Tensile properties of iron-based P/M steels with ferrite + martensite microstructure

The effect of intercritical heat treatments on the tensile properties of iron-based P/M steels was investigated. For this purpose, atomized iron powder (Ancorsteel 1000) was admixed with 0.3 wt.% graphite powder. Tensile test specimens were cold pressed at 700 MPa and sintered at 1120 °C for 30 min under pure argon gas atmosphere. After sintering, ∼20% pearlite volume fraction in a ferrite matrix was obtained. To produce coarse ferrite + martensite microstructures, the sintered specimens were intercritically annealed at 724 and 760 °C and quenched in water. To obtain fine ferrite + martensite microstructures, the sintered specimens were first austenitized at 890 °C and water-quenched to produce a fully martensitic structure. These specimens were then intercritically annealed at 724 and 760 °C and re-quenched. After the intercritical annealing at 724 and 760 °C and quenching, martensite volume fractions were ∼ 18% and 43%, respectively, in both the coarse- and fine-grained specimens. Although the intercritically annealed specimens exhibited higher yield and tensile strength than the as-sintered specimens, their elongation values were lower. Specimens with a fine ferrite + martensite microstructure showed high yield and tensile strength and ductility in comparison to specimens with a coarse ferrite + martensite microstructure. The strength values of specimens increased with increasing martensite volume fraction.     

The Story of Istanbul's Modernisation

Since reform started under Ottoman rule in the early 19th century, Istanbul has undergone a substantial period of modernisation that has spanned more than 150 years. İlhan Tekeli outlines the metropolis' enduring development, characterising Istanbul's transformation into a modern city into four distinct periods. It is a story that bridges the collapse of the Ottoman Empire and the reconstruction of the Turkish Republic as a nation-state, with the initial demise of the city in favour of Ankara; and continues with Istanbul regaining its status as a world city; as it evolves from a monstrous industrial city to an urban region and global centre. Copyright © 2010 John Wiley & Sons, Ltd.     

The profile of temperature and voltage dependent series resistance and the interface states in (Ni/Au)/Al0.3Ga0.7N/AlN/GaN heterostructures

The temperature dependence of capacitance-voltage (C-V) and the conductance-voltage (G/w-V) characteristics of (Ni/Au)/Al_0.3Ga_0.7N/AlN/GaN heterostructures were investigated by considering the effect of series resistance (R_s) and interface states N_ss in a wide temperature range (79-395 K). Our experimental results show that both R_s and N_ss were found to be strongly functional with temperature and bias voltage. Therefore, they affect the (C-V) and (G/w-V) characteristics. The values of capacitance give two peaks at high temperatures, and a crossing at a certain bias voltage point (∼3.5 V). The first capacitance peaks are located in the forward bias region (∼0.1 V) at a low temperature. However, from 295 K the second capacitance peaks appear and then shift towards the reverse bias region that is located at ∼−4.5 V with increasing temperature. Such behavior, as demonstrated by these anomalous peaks, can be attributed to the thermal restructuring and reordering of the interface states. The capacitance (C_m) and conductance (G/w-V) values that were measured under both reverse and forward bias were corrected for the effect of series resistance in order to obtain the real diode capacitance and conductance. The density of N_ss, depending on the temperature, was determined from the (C-V) and (G/w-V) data using the Hill-Coleman Method.     

Optical Imaging Approaches to Monitor Static and Dynamic Cell‐on‐Chip Platforms: A Tutorial Review

Miniaturized laboratories on chip platforms play an important role in handling life sciences studies. The platforms may contain static or dynamic biological cells. Examples are a fixed medium of an organ‐on‐a‐chip and individual cells moving in a microfluidic channel, respectively. Due to feasibility of control or investigation and ethical implications of live targets, both static and dynamic cell‐on‐chip platforms promise various applications in biology. To extract necessary information from the experiments, the demand for direct monitoring is rapidly increasing. Among different microscopy methods, optical imaging is a straightforward choice. Considering light interaction with biological agents, imaging signals may be generated as a result of scattering or emission effects from a sample. Thus, optical imaging techniques could be categorized into scattering‐based and emission‐based techniques. In this review, various optical imaging approaches used in monitoring static and dynamic platforms are introduced along with their optical systems, advantages, challenges, and applications. This review may help biologists to find a suitable imaging technique for different cell‐on‐chip studies and might also be useful for the people who are going to develop optical imaging systems in life sciences studies.     

Oscillator strengths of allowed transitions for O III

The electric dipole oscillator strengths for lines in O III between some singlet and triplet levels have been calculated using the weakest bound electron potential model theory and the quantum defect orbital theory. In the calculations, both multiplet and fine-structure transitions are studied. The calculated oscillator strengths have been compared with available theoretical and experimental results. Good agreement with results in the literature has been obtained.     

Phase stability,microstructural evolution and room temperature mechanical properties of TiO2 doped 8 mol% Y2O3 stabilized ZrO2 (8Y-CSZ)

The effect of TiO₂ dopant on phase stability, microstructural evolution and room temperature mechanical properties of 8 mol% yttria-stabilized cubic zirconia (8Y-CSZ) was studied. The results show that TiO₂ (up to 10 wt%) can be dissolved in solid solution in the zirconia matrix. When the dopant amount is less than 5 wt%, TiO₂ doped 8Y-CSZ remains single phase cubic zirconia. Increased additions of TiO₂ destabilize the cubic phase and cause the formation of tetragonal zirconia with a resultant microstructure consisting of large cubic zirconia grains and small tetragonal zirconia grains. EDS analyses show that yttria is partitioned between these two types of grains. The solubility of TiO₂ is the highest for cubic grains which also have higher yttria concentrations. Room temperature mechanical property measurements show that hardness does not change significantly with additions of TiO₂, but fracture toughness is more than doubled for 10 wt% TiO₂ doped 8Y-CSZ.