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1.
以Ag、Sn、La2O3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La2O3(0wt.%、0.75wt.%、1.5wt.%、2.25wt.%、3wt.%)含量范围内,La2O3掺杂量越高,密度越低。同时电接触材料经烧结后,随La2O3含量增加,其电阻率先降后升,在La2O3含量为0.75wt.%时,电接触材料的电阻率最低。 相似文献
2.
Ferrite-based alloy powders with different contents of La2O3 were laser-clad on AISI 1115 steel substrates. The oxidation kinetic of the coatings was studied by testing the weight gain. Cyclic oxidation tests were performed to determine the eventual weight loss due to spallation. The morphologies and phase structures of the coatings were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The experimental results showed that Cr2O3 was formed on all coatings after oxidation. The coatings with La2O3 exhibited excellent high-temperature oxidation behavior including low oxidation rates and high resistance to spallation. In addition, the effect of La2O3 was discussed. This included the change of transport mechanism in the oxide scales, the increase in the nucleation rate of the oxide, the release of stresses in the oxide scales by refining the oxide grains and the improvement of the adhesion of the oxide scales to the coatings by changing the scale growth mechanisms. 相似文献
3.
Employing a Tian-Calvet-type calorimeter operating in the scanning mode at temperatures from 1120 to 1220 K, the enthalpy change, ΔdH, associated with the decomposition of GaBO3 (=1/2β-Ga2O3+1/2B2O3(liq.)) and the corresponding decomposition temperature, Td, were determined: ΔdH=30.34±0.6 kJ/mol, Td=1190±5 K. Using the transposed-temperature-drop method the thermal enthalpy, H(T)−H(295 K), of GaBO3 was measured as a function of temperature, T, in the region from 760 to 1610 K; the results obtained areOn the basis of the experimental results, the enthalpy and entropy of formation, ΔfH and ΔfS, respectively, of GaBO3 from the component oxides were derived:The enthalpy versus temperature curve shows, apart from a step associated with the decomposition of GaBO3, a further step at 1593 K which is attributed to a monotectic equilibrium. 相似文献
[H(T)−H(295 K)]/(J/mol)=104.8·(T/K)−31 300 (760 K<T<1190 K),
[H(T)−H(295 K)]/(J/mol)=138.8·(T/K)−41 480 (1190 K<T<1590 K).
ΔfH=−30.34 kJ/mol,ΔfS=−25.50 J/(K·mol) at 1190 K,
ΔfH=−10.55 kJ/mol,ΔfS=−5.48 J/(K·mol) at 298 K.
4.
Mineaki Matsumoto Hiroshi Takayama Daisaku Yokoe Kazuo Mukai Hideaki Matsubara Yukio Kagiya Yuuji Sugita 《Scripta materialia》2006,54(12):2035-2039
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. 相似文献
5.
采用热压烧结技术在45钢基片表面制备50EXD602-50WC复合涂层,利用光学显微镜(OM)、扫描电子显微镜(SEM)、能谱仪(EDS)和X射线衍射仪(XRD)进行组织观察、成分以及物相分析,研究了La2O3对涂层组织、表面磨损形貌和耐磨性能的影响。结果表明:涂层中主要含有WC、CuSn相和富Fe相,未添加La2O3的涂层组织中存在较多缺陷,表面磨损严重。随着La2O3的加入,涂层组织和耐磨性能得到不同程度的改善。La2O3质量分数为1.0%时,涂层孔隙率最低仅为0.84%,硬度为54.8HRC,相对耐磨系数9.76。表面磨损形貌平整且无剥落坑,划痕较浅,涂层与母材结合紧密,表现出最佳的耐磨性能。 相似文献
6.
Liping Xue Zhang Lin Dagui Chen Feng Huang Jingkui Liang 《Journal of Alloys and Compounds》2008,458(1-2):144-150
The subsolidus phase relations in the ZnO–MoO3–B2O3, ZnO–MoO3–WO3 and ZnO–WO3–B2O3 ternary systems have been investigated by the means of X-ray powder diffraction (XRD). There is no ternary compound in all the systems. There are five binary compounds and five tie lines in the ZnO–MoO3–B2O3 system. This system can be divided into six 3-phase regions. There are three binary compounds and three tie lines in the ZnO–MoO3–WO3 system. This system can be divided into four 3-phase regions. There are four binary compounds and four tie lines in the ZnO–WO3–B2O3 system. This system can be divided into five 3-phase regions. The possible component regions for ZnO single crystal flux growth were discussed. The phase diagram of Zn3B2O6–ZnWO4 pseudo-binary system has been constructed, and the result reveals this system is eutectic system. The eutectic temperature is 1007 °C and eutectic point component is 70 mol% Zn3B2O6. 相似文献
7.
采用固相法制备La2O3与Sb2O3掺杂的钛酸锶钡陶瓷,研究其介电性能及相变特性。通过X射线衍射法分析体系微观结构并利用扫描电镜观察其表面微观形貌。(La,Sb)共掺杂的钛酸锶钡陶瓷具有典型的钙钛矿结构,且随着Sb2O3掺杂量的增多其平均粒径显著减小。La3+离子以及Sb3+离子均占据钙钛矿晶格的A位。La2O3与Sb2O3添加量的改变显著影响钛酸锶钡基陶瓷的介电常数以及介电损耗。La2O3改性的钛酸锶钡陶瓷其四方?立方相变为二级相变,且居里温度随着La2O3掺杂量的增多向低温方向移动。(La,Sb)共掺杂的钛酸锶钡陶瓷则体现为弥散相变,随着Sb2O3含量的增大而偏离居里-外斯定律越显著。由于Sb3+离子对晶格原位离子的取代使得(La,Sb)共掺杂的钛酸锶钡陶瓷的介电常数最大值下的温度亦随着Sb2O3含量的增大而降低。 相似文献
8.
以La(NO3)3.6H2O、氨水和ZrC为原料,采用非均相沉淀-煅烧法制备La2O3包覆ZrC复合粉末。采用XRD、SEM、EDS等检测方法,对包覆前驱体粉末和La2O3/ZrC复合粉末的成分、结构和组织均匀性进行表征。结果表明:前驱体粉末在750℃下煅烧2 h后,全部转化为La2O3,粉末为近球形,未发生长大;La2O3/ZrC复合粉末的粒径为60~80 nm;包覆后粉末的Zeta电位由48.28 mV变为5.376 mV,ZrC被连续且均匀的La2O3纳米级壳体层包覆。 相似文献
9.
Effect of rod-like grain on properties and toughening mechanism of 3Y-TZP/Al2O3 ceramics 总被引:1,自引:0,他引:1
In-situ rod-like A1203 grain was prepared by adding CAS multiphase additives under the sintering condition of 30 MPa, 1 550℃ and 1 h. The sintering behaviors, microstructure, toughening mechanism and access of Al2O3 ceramics were investigated by SEM, EDS and WDW omnipotent electronic mechanical testing machine, etc, and the crack propagating model of cylindrical crystal/3Y-TZP composite toughening Al2O3 ceramics was established. The results show that the composite additives prompt the anisotropic growth of Al2O3 grain, which strengthens toughening effect of 3Y-TZP in 3Y-TZP/Al2O3 composite ceramics. Moreover, the experimental material density is near to theoretical density, bending strength is 556.35 MPa, and fracture toughness is 6.73 MPa.m1/2. The mechanical properties of the materials are obviously improved. 相似文献
10.
N. Liu M. Shi Y.D. Xu X.Q. You P.P. Ren J.P. Feng 《International Journal of Refractory Metals and Hard Materials》2004,22(6):265-269
Al2O3–TiC composites with a content of 30 wt% TiC with various size of starting powders were manufactured by hot pressing. The Vickers hardness, bending strength and fracture toughness were studied. The experiment results show that the starting powder size has a significant effect on the properties of the Al2O3–TiC composites. The maximum bending strength of the submicron Al2O3 with the fine TiC powders addition is 712 MPa, while the maximum fracture toughness of the same Al2O3 matrix with the large TiC powders addition is 6.5 MPa m1/2. 相似文献
11.
在Q235钢表面用等离子弧熔覆Ni-Cr-B-Si-Fe铁基合金涂层及添加不同含量Al2O3 TiO2铁基合金复合涂层,比较研究了这两种涂层的组织、显微硬度和磨损性能。结果表明,添加Al2O3 TiO2后的铁基复合涂层界面的生长形态发生变化,由初生的细长柱状树枝晶转变为小的枝晶,并且提供了形核的核心,细化了晶粒;其组织主要由晶粒细小的γ-Fe为基,以Cr23C6,Fe3C,Al2O3 TiO2为增强相的复合涂层;熔覆层的显微硬度可达600~655HV0.2。 相似文献
12.
Bing Xu Dezhi WangZhuangzhi Wu Aokui SunQijun Cheng Xiuqi Zan 《International Journal of Refractory Metals and Hard Materials》2010
Sintered Mo with the addition of La2O3/MoSi2 was prepared via the process of solid–solid doping + powder metallurgy. X-ray diffraction experiment, hardness test, three-point bending test and high-temperature tensile test were carried out to characterize the samples. The XRD pattern of a typical sample shows that the sintered Mo was mainly composed of Mo, La2O3 and Mo5Si3. Mo5Si3 was probably formed through the reaction between MoSi2 and the Mo matrix. Densities and fracture toughnesses of both doped Mo and pure Mo were measured and contrasted. Sintered Mo with the addition of 0.2 wt% La2O3/MoSi2 has the highest toughness, while more addition of La2O3/MoSi2 has smaller effect on improving toughness or even embrittles Mo. The results of three-point bending test and high-temperature tensile test show that the bending strength and high-temperature tensile strength of doped Mo are both higher than those of pure Mo. The formation of Mo5Si3 improves the high-temperature strength. The La2O3/Mo5Si3 dispersed in the Mo matrix refined the grains, and thus strengthened the Mo matrix by dispersion strengthening and grain refinement. 相似文献
13.
以机械球磨法制备具有可逆吸放氢性能的NaAlH4-Tm2O3储氢材料体系。利用相同制备方法进一步研究两种不同孔道材料(大孔Al2O3与介孔SiO2)对NaAlH4-Tm2O3体系储氢性能的影响,测试样品的循环吸放氢性能,并对样品吸放氢前后的结构进行表征。结果表明:大孔Al2O3材料的添加并不能明显改善NaAlH4-Tm2O3体系的放氢速率和放氢量,而介孔SiO2的加入使NaAlH4-Tm2O3体系在150℃条件下5 h内的首次放氢量(质量分数)达到4.61%,高于NaAlH4-Tm2O3体系的4.27%,增加了约8.0%。此外,添加介孔SiO2的NaAlH4-Tm2O3体系放氢速率也有所提高。 相似文献
14.
以ZrO(NO3)2·2H2O、Ce(NO3)·6H2O和La2O3为原料,采用柠檬酸法制备了La2Ce2O7粉体,研究了pH值、乙二醇及柠檬酸用量、煅烧温度等工艺参数对La2Ce2O7粉体的影响。结果表明,采用该方法能够制备纯净的La2Ce2O7粉体,最佳实验条件是pH值为5,乙二醇、柠檬酸与金属离子的摩尔比分别是1.8和2,煅烧温度为400℃。 相似文献
15.
采用高分子网络法制备混合纳米粉体,研究稀土氧化物Y2O3和Pr6O11加入量对Al2O3陶瓷相对密度和热导率的影响。采用阿基米德方法测定样品的体积密度,利用激光脉冲法测量试样的热扩散率并计算得出热导率。结果表明:两种添加剂都可以降低Al2O3陶瓷的烧结温度,提高Al2O3陶瓷的热导率,其中Y2O3的促进作用较强;当保温时间相同、烧结温度为1 500~1 650℃时,Al2O3陶瓷的相对密度和热导率都随烧结温度的升高而增大;当烧结温度相同、保温时间为30~120 min时,Al2O3陶瓷的相对密度和热导率也随保温时间的延长而增大。 相似文献
16.
Zhihong Lian Jing Wang Yuhua Lv Shubin Wang Qiang Su 《Journal of Alloys and Compounds》2007,430(1-2):257-261
A valence change from Eu3+ to Eu2+ was observed in the europium ion-doped ZnO–B2O3–P2O5 glasses prepared at high temperature in air. The fluorescence emission spectrum of the sample consists of a broad emission band ascribed to the 5d–4f transition of Eu2+ ion and sharp emission peaks assigned to the transitions of 5Do–7FJ (J = 0, 1, 2, 3, and 4) of Eu3+ ion, indicating that part of Eu3+ can be reduced into Eu2+ in the glass. A charge compensation model is proposed. The rigid tetrahedral network structure of glasses plays an important role in stability of Eu2+. The fabrication conditions are also studied. 相似文献
17.
采用高温固相反应法制备了Eu^3+掺杂ZnO-MgO-La203-B203基质的光致发光光纤,通过轴向拉伸试验测量了该光纤的应力-应变曲线。应用弹脆塑性理论研究了屈服面的变化和应力-应变的本构关系,计算了拉伸弹性模量、拉伸强度、拉伸最大负荷、拉伸强度的应变、断裂伸长率和材料的脆性指数。结果表明,该光纤弹性模量高于普通玻璃和大理石,接近于硬铝合金和轧制铝,其拉伸强度和所能承载的负荷都较大。 相似文献
18.
J.K.M.F. Daguano C. Santos R.C. Souza R.M. Balestra K. Strecker C.N. Elias 《International Journal of Refractory Metals and Hard Materials》2007,25(5-6):374-379
Zirconia and alumina based ceramics present interesting properties for their application as implants, such as biocompatibility, good fracture resistance, as well as high fracture toughness and hardness. In this work the influence of sintering time on the properties of a ZrO2–Al2O3 composite material, containing 20 wt% of Al2O3, has been investigated. The ceramic composites were obtained by sintering, in air, at 1600 °C for sintering times between 0 and 1440 min. Sintered samples were characterized by microstructure and crystalline phases, as well as by mechanical properties. The grain growth exponents, n, for the ZrO2 and Al2O3 were 2.8 and 4.1, respectively, indicating that different mechanisms are responsible for grain growth of each phase. After sintering at 1600 °C, the material exhibited a dependency of hardness as function of sintering time, with hardness values between 1500 HV (120 min) and 1310 HV (1440 min) and a fracture toughness of 8 MPa m1/2, which makes it suitable for bioapplications, such as dental implants. 相似文献
19.
Changan Tian Junliang Liu Jun Cai Yanwei Zeng 《Journal of Alloys and Compounds》2008,458(1-2):378-382
Single phase La9.33Si6O26 ultrafine powder, as a kind of highly activated precursor to prepare medium-to-low temperature electrolyte for solid oxide fuel cells (SOFCs), has been successfully synthesized via a non-aqueous sol–gel and self-combustion approach from the starting materials: lanthanum nitrate (La(NO3)3·6H2O), citric acid, ethylene glycol (EG), tetraethyl orthosilicate (TEOS) and ammonium nitrate. The details of gel's self-combustion were investigated by DTA–TG and the structural characterization of as-synthesized powder from self-combustion was performed by XRD and SEM. The results show that La9.33Si6O26 single phase of apatite-type crystal structure can be directly synthesized by sol–gel self-combustion method without further calcinations on the condition that the molar ratio (R) of NO3− to citric acid and ethylene glycol being 6:1. Such powders composed of well-dispersed particles with an average size of 200 nm and a specific surface area of 5.54 m2/g. It can be sintered to 90% of its theoretical density at 1500 °C for 10 h, about 200 °C lower than the sintering temperature for the powder derived from traditional solid reactions. The sintered material has a thermal expansion coefficient of 9.2 × 10−6 K−1 between room temperature and 800 °C. 相似文献
20.
Houan Zhang Ping Chen Jianhui Yan Siwen Tang 《International Journal of Refractory Metals and Hard Materials》2004,22(6):271-275
MoSi2 matrix composites (RWM) reinforced by the addition of both WSi2 and La2O3 were fabricated by mechanical alloying and self-propagating high-temperature synthesis (SHS) technique. This composite was analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is difficult to synthesize RWM composite by mechanical alloying with Mo–W–Si–La2O3 powder mixture, and suitable by self-propagating high-temperature synthesis. The hardness and toughness of MoSi2 was improved significantly by the addition of both, WSi2 and La2O3 more than by only WSi2. By adding 0.8 wt.% La2O3 and 50 mol.% WSi2 into the MoSi2 matrix, this composite has the highest hardness and toughness and exhibits more wear resistance than monolithic MoSi2 during the sliding wear test under oil lubrication, in this case, the material removal mechanism has been observed to be micro-cutting and micro-fracture. 相似文献