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1.
The influence of TiO2 nanoparticles on the thermal degradation of poly(methyl methacrylate) (PMMA) was investigated by TGA. The studied materials were characterized by Py-GC-MS, TEM, SEM, TGA, DSC and TGA-MS. The PMMA-TiO2 nanocomposites were prepared by melt blending with different (5, 10, 15 and 20 wt% TiO2) loadings. According to TGA results and to the activation energy (determined by the model-free isoconversional method of Vyazovkin), the incorporation of 5 wt% of TiO2 nanoparticles into PMMA stabilizes it by more than 40 °C. However, for higher loading contents, a catalytic effect on the thermal decomposition was observed which increased with the oxide content. The results obtained by Py-GC-MS showed clearly that TiO2 increases the formation of methanol, methacrylic acid and propanoic acid methyl ester during the degradation of PMMA. This catalytic effect could be explained through the interaction of the methoxy group of the methacrylate function with the hydroxyl groups present at the surface of the oxide particles. 相似文献
2.
Niranjan Patra Marco SalernoM. Malerba P. Davide CozzoliAthanassia Athanassiou 《Polymer Degradation and Stability》2011,96(7):1377-1381
The thermal degradation behaviour of oleic acid-capped colloidal anatase TiO2 nanorods, poly(methyl methacrylate), and their nanocomposites has been studied. Thermogravimetric and differential thermal analysis have been carried out in nitrogen atmosphere for both nanorods, and nanocomposites with nanorod loading from 5 to 30 wt% relative to the polymer. Our study shows that the degradation of the oleic acid-capped nanorods in nitrogen is mainly endothermic and occurs in two steps. The thermal stability of the nanocomposites is improved on increasing the filler loading in the considered range, as the nanorods prevent rapid heat diffusion and limit further degradation. This effect seems to be favoured by the nanorods increased mobility, leading to enhanced dispersion in the matrix upon heating the samples during the thermal analysis. 相似文献
3.
Effect of ZnO and organo-modified montmorillonite on thermal degradation of poly(methyl methacrylate) nanocomposites 总被引:1,自引:0,他引:1
A. Laachachi D. Ruch M. Ferriol J.-M. Lopez Cuesta 《Polymer Degradation and Stability》2009,94(4):670-678
Since a few years ago, a topic of interest consists in developing composites filled with nanofillers to improve thermal degradation and flammability property of poly(methyl methacrylate) (PMMA). In the present work, the effects of ZnO nanoparticles and organo-modified montmorillonite (OMMT) on the thermal degradation of PMMA were investigated by thermogravimetric analysis (TGA). PMMA-ZnO and PMMA-OMMT nanocomposites were prepared by melt blending with different (2, 5, and 10 wt%) loadings. SEM and TEM analyses of nanocomposites were performed in order to investigate the dispersion of nanofillers in the matrix. According to TGA results, the addition of ZnO nanoparticles does not affect the thermal degradation of PMMA under an inert atmosphere. However, in an oxidative atmosphere, two contrary effects were observed, a catalytic effect at lower concentration of ZnO in the PMMA matrix and a stabilizing effect when the ZnO concentration is higher (10 wt%). In contrast, the presence of OMMT stabilizes the thermal degradation of PMMA whatever be the atmosphere. Differential thermal analysis (DTA) curves showed surprising results, because a dramatic change of exothermic reaction of the PMMA degradation process to an endothermic reaction was observed only in the case of OMMT. During the degradation of PMMA-ZnO nanocomposites, pyrolysis-gas chromatography coupled to mass spectrometer (Py-GC/MS) showed an increase in the formation of methanol and methacrylic acid while a decrease in the formation of propanoic acid methyl ester occurred. In the case of PMMA-OMMT systems, a very significant reduction in the quantity of all these degradation products of PMMA was observed with increasing OMMT concentration. It is also noted that during PMMA-OMMT degradation less energy was released as the decomposition is an endothermic reaction and the material was cooled. 相似文献
4.
Blandine Friederich Abdelghani Laachachi Michel Ferriol Marianne Cochez 《Polymer Degradation and Stability》2010,95(7):1183-24
Possible relationships between fire-retardant properties and thermal diffusivity for poly(methyl methacrylate) (PMMA) filled by melt blending with titanium dioxide (TiO2), alumina (Al2O3) and boehmite (AlOOH) were investigated for a better understanding of the mode of action of metal oxides as fire-retardants (FR) in PMMA. Fire-retardancy was measured with a cone calorimeter and thermal diffusivity (α) by Laser Flash Analysis (LFA). LFA measurements have shown that heat dispersion is higher with titanium dioxide and boehmite than with alumina despite a larger surface area. For thermal diffusivity, discrepancies between the different nanofillers were only visible from 10 wt% onwards. Thermal degradation of PMMA-oxide nanocomposites and their thermal diffusivity could be linked. Moreover, a bi-linear relationship between the peak of heat release rate (pHRR) and the average of heat release rate (AHRR) showed the occurrence of a barrier effect. 相似文献
5.
The chemisorption of CO2 has been studied on alumina-supported Co-and Ni-promoted molybdenum-oxide (CoMo, NiMo) and, besides those, on monometallic
Co and Ni. Chemisorbed amounts on the monometallic samples were equal to that on the alumina support. XPS measurements were
performed with the NiMo and Ni samples. The amounts of surface Mo-and Al-ions were calculated. It could be established that
molybdenum oxide forms a near to monomolecular layer on the Co-and Ni-promoted molybdena-alumina samples. 相似文献
6.
Milena Marinovi?-Cincovi? 《Polymer Degradation and Stability》2007,92(1):70-74
Colloidal dispersions consisting of β-FeOOH nanorods with three different aspect ratios (4, 75 and 120) were synthesized using thermal hydrolysis of FeCl3 solutions. After surface modification with oleic acid, the β-FeOOH nanorods were incorporated in poly(methyl methacrylate). Transmission electron microscopy and X-ray diffraction were applied for structural characterization of the β-FeOOH nanorods. The influence of inorganic phase on the thermal properties of PMMA matrix was studied using thermogravimetry and differential scanning calorimetry. Improvement of the thermal stability and increase of the glass transition temperature were found with the increase of content of inorganic phase and the increase of aspect ratio. 相似文献
7.
通过溶胶和超临界干燥方法制得了Fe2O3/Al2O3二元气凝胶,其比表面积和孔隙体积分别为246 m2·g-1和1.89 cm3·g-1,并具有较宽的孔径分布。以Fe2O3/Al2O3二元气凝胶作催化剂,通过甲烷催化裂解成功地合成了高质量的单壁纳米碳管。利用FESEM、TEM和HRTEM、Raman光谱等分析手段研究了反应温度对单壁纳米碳管生长的影响。结果表明在900 ℃时合成单壁纳米碳管的质量较高,并且合成的炭产物为毡状,该炭产物主要为高质量的单壁纳米碳管。 相似文献
8.
A series of Al2O3-Fe2O3 mixed oxidic solids with composition ranging from 0 to 100% of Fe2O3 were prepared and examined for structural characteristics. XRD diagrams showed the presence of α-Al2O3 and hematite phases. The analysis of M?ssbauer spectra revealed the existence of two iron containing phases. The specific
surface area of the mixture decreases by the addition of iron and depends on the crystal phases of the mixture.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
9.
Toshihide Baba 《Catalysis Surveys from Japan》2000,4(1):17-29
This review describes the preparation, characterization and application of KNH2 loaded on alumina and KF loaded on alumina. These strong solid bases catalyze a variety of organic reactions in a very selective manner. The reactions include isomerizations of alkenes and alkynes, dimerization of alkynes, Tishchenko reaction, and the reaction of silanes to form of Si–C, Si–N and Si–O bonds. 相似文献
10.
E. Castro Luna A. M. Becerra M. I. Dimitrijewits 《Reaction Kinetics and Catalysis Letters》1999,67(2):247-252
The effect of Rh addition upon catalyst characteristics and performance in methane steam reforming was investigated using
Rh-promoted Ni/Al2O3 catalysts. The number of reduced metal atoms exposed on the surface increased for the Rh-promoted catalysts. Rh-promoted
catalysts showed an increase in CH4 reforming activity; however, constant turnover frequencies for promoted and unpromoted catalysts suggest that the increase
in the number of metal surface atoms caused the activity enhancement. Rh also facilitated reduction of Ni/Al2O3. 相似文献
11.
CO2 chemisorption, BET surface area and the degree of reduction of Mo(VI) (e/Mo) have been determined in MoOx/Al2O3 samples, reduced with hydrogen at temperatures between 673 and 1173 K. The free alumina surface figures calculated from the
surface area and e/Mo values were identical with those obtained from direct CO2 chemisorption measurements. This identity indicates that all of the oxygen ions of the surface molybdenum-oxygen species
block the alumina surface. 相似文献
12.
以"乙酸乙酯(EA)-偏铝酸钠-水"体系在室温下合成了纳米膜组装介孔Al2O3。研究发现:合成反应时间、静置前搅拌时间、NaAlO2用量、EA用量及反应温度等对合成产物的形貌有影响;另外,与用商品γ-Al2O3制备的Pt/γ-Al2O3催化剂相比,纳米膜组装介孔Al2O3制备的Pt/Al2O3催化剂含有部分易被还原的PtOx物种。在硝基苯催化加氢反应中,用合成Al2O3为载体制备的Pt/Al2O3催化剂,比用商品γ-Al2O3制备的Pt/γ-Al2O3催化剂具有更好的催化活性。 相似文献
13.
以异丙醇铝和氧氯化锆为原料,用溶胶-凝胶法在Al2O3中空纤维上制备了Al2O3-ZrO2复合膜。应用TG、DTA、XRD、SEM等测试手段对复合膜的热稳定性、结构、形貌进行了表征。结果表明复合膜的热稳定性比单一由氧化铝或氧化锆制成的膜有显著的提高,在1100℃之前,复合膜以t-ZrO2存在,1200℃时,出现了m-ZrO2和α-Al2O3相。扫描电镜分析表明,膜表面完整、无缺陷。气体渗透实验进一步表明所得膜具有一定的气体选择性,0.3MPa和0.5MPa下对氮气和氩气的分离因子α分别为1.191和1.185,和氮气与氩气的理论分离因子(α=1.194)相当,说明气体通过膜的扩散以Knudsen扩散传质为主。用等温氮气吸附实验测定了非担载膜的孔径大小和分布,最可几孔径约为4.3nm。 相似文献
14.
In the course of our investigations on halogen-free fire-retardant solutions for PMMA, the influence of oxide nanoparticles (TiO2, Al2O3) on the thermal stability and fire behaviour of PMMA blended with phosphinate additives (Exolit OP930 and OP1311) has been studied by thermogravimetric analysis and cone calorimetry. For each mixture, the residues obtained after combustion were examined and characterized by SEM, X-ray diffraction and X-ray microprobe analysis. Some synergistic effects were obtained between nanometric alumina and OP930 additive leading to the reduction of peak of heat released rate and of total heat released up to 30% and to the increase of time to ignition. From the results obtained, it can be proposed that OP930 and OP1311 act principally in the condensed phase, the presence of oxides playing a reinforcement role in the carbonaceous layer promoted by the phosphinate additives. 相似文献
15.
Baowen Wang Rong Yan Dong Ho Lee Ying Zheng Haibo Zhao Chuguang Zheng 《Journal of Analytical and Applied Pyrolysis》2011,91(1):105-113
The sol-gel combustion synthesis (SGCS) for oxygen carrier (OC) to be used in chemical looping combustion (CLC) was first designed and experimented in this work, which is a new method of OC synthesis by combining sol-gel technique and solution combustion synthesis. Cheap hydrated metal nitrates and urea were adopted as precursors to prepare Fe2O3/Al2O3 OC at the molar ratio to unity (Fe1Al1), which was characterized through various means, including Fourier transforms infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffractor (XRD), and N2 isothermal adsorption/desorption method. FTIR analysis on the chemical structure of the dried gel of Fe1Al1 indicated that urea was partly hydrolyzed and the hydrated basic carbonate was formed by the combination of groups such as (Fe(1−yAly)1−xO1−3x, CO32− and -OH-. By analyzing the staged products during SGCS, calcination was found as a necessary step to produce Fe2O3/Al2O3 OC with separate phases of α-Fe2O3 and α-Al2O3. Through TGA-DTA, the decomposition of the dried gel was found to undergo five stages. The analysis of the evolved gases from the gel decomposition using FTIR partially confirmed the staged decomposition and assisted a better understanding of the mechanism of SGCS. XRD identification further substantiated the necessity of calcination to synthesize Fe2O3/Al2O3 OC with separate phases of α-Fe2O3 and α-Al2O3, though it was not necessary for the synthesis of single phase α-Fe2O3 and α-Al2O3. Structural characterization performed on N2 adsorption analyzer displayed that the pore shape of Fe1Al1 particles was heterogeneous. Finally, H2 temperature-programmed reduction (TPR) of Fe1Al1 products in TGA indicated that the reduction reaction of Fe1Al1 OC after calcination was a single step reaction from α-Fe2O3 to Fe, and calcination benefited to improve the transfer rate of the lattice oxygen from the OC to fuel H2. Furthermore, four times of reduction and oxidization (redox) reaction by alternating with H2 and air demonstrated the synthesized OC had good reactivity and sintering-resistance, much suitable to be used in the realistic CLC. Overall, the SGCS method was found superior to other existent methods to prepare Fe2O3/Al2O3 OC for CLC application. 相似文献
16.
Izabela Witoska Stanisaw Karski Joanna Gouchowska 《Reaction Kinetics and Catalysis Letters》2007,90(1):107-115
Hydrogenation of nitrate (NO3
−) in water was studied with 0.8 ×10−3–3.2 ×10−3 mol/dm3 of reactant in the temperature range of 293–313 K over palladium promoted Ag catalysts. Pd-Ag catalysts with a low ratio
of Ag/Pd were characterized by high efficiency in the reduction of nitrates. The degradation of nitrates followed approximately
first order decay and the estimated apparent activation energy was about 4 kJ/mol. 相似文献
17.
Kazuhisa Murata Kiyomi Okabe Isao Takahara Megumu Inaba Masahiro Saito 《Reaction Kinetics and Catalysis Letters》2007,90(2):275-283
Fischer-Tropsch syntheses (FTS) were carried out in a slurry phase over Ru/Al2O3 catalysts using hexadecane as a solvent. The outcome of the FTS was dependent on the oxide support, calcination temperature,
synthesis gas composition and sulfur content. The addition of Mn/Na to Ru/Al2O3 was effective in raising the initial activity and C5+ selectivity, but after 20 hours, the performance of the modified catalyst
was similar to that of the unmodified catalyst. An additional investigation involving the use of fresh vs used catalysts demonstrated that an agglomeration of the metallic Ru, at least in part, does occur during the reaction. 相似文献
18.
N2O decomposition was examined over a series of Al2O3-Fe2O3 mixed oxidic solids with composition ranging from 0 to 100% of Fe2O3. The catalytic activity of the solids runs parallel to the number of atoms of iron in the Al2−x FexO3 solid solution phase. Two compensation effects are present. The first corresponds to catalysts rich in alumina, and the second
one to catalysts rich in hematite.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
19.
以自制不对称双子季铵盐表面活性剂为模板, 在水热合成体系中控制合成系列硅铝比纳米薄层ZSM-5分子筛.采用X射线衍射(XRD)、N2吸附-脱附、X射线荧光光谱(XRF)、扫描电镜(SEM)和27Al魔角旋转核磁共振(27Al MAS-NMR)对合成的样品进行了表征. 详细研究了晶化温度、晶化时间、结构导向剂(SDA)用量、碱度等对合成的影响和纳米薄层ZSM-5分子筛的形成过程. 结果表明: 分子筛硅铝比越高, 结构导向剂用量越大, 所需的晶化时间越短; 晶化温度越高, 晶化时间越短; 且不同硅铝比纳米薄层ZSM-5分子筛的形貌规整度、比表面积和介孔/微孔孔容比例随着硅铝比而变化. 相似文献
20.
Jun Wang Wenzhao Li Chunying Yu Yanxin Chen Yingzhen Zhang 《Reaction Kinetics and Catalysis Letters》1997,62(2):217-224
Recucibility of Mo species in Pt/MoO3 and PtMo/Al2O3 has been investigated by temperature-programmed reduction (TPR), temperature-programmed desorption of hydrogen (H2-TPD) and temperature programmed electronic conductivity (TPEC) techniques. In Pt/MoO3 at H2 atmosphere, it was found by TPEC and TPR that, a slight amount of Pt could activate the transfer of the species and H atoms
between H2 and MoO3, and thus accelerate the reduction of MoO3. In PtMo/Al2O3, TPR and H2-TPD revealed that the reduction of surface Mo species could also be facilitated by Pt. Two kinds of hydrogen molybdenum species
were proposed on the surface of the catalyst after prereduction. 相似文献