International Journal of Self-Propagating High-Temperature Synthesis

Polycrystalline strontium barium niobates Sr x Ba1 − x Nb2O6 (SBN, 0.40 ≤ x ≤ 0.75) were prepared by standard solid state ceramic method at relatively at low temperatures. Thick SBN films prepared by simple, low-cost, screen printing route were characterized by XRD. Preliminary structural analysis exhibits the formation of tetragonal tungsten bronze crystal structure at room temperature. Texture coefficient [TC(hkl)], dislocation density (ρD), density of crystallites per unit surface area (Ψ), mechanical properties, and microwave behavior of synthesized materials are reported.

Polycrystalline Ni-Mn-Al magnetic shape memory (MSM) bulk alloys were produced by SHS from mechanically activated Ni-Mn-Al powder mixtures. The structural properties of products were characterized by XRD, field emission scanning electron microscopy (FESEM), optical microscopy (OM), atomic emission spectroscopy (AES), and energy-dispersive spectroscopy (EDS). The product exhibited soft ferromagnetic and paramagnetic properties.

Cast four-component МАХ compounds (V1–xNbx)2AlC were prepared from V2O5–Nb2O5–Al–C powder mixtures by metallothermic SHS under 5 MPa of Ar and characterized by XRD, SEM/EDS, and video filming. Target product were found to contain (V1–xNbx)2AlC compounds and Al3Nb. Synthesized materials can find their application as structural materials in high-temperature applications in aggressive media.

Phương pháp tổng hợp qua sự cháy trong dung dịch (SCS) là một kỹ thuật chuẩn bị có thể được sử dụng để tổng hợp nhiều loại vật liệu nano vô cơ và chất xúc tác có cấu trúc. Nó dựa trên phản ứng oxi hóa khử tỏa nhiệt tự phát giữa các muối hữu cơ và một chất nhiên liệu được trộn lẫn trong dung dịch nước, dẫn đến việc hình thành các vật liệu nano tinh thể và rắn có độ tinh khiết cao. SCS có thể được coi là một phương pháp tổng hợp hấp dẫn cho các chất xúc tác nhờ vào bản chất đơn giản của quy trình tổng hợp và thời gian phản ứng ngắn. Quá trình này dễ dàng mở rộng cho bất kỳ loại ứng dụng nào, điều này làm cho nó trở nên hấp dẫn về mặt kinh tế. Bài tổng quan ngắn này cung cấp một cái nhìn tổng quan về việc tổng hợp các chất xúc tác có cấu trúc qua SCS và sự ứng dụng gần đây của chúng trong các ứng dụng năng lượng và kiểm soát ô nhiễm.

History of the involvement of our laboratory in SHS research and characterization of the main ideas of this research focused on developing advanced methods of powder synthesis for macro-and nanotechnologies with the use of SHS are overviewed. By the low cost of installations and simplicity of the process, SHS over-shadows most advanced methods of synthesis and has the potential to be developed into large scale production. The mechanism of SHS reactions often differs from that of reactions at lower temperatures and due to this the particulate SHS products may have properties valuable for some specific applications. A more detailed illustration of these problems is presented for SHS-derived powders of compounds, such as SiC and Ti3SiC2, which have unique properties and applications.

Cast silicides of molybdenum, tungsten, and niobium were prepared by combustion synthesis under nitrogen pressure from powder mixtures of respective metal oxides with Al and Si. Upon variation in green composition, cast MoSi2, WSi2, NbSi2, and their solid solutions with variable phase composition have been synthesized. NbSi2 was obtained by combustion in the presence of added heat-generating CaO2-Al powder mixture.

Discussed is the influence of the fuel and water employed in combustion synthesis of single-phase (perovskite) PZN-10PT nanopowder with an x = 0.10 composition. Pb(NO3)2, Zn(NO3)2 · 6H2O, (NH4NbO(C2O4)2), and C8H20O4Ti were used as cation precursors while urea, glycine, glycine/urea (50/50 ratio), and tetraformal triazine (TFTA), as fuels. Two sets of precursors (denoted as set-1 and set-2) were used with each of these fuels, and four different fuels: without and with the addition of 250 mL of water. The results indicated that the highest percentage of perovskite phase in the PZN-10PT nanopowders was obtained using an urea/glycine mixture as a fuel. When the urea/glycine mixture was added to the solution containing cations precursors, the two fuels form a gel in aqueous solution, this gel contributes not only to obtain homogeneously mixed in the starting material but also aids explosive combustion leading to a high-temperature reaction within a shorter period of time, which is a condition that favors the formation of metastable PZN-10PT nanopowders.