Application of FTIR spectra for evaluating interfacial reactions in metal matrix composites

Manufacturing of Saffil/MgLi metal matrix composites by the melt infiltration process is accompanied by extensive interfacial redox reaction between δ-Al₂O₃ fibers (Saffil) and lithium. The present paper deals with the Fourier transform infrared spectroscopy examination of Saffil fibers isolated from Mg–8 wt% Li alloy by the bromine/methylacetate agent focusing on the insertion of Li⁺ ions into δ-Al₂O₃ and their influence on water adsorption. Insertion of Li⁺ into δ-Al₂O₃ is monitored by gradual change of Al–O stretching bands (400–900 cm⁻¹) towards more simple patterns of a spinel-like product assigned as δ(Li) which transforms to LiAl₅O₈ during subsequent annealing. Rapid increase in the water adsorption with increase in Li content, indicated by the changes in H–O–H bending (about 1,650 cm⁻¹) and O–H stretching (about 3,500 cm⁻¹), is connected with the ionicity of the δ(Li) phase, which attracts polar water molecules.     

Preparation and photoluminescence property of a loose powder, Ca3Al2O6:Eu by calcination of a layered double hydroxide precursor

A novel red light-emitting material, Ca₃Al₂O₆:Eu³⁺, which is the first example found in the Ca₃Al₂O₆ host, was prepared by calcination of a layered double hydroxide precursor at 1350 °C. The precursor, [Ca_2.9−xAl₂Eu_x(OH)_9.8](NO₃)_2+x·2.5H₂O, was prepared by coprecipitation of metal nitrates with sodium hydroxide. The material is a loose powder composed of irregular particles formed from aggregation of particles of a few nanometers, as shown in scanning electron microscope (SEM) images. It was found that the photoluminescence intensity reached the maximum when the calcination temperature was 1350 °C and the concentration of Eu³⁺ was 1.0%. The material emits bright red emission at 614 nm under a radiation of λ=250 nm.     

BaTiO3-BaAl2O4-Al2O3复合载体的制备、表征及其Ni基催化剂催化CH4/CO2重整反应性能

以十六烷基三甲基溴化胺为结构导向剂,采用溶胶-凝胶法制备了BaTiO3-BaAl2O4-Al2O3复合载体,采用X射线衍射、红外光谱、N2吸附-脱附、透射电子显微镜和H2程序升温还原等技术对复合载体进行了表征,并以CH4/CO2重整制合成气为探针反应,考察了不同Ni/BaTiO3-BaAl2O4-Al2O3催化剂的性能.结果表明,BaTiO3-BaAl2O4-Al2O3复合载体具有多孔织构特性和较高的比表面积,BaTiO3和BaAl2O4以晶粒状态分布在复合载体的内外表面,晶粒尺寸在20～50nm的范围,复合载体孔径为10～20nm.复合载体上BaTiO3和BaAl2O4的引入,适度削弱了Ni/BaTiO3-BaAl2O4-Al2O3催化剂中Ni物种与γ-Al2O3间的强相互作用,抑止了NiAl2O4尖晶石的生成;当载体中Ba(Ti)含量为17.33%时,其负载的Ni催化剂上CH4/CO2重整制合成气反应的活性和稳定性最高.     

Luminescent properties of Sr<Subscript>3</Subscript>Al<Subscript>2</Subscript>O<Subscript>6</Subscript>: Eu,Pr prepared by sol–gel method

A new red-emitting long afterglow Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphor was synthesized by sol–gel methods using Sr(NO₃)₂, Al(NO₃)₃·9H₂O, Eu(NO₃)₃ and Pr(NO₃)₃ as raw materials. The crystalline structure of the phosphor powders were characterized by X-ray diffraction. Luminescent properties of the phosphor powders were analyzed by the fluorescence spectrophotometer. Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphor powders with single Sr₃Al₂O₆ phase were prepared at 1200 °C for 2 h in the reducing atmosphere. Pr³⁺ doped made the light intensity and the light-lasting time of Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphors improved. The emission peaks of the Sr₃Al₂O₆: Eu²⁺, Pr³⁺ phosphor powders lay at 612 nm with the excitation of 472 nm and the longest afterglow time could last for about 15 min at Pr³⁺ content of 0.06.     

Microstructure development in mixes of calcium aluminate cement with silica fume or fly ash

The most widely identified degradation process suffered by calcium aluminate cement (CAC) is the so-called conversion of hexagonal calcium aluminate hydrate to cubic form. This conversion is usually followed by an increase in porosity determined by the different densities of these hydrates and the subsequent loss of strength. Mixes of calcium aluminate cement (CAC) and silica fume (SF) or fly ash (FA) represent an interesting alternative for the stabilization of CAC hydrates, which might be attributed to a microstructure based mainly on aluminosilicates. This paper deals with the microstructure of cement pastes fabricated with mixtures CAC-SF and CAC-FA and its evolution over time. Thermal analysis (DTA/TG), X-ray diffraction (XRD) and mid-infrared spectroscopy (FTIR) have been used to assess the microstructure of these formulations.     

LiAl5O8∶Tb3+绿色荧光粉的合成及发光性能

采用溶胶-凝胶法合成了Tb³⁺掺杂的LiAl₅O₈荧光粉并对其发光性能进行了研究。XRD分析表明,前驱物在750 ℃下灼烧2 h得到的样品为纯相的LiAl₅O₈。样品的激发谱为一宽带,其最强的峰位于231 nm。发射谱由4组窄带组成,其中最强峰位于542 nm,对应于Tb³⁺离子的⁵D₄→⁷F₅跃迁。最佳的Tb³⁺掺杂摩尔分数为0.01。探讨了Tb³⁺掺杂浓度、电荷补偿剂(Li⁺)和助熔剂(H₃BO₃)对样品发光性能的影响,结果表明,调节激活剂浓度、添加电荷补偿剂和助熔剂均可以在很大程度上提高材料的发射强度。     

The evolution of structural changes in ettringite during thermal decomposition

The thermal decomposition of ettringite, Ca₆[Al(OH)₆]₂(SO₄)₃·∼26H₂O, was studied with pulsed neutron time-of-flight diffraction combined with Rietveld structure refinement. Like prior investigations, transition from a crystalline to amorphous state occurred following the loss of ∼20 water molecules. In contrast to earlier investigations, which relied upon indirect measurements of water and hydroxyl occupancies, the present study inferred the occupancies directly from Rietveld crystal structure refinement of the diffraction data. The decomposition pathway was shown to be more complex than previously envisioned, involving the simultaneous loss of hydroxyl and water molecules. Nuclear magnetic resonance (NMR) spectroscopy studies of the rigid lattice lineshapes of fully and partially hydrated ettringite were performed and confirmed our decomposition model.     

Preparation and Mechanical Properties of Composites Based on Rigid Polyvinyl Chloride Filled with Organic Modified Illite Powder

Illite powder, modified by an aluminate coupling agent, was used as a filler to strengthen polyvinyl chloride (PVC) resin with mechanical properties of rigid PVC/modified illite composite being tested. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were applied for the structural characterization of the raw materials. SEM and Fourier transform infrared spectroscopy (FTIR) measurements were used for demonstrating the effect of modification of the illite powder. Results from tests of mechanical properties showed that, when the dosage of modified illite powder was 2 parts per hundred parts by weight, there was an obvious toughening effect on rigid PVC material; the notched impact strength was increased by 59% in comparison to neat rigid PVC, but the elongation of the composites decreased slightly.     

Studies on the Preparation and Properties of Organic Acid Aluminate Linked Polyacrylamide

The organic acid aluminate (AlOA) was used as a linked agent to enhance the viscosity of partially hydrolyzed polyacrylamide (HPAM) solution. The influencing factors, such as HPAM concentration, pH, temperature, and salinity on the linked polymer system were probed via the investigations on rheological properties, microstructure, and location of the linked polymer systems. The result show that the scattered gelatin particles are contained in the linked polymer network structure. The system behaves as mainly elasticity, and the system belongs to the linear viscoelastic fluid. For the solution with elasticity, its subsequent fluid not only has a boost effect on the front fluid, but also the front fluid has a stronger effect of “drawing” and “dragging” on its side and subsequent fluid. Therefore, it will be important in both theory investigation and the actual oil recovery.     

Luminescence of BaAl2O4:Mn,Ce phosphor

Powder samples of barium aluminate doped with Mn²⁺ and Ce³⁺ were prepared by solid-state reaction method and their photoluminescence and thermoluminescence properties were studied. Substitution of Ca/Sr in place of Ba resulted in enhanced emission from Ce³⁺ ions without changing the spectral profile. Cerium efficiently sensitized the manganese luminescence in barium aluminate. Photoluminescence and thermo luminescence observations have indicated the presence of V_k³⁺ defects in undoped barium aluminate. However, Barium aluminate (either undoped or doped with manganese) did not exhibit long afterglow.