Core/Shell Nanoparticles: Classes, Properties, Synthesis Mechanisms, Characterization, and Applications

Differential scanning calorimetry (DSC) and isothermal calorimetry have been applied extensively to the analysis of light metals, especially Al based alloys. Isothermal calorimetry and differential scanning calorimetry are used for analysis of solid state reactions, such as precipitation, homogenisation, devitrivication and recrystallisation; and solid–liquid reactions, such as incipient melting and solidification, are studied by differential scanning calorimetry. In producing repeatable calorimetry data on Al alloys, sample preparation, reproducibility and baseline drift need to be considered in detail. Calorimetry can be used effectively to study the different solid state reactions and solid–liquid reactions that occur during the main processing steps of Al based alloys (solidification, homogenisation, precipitation). Also, devitrivication of amorphous and ultrafine grained Al based powders and flakes can be studied effectively. Quantitative analysis of the kinetics of reactions is assessed through reviewing the interrelation between activation energy analysis methods, equivalent time approaches, impingement parameter approaches, mean field models for precipitation, the Johnson–Mehl–Avrami–Kolmogorov model, as well as novel models which have not yet found application in calorimetry. Differential scanning calorimetry has occasionally been used in attempts to measure the volume fractions of phases present in Al based alloys, and attempts at determining volume fractions of intermetallic phases in commercial alloys and amounts of devitrified phase in glasses are reviewed. The requirements for the validity of these quantitative applications are also reviewed.

/pdf/analysis-of-aluminium-based-alloys-by-calorimetry-1479axcy9w.pdf

Analysis of aluminium based alloys by calorimetry: quantitative analysis of reactions and reaction kinetics

Aluminum is examined as energy storage and carrier. To provide the correct feasibility study the work includes the analysis of aluminum production process: from ore to metal. During this analysis the material and energy balances are considered. Total efficiency of aluminum-based energy storage is evaluated. Aluminum based energy generation technologies are reviewed. Technologies are categorized by aluminum oxidation method. Particularly, the work focuses on direct electrochemical (anodic) oxidation of aluminum, aluminum–water reaction in alkaline solution, mechanochemical activation of aluminum, mechanical activation of aluminum and high-temperature aluminum–water reaction. The objective is methods overview including technological principle, efficiency, urgent problems and possible application areas.

Aluminum as energy carrier: Feasibility analysis and current technologies overview

Understanding how microorganisms influence the physical and chemical properties of the subsurface is hindered by our inability to observe microbial dynamics in real time and with high spatial resol...

Geophysical imaging of stimulated microbial biomineralization.

Spark plasma sintering of TiNi nano-powder

Synthesis of intermetallic NiAl by SHS reaction using coarse-grained nickel and ultrafine-grained aluminum produced by wire electrical explosion

By using aluminium nanopowder prepared by wire electrical explosion, pure monophase NiAl compound with fine crystallites (≤10μm) and good densification (98% of the theoretical green density) was successfully fabricated by means of self-propagating high-temperature synthesis (SHS) under a high pressure of 50 MPa. Investigation shows that, due to the physical and chemical characteristics of the nanoparticles, the SHS reaction mode and mechanism are distinct from those when using conventional coarse-grained reactants. The SHS reaction process depends on the thermal conditions related to pressure and can occur at a dramatically low temperature of 308oC, which cannot be expected in conventional SHS reaction. With increasing pressure, the SHS explosive ignition temperature (Tig) of forming NiAl decreases due to thermal and kinetic effects.

https://iopscience.iop.org/article/10.1088/0953-8984/14/44/421/pdf

Fabrication of intermetallic NiAl by self-propagating high-temperature synthesis reaction using aluminium nanopowder under high pressure

An in situ energy dispersive x-ray diffraction study on nanocrystalline ZnS was carried out under high pressure up to 30.8 GPa by using a diamond anvil cell. The phase transition from the wurtzite to the zinc-blende structure occurred at 11.5 GPa, and another obvious transition to a new phase with rock-salt structure also appeared at 16.0 GPa-which was higher than the value for the bulk material. The bulk modulus and the pressure derivative of nanocrystalline ZnS were derived by fitting the Birch-Murnaghan equation. The resulting modulus was higher than that of the corresponding bulk material, indicating that the nanomaterial has higher hardness than the bulk material.

An investigation on the pressure-induced phase transition of nanocrystalline ZnS

Thermal characteristic of ultrafine-grained aluminum produced by wire electrical explosion

In situ high-pressure energy-dispersive x-ray diffraction measurements on α-LiIO3 have been performed by using a diamond anvil cell device with synchrotron radiation up to 75 GPa at room temperature. No new phase was found. The second Birch–Murnaghan equation of state is fitted with B0 = 55 ± 3 GPa for the zero-pressure bulk modulus, B0 ' = 2.9 ± 0.4 for its pressure derivative.

Shushan Dong

Papers

Synthesis of intermetallic NiAl by SHS reaction using coarse-grained nickel and ultrafine-grained aluminum produced by wire electrical explosion

Fabrication of intermetallic NiAl by self-propagating high-temperature synthesis reaction using aluminium nanopowder under high pressure

An investigation on the pressure-induced phase transition of nanocrystalline ZnS

Thermal characteristic of ultrafine-grained aluminum produced by wire electrical explosion

High-pressure x-ray diffraction study of LiIO3 to 75 GPa