Topological Anderson Insulator in Cation-Disordered Cu2ZnSnS4

We present the first candidate for the realization of a disorder-induced Topological Anderson Insulator in a real material system. High-energy reactive mechanical alloying produces a polymorph of Cu2ZnSnS4 with high cation disorder. Density functional theory calculations show an inverted ordering of bands at the Brillouin zone center for this polymorph, which is in contrast to its ordered phase. Adiabatic continuity arguments establish that this disordered Cu2ZnSnS4 can be connected to the closely related Cu2ZnSnSe4, which was previously predicted to be a 3D topological insulator, while band structure calculations with a slab geometry reveal the presence of robust surface states. This evidence makes a strong case in favor of a novel topological phase. As such, the study opens up a window to understanding and potentially exploiting topological behavior in a rich class of easily-synthesized multinary, disordered compounds.

The Influence of Complex Doping on Kinetics of Decomposition and Thermal Stability of Mg-Based Mechanical Alloys

Mechanical alloys (MАs) were synthesized by the method of reactive mechanical alloying. At a hydrogen pressure of 0.1 MPa, with the use of thermal desorption spectroscopy, the thermal stability, the kinetics of hydrogen desorption from the hydride phase MgH2 of the obtained MAs were studied. It has been established that the complex doping by of Fe, Si, Ti, leads to a significant improvement in the of hydrogen desorption from the hydride phase MgH2 of MA synthesized by the RMA. Hydrogen capacity CH of MА after reactive grinding for 20 h. was found to be equal to 5.7 % wt. Due to this alloying, the decrease in the thermodynamic stability of MgH2 is not established. The tested materials showed a high potential as hydrogen storage alloys especially for stationary application.

Pengaruh Temperatur Aniling Material Mgalti Terhadap Media Penyimpan Hidrogen

Hidrogen merupakan salah satu sumber energi alternatif di masa depan. Penyimpanan Hidrogen dalam bentuk solid state memiliki keunggulan daripada penyimpanan dalam bentuk gas dan cair. Penelitian ini dilakukan untuk mempelajari pengaruh material MgAlTi dan temperatur aniling material (MgAlTi) hasil preparasi reactive mechanical alloying (RMA) terhadap sifat media penyimpan hidrogen. Penambahan paduan logam Al dan Ti pada paduan logam Mg dilakukan untuk memperbaiki sifat serapan Mg. Penelitian dilakukan dengan memadukan material Mg, Al dan Ti dengan komposisi berat berturut-turut 85, 15 dan 5 %. Ketiga logam dipadukan dengan teknik RMA. Persiapan pemaduan dilakukan dalam glove box yang dialiri gas argon untuk memastikan pengerjaan teknik RMA dalam keadaan inert. Pemaduan teknik RMA dilakukan selama 10 jam dengan dialiri gas Hidrogen. Selanjutnya, paduan Mg85Al15+Ti5 di anil dengan variasi temperatur pemanasan 300; 340; dan 380 °C. Karakterisasi struktur kristal, mikro dan termal uji diobservasi dengan menggunakan X-Ray Difraction, SEM-EDX dan Differential Scanning Calorimetry (DSC). Hasil analisis struktur kristal dan mikro sesudah di aniling menjadi homogen dan hasil ini menunjukkan bahwa temperatur optimum material penyimpan hidrogen terjadi pada temperatur 300 °C. Aktifitas katalis terhadap disosiasi ikatan Mg-H2 dapat menentukan penurunan temperatur desorpsi dibandingkan pengaruh temperatur aniling. Pemaduan teknik RMA pada paduan logam MgAlTi dapat meningkatkan sifat-sifat penyimpanan hidrogen. Hydrogen is an alternative energy source and it has advantages to storage the element in form of solid state compare gas and liquid. The study was conducted to analyse the effect of MgAlTi in aniling temperature used reactive mechanical alloying (RMA) for hydrogen storage. The experimental was carried out to improve the absorption Mg by combination of Mg, Al and Ti materials with 85, 15 and 5% weight composition. The preparation is carried out in the glove box which is flowed with argon gas to ensure the work of the RMA technique in an inert state. The RMA techniques is carried out for 10 hours with Hydrogen gas flowing. Thus, the Mg85Al15 + Ti5 alloy is annealed with a heating temperature variation of 300; 340; and 380 °C. Characterization of crystal structure, micro and thermal tests were observed using X-Ray Difraction, SEM-EDX and Differential Scanning Calorimetry (DSC). The results of analysis of the crystal and micro structures after aniling become homogeneous and this shows that the optimum temperature of the hydrogen storage material occurs at a temperature of 300 °C. Moreover, the catalyst activity against dissociation of Mg-H2 bonds can determine the decrease in desorption temperature compared to the effect of aniling temperature. The integration of RMA techniques in MgAlTi metal alloys can improve hydrogen storage.

Pengamatan In-Situ Tekanan dan Temperatur pada Pembentukan MgH2/Ni melalui Metode Reactive Mechanical Alloying (RMA) untuk Aplikasi Material Penyimpan Hidrogen

<p>The observation on reactive mechanical alloying (RMA) process had been done to form MgH2 material with adding Ni nanoparticles as catalist for hydrogen storage material applications. Pressure and temperature of material forming were recorded by microcontroller set for 30 minutes. Mg with adding Ni 5 wt % was milled by High Energy Ball Mill (HEBM) at H2 atmosphere in 1 atm of pressure. The measurement results showed that the pressure had been changed and temperature also changes up to 38oC. This process proves that the alloying betwen Mg and H2 had been formed. The X-ray diffraction pattern identify MgH2 phase. SEM image showed the morphology of MgH2 particles.</p>