Structure Transition of Nanocrystalline Fe_2O_3

A structure transition of Fe2O3 nanocrystal was studied by using DTA and TG thermal analysis and X-ray diffraction method. We found that size increase of the nanocrystals is larger after the structure transition than that before the transition. It means that the structure transition is beneficial on growth of nanocrystals     

辐射合成水凝胶的结构表征

本文用ＩＲ、ＵＶ光谱、光射线衍射仪及ＤＴＡ与ＴＧ等分析手段，对辐射合成水凝胶进行了结构表征，并探讨了这些结构因素对水凝胶溶胀性能的影响。     

Preparation and characterization of sol-gel derived ZnTiO3 nanocrystals

Nanometer scale cubic ZnTiO₃ has been synthesized by sol-gel method at a lower temperature (600 °C). X-ray diffraction (XRD) analysis shows that the average crystalline size of the sample is ∼8-10 nm. The cubic to hexagonal phase transition of ZnTiO₃ is clearly observed from the XRD patterns of the sample. The thermal behavior of the sample was characterized by the thermogravimetric/differenthermal analysis (TG/DTA), XRD patterns, and the infrared spectra (IR). Transmission electron microscope (TEM) observations of the sample reveal a high microstructural uniformity.     

Synthesis, characterization, high temperature phase transition and electrical properties of solid solution AgScMo2O8

AgScMo₂O₈ was synthesized by wet-chemistry method. The samples were characterized by differential thermal analysis/thermogravimetry, differential scanning calorimetry (DTA/TG, DSC), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The novel structure of the sample is different to the other oxide AgLnMo₂O₈ (Ln = lanthanide). The XRD and DTA/TG, DSC results showed that the formation temperature of AgScMo₂O₈ was found to be as low as 450°C, and AgScMo₂O₈ crystallized in a monoclinic-type structure at room temperature. With increasing of the temperature two phase transition processes (monoclinic to hextetrahedral and tetragonal) appeared. The electrical property of the samples was also investigated by using A.C impedance spectroscopy. It showed that an abrupt increase of electrical conductivity was found around 500°C, which attributes to phase transition. The facts indicted that this kind of material shows a potential application in intermediate-temperature solid oxide fuel cells (SOFCs).     

Correlation of phase transition with the change in TL characteristics in CaSO4:Dy phosphor--effect of thermal treatment

The study is aimed at optimising the glow curve structure of CaSO4:Dy phosphor for dosimetric purpose and also to understand the observed changes owing to thermal treatment in the thermoluminescence (TL) sensitivity and glow curve structure. The reversible changes in the intensities of the lower temperature satellite peak and the main dosimetric glow peak with temperature of thermal treatment in the temperature range 400-700 degrees C indicates the interconversion of defect complexes responsible for the glow peaks in CaSO4:Dy. Phosphor samples subjected to thermal treatment in temperature range beyond 800 degrees C, showed irreversible changes in the intensities of the lower temperature and dosimetric peaks. The changes in TL characteristics of the phosphor for thermal treatments >800 degrees C are attributed to the partial phase transition in the phosphor as confirmed by the XRD and TG/DTA analysis of the phosphor.     

Effect of Ni on the structural, optical, thermal and dielectric properties of ADP single crystals

The effects of the addition of Ni²⁺ on the growth and various properties of ammonium dihydrogen phosphate single crystals grown from aqueous solution by the slow evaporation method have been studied. The grown crystals were subjected to HRXRD, UV-Vis, TG/DTA and dielectric studies. The structural perfection of the grown crystal has been analyzed by high resolution X-ray diffraction rocking curve measurements. UV-Vis studies show that the grown crystal has good transparency in the entire visible region which is an essential requirement for a nonlinear crystal. Higher decomposition temperature was observed from TG/DTA. Dielectric constant and dielectric loss were measured for the grown crystal for different frequencies and temperatures.     

Study of Thermal Behavior and Single Crystal Growth of A 0.8Fe1.81Se2 (A=K, Rb, and Cs)

We have investigated the melting behavior of alkaline iron selenide compounds of composition A _0.80Fe_1.81Se₂ (A=K, Rb, and Cs) by thermogravimetry/differential thermal analysis (TG/DTA). The analysis indicated that all of the compounds melt incongruently and complete melting occurs at 902, 927, and 900 ^°C for A=K, Rb, and Cs, respectively, as confirmed by high temperature optical microscopy (HTOM). Study of DTA shows the structure of the phase separation present in the compounds and both endothermic and exothermic peaks on heating/cooling measurements are clearly observed. The optimum crystallization temperature range is indicated by the significant exothermic peeks on cooling DTA. Large and high quality single crystals can be obtained at a slow cooling/growth rate by the modified Bridgman, flux, or floating zone methods. XRD reflections in the (00l) plane show that all the single crystals represent an intergrowth of two sets of the c-axis characterized by slightly different lattice constants. Magnetization measurements show that the superconducting transition temperature occurs at T _c=31.6 K with shielding fraction volume of ～100 % for K_0.80Fe_1.81Se₂.     

溶胶-凝胶法制备多晶莫来石纤维

以廉价的铝粉、工业盐酸和酸性硅溶胶为主要原料, 通过溶胶凝胶法制备了多晶莫来石纤维. 采用²⁷Al NMR测试了聚合氯化铝溶胶中Al³⁺的聚集状态, 采用XRD、FT-IR、SEM和TG-DTA等手段表征了不同热处理温度下莫来石纤维的物相组成、纤维形貌以及纤维的热分解特性. ²⁷Al NMR结果表明, Al³⁺主要以Keggin结构的Al₁₃形态存在于聚合氯化铝溶胶中. 具有24个活性Al-OH键的Al₁₃聚阳离子易与硅溶胶中的Si-OH发生失水缩聚反应, 生成具有长链结构的纺丝溶液. XRD、FT-IR和TG-DTA结果表明, 纤维热处理到950℃时开始结晶, 到1000℃可获得单一的莫来石晶相, 整个过程的纤维失重在48.24％. 经1250℃热处理, 获得的莫来石纤维的直径为3～5μm, 晶粒尺寸约为240 nm, 拉伸强度为1.1GPa.     

SiO2—TiO2—ZrO2系涂层的制备及其特性

用溶胶－凝胶法（sol-gel method）在不锈钢表面制备了SiO2-TiO2-ZrO2系无机氧化膜（STZ）。用DTA／TG、IR、XRD和SEM等手段研究了涂层制备时由凝胶向玻璃态的转变以及涂层薄膜的显微结构特点，考察了涂层对基体的保护效果。试验结果表明，在溶胶至凝胶最终转变为无机氧化物的过程中形成了无机网络，Si^4 和Zr^4 充当了网络骨架的形成离子。涂层为无定型玻璃态，其间混有石英、锐钛矿或金红石等微晶。     

多层片式电感器用NiCuZn铁氧体的低温烧结

本文利用Bi₂O₃作为烧结促进剂实现了NiCuZn铁氧体在900℃以下烧结．利用TG、DTA、DDTA等分析手段研究Bi₂O₃的低温烧结机理,并确定最佳烧结温度范围在840～900℃之间．X－ray分析结果表明：加入Bi₂O₃后生成另相化合物Bi₃₆Fe₂O₅₇烧结后期少量Fe的固溶有助于稳定高温γ－Bi₂O₃相的立方结构,避免了冷却过程中的晶型转变．Bi36Fe₂O₅₇另相的存在能有效地阻止晶粒长大,从而达到改性的目的．     

含偶氮基团的聚酯型高分子非线性光学材料的合成与表征

采用高温溶液缩聚方法合成了一系列含带推－拉电子结构偶氮基团与介晶基团的聚酯型高分子,并利用红外光谱、元素分析、ＴＧ－ＤＴＡ、热台偏光显微镜及Ｘ射线衍射等手段对其结构、相变行为、热分解过程及结晶性能进行了研究。结果表明,所合成的含偶氮基团与介晶基团的聚酯型高分子均为结晶性无规共聚物,其玻璃化转变温度随聚合物中偶氮含量的增加而升高,而熔融温度则随聚合物中偶氮含量的增加而降低;此外,研究结果还表明,各聚     

CO impurities effect on LaNi4.7Al0.3 hydrogen storage alloy hydrogenation/dehydrogenation properties

LaNi_4.7Al_0.3 alloy was prepared by vacuum induction melting in high purity helium atmosphere, and the ingot was pulverized into 200–400 mesh powder after annealing. X-ray diffraction (XRD) and scanning electron microscopies (SEM) were utilized to study the alloy morphology and phase structure. X-ray photoelectron spectroscopy (XPS) was used for surface analysis. The poisoned alloy was tested at 30 °C in the mixture gas by thermogravimetric and differential thermal analyses (TG + DTA). The hydrogen storage properties were studied by the pressure-composition-temperature test. The activated sample was completely deactivated after only 3 hydriding/dehydriding cycles in hydrogen containing 300 ppm CO at 30 °C, but hydrogen storage capacity did not degrade when tested at 80 °C. Additionally, two different steps appeared in the absorption processes. Combined with XRD, XPS and TG + DTA results, an explanation for this phenomenon is given.     

An improved process for the synthesis of VPI-5 molecular sieve

VPI-5 was synthesized with lesser time duration. The synthesized sample was characterized by XRD, SEM, FT-IR, TG/DTA,²⁷Al and³¹P MASNMR techniques, which shows that the synthesized sample was highly crystalline. Carbon and nitrogen analyses reveal that the sample contains no template molecules, however, TG/DTA analysis shows the presence of physisorbed template molecules. MASNMR results show the presence of three different types of aluminium and phosphorous. Two of them were present as in tetrahedral and the remaining one is present in octahedral environment.     

电化学聚合漆酚钴配合物的研究

将电化学聚合得到的聚漆酚(EPU)与氯化钴异丙醇溶液反应生成聚漆酚钴配合物,采用XPS,FT-IR,DMTA,TG-DTA,AES和EPM等手段对其表征,确定该配合物结构即每个钴离子与EPU分子中二个链节单元的羟基发生配位。配合物的钴含量达8.13％,其电阻为1.74E 11Ω(EPU为7.9E 9Ω)。结果表明钴离子与EPU存在配位作用并形成交链,导致其玻璃化转变温度和耐热性能的提高。     

Nonequilibrium solidification effects induced by a pulsed magnetic field in ionic crystals

A digital DTA study of the process of solidification in KCl pretreated in a weak pulsed magnetic field (PMF) reveals a latent decrease in the enthalpy of solidification, followed by recovery of the initial state 144 h after the treatment. A sharp drop in the enthalpy of solidification observed 72 h after the PMF treatment gives rise to an additional relaxation process (postsolidification effect) revealed by a long-term fluctuational evolution of dissipated heat. According to the X-ray diffraction data, the PMF action upon KCl induces an intracrystalline transformation manifested by a small decrease in the lattice parameter and a sharp increase in the reflection intensity.     

Synthesis and characterization of iron aluminide nanoparticles by DC thermal plasma jet

Intermetallic iron aluminide alloy nanoparticles were synthesized by non-transferred DC plasma spray torch at atmospheric pressure. These powder particles were characterized by vibrating sample magnetometer (VSM), X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM), laser scattering particle size distribution analyzer, energy dispersive X-ray spectra (EDX) and thermo gravimetric-differential thermal analysis (TG/DTA) studies and the results are discussed. Commercially available iron and aluminium powders in the size range between 40 and 100 μm were ball milled with suitable ratio (Fe-85% and Al-15%) by weight to form a iron-aluminium blende; this was used as feed stock to synthesize iron aluminide nanoparticles. These nanoparticles particles were spherical in shape and black in colour, with the size range between 30 and 70 nm observed by ESEM. It is seen that the powders processed at higher power levels (15.3 kW) have more number of single spherical nanoparticles than powders processed at lower power levels (9.8 kW). The formation of iron aluminide nanoparticles is confirmed by XRD analysis and an exothermic reaction by DTA studies.     

含柔性酯基的N-取代马来酰亚胺的合成及溶液聚合

以马来酸酐(MA)、氨基丙酸(Aln)、直链醇为原料,选择合适的溶剂、催化剂,通过三步两釜法合成了侧链含柔性酯基的N-取代马来酰亚胺单体(RAM);以自由基溶液聚合法进行了均聚和共聚;利用IR、TG、DTA对产物(PRAM)进行了表征;并讨论了侧链长度对均聚物溶解性能、热性能的影响,结果表明柔性链长度对溶解性、起始热分解温度影响不大,但玻璃化温度(Tg)随柔性链增长而明显下降。     

掺杂Sb^3^＋的ZnO纳米晶敏感材料的性能

用柠檬酸盐法合成了含Ｓｂ＾３＾＋的ＺｎＯ纳米晶，探讨了Ｓｂ＾３＾＋对ＺｎＯ纳米晶结构和介电性能的影响，研究了灼烧温度及时间，杂质对ＺｎＯ纳米晶晶化过程的影响。用Ｘ射线射，红外光谱，热重差热，透射电镜研究了含Ｓｂ＾３＾＋的ＺｎＯ纳米的晶的性能。     

Phase diagram and order-disorder transition of vacancies in FexVS2 (0.20 < x < 1.00)

The system Fe_XVS₂ has been investigated by X-ray and DTA measurements. In this system, iron atoms are located in the alternative metal layers, and vacancy-ordered structures appear at low temperatures. The order-disorder transition of metal vacancies was confirmed by high temperature X-ray and DTA measurements. The nature of the order-disorder transition can be interpreted by the theory proposed by the present authors (1).     

One-step synthesis and flame retardancy of sheaf-like microcrystal antimony oxychloride

A mild and facile solution route has been developed for large-scale synthesis of sheaf-like antimony oxychloride Sb8O11CI2 (H2O)6 microcrystal at room temperature. The morphologies and structures of the as-prepared products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). A mechanism for the formation of the sheaf-like microstructure was tentatively proposed. The shape regulation was attributed to the capping mode of the PVP-directed antimony oxychloride crystal. The thermogravimetric and differential thermal analysis (TG/DTA) were employed to investigate thermal decomposition mechanism and temperature-dependent phase transition of antimony oxychloride Sb8O11CI2 (H2O)6 in the air. The flammable property determined by the cone calorimeter showed excellent flame retardancy when applied this antimony oxychloride in poly (vinyl chloride) (PVC) polymer.