Powder Size Research Articles

Effects of ultrafine grinding on nutritional, physicochemical and protein composition of Acheta domesticus powder

Acheta domesticus is a new source of high-quality protein, but the accessibility and acceptability of protein is notably limited by the particle size of the house cricket powder, and little information about the effect of particle size on the house cricket powder had been reported. In this study, four kinds of ultrafine cricket powder were obtained by two industrial methods, and compared with the traditional grinding powder. The results illustrated that ultrafine grinding technology could increase the powder properties, such as the thermal stability, crystallinity, color brightness, protein extraction rate and amino acid content, especially the essential amino acid (EAA) content were significantly improved. And the properties and nutrient release of the powder are mainly related to the particle size rather than the method. The results have a certain guiding effect on the development and application of ultrafine house cricket powder as a multifunctional nutrient.

An in-situ three-dimensional study of the dynamic and mechanism during spark plasma sintering of aluminum alloys

An in-situ plasma spark sintering (SPS) apparatus, coupled with laboratory X-ray microscopy, was utilized to three-dimensionally investigate the dynamic evolution process of 7055 aluminum alloy during SPS process. The influences of sintering temperatures and particle morphology on the sintering kinetics were discussed in detail. It was observed that elevating the sintering temperatures enhanced both the rate of densification and the final compactness of the alloy. Furthermore, three-dimensional quantitative analysis of pore evolution indicated that greater discrepancies in powder size between neighboring particles facilitated pore elimination during sintering by increasing available interstitial spaces. Mechanistic analysis rationalized these observations by attributing the enhanced sintering kinetics to the greater particle size disparity, which resulted in higher necking curvature and accelerated densification. The present study therefore provides a comprehensive three-dimensional in-situ quantitative analysis on the dynamic SPS process, and is expected to advance the current comprehension of sintering mechanisms at the micron scale.

Effect of powder feeding rate and size on critical velocity and mechanical properties of cold sprayed Al2O3/2024 deposit

The particle acceleration behavior and deposition mechanism of cold spraying aluminum matrix composites (Al2O3/2024) are complicated by the addition of ceramic particles. The effects of different feeding rates and particle diameters on critical velocity and mechanical properties were studied by numerical simulation and experiment. The results indicate that as the powder feeding rate increases, the impact velocity of gas and particles gradually decreases, and the temperature of gas and particles increases, resulting in an increase in the difference between particle impact velocity and critical velocity. The highest tensile strength of the deposit is achieved at a powder feeding rate of 1 r/min, which is 343 MPa. As the powder feeding rate increases, the performance of the deposits decreases, but it significantly saves time and cost. As the particle diameter increases, the impact temperature first increases and then decreases, resulting in the critical velocity first decreasing and then increasing, and the mechanical performance first increasing and then decreasing. To some extent, the best performance of the deposit is achieved when the size of the metal particle is close to that of the ceramic particle.

Influence on the properties of TMCs of ceramic and intermetallic composite reinforcements (B4C, TixAly and TixSiy) fabricated by inductive hot pressing

Ambitious and competitive, the aerospace industry continuously demonstrates to be one of the leading engineering sectors either at exigence and new technologies development. As lightning the weight of aircrafts is one of the main targets, the spotlight is usually on material research by which new ones may be produced to pursue this aim and still offer the necessary performances. The combination of the properties of titanium and other materials as reinforcements provides really interesting results as titanium matrix composite materials, also known as TMCs. Various samples of titanium matrix composite materials with different reinforcements have been under study to determine the influence of the reinforcements and their respective proportions on the properties of the material. These samples composed of grade 1 commercially-pure titanium as matrix and B4C, TixAly and TixSiy as reinforcements, have been manufactured through powder metallurgy in the same conditions of temperature and pressure via Inductive Hot Pressing (IHP). A total of eight composite materials have been arranged in several different groups to confront their compositions. Thus, this analysis reports results for the influence of the powder size of the matrix and the ceramic reinforcement, the effect of varying the volumetric composition of B4C, and the selection of different intermetallic reinforcements. These tests and the obtained information serve for a project in which the main goal is to determine which compositions of the studied composite materials reach a high enough specific stiffness for a suitable application in the aerospace industry.

Effect of raw material fineness on the properties of inorganic foam materials from solid waste

Solid waste inorganic lightweight materials not only compensate for the flammability of organic materials but also have a lower carbon footprint. They are environmentally safe and cost-effective compared with cement-based foaming materials, and they have good development prospects. This study aimed to improve the chemical foaming reaction kinetics by reducing the particle size of aluminum powder and alkaline solid waste, thereby increasing the expansion degree of solid waste slurry, to further reduce the absolute dry density of inorganic lightweight materials for solid waste and optimize their performance. The influence of the particle size of raw material on the absolute dry density, water absorption, and compressive strength of lightweight materials was investigated. The influence of the particle size of raw material on the macroscopic pore structure of foamed materials was analyzed through binarization of cross-sectional images of specimens. Furthermore, the hydration products and microstructure of materials were characterized using XRD, FTIR, TG-DTG, and SEM to provide a theoretical basis for related research. The experimental results showed that the smaller the particle size of the raw material, the easier it was to carbonize and the lower the flowability of the corresponding cementitious material slurry. Reducing the particle size of raw materials and aluminum powder increased the degree of slurry expansion, thereby reducing the absolute dry density of foaming materials. In addition, reducing the particle size of raw materials and using carbide slag wastewater instead of tap water increased the degree of foaming reaction and hydration reaction, which helped C-(A)-S-H gel formation and promoted the development of sample strength. Finally, the absolute dry density of inorganic lightweight materials was reduced to 0.35 g/cm3 at the minimum, and the corresponding 28-day compressive strength was 0.28 MPa, which met the requirements of the JG/T 266–2011 “foam concrete” specification.

Effect of the SiC powder microscopic morphology on properties of Si/SiC ceramics prepared by spark plasma sintering

AbstractTo solve the problem that Si was volatile and dense Si/SiC ceramics were difficult to achieve by spark plasma sintering (SPS) under a low sintering temperature and pressure, three kinds of SiC powders were used for particle grading and then ball‐milled with different time to further change and regulate their particle size and morphology, and finally nearly dense Si/SiC ceramics were prepared by SPS. The effect of milling time on particle size, morphology, tap density, phase, and microstructure of the SiC powders, as well as on bulk density, microhardness, thermal conductivity, phase, and microstructure of the Si/SiC ceramic, was researched. When the mixed SiC powders were ball‐milled for 12 min, the bulk density, microhardness, and thermal conductivity of Si/SiC ceramic were 2.96 g/cm3, 22.95 GPa, and 152.84 W/(m K), respectively. Ball milling changed the particle gradation and micro‐powder morphology and then affected the powder particle stacking state. Forming continuous pore channels was conducive for the volatile liquid Si to flowing and filling pores in a short time, resulting in denser Si/SiC ceramics at a lower sintering temperature and pressure. This study was useful for the preparation of ceramics containing volatile liquid phase by SPS.

Impact of cocoa variety on physical and chemical properties, reconstitutability, and flowability of cocoa powders

Cocoa of the Criollo, Forastero, and Trinitario varieties grown in the same production area of the Republic of the Congo were simultaneously harvested and similar post-harvesting operations (fermentation in crates followed by sun-drying) were performed. Cocoa powders were then produced according the same process consisting in successive roasting, grinding, fat extraction by pressing, and ultrafine grinding of the defatted mass. In order to investigate the influence of cocoa variety, the main physical and chemical properties (proximate composition, pH, particle size and shape distributions) of powders were characterized and related to cocoa powders abilities to reconstitute and flow. The three varieties showed very close proximal compositions, with lipid contents varying between 21 and 23 % (w/w), which classifies them as defatted cocoa powders. Cocoa powders of all varieties were non-wettable, and not soluble (solubility index around 0.15 g/g), consistently with their high lipid content. The fatty, fibrous, and proteic nature of the product has an impact on the grinding process, resulting in non-wettable powders and particles of varying sizes and shapes. All powders had bimodal particle size distributions, with large particles around 500 μm and small ones around 25 μm. However, slight differences between varieties were observed for some shape and functional properties. Trinitario and Forastero cocoa particles were slightly less spherical. The Criollo cocoa powder was relatively more compressible than the Trinitario variety. No significant difference of flow properties was attributable to cocoa variety. Basic flowability energy of all cocoa powders were relatively high, ranging from 908 to 973 mJ, which could denote a low aptitude to flow that may be related to the probable softness and stickiness of particle surface due to the high lipid content of cocoa powders. Specific energy values required to make studied cocoa powders flow were in the range between 6.61 and 6.99 mJ/g, which corresponds to intermediate values indicating a moderate level of cohesion and thus a fair flowability. The flow parameters obtained from the shear cell test showed no significant difference of cohesion (comprised between 1.54 and 1.70 kPa), flow factor (ranging from 2.53 to 2.76), and internal angle of friction (between 33.4 and 33.9°) linked to cocoa variety. This may be explained by the impact of particle size, as higher particles are generally less cohesive due to their lower surface specific area implying less interparticular contact points. Apart from these slight differences, all varieties showed similar properties and thus could be blended instead of being sorted in the cocoa manufacturing process. This study permitted to highlight that the terroir, the method of harvesting and preparing the beans, and then producing the powder have probably more impact on the physical and chemical and functional properties of cocoa powders than their variety.

Non-invasive estimation of the powder size distribution from a single speckle image

Non-invasive characterization of powders may take one of two approaches: imaging and counting individual particles; or relying on scattered light to estimate the particle size distribution (PSD) of the ensemble. The former approach runs into practical difficulties, as the system must conform to the working distance and other restrictions of the imaging optics. The latter approach requires an inverse map from the speckle autocorrelation to the particle sizes. The principle relies on the pupil function determining the basic sidelobe shape, whereas the particle size spread modulates the sidelobe intensity. We recently showed that it is feasible to invert the speckle autocorrelation and obtain the PSD using a neural network, trained efficiently through a physics-informed semi-generative approach. In this work, we eliminate one of the most time-consuming steps of our previous method by engineering the pupil function. By judiciously blocking portions of the pupil, we sacrifice some photons but in return we achieve much enhanced sidelobes and, hence, higher sensitivity to the change of the size distribution. The result is a 60 × reduction in total acquisition and processing time, or 0.25 seconds per frame in our implementation. Almost real-time operation in our system is not only more appealing toward rapid industrial adoption, it also paves the way for quantitative characterization of complex spatial or temporal dynamics in drying, blending, and other chemical and pharmaceutical manufacturing processes.

Hydrogen production from aluminum-water reactions at low Temperatures: based on an in-situ two powders of different particle sizes

To investigate the granule reaction of two-micron aluminum powders with water at low temperatures, differential scanning calorimetry was used to analyze the initial exothermic temperature. Additionally, adiabatic accelerated calorimetry was employed to study the exothermic reaction under adiabatic conditions. The hydrogen production and particle size variation were investigated in order to gain insights into the Al-water reaction in a reactor with no induction time. Through focused beam reflectance measurement analysis, it was observed that during the reaction process of Al-water, particle sizes initially increased and then decreased. Specifically, the particle size of 3 µm aluminum powder experienced a 189% increase after the reaction while 25 µm aluminum powder decreased by 29%. Ultimately, both types of particles reached similar final sizes around 13.89 µm. The process of Al-water reaction was explained and hydrogen production was analyzed, and the kinetic model was obtained.

Use of pumice stone and silica fume as precursor material for the design of a geopolymer.

Geopolymers are alternative materials to cement because they require less energy in their production process; hence, they contribute to the reduction in CO 2 emissions. This study aims to evaluate the possibility of using industrial residues such as silica fume (SF) to improve the physical and mechanical properties of a pumice stone (PS)-based geopolymer. Through an experimental methodology, the process starts with the extraction, grinding, and sieving of the raw material to carry out the physical and chemical characterization of the resulting material, followed by the dosage of the geopolymer mixture considering the factors that influence the resistance mechanical strength. Finally, the physical and mechanical properties of the geopolymer were characterized. This research was carried out in four stages: characterization of the pumice stone, design of the geopolymer through laboratory tests, application according to the dosage of the concrete, and analysis of the data through a multi-criteria analysis. It was determined that the optimal percentage of SF replacement is 10%, which to improves the properties of the geopolymer allowing to reach a maximum resistance to compression and flexion of 14.10 MPa and 4.78 MPa respectively, showing that there is a direct relationship between the percentage of SF and the resistance. Geopolymer preparation involves the use of PS powder with a composition rich in silicon and aluminum. The factors influencing strength include the ratio of sodium silicate to sodium hydroxide, water content, temperature, curing time, molarity of sodium hydroxide, and binder ratio. The results showed an increase in the compression and flexural strength with 10% SF replacement. The geopolymer's maximum compressive strength indicates its non-structural use, but it can be improved by reducing the PS powder size.

Corrosion Evaluation of Metal Binder-Jetted Stainless Steel Parts: Influence of Printing Parameters on Performance

Additive manufacturing is a rapidly expanding fabrication process in both research and industry, capable of constructing parts layer by layer from a 3D CAD model. ASTM recognizes seven distinct additive manufacturing processes, with the majority capable of producing metal components. Among these technologies, binder jetting stands out, offering the potential to create a variety of metallic parts for applications in the biomedical and energy sectors at reduced costs and shorter lead times. Achieving acceptable corrosion resistance is crucial for such applications. Binder jetting exhibits advantages such as relatively high part density (~99%) and good surface roughness (~6μm for as-sintered parts), making it an ideal candidate for investigating corrosion behavior, given the general correlation between low surface roughness, high density, and improved corrosion performance. Despite its promise, binder jetting lacks standardized procedures for producing parts with specific properties, necessitating users to determine parameters through trial and error. The corrosion behavior of parts created through binder jetting remains uncertain due to various influencing parameters. This study focuses on two key printing factors: layer thickness and binder saturation, chosen due to their impact on surface roughness, density, and thereby on corrosion. Existing literature suggests that increased layer thickness may reduce powder bed density, potentially affecting green part density and causing more significant shrinkage during sintering. Simultaneously, binder saturation is recognized as a critical factor influencing final part quality. Predicting the combined impact of layer thickness and binder saturation on corrosion performance proves challenging. To unravel this relationship, we conducted experiments using an ExOne Innovate Plus metal binder jetting machine and 316L stainless steel metal powder (mean powder size of 22μm) which is widely recognized as the most common powder in research. A number of test runs were conducted by varying layer thickness and binder saturation, offering insights into their nuanced interplay in the context of corrosion performance. Initially, to address insufficient green strength, printer drying time and curing cycle time were optimized by conducting a series of experiments changing the drying time and curing time. Subsequent printing involved changing binder saturation parallel to the layer thickness variations, resulting in distinct parts with varying properties. Then the predetermined curing cycle was executed, followed by de-powdering, and sintering in a furnace. Sintering is imperative to increase the part density and enhance the overall strength of the final product. However, it's essential to acknowledge that sintering may adversely impact corrosion resistance due to the remaining porosity and surface fissures. The choice of sintering profile becomes crucial, necessitating careful consideration to minimize elemental migration during sintering and mitigate porosity. Scanning electron microscopy and optical microscopy are used to analyze sintered parts and interpret corrosion mechanisms. Electrochemical tests were conducted to identify corrosion rates, corrosion potential, passivation behavior, pitting potential, etc. in contrast with conventionally manufactured 316L in M NaCl solution. This study offers insights and recommendations aimed at enhancing the corrosion resistance of binder jetted stainless steel parts.

Optimising corn (Zea mays) cob powder as an effective sorbent for diverse gel matrices: exploring particle size and powder concentration effects

SummaryThis study aims to valorise a plant waste, corn cobs (Zea mays) enriched with fibres (cellulose of 19.09–19.18% and hemicellulose of 34.04–60.13%), to create gel‐like sorbents. Corn cobs (CB) were dried, grounded and sieved to obtain 500, 250 and 125 μm powder size fractions. Various CB powder concentrations (10–40% w/w) were mixed with distilled water and rice bran oil for 2 min at ambient temperature to form hydrogel‐like and oleogel‐like sorbents, respectively. Visual appearance indicated that selected gels formed by 250 and 125 μm CB powders were self‐sustained right after mixing, while the largest particles (500 μm) could not fabricate gels at the CB concentrations studied. FTIR results suggested that the gelation process was primarily attributed to physical absorption rather than chemical binding. Comprehensive analyses of microstructure, physicochemical properties and rheological behaviour indicated that gelation was due to fibre–fibre interaction (125 μm) and oil/water–fibre interaction (250 μm). An increase in CB powder concentration enhanced the microstructural density and hardness of gels. Thus, 250 μm particles and higher absorbent concentrations resulted in brittle sorbents characterised by high hardness but low cohesiveness. The 250 μm particles also exhibit a superior antioxidant profile and lower oil/water loss than the 125 μm CB particles due to effective intra‐particle trapping mechanisms.

Particle size analysis of yellowfin tuna (Thunnus albacares) skin collagen powder using papain-soluble collagen method with varying NaCl concentrations: an experimental laboratory

ABSTRACTIntroduction: The skin of yellowfin tuna (Thunnus albacares) contains high protein, which could potentially be a halal collagen product. Collagen extraction using the papain-soluble collagen method has the advantage of producing a higher collagen yield compared to the acid method. Particle size, one of the physical properties of collagen, plays a crucial role in its efficacy in dentistry. This study aims to analyze the particle size of collagen powder synthesized from Thunnus albacares skin using the papain-soluble collagen method, with varying concentrations of NaCl. Methods: Type of research is an experimental laboratory. Thunnus albacares skin was synthesized by chopping, cleaning, and soaking in a 0.1 M NaOH solution. The extraction process used the enzyme papain and 0.5 M of acetic acid. Samples were divided into four groups, each with different concentrations of NaCL: 0, no NaCL;, 0.9 M NaCl, 1.3 M NaCl, and 1.7 M NaCl. After centrifugation, the samples were freeze-dried. The particle size of collagen powder was measured using a Particle Size Analyzer test tool. The data collected was then analyzed using the Mann-Whitney test. Results: Particle size distributions are as follows: K group (3.36 nm), P1 (1.842 nm), P2 (3.36 nm), and P3 (10.12 nm). There is a significant difference in groups K-P1 and P3, P1-P2 and P3, and P2-P3 (p<0.05). However, there is no significant difference in groups K-P2 (p>0.05). Conclusion: Particle size of this research produced nano-sized collagen powder, with the lowest particle size observed in the 0.9 M NaCl group, measuring at 1.842 nm. The particle size increased in the group without NaCl and in the 1.3 M NaCl group at 3.36 nm, and reached the highest value in the 1.7 M NaCl group at 10.12 nm.

Microstructures and properties of Pr,Ce:Gd2O2S ceramics fabricated from powders synthesized at different initial water bath temperatures

Crystallized precursor with stacked layered was synthesized in hot water bath using oxide powders and concentrated sulfuric acid as raw materials. Gd2O2S powders with high phase purity were obtained by reducing the precursor under flowing hydrogen atmosphere. The influence of initial bath temperature of Gd2O3 and H2SO4 on the microstructure of Gd2O2S powders was investigated. The Gd2O2S:Pr,Ce powders showed a stacked layered structure and as the initial water bath temperature increases, the particle size of the flaky powders also increases. Using the synthesized powders, Gd2O2S:Pr,Ce scintillation ceramics were fabricated through pre-sintering in vacuum followed by HIP post-treatment in argon atmosphere. The Gd2O2S:Pr,Ce ceramics fabricated from the powders synthesized at lower initial water bath temperature show a rapid densification rate during pre-sintering. The Gd2O2S:Pr,Ce ceramic sample fabricated from powders synthesized at 7°C showed the highest optical transmittance, XEL intensity, and light yield value of 25,800 ph/MeV @ 662 keV γ rays. The PL decay time of Pr3+3P0→3H4 transition was measured to be ∼2.87 μs for all ceramic samples. The effect of the initial water bath temperature on optical transmittance and light yield of Gd2O2S:Pr,Ce ceramics was also discussed.

To-pack or Not-to-pack: Towards Improved Graphite Electrochemical Oxidation Through Electrode Design.

Fabrication of batch-wise efficient, user- and environmentally-friendly, and well-defined yield methods for the synthesis of graphite oxide, the main precursor to graphene oxide and its reduced derivative, is an essential and robust research field, yet is sparingly investigated or innovated in recent years. This Concept review showcases recent advances in the fabrication of electrochemical set ups that meet aforementioned design parameters, wherein working electrode construction is seen to play a key role in shaping the yield characteristics and aiding the mechanistic understanding of efficiency of adopted methods. Particularly, these advances pave the way for new and various tunable design parameters by fabricating different methods of encapsulating graphite powder instead of using conventional bare monolith forms of graphite as working electrode. Encapsulation geometry, pressure, and matrix material, as well as powder size are examples of such tunable design parameters, absent in the monolith methods. The encapsulation validates authenticity of real-time monitoring of electrochemical intercalation, exfoliation, and oxidation of graphite powder, thereby offering excellent and well-defined control on yield.

Effects of particle size and flow properties on the performance of ceramic-coated separators in Lithium-ion batteries

This study investigates the relationship between particle size and flow properties of boehmite powders and their impact on ceramic-coated separators for lithium-ion batteries, specifically exploring how these properties influence the performance of the separators. The separators coated with BH-3 powder, with larger sizes and better flow properties than BH-1 and BH-2, showed superior characteristics with the minimum deviation when measuring physical properties such as thickness and roughness. The BH-3 coated separators, with <10% shrinkage at 150 °C for 1 h, showed the highest ion conductivity (0.69 mS cm−1) and superior electrochemical properties compared to bare PE separators. These results highlight the importance of the excellent flow properties of the boehmite powders, which reduces the slurry viscosity, facilitates the formation of a uniform coating layer, and consequently enhances the performance of the separator.

Particle grading and debinding process of zirconia ceramic based on digital light process

Digital light processing technology has the advantages of high molding accuracy and the ability to prepare complex structures, which is commonly used in the preparation of resin or ceramics. By mixing two particle sizes of zirconia powders, this paper successfully prepared a 60 vol% slurry with a low viscosity of 1.28 Pa s at shear rate was 50 s−1. By systematically studying the rheological properties of the mixed slurry, the curing depth was exceeding 100 μm at exposure time of 3 s. Furthermore, by investigating the debinding process of the printed sample, it is found that the sintering sample after debinding in vacuum has the highest density. This work has a positive significance for the preparation and debinding process of high solid loading ceramic slurry.

Evaluation of tribo-mechanical measurements and thermal expansion of Cu-based nanocomposites reinforced by high strength hybrid ceramics

It is known that Copper’s (Cu) electrical conductivity makes it a desirable material for use in industry. Due to poor properties such as hardness, thermal expansion, and corrosion resistance, its applications are limited. This manuscript solves these problems while maintaining no breakdown in electrical conductivity. In this study, high-strength ceramics (SiC nanoparticles and graphene nanosheets) were used as reinforcements in the manufacture of Cu-based hybrid nanocomposites using powder metallurgy technique. X-ray diffraction analysis (XRD) was used to investigate phase composition and crystal size of the milled powders. Transmission electron microscopy (TEM) and field emission scanning electron microscopy (FESEM), respectively examined the microstructure of the prepared powder powders and sintered nanocomposites. Then, various properties of the sintered samples are measured, including physical, electrical and thermal properties and wear resistance. The obtained XRD technique and TEM images showed decreases in the crystal and particle size of milled samples reaching up to 14.08 and 28.30 nm, respectively for the sample contained 8 vol. % SiC + 0.8 vol. % graphene (SG8). A surprising improvement in the mechanical properties of up to 809.15, 341.84 MPa and 336.56 GPa for microhardness, strength and longitudinal modulus for the sample containing the highest reinforcements, achieving an improvement of up to 122, 61.37 and 41 percent compared to the Cu matrix. Moreover, there was a noticeable improvement in the coefficient of thermal expansion (CTE) and wear rate values of the samples by increasing the percentages of hybrid reinforcements in the examined sintered nanocomposite samples. The Sample SG8 recorded the lowest value, decreasing by about 50.2 and 76.5% compared to the SG1 sample. Finally, adding reinforcements to the Cu matrix had a negative effect on the relative density and electrical conductivity, and the lowest values was 92.94% and8.59 × 106 S/m, respectively for the SG sample.

(Kesan Rawatan Permukaan pada Ikatan Struktur Mikro antara Muka Zirkonia-Dentin terhadap Saiz Zarah Serbuk Zirkonia yang Berbeza)

Zirconia-based materials have emerged as promising resources for dental restoration applications owing to their excellent strength and aesthetic appearance. In clinical practices, surface treatment on zirconia is essential to ensure enhanced dental bonding. In this study, a novel method was used to produce zirconia block, and the influence of surface treatment on zirconia-dentine microstructure bonding interface was investigated for different particle sizes of zirconia powder. The particle sizes used in this study were 90 and 30 nm on the basis of manufacturer claims. A zirconia block of both particle sizes underwent surface treatment airborne-particle abrasion (50 μm, 0.4 MPa). Dentine specimens were prepared from extracted premolars stored in 0.1% tymol solution before being randomly cemented with the zirconia block sample by using self-adhesive resin cement (RelyX U2000 Clicker, 3M) and then light polymerised. The results after surface treatment showed higher surface roughness values for 90 and 30 nm at 0.17 and 0.18 μm, respectively, than those of the sample without surface treatment at 0.05 and 0.06 μm, respectively, showing no significant difference between particle sizes. Surface treatment improved the bonding of zirconia because the surface roughness allowed for enhanced interlocking of the cement onto the zirconia surface. However, the unbonded dentine and cement was due to the existence of a smear layer on the dentine surface that prevented the selfadhesive resin cement to work well with the dentine surface. Thus, dentine primer must be used to chemically remove the layer and allow for proper bonding between the resin cement and dentine surface.

Tailoring Laser Powder Bed Fusion Process Parameters for Standard and Off-Size Ti6Al4V Metal Powders: A Machine Learning Approach Enhanced by Photodiode-Based Melt Pool Monitoring

An integral part of laser powder bed fusion (LPBF) quality control is identifying optimal process parameters tailored to each application, often achieved through time-consuming and costly experiments. Melt pool dynamics further complicate LPBF quality control due to their influence on product quality. Using machine learning and melt pool monitoring data collected with photodiode sensors, the goal of this research was to efficiently customize LPBF process parameters. A novel aspect of this study is the application of standard and off-size powder feedstocks. Ti6Al4V (Ti64) powder was used in three size ranges of 15–53 µm, 15–106 µm, and 45–106 µm to print the samples. This facilitated the development of a process parameters tailoring system capable of handling variations in powder size ranges. Ultimately, per each part, the associated set of light intensity statistical signatures along with the powder size range and the parts’ density, surface roughness, and hardness were used as inputs for three regressors of Feed-Forward Neural Network (FFN), Random Forest (RF), and Extreme Gradient Boosting (XGBoost). The laser power, laser velocity, hatch distance, and energy density of the parts were predicted by the regressors. According to the results obtained on unseen samples, RF demonstrated the best performance in the prediction of process parameters.