Pressing Of Powders Research Articles

Impact Assessment of Natural Stone Processing Techniques on the Grain Composition of Sludge Admixtures for Press Powder

Impact Assessment of Natural Stone Processing Techniques on the Grain Composition of Sludge Admixtures for Press Powder

Finite element modelling of ultrasonic assisted hot pressing of metal powder

Finite element modelling of ultrasonic assisted hot pressing of metal powder

Numerical simulation study on hot pressing of ceramic/metal powders

This study utilizes the multi-particle finite element method (MPFEM) to establish 2D and 3D hot pressing models for particle-reinforced aluminum matrix composites. The hot pressing of 6061Al powder and 10 % volume fraction SiCp/6061Al composite powder are simulated under a temperature range of 430–510 °C and pressures ranging from 15 to 30 MPa. The densification mechanism of the composites is elucidated by analyzing the evolution of density and microscopic particle behavior. The analysis reveals that elevating both the pressing temperature and pressure effectively increases the relative density of the powders, with the maximum growth rate occurring at 25 MPa. Notably, the barrier effect created by SiC particles in the 6061Al matrix restricts the plastic deformation and flow of matrix particles, leading to a lower final relative density for the composite powder compared to pure 6061Al powder. Microscopic observations indicate that particle rearrangement dominates in the initial pressing stage, while plastic deformation and particle flow become crucial factors for enhancing relative density in the later stage. Further stress-strain analysis demonstrates that 6061Al particles effectively fill pores through plastic deformation, resulting in stress concentration primarily on the harder SiC particles.

Characterization of a hydrothermally aged experimental alumina-toughened zirconia composite

ObjectivesTo assess the effects of different aging protocols on chemical, physical, and mechanical properties of an experimental ATZ composite compared to a zirconia. MethodsDisc-shaped specimens were obtained through uniaxial pressing of commercial powders (Tosoh), ATZ comprised of 80%ZrO2/20%Al2O3 (TZ-3YS20AB) and 3Y-TZP (3Y-SBE). The specimens of each material were divided into different groups according to the aging protocol: immediate, autoclave aging and hydrothermal reactor aging. The aging protocols were performed at 134 ºC for 20 h at 2.2 bar. Crystalline evaluations were performed using X-Ray Diffraction. The nanoindentation tests measured the elastic modulus (Em) and hardness (H). Biaxial flexural strength was performed, and Weibull statistics were used to determine the characteristic strength and Weibull modulus. The probability of survival was also determined. The Em and H data were analyzed by one-way ANOVA and Tukey test. ResultsDiffractograms revealed the presence of monoclinic phase in both materials after aging. The hydrothermal reactor decreased the Em for ATZ compared to its immediate condition; and the H for both ATZ and 3Y-TZP regarding their immediate and autoclave aging conditions, respectively. The aging protocols significantly increased the characteristic strength for ATZ, while decreased for 3Y-TZP. No difference regarding Weibull modulus was observed, except for 3Y-TZP aged in reactor. For missions of up to 500 MPa, both materials presented a high probability of survival (>99 %) irrespective of aging condition. SignificanceThe synthesized ATZ composite exhibited greater physical and microstructural stability compared to 3Y-TZP, supporting potential application of the experimental material for long-span reconstructive applications.

Optical Ceramics Obtained by Hot Pressing of CVD-ZnSe Powder

Optical Ceramics Obtained by Hot Pressing of CVD-ZnSe Powder

Instantiations of Multiscale Kinship in Pressing‐Defect Distributions in Yttria‐Stabilized Zirconias by Powder Partitioning

Modern dry pressing of ceramic powders using spray‐dried granulates cannot avoid the occurrence of defects related to persisting inter‐ and intra‐granulate interstitial voids. These constitute the parent defect size population limiting the application of polycrystalline ceramics in high‐stress conditions. The mitigation of such defects could widen the range of application in technical and biomedical engineering, reduce the safety range for design, and extend the lifetime of components. Herein, the Weibull size‐effect on strength in size‐partitioned Yttria‐stabilized zirconias (YSZ) feedstocks is used to explore the viability of changing the density distribution of granulate sizes as an effective strategy to obtain a denser particle packing that could reduce the size distribution of strength‐limiting pressing defects. In a direct assessment of critical defect size using multiscale strength testing with a dataset of ≈1300 values, the success of such an approach in increasing the strength reliability for small volume components is demonstrated, along with its ultimate failure in altering the defect size distribution in sintered YSZ ceramics across several length scales. Finally, it is shown that granule morphology (spherical or dimpled) fails to affect the defect density and size distribution in YSZ ceramics.

Effect of mo content on the microstructure and properties of powder metallurgy iron based friction materials

This article uses powder pressing and sintering methods to prepare iron-based friction materials. The influence of molybdenum on the microstructure and comprehensive properties of powder metallurgy friction materials was studied from the aspects of density, hardness, and wear resistance. The results show that with the increase of Mo mass fraction, the sintering density of iron-based friction materials gradually increases, and the hardness of sintered materials first shows an increasing trend. As the Mo content increases by more than 12%, the hardness of sintered friction materials decreases. With the addition of Mo, the wear amount of the friction material first decreases and then increases. When the mass fraction of Mo added to the sintered friction material is 12%, the wear rate of the material is lower than that of other samples, and it has good wear resistance. Adding Mo element to iron copper based friction materials improves the wear resistance of sintered friction materials due to the strengthening effect of Mo.

Determination of optimal technological parameters of fluoropolymer briquetting

The paper discusses the fundamentals of processing fluoropolymers into products and outlines the main operations carried out at each individual technological stage of their processing. It is proven that the preparatory stage of processing fluoropolymers into products significantly affects the quality of the resulting products and their cost. To establish the maximum pressure during briquetting, a granulometric analysis of press powders of polytetrafluoroethylene, copolymer of tetrafluoroethylene with ethylene, and polyvinylidene fluoride was conducted. According to the research results, the main particle size of polytetrafluoroethylene is 20–30 m, for the copolymer of tetrafluoroethylene with ethylene it is 2 m, and for polyvinylidene fluoride it is 5–10 m. This indicates that these polymers should briquette well at relatively low pressures up to 50 MPa. The optimal technological parameters for briquetting press powders such as pressure and holding time under pressure were determined. Their influence on the strength properties of briquetted materials based on fluoropolymers is discussed. It was determined that for the investigated press powders based on fluoropolymers, the optimal briquetting pressure and holding time under pressure are 25–30 MPa and 60–90 s, respectively.

Preparation of Ceramic Press Powder Based on Aluminosilicate Clay Raw Materials and Ash and Slag Waste from Thermal Power Plants Synthesized by Vitreous Microspheres

The possibility of using 3-component charges in the production of wall ceramics by semi-dry pressing from aluminosilicate loams in a composition with ash and slag waste from CHP plants, cullet and silica gel obtained by the sol-gel method is considered. The physicochemical processes and phase formations occurring in the production of ceramic materials using WCO at the firing stage have been studied. It was found that the introduction of fluxes in the form of cullet and silica gel reduces the temperature of heat treatment and are intensifiers of mineral neoplasms that increase mechanical strength compared with samples made from 2-component compositions «loam + ASW».

Evolution of the structural parameters and magnetic characteristics in “ferrite/polymer” nanocomposites

Binary and ternary composites based on soft magnetic spinels CoFe2O4 (or CFO) and Ni0.4Cu0.2Zn0.4Fe2O4 (or NCZFO) were produced. Binary CFO/NCZFO ceramic composite was consist of two magnetic phases with 1:1 ratio. Ternary CFO:FEP, NCZFO:FEP and [CFO/NCZFO]:FEP composites were produced by the thermal pressing of the initial ceramic powders (20 wt%) and fluorinated ethylene propylene – FEP (80 wt%). XRD, SEM and VSM investigation were carried out. The impact of the chemical composition and phase ratio of the composites on crystal structure, microstructure and magnetic properties were established. Magnetic measurements were performed at 300 and 10 K in the fields up to 70 kOe. It was demonstrated the synergetic effect for ceramic composite with the violation of the principle of additivity in two-phase ceramic composites.

Chloride electrode composed of ubiquitous elements for high-energy-density all-solid-state sodium-ion batteries

Inexpensive and safe energy-storage batteries with high energy densities are in high demand (e.g., for electric vehicles and grid-level renewable energy storage). This study focused on using NaFeCl4, comprising ubiquitous elements, as an electrode material for all-solid-state sodium-ion batteries. Monoclinic NaFeCl4, expected to be the most resource-attractive Fe redox material, is also thermodynamically stable. The Fe2+/3+ redox reaction of the monoclinic NaFeCl4 electrode has a higher potential (3.45 V vs. Na/Na+) than conventional oxide electrodes (e.g., Fe2O3 with 1.5 V vs. Na/Na+) because of the noble properties of chlorine. Additionally, NaFeCl4 exhibits unusually high deformability (99% of the relative density of the pellet) upon uniaxial pressing (382 MPa) at 298 K. NaFeCl4 operates at 333 K in an electrode system containing no electrolyte, thereby realizing next-generation all-solid-state batteries with high safety. A high energy density per positive electrode of 281 Wh kg−1 was achieved using only a simple powder press.

Large area hole defect repair of titanium alloys by powder pressing and vacuum sintering

A simple and efficient powder metallurgy method to repair the large area hole defect of titanium alloys was addressed in this work. The titanium-based powder mixture was pressed in the defect area by cold isostatic pressing and then sintered at elevated temperature. Three powder systems Ti–Ni/Ti–Sn/Ti–Ni–Sn were chosen according to liquid phase sintering theory. Ti–7Ni–5Sn powder system led to better densification and interface bonding by sintering at 1200 °C. After repair, the strength reached more than 95 % that of the Ti–6Al–4V matrix.

Relationship among the powder mass, press charge, and final properties of an LSGM electrolyte for solid oxide cells

Relationship among the powder mass, press charge, and final properties of an LSGM electrolyte for solid oxide cells

An enhanced DPC model for metal powder incorporating yield strength of solid-state

The Drucker-Prager/Cap (DPC) Model has a significant drawback in metal powder metallurgy simulations, which is the potential for the von Mises stress to exceed the yield strength of the solid state. To address this issue, this paper introduces a novel hardening law that effectively restricts the von Mises stress within the yield strength of solid alloy. As the powder becomes denser, the yield surface of the DPC model gradually approach towards the von Mises yield surface. To validate the proposed model, both micro-scale finite element simulations and published experimental data were used. The effectiveness of the proposed model was demonstrated through its application in the simulation of two scenarios: cold die compaction of aluminum powder and hot isostatic pressing of a Nickel based superalloy. The results indicate that the proposed model outperforms the original DPC model and is more suitable for powder metallurgy simulations.

Effect of Ruthenium Targets on the Growth and Electrical Properties of Sputtering Ruthenium Films

Ruthenium targets were prepared by vacuum hot pressing of ruthenium powder with different morphologies. Ruthenium films were then deposited on a SiO2/Si(100) substrate for different times by radio frequency (RF) magnetron sputtering. The relationship in terms of the microstructure and electrical properties between the ruthenium targets and resultant films at different conditions were studied by means of field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and four-point probe. The results showed that parameters such as the average deposition rate, surface roughness, crystallisation properties and growth rate were directly related to the homogeneity of the microstructure of the ruthenium targets, but there was no correlation between the crystal orientations of the films and the targets. Moreover, the resistivity of ruthenium films was positively correlated with that of the ruthenium targets.

Delicate control of graphite flakes alignment in the copper matrices via powder selections and filling processes

Due to the anisotropy properties of graphite flakes (Gf), the control of their orientation inside copper (Cu) matrice is strictly correlated with the final properties of such metal matrix composite (MMC). In this study, MMCs are fabricated by powder metallurgy process using three types of Cu powder particles (flake, dendritic, and spherical) as well as different powder filling methods. By using Cu flake powder with a relatively lower apparent density as compared to the two other Cu powder types (dendritic and spherical), high aligned Gf could be easily obtained, after uniaxial hot pressing, in a one-step powder filling approach. For the other two types of powders, a comparable orientation degree of Gf could be achieved only via several steps of delicate powder pressing. In-plane thermal conductivities of Cu/Gf composites were enhanced by improving the orientation degree of Gf, agreeing with effective medium approximation predictions (Maximum TC up to 540 W mK−1). A modeling, based on the apparent density of Cu powders, was discussed to show the effect of the alignment process on the final thermal property of such MMCs. This model supplies a basic guideline to obtain highly orientated Gf.

Fired electrical porcelain scrap (chamotte waste) recycling and reuse as an alternative raw material for sustainable porcelain stoneware production

The development of new sustainable ceramic formulations that incorporate industrial waste is a practice that meets the efficiency and sustainability criteria that today's society demands for an industry with high energy and non-renewable mineral sources consumption. In this research, fired electrical porcelain scrap (chamotte waste) was recycled and reused in the porcelain stoneware manufacture, partially replacing the quartz and feldspar from the triaxial system at 5, 10, 15, 20, and 30 wt%. The experimental samples were obtained after uniaxial pressing of ceramic mixture powders at 30 MPa and firing at 1260 °C following a fast-firing process (90 min cold to cold). The technological properties were studied by bulk density, apparent porosity, linear shrinkage, water absorption, cold crushing strength, and Vickers microhardness. The microstructural aspects and the amount of crystalline and amorphous phases in the ceramic bodies were analyzed by scanning electron microscope and X-ray diffraction, respectively. The best technical characteristics were achieved with the incorporation of 15 wt% of chamotte in the new ceramic formulations, yielding a density value of 2.41 g/cm3, and percentages of linear shrinkage and water absorption of 11.2 and 0.08 %, respectively, as well as mechanical resistance of 314.94 MPa and microhardness of 7.07 GPa. The mechanical resistance achieved by the experimental sample containing 15 wt% of chamotte waste means six times the value obtained by the control sample (0 wt% of chamotte addition) and was attributed to a higher mullite phase content and well-dispersed crystals (primary and secondary mullite) in the ceramic body. The results suggest and advance in the design and development of a best-performance porcelain stoneware materials elaborated by a sustainable and ecological route.

High-purity corundum grinding balls, obtained by quasi-isostatic pressing

The influence of the composition of press powders based on alumina CT 3000 LS SG, quasi-isostatic pressing and firing parameters on the structural and mechanical characteristics of grinding balls with a diameter of 40 mm is shown. Process parameters of production of high-density corundum balls are optimized on the basis of revealed regularities. The results of complex studies of physical and mechanical properties of ceramic articles are given. The determining effect of the particle size of raw material component on the hardness, density and operational characteristics of the grinding bodies was revealed.

Modes of wear of babbitt-based composite materials produced by hot pressing

The effect of additives of Ti2NbAl intermetallic compound on the friction of B83 babbitt samples obtained by hot pressing was studied using optical, electron microscopy and EDS analysis. The structure, friction surface and wear products were studied. Tribological tests were carried out on a universal test system under conditions of dry sliding friction according to the scheme of axial loading: a steel bush against a disk of the material under study. The temperature values near the friction zone were recorded. The limits of application of the material depend on the mode and mechanism of wear occurring in the tribocontact. Changes in the mode and mechanism of wear were assessed by differences in the behavior of the friction coefficient, temperature, difference in the state of friction surfaces, wear intensity and wear products. The results obtained indicate the prospects of using the method of hot pressing of powder from the B83 alloy and discrete particles of the high-strength Ti2NbAl intermetallic phase to get composite materials with improved tribological properties compared to a babbitt alloy. The introduction of reinforcing high-modulus particles of intermetallic compounds changed the structure of the material and affected the friction processes in babbitt, pushing aside the onset of change in the mode of wear towards more severe friction conditions. A significant decrease in the wear intensity of babbitt-based composite materials compared to the original alloy makes it possible to predict an increase in the service life of tribo-units. The data obtained enable us to determine and recommend modes that improve the performance of tribo-nodes in the manufacture of both volumetric inserts and plain bearings made of B83 alloy and, moreover, to create new functionally organized layered compositions with enhanced tribotechnical properties with a base of structural steels and working surface layers not only using B83 babbitt, but also of composite materials based on B83 babbitt.

Investigation of the Microstructure of Porous Tube-Shaped Elements Made of Ti-Powder Materials

The method of powder metallurgy for the manufacture of titanium products has the advantages of low cost of raw titanium, short technological process, low energy consumption, and less equipment investments. This allows to significantly reduce the total costs. The method is a potential technology to manufacture inexpensive products from titanium alloys. Due to its high strength, low specific weight and high corrosion resistance, titanium is widely used in aerospace and automotive industries and biomedicine. Among various applications of titanium, tube- and disc-shaped products from titanium powder are essential. The paper presents the results on the investigation of products made of titanium powder by the method of magneto-pulse pressing. Titanium powders with a particle size of 160-1000 mm produced by grinding titanium sponge and its powder compositions were used in the investigation. Investigation results on microstructure and porosity are also discussed. The mean porosity of the samples after sintering was 25-28% for products of 4-6 mm thick. With increasing thickness, the porosity increases to 35% and more, while it was non-uniform both over the cross-section of a tube-shaped product and along its length. The outer surface of the product was found to have a looser microstructure. This can be explained by the application of an intermediate fusible layer to the inner wall of the shell, which makes easier the removal of the shall after pressing. The studies generally confirm the possibility tof using the magneto-pulse pressing of titanium powders in shells to manufacturesmall product batches.