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1.
利用9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)和马来酸酐(MA)对淀粉进行改性得到磷化淀粉(DOPOMASt),通过红外光谱(FTIR)、核磁共振谱(1H-NMR)和X射线光电子能谱(XPS)确定其结构.利用DOPOMASt作为碳源,与聚磷酸铵(APP)复配后通过熔融共混制备了阻燃聚乳酸(PLA)复合材料.采用垂直燃烧(UL-94)、极限氧指数(LOI)、热重分析(TGA)研究DOPOMASt对PLA的阻燃性能和热性能的影响.利用扫描电子显微镜(SEM)观察阻燃剂在PLA中的分散和燃烧后残炭的微观形貌,同时采用TG-IR联用技术对PLA复合材料热降解气相产物进行分析.结果表明,DOPOMASt促进APP在PLA中分散均匀,当DOPOMASt和APP质量比为1∶1,总质量为10%时,LOI达到26.0%且通过UL-94 V0测试.DOPOMASt与APP协效阻燃促进PLA树脂成碳,形成更加致密的炭层并减少可燃气体的产生,赋予PLA良好的阻燃性能.  相似文献   
2.
采用熔融共混技术,将聚磷酸铵(APP)和氢氧化铝(ATH)引入到聚氨酯弹性体(TPU)中,制备了一系列热塑性聚氨酯/聚磷酸铵/氢氧化铝(TPU/APP/ATH)复合材料。采用傅里叶红外光谱(FTIR)、X-射线光电子能谱(XPS)、扫描电镜(SEM)、激光拉曼光谱研究了TPU和阻燃TPU(FR-TPU)复合材料燃烧后炭渣的微观形貌、表面结构、元素组成、键合状态和石墨化程度,结合阻燃性能测试,揭示APP和ATH的协同阻燃机制。SEM分析表明相较于APP与ATH单独使用,TPU/APP/ATH炭层的空洞结构更少,炭渣的致密性更高。XPS分析表明FR-TPU的炭渣中C元素含量相比于纯TPU有所降低,O元素的含量有所上升,其中TPU/APP10/ATH10的C元素含量从88.2%降至69.24%,O元素的含量从8.07%升至17.78%,P和Al元素含量相较于单独添加分别从11.74%和16.36%下降至3.91%和3.31%。在此基础上,通过对C元素的分峰拟合发现TPU炭渣中C—C/C—H,C—O/C—N和CO/CN含量分别为61.05%,35.65%和3.30%;TPU/APP10/ATH10炭渣中三种结构含量分别为45.38%,45.00%和9.63%,说明ATH和APP复配使用有利于C元素形成酯、醚、羰基、羧酸(盐)、酯基等结构。通过对O元素的分峰拟合发现,TPU炭渣中O2/H2O,—O—,O三种结构含量分别为28.75%,44.36%和26.89%;TPU/APP10/ATH10炭渣中O2/H2O,—O—,O三种结构含量分别为44.33%,32.78%和22.89%,说明APP和ATH的加入有利于炭渣中O元素形成O2/H2O结构。通过对N元素的分峰拟合发现,TPU炭渣中—NH—,N结构的N元素含量分别为40.93%和59.07%;TPU/APP10/ATH10中—NH—,N结构的N元素含量分别47.17%和52.83%,说明ATH与APP复配使用促进了—NH—结构的形成。拉曼测试表明,相比于单独使用,APP和ATH复配使用,炭层的石墨化程度更好,致密性更高。以上分析结合阻燃测试可以得出TPU/APP/ATH复合材料阻燃机制:ATH受热分解生成氧化铝,吸收热量并释放大量水蒸气,有效促进APP降解,生成不燃性的氨气和聚磷酸,氨气和水蒸气稀释可燃性气体的浓度。随着温度继续升高,氧化铝可继续与聚磷酸反应生成偏磷酸铝[Al(PO3)3],同步催化聚氨酯基体成炭,形成高度石墨化炭层,石墨化炭层与偏磷酸铝一起覆盖在基体表面,有效抑制燃烧区域物质以及能量的输运,从而达到阻燃目的。  相似文献   
3.
This review examines the most recent electrochemical developments for nitrate, nitrite and ammonium detection for on-site water monitoring. There remains a high demand for effective field-based detection of the dissolved inorganic nitrogen (DIN) analytes to aid in mitigating nitrogen loading. Electrochemical approaches show increasing potential to fill this role as advancements in nanotechnology continually improve analytical performance and on-site applicability. However, translating these improvements into the field still faces the resonating challenges of reaching analytical proficiency (selectivity, sensitivity, robustness, stability), practical end-user functionality, minimal matrix interferences and cost effectiveness. Herein, we elaborate on these challenges via a critical evaluation of current studies and examine how realistic the prospects of on-site nitrate, nitrite and ammonium are. We also present recommendations in addressing these gaps to conclude the review.  相似文献   
4.
采用胶晶模板法制备出具有三维多孔结构的纳米CoFe_2O_4。利用X射线衍射仪(XRD)、傅里叶变换红外(FT-IR)光谱仪、扫描电镜(SEM)、透射电镜(TEM)和N_2吸附-脱附对样品的晶型和形貌结构等进行表征,采用差示扫描量热法(DSC)对比研究多孔纳米CoFe_2O_4和球形纳米CoFe_2O_4对高氯酸铵(AP)的热分解性能的影响,并考察这两种催化剂对AP催化热分解的动力学参数。结果显示,制备出的多孔纳米CoFe_2O_4样品具有典型的尖晶石结构,孔径约200 nm;比表面积明显高于40 nm球形CoFe_2O_4,达到55.646 m~2?g~(-1)。DSC测试结果表明:多孔纳米CoFe_2O_4的加入促进了AP的热分解,最高使AP的高温分解峰温降低91.46°C,能量释放最高达1120.88 J?g~(-1),是纯AP分解放热量的2.3倍;多孔纳米CoFe_2O_4具有较高的比表面积,能提高催化反应的接触面积,使AP的高温分解峰温度更低,反应活化能较小,从而表现出比球形纳米CoFe_2O_4更高的催化活性。此外,对多孔纳米CoFe_2O_4催化AP的热分解机理进行初步探索,纳米多孔催化剂对气态中间产物的作用促进了AP的热分解。  相似文献   
5.
Effects of ammonium surfactants with different hydrocarbon chain lengths (C8, C12, C16, and C18) on the colloidal forces between bitumen and silica were studied by atomic force microscopy. The results showed that the chain length of the ammonium surfactants had a significant impact on both the long-range interaction and adhesion forces. With the addition of surfactants with relative short chains of C8 and C12 in the solutions, the long-range repulsive force decreased or even became strong attractive force, while it became repulsive again in solutions of surfactants with long chains of C16 and C18. It was further observed that addition of Ca2+ in various surfactants solutions would either depress or enhance the colloidal interactions based on the surfactant chain lengths. It was believed that variation of the interaction behaviors resulted from the mono-layer or bilayer adsorption of various surfactant molecules on the negatively charged surfaces of bitumen and silica, which affected the surface wettability and the surface charge characteristics and then greatly changed the colloidal interactions. The findings indicated that, to have a high bitumen recovery and good froth quality, the surfactant type and concentration of the di-valent metal ions in the oil sand processing slurry must be well considered.  相似文献   
6.
A sequential modification by sodium hydroxide (NaOH) and ammonium hexafluorosilicate ((NH4)2SiF6) solution was used for preparing MTP (methanol to propylene reaction) catalyst for the first time. The parent and modified samples were characterized by diverse techniques including powder X-ray diffraction (XRD), X-ray fluorescence (XRF) spectroscopy, N2 adsorption-desorption, transmission electron microscopy (TEM), and NH3 temperature-programmed desorption (NH3-TPD). The effect of modification on the physicochemical properties, such as framework, chemical composition, texture, and acidity, were investigated in detail. The results showed that the mesopore volume of the zeolite catalyst increased significantly following sequential NaOH and (NH4)2SiF6 modification. The acidity was also modulated effectively. The composite modification method successfully overcame the disadvantages associated with individual simple alkali and (NH4)2SiF6 treatments. For instance, using a simple alkali treatment would destroy the framework of the zeolite easily, whereas using a simple (NH4)2SiF6 treatment would only modify the external surface of the zeolite owing to the limited diffusion of the ammonium hexafluorosilicate molecule. When used in MTP reaction, the induction period of the composite modified sample was greatly shortened, and the initial selectivity for propylene increased to 43% under the following operating conditions: T=470 ℃, p=0.1 MPa (pMeOH=50 kPa), and weight hourly space velocity (WHSV)=2 h-1. Moreover, the composite modified zeolite catalyst exhibited significantly improved stability, and the catalytic lifespan was triple that of the parent sample.  相似文献   
7.
Inorganic-organic or hybrid perovskite materials, which are the complementary counterparts of pure inorganic perovskites, can provide many new opportunities in the researches of phase transitions, critical phenomena, and relevant properties, as they combine the characteristics of inorganic and organic components. Therefore, the hybrid perovskites of ammonium metal formate framework are very promising, and their properties have been found to be strongly dependent on the characteristics of the constituent metal ions and/or ammonium ions. Herein, we used solid solution strategies, borrowed from solid state chemistry, to investigate the anisotropic diluted magnetic hybrid perovskite system of [CH3NH3][CoxZn1-x(HCOO)3], wherein the B-sites are occupied by the mixed metal ions of Co2+ and Zn2+. The solid solution compounds of this series in the range x = 0–1 (or the molar percent Co% = 0–100%) were successfully prepared using conventional solution chemistry methods. The resulting compounds were demonstrated to be iso-structural by using both single-crystal and powder X-ray diffraction analyses. The solid solution crystals belong to the orthorhombic space group Pnma, with the cell parameters being a = 8.3015(2)–8.3207(3) Å, b = 11.6574(4)–11.6811(5) Å, c = 8.1315(3)–8.1427(4) Å, and V = 787.89(5)–790.98(7) Å3. The perovskite structure consists of a simple cubic anionic metal-formate framework and CH3NH3+ cations which are located in the framework cavities, with N―H···O hydrogen bonds formed between the framework and the cation. The members of this series showed negligible changes (< 0.4%) in their respective lattice and structural parameters. Thus, the prepared solid solution compounds constitute good molecule-based examples for the study of magnetic dilution under almost the same structural parameters and molecular geometries. Upon dilution, the magnetization per mole of Co at low temperatures and low fields was suppressed by the magnetic anisotropy of Co2+ and gradual destruction of the large spin canting between coupled Co2+ ions, in contrast to the magnetization enhancement observed in the isotropic diluted system of [CH3NH3][MnxZn1-x(HCOO)3] with the same perovskite structure. The percolation limit was estimated as (Co%)P = 27(1)% (or xP = 0.27(1)) from the magnetic data, which was slightly lower than that predicted by the percolation theory for a simple cubic lattice (31%); this trend was due to the strong magnetic anisotropy of the present system. In addition, rare incommensurate phase transitions were primarily detected below ~120 K for the pure Co and Zn members, which may also affect the magnetic properties of the materials.  相似文献   
8.
描述了一个以立体化学中非对映选择性为知识重点,以无水无氧操作为操作重点的微量不对称合成实验。(R)-N-叔丁基亚磺酰亚胺在无水无氧环境中,经过锌参与的烯丙基化,在不同的溶剂、添加剂条件下以不同的选择性得到了一对非对映异构体,以较高的产率得到终产物。烷基化反应产物的非对映体比率(dr)通过1H与19F NMR以及手性HPLC确定。总体来说,这一实验所用试剂易得,反应条件温和,速率快,产率高;学生在学习无水无氧操作(Schlenk技术)的同时,还能够熟悉立体化学的基本概念,了解如何通过调节反应溶剂和添加剂实现立体化学结果的逆转,并掌握使用手性HPLC和NMR确定光学活性物质的dr值的方法。  相似文献   
9.
建立一种酸碱电位滴定法直接测定硫酸铵中氮含量的方法。样品溶解后,可直接用氢氧化钠标准滴定溶液进行滴定。为了保证检测的准确度,分别使用硫酸铵高纯试剂和邻苯二甲酸氢钾基准试剂对氢氧化钠标准滴定溶液进行标定,并对标定结果进行比较,两种方法基本无差异。同时,通过适量硫酸的加入避免了样品中游离硫酸对检测结果的影响。该方法检测速度快、检测精度高、绿色环保、易于控制,非常适合于硫酸铵中氮含量的检测。将本方法与蒸馏后滴定法(仲裁法)检测结果进行比较,两种方法无显著性差异。采用本方法测得氮含量的加标回收率为99.9 %-100.3 %,相对标准偏差(RSD,n=5)为0.03 %-0.05 %。分别使用实验方法和蒸馏后滴定法测定不同样品的氮含量,结果相吻合。  相似文献   
10.
(2R,3aR,8bR)- and (2S,3aS,8bS)-2-Methyl indoline dye tetrabutylammonium carboxylates exhibited the highest conversion efficiency among four regio and stereo isomers. These indoline dyes also showed higher conversion efficiency than DN350.  相似文献   
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