结合发泡升温曲线、泡沫生长高度及凝胶时间考察了Al2O3、TPU、PE与GP这4种微粉对于PU泡沫内部高反应热的影响。结果表明,PE微粉最适合用在PU发泡体系中起降温效果,可解决烧芯问题,同时对PU发泡生长过程影响较小,还可缩短凝胶时间,主要...结合发泡升温曲线、泡沫生长高度及凝胶时间考察了Al2O3、TPU、PE与GP这4种微粉对于PU泡沫内部高反应热的影响。结果表明,PE微粉最适合用在PU发泡体系中起降温效果,可解决烧芯问题,同时对PU发泡生长过程影响较小,还可缩短凝胶时间,主要是由于PE的相变储能效应,即在反应前期体系升温时吸热熔融,储存了部分能量,而在反应后期体系降温时结晶产生放热效应,有利于缩短泡沫的养生期。当PE添加质量分数为3%时,PE/PU泡沫的拉伸强度、压缩强度与断裂伸长率分别比PU泡沫提高了67%、26%与35%,且在1.5-6.0 k Hz时的吸声系数亦有明显提升。展开更多
The precursor of nanocrystalline ZrO2 was synthesized by solid-state reaction at low heat using ZrOCl2·8H2O,and Na2CO3·10H2O as raw materials.The nanocrystalline ZrO2 was obtained by calcining the precursor....The precursor of nanocrystalline ZrO2 was synthesized by solid-state reaction at low heat using ZrOCl2·8H2O,and Na2CO3·10H2O as raw materials.The nanocrystalline ZrO2 was obtained by calcining the precursor.The precursor and its calcined products were characterized using TG/DTA,FT-IR,XRD,and SEM.The results showed that the precursor dried at 353 K was a zirconyl carbonate compound.When the precursor was calcined at 673 K for 150min,highly crystallization ZrO2 with tetragonal structure (space group P42/nmc (137)) was obtained with a crystallite size of 24 nm.However,when the precursor was calcined at 1023 K for 150min,highly crystallization ZrO2 with monoclinic structure (space group P21/c (14)) was obtained with a crystallite size of 20 nm.The mechanism and kinetics of the thermal process of the precursor were studied using DTA and XRD techniques.Based on the Kissinger and Arrhenius equation,the values of the activation energies associated with the thermal process of the precursor were determined to be 26.80 and 566.73 kJ·mol-1 for the first and third steps,respectively.The mechanism of ZrO2 phase transition from tetragonal to monoclinic structure is the random nucleation and growth of nuclei reaction.展开更多
Precursor of nanocrystalline Zno.sNio.sFe2O4 was obtained by grinding mixture of ZnSO4.7H2O, NiSO4.6H2O, FeSO4.7H2O, and Na2CO3.10H2O under the condition of suffactant polyethylene glycol （PEG）-400 being present at ...Precursor of nanocrystalline Zno.sNio.sFe2O4 was obtained by grinding mixture of ZnSO4.7H2O, NiSO4.6H2O, FeSO4.7H2O, and Na2CO3.10H2O under the condition of suffactant polyethylene glycol （PEG）-400 being present at room temperature, washing the mixture with water to remove soluble inorganic salts and drying it at 373 K. The spinel Zn0.5Ni0.5Fe2O4 was obtained via calcining precursor above 773 K. The precursor and its calcined products were characterized by differential scanning calorimetry （DSC）, Fourier transform infrared （FF-IR）, X-ray diffraction （XRD）, and vibrating sample magnetometer （VSM）. The result showed that Zn0.sNio.sFe204 obtained at 1073 K had a saturation magnetization of 74 A.mLkg-1. Kinetics of the crystallization process of Zn0.5Ni0.5Fe2O4 was studied using DSC technique, and kinetic parameters were determined by Kissinger equation and Moynihan et al. equation. The value of the activation energy associated with the crystallization process of Zr0.5Ni0.5Fe2O4 is 220.89 kJ-mol-1. The average value of the Avrami exponent, n, is equal to 1.59±0.13, which suggests that crystallization process of Zn0.5Ni0.5Fe2O4 is the random nucleation and growth of nuclei reaction.展开更多
文摘结合发泡升温曲线、泡沫生长高度及凝胶时间考察了Al2O3、TPU、PE与GP这4种微粉对于PU泡沫内部高反应热的影响。结果表明,PE微粉最适合用在PU发泡体系中起降温效果,可解决烧芯问题,同时对PU发泡生长过程影响较小,还可缩短凝胶时间,主要是由于PE的相变储能效应,即在反应前期体系升温时吸热熔融,储存了部分能量,而在反应后期体系降温时结晶产生放热效应,有利于缩短泡沫的养生期。当PE添加质量分数为3%时,PE/PU泡沫的拉伸强度、压缩强度与断裂伸长率分别比PU泡沫提高了67%、26%与35%,且在1.5-6.0 k Hz时的吸声系数亦有明显提升。
基金financially supported by the National Natural Scientific Foundation of China (No.201161002)
文摘The precursor of nanocrystalline ZrO2 was synthesized by solid-state reaction at low heat using ZrOCl2·8H2O,and Na2CO3·10H2O as raw materials.The nanocrystalline ZrO2 was obtained by calcining the precursor.The precursor and its calcined products were characterized using TG/DTA,FT-IR,XRD,and SEM.The results showed that the precursor dried at 353 K was a zirconyl carbonate compound.When the precursor was calcined at 673 K for 150min,highly crystallization ZrO2 with tetragonal structure (space group P42/nmc (137)) was obtained with a crystallite size of 24 nm.However,when the precursor was calcined at 1023 K for 150min,highly crystallization ZrO2 with monoclinic structure (space group P21/c (14)) was obtained with a crystallite size of 20 nm.The mechanism and kinetics of the thermal process of the precursor were studied using DTA and XRD techniques.Based on the Kissinger and Arrhenius equation,the values of the activation energies associated with the thermal process of the precursor were determined to be 26.80 and 566.73 kJ·mol-1 for the first and third steps,respectively.The mechanism of ZrO2 phase transition from tetragonal to monoclinic structure is the random nucleation and growth of nuclei reaction.
基金financially supported by the National Natural Science Foundation of China (No.21161002)the Guangxi Science and Technology Agency Research Item,China (No.0992001-5)
文摘Precursor of nanocrystalline Zno.sNio.sFe2O4 was obtained by grinding mixture of ZnSO4.7H2O, NiSO4.6H2O, FeSO4.7H2O, and Na2CO3.10H2O under the condition of suffactant polyethylene glycol （PEG）-400 being present at room temperature, washing the mixture with water to remove soluble inorganic salts and drying it at 373 K. The spinel Zn0.5Ni0.5Fe2O4 was obtained via calcining precursor above 773 K. The precursor and its calcined products were characterized by differential scanning calorimetry （DSC）, Fourier transform infrared （FF-IR）, X-ray diffraction （XRD）, and vibrating sample magnetometer （VSM）. The result showed that Zn0.sNio.sFe204 obtained at 1073 K had a saturation magnetization of 74 A.mLkg-1. Kinetics of the crystallization process of Zn0.5Ni0.5Fe2O4 was studied using DSC technique, and kinetic parameters were determined by Kissinger equation and Moynihan et al. equation. The value of the activation energy associated with the crystallization process of Zr0.5Ni0.5Fe2O4 is 220.89 kJ-mol-1. The average value of the Avrami exponent, n, is equal to 1.59±0.13, which suggests that crystallization process of Zn0.5Ni0.5Fe2O4 is the random nucleation and growth of nuclei reaction.
