Wide Particle Size Distribution Research Articles

Optimising the feeding system for improving pellet distribution levels in gas-based shaft furnace based on the improved analytic hierarchy process

To improve the gas flow distribution inside the gas-based shaft furnace and ensure the chemical reaction, the discrete element method was used to calculate the effects of revolving chute inclination, particle size mass distribution, particle size distribution width, and hopper angle on the pellet distribution indicators (particle segregation, porosity, gas permeability and feeding time). An improved analytic hierarchy process was presented to fully analyse the nine schemes set up as part of the research. The findings demonstrated that the positive segregation of small particles at the furnace's centre and wall occurred with several feeding systems. The largest influences on porosity were differences in particle size mass distribution and particle size distribution width, and an increase in the proportion of small particles resulted in a significant decrease in porosity. The increase of the mass ratio of large particles made the highest permeability, but also caused uneven distribution of the furnace charge along the radial direction. The simulation results and the ranking of benefits and drawbacks produced by the improved analytic hierarchy process approach agree, demonstrating the applicability of the method to optimise the feeding system as well as its value in identifying the major influences on the feeding system.

Numerical study of a chemical looping combustion system: Effects of fuel type and particle size distributions on the operating performance

Chemical looping combustion (CLC) using biomass offers a promising pathway for achieving negative carbon emissions. However, the different properties of coal and biomass affect reaction performance, which has not been fully explored in the CLC system. Additionally, the effects of particle size distributions (PSDs) of solid fuels and oxygen carriers (OCs) are inadequately addressed. In this study, a 3D reactive model using the computational particle fluid dynamics (CPFD) method is developed to investigate the effects of PSDs of both solid fuels and oxygen carriers on operating performance with coal and biomass as fuels. Results indicate that the average residence time in FR of coal and biomass particles is 0.86 s and 0.68 s, respectively, but biomass outperforms coal in reaction efficiency. For coal-fueled CLC, the average residence time is 0.46 s for coal particles with diameters of 100–200 μm, whereas it reaches 0.86 s for coal diameters of 300–700 μm. However, the reaction performance is better with smaller coal sizes due to char gasification being the rate-limiting step. In comparison, for biomass-fueled CLC, the reaction efficiency remains consistent across various particle sizes under the specified conditions due to the rapid release of volatile components and the low content of char. Additionally, it is found that the OC conversion ratio is mainly determined by their residence time in the zones with relatively higher concentrations of the combustible gas in FR. Employing OCs with overly wide PSDs such as 300–800 μm can compromise the material seal above the AR, increase the risk of gas leakage and decrease the separation efficiency of the inertial separator.

A Review of Analytical Methods for Microplastics in Soils

Microplastics (MPs), as an emerging environmental pollutant, pose a potential threat to ecosystems and human health, and the study of their analytical methods has become particularly important. In this paper, the current research progress of analytical methods for MPs in soil is reviewed. The sources, ecological impacts and possible health risks of MPs are introduced, and the urgency of accurate detection and quantitative analysis of MPs is emphasized. Subsequently, MPs’ analytical methods based on different principles, including visual analysis, chemical analysis, spectroscopic techniques, microscopic observation, and mass spectrometry, are systematically outlined in response to the wide range of sample sources and wide particle size distribution of MPs. For each method, the advantages, limitations and scope of application are highlighted and evaluated, and the directions and development trends for future improvement are proposed. The review of this paper is expected to promote the continuous improvement and innovation of MPs analytical methods and provide more effective technical support and scientific basis for solving the MPs’ pollution problems.

Preparation and in vitro/in vivo evaluation of uniform-sized Goserelin-loaded sustained release microspheres

Sustained release microspheres loaded with goserelin are regarded as a promising candidate for treating prostate cancer and other sex hormone diseases. However, their widespread adoption has been hindered by issues such as wide particle size distribution and unstable release characteristics. To address these challenges, we employed a combination of the solid-in-oil-in-water microspheres preparation approach (S/O/W) and innovative premix membrane emulsification technology and deeply investigated the effects of four key parameters on the loaded performance of microspheres and the microscopic mechanisms behind them. With this approach, we successfully produced goserelin-loaded sustained release microspheres of narrow particle size distribution (Span 0.642), remarkable encapsulation efficiency (DL = 4.23 %, EE = 93.98 %), low initial burst release (about 0.50 % within 2 h), and compatibility with small injection needles (23-G, inner diameter 0.33 mm, outer diameter 0.64 mm, maximal force 59 N). In the animal model(administered dose, 2.4 mg·Kg−1), goserelin long-acting sustained release microspheres sustained release for over 32 days, maintaining effective concentrations above 2 ng·mL−1, and effectively reduced serum testosterone concentrations to castration levels (<1.0 ng·mL−1) by day 4, maintaining this inhibition for up to 21 days, exhibiting comparable efficacy to the positive control group. In vivo release kinetics analysis revealed that goserelin-loaded sustained release microspheres exhibited a release pattern dominated by diffusion with corrosion assistance in vivo. In summary, the systematic and comprehensive evaluation of uniform-sized goserelin-loaded sustained release microspheres has highlighted their excellent translational potential, and the study herein may provide new strategies and ideas for the development of microsphere dosage forms.

Research on the Collection Characteristics of a Hydraulic Collector for Seafloor Massive Sulfides

Ore collection is very important in deep-sea mining for seafloor massive sulfide (SMS). In view of the characteristics of SMS ores produced by mechanical crushing, which contain coarse particles and a wide particle size distribution, in-depth research on the collection process with a device combining a rotary crushing head and a flat suction mouth was conducted. In this paper, solid–liquid two-phase flow in the hydraulic collection process with a drum rotation is carried out using the computational fluid dynamics-discrete element method (CFD-DEM), and the flow field characteristics and particle motion characteristics are analyzed. The results indicate that particles with a maximum diameter of 20 mm can be effectively collected when the suction velocity is 3 m/s. The collection process of SMS mainly goes through three stages: particle disturbance start-up, partial particle influx, and stable collection. In addition, the appropriate drum speed facilitates the collection of SMS ore. Finally, the correctness of the numerical method was assessed using similarity experiments. This work can be used to guide the design of underwater mining equipment.

A super-toughened polyethylene naphthalene (PEN) enabled by polyacrylate elastomer with low crosslink density and reactivity

In elastomer toughening of polyester plastics, both the particle size distribution of the elastomer and the interfacial strength between the elastomer and matrix are key factors for toughness. In this work, bi-functional polyacrylate elastomers with controllable crosslinking density and reactivity were designed for enhancing the toughness of polyethylene naphthalene (PEN) matrix. Firstly, the elastomers with crosslinked structure possess increased melt viscosity and endowed wide particle size distribution, which contribute to the construct of thin matrix ligament and make PEN matrix more susceptible to shear-yield. Secondly, the high interfacial strength between elastomer and matrix can facilitate the transfer of external stress from PEN matrix to the elastomer, protecting the matrix from destroying. The resulted PEN blends exhibit an excellent impact resistance of 45.20 kJ/m2 and a high tensile toughness of 3.586 MJ/m3, which are 21.73 times and 47.81 times higher, respectively, than the virgin PEN. The present work may provide an effective approach for designing polyester blends with enhanced impact resistance and tensile toughness.

Influence of powder particle size distribution on the creep performance of Ti-48Al-2Cr-2Nb alloy fabricated via electron beam-powder bed fusion

The effects of particle size distributions (PSDs) on the microstructure and creep behavior of Ti-48Al-2Cr-2 Nb fabricated via electron beam-powder bed fusion (EB-PBF) were investigated. Three PSDs of 45–150 (PSD-A), 38–150 (PSD-B), and 38–180 µm (PSD-C) were used as powder feedstock. Widening the PSD range decreased the relative density of fabricated parts and promoted the formation of banding microstructure. Moreover, samples fabricated with wider PSDs had a higher volume of lack-of-fusion (LoF) defects; however, the content of gas pores decreased significantly in PSD-C, which was related to the presence of coarse powder particles. The volume of the LoF defects in PSD-C was approximately 2.8 times of the same defects in PSD-A, which influenced the creep performance (at 750℃) and failure mechanism of Ti-48Al-2Cr-2 Nb. A longer steady-state creep period at different stress levels was identified for the samples fabricated with the narrowest PSD (45–150 µm). Widening the PSD span also caused weakness in the creep properties and data scattering at higher stress levels of 300 and 350 MPa. The LoF defects and coarse grains accelerated the crack initiation and propagation in Ti-48Al-2Cr-2 Nb during creep. This study represents the first report on the impact of PSD on the creep properties of TiAl alloys fabricated via EB-PBF, which offers new insights and enhances understanding of the powder-process-microstructure-property relationship.

Assessment of the opportunities of demolition waste using as a building material of the future in Ukraine

The object of research is the potential of secondary use of waste from the destruction of buildings and structures, which were formed as a result of the military aggression of the Russian Federation on the territory of Ukraine. For Ukraine, the issue of demolition waste is critical at the level of environmental safety and ensuring the demand for building materials for the reclamation of Ukraine according to the principles of the circular economy. To date, there are no official methods that would allow to determine the exact amount of destruction and the quality of the material formed, which complicates the development of mechanisms for its utilization in production. The key industry considered during the research for disposal of demolition waste is the industry of construction materials production. In the course of research, it was determined that most of the generated waste is waste from the destruction of buildings and structures made of precast concrete, however, considering that these wastes are generated by the action of explosions from shells. It is very difficult to ensure their compliance with the requirements of current standards due to the inclusion that such waste can contain. Therefore, the problem considered by this study is the determination of the nature of waste from the destruction of buildings and structures, their physical, mechanical and chemical characteristics, in the context of the final applications of products based on them. The results of the study showed that when reproducing the concrete mix for tared concrete for civil purposes, which do not have high requirements for stability in aggressive operating conditions, when replacing natural aggregate crushed to a fraction of 5 to 20 mm, the requirements for concrete strength are achieved in the level of C40/50 strength class. But the rheological characteristics deteriorate due to the high absorption of water from the concrete mixture by the studied material. Research has shown that for further use in the production of ready-mixed concrete and precast concrete products, it is necessary to prepare demolition waste with a wide particle size distribution and low dust content. This can ensure a high level of recycling and meet the demand for concrete in the reconstruction of Ukraine. The fine aggregate from the demolition waste crushing process can be considered as secondary cementitious material for cement production.

Densification and rheological behaviors of 8YSZ powders for Vat photopolymerization-based additive manufacturing

Vat photopolymerization additive manufacturing technology allows the shaping of ceramic structures with limitless opportunities in terms of design freedom, structural resolution, and improving processing speed while reducing cost and wastage. The quality of a final product is influenced by the raw materials and processing routes. The particle size distribution of ceramic powders significantly affects ceramic slurry's rheology and cure behaviour as well as the densification process during sintering. This work studies the rheological properties of slurries prepared from 8 mol.% yttria-stabilized zirconia powders with various particle size distributions and densification of green bodies prepared from these suspensions. The suspension with a narrow particle size distribution showed a non-Newtonian behavior with a viscosity of >1 Pa s at a solid loading above 29 vol%, and a significant densification at a sintering temperature of 1400 °C. The viscosity of a suspension prepared from a powder with a wide particle size distribution was <1 Pa s in a solid loading range of 29–37 vol%. The higher cure depth at a lower exposure energy for slurry with coarse particles allowed a reduction of the printing time, while suspension with fine particles can be used for high-resolution printing with longer exposure time.

Numerical Simulation of Rainfall-Induced Erosion on Infiltration and Slope Stability

In slopes where a mixture of coarse and fine particles is present, the infiltration of rainfall can cause the migration of fine particles. This migration alters the hydraulic properties of the soil and has implications for slope stability. In this study, the slope under investigation is a tailings dam composed of loosely consolidated soil with a wide particle size distribution. Due to rainfall infiltration, fine particles tend to migrate within the voids of the coarse particle framework, leading to changes in hydraulic properties and inducing slope instability. The classical internal erosion constitutive model, known as the Cividini and Gioda erosion criterion, is commonly used to predict the behavior and effects of fine particle erosion in geotechnical engineering. However, certain parameters in this erosion criterion equation, such as long-term density, are challenging to obtain through experiments. To investigate the coupled evolution of seepage and erosion within landfill slopes under the influence of rainfall infiltration and to understand the mechanisms of slope instability, this research assumes the erosion of fine particle suspension and adopts the Worman and Olafsdottir erosion criterion to establish a coupled model of unsaturated seepage and internal erosion. The developed model simulates the coupled response of seepage and erosion in unsaturated landfill slopes under three different rainfall intensities. It is then combined with the infinite slope model to quantitatively analyze the impact of fine particle migration on soil permeability and slope stability. The numerical simulations provide the following findings: The Worman and Olafsdottir erosion criterion, unlike the Cividini and Gioda erosion criterion, only requires the determination of the soil’s gradation curve to estimate the erosion rate. Internal erosion primarily occurs within the leading edge of moisture penetration, accelerating the advancement of the wetting front and reducing slope stability. When the rainfall intensity is lower than the saturated permeability coefficient, the influence of internal erosion can be disregarded. However, under rainfall intensities equal to or greater than the saturated permeability coefficient, considering internal erosion results in a difference in the depth of the wetting front of up to 34.2 cm after 6 h in the R2 scenario. The safety factor without considering internal erosion is 1.12, whereas considering internal erosion yields safety factors between 1.08 and 1.09. In the R3 scenario, the difference in the depth of the wetting front reaches 53.8 cm after 6 h, with a safety factor of 1.12 without considering internal erosion and safety factors between 1.06 and 1.07 when considering internal erosion.

Prediction of the sulfur driven autotrophic denitrification process via CFD-DEM approach

Sulfur driven autotrophic denitrification is an economic and efficient means to purify the nitrogenous wastewater. The long-term experimental study is quite time-consuming and expensive. In this work, a coupled computational fluid dynamics-discrete element method (CFD-DEM) is implemented to investigate the performance of long-term operating sulfur autotrophic denitrification process. The evolution of particle accumulation and nitrate removal efficiency in the packed bed reactors with different tube diameters and sulfur particle sizes are simulated. It is found that the NO-3-N removal rates for different tube diameters are close and a wider particle size distribution is shown in the slender reactor. The small particle bed shows a better NO-3-N removal efficiency.

Fabrication, characterization and application of Pickering emulsion gels stabilized by defatted grape seed powder

The feasibility of defatted grape seed powder (DGSP) stabilizing Pickering emulsion gels as butter substitute was investigated. The Pickering emulsion gel was constructed using DGSP through high-speed homogenization, and the effects of particle concentration (c) and oil-phase (Medium chain triglyceride) volume fraction (φ) on its structure and properties were investigated. Its application as a butter substitute was also evaluated. The results showed that DGSP had various particle shapes, a wide particle size distribution (3–130 μm), and a three-phase contact angle of 128.9 ± 2.3°. The O/W Pickering emulsion gels with φ ≥ 60% could be obtained at c ≥ 2%. The droplet diameter was negatively correlated with c and positively correlated with φ, while the gel strength was positively related to c and φ. The resulting emulsion gel demonstrated solid-like viscoelastic behavior and pseudoplasticity, and had the potential to serve as a butter substitute. The results can promote the application of grape seeds in food.

A Novel PBM for Nanomilling of Drugs in a Recirculating Wet Stirred Media Mill: Impacts of Batch Size, Flow Rate, and Back-Mixing.

We examined the evolution of fenofibrate (FNB, drug) particle size distribution (PSD) during the production of nanosuspensions via wet stirred media milling (WSMM) with a cell-based population balance model (PBM). Our objective was to elucidate the potential impacts of batch size, suspension volumetric flow rate, and imperfect mixing in a recirculating WSMM. Various specific breakage rate functions were fitted to experimental PSD data at baseline conditions assuming perfect mixing. Then, the best function was used to simulate the PSD evolution at various batch sizes and flow rates to validate the model. A novel function, which is a product of power-law and logistic functions, fitted the evolution the best, signifying the existence of a transition particle size commensurate with a grinding limit. Although larger batches yielded coarser and wider PSDs, the suspensions had identical PSDs when milled for the same effective milling time. The flow rate had an insignificant influence on the PSD. Furthermore, the imperfect mixing in the mill chamber was simulated by considering more than one cell and different back-mixing flow ratios. The effects were weak and restricted to the first few turnovers. These insights contribute to our understanding of recirculating WSMM, providing valuable guidance for process development.

An improved semi-resolved computational fluid dynamics-discrete element method for simulating liquid–solid systems with wide particle size distributions

Vertical hydraulic transport of particles with wide particle size distributions is a crucial process for coal physical fluidized mining. In the present study, an improved semi-resolved computational fluid dynamics (CFD)-discrete element method was developed to simulate particle flows with wide particle size distributions. In this model, the CFD cells allocated to the particle volume and the momentum source term were defined as the dependent domain and the influential domain, respectively. On this basis, the two-way domain expansion method and the one-way domain expansion method were adopted for the liquid–solid simulation of coarse and fine particles, respectively. The dependent domain expansion coefficient and the influential domain expansion coefficient were proposed to determine the spatial range of the dependent domain and influential domain for the coarse particles, and the optimal modeling strategy for the dependent domain and influential domain expansion coefficient for the coarse particles was determined. Furthermore, a volume expansion method and a momentum source expansion method were proposed for calculating the solid volume fraction of the dependent domain and the source term of the influential domain for the coarse particles. Furthermore, the sample point method was adopted to obtain the solid volume fraction in the dependent domain for the fine particles, and the momentum source term was only updated to the particle-located cell. Subsequently, single-particle settling and binary-particle fluidizing numerical experiments were used to verify the calculation accuracy of the model. The investigation can provide a new method for numerical simulation of liquid–solid flow with wide particle size distributions.

Improved synthesis of metformin hydrochloride-sodium alginate (MH-NaALG) microspheres using ultrasonic spray drying

Metformin Hydrochloride (MH), an orally administered antidiabetic drug from the biguanide family, encounters issues of wide particle size distribution, inefficient dissolution rates and short half-life leading to excess dosage which can result in lactic acidosis. Novel approaches that yield smaller particle size and uniform distribution at higher yields are significant to tackle problems associated with solubility and optimum dosage levels of the administered drugs. In the current research related to microsphere synthesis, a controlled process based on pressure and ultrasonic nozzles for the atomization of liquid, was applied with an objective of optimizing particle size of microspheres of MH in sodium alginate, a biopolymer excipient matrix. The study carried out in spray dryer elucidated parameter optimization using one variable at a time approach by varying important parameters as inlet temperature of air (120°C–150 °C), rate of flow of feed (1.5 mL/min-3 mL/min), aspirator rate (800 rpm–1400 rpm) and polymer content in feed solution (1 g–8 g) using ultrasonic and pressure nozzles for comparison with the target output parameter as particle size and yield. While the particle size at optimum conditions were <10 μm for both types of atomization, ultrasound assisted spray drying exhibited narrower distribution compared to the pressure atomization. Particle characterization performed using SEM, optical microscopy, FTIR, XRD and DSC revealed slight deformation with no chemical interaction and slight decrease in crystalline nature of pure drug. Overall, an improved process based on the use of ultrasound with optimized parameters has been demonstrated for synthesis of MH containing microspheres.

The impact of different stirrer designs and mill orientations on the grinding efficiency

The primary objective of this research is to examine the impact of various stirrer designs in different mill orientations on the efficiency of calcite grinding in a dry stirred mill. In the context of the research, a series of batch grinding experiments were performed using a laboratory-scale stirred mill that could be oriented vertically or horizontally. Four distinct stirrer designs, namely 3-pin, 5-pin, 3-disc, and 5-disc, all with the same diameters, were employed in these studies. Stress intensity analysis was used to evaluate the experimental outcomes. The findings indicated that the number of stirrers present on the shaft, whether in the form of pins or discs, significantly influenced the effectiveness of the grinding process. Furthermore, the horizontal orientation performance of the 5-disc design provided the best particle fineness compared to other combinations. Additionally, the batch grinding experiments provided indications that the disc design yielded favorable results when employed in the horizontal mill configuration, while the pin design proved to be successful when utilized in the vertical mill configuration. Aside from these, design variations had an impact on the particle size distribution width characteristics of the products. The design parameters were also evaluated in terms of the stress intensity-particle size distribution width relationship.

Microfluidic production of silver nanoparticles demonstrates ability for on demand synthesis of a wide size distribution of particles

Silver nanoparticles (AgNP) can help prevent infection of virus and bacteria. The size and morphology of AgNP can be crucial to function, with smaller nanoparticles (< 20 nm) able to penetrate the cell wall. This is significant as oxidative stress and genotoxicity are associated with some sizes and coatings of AgNP, contraindicating the use of AgNP to reduce infection. We present evidence that a microfluidic chip can synthesize larger sizes and distributions of AgNP from the nano-to-micro size range. We show results from a microfluidic mixing chip that can produce a wide range of nano-to-micro size (~ 24–400 nm) AgNP. Synthesis is based on a modified Turkevich method, using a single-step AgNP synthesis on the microfluidic chip using two chemical components, trisodium citrate (NaCit) and AgNO3. To make AgNP more accessible, we describe the microfluidic chip and conditions capable of synthesis. We also describe how modification of flow rate and chemical reagent concentration change particle diameter during production. In our experiments, we found that AgNP production created a visible adsorption line in the microfluidic device, possibly owing to AgNP surface interaction at the polydimethylsiloxane (PDMS) interface. We characterize these particles with dynamic light scattering (DLS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Based on optical light microscopy, we hypothesize that AgNP formation primarily occurs at the interface between the two chemical reagent streams. We also conclude that AgNP size increases could be due to interaction with the PDMS surface, which is known to be porous. Future work will help to understand how surface interaction may influence the formation of larger particles.

Dynamic in situ measurement of axial segregation of E-CAT particles in a bubbling fluidized bed

The present paper summarizes comprehensive in situ measurements of the temporal segregation/mixing behavior of the non-spherical Geldart B and D E-CAT particles mixture in a bubbling fluidized bed. The experiments are performed for both unsieved and sieved E-CAT particles with varying particle size distribution width and at the fluidization velocity ranging from 1.3 to 5Umf. The high-speed pressure and image data were used to provide time-resolved quantification of dynamic expanded bed height and pressure drop during the experiment. In parallel, a hybrid machine learning-aided image processing algorithm has been developed for quantifying the instantaneous particle size distribution at varying axial locations. Results reveal that the segregation exists only at low fluidization velocities (1.3 and 1.6Umf) for unsieved cases with a wider size distribution. In contrast, particles with a narrower distribution exhibited well-mixed behavior for the full range of tested gas velocities. The segregation intensity and spatial extent were found to correlate with particle size distribution width and fluidization velocity, respectively. In addition, by analyzing pressure, expanded bed height, particle size and motion, and bubble characteristics, we provided a comprehensive multi-scale dynamic view of the segregation process. This in-depth understanding of the process, coupled with the time-resolved datasets obtained, can be instrumental for benchmarking numerical models in solid–gas multiphase flows and for optimizing the design of fluidized beds.

Effect of gradation and relative density on shear strength of coral sand

ABSTRACT Due to the wide particle size distribution of coral sand, There are significant differences in mechanical behaviour of coral sand with different particle size distribution. It is of great significance to propose a quantitative analysis method for mechanical properties considering the effect of gradation. In this study, 27 groups of coral sand specimens with particle size ranging from 5 mm to 0.125 mm were prepared. The consolidated undrained (CU) triaxial shear tests were carried out and the influence of gradation and relative density on the shear characteristic were discussed. The grading and relative density of coral sand are controlled by the median particle size (d50) and relative density (Dr), The results show that the peak deviator stress decreased, and the effective internal friction angle first increased and then decreased with the increase of d 50. Both the peak deviator stress and effective internal friction angle of coral sand increase with the relative density. A parabolic relationship was founded between the effect internal friction and d 50 as D r was constant. The effective friction angle peaked when d 50 was 2 mm. Finally, a calculation method of shear strength parameter considering the gradation and relative density of coral sand was proposed.

Surveying the Effects of Aging a High C-Containing Co-Based Superalloy From the As-Cast and Solution Heat-Treated Conditions

The microstructure of the high carbon-containing cobalt-based superalloy, Co-101, has been studied in the as-cast state and following a variety of heat treatments. In the as-cast state both M7C3 and Mo-rich M23C6 carbides were observed in the interdendritic regions. After thermal exposure at temperatures between 1000 °C and 1250 °C for 1, 10, and 100 hours, the M7C3 interdendritic carbide network was observed to transform into a Mo-lean M23C6 carbide. These changes were rationalized with thermodynamic calculations. The carbide transformation liberated carbide-forming elements that resulted in the precipitation of intragranular carbides in the dendritic regions at temperatures below 1150 °C. These carbides in the cast-aged material preferentially formed at the dendrite peripheries early during exposure, leading to wide particle size distributions. Peak hardness in the cast-aged material was attained within the first 10 hours of exposure and softening was observed thereafter. After solution heat treating at 1250 °C for 10 hours, the microstructure of Co-101 comprised an M23C6 interdendritic carbide network and solid solution dendrites supersaturated with carbide-forming elements. Subsequent aging of this microstructure for 100 hours at 900 °C led to a high number density and narrow particle size distribution of intragranular carbides. The characteristics of these carbides in the solution-aged material resulted in greater hardness, which was retained for longer durations of exposure, than the cast-aged specimens.