RESUMEN
While lead sulfide shows notable thermoelectric properties, its production costs remain high, and its mechanical hardness is low, which constrains its commercial viability. Herein, we demonstrate a straightforward and cost-effective method to produce PbS nanocrystals at ambient temperature. By introducing controlled amounts of silver, we achieve p-type conductivity and fine-tune the energy band structure and lattice configuration. Computational results show that silver shifts the Fermi level into the valence band, facilitating band convergence and thereby enhancing the power factor. Besides, excess silver is present as silver sulfide, which effectively diminishes the interface barrier and enhances the Seebeck coefficient. Defects caused by doping, along with dislocations and interfaces, reduce thermal conductivity to 0.49 W m-1 K-1 at 690 K. Moreover, the alterations in crystal structure and chemical composition enhance the PbS mechanical properties. Overall, optimized materials show thermoelectric figures of merit approximately 10-fold higher than that of pristine PbS, alongside an average hardness of 1.08 GPa.
RESUMEN
The microstructure, revealed by X-ray diffraction and transmission Mössbauer spectroscopy, magnetization versus temperature, external magnetizing field induction and mechanical hardness of the as-quenched Fe75Zr4Ti3Cu1B17 amorphous alloy with two refractory metals (Zr, Ti) have been measured. The X-ray diffraction is consistent with the Mössbauer spectra and is characteristic of a single-phase amorphous ferromagnet. The Curie point of the alloy is about 455 K, and the peak value of the isothermal magnetic entropy change, derived from the magnetization versus external magnetizing field induction curves, equals 1.7 J·kg-1·K-1. The refrigerant capacity of this alloy exhibits the linear dependence on the maximum magnetizing induction (Bm) and reaches a value of 110 J·kg-1 at Bm = 2 T. The average value of the instrumental hardness (HVIT) is about 14.5 GPa and is superior to other crystalline Fe-based metallic materials measured under the same conditions. HVIT does not change drastically, and the only statistically acceptable changes are visibly proving the single-phase character of the material.
RESUMEN
Bone loss associated with skeletal trauma or metabolic diseases often requires bone grafting. In such situations, a biomaterial is necessary for migrated cells to produce new tissue. In this study, agarose-chitosan was implanted in the femoral condyle of New Zealand White rabbits that were divided into three groups: Group I was used as control; Groups II and III were used as implanted tissue with agarose-chitosan and presenting empty defects, respectively. This study evaluated the agarose-chitosan biocompatibility by determining the in vivo genotoxicity, oxidative stress balance that correlated with the hardness mechanical property. Moreover, the histopathological and quantitative elements analyzed by using inductively coupled plasma optical emission spectrometry were determined. After 30 days of implantation, the in vivo analysis of genotoxicity showed that agarose-chitosan did not induce chromosome aberration or micronucleus damage. A significant decrease in thiobarbituric and acid-reactive substance was observed after agarose-chitosan implantation in the bone tissue. Superoxide dismutase, catalase and glutathione peroxidase were significantly enhanced in agarose-chitosan-treated group compared with that of control group. A negative correlation coefficient of the mechanical property with malonyldialdehyde level was detected (R = -0.998). The histological study exhibited a significantly increased angiogenesis and newly formed tissue. No presence of inflammatory process, necrotic or fibrous tissue was detected. Major and trace elements such as Ca, P, Zn, Mg and Fe were increased significantly in the newly formed bone. These findings show that agarose-chitosan biomaterial implantation might be effective for treating trauma and bone regeneration.
