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Antonio Martins Figueiredo Neto - One of the best experts on this subject based on the ideXlab platform.
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Effect of surfactant alkyl chain length on lyotropic uniaxial to biaxial cholesteric phase transitions
'Springer Science and Business Media LLC', 2019Co-Authors: Erol Akpinar, Nazli Uygur, Seda Uyanik, Antonio Martins Figueiredo NetoAbstract:Some ionic surfactant-based lyotropic mixtures, exhibiting cholesteric phases, were prepared to investigate the effect of the surfactant alkyl chain length on a) uniaxial-to-biaxial phase transitions and b) stabilization of different cholesteric phases. Potassium alkanoates, KCx, (Potassium undecanoate, KC11, Potassium dodecanoate, KC12, and Potassium tridecanoate, KC13) were chosen as the surfactant molecules. The lyotropic mixtures, which were composed of KCx/Potassium Sulfate (K2SO4)/decanol (DeOH)/water/brucine, where brucine is a chiral dopant molecule, were studied. Partial phase diagrams were constructed to show how the surfactant alkyl chain affects the phase topologies in the phase diagrams. It was observed that the presence of a longer surfactant alkyl chain in the mixture favors the stabilization of the larger discotic cholesteric, ChD, and cholesteric biaxial, ChB, phase domains. The phase transitions from the uniaxial cholesteric to biaxial cholesteric phase were shifted to lower temperatures
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study of the cholesteric to cholesteric phase transitions on the lyotropic mixture of kl k2so4 1 undecanol water brucine presenting the cholesteric biaxial phase
Molecular Crystals and Liquid Crystals, 2013Co-Authors: Erol Akpinar, Dennys Reis, Antonio Martins Figueiredo NetoAbstract:Lyotropic cholesteric liquid crystalline phases were prepared by doping the quaternary mixture of Potassium laurate (KL)/Potassium Sulfate (K2SO4)/1-undecanol (UndeOH)/water with brucine. The phase diagram was constructed as a function of the brucine concentration. Three cholesteric phases were identified: cholesteric biaxial, calamitic uniaxial, and discotic uniaxial. It was observed that there is a critical brucine concentration (X* b ) to cholesterize the nematic host phase when the mixture is confined in a thin sample holder, below which the cholesteric helical arrangement is not achieved. The helical twisting power of brucine was calculated as 12.12 ± 0.40 μm−1.
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effect of alkyl chain length of alcohols on cholesteric uniaxial to cholesteric biaxial phase transitions in a Potassium laurate alcohol Potassium Sulfate water brucine lyotropic mixture evidence of a first order phase transition
Journal of Physical Chemistry B, 2013Co-Authors: Dennys Reis, Erol Akpinar, Antonio Martins Figueiredo NetoAbstract:Lyotropic cholesteric liquid crystalline phases were prepared by doping the quaternary mixture of Potassium laurate (KL)/Potassium Sulfate (K2SO4)/alcohol (n–OH)/water with the chiral agent brucine. Different long-chain alcohols whose alkyl chains (n) vary from 8 (1-octanol) to 16 (1-hexadecanol) were used. The cholesteric uniaxial to cholesteric biaxial phase transitions were investigated by measuring the birefringences via polarizing optical microscopy, and the phase diagram was constructed as a function of the alkyl chain length of the alcohols. Alcohols with 9 ≤ n ≤ 12 presented the three cholesteric phases (cholesteric discotic—ChD, cholesteric biaxial—ChB, and cholesteric calamitic—ChC). The ChD-to-ChB transition was shown to be continuous, with a bare correlation length bigger than the typical micellar dimensions. Mixtures with n = 8 and n = 13 showed a first-order phase transition between the ChD and the ChC phases, without the presence of the ChB phase in between. These results are interpreted in...
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effect of alkyl chain length of alcohols on cholesteric uniaxial to cholesteric biaxial phase transitions in a Potassium laurate alcohol Potassium Sulfate water brucine lyotropic mixture evidence of a first order phase transition
Journal of Physical Chemistry B, 2013Co-Authors: Dennys Reis, Erol Akpinar, Antonio Martins Figueiredo NetoAbstract:Lyotropic cholesteric liquid crystalline phases were prepared by doping the quaternary mixture of Potassium laurate (KL)/Potassium Sulfate (K(2)SO(4))/alcohol (n-OH)/water with the chiral agent brucine. Different long-chain alcohols whose alkyl chains (n) vary from 8 (1-octanol) to 16 (1-hexadecanol) were used. The cholesteric uniaxial to cholesteric biaxial phase transitions were investigated by measuring the birefringences via polarizing optical microscopy, and the phase diagram was constructed as a function of the alkyl chain length of the alcohols. Alcohols with 9 ≤ n ≤ 12 presented the three cholesteric phases (cholesteric discotic-Ch(D), cholesteric biaxial-Ch(B), and cholesteric calamitic-Ch(C)). The Ch(D)-to-Ch(B) transition was shown to be continuous, with a bare correlation length bigger than the typical micellar dimensions. Mixtures with n = 8 and n = 13 showed a first-order phase transition between the Ch(D) and the Ch(C) phases, without the presence of the Ch(B) phase in between. These results are interpreted in terms of the nanosegregation of the alcohol molecules in the micelles with respect to the main amphiphiles molecules.
Dennys Reis - One of the best experts on this subject based on the ideXlab platform.
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study of the cholesteric to cholesteric phase transitions on the lyotropic mixture of kl k2so4 1 undecanol water brucine presenting the cholesteric biaxial phase
Molecular Crystals and Liquid Crystals, 2013Co-Authors: Erol Akpinar, Dennys Reis, Antonio Martins Figueiredo NetoAbstract:Lyotropic cholesteric liquid crystalline phases were prepared by doping the quaternary mixture of Potassium laurate (KL)/Potassium Sulfate (K2SO4)/1-undecanol (UndeOH)/water with brucine. The phase diagram was constructed as a function of the brucine concentration. Three cholesteric phases were identified: cholesteric biaxial, calamitic uniaxial, and discotic uniaxial. It was observed that there is a critical brucine concentration (X* b ) to cholesterize the nematic host phase when the mixture is confined in a thin sample holder, below which the cholesteric helical arrangement is not achieved. The helical twisting power of brucine was calculated as 12.12 ± 0.40 μm−1.
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effect of alkyl chain length of alcohols on cholesteric uniaxial to cholesteric biaxial phase transitions in a Potassium laurate alcohol Potassium Sulfate water brucine lyotropic mixture evidence of a first order phase transition
Journal of Physical Chemistry B, 2013Co-Authors: Dennys Reis, Erol Akpinar, Antonio Martins Figueiredo NetoAbstract:Lyotropic cholesteric liquid crystalline phases were prepared by doping the quaternary mixture of Potassium laurate (KL)/Potassium Sulfate (K2SO4)/alcohol (n–OH)/water with the chiral agent brucine. Different long-chain alcohols whose alkyl chains (n) vary from 8 (1-octanol) to 16 (1-hexadecanol) were used. The cholesteric uniaxial to cholesteric biaxial phase transitions were investigated by measuring the birefringences via polarizing optical microscopy, and the phase diagram was constructed as a function of the alkyl chain length of the alcohols. Alcohols with 9 ≤ n ≤ 12 presented the three cholesteric phases (cholesteric discotic—ChD, cholesteric biaxial—ChB, and cholesteric calamitic—ChC). The ChD-to-ChB transition was shown to be continuous, with a bare correlation length bigger than the typical micellar dimensions. Mixtures with n = 8 and n = 13 showed a first-order phase transition between the ChD and the ChC phases, without the presence of the ChB phase in between. These results are interpreted in...
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effect of alkyl chain length of alcohols on cholesteric uniaxial to cholesteric biaxial phase transitions in a Potassium laurate alcohol Potassium Sulfate water brucine lyotropic mixture evidence of a first order phase transition
Journal of Physical Chemistry B, 2013Co-Authors: Dennys Reis, Erol Akpinar, Antonio Martins Figueiredo NetoAbstract:Lyotropic cholesteric liquid crystalline phases were prepared by doping the quaternary mixture of Potassium laurate (KL)/Potassium Sulfate (K(2)SO(4))/alcohol (n-OH)/water with the chiral agent brucine. Different long-chain alcohols whose alkyl chains (n) vary from 8 (1-octanol) to 16 (1-hexadecanol) were used. The cholesteric uniaxial to cholesteric biaxial phase transitions were investigated by measuring the birefringences via polarizing optical microscopy, and the phase diagram was constructed as a function of the alkyl chain length of the alcohols. Alcohols with 9 ≤ n ≤ 12 presented the three cholesteric phases (cholesteric discotic-Ch(D), cholesteric biaxial-Ch(B), and cholesteric calamitic-Ch(C)). The Ch(D)-to-Ch(B) transition was shown to be continuous, with a bare correlation length bigger than the typical micellar dimensions. Mixtures with n = 8 and n = 13 showed a first-order phase transition between the Ch(D) and the Ch(C) phases, without the presence of the Ch(B) phase in between. These results are interpreted in terms of the nanosegregation of the alcohol molecules in the micelles with respect to the main amphiphiles molecules.
Erol Akpinar - One of the best experts on this subject based on the ideXlab platform.
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Effect of surfactant alkyl chain length on lyotropic uniaxial to biaxial cholesteric phase transitions
'Springer Science and Business Media LLC', 2019Co-Authors: Erol Akpinar, Nazli Uygur, Seda Uyanik, Antonio Martins Figueiredo NetoAbstract:Some ionic surfactant-based lyotropic mixtures, exhibiting cholesteric phases, were prepared to investigate the effect of the surfactant alkyl chain length on a) uniaxial-to-biaxial phase transitions and b) stabilization of different cholesteric phases. Potassium alkanoates, KCx, (Potassium undecanoate, KC11, Potassium dodecanoate, KC12, and Potassium tridecanoate, KC13) were chosen as the surfactant molecules. The lyotropic mixtures, which were composed of KCx/Potassium Sulfate (K2SO4)/decanol (DeOH)/water/brucine, where brucine is a chiral dopant molecule, were studied. Partial phase diagrams were constructed to show how the surfactant alkyl chain affects the phase topologies in the phase diagrams. It was observed that the presence of a longer surfactant alkyl chain in the mixture favors the stabilization of the larger discotic cholesteric, ChD, and cholesteric biaxial, ChB, phase domains. The phase transitions from the uniaxial cholesteric to biaxial cholesteric phase were shifted to lower temperatures
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study of the cholesteric to cholesteric phase transitions on the lyotropic mixture of kl k2so4 1 undecanol water brucine presenting the cholesteric biaxial phase
Molecular Crystals and Liquid Crystals, 2013Co-Authors: Erol Akpinar, Dennys Reis, Antonio Martins Figueiredo NetoAbstract:Lyotropic cholesteric liquid crystalline phases were prepared by doping the quaternary mixture of Potassium laurate (KL)/Potassium Sulfate (K2SO4)/1-undecanol (UndeOH)/water with brucine. The phase diagram was constructed as a function of the brucine concentration. Three cholesteric phases were identified: cholesteric biaxial, calamitic uniaxial, and discotic uniaxial. It was observed that there is a critical brucine concentration (X* b ) to cholesterize the nematic host phase when the mixture is confined in a thin sample holder, below which the cholesteric helical arrangement is not achieved. The helical twisting power of brucine was calculated as 12.12 ± 0.40 μm−1.
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effect of alkyl chain length of alcohols on cholesteric uniaxial to cholesteric biaxial phase transitions in a Potassium laurate alcohol Potassium Sulfate water brucine lyotropic mixture evidence of a first order phase transition
Journal of Physical Chemistry B, 2013Co-Authors: Dennys Reis, Erol Akpinar, Antonio Martins Figueiredo NetoAbstract:Lyotropic cholesteric liquid crystalline phases were prepared by doping the quaternary mixture of Potassium laurate (KL)/Potassium Sulfate (K2SO4)/alcohol (n–OH)/water with the chiral agent brucine. Different long-chain alcohols whose alkyl chains (n) vary from 8 (1-octanol) to 16 (1-hexadecanol) were used. The cholesteric uniaxial to cholesteric biaxial phase transitions were investigated by measuring the birefringences via polarizing optical microscopy, and the phase diagram was constructed as a function of the alkyl chain length of the alcohols. Alcohols with 9 ≤ n ≤ 12 presented the three cholesteric phases (cholesteric discotic—ChD, cholesteric biaxial—ChB, and cholesteric calamitic—ChC). The ChD-to-ChB transition was shown to be continuous, with a bare correlation length bigger than the typical micellar dimensions. Mixtures with n = 8 and n = 13 showed a first-order phase transition between the ChD and the ChC phases, without the presence of the ChB phase in between. These results are interpreted in...
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effect of alkyl chain length of alcohols on cholesteric uniaxial to cholesteric biaxial phase transitions in a Potassium laurate alcohol Potassium Sulfate water brucine lyotropic mixture evidence of a first order phase transition
Journal of Physical Chemistry B, 2013Co-Authors: Dennys Reis, Erol Akpinar, Antonio Martins Figueiredo NetoAbstract:Lyotropic cholesteric liquid crystalline phases were prepared by doping the quaternary mixture of Potassium laurate (KL)/Potassium Sulfate (K(2)SO(4))/alcohol (n-OH)/water with the chiral agent brucine. Different long-chain alcohols whose alkyl chains (n) vary from 8 (1-octanol) to 16 (1-hexadecanol) were used. The cholesteric uniaxial to cholesteric biaxial phase transitions were investigated by measuring the birefringences via polarizing optical microscopy, and the phase diagram was constructed as a function of the alkyl chain length of the alcohols. Alcohols with 9 ≤ n ≤ 12 presented the three cholesteric phases (cholesteric discotic-Ch(D), cholesteric biaxial-Ch(B), and cholesteric calamitic-Ch(C)). The Ch(D)-to-Ch(B) transition was shown to be continuous, with a bare correlation length bigger than the typical micellar dimensions. Mixtures with n = 8 and n = 13 showed a first-order phase transition between the Ch(D) and the Ch(C) phases, without the presence of the Ch(B) phase in between. These results are interpreted in terms of the nanosegregation of the alcohol molecules in the micelles with respect to the main amphiphiles molecules.
Jiangong Li - One of the best experts on this subject based on the ideXlab platform.
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low temperature synthesis of single crystal alpha alumina platelets by calcining bayerite and Potassium Sulfate
Journal of Materials Science & Technology, 2011Co-Authors: Xinghua Su, Jiangong LiAbstract:Single-crystal alpha alumina (α-Al 2 O 3 ) platelets were synthesized by calcining a powder mixture of bayerite (α-Al(OH) 3 ) and Potassium Sulfate (K 2 SO 4 ) at 900°C. The crystalline phase evolutions and morphologies of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The synthesized samples mainly consisted of single-crystal α-Al 2 O 3 platelets with a diameter of 0.5–1.5 μm and a thickness of 50–150 nm. Moreover, with 3, 5, and 8 wt% (referred to the obtained alumina) α-Al 2 O 3 seeds adding into the powder mixture of bayerite and Potassium Sulfate, the average diameter of α-Al 2 O 3 platelets can be reduced to 450, 240, and 220 nm, respectively. It is found that the sequence of the phase transformation is the bayerite (α-Al(OH) 3 ) → boehmite (γ-AlOOH) → γ-Al 2 O 3 → α-Al 2 O 3 . Further analysis indicated that K 2 SO 4 can promote the phase transformation from γ-Al 2 O 3 to α-Al 2 O 3 and the formation of single-crystal α-Al 2 O 3 platelets might be attributed to the liquid phase K 3 Al(SO 4 ) 3 .
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effect of Potassium Sulfate on the low temperature formation of alpha alumina platelets from bayerite
Journal of the American Ceramic Society, 2010Co-Authors: Xinghua Su, Suqiang Li, Jiangong LiAbstract:The effect of Potassium Sulfate (K2SO4) on the phase transformation from bayerite [α-Al(OH)3] to α-Al2O3 has been studied. K2SO4 and γ-Al2O3 react and form K3Al(SO4)3. Decomposition of K3Al(SO4)3 can supply the α-Al2O3 seeds for heterogeneous nucleation, accelerate the transformation from the γ-Al2O3 to α-Al2O3, and lower the formation temperature of α-Al2O3. α-Al2O3 particles grow into hexagonal platelets in the presence of the liquid phase K3Al(SO4)3. The α-Al2O3 platelets obtained by a 900°C calcination of the bayerite and K2SO4 mixture have an average diameter of 1 μm and an average diameter/thickness ratio of 10.
Barbara Pacewska - One of the best experts on this subject based on the ideXlab platform.
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physicochemical properties of the products of basic aluminium Potassium Sulfate decomposition in hydrogen atmosphere
Journal of Thermal Analysis and Calorimetry, 1995Co-Authors: Barbara Pacewska, T Zmijewski, Maria MioduskaAbstract:Low-temperature modifications of aluminium oxide were obtained by thermal decomposition of basic aluminium-Potassium Sulfate at temperatures 550, 600, and 650°C. Physicochemical properties of the obtained oxides were studied with particular consideration to phase composition and porous structure. It has been shown how the decomposition parameters of the basic salt used determine the porous structure of the obtained oxides.
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properties of aluminium oxides obtained by calcination of the products of reductive roasting of basic aluminium Potassium Sulfate
Journal of Thermal Analysis and Calorimetry, 1995Co-Authors: T Zmijewski, Barbara Pacewska, Janusz PysiakAbstract:The influence of calcination conditions on changes in phase composition and porous structure was studied for hydrous aluminium oxide, obtained by leaching out Potassium salts from the products of roasting basic aluminium-Potassium Sulfate in hydrogen atmosphere at 600°C. The product of calcination at 350°C in vacuum has the most developed porous structure with most pores of internal radius within 10–60 A. Calcination in air atmosphere at temperatures 700, 800, 900, or 1000°C resulted in decrease of specific surface of aluminium oxide and increase of the share of pores with internal radius above 60 A in the overall porosity of the samples. The reconstruction of the porous structure proceeds mainly as a result of coalescent sintering.