Powder Charge Research Articles

Letter: Driving waveforms based on powder charge for a quick‐response liquid‐powder display

Abstract— A driving waveform based on the powder charge of a quick‐response liquid‐powder display (QR‐LPD®) was investigated. The charging mechanisms for contact charging and triboelectric charging determine the powder charge of a QR‐LPD®. In this letter, driving waveforms containing both charging mechanisms are used for driving a QR‐LPD®. As the experimental results indicate, the charge of the powder accumulates according to the image refresh times. The waveform of a pixel voltage with a slight frictional charge achieves a better contrast ratio for a QR‐LPD®.

Xerorradiografía

Xeroradiography is a diagnostic imaging technique in which X-ray images are recorded electrically rather than chemically, on an aluminium plate coated with selenium. The latent image is made visible by an electrically charged fine powder, so that the image is formed by attraction and repulsion of charges. The xeroradiography was mainly used in the study of soft tissue.

Evaluation of effect of blast design parameters on flyrock using artificial neural networks

Flyrock, the propelled rock fragments beyond a specific limit, can be considered as one of the most crucial and hazardous events in the open pit blasting operations. Involvement of various effective parameters has made the problem so complicated, and the available empirical methods are not proficient to predict the flyrock. To achieve more accurate results, employment of new approaches, such as artificial neural network (ANN) can be very helpful. In this paper, an attempt has been made to apply the ANN method to predict the flyrock in the blasting operations of Sungun copper mine, Iran. Number of ANN models was tried using various permutation and combinations, and it was observed that a model trained with back-propagation algorithm having 9-5-2-1 architecture is the best optimum. Flyrock were also com- puted from various available empirical models suggested by Lundborg. Statistical modeling has also been done to com- pare the prediction capability of ANN over other methods. Comparison of the results showed absolute superiority of the ANN modeling over the empirical as well as statistical models. Sensitivity analysis was also performed to identify the most influential inputs on the output results. It was observed that powder factor, hole diameter, stemming and charge per delay are the most effective parameters on the flyrock.

Effect of microparticles of titanium diboride and nanoparticles of titanium carbonitride on the structure and properties of deposited metal

Formation of composite structure in a wear-resistant metal obtained by introduction of refractory microparticles of titanium diboride and nanoparticles of titanium carbonitride charged with powder wire into the molten pool is considered. Dependences of the hardness and abrasive wear resistance of the deposited metal on the content of powder titanium diboride and carbon in the charged powder wire are determined.

Powder and Film Charging Characteristic Estimation by the Standard Carrier of Imaging Society Japan

Two-component developers which consist of toners and carriers are widely used in modern electrostatic copying machines and laser printers which utilize electrophotographic printing process. Toner charge is essential in electrophotography. The toners are triboelectrically charged by the carriers when they come in to contact. Although there are several factors which come to effect in quality in electrophotography, control of adhesion of triboelectrically charged toner particles is crucial. As such the estimation of toner electrostatic properties is very important. ISJ (The Imaging Society Japan) has proposed the standard carriers with different charging abilities for estimating toner charging property as a standard method of measurement. The electrostatic surface potentials, when the films come in to contact with standard carriers are discussed. Further, Tungsten is used for film charging to understand the charging property. The contact is carried out as carriers and Tungsten beads are rolling on the film. It is confirmed that the standard carriers proposed by the committee of ISJ show same tendency in the film charging estimation as against standard toner. It is proposed that the standard carriers are useful to estimate the charging properties of various shape material.

Structure of the Borosilicate Zeolite Catalyst SSZ-82 Solved Using 2D-XPD Charge Flipping

The structure of the calcined borosilicate zeolite catalyst SSZ-82 ([Si(61.3)B(4.7)O(132)], Pmmn, a = 24.2783(4), b = 11.4665(2), and c = 14.1127(3) Å) has been solved from X-ray powder diffraction (XPD) data using the recently developed 2D-XPD charge flipping approach. The electron density maps generated with the more conventional powder charge flipping (pCF) algorithm could not be interpreted easily, so this new method, which begins by phasing low-resolution, 2D subsets of the data, was applied. Crystallographic phases were derived for the three main projections ([100], [010], and [001]) by using just the corresponding subsets of reflections (0kl, h0l, and hk0, respectively) from the full set of 3039 extracted intensities. These phases were then imposed on the (otherwise random) starting phases in the application of the pCF algorithm to the full data set. The framework structure, with 11 Si/B atoms in the asymmetric unit and a novel 12-/10-ring 2D channel system, could be seen clearly in the resulting electron density map. This is the first application of the 2D-XPD method to data collected on a material of unknown structure. Rietveld refinement of the structure revealed the positions of the B atoms in the framework and indicated that some water had been readsorbed in the pores.

Electrostatic charge dependence on surface hydroxylation for different Al 2O 3 powders

The effect of surface chemistry on the electrostatic charge in α-Al 2O 3 powders was studied. Net charge and tribo-charge of dry powders were measured by the Faraday double cup procedure. High electrostatic charge values were observed in powders with high surface hydroxylation by IR spectroscopy. The nature of hydroxyl groups at the surface determines the polarity of the electrostatic charge. Mixture of particles having intrinsic electrostatic positive and negative charges follows the lever rule. Dry mixtures of differently charged particles favour the dispersion of smaller particles on the surface of the largest ones. An effective random dispersion was achieved by a low-energy process that allowed preserving the morphology of the supporting and supported particles.

Pushing the limits of powder charge flipping

Pushing the limits of powder charge flipping

Factors affecting the electrostatic charge of ceramic powders

Los fenomenos de carga electroestatica en polvos ceramicos se producen cuando las superficies de los mismos entran en contacto entre si y con los elementos que las contienen. La acumulacion de cargas electrostatica es importante en polvos ceramicos dado su caracter aislante y debido al riesgo de explosiones por descarga. En este trabajo se estudian los principales factores que afectan a la aparicion de carga neta y la tribocarga en las particulas de polvo ceramico. En polvos ceramicos de alumina se ha comprobado que las particulas mas finas presentan un aumento de la carga electrostatica con una polaridad negativa. Se ha observado una correlacion entre la naturaleza de los grupos OH- superficiales y la carga electrostatica. La carga neta y la tribocarga en polvos ceramicos se pueden reducir si se compensan los sitios superficiales que soportan dicha carga. La dispersion en seco de nanoparticulas sobre microparticulas permite la compensacion de la carga superficial con una importante modificacion del estado de aglomeracion de los polvos ceramicos.

Electrostatic charge interactions in ordered powder mixes.

A method is described for measuring the electrostatic charge generated in powders following contact with a plane substrate. The method uses a Faraday well connected to an electrometer and allows the specific charge of powders to be determined. Of the various drugs and excipients studied, most charged electronegatively following contact with glass surfaces, but became electropositive after contact with polyethylene surfaces. The charge interactions of drug and excipient powders modified the behaviour of ordered mixes formed in similar conditions to those of charge measurement. Powders with like charges formed less stable ordered mixes than those in which drug and excipient particles carried opposite charges. Following triboelectrification in an air cyclone constructed of brass, powders had charges at least 100 times greater than those formed after contact with glass surfaces. Optimization of the triboelectric charging conditions allowed ordered mixes to be prepared in which a maximum electronegative charge was applied to the excipient whilst the drug was given a maximum electropositive charge. Studies of segregation/stability showed that ordered mixes subjected to triboelectrification were less prone to segregation than uncharged powders.

Formation of a uniform charge composed of highly dispersed and ultradispersed powders

In modern powder metallurgy, powders that are in a highly dispersed state are being used more and more to create new materials composed of powders which are dissimilar from one another. This trend has engendered a need to mix charges that are made up of powders which differ in their physico-mechanical properties. The mixing operation must be highly productive while also ensuring the disintegration of conglomerates in the charge. This article describes a method and equipment that solve these problems by subjecting the powder charge to vibro-aereational mixing.

Fragmentation in small-scale confined blasting

Design of sub-level blasting rounds and optimisation has become more important now when the sizes of the blasting rings get larger. Sufficient fragmentation is one of the key factors, and in confined blasting as in sub-level caving, this influences the mobilisation of the blasted ring. Model scale tests have been made to understand the mechanisms of rock breakage and therefore fragmentation under relatively confined conditions. By using the acoustic impedance between the blasted material and the confining debris, a relationship for fragmentation has been found depending on material, specific charge (powder factor) and physical properties of the debris. The results can be comparable with confined blasting in large scale.

Formation of Zirconia Films by the Aerosol Gas Deposition Method (By Jetting of Positive Charged Powder)

Formation of Zirconia Films by the Aerosol Gas Deposition Method (By Jetting of Positive Charged Powder)

Mating Behaviors of Cydia pomonella (Lepidoptera: Tortricidae) as Influenced by Sex Pheromone in Electrostatic Powder

Entostat is an electrostatically charged wax powder that can adhere strongly to insect cuticle, making it an ideal carrier to deliver pheromone for pheromone-based confusion techniques. We investigated the attractiveness of Cydia pomonella (L.) (Lepidoptera: Tortricidae) males treated with pheromone-laden Entostat powder to naive conspecifics as well as mating behaviors of males after such treatment in a laboratory flight tunnel. Male moths exposed to Entostat containing 1% E,E-8,10-dodecadien-1-ol (codlemone) acquired and retained the largest amount of the powder and became more attractive as point sources to naive moths compared with those treated with powder containing 5 or 10% codlemone. All Entostat-exposed males remained as attractive as a 0.1-mg codlemone lure for up to 24 h in flight tunnel investigations. Male moth orientation to normally attractive sources of codlemone was completely disrupted directly after treatment with Entostat powder. Males' ability to orient to 0.1-mg lures recovered progressively over a 6-d postexposure interval; however, their responses never reached the levels observed with untreated control moths. Entostat-exposed moths retained detectable amounts of codlemone up to 4 d. Our laboratory flight tunnel results suggest that the mode of action of Entostat powder as an autodissemination control tactic may be due to creating both attractive false point sources after exposure to the powder as well as directly inhibiting contaminated males' capability to orient to pheromone.

Electrical stress and strain in lunar regolith simulants

Experiments to entrain dust with electrostatic and fluid-dynamic forces result in particulate clouds of aggregates rather than individual dust grains. This is explained within the framework of Griffith-flaw theory regarding the comminution/breakage of weak solids. Physical and electrical inhomogeneities in powders are equivalent to microcracks in solids insofar as they facilitate failure at stress risers. Electrical charging of powders induces bulk sample stresses similar to mechanical stresses experienced by strong solids, depending on the nature of the charging. A powder mass therefore “breaks” into clumps rather than separating into individual dust particles. This contrasts with the expectation that electrical forces on the Moon will eject a submicron population of dust from the regolith into the exosphere. A lunar regolith will contain physical and electrostatic inhomogeneities similar to those in most charged powders.

Construction of an organic crystal structural model based on combined electron and powder X-ray diffraction data and the charge flipping algorithm

The structure of an organic dye 1,5-diaminoanthraquinone (DAAQ) nanowire was studied by both electron diffraction and X-ray powder diffraction. The unit cell of the crystal was determined from a series of tilted selected area electron diffraction patterns (monoclinic: a=3.78 Å, b=9.73 Å, c=15.01 Å and β=82.4 °). By using precession electron diffraction, the following extinction conditions were determined, 0k0: k=2n and 00l: l=2n, which give the space group as P2₁/C (no. 14). The powder charge flipping algorithm was applied to resolve the phase problem and the structural model of the DAAQ crystal was built.

Electrophoretic deposition of doped ceria in anti-gravity set-up

An innovative anti-gravity set-up has been designed and fabricated to consolidate doped ceria powder by electrophoretic deposition. In this set-up, the charged ceramic powders dispersed in non-aqueous suspension moved upward in opposite direction to gravity under the influence of an external applied field and were consequently deposited on the lower face of upper electrode placed horizontally parallel above the counter electrode. Electrophoretic deposition using this innovative technique was found more superior to the conventional electrophoretic deposition using vertically arranged electrodes where a very broad particle size range was used. The deposit thus obtained predominantly contained finer particles which can move relatively easily against gravity. It enabled formation of homogeneous compact films. This paper presents the results of detailed investigation on the effect of different process parameters such as concentration of particles, duration, addition of charge modifier etc. on forming a deposit. A comparison of deposition yield in anti-gravity set-up vis-à-vis conventional set-up is also presented.

Experimental study on electrostatic charging of polymer powders in mixing processes

Powder mixing is often carried out in the chemical and pharmaceutical industries. Electrostatic charges generated on polymer powders during mixing may lead to electrostatic problems due to the poor conductivity of those powders. In this study, we investigated the electrostatic charges, surface potential, and apparent volume resistivity of sample powders using a simple mixing device utilizing the Faraday cup method. To neutralize the charged powders, we also applied an AC-type ionizer in the mixing study. A commercial polyethylene powder with a mean particle size of 585 μm was tested in this experiment. The charge-to-mass ratios at the end of 600 s of mixing were −0.075 nC/g at 295 rpm agitation speed, −0.21 nC/g at 495 rpm, and −0.31 nC/g at 660 rpm, high enough to cause electrostatic agglomeration and adhesion. The electric fields based on the surface potential on the powders were several hundreds of V/cm, too small to give rise to brush discharge. The apparent volume resistivity of powders estimated by a simple measurement system is 1.0 × 10 16 Ωm, in reasonable agreement with that acquired by the conventional test cell method (5.9 × 10 15 Ωm). The charging level on the polymer powders was reduced with an AC-ionizer.

Addition of fines for the reduction of powder charging in particle mixers

Experiments were carried out to study the effectiveness of fine powders as an additive on the reduction of electrostatic charge build-up for glass beads, polyethylene resins and starch powders in a mechanical shaking device. Four fine powders, carbon nanotubes (CNTs), Larostat 519, activated carbon and aluminum powders were tested on their effectiveness on charge reduction. It is found that particle size does have a significant effect on charge build-up of the bulk powder. The addition of small fraction of fine glass beads (150–170 μm) into coarse glass beads (210–300 μm) led to observable charge reduction, indicating that small particles added to large bulk powders can help reduce electrostatic charge build-up. Compared to other additives of larger sizes, CNT is a much more effective antistatic agent. Aluminum powder performed poorest among all additives tested. CNTs out-performed the commercial antistatic powder, Larostat 519, in reducing the charge generated by shaking action. Furthermore, better charge dissipation was observed at higher CNT contents. The experiment also revealed that conductivity alone was not a good indicator of antistatic capability because aluminum powder, despite having a good conductivity, performed poorly.

Kinetics of mechanically induced anatase-to-rutile phase transformations under inelastic impact conditions

This work investigates the kinetics of the anatase-to-rutile phase transformation of TiO 2 powders during ball milling. Two elementary stages are observed, namely the transformation of anatase to the TiO 2 II phase and of this latter to rutile. Such consecutive reactions were studied under inelastic impact regimes. Based on a suitable modeling of transformation kinetics, the fraction of powder processed on average at each collision was estimated. The mass of powder involved in phase transformation and microstructural refinement processes at each collision was then worked out by a systematic variation of the powder charge inside the reactor.