Sub-millisecond lithiothermal synthesis of graphitic meso-microporous carbon.

Porous carbons with concurrently high specific surface area and electronic conductivity are desirable by virtue of their desirable electron and ion transport ability, but conventional preparing methods suffer from either low yield or inferior quality carbons. Here we developed a lithiothermal approach to bottom-up synthesize highly meso-microporous graphitized carbon (MGC). The preparation can be finished in a few milliseconds by the self-propagating reaction between polytetrafluoroethylene powder and molten lithium (Li) metal, during which instant ultra-high temperature (>3000 K) was produced. This instantaneous carbon vaporization and condensation at ultra-high temperatures and in ultra-short duration enable the MGC to show a highly graphitized and continuously cross-coupled open pore structure. MGC displays superior electrochemical capacitor performance of exceptional power capability and ultralong-term cyclability. The processes used to make this carbon are readily scalable to industrial levels.

Practical Guide to Measuring Wetland Carbon Pools and Fluxes.

Wetlands cover a small portion of the world, but have disproportionate influence on global carbon (C) sequestration, carbon dioxide and methane emissions, and aquatic C fluxes. However, the underlying biogeochemical processes that affect wetland C pools and fluxes are complex and dynamic, making measurements of wetland C challenging. Over decades of research, many observational, experimental, and analytical approaches have been developed to understand and quantify pools and fluxes of wetland C. Sampling approaches range in their representation of wetland C from short to long timeframes and local to landscape spatial scales. This review summarizes common and cutting-edge methodological approaches for quantifying wetland C pools and fluxes. We first define each of the major C pools and fluxes and provide rationale for their importance to wetland C dynamics. For each approach, we clarify what component of wetland C is measured and its spatial and temporal representativeness and constraints. We describe practical considerations for each approach, such as where and when an approach is typically used, who can conduct the measurements (expertise, training requirements), and how approaches are conducted, including considerations on equipment complexity and costs. Finally, we review key covariates and ancillary measurements that enhance the interpretation of findings and facilitate model development. The protocols that we describe to measure soil, water, vegetation, and gases are also relevant for related disciplines such as ecology. Improved quality and consistency of data collection and reporting across studies will help reduce global uncertainties and develop management strategies to use wetlands as nature-based climate solutions. Supplementary Information: The online version contains supplementary material available at 10.1007/s13157-023-01722-2.

Ignition and Combustion Characteristic of B·Mg Alloy Powders.

Boron and its alloys have been explored a lot and it is expected that they can replace pure aluminum powder in the energetic formulation of active materials. MgB2 compounds were prepared and characterized by a combination of mechanical alloying and heat treatment. The ignition and combustion of boron-magnesium alloys were studied with the ignition wire method and laser ignition infrared temperature measurement. The results show that MgB2 has good ignition characteristics with maximum ignition temperatures obtained by the two various methods of 1292 K and 1293 K, respectively. Compared with boron, the ignition temperature of MgB2 is greatly reduced after alloying. The ignition reaction of MgB2 mainly occurs on the surface and the ignition process has two stages. In the initial stage of ignition, the large flame morphology and combustion state are close to the combustion with gaseous Mg, whereas the subsequent combustion process is close to the combustion process of B. Compared with boron, the ignition temperature of MgB2 is greatly reduced which suggests that MgB2 may be used in gunpowder, propellant, explosives, and pyrotechnics due to its improved ignition performance.

Preparation and Characterization of Mg-Al-B Alloy (Mg0.5Al0.5B2) Via High-Temperature Sintering.

Boron and its alloys have long been explored as potential fuel and increasingly replace pure aluminum powder in high-energy formulations. The ignition and burning properties of boron can be improved by making boron alloys. In this study, an Mg-Al-B alloy was synthesized from magnesium, aluminum and boron powders in a 1:1:4 molar ratio by preheating to 600 °C for 30 min, followed by high-temperature sintering in a tube furnace. The effects of sintering temperature (700-1000 °C) and holding time (0.5-10 h) on the phase composition of mixed powders were studied. After the samples were cooled to room temperature, they were ground into powder. The phase composition, micromorphology and the bonding forms of elements of the synthesized samples were studied using XRD, SEM and XPS. The results show that each element exists in the form of simple substance in the alloy. The influence of the sintering temperature on the synthesis reaction of Mg0.5Al0.5B2 is very important, but holding time has little effect on it. With the increase of sintering temperature, the content of the Mg0.5Al0.5B2 phase gradually increases, and the phase content of residual metal gradually decreases. The phase and morphology analyses show that the optimum sintering temperature is 1000 °C with a minimum holding time of 0.5 h. It is expected to be used in gunpowder, propellant, explosives and pyrotechnics with improved characteristics.