Influence of sintering temperature on the thermoelectric properties of Ba_8Ga_(16)Si_(30) clathrate treated by spark plasma sintering

A series of Ba8Ga16Si30 clathrate samples were prepared by arc melting, ball milling, acid washing, and spark plasma sintering （SPS）. X-ray diffraction analysis revealed that the lattice of the Ba8Ga16Si30 samples expanded as the SPS temperature was increased from 400 to 750℃. Lattice contraction recurred when the SPS temperature was further increased in the range of 750-1000℃. This phenomenon can be explained by the variation of Ga content in the lattice. The thermoelectric figure of the merit ZT value of clathrates increased with the increase in SPS temperature and reached a maximum when the sample was subjected to SPS at 800℃. A further increase in SPS temperature did not contribute to the improvement of ZT. The variation of the lattice parameter a vs. SPS temperature T was similar to the variation ob-served in the ZT-T curve.

Hypoparathyroidism with Fahr’s syndrome: A case report and review of the literature

BACKGROUND Hypoparathyroidism with basal ganglia calcification is clinically rare.Here,we report a case of Fahr’s syndrome due to hypoparathyroidism and review the literature in terms of etiology,clinical manifestation,diagnosis,and treatment.CASE SUMMARY A 62-year-old man experienced repeated twitching of both hands in recent 10 years.On July 28,2017,the patient was admitted to our hospital due to slow response and speech difficulties.On medical examinations,he had a positive Chvostek sign,while no Albright’s hereditary osteodystrophy signs or history of neck surgery or radiation,and his family members had no similar medical history.Laboratory examinations revealed hypocalcemia,hyperphosphatemia,and low parathyroid hormone(PTH)levels.Computed tomography revealed basal ganglia calcification.Based on these investigations,a diagnosis of Fahr’s syndrome due to hypoparathyroidism was suggested.After receiving intravenous calcium gluconate to relieve symptoms,the patient continued to take oral calcium carbonate and calcitriol for treatment.CONCLUSION The possibility of hypoparathyroidism should be considered in patients with chronic hypocalcemia,recurrent tetany,and even neuropsychiatric symptoms.Hypoparathyroidism is a common cause of basal ganglia calcification.Therefore,it is recommended that blood calcium,phosphorus,and PTH levels should be measured in all individuals with basal ganglia calcification to exclude hypoparathyroidism.

Martensitic transformation and magnetic properties in Mn_(49-x)Cu_(x)Ni_(41)Sn_(10)(x=0-2)

The crystal structure,phase transition,metamagnetic behavior and magnetic entropy change(ΔS_(M))of the Mn_(49-x)Cu_(x)Ni_(41)Sn_(10)(x=0-2)alloys were systematically studied.The results of experiment about crystal structure confirm that Mr_(49-x)Cu_(x)Ni_(41)Sn_(10)alloys have a highly ordered cubic L2_(1)Heusler structure.With Cu element improving,all samples have a martensitic transformation and inverse martensitic transformation by analyzing the result of magnetic measurement.The saturation magnetization of samples decreases gradually,the martensitic transformation temperature(T_(M))of as-annealed samples increases to a high-temperature area,and the Curie temperature(T_(C))of samples moves to a low-temperature area with the content of Cu element increasing from x=0 to x=2.The positive values of magnetic entropy change(ΔS_(M))of all alloys were investigated near the martensitic transformation.When the applied magnetic field is 3 T,a worthwhile value ofΔS_(M)can reach up to 32.0 J·kg^(-1)·K^(-1)in Mn_(47)Cu_(2)Ni_(41)Sn_(10)alloy.

Recent progress in Heusler-type magnetic shape memory alloys

Magnetic shape memory alloys(MSMAs), both in condensed matter physics and in material science, are one of the most extensive research subjects. They show prompt response to the external magnetic field and give rise to large strain and have fine reversibility. The well-known example is Heusler-type MSMAs, which possess excellent multifunctional properties and have potential applications in energy transducer, actuator, sensor, microelectromechanical system, and magnetic refrigerator. In this paper, it is shown the recent progress in magnetostructural transformation, magnetic properties, shape deformation, magnetocaloric effect as well as magnetic field-induced shape memory effect in Ni–Mn–Ga, Ni Mn Z(Z = In, Sn, Sb),and Ni Co Mn Z(Z = In, Sn, Sb, Al) Heusler-type MSMAs.The remaining issues and possible challenges are briefly discussed.