Characterization of powder flow behavior for additive manufacturing

Karl, David; Spitzer, Andrea; Gurlo, Aleksander; Günster, Jens; Zocca, Andrea

doi:10.1016/j.addma.2021.102250

Cited by 17 publications

(24 citation statements)

References 26 publications

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“…Because the surface chemical condition constitutes an additional factor that may affect particle–particle interaction and hence flow as well as the sintering, it is of paramount importance to couple this information as well to the overall powder characterization. Considering oxides of copper, CuO is a weak base, whereas Cu 2 O is supposed to show stronger basic properties in a Lewis sense 20 . Both are characterized as being metal deficient p‐type extrinsic semiconductors, with band gaps of 1.2 and 2.17 eV for CuO and Cu 2 O, respectively.…”

Section: Resultsmentioning

confidence: 99%

“…Considering oxides of copper, CuO is a weak base, whereas Cu 2 O is supposed to show stronger basic properties in a Lewis sense. 20 Both are characterized as being metal deficient p-type extrinsic semiconductors, with band gaps of 1.2 and 2.17 eV for CuO and Cu 2 O, respectively. In as-received conditions, it can be expected that there is hydroxide formation as well.…”

Section: Surface Chemical Analysismentioning

confidence: 99%

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Surface chemical and geometrical properties of pure copper powder intended for binder jetting and sintering

Nyborg

Cao

2022

Surface & Interface Analysis

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One novel important application of sinter‐based additive manufacturing involving binder jetting is copper‐based products. Three different variants of nominally pure copper powder having particle size distributions with D90 < 16, 22, or 31 μm were investigated in this study. The packing behavior and the flow properties using dynamic test and shear cell, as well as specific surface area were evaluated. The analyses employed illustrate the multidimensional complexity. Because different measurements capture different aspect of the powder, it is imperative to apply a characterization approach involving different methods. Surface chemical analysis by means of X‐ray photoelectron spectroscopy (XPS) showed that all powder variants were covered by Cu2O, CuO, and Cu (OH)2, with Cu2O being dominant in all cases. The finest powder with D90 < 16 μm tended to have higher relative amount of copper in divalent state. The average apparent oxide thickness estimated by XPS depth profiling showed that the two coarser variants had similar overall average oxide thickness, whereas the finest one possessed smaller oxide thickness. The surface chemistry of the powder grades is found to be related to their rheological behavior in dynamic condition. Considering the specific surface areas in combination with the average oxide thicknesses, the amount of surface bound oxygen was estimated to be about ~220 ppm for all three variants. Specific concerns need to be taken during the sintering of powder to keep oxygen level below that of electrolytic pitch copper (400 ppm).

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Section: Resultsmentioning

confidence: 99%

Section: Surface Chemical Analysismentioning

confidence: 99%

Surface chemical and geometrical properties of pure copper powder intended for binder jetting and sintering

Nyborg

Cao

2022

Surface & Interface Analysis

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“…Fine powders, which are generally cohesive, have angles of repose greater than 40° 28 ; for granular materials (larger than 100 μm), the angle of repose does not appear to change in any systematic way with particle size. The angle of repose gradually decreases as the mean size increases, indicating that the powders change from cohesive to more free flowing with increasing mean size 18,29 . The angle of repose decreases with increasing grain size for diameters lower than 50 μm 30 ; afterward, they are constant.…”

Section: Theoretical Background—characterization Of Flow Properties O...mentioning

confidence: 96%

“…There are two experimental parameters that distinguish the methods: the distance between the funnel and the base (fixed height of funnel or raising the funnel as the heap grows, which leads to a variable funnel height) and the geometry of the base (fixed base size or geometrically large base area, enabling the formation of a variable cone diameter of material) 19 . In the case of a fixed base area without lateral boundary, for example in form of a circular platform, excess material is allowed to fall from the base plate 20,29 …”

Section: Theoretical Background—characterization Of Flow Properties O...mentioning

confidence: 99%

Flow properties of powdery or granular filling substances of dangerous goods packagings—Comparison of the measurement of the angle of repose and the determination of the Hausner ratio

et al. 2022

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To ensure safety when transporting dangerous goods, it is important to specify the flow properties of the respective solid filling substance of the packagings. For this purpose, the angle of repose is currently used for the UN approvals in Germany. Measurements were carried out on 12 powdery or granular substances applying the angle of repose measuring methods customary in the test centres. The results of the methods differ significantly from each other. In addition, some of the techniques cannot be applied for very cohesive or coarse‐grained materials. The results for the angle of repose show a strong scatter for some constellations (coefficient of variation more than 20%). Safety during transport of dangerous goods cannot be guaranteed with this currently practised system of measuring the angle of repose. As a consequence, an alternative parameter to characterize the flow properties of bulk materials should be used in the recognized test centers for dangerous goods packagings, such as the Hausner ratio. This approach leads to more precise test results for the substances examined (maximum coefficient of variation 2.8%). It also has advantages in terms of applicability and occupational safety. Since the flow properties are safety‐relevant, both in terms of mechanical safety and safety against the release of dangerous substances, the testing practice in the recognized test labs should be improved and standardized.

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“…[ 7 ] For further glimpses of exciting nanomaterials research, the reader is referred to the article collection in this special issue. These skills on nanomaterials extend all the way into structural materials and component processing, where AM is increasingly profiting from particle handling and property determination (such as size, shape, flowability [ 8 ] ) to push boundaries in 3D printing. Being another excellent topical fit with Advanced Engineering Materials , more than a handful of contributions to this issue underline the institutional leadership in AM of metallic and inorganic structural materials.…”

Section: Figurementioning

confidence: 99%

The Federal Institute of Materials Research and Testing (BAM) – 150 Years of Enabling Scientific and Technological Breakthrough

2022

Adv Eng Mater

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Characterization of powder flow behavior for additive manufacturing

Cited by 17 publications

References 26 publications

Surface chemical and geometrical properties of pure copper powder intended for binder jetting and sintering

Surface chemical and geometrical properties of pure copper powder intended for binder jetting and sintering

Flow properties of powdery or granular filling substances of dangerous goods packagings—Comparison of the measurement of the angle of repose and the determination of the Hausner ratio

The Federal Institute of Materials Research and Testing (BAM) – 150 Years of Enabling Scientific and Technological Breakthrough

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