Papers by Keyword: Grain Size

Abstract: We report on experimental results of the temperature dependence of inductive (total) magnetic moment and remanent magnetic moment at saturation field for electrodeposited nanocrystalline Ni films with thicknesses ranging from 350 nm to 20 μm. We have found that the amplitude of roughness and crystallite size significantly affected the remanent saturation magnetic moment and coercivity.

Abstract: Due to their soft operational capacity and magnetic properties, Iron Nickel alloys are of great commercial interest. A simple and inexpensive technique for the production of Nickel-Iron thin films is electrodeposition. A lot of physical and chemical parameters (substrates, concentration, current density, potential, temperature, pH, agents of addition......) can significantly influence the physical properties, such as homogeneity, bright, structure and morphology of the Ni-Fe deposits. This paper presents a study into some characteristics of Ni-Fe deposits on Copper substrates. All the electrochemical experiments were performed in a three electrode cell in which the volume of the bath was 150ml. Electrodeposition of Ni-Fe was carried out potensiostatically from a Brenner type electrolytic bath in [0.1 aqueous solutions of Ni-Fe. The applied potential is-1.20V and the deposition time varies from 10 min to 30 min for all experiments.

Abstract: Gadolinium doped barium titanate (Gd-BaTiO₃) thin films with the molar ratio of 70:30 have been fabricated on SiO₂/Si substrates using sol-gel technique. The effect of number of deposited layers on the grain size and surface morphology has been investigated using an atomic force microscope in contact mode. AFM micro-images show that the films have well distributed grains, dense and crack free surface. In general, the results show that the grain size increases from ~170 nm to ~189 nm as the number of deposited layers increase from one to four layers which attributed to the grain growth mechanism during heating and annealing processes. However, the surface of the films is analysed through amplitude parameters to find out that the films surface is smooth with a predominant for peaks and relatively low number of high peaks and low valleys.

Abstract: Microstructure and pre-existing surface flaws in smooth notch geometries significantly affect the fatigue life of welded joints. Traditionally, a welded joint is assumed to incorporate crack-like defects and the crack propagation dominates the total fatigue life. For a smooth weld notch geometry, the macro crack initiation period becomes more significant, and this difference cannot be modelled with the existing stress or fracture mechanics ‑based approaches. In this paper, a microstructure and strain ‑based fatigue life approach is presented. In the approach, the fatigue damage process is modelled as a repeated crack initiation process within a material volume related to the microstructure. The novelty of the developed approach is that the size of the damage zone is defined from the grain size statistics without using fracture mechanics. The approach is able to consider the changes in the stress gradient, stress triaxiality and plasticity during the fatigue crack initiation and growth. The developed approach has been validated with experiments on submerged-arc and laser-hybrid welded joints. The predicted fatigue life, crack growth path and rate showed good agreement with the experiments. For a welded joint with smooth and favourable notch shape, the short crack growth, i.e. macro crack initiation period is dominant and it has a significant influence on the fatigue life.

Abstract: The effect of different grain sizes on the fatigue performance of high manganese TWIP steel (Twinning-Induced Plasticity) in the low-cycle fatigue regime was investigated. The average grain sizes in the fine grained condition were 2 5 μm and after heat treatment in the coarse grained condition about 80 μm were obtained. Pronounced twin-dislocation interactions especially in small grains strengthen the steel during monotonic deformation. Twin boundaries act as obstacles for dislocation slip, and thus, further reduce the effective grain size, which affects the fatigue response as well. The samples were monotonically and cyclically deformed at room temperature. The results reveal that the grain size has a significant influence on the mechanical as well as on the cyclic performance. Especially under cyclic loading differences in the resulting stress levels and cyclic stability can be observed. To clarify the microstructure evolution before and after fatigue with different constant strain amplitudes the samples were analyzed by means of transmission electron microscopy (TEM).

Abstract: Alumina and zirconia are important materials for energy and optical applications. In this study, the effect of thermal cycling on grain size and residual stress was reported. Residual stress was measured using X-ray diffraction (XRD) sin2ψ method for the as-received and the samples after thermal cycling up to 900 cycles. For alumina, the measured residual stress is approximately 96 MPa in tensile for the as-received material, and increases to its highest value of 480 MPa after 650 thermal cycles. The residual stress decreases from 480 MPa to 96 MPa in tensile with increased thermal cycling from 650 to 900 cycles. The crystallized grain size calculated from the diffraction pattern shows that the mean crystallized grain size is about 93 nm for the as-received and increases to 232 nm after 650 thermal cycles. This result is consistent with the enlarged grain size observed by scanning electron microscopy for the alumina after 650 thermal cycles reported earlier. With continued thermal cycling up to 900 cycles, the crystallized grain size is greatly reduced to 104 nm. It suggests that evolution of the crystallized grain size is correlated with the residual stress. For yttria-stabilized tetragonal zirconia (Y-TZP), the mechanical properties at room temperature, are consistent with the property values provided by the manufacturer. The Young’s modulus of shows a non-linear inverse relationship with increasing temperature. The degradation of the Young’s modulus mostly occurs prior to 400 °C and to a less extent in the temperature range of 400 °C up to 850 °C. The Vickers hardness number for the as-received Y-TZP material decreases to a very small extent after 560 thermal cycles and increases approximately 2%, after 1200 thermal cycles. This is consistent with the trend of the Young’s modulus for thermal-cycled specimens.

Abstract: This paper presents the relationship between spin coating speed, heat treatment time, and annealing temperature in response to the grain size in ferroelectric Barium Strontium Titanate (BST). Many fundamental issues such as heat conduction, contact deformation, mechanical stress, and friction can be explained and distinguished through the understanding of the grain size. The investigation was done using a full factorial design of experiment (DOE). Analysis was done quantitatively by plotting the main effects graphs. The results suggest that higher spin coating speed and the annealing temperature decreases the grain size while the heat treatment time is directly proportional to the value of grain size.

Abstract: Indium Tin Oxide (ITO) is a transparent conducting material. The particular electrical and optical properties of the ITO make it becomes an important material that being applied in optoelectronic filed. In this paper, investigation on various parameters in time of deposition and ITO layer on specimen was done. The AFM (Atomic Force Microscope) was used to investigate grain size on specimen. It shows more layer deposition of ITO, it will increase grain size on the specimen. In addition, grain size on specimen was increased after annealing process compared test specimen before annealing process. Besides that, semiconductor parametric analyser was used to examine resistance on ITO films. The higher value of resistance is showed on test specimen after heat treatment compared to test specimen before heat treatment.

Abstract: We reported a systematic study of the effect of Zr content on the structural and magnetic properties of rapidly quenched Sm (Co_balFe_0.11Cu_0.10Zr_x)₇ alloys with x varying from 0 to 0.04. The results show that the addition of Zr greatly affected the microstructure and magnetic properties of the heat-treated ribbons. The Zr-free ribbon had crystallized as the 1:7H structure as the main phase while the ribbon with Zr addition adopted the 2:17R structure type. A Sm₂Co₇ phase was observed in the heat-treated ribbons when the Zr content x increased to 0.04. It is found that while the Zr content was increased from 0 to 0.04, saturation magnetization of the heat-treated ribbons was decreased from 11.9kGs to 3.3 kGs, and the intrinsic coercivity was increased from 0.07 kOe to 11.7 kOe. The highest intrinsic coercivity, H_ci=11.7 kOe, was obtained in the ribbon with Zr content of 0.03.

Abstract: Thin films CuInSe₂ (CIS) cells have been fabricated by the electro chemical method. Some of the physical properties such as lattice parameter, crystal structure and grain size of CuInSe₂ (CIS) films with different Cu/In ratios ( 0.50-1.1) were determined using X-ray diffractornetry. The surface morphology with different Cu/In ratios was studied using a scanning electron microscope. The SEM studies on these films showed that the grain size increases the Cu/In ratios increases from 0.49 to 1.1. The variation of the band gap with different Cu/In ratio was determined from optical absorption measurements. The results showed that the band gap decreases as the Cu/In ratio increases over the considered range of composition. Key words: Thin films, Lattice Parameter , Optical Absorption, grain size