• Elastomers and Composites
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• v.53 no.2
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• pp.86-94
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• 2018

The effect of the NCO index and catalyst type on the thermal stability of poly(urethane-isocyanurate) (PUIR) foams was investigated to identify a method for enhancing the flame resistance of PUIR. PUIR foams were prepared using 4,4-diphenylmethane diisocyanate (MDI) and [(diethylene glycol)adipate]diol, which were synthesized by esterification of adipic acid and diethylene glycol. Dabco K-15, Dabco TMR-30, and Toyocat RX-5 were used as the catalysts for trimerization and gelation. The amount of urea and isocyanurate groups in PUIR was semi-quantitatively determined by normalizing their absorbance with the phenyl absorbance measured by FT-IR. The normalization data showed that Dabco TMR-30 effectively generated isocyanurate groups in PUIR. As a result, Dabco TMR-30 effectively raised the decomposition temperature and increased the 800 K and 900 K residues of the PUIR foam synthesized with an NCO index of 200.

• Elastomers and Composites
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• v.23 no.3
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• pp.213-222
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• 1988

The thermal decomposition of poly(n-butyl methacrylate)(Pn-BMA) was studied using a dynamic and isothermal thermogravimetry in nitrogen gas with 50ml/min at several heating rates from 1 to $20^{\circ}C/min$, and at several heating temperature from 320 to $370^{\circ}C$. The mathematical techniques used for calculation of activation energy were Kissinger, Anderson, Chatterjee-Conrad, Friedman, Fuoss, Ozawa and isolthermal method. The range of activation energies obtained using the several techniques was between 43 and 51Kcal/mol except Chatterjee-Conrad and this range agreed with each other very well. The thermal degradation of Pn-BMA was considered to be carried out by main chain scission.

• Steel and Composite Structures
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• v.46 no.5
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• pp.637-647
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• 2023

Nonlinear free vibration and stability responses of a carbon nanotube reinforced composite beam under temperature rising are investigated in this paper. The material of the beam is considered as a polymeric matrix by reinforced the single-walled carbon nanotubes according to different distributions with temperature-dependent physical properties. With using the Hamilton's principle, the governing nonlinear partial differential equation is derived based on the Euler-Bernoulli beam theory. In the nonlinear kinematic assumption, the Von Kármán nonlinearity is used. The Galerkin's decomposition technique is utilized to discretize the governing nonlinear partial differential equation to nonlinear ordinary differential equation and then is solved by using of multiple time scale method. The critical buckling temperatures, the nonlinear natural frequencies and the nonlinear free response of the system is obtained. The effect of different patterns of reinforcement on the critical buckling temperature, nonlinear natural frequency, nonlinear free response and phase plane trajectory of the carbon nanotube reinforced composite beam investigated with temperature-dependent physical property.

• Steel and Composite Structures
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• v.44 no.4
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• pp.557-567
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• 2022

Nonlinear free vibration analysis of a functionally graded beam resting on the nonlinear viscoelastic foundation is studied with uniform temperature rising. The non-linear strain-displacement relationship is considered in the finite strain theory. The governing nonlinear dynamic equation is derived based on the finite strain theory with using of Hamilton's principle. The Galerkin's decomposition technique is utilized to discretize the governing nonlinear partial differential equation to nonlinear ordinary differential equation and then is solved by using of multiple time scale method. The influences of temperature rising, material distribution parameter, nonlinear viscoelastic foundation parameters on the nonlinear free response and phase trajectory are investigated. In this paper, it is aimed that a contribution to the literature for nonlinear thermal vibration solutions of a functionally graded beam resting on the nonlinear viscoelastic foundation by using of multiple time scale method.

• Journal of the Society of Disaster Information
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• v.19 no.3
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• pp.532-544
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• 2023

Purpose: To identify and evaluate the risk of chemical fire causative substances by using thermal analysis methods (DSC, TGA) for the hazards and physical property changes that occur when newly used biofuels are mixed with existing fuels It is to use it for identification and evaluation of the cause of fire by securing data related to the method and the hazards of the material according to it. Method: The research method used in this experiment is the differential scanning calorimeter (DSC: Difference in heat flux) through quantitative information on the caloric change from the location, shape, number, and area of peaks. flux) was measured, and the weight change caused by decomposition heat at a specific temperature was continuously measured by performing thermogravimetric analyzer (TGA: Thermo- gravimetric Analyzer). Result: First, in the heat flux graph, the boiling point of the material and the intrinsic characteristic value of the material or the energy required for decomposition can be checked. Second, as the content of biodiesel increased, many peaks were identified. Third, it was confirmed through analysis that substances with low expected boiling points were contained. Conclusion: It was shown that the physical risk of the material can be evaluated by using the risk of biodiesel, which is currently used as a new energy source, through various physical and chemical analysis techniques (DSC + TGA).In addition, it is expected that the comparison of differences between test methods and the accumulation and utilization of know-how on experiments in this study will be helpful in future studies on physical properties of hazardous materials and risk assessment of materials.

• Journal of the Korean institute of surface engineering
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• v.32 no.6
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• pp.686-694
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• 1999

Insoluble anodes of the Ta/Ir mixed metal oxide for electrodeposition of Ni-W alloy in ammoniacal citrate bath were prepared by thermal decomposition method. Ti plate was etched in boiling oxalic acid solution and coated with ethanol solution of $TaCl_{5}$ and $IrCl_4$ mixed in a fixed ratio, followed by drying and treating at various temperatures. The coating layer of these insoluble anode was characterized by SEM, EDX, XRD and DSC. The decomposition rate of citric acid in plating bath was determined by measuring the $CO_2$ gas evolved at the anodes with Gas Chromatography. Evolution of $CO_2$ gas from Ta/Ir oxide anodes decreased about 5% compared with that of Pt. The $CO_2$ gas evolution was increased with the amount of Ir-oxide in the coatings. The coatings which have more than 40% ratio of Ta content and heat-treated at the temperature higher than $400^{\circ}C$ showed better efficiency

• Journal of Magnetics
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• v.11 no.3
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• pp.123-125
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• 2006

Co-ferrite nanoparticles have been synthesized by the decomposition of iron(III) acetylacetonate, $Fe(acac)_3$ and Co acetylacetonate, $Co(acac)_2$ in benzyl/phenyl ether in the presence of oleic acid and oleyl amine at the refluxing temperature of $295^{\circ}C$/$265^{\circ}C$ for 30 min. before cooling to room temperature. Particle diameter detected by PSA can be turned from 4 nm to 20 nm by seed-mediated growth and reaction conditions. Structural and magnetic characterization of Co-ferrite were measured by use of HRTEM, SAED (selected area electron diffraction), XRD and SQUID. The as-synthesized Co-ferrite nanoparticles have a cubic spinel structure and coercivity of 20 nm $CoFe_{2}O_{4} nanoparticles reached 1 kOe at room temperature and 18 kOe at 10 K.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.117-121
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• 2011

Size-controlled Ag nanoparticles (NPs) were prepared from the decomposition of Ag(I) carboxylates using ethanolamine derivatives as a reducing agent without an additional stabilizing agent. The size of the Ag NPs with a narrow size distribution (sub-10 nm to ca. 40 nm) was controlled precisely by varying the processing parameters, such as the type of reducing agent and the chain length of the carboxylate in the Ag(I) carboxylate. The optical properties, surface composition and crystallinity of the Ag NPs were characterized by ultraviolet-visible spectroscopy, gas chromatography-mass spectrometry, thermal gravimetric analysis, transmission electron microscopy and X-ray diffraction.

• Journal of the Korean Ceramic Society
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• v.39 no.1
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• pp.74-78
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• 2002

In this study, the solution combustion method was employed to synthesize perovskite PZT ceramics. Multicomponent oxides can be prepared by the solution combustion synthesis using redox exothermic reaction of precursor solutions. The results of DTA/TG showed exothermic peaks in 214$^{\circ}C$ and 350$^{\circ}C$. Those were caused by the differences of the thermal decomposition behavior of oxidizer and fuel. The combustion reaction was completed at 370$^{\circ}C$ during heating procedure, but the product was not transformed into perovskite. The thermal decomposition behavior of both oxidizer and fuel were considered during solution combustion process at 600$^{\circ}C$, which showed tetragonal single phase PZT ceramics with 50 nm crystalline size. The lattice constant a was 3.997 ${\pm}$ 0.001 ${\AA}$ and the lattice constant c was 4.147${\pm}$0.001 ${\AA}$.

• Journal of Sericultural and Entomological Science
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• v.37 no.2
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• pp.142-153
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• 1995

This study is undertaken to investigate proper condition and dissolution method of silk fibroin to use it functional material as powder or membrane. Silk fibroin was dissolved with calcium chloride ethanol aqueous solution and hydrochloric acid. When silk fibron was dissolved with calcium chloride ehanol aqueous solution, main chain of silk fibroin was degradaded and molecular conformation was changed. Silk fibroin powder was made from silk fibroin solution. It showed lower thermal decomposition temperature and crystallinity than those of native silk fibroin. And Its molecular conformation was random coil structure. By acid gydrolysis, main chain of silk fibroin was attacked randomly. Silk fibroin powder from hydrolysate showed high crystallinity and thermal decomposition temprature. $\beta$-form molecular conformation was found by IR and X-ray diffraction. Silk fibroin powder form dissolved part with hydrochloric acid showed low thormal decomposition temperature but high crystallinity. During acid hydrolysis, transition of molecular structure of silk fibroin occurred, and it changed to $\alpha$-helix. Silk fibroin film was achieved by casting silk fibroin solution by ehanol solution or saturated vapor treatment, and its molecular conformation changed to $\beta$structure.