energies were compared to data for these carbides from other sources. Available Gibbs energy data for the third pure chromium carbide, Cr₃C₂, were also evaluated. For each of these three compounds, a separation of the values for the Gibbs energy of formation into two distinct groups was observed. Each of these groups can be classed according to the nature of the experimental study used, whether it be a high temperature solid-gas equilibration involving a system of a carbide-chromic oxide-carbon (or chromium) with carbon monoxide, on one hand, or a series of investigations concerned mainly with electrolytic cell measurements, plus the work on which the present study is based. It is suggested that the differences in the Gibbs energies of formation for the respective carbides are associated with 1) the nonstoichiometric nature of these carbides and 2) possible dissolution of oxygen in the carbides during the equilibration studies.     

The relative stabilities of Cr23C6/ Cr7C3/ and Cr3C2 and the phase relationships in ternary Cr-Mo-C system

The thermodynamic properties of CrC_6/23, CrC_3/7, CrC_2/3, and MoC_1/2 reported in the literature have been correlated with the relative stabilities of these carbide phases derived from ternary phase diagrams. On the basis of the free energy of formation for one of the carbides and the free energy changes for the various equilibria occurring in ternary Mo-Cr-C system at 1300°C, free energies of formation for the stable and unstable carbide phases have been obtained. Using this free energy data, a calculated ternary Mo-Cr-C phase diagram is presented which agrees well with the experimentally determined one.