Model Building and Anisotropy of PrFeB Permanent Magnetic Materials

This paper considers that the crystal grains of HDDR Pr2Fe14B permanent magnetic material are cubic, the size is 0.3 μm, and the crystal grains are in simple cubic accumulation. It is considered that there are boundary phases between grains. It is assumed that the boundary phases are non-magnetic phases with the thickness of d, and evenly distributed between grains. The anisotropy expression of single grain boundary is given considering structure defect and intergranular exchange coupling interaction. Based on micro-magnetic simulation calculation, the variation of the average anisotropy of a single grain with the structural defects and boundary phases was calculated. The results show that when the thickness of structural defects is constant, the average anisotropy of a single grain decreases with increasing of grain boundary phase thickness, and while the thickness of grain boundary phase is constant, it also decreases with increasing of structural defect thickness.

Experimental and theoretical investigation of sulfur-doped g-C_(3)N_(4)nanosheets/FeCo_(2)O_(4)nanorods S-scheme heterojunction for photocatalytic H_(2)evolution

g-C_(3)N_(4)emerges as a promising metal-free semiconductor photocatalyst due to its cost-effectiveness,facile synthesis,suitable visible light response,and robust thermal stability.However,its practical application in photocatalytic hydrogen evolution reaction(HER)is impeded by rapid carrier recombination and limited light absorption capacity.In this study,we successfully develop a novel g-C_(3)N_(4)-based step-scheme(S-scheme)heterojunction comprising two-dimensional(2D)sulfur-doped g-C_(3)N_(4)nanosheets(SCN)and one-dimensional(1D)FeCo_(2)O_(4)nanorods(FeCo_(2)O_(4)),demonstrating enhanced photocatalytic HER activity.The engineered SCN/FeCo_(2)O_(4)S-scheme heterojunction features a well-defined 2D/1D heterogeneous interface facilitating directed interfacial electron transfer from FeCo_(2)O_(4)to SCN,driven by the lower Fermi level of SCN compared to FeCo_(2)O_(4).This establishment of electron-interacting 2D/1D S-scheme heterojunction not only facilitates the separation and migration of photogenerated carriers,but also enhances visible-light absorption and mitigates electron-hole pair recombination.Band structure analysis and density functional theory calculations corroborate that the carrier migration in the SCN/FeCo_(2)O_(4)photocatalyst adheres to a typical S-scheme heterojunction mechanism,effectively retaining highly reactive photogenerated electrons.Consequently,the optimized SCN/FeCo_(2)O_(4)heterojunction exhibits a substantially high hydrogen production rate of 6303.5μmol·g^(-1)·h^(-1)under visible light excitation,which is 2.4 times higher than that of the SCN.Furthermore,the conjecture of the S-scheme mechanism is confirmed by in situ XPS measurement.The 2D/1D S-scheme heterojunction established in this study provides valuable insights into the development of high-efficiency carbon-based catalysts for diverse energy conversion and storage applications.

Field-driven merging of polarizations and enhanced electrocaloric effect in BaTiO_(3)-based lead-free ceramics

Solid-state cooling technology based on electrocaloric effect(ECE)has been advanced as an alternative to replace the vapour-compression approach to overcome the releasing of the global warming gases.However,the development in high ECE materials is still a challenge.In this work,polarization merging strategy was proposed to achieve a large ECE in xBa(Sn_(0.07)Ti_(0.93))O_(3)–(1−x)Ba(Hf_(0.1)Ti_(0.9))O_(3) ferroelectric ceramics,where x=0,0.2,0.4,0.6,0.8,and 1.Ba(Sn_(0.07)Ti_(0.93))O_(3) with an orthorhombic phase and Ba(Hf_(0.1)Ti_(0.9))O_(3) with a rhombohedral phase at room temperature were prepared beforehand as precursors,and phase-coexisted xBSnT–(1−x)BHfT ceramics were formed via a solid-state reaction approach.Phase coexisting structures were confirmed using the X-ray diffraction.The merged polarization was confirmed by the dielectric and ferroelectric properties.Optimal ECEs were obtained for 0.2BSnT–0.8BHfT ceramics,i.e.,adiabatic temperature change DT=2.16±0.08 K at 80℃and 5 MV/m,and DT=3.35±0.09 K at 80℃and 7 MV/m.