Evaluation of Foaming and Nucleation and Growth Mechanism of Soy-Based Polyurethane Foams

2018 ◽  
Vol 913 ◽  
pp. 738-745 ◽  
Author(s):  
Xiao Zhang ◽  
Xin Xing Zhou
Keyword(s):  
Growth Mechanism ◽  
Nucleation And Growth ◽  
Polyurethane Foams ◽  
Molar Ratio ◽  
Foam Formation ◽  
Isocyanate Index ◽  
Diffusion Controlled ◽  
Key Factor ◽  
Polyether Polyol ◽  
Nucleation And Growth Mechanism

The foaming and nucleation and growth mechanism of soybean oil-based polyurethane (SPU) were determined by the degree of hydrogen bonding, and isocyanate groups. New types of SPU were prepared by the different NCO/OH molar ratio (isocyanate index) from 1.0 to 2.0 in a soy polyol/polyether polyol (MDI) system. Foaming and nucleation and growth mechanisms of SPU were studied by fluorescence microscope (FM), scanning electron microscope (SEM), energy disperse spectroscopy (EDS) and Fourier transform infrared spectroscopy (FT-IR). It indicated that the isocyanate index affected remarkably the velocity of foaming and the critical nucleation radius of SPU and the ester functional group increased with the increase of isocyanate index. The nucleation and growth phase transition were dominated by the diffusion controlled nucleation and isocyanate content was the key factor of foam formation.

Spontaneous Oxidation Route to Se/Te Alloys Nanorods at Room Temperature

2011 ◽  
Vol 284-286 ◽  
pp. 680-683
Author(s):  
Rong Bo Zheng ◽  
Xue Lian Guo ◽  
Kang Zheng
Keyword(s):  
Dissolved Oxygen ◽  
Growth Mechanism ◽  
Room Temperature ◽  
Nucleation And Growth ◽  
Molar Ratio ◽  
Temperature Phase ◽  
Phase Structures ◽  
Sem And Tem ◽  
Nucleation And Growth Mechanism ◽  
Spontaneous Oxidation

The Se/Te alloys nanorods have been synthesized through spontaneous oxidation of NaHE (E = Se and Te) by dissolved oxygen at room temperature. Phase structures and morphologies of the Se/Te products are investigated by XRD, EDS, SEM, and TEM. The composition of Se/Te alloys could be tuned via simply changing the value of n (n denoted as molar ratio of the starting reagent Se to Te). In order to obtain pure Se/Tealloys nanorods, the value of n should be higher than 3. Otherwise, by-product t-Te would be formed. A possible nucleation and growth mechanism of the Se/Te nanorods was discussed.

Formation of coherent twins in YBa2Cu3O7–δ superconductors

1989 ◽  
Vol 4 (4) ◽  
pp. 795-801 ◽  
Author(s):  
C. J. Jou ◽  
J. Washburn
Keyword(s):  
Oxygen Uptake ◽  
Growth Mechanism ◽  
Oxygen Uptake Rate ◽  
Nucleation And Growth ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Transmission Electron Microscopic ◽  
Twin Formation ◽  
Boundary Model ◽  
Nucleation And Growth Mechanism

A nucleation-and-growth mechanism for the twin formation in YBa2Cu3O7–δ superconductors based on the oxygen uptake rate curve and published transmission electron microscopic observations is proposed together with an oxygen-depleted twin boundary model. The difficulty of reaching stoichiometric YBa2Cu3O7 is explained.

scholarly journals Nucleation/Growth and Optical Proprieties of Co-doped ZnO Electrodeposited on ITO Substrate

2021 ◽  
Vol 12 (5) ◽  
pp. 6776-6787
Keyword(s):  
Cyclic Voltammetry ◽  
Growth Mechanism ◽  
Supporting Electrolyte ◽  
Saturated Calomel Electrode ◽  
Nucleation And Growth ◽  
Visible Range ◽  
Zno Films ◽  
Doped Zno ◽  
Nucleation And Growth Mechanism ◽  
Co Doped

A Co-doped ZnO layer was prepared by electrodeposition method on indium doped tin oxide (ITO) substrate using a cathodic reduction from nitrate medium with different doping percentages of cobalt. The bath temperature was controlled at 70 °C. The films were cathodically electrodeposited in a bath containing 5 mM Zn(NO3)2. 6H2O, while the source of Co is Co(NO3)2.6H2O where 0.1M KNO3 was used as supporting electrolyte. The nucleation and growth mechanism of Co-doped ZnO nuclei have been studied by cyclic voltammetry and chronoamperometry. The cyclic voltammetry shows that the electrodeposition of ZnO and Co-doped ZnO at a negative potential around -1.0 V versus saturated calomel electrode (SCE) is a quasi-reversible reaction controlled by the diffusion process. Comparing current transients curves obtained by the chronoamperometric method with the theoretical curves of current density j versus t ½ allows us to say that the nucleation is 3D instantaneous, as shown in SEM analysis. The presence of Co does not modify the nucleation and growth mechanism. The XRD patterns show that the substitution of zinc by cobalt does not change the würtzite crystal structure, but the crystallite size decreases with the cobalt percentage. The transmittance spectra indicate that the Co-doped ZnO films are transparent in the visible range. The optical gap increases with the doping percentage of cobalt.

Study of Nucleation and Growth Mechanism of the Metallic Nanodumbbells

2012 ◽  
Vol 134 (9) ◽  
pp. 4384-4392 ◽  
Author(s):  
Galyna Krylova ◽  
Lisandro J. Giovanetti ◽  
Felix G. Requejo ◽  
Nada M. Dimitrijevic ◽  
Alesia Prakapenka ◽  
...  
Keyword(s):  
Growth Mechanism ◽  
Nucleation And Growth ◽  
Nucleation And Growth Mechanism
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