Does organic modification of layered double hydroxides improve the fire performance of PMMA?

The effect of modified layered double hydroxides (LDHs) on fire properties of poly(methyl methacrylate) is investigated. Organically-modified LDHs were prepared via rehydration of calcined hydrotalcite in a palmitate solution. Composites consisting of the organo-LDHs, unmodified hydrotalcite and calcined oxides were prepared with poly(methyl methacrylate) using melt blending. Thermal and fire properties of the (nano)composites were studied. The thermogravimetric analyses of the composites show an increase in thermal stability. Fire performance, evaluated using cone calorimetry, show that organically-modified LDHs composites give the best reductions in peak heat release rate, PHRR, i.e., 51% at 10% weight loading. Dispersion of the LDHs was characterized using transmission electron microscopy and X-ray diffraction. Nanocomposite formation was observed with organically-modified LDHs, while the unmodified LDH composites gave only microcomposites.     

Sonochemical synthesis and characterization of new nanostructures cobalt(II) metal-organic complexes derived from the azo-coupling reaction of 4-amino benzoic acid with anthranilic acid,salicylaldehyde and 2-naphtol

Nanostructures of three new cobalt(II) complexes, (CoL₁)·0.5DMF·1.5MeOH (1), [H₂L₁ = 5-(4-Carboxy phenyl azo) anthranilic acid], (Co(L₂)₂)·1.5MeOH (2), [HL₂ = 5-(4-Carboxy phenyl azo) salicylaldehyde] and (Co(L₃)₂)·0.5 DMF·0.5MeOH (3), [HL₃ = 1-(4-Carboxy phenyl azo) 2-naphtol], have been synthesized by the reaction of H₂L₁, HL₂ and HL₃ with Co(OAc)₂·4H₂O through sonochemical process. Calcination of the nano-sized compounds 1–3 yield Co₃O₄ nanoparticles at 450 °C under air atmosphere. These nanostructures were characterized by X-ray powder diffraction (XRD) and Scanning Electron Microscopy (SEM). Thermal stability of compounds 1–3 was studied by thermogravimetric (TG) and differential thermal analyses (DTA).     

溶胶-凝胶法制备K-Co-Mo催化剂的结构及其合成低碳醇性能研究──焙烧温度的影响

采用溶胶凝胶法制备 Ｃｏ Ｍｏ Ｏ４ 催化剂, 经 Ｋ 助化后分别在空气中于４００～８００ ℃下进行焙烧, 得到氧化态样品, 然后经硫化制得硫化态 Ｋ Ｃｏ Ｍｏ 催化剂, 对氧化态样品的乙醇分解性能及硫化态样品的 Ｃ Ｏ 加氢合成低碳醇的反应性能进行了测试． 运用 Ｘ 射线衍射（ Ｘ Ｒ Ｄ ）和扩展 Ｘ光吸收精细结构（ Ｅ Ｘ Ａ Ｆ Ｓ ）对样品进行结构表征． 乙醇分解性能测试表明, 催化剂的表面酸性较弱, 且随着焙烧温度的升高变化不大． 合成醇性能测试结果则显示, 催化剂的焙烧温度升高后,其合成醇的产率逐步降低, 但醇选择性基本不变． 经 ４００ ℃焙烧的样品, 具有最好的催化活性．结构分析结果表明, 氧化态样品中存在多种 Ｋ Ｍ ｏ Ｏ 物种, 且随着焙烧温度的提高, 钾钼之间作用增强, 样品更难以被完全硫化．     

热处理温度对锂氧气电池用Co-N/C催化剂催化性能的影响

开发低成本、高效的空气电极催化剂是发展锂空气电池的关键课题之一. 采用邻菲咯啉(phen)为配体制备Co(phen)₂配合物,负载于BP2000 碳载体上,并分别在600、700、800 和900 ℃的温度下进行热处理,制备得到碳支撑的Co-N催化剂(Co-N/C). 对催化剂的氧还原反应/析氧反应(ORR/OER)活性进行了表征,并且与典型的CoTMPP/C催化剂进行了比较. 同时研究了煅烧温度对Co-N/C催化剂的组成和结构的影响. 电化学测试结果表明,热处理温度为700-800 ℃时催化剂具有较好的电化学性能. Co-N/C催化剂具有电化学性能优良与低成本的特点,是一种良好的锂氧气电池催化剂.     

制备条件对Pd催化剂上C3H6选择性还原NO性能的影响

采用浸渍法和溶胶凝胶法,制备了Pd/AI2O3和Pd/AI2O3-CeO2样品,并测定了不同温度焙烧后催化剂的物相、比表面积及对丙烯选择性还原NO的活性。对于Pd/AI2O3,随着焙烧温度的提高,其NO的最大转化率逐渐下降,对应的反应温度在290－310℃左右,而溶胶凝胶法制备的样品活性略高于浸渍法制备的样品;对于Pd/AI2O3-CeO2,经600℃焙烧后,其NO的最大转化率为22％,900℃焙烧的催化剂样品上NO的最大转化率达到40％左右,对应的反应温度也逐渐下降,说明活性随焙烧温度的提高而明显提高,溶胶凝胶法和浸渍法制备的样品结果很接近,浸渍法制备了若干不同Pd负载量的Pd/AI2O3样品,活性测定的结果表明,Pd含量在0．5％左右的催化剂样品中具有最高的活性。     

Calcination Effect on the Photoluminescence,Optical, Structural,and Magnetic Properties of Polyvinyl Alcohol Doped ZnFe2O4 Nanoparticles

Abstract

Spinel ferrite based nanoparticle material has been at the forefront of contemporary nanotechnology for use in various industrial and biomedical applications. The preparation and characterization of zinc ferrite nanoparticles (ZFNPs) doped with polyvinyl alcohol (PVA) are reported in this work. The formulated ZFNP/PVAs were characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy, photoluminescence (PL) and a vibrating sample magnetometer (VSM). The XRD established the cubic spinel crystal structure of the as-prepared and calcined sample with an increase in the crystallite size after the calcination. The SEM analysis showed a spherical morphology within the range of 10-40?nm after calcination. The bandgap energy was enhanced after calcination. The PL analysis revealed a prominent peak in the UV band, which showed the characteristics of the formulated nanostructure. Transformation to a superparamagnetic nature was observed after calcination. It is noteworthy that after calcination of the formulated ZFNP/PVAs, the structural, optical, bandgap energy, morphology, photoluminescence and the magnetic properties were influenced and enhanced for various applications, chiefly for hyperthermia, magnetic resonance imaging, drug delivery and allied disciplines.     

Selective adsorption of epigallocatechin gallate onto highly reusable gallium doped mesoporous TiO2 nanoparticles adsorbent

This work describes a potential selective adsorption of epigallocatechin gallate by Ga-doped TiO₂ nanoparticles (NPs) and showed excellent adsorption (～99%) and desorption capacity even after the 7th run. The work reports about a surfactant mediated template based synthesis of both pristine and Ga-doped TiO₂ mesoporous NPs to study the adsorption behavior EGCG. EGCG is the most abundant and bio-active compound capable of showing free radical scavenging activity, anticancer, antibacterial, and several other physiological functions. Therefore, extraction of EGCG is highly desirable for incorporation in food items that can effectively increase their nutritional and medicinal values. The pore diameter of the synthesized materials was found to be in the range 8.76–10.38 nm and the specific surface area was found to be around 25.80–58.72 m²/g. The particle size decreased from 25 nm to 15 nm in presence of Ga. A mixture of anatase and brookite phase was observed for all the synthesized TiO₂ NPs. The band gap value initially (3.40 eV) decreased in presence of minute amounts of Ga (3.44 eV) but then increased (3.59 eV) with the increase of Ga percentage. The point of zero charge (PZC) value of the materials lies in the range of 6.6–7.2. The adsorption study was carried out at different pH (1, 3, 5, 7 and 9) with variation of shaking time (1 h, 3 h, 5 h and 7 h). The material containing maximum Ga in the Ga-doped set (Set 3 TiO₂ NPs) showed highest adsorption percentage (99.45%) in pH 1 medium after 5 h shaking. The adsorption isotherm and the kinetics follow the Langmuir model and pseudo-second order respectively. Desorption was studied under high energy gamma rays, shaking, sonication and UV irradiation. The highest desorption (～96%) was obtained with sonication for 30 min.     

焙烧温度对酯加氢制醇Cu-Al-Ba催化剂性能的影响(英文)

通过共沉淀法在不同焙烧温度下制备了新型无铬Cu-Al-Ba催化剂.测试了其在高压釜中将棕榈油甲酯加氢制备高碳醇的反应性能.结果表明催化剂的焙烧温度对催化性能有较大影响.在从150℃升至750℃的过程中,高碳醇的收率显示了三个阶段的变化,相应地,催化剂前驱体的热重(TG-DTG)曲线也显示了三个阶段的失重.X射线衍射(XRD)、X射线荧光(XRF),透射电镜-能谱分析-选区电子衍射(TEM-EDS-SAED)、N2物理吸附和程序升温还原(TPR)表征表明,催化剂是由一种孔雀石-勃石-碳酸钡前驱体制得的.在300或550℃焙烧后,催化剂组成为晶态的CuO、BaCO3和非晶态的Al2O3.其中,非晶态的Al2O3为CuO的高分散提供了大的比表面,杆状的BaCO3组分有利于提供微孔结构.在更高的焙烧温度750℃,新物相BaAl2O4的形成破坏了催化剂中的非晶态结构,导致其比表面积和孔容的急剧下降,并引起CuO物种的聚结.550℃焙烧的催化剂显示了最高的高碳醇收率,达到92.3%,这归因于其大的比表面积、大孔容和较高的CuO分散性.     

焙烧温度对SiO2负载的Co3O4纳米粒子表面氧缺陷浓度和CO氧化催化性能的影响

以传统的浸渍法,在不同焙烧温度下制备了用于CO氧化反应的Co₃O₄/SiO₂催化剂．通过激光拉曼光谱(Raman)、X射线光电子能谱(XPS)、X射线衍射(XRD)、程序升温还原(TPR)和X射线吸收精细结构谱(XAFS)表征了该系列催化剂的结构．在所有的催化剂中,XRD和Raman光谱都只检测到了Co₃O₄晶相的存在．与Co₃O₄体相相比,XPS结果表明在200 oC焙烧的(Co₃O₄(200)/SiO₂)催化剂中Co₃O₄表面上存在着过量的Co²⁺．与XPS的结果一致,TPR结果表明Co₃O₄(200)/SiO₂催化剂中Co₃O₄表面上存在氧缺陷, 并且XAFS结果也表明Co₃O₄(200)/SiO₂催化剂中Co₃O₄具有更多的Co²⁺．提高焙烧温度使得过量的Co²⁺进一步氧化为Co³⁺,同时降低了表面氧缺陷浓度,从而得到计量比的Co₃O₄4/SiO₂催化剂．在所有的负载催化剂中Co₃O₄(200)/SiO₂催化剂表现出了最好的CO氧化催化性能,表明过量Co²⁺和表面氧缺陷的存在能够促进Co₃O₄催化CO氧化反应的活性.     

Synthesis and thermal evolution of TiO2-RuO2 xerogels

Gels of the Ti Ru O system, where , 0.001, 0.01, 0.02, 0.05, 0.1, 0.15, 0.2, 0.3 and 0.5 (mol), have been synthesized by a polymeric sol-gel route from Ti (IV)-iso-propoxide and Ru (III) acetyl-acetonate (acac). The mechanisms of the hydrolysis and polycondensation reactions were studied by using Fourier Transform Infrared Spectroscopy (FTIR). The evolution of the xerogels as a function of temperature was also determined. At temperatures, as low as 200°C, mixtures of antase Ti Ru O (Ass) solid solution and rutile Ti Ru O solid solution (Rss) were attained for compositions with 0.3. For , only the anatase phase is present (A) and for , mixtures of anatase Ti Ru O (Ass) solid solution, rutile Ti Ru O solid solution (Rss) and Ru Ti O (RuO ss) solid solution were attained. RuO catalyzes the anatase to rutile transformation, even at RuO contents as low as 0.001 mol. Although, from 300 to 400°C the solid solubility of RuO into rutile-TiO phase is located at , from 500°C that value is located in the 0.05 range. This fact could be due to the metastability of the rutile solid solutions containing ruthenium oxide above 400°C. According to semiquantitative transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDX) analyses, at 700°C, there are compositional variations in both solid solutions, Rss and RuO ss. Thus, the system is chemically heterogeneous. The amount of Ti ions hosted into the RuO lattice in the solid solution is lower than that of Ru ions into the rutile-TiO lattice. At this temperature, the contents of these solid solutions are mol% RuO into the TiO lattice (the maximum value found) and around 8.0 mol% TiO (the maximum value found) into RuO . The RuO volatilization can promote the segregation of the ruthenium oxide giving rise to the heterogeneity and the metastability observed in this system.