La_2O_3/LDPE复合材料非等温结晶性能研究

利用差示扫描量热仪(DSC)考察了氧化镧(La2O3)/低密度聚乙烯(LDPE)复合材料的非等温结晶行为。通过Jeziorny法、Ozawa法及莫志深法研究了复合材料的非等温结晶动力学。结果表明:在添加La2O3后,LDPE成核速率降低,结晶度下降,晶体粒径分布变宽。在非等温结晶动力学分析中,Jeziorny法lg[-ln(1-Xt)]～lgt关系曲线在结晶前期和中期具有较好的线性关系,结晶后期产生较大偏离;Ozawa法并不适用;而莫志深法适用于该体系的研究,表明La2O3的加入使LDPE结晶速率增大。     

锶渣混凝土在农村公路中的应用

通过室内强度试验结果与现场施工条件确定了锶渣混凝土的水泥用量,阐述了锶渣混凝土面层施工的主要工序,并说明了锶渣混凝土面层施工中的关键性控制要点,以促进其在农村公路中的应用和推广。     

Exploration of 1D-2D LaFeO3/RGO S-scheme heterojunction for photocatalytic water splitting

Sustainable energy innovation is spearheading the way to achieve decarbonisation through commercially viable and highly competitive renewable technologies for green hydrogen. Photocatalytic water splitting has received global attention, as it promotes the direct conversion of solar energy to chemical energy and hydrogen production. Lanthanum orthoferrite (LaFeO₃) has been selected due to its narrow bandgap perovskite-oxides (ABO₃) type nature, low cost and high chemical stability but it is limited with fast charge recombination. To circumvent its constraint of fast charge recombination, an efficient graphene-based nanocomposite has been prepared by employing reduced graphene oxide (RGO) nanosheets as charge separators for visible light driven photocatalytic water splitting. Here, we present a thorough physical and spectroscopic characterization of the Lanthanum orthoferrite/Reduced Graphene oxide (LaFeO₃/RGO) nanocomposites, and investigate its photocatalytic and photoelectrochemical performance. The photocurrent density of the nanocomposites demonstrated ∼21 times higher in comparison to pure LaFeO₃. The as-prepared nanocomposites have been successfully used as photocatalysts for H₂ generation through water reduction under visible light. A significant enhancement in H₂ generation has been recorded for nanocomposites (∼82 mmol g⁻¹ h⁻¹) as compared to that of bare LaFeO₃ (∼9 mmol g⁻¹ h⁻¹) which is among the highest values obtained using noble-metal-free graphene-based photocatalytic nanocomposites. This work offers a facile approach for fabricating highly efficient 1D-2D heterostructure for photocatalysis application.     

包覆量对铝酸锶复合包覆效果的影响

目的对铝酸锶进行复合包覆处理,以提高荧光粉的抗水解性能。方法采用液相水解法在铝酸锶表面包覆SiO2/Al2O3膜,并对膜层进行耐水性、发光性能测试及形貌分析,研究包覆量对包覆效果的影响。结果包覆量对包膜效果有着重要的影响。包覆量太低,荧光粉的耐水性能受到限制,很容易发生水解;包覆量太高,会影响荧光粉的发光性能,发光亮度降低。结论要想得到包膜效果较好的产品,SiO2和Al2O3占铝酸锶的质量百分比最好控制在5%左右。     

Microstructure and biocorrosion behaviors of solution treated and as-extruded Mg–2.2Nd–xSr–0.3Zr alloys

Mg–2.2Nd–xSr–0.3Zr alloys (x=0, 0.4 and 0.7, mass fraction, %) were prepared by gravity casting. Solution treatment was conducted on the as-cast alloys to homogenize microstructure, and hot extrusion was subsequently conducted. Microstructure was observed using an optical microscope and a scanning electron microscope. Biocorrosion behaviors of the alloy in simulated body fluid were analyzed by mass loss, hydrogen evolution and Tafel polarization experiments. The results show that the amount of residual eutectic phase of the solution treated alloys increases with increasing Sr addition, and the grains are significantly refined after hot extrusion. The corrosion resistance of the solution treated alloys deteriorates apparently with increasing Sr addition, while the corrosion resistance of the as-extruded alloys is improved with Sr addition. Nevertheless, the biocorrosion behavior of the as-extruded alloys obtained by Tafel polarization shows different trends from those obtained by the other two methods.     

Reliability of atom column positions in a ternary system determined by quantitative high-resolution transmission electron microscopy

Employing an iterative structure refinement procedure, we have determined the atomistic structure of the Σ3 (111) grain boundary in strontium titanate (SrTiO₃) from high-resolution transmission electron microscopy (HRTEM) images. This grain boundary serves as a model system to study the effect of column occupancies on the reliability of the column positions. In this paper we introduce a method to derive confidence regions for the positions of individual atom columns at crystal defects. Based on a statistical approach we first determine the reliabilities of different types of atom columns in regions of unfaulted crystal. Next we extrapolate these reliabilities to obtain the reliabilities of individual atom columns at the grain boundary. The method accounts correctly for random errors and promises to be generally applicable provided that repetitive units of unfaulted crystal structure are contained in the HRTEM image. Under the conditions of the present study, the reliability of a column position correlates with the projected electrostatic potential of the column. Accordingly, the reliabilities of the column positions at the boundary vary with the column type: 0.008 nm for Sr–O columns, 0.014 nm for Ti columns, and 0.018 nm for O–O columns.     

Thermal behaviour of strontium tartrate single crystals grown in gel

Thermal behaviour of strontium tartrate crystals grown with the aid of sodium metasilicate gel is investigated using thermogravimetry (TG) and differential thermal analysis (DTA). Effect of magnetic field and dopant (Pb)²⁺ on the crystal stability is also studied using thermal analysis. This study reveals that water molecules are locked up in the lattice with different strengths in the grown crystals.     

Structural and ferroelectric properties of lanthanum modified BPZT ceramics

Lanthanum modified Ba_0.80Pb_0.20Ti_0.90Zr_0.10O₃ (BPZT) ceramics with composition Ba_0.80−xLa_x Pb_0.20Ti_0.90Zr_0.10O₃; x = 0–0.01 in steps of 0.0025 were prepared by conventional solid state method. All the samples were sintered at 1325 °C after compacting in circular discs. Detailed structural and ferroelectric properties were carried out for sintered specimens. X-ray diffraction analysis for all the sintered specimens shows tetragonal structure with perovskite. Coercive field (E_c) and remanent polarization (P_r) to spontaneous polarization (P_s) ratio (P_r/P_s) was found to decrease with increase in temperature. P_r/P_s ratio was found to decrease with increase in x, except x = 0.0025.     

锶铁氧体胶态振动注模成形技术研究

通过絮凝、振动脱水工艺处理,获得固相体积分数达50%的锶铁氧体浆料,实现了高质量锶铁氧体坯体的胶态振动注模成形.分析了工艺条件对成形过程及样品质量的影响.实验表明:胶态注模成形比凝胶注模成形需要加入更多的单体与交联剂才能得到坯体强度相当的坯体;烧成后的锶铁氧体的剩余磁感应强度为420 mT,矫顽力H_(cb)为270 kA/m,最大磁能积(BH)_(max)为34 kJ/m~3.     

Subsolidus Phase Relations in the Pseudoternary System SrO·6M2O3 (M = Fe, Cr, Al) in Air

Crystalline powder samples belonging to the pseudoternary system SrO·6M₂O₃ (M = Fe, Al, Cr) were synthesized in air. The limit of the magnetoplumbite-type (M-type) phase solid solution is governed by the presence of Cr³⁺ in the structure and is accompanied by the formation of a chromate and a sesquioxide. The extension of the solid solution in the Cr-containing pseudobinaries depends to a large extent on the crystallographic site preference of the host cation. The extension of the M-type solid solution is also narrowed at a lower temperature.