过渡金属氧化物对阻燃剂聚磷酸铵热分解的影响机制

过渡金属氧化物(MO)可以显著影响聚磷酸铵(APP)的热分解过程,进而改善APP复配膨胀阻燃聚合物材料的阻燃效率。将ZnO、Fe2O3、TiO2掺入到APP中,采用热失重分析(TGA)、X射线光电子能谱(XPS)和X射线衍射分析(XRD),考察了3种MO对APP热分解行为的影响,分析了相互作用过程中金属原子和磷原子化学结合状态的变化以及高温热分解产物的物相结构。TGA和XPS图谱分析结果表明,MO可降低APP的起始热分解温度,并催化APP释放NH3和H2O,而在热分解后期由于金属磷酸盐的形成可显著增加APP的高温残留量。3种MO催化APP热分解脱NH3和H2O的活性由大到小的顺序是:ZnO>Fe2O3>TiO2,而对APP凝聚相热分解P-O产物的交联能力从大到小的顺序为:Fe2O3>ZnO>TiO2。XRD结果显示,ZnO在高温下与APP反应生成了Zn(PO3)2晶体,而Fe2O3和TiO2与APP反应分别生成了Fe4(P2O7)3和TiP2O7晶体。     

[NH3(CH2)5NH3][Fe2{O3PC(CH3)(OH)(PO3H)}2]·2H2O:一个新的二膦酸亚铁化合物的合成、结构与性质研究

通过水热合成得到一个新的有机二膦酸亚铁化合物[NH₃(CH₂)₅NH₃][Fe₂^Ⅱ{O₃PC(CH₃)(OH)(PO₃H)}₂]·2H₂O,该化合物包含阴离子型共价双链[Fe₂^Ⅱ{O₃PC(CH相似文献   

纳米Zn-Co铁氧体的固相合成及电磁损耗特性研究

采用NH₄HCO₃与FeCl₃·6H₂O，Zn(NO₃)₂·6H₂O，Co(NO₃)₂·6H₂O进行室温固相反应制得前驱物，经微波加热处理后，进而热分解分别制得复合氧化物ZnFe₂O₄、CoFe₂O₄和Co_0.5Zn_0.5Fe₂O₄。由激光粒度分析仪、XRD和SEM表征：获得了颗粒分布比较均一、平均粒度为65 nm左右、立方晶系尖晶石结构的纳米铁氧体粉体。经测试样品的相对介电常数和相对磁导率后，研究了它们的电磁损耗特性。结果表明：Co_0.5Zn_0.5Fe₂O₄在100～1 800 MHz内比另外两种铁氧体具有更好的电磁损耗特性。     

Bi2Fe4O9纳米粉体:水热法制备及表征

Bi₂Fe₄O₉ nanoparticles were prepared at low temperature via a facile, one-step hydrothermal synthesis process using iron(Ⅲ) nitrate nonahydrate(Fe(NO₃)₃·9H₂O) and bismuth nitrate pentahydrate (Bi(NO₃)₃·5H₂O) as starting materials and sodium hydroxide (NaOH) as the precipitant and mineralizer. XRD results indicate that the as-prepared nanoparticles are pure Bi₂Fe₄O₉. SEM images reveal that the as-prepared Bi₂Fe₄O₉ nanoparticles have a sheet-like morphology. The Bi₂Fe₄O₉ nanoparticles thus obtained are paramagnetic at room temperature as shown by magnetic measurements.     

一锅法制备S型异质结光催化剂Fe2O3/Fe2TiO5及其高效降解有机污染物性能

首次采用简单的一锅法制备了Fe₂O₃/Fe₂TiO₅异质结纳米材料。构建S型异质结后,与纯的Fe₂O₃和Fe₂TiO₅相比,Fe₂O₃/Fe₂TiO₅复合材料表现出更高的光催化降解速率和效率。经过2.5 h的光照后,Fe₂O₃/Fe₂TiO₅可以降解接近100%的亚甲基蓝（MB）。在Fe₂O₃/Fe₂TiO₅复合材料中,Fe₂O₃和Fe₂TiO₅之间形成了内建电场,可以促进光生电子-空穴对的分离。因此,具有更高能量的Fe₂TiO₅导带中的电子和具有更高能量的Fe₂O₃价带中的空穴可以得到有效的保留,从而使它们更加有效地扩散到催化剂表面,并参加降解反应。此外,Fe₂O₃/Fe₂TiO₅复合材料具有很好的光催化稳定性。     

掺杂Fe2O3对吸附相反应技术制备TiO2的形貌和光催化性能的影响

利用吸附相反应技术制备得到了掺杂不同浓度的Fe₂O₃的TiO₂复合光催化剂。通过透射电子显微镜(TEM)、紫外可见光谱和X射线衍射(XRD)研究不同掺杂浓度对TiO₂形貌和结晶过程的影响,并利用3种波长光源下的甲基橙光降解实验考评了各个复合光催化剂的催化活性。结果表明,掺杂后复合光催化剂中Fe₂O₃分散性较好较均匀。在TiO₂紫外可见吸收光谱中由于Fe₂O₃的掺杂而出现了红移,而且随着掺杂浓度增加红移越来越明显,复合光催化剂的禁带宽度也越来越小。在焙烧过程中无定形Fe₂O₃或Fe³⁺进入了TiO₂的晶格结构,从而抑制了TiO₂的结晶过程。半导体禁带宽度的减少以及TiO₂结晶过程的抑制作用,都导致紫外光下复合光催化剂催化活性的降低。但Fe₂O₃的掺杂也使得复合光催化剂在可见光区出现了一定的光催化活性。     

Fe2O3含量对Cu-Fe/铝土矿水煤气变换催化剂结构和性能的影响

利用具有高比表面积和介孔结构的改性铝土矿为载体,采用并流共沉淀法制备不同Fe₂O₃含量的Cu-Fe/铝土矿催化剂。以水煤气变换反应为探针反应,考察了催化剂性能。利用X射线荧光元素分析(XRF)、X射线粉末衍射(XRD)、H₂程序升温还原(H₂-TPR)、CO程序升温脱附(CO-TPD)和X射线光电子能谱(XPS)等对催化剂进行了表征。结果表明:负载的Fe₂O₃能显著提高CuO/改性铝土矿催化剂的水煤气变换活性特别是热稳定性能,且随负载的Fe₂O₃含量增加而提高,当负载量为20%时达到最佳。其原因是负载的Fe₂O₃和CuO之间发生了相互作用,形成了类似于CuFe₂O₄复合氧化物,且随负载的Fe₂O₃含量的增加而增强,这种相互作用同时促进了CuO和Fe₂O₃的还原,抑制了CuO的烧结,进而提高了催化剂的性能。     

铜物种对Cu/Fe2O3水煤气变换反应催化剂性能的影响

采用共沉淀法制备了系列铜负载量不同的Cu/Fe₂O₃水煤气变换(WGS)催化剂,并考察了铜负载量对催化剂结构和水煤气变换反应性能的影响. 结果表明,Cu/Fe₂O₃催化剂呈现出良好的水煤气反应性能,当CuO质量分数为20%时,催化剂的WGS性能最优,250 ℃时CO转化率高达97.2%,同时热稳定性也最好. 运用X射线粉末衍射(XRD)、N₂物理吸脱附和H₂程序升温还原(H₂-TPR)等手段对Cu/Fe₂O₃催化剂的物相、织构特征及还原性能进行了表征,结果表明,CuFe₂O₄物种的存在极大地改善了催化剂的还原性能和WGS反应活性. 这是由于CuFe₂O₄特殊的尖晶石结构有利于Cu微晶的稳定;同时,CuFe₂O₄在低温下即被还原为单质铜,有利于促进催化剂体系中电子的转移. 此外,通过(NH₄)₂CO₃溶液处理,研究了独立相CuO对Cu/Fe₂O₃催化剂WGS反应性能的影响,结果发现,独立相CuO的存在,有利于H原子在各组分传递,从而促进催化剂的CuFe₂O₄的还原,改善Cu/Fe₂O₃催化剂的WGS反应性能.     

水热法合成多金属氧酸盐棒状超细晶体

以SrCl₂·6H₂O、(NH₄)₆P₂Mo₁₈O₆₂·nH₂O为原料，在PEG-600/H₂O微乳体系中于80～130 ℃温度下水热反应8～12 h，从而制得一种多金属氧酸盐棒状超细晶体，组成是Sr₃P₂Mo₁₈O₆₂·nH₂O。该超细晶体具有长棒状形貌、高结晶度且分散性能较好，长度范围在10.0～20.0 μm，径度在1.0～2.0 μm。对反应体系中的PEG-600/H₂O体积比(V_PEC-600∶V_H2O)、水热温度以及(NH₄)₆P₂Mo₁₈O₆₂·nH₂O/SrCl₂·6H₂O质量比(W_POMs∶W_SrCl2·6H2O)3个影响因素进行了探讨，结果表明：V_PEC-600∶V_H2O主要对棒状超细晶体的形貌、长径比以及晶体结晶度有着重要影响，体积比在范围V_PEC-600∶V_H2O=(1.50～2.00)∶1.00有利于大长径比的棒状超细晶体的形成；水热温度则优选80～130 ℃范围，过低则不发生反应，过高则发生了多金属氧酸盐与PEG-600的氧化-还原反应；W_POMs∶W_SrCl2·6H2O基本上不影响超细晶体的形成。还初步探讨了该棒状超细晶体的形成机理。     

浸渍/共沉淀法对BaO改性单Pd催化剂净化甲醇汽油车尾气性能的影响

采用浸渍和共沉淀两种方法分别制备了BaO改性的Pd/CeO₂-ZrO₂-La₂O₃-Al₂O₃催化剂.运用N₂吸附-脱附,X射线衍射(XRD),H₂程序升温还原(H₂-TPR),NH₃程序升温脱附(NH₃-TPD),透射电子显微镜(TEM)和X射线光电子能谱(XPS)对催化剂进行表征,并考察其对甲醇,CO, C₃H₈ 和 NO的催化性能.活性测试结果表明,BaO的引入可明显改善Pd催化剂对甲醇,CO, C₃H₈和NO的催化活性,且浸渍法最佳,起燃温度(T₅₀)分别降低了43,31,45和35 ℃.XRD,H₂-TPR及XPS结果表明,浸渍法引入BaO主要通过表面改性方式,强化Pd-Ce界面间的相互作用,改善催化剂的还原性能,进而提高催化剂的低温活性;而共沉淀法则是通过结构改性方式增加CeO₂晶格缺陷,加速活性氧物种的流动,Ce³⁺浓度的增加是促使CO氧化活性显著提高的主要原因.     

Effects of metal oxides on intumescent flame‐retardant polypropylene

Variable amounts of transition metal oxides (MO), such as MnO₂, ZnO, Ni₂O₃, etc., were incorporated into blends of polypropylene (PP)/ammonium polyphosphate (APP)/dipentaerythritol (DPER) with the aim of studying and comparing their effects with main‐group MO on intumescent flame retardance (IFR). The PP/IFR/MO composites were prepared using a twin‐screw extruder, and the IFR behavior was evaluated through oxygen index and vertical burning tests. The progressive enhancement of flame retardancy has proved to be strongly associated with the interaction between APP and MO. With the aid of thermogravimetry (TG) analysis, Fourier transform infrared (FTIR) spectra and scanning electron microscopy, Ni₂O₃ has been shown to be the most effective among the aforementioned three MO. The flame‐retardant mechanism of the IFR system is also discussed in terms of catalytic charring, which relates to complex formation through the d‐orbitals of the transition metal elements. It is considered that the melt viscosity of a PP/APP/DPER blend containing Ni₂O₃ corresponds well to the gas release with increasing temperature. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation of New Magnetic Nanocatalysts Based on TiO2 and ZnO and Their Application in Improved Photocatalytic Degradation of Dye Pollutant Under Visible Light

Photocatalytic degradation of methyl orange (MO) as a model of an organic pollution was accomplished with magnetic and porous TiO₂/ZnO/Fe₃O₄/PANI and ZnO/Fe₃O₄/PANI nanocomposites under visible light irradiation. The structures of nanocomposites were characterized by various techniques including UV–Vis absorption spectroscopy, XRD, SEM, EDS, BET and TGA. Optical absorption investigations show two λ_max at 450 and 590 nm for TiO₂/ZnO/Fe₃O₄/PANI nanocomposites respectively possessing optical band gaps about 2.75 and 2.1 eV smaller than that of the neat TiO₂ and ZnO nanoparticles. Due to these optical absorptions, the nanocomposites can be considered promising candidates as visible light photocatalysts to produce more electron‐hole pairs. The degradation of MO, extremely increased using polymeric photocatalysts and decolorization in the presence of visible light achieved up to 90% in less than 20 min in comparison with the neat nanoparticles (about 10%). All these advantages promise a bright future for these composites as useful photocatalysts. The degradation efficiency of MO using stable nanocomposites was still over 70% after ten times reusing. The highest decolorizing efficiencies were achieved with 0.75 g L^?1 of catalyst and 10 mg L^?1 of MO at natural pH under visible light irradiation in less than 20 min.     

Study on combustion property and synergistic effect of intumescent flame retardant styrene butadiene rubber with metallic oxides

Effect of metallic oxides on flame retardancy and the thermal stability of styrene butadiene rubber (SBR) composites based on ammonium polyphosphate (APP) and pentaerythritol (PER) was studied by the limiting oxygen index (LOI), UL 94, the cone calorimeter tests, and thermogravimetry analysis (TGA), respectively. Scanning electron microscopy (SEM) and wide‐angle X‐ray diffraction (WAXD) were used to analyze the morphological structure and the component of the residue chars formed from the SBR composites accordingly. The addition of zirconium dioxide (ZrO₂) at a loading of 3.4 phr could improve the UL 94 test rating of the composite to V‐0. The TGA data illustrated that the metallic oxides could enhance the thermal stability of the SBR/Intumescent flame retardant additives (IFRs) composites at high temperature and increase the residue. Cone calorimeter test gave much clear evidence that the incorporation of ZrO₂ into SBR/IFRs composites resulted in the significant deduction of the heat release rate (HRR) values, and the SEM images showed that the char layers of the composites containing the metallic oxides became more compact. From the WAXD pattern, zirconium phosphate (ZrP₂O₇) may be formed by the reaction between ZrO₂ and APP. Due to the addition of ZrO₂ and the formation of ZrP₂O₇, the flame retardancy of the composite was improved. Copyright © 2009 John Wiley & Sons, Ltd.     

Synergistic effect of cocondensed nanosilica in intumescent flame‐retardant polypropylene

Amino‐functionalized nanosilica (SiO₂‐NH₂) was prepared through cocondensation method using aminopropyltriethoxysilane as comonomer to hydrolyze and cocondense with tetraethylorthosilicate. The synergistic effect of combination of ammonium polyphosphate and pentaerythritol with SiO₂‐NH₂ on the thermal and flame‐retardant properties of intumescent flame‐retardant (IFR) polypropylene (PP) has been investigated by thermogravimetric analysis (TGA), scanning electron microscopy, Raman spectra, X‐ray diffraction (XRD), limiting oxygen index (LOI), and UL 94 tests. When 1.0 wt.% SiO₂‐NH₂ was added, the LOI value of the PP/IFR composite with 25 wt.% of IFR increased from 26.6% to 31.7%, while the UL 94 rating raised from not classified to V‐0. The TGA data demonstrated that the SiO₂‐NH₂ nanoparticles increased the charred residue of the PP/IFR composites. The morphological structures and the orderliness of the charred residue proved that SiO₂‐NH₂ promoted the formation of compact intumescent charred layer, which effectively protected the underlying polymer from burning. The XRD patterns of the charred residue indicated that nanosilica reacted with APP to form SiP₂O₇ crystal structure during combustion, which was beneficial to the formation of compact charred layers. In comparison with the inorganic SiO₂‐cal nanoparticles, the amino‐functionalized nanosilica revealed much more efficient synergistic flame‐retardant effect due to the difference of surface properties.     

Effect of Fe3O4‐doped sepiolite on the flammability and thermal degradation properties of epoxy composites

As‐received sepiolite/epoxy systems and Fe₃O₄‐doped sepiolite/epoxy systems were prepared, and the contents of sepiolite and Fe₃O₄‐doped sepiolite were kept as 2 and 4 wt%, respectively. Compared with sepiolite, the effect of Fe₃O₄‐doped sepiolite on the flame retardancy, combustion properties, thermal degradation, thermal degradation kinetics and thermomechanical properties of epoxy resin was investigated systematically by limiting oxygen index (LOI), cone calorimeter (Cone), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Some interesting results had been acquired. The addition of sepiolite decreased heat release rate, total smoke production and smoke production rate, and obviously improved LOI values of epoxy composites. Compared with sepiolite, the addition of Fe₃O₄‐doped sepiolite further reduced parameters mentioned above of epoxy composites, and further enhanced LOI values and char residues after cone test. There might be a synergistic effect between sepiolite and Fe₃O₄ on flame retardant epoxy composite. TGA results indicated that the addition of sepiolite had a slight effect on the thermal degradation of epoxy composites; however, the addition of Fe₃O₄‐doped sepiolite accelerated the thermal degradation of epoxy composites. DMA results showed that the addition of both sepiolite and Fe₃O₄‐doped sepiolite increased the glass transition temperature (T_g) of epoxy composite. The results obtained in this paper supplied an effective solution for developing excellent flame retardant properties of polymeric materials. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and properties of magnetically separable Fe3O4/TiO2/Bi2O3 photocatalysts

The Fe₃O₄/TiO₂/Bi₂O₃ composites were synthesized by a sol–gel method and used as improved photocatalysts for the degradation of methyl orange (MO) under simulated sunlight at room temperature. The as-prepared Fe₃O₄/TiO₂/Bi₂O₃ composites were characterized by X-ray diffraction, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and diffuse reflectance spectroscopy (DRS). TEM analysis reveals that the composite has a core–shell structure and diameters of Fe₃O₄ core is about 200 nm. DRS results reveal that all composites showed red shift in optical absorption. TiO₂, Fe₃O₄, and Bi₂O₃ exist mainly as separate phases in the Fe₃O₄/TiO₂/Bi₂O₃ composites based on XPS analysis. The photocatalytic degradation of MO with the prepared photocatalysts was studied under simulated sunlight illumination. Photocatalytic reactivity test indicated that the removal efficiency of MO with the Fe₃O₄/TiO₂/Bi₂O₃ photocatalyst was higher than that of pure TiO₂ and Fe₃O₄/TiO₂. Recovery rate of Fe₃O₄/TiO₂/Bi₂O₃ photocatalysts achieved 80 % after five times reuse.     

Catalytic Properties of TiO<Subscript>2</Subscript>/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles in Plasma Chemical Treatment

We proposed here a new process coupling dielectric barrier discharge (DBD) plasma with magnetic photocatalytic material nanoparticles for improving yield in DBD degradation of methyl orange (MO). TiO₂ doped Fe₃O₄ (TiO₂/Fe₃O₄) was prepared by the sol-gel method and used as a new type of magnetic photocatalyst in DBD system. It was found that the introduction of TiO₂/Fe₃O₄ in DBD system could effectively make use of the energy generated in DBD process and improve hydroxyl radical contributed by the main surface Fenton reaction, photocatalytic reaction and catalytic decomposition of dissolved ozone. Most part of MO (88%) was degraded during 30 min at peak voltage of 13 kV and TiO₂/Fe₃O₄ load of 100 mg/L, with a rate constant of 0.0731 min^?1 and a degradation yield of 7.23 g/(kW h). The coupled system showed higher degradation efficiency for MO removal.     

Enhancement of a hyperbranched charring and foaming agent on flame retardancy of polyamide 6

A hyperbranched polyamine was prepared using an A₂ + B₃ approach. It acted as a hyperbranched charring and foaming agent (HCFA) in combination with ammonium polyphosphate (APP) to form a new intumescent flame retardant (IFR) system for polyamide 6 (PA6). Effect of HCFA on flame retardant and thermal degradation properties of IFR‐PA6 was investigated by limiting oxygen index (LOI), UL‐94 vertical burning, cone calorimeter, and thermogravimetric analysis (TGA) tests. The IFR system presented the most effective flame retardancy in PA6 when the weight ratio of APP to HCFA was 2:1. The LOI value of IFR‐PA6 could reach 36.5 with V‐0 rating when the IFR loading was 30 wt%. Even if the loading decreased to 25 wt%, IFR‐PA6 could still maintain V‐0 rating with an LOI value of 31. TGA curves indicated that APP would interact with both PA6 and HCFA in PA6/APP/HCFA composite under heating. The interaction between APP and HCFA improved the char formation ability of IFR system and then much more char was formed for PA6/APP/HCFA composite than for PA6/APP. Therefore, better flame retardancy was achieved. Moreover, the structure and morphology of char residue were studied by Fourier transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results indicated that compact and foaming char layer containing P‐O‐C structure was formed for PA6/APP/HCFA system during combustion. Copyright © 2010 John Wiley & Sons, Ltd.     

Flame retardancy and thermal degradation of halogen-free flame-retardant biobased polyurethane composites based on ammonium polyphosphate and aluminium hypophosphite

In this work, based on castor oil (CO), flame retardant polyurethane sealants (FRPUS) with ammonium polyphosphate (APP) and aluminum hypophosphite (AHP) were prepared. The synergistic flame retardant effects between APP and AHP on flame retardancy, thermal stability, and flame retardant mechanisms of FRPUS were investigated. It was found that when the mass ratio of APP and AHP was 5:1, the limiting oxygen index (LOI) value of FRPUS increased to 35.1%, In addition, at this ratio, the parameters from cone calorimeter testing (CCT) were reduced; these parameters include peak heat release rate (PHRR), total heat release (THR), smoke production rate (SPR) and total smoke production (TSP). The thermal decomposition behavior of the FRPUS was investigated by thermogravimetric analysis (TGA). The results showed that AHP improved the thermal stability of the PUS/APP system and increased char residue at high temperatures. Moreover, the residual carbon was investigated by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM), gas phase pyrolysis products were investigated by thermogravimetric analysis/infrared spectrometry (TG-IR) and thermogravimetric analysis/mass spectrometry (TG-MS). It was observed that the flame retardant mechanisms of the APP/AHP system was the combination of gas and condensed phase flame retardant mechanisms.