Gas Extrusion Research Articles

Examining 1,4,2‐Dioxazol‐5‐One as an Alternative Reagent to Acyl Azides in the Staudinger Reaction

AbstractIn this study, we explore 1,4,2‐dioxazol‐5‐one as an alternative reagent to acyl azides in the Staudinger reaction, providing a safe and efficient method for synthesizing N‐acyliminophosphoranes under metal‐free conditions. This approach involves a heat‐promoted nucleophilic attack of phosphines on 1,4,2‐dioxazol‐5‐ones, followed by the extrusion of CO2 gas, resulting in the formation of the P−N coupling product. The synthetic utility of this metal‐free imidization of phosphine was demonstrated through a gram‐scale reaction and its suitability for subsequent transformations. Density functional theory (DFT) calculations were employed to elucidate the overall reaction pathway leading to the formation of N‐acyliminophosphoranes.

Mechanical Properties of Composite Rods Produced by Hot Gas Extrusion of the Nickel and Aluminum Powder Mixtures in a Steel Shell

Mechanical Properties of Composite Rods Produced by Hot Gas Extrusion of the Nickel and Aluminum Powder Mixtures in a Steel Shell

New insights into dynamic disaster monitoring through asynchronous deformation induced coal-gas outburst mechanism of tectonic and raw coal seams

The coalbed methane energy resources waste, environmental pollution and miner's health remain challenging problems in worldwide mining operations accompanied by coal-gas outbursts; thus, the safe and efficient yield of these resources plays a vital role in the world's energy market. The tectonic coal development is a significant geological feature of coal and gas outburst sites, and the study of coal and gas outburst mechanism should be based on more precise geological occurrence characteristics. In this paper, the geological characteristics of coal and gas outburst sites were analyzed. The failure law of coal body under the stratified occurrence of tectonic coal and raw coal seam with different thickness was studied. The mechanical equilibrium equation of non-synchronous deformation of tectonic coal and raw coal was constructed, the initiation criterion of coal and gas outburst was established based on the support body model, and a case study was carried out. The results show that with the thickness increase of the tectonic coal seam, the peak displacement of the driving face increases. The outburst start-up and development of coal and gas outburst, coal and gas extrusion outburst and coal and gas collapse outburst were deeply analyzed, as well as the internal reasons of the occurrence of coal-gas outburst portent are explained, based on the support body model. The development process from the start to the end of coal and gas outburst is revealed, and a new perspective is proposed for the prevention and control of coal and gas outburst: improving the strength of support body is also of great significance for the prevention and control of coal and gas outburst.

3D-printed piezoelectric scaffolds composed of uniform core-shell structured BaTiO3@ bioactive glasses particles for bone regeneration

The piezoelectric property and biocompatibility of barium titanate (BTO) is exceptional, whereas its biological activity is limited. Bioactive glasses (BG) are widely recognized for osteoinductive bioactivities. Hence, it is meaningful to explore the reasonable design of BTO and BG combinations to achieve bioactive piezoelectric tissue engineering scaffolds that mimic natural bone. In this study, homogeneous core-shell particles of BTO wrapped in BG layer were firstly fabricated via a sol-gel process. Various BG weight ratios (5 wt%, 10 wt%, and 15 wt%) in BTO@BG particles have been able to achieve the shell thickness in the range of 4 nm–16 nm. Furthermore, the composite particles were three-dimensionally printed into porous scaffolds through gas extrusion using polyvinyl pyrrolidone as binders. The composite scaffolds have been extensively characterized with respect to their physical and functional properties. Desirable piezoelectric scaffolds (BTO@15BG-S) with compressive strength at ∼66 MPa, and piezoelectric constant (d33) of ∼1.1 pC/N were obtained after sintering and polarization. Our findings indicated that higher sintering temperatures led to denser scaffolds with reduced porosity, increased compressive strength and higher d33 constant. Additionally, an increase in the amount of BG coating promoted scaffold calcination via melt filling in pores, while reduced the piezoelectric constant d33. Among all scaffolds, BTO@15BG-S exhibited superior ability to induce apatite formation when sintered at 1250 °C and soaked in simulated body fluid for 7 days. In vitro culture rat bone marrow mesenchymal stem cells (rBMSCs) and cellular assessments confirmed that polarized piezoelectric ceramic scaffolds could effectively enhance cell adhesion, proliferation, and osteogenic differentiation compared to unpolarized scaffolds. An increase in BG coating amount enhanced the capacity of piezoelectric ceramic scaffolds to upgrade osteogenesis activities of rBMSCs. These results rendered BTO@BG-S composite scaffolds promising candidate in the field of bone repair.

Three-Dimensional Bioprinting of Strontium-Modified Controlled Assembly of Collagen Polylactic Acid Composite Scaffold for Bone Repair.

In recent years, the incidence of bone defects has been increasing year by year. Bone transplantation has become the most needed surgery after a blood transfusion and shows a rising trend. Three-dimensional-printed implants can be arbitrarily shaped according to the defects of tissues and organs to achieve perfect morphological repair, opening a new way for non-traumatic repair and functional reconstruction. In this paper, strontium-doped mineralized collagen was first prepared by an in vitro biomimetic mineralization method and then polylactic acid was homogeneously blended with the mineralized collagen to produce a comprehensive bone repair scaffold by a gas extrusion 3D printing method. Characterization through scanning electron microscopy, X-ray diffraction, and mechanical testing revealed that the strontium-functionalized composite scaffold exhibits an inorganic composition and nanostructure akin to those of human bone tissue. The scaffold possesses uniformly distributed and interconnected pores, with a compressive strength reaching 21.04 MPa. The strontium doping in the mineralized collagen improved the biocompatibility of the scaffold and inhibited the differentiation of osteoclasts to promote bone regeneration. This innovative composite scaffold holds significant promise in the field of bone tissue engineering, providing a forward-thinking solution for prospective bone injury repair.

Characterizing Håkon Mosby Mud Volcano (Barents Sea) cold seep systems by combining ROV-based acoustic data and underwater photogrammetry

Cold-seeps have a unique geo-ecological significance in the deep-sea environment. They impact the variability of present-day submarine sedimentary environments, affecting the evolution of the landscape over time and creating a variety of submarine landforms, one of which is Mud Volcanoes (MVs). MVs form due to the extrusion of mud, fluids, and gas, mainly methane, from deeper sedimentary layers. These natural gas seepage systems could significantly affect climate change and the global carbon cycle. We present a comprehensive method that combines ROV-based multibeam mapping and underwater photogrammetry to enhance the understanding of the physical relationships between geomorphic units characterizing the Håkon Mosby Mud Volcano (HMMV) and the distribution of associated habitats. HMMV is indeed characterized by high thermal and geochemical gradients from its center to the margins resulting in a clear zonation of chemosynthetic communities. Our approach integrates multi-resolutions and multi-sources data acquired using a work-class ROV. The ROV-based microbathymetry data helped to identify the different types of fine-scale submarine landforms in the central part of HMMV. This revealed three distinct geomorphic units, with the central hummocky region being the most complex. To further study this area, ROV images were analyzed using a defined Structure from Motion workflow producing millimetric resolution 2D and 3D models. Object-Based Image Analysis (OBIA), applied on orthomosaics, allowed us to obtain a fine classification of main benthic communities covering a total area of 940m2, including the active seepage area of the hummocky rim. Four major substrate types were identified in these regions: uncovered mud, bacterial mats high-density, bacterial mats low-density, sediments and tubeworms. Their relationship with terrain morphology and seepage activity were investigated at different spatial scales, contributing to a deeper understanding the ecological functioning of cold seep ecosystems in MVs. The applied workflow is proposed as an innovative processing technique for future studies on cold-seep systems. Geomorphic and ecological processes in extreme environments are inherently linked and marked by spatial patterns typifying associated habitats and sedimentary environments. This is poorly investigated in previous studies, leaving a substantial gap in the geomorphological drivers responsible for habitat distribution and extent in cold seep systems.

Porosity of Nickel Nanopowder Compacts Consolidated by Gas Extrusion

Porosity of Nickel Nanopowder Compacts Consolidated by Gas Extrusion

Structure and Phase Formation in Ni + Al Powder Mixture Enclosed in a Steel Cartridge during Hot Gas Extrusion

Structure and Phase Formation in Ni + Al Powder Mixture Enclosed in a Steel Cartridge during Hot Gas Extrusion

Пористость консолидированных методом газовой экструзии компактов из никелевых нанопорошков

The method of hot gas extrusion differs from other methods of metal pressure treatment in that the processed material is subjected to intense plastic deformation by extrusion under conditions of high isostatic pressure of inert gas and heating in the area of plastic deformation. The method makes it possible to process powder materials, while inevitably there is a need to control mechanical properties by controlling porosity and pressure inside the pores. The paper presents a method for calculating the pressure inside the pores from the minimum size of the closed pore. The pore pressure was evaluated on materials obtained by the consolidation of nickel nanopowders by hot gas extrusion. Quantitative processing of the material cross-section view images obtained by scanning electron microscopy showed that the minimum pore size is 220 nm. The formula for calculating the pore pressure is derived from the formula for calculating the critical pore radius. It takes into account the external impact pressure (the gas pressure during the extrusion process was equal to 400 MPa), the surface tension coefficient and the yield strength of nickel (at the extrusion start temperature of 910 °С), as well as the minimum pore radius. The proposed method for calculating the pressure inside a closed pore will allow us to evaluate the mechanical properties of materials obtained by various methods of powder metallurgy.

Механические свойства композитных стержней, полученных горячей газовой экструзией смеси порошков никеля и алюминия в стальной оболочке

The aim of the work is to determine the influence of the hot gas extrusion (HGE) parameters on the phase composition and mechanical properties of composite rods at room temperature consisting of a core with reaction products of a Ni – Al powder mixture and a steel shell. Composite rods were obtained under three different modes of HGE: in the 1st mode, the temperature of the extrusion beginning process (TE) was equal to 730 °С, and the gas pressure (PG) in the chamber with the starting materials was 210 MPa, in the 2nd mode TE — 600 °C, PG — 290 MPa and in the 3rd mode TE — 580 °C, PG — 380 MPa. The numbering of the rods is similar to the HGE modes. The study of mechanical properties was carried out by a three-point bending test and microhardness measurement. The study of the phase composition showed that rod 1 has the greatest completeness of the initial powder mixture reaction. The green nickel and aluminum were found in the core of rod 3. Three-point bending tests have shown that the yield strength of the composite rod will be higher than the yield strength of the steel rod if there are also more plastic inclusions in the core, such as the green nickel and aluminum, as in rod 3. Microhardness measurements have shown that the rods with the greatest completeness of the reaction (rods 1 and 2) have highest average microhardness.

Reactivity of a β-diketiminate ytterbium(II) hydride with cyclopentadiene derivatives

Cyclopentadienyl ligands are ubiquitous in lanthanide chemistry and have been used extensively to stabilize low-valent lanthanide(II) complexes. We now report the reactions of the β-diketiminate ytterbium(II) hydride [(BDIDipp)Yb(H)]2 (BDIDipp = HC{C(Me)NDipp}2, Dipp = 2,6- i Pr2C6H3) with tetramethylcyclopentadiene, pentamethylcyclopentadiene, indene, and fluorene; to provide ready access to the heteroleptic ytterbium(II) η5-C5R5 cyclopentadienides with extrusion of hydrogen gas. The tetramethylcyclopentadienyl, pentamethylcyclopentadienyl, indenyl, and fluorenyl compounds were characterized by 1H and 13C{1H} NMR, elemental analysis, and single crystal X-ray diffraction. These data indicated that each heteroleptic cyclopentadienide exists as a mononuclear species in both solution and the solid state, formulated with retention of the oxidation state on the ytterbium(II) center. Additionally, the pentamethylcyclopentadienyl derivative was characterized by single crystal neutron diffraction, a study that explored the nature of an agostic interaction between a methyl group and the ytterbium(II) center.

Continuous Flow Generation of Acylketene Intermediates via Nitrogen Extrusion.

A flow chemistry process for the generation and use of acylketene precursors through extrusion of nitrogen gas is reported. Key to the development of a suitable continuous protocol is the balance of reaction concentration against pressure in the flow reactor. The resulting process enables access to intercepted acylketene scaffolds using volatile amine nucleophiles and has been demonstrated on the gram scale. Thermal gravimetric analysis was used to guide the temperature set point of the reactor coils for a variety of acyl ketene precursors. The simultaneous generation and reaction of two reactive intermediates (both derived from nitrogen extrusion) is demonstrated.

Gas Extrusion Treatment of Thermally Hardened Steel and Alloys in the Mode of Deformation-Thermal Hardening

Gas Extrusion Treatment of Thermally Hardened Steel and Alloys in the Mode of Deformation-Thermal Hardening

Numerical simulation of primary atomization process of liquid jet in subsonic crossflow

Studies of primary atomization of liquid transverse jets in subsonic crossflow consider surface waves as the main cause of jet fragmentation. The characteristics of surface waves during jet fragmentation have been initially analyzed, but there is a lack of understanding of the mechanism of surface wave generation and development. This paper investigates the primary atomization of liquid transverse jets in subsonic crossflow based on the numerical method of Large Eddy Simulation (LES) with the coupled level set and volume of fluid method (CLSVOF) interface tracking, combined with adaptive mesh encryption techniques, where the liquid phase medium is water. This paper focuses on the fine structure of the primary atomization of the jet column, including the evolution of the jet column and the process of shedding the surface of the jet column, to clarify the physical process of primary fragmentation of the jet. The near-field flow structure and gas–liquid interaction are also analyzed to investigate the mechanism of primary atomization of liquid transverse jets and the mechanism of surface wave generation and development in subsonic flows. The results show that the shear action of gas and liquid leads to the generation of Kelvin–Helmholtz (KH) unstable wave, and KH surface wave dominates the surface breaking of jet column. The extrusion of gas and liquid results in the unstable fluctuation of Rayleigh–Taylor (RT), and the RT surface wave dominates the jet column, and finally the cylindrical fracture occurs. The development trend of RT surface wave is to increase the wavelength along the jet direction. When the wavelength of the RT surface wave develops from 0.12 mm to 1.2 mm, the jet column will be columnar broken at the trough of the last RT wave.

Molecular Dynamics Study on Regimes of Head-on Droplet Collision

The head-on collision of two water droplets with a diameter of 10 nm in an atmospheric environment was investigated via molecular dynamics simulations. The gas molecules between droplets were visualized, and the phenomena of gas extrusion and gas molecules being captured were found. By observing and analyzing the holes regime, a "periphery-sucking" mechanism was proposed to explain the thinning in the middle of the expanding disk and the holes appearing. It was found that the splattering regime can be divided into the limited splattering regime and the divergent splattering regime. The splattering modes and droplet characteristics of the two regimes are markedly different. The non-bonded interactions and intermolecular hydrogen bond were analyzed, and it was found that increasing the Weber number (We) can effectively promote the mixing of the two droplets, promote the formation of an intermolecular hydrogen bond between the two droplets, and reduce the average lifetime of the intermolecular hydrogen bond. The radial distribution function between the water molecules was plotted, showing that increasing the We makes the water molecules more dispersed as a whole in the collision process.

Composite rods by high-temperature gas extrusion of steel cartridges stuffed with reactive Ni–Al powder compacts: Influence of process parameters

Steel clad NiAl rods were prepared by high-temperature gas extrusion (HTGE) of steel cartridges stuffed with reactive Ni–Al powder compacts upon variation in warmup temperature Tw (600–780 °C) and gas (Ar) pressure P (200–480 MPa). A largest amount of NiAl and Ni3Al intermetallics in rod core was obtained at Tw = 780°С and P = 200 MPa. For Tw < 660°С (m.p. of Al), the rod core was found to contain significant amounts of unreacted Al and Ni. A transition zone of Al–Fe intermetallics (10 μm thick) was found only in the rod obtained at Tw = 780°С and P = 200 MPa. The core material of such rods exhibited a largest mean value of hardness (1050 HV). It is suggested that the yield of target intermetallics can be improved by using charge compacts prepared from mechanically activated Ni–Al blends. Combined use of (a) in-situ synthesis of target product in a core and (b) extrusion of the entire fixture seem promising for fabrication of composite materials with unique properties.

Study on the Parameter Equation of Coal and Gas Outburst Hole

Studying the parameters of a coal and gas hole (CGOH), such as the hole shape, hole size and volume, coal quantity of CGOH, coal throw distance, calculated hole density, and gas pressure, is helpful in revealing the coal and gas outburst mechanism. In this study, we found that there were close mathematical relationships between these parameters. A nonlinear composite function relationship (CGOH parameter equation) was observed between the coal quantity, CGOH volume, and throw distance. The correctness of these relationships was verified using the Origin software. The stagnation point and inflection point of the parameter curve were obtained through the derivation of the parameter equation, and the transformation path from coal and gas outburst to coal and gas extrusion or dumping was clarified. At the same time, the equations of gas pressure, coal quantity, and throw distance are derived.

Обработка газовой экструзией термически упрочняемых сталей и сплавов в режиме деформационно-термического упрочнения

Thermally hardened alloys based on iron (50 Cr – V – N type steel), titanium (VT-14), and aluminum (D16) were subjected to deformation by gas extrusion with local heating in the mode of deformation-thermal hardening with high degrees of deformation 90 % or more to obtain a thin wire at the output. Gas extrusion was performed at various combinations of processing parameters — gas pressure, deformation temperature, extrusion speed. The wire deformed under various combinations of processing parameters was cooled in air, subjected to tempering or aging and a tear test. The mechanical properties obtained as a result of the tests were compared with the data on the mechanical properties of the initial, undeformed alloys, heat-treated and non-heat-treated. On all gas-extruded alloys, the mechanical properties exceeded the initial ones both in strength and plasticity. The combination of gas extrusion parameters (gas pressure, deformation temperature, extrusion speed) has a decisive influence on the combination of strength and ductility of alloys treated by gas extrusion.

Effect of the Gas Extrusion Conditions on the Structure and Mechanical Properties of an Aluminum Alloy Reinforced by Nanocrystalline Graphite

Abstract—The effect of the gas extrusion (GE) conditions (temperature, pressure) on the structural-phase composition and the mechanical properties of the composite material (CM) based on an aluminum alloy reinforced by nanocrystalline graphite is studied. The possibility of controlling the structural component size in the bulk composites by varying the GE conditions is experimentally shown. The synthesized bulk CMs have a high hardness and strength at satisfactory plasticity. A comparative analysis of the experimental results with the available properties of the powder CMs based on aluminum alloys A15083, A12009, and A12024 reinforced with carbon nanotubes or graphene and consolidated by a combination of methods (two-stage treatment) demonstrates the efficiency of the developed approach for producing aluminum-matrix CMs.

The Use of Gas Extrusion for the Synthesis of a High-Strength Composite Based on a 5xxx Series Aluminum Alloy Strengthened with Carbon Nanostructures

Composite materials based on a 5xxx series aluminum alloy strengthened with 0.1 wt % of multiwalled carbon nanotubes (MWCNTs) or 0.1 wt % WC1 –x/MWCNTs were synthesized by high-energy ball milling and subsequent gas extrusion. The structural phase composition and physicomechanical properties of bulk composites are characterized. A comparison with published data on the properties of composites based on 5xxx series aluminum alloys reveals promises of using gas extrusion for consolidation, as well as the effectiveness of the use of strengthening microadditives of MWCNT hybrid nanostructures to increase strength.