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121.
高铝锌基合金的摩擦磨损性能与磨损机制 总被引:5,自引:4,他引:5
高铝锌基合金是铜合金和铝合金等高强度磨损件的理想替代材料,虽然人们已经就其耐磨性能进行了一些研究,但对这种合金更全面的摩擦学性能研究,尤其是有关它的磨损机理之研究却还是一个尚未深入开展的课题。为了对合理选用高铝锌基合金材料提供科学依据,在干摩擦和30#机械油润滑条件下,对高铝锌基合金同材质摩擦副及其与45#钢配副的摩擦磨损性能在SRV滑动摩擦磨损试验机和M200磨损试验机上进行了考察,并且利用俄歇电子能谱仪、扫描电子显微镜和Talysurf5P-120形貌检测系统等分析和检测了磨损表面的组成变化、形貌和磨痕特征,提出了ZA27合金在不同工况下的磨损机制. 相似文献
122.
These studies were conducted to determine the discrepancies between the spectroscopic data of the isolated and synthetic samples of the marine natural product (+)-elisabethadione. Attempts at the re-isolation of (+)-elisabethadione from Pseudopterogorgia elisabethae were unsuccessful, but during these efforts, two related natural products of O-methylelisabethadione (8) and O-methyl-nor-elisabethadione (9) were discovered. The total syntheses of these new natural products were accomplished by using the combined C-H activation/Cope rearrangement as the key step and the previously synthesized elisabethadione was converted to O-methylelisabethadione. These studies confirmed that the synthetic sample of (+)-elisabthadione was assigned the correct structure. The considerable differences in the data between the synthetic and natural samples of (+)-elisabethadione lead to the conclusion that the structure of the natural material was either miss-assigned or the published spectral data were incorrect. During the course of these studies, questions arose about the assigned structure of another natural product, elisabethamine, which was proposed to be an aminohydroquinone. Attempts at the synthesis of this compound revealed that the aminohydroquinone structure was unstable in air as it was readily oxidized to the quinone. 相似文献
123.
Zhu Z Brynda M Wright RJ Fischer RC Merrill WA Rivard E Wolf R Fettinger JC Olmstead MM Power PP 《Journal of the American Chemical Society》2007,129(35):10847-10857
The synthesis and structural characterization of the first homologous, molecular M-M bonded series for the group 12 metals are reported. The compounds Ar'MMAr' (M = Zn, Cd, or Hg; Ar' = C(6)H(3)-2,6-(C(6)H(3)-2,6-Pr(i)(2))(2)) were synthesized by reduction of the corresponding arylmetal halides by alkali metal/graphite (Zn or Hg) or sodium hydride (Cd). These compounds possess almost linear C-M-M-C core structures with two-coordinate metals. The observed M-M bonds distances were 2.3591(9), 2.6257(5), and 2.5738(3) A for the zinc, cadmium, and mercury species, respectively. The shorter Hg-Hg bond in comparison to that of Cd-Cd is consistent with DFT calculations which show that the strength of the Hg-Hg bond is greater. The arylmetal halides precursors (Ar'MI)(1 or 2), and the highly reactive hydrides (Ar'MH)(1 or 2), were also synthesized and fully characterized by X-ray crystallography (Zn and Cd) and multinuclear NMR spectroscopy. The arylzinc and arylcadmium iodides have iodide-bridged dimeric structures, whereas the arylmercury iodide, Ar'HgI, is monomeric. The arylzinc and arylcadmium hydrides have symmetric (Zn) or unsymmetric (Cd) mu-H-bridged structures. The Ar'HgH species was synthesized and characterized by spectroscopy, but a satisfactory refinement of the structure was precluded by the contamination of monomeric Ar'HgH by Ar'H. It was also shown that the decomposition of Ar'Cd(mu-H)(2)CdAr' at room temperature leads to the M-M bonded Ar'CdCdAr', thereby supporting the view that the reduction of the iodide proceeds via the hydride intermediate. 相似文献
124.
Rivard E Fischer RC Wolf R Peng Y Merrill WA Schley ND Zhu Z Pu L Fettinger JC Teat SJ Nowik I Herber RH Takagi N Nagase S Power PP 《Journal of the American Chemical Society》2007,129(51):16197-16208
A series of symmetric divalent Sn(II) hydrides of the general form [(4-X-Ar')Sn(mu-H)]2 (4-X-Ar' = C6H2-4-X-2,6-(C6H3-2,6-iPr2)2; X = H, MeO, tBu, and SiMe3; 2, 6, 10, and 14), along with the more hindered asymmetric tin hydride (3,5-iPr2-Ar*)SnSn(H)2(3,5-iPr2-Ar*) (16) (3,5-iPr2-Ar* = 3,5-iPr2-C6H-2,6-(C6H2-2,4,6-iPr3)2), have been isolated and characterized. They were prepared either by direct reduction of the corresponding aryltin(II) chloride precursors, ArSnCl, with LiBH4 or iBu2AlH (DIBAL), or via a transmetallation reaction between an aryltin(II) amide, ArSnNMe2, and BH3.THF. Compounds 2, 6, 10, and 14 were obtained as orange solids and have centrosymmetric dimeric structures in the solid state with long Sn...Sn separations of 3.05 to 3.13 A. The more hindered tin(II) hydride 16 crystallized as a deep-blue solid with an unusual, formally mixed-valent structure wherein a long Sn-Sn bond is present [Sn-Sn = 2.9157(10) A] and two hydrogen atoms are bound to one of the tin atoms. The Sn-H hydrogen atoms in 16 could not be located by X-ray crystallography, but complementary M?ssbauer studies established the presence of divalent and tetravalent tin centers in 16. Spectroscopic studies (IR, UV-vis, and NMR) show that, in solution, compounds 2, 6, 10, and 14 are predominantly dimeric with Sn-H-Sn bridges. In contrast, the more hindered hydrides 16 and previously reported (Ar*SnH)2 (17) (Ar* = C6H3-2,6-(C6H2-2,4,6-iPr3)2) adopt primarily the unsymmetric structure ArSnSn(H)2Ar in solution. Detailed theoretical calculations have been performed which include calculated UV-vis and IR spectra of various possible isomers of the reported hydrides and relevant model species. These showed that increased steric hindrance favors the asymmetric form ArSnSn(H)2Ar relative to the centrosymmetric isomer [ArSn(mu-H)]2 as a result of the widening of the interligand angles at tin, which lowers steric repulsion between the terphenyl ligands. 相似文献
125.
126.
1,3,5,7-四乙酰基-1,3,5,7-四氮杂环辛烷合成反应中间体的制备分离 总被引:1,自引:0,他引:1
1,3,5,7-四乙酰基-1,3,5,7-四氮杂环辛烷(TAT)是高能炸药奥克托今(HMX)重要的合成反应前体之一,1,5-二乙酰基-1,3,5,7-四氮杂环辛烷(DAPT)醋酐酰解法和乙腈甲醛小分子缩合法均能制备得到TAT.采用半制备高效液相色谱制备分离了上述两种制备方法反应原液中的六种中间体,分别是1-乙酰氧甲基-3,5,7-三乙酰基-1,3,5,7-四氮杂环辛烷、1,3,5-三乙酰基-1,3,5,7-四氮杂环辛烷、1-乙酰氧甲基-3,5,7-三乙酰基-1,3,5,7-四氮杂环辛烷、N,N’-亚甲基二乙酰胺、三乙酰胺二亚甲基三胺和四乙酰胺三亚甲基四胺,为反应机理研究提供了有力的证据.DAPT醋酐酰解法反应原液样品的最佳制备色谱条件为:正相硅胶柱(20 mm×250 mm,10~20μm),流动相:V(乙腈)∶V(甲醇)=95∶5,流速为10 mL·min-1,检测波长为215 nm,进样量为1 mL,样品浓度30 mg/mL.乙腈甲醛小分子缩合法反应原液样品的最佳制备色谱条件为:正相硅胶柱(20 mm×250 mm,10~20μm),流动相:V(乙腈)∶V(水)=90∶10,流速为10 mL·min-1,检测波长为215 nm,进样量为1 mL,样品浓度30 mg/mL.制备得到的中间体经HPLC分析知纯度均在97%以上,可直接作为结构鉴定的标准样品. 相似文献
127.
128.
采用静水生物测试手段,试验了Pb、Cu不同质量浓度(0.00、0.10、0.25、0.50、1.00mg.L-1)及不同时间(10、20、30 d)对泥鳅卵细胞发育的胁迫。显微观察结果显示,在重金属染毒10、20、30 d后,泥鳅卵细胞胞质外渗、萎缩、干瘪,高质量浓度组卵细胞受损尤为明显。泥鳅卵细胞对不同质量浓度处理组重金属均表现出时间-剂量效应。在各质量浓度处理组中,随着染毒时间的延续,泥鳅卵巢及卵细胞均出现功能丧失和生物学死亡的现象。 相似文献
129.
在天体空间或实验室的等离子体中可能存在能量为若干keV量级的光子的线辐射,它们源于一种新的原子核物质结构形态(核核两体的松聚合)形成之时.对两个原子核组成的体系,采用库仑势垒与核力方势阱相组合的作用势,求解核核两体的定态薛定谔方程,得到了两体松束缚态的波函数和可能的能量本征量(核的长程库仑能的数量级)并说明了这种松束缚态的存在条件.对某些轻核,基态的结合能为若干keV. 相似文献
130.
Bingbao Mei Songqi Gu Xianlong Du Zhongliang Li Hanjie Cao Fei Song Yuying Huang Zheng Jiang 《X射线光谱测定》2020,49(1):251-259
A wavelength-dispersive X-ray spectrometer based on von Hamos geometry for in/ex situ resonant inelastic X-ray scattering (RIXS) studies at BL14W1-X-ray absorption fine structure (XAFS) beamline of Shanghai Synchrotron Radiation Facility (SSRF) is reported. The design considerations and the operational characteristics of the spectrometer are described in detail. With a Si(444) bent crystal, the spectrometer provides an energy range from 8 to 9 keV, which enables the measurement of K-edge X-ray spectroscopy of some transition metal complexes and L-edge X-ray spectroscopy of some 5d transition metal complexes. Based on von Hamos geometry, the process of the collection of RIXS is considerably simplified. The collection of full RIXS planes of tungstic samples requiring spectral resolutions is presented, demonstrating the speciation capabilities of the instrument. Taking the series of oxide-derived copper catalysts for carbon dioxide electrochemical reduction as the research model, the in situ RIXS were measured to probe dynamic changes in electronic structure. Finally, the comparison between in situ RIXS and in situ conventional XAFS is presented, demonstrating more competitive spectral resolution of RIXS. 相似文献