Direct demonstration of complete combustion of gas-suspended powder metal fuel combustion using bomb calorimetry

Off-the-shelf calorimeters are typically used for hydrocarbon-based fuels and not designed for simulating metal powder oxidation in gaseous environments. We have developed a method allowing a typical bomb calorimeter to accurately measure heat released during combustion and achieve nearly 100% of the reference heat of combustion from powder fuels such as aluminum. The modification uses a combustible organic dispersant to suspend the fuel particles and promote more complete combustion. The dispersant is a highly porous organic starch-based material (i.e., packing peanut) and allows the powder to burn as discrete particles thereby simulating dust-type combustion environments. The demonstrated closeness of measured Al heat of combustion to its reference value is evidence of complete metal combustion achieved in our experiment. Beyond calorific output under conditions simulating real reactive systems, we demonstrate that the calorimeter also allows characterization of the temporal heat release from the reacting material and this data can be extracted from the instrument. The rate of heat release is an important additional parameter characterizing the combustion process. The experimental approach described will impact future measurements of heat released during combustion from solid fuel powders and enable scientists to quantify the energetic performance of metal fuel more accurately as well as the transient thermal behavior from combusting metal powders.

Production and Characterization of Commercial Aluminum Powders by a New Nozzle Design and Atomization Unit

A large area cross section of the production of spherical metal powders by gas atomization in the manufacturing method. Powder metal characteristic improves with small powder size. This aim was realized by vertical gas atomization unit, a new a closely-matched nozzle system and manufacture. In the experimental studies, pure aluminium powders which has an important place in the automotive, air and defence industries were produced. In the studies carried out with the Vertical Gas Atomization unit, aluminium was superheated up to 900°C and atomized at different gas pressures (20-30 bar). Scanning electron microscope (SEM) and particle size measuring device were used for the characterization and size measurements of the produced powders, respectively. The average particle size of the finest powder produced with increasing atomization pressure was determined as d50=19.50µm. Aluminium powder shape and morphology was used as spherical and very little satellization was seen. Keywords: Powder Metallurgy, Atomisation, Nozzle, Al powder, Characterisation

Spreadability of Metal Powders for Laser-Powder Bed Fusion via Simple Image Processing Steps

This paper investigates the spreadability of the spherical CoCrWMo powder for laser- powder bed fusion (PBF-LB) by using image processing algorithms coded in MATLAB. Besides, it also aims to examine the spreadability dependence with the other characteristics such as powder size distribution, apparent density, angle of repose. Powder blends in four different particle size distributions are prepared, characterized, and spreadability tests are performed with the PBF-LB. The results demonstrate that an increase in fine particle ratio by volume (below 10 µm) enhances the agglomeration and decreases the flowability, causing poor spreadability. These irregularities on the spread layers are quantified with simple illumination invariant analysis. A clear relation between powder spreadability and 3D printed structures properties in terms of residual porosity could not be defined since structural defects in 3D printed parts also depends on other processing parameters such as spatter formation or powder size over layer height ratio.

INVESTIGATION OF THE INTERACTION OF UDP METALS WITH PRODUCTS OF THERMAL DECOMPOSITION OF TETRAZOLE BINDER

В статье приводятся экспериментальные исследования ультрадисперсных металлических порошков алюминия, меди, железа, вольфрама, титана, цинка, никеля, сплавов меди с алюминием, меди с железом и латуни. Описаны термические свойства их смесей с метилполивинилтетразолом, пластифицированным динитратпропиленгликолем; указаны численные величины значимых характеристик.Результаты исследования показали, что существенное количество тепла выделяется при нагреве порошков алюминия, цинка, титана и железа; при нагреве смесей со связующим, наилучшие результаты соответствуют сплаву меди с железом, алюминию и сплаву меди с алюминием. The article presents experimental studies of ultrafine metal powders of aluminum, copper, iron, tungsten, titanium, zinc, nickel, alloys of copper with aluminum, copper with iron and brass. The thermal properties of their mixtures with methyl polyvinyl tetrazole and plasticized propylenglycoldinitrate are described; numerical values of significant characteristics are indicated.The results of the study showed that a significant amount of heat is released when heating aluminum, zinc, titanium and iron powders; when heating mixtures with a binder, the best results correspond to an alloy of copper with iron, aluminum and an alloy of copper with aluminum.

INFLUENCE OF NANODISPERSED METAL POWDERS ON THE COMBUSTION OF ENERGY CONDENSED SYSTEMS BASED ON AMMONIUM NITRATE WITH DIFFERENT TYPE OF POLYMER BINDER

Определены особенности горения энергетических композиций на основе инертного и активного горючих-связующих с нитратом аммония в диапазоне давлений до 10 Мпа. Представлен сравнительный анализ влияния наноразмерных порошков металлов на процесс горения композиций с различными наполнителями: октоген, нитрат аммония, CL-20. Показана эффективность нанопорошков металлов (Cu, Ni, Mo, Al, Zn) и неметалла (B) в качестве катализаторов горения. The features of combustion of energy compositions based on inert and active combustible binders with ammonium nitrate in the pressure range up to 10 MPa have been determined. A comparative analysis of the effect of nanosized metal powders on the combustion process of compositions with various fillers: HMX, ammonium nitrate, CL-20 is presented. The efficiency of metal (Cu, Ni, Mo, Al, Zn) and non-metal (B) nano powders as combustion catalysts is shown.

Development of Ti PVD Films to Limit the Carburization of Metal Powders during SPS Process

Spark plasma sintering technique is used for the fabrication of dense materials with a fine-grained microstructure. In this process, a powder is placed into a graphite mold and a uniaxial pressure is applied by two graphite punches. A graphite foil is inserted between the punches and the powder and between the mold and the powder to ensure good electrical, physical and thermal contact. One of the major drawbacks during sintering of metal powders is the carburization of the powder in contact with the graphite foils. In this study, a PVD coating of titanium was applied on the graphite foils in contact with the metal powder (pure iron). The results are promising, as the investigations show that the application of a Ti PVD film of 1.5 and 1.1 µm thickness is effective to completely avoid the carburization of iron powder. Carbon diffuses inside the PVD film during sintering. In parallel, iron diffusion was revealed inside the Ti coating of 1.5 µm thickness. On the other hand, a Ti PVD film of 0.5 µm thickness provides a protection against carbon diffusion just on the sides in contact with the mold, proving that the coating thickness represents an important parameter to consider.

Operations for the preparation of metal powders for hot isostatic pressing

Powder metallurgy as a method of manufacturing and processing metals is very diverse in its technological methods. This makes it possible to obtain parts of the required quality and necessary properties. Using the methods of powder metallurgy production, specialists can produce the latest composite materials, the production of which is impossible by traditional methods. The production of machine parts and mechanisms from metal powders provides significant savings on material, due to the low consumption coefficient. Metal powders are usually manufactured in specialized factories, but sometimes they are produced directly by the consumer; in this case, the manufacturing process is built in direct accordance with the requirements of this consumer. If the powder comes from a third-party supplier, there is a need for special preparation operations, before starting production, to give the powder certain chemical and physical characteristics. Hot isostatic pressing technology is a complex technological process in which a large number of parameters affect the quality of the final product. The complexity of the GIP process lies in various thermal, physical, and mechanical interactions. In this regard, a large role is played by the processes for preparing the powder for the GIP. The article describes the main operations for the preparation of powder for hot isostatic pressing.

Stimulation of plasma-spark sintering of mixtures of oxide-non-oxide components by adding a solid solution TaB2‒NbC and through a nickel melt in mixtures of metal powders

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