The thermal decomposition of ammonium paratungstate

The thermal decomposition of monoclinic, orthorhombic and freeze-dried ammonium paratungstate (APT) has been studied over the temperature range 100 to 500°C using thermogravimetry, evolved gas analysis. X-ray diffraction and electron optical techniques. The particle morphologies of the original APT have been related to the morphologies of the products of decomposition. A mechanism of decomposition which postulates the formation and subsequent decomposition of amorphous ammonium metatungstate is proposed and substantiated by X-ray diffraction analysis and evolved gas analysis.     

Influence of Al2O3 support on the thermal decomposition of ammonium metavanadate

The thermal decomposition of ammonium metavanadate (AMV) supported on aluminium oxide was investigated using differential thermal analysis, thermogravimetry, infrared and X-ray diffraction techniques. The results obtained revealed that the decomposition of AMV supported on alumina proceeded in three decomposition stages. Alumina was found to enhance only the decomposition of the intermediate ammonium hexavanadate to produce V₂O₅. In addition, the values of activation energies of the various decomposition stages were accompanied by a significant decrease on decreasing the concentration of AMV. The infrared spectra indicated that the band corresponds to the surface site V=O strongly affected by the presence of Al₂O₃. Finally, an interaction between Al₂O₃ and V₂O₅ occurred at 660 °C giving well-crystallized AlVO₄.     

Synthesis, characterization and catalytic activity of CdO nanocrystals

In this paper, we report the synthesis of nanocrystalline cadmium oxide (CdO) and its characterization by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Its catalytic activity was investigated on the thermal decomposition of 1,2,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), ammonium perchlorate (AP), hydroxyl terminated polybutadiene (HTPB) and composite solid propellants (CSPs) using thermogravimetric analysis (TG), simultaneous thermogravimerty and differential scanning calorimetry (TG-DSC) and ignition delay measurements. Kinetics of thermal decomposition of AP + CdO has also been investigated using model free (isoconversional) and model-fitting approaches which have been applied to data for isothermal TG decomposition. All these studies show enhancement in the rate of decomposition of AP, HTPB and CSPs but no effect on HMX. The burning rate of CSPs has also been found to be increased with CdO nanocrystals.     

Preparation and thermal decomposition of hexa-ammonium tetraphosphate dihydrate(NH4)6P4O13·2H2O

Hexa-ammonium tetraphosphate dihydrate, (NH4)6P4O13·2H2O (HATP), was prepared by the hydrolysis of sodium cyclo-tetraphosphate with sodium hydroxide solution, followed by ion-exchange with ammonium. Thermal decomposition in static air was first carried out dynamically, at a heating rate of 5 K min-1 as used in thermal analysis (thermogravimetric-differential thermal analysis), and also isothermally. To examine the effect of humidity on the thermal decomposition, HATP was heated isothermally in streams of dry and humid air. The products were characterized by X-ray diffraction analysis and high-performance liquid chromatography–flow injection analysis. At 100°C, HATP was decomposed to mono- and triphosphates and to 2 mol diphosphate, and this was accelerated by humidity. Further degradation of the triphosphate to mono- and diphosphates took place slowly. The 2 mol diphosphate also decomposed slowly to 4 mol monophosphate. At temperatures above 150°C, the form I of ammonium polyphosphate (I-APP) was produced. I-APP was further hydrolysed by humidity to shorter-chain phosphates, such as mono-, di- and triphosphates. This revised version was published online in November 2006 with corrections to the Cover Date.     

粘胶活性碳纤维预浸剂的热分解作用及效能评选

用热失重分析方法研究了磷酸铵盐、磷酸、硫酸铵对粘胶纤维的热分解促进作用.空气的存在有利于磷酸氢二铵对粘胶的分解反应,但对其余几种的影响不大.本文提出用峰高/半高宽之比表征热分解峰的形态.该值越低,即热分解峰越平坦,表明反应越缓和,则越有利于提高粘胶纤维的碳化活化得率.实验结果证实了这一观点.磷酸氢二铵/粘胶的热分解峰最平坦,作用效果最好;磷酸二氢铵和磷酸相当,磷酸铵次之,硫酸铵作用时比表面积很低.未预浸处理的粘胶热分解最激烈,产品得率和比表面积也最低.     

Cu/Fe hydrotalcite derived mixed oxides as new catalyst for thermal decomposition of ammonium perchlorate

Cu/Fe mixed oxides (Cu/Fe-MOs) were prepared by calcination of Cu/Fe hydrotalcite (Cu/Fe-HT) precursors. They were used as new catalyst for thermal decomposition of ammonium perchlorate (AP) and their catalytic activity was studied by thermal gravimetric and differential thermal analysis. With the addition of 4 wt.% Cu/Fe-MOs, thermal decomposition of AP was accelerated by 104 °C. Higher catalyst addition favors further decomposition of AP. The catalytic activity order is: Cu/Fe-MOs-500 > Cu/Fe-MOs-800 > CuO·Fe₂O₃. The proposed catalytic mechanism is the presence of O₂⁻ on the surface of Cu/Fe-MOs which can simplify thermal decomposition of AP.     

纳米NiFe2O4的制备及其对高氯酸铵的热分解催化性能

采用水热法制备出纯相的NiFe2O4纳米颗粒。利用X射线衍射仪(XRD),透射电镜(TEM)和傅里叶变换红外光谱仪(FT-IR)对样品进行了表征,并运用热分析法和质谱仪研究了样品对高氯酸铵的热分解催化性能。结果表明,制备的NiFe2O4纳米颗粒粒径约为5.0nm,对高氯酸铵的热分解具有很高的催化活性。当NiFe2O4纳米颗粒的添加量达到10%时,对高氯酸铵的热分解催化性能最好,可使高氯酸铵的高温分解温度降低89.8℃。     

添加AP的乳化炸药基质的热分解研究

利用C80微热量热仪研究了分析纯硝酸铵、典型配方的乳化炸药基质以及含有高氯酸铵(AP)的乳化炸药基质的热分解过程。通过C80热流曲线所得出的结果,采用单一非等温曲线法,求出了相应的动力学参数。结果表明:AP不但可以消弱AN晶变的热效应,而且具有稳定AN晶型的作用;AP对乳化炸药基质的热分解具有一定的催化作用,但催化作用不显著。     

添加AP的乳化炸药基质的热分解研究

利用C80微热量热仪研究了分析纯硝酸铵、典型配方的乳化炸药基质以及含有高氯酸铵(AP)的乳化炸药基质的热分解过程。通过C80热流曲线所得出的结果,采用单一非等温曲线法,求出了相应的动力学参数。结果表明:AP不但可以消弱AN晶变的热效应,而且具有稳定AN晶型的作用;AP对乳化炸药基质的热分解具有一定的催化作用,但催化作用不显著。     

Nanoferrites: Catalyst for Thermal Decomposition of Ammonium Per Chlorate

Nanoferrite nanoparticles were synthesized by chemical coprecipitation method. The ferrite nanoparticles such as Zn, Mn, Ni, Co, and Cu were prepared. All nanoparticles were characterized by x-ray diffraction and scanning electron microscopy. The average particle of Zn, Mn, Co, Ni and Cu ferrite are 6.8, 2.7, 5.2, 1.1 and 3.9 nm respectively. The effect of ferrite nanoparticles on the thermal decomposition of ammonium per chlorate was studied using thermogravimetic analysis, differential scanning calorimetric (DSC) studies. Activation energy of high temperature decomposition of different alloy nanoparticles was calculated using DSC by Kissinger equation. The catalytic activity of nanoferrites is much sensitive to oxygen and may be effective to improve the thermal decomposition AP-based propellants.     

阻燃协效剂与膨胀型阻燃剂在木粉/聚丙烯复合材料中的阻燃协效性

采用膨胀型阻燃剂（IFR）分别与蒙脱土（MMT）、硼酸锌（ZB）、MnO2阻燃协效剂复配制备了阻燃型红松木粉/聚丙烯复合材料。借助TG、DTG、DSC热分析技术深入探讨了IFR与阻燃协效剂间的协效性;并利用FTIR、SEM对协效性进行了验证。结果表明：三种阻燃协效剂与IFR间都存在一定的协效性;MMT的加入降低了热分解...     

Synthesis and characterization of KNd2Ti3O9.5 nanocrystal and its catalytic effect on decomposition of ammonium perchlorate

A novel kind of perovskite type oxide KNd₂Ti₃O_9.5 nanocrystals with an average size of 12 nm were successfully fabricated by a stearic acid sol–gel method (SAM) using Ti(OBu)₄, KOH, Nd₂O₃ and stearic acid as the raw materials. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the products. The catalytic effect of the KNd₂Ti₃O_9.5 nanoparticles on thermal decomposition of ammonium perchlorate (AP) was investigated by differential thermal analysis (DTA) and thermal gravimetry (TG) experiments. Results indicated that the obtained KNd₂Ti₃O_9.5 nanocrystals took on cubic structure and presented both good dispersibility and uniform crystallite size. Also, they have an intense catalytic effect on the thermal decomposition of AP. Adding 2% of KNd₂Ti₃O_9.5 nanoparticles to AP can obviously decrease the thermal decomposition temperature of AP by 50 °C, increase the heat of decomposition from 590 J g⁻¹ to 1659 J g⁻¹ and obviously quicken the decomposition reaction rate.     

Nano-metal oxide: potential catalyst on thermal decomposition of ammonium perchlorate

In this review, an attempt to collect the summarised data of literature on catalytic effect of nano-oxides, such as mono oxides, mixed oxide, binary and ternary ferrites and rare earth metal oxides on the thermal decomposition of ammonium perchlorate (AP) is made. Influence of size effect of oxides on thermal decomposition of AP and comparison of bulk and nanosized oxides is also discussed here. Several experimental results revealed that due to small size and large surface area nanosized metal oxides are more potential catalysts on thermal decomposition of AP compared to their bulk size oxides.     

Fe2O3纳米粒子的醋酸改性对其催化高氯酸铵热分解的影响

利用表面改性法对Fe2O3纳米粒子进行醋酸改性,用TEM和纳米粒度测试仪对Fe2O3纳米粒子进行了形貌和粒度表征,用FTIR和XPS对改性后的Fe2O3纳米粒子进行了结构表征,用DTA研究了醋酸改性处理对Fe2O3纳米粒子的高氯酸铵(AP)热分解催化性能的影响.结果表明,用凝胶-溶胶法制备了平均粒径为40nm,窄粒度分布的Fe2O3纳米粒子,醋酸改性处理改善了Fe2O3纳米粒子的分散性.FTIR和XPS结果表明,Fe2O3纳米粒子与醋酸分子发生了化学键合.DTA结果表明,Fe2O3纳米粒子的醋酸改性能提高Fe2O3纳米粒子的AP热分解催化性能;随着Fe2O3纳米粒子含量的增加,醋酸改性的效果越明显.     

二钼酸铵的热分解行为研究

采用DTA、TG和XRD等检测手段研究了二钼酸铵的热分解行为,结果表明：二钼酸铵的热分解经历了两个阶段,所对应的反应温度分别在180℃左右及300℃左右,二钼酸铵热分解反应第一步为：4（NH4）2MO2O7→180℃ （NH4）4MO8O26＋4NH3↑＋2H2O↑;第二步为（NH4）4MO8O26→300℃ 8MoO3＋4NH3↑＋2H2O↑。     

Use of microwave radiation for preparing uranium oxides from its compounds

The formation of uranium oxides by thermal decomposition of uranyl diaquadihydroxylaminate monohydrate, ammonium diuranate, ammonium tricarbonatouranylate, and uranium peroxide under the action of microwave (MW) radiation was studied. Uranium dioxide is formed by decomposition of these compounds in a reducing atmosphere at the MW radiation power of 600 W and treatment time of 5–10 min. In air, under the same conditions, U₃O₈ is formed. Under the action of MW radiation, substandard ceramic pellets of UO₂ fuel can be readily converted in air to powdered U₃O₈. The use of MW radiation for thermal decomposition of uranium compounds allows the power and time consumption to be considerably reduced relative to the process with electrical resistance furnaces. A quick method for gravimetric testing of the composition of uranium oxides (UO₂ or U₃O₈) using MW radiation was suggested.     

Transition metal oxide nanoparticles: Potential nano-modifier for rocket propellants

ABSTRACT

TiO₂, ZnO₂, and CrO₂ nanoparticles were prepared by novel quick precipitation method, where transition metal oxides were used as catalyst. All nanoparticles were characterized by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The average particle size for TiO₂, ZnO₂, and CrO₂ was 44.8, 13.4, and 77.6 nm, respectively. Catalytic properties of these nanomaterials were studied using ammonium perchlorate (AP)/hydroxy-terminated polybutadiene (HTPB) propellant by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). Both experimental results reveal that there is an increase in the thermal decomposition of propellants in the presence of transition metal oxide nanoparticles. Activation energy of high-temperature decomposition (HTD) of propellant with transition metal oxide nanoparticles was calculated by Kissinger equation. Burning rates of propellants were also calculated.     

Thermal destruction of polymer-salt compositions containingd-metals in the form of oxygen-bearing anions

The behavior of polymer-salt compositions consisting of water-soluble nonionogenic polymers and salts containingd-metal-oxygen anions was studied in the range 20-700°C by thermal analysis, conductometry, optical microscopy, x-ray diffraction, and dilatometry. The salts used were ammonium heptamolybdate, ammonium B-paratungstate, and ammonium metavanActate and the polymers were poly(vinyl alcohol), polyvinylpyrrolidone, and methyl cellulose. The films prepared by drying the precursor compositions were found to retain, during heating, the polymer-salt molecular complexes formed at room temperature. The mechanism of the thermal destruction of the salts in the polymer-salt films was shown to differ from that in pure salts because, in the films, mutual stabilization of the polymer and salt took place. In the polymer-salt compositions, oxides were formed directly from amorphous precursors, without formation of intermediates, characteristic of the decomposition of pure salts. The oxides thus prepared consisted of fine particles and exhibited photochromic effect due to partial reduction of metal ions.     

非爆炸且不可还原农用硝酸铵的热稳定性评估

绍了一种测试含能材料热稳定性的新方法——加速度量热仪，并用此法研究了硝酸铵和非爆炸且不可还原农用硝酸铵的热分解过程，得到了绝热分解温度与压力随时间的变化、自加热速率与分解压力随温度的变化曲线，计算了分解动力学参数表观活化能和指前因子，讨论了放热反应系统的热惰性因子对测试结果的影响，表明非爆炸且不可还原农用硝酸铵具有良好的热稳定性、安全性及其热稳定性的提高是爆炸特性得以消除的原因。     

离子液体/磷酸锆抗菌材料的制备及耐热性研究

以α-磷酸锆(分子式: Zr(HPO₄)₂·H₂O, 以下简称α-ZrP)为载体, 三种季铵型离子液体: 溴化十六烷基三甲基咪唑(C₁₆MIMBr)、氯化十六烷基二甲基苄基铵(C₁₆HDBACCl)和氯化十六烷基三甲基铵(C₁₆CTACCl)被引入α-ZrP层间, 制备得到三种离子液体/α-磷酸锆(IL-ZrP)复合抗菌材料. 通过X射线衍射法(XRD)、红外光谱分析(FTIR)、热重-红外联用分析(TG-FTIR)对材料的结构、组成和热稳定性进行表征. XRD结果表明: 相对于α-ZrP, 三种复合抗菌材料的层间距明显增大, 这证明离子液体已经成功地嵌入到α-ZrP的层间. TG-FTIR实验显示三种离子液体在复合抗菌材料中分别占53.11wt%、50.65wt%和51.25wt%. 三种纯离子液体的热分解起始温度分别为174℃、198℃和219℃, 而离子液体/α-ZrP(IL-ZrP)复合抗菌材料中所含的离子液体的热分解起始温度为219℃、225℃和263℃, 这表明α-ZrP能有效提高离子液体的耐热性. 抗菌性能检测结果表明: 在三种复合材料中, C₁₆MIMBr-ZrP具有较好的抗菌效果(在24 h内, 其对大肠杆菌、金色葡萄球菌的最小抑菌浓度均小于19 mg/L).