INFLUENCE OF MODIFIERS ON COKED FOAM STRUCTURE AND PROPERTIES FORMED WITH THERMAL DECOMPOSITION OF WOOD

ABSTRACTThree examples pertaining to the influence of heavy doping on the microscopic perfection of as-grown InP crystals, thermal decomposition of InP crystals and epi-layers and optically induced degradation of InGaAsP epi-layers have been chosen to delineate some of the correlations observed between microstructure and properties in these materials. It is shown that the macroscopic perfection can be significantly improved by highly doping with Zn, S, and Se. However, in the case of Zn, not all of the dopant atoms are in solid solution and some of them have clustered to form precipitates, whereas these features are not seen in highly S- and Se-doped crystals.Thermal decomposition of epi-layers introduces areas which appear dark in a photoluminescence scan. It is argued that these regions evolve due to the out diffusion of P. In addition, when InP epi-layers are grown on thermally-decomposed substrates, dislocation density in the epi-layers is higher than that in the substrate. Arguments have been developed to rationalize these observations.Non-luminescent regions develop in InGaAsP epilayers by optical pumping. These areas are associated with dislocation clusters which appear to evolve by glide of the existing dislocations.

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Hydraulic resistance of rigid polyurethane foams. II. Effect of variation of surfactant, water, and nucleating agent concentrations on foam structure and properties

Journal of Applied Polymer Science ◽

10.1002/app.20762 ◽

2004 ◽

Vol 93 (6) ◽

pp. 2830-2837 ◽

Cited By ~ 8

Author(s):

Pravakar Mondal ◽

D. V. Khakhar

Keyword(s):

Hydraulic Resistance ◽

Nucleating Agent ◽

Polyurethane Foams ◽

Structure And Properties ◽

Foam Structure ◽

Rigid Polyurethane Foams

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Thermosetting polyester foams by infiltration in soluble preforms

Journal of Cellular Plastics ◽

10.1177/0021955x17728874 ◽

2017 ◽

Vol 54 (4) ◽

pp. 707-718 ◽

Cited By ~ 1

Author(s):

Fabrizio Quadrini ◽

Carmine Lucignano ◽

Loredana Santo

Keyword(s):

Polyester Resin ◽

Unsaturated Polyester ◽

Unsaturated Polyester Resin ◽

Structure And Properties ◽

Compression Tests ◽

Foam Structure ◽

Cyclic Compression ◽

Foam Properties

Rigid thermosetting foams are produced by infiltration of an unsaturated polyester resin into a soluble preform. In the experimentation, preforms were made of carbamide particles which were compacted at different values of pressure to change the foam structure and properties. After resin polymerization, carbamide particles are evacuated by immersion in water, leaving pores into the samples. Foams with porosity ranging from 52% to 77% were obtained as a function of the preform density. Quasi-static and cyclic compression tests were performed to evaluate foam properties. By increasing porosity, the foam strength reduces as well as the energy adsorbed at failure, and the energy lost in each single loading–unloading cycle.

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Impact of the anion and chalcogen on the crystal structure and properties of 4,6-dimethyl-2-pyrimido(thio)nium halides

Acta Crystallographica Section C Structural Chemistry ◽

10.1107/s2053229620005525 ◽

2020 ◽

Vol 76 (5) ◽

pp. 468-475

Author(s):

Andrzej Okuniewski ◽

Damian Rosiak ◽

Jarosław Chojnacki

Keyword(s):

Crystal Structure ◽

Thermal Decomposition ◽

Hydrogen Bonds ◽

Luminescent Properties ◽

Structural Motif ◽

Structure And Properties ◽

X Ray Diffraction ◽

One Dimensional ◽

X Ray ◽

Chloride Monohydrate

By the reaction of urea or thiourea, acetylacetone and hydrogen halide (HF, HBr or HI), we have obtained seven new 4,6-dimethyl-2-pyrimido(thio)nium salts, which were characterized by single-crystal X-ray diffraction, namely, 4,6-dimethyl-2-oxo-2,3-dihydropyrimidin-1-ium bifluoride, C6H9N2O+·HF2 − or (dmpH)F2H, 4,6-dimethyl-2-oxo-2,3-dihydropyrimidin-1-ium bromide, C6H9N2O+·Br− or (dmpH)Br, 4,6-dimethyl-2-oxo-2,3-dihydropyrimidin-1-ium iodide, C6H9N2O+·I− or (dmpH)I, 4,6-dimethyl-2-oxo-2,3-dihydropyrimidin-1-ium iodide–urea (1/1), C6H9N2O+·I−·CH4N2O or (dmpH)I·ur, 4,6-dimethyl-2-sulfanylidene-2,3-dihydropyrimidin-1-ium bifluoride–thiourea (1/1), C6H9N2S+·HF2 −·CH4N2S or (dmptH)F2H·tu, 4,6-dimethyl-2-sulfanylidene-2,3-dihydropyrimidin-1-ium bromide, C6H9N2S+·Br− or (dmptH)Br, and 4,6-dimethyl-2-sulfanylidene-2,3-dihydropyrimidin-1-ium iodide, C6H9N2S+·I− or (dmptH)I. Three HCl derivatives were described previously in the literature, namely, 4,6-dimethyl-2-oxo-2,3-dihydropyrimidin-1-ium chloride, (dmpH)Cl, 4,6-dimethyl-2-sulfanylidene-2,3-dihydropyrimidin-1-ium chloride monohydrate, (dmptH)Cl·H2O, and 4,6-dimethyl-2-sulfanylidene-2,3-dihydropyrimidin-1-ium chloride–thiourea (1/1), (dmptH)Cl·tu. Structural analysis shows that in 9 out of 10 of these compounds, the ions form one-dimensional chains or ribbons stabilized by hydrogen bonds. Only in one compound are parallel planes present. In all the structures, there are charge-assisted N+—H...X − hydrogen bonds, as well as weaker CAr +—H...X − and π+...X − interactions. The structures can be divided into five types according to their hydrogen-bond patterns. All the compounds undergo thermal decomposition at relatively high temperatures (150–300 °C) without melting. Four oxopyrimidinium salts containing a π+...X −...π+ sandwich-like structural motif exhibit luminescent properties.

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