Crystalline Phase Change in Yttria-Partially-Stabilized Zirconia by Low-Temperature Annealing

Changes in the phase composition and microstructure of yttria-partially-stabilized zirconia by low-temperature annealing were investigated at 100° to 500°C using bodies sintered from coprecipitated fine ZrO₂-Y₂O₃ powders at varied temperatures. Tetragonal zirconia on the surfaces of bodies sintered at <1500°C transformed to the monoclinic phase at 100° to 400°C. Transformation behavior was strongly affected by grain size.     

OCCURRENCE OF RUPTURES ON THE SURFACE OF FOODS DURING FRYING

An attempt was made to clarify the mechanism of ruptures on the surface of foods occurring during frying. Two different products were fried in a corn oil bath at a temperature of 160C or 180C. One of the products was ellipsoidal croquettes coated by the crust with different thicknesses ranging from 1 mm to 4 mm, while the other was ring doughnuts consisting of the three different compositions of a fixed size. The type of ruptures on the crust of croquette samples could roughly be divided into two categories according to the results obtained by the precise observations during the process of frying, i.e., a small hole and a crack. The small hole, like a pinhole, occurred in the crust of the croquette with 1 mm thickness early in the procedure, while the cracks could be observed with the crusts of croquettes more than 2 mm thicknesses after 120 s or more of frying time. The cracks also occurred on the curved surface of all the doughnut samples tested, although the location of cracks on the three surfaces, i.e., upper, outer and inner, was much influenced by the composition of the samples. A variety of measurements were made to obtain information on the changes in mechanical properties of the core region and crusted surfaces of the samples in the frying process so as to confirm generalized simple considerations assumed for the occurrence of ruptures.     

Abalone (Hariltis discus): Seasonal Variations in Chemical Composition and Textural Properties

Seasonal changes in adenosine 5′-triphosphate, total free amino acids, and total oligopeptides in abalone meat were analyzed. Levels were higher in summer and lower in winter. In both seasons, the most abundant free amino acid was taurine followed by arginine, glycine, glutamine, and glutamic acid. The largest peptide-bond amino acid was glutamic acid + glutamine. The collagen content decreased in summer and increased in winter. The breaking stress values of the meat were low in summer and high in winter, indicating that summer abalone would be more tender. Scanning electron microscopy revealed the collagen network was more compact in winter.     

超薄钛酸铅纳米管铁电性和力电耦合特性的第一性原理研究

利用基于密度泛函理论的第一性原理的方法研究了超薄钛酸铅(PbTiO₃)纳米管的铁电性及力电耦合特性。研究发现对于钛酸铅铁电纳米管结构, 即使在其特征尺寸小于铁电薄膜的铁电临界尺寸时, 依然存在自发极化。钛酸铅铁电纳米管结构不存在铁电临界尺寸。对纳米管力电耦合效应的研究发现, 轴向应变作用会引起包括极化沿轴向方向的铁电相、顺电相和极化沿周向方向的铁电相在内的丰富的相转变。这种相的转变是由于轴向应力所导致的Pb-O共价键的变化所引起的。另一方面, 研究了钛酸铅纳米管结构的机械强度, 明确了在轴向拉伸和压缩作用下纳米管的临界载荷。     

Synthesis and Thermal Stability of Aluminum Titanate Solid Solutions

Aluminum titanate solid solutions with empirical formulas of Al₂Ti_1-xZr_xO₅, Al_6(2-x)(6+x)Si_6x/(6+x)□_6x/(6+x)TiO₅, and Al_2(1-x)Mg_xTi_1+xO₅ were synthesized by reaction sintering and annealed at 900° to 1300°C in air to evaluate the thermal stability. Substitution of Al in Al₂TiO₅ by Si and 2Al by Mg and Ti ions to form solid solutions such as AI_{6(2-x)/(6+x)l-Si}6x/(6+x)□_6x/(6+x)TiO₅, and Al_2(1-x)Mg_xTi_1+xO₅ was effective in controlling the thermal decomposition, but substitution of Ti by Zr had little effect.     

Fabrication of Si3N4 Ceramics with Metal Nitride Additives by Isostatic Hot-Pressing

High-density Si₃N₄ ceramics with nitride additives such as TiN, AlN, ZrN, VN, NbN, YN, TUN, Mg₃N₂, and HfN were fabricated by isostatic hot-pressing. The temperature dependence of Vickers microhardness, fracture toughness, and thermal conductivity were measured; these properties, as well as microstructure, were strongly influenced by the additive used.     

Structure of Inclusion Complexes of Cyclodextrins with Triglyceride at Vegetable Oil/Water Interface

The interfacial tension of vegetable oil (soybean oil or coconut oil)/ water interface decreased with the increase of cyclodextrin (CD) concentration. The interfacial excess and interfacial area were calculated from the Gibbs’ adsorption equation. The average number of CD molecules including a fatty acid residue of soybean oil at the interface was estimated at 2.4 for each of α-CD and β-CD. The average number of CD molecules complexed with a fatty acid residue of coconut oil was 1.8 for α-CD and 1.7 for β-CD. These results suggested that the CD molecules formed the inclusion complex with the triglyceride according to the chain length of fatty acid residue at the interface.     

Possible Existence of Dense Ferrimagnetic Perovskite Allotropic Form of Yttrium Iron Garnet

Mixed oxides with the same chemical composition as yttrium iron garnet (YIG) were maintained at 900°C and 20 kbars for 30 min. X-ray diffraction showed that the product was single-phase. Since the diffraction pattern could be indexed as a structure similar to yttrium ortho-ferrite, YFeO₃, the product was considered to be a deformed type of perovskite. Subsequently, the lattice constants were calculated to be a = 5.27, b = 5.57, and c = 7.59 A. Both measured and calculated densities were about 6% greater than those of YIG. This material, therefore, can be called a dense allotropic form of YIG. Ferrimagnetism was observed in this phase; the Curie temperature and the magnetic moment at room temperature were estimated to be 625° C and 63 emu/g, respectively. This dense form converted to YIG on heating at 900° C for 4 hr in air. The transformation of YIG to a dense form at high pressures is inconsistent with the results reported by Marezio et al. Some possible reasons for this discrepancy are discussed.     

PERCEPTION OF GRITTINESS IN AN OIL-IN-WATER EMULSION

Microcrystalline cellulose was dispersed as a gritty substance in an emulsion, and sensory evaluation was conducted to examine the effect of the presence of oil on grittiness felt in the mouth. Samples were prepared with three types of microcrystalline cellulose of average particle size 14, 38, and 76 μm and with a concentration in water of 0.03–2.7%, with three types of emulsion with an oil-volume fraction of 0.2–0.7, and with three rates of homogenization of 500–15,000 rpm. The flow behavior and loss modulus of each sample were measured and sensory evaluation was made of the perceived grittiness. A multiple regression analysis of the data shows that the proportion of people who could perceive grittiness was influenced by the following factors and in that order: concentration of microcrystalline cellulose, oil droplet size, loss modulus, and particle size of microcrystalline cellulose. The proportion of people who perceived grittiness also increased with increasing oil droplet size. This was conceivably caused by the uneven distribution of microcrystalline cellulose particles promoted by large oil droplets. An equation was developed relating the proportion of people perceiving grittiness to the physical properties of the sample. The result indicates that factors effecting grittiness perception are identical for emulsions, aqueous suspensions, viscous suspensions and gels, studied previously.     

抗晶间腐蚀奥氏体不锈钢的晶界工程

Sensitization by chromium depletion due to chromium carbide precipitation at grain boundaries in austenitic stainless steels can not be prevented perfectly only by previous conventional techniques, such as reduction of carbon content, stabilization-treatment, local solution-heat-treatment, etc. Recent studies on grain boundary structure have revealed that the sensitization depends strongly on grain boundary character and atomic structure, and that low energy grain boundaries such a~ coincidence-site-lattice (CSL) boundaries have strong resistance to intergranular corrosion. The concept of grain boundary design and control has been developed as grain boundary engineering (GBE). GBEed materials are characterized by high frequencies of CSL boundaries which are resistant to intergranular deterioration of materials, such as intergranular corrosion. A thermomechanical treatment was tried to improve the resistance to the sensitization by GBE. A type 304 austenitic stainless steel was cold-rolled and solution-heat-treated, and then sensitization-heat-treated. The grain boundary character distribution was examined by orientation imaging microscopy (OIM). The intergranular corrosion resistance was evaluated by electrochemical potentiokinetic reactivation (EPR) and ferric sulfate-sulfuric acid tests. The sensitivity to intergranular corrosion was reduced by the thermomechanical treatment and indicated a minimum at a small roll-reduction The frequency of CSL boundaries indicated a maximum at the small reduction. The ferric sulfate-sulfuric acid test showed much smaller corrosion rate in the thermomechanical-treated specimen than in the base material. A high density of annealing twins were observed in the thermomechanical-treated specimen. The results suggdst that the therrmomechanical treatment can introduce low energy segments in the grain boundary network by annealing twins and can arrest the percolation of intergranular corrosion from the surface. The effects of carbon content and other minor elements on optimization in grain boundary character distribution (GBCD) and thermomechanical parameters were also examined during GBE.