High Relative Density Research Articles

Non-iterative border-peeling clustering algorithm based on swap strategy

Border-Peeling algorithm is a recently proposed density based clustering algorithm. The method of peeling off border points by continuous iteration and calculating the density influence value by using the Gaussian kernel distance makes the algorithm more complex. At the same time, there is a risk of excessive peeling of small clusters on unbalanced datasets, which leads to a large number of noise misidentification. In order to reduce the time consumption and improve the clustering performance on unbalanced datasets, this paper proposes a non-iterative border-peeling clustering algorithm. First, the potential core points are determined by the centroids of k-nearest neighbor. Secondly, the points with lower local relative density in the core points and the points with higher relative density in the border points are exchanged to complete the distinction between the core points and the border points. Then basic DBSCAN method is used to cluster core points and noise points. Finally, the associations between the border points and the core points are based on the number of reverse nearest neighbors of the border points in the core points. Our method has achieved competitive results on 10 synthetic datasets and 8 UCI real-world datasets.

Synthesis and formation mechanism of ZrC–SiC–TiC ceramic powders with high-sinterability via sol-gel process and carbothermal reduction

In this work, high-sinterability ZrC–SiC–TiC ceramic powders were synthesised through a sol-gel approach coupled with subsequent carbothermal reactions. Specifically, MgCl2 was utilised as an additive to enhance the sintering activity of the powders. Experimental results revealed that the introduction of Mg and variation in Zr/Ti molar ratios significantly influenced the phase and morphological evolution of the precursor. In the form of a Mg–Si–O liquid phase, Mg promoted carbothermal reduction and solid-solution reactions. It ultimately remained as amorphous Mg–Si–O oxide in the final ZrC–SiC–TiC ceramic powders, effectively improving the sintering activity of ceramic powders. Consequently, dense Mg-modified ZrC–SiC–TiC ceramics with high relative density up to 99.2 % were successfully fabricated by spark plasma sintering at 1700 °C and 30 MPa.

Enhancing NiZn ferrite properties through microwave sintering: A comparative study

The structural, microstructural, morphological, and electromagnetic properties of a micro- and nanostructured nickel–zinc ferrite ((Cu0.12Ni0.23Zn0.65)Fe2O4) were studied after sintering between 900 and 1100°C. The microparticulated ferrite (MICRO) was a commercial material, while the nanoparticulated ferrite (NANO) was obtained through high energy milling of the former. The effect of microwave heating (MW), compared to traditional infrared sintering (IR), was investigated.Microwave sintering successfully controlled the grain growth of both granulometries and produced sintered bodies with high relative densities (low porosity), small average grain size, narrow grain size distribution, and a high value of the complex magnetic permeability-imaginary part (μ″) for the MICRO ferrite. In the case of the NANO ferrite, microwave sintering yielded values similar to those obtained by conventional IR.Microwave sintering significantly affected the densification and grain growth processes for both granulometries studied. Additionally, reducing the granulometry of the starting ferrite powder had a noticeable impact on the microstructure and electromagnetic properties of the sintered ferrites, regardless of whether microwave or infrared radiation was used. However, the magnetic property (μ″) decreased when the particle size of the starting powder was reduced from micro to nanometric scale, irrespective of the sintering source. This observation is supported by our previously published mathematical models that establish relationships between the complex magnetic permeability, magnetization mechanisms, angular frequency, and ferrite microstructure.

Interfacial regulation and fracture mechanism of Al–Si/SiC composites infiltrated under super-gravity field

We reported a novel method to prepare Al–Si/SiC composites infiltrated under super-gravity field without Mg addition. Noted that centrifugal force acted as the main driving force to overcome the penetration resistance, making it feasible to obtain the Al–Si/SiC composite with high relative density (≥99.3 %). The interfacial reaction between Al and SiC was retarded by Si addition under super-gravity field. Interestingly, the rod-like eutectic Si was detected at Al–SiC interface with semi-continuous distribution, leading to the excellent bending strength (342.6 ± 1.0 MPa), enhanced thermal conductivity (173 W/m K at 373 K), and relatively low coefficient of thermal expansion (8.90 × 10−6 K−1 ranged from 323 to 373 K). The interfacial regulation and fracture mechanism were discussed in details.

Crystal structure, chemical bonding and infrared reflectivity of microwave dielectric SrIn2O4 ceramics

In this work, the orthorhombic structured SrIn2O4 ceramics with a space group Pnam were synthesized by a solid-state reaction method. A high relative density (96.5%) coupled with excellent microwave dielectric properties (εr ~ 12.3, Q × f = 96,900 GHz, τf ~ -61.6 ppm/°C) were obtained as sintered 1300 °C for 4 h. The bond valence analysis demonstrates that the large sized cation Sr2+ exhibits a compressed state, while the In3+ exhibits a weaken rattling effect. The P-V-L chemical bond theory analysis indicates that the In-O bonds play a key role in affecting the dielectric loss. The thermally conductivity activation energy Edc (0.94 eV) of SrIn2O4 was obtained by the dielectric spectroscopy, indicating that the Edc was contributed to the double ionized oxygen vacancies. Furthermore, the intrinsic dielectric properties (εr ~ 11.2, Q × f = 148,900 GHz) of SrIn2O4 were obtained by infrared reflectivity spectroscopy.

Metoda obliczania jednostkowego składu węglowodorów na podstawie skumulowanego składu frakcyjnego próbek ropy naftowej i kondensatu

The composition of oils is the main source of information that enables the evaluation and modeling of their physical, thermal and chemical properties (including their critical properties) across a wide range of state parameters. The more comprehensively the composition of oils is analyzed, the more precise information is provided for calculations and problem-solving in the field of oilfield mechanics and related areas, such as the extraction, preparation, transportation, and processing of oils and their fractions. The principal constituents of oils are hydrocarbons. Oils contain hydrocarbons of three homologous series: paraffins, naphthenes and aromas. In oils, there may be hydrocarbons of a mixed composition containing both naphthenic and aromatic rings. In addition to hydrocarbons, oils also contain oxygen, sulfur, nitrogen and other constituents. These compounds are the primary elements of asphaltene-resinous substances (ARS) found in oil. They are characterized by high relative densities (often exceeding 1 g/cm3), dark coloration, and relative chemical instability when exposed to elevated temperatures, oxygen, adsorbents, etc. The composition of asphaltene-resinous substances encompasses a wide range of substances. The validity of the proposed technique is justified by the observation that the data of molecular weight, Watson characteristic factor, and experimental density calculated from molar compositions should align on the same surface with a high degree of correlation. In addition, the experimental and calculated values, in terms of molecular composition, of molecular weights should lie on a straight line passing through the origin of coordinates with a slope coefficient equal to unity and exhibit high degree of correlation.

Effect of dual-laser powder bed fusion on surface quality, internal defects and properties of 316L stainless steel

Dual-laser powder bed fusion has excellent potential in the preparation of high-performance components due to its ability to suppress defects and control properties during the formation. This paper investigates the effects of various remelting intervals and remelting laser power on the mechanical properties, internal defects, and surface quality of dual-laser powder bed fusion 316L. Compared to increasing laser power, shortening melting intervals offers a more effective compensation for energy losses resulting from the rapid cooling effects of LPBF. Higher surface quality (Ra = 5.876, Str = 0.633) and higher relative density (99.28 %) can be attained with a shorter remelting interval. However, due to excessive energy that increases porosity and grain size, the improvement in mechanical properties (667.19 MPa, 49.3 %) is less than long-interval remelting (703.55 MPa, 50.4 %). In comparison to vary remelting time interval at the high laser power, the depth of the melting pool can be controlled more precisely within a shorter interval by varying the laser power. However, the semi-melting of the spatter caused by applying a medium remelting laser power introduces new lack of fusion voids. This study highlights the advantages of dual-laser powder bed fusion in ensuring consistent formation and demonstrates its potential for producing customized microstructures and high-quality surfaces. Furthermore, it presents a novel approach for the dual-laser powder bed fusion of high refractive materials and room temperature brittleness materials.

Achieving high thermal conductivity of Al–50Si alloy through heat treatment and its microstructural evolution

Al–50Si alloys were prepared by powder extrusion and characterized for electronic packaging. The optimization of powder size, extrusion temperature, and heat treatment parameters was performed to enhance the microstructure and thermo-physical properties. The alloy exhibits a high relative density >99 %, a low coefficient of thermal expansion (CTE) < 10 × 10−6/K, and a good thermal conductivity (TC) ∼117 Wm−1K−1 achieved by employing a large size powder and high extrusion temperature during the extrusion process. Subsequent heat treatment of the optimized alloy at 550 °C for various time reveals a fluctuating increasing trend in TC during the heat treatment process. The TC values exhibit periodic fluctuations as they alternate between increments and decrements, primarily resulting from the recrystallization and secondary recrystallization of Al grains during heat treatment process. Notably, the maximum TC value (∼159.1 Wm−1K−1) at room temperature is obtained after heating the alloy to 550 °C for 26 h. Compared to the as-extruded alloy, the TC of heat-treated alloy increases by approximately 36 %, which can be attributed to the elimination of eutectic Si and growth of Si and Al grains within the alloy. The study may shed light on the mechanism underlying the improvement in thermal conductivity of Al–50Si alloy by microstructural evolution.

Heating properties of ITO ceramics with different Sn/In ratios

Indium tin oxide (ITO) ceramics with different SnO2 contents were fabricated using the conventional solid-state reaction. The phase structure, microstructure, electrical conductivity, heating, and mechanical properties were investigated in detail. The results showed that pure ITO ceramics with high relative density were obtained successfully. The ITO ceramics were cut into regular rectangles to serve as electrical heaters. Additionally, their saturation temperatures and thermal response times were tested at different voltages. The results showed that ITO ceramics with 10% SnO2 had the fastest thermal response rate and reached a saturation temperature of 376∘C at 1.5[Formula: see text]V voltage, the highest temperature reported in the literature for In2O3 ceramics. Moreover, In2O3 with 10% SnO2 showed good mechanical properties. Hence, ITO ceramics, as electrical heaters with low driving voltage and high response speed, are expected to have potential heating applications such as domestic heating and industrial production.

Density-graded Voronoi honeycombs – A local transversely isotropic description

Density-graded cellular materials, in which their relative density varies with location, are amenable to design for multi-functions, and have been used in mechanical buffers and protective structures. To estimate the force–deformation responses of density-graded cellular materials efficiently without resorting to modelling individual cells, a constitutive model based on local transverse isotropy is adopted. Metallic Voronoi honeycomb-like specimens with cell sizes that vary with position, are fabricated via 3D printing, to represent a density-graded cellular material with local transverse isotropy that varies with position. From quasi-static compression tests and cell-based finite element (FE) simulations, the influence of relative density on the continuum constitutive model is investigated and demonstrated to be significant. The model is then used to predict the global stress–strain response and deformation of cellular materials with positive and negative density-gradients, defined along the loading direction, subjected to uniaxial quasi-static compression, quasi-static indentation, and dynamic compression. The results show that for quasi-static compression, severe plastic deformation progresses from the low relative density region to the high relative density region; however, impact loading and indentation of negative density-gradient Voronoi honeycombs generates two zones of gross deformation – in the vicinity of the applied load and the opposite lower density end. Predictions based on the proposed constitutive model display good correlation with experimental and cell-based FE results.

Effects of boron source on properties of pressureless solid-state sintered silicon carbide ceramics

The effects of the boron source (B, BN, and B4C) on the thermal, electrical, and mechanical properties of pressureless solid-state sintered SiC ceramics were investigated. A high relative density of 99.9 % was successfully achieved for all ceramic specimens using an appropriate additive composition and ideal sintering conditions. SiC ceramics sintered with B and B4C additives displayed higher electrical and thermal conductivities and higher flexural strength than those sintered with the BN additive at the same relative density. The presence of intrinsically-weak, electrically-insulating BN grains at the junction and grain boundaries increased both the fracture toughness and electrical resistivity, while the flexural strength and thermal conductivity of the ceramics decreased. The electrical resistivity, thermal conductivity, and flexural strength of the SiC ceramics were able to be adjusted with values ranging from 3.2 × 104–1.6 × 106 Ω‧cm, 72.4–147.5 W‧m−1‧K−1, and 386–545 MPa, respectively, depending on the boron source used.

Novel LiCa(PO3)3 and LiSr(PO3)3 microwave dielectric ceramics

Novel LiCa(PO3)3 and LiSr(PO3)3 phases were produced by conventional solid-state synthesis and formed into ceramic pellets followed by conventional sintering. The crystal structure, ceramic microstructure, microwave dielectric properties and ac conductivity were investigated. A triclinic space group P1- was obtained from Rietveld refinements, and the lattice vibration modes were determined by Raman spectroscopy. The optimum sintering conditions for LiCa(PO3)3 and LiSr(PO3)3 ceramics were 700 ℃ and 625 ℃, respectively, both for 10 h. Dense glass-free ceramic microstructures were confirmed by SEM. High relative densities of 94.6 % and 93.8 %, low microwave εr values of 5.85 and 5.62 at 14 GHz, and high quality factors Q×f of 25,200 and 23,450 GHz at 14 GHz were detected. Large negative τf of − 105 and − 106 ppm/°C were obtained, which are uncommon but highly valuable for offsetting positive τf values of other systems. Moderate Li+-ion conduction was detected in both compounds by ac impedance spectroscopy.

Room temperature fabrication and post-impregnation of LMO-ST composites: Engineering and modeling of dielectric properties

In this work, the effect of changing the Li2MoO4-SrTiO3 (LMO-ST) compositional proportion (1–100 wt%) on the microstructure, dielectric properties, and relative density of LMO-ST composites fabricated at room temperature was investigated. The results showed that increasing the LMO binder content resulted in a higher relative density (up to 93%), but a lower dielectric constant in the range of 75 to 5. Good agreement between the experimental results and the predicted values of relative permittivity was obtained using the Lichtenecker model, reformulated for a three-phase composite system. Modeling further explained the detrimental effects of porosity on the dielectric properties. To address this issue, impregnation with titanium (IV) isopropoxide (TTIP) was found to reduce overall porosity and improve relative permittivity from 72 to 99 at 1 MHz. The room temperature fabrication offers a wide range of relative permittivity for LMO-ST composites.

Material-agnostic machine learning approach enables high relative density in powder bed fusion products

This study introduces a method that is applicable across various powder materials to predict process conditions that yield a product with a relative density greater than 98% by laser powder bed fusion. We develop an XGBoost model using a dataset comprising material properties of powder and process conditions, and its output, relative density, undergoes a transformation using a sigmoid function to increase accuracy. We deeply examine the relationships between input features and the target value using Shapley additive explanations. Experimental validation with stainless steel 316 L, AlSi10Mg, and Fe60Co15Ni15Cr10 medium entropy alloy powders verifies the method’s reproducibility and transferability. This research contributes to laser powder bed fusion additive manufacturing by offering a universally applicable strategy to optimize process conditions.

Synthesis and characterization of layered quaternary Mo4/3Lu2/3AlB2 ceramics fabricated by spark plasma sintering

A new high-purity i-MAB phase of Mo4/3Lu2/3AlB2 ceramic (95.06 wt% Mo4/3Lu2/3AlB2 and 4.94 wt% MoB) was successfully synthesized with Mo, Al, Lu, and B as raw materials by spark plasma sintering at 1250 °C. The dense sample with a high relative density of 98.9 % possessed good physical and mechanical properties. The average thermal expansion coefficient from room temperature to 1200 °C was determined to be 8.38 × 10−6 K−1. The heat capacity, thermal conductivity, and electrical conductivity were measured to be 0.28 J·g−1·K−1, 9.90 W·m−1·K−1, and 1.22 × 106 Ω−1·m−1 at room temperature, respectively. Additionally, Vickers hardness was tested to be 10.29 GPa under a load of 10 N, fracture toughness was determined to be 5.13 MPa·m1/2, and compressive and flexural strengths were tested to be 1567 MPa and 468 MPa, respectively. Present research adds a new member to the family of structural-functional ceramics.

Modified poly(phenylene oxide)/(CaSr)TiO3 composites with ultrahigh permittivity and low loss for microwave substrates

Polymer/ceramic composites used as microwave dielectric combine the excellent dielectric properties of ceramic with the toughness of polymer. The properties of composites are not only determined by the properties of components but also influenced by the polymer-ceramic interface. In this work, we conducted experiments and simulations on the dielectric properties and thermal conductivity of modified poly(phenylene oxide)/(CaSr)TiO3 (mPPO/CST) composites. A comparison of composites filled with different sizes (2.5, 11, and 20 µm) of CST fillers demonstrates that smaller particle (more filler-matrix interface) is beneficial to mechanical properties but detrimental to dielectric properties and heat transfer. The finite element simulation results are in good agreement with the experimental values, which is of significance for guiding future experiments. The composite filled with 80 wt. % CST20 has a high relative density of 97%, an ultrahigh εr of ∼20, and a low tan δ of 0.0019 at 10 GHz. Meanwhile, the mPPO/CST composites are eco-friendly and suitable for mass production and are promising candidates for automotive and aerospace applications.

Crystal structure, bond characterization and lattice energy of B-site 1:3 ordering inverse spinel Li1.25Ga0.25Ti1.5O4 ceramic

In this work, inverse spinel structured Li1.25Ga0.25Ti1.5O4 ceramics with a space group of P4332 were synthesized by a solid-state reaction method. XRD, SAED, HRTEM, and Raman spectra analysis demonstrated that the Li1.25Ga0.25Ti1.5O4 ceramic was formed a A-site 1:3 disordered and B-site 1:3 ordered spinel structured. A high relative density (98.7%) with excellent microwave dielectric properties of εr = 23.8, Q×f = 93,800 GHz, and τf = –21.9 ppm/oC were obtained in 1110 °C for 4 h. Bond valence analysis demonstrated that the average cations of Li1.25Ga0.25Ti1.5O4 were in the rattling state, and the polarizability of Ti4+ was underestimated. The P–V-L chemical bond theory and lattice energy analysis results indicated that B–O bonds were the main factor to affect the εr and Q × f, and the under-bonding Ti4+and Ga3+ has a significant effect on the τf. All the results show that the Li1.25Ga0.25Ti1.5O4 ceramic might be a potential candidate for 5 G communication technology.

Hot-Pressing Deformation Yields Fine-Grained, Highly Dense and (002) Textured Ru Targets.

Ruthenium (Ru) is a refractory metal that has applications in the semiconductor industry as a sputtering target material. However, conventional powder metallurgy methods cannot produce dense and fine-grained Ru targets with preferred orientation. Here, we present a novel method of hot-pressing deformation to fabricate Ru targets with high relative density (98.8%), small grain size (~4.4 μm) and strong (002) texture. We demonstrate that applying pressures of 30-40 MPa at 1400 °C transforms cylindrical Ru samples into disk-shaped targets with nearly full densification in the central region. We also show that the hardness and the (002)/(101) peak intensity ratio of the targets increase with the pressure, indicating enhanced mechanical and crystallographic properties. Our study reveals the mechanisms of densification and texture formation of Ru targets by hot-pressing deformation.

Morpho-anatomical adaptations of dominantly grown wild Datura inoxia to wastewater resource: Productivity and ecological issues

With the increasing global water scarcity, wastewater irrigation has become widespread, but it can have detrimental ecological consequences. Although wastewater contains valuable nutrients for plants, improper treatment or the use of untreated wastewater in irrigation can negatively impact soil fertility and plant growth. This study is divided into two parts: firstly, a phytosociological survey was conducted to identify plant species with the highest importance value index (IVI) in the vicinity of wastewater-irrigated areas. Secondly, a comparative morpho-anatomical analysis was carried out to investigate the morpho-anatomical adaptations of the species with the highest IVI under wastewater irrigation compared to normal water irrigation. The results of the phytosociological survey revealed the presence of 51 plant species in the vicinity of the wastewater-irrigated areas, with varying relative densities and coverage. Datura inoxia exhibited the highest IVI (28.79), followed by Xanthium strumarium (24.34), while Lippia nodiflora showed the lowest IVI (1.86). The morphological growth of D. inoxia was superior under normal water irrigation, but the average root length was greater under wastewater irrigation. Regarding cell anatomy, cell thickness and cell area characteristics in the dermal, ground, and vascular tissues of the stem and root tended to be greater under wastewater treatment. However, the opposite trend was observed in leaf anatomical analysis, possibly due to the combined effect of wastewater and climatic conditions. Stem and root xylem thickness were greater under wastewater irrigation, whereas phloem thickness was higher under normal water irrigation. The number of vascular bundles in the stem, root, and leaf was higher under wastewater treatment compared to normal water irrigation, but their arrangement was circular in the latter and scattered under wastewater irrigation. Datura inoxia demonstrated strong adaptive potential under wastewater irrigation, as indicated by its highest relative density, coverage, and IVI, suggesting its suitability for phytoremediation. However, due to the low relative density, coverage, and IVI of many other species, the use of untreated wastewater for irrigation cannot be appreciated.

Raman spectra, bond characteristics, and microwave dielectric properties of Gd2Mo3O12 ceramics

Gd2Mo3O12 ceramics were prepared using the traditional solid-phase reaction method. All samples were found to possess an orthorhombic crystal structure with a space group of Pba2, as revealed by refined XRD results. The ceramic sintered at 1000 °C exhibited a high relative density of 96.95% and superior microwave dielectric properties, including εr of 9.42 ± 0.05, Q × f of 49258 ± 1200 GHz, and τf of -71.8 ± 0.7 ppm/°C. The results suggest a correlation between an increase in εr and higher relative density, and a more compact and uniform microstructure can lead to higher Q × f value. Chemical bonding theories and Raman spectroscopy analysis reveal that Mo-O bonds, rather than Gd-O bonds, dominate the microwave dielectric properties. Furthermore, the εr of Gd2Mo3O12 ceramic was closely related to bond ionicity, while Q × f and τf were mainly determined by lattice energy and bond energy, respectively.