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Improved Biodegradable Implant Materials for Orthopedic Applications
Published in Ashwani Kumar, Mangey Ram, Yogesh Kumar Singla, Advanced Materials for Biomechanical Applications, 2022
Kundan Kumar, Shashi Bhushan Prasad, Ashish Das, Mukul Shukla
Powder metallurgy is a solid-state method of fabrication of Mg matrix composites where steps of manufacturing are the production of powders, blending, compaction, sintering, and secondary finishing operations as shown in Figure 11.4. There are several methods of production of powder such as milling, atomization, chemical reduction, and electrolytic deposition. Blending is used for the uniform mixing of Mg matrix and reinforcement particles. Desired shapes and sizes are obtained using the die and punch to produce a green compact in the comparison process.
Powder Metallurgy
Published in Zainul Huda, Manufacturing, 2018
A powder is a finely divided solid; each powder particle is smaller than 1 mm in its maximum. The processing of metal powders and the final properties of the sintered P/M products strongly depends on the characteristics of the powders. The powder characteristics include (1) particle shape, (2) particle size, (3) particle-size distribution, (4) chemical composition, (5) structure, (6) surface conditions, (7) powder flow rate, and (8) apparent density.
Synthesis of Powders
Published in M. N. Rahaman, Ceramic Processing and Sintering, 2017
As an example, Fig. 2.25 shows CeO2 powders (average particle size ~15 nm) produced from a suspension of amorphous, gelatinous cerium (hydrous) oxide under hydrothermal conditions (~300°C and 10 MPa pressure for 4 h). CeO2 has a cubic crystal structure; the faceted nature of the particles is an indication that they are crystalline. High-resolution transmission electron microscopy also revealed that the particles are single crystals (70). A disadvantage of very fine powders is that they are difficult to consolidate to high packing density and are very prone to agglomeration, particularly in the dry state. Because of their high surface area, the powders may contain a high concentration of chemically bonded hydroxyl groups on their surfaces. Incomplete removal of the hydroxyl groups prior to sintering may limit the final density of the fabricated material.
Spray-drying optimization for Dunaliella salina and Porphyridium cruentum biomass
Published in Drying Technology, 2023
Nevzat Konar, Yasar Durmaz, Basak Gurbuz, Derya Genc Polat, Behic Mert
The size and morphology of the particles are important parameters for the characterization of powders. These properties are used to determine usage possibilities for food applications. For example, the increase in particle size of algal components in spreads and chocolates negatively affects flow and sensory properties.[34,35] The mean particle sizes for P. cruentum and D. salina were 80.1–143.7 µm and 112.7–143.0 µm, respectively (Table 3). The effects of process variables were significant for both microalgae (p < .05). As a result of the encapsulation of different biological materials with the spray-dryer, the average particle size was found to be >50 µm.[36–38] In addition, this value was 34.8–74.2 µm for another commonly used microalgae, C. vulgaris.[8] The possible reason for the relatively larger particle sizes is the agglomeration of substances that make up the composition of the D. salina and P. cruentum’s cell and cell wall.
Thermal damages in spray drying: Particle size-dependent protein denaturation using phycocyanin as model substrate
Published in Drying Technology, 2023
Nora Alina Ruprecht, Reinhard Kohlus
In summary, to minimize protein denaturation during spray drying, the ideal drop size should either be very small for fast drying or very large to ensure the residence time of the particles in the dryer to be entirely within the constant drying rate regime. Very small particles may have poor powder handling properties, such as low flowability and a tendency to generate dust. To overcome these disadvantages, an additional agglomeration step may be required. As small particles are cohesive and may not aerate well,[63] nozzle zone agglomeration can be performed. A previous study[14] utilizing the spray dryer setup described by Fröhlich et al.[64–67] did not observe an increase in phycocyanin denaturation during nozzle zone agglomeration, as the prolonged residence time in the fines return occurred in a dry particle state. Alternatively, if very large drops are generated to minimize protein denaturation, the generated particles may exit the dryer with a still high moisture content. In this case, an additional post-drying step to obtain a dry powder is required. As moist particles are prone to stickiness, an integrated fluidized bed can be employed for post-drying. To optimize protein retention, the fluidized bed air temperature should be maintained below the denaturation temperature. This will be investigated in a future study.
A methodology for the decentralised design and production of additive manufactured spare parts
Published in Production & Manufacturing Research, 2020
Joaquin Montero, Sebastian Weber, Matthias Bleckmann, Kristin Paetzold
Powder Bed Fusion (PBF) is an AM ‘process in which thermal energy selectively fuses regions of a powder bed’ (DIN, 2017). The powder material can be metal, polymer or ceramic. Within the scope of this contribution, only Laser PBF (L-PBF) is covered, which is a PBF process that uses a laser as an energy source. L-PBF systems are offered under different names depending on the manufacturer, e.g., Selective Laser Melting (SLM®) by SLM Solutions®, Direct Metal Laser Sintering (DMLS®) by EOS®, Selective Laser Sintering (SLS®) by 3D Systems®. Although melting (fusing of fully molten particles) and sintering (fusing of partially molten particles) are different binding mechanisms between the powder particles (Mercelis & Kruth, 2006; Roberts, 2012). Both are considered PBF processes by the ISO/ASTM standards.