Maximum Relative Density Research Articles

Correlation between chemical bond characteristics and microwave dielectric properties of KLa(MoO4)2 ceramics

This investigation details the synthesis process of KLa(MoO4)2 ceramic utilizing a solid-state route method, alongside an analysis of its structural characteristics and the correlation between chemical bonds and microwave dielectric properties. The KLa(MoO4)2 phase was identified to possess a Monoclinic structure (C2/c space group). Sintering the sample at 820 °C resulted in a maximum relative density of 94.6% and impressive microwave characteristics: εr = 9.63, Q×f = 50,100 GHz, and τf = -75.7 ppm/°C. Correlations between relative density and dielectric properties were observed. Further, application of the P-V-L bond theory facilitated the analysis of chemical bond parameters and their impact on microwave dielectric properties. The dielectric properties were correlated to chemical bond iconicity, packing fraction, lattice energy and bond valences.

Defects, microstructure and associated mechanical properties of Inconel 718 fabricated by selective electron beam melting

Comprehensive characterizations and evaluations were conducted on the relationship between process parameters and density in the Inconel 718 (IN718) alloy fabricated by selective electron beam melting (SEBM). Additionally, the microstructure and anisotropy of tensile properties were evaluated in both the as-built state and after solution treatment and aging (STA). During different stages of energy density, the primary contributors to the porosity rate transitioned from the lack of fusion (LF) pores to the inclusion of spherical and shrinkage pores, resulting in a maximum relative density of 98.95 %. The as-built parts displayed notable parallel texture to the building direction, and a significant tensile anisotropy supported by the Taylor factor. The matrix of these parts consisted of δ, γ', γ″, and carbonitrides, with a considerable presence of δ precipitation leading to a reduction in γ″ content and lower strength. After heat treatment, the δ dissolved, and γ″ precipitated extensively, while the carbonitrides and texture were retained. However, unique tensile results contradicting the predictions made by computational modeling were observed, we propose a new insight attributed to the presence of shrinkage pores along the build direction and use finite element analysis to support this view.

Experimental studies on mechanical properties of metal fused filament fabricated SS316L

Fused filament fabrication is a simple and commercially popular additive manufacturing (AM) technique for developing high-accuracy polymer-based materials. In this experiment, a retrofit type of setup was developed to manufacture stainless steel 316L–based products. The current study focuses on the encapsulation of stainless steel with polylactic acid to prepare the filament for 3D printing. The effects of printing parameters such as layer thickness, infill density, and extruder temperature on responses like density, surface roughness, micro-hardness, and material/filament consumption have been studied. A Box–Behnken design approach was employed to systematically evaluate 15 specimens under varying conditions. The results revealed that a maximum relative density of 97% was achieved with a layer thickness of 0.2 mm, an extruder temperature of 215°C, and a 100% infill density. Additionally, the optimized infill density demonstrated a significant effect on both hardness and surface roughness, confirming the importance of precise control over processing conditions for improving the performance of the printed parts. The findings contribute to the advancement of metal-polymer composite filaments in additive manufacturing, highlighting their potential for producing complex, high-performance components.

Analysis of co-relation on LPBF process parameter on wear characteristics of Cu-Cr-Zr alloy

Copper alloy bearings, gears, and fasteners have a significant impact on industrial sectors. However, due to the defect formation and void generation during the manufacturing of copper alloy parts using (Laser Powder Bed Fusion) LPBF technique, the wear resistance of the copper alloy was significantly affected. Hence, the prime novelty of the current research is enhancing wear resistance by analyzing the interaction of combined LPBF parameters. In order to decrease cavity forms and reduce the wear rate of the printed Cu alloy components, the important LPBF process parameters such as Scan Velocity (SV) of 550, 750, and 950 mm s−1, Laser Power (LP) of 460, 540, and 620 W, and Re-melting Range (RR) of 5, 25, and 45% were selected and studied. The results of the experimental investigation were supported by the use of Grey Relation Analysis (GRA). A comparative study was conducted with five distinct parameter combinations to investigate the relative influence of each parameter on the relative density, wear rate and elastic modulus. The research findings verify that the application of optimal SV of 750 mm s−1 and RR of 45% with maximum LP of 460 W resulted in the maximum relative density of 99.91%, minimal wear rate of 0.52 × 10−5 mm3/Nm, and maximum elastic modulus of 140.22 GPa.

Transient liquid phase sintering in spark plasma sintered tungsten heavy alloys with Nb and Mo additives

In the present investigation spark plasma sintered tungsten heavy alloys of composition 90W-7Ni-3Fe, 84W-7Ni-3Fe-6Mo, and 84W-7Ni-3Fe-6Nb were analyzed to determine the effect of Mo and Nb addition on microstructure and phase formation. The alloys were sintered at temperatures ranging from 1150 °C to 1275 °C and at a fixed sintering pressure of 30 MPa. Nb added alloy exhibited a maximum relative density of 99% at sintering temperature of 1200 °C. Whereas the base alloy and Mo added alloy, exhibited a maximum relative density of 97.9% and 95.9% at 1150 °C respectively. Transient liquid phase sintering was found to play a crucial role in the base alloy and Mo added alloy whereas the Nb added alloy was found to undergo persistent liquid phase sintering. Microstructure characterisation by SEM revealed formation of finer tungsten grains with average grain size ranging from 1 μm to 4.3 μm. Mo addition restricted the tungsten grain growth while Nb addition promoted the tungsten grain growth compared to the base alloy. Phase analysis by XRD revealed the formation of Ni4W intermetallic (at lower temperatures) for the base alloy, NbO2 and NbW intermetallics for Nb added alloy and MoNi rich phase for Mo added alloys. Hardness measured by Vickers hardness method revealed a declining trend in hardness with increase in sintering temperature, owing to tungsten grain growth in all the alloys and along with Kirkendall pore formation and growth for the base alloy and Mo added alloy. Nb addition resulted in maximum hardness of 678 HV1 which is highest ever reported for SPSd WHA with 90 wt% concentration of W.

Phase Transformation and Mechanical Optimization of Eggshell-Derived Hydroxyapatite across a Wide Sintering Temperature Range.

Calcium phosphate, particularly hydroxyapatite (HA), bears a close resemblance to human bones, rendering it a prevalent material in biomedical applications. This study focuses on the successful preparation of HA using a precipitation method with eggshell as a raw material. Subsequently, the HA powder was press-formed and sintered at various temperatures to investigate the impact of sintering temperature on the mechanical properties, including hardness, compressive strength, and fracture toughness, of the sintered HA samples (E-HA). Statistical analyses, including one-way ANOVA and Tukey's post-hoc test, were conducted to determine significant differences in these properties at different sintering temperatures. Experimental findings revealed that as the sintering temperature increased, HA partially transformed into β-TCP between 800 and 1300 °C, with α-TCP observed at 1400 °C. The elimination of pores led to an increase in relative density, with a maximum relative density of 94.5% achieved at 1200 and 1300 °C. E-HA sintered at 1200 °C exhibited the highest hardness (5.08 GPa), compressive strength (255.79 MPa), and fracture toughness (1.21 MPa·m0.5). However, at 1400 °C, a slight decrease in apparent density (2.90 g/cm3) was noted due to the presence of α-TCP, along with significant grain growth. This study's objective is clearly aligned with the study design, incorporating detailed statistical analyses to validate the findings. Furthermore, bacterial culture experiments were conducted using sintered E-HA, Chem-HA (HA synthesized from reagent-grade calcium carbonate), and Comm-HA (commercial HA). Streptococcus mutans was cultured on the surfaces of sintered E-HA, Chem-HA, and Comm-HA samples for 20 h. After culturing, the OD values for all samples were below 0.2, indicating significant antibacterial efficacy. The comparable OD values and bacterial counts (p > 0.05) suggest that the source of HA does not impact its antibacterial properties. This underscores the potential of eggshell-derived HA as an effective material for biomedical applications.

Production of X-ray absorbing ceramics and products based on them for radiotherapy of the periorbital eye region

The paper presents an innovative method for producing high-density ceramics based on bioinert tantalum oxide (Ta2O5) and eye shield products utilizing spark plasma sintering (SPS) technology. Eye shields are in high demand for protecting the cornea and other parts of the eye from ionizing radiation during periorbital eye procedures, such as laser therapy, radiotherapy, and Mohs micrographic surgery (MMS). The dynamics of consolidation of microcrystalline Ta2O5 powder under spark plasma heating conditions in the temperature range of 1000–1400 °C were investigated. The structure, phase, and elemental composition of polycrystalline ceramic samples, including the calculation of crystal structure parameters, were studied using XRD, SEM, and EDS methods. The optimal SPS parameters for achieving maximum relative density (up to 100 %) and Vickers microhardness (up to 510 H V) of the obtained ceramics were determined. The performance properties of the ceramics were examined under conditions of a session of short-focus radiation therapy applied to the periorbital facial area. A dosimetric assessment of the absorbing capacity of the ceramics under X-ray irradiation in modes from 40 to 120 keV was conducted. A prototype of a ceramic eye shield product based on Ta2O5 was developed and manufactured for the first time using SPS technology.

Crack elimination and strength enhancement mechanisms of selective laser melted Si-modified Al−Mn−Mg−Er−Zr alloy

In order to increase the processability and process window of the selective laser melting (SLM)-fabricated Al−Mn−Mg−Er−Zr alloy, a novel Si-modified Al−Mn−Mg−Er−Zr alloy was designed. The effect of Si alloying on the surface quality, processability, microstructure, and mechanical properties of the SLM-fabricated alloy was studied. The results showed that introducing Si into the Al−Mn−Mg−Er−Zr alloy prevented balling and keyhole formation, refined the grain size, and reduced the solidification temperature, which eliminated cracks and increased the processability and process window of the alloy. The maximum relative density of the SLM-fabricated Si/Al−Mn−Mg−Er−Zr alloy reached 99.6%. The yield strength and ultimate tensile strength of the alloy were (371±7) MPa and (518±6) MPa, respectively. These values were higher than those of the SLM-fabricated Al−Mn−Mg−Er−Zr and other Sc-free Al−Mg-based alloys.

Optimized control of laser processing parameter on microstructural evolution and mechanical behavior in CoCrNi medium entropy alloy

In this study, the processing parameters of a laser powder bed fusion (LPBF)-fabricated CoCrNi alloy were systematically investigated for their impact on mechanical properties, microstructure, and fracture characteristics when the relative density exceeds 99%. The maximum relative density of 99.89% was attained at a laser power of 225 W, and scan speed of 1000 mm/s, accompanied by a hardness value of 276.83 HV. However, it is important to note that the highest relative density did not correspond to the maximum σUTS. Tensile testing revealed that increasing the laser power at the same scan speeds led to a decrease in elongation. The LPBF-fabricated CoCrNi alloy exhibited enhanced defect tolerance due to its cellular microstructure, which confined ductile dimple sizes to the nanoscale and impeded crack propagation through pinning effects. At scan speeds of 1000 mm/s and energy densities below 83 J/mm³, an increased presence of unmelted powder and pores was observed. Besides, it was confirmed that the <110> crystallographic texture displayed the strongest orientation within the sample. Theoretical calculations indicated that over 50% of the yield strength is attributed to the dislocation structure. These findings contribute to the process optimization of LPBF, providing a valuable reference for adjusting process parameters to enhance material mechanical properties, particularly when targeting relative densities above 99%.

Novel high-hardness and low-loss microwave dielectric ceramic LiZnMgGaTi2O8

Inorganic oxide ceramics are essential for microwave applications due to their stable structure and exceptional performance. LiZnMgGaTi2O8 ceramics were prepared using the solid-phase method. XRD and TEM confirmed that the ceramics possess spinel structures. The ceramics had a maximum relative density of 94.57 % and a Vickers hardness of 8.58 GPa when sintered at 1220 °C. The ionic polarizability of Ti4+ in the ceramics exceeds the Shannon value, leading to a 20.3 % deviation between εth and εr. The activation energy of the impedance spectrum fitting is 1.302 eV, indicating a low concentration of oxygen vacancies in the ceramic. Hence, the Q × f value of the ceramics is primarily influenced by relative density. The optimal microwave dielectric properties of LiZnMgGaTi2O8 ceramics are εr = 15.68, Q × f = 66,620 GHz, and τf = −30.9 ppm/°C. The test curves of εr and dielectric loss remain nearly parallel to the x-axis from −80 °C to 80 °C, demonstrating the excellent stability of LiZnMgGaTi2O8 ceramics.

Design of highly active and stable (K0.48Na0.48Li0.04)(Nb0.975Sb0.025)O3–(Bi0.5Na0.5)(Zr0.8Ti0.2)O3 lead–free piezoelectric ceramics by constructing rhombohedral–tetragonal phase boundaries at room temperature

Traditional piezoelectric materials cause serious environmental and health issues because of their lead–containing substances, and thus lead–free piezoelectric ceramics would have many applications. In this study, we successfully prepared the lead–free ceramics (1-x) (K0·48Na0·48Li0.04) (Nb0·975Sb0.025)O3–x (Bi0·5Na0.5) (Zr0·8Ti0.2)O3 ((1-x)KNLNS–xBNZT, x = 0, 0.005, 0.0075, 0.01, 0.015, 0.02 and 0.03) with rhombohedral–tetragonal (R–T) phase coexistence near room temperature, employing con–entional solid sintering. The minimum cell volume of the ceramics and R–T phase coexistence in them were achieved at a doping amount x = 0.01, which facilitated the optimal performance of the ceramics (d33∼467 pC/N ± 14 pC/N, Tc∼272 °C, εr∼1676, kp∼0.42, where d33: piezoelectric constant; Tc: Curie temperature; εr: dielectric constant; kp: electromechanical coefficient). The ceramics exhibited microstructures with high density and low porosity and had a maximum relative density of 95.68 %. At x = 0.01, the ceramics exhibited a uniformly distributed small domain structures with nanodomains, accounting for their high-voltage electrical properties. Because these stable and reliable piezoelectric (1-x)KNLNS–xBNZT ceramics exhibit excellent electrical performance, they can replace lead–based materials. The direct solid–phase sintering method provides prospects for the large–scale application of the lead–free piezoelectric ceramics.

Influence of defects formation on the cracking behavior of LPBFed Cu-Cr-Zr alloy: Micro-mechanism and CRITIC-WASPAS approach

Advanced strategies and techniques in the Laser Powder Bed Fusion (LPBF) process for printing Cu-Cr-Zr alloy must be created to overcome the major flaws such as cavity formation, unstable thermal capillary convection and thermodynamic instability. In this research, the significant process variables in the LPBF techniques such as Laser Power (LP) of 430, 500 and 570 W, Scanning Velocity (SV) of 550, 750 and 950 mm/s, Hatching Distance (HD) of 0.06, 0.08 and 0.10 mm were considered into account to fabricate a crack-free Cu alloy coupon with maximum Relative Density (RD), Ultimate Tensile Strength (UTS) and Reduced Elastic Modulus (REM). To optimize the process variables, a Criteria Importance Through Intercriteria Correlation (CRITIC) associated with the Weighted Aggregated Sum Product Assessment (WASPAS) approach was employed. Finally, the confirmation experiments were performed for the optimal settings (LP of 430 W, SV of 750 mm/s and HD of 0.06 mm) and the initial settings (LP of 570 W, SV of 550 mm/s and HD of 0.10 mm). The optimal settings show an 8.6 % enhancement in relative density of 99.82 %, which also reflects in 47 % improvement in UTS of 336 MPa and a 27.8 % enhancement in REM of 147.45 GPa compared with the initial settings. With the help of fracture morphology, the effect of defect development on the propagation of fractures on the printed coupons was also investigated. Moreover, the confirmation experiments aligned more with the CRITIC-integrated WASPAS approach.

Densification of hydroxyapatite through cold sintering process: Role of liquid phase chemistry and physical characteristic of HA powder

Hydroxyapatite is a well-known bioactive material widely employed in bone regeneration applications. Densifying hydroxyapatite at the nanoscale remains challenging with conventional sintering methods. This investigation focuses on the densification of commercially available nano-hydroxyapatite powders through the cold sintering process, utilizing water, acetic acid, and phosphoric acid solutions as transient liquids under 360 MPa pressure at 200 °C. The study systematically examines the influence of physical parameters of hydroxyapatite powder, liquid nature, and ionic concentrations of acid solutions on densification and microstructural characteristics. The relative density of consolidated samples varied with respect to the ionic concentration of the acid solution. Notably, a maximum relative density of 90% has been achieved for hydroxyapatite cold sintered using 2 M phosphoric acid solution without changing the original phase of hydroxyapatite. Overall, this study offers valuable insights into the impact of liquid chemistry on the densification of hydroxyapatite using the cold sintering technique.

Improving the Energy Storage Performance of Barium Titanate-Based Ceramics through the Addition of ZnO-Bi2O3-SiO2 Glass

Lead-free ceramics with excellent energy storage performance are important for high-power energy storage devices. In this study, 0.9BaTiO3-0.1Bi(Mg2/3Nb1/3)O3 (BT-BMN) ceramics with x wt% ZnO-Bi2O3-SiO2 (ZBS) (x = 2, 4, 6, 8, 10) glass additives were fabricated using the solid-state reaction method. X-ray diffraction (XRD) analysis revealed that the ZBS glass-added ceramics exhibited a perovskite structure, with the maximum relative density achieved at x = 6. The average grain size reduced obviously as the glass additive wt% increased. Also, the dielectric constant decreased and the breakdown strength increased with increases in the glass additives. The optimal energy storage density of 1.39 J/cm3 with an energy storage efficiency of 78.3% was obtained at x = 6 due to high maximum polarization and enhanced breakdown strength. The results demonstrate that this material is a potential candidate for high-pulse-power energy storage devices.

Characterization of a functionally graded material produced using a new designed blender

Abstract One of the techniques widely used for fabrication of FGMs (Functionally Graded Materials) is powder metallurgy. However, producing a FGM with smooth gradient in its constituents mixture has remained a challenge yet to be met. The purpose of this research is design and manufacturing a blender for producing a functionally graded material with smooth gradient of its constituent materials. The blender was used to mix magnesium and titanium dioxide to produce Magnesium/titanium dioxide FGMs. The powder mixture was then compacted by Instron, drop hammer, and split Hopkinson bar at 600 °C. The microstructure and relative density of the functionally graded samples fabricated at different strain rates were studied in this work. SEM images clearly demonstrated a continuous and functional distribution of Mg and TiO2 particles in the produced FGM samples. It was also shown that increasing the compaction loading rate resulted in a higher relative density in the FGM samples. The maximum relative density (92%) was observed for the samples produced by Hopkinson bar. This level of density was 7% and 17% higher than the densities of the samples fabricated using drop hammer and Instron, respectively. The improvement of relative density in dynamic compaction methods is attributed to the increased compaction pressure and process being adiabatic.

Saturation of spiral instabilities in disc galaxies

ABSTRACT Spiral density waves can arise in galactic discs as linear instabilities of the underlying stellar distribution function. Such an instability grows exponentially in amplitude at some fixed growth rate β before saturating non-linearly. However, the mechanisms behind saturation, and the resulting saturated spiral amplitude, have received little attention. Here, we argue that one important saturation mechanism is the non-linear trapping of stars near the spiral’s corotation resonance. Under this mechanism, we show analytically that an m-armed spiral instability will saturate when the libration frequency of resonantly trapped orbits reaches $\omega _\mathrm{lib} \sim \mathrm{a\, \, few}\times m^{1/2} \beta$. For a galaxy with a flat rotation curve, this implies a maximum relative spiral surface density $\vert \delta \Sigma /\Sigma _0\vert \sim \mathrm{a\, \, few} \times (\beta /\Omega _\mathrm{p})^2 \cot \alpha$, where Ωp is the spiral pattern speed and α is its pitch angle. This result is in reasonable agreement with recent N-body simulations, and suggests that spirals driven by internally-generated instabilities reach relative amplitudes of at most a few tens of per cent; higher amplitude spirals, like in M51 and NGC 1300, are likely caused by very strong bars and/or tidal perturbations.

CALPHAD-aided design of high-strength Al-Si-Mg alloys for sufficient laser powder bed fusion processability

This study proposes a design concept for an Al-Si-Mg ternary alloy to achieve both high strength and laser-based powder bed fusion (PBF-LB) processability using calculation of phase diagrams (CALPHAD). The thermodynamic calculations using the CALPHAD method evaluated the Al-10Si-4.5Mg (wt%) alloy composition for strengthening by both the Si and Mg2Si phases and high PBF processability by reducing the risk of hot tearing behind the small freezing range of 27 °C and crack susceptibility index (|dT/d(Fs1/2)|) of 77 °C. The PBF-LB Al-10Si-4.5Mg alloy sample (processed by laser power of 128 W and laser scanning velocity of 1000 mm/s) exhibited a fine three-phase microstructure and exceptional hardness of 199 HV. No hot tearing occurred, whereas many cracks preferentially propagated along the melt pool boundaries during the PBF-LB process. The severe lateral cracking resulted in a maximum relative density of 96 % in the Al-10Si-4.5Mg alloy samples. Preferential cracking could be responsible for the localization of the relatively coarse particles of the brittle Mg2Si phase in the cellular microstructures of the melt pool boundaries. Understanding the lateral cracking mechanism can provide new insights into alloy modification using the controlled solidification path to avoid a specific two-phase eutectic reaction (L→α-Al+Mg2Si) to improve the PBF processability. A modified alloy composition of Al-10Si-3Mg (wt%) was assessed using the CALPHAD approach. PBF-LB processing using the modified alloy powder alleviated cracking and improved the maximum relative density to 98 % for the PBF-LB manufactured samples. This result accentuated the validity of the design strategy for Al-Si-Mg ternary alloy utilizing the CALPHAD method.

Mechanical and electrical properties of 3Y‐TZP/TiSi2 composites sintered at different temperatures

AbstractVarious amounts of TiSi2 (30, 40, and 50 wt.%) were added to 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y‐TZP) to fabricate 3Y‐TZP/TiSi2 composites by vacuum sintering. The effects of the TiSi2 added amount, as well as the sintering temperature on the microstructure, mechanical, and electrical characteristics of the 3Y‐TZP/TiSi2 composites were examined. The sintered samples consisted of three phases: tetragonal (t‐ZrO2), TiSi2, and reaction product Ti5Si3. The maximum bending strength and relative density of the composites, reaching 501.20 MPa and 98.59% respectively, were achieved at a TiSi2 content of 30 wt.% and sintering temperature of 1500°C. The resistivity of 3Y‐TZP/TiSi2 composites showed a nonlinear decrease with increasing TiSi2 content. These results indicated that 3Y‐TZP/TiSi2 composites had a typical percolation threshold phenomenon due to the different TiSi2 content and a conductivity model of 3Y‐TZP/TiSi2 composites at room temperature was founded on the generalized effective medium equation. The resistivity of the composites could optionally adjust between 102 and 10−4Ω·cm with 30–50 wt.% TiSi2 under room temperature. Overall, the 3Y‐TZP/TiSi2 composites show great potential for applications in the heat‐not‐burn tobacco field.

Study the prevalence of predatory bugs of Southern Rajasthan in soybean crop

The present investigation was carried out during Kharif season 2021-22 and 2022-23 in Udaipur district in Southern Rajasthan. The aim of the survey is to record the diversity of different species of prevailing predators on the soybean crops ecosystem. The survey on the diversity of predatory bugs was carried out under the agro-climatic conditions of Udaipur, Rajasthan. The predatory bugs of soybean crop during the Kharif seasons, 2021-22 and 2022-23 were found such as pentatomid, reduviid, mirid and anthocorid. The dominant predatory bugs of soybean crops were observed as Pentatomidae family bugs with the maximum mean and relative density from all surveyed locations. While the population of anthocorid bugs was found minimum.

Effect of phase transformation in cold sintering of aluminum hydroxide

Cold sintering of gibbsite and boehmite, which are difficult to densify by conventional sintering processes that require heating above 1000 °C owing to thermal decomposition, was attempted at various CSP temperatures. When boehmite particles were cold sintered, densification did not progress substantially, with a maximum relative density of 62% achieved at 200 °C. On the other hand, when gibbsite particles were cold sintered, the relative density of the hardened bodies increased significantly with temperature up to 150 °C, with a maximum value of 82%. However, when gibbsite was cold sintered at temperatures above 200 °C, phase transformation from gibbsite to boehmite took place, and the relative density of the hardened body decreased significantly. The precipitated boehmite particles bonded to each other to form a three-dimensional network, and the hardened body fabricated at 250 °C showed a compressive strength of 115 MPa despite a low relative density of 62%.