Application of a Tough Surface Layer to a Fiber-Bonded Composite

The feasibility of creating "tough surface material" using oxide-fiber-reinforced oxide matrix ceramics was studied. Al₂O₃ fiber/(ZrO₂, Al₂O₃) matrix composite was used as the surface material of a Si–Ti–C–O-fiber-bonded composite. The sintering of the matrix (ZrO₂ and Al₂O₃) of the surface composite layer (SCL) and its bonding to the fiber-bonded composite (FBC) were done simultaneously by vacuum hot pressing. A spherical indentation test demonstrated the advantage of the SCL in reducing the damage of the base FBC from an indenter, because the high fracture resistance of the surface composite layer could reduce the stress concentration by the cumulative microfracture process.     

Radioactive Metal Isotopes Stabilized in a Geopolymer Matrix: Determination of a Leaching Extract by a Radiotracer Method

The stabilization of radioactive metal ions in inorganic polymer matrices of aluminum silicates, also called geopolymers, is demonstrated. The strength of the metal–ion bonds was then tested by leaching in water and sulfuric-acid solutions. The experiments were carried out by the radioactive-tracer method with ¹⁵²Eu, ¹³⁴Cs, ⁶⁰Co, and ⁵⁹Fe isotopes.     

Fracture Mechanics of a Shaft-loaded Blister Test - Transition from a Bending Plate to a Stretching Membrane

A linear elastic solution is proposed for a circular disc in transition from a plate-like (pure bending) to a membrane-like behavior (pure stretching) under a central point load. The strain energy release rate for film delamination is found to be G = χ(Pw₀/πa²) with χ a numerical constant varying from 1/2 for a plate-like disc to 1/4 for a thin flexible membrane.     

Strengthening of a Sintered Silicon Nitride by a Post-Fabrication Heat Treatment

The strength improvement of an injection-molded and sintered silicon nitride ceramic (15.5 wt% Y₂O₃+10.1 wt% SiO₂) produced by an oxidation heat treatment at 1500°C is reported. The ceramic retains its strength after prolonged intermediate temperature exposure in air, whereas the untreated material suffers various degrees of cracking.     

Reinforcement of a Reticulated Porous Ceramic by a Novel Infiltration Technique

The strength of a reticulated porous ZrO₂ ceramic was improved significantly by applying a novel infiltration technique. In a conventional reticulated porous ZrO₂ cellular ceramic, a polymer foam is coated with the ceramic. Heat treatment produces triangularly shaped pore channels within most of the ceramic struts of the reticulated body. These channels are detrimental to mechanical strength. In an infiltration process under vacuum, a ZrO₂ slurry was filled partially into the triangular pore channels of the ZrO₂ body. Accordingly, the tips of these triangular pore channels became rounded and previously cracked strut walls were mended. As a result, the compressive strength of the reticulated ZrO₂ was more than doubled compared with that obtained from specimens not subjected to the infiltration process.     

Role of a surfactant in the electrical potential oscillation across a liquid membrane

Electrical potential oscillation across a liquid membrane of a water/octanol/water system, in which a surfactant and ethanol are present in one of the waters, and electrical potential between octanol and aqueous phases of the octanol/water system were measured. On using sodium dodecyl sulfate (SDS) as the surfactant, potential oscillation was initiated with a sudden potential change toward the more negative potential. The upper potential (E_A,SDS) and lower potential (E_B,SDS) of the first oscillation were affected by the electrolyte added to the aqueous phase containing no previous surfactant. With hexadecyltrimethylammonium bromide (CTAB) as the surfactant, direction of the pulse was opposite that when using SDS. The lower potential (E_A,CTAB) and upper potential (E_B,CTAB) of The first oscillation were affected by the electrolyte. For instance, E_A,SDS and E_B,CTAB were greatly affected by halide ion size. In contrast, E_A,CTAB and E_B,SDS were only slightly affected by this parameter. The effects of the electrolytes on E_A,SDS and E_B,SDS were essentially the same as those on potentials at the interface between the octanol and aqueous phases of the octanol/water system in the absence of SDS (E_C,SDS) and presence of SDS (E_D,SDS), respectively. The effects of electrolytes on E_A,CTAB and E_B,CTAB were also basically the same as those on the potentials at the interface between the octanol and aqueous phases of the octanol/water system in the absence of CTAB (E_C,CTAB) and presence of CTAB (E_D,CTAB), respectively. Potential oscillation thus appears quite likely due to the repetitive formation and destruction of the surfactant layer adsorbed on the octanol/water interface.     

Wall effects in flow past a circular cylinder in a plane channel: a numerical study

This paper describes a numerical study on the steady flow of an incompressible Newtonian fluid past a circular cylinder confined in a plane rectangular channel. Using FLUENT (version 6), two-dimensional steady state computations were carried out for an uniform inlet velocity and for different values of the Reynolds numbers in the range between 0.1 and 200 and blockage ratios (ratio of the channel width to the cylinder diameter) in the range between 1.54 and 20. The flow parameters such as drag coefficient, length of the recirculation zone, and the angle of separation are presented as functions of the Reynolds number and blockage ratio. The total drag coefficient (C_D) was found to decrease with an increase in the blockage ratio (λ) for a fixed value of the Reynolds number (Re) and to decrease with increasing Reynolds number for a fixed value of λ. Similarly, for a fixed value of λ, both the angle of separation and the length of the recirculation zone increase with the increasing Reynolds number.     

Growth of a Bonelike Apatite Layer on a Substrate by a Biomimetic Process

A dense and uniform bonelike apatite layer was formed on a substrate by the following biomimetic method. The substrate was first placed on granular particles of CaO, SiO₂-based glass soaked in a simulated body fluid (SBF) with ion concentrations nearly equal to those of human blood plasma and then soaked in another fluid highly supersaturated with respect to the apatite. The thickness of the apatite layer increased in proportion to the soaking time in the second solution. The rate of increase in the thickness of the apatite layer increased from 0.5 to 7.0 μm/day with increasing temperature of the second solution from 10° to 60°C, increased from 0.15 to 1.7 μm/day with increasing ion concentrations of the second solution from 0.2 to 1.5 times those of the SBF, and doubled by shaking the second solution. These results indicate that the growth of the apatite layer is controlled by mass transport across the interface between the crystal and the fluid.     

Bonelike Hydroxyapatite Induction by a Gel-Derived Titania on a Titanium Substrate

Gel-derived titania coating on commercial pure (c.p.) titanium induces hydroxyapatite formation onto its surface from a simulated body fluid (SBF, a metastable calcium phosphate solution). The induced apatite is similar to bone apatite in that it is poorly crystallized, calcium-deficient, and carbonate-containing. Furthermore, the carbonate (CO^2–3) groups go into the apatite lattice and lie at the positions of PO^3–4 and OH^– to replace these ionic groups, resembling the (CO^2–3) groups of bone apatite. Therefore, the apatite induced by the gel-derived titania is said to be bonelike. A chemical stimulation, stemming from abundant hydroxyl groups and negative charges at the surface of the titania gel, is believed to be responsible for the bonelike apatite induction. The potential of bone-bonding is predicted for the gel-derived titania, for it is an efficient bonelike apatite inducer in the SBF.     

Water-tolerant catalysis of a silica composite of a sulfonic acid resin, Aciplex

A silica composite of a perfluorocarbonsulfonic acid resin, Aciplex, has been used as a solid acid catalyst for a variety of reactions concerning water. The Aciplex–SiO₂ composite containing 20 wt% Aciplex has a surface area of 1.3 m² g⁻¹ and possesses an ion-exchanged capacity of 0.46 meq. g⁻¹ after pretreatment at 423 K, which is higher than that of 13 wt% Nafion–SiO₂ (0.12 meq. g⁻¹). The acid strengths estimated from an initial heat of adsorption of NH₃ were similar for these polymer resin composites. It was found that the Aciplex–SiO₂ was more active than typical solid acids such as Cs_2.5H_0.5PW₁₂O₄₀, H-ZSM-5, and SO₄²⁻/ZrO₂ for hydrolysis of ethyl acetate in excess water and esterification of acrylic acid with 1-butanol, while it was less active than Cs_2.5H_0.5PW₁₂O₄₀ for N-alkylation of acrylonitrile with 1-adamantanol and solid–solid hydrolysis of 2-naphthyl acetate. The Aciplex–SiO₂ was superior in activity to Nafion–SiO₂ for all the above reactions and in thermal stability. These results indicate that Aciplex–SiO₂ is a promising solid acid catalyst for reactions involving liquid phase water.     

Catalytic combustion of methane over bimetallic catalysts a comparison between a novel annular reactor and a high-pressure reactor

The effects of adding a co-metal, Pt or Rh, to Pd/γ-Al₂O₃ catalysts were studied with respect to the catalytic activity for methane combustion and compared to a Pd/γ-Al₂O₃ catalyst, using both a pressurized pilot-scale and a lab-scale annular reactor. Temperature programmed oxidation (TPO) experiments were also carried out to investigate the oxygen release/uptake of the catalyst materials. Palladium showed an unstable behavior both in the pilot and lab-scale experiments at temperatures well below the PdO to Pd transformation. An addition of Pt to Pd stabilized, and in some cases increased, the catalytic activity for methane combustion.

The TPO experiments showed that the oxygen release peak was shifted to lower temperatures even for low additions of Pt, i.e. Pd:Pt=2:1. For additions of rhodium only small beneficial effects were seen. The steady-state behavior of the lab-scale annular reactor correspond well to the pressurized pilot-scale tests.     

Development of a catalytically assisted combustor for a gas turbine

A catalytically assisted low NO_x combustor has been developed which has the advantage of catalyst durability. This combustor is composed of a burner section and a premixed combustion section behind the burner section. The burner system consists of six catalytic combustor segments and six premixing nozzles, which are arranged alternately and in parallel. Fuel flow rate for the catalysts and the premixing nozzles are controlled independently. The catalytic combustion temperature is maintained under 1000°C, additional premixed gas is injected from the premixing nozzles into the catalytic combustion gas, and lean premixed combustion at 1300°C is carried out in the premixed combustion section. This system was designed to avoid catalytic deactivation at high temperature and thermal or mechanical shock fracture of the honeycomb monolith. In order to maintain the catalyst temperature under 1000°C, the combustion characteristics of catalysts at high pressure were investigated using a bench scale reactor and an improved catalyst was selected for the combustor test. A combustor for a 20 MW class multi-can type gas turbine was designed and tested under high pressure conditions using LNG fuel. Measurements of NO_x, CO and unburned hydrocarbon were made and other measurements were made to evaluate combustor performance under various combustion temperatures and pressures. As a result of the tests, it was proved that NO_x emission was lower than 10 ppm converted at 16% O₂, combustion efficiency was almost 100% at 1300°C of combustor outlet temperature and 13.5 ata of combustor inlet pressure.     

Simulation of a Spray Dryer Fitted with a Rotary Disk Atomizer Using a Three-Dimensional Computional Fluid Dynamic Model

Spray dryers fitted with a rotary disk atomizer are widely used in many industries requiring high throughputs to produce powders from liquid streams. The interaction between droplets or particles and the drying medium within the drying chamber is still not well understood and hence difficult to model reliably. In this article CFD results are presented to describe the behavior of the performance of a spray dryer fitted with a rotary disk atomizer in a cylinder-on-cone chamber geometry. Four different turbulence models, i.e., standard k - ε, RNG k - ε, Realizable k - ε, and Reynolds stress models were tested and compared to simulate the swirling two-phase flow with heat and mass transfer in the chamber. The results of this investigation can provide further insight into turbulent swirling flow modeling. The predicted results, such as, air flow patterns, air velocity and temperature, distributions, particle/droplet trajectories, drying performance etc., are obtained using the CFD code FLUENT6.1. Comparison with available limited experimental data shows that CFD results display reasonable agreement. Predicted results also show that the RNG k - ε model performs better in this specific case.     

Test results of a catalytically assisted combustor for a gas turbine

A catalytically assisted ceramic combustor for a gas turbine was designed and tested to achieve low NO_x emissions. This combustor is composed of a burner and a ceramic liner. The burner consists of an annular preburner, six catalytic combustor segments and six premixing nozzles, which are arranged in parallel and alternately. In this combustor system, catalytic combustion temperature is controlled under 1000 °C, premixed gas is injected from the premixing nozzles to the catalytic combustion gas and lean premixed combustion over 1300 °C is carried out in the ceramic liner. This system was designed to avoid catalyst deactivation at high temperature and thermal shock fracture of the ceramic honeycomb monolith of the catalyst. A 1 MW class combustor was tested using LNG fuel. Firstly, NO_x emissions from the preburner were investigated under various pressure conditions. Secondly, two sets of honeycomb cell density catalysts and one set of thermally pretreated catalysts ware applied to the combustor, and combustion tests were carried out under various pressure conditions. As a result, it was found that the main source of NO_x was the preburner, and total NO_x emissions from the combustor were approximately 4 ppm (at 16% O₂) at an adiabatic combustion temperature of 1350 °C and combustor inlet pressure of 1.33 MPa.     

Effect of a promoter on the methanation activity of a Mo-based sulfur-resistant catalyst

The effect of adding Co, Ni or La on the methanation activity of a Mo-based sulfur-resistant catalyst was investigated. As promoters, Co, Ni and La all improved the methanation activity of a 15% MoO₃/Al₂O₃ catalyst but to different extents. Similar improvements were also found when Co, Ni or La was added to a 15% MoO₃/25%-CeO₂-Al₂O₃ catalyst. The promotion effects of Co and Ni were better than that of La. However, the catalytic methanation activity deteriorated the most with time for the Ni-promoted catalyst. The used catalysts were analyzed by nitrogen adsorption measurement, X-ray diffraction and X-ray photoelectron spectroscopy.     

120 kt/a硫磺制酸装置的扩产改造

介绍了硫磺制酸装置由120kt／a扩产到150kt／a的改造情况。采用快速熔硫替代原静态熔硫，大大减少了熔硫蒸汽消耗。催化剂装填总量由105．37m^3增加到119．2m^3，平均总转化率提高到99．83％。更换二吸酸循环泵，提高循环酸量。为降低尾气酸雾排放，二吸塔设置纤维除雾器。改造后，系统运行正常，年产量由120kt提高到150kt，饱和蒸汽产量增加42kt。     

Dissolution of phase-separated domains after a jump to a temperature in the single-phase region

Phase-separated domains prepared in the two-phase region were dissolved at a temperature in the single-phase region, and their dissolution dynamics was studied by using the time-resolved light scattering (TRLS) technique and a scanning electron microscope (SEM). The time t_ps of preparation of domains was chosen to be long enough for phase separation to proceed into the late stage. The scattered light intensity at small wavenumbers increased before it attenuated. As t_ps increased, the increase at smaller wavenumbers became more significant and the peak intensity decreased only slightly with dissolution time. The characteristic wavenumber q_m evaluated from TRLS and SEM followed the power-law relation q_mt^−0.3.     

Induction of a Melanoma‐Specific Antibody Response by a Monovalent,but not a Divalent,Synthetic GM2 Neoglycopeptide

Human tumor cell‐specific antibodies were induced in mice after immunization with a synthetic glycopeptide, which is based on the GM2 ganglioside carbohydrate moiety produced on a gram scale in bacteria. Such neoglycopeptides represent a promising cancer vaccine strategy for active immunotherapy targeting carbohydrates.

     

Spherulitic Growth from a Phase-Separated Vitreous Matrix in a Cordierite–Y-Stabilized Zirconia Glass-Ceramic

Crystallization behavior, especially spherulitic growth of a cordierite–3 mol% Y₂O₃–ZrO₂ glass composition annealed at 950° to 1370°C was studied by optical and electron microscopy. Microstructural analysis revealed that glass-inglass phase separation occurred prior to the crystallization of β-quartz solid solution ( ss ). ZrO₂ was involved in promoting the nucleation of β-quartz ss ; the crystallization evolved from a cellular to a spherulitic morphology, and β-quartz transformed to α-cordierite as the temperature was raised. ZrO₂ was eventually expelled intergranularly and intragranularly to form slightly misoriented domains upon annealing, and the dendritic or clustered tetragonal t -ZrO₂ crystals transformed to monoclinic ( m ) in symmetry. A possible dragging force exerted between α-cordierite and a glassy droplet phase is proposed to explain the corrugated cordierite/glass interface.