聚乙烯/石墨层间化合物热降解过程的TG-FTIR研究

将含磷化合物插层石墨层间化合物(GIC)用于聚乙烯(PE)的阻燃,采用氧指数(LOI)方法评价了PE/GIC的阻燃性能,并采用热分析-红外光谱联用技术(TG-FTIR)研究了PE/GIC的热降解过程,探讨了GIC的阻燃机理。研究表明,不同含磷化合物插层GIC阻燃聚乙烯的氧指数有显著差别,其中以多聚磷酸铵-GIC的阻燃效果较好,氧指数较高。TG-FTIR研究结果表明,GIC并未显著影响PE的热降解方式,但由于GIC体积膨胀所发生的氧化还原反应导致部分PE热降解提前并发生热氧化降解,促进了后期成炭的石墨化过程。     

石墨氧化过程的XRD/XPS研究

石墨用强氧化剂如硝酸、高氯酸、氯酸钾或高锰酸钾等处理后,在石墨层间形成一种没有化学计量的层间化合物,通常叫做氧化石墨,又称石墨酸犤1犦。氧化石墨的研究历史可追溯到1855年犤2犦,期间,有关氧化石墨的制备及表征的报导获得了广泛的重视。就目前的研究现状而言,普遍认为化学法制备的氧化石墨中存在羟基、环氧官能团和双键结构犤3犦,这一结果已经得到广泛的证实,如FTIR犤4犦结果表明氧化石墨中含有C-OH、-OH、C=O等基团,13CNMR犤5犦也检测到与醚或羟基相联的碳原子,并发现sp2杂化的碳原子,元素分析的结果表明犤6犦,氧化石墨中的C/…     

磷酸铵与多聚磷酸铵插层可膨胀石墨的制备

Expandable graphite intercalated by ammonium phosphate (AP) or ammonium polyphosphate (APP) was prepared by direct intercalation and two-step method, respectively. The products from two-step method show higher expansion volume, more weight increase and more weight loss after expansion, suggesting that the two-step method is a favorable method for preparation of APP intercalated EG. XRD provides convincing evidence for successful formation of APP-EG by showing strong diffraction peak at much lower 2θ angle. Scanning electron microscopy (SEM) with energy dispersive X-ray Spectroscopy (EDS) gives more evidence for intercalation of APP in the graphite layers.     

Structures and magnetic properties of Fe and Ni monoatomic chains encapsulated by an Au nanotube

Structures and magnetic properties of transition metal(TM) Fe or Ni monoatomic chains(MACs) encapsulated by a Au(5,5) nanotube(Fe@Au and Ni@Au) are investigated using the density functional theory(DFT).The calculated results show that both Fe@Au and Ni@Au prefer to adopt ferromagnetic(FM) orders as ground states.In particular,the Fe@Au keeps the magnetic properties of free-standing Fe MAC,indicating that this system may be viewed as a new candidate in electromagnetic devices.     

Microstructures and Mechanical Properties of AlCrFeNiMo_(0.5)Ti_x High Entropy Alloys

Effects of Ti addition on the microstructures and mechanical properties of AlCrFeNiMo_(0.5) Ti_x(X = 0, 0.25, 0.4,0.5, 0.6, 0.75) high entropy alloys(HEAs) are investigated. All these HEAs of various Ti contents possess dual BCC structures, indicating that Ti addition does not induce the formation of any new phase in these alloys. As Ti addition X varies from 0 to 0.75, the Vickers hardness(HV) of the alloy system increases from 623.7 HV to766.2 HV, whereas the compressive yield stress firstly increases and then decreases with increasing X above 0.5.Meanwhile, the compressive ductility of the alloy system decreases with Ti addition. The AlCrFeNiMo_(0.5)Ti_(0.6) and AlCrFeNiMo_(0.5)Ti_(0.75) HEAs become brittle and fracture with very limited plasticity. In the AlCrFeNiMo_(0.5)Ti_x HEAs, the AlCrFeNiMo_(0.5) HEA possesses the highest compressive fracture strength of 4027 MPa and the largest compressive plastic strain of 27.9%, while the AlCrFeNiMo_(0.5)Ti_(0.5) HEA has the highest compressive yield strength of 2229 MPa and a compressive plastic strain of 10.1%. The combination of high strength and large plasticity of the AlCrFeNiMo_(0.5) Ti_x(X = 0, 0.25, 0.4, 0.5) HEAs demonstrates that this alloy system is very promising for engineering applications.     

可控构建环形的壳聚糖/Fe3O4复合凝胶研究

基于液滴冲击液面所形成环形涡流构建环形的壳聚糖/Fe3O4复合凝胶,研究环形凝胶的可控制备规律,并表征了壳聚糖/Fe3O4复合凝胶的物相组成、形貌及含水率.通过控制NaNO2的用量及降解时间,实现不同分子量壳聚糖制备.XRD结果表明实现了壳聚糖/Fe3O4复合凝胶的制备.环形的壳聚糖/Fe3O4复合凝胶的最佳制备参数为液滴下落高度为9-15 cm,壳聚糖分子量范围为3.4×105-7.1 ×104.环形涡流的存在及冷冻过程引起壳聚糖/Fe3O4复合凝胶外部孔径大于复合凝胶内部孔径,孔大小约为10 ～ 50 μ,m.壳聚糖/Fe3 O4复合凝胶的含水率约为94;.     

氧化石墨的制备及其有机化处理

Graphite oxide(GO) was successfully prepared by using expandable graphite， which is a new starting material instead of the normally adopted natural graphite. XRD and XPS data indicated that， in the same reaction condition due to the application of expandable graphite， the extent of oxidation for the product， GO， was considerably en-hanced and the period required for oxidation was greatly shortened. In addition， the prepared GO was modified by surfactant， that is the new sample， S-GO， was obtained. As a consequence the extended interlayer space has proved itself to be successfully intercalated by the surfactant.