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Applying an impulsive force to a powder layer shaped with a concave surface generates a sharp powder jet. This phenomenon has been proposed as a method for evaluating the flowability of powders from small amount of samples. In this study, we systematically varied the radius of the initial concave shape as a controllable parameter and quantitatively examined the resulting jet dynamics, focusing on ejection velocity and maximum height. Our high-speed observations revealed that increasing the concave radius led to broader jets with significantly reduced velocity and maximum height. These dynamic quantities followed a scaling relation with drop height, while the scaling coefficient decreased with the concave radius, indicating that the surface geometry directly governs the extent of energy dissipation. Furthermore, a minimal mechanical model incorporating the sliding distance and velocity squared type dissipation of the powder flow reproduces the observed linear dependence of the jet height on the concave radius. These findings establish powder jets as a sensitive probe of dissipation in dynamic powder flow and provide a quantitative framework for comparing powder specific interactions

A custom apparatus designed to isolate and replicate the spreading process of metal powder in additive manufacturing demonstrates a sudden and unexplained increase in packing density beyond layers 5 to 10. We replicate the experiments that lead to densification with the discrete element method (DEM) using \lethe{}, an open-source software framework. We show that large-scale multi-layer DEM simulations are able to reproduce the densification observed experimentally. Using the Lagrangian simulation results, we highlight significant particle displacement in the powder bed at lower layer number, accompanied by static zones generated by the vertical wall surrounding the powder bed. The amplitude of the densification and the layer number at which it starts to occur is correlated to the distance between those two vertical walls which delimit the powder spreading area. This study addresses the gap between mono-layer powder spreading studies on hard-flat surfaces and the actual metal powder-based additive manufacturing processes by providing a better understanding of how the powder bed behaves during multi-layer spreading.

Powder bed additive manufacturing processes such as laser powder bed fusion (LPBF) or binder jetting (BJ) benefit from using fine (D50 $\leq20~μm$) powders. However, the increasing level of cohesion with decreasing particle size makes spreading a uniform and continuous layer challenging. As a result, LPBF typically employs a coarser size distribution, and rotating roller mechanisms are used in BJ machines, that can create wave-like surface profiles due to roller run-out. In this work, a transverse oscillation kinematic for powder spreading is proposed, explored computationally, and validated experimentally. Simulations are performed using an integrated discrete element-finite element (DEM-FEM) framework and predict that transverse oscillation of a non-rotating roller facilitates the spreading of dense powder layers (beyond 50% packing fraction) with a high level of robustness to kinematic parameters. The experimental study utilizes a custom-built mechanized powder spreading testbed and X-ray transmission imaging for the analysis of spread powder layers. Experimental results generally validate the computational results, however, also exhibit parasitic layer cracking. For transverse

Autonomous manipulation of powders remains a significant challenge for robotic automation in scientific laboratories. The inherent variability and complex physical interactions of powders in flow, coupled with variability in laboratory conditions necessitates adaptive automation. This work introduces FLIP, a flowability-informed powder weighing framework designed to enhance robotic policy learning for granular material handling. Our key contribution lies in using material flowability, quantified by the angle of repose, to optimise physics-based simulations through Bayesian inference. This yields material-specific simulation environments capable of generating accurate training data, which reflects diverse powder behaviours, for training "robot chemists". Building on this, FLIP integrates quantified flowability into a curriculum learning strategy, fostering efficient acquisition of robust robotic policies by gradually introducing more challenging, less flowable powders. We validate the efficacy of our method on a robotic powder weighing task under real-world laboratory conditions. Experimental results show that FLIP with a curriculum strategy achieves a low dispensing error of 2.12 +

Controlling the size of powder particles is pivotal in the design of many pharmaceutical forms and the related manufacturing processes and plants. One of the most common techniques for particle size reduction in process industry is powder milling, whose efficiency relates to the mechanical properties of powder particles themselves. In this work, we first characterize the elastic and plastic response of different pharmaceutical powders by measuring their Young modulus, the hardness and the brittleness index via nano-indentation. Subsequently, we analyze the behavior of those powder samples during comminution via jet-mill at different process conditions. Finally, the correlation between single particle mechanical properties and milling process results is illustrated; the possibility to build a predictive model for powder grindability, based on nano-indentation data, is critically discussed

Shear cell tests have been conducted on twenty different lactose powders, most of which commercially available for oral or inhalation purposes, spanning a wide range of particle sizes, particle morphologies, production processes. The aims of the investigation were: i) to verify the reliability of the technique in evaluating and classifying the flowability of powders; ii) to understand the connection between the flowability of a powder and the morphological properties of its particles; iii) to find a general mathematical relationship able to predict the yield locus shape given the particle size, shape and consolidation state of a lactose powder. These aspects and their limitations are detailed in the manuscript together with other interesting findings on the stick-slip behavior observed in most of the lactose powders examined.

Accurate modelling of diffraction peak shapes is essential for extracting microstructural information from nanocrystalline materials. Common-volume functions are widely used to describe finite-size and shape broadening in powder diffraction, but analytical expressions are available only for a limited set of ideal geometries. Here, we introduce a generalized Fourier-based framework in which crystal-domain shape deformation, lattice deformation, and relative shape-lattice misorientation are treated as independently refinable tensor operations within a unified formalism. The approach enables continuous affine transformations of both crystal shape and lattice base while preserving analytical evaluation of directional Fourier coefficients. As a result, complex particle shapes, anisotropic deformations, and arbitrary relative orientations between shape and lattice can be modelled within a single reciprocal- and real-space framework, including coupled shape-lattice transformations not accessible using conventional powder diffraction line-profile methods. The formalism can be applied to individual diffraction peaks, full powder patterns, and total-scattering shape corrections. Validation a

We report the development of a cryogenic powder filter that simultaneously offers high attenuation of radio-frequency (RF) signals in the gigahertz (GHz) range and minimized parasitic capacitance to ground. Conventional powder filters, which consist of a signal line passing through a metal powder-filled housing, attenuate high-frequency signals via the skin effect. However, these designs often suffer from significant parasitic capacitance between the signal line and the grounded chassis, which can compromise the performance of sensitive measurement setups by limiting their frequency bandwidth. In this work, we demonstrate that a multilayer powder filter design effectively achieves both high RF attenuation and reduced parasitic capacitance. This solution suppresses sample heating due to the unintentional intrusion of RF signals through the wiring, without degrading the performance of the measurement setup.

Lactose is the major component of milk powders and is normally found to be in a glassy/amorphous state. During storage, lactose is known to participate in physicochemical processes, including crystallization on the surface and reaction with proteins such as $β$-lactoglobulin. Lactose needs to be mobile to participate in such processes. However, there is a lack of evidence of its mobility in milk powders. In this study, we demonstrate that some of the lactose becomes mobile when milk powders are exposed to humid air $-$ an inappropriate storage condition. This mobility is evidenced by peaks in magic angle spinning $^{1}\mathrm{H}$ NMR spectra of milk powders in the range of 3.5 ppm to 4.0 ppm, which stem from lactose molecules displaying considerable rotational mobility. These signals have a longitudinal relaxation time constant T1 similar to that of mobile water according to 2D T1$-δ(^{1}\mathrm{H})$ experiments under magic angle spinning. Furthermore, 2D $^{1}\mathrm{H}-^{13}\mathrm{C}$ HSQC magic angle spinning experiments of skim milk powder demonstrate the same fingerprint as that of lactose in the solution, confirming our observations.

Triboelectrification of granular materials is a poorly understood phenomenon that alters particle behaviour, impacting industrial processes such as bulk powder handling and conveying. At small scales ($< 1 g$) net charging of powders has been shown to vary linearly with the total particle surface area and hence mass for a given size distribution. This work investigates the scaling relation of granular triboelectric charging, with small, medium ($< 200 g$), and large-scale ($\sim 400 kg$) laboratory testing of industrially relevant materials using a custom powder dropping apparatus and Faraday cup measurements. Our results demonstrate that this scaling is broken before industrially relevant scales are reached. Charge (Q) scaling with mass (m) was fitted with a function of the form $Q \propto m^b$ and $b$ exponents ranging from $0.68\ \pm\ 0.01$ to $0.86\ \pm\ 0.02$ were determined. These exponents lie between those that would be expected from the surface area of the bulk powder ($b = 2 / 3$) and the total particle surface area ($b = 1$). This scaling relation is found to hold across the powders tested and at varying humidities.

Local magnetic order and anisotropy are often central for understanding fundamental behavior and emergent functional properties in quantum materials and beyond. Advances in neutron powder diffraction experiments and analysis tools now allow for quantitative determination. We demonstrate this here with complementary total neutron scattering and polarized neutron measurements on the HB-2A neutron powder diffractometer at the High Flux Isotope Reactor (HFIR). In recent years, magnetic pair distribution function (mPDF) analysis has emerged as a powerful technique for probing local magnetic spin ordering of magnetic materials. This method can be broadly applied to any magnetic material but is particularly effective for studying systems with short-range magnetic order, such as materials with reduced dimensionality, geometrically frustrated magnets, thermoelectrics, multiferroics, and correlated paramagnets. Magnetic anisotropy often underpins the short-range order adopted. Half-polarized neutron powder diffraction (pNPD) can be used to determine the local susceptibility tensor on the magnetic sites to quantify the magnetic anisotropy. Combining the techniques of mPDF and pNPD can therefo

The powder stream from a side feed nozzle, or part of the powder stream in some coaxial nozzles, in a directed energy deposition via powder feeding (DED-PF) machine, can be modeled using a particle velocity field that has a constant downward component and a linearly increasing outward component, in proportion to the powder stream's center line distance. However, when the powder stream is subject to a force field, it was found that the shape of the powder concentration function close to the center of the powder stream diverges considerably at high degrees of focusing. This discrepancy is reduced by modeling the powder stream based on the ray representation of a Gaussian beam. Experimental results from high-speed camera particle tracking and numerically extrapolating the trajectories to the nozzle exit suggests that the statistics of the powder stream correspond to this model. A novel method to compute the particle concentration along the stream using an optical system analog, with the focusing force field modeled as the transfer matrix of a graded refractive index (GRIN) lens, is also demonstrated. This method is orders of magnitude faster than the corresponding Lagrangian simulatio

One of the major barriers in adapting the existing EB-PBF process parameters to a new powder material system is controlling the preheating conditions such that every layer of powder results in enough partial sintering to create a coherent powder cake. To be able to understand the powder sintering process and adapt it to other materials, we must look at the degree of sintering and the effective thermal conductivity of the powder bed. An in-depth understanding of these characteristics will help tailor the preheating conditions and furthermore, make it easier to remove/de-powder intricate parts after build completion without compromising the advantages of the preheating phenomenon. This study evaluates the impact of preheating temperature on the in-situ powder cake properties. Three different preheat temperatures, 650 °C, 690 °C and 730 °C, are employed to a Ti-6Al-4V powder cake and in each standalone build, unique powder-capture artefacts are fabricated to be able to analyze the in-situ powder cake properties using X-ray computed tomography. An empirically-derived model for thermal conductivity of the powder cake as a result of changing the preheating temperatures, was obtained. The

The use of computational techniques in the design of dry powder inhalers (DPI), as well as in unravelling the complex mechanisms of drug aerosolization, has increased significantly in recent years. Computational fluid dynamics (CFD) is used to study the air flow, inside the DPI, during the patient inspiratory act while discrete element methods (DEM) are used to simulate the dispersion and aerosolization of the drug product powder particles. In this work we discuss the possibility to validate a coupled CFD-DEM model for the NextHaler DPI device against previously published experimental data. The approximations and assumptions made are deeply discussed. The comparison between computational and experimental results is detailed both for fluid and powder flows. Finally, the potential and possible applications of a calibrated DPI model are discussed as well as the missing elements necessary to achieve a fully quantitatively predictive computational model.

This study investigates the impact of resonant acoustic powder mixing on the delay time of the W-KClO4-BaCrO4 (WKB) mixture and its potential implications for powder and material synthesis. Through thermal analysis, an inverse linear relationship was found between thermal conductivity and delay time, allowing us to use thermal conductivity as a reliable proxy for the delay time. By comparing the thermal conductivity of WKB mixtures mixed manually and using acoustic powder mixer, we found that acoustic powder mixing resulted in minimal deviations in thermal conductivity, proving more uniform mixing. Furthermore, DSC analysis and Sestak-Berggren modeling demonstrated consistent reaction dynamics with a constant activation energy as the reaction progressed in samples mixed using acoustic waves. These findings underscore the critical role of uniform powder mixing in enhancing the thermodynamic quality of the WKB mixture and emphasize the importance of developing novel methods for powder and material synthesis.

The spreading behaviour of cohesive sand powder is modelled by Discrete Element Method, and the spreadability and the mechanical jamming are focused. The empty patches and total particle volume of the spread layer are examined, followed by the analysis of the geometry force and jamming structure. The results show that several empty patches with different size and shapes could be observed within the spread layer along the spreading direction even when the gap height increases to 3.0D90. Large particles are more difficult to be spread onto the base due to jamming, although their size is smaller than the gap height. Size segregation of particles occurs before particles entering the gap between the blade and base. There are almost no particles on the smooth base when the gap height is small, due to the full-slip flow of particles. The difference of the spread layer and spreadability between the cases with rough and smooth base is reduced by the increase of the gap height. An interesting correlation between jamming effect and local defects (empty spaces) in the powder layer is identified. The resistance to particle rolling is important for the mechanical jamming reported in this work. T

In this paper, we present the results of single-track experiments conducted for different fractions of standard AlSi10Mg powder, which were sieved to achieve varying mean size of the particles. We observed strong differences in the melting behaviour of fractions at relatively low levels of input energy in laser powder bed fusion (LPBF) process. Namely, the remarkable particle size effect arises for the position of lack of fusion boundary, i.e. for the range of process parameters where the laser power becomes sufficient for complete through-thickness melting of the powder layer at given laser scanning speed. We established that this boundary corresponds to an approximately constant linear energy density at low levels of Peclet number (Pe < 2), while the constant enthalpy density defines this boundary at the higher levels (Pe > 2). Specifically, when the mean particle size ranges from 28 to 64 microns, the required linear energy density for stable track formation ranges from 50 to 167 J/m and the nominal enthalpy density ranges from 4.4 to 15 J/mm^3. Based on the scaling law analysis and numerical simulations, we show that observed phenomena can be attributed to the change of a

A path to lowering the economic barrier associated with the high cost of metal additively manufactured components is to reduce the waste via powder reuse (powder cycled back into the process) and recycling (powder chemically, physically, or thermally processed to recover the original properties) strategies. In electron beam powder bed fusion, there is a possibility of reusing 95 - 98% of the powder that is not melted. However, there is a lack of systematic studies focusing on quantifying the variation of powder properties induced by number of reuse cycles. This work compares the influence of multiple reuse cycles, as well as powder blends created from reused powder, on various powder characteristics such as the morphology, size distribution, flow properties, packing properties and chemical composition (oxygen and nitrogen content). It was found that there is an increase in measured response in powder size distribution, tapped density, Hausner ratio, Carr index, basic flow energy and specific energy, dynamic angle of repose, oxygen, and nitrogen content, while the bulk density remained largely unchanged.

COSINE-200 is the next phase experiment of the ongoing COSINE-100 that aims to unambiguously verify the annual modulation signals observed by the DAMA experiment and to reach the world competitive sensitivity on the low-mass dark matter search. To achieve the physics goal of the COSINE-200, the successful production of the low-background NaI(Tl) detectors is crucial and it must begin from the mass production of the ultra-low background NaI powder. A clean facility for mass-producing the pure-NaI powder has been constructed at the Center for Underground Physics (CUP) in Korea. Two years of operation determined efficient parameters of the mass purification and provided a total of 480 kg of the ultra-pure NaI powder in hand. The potassium concentration in the produced powders varied from 5.4 to 11 ppb, and the maximum production capacity of 35 kg per two weeks was achieved. Here, we report our operational practice with the mass purification of the NaI powder, which includes raw powder purification, recycling of the mother solution, and recovery of NaI from the residual melt that remained after crystal growth.