Surface Of Powder Particles Research Articles

Solid‐State Processing of Nascent Disentangled UHMWPE Reactor Powders Mixed with Carbon Nanoparticles

AbstractAspects of solid‐state processing of nascent disentangled ultra‐high‐molecular‐weight polyethylene (UHMWPE) powders of different syntheses mixed with electrically conductive carbon nanoparticles (NPs) of various types are studied. Effect of multiple parameters of the processing procedures on the electrophysical characteristics of the composite samples is investigated. Such parameters include time of preliminary ultrasonication (US) of NPs, time of US of UHMWPE/NPs mixtures, molding time, temperature, and pressure, deformation degree, etc. It is observed that by selecting optimal values of such parameters it is possible to obtain samples of composites with an extremely segregated structure made of the NPs, with NPs distributed evenly on the surfaces of the compacted UHMWPE powder particles. This ensures high levels of conductivity at very low values of NPs content. The segregated structure is retained when the composites are strengthened using the solid‐state uniaxial shear deformation process. While conductivity of most of the composites filled with various types of NPs monotonously decreases with the deformation ratio, conductivity of the composites filled with exceptionally long double‐walled carbon nanotubes is maintained. The processed oriented composites are also characterized by high EMR shielding properties, as well as interesting temperature dependencies of the electrical conductivity.

Synthesis and alloying of zinc sulfide in a homogeneous system based on dodecane, its identification and optical properties

Zinc sulfide doped with Mn2+ ions was synthesized in a homogeneous dodecane medium by the method of emerging reagents. By methods of chemical and X-ray phase analysis, IR spectroscopy, electron microprobe microscopy, identification of products was carried out, photographs of the surface of powder particles (SEM) were recorded. Based on the totality of the results, a conclusion is made about the formation of nanoscale objects having a polytype structure with a predominance of distorted cubic crystals forming agglomerates up to 10 microns in size in ZnS powder and up to 100 microns in ZnS–Mn powder. The formation of nanoscale ZnS particles is confirmed by spectral data. The effect of manganese ions on the photoluminescence (FL) of the powder is manifested by a change in the type of the descending branch of the ZnS–Mn FL band, it is associated with recombination processes at the levels of defects formed by Mn2+ ions in the ZnS structure at their low concentration.

Dispersed CeO2 Nanorods with Low-Speed Mixing for Mechanical Properties Promotion of PTA Steel Coatings

The plasma-transferred arc technology has been observed to induce preferential grain orientation in multiple directions, leading to nonuniform grain growth within the alloy coating material. The addition of nano-oxides can act as heterogeneous nucleation sites, reducing the preferred orientation of grains. In this study, a low-speed mixing method was employed to coat highly dispersed CeO2 nanorods (CNRs) onto the surface of 14Cr2NiSiVMn alloy powder particles. The aim was to analyze the influence of dispersed CNRs on grain growth orientation in different directions and the refinement and heterogeneous nucleation effect of CNR additives. The addition of 0.5 wt.% CNRs resulted in the refinement of dendritic grains along both the perpendicular and parallel directions to the coating cladding direction, leading to the formation of more uniform equiaxed crystals. The combination of Ce with Si and V elements formed submicron particles, which promoted grain nucleation and reduced defects in the coating. Consequently, the mechanical performance of the sample significantly improved. In the deposition direction, there was a notable improvement in microhardness (20.4%), tensile strength (97.6%), and elongation (59.0%). In the perpendicular deposition direction, the tensile strength increased by 88.1%, and the elongation increased by 33.9%. Additionally, the weight loss due to wear decreased by 44.2%, and the relative wear resistance improved by 79.3%.

Characteristic analysis of high-speed steel powder prepared by gas atomisation

The performance of high-speed steel (HSS) powder is a prerequisite for the preparation of high-performance powder metallurgy HSS. The physical properties, microstructure, and solidification characteristics of HSS powder prepared by nitrogen gas atomisation were systematically studied and analysed in detail. For the atomised TPM558 HSS powder, the morphology is spherical and the particle size distribution is wide. The smooth small particles of satellite powder attach to the surface of large particles. Shrinkage pits caused by solidification shrinkage exist on the surface of large particles. The average cooling rate is between 104 and 106 K·s−1, with the increase of cooling rate, the powder surface tends to be smooth, and the grain structure is transformed in the order of cellular to dendritic to radial. The single powder particle surface shows fine-equiaxed grains, while the internal presents columnar grains. The crystalline phases of the powder are austenite, ferrite, martensite, and carbide, and the carbide includes MC carbide with face-centred structure and M2C carbide with hexagonal structure. The average nano-hardness of the powder is 9.93 GPa, resulting in poor formability, and it can be pressed and formed only after adding binder.

Microstructure Characterization and Mechanical Properties of Polymer‐Derived (HfxTa1−x)C/SiC Ceramic Prepared upon Field‐Assisted Sintering Technique/Spark Plasma Sintering

The high‐temperature microstructural evolution and mechanical properties of two SiC‐based polymer‐derived ceramics with different Hf:Ta molar ratios are investigated using electron microscopy techniques and manipulated by nanoindentation. The as‐pyrolyzed ceramic powder consists of an amorphous Si(HfxTa1−x)C(N,O) structure (where x = 0.2, 0.7) with localized nanocrystalline transition metal carbides (TMCs). Subsequent application of the field‐assisted sintering technique (FAST) for high‐temperature consolidation results in a crystalline (HfxTa1−x)C/SiC ultra‐high temperature ceramic nanocomposite. The microstructure contains powder particle‐sized grains and sinter necks between the former powder particles. The powder particles consist of a β‐SiC matrix and small TMCs. Large TMCs are observed on the internal surfaces of former powder particles. This is due to the pulsed direct current and the resulting Joule heating that facilitates diffusion as well as oxygen impurities. Sinter necks of large β‐SiC grains form during the FAST process. The microstructural regions are assessed using high‐throughput nanoindentation. The hardness for SiC/(Hf0.7Ta0.3)C is measured on the formed grains and the sinter necks giving mean hardness values of about 27 and 37 GPa, respectively.

Effect of Powder Particle Surface Treatment on DC Magnetic Properties of Compacted Iron Cores

Effect of Powder Particle Surface Treatment on DC Magnetic Properties of Compacted Iron Cores

PROPERTIES AND GENERALIZED SCHEME FOR PRODUCTION OF MILK POWDER

Presently, the functional qualities of milk proteins have led to milk powders, being mostly regarded as food components. When milk powders are maintained, numerous physicochemical problems develop, the most of them being generated by the lactose glass transition. They have significant effects on milk powders physical (flow ability) properties. First, powder particle surface microstructure and chemical composition are altered by lactose crystallization. As a result, milk powder's capacity travel is reduced. Milk proteins solubility is harmed because their structural integrity has been destroyed. Additionally, caking and particle collapse occur, and these processes primarily decrease the physical properties of milk powders(Flow capability and density). The unfolding of proteins, which reduces solubility and may also be encouraged by the mechanical stresses that appear. Lastly, enzymatic and chemical reactions (Maillard reaction) occur in order, implementing molecular mobility. Milk powder's solubility is mostly decreased by protein interactions and aggregations, which are enhanced by the Maillard process and oxidation. Emulsifying and foaming characteristics are also decreased by the Maillard process. Additionally demonstrated that milk components, time, and their physical state. The main factors that have been considered are the relative humidity and temperature of the storage

Corrosion Resistance of Fe-Cr-Si Alloy Powders Prepared by Mechanical Alloying

Powders with nanometric crystallites of two ternary alloys Fe0.90Cr0.05Si0.05 and Fe0.85Cr0.10Si0.05 were prepared by mechanical alloying (MA) in a planetary high-energy ball mill at various milling times followed by annealing in a vacuum at 900 K to induce an oxygen-induced surface segregation of Cr and Si atoms. The prepared powders were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The obtained results show that all prepared powders crystallize in the body-centered cubic structure and are composed of micrometric particles, which are polycrystalline and consist of many nanometric crystallites. The mean size of the particles as well as the crystallites decreases progressively with milling time. In order to study the anti-corrosion properties of the obtained materials, the powders were exposed to atmospheric gases at 870 K. After each oxidation step, the formation of iron oxides was investigated using 57Fe transmission Mössbauer spectroscopy (TMS). It was found that the powders of Fe0.90Cr0.05Si0.05 and Fe0.85Cr0.10Si0.05 obtained after 10 and 20 h of MA are extremely resistant to oxidation. This result can be connected with the fact that XPS measurements reveal a high concentration of Cr and Si atoms on the surface of powder particles.

Battery Materials: In-Situ Analysis with the Scanning Electron Microscope

The concept of decarbonisation has been gradually gaining ground. As a result, emphasis has been given to green energy technology in an attempt to offset the need for fossil fuels. The alternative to fossil fuels could be batteries. Not only can batteries be used for stationary energy storage but also for powering electric vehicles. However, more is increasingly required from batteries: they have to store more energy, perform reliably and function for longer, often under extreme conditions depending on the latitude. Among the different battery technologies that have been developed over the years, lithium ion batteries stand out. The main reason is their superior energy and power density, which can support demanding applications such as electromobility. The drive to make batteries more efficient and able to hold more energy, and eventually deliver more power requires in-depth analysis of materials; in order to understand what promotes or undermines materials performance, what leads to failure, and ultimately, the knowledge to design materials for the next generation of batteries.The scanning electron microscope is a powerful tool supporting in situ analysis of materials. In the short-term, as far as cathode precursor powders are concerned, costs are reduced by early detection of impurities and contamination. In the long-term, the battery quality and performance are safeguarded as failure caused by the presence of contaminants is minimised (contamination particles cause short-circuits by penetrating through the battery components). Scanning electron microscope(SEM)-based quality assurance/quality control of battery powders is routinely done with energy dispersive spectroscopy (EDS) and comes with the advantage of high throughput and minimum instrument down time.Battery materials analysis often focuses on formulation testing. That can be either at the industrial level (enquiring if the result is the intended) or R&D level, that is, experimenting with different recipes to single out the optimal one(s). One of the aspects that can be checked using SEM-based analytical techniques is the composition and distribution of coatings and dopants on the powder particle surface. The addition of coatings (Figure 1A) and dopants (Figure 1B) is crucial to ensuring battery performance. They act as performance enhancers (coatings) and dendrite formation suppressants (dopants). These can be detected and mapped in high resolution with SEM-EDS and they can be analysed more accurately with SEM-WDS. At a later stage, the same techniques can be applied to analyse black mass, the material coming from shredded, spent batteries.Given that the atomic numbers (Z) of the elements comprising the battery powders are often close, there is a limit to the information that an electron image can provide due to the closeness of the grey levels. However, there is need to characterise the internal structure of precursor cathode powders as well as other properties such as shape, size, grain boundaries and texture. SEM-EBSD can bypass this issue and can provide information about the particle internal structure by utilising backscattered electrons. The internal structure information of the particles can be used to study cracking development and propagation. A useful tool for battery components post-mortem analysis. The incorporation the Raman-in-SEM, RISE system provides an additional dimension to battery analysis, meaning we can access a wealth of molecular information. Raman spectroscopy can be employed to aid with the analysis of lithium-containing cathode materials in addition to investigating graphitic carbon anode materials.The primary benefit of the SEM-based techniques briefly discussed here is that they can all be applied in the same SEM chamber, in situ, allowing for data to be obtained under the same conditions as part of the same experiment/workflow, promoting, thus, efficiency and throughput – even more so for beam and/or air sensitive samples, saving time required for sample (re)preparation. Another practical benefit is straightforward data correlation which is facilitated when the exact same sample locations have been analysed. Figure 1

Effect of TaC on microstructure and mechanical properties of 316L stainless steel by selective laser melting

Selective laser melting (SLM) is a rapid processing technology used to directly manufacture metal terminal components. TaC is often utilized to enhance mechanical properties of metal due to its excellent performance. In this study, SLM was employed to manufacture TaC/316 L composites with varying TaC volume content. The effect of TaC content on the microscopic appearance and mechanical properties of SLM-316 L stainless steel was then explored. The TaC admixture was efficiently and effectively distributed on 316 L powder particle surfaces using short-duration high energy ball milling. Under the optimal parameters for SLM, the relative densities of the specimens reached over 99.0% because of the high wettability of 316 L with TaC. Moreover, grain refinement was observed after microstructural analysis due to interactions between the TaC and 316 L. Tensile, Charpy impact, and microhardness tests demonstrated that the adjunction of 0.5 vol% and 1.5 vol% TaC provided a significantly enhanced yield strength (increased by 7.4% and 30.9%), ultimate tensile strength (increased by 5.6% and 27.1%), and microhardness (increased by 9.9% and 22.7%). The impact toughness (reduced by 20.3% and 51.4%) and ductility (reduced by 23.1% and 39.5%) were maintained.

Improving the Interparticle Bonding and Ductility of Cold Sprayed Aluminum Alloys by Deformation Processing

Cold spray (CS) can produce thick coatings and free-standing bulk materials and is adaptable to additive manufacturing, including on-site repair. However, the structural applications of CS materials have been limited by the inherently incomplete interparticle metallurgical bonding in CS materials. In this work, an ultrasonic washing test (UWT) was used to semi-quantitatively assess the extent of interparticle bonding in CS Al6061 and CS Al2024 in relation to key CS parameters and post-CS deformation processing. Results indicate that spraying with a lighter gas or a softer powder promotes the interparticle bonding, although full metallurgical bonding is hardly achieved even by spraying at high deposition efficiencies. Sprayed particles remain in the deposit only because they acquire partial bonding that is sufficient to prevent them from bouncing off. Post-CS rolling and T6 heat treatment increase the interparticle bonding and hence ductility of CS Al alloys. Ultrasonic ironing (UI), a new post-CS deformation processing technique, also produces similar effects. The increased interparticle bonding by post-CS deformation processing arise from fragmentation of oxide layers inherited from powder particle surfaces and consequent metal-to-metal joining at the particle boundaries.

Electrochemical Behavior of Mixed Cu Powder and LiCl/Li13In3-Coated Li Powder Anodes in Lithium Metal Secondary Batteries

A novel anode consisting of a mixture of Cu powder and LiCl/Li13In3-coated Li powder was developed and tested for use in Li metal secondary batteries (LMSBs). The aim was to improve the electrochemical performance as suppress dendrite formation and volume change on the Li metal electrode. A LiCl/Li13In3 composite film was deposited on the surface of Li powder particles using a facile liquid treatment method. The coated Li powder was mixed with Cu powder to produce a Li–Cu composite electrode (LCE) for LMSBs. It has been proven through scanning electron microscopy (SEM) and analysis of the coating layer using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and depth profile analysis that LiCl/Li13In3 has formed well on the surface of the Li powder. The coated LCE exhibited improved electrochemical properties in both the symmetric cell and full cell tests. Through electrochemical impedance spectroscopy (EIS) measurement, it has been determined that after 50 cycles, the impedance of the coated LCE is 98 Ω. In particular, even when a large amount of Li was used (40%, 1544 mAh g−1), it exhibited improved electrochemical behavior over 50 cycles in a symmetric cell test. In addition, in a full cell test with LiV3O8 as a cathode at a 2 C rate, the capacity retention was 96% after 50 cycles. SEM images showed that dendrite growth and volume change were suppressed by the novel electrode architecture.

Pore formation driven by particle impact in laser powder-blown directed energy deposition.

Process defects currently limit the use of metal additive manufacturing (AM) components in industries due to shorter fatigue life, potential for catastrophic failure, and lower strength. Conditions under which these defects form, and their mechanisms, are starting to be analyzed to improve reliability and structural integrity of these highly customized parts. We use in situ, high-speed X-ray imaging in conjunction with a high throughput laser, powder-blown directed energy deposition setup to observe powder particle impact behavior within the melt pool. Through fundamental observations of the stochastic, violent powder delivery in powder-blown DED, we uncover a unique pore formation mechanism. We find that a pore can form due to air-cushioning, where vapor from the carrier gas or environment is entrapped between the solid powder particle surface and liquid melt pool surface. A critical time constant is established for the mechanism, and X-ray computed tomography is used to further analyze and categorize the new type of "air-cushioning" pores. It is shown that the air-cushioning mechanism can occur under multiple laser processing conditions, and we show that air-cushioning pores are more likely to be formed when powder particles are larger than 70 m. By quantifying the effect of powder particle impact, we identify new avenues for development of high-quality laser, powder-blown DED products. Furthermore, we deepen knowledge on defect formation in metal additive manufacturing, which is being increasingly utilized in high performance situations such as aerospace, automotive, and biomedical industries.

Novel Functional Soft Magnetic CoFe2O4/Fe Composites: Preparation, Characterization, and Low Core Loss.

In this study, composites CoFe2O4/Fe were successfully synthesized by in situ oxidation, and their composition, structure, and magnetic properties have been investigated. According to the analysis of X-ray photoelectron spectrometry measure results, the cobalt ferrite insulating layer was completely coated on the surface of Fe powder particles. The evolution of the insulating layer during the annealing process has been discussed, which is correlated to effects on the magnetic properties of the composites CoFe2O4/Fe. The amplitude permeability of the composites reached a maximum of 110, and their frequency stability reached 170 kHz with a relatively low core loss of 253.6 W/kg. Therefore, the composites CoFe2O4/Fe has potential application in the field of integrated inductance and high-frequency motor, which is conducive to energy conservation and carbon reduction.

Spectroscopic characterisation of acidified milk powders

The production of acidified milk powders by spray drying is challenging due to particle deposition on the dryer surface, which reduces yield, and may impair product quality. The composition, especially lactic acid concentration, and powder particle surface properties, are important in this context. This study explored the possibility of monitoring the drying process using vibrational spectroscopy techniques such as near-infrared (NIR), attenuated total reflection (ATR) and Raman imaging. The results showed that these techniques provide complementary qualitative measurements regarding the composition of acidified milk powders that are useful for understanding and controlling their production. Raman imaging revealed lactic acid surface composition providing better understanding of wall deposition during spray drying. NIR and ATR provided information about the composition and molecular structural changes in powders occurring during the prolonged exposure of powder to the high drying temperature, which may be applicable for on-line and at-line process control, respectively.

Novel in-situ controllably grown CSH: Synthesis, characterization and the effect on cement hydration

CSH nanoparticles are distinctly different from other nano-additives because they are supposed to be ideal nucleation substrates for hydration products. One of the biggest obstacles is the difficulty in achieving a good dispersion of CSH nanoparticles in the matrix. We utilize a novel method to prepare composites by in-situ grown CSH nanoparticles (ICSH) on the surface of iron tailings powder (ITP) particles, and the growth amount and Ca/Si ratio of CSH can be precisely controlled. The results show that the agglomeration of CSH nanoparticles can be reduced by using the inert ITP admixture which is easy to disperse uniformly in cement-based materials. Studies on the properties of modified cement show that ICSH is significantly better than pure CSH powder in improving early hydration, pore structure and long-term compressive strength. These improvements are mainly attributed to the good dispersion of ICSH and the rigid system of the ITP matrix. This study provides theoretical guidance for improving the dispersion of nanoparticles in cement matrices.

Combined effect of a spread powder particle size distribution, surface machining and stress-relief heat treatment on microstructure, tensile and fatigue properties of 316L steel manufactured by laser powder bed fusion

Combined effect of a spread powder particle size distribution, surface machining and stress-relief heat treatment on microstructure, tensile and fatigue properties of 316L steel manufactured by laser powder bed fusion

Фазовый состав и структура порошка хромовой бронзы БрХ

Methods of the X-ray phase analysis, as well as optical and scanning electron microscopy supplemented by construction of the distribution maps for such chemical elements as oxygen and copper demonstrated presence in the structure of the PR-BrX brand powder made of bronze with the FСС lattice of oxygen-containing phases, i.e., copper oxides (CuO, Cu2O) located along the grain boundaries and on the powder particle surface. Using these methods demonstrated that annealing in the ammonia at a temperature of 450 °C promoted reduction of the oxide phases to the single-phase structure of the initial solid solution. It was found out that the presence of oxides on the powder particles surface and grain boundaries inside these particles made the oxidized powder unsuitable for use in the selective laser melting technology. This is due to reduction of the oxides, and, consequently, to the outgassing and excessive porosity of objects during the laser 3D printing. It was proved that reductive annealing in ammonia formed a single-phase structure of powder particles based on the FCC copper, which made it possible to grow objects with small porosity not exceeding 2.5 % using various laser processing modes

Honeycomb-like structured ZnFe2O4@C derived from ZnFe2O4@ZIF-8 for electromagnetic wave absorption

In this paper, ZnFe2O4@Zeolitic imidazolate framework-8 (ZIF-8) composites were prepared by Sol-Gel self-propagating combustion method and in situ growth method. Honeycomb-like structured ZnFe2O4@C composites were obtained using ZnFe2O4@ZIF-8 as the precursor in Ar atmosphere carbonization at 800℃. The honeycomb-like structure is conducive to enhance the polarization and reflection on the surface of powder particles, which ameliorate the EMW absorption properties of the materials significantly. Wherein, the carbon content can be controlled by ZIF-8 coating. The composite with 5% ZIF-8 (wt%) shows excellent reflection loss value of −36.5 dB at 9.4 GHz with a matching thickness of 2.0 mm, and the corresponding effective absorption bandwidth is 3.5 GHz (7.6–11.1 GHz). The composite with 10% ZIF-8 (wt%) obtain a minimum reflection loss value of −37.8 dB at 10.0 GHz when the thickness is 2.0 mm, and the effective absorption bandwidth is 3.5 GHz (7.9–11.3 GHz).

Fabrication and characterization of aluminum-based powders multi-reinforced with nano- and microparticles

Multi-reinforced powders were obtained by high-energy ball milling in a planetary mill. The process of obtaining heterogeneous powders consisted of two stages. At the first stage, a nanocomposite powder of AlMg6 + 0.3 wt.% C60 was obtained. In the second stage, 10, 30, 50, and 70 wt.% Al2O3 were added to the obtained nanocomposite powder and processing continued. Methods such as scanning electron microscopy, X-ray diffraction, and particle size analysis were used to characterize the obtained powders. It is shown that after the first stage of processing, the particles of the composite powder are characterized by an irregular shape. C60 reinforcing particles in the form of nanosized agglomerates were fixed on the surface of aluminum powder particles. After the second stage of processing, the particle size of the powder mixture decreased from 17.8 to 12.3 μm, while the proportion of Al2O3 particles increased from 10% to 70% by weight. It is shown that the synthesized heterogeneous powders were a mechanical mixture consisting of complex composition agglomerates and micro-sized ceramic particles. Complex composition agglomerates were formed from nanocrystalline matrix material particles and C60, and also with Al2O3 microparticles embedded in them, as well as located on the surface. The concentration of Al2O3 particles on the surface and inside the agglomerates increased with increasing weight fraction of ceramic particles in the mixture. It has been found that the introduction of 10-70 wt. % Al2O3 into the powder mixture increases the microhardness of the powder particles by approximately 16-23%. The resulting multi-reinforced powder mixtures can be utilized for coating deposition using the cold gas dynamic spraying method.