Dry mixing of cathode composite powder for all-solid-state batteries using a high-shear mixer

All-solid-state lithium-ion batteries (ASSLIBs) are promising candidates for next-generation batteries because of their various attractive properties. The uniform mixing of active materials (AMs) and solid electrolytes (SEs) is important for high-performance ASSLIBs. However, most AMs and SEs have poor flowability owing to their small particle size, which makes it difficult to uniformly mix the AM and SE particles. This study is focused on a high-shear mixer (HSM) as a scalable method to uniformly mix the AM and SE particles. The objective of this study is to determine the optimal operating conditions for HSM and its effectiveness in AM-SE mixing. The higher rotating speed of the chopper caused uniform SE dispersion by deagglomerating the SE particles and improving the adhesion of SE onto the AM particles, affording an electrode with well-balanced electrical/ionic conductivity and lower internal resistance. The ASSLIB with this electrode exhibited lower electrode polarization and excellent rate and cycle performance. Additionally, it has been demonstrated that the HSM could lead to a more uniform SE dispersion than conventional lab-scale mixing methods, resulting in significantly improved battery performance. Moreover, insights into the process-homogeneity-performance relations have been obtained.     

DEM simulation for optimal design of powder mixing in a ribbon mixer

A ribbon mixer is often employed in powder mixing in a wide range of engineering fields. The structure of the ribbon mixer is extremely complicated. This structure makes it difficult to understand the mixing mechanism by experimental approaches due to problems related to accurate sampling. At present, the mixing mechanism in the ribbon mixer is empirically identified as convection, despite a lack of precise assessment. Additionally, experimental investigations to find the optimal design of the ribbon mixer have not been sufficiently conducted because of its prohibitive cost. As such, there is a lack of sufficient discussion concerning the design for better mixing in the ribbon mixer. Numerical technologies represent a promising approach for solving the aforementioned problems. Significant improvements in computer hardware have enabled numerical models such as the discrete element method (DEM) to be positively employed in powder mixing. In the current study, an identification approach is developed for convective mixing, and besides, the study explores an effective parameter for better mixing in the ribbon mixer using the DEM. A swept volume measurement approach due to paddle movement is newly developed to identify the main mixing mechanism as convection. Sensitivity analyses are performed to find an effective parameter for better mixing. Through the sensitive analyses, the blade width is indicated as an important factor for achieving better mixing. Moreover, this study shows that the relationship between the swept volume and mixing index remains, even if the paddle width changes. Thus, the swept volume measurement method is revealed as useful for identifying the mechanism as convection in the ribbon mixer. Thus, not only novel finding regarding the blade width for better mixing but also the development of an approach for identifying convective mixing in the ribbon mixer is presented herein. Incidentally, convection being the dominant mechanism is consistent with the novel finding regarding blade width achieving better mixing.     

橡胶连续混炼粉料混合均匀性仿真及实验研究

为了提高橡胶连续混炼中混炼胶质量稳定性,实现炭黑等粉体物料精确配比和均匀性混合问题,针对粉体物料在混合和输送过程存在复杂的物理性质,建立了炭黑等混合粉料的球体颗粒模型和Hertz接触力-位移模型,采用EDEM对典型粉体物料混合均匀性进行模拟仿真和粉体物料混合实验,对炭黑等粉体物料在橡胶连续混炼工艺中的混合均匀性进行分析,探求橡胶粉料连续混合和输送机理.研究发现:粉体物料混合仿真与实验测试结果具有较高的拟合性,表明在橡胶连续混炼工艺中可以在保证混合均匀性的前提下实现多粉体混合物的连续称量和输送,同时也验证了运用EDEM数据模拟仿真粉体物料混合的可行性.     

DEM analysis of powder deaggregation and discharge from the capsule of a carrier-based Dry Powder Inhaler

In carrier-based Dry Powder Inhalers (DPI), fine API powder covers the surface of bigger carrier particles giving rise to dry coated particles, such that their flow properties are improved. In the hard-shell capsule of Cyclohaler DPI, powder deaggregation and discharge occurs as a result of the centrifugal motion and the subsequent aerodispersion to the mouthpiece induced by the patient’s inhalation. In this work, the crucial initial transient of this dispersion process was analysed through DEM (Discrete Element Method) simulations, by considering the solid phase only. The accelerated rotational motion of the capsule was simulated in the frame of reference of an observer rotating with the capsule, appropriately considering fictitious forces. The effect of the vibrations due to collisions between the capsule and the inhaler on powder discharge was evaluated as well for carrier particle systems. The results provide a punctual mapping of the particle-wall collisions within the capsule, allowing the path of the solids to be tracked until discharge. Simulations were carried out on drug-carrier blends with extreme size difference, considering adhesive interactions, elucidating the early-stage dynamics of the detachment process that occurs inside the capsule due to the interactions between particles and between particles and walls.     

A review of processing techniques for graphene-reinforced metal matrix composites

In the quest to enhance reinforcement efficiency of graphene in metal matrices, various processing techniques have been devised over recent years. As the advancement in this field nowhere seems to slow down, the processing aspects of graphene-reinforced metal matrix composites are becoming more relevant than ever. In that premise, there lies an imminent need for a critical assessment of existing fabrication routes and their ability to extend a solution for the primary challenges of agglomeration, dispersion, interfacial interaction and structural integrity of graphene in metal matrix composites. This review presents a brief yet a meaningful insight to the processing techniques for graphene-reinforced metal matrix composites, while highlighting the key findings from individual studies, thereby expressing the primitive challenges and strengthens of these techniques. A critical evaluation of state of the art is presented alongside an inclusive review of improvement in mechanical, thermal, and electrical properties of composites fabricated by various processing routes. In the consideration of reviewed literature, it is established that a comprehensive processing strategy with a potential to simultaneously address all of the key processing challenges of graphene, is yet to nurture. Conclusively, future road map and a potential solution encompassing hybrid processing strategies, is opined.     

On the processing properties and friction behaviours during compaction of powder mixtures

ABSTRACT

Iron-based powder mixtures were prepared by dry and wet mixing method. The friction properties during compaction were tested by measuring the internal and external friction coefficient. The test results showed that the wet mixing process could realise the homogeneity of lubricant and improve the processing properties of the powder mixtures. With 0.6 wt-% lubricants, wet mixing powder mixtures have a flow rate of 29.6 s/50?g, an apparent density of 3.18?g?cm^–3, a repose angle of 35.5°, and the friction coefficient during the compaction is 0.223. An equation to calculate the total (both internal and external) friction forces during the compaction process is proposed, and then the factors influencing the friction coefficient during compaction were quantitatively analysed.     

A novel mixing method for powder metallurgy copper-carbon nanotube composites

In this study, copper matrix composite materials with different ratios of carbon nanotubes were produced. The biggest problem faced in the production of carbon nanotube-reinforced composites is that carbon nanotubes do not distribute homogeneously in the matrix. A novel mixing technique was applied to overcome this problem. Hot pressing was used in sample production. A second high-pressure densification process was applied following the hot pressing process for enhancing the properties. The properties of both the hot-pressed specimens and the specimens to which a second high-pressure densification process was applied were characterized with the density measurements, microstructure examinations, and mechanical tests. The microstructure examinations showed that carbon nanotubes could be distributed homogeneously in the copper matrix with the mixing process applied. It was found out that the high-pressure densification process applied following the hot-pressing process increased the relative density and thus, all mechanical properties.     

Preparation of nitinol by non-conventional powder metallurgy techniques

The aim of the present paper was to compare the evolution of Ni–Ti intermetallics in two non-conventional production techniques for the synthesis of NiTi shape memory alloy. Short term ultrahigh energy mechanical alloying is proposed to be able to describe the early stages of the milling process, which was not described in the literature previously, and to obtain intermetallics in shorter process durations. The reactive sintering using high heating rate (>300°C?min^??1) is a process designed to suppress the formation of secondary intermetallics and to reduce the porosity of the product. The same phases' formation sequence was determined for both processes. The detrimental Ti₂Ni phase forms preferentially, and therefore, its presence cannot be avoided in any of the investigated techniques.     

Preparation and characterization of nanocrystalline Nd-YAG powder

Nanocrystalline materials have assumed notable importance in a wide variety of fields owing to numerous possible applications offered by them. These include transparent ceramics wherein they facilitate synthesis as well as sintering at significantly lower temperatures. We report preparation of nanocrystalline neodymium doped yttrium aluminum garnet (YAG) with an ultimate intent to make transparent Nd-YAG ceramic. The Liquid Mix method employed involves mixing of metal nitrates with excess amounts of citric acid followed by dissolution and polymerization in ethylene glycol to form complex chelates. Amorphous powder obtained by firing of polymeric chelate compound at 400 °C permits formation of nanoparticles of Nd:YAG at as low a crystallization temperature as 920 °C as shown by the thermal analysis. Progressive evolution of well crystallized phase-pure YAG was studied by XRD of amorphous powders subjected to different calcination temperatures. Scanning electron microscopic (SEM) study of the crystalline material shows that particle size ranges between 50 and 100 nm.     

A review of systematic evaluation and improvement in the big data environment

The era of big data brings unprecedented opportunities and challenges to management research. As one of the important functions of management decision-making, evaluation has been given more functions and application space. Exploring the applicable evaluation methods in the big data environment has become an important subject of research. The purpose of this paper is to provide an overview and discussion of systematic evaluation and improvement in the big data environment. We first review the evaluation methods based on the main analytic techniques of big data such as data mining, statistical methods, optimization and simulation, and deep learning. Focused on the characteristics of big data (association feature, data loss, data noise, and visualization), the relevant evaluation methods are given. Furthermore, we explore the systematic improvement studies and application fields. Finally, we analyze the new application areas of evaluation methods and give the future directions of evaluation method research in a big data environment from six aspects. We hope our research could provide meaningful insights for subsequent research.     

Recent progress on the discrete element method simulations for powder transport systems: A review

Powder transport systems are ubiquitous in various industries, where they can encounter single powder flow, two-phase flow with solids carried by gas or liquid, and gas–solid–liquid three-phase flow. System geometry, operating conditions, and particle properties have significant impacts on the flow behavior, making it difficult to achieve good transportation of granular materials. Compared to experimental trials and theoretical studies, the numerical approach provides unparalleled advantages over the investigation and prediction of detailed flow behavior, of which the discrete element method (DEM) can precisely capture complex particle-scale information and attract a plethora of research interests. This is the first study to review recent progress in the DEM and coupled DEM with computational fluid dynamics for extensive powder transport systems, including single-particle, gas–solid/solid–liquid, and gas–solid–liquid flows. Some important aspects (i.e., powder electrification during pneumatic conveying, pipe bend erosion, non-spherical particle transport) that have not been well summarized previously are given special attention, as is the application in some new-rising fields (ocean mining, hydraulic fracturing, and gas/oil production). Studies involving important large-scale computation methods, such as the coarse grained DEM, graphical processing unit-based technique, and periodic boundary condition, are also introduced to provide insight for industrial application. This review study conducts a comprehensive survey of the DEM studies in powder transport systems.     

Explosion risk evaluation during production of coating powder

Powder coating is widely used in industry to prevent equipment corrosion. More than 600 companies produce coating powder in China, but most do not understand the explosion hazard of such products. In the present investigation the explosibility parameters of a coating powder were determined. Results showed that the coating powder is explosible, though the ignition energy is higher than those of normal dusts such as coal powder and corn starch. Based on these experimental findings, a systematic explosion protection method is proposed, with explosion isolation and explosion venting being adopted as the main protective methods.     

A review of co-milling techniques for the production of high dose dry powder inhaler formulation

Drug delivery by inhalation offers several advantages compared to other dosage forms, including rapid clinical onset, high bioavailability, and minimal systemic side effects. Drug delivery to the lung can be achieved as liquid suspensions or solutions in nebulizers and pressurized metered-dose inhalers (pMDI), or as dry powders in dry powder inhalers (DPIs). Compared to other delivery systems, DPIs are, in many cases, considered the most convenient as they are breath actuated and do not require the use of propellants. Currently, the delivery of low drug doses for the treatment of lung conditions such as asthma and chronic obstructive pulmonary disease are well established, with numerous commercial products available on the market. The delivery of low doses can be achieved from either standard carrier- or aggregate-based formulations, which are unsuitable in the delivery of high doses due to particle segregation associated with carrier active site saturation and the cohesiveness of micronized aggregates which have poor flow and de-agglomeration properties. High-dose delivery is required for the treatment of lung infection (i.e. antibiotics) and in the emerging application of drug delivery for the management of systemic conditions (i.e. diabetes). Therefore, there is a demand for new methods for production of high-dose dry powder formulations. This paper presents a review of co-mill processing, for the production of high-efficiency inhalation therapies, including the jet mill, mechanofusion, or ball mill methodologies. We investigate the different techniques, additives, and drugs studied, and impact on performance in DPI systems.     

A review on the light extraction techniques in organic electroluminescent devices

Organic electroluminescent devices are becoming increasingly important because of their potential applications for large area flat-panel displays and general lighting. The internal quantum efficiency of these devices have been achieved near 100% using electro-phosphorescent materials with proper management of singlet and triplet excitons, however, the external quantum efficiency of conventional devices remains near 20% because of losses due to wave-guiding effect. Recently, there has been great progress to enhance the light out-coupling efficiency of organic electroluminescent devices by means of various internal and external device modification techniques. In this review we report recent advances in light out-coupling techniques, such as, substrate modification methods, use of scattering medium, micro-lens arrays, micro-cavity effect, photonic crystals and nano-cavity, nano-particles, nano-structures and surface plasmon-enhanced techniques that have been implemented to enhance the external extraction efficiency of organic electro-luminescent devices.     

Investigating the effects of excipients on the powder flow characteristics of theophylline anhydrous powder formulations

Pharmaceutical excipients may have a great effect on properties affecting tablet production. To determine if formulations containing theophylline anhydrous would have properties allowing them to be easily tableted, functional parameters affecting powder flow were evaluated. The Carr Flowability Indices were used for this evaluation. Formulations to be studied include theophylline anhydrous as the active ingredient, hydrous lactose and dicalcium phosphate dihydrate as diluents, polyvinylpyrrolidone as a binder, and fumed silica as a flow promoter. The effect of each component on powder flow is discussed.     

A density-dependent endochronic plasticity for powder compaction processes

This paper is concerned with the numerical modeling of powder cold compaction process using a density-dependent endochronic plasticity model. Endochronic plasticity theory is developed based on a large strain plasticity to describe the nonlinear behavior of powder material. The elastic response is stated in terms of hypoelastic model and endochronic plasticity constitutive equations are stated in unrotated frame of reference. A trivially incrementally objective integration scheme for rate constitutive equations is established. Algorithmic modulus consistent with numerical integration algorithm of constitutive equations is extracted. It is shown how the endochronic plasticity describes the behavior of powder material from the initial stage of compaction to final stage, in which material behaves as solid metals. It is also shown that some commonly used plasticity models for powder material can be derived as special cases of the proposed endochronic theory. Finally, the numerical schemes are examined for efficiency in the modeling of a plain bush, a rotational-flanged and a shaped tablet powder compaction component.     

A novel mixing method for levitated particles using electrostatic fields

A continuous particle mixing system using electrostatic forces and vibrations was developed. The system consists of two symmetrically arranged devices. The same or different types of charged particles were continuously fed from each device in a dispersed state and mixed instantaneously in the space between devices. When charged particles with opposite polarities were fed from each device by changing the direction of the electric field, the particles were homogeneously mixed. The electric field and particle trajectories were numerically calculated to elucidate the particle-mixing mechanism. Furthermore, the mixing state of the particles was evaluated quantitatively using Shannon entropy.     

A system for powder transport based on piezoelectrically excited ultrasonic progressive waves

The transport and dosage of granular materials are an important part of Process Engineering. Thereby, the food, chemical, pharmaceutical and coating industries set high demands on the transport and dosage performances of the used plants. In this context, Ultrasound Process Technology in the past years has developed itself into an attractive alternative compared to presently used classical technologies.

This paper describes the application of ultrasonic progressive waves in a powder-feeding device. The use of a specific pipe material with appropriate damping characteristics allows to generate a progressive wave using a single piezoelectric actuator. Small objects can be carried along the surface of a pipe by the elliptic motion at the surface, which is the result of a flexural progressive wave. The operational principle is the same as in travelling wave ultrasonic motors.

It was experimentally confirmed that the device can be used for feeding and supplying small amounts of powder. The powder-fed performance, however, strongly depends on environmental conditions, so that a control of the system is required. Construction and characteristics of a trial device are shown.     

Binder jetting of well-controlled powder agglomerates for breakage studies

Based on the similarity between the solidification process of the Additive Manufacturing (AM) binder jetting technique and wet granulation mechanisms, binder jetting is used to print powder granules with controlled geometry and strength. Powder granules with different strengths were achieved by changing the printing parameters, including the layer thickness and saturation level. The printed powder granules were then characterised for their structural properties such as their porosity and printing accuracy. Different parameter settings were found to have a significant influence on surface roughness. The strength of powder granules was improved by increasing the print saturation level, without compromising the printed geometry. A breakage study was carried out by compression tests of granules printed with different shapes and strengths. The relationship between print setting, structure and strength was established and discussed. This study demonstrates that AM powder granules with designed shapes and well-controlled strengths may act as ideal calibration particles for a range of industrial applications.