Hot-pressed Materials Research Articles

A Comparative Study of Airbag Covers for Automotive Safety Using Coconut Shell Fiber/PP Composite Materials

In this study, we compared the physical properties of coconut fiber/polypropylene (PP) composite materials with coconut fiber as a reinforcing agent, produced through a hybrid injection molding process and a layered hot-pressing process. Through comparative experiments, the mechanical properties of both the hybrid injection-molded and layered hot-pressed materials were validated. The results indicated that, when using a coconut fiber content of 5%, the layered hot-pressed composite material exhibited optimal comprehensive performance. Specifically, its tensile strength reached 25.12 MPa, showing a 37.6% increase over that of pure PP materials of the same brand and batch. Its tensile modulus was 1.17 GPa, representing an 11.4% decrease. Additionally, its bending strength was 35.94 MPa, marking a 49.8% increase, and its bending modulus was 2.69 GPa, which is nearly double that of pure PP materials. Furthermore, through Creo modeling and an ANSYS simulation analysis, it was verified that this material could be applied to airbag covers in the field of automotive safety. This study confirmed that layered hot-pressed coconut fiber/PP composite materials exhibit superior mechanical properties to traditional materials and injection-molded composite materials, making them more suitable for airbag covers.

Effect of Induction Heating on Surface Properties of Hot-Pressed Ceramics Based on Nanopowders Si3N4 and TiN

The effect of induction heating on the surface properties of hot-pressed ceramics based on plasma chemical nanopowders Si3N4 and TiN (additives: Al2O3, AlN, and Y2O3) has been studied. The research demonstrates the formation of a modified layer on the surface of the hot-pressed material. The study examines the porosity, hardness, fracture toughness, brittleness, distribution of elements, and wear of hot-pressed ceramics on the surface before and after additional grinding. Removal of the surface porous layer results in increased density and hardness, leading to a higher number of acoustic emission signals during scratching with a Vickers indenter. A different response to scratching indicates a transgranular or intergranular fracture of the structure. The presence of porosity and carbon contamination on the surface layer of materials negatively impacts the properties of TiN-reinforced ceramics based on Si3N4-Al2O3-AlN (SIALON). However, the addition of Y2O3 effectively prevents carbon penetration and reduces the effect of grinding. Additionally, the dark-colored tone observed on the outer volume of the samples suggests a non-thermal microwave effect of the induction furnace.

Physical and mechanical properties of materials based on Ti<sub>3</sub>SiC<sub>2</sub>

Using various initial components, a complex titaniumsilicon carbide of the composition Ti3SiC2 was synthesized in a high-temperature furnace at 1400 °C for 1 h and by hot pressing at a temperature of 1350 °C, a pressure of 30 MPa, for 15 min. The Rietveld method was used to calculate the content of the Ti3SiC2 phase, which, upon hot pressing, of the Ti : Si : TiC components in a ratio of 1 : 1,2 : 1,8 98,6 vol. %. The microstructure was investigated and the phase composition of hot-pressed materials was studied. The physical and mechanical characteristics of sintered and hot-pressed materials based on the Ti3SiC2 phase have been studied. Ill. 2. Ref. 24. Tab. 3..

Investigation of the Phase Composition and Analysis of the Properties of Sintered and Hot-Pressed Materials Based on Silicon Nitride

Investigation of the Phase Composition and Analysis of the Properties of Sintered and Hot-Pressed Materials Based on Silicon Nitride

Effect of Mo2C addition on the mechanical properties and oxidation resistance of ZrB2-SiC ceramics

Simple hot pressing and vacuum pre-treatment at 1600 °C followed by hot pressing were used for obtaining dense composites of ZrB2–15 vol% SiC– 5 vol% Mo2C. The room temperature strength was around 820 MPa for the hot-pressed material and 650 MPa for the material obtained by use of thermally treated powders. At 1800 °C, the strength converged to 154 and 182 MPa, respectively, as was mostly driven by SiC grain sliding. Oxidation in static air at 1600 °C for 2 h showed the formation of a 3-layered scale for both materials but with different thickness. The outermost layer was a borosilicate glass; the intermediate layer consisted of a phase based on zirconium oxide, silicon oxide, molybdenum boride and oxide; and the last layer was a silicon-depleted boride matrix. The two-step processing route resulted in a material with higher oxidation resistance, due to coarser grain size and higher amount of (Mo,Zr)B phase, which remained stable as solid compound in the sub-scales.

Fabrication and Characterization of Zirconium Silicide for Application to Gas-Cooled Fast Reactors

Zirconium silicide (Zr3Si2) is a heavy reflector material particularly effective for application to a Gas-cooled Fast Reactor (GFR) such as the General Atomics Energy Multiplier Module (EM2) and Fast Modular Reactor (FMR). In this work, the manufacturability of a high-density Zr3Si2 compound, in the Zr3Si2 phase, was investigated using hot-pressing and spark-plasma-sintering methods. The microstructure, composition, and thermal properties of the resulting hot-pressed material were measured, resulting in a 96% relative density and a 96% phase pure material. The thermal properties were consistent with those necessary for use under GFR operating conditions. The structural and dimensional stability of the material was also measured before and after neutron irradiation up to 1017 n/cm2 in the research reactor, resulting in an average linear dimensional change of <0.12%. The preliminary irradiation tests also confirmed the micromechanical stability of the Zr3Si2 phase, with no evidence of microcracking after irradiation. The results of the irradiation tests verify the fabrication method of Zr3Si2 for nuclear applications, but further irradiation tests under high-temperature and high-irradiation conditions will be required to qualify the material for GFR applications.

Effects of benzotriazole and imidazoline on the tribocorrosion behaviors of a WC-based material in saline silica slurries

To improve the performance of impregnated diamond bit in saline drilling fluid, the effects of benzotriazole and imidazoline on the abrasion–corrosion behaviors of a hot-pressed WC-based material and its binder material in saline silica slurries were investigated with a modified abrasion test rig. The morphology of worn surface and corrosion products after tribocorrosion test were analyzed by scanning electron microscopy and Raman spectroscopy, respectively. The results indicated that benzotriazole was a better corrosion inhibitor for the two hot-pressed materials than imidazoline. In abrasion-corrosion tests, the addition of benzotriazole into saline slurry reduced the total weight loss considerably and produced a negative abrasion–corrosion synergy, while imidazoline had hardly noticeable effects, especially to the binder material. The negative synergy could be related to the change in contact condition between abrasive particles and worn surface, owing to the decrease in the adsorption of benzotriazole on the worn surface as a result of cathodic protection. By lowering the corrosion rate of the binder around WC particles and thus lessening the undermining of WC particles, benzotriazole significantly improved the anti-tribocorrosion performance of the WC-based material.

Determination of the Temperature Coefficient of Linear Expansion of Materials Based on Silicon Carbide

Information on the temperature coefficient of linear expansion (TCLE) of materials based on silicon carbide is presented. It is shown that the different polytypes 3C (cubic modification) and 4H and 6H (hexagonal modifications) are characterized by different thermal expansions, the difference between the values of which increases with increasing temperature. The TCLEs of reaction-sintered, liquid-phase-sintered, and hot-pressed silicon carbide materials are determined in the range 20 – 1800°C.

Analysing the Microstructures and Pin-on-Disc Wear Properties of 1010 Steel-Based and B&amp;lt;sub&amp;gt;4&amp;lt;/sub&amp;gt;C-Added Materials Produced through Powder Metallurgy

The present study makes use of two distinct production methods. The first method involves producing 1010 steel-based materials containing SiC, MgO, H3BO3, and B4C (wt%10 - wt%30) with varying weights through powder metallurgy. This step was followed by hot pressing. In the second group, after all the chemicals were stirred, 20 ml of epoxy and epoxy hardener were added to the mixture. Then, the mixture was set aside to harden. XRD and SEM-EDS analyses were conducted on the mixture to observe the morphological impacts. Furthermore, friction coefficient values of the materials were also identified following wear tests under varying weights. The XRD analyses revealed the phase structures of Fe3C, SiC, MgO, H3BO3, B4C, and Fe2O3. As for the SEM-EDS analyses, they concluded the surface appearance of S60 and S55B20, the hot-pressed materials, dependent on liquid phase sintering. SEM of epoxy- based S60E20 and S55B20E20 revealed white spherical structures and a flat matrix structure with shallow surface holes. In the pin-on-disc wear experiment, the friction coefficient value was reduced with the addition of SiC, MgO, and H3BO3 (S60) to 1010 steel (S100). By adding various amounts of B4C, the friction coefficient was reduced even further, resulting in the improvement of wear properties.

An Advanced TiAl Alloy for High-Performance Racing Applications.

Requirements and strict regulations for high-performance racing applications involve the use of new and innovative lightweight structural materials. Therefore, intermetallic γ-TiAl-based alloys enable new opportunities in the field due to their lower density compared to commonly used Ni-base superalloys. In this study, a β-solidifying TiAl alloy was examined toward its use as structural material for inlet and outlet valves. The nominal composition of the investigated TNM alloy is Ti–43.5Al–4Nb–1Mo–0.1B (in at%), which enables an excellent formability at elevated temperatures due to the presence of bcc β-phase. Different hot-extrusion tests on an industrial scale were conducted on the cast and hot isostatic pressed material to determine the ideal microstructure for the respective racing application. To simulate these operation conditions, hot tensile tests, as well as rotational bending tests, at room temperature were conducted. With a higher degree of deformation, an increasing strength and fatigue limit was obtained, as well as a significant increment of ductility. The fracture surfaces of the rotational bending test specimens were analyzed using scanning electron microscopy, revealing the relationship between crack initiation and microstructural constituents. The results of this study show that the mechanical performance of extruded TiAl material can be tailored via optimizing the degree of hot-extrusion.

Tetrahedrite Sintering Conditions: The Cu11Mn1Sb4S13 Case

Manganese-doped tetrahedrites, with Cu11Mn1Sb4S13 composition and synthesized by the solid-state method, were hot-pressed at temperatures ranging between 788 K and 848 K. The structure, microstructure, phase purity and thermoelectric properties of the materials were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and density studies. According to the XRD analysis, all the hot-pressed materials presented a main tetrahedrite phase. However, very small amounts of chalcostibite (CuSbS2) were detected by SEM–EDS. While keeping the pressure constant at 60 MPa, an increase in density with hot-pressing temperature was observed, reaching a maximum relative density of 97% for the samples hot-pressed at 848 K. Measurements of the electrical transport properties indicated higher thermal conductivity, electrical conductivity and Seebeck coefficient for the denser samples, with a greater power factor leading to an increase of > 10% in the figure of merit ( $$zT$$ ) relative to the less dense materials.

Development and Characterization of Environmentally Friendly Insulation Materials for the Building Industry from Olive Pomace Waste

This work is focused on the upgrading olive oil pomace to obtain high environmentally friendly insulation materials for the construction and building industry. Upgrading of these wastes has been carried out by using the wet-laid technology in combination with different thermoplastic binder fibers both from natural and synthetic origin. After the wetlaid process, the obtained veils or non-wovens were subjected to different processes: a hot-press moulding process or a continuous lamination process. The acoustic insulation properties were obtained by the Kundt’s tube while the thermal insulating properties were obtained through determining heat transmission resistance (R) and heat absorption parameter (?). These tests have revealed the excellent insulation properties of the olive pomace-derived materials, specifically, those based on high surface density non-wovens. The complementary process that follows wet-laid, i.e. hot-press moulding or continuous lamination process has a remarkable effect on insulation behaviour. In particular, the hot-pressed materials from olive pomace show better acoustic insulation while the continuously laminated materials offer the best thermal insulation properties.

Hardness and fracture-toughness of hot-pressed LaB6-TiB2 ceramics

Microstructural analysis and investigations of mechanical properties via indentation-techniques have been performed on a LaB6 - 15 vol. % TiB2 ceramics, obtained by the hot-pressing at T = 1900 °C and P = 30 MPa in argon gas. The relative density of hot-pressed material was up to 97% of theoretical. XRD, SEM and EDX analysis of ceramics were performed. The Vickers hardness (18.5 GPa) and fracture-toughness (3.9 MPa-m1/2) were compared with the values, measured on a single-crystalline LaB6 (Hv = 21 GPa, KIc = 2.4 MPa-m1/2) and arc-melted eutectic composite LaB6-TiB2 (Hv = 23 GPa, KIc = 6.7 MPa-m1/2).

Compositional disorder and sintering of entropy stabilized (Hf,Nb,Ta,Ti,Zr)B2 solid solution powders

Entropy-stabilized (Hf,Nb,Ta,Ti,Zr)B2 solid solution powders produced by a carbo/boro-thermal reduction followed by solid solution formation were first analysed by synchrotron radiation x-ray diffraction, and their long range periodicity (i.e. lattice parameters) as well as the micro-strain intended as lattice disorder were quantitatively determined. A model to describe the micro-strain was proposed. The as-synthesized (Hf,Nb,Ta,Ti,Zr)B2 solid solution powders were then hot-pressed at 2200 K and 50 MPa until near full densification was achieved. The hot-pressed material had a residual micro-porosity of 1.3 vol.% and consisted of a (Hf,Nb,Ta,Ti,Zr)B2 ceramic matrix, 0.3-1 μm grain size range, and of a residual 10 vol.% B4C particulate component, grain size in the range 0.2-2 μm. B4C was a side product of the former synthesis and, after hot-pressing, remained trapped along the grain boundaries of the primary (Hf,Nb,Ta,Ti,Zr)B2 solid solution ceramic matrix. Micro-hardness HV0.2 = 22.7 ± 1.9 GPa for 1.96 N applied force was measured.

Effect of annealing and potassium substitution on the thermoelectric and magnetic properties of directionally grown Bi2Sr2Co2Oy ceramics

Bi2Sr2−xKxCo2Oy (x=0.0, 0.025, 0.050, 0.075, 0.100, 0.125, and 0.15) ceramic materials have been fabricated using a classical ceramic process, followed by texturing through directional solidification. SEM analysis of samples, before and after annealing has shown that grains were aligned along the growth direction. While as-grown samples have several phases, besides the thermoelectric one, the annealed ones show much higher thermoelectric phase content. In addition, K-substitution increases the thermoelectric phase content and enhances grain orientation. These improvements decrease the electrical resistivity without significant changes in Seebeck coefficient. The maximum power factor value for 0.10K-substituted annealed samples has been found as 0.20mW/K2m. This is superior to the highest reported for hot-pressed materials. However, all samples have similar magnetic properties.

Thermal properties and laser processing of hot-pressed materials from Ti\u2013Al\u2013C system

The work concerns the characterization of polycrystalline materials composed in Ti–Al–C system such as Ti2AlC and Ti3AlC2. The starting powders were synthesized from metal powder in nitrogen overpressure with the use of SHS method. Such obtained powders were chemically described and hot-pressed at temperatures 1100 °C and 1300 °C. The densification measurements were taken on obtained sintered bodies. The chemical composition analysis and microstructural observation of hot-pressed materials were made. The obtained MAX phase Young’s modulus was examined in the temperature range 25–600 °C by resonance method. The thermal properties of the thermogravimetric analysis were made in air flow to determine the oxygen resistance. The MAX phase polycrystals were taken under laser flash analysis, which allowed to measure directly thermal diffusivity and specific heat and to calculate indirectly thermal conductivity up to the temperature of 700 °C. Additionally, the polycrystalline material was laser treated in continuous work mode. The hot-pressed MAX nanolaminates were laser ablation and laser welding processed, which is new in the literature. The laser beam-treated material places were microstructurally investigated by scanning electron microscopy and chemically by energy-dispersive X-ray spectroscopy. The result of laser processing was discussed regarding material preparation route and its thermal properties.

Physical and Mechanical Properties of Hot-Pressed Materials of the ZrB2–TaC–SiC System

High-density (with a relative density of up to 98.8%) ultra-high-temperature ceramic materials (UHTCs) based on the ZrB2–TaC–SiC system were obtained by hot pressing for 15 min at 2000°C 30 MPa of pressure in an argon atmosphere. Phase composition, lattice parameters, microstructure, flexural strength, Vickers hardness and crack resistance were studied. The maximum values of strength, hardness and crack resistance were 440 MPa, 20.3 GPa and 5.3 MPa·m1/2, respectively. The effect of the ZrB2/TaC ratio on the lattice constants and the mechanical properties of the material is established.

Silicon Carbide Liquid-Phase Sintering with Various Activating Agents

Silicon-carbide materials with 5 – 10 wt.% additions of oxides were prepared by liquid-phase sintering at 1860 – 2100 °C. The highest physicomechanical properties were achieved in SiC material containing 20 wt.% of a three-component eutectic composition in the MgO–Y2O3–Al2O3 system. The mechanical characteristics of liquid phase-sintered materials containing 15 wt.% of the three-component oxides additive exceed those of both the reactive-sintered and the solid-phase sintered materials and approach those of hot-pressed materials. Ill. 5. Ref. 30. Tab. 2.

The Influence of Activation Preprocessing of the B4C and SiC Powder Mixture with Al on the Phase Composition, Structure, and Properties of Hot-Pressed Composites

The paper examines how the conditions of activation preprocessing (dry and wet grinding) of B4C–Al and SiC–Al powder mixtures in a planetary-ball mill influence the formation of phases in the mixtures and the phase composition, structure, and mechanical properties of the associated hot-pressed materials. It is shown that dry grinding, unlike the conventional powder charge preparation method, induces the mechanochemical synthesis of new phases in the B4C–Al powder mixture along with its mechanical activation. The formation of new phases in the SiC–Al powder mixture does not depend on the conditions of activation preprocessing. Secondary phases form in the hot pressing of the B4C–Al and SiC–Al powder mixtures. The structure and micromechanical characteristics of the materials indicate that dry grinding of the B4C–Al and SiC–Al powder mixtures has a greater activation effect on the hot pressing process, structural uniformity, phase composition, and mechanical properties compared to the conventional powder charge preparation method.

Low-Cost Mechanically Alloyed Copper-Based Composite Reinforced with Silicate Glass Particles for Thermal Applications

A nanocrystalline copper-based composite reinforced with 40 vol.% silicate glass particles was successfully produced by mechanical alloying followed by hot pressing. The raw materials of crushed copper chips and soda-lime glass debris were processed in a planetary ball mill for up to 7 h. It was shown that silicate glass as alloying addition has a positive effect on the strengthening of copper and decreases its thermal expansion coefficient. During mechanical alloying, the microhardness of the composite powder particles increases to about 320 HV. The hot-pressed material demonstrates good thermal stability and increased compressive strength compared with consolidated milled copper.