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1.
航空发动机的效率与转动叶片和机匣之间的间隙密切相关。为了控制转子和静子之间的间隙,需要在机匣表面制备可磨耗的封严涂层。在发动机的高温端,ZrO 2-8wt% Y 2O 3涂层是经常采用的封严涂层基体。涂层中的孔隙可以增加涂层的可磨耗性。本文利用聚苯酯(PHB)增加等离子喷涂的ZrO 2-8 wt% Y 2O 3涂层的孔隙率。为了避免聚苯酯在等离子喷涂过程中的烧损,利用溶胶-凝胶法在聚苯酯颗粒表面沉积一层TiO 2层。文中将讨论采用此方法制成的涂层的形态、孔隙率、硬度和可磨耗性。结果表明,在喷涂粉末中混合包覆型的聚苯酯后,涂层的孔隙率将会得到提升,涂层硬度将会下降。磨耗试验的结果表明涂层的磨耗深度随着涂层孔隙率的增加而增加。 相似文献
2.
基于密度泛函理论(DFT)的第一原理方法计算了四方相和立方相中2种不同的Li 7La 3Zr 2O 12(LLZO)固体电解质材料的能带结构,晶格参数,态密度和成键特性。基于理论计算结果,通过电子结构特性解释了四面体相的离子电导率低于立方相的离子电导率的原因。基于LLZO的第一性原理计算,设计了2种晶体结构的LLZO材料,并通过高温固相法制备并分析了不同烧结时间的LLZO颗粒的性能。探索了合成工艺参数对Li 7La 3Zr 2O 12性能的影响。立方晶Li 7La 3Zr 2O 12(C-LLZO)的平均晶格大小为 a= b= c=1.302 246 nm,而四方Li 7La 3Zr 2O 12(T-LLZO)的平均晶格大小为 a= b=1.313 064 nm, c=1.266 024 nm。在1000 ℃下烧结12 h的C-LLZO为纯立方相,在室温(25 ℃)下最大离子电导率为9.8×10 -5 S·cm -1。T-LLZO在室温(25 ℃)下的离子电导率为5.96×10 -8 S·cm -1,在800 ℃下烧结6 h具有纯的四方相结构,与计算结果基本吻合。 相似文献
3.
以五水四氯化锡和硝酸镧为原料,采用化学共沉淀法在烧结温度920℃条件下合成了锡酸镧粉体。通过高能球磨法+成型烧结工艺制得Ag-La 2Sn 2O 7电接触复合材料。重点考察了胶凝剂浓度、烧结工艺对La 2Sn 2O 7粉体形貌及物相的影响,并对Ag- La 2Sn 2O 7电接触材料的物理性能进行了分析。研究结果表明:以碳酸氢铵为胶凝剂,于烧结温度920℃,2h条件下获得具有网孔结构的La 2Sn 2O 7粉体;于成型压力1200MPa,烧结温度900℃,6h条件下制得的Ag-La 2Sn 2O 7电接触材料表现出较佳的电阻率和硬度值。经过热挤压工艺,Ag-La 2Sn 2O 7电接触材料发生了大塑性变形,颗粒在热挤压过程中发生流动变形,形成类纤维状结构的排列分布状态,表现出更低的电阻率。 相似文献
4.
以Ag、Sn、La 2O 3粉为原料,采用机械合金法制备复合粉体。结合氧化法与粉末冶金工艺,对复合粉体进行氧化、压制、烧结。采用扫描电镜(SEM)和能谱仪、硬度计、金相显微镜、金属电导率测量仪等对复合粉体氧化前后的形貌以及电接触材料烧结前后的性能进行表征。结果表明:烧结后,电接触材料硬度较于烧结前明显下降。同时电接触材料随Sn含量增大,电阻率升高,密度反而下降。在一定的La 2O 3(0wt.%、0.75wt.%、1.5wt.%、2.25wt.%、3wt.%)含量范围内,La 2O 3掺杂量越高,密度越低。同时电接触材料经烧结后,随La 2O 3含量增加,其电阻率先降后升,在La 2O 3含量为0.75wt.%时,电接触材料的电阻率最低。 相似文献
5.
以仲丁醇铝为前驱体,采用溶胶-凝胶法结合丙酮-苯胺原位生成水技术,通过乙醇超临界干燥,制备出不同含量(1.5 mol%~12 mol%)La 2O 3掺杂的氧化铝气凝胶。采用电子扫描电镜(SEM)、透射电子显微镜(TEM)、X线衍射仪(XRD)、N 2吸附分析仪等仪器表征了La 2O 3掺杂对氧化铝气凝胶的微结构和耐温性能的影响。结果表明:La 2O 3的引入使氧化铝气凝胶的形貌由球状颗粒向大的片状结构转变。适量的La 2O 3掺杂能提高氧化铝气凝胶的比表面积,9 mol% La 2O 3掺杂的氧化铝气凝胶比表面积最大。通过La 2O 3掺杂,能够抑制氧化铝晶粒在高温下的生长和α-Al 2O 3的相变,提高氧化铝气凝胶的耐温性能。1200℃热处理后,La 2O 3掺杂的氧化铝气凝胶仍维持在θ-Al 2O 3,比表面积为86.5 m 2/g,高于未掺杂的氧化铝气凝胶(46 m 2/g)。 相似文献
6.
为探究 La 2Zr 2O 7(LZO)涂层服役于 CMAS 环境中其微观结构、力学性能的变化及封阻渗透的原因,采用大气等离子制备了以 Al 2O 3 为基体的 LZO/ 8YSZ 双陶瓷热障涂层( TBCs) ,并辅以 8YSZ 单陶瓷 TBCs 作对比。 利用 XRD、SEM 和 EDS 研究了 8YSZ 和 LZO/ 8YSZ 单双陶瓷 TBCs 的相结构和微观组织;利用维式硬度计和 Image Pro plus 软件研究了腐蚀后的涂层硬度及渗透深度。 结果表明:1250 ℃ CMAS 腐蚀 12 h 后,LZO/ 8YSZ 双陶瓷 TBCs 中 LZO 反应厚度约为 57 μm;反应层物相以球状 ZrO 2 和棒状 Ca 2La 8( SiO 4 ) 6O 2 为主,并伴有少量 CaAl 2 Si 2O 8 和 M gAl 2O 4 。 而 8YSZ 单陶瓷 TBCs 腐蚀深度约为 300 μm( 整个 8YSZ 层厚) ,截面变为以球状 m-ZrO 2 为主的疏松结构。 腐蚀后 8YSZ、LZO 反应层硬度均有所增加,但提高的面内刚度未引发反应/ 未反应层间开裂。 LZO 陶瓷层作为双陶瓷 TBCs 牺牲防护层,依靠 La 同 CMAS 反应生成致密磷灰石(Ca 2La 8( SiO 4 ) 6O 2 )的封阻作用,有效减少 CMAS 渗入,抑制了内部 8YSZ 的不稳定性。 相似文献
7.
目的 通过热喷涂涂层,解决 350 MW 超临界机组再热第一级静叶栅的高温冲蚀问题。 方法 采用超音速火焰喷涂制备了 NiCr-Cr 3C 2 涂层,测试了涂层的显微组织、孔隙率、显微硬度、结合强度及高温冲蚀性能,并对涂层在冲蚀条件下的失效机理进行分析。 结果 实验室条件下, NiCr-Cr 3C 2 涂层孔隙率为 0 . 98% ,显微硬度达到 1061 . 2 HV0 . 3 ,结合强度约为 80 MPa。 装机试车时,0 . 22 mm 厚的 NiCr-Cr 3C 2涂层可使再热第一级静叶的寿命延长 3 倍左右。 结论 采用 NiCr-Cr 3C 2 涂层可显著延长静叶寿命,小角度粒子犁削冲蚀是涂层加速失效的主要原因。 相似文献
8.
采用搅拌摩擦加工方法在Al基体中添加不同La 2O 3含量的混合粉末(Ni+La 2O 3),制备 (Ni+La 2O 3)/Al复合材料。采用SEM、EDS、 EPMA及XRD对复合区微观结构及相组成进行分析,采用室温拉伸试验对 (Ni+La 2O 3)/Al复合材料力学性能进行了测试。结果表明,随着La 2O 3含量的增加,(Ni+La 2O 3)/Al复合材料的组织和性能先变好后变差。当La 2O 3添加量达到5%时,复合材料中Al 3Ni增强颗粒分布均匀、颗粒数量最多,块状的Ni粉团聚减少,其抗拉强度达到最大值215MPa,相比Ni/Al复合材料(抗拉强度176MPa),其抗拉强度提高了22%;当La 2O 3的添加量为7%时,复合材料中Al 3Ni增强颗粒含量减少,块状Ni粉团聚重新出现,抗拉强度下降至201MPa。 相似文献
9.
本文以BaCO 3、MgO、Ta 2O 5为原料,采用固相反应法合成了Ba(Mg 1/3Ta 2/3)O 3(简称BMT)陶瓷粉末,利用大气等离子喷涂技术制备了BMT/YSZ双层陶瓷涂层。利用XRD、SEM和金相显微镜检测了BMT粉体及涂层的物相组成和显微结构。采用水淬法考核了涂层的抗热震性能。结果表明:1450℃下煅烧4h可合成出具有复合钙钛矿结构的BMT粉末,粉末具有良好的高温相结构稳定性。等离子喷涂制备的BMT/YSZ涂层组织致密,涂层系统中各界面结合紧密。涂层在室温至1150℃间热震9次后发生片状剥落,剥落位置位于BMT层间,BMT材料低的断裂韧性和第二相Ba 3Ta 5O 15的存在是导致涂层失效的主要原因。 相似文献
10.
本文采用甘氨酸-硝酸盐法(GNP)和溶胶凝胶法分别合成了Sm 0.1Nd 0.1Ce 0.8O 1.9(SNDC) 和La 2Mo 2O 9(LAMOX)粉末,并用常压烧结的方法制备了不同比例的SNDC和LAMOX的复合材料,通过XRD和SEM等手段表征了不同复合比例样品的物相和表面形貌并测试了烧结样品的电导率。结果表明,复合样品的电导率在相变点前后随着复合量增加变化趋势相反,其中LAMOX含量为20mol%的样品在550℃时的电导率能达到0.01S/cm,高于同温度下SNDC电导率。 相似文献
11.
The new phases KFe 2(SeO 2OH)(SeO 3) 3 and SrCo 2(SeO 2OH) 2(SeO 3) 2 have been synthesized under low-hydrothermal conditions and their structures were determined by single-crystal X-ray methods. Both compounds are monoclinic; KFe 2(SeO 2OH)(SeO 3) 3: space group P2, A = 9.983(4), B = 5.270(1), C = 10.614(4) Å, β = 97.42(2)°, V = 553.7 Å 3, Z = 2; SrCo 2(SeO 2OH) 2(SeO 3) 2: space group P2 ln, A = 14.984(2), B = 5.286(1), C = 13.790(2) Å, β = 94.72(1)°, V = 1088.5 Å 3 , 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
). 相似文献
12.
We applied our model to the enthalpy of mixing data of the binary systems Na 2O-SiO 2, Na 2O-GeO 2, Na 2O-B 2O 3, Li 2O-B 2O 3, CaO-B 2O 3, SrO-B 2O 3, and BaO-B 2O 3. 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-SiO 2, CaO-Al 2O 3, PbO-B 2O 3, PbO-SiO 2, ZnO-B 2O 3, and ZnO-SiO 2 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. 相似文献
13.
The MoS 2 powders were coated with Al 2O 3 (5 wt.%) through controlling hydrolysis of Al (NO 3) 3·9H 2O. MoS 2 powder coated with Al 2O 3 was written as MoS 2/Al 2O 3 hereinafter. MoS 2/Al 2O 3 powders were put into Ni plating electrolyte bath. Cetyltrimethylammonium bromide (CTAB) — the surfactant was also put into the bath. The experiment proves that MoS 2/Al 2O 3 particles were absorbed onto the Ni plate. The amount of MoS 2/Al 2O 3 deposited on Ni plate rises with the increasing concentration of MoS 2/Al 2O 3 in the bath. The microhardness, micro-surface, phase and the tribological property of the MoS 2/Al 2O 3 multi-plating coating were measured and analyzed. The performances of microhardness and wear resistance of the Ni-MoS 2/Al 2O 3 composite are better than those of Ni-MoS 2 composite. 相似文献
14.
LiBH 4 films were prepared by pulsed laser deposition using a LiB target in a background pressure of hydrogen. The corrosion characteristics of LiBH 4 films were measured by exposing them to a gas mixture of CO 2/H 2O/O 2/N 2 at ambient temperature for 1–24 h. Scanning electron microscopy images show some cracks on the surface of corrosion films, which could act as easy paths for H 2O and CO 2 to further react with Li + and B 3+. The X-ray photoelectron spectroscopy results and theoretical analysis show that LiBH 4 tends to react with H 2O and CO 2 to form Li 2B 4O 7, Li 2CO 3 and LiOH during the corrosion process. 相似文献
15.
High density polycrystalline CaCd 2Sb 2 and EuCd 2Sb 2 intermetallics are synthesized by Spark Plasma Sintering and their thermoelectric properties are investigated. X-ray diffraction measurements reveal both materials have a structure in space group, containing a small amount of CdSb as a second phase. Thermoelectric measurements indicate both are p-type conductive materials. The figure of merit value of CaCd 2Sb 2 is 0.04 at 600 K and that of EuCd 2Sb 2 is 0.60 at 617 K. Theoretical calculations show that CaCd 2Sb 2 is a degenerate semiconductor with a band gap of 0.63 eV, while EuCd 2Sb 2 is metallic with DOS of 13.02 electrons/eV. For deeper understanding of the better thermoelectric properties of EuCd 2Sb 2, its low temperature magnetic, transport and heat capacity properties are investigated. Its Nèel temperature is 7.22 K, convinced by heat capacity anomaly at 7.13 K. Hall effect convinced that it is a p-type conductive material. It has high Hall coefficient, high carrier concentration and high carrier mobility of +1.426 cm 3/C, 4.38 × 10 18/cm 3 and 182.40 cm 2/Vs, respectively. They are all in the magnitude of good thermoelectric materials. The Eu 4 f level around Fermi energy and antiferromagnetic order may count for the better thermoelectric properties of EuCd 2Sb 2 than that of CaCd 2Sb 2. 相似文献
16.
Results of a powder X-ray diffraction investigation of new ternary compounds are reported. The compounds Y 6CoBi 2 [ a=0.8312(1) nm, c=0.4144(1) nm], Ho 6CoBi 2 [ a=0.8246(2) nm, c=0.4095(1) nm], and Tm 6CoBi 2 [ a=0.8155(2) nm, c=0.4066(1) nm] crystallize in the hexagonal Zr 6CoAs 2-type structure (space group P6 b2 m No. 189). The Zr 6CoAs 2-type structure is a superstructure of the Fe 2P-type structure. 相似文献
17.
We have investigated the magnetic properties and the 155Gd Mössbauer spectra of the ThCr 2Si 2-type compounds GdNi 2Sb 2, GdCu 2Sb 2 and GdAl 2Ga 2. These three compounds were found to order antiferromagnetically, with TN=6.5 K, 15.8 K, and 42.4 K respectively. The electric field gradient V22 derived from the quadrupole splitting of the Mössbauer spectra gives rise to a sign change at the end of the T3d series in GdT 2Sb 2, as was observed previously also for the corresponding compounds with Si and Ge. This behaviour was explained in terms of decreasing hybridization between the Gd valence electron states and the d electron states of the T atoms. 相似文献
18.
探究了使用大气等离子喷涂设备制备适合热喷涂使用的球形CaF2/BaF2共晶粉末的可能性。68%BaF2、32%CaF2粉末(质量分数)经过1 100℃真空烧结后,形成致密的块状氟化物共晶。机械破碎后的氟化物共晶经过等离子焰流重熔后得到了球形的氟化物共晶。使用F14-1流动性和松装密度测定仪测量球化前后粉末的流动性和松装密度。采用扫描电子显微镜,XRD表征球化前后粉末的形貌和物相组成。结果表明:球化后的粉末呈现较好的球形,球化后粉末的流动性和松装密度较球化前也有较大的改善:球化后共晶粉末的流动时间为55.20s/50g,松装密度为1.89g/cm3;另外,球化后共晶粉末还表现出良好的高温润滑性能:含有10%CaF2/BaF2共晶(质量分数)的镍基涂层在600℃和800℃的平均摩擦因数都小于0.3。 相似文献
19.
The effects of La 2O 3 addition on thermal conductivity, phase stability and thermal cycle life of Y 2O 3 stabilized ZrO 2 plasma sprayed coatings were investigated. Although low thermal conductivity as well as high resistance to sintering was achieved by La 2O 3 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. 相似文献
20.
Several binary stannides of the early transition metals T have been reported with the composition T 2Sn 3 previously. However, the present structure refinements from single-crystal X-ray data show that they have the compositions VSn 2, NbSn 2 and CrSn 2 ( R = 0.028, R = 0.018 and R = 0.021 with 17 variable parameters and 828, 512 and 440 structure factors respectively). Their orthorhombic Mg 2Cu-type structure is closely related to the structures of MoSn 2 (Mg 2Ni type) and CuAl 2. The latter structure type was confirmed for NbSnSb by a structure refinement from single-crystal data ( R = 0.010 for eight variables and 254 F values). Electrical conductivity measurements show CrSn 2 and MoSn 2 to be metallic conductors. 相似文献
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