Microstructure and giant baro-caloric effect induced by low pressure in Heusler Co_(51)Fe_(1)V_(33)Ga_(15) alloy undergoing martensitic transformation

Solid-state refrigeration based on the magneto-or mechano-caloric effect,including elasto-and barocaloric in ferroic phase transition materials is promising to replace the current vapor compression refrigeration in consideration of environmental-friendliness and energy-saving.However,both high driven field and small thermal changes in all of these caloric materials hinder the development of solid-state refrigeration.Here we report a giant baro-caloric effect near room temperature induced by a low hydrostatic pressure in Co-based Co_(51)Fe_(1) V_(33)Ga_(15) Heusler alloy.The maximum adiabatic temperature change under the applied pressure change ofΔp=0.1-100 MPa can be as high asΔ_(Tad)^(Max)=7.7 K(Δ_(Tad)^(Max)/Δpreaches up to~7.7 K kbar-1),surpassing theΔ_(Tad)^(Max)/Δpvalue reported hitherto in baro-caloric alloys.In addition,the microstructure is also studied by using the electron microscopes.Along with the austenite and martensite,the submicron V-rich particles are precipitated in this alloy,which are believed to account for enhancing mechanical properties.

Removal of Cs＋ from water and soil by ammonium-pillared montmorillonite/Fe3O4 composite

To remove cesium ions from water and soil, a novel adsorbent was synthesized by following a one-step co-precipitation method and using non-toxic raw materials. By combining ammonium-pillared montmorillonite （MMT） and magnetic nanoparticles （Fe304）, an MMT/ Fe304 composite was prepared and characterized. The adsorbent exhibited high selectivity of Cs＊ and could be rapidly separated from the mixed solution under an external magnetic field. Above all, the adsorbent had high removal efficiency in cesium-contaminated samples （water and soil） and also showed good recycling performance, indicating that the MMT/Fe304 composite could be widely applied to the remediation of cesium-contaminated environments. It was observed that the pH, solid/liquid ratio and initial concentration affected adsorption capacity. In the presence of coexisting ions, the adsorption capacity decreased in the order of Ca2 〉 M 〉 IC 〉 Na＋, which is consistent with our theoretical prediction. The adsorption behavior of this new adsorbent could be expressed by the pseudo-second-order model and Freundlich isotherm. In addition, the adsorption mecha- nism of Cs was NH4 ion exchange and surface hydroxyl group coordination, with the former being more predominant.

Large magnetocaloric effect and magnetoresistance in ErNi single crystal

The magnetic properties,magnetocaloric effect and magnetoresistance in Er Ni single crystal have been investigated in detail.With decreasing temperature,Er Ni single crystal undergoes two successive magnetic transitions:a paramagnetic to ferromagnetic transition at T_(C)=11 K and a spin-reorientation transition at TS_(R)=5 K.Meanwhile,a sharp field-induced metamagnetic transition is observed below the T_(C)along the a axis.Er Ni single crystal possesses a giant magnetocaloric effect around T_(C).The maximum magnetic entropy change is-36.1 J(kg K)^(-1)along the a axis under the field change of 0-50 k Oe.In particular,the rotating magnetocaloric effect in Er Ni single crystal reaches its maximum under a relatively low field,and the maximum rotating entropy change with a value of 9.3 J(kg K)^(-1)is obtained by rotating the applied field from the[011]to[100]directions under 13 k Oe.These results suggest that Er Ni could be a promising candidate for magnetic refrigeration working at liquid-helium temperature region.Moreover,a complicated transport behavior is uncovered in Er Ni single crystal,which is attributed to the complex magnetic states and magnetic polaronic effect.Both positive and negative magnetoresistance are observed.A considerable large magnetoresistance with the value of-34.5%is acquired at 8 K under50 k Oe when the field is along the[100]direction.