Mechanical Properties of Hot Isostatically Pressed Zirconia-Toughened Alumina Ceramics Prepared from Coprecipitated Powders

Amorphous Al₂O₃–ZrO₂ composite powders with 5–30 mol% ZrO₂ have been prepared by adding aqueous ammonia to the mixed solution of aqueous aluminum sulfate and zirconium alkoxide containing 2-propanol. Simultaneous crystallization of γ-Al₂O₃ and t -ZrO₂ occurs at 870°–980°C. The γ-Al₂O₃ transforms to α-Al₂O₃ at 1160°–1220°C. Hot isostatic pressing has been performed for 1 h at 1400°C under 196 MPa using α-Al₂O₃– t -ZrO₂ composite powders. Dense ZrO₂-toughened Al₂O₃ (ZTA) ceramics with homogeneous-dispersed ZrO₂ particles show excellent mechanical properties. The toughening mechanism is discussed. The microstructures and t / m ratios of ZTA are examined, with emphasis on the relation between strength and fracture toughness.     

粉煤灰替代率对混凝土内钢筋腐蚀的影响

为研究不同粉煤灰替代率对混凝土内钢筋腐蚀行为的影响,制作了粉煤灰替代率0%,15%,30%和45%和氯离子含量0.1%,0.5%,1.5%,3.0%和5.0%的混凝土试件.对混凝土内钢筋的腐蚀电流密度、腐蚀电位、阴极极化曲线、混凝土电阻率、混凝土孔隙液pH值等进行了测量.结果表明,钝化状态的钢筋,随着粉煤灰替代率的增加,钢筋腐蚀电位显著增大,而腐蚀电流密度均维持在较低水平无明显变化;活化状态的钢筋,随着粉煤灰替代率的增加,钢筋腐蚀电流密度显著下降,且氯离子舍量越高,钢筋腐蚀电流密度的降幅越大,最大降幅达84%,而腐蚀电位均维持在较低负值水平无明显变化.粉煤灰的添加可以起到对混凝土内钢筋腐蚀的保护作用.     

Diagnostic system to measure spatial and temporal profiles of shock front using compact two-stage light-gas gun and line reflection method

A diagnostic system has been developed to obtain spatial and temporal profiles of shock front. A two-stage light-gas gun is used to accelerate impactors in velocity range with 4-9 km/s. The system consists of the Faraday-type electromagnetic sensors to measure impactor velocity, optical system with high-speed streak camera to measure shock-wave velocities, and the delay trigger system with self-adjustable pre-event pulse generator. We describe the specifications and performance of this system and data-analysis technique on the tilt and distortion of the shock front. Finally, we obtained the Hugoniot data of copper for system demonstration.     

Controlling Interface Intermixing and Properties of SrTiO3‐Based Superlattices

By combining state‐of‐the‐art microscopy, spectrosccopy, and first‐principles calculations, atomic‐scale intermixing behavior at heterointerfaces in SrTiO₃‐based superlattices is investigated. It is found that Nb is confined to a unit‐cell thickness without intermixing, whereas Ba diffuses only to the adjoining Nb‐doped SrTiO₃ layer. It is revealed that the intermixing behaviors at the heterointerfaces are determined by not only the migration energy, but also by the vacancy‐formation energy and the Fermi energy of each layer. Based on these results, we find a method to control the atomic‐scale intermixing at the nonpolar heterointerfaces and clearly demonstrate the property improvements obtained by constructing an abrupt heterointerface.     

Synthesis of Zeolite A from Aluminoborosilicate Glass Used in Glass Substrates of Liquid Crystal Display Panels and Evaluation of Its Cation Exchange Capacity

Synthesis of zeolite A from aluminoborosilicate glass used in liquid crystal display (LCD) panel glass substrate was attempted. Mixture of aluminoborosilicate glass and sodium aluminate was hydrothermally treated with sodium hydroxide solution for 10.8–345.6 ks at 368–423 K. Aluminoborosilicate glass was also acid treated with nitric acid before hydrothermal treatment. Obtained samples were characterized by X‐ray diffraction and scanning electron microscope observation. Zeolite A, hydroxysodalite, and zeolite P were synthesized, and with the specific conditions of hydrothermal treatment, a single phase of zeolite A was successfully obtained. Acid treatment was effective for synthesis of a single phase of zeolite A, because the components of aluminoborosilicate other than SiO₂ preferentially eluted for acid solution and during following hydrothermal treatment SiO₂ was supposed to elute for alkaline solution. Cation‐exchange capacities (CECs) were investigated for these products. It was clarified that CEC of the product with a single phase of zeolite A obtained from aluminoborosilicae glass was 4.2 mol/kg. CEC of the product consisted of zeolite A and hydroxysodalite was 3.9 mol/kg, and the one consisted of zeolite A, hydroxysodalite, and zeolite P was 2.6 mol/kg. This results shows that aluminoborosilicate glass could be expected to be recycled in zeolite A with good CEC by the appropriate process.     

Synthesis of 3‐Aryl‐1‐trifluoromethyltetrahydroisoquinolines by Brønsted Acid‐Catalyzed C(sp3)?H Bond Functionalization

A concise route to 3‐aryl‐1‐trifluoromethyltetrahydroisoquinolines by a benzylic [1,5]‐hydride shift‐mediated C H bond functionalization was developed. The [1,5]‐hydride shift of the benzylic C(sp³) H bond to the trifluoromethylketimine derived from para‐anisidine occurred smoothly to produce cis‐1‐trifluoromethyl‐3‐aryltetrahydroisoquinolines in good to excellent chemical yields with good diastereoselectivities. In contrast, use of the N H ketimine furnished N‐unprotected tetrahydroisoquinolines in good yields in favor of the trans‐isomer.

     

Diosgenin present in fenugreek improves glucose metabolism by promoting adipocyte differentiation and inhibiting inflammation in adipose tissues

In obesity, adipocyte hypertrophy and chronic inflammation in adipose tissues cause insulin resistance and type‐2 diabetes. Trigonella foenum‐graecum (fenugreek) can ameliorate hyperglycemia and diabetes. However, the effects of fenugreek on adipocyte size and inflammation in adipose tissues have not been demonstrated. In this study, we determined the effects of fenugreek on adipocyte size and inflammation in adipose tissues in diabetic obese KK‐Ay mice, and identified the active substance in fenugreek. Treatment of KK‐Ay mice with a high fat diet supplemented with 2% fenugreek ameliorated diabetes. Moreover, fenugreek miniaturized the adipocytes and increased the mRNA expression levels of differentiation‐related genes in adipose tissues. Fenugreek also inhibited macrophage infiltration into adipose tissues and decreased the mRNA expression levels of inflammatory genes. In addition, we identified diosgenin, a major aglycone of saponins in fenugreek to promote adipocyte differentiation and to inhibit expressions of several molecular candidates associated with inflammation in 3T3‐L1 cells. These results suggest that fenugreek ameliorated diabetes by promoting adipocyte differentiation and inhibiting inflammation in adipose tissues, and its effects are mediated by diosgenin. Fenugreek containing diosgenin may be useful for ameliorating the glucose metabolic disorder associated with obesity.     

Photodegradation of polymer-dispersed perylene di-imide dyes

Polymer-dispersed perylene di-imide dye photodegradation is investigated by monitoring the fluorescence intensity as a function of 532 nm laser pulses. Anaerobically irradiated polymer-dye films exhibited an accelerated decrease in fluorescence intensity, which was partially recovered upon exposure to oxygen. Decelerated photodegradation rates were observed for perylene di-imide ethanol solutions upon the addition of a singlet oxygen quenching antioxidant. These observations suggest reversible photoreduction and type II photo-oxidation as important photodegradation mechanisms. Type II photo-oxidation for perylene red 532 nm irradiation is supported by a singlet oxygen quantum yield of 0.09+/-0.03, determined via detection of time-resolved O2 (a1delta(g) --> X3sigma(g)-) infrared phosphorescence.