Decomposition of chlorofluorocarbons on TiO2ZrO2

The decomposition of chlorofluorocarbons (CFCs) in the presence of water was examined over a variety of solid acid catalysts. The TiO₂ZrO₂ catalyst was found to have the highest activity and longest life among the catalysts examined. The activity of the TiO₂ZrO₂ catalysts depended upon the content of TiO₂. At the contents of TiO₂ from 58 to 90 mole%, the TiO₂ZrO₂ catalysts exhibited high activity, and these catalysts were proven to contain TiZrO₄ crystal. From the study of the XRD peak intensity of the TiZrO₄ crystal, it was highest on the TZ-58 which contained 58 mole% of TiO₂, and decreased with increasing the content of TiO₂. Furthermore, the conversion of CFC113 measured at 673 K was highest at TZ-58, and decreased gradually with increasing TiO₂ content. Therefore, the TiZrO₄ crystal influences the activity of decomposition of CFC113. However, the TiO₂ZrO₂ catalyst was gradually deactivated during the reaction due to the elimination of titanium atoms. A good relationship was found between the activity on TiO₂ZrO₂ catalyst and bond energy of CCl in the compounds of chlorofluorocarbons and hydrochlorocarbons, suggesting that the rate controlling step was the cleavage of CCl bond.     

Microscopic structure of athabasca oil sand

A refined structural model for in situ oil sands is proposed in terms of the mutual arrangement of sand grains, fines, water and bitumen. In the Athabasca deposit, the sand grains consist mainly of quartz and their packing is such that the porosity is about 35%. In rich oil sand, 10–15% of the pore space is occupied by connate water whereas the remainder is occupied by bitumen. For lower grade oil sands, a direct correlation exists between the water content and the amount of fines (particles smaller than 44 μm) and an inverse correlation exists between the bitumen content and the amount of fines. These relationships are successfully explained in terms of the irreducible water saturation in a porous medium and the double layer interaction between sand and bitumen surfaces.     

Intrinsic Elastic, Dielectric, and Piezoelectric Losses in Lead Zirconate Titanate Ceramics Determined by an Immittance-Fitting Method

The material coefficients of "soft" and "hard" lead zirconate titanate (PZT) ceramics were determined as complex values by the nonlinear least-squares-fitting of immittance data measured for length-extensional bar resonators. The piezoelectric d -constant should be a complex value to obtain a best fitting between observed and calculated results. Because the elastic, dielectric, and piezoelectric losses determined in this process were not "intrinsic" losses, a calculation process to evaluate the "intrinsic" losses was proposed. It was confirmed that the intrinsic losses were smaller than the corresponding extrinsic losses. The intrinsic piezoelectric loss existed in both soft and hard PZTs; ∼50% of the loss of piezoelectric d -constant was derived from the elastic and dielectric losses. The most notable difference between the soft and hard PZTs was observed in their elastic losses.     

Biocomposites Made from Short Abaca Fiber and Biodegradable Polyesters

Natural fiber‐reinforced biodegradable polyester composites were prepared from biodegradable polyesters and surface‐untreated or ‐treated abaca fibers (length ca. 5 mm) by melt mixing and subsequent injection molding. Poly(butylene succinate)(PBS), polyestercarbonate (PEC)/poly(lactic acid)(PLA) blend, and PLA were used as biodegradable polyesters. Esterifications using acetic anhydride and butyric anhydride, alkali treatment, and cyanoethylation were performed as surface treatments on the fiber. The flexural moduli of all the fiber‐reinforced composites increased with fiber content. The effect of the surface treatment on the flexural modulus of the fiber‐reinforced composites was not so pronounced. The flexural strength of PBS composites increased with fiber content, and esterification of the fiber by butyric anhydride gave the best result. For the PEC/PLA composites, flexural strength increased slightly with increased fiber content (0–20 wt.‐%) in the case of using untreated fiber, while it increased considerably in the case of using the fiber esterified by butyric anhydride. For the PLA composite, flexural strength did not increase with the fiber reinforcement. The result of soil‐burial tests showed that the composites using untreated fiber have a higher weight loss than both the neat resin and the composites made using acetylated fiber.

Flexural modulus of PBS composites as a function of fiber content.     

Guinea pig bone marrow cells treated with platelet-activating factor generate factor(s) which affects their DNA synthesis and microbicidal activity

We have previously reported that platelet-activating factor (PAF) induces proliferation and microbicidal activity of guinea pig bone marrow cells. In the present study, we have found that the conditioned medium of PAF- or nonmetabolizable PAF agonist-treated guinea pig bone marrow cells augmented DNA synthesis and induced microbicial activity of bone marrow cells. A PAF specific antagonist, CV-6209, inhibited generation of the active conditioned medium by PAF. Addition of the PAF antagonist only partially suppressed the augmentative effect of the active conditioned medium on DNA synthesis; this is consistent with the fact that, because of the rapid breakdown, no appreciable amount of PAF remained in the conditioned medium of PAF-treated cells. Although mouse bone marrow cells did not respond to PAF unlike guinea pig cells, their DNA synthesis was significantly enhanced by the conditioned medium of PAF-treated guinea pig bone marrow cells. Thus, some newly generated factor(s) distinct from the originally inoculated PAF seemed to modulate the bioactions of PAF on bone marrow cells. An appreciable amount of PAF was produced by calcium ionophore-treated guinea pig bone marrow cells. These findings indicate that PAF synthesized in guinea pig bone marrow cells induces generation in the cells of some factor(s) which affects proliferation or microbicidal activity. Presented at The Third International Conference on Platelet-Activating Factor and Structurally Related Ether Lipids, Tokyo, Japan, May 1989.     

Microstructure and Thermal Shock Resistance of Molten Glass-Coated Carbon Materials Fabricated by Interfacial Control

Carbon substrates were coated completely with a molten silicate glass, where the wettability of carbon to glass was improved by infiltration and pyrolysis of perhydropolysilazane. Microstructures of the carbon–glass interface were dependent on P n ₂ during coating. Coating at lower P n ₂ induced the formation of cristobalite at the carbon–glass interface. When the coating was performed at higher P n ₂, the glass and carbon were strongly adhered, without the formation of cristobalite. Coating at higher P n ₂ improved the thermal shock resistance of the glass layer, because crack initiation was not induced by the phase transformation of cristobalite during the cooling process. In the case of coating at higher P n ₂, an oxynitride glass layer was formed at the glass subsurface by dissolution of N₂. A porous glass subsurface layer with uniform spherical micro-pores could be produced by soaking near the glass transition temperature in a steam environment. The porous layer with fine and homogeneous microstructure acts as a thermal shock absorbing layer, so that glass-coated carbon with a porous glass layer has excellent thermal shock resistance in addition to steam oxidation resistance.     

Synthesis of Ba2NaNb5O15 Powders and Thin Films Using Metal Alkoxides

Transparent and highly oriented Ba₂NaNb₅O₁₅ (BNN) thin films have been prepared by using metal alkoxides. A homogeneous precursor solution was prepared by the controlled reaction of NaOC₂H₅, Nb(OC₂H₅)₅, and barium metal. The BNN precursor included a molecular-level mixture of NaNb(OC₂H₅)₆ and Ba[Nb(OC₂H₅)₆]₂ in ethanol. The alkoxy-derived powder crystallized to a low-temperature phase, and then transformed to orthorhombic BNN (tungsten bronze) at 600°C. BNN precursor films on substrates crystallized to orthorhombic BNN at 800°C via the low-temperature phase. Highly (002) oriented BNN films of tungsten bronze structure were successfully prepared on MgO (100) substrates at 700°C by using BNN underlayer.     

Sintering of Al2O3–TiC Composite in the Presence of Liquid Phase

The results obtained from the sintering of Al₂O₃–50TiC (in weight percent) composite in the temperature range from 1650° to 1800°C with addition of Y₂O₃ are presented. Densification is accelerated by the formation of liquid at temperatures above 1750°C, and 99% of theoretical density can be achieved by vacuum sintering at 1800°C for 15 min. The liquid presented at the sintering temperature is crystallized to YAG (Y₃Al₅O₁₂) during cooling.     

Radiation-induced polymerization of ethylene in pilot plant. III. Heavy-phase recycling process

Radiation-induced polymerization of ethylene using aqueous tert-butyl alcohol as medium was carried out in a large-scale pilot plant with a 50-liter central source-type reactor at a pressure of 105 to 395 kg/cm², temperature of 30° to 80°C, mean dose rate of 4.5 × 10⁴ to 1.9 × 10⁵ rads/hr, ethylene feed rate of 5.5 to 23.5 kg/hr, and medium feed rate of 21 to 102 l./hr. The space–time yield and molecular weight of the polymer were in the range of 4.7 to 16.8 g/l.-hr and 1.3 × 10⁴ to 8.9 × 10⁴, respectively. The space–time yield and molecular weight increased with mean residence time at 30°C, whereas at 80°C they became almost independent of the time. The space–time yield increased with pressure and dose rate, slightly decreased with temperature, and was maximum at ethylene molar fraction of 0.5. The polymer molecular weight increased with pressure and ethylene molar fraction, and decreased with dose rate and temperature. The total amount of deposited polymer on the reactor wall, source case wall, and scraping blades was usually less than 1 kg, which was negligibly small for the analysis of polymerization. Continuous discharge of the polymer slurry and production of fine-powder polyethylene were successfully carried out. In the central source-type reactor, a dose rate of 1.9 × 10⁵ rads/hr was obtained with a ⁶⁰Co source of ca. 12 kCi.     

Pulsed Electric Current Sintering of Silicon Nitride

Pulsed electric current sintering (PECS) has been used to densify α-Si₃N₄ powder doped with oxide additives of Y₂O₃ and Al₂O₃. A full density (>99%) was achieved with virtually no transformation to β-phase, resulting in a microstructure with fine equiaxed grains. With further holding at the sintering temperature, the α-to-β phase transformation took place, concurrent with an exaggerated grain growth of a limited number of elongated β-grains in a fine-grained matrix, leading to a distinct bimodal grain size distribution. The average grain size was found to obey a cubic growth law, indicating that the growth is diffusion-controlled. In contrast, the densification by hot pressing was accompanied by a significant degree of the phase transformation, and the subsequent grain growth gave a broad normal size distribution. The apparent activation energy for the phase transformation was as high as 1000 kJ/mol for PECS, almost twice the value for hot pressing (∼500 kJ/mol), thereby causing the retention of α-phase during the densification by PECS.