Critical Factors Affecting the Wettability of α-Alumina by Molten Aluminum

The wetting behaviors of α-Al₂O₃ single crystals with three different faces—R(01[Onemacr]2), A(01[Twomacr]0), and C(0001)—and polycrystals (PC) by molten aluminum were studied over a wide temperature range using both a conventional and an improved sessile-drop method. The critical factors affecting the wettability, such as temperature, atmosphere, substrate surface roughness, and crystallographic orientation, and the influence from the experimental technique, were thoroughly investigated. The results show that the aluminum surface oxidation and the thickness of the oxide film have a pronounced effect on the wettability, especially at low temperatures. To eliminate this effect, the experimental temperature must be over a critical value. Vacuum favors lowering this value compared with atmosphere, and the improved sessile-drop method, particularly using an impingement-dropping mode (I-mode), helps to weaken this effect by mechanical disruption and removal of the oxide film. However, the dropping distance and the dropping force must be controlled to prevent a receding contact angle. The effects of the substrate surface roughness and temperature are not significant in the case of a clean and a fine-prepared aluminum surface. On the other hand, the effect of the aluminum crystallographic orientation is noticeable and the wettability is in the order of R > A > PC > C. The intrinsic contact angles of the Al/α-Al₂O₃ system in the temperature range 1000°–1500°C were estimated to be 76°–85° for the R and A faces, 88°–100° for the C face, and 77°–90° for the polycrystal, depending on the temperature.     

Rheological studies on cordierite honeycomb extrusion

The rheological parameters for a cordierite honeycomb extrusion were investigated using the Benbow–Bridgwater model. The extrusion pastes were formulated using typical binders, plasticizers, lubricants and pore-forming agents normally used for such extrusions. Pastes were found to have good pseudo-plasticity, low bulk yield and very low die-land shear stress, compared with the velocity dependent components of the respective pressure drops. In some formulation, reduced velocity contribution to the extrusion pressure with increased binder content found useful for better honeycomb extrusion. These characteristics of the honeycomb extrusion batches were analyzed by using dynamic bulk and shear stress components derived from the Benbow–Bridgwater six-parameter model and compared with the results of honeycomb extrusion trials. Plasticizing agents like polyethylenglycol (PEG) and glycerin were found to decrease the die entry pressure but showed no external lubricating effect leading to higher die-land pressure. Pore-forming agent, graphite was found to reduce both die entry and die land pressures, whereas, carbon increases the die entry pressure.     

Synthesis of sulfonated polynaphthalene,polyanthracene, and polypyrene as strong solid acids via oxidative coupling polymerization

Oxidative coupling polymerization of naphthalene, anthracene, and pyrene with FeCl₃ in nitrobenzene under nitrogen gave polynaphthalene (PNP), polyanthracene (PAT), and polypyrene (PPR) in good yields, respectively. PNP, PAT, and PPR were transformed into sulfonated PNP (S‐PNP), S‐PAT, and S‐PPR by the treatment with chlorosulfonic acid in dichloromethane at 25°C for 24 h under nitrogen, respectively. The activities of S‐PPR were higher than those of S‐PNP and S‐PAT. For the hydrolysis of cyclohexyl acetate and oleyl acetate in water, activities of S‐PPR, S‐PAT, and S‐PNP were considerably higher than those of the other conventional solid acids. Rate constants of S‐PPR were 2.8 and 11.7 times larger than those of the sulfonated condensed polynuclear aromatic (S‐COPNA(PR)) resin (PR = pyrene) for the hydrolysis of cyclohexyl acetate and oleyl acetate, respectively. S‐PPR, S‐PAT, and S‐PNP were reused without significant loss of activities. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Estimation of Indoor Air PAH Concentration Increases by Cigarette,Incense-Stick,and Mosquito-Repellent-Incense Smoke

Smoke from cigarette smoking and burning of incense sticks and mosquito-repellent incense, which is particularly used in summer, are thought to be primary factors of indoor air pollution by polycyclic aromatic hydrocarbons (PAHs) in Japanese houses. In this study, these respective smokes as indoor air pollutants were evaluated by quantifying their particulate matter (PM) and 7 PAHs. PM and PAHs in smoke from 5 popular brands of Japanese cigarettes were collected on the glass fiber filter by the international smoking mode. PM was quantified by weighing the filter before and after trapping them. PAHs were analyzed by HPLC after extracting the filter with ethanol/benzene (1:3, by vol.). Similarly, evaluation of smoke respectively generated by natural burning of 4 brands of incense sticks and 3 brands of mosquito-repellent incenses was also conducted. As the results of these experiments, the average concentrations of PM and benzo[a]pyrene in a 35 m³ closed room were estimated to increase 1630 μg/m³ and 8.2 ng/m³, respectively, by smoking of 3 cigarettes; 1320 μ/m³ and 4.1 ng/m³, respectively, by burning of 2 incense sticks; and 2510 μg/m³ and 17.3 ng/m³, respectively, by burning of 8 cm of mosquito-repellent incense.     

Potential of the Angiotensin Receptor Blockers (ARBs) Telmisartan,Irbesartan, and Candesartan for Inhibiting the HMGB1/RAGE Axis in Prevention and Acute Treatment of Stroke

Stroke is a major cause of mortality and disability worldwide. The main cause of stroke is atherosclerosis, and the most common risk factor for atherosclerosis is hypertension. Therefore, antihypertensive treatments are recommended for the prevention of stroke. Three angiotensin receptor blockers (ARBs), telmisartan, irbesartan and candesartan, inhibit the expression of the receptor for advanced glycation end-products (RAGE), which is one of the pleiotropic effects of these drugs. High mobility group box 1 (HMGB1) is the ligand of RAGE, and has been recently identified as a lethal mediator of severe sepsis. HMGB1 is an intracellular protein, which acts as an inflammatory cytokine when released into the extracellular milieu. Extracellular HMGB1 causes multiple organ failure and contributes to the pathogenesis of hypertension, hyperlipidemia, diabetes mellitus, atherosclerosis, thrombosis, and stroke. This is the first review of the literature evaluating the potential of three ARBs for the HMGB1-RAGE axis on stroke therapy, including prevention and acute treatment. This review covers clinical and experimental studies conducted between 1976 and 2013. We propose that ARBs, which inhibit the HMGB1/RAGE axis, may offer a novel option for prevention and acute treatment of stroke. However, additional clinical studies are necessary to verify the efficacy of ARBs.     

Fabrication and characterization of porous ZrO2 with a high volume fraction of fine closed pores

A novel technique for the fabrication of porous ZrO₂ with a high volume fraction of fine closed pores was investigated. A partially stabilized ZrO₂ (3 mol% Y₂O₃; Y-PSZ) body, with a 97–99% relative density and containing a small amount of impurities, exhibited a large volume expansion related to the formation of closed pores after heating at 1700 °C for 10 min in N₂. These closed pores seemed to mainly form due to the vaporization of hydroxyl apatite: Ca₁₀(OH)₂(PO₄)₆ as an impurity and superplasticity of the ZrO₂ during heating. Porous ZrO₂ with approximately 24.6% closed pores (total porosity: 26.7%) was successfully fabricated by the addition of 1 mass% SiO₂, 1 mass% TiO₂, and 1 mass% hydroxyl apatite. The closed pore size and morphology of the resultant porous ZrO₂ bodies were investigated, and the formation mechanism of the closed pores was examined on the basis of chemical thermodynamics.     

Effect of Divalent Cation Additives on the γ-Al2O3-to-α-Al2O3 Phase Transition

The effect on the γ-Al₂O₃-to-α-Al₂O₃ phase transition of adding divalent cations was investigated by differential thermal analysis, X-ray diffractometry, and surface-area measurements. The cations, Cu²⁺, Mn²⁺, Co²⁺, Ni²⁺, Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺, were added by impregnation, using the appropriate nitrate solution. These additives were classified into three groups, according to their effect: (1) those with an accelerating effect (Cu²⁺ and Mn²⁺), (2) those with little or no effect (Co²⁺, Ni²⁺, and Mg²⁺), and (3) those with a retarding effect (Ca²⁺, Sr²⁺, and Ba²⁺). The crystalline phase formed by reaction of the additive with γ-Al₂O₃ at high temperature was a spinel-type structure in groups (1) and (2) and a magnetoplumbite-type structure in group (3). In groups (2) and (3), a clear relationship was found between the transition temperature and the difference in ionic radius of Al³⁺ and the additive (Δ r ): The transition temperature increased as Δ r increased. This result indicates that additives with larger ionic radii are more effective in suppressing the diffusion of Al³⁺ and O²⁻ in γ-Al₂O₃, suppressing the grain growth of γ-Al₂O₃, and retarding the transformation into α-Al₂O₃.     

Wacker type and π-allyl type oxidations of propylene controlled by fuel cell system in the gas phase

Oxidation of propylene applying the (C₃H₆, Pd/H₃PO₄/Pt, O₂) fuel cell system in the gas phase produced acrolein and acrylic acid, the -allyl type oxidation products. However, addition of H₂PdCl₄ or HCl to the electrolyte reduced the -allyl oxidation, but enhanced Wacker type oxidation producing acetone. Direction to either Wacker type or -allyl type oxidation can easily be controlled electrochemically by applying the fuel cell system in the gas phase.     

Polymerization of methyl methacrylate with Ni(acac)2–methylaluminoxane catalyst

Polymerization of methyl methacrylate (MMA) with nickel(II) acetylacetonate [Ni(acac)₂] in combination with methylaluminoxane (MAO) was investigated. Ni(acac)₂ was found to be an effective catalyst for the polymerization of MMA. From a kinetic study of the polymerization of MMA with the Ni(acac)₂–MAO catalyst, the overall activation energy was estimated to be 15 kJmol⁻¹. The polymerization rate (R_p) was expressed as follows: R_p = k [MMA]^1.0[Ni(acac)₂–MAO]^0.6 (the MAO/Ni mole ratio was kept constant). The mechanism for the polymerization of vinyl monomers with the Ni(acac)₂–MAO catalyst is discussed. © 2000 Society of Chemical Industry