Effects of argon sintering atmosphere on luminescence characteristics of Ca6BaP4O17:Sm3+ phosphors

In this paper, Ca₆BaP₄O₁₇:Sm³⁺ and Li⁺ co-doped Ca₆BaP₄O₁₇:Sm³⁺ phosphors were synthesized in air and argon atmospheres using a solid-state reaction method. The phosphor morphologies and crystal structure were studied using scanning electron microscopy and X-ray diffraction, respectively. The emission and absorption characteristics were investigated using photoluminescence emission spectroscopy and diffuse reflectance spectroscopy. The surface states and composition of phosphor were investigated using X-ray photoelectron spectroscopy. The emission integrated intensities of the phosphors sintered in an argon atmosphere increased 3.5 fold than the ones sintered in air atmosphere, with Li⁺ ions becoming embedded in the lattice of the Ca₆BaP₄O₁₇:Sm³⁺ phosphor. This occurs because there are fewer defect/oxygen vacancies and less of the secondary phase forms, leading to better Sm³⁺ emission. The results suggest that sintering a mixture of the raw materials of a phosphor in an argon atmosphere is a good approach for synthesizing Ca₆BaP₄O₁₇:Sm³⁺ phosphor powders. The color purity and CIE values of an optimized phosphor sample sintered in an argon atmosphere with an Li⁺ ion compensator were calculated to be ~ 99.6% and (0.612,0.386) in the orange–red region under 405-nm excitation, respectively. Moreover, the solid solubility of Sm³⁺ ions in the Ca₆BaP₄O₁₇ host can be enhanced by using an argon atmosphere in the synthesis process.     

融入局部几何特征的流形谱聚类图像分割

为了改善谱聚类图像分割的精准性和时效性,文中提出融入局部几何特征的流形谱聚类图像分割算法.首先,考虑图像数据的流形结构,在数据点的K近邻域内执行局部PCA,得到数据间本征维数的关系.然后,引入流形学习中的局部线性重构技术,通过混合线性分析器得到数据间局部切空间的相似性,结合二者构造含有局部几何特征的相似性矩阵.再利用Nystr m技术逼近待分割图像的特征向量,对构造的k个主特征向量执行谱聚类.最后,在Berkeley数据集上的对比实验验证文中算法的准确性和时效性优势.     

混炼方式对螺旋纳米碳纤维增强天然橡胶复合材料力学性能的影响

采用干法和湿法两种混炼工艺制备了螺旋纳米碳纤维(HCNFs)/炭黑(CB)/天然橡胶(NR)复合材料,通过扫描电镜、拉伸试验机和应变扫描仪分别对所制备复合材料的界面形貌、力学性能和Payne效应进行了测试分析,考察了混炼方式对复合材料宏观力学性能及Payne效应的影响。结果表明,与纯CB填料相比,在干湿两种混炼方式下,添加适量的HCNFs(1～6份)能提高HCNFs/CB/NR复合材料的300%定伸应力、扯断伸长率、拉伸强度和硬度。与干法混炼相比,湿法混炼能明显增强HCNFs/CB/NR复合材料的Payne效应,并提升在HCNFs高添加量(2～6份)条件下的拉伸强度和扯断伸长率,这主要源于湿法混炼能够有效改善HCNFs在橡胶基质中的分散性。     

山东某难选贫磁铁矿石工艺矿物学研究

山东某难选贫磁铁矿石一直处于待开发状态。为了给矿石资源的开发利用提供依据，进行了系统的工艺矿物学研究。结果表明：①矿石中的主要有用矿物为磁铁矿，其次为假象赤铁矿和赤铁矿，含量分别为13.93%、5.65%和3.31%，褐铁矿分布较少为1.01%；主要脉石矿物为石英，其次为黑云母、碳酸盐类矿物和辉石，含量分别为39.12%、11.23%、7.78%和6.57%。②矿石主要构造为块状构造、层纹状构造，少量角砾状构造；主要结构有条带状结构、粒状结构，其次为脉状结构、交织结构，少量交代残余结构、辉绿结构、浸染状结构、斑状结构和纤维状结构。③矿石中有用铁矿物结晶粒度微细，主要分布在-0.04 mm粒级，其中磁铁矿（含假象赤铁矿）和赤、褐铁矿分布率分别为63.29%和72.50%，而-0.01 mm粒级分布率则占21.13%和29.16%，因此，欲使铁矿物与脉石达到较好解离，矿石必须细磨。     

Production and Heat Treatment of Ti6–Al5.5–V–1.8Sn Powder Titanium Alloy

The mechanical properties of Ti6–Al5.5–V–1.8Sn powder titanium alloy are investigated as a function of its structure, which, in turn, depends on its production and heat treatment (quenching and aging).     

Strain Concentration Effect in Cu–Al–Ni Single Crystals under a Longitudinal Bending Force

The behavior of a superelastic Cu?14.2% Al?4%Ni single crystal in the case of high reversible strains under a longitudinal bending force was investigated. The effect of strain confinement along the crystal length was revealed and studied. The highest reversible strains (up to 10%) were shown to be confined within the central part of the bent crystal.     

Chemical-Spectroscopic Determination of the Isotope Composition and Gravimetric Content of Uranium in Uranium–Aluminum Alloys and Products of Their Processing

Conditions of chemical separation of Al macroamounts and U microamounts, followed by atomic emission spectroscopic determination of the isotope composition and gravimetric content of U, were studied. An algorithm was developed for constructing calibration plots to determine the ²³⁵U/²³⁸U isotope ratio in various samples from nuclear fuel reprocessing. Optimum conditions of the spectral analysis for the U content were found by mathematical design of the experiment: NaCl content 2%, current 18 А, and exposure time 40 s. With the use of these conditions and of a specially developed form of carbon electrode, the uranium detection limit was decreased from 10^–3 to 10^–5%.     

Strength Assessment of Welded Joints of High-Strength Alloy Steels by Indentation Method

Strength of Materials - The paper presents the indentation method for strength assessment of the welded joints in high-strength alloy steels, including base metal, heat-affected zone, and welded...