The effect of Co, Pd and Pt ultrathin films on the kinetics of the formation of Ni-silicide by reactive diffusion is investigated. 50 nm Ni/1 nm X/ 50 nm Ni (X?=?Co, Pd, Pt) deposited on Si(100) substrates are studied using in-situ and ex-situ measurements by X-ray diffraction (XRD). The presence of Co, Pd or Pt thin films in between the Ni layers delays the formation of the metal rich phase compared to the pure Ni/Si system and thus these films act as diffusion barriers. A simultaneous silicide formation (δ-Ni2Si and NiSi phases) different from the classic sequential formation is found during the consumption of the top Ni layer for which Ni has to diffuse through the barrier. A model for the simultaneous growth in the presence of a barrier is developed, and simulation of the kinetics measured by XRD is used to determine the permeability of the different barriers. Atom probe tomography (APT) of the Ni/Pd/Ni system shows that the Pd layer is located between the Ni top layer and δ-Ni2Si during the silicide growth, in accordance with a silicide formation controlled by Ni diffusion through the Pd layer. The effect of the barrier on the silicide formation and properties is discussed.
Thermal energy storage (TES) materials constituted by a microencapsulated paraffin having a melting temperature of 6°C and a thermoplastic polyurethane (TPU) matrix were prepared through fused deposition modeling. Scanning electron microscope (SEM) micrographs demonstrated that the microcapsules were homogeneously distributed within the matrix, with a rather good adhesion within the layers of 3D printed specimens, even at elevated concentrations of microcapsules. The presence of paraffin capsules having a rigid polymer shell lead to a stiffness increase, associated to a decrease in the stress and in the strain at break. Tensile and compressive low-cycles fatigue tests showed that the presence of microcapsules negatively affected the fatigue resistance of the samples, and that the main part of the damage occurred in the first fatigue cycles. After the first 10 loading cycles at 50% of the stress at break, a decrease in the elastic modulus ranging from 60% for neat TPU to 80% for composite materials was detected. This decrease reached 40% of the original value at 90% of the stress at break after 10 cycles. Differential scanning calorimetry tests on specimens after fatigue loading highlighted a substantial retention of the original TES capability, in the range of 80%–90% of the pristine value, even after 1000 cycles, indicating that the integrity of the capsules was maintained and that the propagation of damage during fatigue tests took probably place within the surrounding polymer matrix. It could be therefore concluded that it is possible to apply the developed blends in applications where the materials are subjected to cyclic stresses, both in tensile and compressive mode. 相似文献
In high-speed rolling element bearings, the drag forces can be prominent and it is demonstrated in this investigation that the classical models may not be appropriate for correctly estimating this power loss contribution. A modification of the models is thus proposed, including the usual drag forces formulation relying upon the drag coefficient to be evaluated from a numerical computational fluid dynamics (CFD) approach. A three-dimensional approach that considers both the rings and the cylinder ends seems the only adequate approach to be used because a two-dimensional approach predicts a drag coefficient value that is too low. When using the former computed drag coefficient for the evaluation of the total power losses, high values of oil volume fraction must be employed to recover the measured power losses. 相似文献
Controlling the electromechanical response of piezoelectric biological structures including tissues, peptides, and amino acids provides new applications for biocompatible, sustainable materials in electronics and medicine. Here, the piezoelectric effect is revealed in another class of biological materials, with robust longitudinal and shear piezoelectricity measured in single crystals of the transmembrane protein ba3 cytochrome c oxidase from Thermus thermophilus. The experimental findings from piezoresponse force microscopy are substantiated using a range of control measurements and molecular models. The observed longitudinal and shear piezoelectric responses of ≈ 2 and 8 pm V−1, respectively, are comparable to or exceed the performance of commonly used inorganic piezoelectric materials including quartz, aluminum nitride, and zinc oxide. This suggests that transmembrane proteins may provide, in addition to physiological energy transduction, technologically useful piezoelectric material derived entirely from nature. Membrane proteins could extend the range of rationally designed biopiezoelectric materials far beyond the minimalistic peptide motifs currently used in miniaturized energy harvesters, and the finding of robust piezoelectric response in a transmembrane protein also raises fundamental questions regarding the molecular evolution, activation, and role of regulatory proteins in the cellular nanomachinery, indicating that piezoelectricity might be important for fundamental physiological processes. 相似文献
Ru(II) polypyridyl complexes are compounds of great interest in cancer therapy due to their unique photophysical, photochemical, and biological properties. For effective treatment, they must be able to penetrate tumor cells effectively and selectively. The development of nanoscale carriers capable of delivering Ru(II) polypyridyl complexes has the potential to passively or selectively enhance their cellular uptake in tumor cells. Many different strategies have been explored to incorporate Ru(II) polypyridyl complexes into a variety of nanosized constructs, ranging from organic to inorganic materials. Herein, recent developments in nanomaterials loaded with Ru(II) polypyridyl complexes are highlighted. Their rational design, preparation, and physicochemical properties are described, and their potential applications in cancer therapy are eventually discussed. 相似文献
In this study, the accumulation of GABA and its inherent factors across different varieties of mung bean (Vigna radiata L.) in response to heat and relative humidity (HRH) were investigated. Results showed the average GABA content in mung bean varieties was increased 7.52 times following HRH treatment, and the black mung bean variety (A8) exhibited the highest GABA accumulation capability (1.76–84.57 mg per 100 g DW). From the perspective of GABA shunt metabolites, the free glutamic acid content of mung beans significantly decreased (P < 0.05) after HRH treatment and presented a significant correlation (P < 0.05) with GABA content. In polyamine degradation pathway, although the average levels of spermine and spermidine of mung bean varieties significantly decreased (P < 0.05) after HRH treatment, no significant correlation with GABA content was identified. Hence, the GABA accumulation was predominantly attributed to GABA shunt. Besides, free amino acids including glutamic acid, serine, ornithine, arginine and glycine in mung beans showed a significant positive correlation (P < 0.05) with GABA content and increment following HRH treatment, which suggested that mung beans enriched in these free amino acids might accumulate higher amounts of GABA after HRH treatment and be useful for industrial applications. 相似文献
The International Journal of Advanced Manufacturing Technology - This paper presents an hybrid numerical/analytical modeling for estimation of cutting forces in machining process. The approach... 相似文献
Magnetic Resonance Materials in Physics, Biology and Medicine - Quantitative analysis in MRI is challenging due to variabilities in intensity distributions across patients, acquisitions and... 相似文献