Powder Porosity Research Articles

The Effect of Carrier Quantity and Drying Method on the Physical Properties of Apple Juice Powders

The study aimed at the evaluation of the physical properties of apple juice powders mixed with different concentration of maltodextrin obtained by freeze-, vacuum and spray drying methods. Due to the chemical composition of apple juice there was a possibility to obtain apple juice powders by freeze-, spray and vacuum drying, excluding vacuum drying at 40 °C when 15% and 20% of maltodextrin were added. The moisture content of powders was more dependent on the drying method than on the quantity of maltodextrin added. The spray drying process in the context of an increase in maltodextrin quantity resulted in a decrease in the water activity of apple powders, whereas low temperature processes increased its values. Lower values of true density were observed after spray drying in comparison to freeze- and vacuum drying processes. The application of selected drying methods resulted in the formation of different particles’ size of apple powders influencing the bulk density of the products. The highest values of bulk density were indicated for powders obtained by vacuum drying due to the bigger size of the particles (crystalized structure). The porosity of apple juice powders was strictly related to the bulk density. Colour parameters of powders were more influenced by drying techniques than the quantity of maltodextrin (15% up to 35%) added.

Review—Phosphor Plates for High-Power LED Applications: Challenges and Opportunities toward Perfect Lighting

In the past decades, solid-state lighting based on phosphors as energy converters has been a fast-growing industry. Phosphor-converted white light-emitting diodes (pc-wLEDs) enable high-power applications and miniaturization; for this, the phosphor must have good stability and high efficiency. In order to satisfy this demand, phosphor plates have been proposed instead of conventional organic-based phosphor binders. In this review, such phosphor plates are categorized according to their synthesis methods, and the advantages and disadvantages of each category are detailed. In addition, we describe the major aspects of phosphor plates that require improvement for applications in high-power devices. For the fabrication of high-power LEDs, the phosphor configuration, color purity, porosity, and particle size of glass powders are key properties to enhance the luminescence efficiency and reduce the generation of heat inside wLED packages, thereby improving thermal stability.

Influence of Melt State on the Properties of Nickel-based Powders for Wear-Resistant Coat

The influence of time-temperature treatment on properties of the PG-SR-type alloys in cast condition, in produced powders and coatings is studied in this work. The temperature dependence of physical properties were obtained. These results and the comparative metallographic analysis have allowed offering the mode for time-temperature treatment of the liquid PG-SR-type alloys. Use of the time-temperature treatment when producing metal powders and coatings are as follows: the dispersibility of powders increases; the yield of powder fractions used for applying coatings increases; the powder porosity and oxidation decreases; oxidation resistance in various media increases; corrosion-, heat-, and wear resistance increases.

Al-Limestone and Al-Granite Composites Prepared by Cold Spraying

Two types of aluminium metal matrix composites (Al-MMCs) were prepared by cold spray process. The first Al-MMC was reinforced with granite rock and the second was reinforced with limestone rock particles. Al powder and rock powders (granite or limestone) were mixed to homogeneous mixtures and sprayed onto the Al substrate. The microstructure of as-sprayed composites was compared with microstructure of MMCs reinforced with commercially available Al2O3. The microstructures of Al-MMCs reinforced with granite and limestone were affected by hardness of rocks, particle sizes and compositions of the mixture. The coating is formed through high velocity impact of solid powders. The diameter of Al powder was about 30 μm and diameters of rock powders were from 5 to100 μm. Rock particles are distributed uniformly through the coating, maintaining their irregular morphologies. However, some large sized particles cracked and fragmented. The powder porosity was approximately 2.3 % for both types of Al-MMCs. Porous microstructure leads to lower critical velocity. The results indicate that, introducing irregular morphologies and/or pores into the feedstock. High quality metallic coatings can be more easily deposited by cold spray.

Transient Thermo-mechanical Modeling of stress Evolution and Re-melt Volume Fraction in Electron Beam Additive Manufacturing Process

The quality of parts produced using powder bed fusion additive manufacturing processes viz. electron beam melting mainly depends on the energy source, raster scan pattern, and stress evolution due to concentrated heat addition. In the present work, effort has been made to analyze the relationship between various process parameters such as input power, penetration depth, raster scan hatch spacing, powder porosity and their effects on the temperature profile, stress evolution and re-melt volume, using a three-dimensional thermo-mechanical simulation of the EBAM process on AISI 316L stainless steel, implemented using the COMSOL® multiphysics modelling platform. The volume fraction of re-melt material shows a non-linear and non-monotonic dependence on the electron beam size. The results of this study pave way for robust design of the EBAM process from simulation point of view.

Influences of the Air in Metal Powder High Velocity Compaction

During the process of metal powder high velocity impact compaction, the air is compressed sharply and portion remains in the compacts. In order to study the Influences, a discrete density volleyball accumulation model for aluminium powder was established with the use of ABAQUS. Study found that the powder porosity air obstruct the pressing process because remaining air reduced strength and density of the compacts in the current high-speed pressing (V≤100m/s). When speed further increased (V≥100m/s), the temperature of the air increased sharply, and was even much higher than the melting point of the material. When aluminium powder was compressed at a speed of 200m/s, temperatures of air could reach 2033 K, far higher than the melting point of 877 K. Increased density of powders was a result of local softening and even melt adhesive while air between particles with high temperature and pressure flowed past.

Laboratory experiments on bentonite pellet saturation

Abstract The aim of the DOPAS project is to address the design basis, reference designs and strategies for the plugs and seals to be used in geological disposal facilities. The Czech ‘Experimental Pressure and Sealing Plug’ (EPSP) experiment has the following objectives: to develop, monitor and verify the functionality of an in situ experimental plug, and to determine and describe in detail the materials to be used with respect to experimental plug construction. The functionality of the experimental plug will be verified by means of conducting pressure tests after the construction phase of EPSP. The internal bentonite section of the EPSP will be constructed from bentonite pellets with a dry density of 1850 kg m −3 ; the pellets will disintegrate following saturation and swelling to form a homogeneous material with a dry density of around 1400 kg m −3 . This process leads to the question of the pore space of the bentonite material: that is, whether it will be possible to employ a numerical model for homogeneous compacted bentonite powder porosity instead of that of the double pore/void space of the bentonite pellets used in the experiment. For this reason, a laboratory physical model (PHM – physical hydraulic model) was incorporated into the DOPAS project for the purpose of describing the saturation and disintegration of the bentonite pellets. The aim of this paper is to describe the results of the space distribution of relative humidity in a sample consisting of bentonite pellets with a view to subsequent numerical modelling and to extend the current knowledge concerning the behaviour of the bentonite pellets used in the EPSP experiment. The results show that following water saturation and the swelling of the bentonite the pellets form a homogeneous mass in the same way as does the compacted bentonite powder. After a period of 160 days, the pellets attained 100% relative humidity at a distance of 12.5 cm and swelling pressure recorded at the end of the model was seen to slowly increase over this time period.

Production of mango powder by spray drying and cast-tape drying

The production of mango powder by spray drying and cast-tape drying, with and without the addition of maltodextrin was investigated. Moisture, particle size distribution, bulk density, particle density, porosity, morphology, total carotenoids content, water sorption isotherms, glass transition temperature and color of mango powders from both drying processes were compared. Powders resulting from cast-tape drying had irregular structure, different from the spherical structures showed by powders produced by spray drying. Cast-tape drying process resulted in powders with bulk densities of 0.8gcm−3 (with maltodextrin) and 0.7gcm−3 (without maltodextrin), higher than the observed for analogous powders produced by spray drying (bulk densities of 0.45 and 0.5gcm−3). Also, porosity of powders from cast-tape drying (below 60%) was lower than that of powders produced by spray drying. Mango powders produced by spray drying without maltodextrin showed the highest carotenoid concentration (113μm of carotenoidg−1 of dry mass). The state diagrams show that mango powders produced by spray drying exhibit slightly lower stability than those produced by cast-tape drying. Cast-tape drying is a suitable procedure for the production of mango powders and allows producing powders from whole fruit pulp, without the addition of maltodextrin.

High resolution pore size analysis in metallic powders by X-ray tomography

The deployment of additive manufacturing processes relies on part quality, specifically the absence of internal defects. Some of those defects have been associated with porosities in the powder feedstock. Since the level of porosity in the powder is generally very low, standard characterisation techniques such as pycnometry and metallography are not suitable for quantification. However, the quantification of such micro sized porosity in metallic powders is crucial to better understand the potential source of internal defects in final components and for quality control purposes. X-ray tomography with a 3 μm resolution offers the possibility to visualise pores in large volume of powder and to quantify their geometrical features and volume fraction using image analysis routines. This combination is unique and demonstrates the power of the approach in comparison to standard powder characterisation techniques. Results presented show the prospects and limits of this technique depending on the imaging device, material and image analysis procedure.

Characterization and photocatalytic activity of mixed nanocrystalline TiO2 powders prepared by xerogel-hydrothermal method in different acid solutions

TiO2 nanoparticles(NPs)were prepared via the hydrothermal route of TiO2 xerogel in nitric acid, hydrochloric acid and acetic acid. The physico-chemical properties of the powders were characterized by X-ray diffraction(XRD)and N2 adsorption desorption techniques. The effects of the different acids on the structure(crystal phase)and texture(primary particle size and porosity)of the TiO2 powders were explored. Results indicated that acetic acid facilitated the formation and stability of pure anatase phase. On the other hand, nitric acid and hydrochloric acid led to the transformation from anatase to rutile. The catalyst synthesized via the hydrothermal route of TiO2 xerogel in the low concentration hydrochloric acid solution(Ti-HCl-0.15)had the highest photocatalytic activity than the catalysts obtained in the other two acid solutions. The effects of the different acids were discussed in terms of acid strength, chelating effect and the thermal stability of the adsorbed acidic anions.

Glycine-nitrate combustion synthesis of CeFeO3-based nanocrystalline powders

Glycine-nitrate combustion method was used to obtain powders based on CeFeO3 nanocrystals with average crystallite size in the range from 33 ± 3 to 51 ± 5 nm. The influence exerted by parameters of the glycine-nitrate combustion process and, in particular, by the glycine-nitrate ratio (G/N) on the composition and crystallite size of the synthesis products was determined. The optimal G/N ratio at which nanocrystalline cerium orthoferrite is formed with the minimum amount of impurity phases Fe2O3 and CeO2 was found to be 0.8. It was demonstrated that the composition of the starting solution affects the nature of the phase heterogeneity in the resulting product, crystallite size, and porosity of the nanocrystalline powders being formed. The patterns determined in the study make it possible to optimize the technology of nanocrystalline powders based on CeFeO3 in order to obtain powders with prescribed phase composition and crystallite sizes to enable their use as a basis for photocatalytic materials.

The porosity of NiCo2O4 films and powders by three common preparation techniques

The spinel NiCo2O4 has been prepared as a powder and a film by three common techniques: thermal decomposition, co-precipitation and spray pyrolysis. The porous nature of these materials has been investigated by a combination of nitrogen adsorption and mercury intrusion porosimetry. It is shown that thermal decomposition yields a material of low meso-porosity with the majority of pores being confined to the macropore region. Both co-precipitation and spray pyrolysis yield powders of appreciable BET surface area and meso-porosity in a mono-modal distribution. The pore size distributions indicate smaller pores in the case of the co-precipitated sample. The preparation of films by co-precipitation and spray pyrolysis is shown to introduce a second region of meso-porosity. The deposition of co-precipitated powder as a film is investigated through the addition of a PTFE binder with and without a pressing step in the process. Porosity is shown to decrease through the addition of PTFE with no pressing and decrease further again when the film is subjected to pressing.

Flow Characterization of Ambiently and Cryogenically Ground Black Pepper (Piper nigrum) Powder as a Function of Varying Moisture Content

AbstractThe knowledge about flow properties of powders is important in case of developing powder processes and handling procedures, packaging practices and transporting the processed powders. Major flow‐characterizing parameters such as angle of slide, apparent and tapped volume, poured and compacted densities, Hausner ratio, Carr index, compressibility index, different angle of repose and particle size distribution for black pepper powder (BPP) under ambient and cryogenic grinding conditions for different moisture contents (MC) were studied. Angle of slide was found to increase from 39° to 51° with increasing MC. Bulk density of porous and compacted BPP was found to decrease with increasing MC. The powder porosity was found to increase with increasing MC (25.9–27.4% for ambient grinding and 23.2–25.8% for cryogenic grinding). Hausner ratio and Carr index were higher in case of ambiently ground BPP as compared with cryogenically ground BPP. Static angle of repose was found to be higher for ambiently ground powder than for cryogenically ground powder, and showed an increasing trend in both the cases of ambient (65.85–70.25°) and cryogenic grinding (62.78–69.34°) with increasing MC. The flow characteristics of BPP as a function of MC may aid in better selection/design of appropriate handling, transportation, packaging and processing practices for BPP.Practical ApplicationsThe flow properties of ambiently and cryogenically ground black pepper powder will be useful to have control over processing parameters and will lead to improved quality and output of the black pepper powder. The study on flow properties of black pepper powder facilitates the reliable information for design of equipments for handling, processing, packaging and transportation of ground powder spices, which will in turn be economically helpful for powder‐processing industries. Powder sticking on the surface of processing equipments and agglomeration of powder particles creates problem in processing and also leads to loss of economy. Such type of difficulties can be handled with the help of present studies.

Effect of Iron Powder Preparation Method on Powder Steel Compact Formation During Electric-Contact Compaction

A dependence is given for porosity of iron powder and iron-graphite composite based on atomized and reduced powders on different electric-contact compaction regimes. A dependence is determined for the amount of bonded carbon on process regime. Limiting processes are established during formation of powder steel by electric-contact compaction.

Studying the porosity of powders under pressure compaction in deaeration mixers

A method of determining the porosity function of a finely dispersed mixture in the process of its mechanical compaction (deaeration) in a roll-tape nip depending on the Cartesian coordinates in the longitudinal plane of the device’s roller with consideration for the physicochemical characteristics of a deaerated mixture was proposed and taken as a basis for the engineering technique of calculating the two-stage roll-tape compacting unit of the apparatus designed to perform the consecutive engineering operations of the premixing of powders and the deaeration of their mixtures.

Application of N-hexoyl chitosan derivatives with high degree of substitution in the preparation of super-disintegrating pharmaceutical matrices

The present work investigated the utilization of degree of substitution in preparing N-hexoyl chitosan matrices with superdisintegration power. Different degrees of substitution of N-hexoyl chitosan (58, 67 and 75%) were prepared and evaluated. The study includes characterization of the derivatives using DSC, FTIR, surface tension, particle size, zeta potential, moisture uptake, powder flowability and powder porosity analysis. In addition, pressure-displacement, compact surface roughness using AFM, tensile strength, compact disintegration and dissolution studies. The studies indicated that the best superdisintegrant was due to the N-hexoyl chitosan with degree of substitution 57%. A compact of N-hexoyl chitosan with degree of substitution 57% showed water sorption more than 5 times increase of its initial weight. In addition, it showed a fast disintegration time i.e. less than 0.5 min. Such material could be a potential for the preparation of orodispersible tablets.

Fundamental modeling, functional attributes, porosity, cohesivity index (Hausner ratio) and compressibility of expanded-granule powder of Egyptian Ras pure cheese

Food industries and restaurants are increasingly soliciting high functionality cheese dried powder. Spray-drying is usually inadequate for cheese. Grinding of airflow dried cheese is very difficult because the product is compact and too hard. Instant controlled pressure drop DIC texturing assisted Swell-Drying SD usually allows the product to be more appropriated to obtain crispy snacks, leading to an innovative concept of cheese powder. The present work aimed at defining and optimizing this operation for the well-known Egyptian Ras Cheese. Relative expansion ratio, porosity, compressibility, and cohesivity were measured. Compared to Hot-Air Dried HAD, they were up to 210%, 120%, 856%, and 165%, respectively; all depending on DIC operating parameters. This was confirmed by scanning electron microscopy observations. Thanks to the instant autovaporization, vapor is generated within the product developing structural modification with vacuoles and cavities. Swell-Drying-grinding process allowed obtaining cheese powder with a well-controlled quality depending on consumer requirements.

Characterization Of The Graded Microstructure In Powder Sintered Porous Titanium

Abstract The proposed sintering process produce porosity and functional graded microstructure in the sinterd titanium powders. Titanium powders with different micro sizes were sintered at the proposed temperature region at 1200 and 1300°C for 2h. The apatite-forming on the graded microstructure is observed by immersion test in Hanks balanced salt soluion at 37°C. Sintering condition of titanium powders is estimated by thermogravitmetry-differential thermal analysis (TG-DTA). The synthersied surface structures and apatite-forming ability were characterized by a field emission scanning electron microscopy (FE-SEM) observation and energy dispersive X-ray spectroscopy (EDS) analysis. As results, these graded microstructure of sintered porous titanium powders reveals apatite-forming ability as osseointegration by calcification in Hanks balanced salt soluion(HBSS) at 37°C.

The Analysis of Microstructure and the Properties of the Metallic-Matrix Composite on the Basis of the Copper and Aluminum Oxide

The article is devoted to the analysis of the possibilities to obtain gradient materials by the method of spark plasma sintering. Pure copper powders consisting of particles with the average particle size 100 microns and the nanodispersed powder of aluminum oxide were used in this study. Two powder compositions - pure copper powder and a mixture of copper powder and aluminum oxide powder were sintered:. As a result of the sintering process a sample with a double-area structure has been formed with a well-defined boundary between these areas. After sintering the copper powder porosity remained at the initial level. But having been mixed and sintered, the aluminum oxide powder particles agglomerated up to the average particle size of 80 – 100 microns.

The Analysis of Microstructure and the Properties of the Metallic-Matrix Composite on the Basis of the Copper and Aluminum Oxide

The article is devoted to the analysis of the possibilities to obtain gradient materials by the method of spark plasma sintering. Pure copper powders consisting of particles with the average particle size 100 microns and the nanodispersed powder of aluminum oxide were used in this study. Two powder compositions - pure copper powder and a mixture of copper powder and aluminum oxide powder were sintered:. As a result of the sintering process a sample with a double-area structure has been formed with a well-defined boundary between these areas. After sintering the copper powder porosity remained at the initial level. But having been mixed and sintered, the aluminum oxide powder particles agglomerated up to the average particle size of 80 – 100 microns.