Phase stability of B2O3-added Ba2Ti9O20 ceramic: Processing effects

2003 ◽  
Vol 18 (1) ◽  
pp. 201-207 ◽  
Author(s):  
Sea-Fue Wang ◽  
Chuang-Chung Chiang ◽  
Chai-Hui Wang ◽  
Jinn P. Chu
Keyword(s):  
Phase Transformation ◽  
Phase Stability ◽  
Sintering Temperature ◽  
Host Material ◽  
Minor Amount ◽  
Reaction Products ◽  
Effective Role ◽  
Processing Effects ◽  
A Minor

Preparation of dense and phase-pure Ba2Ti9O20 is generally difficult to achieve using solid-state reaction, since there are several thermodynamically stable compounds in the vicinity of the desired composition. This study investigated the effects of B2O3 on the densification, microstructural evolution, and phase stability of Ba2Ti9O20. Samples from the host material (2BaO · 9TiO2) with and without the addition of 5 wt% B2O3 were prepared through different processing routes. For the pure host material sintered at temperatures ranging from 800 to 1100 °C, the reaction products followed the sequence of BaTi2O5 → BaTi4O9 → BaTi5O11 → Ba2Ti9O20. The phase transformation proceeded faster in the bulk compared to the free surface of the sample. BaTi5O11 and BaTi4O9 with a minor amount of Ba2Ti9O20 were found in the ground powder of ceramics sintered at 1100 °C. For the samples prepared from host material with the addition of 5 wt% B2O3, Ba2Ti9O20 started to form at temperatures as low as 800 °C. The sequence of reaction products followed Ba4Ti13O30 → BaTi4O9 → BaTi5O11 → Ba2Ti9O20. Sintering at above 1000 °C yielded pure Ba2Ti9O20 phase, suggesting the effective role of B2O3 on the phase stability of Ba2Ti9O20. It was found that precalcination of host material before the addition of B2O3 gives an additional benefit to the Ba2Ti9O20 formation. Crystallization of pure Ba2Ti9O20 phase was completed at a sintering temperature as low as 900 °C without any solid solution additive such as SnO2 or ZrO2, due to the fact that the phase transformation of the samples began with BaTi4O9 and BaTi5O11 during sintering. Also, B2O3 was found to be unstable during the high-temperature sintering at 1200 °C, and the results are discussed.

scholarly journals The role of disulphide bonds in human intestinal mucin

1979 ◽  
Vol 181 (3) ◽  
pp. 725-732 ◽  
Author(s):  
Janet F. Forstner ◽  
Inderjit Jabbal ◽  
Rauf Qureshi ◽  
David I. C. Kells ◽  
Gordon G. Forstner
Keyword(s):  
Goblet Cell ◽  
Buoyant Density ◽  
Minor Amount ◽  
Mucin 1 ◽  
Acetylneuraminic Acid ◽  
Disulphide Bonds ◽  
Intestinal Mucin ◽  
Mucin 2 ◽  
A Minor

Goblet-cell mucin (mucin 1) was isolated and purified from human small-intestinal scrapings. After application of mucin 1 to DEAE-Bio-Gel (A) columns, most of the glycoprotein (76–94% of hexoses) was eluted in the first peak (designated mucin 2). Minor amounts of acidic glycoproteins were eluted with 0.2m- and 0.4m-NaCl in later peaks. Analyses of mucin 1 and mucin 2 revealed mucin 2 to be a monodisperse highly glycosylated glycoprotein containing 6.3% by wt. of protein, N-acetylgalactosamine, N-acetylglucosamine, galactose and fucose. Mucin 1 was similar in composition, but was polydisperse and contained more protein (12.3% by wt.) as well as N-acetylneuraminic acid. Analytical CsCl-gradient ultracentrifugation showed both mucin 1 and mucin 2 to have a major component with an average buoyant density of 1.47000g/ml. Mucin 1 also contained a slightly less-dense minor glycoprotein component. After exhaustive reduction and alkylation mucin 1 retained its major component, but partly dissociated into two lighter glycoprotein components. Mucin 2, in contrast, did not change its density distribution after reduction. Band ultracentrifugation in 2H2O-containing iso-osmotic buffers showed that mucin 1 contained a major fast-sedimenting component (so=37±2S), and a minor amount of a slower-sedimenting component. After reduction there was an increased quantity of the latter component, for which an so value of 14.5S was calculated. In contrast, mucin 2 was unaltered by reduction (so=33±2S). These findings indicate that the major component of goblet-cell mucin (mucin 2) does not dissociate after S–S-bond reduction, and thus does not apparently rely for its polymeric structure on the association of subunits through covalent disulphide bonds. However, the effects of reduction on mucin 1 suggest that in the native mucin intramolecular disulphide bonds in the minor glycoproteins may stabilize their structure, permitting secondary non-covalent interactions to develop with the major dense mucin (mucin 2) protein.

The Chemistry of Vulcanization. IX. Accelerating Mechanism of 2-Aminothiobenzothiazole

1962 ◽  
Vol 35 (2) ◽  
pp. 484-490
Author(s):  
Haruko Fukuda ◽  
Jitsuo Tsurugi
Keyword(s):  
Zinc Salt ◽  
Minor Amount ◽  
Reaction Products ◽  
Reaction Sequence ◽  
Minor Degree ◽  
A Minor ◽  
Sulfur Radical ◽  
Homolytic Dissociation ◽  
Free Sulfur

Abstract 2-Aminobenzothiazole, i.e., 2-aminobenzothiazolylaulfenamide, MSNH2 was used as a model of the commercial sulfenamide type accelerators. Behavior of MSNH2 was studied in diphenylmethane, DPM, which served as a hydrocarbon containing α-methylenic hydrogen. MSNH2 decomposes in DPM at 140–160° to give MS· and ·NH2 together with a minor amount of free sulfur radical. This suggests homolytic dissociation of the S—N bond as well as the C—S bond of MSNH2, though the latter bond dissociates in minor degree. Dissociation of both bonds makes the reaction sequence complicated. When sulfur was added to the MSNH— DPM system, the radical MS· (or M·) opens the sulfur ring to accelerate the reaction of DPM with sulfur. The presence of sulfur results in the less complicated reaction products. The activating mechanism of zinc butyrate in the reaction involving MSNH2, sulfur and DPM is the same as that involving thiazole type accelerators. However, the zinc salt of MBT which is produced from MSNH2 and zinc butyrate interacts with the radical ·NH2, giving an intermediate 2-amino-benzothiazole, MNH2. The latter reacts with zinc butyrate to give N-(2-benzo-thiazolyl) butyramide, RCONHM. Evolution of ammonia was observed even in the presence of sulfur and zinc butyrate.

scholarly journals Enhancing the phase stability of ceramics under radiation via multilayer engineering

2021 ◽  
Vol 7 (26) ◽  
pp. eabg7678
Author(s):  
Hongliang Zhang ◽  
Jianqi Xi ◽  
Ranran Su ◽  
Xuanxin Hu ◽  
Jun Young Kim ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Phase Stability ◽  
First Principles Calculations ◽  
Tem Analysis ◽  
Promising Strategy ◽  
Transmission Electron ◽  
Radiation Induced ◽  
Composition Changes ◽  
Annealing Defects

In metallic systems, increasing the density of interfaces has been shown to be a promising strategy for annealing defects introduced during irradiation. The role of interfaces during irradiation of ceramics is more unclear because of the complex defect energy landscape that exists in these materials. Here, we report the effects of interfaces on radiation-induced phase transformation and chemical composition changes in SiC-Ti3SiC2-TiCx multilayer materials based on combined transmission electron microscopy (TEM) analysis and first-principles calculations. We found that the undesirable phase transformation of Ti3SiC2 is substantially enhanced near the SiC/Ti3SiC2 interface, and it is suppressed near the Ti3SiC2/TiC interface. The results have been explained by ab initio calculations of trends in defect segregation to the above interfaces. Our finding suggests that the phase stability of Ti3SiC2 under irradiation can be improved by adding TiCx, and it demonstrates that, in ceramics, interfaces are not necessarily beneficial to radiation resistance.

Anti-biofilm surfaces from mixed dopamine-modified polymer brushes: synergistic role of cationic and zwitterionic chains to resist staphyloccocus aureus

2019 ◽  
Vol 7 (12) ◽  
pp. 5369-5382 ◽  
Author(s):  
Yuanyuan He ◽  
Xinyuan Wan ◽  
Kecen Xiao ◽  
Weiwei Lin ◽  
Jiehua Li ◽  
...  
Keyword(s):  
Polymer Brushes ◽  
Minor Amount ◽  
Modified Polymer ◽  
Staphyloccocus Aureus ◽  
A Minor

The dominant amount of antifouling D-PSBMA with a minor amount of bactericidal D-PQAs facilitate the synergistic anti-biofilm effect.

scholarly journals Ye’elimite synthesis by chemical routes and role of iron

2021 ◽  
Vol 348 ◽  
pp. 01009
Author(s):  
Fatima-Zahra Abir ◽  
Mohamed Mesnaoui ◽  
Younes Abouliatim ◽  
Lhbib Nibou ◽  
Youssef El Hafiane ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Iron Oxide ◽  
Chemical Synthesis ◽  
Carbon Footprint ◽  
Sintering Temperature ◽  
Orthorhombic Phase ◽  
Cement Industry ◽  
Minor Phase ◽  
A Minor

The cement industry has been taking significant steps for years to reduce its carbon footprint by opting for alternative less polluting materials such as sulfo-aluminous cements (CSA). These binders, compared to ordinary Portland cements (OPC), have two advantages: reduction of the CO2 emissions and energy saving because the sintering temperature of CSA cements is much lower than ordinary cement (Portland). The aim of this work is to study the effect of iron oxide on the formation of the ye'elimite phase, which represents the main phase of (CSA).This study details the protocol for the chemical synthesis of ye’elimite containing increasing amounts of iron (general formula: Ca4Al(6-2x)Fe2xSO16 with x = 0.00 to 1.13). The maximum ye’elimite content is reached at a sintering temperature of 1250°C. The presence of iron promotes the formation of cubic ye'elimite at the expense of the orthorhombic phase. The total incorporation of iron in ye’elimite structure is possible when x < 0.12. Beyond this content, the ferritic phase (CaO)2(Al2O3,Fe2O3) appears as a minor phase and its quantity becomes more important with the increase of the percentage of iron introduced in the synthesis. Finally, the electron microscopy allows to observe nanometric grains assembled in larger aggregates.

The 5.6-Kilodalton Protein in Isolated Chlorosomes of Chloroflexus aurantiacus Strain Ok -70-fl is a Degradation Product

1990 ◽  
Vol 45 (7-8) ◽  
pp. 823-828 ◽  
Author(s):  
Kai Griebenow ◽  
Alfred R. Holzwarth ◽  
Kurt Schaffner
Keyword(s):  
Protease Inhibitors ◽  
Proteolytic Activity ◽  
Degradation Product ◽  
Room Temperature ◽  
Chloroflexus Aurantiacus ◽  
Minor Amount ◽  
Phenylmethylsulfonyl Fluoride ◽  
A Minor

Abstract Chlorosomcs containing BChl a790 have been isolated from Chloroflexus aurantiacus on sucrose density gradients using the detergents Miranol. Deriphat. N.N-dimethyldodecyl- aminc-N-oxidc, and dodecyl-p-D-rnaltoside. All freshly prepared samples cither lack the poly- peptide of approximately 5 kDa. which appears identical with the 5.6-kDa protein previously assigned the role of BChl c-binding [R. G. Feick and R. C. Fuller. Biochemistry 23, 3693- 3700 (1984)]. or they contain only a minor amount thereof. This polypeptide accumulates in the chlorosomcs in vitro at room temperature within 24 h after isolation. The reaction cannot be prevented simply by addition of the protease inhibitors benzamidinc. F.-caproic ac|d. and phenylmethylsulfonyl fluoride. However, upon denaturation, as required lor gel electrophore- sis, of the freshly isolated chlorosome sample the formation of the 5-kDa polypeptide is inhibit- ed. We conclude that this species, viz. 5.6-kDa protein, is a degradation product of another - as yet unidentified - protein present in the chlorosome preparations. Despite the pronounced proteolytic activity which affords the 5-kDa fragment, the native absorption and fluorescence properties of BChl c and BChl a arc essentially not changed in these chlorosome preparations.

The Effect of Path Length and Display Size on Memory for Spatial Information

2012 ◽  
Vol 59 (3) ◽  
pp. 147-152 ◽  
Author(s):  
Katherine Guérard ◽  
Sébastien Tremblay
Keyword(s):  
Path Length ◽  
Potential Role ◽  
Spatial Information ◽  
Recall Performance ◽  
Minor Role ◽  
Length Effect ◽  
Serial Memory ◽  
Fixed Reference ◽  
A Minor

In serial memory for spatial information, some studies showed that recall performance suffers when the distance between successive locations increases relatively to the size of the display in which they are presented (the path length effect; e.g., Parmentier et al., 2005) but not when distance is increased by enlarging the size of the display (e.g., Smyth & Scholey, 1994). In the present study, we examined the effect of varying the absolute and relative distance between to-be-remembered items on memory for spatial information. We manipulated path length using small (15″) and large (64″) screens within the same design. In two experiments, we showed that distance was disruptive mainly when it is varied relatively to a fixed reference frame, though increasing the size of the display also had a small deleterious effect on recall. The insertion of a retention interval did not influence these effects, suggesting that rehearsal plays a minor role in mediating the effects of distance on serial spatial memory. We discuss the potential role of perceptual organization in light of the pattern of results.

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