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61.
采用化学气相沉积法在硬质合金基体上沉积具有不同织构择优的α-Al2O3涂层,通过扫描电子显微镜(SEM)、X射线衍射(XRD)分别对其微观组织和机械性能进行分析。研究结果表明,通过改善过渡层的氧化气氛,氧化铝的过渡层结构为针状物,成功制备不同织构的氧化铝涂层,涂层结合力良好。 相似文献
62.
以整体型α-Al2O3为载体,晶种胶作导向剂,通过凝胶预陈化路线合成了多级孔道FAU整体材料。对合成的样品进行了FT-IR、XRD、SEM和N2吸附脱附表征。根据实验结果确定了晶种胶、凝胶预处理及预陈化步骤的作用,同时提出了不同路线生成氧化铝复合物可能的合成机理。结果发现:负载的FAU沸石的粒径、形状及数量可通过改变晶化凝胶的组成,并且α-Al2O3载体的结构没有明显改变。具有简单、可重现且易将三重孔道结构融于成型的整体材料中的特点,通过晶种胶预处理的凝胶预陈化路线可加强载体内表面与沸石间的界面作用,形成纯相FAU晶体沉积在α-Al2O3载体骨架表面的形貌。另外,该方法可为其他的多级孔道沸石的合成提供思路。 相似文献
63.
Amila Turalić Prof. Jasmina Đeđibegović Dr. Zsófia Hegedüs Prof. Tamás A. Martinek 《Chembiochem : a European journal of chemical biology》2020,21(14):2060-2066
The incorporation of β-amino acids into a peptide sequence has gained particular attention as β- and α/β-peptides have shown remarkable proteolytic stability, even after a single homologation at the scissile bond. Several peptidases have been shown to cleave such bonds with high specificity but at a much slower rate compared to α-peptide bonds. In this study, a series of analogs of dipeptidyl peptidase-4 (DPP-4) substrate inhibitors were synthesized in order to investigate whether β-amino acid homologation at the scissile bond could be a valid approach to improving peptide stability towards DPP-4 degradation. DPP-4 cleaved the α/β-peptide bond after the N-terminal penultimate Pro with a broad specificity and retained full activity regardless of the β3-amino acid side chain and peptide length. Significantly improved half-lives were observed for β3Ile-containing peptides. Replacing the penultimate Pro with a conformationally constrained Pro mimetic led to proteolytic resistance. DPP-4 cleavage of α/β-peptide bonds with a broad promiscuity represents a new insight into the stability of peptide analogs containing β-amino acids as such analogs were thought to be stable towards enzymatic degradation. 相似文献
64.
A new type collector α-Bromodecanoic acid (CH3(CH2)7CHBrCOOH, α-BDA) was synthesized by solvent-free method (Hell–Volhard–Zelinski reaction) in laboratory for the flotation of quartz mineral at a relatively low temperature of 16 °C. The adsorption mechanism of α-BDA collector on quartz mineral surface was established by zeta potential measurements, contact angle measurements, Fourier transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS), in conjunction with the results of quartz micro-flotation tests. The flotation results showed that the activator Ca(II) functioned as an indispensable and crucial factor on the recovery of pure quartz. When the quartz was floated with α-BDA alone at strong alkaline conditions (pH ⩾ 11.50), the recovery rate reached to only 11.9%. However, when using the activator Ca(II) at a concentration of 4 × 10−4 mol/L, the collector exhibited an excellent performance, where about 99.5% of the quartz had been floated at or above pH value 11.50 at 16 °C. The study revealed that the α-BDA collector had adsorbed on the surface of pure quartz in the forms of electrostatic interaction, hydrogen bonding and chemical adsorption based on the results of zeta potential measurements, contact angle measurements, FT-IR spectra, and XPS. 相似文献
65.
66.
Present paper proposes a new technique based on double parametric form of fuzzy numbers to solve an uncertain beam equation using Adomian decomposition method subject to unit step and impulse loads. Uncertainties appear in the initial conditions are considered in terms of triangular convex normalized fuzzy sets. Using the single parametric form viz. α-cut form of fuzzy numbers, the fuzzy beam equation is converted first to an interval based fuzzy differential equation. Next this differential equation is transformed to crisp form by applying double parametric form of fuzzy numbers. Finally the same is solved by Adomian decomposition method symbolically to obtain the uncertain bounds of the dynamic response. Obtained results are depicted in term of plots to show the efficiency and powerfulness of the present analysis. 相似文献
67.
Dilek Turan Alper Uludag Servet Turan 《International Journal of Applied Ceramic Technology》2019,16(1):404-409
SiAlONs are important materials for high-temperature applications and creep properties of SiAlONs are largely controlled by the amount and type of sintering additives. It has been established that heat treatment can reduce the amount of amorphous intergranular phase through crystallization. However, there is no study on the creep behavior of heat-treated SiAlON ceramics containing multication sintering additives. Therefore, the aim of the study was to investigate the effect of heat treatment on the creep properties of multication containing (Y-Sm-Ca oxides) α/β-SiAlON ceramics. The heat treatments of the sintered samples were carried out at 1600°C for 2 hours. The creep tests were carried out in the range 1300-1400°C under different loads (50-150 MPa). The existing phases and the microstructures of samples before and after creep were investigated using XRD and SEM techniques. It was found that heat treatment resulted in a better creep performance compared to as-sintered samples. The activation energy and stress exponent for heat-treated SiAlONs were also calculated as 708 ± 45 kJ/mol and 1.4, respectively. Compared to the sintered sample values, the results suggested that the acting creep mechanism of grain-boundary sliding and cavitation was reduced with the heat treatment. 相似文献
68.
69.
Atsushi Sakon Kunihiro Nakajima Sin-ya Hohara 《Journal of Nuclear Science and Technology》2019,56(2):254-259
Even a zero-power reactor core containing highly enriched uranium has a weak neutron source inherent in uranium 235, and consequently, a neutron counter placed closely to the core without external neutron source registers a certain counting rate. The study of the counting is very important for zero-power reactor physics experiments with a high precision. In this experimental study, first, at a shutdown state of the UTR-Kinki reactor without start-up neutron source, a pulse height distribution of output signals from a neutron proportional counter was measured to confirm that these signals resulted from neutron detections. At several subcritical states of the UTR, then, the Feynman-α analysis was carried out to confirm that the neutrons detected by the counter must be fission neutrons multiplied by fission chain reactions. The correlation amplitude measured in the Feynman-α analysis was much higher than that measured in a previous drive by start-up source. Further, it was also confirmed that the subcriticality dependence of neutron counting rate followed the source multiplication formula. This feature indicated that the one-point model was very successful in the subcritical range including the shutdown state. 相似文献