Recycling Of Powder Research Articles

One-Pot Fabrication of Hierarchical Floating Bi–Bi2S3–Bi2WO6/Expanded Perlite Photocatalysts for Efficient Photocatalysis of Organic Contaminants Utilized Sunlike Illumination

Photocatalysis currently faces a number of challenging issues, such as low efficiency, expensive precursors of noble metals, and difficult recycling of powder, which are grievous impeders for powde...

Effect of Powder Recycling in Laser-based Powder Bed Fusion of Ti-6Al-4V

Additive manufacturing (AM) has shown promise to process parts for end-use applications, however stringent requirements must be fulfilled in terms of reliability and predictability. The expensiveness of raw materials for AM, especially for metal-based Powder Bed Fusion (PBF), brings about the need for a careful recycling of powder, but the effect of powder reuse on both processing conditions and final part performance is still the focus of intensive research in the open literature. Although ASTM F2924-14 specifies the virgin-to-used powder ratio to be introduced to manufacture titanium-6aluminum-4vanadium (Ti-6Al-4V) components by PBF, a deeper understanding of the effect of powder recycling on the mechanical properties of finished parts is expected to foster a more efficient and safe reuse. The present contribution is therefore addressed to investigate the consequence of Ti-6Al-4V powder recycling on the flowability, particle size distribution and morphology of the feedstock material as well as on the density and tensile performance of built parts. In order to quantify the recyclability of powders, a new average usage (AUT) parameter is defined to account for both the real usage time of the powder and the virgin-to-used powder mixing ratio. The new parameter, whose applicability can be readily extended to any kind of feedstock powder, offers a significant contribution to achieve a more consistent and economical recycling of raw materials for PBF processing.

Assessment of strength development in cemented coastal silt admixed granite powder

The harmless treatment and even the effective reuse of wasted rock powders have become immediate tasks for multiple stone fabricating plants. However, there are poor techniques at present used to dispose of wasted rock powders properly and scientifically. In this paper, the concept of cemented coastal silt admixed granite powder (CCSAGP) was developed to address the recycling of granite powder as well as to improve the strength of cemented coastal silt. The granite powder, as an admixture, was first admixed into the cemented coastal silt, and the development of strength in CCSAGP specimens was assessed experimentally. This paper focuses on the roles of granite powder content, cement content, type of cement, and curing time in the development of strength in CCSAGP specimens. The results obtained show that the unconfined compressive strength of the CCSAGP specimens increases generally with an increase in granite powder content, cement content, and curing time. The inclusion of 10%-20% granite powder into the cemented coastal silt is clearly conducive to the development of strength in CCSAGP specimens, but the development of strength depends upon a number of factors. The role of the type of cement in the strength development of CCSAGP specimens is related to the growth in cementitious products, which demonstrates significant time-dependence. Moreover, scanning electron microscopy (SEM) experiments demonstrate that the microstructural evolution of the CCSAGP specimens exhibits three main effects, namely, a grain gradation effect, a cementation effect and a skeleton effect. Field investigations suggest that the field strength of deep mixing columns with admixing 10%, 15% and 20% granite powder is well enhanced when compared with columns without admixing granite powder.

Revealing the Effects of Powder Reuse for Selective Laser Melting by Powder Characterization

In a selective laser melting process, it is common to reuse the powder in consecutive cycles of the route because it is more sustainable and cost effective. However, it is unknown whether reusing the material has an influence on the process. In this paper, Inconel 718, Ti6Al4V, AlSi10Mg and Scalmalloy are characterized to determine the impact of reusing powders on the additive manufacturing (AM) process under an argon high-purity atmosphere. Virgin powders were taken from the suppliers and compared to powders that had been used in the process for a long period of time with periodic ‘rejuvenation’. A well-structured characterization procedure, combining many existing techniques, is proposed, determining changes in the morphology, composition (chemical and microstructure) and flowability. Clear differences between the virgin and used state are revealed by the characterizations; AlSi10Mg, appears to be the most sensitive to reuse with changes in particle size distribution and morphology, and with an increase in the oxygen content. The main contribution of this paper is providing insight into the effects of reuse for four commonly used AM powders, by means of a simple but well-structured method that links the particle feature characterization process to the flowability of metal AM powders. The provided insights enable enhanced decision-making on recycling and reuse of powder for specific AM processes.

Closed-loop recycling of polyamide12 powder from selective laser sintering into sustainable composites

A considerable amount of powder residue is generated during the selective laser sintering (SLS) process. Processing the powder residue into filaments for extrusion-based additive manufacturing (EAM) provides an opportunity to recycle SLS residue without significantly reducing its value. In this study, the feasibility of using a milled carbon fiber (mCF)/recycled polyamide12 (rPA12) composite filament for EAM was demonstrated. A microscopic study on the morphology of mCF showed that mCF is a short and smooth fiber. The mCF did not significantly change the melting temperature, crystallization temperature or crystallinity of rPA12 as measured by differential scanning calorimetry (DSC). A morphological study on the fracture-surface of the composites revealed that there was moderate interfacial interaction between the mCF and PA12. Tensile strength, tensile modulus, flexural strength, flexural modulus and impact strength of rPA12 were improved by 35%, 163%, 61%, 138% and 23%, respectively with the addition of 30 wt.% mCF.

Recycling of waste biomass and mineral powder for preparation of potassium-enriched compost

An attempt was made to recycle waste biomass and mineral powder (waste mica) as an alternative source of potassium (K) through composting technology. Two different waste biomass, isabgol straw and palmarosa distillation waste along with two levels of waste mica (2 and 4% as K) were used for preparation of enriched composts. A notable decrease of C:N ratio was observed at the end of the composting (150 days) as an indicator of compost maturity. The mature composts were evaluated for K-supplying capacity through laboratory leaching and soil incubation study. Significantly higher water-soluble K released initially followed by a sharp decrease up to 21 days of leaching thereafter gradually decreased up to 35 days of leaching. Water-soluble K was released from K-enriched (mica charged) compost significantly higher than the ordinary compost throughout the leaching period. Soil incubation study also revealed that application of K-enriched compost greatly improved the available K (water soluble and exchangeable) pools in K-deficient soil which indicated that a considerable amount of K releases during composting. Therefore, K-enriched compost could be an effective alternative of costly commercial K fertilizer and eco-friendly approach to utilize low-cost waste mineral powder and plant residue.

Recovery of silicon powder from kerf loss slurry waste using superconducting high gradient magnetic separation technology

A major challenge in recycling of silicon powder from kerf loss slurry waste is the complete removal of metal particles. The traditional acid leaching method is costly and not green. In this paper, a novel approach to recover high-purity Si from the kerf loss slurry waste of solar grade silicon was investigated. The metal impurities were removed with superconducting high gradient magnetic separation technology. The effects of process parameters such as magnetic flux density, slurry density, and slurry flow velocity on the removal efficiency were investigated, and the parameters were optimized. In one lot of control experiments, the silicon content was increased from 90.91 to 95.83%, iron content reduced from 3.24 to 0.57%, and aluminum content from 2.44 to 1.51% under the optimum conditions of magnetic flux density of 4.0 T, slurry density of 20 g/L, and slurry flow velocity of 500 mL/min. The result indicates that the superconducting high gradient magnetic separation technology is a feasible purifying method, and the magnetic separation concentrate could be used as an intermediate product for high-purity Si powder.

Integral recycling of municipal solid waste incineration (MSWI) bottom ash fines (0–2 mm) and industrial powder wastes by cold-bonding pelletization

The cold-bonding pelletizing technique is applied in this study as an integrated method to recycle municipal solid waste incineration (MSWI) bottom ash fines (BAF, 0–2mm) and several other industrial powder wastes. Artificial lightweight aggregates are produced successfully based on the combination of these solid wastes, and the properties of these artificial aggregates are investigated and then compared with others’ results reported in literature. Additionally, methods for improving the aggregate properties are suggested, and the corresponding experimental results show that increasing the BAF amount, higher binder content and addition of polypropylene fibres can improve the pellet properties (bulk density, crushing resistance, etc.). The mechanisms regarding to the improvement of the pellet properties are discussed. Furthermore, the leaching behaviours of contaminants from the produced aggregates are investigated and compared with Dutch environmental legislation. The application of these produced artificial lightweight aggregates are proposed according to their properties.

Environmental Sustainability of Laser Metal Deposition: The Role of Feedstock Powder and Feedstock Utilization Factor

Metal additive manufacturing (AM) is commonly promoted as a sustainable technology because of its capability to produce engineering components of complex geometries in a single step. Prior studies on environmental impact assessment of metal AM have underestimated the resource consumption due to the overestimation of the material utilization factor and neglecting the energy consumption needed to produce the desirable feedstock powder. This paper aims to address the role of feedstock powder and the actual material utilization factor in environmental impact assessment of laser metal deposition. Recycling and reuse of the unfused powder as the feedstock for subsequent depositions are proposed.

Surface chemical-bonds analysis of silicon particles from diamond-wire cutting of crystalline silicon

The recycling of the Si powder resulting from the kerf loss during silicon ingot cutting into wafers for photovoltaic application shows both significant and achievable economic and environmental benefits. A combined x-ray photoelectron spectroscopy (XPS), attenuated total reflection (ATR)-Fourier transform infrared (FTIR) and micro-Raman spectral analyses were applied to kerf-loss Si powders reclaimed from the diamond wire cutting using different cutting fluids. These spectroscopies performed in suitable configurations for the analysis of particles, yield detailed insights on the surface chemical properties of the powders demonstrating the key role of the cutting fluid nature. A combined XPS core peak, plasmon loss, and valence band study allow assessing a qualitative and quantitative chemical, structural change of the kerf-loss Si powders. The relative contribution of the LO and TO stretching modes to the Si-O-Si absorption band in the ATR-FTIR spectra provide a consistent estimation of the effective oxidation level of the Si powders. The change in the cutting media from deionized water to city water, induces a different silicon oxide layer thickness at the surface of the final kerf-loss Si, depending on the powder reactivity to the media. The surfactant addition induces an enhanced carbon contamination in the form of grafted carbonated species on the surface of the particles. The thickness of the modified surface, depending on the cutting media, was estimated based on a simple model derived from the combined XPS core level and plasmon peak intensities. The effective nature of these carbonated species, sensitive to the water quality, was evidenced based on coupled XPS core peak and valence band study. The present work paves the way to a controlled process to reclaim the kerf-loss Si powder without heavy chemical etching steps.

Feasibility Study of Zirconia Waste Recycling Obtained during the Machining of Single and Multiple Dental Prosthesis

Zirconia ceramic stabilized with 3% yttria (3Y - TZP) is the most used ceramic dental materials. During the machining of zirconia blocks in the laboratory to prepare the various types of prostheses, much of the material is lost in powder form, which is subsequently discarded. This study investigates the possibility to recycling of zirconium oxide powder obtained during milling of dental crowns and bridges. Uniaxial and isostatic pressed samples were prepared, sintered and compared to the commercial material. The results indicated that the isostatic pressed samples shows good physical and mechanical properties, comparable to the commercial material, demonstrating the viability to use this recycle material in the same process.

Recycling of waste artificial marble powder in HDPE‐wood composites

Waste artificial marble powder (AMP), an industrial waste generated from artificial marble processing, was recycled and incorporated in high‐density polyethylene (HDPE)‐wood composites. The results showed that waste AMP was mainly made up of aluminum hydroxide (Al(OH)3) and unsaturated polyester. Incorporating waste AMP into HDPE‐wood composites could increase the flexural strength and flexural modulus of composites but obviously decrease the notched impact strength. However, with the addition of maleic anhydride grafted polyethylene (MAPE), the mechanical properties of AMP/HDPE‐wood composites increased greatly. With 60 phr (parts per hundreds of resin) waste AMP, the notched impact strength and tensile strength of composites reached to 5.03 kJ/m2 and 28.0 MPa, respectively, increased by 98.1% and 55.6% compared to the composites without MAPE. Scanning electron microscopy (SEM) photographs revealed that MAPE improved the interfacial adhesion between fillers and HDPE matrix. In addition, the incorporation of waste AMP increased the heat resistance, limiting oxygen index (LOI) value of composites and decreased the horizontal burning rate. This study provides a new method for resource utilization of waste AMP, which could improve the performances of composites and avoid environmental pollution. POLYM. COMPOS., 39:2347–2355, 2018. © 2016 Society of Plastics Engineers

Recycling of silicon metal powder from industrial powder waste streams

Most industries today have waste or side streams that are deposited or sold as bi-products. Industries that are cutting and grinding silicon metal, such as the photovoltaic and semi-conductor industry, are depositing valuable metal powder materials. ReSiTec has worked on research projects for several years and developed new technology for recycling and purification of valuable metal powders. The focus has been silicon metal powder from cutting and grinding production. The process has been developed to collect fine particles, with a size range of 0–150 μm, from highly diluted waste water. Furthermore, known separation and classification techniques for metal powder processing have been adapted with the purpose of purifying and upgrading silicon metal powder from waste to new products. The tests performed were successful and the results showed an increase in purity level from 50% to >99% metallic silicon and an acceptable yield. It is believed that this new technology can be suitable for similar types of industrial metal powder waste streams. Today, ReSiTec is supporting the process industry with R&D services and is producing more than 500 tons per year of recycled, high-purity silicon metal powder.

Improvement of the properties of gypsum-based composites with recycled isostatic graphite powder from the milling production of molds for Electrical Discharge Machining (EDM) used as a new filler

The study here exposed was developed in order to contribute to the recycling and re-valorization of isostatic graphite powder as filler in gypsum pastes. Graphite powder is a waste product obtained from isostatic graphite blocks ground for mold production. The design of these molds is previously processed by Computer-Aided Manufacturing (CAM) and CAD/CAM software applications that uses a tool path for three-dimensional modeling to assist computer-numerically controlled (CNC).In order to contribute to the knowledge of this material as filler, this paper describes and assesses the microstructure of gypsums with graphite, through the use of a Scanning Electron Microscope and an Energy Dispersive X-ray Spectroscopy (SEM/EDX). Furthermore, the density, water absorption, and mechanical properties of gypsum pastes with addition of graphite filler have been analyzed.In order to deepen on the knowledge of the influence in the behavior of gypsum commonly used in building, several series of gypsum pastes with 0–5–10–15–20–25% of graphite filler by weight replacement of gypsum, and three different water/gypsum ratios – one of them with plasticizer – have been tested. It was observed that isostatic graphite powder from milled molds for Electrical Discharge Machining (EDM) significantly increases the mechanical properties of the gypsum pastes, more than other conventional fillers. This has been achieved by the great compatibility of the gypsum microstructure and the graphite micro-grains, which fill the microstructure of the pastes and increase the density of the hardened paste. The progressive increase of the amount of graphite influences the pastes properties, increasing their density and their mechanical resistances and reducing their porosity.

Recycled granulate obtained from waste alumina-rich refractory powder by the cold bonding process

Within the scope of the present study the cold-bonding process was used for the recycling of waste filter powder which was mixed with two different binders in different concentrations; alumino-silicate cement and potassium water glass, and combinations of these two materials, and hardened at room temperature. Selected samples were also fired at 1200°C. Tests to determine tensile and compressive strength, density and porosity, as well as dilatometry and SEM analyses, were performed. As expected, compressive strength increased as a function of the concentration of the potassium water glass. When combinations of both binders were used, compressive strengths were higher, but a significant increase in strength was also achieved by firing the samples. The compressive strengths of the non-fired samples were in the range from 0.8 to 2.4MPa, whereas after firing strengths of up to 36MPa were obtained. During the firing density increased, and porosity was reduced, while the average pore size increased. The results of dilatometric analysis showed that the granulate produced with cement shrink upon firing up to 300°C, but then start slowly to expand, whereas the granulate produced by water glass first expanded on firing up to 800°C, and then began to shrink swiftly. In the case of combinations of the two binders, shrinkage as well as expansion on firing was less pronounced. Selected granulate prepared using potassium water glass were also tested in a refractory concrete matrix in order to verify their usability.

Recycling of non-metallic powder from printed circuit board waste as a filler material in a fiber reinforced polymer

Recycling of non-metallic powder from printed circuit board waste as a filler material in a fiber reinforced polymer

Moisture based three-dimensional printing of calcium phosphate structures for scaffold engineering

Powder based three-dimensional printing (3DP) allows great versatility in material and geometry. These characteristics make 3DP an interesting method for the production of tissue engineering scaffolds. However, 3DP has major limitations, such as limited resolution and accuracy, hence preventing the widespread application of this metho engineering. In order to reduce these limitations deeper understanding of the complex interactions between powder, binder and roller during 3DP is needed. In the past a lot of effort has been invested to optimize the powder properties for 3DP for a certain layer thickness. Using a powder optimized for an 88μm layer thickness, this study systematically quantifies the surface roughness and geometrical accuracy in printed specimens and assesses their variation upon changes of different critical parameters such as the moisture application time (0, 5, 10 and 20s), layer thickness (44 and 88μm) and the number of specimens printed per batch (6 and 12). A best surface roughness value of 25μm was measured with a moisture application time (using a custom made moisture application device mounted on a linear stage carrying the print head) of 5s and a layer thickness of 44μm. Geometrical accuracy was generally higher for the 88μm thick layer, due to a less critical powder bed stability. Moisture application enabled 3DP of a 44μm thick layer and improved the accuracy even for a powder initially optimized for 88μm. Moreover, recycling of the humidified powder was not only possible but, in terms of reactivity, even beneficial. In conclusion, moisture-based 3DP is a promising approach for high resolution 3DP of scaffolds.

폐 TFT-LCD 유리분말을 혼입한 고강도 콘크리트 파일의 특성

In order to examine the P.H.C pile raw material using glass forming ceramic. The used materials is ordinary portland cement, waste TFT-LCD glass powder and reactive agent(Ca(OH)₂). The first experiment is characteristics analysis of the waste TFT-LCD glass powder, For the second experiment is mortar and concrete compressive strength for using of the concrete file raw material for waste TFT-LCD glass powder. The results of experiment showed that the substitution ratio of 10% waste TFT-LCD glass powder and 1% reactive agent(Ca(OH)₂) was excellent at a point of view for the physical characteristic. The study's most important finding is that the recycling of waste TFT-LCD glass powder.

Recycling of Cu powder from industrial sludge by combined acid leaching, chemical exchange and ferrite process

A method in combination of acid leaching, chemical exchange and ferrite process was applied to recycle copper and confer higher chemical stability to the sludge generated from etching process in printed circuit board industry. Ninety-five percent copper could be recycled in the form of powder from the sludge. Moreover, not only the wastewater after chemical exchange can be treated to fulfill the effluent standard, but also the sludge can satisfy the toxicity characteristic leaching procedure (TCLP) limits made by Taiwan's environmental protection administration.

Development and Subjects of Recycled Aggregate Concrete in Japan

The quality of RCA is influenced by the processing method and quality of original concrete. The general character of RCA, RCA and TR A 0006-2000(concrete using recycled aggregate) are introduced. The execution of RAC work, examples of real constructions with RAC, recycling of concrete powder originated from production of RAC and barriers of using RAC are discussed.