超导PbO/YBa2Cu3O7-δ复合氧化物摩擦磨损性能

为适应从低温到高温宽温范围的使用条件,用溶胶-凝胶法制备了YBa2Cu3O7-δ超导材料,用摩擦磨损试验机测试了YBa2Cu3O7-δ从室温至液氮温度的摩擦学性能.结果表明:室温20℃下,YBa2Cu3O7-δ与对偶件不锈钢盘对摩时,摩擦因数在0.5左右,当温度降到超导转变温度以下时(液氮温度-196℃)摩擦因数大幅度降低,YBa2Cu3O7-δ超导态摩擦因数是正常态值的一半,实验直接证明了电子激励对摩擦能量耗散的作用.为改善室温下YBa2Cu3O7-δ摩擦学性能,掺杂不同质量分数PbO作为润滑组元,制备了PbO/YBa2Cu3O7-δ超导固体润滑复合材料,取得良好效果.PbO掺杂不影响PbO/YBa2Cu3O7-δ复合材料的超导电性,在正常的载荷和滑行速度下15%PbO/YBa2Cu3O7-δ复合材料摩擦因数为0.2至0.3,磨损率为4.35×10-4mm3·(N·m)-1,分析了PbO/YBa2Cu3O7-δ复合材料减摩耐磨机制.     

超导材料YBa2Cu3O7-δ摩擦学性能研究现状

一些超导材料在超导转变温度下表现出摩擦系数突然降低,引起科学家极大关注,因而对摩擦的微观起源进行了研究,并探讨了声子的产生和电子激励对摩擦的贡献.综述了低温摩擦学的主要研究方法,重点总结了YBa2Cu3O7-δ在正常态及超导态下的摩擦学特性,分析了YBa2Cu3O7-δ在超导态下具有较低摩擦系数的摩擦机理,展望了YBa2Cu3O7-δ在摩擦学方面的应用前景.     

Ag/Bi2Sr2CaCu2Ox复合材料摩擦学特性

釆用固态反应法合成超导体Bi₂Sr₂CaCu₂O_x(Bi2212),使用摩擦实验机从液氮温度至室温对其摩擦学特性进行研究。研究表明：室温Bi2212与不锈钢盘对摩时摩擦系数约为0.35,当温度降至超导转变温度以下(液氮温度),摩擦系数大幅度降低至0.11,非常稳定。为改善Bi2212常温摩擦性能,添加Ag制备出Ag/Bi2212超导复合材料,XRD、SEM和EDS分析表明,Ag未进入Bi2212晶格,保证了Bi2212的超导电性,Ag的添加提高了复合材料密度和韧性,在正常载荷和滑行速度下Ag质量分数为10 %时摩擦系数为0.2,15%Ag/Bi2212磨损率最低,为9. 5×10-5 mm3 (N·m)-1。分布基体中的Ag能有效抑制裂纹萌生和扩展并在摩擦作用下向表面转移,在摩擦表面形成一层Ag转移膜,其低剪切强度起到很好的润滑作用,同时将摩擦产生的热量及时传导出去,使复合材料表现出良好的减摩耐磨性能。     

CNTs/NbSe_2/Cu基自润滑复合材料的制备及其摩擦学性能研究

将CNTs、Se粉和Nb粉按一定化学计量比均匀混合,通过固相反应生成碳纳米管(CNTs)/NbSe2复合材料,然后以生成的CNTs/NbSe2复合材料为固体润滑相,Cu为基体相,通过粉末冶金的方法制备出了CNTs/NbSe2/Cu基自润滑复合材料。利用UMT-2摩擦磨损试验机对材料的摩擦磨损性能进行评价,结果表明NbSe2/Cu基自润滑复合材料具有较好的摩擦学性能,磨痕平滑;随着1%(质量比)CNTs的加入,CNTs/NbSe2/Cu基自润滑复合材料摩擦学性能更为优异,其磨痕更平滑。这是由于具有优异润滑性能的NbSe2和均匀弥散分布在Cu基体中的大长径比管状结构的CNTs一起起到了协同强化和减摩耐磨作用,最终导致材料的机械和摩擦学性能同时提高。     

新型自润滑YBa_2Cu_3O_7/Cu复合材料的制备及性能

采用草酸盐共沉淀法制备了YBa2Cu3O7(YBCO)粉体,利用真空热压烧结法制备了不同质量分数的YBCO/Cu复合材料,测定了YBCO/Cu复合材料的密度、硬度和电导率,利用MMU-5GA磨损试验机对YBCO/Cu复合材料进行了摩擦磨损试验。采用XRD、SEM和TEM对YBCO粉体及YBCO/Cu复合材料的微观结构、磨损表面形貌及物相组成进行了表征。研究了YBCO质量分数对YBCO/Cu复合材料组织及性能的影响。结果表明:所制备的YBCO粉体物相为Y123相,其层状结构明显,粉体纯度高、杂质少,粒度达到纳米级;纳米YBCO可显著细化YBCO/Cu复合材料的基体组织,提高复合材料的摩擦学性能。随着YBCO质量分数增加,基体组织中纳米YBCO颗粒分布均匀度降低,逐渐出现团聚;YBCO/Cu复合材料的电导率和密度降低,硬度先升高后降低,摩擦系数逐渐减小。3%YBCO/Cu复合材料的摩擦磨损性能最好。YBCO/Cu复合材料强化机制为Orowan强化、热错配强化和细晶强化;其磨损机制主要为塑变磨损、磨粒磨损和疲劳剥落。     

梯度自润滑复合材料在不同滑动摩擦下的摩擦学特性

梯度自润滑复合材料是一种新型润滑材料,利用粉末冶金工艺设计和制备了该材料,考察了其在不同摩擦条件下的摩擦学特性,并对其摩擦磨损机理进行了分析和研究.结果表明:梯度自润滑复合材料随着复合固体润滑剂含量的增多,摩擦学性能明显改善,但润滑剂含量过高将导致材料表面硬度过低;该材料适用于高载倚下的润滑部件;脂润滑条件下,复合固体润滑剂与润滑脂结合在摩擦面上形成的膏状润滑膜使梯度自润滑复合材料的摩擦学性能显著改善;在脂润滑高载荷条件下,梯度自润滑复合材料的磨损主要发生在磨损初期,之后磨损极小,摩擦系数也趋于减小.     

Fe-20Cu基自润滑摩擦材料的摩擦学性能研究

为探究双润滑组元G-MoS2(G表示石墨)对Fe-20Cu基自润滑摩擦材料组织及性能的影响,通过粉末冶金热压法制备了Fe-20Cu基自润滑摩擦材料,并对其进行扫描电镜、X射线衍射表征以及摩擦学性能测试分析.结果 表明:在Fe-20Cu基自润滑摩擦材料中,随着G-MoS2含量的升高,摩擦材料硬度和抗压强度先增大后减小.当...     

含NbSe2的铜基电接触复合材料的制备及其真空摩擦学性能研究

本研究采用粉末冶金工艺制备出含纳米NbSe₂(1wt%~9wt%)的铜-石墨自润滑复合材料。在微摩擦试验机及超低温摩擦试验机上进行摩擦磨损实验, 通过X射线衍射仪(XRD)、扫描电子显微镜(SEM )等分析其物相、形貌及磨痕, 并探讨了该复合材料在大气、真空试验条件下的磨损机理。结果表明: NbSe₂的加入显著提高铜基复合材料的摩擦学性能; 真空干摩擦条件下不含NbSe₂复合材料的摩擦系数有所增大, 但添加NbSe₂(5.5wt%)的自润滑复合材料摩擦系数更小(μ=0.185), 承载能力更高, 其磨损是粘着磨损、接触疲劳磨损共同作用的结果。     

Al2O3/TiC/CaF2自润滑陶瓷材料的研究

采用热压工艺制备了Al2O3/TiC/CaF2自润滑陶瓷材料,测量了其力学性能.结果表明,当CaF2含量为10%(质量分数,下同)时,Al2O3/TiC/CaF2自润滑陶瓷材料的强度和硬度最高,分别达到了589MPa和HV1537.其微观结构显示,Al2O3/TiC/CaF2自润滑陶瓷材料的晶粒大小均匀,基体组织成网状结构,有利于提高材料的强度.对Al2O3/TiC/CaF2自润滑陶瓷材料室温干摩擦下的摩擦磨损行为进行了研究,当CaF2含量为10%时,摩擦系数最低,约为0.28左右,CaF2含量为15%的陶瓷反而具有较大的摩擦系数,达到了0.32左右.研究表明,Al2O3/TiC/CaF2自润滑陶瓷材料能形成有效的减磨层,从而显著降低摩擦系数和磨损因子,具有一定的自润滑性能.     

Eu2O3掺杂对压敏-电容双功能陶瓷材料CaCu3Ti4O12电性能的改善效果

以稀土氧化物Eu2O3为添加剂,采用固相反应法制备了不同掺杂比例(x=0、0.2％、0.5％、1％(质量分数))的CaCu3Ti4O12(CATO)陶瓷样品.采用X射线衍射仪(XRD)和扫描电镜(SEM)对掺杂样品的微观形貌变化进行测量分析；利用一直流高压电源测试样品的J-E非线性特征；利用Anglent4294型精密阻抗分析仪测试样品的电介性能.掺杂后样品的晶格结构并未发生明显的改变,但是平均晶粒尺寸减小,晶界处富Cu相消失；纯CCTO的XRD图谱中出现了富Cu相,掺杂样品的图谱中并未出现上述杂相；Eu2O3掺杂提高了样品内部的肖特基势垒高度,增加了势垒阻挡层的数目,使得样品的压敏电压和非线性系数明显提高,材料的压敏电阻性明显改善,电介-频率稳定性增强.     

Investigation of Instability of Lattice of Bi_2Sr_2CaCu_2O_x

Bi2Sr2CaCu2Ox superconductor was studied by differential scanning calorimetry (DSC) and thermogravimetry (TG) in different atmospheres. It is discovered that there is a thermal anomaly in the DSC curve, associated with a weight loss in the TG curve before the melting of the sample. Careful thermal analysis and high temperature X-ray diffraction reveal that the thermal anomaly and the weight loss show an instability of the crystalline Iattice. By annealing the sample in oxygen and argon, respectively and then by TC measurement and thermal analysis, the coincidence of transition temperature with the instability is found. The coincidence is further confirmed by Y-doped 2212 phase.     

Microstructure, Mechanical and Tribological Properties of Ag/Bi2Sr2CaCu2O x Self-lubricating Composites

Ag/Bi₂Sr₂CaCu₂O _x self-lubricating composites were successfully fabricated by a facile powder metallurgy method. The structure and morphology of the as-synthesized composites and the worn surface after tribometer testing are characterized by using X-ray diffraction and scanning electron microscopy together with energy dispersive spectrometry. The results indicated that self-lubricating composites are composed of superconductor phase and Ag phase. Moreover, the effects of Ag on mechanical and tribological properties of the novel composites were investigated. The friction test results showed that the friction coefficient of the pure Bi2212 against stainless steel is about 0.40 at ambient temperature and abruptly decreases to about 0.17 when the temperature is cooled to 77 K. The friction coefficients of the composites from room temperature to high temperature were lower and more stable than those of pure Bi₂Sr₂CaCu₂O _x . When the content of Ag is 10 wt.%, the Ag/Bi₂Sr₂CaCu₂O _x composites exhibited excellent tribological performance, the improved tribological properties are attributed to the formation of soft metallic Ag films at the contacted zone of the composites.     

Fabrication of Grain-oriented (Bi,Pb)_2Sr_2Ca_2Cu_3O_x Superconducting Tapes Using Magnetic Field and Vibration Technique

Highly textured (Bi,Pb)2Sr2Ca2Cu3Ox superconducting tapes have been fabricated by means of magnetic-field and vibration technique. This method is an effective way of improving the degree of grain alignment and density of oxide core in tapes after heat treatment and pressing cycles.Jc of above 20% was increased than that without treatment.     

超导Ag/Bi1.6Pb0.4Sr2Ca2Cu3O10-x复合氧化物摩擦磨损性能

为适应20℃～-200℃ 温度的适用范围,采用固相法制备了Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10-x超导材料,用摩擦磨损试验机测试了Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10-x从液氮温度至室温的摩擦学性能。结果表明 : 在室温 20℃下,Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10-x与对偶件轴承钢盘对摩时,摩擦系数约为0.35,当温度降到超导转变温度以下时(液氮温度-170℃)摩擦系数大幅度降低,Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10-x超导态摩擦系数为正常态值的一半,实验证明了电子激励对摩擦能量耗散的作用。为改善室温下Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10-x摩擦学性能,掺杂不同质量分数 Ag作为润滑组元,制备了Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10-x超导固体润滑复合材料,取得良好耐磨减摩效果。Ag掺杂不影响Ag/Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10-x复合材料的超导性,在正常载荷和滑动速度下10 wt%Ag/ Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10-x复合材料摩擦系数为0.2~0.3,磨损率为4.57×10-4 mm3·(N·m)-1。     

Ag/TiO2纳米粒子的制备及其光催化降解苯酚的性能研究

采用溶胶-凝胶法制备了TiO₂和Ag/TiO₂纳米粒子,采用涂覆法制备了TiO₂和Ag/TiO₂纳米粒子光催化剂基板样品。使用XRD、SEM和拉曼光谱等手段,对TiO₂和Ag/TiO₂纳米粒子进行了晶格结构和表面形貌研究;通过UV-Vis,研究了TiO₂和Ag/TiO₂纳米粒子光催化剂基板样品在光催化反应器中对苯酚的光催化降解性能。结果表明,制备的TiO₂和Ag/TiO₂纳米粒子均为纯净的金红石相,二者表面形貌并没有明显区别,Ag单质粒子成功负载在TiO₂纳米材料上;Ag单质粒子的负载,明显增强了TiO₂纳米粒子对可见光的吸收,且Ag/TiO₂纳米粒子薄膜对苯酚的光催化降解性能明显优于TiO₂纳米粒子薄膜;在光催化降解1 h后,TiO₂纳米粒子薄膜仅催化降解了溶液中30%(质量分数)的苯酚,且光催化降解出现了饱和趋势,而Ag/TiO₂纳米粒子薄膜可催化降解溶液中50%(质量分数)的苯酚,且在光催化降解3 h后,仍未出现饱和趋势。     

The influence of the structure on the electrical and magnetic properties of Bi2Sr2CaCu2O8+δ single crystals

The correlation between the structure, chemical composition, electrical and magnetic properties of Bi2Sr2CaCu2O8+δ single crystals is presented. As revealed by SEM measurements, the small samples (approximately 1 mm×1 mm×0.2 mm) are stacks of thin plates (1–2 μm). Microcompositional measurements (energy dispersive spectroscopy) show the Bi2Sr2CaCu2O8+δ (2212)-phase and a small quantity of residual phases enriched in bismuth and strontium and calcium-deficient. Magnetically modulated microwave absorption measurements (MAMMA) lead to a value for the anisotropy of the upper critical field of about 7, which is more than twice the reported value for YBa2Cu3O7-δ single crystals (also determined from MAMMA responses). The plot of the resistance versus temperature suggests that only the first 10–20 plates from the surface of the sample have a contribution to the sample conductivity. The imaginary part, X″, of the magnetic susceptibility of our samples shows three peaks. This revised version was published online in November 2006 with corrections to the Cover Date.     

Ag3PO4/BigFe4O9复合催化剂的制备及其光催化性能

利用水热法成功地制备得到具有高效光催化活性的Ag3PO4/Bi2Fe4O9复合型光催化剂.使用X-射线多晶粉末衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)对样品进行表征,并以罗丹明B为目标降解物对其光催化性能进行研究.结果表明:样品是由纳米Ag3 PO4颗粒负载在片状四边形的Bi2Fe4O9表面组成的,当Ag3PO4的负载量为4wt％时,复合材料的光催化效果最好,在可见光(波长＞420nm)照射下,1.5h内对100mL浓度为10-5mol.L-1罗丹明B溶液的脱色率可达98.7％.     

Ag/TiO2光催化薄膜清除乙烯气体的研究

乙烯对果蔬的生长有积极的作用,它可以促进果蔬的成熟,使其变得香甜可口。但果蔬成熟后乙烯的存在又可以加速果蔬的熟化程度,使其变得脆弱、易腐烂。因此,清除乙烯将对果蔬保鲜产生积极的影响。本文采用溶胶一凝胶方法制备了TiO2及Ag／TiO2薄膜。利用气相色谱法通过在自制的反应器内进行检测清除乙烯的实验,比较了TiO2薄膜和Ag／TiO2薄膜的光催化清除乙烯性能。结果发现,TiO2薄膜有较好的光催化清除乙烯性能,掺杂适量的Ag后,Ag／TiO2薄膜有更好的清除乙烯性能。本文还用XRD、SEM对TiO2及Ag／TiO2薄膜的形貌、物相结构、颗粒尺寸进行了表征分析并对实验结果进行了讨论。     

Synthesis,characterization, antibacterial and photocatalytic performance of Ag/AgI/TiO2 hollow sphere composites

Dispersed TiO₂ hollow spheres were successfully prepared which was obtained via Ostwald ripening under solvothermal conditions without any templates or surfactants. Then, the AgI/TiO₂ was synthesized by the deposition−precipitation process. Finally, Ag/AgI/TiO₂ was obtained by a photocatalytic reduction way. Their characteristics were analyzed by XRD, SEM, HRTEM, N₂ adsorption−desorption measurements and UV-vis absorption spectra. To demonstrate the potential applications of such composites, their antibacterial activity against Escherichia coli (E. coli) was studied by microcalorimetry for the first time, and their photocatalytic performance for degradation of different organic dyes under simulated UV and visible light was discussed. The results indicated that Ag/AgI/TiO₂ hollow spheres revealed elevated antibacterial and photocatalytic activity because of their unique morphology, hollow structure and high surface area. The mechanism of the excellent antibacterial and photocatalytic activity of Ag/AgI/TiO₂ hollow spheres are discussed which are attributed to the synergetic effect of Ag, AgI and TiO₂. It suggested that the new Ag/AgI/TiO₂ photocatalyst has broad application prospects in solar cell, sensor, antibacterial, catalysis and nanotechnology.