影响水合法制备阻燃剂氢氧化镁的主要因素

从反应机理入手,本论文对水合法制备阻燃级氢氧化镁进行了研究和探讨,找到了导致水合法制备氢氧化镁纯度低、反应时间长原因所在,并确定改进方法。在氧化镁水化阶段,增加氧化镁的活性,降低反应的活化能;或升高反应温度与增加搅拌速度,增加反应分子能量,均可增加反应速度。在氢氧化镁结晶阶段,由于非均匀成核占主导地位,新生成的氢氧化镁包裹在氧化镁颗粒表面阻止氧化镁与水继续反应。使用高剪接乳化剂可以有效的阻止氢氧化镁在氧化镁表面的结晶。

服装中的有害物质及防护

本文从服装的作用分析入手,介绍了服装中常见的有害物质,提出了有害物质对人体的危害及防护措施。

Investigation of Cathode Catalysts for Intermediate-temperature H2S-Air Fuel Cells

Abstract Cathode catalysts comprising composite NiO, NiO-Pt, or LiNiO2 have been developed for electro- chemical oxidation of hydrogen sulfide in intermediate-temperature solid oxide fuel cells （ITSOFCs）. All catalysts exhibited good electrical conductivity and catalytic activity at operating temperature. Composite NiO catalysts were found to be more active and have lower over potential and higller current density than pure Pt although the electrical conductivity of NiO itself is lower than that of Pt. This problem has been overcome by either admixing as high as 10% （by mass）Ag powder into NiO_ cathode layer or using composite NiO c atalysts such as NiO-Pt and LiNiO2 catalysts. Composite catalysts like NiO with Ag, electrolyte and starch admixed, NiO-Pt, which was prepared from a mixture of NiO and Pt powders, by admixing electrolyte and starch, and LiNiO2, which is derived from the reaction of LiOH-H2O and NiO with electrolyte and starch admix_ed have been shown to be feasible and effective in an intermediate-temperature H2S-air fuel cell. A fuel cell using Li2SO4-based proton-conducting membrane as electrolyte, metal sulfides as anode catalysts, and composite NiO as cathode catalysts produced a maximum current density about 300mA·cm^-2 and maximum power density over 80 mW-cm-2 at 680℃.

An Intermediate-temperature H_2S Fuel Cell with a Li_2SO_4-based Proton-conducting Membrane

A laboratory-scale intermediate-temperature H2S fuel cell with a configuration of H2S, (metal sulfide-based composite anode)/Li2SO4+Al2O3/(NiO-based composite cathode), air was developed and studied for production of power and for desulfurization of a fuel gas process stream. The cell was run at typical temperature (600—650℃) and ambient pressure, but its electrochemical performance may be limited by electrolyte membrane thickness. The membrane and its performance in cell have been characterized using scanning electron microscope (SEM) and electrochemical impedance spectrum (EIS) techniques. Composite anodes based on metal sulfides, Ag powder and electrolyte behaved well and stably in H2S stream, and composite cathodes based mainly on nickel oxide, Ag powder and electrolyte had superior per-formance to Pt catalyst. The maximum power density of up to 70mW?cm-2 and current density of as high as 250mA?cm-2 were obtained at 650℃. However, the long-term cell stability remains to be investigated.

Mass production of high-performance single atomic FeNC electrocatalysts via sequenced ultrasonic atomization and pyrolysis process

Mass production of highly efficient,durable,and inexpensive single atomic catalysts is currently the major challenge associated with the oxygen reduction reaction(ORR)for fuel cells.In this study,we develop a general strategy that uses a simple ultrasonic atomization coupling with pyrolysis and calcination process to synthesize single atomic FeNC catalysts(FeNC SACs)at large scale.The microstructure characterizations confirm that the active centers root in the single atomic Fe sites chelating to the four-fold pyridinic N atoms.The identified specific Fe active sites with the variable valence states facilitate the transfer of electrons,endowing the FeNC SACs with excellent electrochemical ORR activity.The FeNC SACs were used as cathode catalysts in a homemade Zn-air battery,giving an open-circuit voltage(OCV)of 1.43 V,which is substantially higher than that of commercial Pt/C catalysts.This study provides a simple approach to the synthesis of single atomic catalysts at large scale.