Particle Size Distribution Characteristics Research Articles

Reformulation of white chocolate with soy- and coconut-based vegetable ingredients incorporating encapsulated cinnamon extract: investigation of physicochemical, antioxidant, and sensory properties

ABSTRACT White chocolate, which does not contain cocoa mass, is less healthy than dark and milk chocolate. Due to its milk content, white chocolate can also cause issues for those with lactose intolerance or dairy allergies. To overcome these problems, a study was conducted by adding highly antioxidant encapsulated cinnamon extract (ECE) to vegan white chocolate formulated with different levels of soy protein isolate (SPI) and coconut flour (CF). This study aimed to examine the chocolate’s total phenolics, flavonoids, antioxidant activity (IC₅₀), protein and fat content, particle size distribution, texture, color, melting point, and sensory characteristics. The results showed that the addition of SPI and CF had a significant impact on the properties of the white chocolate, except for hardness. Incorporating 2% (w/w), ECE significantly increased the total phenolics, flavonoids, and antioxidant activity. Total phenolics and flavonoids were positively correlated with antioxidant activity. Vegan white chocolate formulated with 27% SPI, 10% CF, and 2% ECE was acceptable to panelists, and thus, this product can be potentially consumed by lactose-intolerant and vegan consumers.

Multifractal characteristics of soil particle size distribution of abandoned homestead reclamation under different forest management modes

In this study, fast-growing poplar reclaimed from abandoned homestead in Xixian New District, Xi’an City, Shaanxi Province, was used as the research object to explore the multi-fractal characteristics of soil particle size distribution under different management modes of abandoned land (control), irrigation, fertilizer irrigation and mixed fertilizer irrigation. The results showed that the mean values of soil clay, silt and sand in abandoned land were 14.58%, 81.21% and 4.22% respectively, 14.08%, 79.92% and 5.99% under irrigation, 15.17%, 81.19% and 3.64% under fertilizer irrigation, and 16.75%, 80.20% and 3.05% in mixed fertilizer treatment. From 40 cm, with increasing soil depth, soil clay particles increase under irrigation, fertilizer irrigation, and mixed fertilizer irrigation modes. The single fractal dimension of soil particle size distribution (D) in each treatment ranges from 2.721 to 2.808. At 60–100 cm, D shows fertilizer irrigation > mixed fertilizer irrigation > irrigation > abandoned land, indicating that fertilization and irrigation can increase the fine-grained matter of deep soil particles and reduce soil roughness. Compared with abandoned land, under irrigation, fertilizer irrigation and mixed fertilizer modes the capacity dimension (D0), entropy dimension (D1), correlation dimension(D2), shape characteristics of the multifractal spectrum (Δf) and overall inhomogeneity of the soil particle size distribution (D0–D10) indicate an uneven distribution of soil particle size; fractal structure characteristics of soil (D−10–D0) indicate a simplified soil structure, and degree of dispersion of soil particle size distribution (D1/D0) indicates that soil particle size is distributed in dense areas. Pearson correlation analysis showed that D was significantly correlated with clay, sand, D0–D10, soil organic matter (SOM) and soil available phosphorus (SAP) (P < 0.05). Stepwise regression analysis showed that clay was the main controlling factor of D and D0–D10 changes. The research results can provide some potential indicators for the quality evaluation of abandoned homestead reclamation.

Unlocking the nanoparticle emission potential: a study of varied filaments in 3D printing.

This study investigates nanoparticle emission during 3D printing processes, assessing various filament materials' impact on air quality. Commonly used 3D printers, including both filament and resin-based types, were examined. The study's scope encompasses diverse filament materials like ABS (acrylonitrile butadiene styrene), PLA (polylactic acid), PETG (polyethylene terephthalate glycol), ASA (acrylonitrile styrene acrylate), TPU (thermoplastic polyurethane), PP (polypropylene), nylon, and wood-based variants, alongside three types of resins. The research delves into the relationship between the type of material and nanoparticle emissions, emphasizing temperature's pivotal role. Measurement instruments were employed for nanoparticle quantification, including an engine exhaust particle sizer spectrometer, condensation particle counter, and nanozen dust counters. Notably, results reveal substantial variations in nanoparticle emissions among different filament materials, with ASA, TPU, PP, and ABS showing considerably elevated emission levels and characteristic particle size distribution patterns. The findings prompt practical recommendations for reducing nanoparticle exposure, emphasizing printer confinement, material selection, and adequate ventilation. This study offers insights into potential health risks associated with 3D printing emissions and provides a basis for adopting preventive measures.

Inhibiting effects of humic acid on iron flocculation hindered As removal by electro-flocculation on air cathode iron anode

Activated carbon air cathode combined with iron anode oxidation-flocculation synergistic Arsenic (As) removal was a new groundwater purification technology with low energy consumption and high efficiency for groundwater with high As concentration. The presence of organic matter such as humic acid (HA) had ambiguous effects on formation of organic colloids in the system. The effects of the particle size distribution characteristics of these colloids on the formation characteristics of flocs and the efficiency of As purification was not clear. In this work, we used five different pore size alumina filter membranes to separate mixed phase solutions and studied the corresponding changes in iron and arsenic concentrations in the presence and absence of humic acid conditions. In the presence of HA, the arsenic concentration of < 0.05 µm particle size components was 1.01, 1.28, 3.07, 7.69, 2.85 and 1.24 times of that in the absence of HA. At the same time, the arsenic content in 0.05–0.1 µm and 0.1–0.45 µm particle size components was also higher than that in the system without HA, which revealed that the presence of HA hindered the flocculation behavior of As distribution to higher particle sizes in the early stage of the reaction. The presence of HA affected the flocculation rate of iron flocs from small to large particle size fractions and it had limited effect on the behavior of large-size flocs in adsorption of As. These results provide a theoretical basis for targeted, rapid, and low consumption synergistic removal of arsenic and organic compounds in high arsenic groundwater.

A review and analysis of particle size parameters and their relationships to physical properties of growing media

AbstractAn expanded description of particle morphology and the analysis of its relationships with physical properties may help to optimize the selection of raw materials and particle size fractions used as growing media constituents. Previous works have described the outlines of these relations based mostly on sieving procedures to characterize particle size distribution. They have shown limited and sometimes contradictory results due to the different methods used, size fractions selected, and physical properties measured. Also, sieve analysis, which separates particles based on their width, is less accurate for non‐spherical particles, which is the case for most growing media constituents. Recent works have promoted the use of dynamic image analysis (DIA) to precisely analyze both particle length and width. Five raw materials were chosen (white and black peats, coir, pine bark, and wood fiber) and sieved to obtain various particle size fractions. For each particle size fraction and the raw materials, the mean weight diameter (MWD), derived from sieving, was calculated, whereas mean particle length and width were determined using a DIA tool, the QicPic device. Also, physical properties were assessed from water retention curves established using Hyprop systems. The statement that the larger the particle size, the higher the air‐filled porosity (AFP), the lower the water holding capacity (WHC) was more precisely redefined. Large variations in WHC and AFP mainly occurred for finest particle size fractions, whereas changes were conversely very small or non‐existent for larger particle sizes. From data obtained for each particle size fractions, regression models were established to relate mean particle length and width (both determined using DIA) and MWD (determined from sieving) with WHC and AFP. Mean particle length was identified as the most relevant parameter for predicting WHC and AFP of the raw materials tested.

Effect of inlet velocity on the hydraulic and filtering performance of a Y‐type screen filter

AbstractUneven sediment distribution affected by inlet velocity, particle size distribution and flow field characteristics leads to local clogging in a Y‐type screen filter. This study revealed the detailed flow field characteristics and distribution of sediments on the screen via computational fluid dynamics combined with the discrete element method (CFD–DEM) simulations and experimental tests. The results showed that the distribution of the flow rate on the filter screen was extremely uneven, with the maximum flow rate being 11.72 times greater than the minimum rate. The flow rate was distributed symmetrically on the two sides along the outlet centreline, as shown by the unfolded drawing of the filter core. Numerical simulation and experimental tests using sandy water showed that the number and average particle diameter on the screen decreased, and the number and average particle diameter in the plug increased, with increasing inlet velocity. The sediments on the screen were distributed intensively, and the plugging extent coefficient and the anti‐clogging performance improved. However, this process was more likely to cause local clogging and worsen the filtration performance. Therefore, low‐speed filtering should be applied if the filtering effect is needed, and high‐speed filtering should be applied if the filtering efficiency is favourable but the flushing frequency increases.

Sediment imaging and factorized Haar wavelet transformation techniques for characterizing particle size distributions of granular soils

The particle size distribution (PSD) significantly influences various mechanical behaviors of granular soils. Advances in automation and camera technology allow for a rapid, green, and accurate PSD determination. This study develops a new sediment imaging system, mainly consisting of a sediment column filled with water and a line-scan camera driven by programmable logic controller, which can automatically capture high-resolution soil segregation images. The soil particles settle through the sediment column and segregate by size, which is scanned to generate sediment images. Naturally, the coarsest particles settle at the bottom of the image, while the finest particles are located at the top. Therefore, the analysis of the sediment image enables the determination of PSD. The higher sediment column, despite of poor operationality, yields better particle segregation quality and thus the more accurate PSD result. This study proposed a factorized Haar wavelet transformation (FHWT) algorithm that can account for less perfect segregation of particles by size, enabling to shorten the height of sediment column. The proposed hardware and FHWT are evaluated by six natural sands with different colors, internal textures, and geological origins. An excellent match between image-based PSDs and sieving-based PSDs are observed. Based on FHWT, four sediment columns with different heights of 2.1 m, 1.5 m, 1.0 m, 0.5 m are tested. The results indicate that columns higher than 1.0 m yield acceptable particle segregation results. Furthermore, the proposed FHWT is also adaptable to process high-resolution images captured by advanced cameras.

Evaluation of the effects of long‐term maize–peanut intercropping on soil aggregate stability based on different methods

AbstractIntercropping is an effective measure to increase crop yield and improve soil structure. The soil aggregate is the basic unit of soil structure, and its stability is affected by intercropping system. To study the effects of intercropping system on soil aggregate stability, the particle size distribution and stability characteristics of soil aggregates under three planting patterns of maize only (SM), peanut only (SP) and maize intercropped with peanut (M‐P) were evaluated by dry sieving (mainly used to determine the mechanical stability of soil aggregates), wet sieving (mainly used to determine the water stability of soil aggregates) and Le Bissonnais (mainly used to distinguish different decomposition mechanisms of soil aggregates) (including slow wetting (SW), wet stirring (WS) and fast wetting (FW) tests) methods. The results showed that the particle size distribution of soil aggregates was mainly the &gt;2 mm fraction in the dry sieving test, the 1–0.5 mm and &lt;0.053 mm fractions in the wet sieving test, the &gt;2 mm fraction in the SW test, the &gt;2 mm and 2–1 mm fractions in the WS test and the 1–0.5 mm and 0.5–0.25 mm fractions in the FW test. The mean weight diameter (MWD), geometric mean diameter (GMD) and R0.25 of soil aggregates in the three determination methods were all ranked as SP &lt; SM &lt; M‐P, indicating that intercropping could increase the proportion of large aggregates and improve the stability of soil aggregates. In the three tests using the Le Bissonnais method, the MWD order was FW &lt; WS &lt; SW, indicating that the soil aggregates in this area were the most sensitive to slaking effects and the least sensitive to mechanical breakdown, and intercropping could reduce the sensitivity of soil aggregates to slaking effects and mechanical breakdown. In addition, the MWD of dry sieving was significantly positively correlated with the MWD of SW and WS, and the MWD of wet sieving was significantly positively correlated with the MWD of FW. The results of this study could provide a reference for better understanding of farmland soil structure and aggregate stability under intercropping system in the North China Plain.

The Numerical Investigation of Solid–Liquid Two-Phase Flow Characteristics Inside and Outside a Newly Designed 3D Sediment Trap

Sediment transport serves as a link for material exchange between land and sea. Using sediment traps, we can observe the capture and transport processes of sediments. Based on the sediment particle size distribution characteristics in Jiaozhou Bay, this paper analyzes the influence of a newly designed 3D sediment trap on the water–sand two-phase flow process inside and outside a trap device during its operation. Meanwhile, under a certain concentration condition, a numerical formula model is researched and proposed to evaluate the impact of the device’s structure, the environmental flow speed, and the particle size on particle capture efficiency. This model is based on the CFD-DPM coupling in Fluent 2021R1 software, and the particle filtration process is solved using a combination of porous media and UDF functions. Finally, by analyzing the distribution of sediment movement in the fluid domain, two concepts, namely the percentage of particles entering the tube and the effective capture rate, are proposed. Suggestions for optimizing the structure of the trap are put forward to achieve optimal capture effects.

Experimental Study on Activation Energy and Microstructure of Nano- and Micro-Sized Pozzolanic Materials as Cementitious Composite Binder

Silicate-based nano- and micro-sized binders were used with ordinary Portland cement to evaluate their influence on the setting time, activation energy, mechanical properties, and microstructure. It was found that the setting time was reduced due to the pozzolanic reaction of the silicate-based binders and the densification of the microstructure. However, there is a lack of research on nano-sized pozzolanic materials. Therefore, in this study, research on activation energy and microstructure was conducted. The compressive strength increased owing to a reduction in the porosity in the microstructure, and activation energy also tended to decrease. Moreover, using both micro-silica and a small proportion of nano-silica was more effective in reducing the setting time and activation energy than using any of them individually. The study established that adding a small proportion of nano-silica could reduce the setting time and increase the compressive strength because it positively influenced the pozzolanic reaction and filled the pores between micro-silica and cement, which were composed of relatively larger particles, with smaller particles. Because nanomaterials may degrade flowability due to their large specific surface area, it is deemed necessary to consider the addition of chemical admixtures during mix design. A characteristic has been revealed when nanomaterials are used, and special attention to the particle size distribution characteristics is required because the imbalance in particle size distribution may increase the porosity inside the microstructure. Therefore, it is recommended to use micro-sized pozzolanic materials together when using nano-sized pozzolanic materials.

Effect of Reaction Temperature on the Degradation and Oxidation Behavior of Particulate Matter by Nonthermal Plasma

Diesel particulate matter (PM), especially small particle size PM, has been highlighted as a hazard to the environment and people. Nonthermal plasma (NTP) has shown significant low temperature (<200°C) advantage for PM degradation. In this paper, we conducted online PM degradation experiments at different reaction temperatures with a self-built NTP injection system to investigate the changes of PM particle size distribution, micro-nano structure, graphitization degree and oxidation characteristics of elemental carbon (EC) before and after NTP action. The maximum removal rate increased from 90 ℃ (25% load) to 130 ℃ (100% load) with the increase of the load, and there was a “trade-off” effect between PM decomposition and NTP pyrolysis. The average microcrystalline length, microcrystalline spacing and microcrystalline curvature of PM particles showed an overall trend of decreasing and then increasing with the increase of temperature. When the reaction temperature was 130 ℃ (75% load), the microcrystalline structure parameters of the carbon particles showed extreme values, and the newly exposed “shells” were rearranged under the action of van der Waals force, and the graphitization of PM increased and the overall oxidation activity was weakened. The reaction between NTP and carbon particles goes through the process of surface oxidation, simultaneous oxidation of surface and interior, and the fragmentation of carbon particles to complete disappearance.

Fractal Characteristics of the Particle Size Distribution of Soil along an Urban–Suburban–Rural–Desert Gradient

In order to investigate the difference in particle size distribution of soil along an urban–suburban–rural–desert (USRD) gradient in an arid zone, surface soil (0–20 cm) samples were gathered at the urban, suburban, rural, and desert gradients in Urumqi, a northwestern Chinese city. Laser diffraction technology was adopted for determining the particle size distribution of the soil. Comparisons were made regarding the particle size distribution traits and soil properties in different gradient zones based on parameters such as the mean particle size (MG), fractal dimension (Dv), sorting coefficient (ơG), kurtosis (KG), and skewness (SKG). Results indicate that (1) particle size distribution in the urban, suburban, and rural soils was mainly sand particle sizes, whereas the desert soil was mainly composed of silt particle sizes. The average Dv value ranking for soil in each gradient is desert &gt; suburban &gt; urban &gt; rural. (2) The width and peak of the soil particle size frequency curve ranged within 0–500 μm, and the width and peak of the soil particle size frequency curve of each gradient were different. (3) The MG of rural soil was the highest, whereas the MG of desert soil was the lowest. The ơG values of the surface soil of each gradient were all greater than 4.0, and the sorting performance was extremely poor. The SKG of the desert and urban soil particle size showed extremely positive and negative skewness, respectively, while the SKG of the rural and suburban soil particle size showed extremely negative skewness. The KG values of the particle sizes of the rural and suburban soils exhibited narrow and medium peaks, whereas those of the urban and desert soils exhibited very broad and flat peaks. (4) The Dv of the soil in each gradient was strongly influenced by the soil particle size distribution, with the clay content of the soil playing a dominant role. Finally, the fractal dimension was identified as an indicator of the characteristics of the fine particle matter content in the soil structure. The novel contribution of this work is to clarify the fractal differences in the particle size distribution of soil along an urbanization gradient. The present research findings can offer fundamental information relating to the characteristics of soil particle size distribution along an urbanization gradient zone.

Turning fly ash and waste gypsum into a resource for backfilling applications

Flue Gas Desulfurization Gypsum (FGDG), an industrial by-product generated by power plants, was thermally treated and incorporated in cement-free fly ash bricks. This study aimed to determine the effects of using a thermally treated FGDG as an additive to improve the mechanical and structural properties of cement-free fly ash bricks. FGDG was thermally treated for 2 h at different temperatures. The influence of varying amounts (10–50%) of thermally treated FGDG on the performance of cement-free bricks was analyzed through mechanical properties, micrography, durability, the evolution of particle size distribution and environmental characteristics experiments. The effect of curing temperatures and curing age on the strength development and microstructural properties was also investigated. A Toxicity Characteristic Leaching Procedure (TCLP) was carried out to determine the leachability of metals from the synthesized FA cement-free brick. The results showed that the FGDG had a high calcium oxide content. In contrast, FA is mainly composed of silica, and both materials carry cementitious properties making both good raw materials for this study. The FA cement-free bricks containing 30% of thermally treated FGDG, oven-cured at 60 ℃, yielded the highest unconfined compressive strength (UCS) of 7.14 MPa. However, curing at ambient temperature for 28 days yielded a better UCS of 7.37 MPa. The particle size distribution showed that particles transformed from fine particles at 7 days to larger particles at 28 days due to particle growth. Durability tests showed that the developed bricks could withstand 7 wet/dry cycles. The TCLP showed that the leachability concentrations of all metals are within the limit and, therefore, can be potentially used as a building material in backfilling. The synthesis of FA/FGDG composite will aid in reducing the generated waste gypsum in landfills consequently eradicating human health challenges and loss of biodiversity. This paper showed that developing FA/FGDG composites will reduce their environmental impact and make them a resource for other valuable products such as backfilling applications and green building bricks.

Coefficient of permeability prediction of soils using gene expression programming

The coefficient of permeability is the most important parameter for characterizing the permeability characteristics of soil. In this study, a database of the coefficient of permeability (k) for soils was compiled firstly, including effective size (d10), mean grain size (d50), the particle diameters at the cumulative percent content of 60% (d60) and void ratio (e), which can reflect the impact of the particle size distribution characteristics. Gene expression programming (GEP), was employed to develop a predictive equation of k, which is convenient for engineering application. The GEP model was compared with eight empirical models and other artificial intelligence models (i.e., random forest (RF) and group method of data handling (GMDH)). The results show that the GEP model and RF model have the highest accuracy, followed by GMDH model and empirical models. Then, the sensitivity analysis was conducted. According to the results, k increases with increasing d10, d50 and e; the effective size d10 has the largest influence on k, followed by d50 and e, which indicates that fine particle content has the control effect on seepage and the effect of soil gradation parameters on k is greater than that of void ratio. Additionally, the SHAP and PDP analysis were conducted to investigate the feature importance and conditional expectation of each feature. The feature importance order is d10 > d50 > e > d60, and the SHAP values of d10, d50 and e increase with the increase of them, while the SHAP value of d60 is basically unchanged.

Permeability enhancement and coal fines removal through oxidation treatment in coalbed methane reservoirs

This study utilized anthracite coal samples from Zhijin Block and applied NaClO as the oxidant to investigate the effects of oxidation treatment on permeability enhancement and coal fines migration. Subsequent to oxidation treatment, the coal samples demonstrated an average increase of 42.17% in the equivalent hydraulic aperture (EHA). This treatment also resulted in the expansion of fluid flow channels, contributing to an average permeability enhancement of 108.85% in the coal samples. Resulting from the non-uniform dissolution of the oxidant on the fracture surface of coal, self-propping fractures were formed, effectively maintaining the conductivity of fractures. The oxidation treatment converted the wettability of fracture surface from hydrophilic to hydrophobic. This transformation proved advantageous for the dewatering process within the fractures. Moreover, even under high confining stress, the 5 wt% NaClO solution still exhibited a favorable permeability enhancement effect on coal. The oxidation treatment resulted in a particle size degradation rate of 40.38%. Considering the properties and particle size distribution characteristics of both the coal fracture surface and coal fines, the affirmative impact of oxidation treatment on coal fines removal was analyzed based on the extended DLVO theory. The calculated results showed that the adhesion force between coal fines and fracture surface was weakened. Coupled with the effect of fracture widening, the outcome was a notable 26.99% increase in the quantity of coal fines that migrated with the fluid under the drag force after oxidation treatment. The research results presented in this paper provide another option for enhancing permeability of coalbed methane reservoirs, which has important reference significance for the broader economic development of such reservoirs.

Influence mechanism of dispersion and agglomeration characteristics of micron/nano carbon dust on its combustion kinetics and explosion process

Due to the widespread use of lithium-ion batteries, evaluations of the flammability and explosive characteristics of carbon dust materials as anodes require attention. Carbon dust often reaches the micron/nano scale, and dust particle state and explosion risk generated in different industrial scenarios are different, which is in urgent need of research. Nanoscale dust has relatively static coagulation properties and shows characteristics of dispersion and reagglomeration under a certain airflow. The particle size characteristics affect its thermodynamic characteristics and various consequence parameters of dust explosion. The oxidation and combustion characteristics are mainly affected by dust particle size distribution characteristics. The apparent activation energy is mainly affected by the proportion of small and medium-sized particles and pre-exponential index factor is mainly affected by the dust overall average particle size and specific surface area. The explosion consequence parameters are affected by the thermodynamic parameters, by the disturbance state, particle distribution degree of dust cloud and other factors, which affect the heat radiation and heat transfer process to some extent resulting in different explosion consequence parameters. Due to the agglomeration characteristics of nano-level dust, the minimum ignition energy and minimum ignition temperature of nano-level dust are generally smaller than that of micron level dust.

A promising method for the liberation and separation of solar cells from damaged crystalline silicon photovoltaic modules

Reasonable and efficient recycling of waste crystalline silicon (c-Si) photovoltaic (PV) modules benefits environmental protection and resource conservation. The liberation and separation of solar cells in modules is the key to achieving effective recycling. The recovery of intact waste modules has been studied by some scholars, but few have specifically examined damaged modules. This study focused on modules that have been broken during transportation, installation, use, or disassembly. Two liberation methods, mechanical crushing and pyrolysis were compared from the perspectives of particle size distribution and morphological characteristics of products. In addition, for separating glass particles and solar cells of coarse fraction, an environmentally-friendly technology of gas-solid fluidized bed was introduced based on their shape and density difference. The effects of airflow velocity and fluidizing time on separation efficiency were investigated for different size fractions. Results showed that pyrolysis was a more suitable liberationliberation method for damaged modules. Higher liberation efficiency could be obtained by pyrolysis, and over-crushing of glass particles and solar cells could be avoided. The optimum pyrolysis conditions were found to be at 500 °C with a holding time of 30 min. The recovery and concentration of solar cells in the >4 mm size fraction were 91.09% and 84.4%, respectively, under the following conditions: 85 m3/h airflow velocity; 90s fluidizing time. For the 2–4 mm size fraction, the recovery and concentration were 82.29% and 80.52% under airflow velocity of 75 m3/h, fluidizing time of 90s. This research presents an alternative process for recovering damaged c-Si PV modules.

Dust diffusion laws during partition excavation by boom-type roadheader in a metro tunnel

When the drill bit of the boom-type roadheader cuts the dolomite at the tunnel face, it generates a lot of dust, which will have an adverse impact on human health and the surrounding environment. In order to clarify the laws of dust diffusion during partition excavation by a boom-type roadheader in a metro tunnel, the respirable dust and particle size distribution characteristics of tunnelling dust are studied through field experiments. Combined with FLUENT numerical simulation, the axial and radial diffusion laws of dust in the air field and the upper and lower parts of the tunnel face are further explored. The results show that at a position 5 m away from the tunnel face, the excavation dust concentration in the lower partition is 65.88% higher than that in the upper partition, and the concentration of respirable dust reaches 313.46 mg/m3, which has a greater impact on a boom-type roadheader operator. In the simulated excavations in the upper and lower partitions, the optimal distance between the air duct outlet and tunnel face is 12 m and 15 m, respectively, and 550 m3/min is the optimal pressure airflow.

Study on the influence of oxygen content evolution on the mechanical properties of tantalum powder fabricated by laser powder bed fusion

In this work, the influence of reuse times on the properties of tantalum powder and its laser powder bed fusion (LPBF) product was investigated. For this purpose, a batch of tantalum powder was reused up to 16 times, and the particle size distribution, flowability, surface topography, and other characteristics of the powder were studied after different reuse times. The mechanical properties of the finished product samples were also tested. Results from the powder reuse showed that the particle size distribution of tantalum powder changed from 30.1 μm to 33.8 μm, and the oxygen content increased from 310 ppm to 450 ppm. The density and fracture strain of tensile specimens decreased from 16.57 g/cm3 to 16.48 g/cm3 and from 37.9% to 11.6%, respectively. The ultimate tensile strength and microhardness decreased after reaching a peak, ranging from 504 MPa to 614 MPa, and 227 HV to 245 HV, respectively. In addition, it was found that the oxides were mainly tantalum pentoxide, along with monovalent and bivalent oxides. The change in tensile properties was likely related to the interstitial solution of oxygen atoms. This study provides a reference for the reusability of LPBF tantalum powder.

Experimental investigation on the particle size distribution characteristics of ice slurry in double-tube heat exchanger

Experimental investigation on the particle size distribution characteristics of ice slurry in double-tube heat exchanger