‘Age-hardened alloy’ based on bulk polycrystalline oxide ceramic

We report here for the first time the development of ‘age-hardened/toughened’ ceramic alloy based on MgO in the bulk polycrystalline form. This route allows for the facile development of a ‘near-ideal’ microstructure characterized by the presence of nanosized and uniformly dispersed second-phase particles (MgFe₂O₄) within the matrix grains, as well as along the matrix grain boundaries, in a controlled manner. Furthermore, the intragranular second-phase particles are rendered coherent with the matrix (MgO). Development of such microstructural features for two-phase bulk polycrystalline ceramics is extremely challenging following the powder metallurgical route usually adopted for the development of bulk ceramic nanocomposites. Furthermore, unlike for the case of ceramic nanocomposites, the route adopted here does not necessitate the usage of nano-powder, pressure/electric field-assisted sintering techniques and inert/reducing atmosphere. The as-developed bulk polycrystalline MgO–MgFe₂O₄ alloys possess considerably improved hardness (by ~52%) and indentation toughness (by ~35%), as compared to phase pure MgO.     

Electrical conductivity of Nd and Ce co-doped Gd2Zr2O7 ceramics

In this study, (Gd_{1? x} Nd _x )₂(Zr_{1? x} Ce _x )₂O₇ (0 ≤ x ≤ 0.5) ceramics have been prepared by pressureless sintering at 1973 K to investigate the influence of Nd and Ce co-doping on their electrical conductivity. The electrical conductivity of the ceramics was investigated by impedance spectroscopy measurements from 723 to 1173 K over the frequency range of 20 Hz to 2 MHz in air. The measured values obey the Arrhenius relation. For each composition, the grain conductivity gradually increases with increasing temperature from 723 to 1173 K. At a given temperature, it gradually decreases with increasing neodymium and cerium contents from x = 0 to 0.3; thereafter, the grain conductivity exhibits a slight increase with further increasing neodymium and cerium contents up to x = 0.5.     

齐国陶瓷工艺与造型装饰特色

齐国的陶瓷是齐文化的重要组成部分,在中国陶瓷发展史上占有重要地位。由先齐地区大汶口文化的白陶、龙山文化的黑陶、特别是极具地域特征的齐国日常生活类陶器与各种反映社会现实生活的艺术品、建筑陶构件等,都充分体现出豪放与沉稳的双重造型特色以及丰富多彩的装饰艺术风格。这不仅构成了齐国独特的陶瓷文化体系,也对丰富和发展我国传统陶瓷文化起了重要作用,并影响后世陶瓷发展长达数千年。     

An ordered arrangement of atom columnar clusters in a pentagonal quasiperiodic lattice of an Al-Ni-Co decagonal quasicrystal

The structure of an Al-Ni-Co decagonal quasicrystal (called the S1-type superstructure), which shows diffraction patterns with superlattice reflections, has been studied by atomic-scale observations of electron microscopy. The structure of the decagonal quasicrystal can be characterized as an ordered arrangement of two kinds of atom columnar cluster with different directions of pentagonal symmetry. A fundamental lattice, which is constructed by connecting all the atom clusters, shows a pentagonal quasiperiodic lattice with a bond length of about 2 nm. The pentagonal lattice is divided into two superlattices, which are constructed by connecting atom clusters with the same directions of pentagonal symmetry, with a bond length of 2