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New method of hot pressing of chips waste with continuous muffle heating and device for its realization are offered.

The bending angle at the peak load is regarded as the most important parameter for evaluating bending properties of hot-press-forming (HPF) steels. However, it is not a mechanics-based parameter for the bending criterion, and the data interpretation is difficult because bending criteria in relation with microstructures and associated bending mechanisms have not been verified yet. In this study, effects of coating and baking treatments on bending angles at the peak load of three kinds of 1470 MPa-grade HPF steels were investigated by interrupted three-point bending tests coupled with direct microstructural observation. According to direct observations of sequential cracking processes of V-shaped crack (V-crack), bending procedures were classified into four stages: (1) formation of small V-crack, (2) increase in number and size of V-cracks, (3) initiation of shear-crack propagation from the V-crack tip, and (4) further propagation and opening of the shear crack. The minimum bending angle required for initiating the shear-crack propagation from the V-crack tip was defined as a critical angle, which meant the boundary between the 2nd and 3rd stages. The present bending behavior related with critical bending angle and V-cracking could be interpreted similarly by the fracture-mechanics concept, i.e., the initiation of shear-crack propagation.

Hot-press compression molding was attempted to resinify two renewable source-derived linear (1→3)-β-D-glucan polymers, i.e., paramylon or curdlan via the generation of reactive aldehyde groups that tend to crosslink with hydroxyl groups of the glucans. As for the paramylon, the optimal molding temperature was found to be around 220 °C, keeping the pressure at 20 MPa for 3 min, due to its highly crystalline structure. On the other hand, the curdlan resin was producible in the temperature range of 180–240 °C at the same pressure and pressing time. Dynamic mechanical analysis revealed a large temperature dependence of the loss modulus, E", for the paramylon-based polymer resin whereas the semi-crystalline curdlan resin was stable in terms of both the storage and loss moduli, E' and E", up to 160 °C. The vaporization of the water formed during the molding, due to the thermal decomposition, and the adsorption of moisture due to the hydrophilic property of the paramylon affected the thermal stability. The curdlan resin exhibited flexural strength and modulus extremely superior to those of regenerated and esterified curdlan films, and even a little superior to those of polyamide-12. The strain at break was comparable to the yield strain of an epoxy resin. On the other hand, the paramylon-based polymer resin was producible, but the resinification property and thermal stability of the paramylon resin was inferior to the curdlan resin due to the former's highly crystalline structure. [ABSTRACT FROM AUTHOR]

Dense boron carbide bearings with a central through hole were fabricated by hot-press sintering. When the sintering temperature was above the critical grain growth temperature, an increase in the applied pressure at 2100 °C caused a distinct abnormal grain size region. Two grain growth mechanisms were explored; normal grain growth (NGG) is controlled by a grain boundary diffusion mechanism whereas the abnormal grain growth (AGG) pattern abides by the 'Bose–Einstein' grain growth law. [ABSTRACT FROM AUTHOR]

In the present research an Al–7.7%Mn–4.9%Zr–3.2%Cu (wt%) alloy was processed by mechanical alloying (MA) followed by hot press sintering. The microstructure, phase composition, and mechanical properties of the MA granules and sintered samples were investigated. The dissolution of Mn, Zr, and Cu with further precipitation of the Al6Mn phase were observed during high-energy ball milling. In the alloy processed without stearic acid after milling for ~10 h, an Al-based solid solution with ~4.9 wt%Zr, ~3.2 wt%Cu and a ~5 wt%Mn with a grain size of ~16 nm and a microhardness of ~530 HV were observed. The addition of stearic acid facilitated Mn dissolution and precipitation of the Al6Mn phase during milling but led to the formation of the ZrH2 phase that decreased the Zr solute and the microhardness. Precipitation of the Al6Mn, L12–Al3Zr, and Al2Cu phases during annealing and sintering of the MA granules in the temperate range of 350–375 °C was observed, and an additional Al20Cu2Mn3 phase was precipitated at 400–450 °C. Hot-press sintering at 450 °C provided a low fraction of cavities of ~1.5%, the yield strength of 1100 MPa, ultimate compressive strength of 1200 MPa, strain at fracture of 0.5% at room temperature, the yield strength of 380 MPa, ultimate compressive strength of 440 MPa, and strain at fracture of 3.5% at 350 °C. The microstructural evolution during high-temperature deformation on the sample surface was studied and the differences in deformation behavior for the alloys sintered at different temperatures were discussed. [ABSTRACT FROM AUTHOR]

In this study, wet ball milling and hot press methods were used to prepare nanocomposite from ultra-high molecular weight polyethylene (UHMWPE) as a matrix, and modified multi wall carbon nanotubes (MWCNTs) as reinforcement nano-additives. Two batches of MWCNTs were used (Pristine-MWCNTs-B1, and Pristine-MWCNTs-B2). First, the MWCNTs were oxidized (oxide-MWCNTs) by wet chemistry using strong acids, then further functionalized with an amide group (A-MWCNTs). Fourier-transform infrared spectroscopy (FTIR), and Thermal gravimetric analysis (TGA) results confirm the functionalization of the MWCNT with the amide group. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to examine the surface morphology and crystalline behavior of MWCNT after functionalization. Ball milling was used to mix the UHMWPE with pristine MWCNT (1.5% wt), Oxide-MWCNT (1.5% wt), and A-MWCNTs (0.5–2% wt). Then, hot press melting was used to prepare the nanocomposite sheets. Fourier transform infrared spectroscopy (FTIR) confirmed the impact of the balls milling process with time factor on UHMWPE crystallinity and the interaction of the functionalization MWCNT with the UHMWPE matrix. The structure (crystallinity, crystal size) was validated using X-ray diffraction (XRD) patterns. Thermal gravimetric analysis (TGA), differential scanning calorimeter (DSC), and universal testing machine (UTM) were utilized to analyze the structural, thermal, and mechanical properties of the nanocomposites, respectively. The results showed that UHMWPE crystallinity increased after 2 h of ball milling, while crystallinity decreased when pristine-MWCNT, oxide-MWCNTs, and A-MWCNTs (0.5–2 wt%) were added without affecting the crystal structure of UHMWPE. The results showed that adding 1.5 wt% A-MWCNTs-(B1, B2)/UHMWPE increased thermal stability by 16 °C and elongation at the break by up to 74% when used 1.5 wt% A-MWCNT-B1 and 2 wt% A-MWCNT-B2. This shows that the ball milling methods and amide group improved the dispersion and interface interaction between MWCNTs and UHMWPE matrix. [ABSTRACT FROM AUTHOR]

The effects of periodic hot-press drying on drying behavior and mechanical damage to Chinese fir lumber were investigated by taking the heating platens' temperature (TP) and compression ratio (Rc) as experimental factors. The temperature and pressure inside lumber were analyzed during drying process. The results were as follows. The drying rate of lumber was significantly increased with increasing TP and Rc. Scanning electron microscope (SEM) micrographs showed that bordered pit membranes, cross-field pits, middle lamella between adjacent cells, and tracheid walls were damaged after drying, and the damage became more severe with higher TP and Rc. Detachments between ray parenchyma cells and tracheids were observed at 170 °C. Nitrogen-adsorption measurement results demonstrated that more cell wall pores in the 2.5~6.2 nm pore diameter range were generated at higher TP, resulting in an enlarged specific surface area and pore volume of cell walls. These structural changes contributed to accelerating moisture migration and decreasing the drying time. Furthermore, fluctuating pressure inside lumber was the main driving force leading to moisture migration and cell tissue damage in lumber during drying. The influence of TP on internal temperature (TM) and pressure (PM) was greater than Rc. With the increase in TP from 130 to 170 °C at the Rc of 10%, the maximum TM and PM were increased by 30.90% and 39.84%, respectively. However, TP should not be too high to prevent the formation of macro-cracks caused by high pressure, which may significantly affect wood's mechanical properties. These results provide theoretical support for periodic hot-press drying processes' improvement and high-value utilization of Chinese fir. [ABSTRACT FROM AUTHOR]

Due to the short dwell time of processing temperature and pressure, the quality of the composite manufactured by AFP was not equal to the traditional processing method like autoclave or hot-press. Deeply understanding the mechanism of differences was conducive to improving the performance of the composite manufactured by AFP. In this study, the properties of high-performance carbon fiber reinforced polyphenylene sulfide (CF/PPS) thermoplastic composites manufactured by laser-assisted automated fiber placement (LAFP) in-situ consolidation and hot-press was characterized and compared. The temperature history of LAFP in situ consolidation indicated that the heating and cooling process occurred during a few seconds. And the crystallinity was only 21.6% for the laminate from LATP, while the void content was 2.75%. Due to the low crystallinity, high void content and low interlaminar bonding, the ILSS of the laminate from LAFP in situ consolidation was 34.9% lower than that of hot-press. However, the mode Ⅰ fracture toughness was 103.7% higher than hot-press. [ABSTRACT FROM AUTHOR]

Both particle size and processing conditions can affect the magnetic properties of ferrite materials. In this work, the two-step hot-press procedures (hot-press magnetic orientation followed by hot-press sintering) is designed for fabrication of high quality BaFe 12 O 19 thick films. The effects of pre-sintering particle size (G pre) on the microstructure and magnetic properties of the thick films are investigated. Results show that reducing G pre increase c -axis orientation and remanence ratio (RR) of sintered thick film greatly. This should be due to the reduced energy barriers for grain orientation during the hot-press magnetic orientation process. Decreasing G pre from 920 nm to 170 nm leads to larger coercivity (H c), while the saturation magnetization does not change notably above G pre = 170 nm. The H c mechanism is further analyzed by the G pre dependent anisotropy field H k and the first-order-reversal curves of the thick film. Results show that H k increases with reducing G pre , while the inter-grain interactions are not notably affected by G pre. Therefore, the increase of H c should be contributed by both the decrease of sintered particle size and the improved RR of the film after hot-press magnetic field orientation. The above results show that the two-step hot-press sintering prepared hexaferrite thick films with optimized G pre is a good candidate for the realization of self-biased high frequency devices. [ABSTRACT FROM AUTHOR]

Relaxor ferroelectric PbMg 1/3 Nb 2/3 O 3 -PbTiO 3 (PMN-PT) ceramics are high-performance piezoelectric materials that are widely used in many electronic devices. However, it is extremely difficult to manufacture thin piezoelectric components dozens of micrometers in size using commercial coarse-grained PMN-PT ceramics. This limits the application of PMN-PT ceramics to high-frequency ultrasonic devices. In this work, we prepared a dense, fine-grained PMN-PT ceramic at low temperature using a hot-press sintering (HPS) method. The HPS ceramic had small grains with an average size of 1 μm and maintained high performance with a large permittivity (ε r = 4500), piezoelectricity (d 33 = 650 pC/N), and electrostrain (S E = 0.14% at 20 kV/cm). The large volume fraction of grain boundaries led to stronger relaxor behavior of the fine-grained PMN-PT ceramic than of the normal coarse-grained one. Owing to its small grains and high piezoelectric performance, this fine-grained PMN-PT ceramic meets the strict requirements of manufacturing thin piezoelectric components. Our results demonstrate that PMN-PT ceramics have great potential for developing low-cost, high-frequency ultrasonic devices by replacing expensive piezoelectric single crystals. [ABSTRACT FROM AUTHOR]

Transparent Lanthanum-modified lead zirconate titanate ceramics (PLZT 7.4/70/30) with low content of excess lead oxide (PbO) were successfully prepared by a novel vacuum/oxygen hot press sintering process. The phase structure, microstructure, electrical properties and electro-optic scattering performance of PLZT ceramics as a function of excess PbO in the starting powders have been studied and analyzed. As a result, these ceramics exhibited an ultra-high optical transmittance (>69.4% at 1064 nm; thickness 1 mm) from visible to near-infrared wavelength. Herein, we significantly reduce the use of PbO as an auxiliary agent for sintering. This puts forward a good route to meet the objectives of environmental protection and sustainable development. [ABSTRACT FROM AUTHOR]

In this research, Co-30 mass% Cr alloys were fabricated by a vacuum hot-press sintering process. Different amounts of submicron cobalt and chromium (the mean grain size is 800 and 700 nm, respectively) powders were mixed by ball milling. Furthermore, this study imposed various hot-press sintering temperatures (1100, 1150, 1200 and 1250°C) and pressures (20, 35 and 50 MPa), while maintaining the sintering time at 1 h, respectively. The experimental results show that the optimum parameters of hot-press sintered Co-30 mass% Cr alloys are 1150°C at 35 MPa for 1 h. Meanwhile, the sintered density reaches 7.92 g·cm-3, the closed porosity decreases to 0.46%, and the hardness and transverse rupture strength (TRS) values increase to 77.2 HRA and 997.1 MPa, respectively. While the hot-press sintered Co-30 mass% Cr alloys at 1150°C and 20 MPa for 1 h, the electrical conductivity was slightly enhanced to 1.79 × 104 S·cm-1, and the phase transformation (FCC → HCP) of cobalt displayed a slight effect on sintering behaviors of Co-30 mass% Cr alloys. All these results confirm that the mechanical and electrical properties of Co-30 mass% Cr alloys are effectively improved by using the hot-press sintering technique. [ABSTRACT FROM AUTHOR]

A novel method based on hot press sintering was proposed to fabricate the Al/Ti laminated composite, and the effects of sintering parameters on microstructure, interfacial structure, and mechanical properties were thoughtful examined. The results showed that insufficient sintering caused obvious voids and cracks at Al/Ti interface. With the increase of temperature or holding time, a good metallurgical bonding without defects was achieved, and both the recrystallization fraction and grain size of α phase in Ti layer increased, accompanied by the transformation of α to β phase and growth of intermetallic phase. The microstructure variation of Al layer is not evident with changing the sintering parameters. Due to the relatively low formation energy, the nanoscale TiAl 3 phase with massive stacking faults formed at Al/Ti interface, and lots of dislocations existed at Al layer near the interface. The voids and cracks formed at Al/Ti interface led to the premature failure of laminate. On the basis of the metallurgical bonding and small TiAl 3 phase, the high fraction and texture intensity of α phase were the dominated strengthening factors. Moreover, the back stress generated at Al/Ti interface contributes to an extra strengthening. The superior mechanical properties of Al/Ti laminate with a tensile strength of 670.9 MPa and a fracture strain of 0.33 were obtained with the sintering temperature of 600 °C and holding time of 2 h. [Display omitted] • A superior combination of strength and fracture strain of Al/Ti laminate was obtained by hot press sintering. • Grain size, recrystallization fraction, and texture intensity of α phase were sensitive to sintering parameters. • Nanoscale TiAl 3 phase with massive stacking faults formed toward Al layer at Al/Ti interface. • Achieving metallurgical bonding and minimizing the size of TiAl 3 facilitate a strong strengthening effect. [ABSTRACT FROM AUTHOR]

High-strength hot press forming (HPF) steel sheets are coated mostly by Al-Si to prevent the decarburization or oxidation of sheet surfaces, but become vulnerable to hydrogen embrittlement (HE) as H atoms supplied from moisture in a furnace penetrate through the molten coating into the steel substrate during the HPF process. In this study, 0.1-wt% of Sn was added to a 1.5-GPa-grade reference HPF steel (referred to as 0.1Sn and Ref steels), and their coating microstructures including Sn-enriched zone and Kirkendall and surface voids were examined after laboratory-scale HPF simulation tests. The content of diffusible H atoms immediately after the HPF simulation at 900 °C was 0.111 wt.ppm in the Ref sheet, decreased slowly as the elapsed time increased, and remained to be 0.030 wt.ppm even after 17 days. In the 0.1Sn sheet, it was about half of that of the Ref sheet (0.061 wt.ppm), and decreased rapidly to nil after 3 days. These results indicated that the 0.1Sn steel showed excellent H-intrusion and emission behavior, which would favorably work for better resistance to HE, by optimally controlling the multi-mechanisms of enrichment of Sn solutes and population of coating voids. The presence of Sn-enriched zone and voids played an important role in blocking the H intrusion to the substrate and in accelerating the H emission to the coating surface, respectively. • Sn-enriched zone blocks the H intrusion to the substrate. • Voids accelerate the H emission to the coating surface. • If less H comes in and goes out quickly, it is resistant to hydrogen embrittlement. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the improvement in the hydrophobicity of cellulose through gas grafting treatment with long chain fatty acid chloride using high pressure during pressing at high temperature. To do this, the gas grafting treatment was performed on the cellulose sheet using a hot pressing method, and then the hydrophobization effect was analyzed. It was found that the gas grafting treatment by hot pressing using high pressure during pressing at high temperature produced cellulose sheets of high hydrophobicity. Especially, it was notable that the hydrophobization efficiency enhanced with an increase of the pressing pressure. In addition, the gas grafting efficiency was improved when polyvinyl alcohol (PVA) was coated to obtain high resistance to air permeability. These results indicate that protecting the loss of fatty acid gas by coating of polyvinyl alcohol (PVA) on the cellulose sheet surface contributed to the improvement of gas grafting efficiency., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The incorporation of high dielectric constant filler particles into thermoplastics is an attractive approach to develop materials with high dielectric strength, low dielectric loss, and mechanical stiffness, for electronic packaging purposes. Herein, we report the preparation and properties of polystyrene (PS) based low loss 0–3 composites with inorganic PbZr0.3Ti0.7O3 (PZT) filler particles in concentrations ranging from 0%–20% (w/w). The PZT particles were synthesized using the sol‐gel process and the composites were prepared by a two‐step, solvent‐free approach: (1) melt mixing, followed by (2) hot press. The thermal and mechanical properties of the composite samples were investigated. The dielectric behavior of the as‐synthesized composites showed pronounced improvement over pure PS, as is seen from the increased dielectric constant and extremely low loss tangent. For 20 wt.% PZT loading, the dielectric constant of the composite is as high as 12 at 1 MHz frequency, which is about five times greater than that of pure PS (ε = 2.5). All the PZT/PS composites exhibit remarkably low dielectric losses, even at lower frequencies (tan δ ≤ 0.04), which is better than reported literature values of PS based composites. The variation in dielectric constants of the samples with increasing temperatures was also recorded. [ABSTRACT FROM AUTHOR]

Trapped-flux magnets made of stacks of superconducting tapes are an interesting and important alternative to the application of rare-earth permanent magnets and trapping flux in bulk superconductors. Many applications, such as electric motors, can require the complex shapes of magnetic elements to combat issues such as demagnetization during the operation. Therefore, a reliable production technique of high temperature superconductor (HTS) stacks with different geometries is required to meet the needs of industry. In this article, a method of shaping the epoxy-glued stacks of superconducting tapes is proposed and investigated. The application of hot press allows to easily change the shape of the stack. The influence of shaping the stack on the density of trapped magnetic flux as well as critical current are presented. Experimental and numerical analyses are performed and their results are matched to find the change in the superconducting properties of the tapes. They show that with the proper process parameters the stacks can be shaped with only minor decrease of performance. However, strong degradation is observed if the applied force is too high. The observed problems are discussed and the possible solutions are proposed. [ABSTRACT FROM AUTHOR]

The safe treatment and disposal of high-level radioactive graphite is an essential challenge in the governance of irradiated graphite. SiC has an insurmountable defect in densification sintering at low temperatures, although it is an ideal host material for immobilizing high-level radioactive graphite. To solve this issue, we employ ZCAS (short for ZnO–CaO–Al 2 O 3 –SiO 2 glass) as a sintering aid to prepare SiC-ZCAS composite ceramic with the relative density up to 98% by vacuum hot-press sintering. For investigating the optimum formula and technological conditions of (1-x) SiC-x ZCAS composite ceramic, the effects of synthesis and sintering process on preparation (1-x) SiC-x ZCAS (x = 25-40 wt%) composites were investigated in detail. The results show that the SiC-ZCAS composite powder with x = 25-40 wt% can be synthesized at 1350 °C for 2 h when the Si/C mole ratio is 1.05:1. The relative density, Vickers hardness, and thermal conductivity of SiC-ZCAS composites ceramic increase rapidly by increasing sintering temperature and pressure. However, these properties will display different effects from the increase in the content of ZCAS, such as continuous elevation of the relative density and dramatic depression of thermal conductivity. the Vickers hardness starts to decline when the content of ZCAS is 30 wt%. Considering the above mentioned, we can conclude that the 0.7SiC-0.3ZCAS composite ceramic has choiceness comprehensive properties when sintered at 1550 °C and 60 MPa for 1 h, with the relative density, Vickers hardness and thermal conductivity of 95.5%, 1084 (HV 10) and 7.104 W/m·k, respectively. [ABSTRACT FROM AUTHOR]

Effects of the starting TiC particle size on the phase compositions, microstructures and mechanical properties of B 4 C–TiB 2 composites prepared by reactive hot-press sintering of TiC–B mixtures were investigated. B 4 C–TiB 2 composites were prepared from a single grade amorphous B powder (0.9 μm) and three different TiC powders (50 nm, 0.8 μm and 3.0 μm), respectively. The composites prepared from 50 nm and 3.0 μm TiC powders exhibited finer microstructures and higher hardness (29–30 GPa). The composite prepared from 0.8 μm TiC powder showed the coarsest microstructure but possessed the highest strength of 659 MPa due to its homogenous phase distribution without C impurity and abnormal grain growth that presented in the other two composites. The results indicated that the mechanical properties of B 4 C–TiB 2 composite could be controlled by the particle size matching between TiC and B powders. [ABSTRACT FROM AUTHOR]

We investigated the thermoelectric (TE) properties of GeTe by incorporating Bi 2 Te 3 in the GeTe system. The addition of Bi 2 Te 3 into the GeTe matrix leads to phonon scattering caused by stacking fault or structural defect, resulting in a substantial reduction in lattice thermal conductivity κ lat. We observed a significant decrease in total thermal conductivities in the vertical and horizontal pressing directions, respectively. The optimized carrier properties and low thermal conductivity in the composites have led to a remarkable improvement in the dimensionless figure of merit (zT) 1.26 at 650 K. This study highlights the potential for creating high-performance thermoelectric materials through GeTe-Bi 2 Te 3 compounds, emphasizing the importance of defect engineering and stacking faults in reducing thermal conductivity and improving thermoelectric efficiency. • TE studied performed for the (GeTe) x (Bi 2 Te 3) 1-x layered structure composition. • Shift in the XRD peak shows the doping of Bi in the GeTe lattice. • The reduction in thermal conductivity observed for both horizontal and vertical direction of pressing. • Figure of merit (zT) reaching a maximum value of 1.26 at 650 K. [ABSTRACT FROM AUTHOR]

Scanning Electron Microscope (SEM) is a crucial tool for studying microstructures of ceramic materials. However, the current practice heavily relies on manual efforts to extract porosity from SEM images. To address this issue, we propose PSTNet (Pyramid Segmentation Transformer Net) for grain and pore segmentation in SEM images, which merges multi-scale feature maps through operations like recombination and upsampling to predict and generate segmentation maps. These maps are used to predict the corresponding porosity at ceramic grain boundaries. To increase segmentation accuracy and minimize loss, we employ several strategies. (1) We train the micro-pore detection and segmentation model using publicly available Al2O3 and custom Y2O3 ceramic SEM images. We calculate the pixel percentage of segmented pores in SEM images to determine the surface porosity at the corresponding locations. (2) Utilizing high-temperature hot pressing sintering, we prepared and captured scanning electron microscope images of Y2O3 ceramics, with which a Y2O3 ceramic dataset was constructed through preprocessing and annotation. (3) We employed segmentation penalty cross-entropy loss, smooth L1 loss, and structural similarity (SSIM) loss as the constituent terms of a joint loss function. The segmentation penalty cross-entropy loss helps suppress segmentation loss bias, smooth L1 loss is utilized to reduce noise in images, and incorporating structural similarity into the loss function computation guides the model to better learn structural features of images, significantly improving the accuracy and robustness of semantic segmentation. (4) In the decoder stage, we utilized an improved version of the multi-head attention mechanism (MHA) for feature fusion, leading to a significant enhancement in model performance. Our model training is based on publicly available laser-sintered Al2O3 ceramic datasets and self-made high-temperature hot-pressed sintered Y2O3 ceramic datasets, and validation has been completed. Our Pix Acc score improves over the baseline by 12.2%, 86.52 vs. 76.01, and the mIoU score improves from by 25.5%, 69.10 vs. 51.49. The average relative errors on datasets Y2O3 and Al2O3 were 6.9% and 6.36%, respectively. [ABSTRACT FROM AUTHOR]

The anisotropic material behavior of continuous-fiber-reinforced composites that is evident in their mechanical properties should also be considered in their processing. An important step in the processing of thermoplastic unidirectional (UD) fiber-reinforced tapes is consolidation, where a layup consisting of locally welded UD tape layers is firmly bonded. Compression of the molten thermoplastic matrix material during consolidation leads to a squeeze flow, the direction of which is determined by the fibers. This work presents a model that describes the influence of fiber direction on compression and flow behavior, implemented in the computational fluid dynamics (CFD) software tool OpenFOAM®. To validate the simulation results, we performed experiments in a laboratory consolidation unit, capturing the squeeze flow with cameras and then quantifying it by gray-scale analysis. The specimens used were UD polycarbonate tapes (44% carbon fibers by volume) of various sizes and with various fiber directions. The simulation allows prediction of the changes in specimen geometry during consolidation and is a first step towards optimizing the process by avoiding extensive squeeze flow. [ABSTRACT FROM AUTHOR]

Shape memory composites now have a wide range of applications in aerospace, medical devices, and smart structures. Seven graphene‐carbon oxide/glass fiber (GO‐CF/GF) hybrid reinforced shape memory composites were prepared using vacuum infiltration hot pressing system (VIHPS) and the shape memory properties of the materials were investigated in 100°C test. By comparing and analyzing the microstructure and shape memory properties of composites containing different volume fractions of GFs, the mechanism of the influence of different hybrid contents of GFs on the organizational properties and shape memory properties was investigated. The results show that when the reinforcement of the composites were all carbon fibers, the composites had the largest elasticity modulus, harder material and the fixation rate of 77.15%, the recovery rate of 95.17%, the porosity of 0.80% and the shape recovery force of 7.98 N. When the reinforcement of the composites were glass fibers, the composites had the smallest elasticity modulus, softer material and the fixation rate of 94.89%, the recovery rate of 77.21%, the porosity of 13.56% and the recovery force of 2.28 N. The results of this test can lay a foundation for subsequent research on fibers with different mixing ratios. Highlights: The GO‐CF/GF/EP prepared by VIHPS has excellent shape memory properties.Fiber hybrid ratio affects the composite's porosity and its properties.Fiber hybrid ratio affects the composite's shape fixation, recovery, and memory force.The shape fixation of G6 decreases the lowest with test cycles.Carbon fiber content changes the zero‐stress plane of GO‐CF/GF/EP. [ABSTRACT FROM AUTHOR]

In the automotive industry, the demand for ultra-high-strength steel is increasing due to the CO2 emission and safety regulations. Hot-press forming (HPF) steels are a type of boron-alloyed high-strength steel fabricated via hot-press forming, which enables both high strength and elongation. Because HPF is conducted at high temperatures (900–950 °C) for a few minutes, its surface is coated with Al–Si or Zn to prevent surface oxidation and decarburizing. However, the coating layer often influences the properties of the welds. In this study, friction stir spot welding (FSSW) is used to weld dissimilar metals, i.e., an Al alloy and Al–Si-coated HPF steel. The effects of Al–Si coating on the mechanical and metallurgical properties of the hook formation on the weld are investigated. The shape of the hook, which is formed during FSSW, changes from bent to straight shape due to the presence of Al–Si and the HPF process. The joint strength of the straight hook-shaped specimens is demonstrated to be lower than that of the bent hook-shaped specimens. This difference in strength is because the hard Fe–Al–Si intermetallic (IMC) layer on the outer surface of the hook disturbs the bending of the hook during the welding. On the outer surface of the hook, a Fe–Al–Si IMC layer of chemical composition similar to that of the coating layer formed during HPF is observed. This formation is different from the inner surface of the hook, wherein a thin Fe–Al IMC layer is reconstructed between aluminum and steel. Thus, the hard Fe–Al–Si intermetallic layer transformed during the HPF process is the primary cause of the straight hook shape. [ABSTRACT FROM AUTHOR]

Linear dielectric ceramics have received much attention due to high power density, fast discharge speed and ultralow dielectric loss, which are expected as promising candidates for the pulsed power system applications. However, their relatively low dielectric breakdown strength usually cannot meet the requirements of practical application. In this work, we adopt hot-press sintering method to enhance the dielectric breakdown strength of the TiO 2 -SiO 2 -Al 2 O 3 based ceramics, and the dielectric breakdown strength reaches 77.5 kV/mm, which is 1.8 times as large as samples prepared by conventional sintering method. The effect of different sintering methods on microstructure, dielectric properties and dielectric breakdown strength is investigated. The improvement of dielectric breakdown strength can be ascribed to improved bulk density, smaller grain size, and reduced reduction of Ti4+ to Ti3+, associated with the applied external pressure and lower sintering temperature. Eventually, large power density (18.20 MW/cm3) is obtained in pulse overdamped discharge circuit. Meanwhile, the stored energy is also released in a short time (about 11.3 ns to release 90% of saturated energy density value). [ABSTRACT FROM AUTHOR]

Super-hard diamond drill bits were prepared with microwave hot press sintering (MHPS) method at low sintering temperature. The micro-structures were analyzed using SEM. The samples were characterized for their properties such as bending strength, hardness, relative density and compression and tensile test. The purity of the diamond in samples was investigated by Raman spectroscopy. The results display that when MHPS method is applied to the manufacture of diamond drill bits, it has prominent advantages such as shorter sintering time, lower sintering temperature et al. And the samples prepared with MHPS at 860 °C show excellent performance. The values of hardness, relative density and bending strength are 106.6 HRB, 97.6% and 895.8 MPa respectively. Thus, a reaction kinetic study was performed to analyze reaction mechanism. And a potential sintering mechanism of MHPS is discussed. This work will provide a theoretical basis for the preparation of diamond tools through MHPS process. Unlabelled Image • Microwave hot press sintering is used to make prealloyed superhard material. • The samples show excellent comprehensive properties sintered at 860 °C. • The mechanism of microwave hot press sintering to make samples is studied. [ABSTRACT FROM AUTHOR]

This paper mainly concerns the thermo-mechanical analysis to evaluate the process parameters in the hot press forming with the 22MnB5 sheet such as the austenitization temperature, transport and quenching time for enhancing the efficiency in the production cycle. It is noted that the transport time is most influencing process parameter in the hot press forming to increase production efficiency without sacrificing the strength of the final product. In addition, we newly proposed a scheme to reproduce the flow curves of the hot stamped 22MnB5 sheet with respect to the martensite fraction by correlating the numerical analyses and tensile test results. To take into consideration of the strength variation in the hot stamped door impact beam, entire part is partitioned into several domains on which adaptive flow curves are assigned with respect to the martensite fraction. It demonstrates a good agreement with experimental 3-point bending test with the hot stamped door impact beam when applying the proposed method adopting adaptive flow curves with respect to the martensite fraction. [ABSTRACT FROM AUTHOR]

Abstract Lead-free Bi 1−x Sm x Fe 0.95 Sc 0.05 O 3 (x = 0.15–0.19) ceramics were fabricated by rapid hot press sintering, and their structure, ferroelectric and energy storage properties were comprehensively investigated. All the samples are in the mixed phases with R3c rhombohedral and Pbnm orthorhombic structures. With increasing x , the ferroelectric polarization decreases gradually, while the polarization loop becomes gradually slimed too. An high recoverable energy density (˜2.21 J/cm3) and a large efficiency (˜76%) with good thermal stability (20 °C–120 °C) are obtained under electric field (230 kV/cm) for the optimized sample x = 0.17. Moreover, transmission electron microscopy and piezo-response force microscopy measurements reveal that the presence of two-phase coexistence favors the formation of polar nano-regions, leading to the linear-towards polarization behaviors and the enhanced dielectric breakdown field, which is responsible for the superior energy storage performance of Bi 1−x Sm x Fe 0.95 Sc 0.05 O 3 ceramics. These results indicate a significant step to tailor lead-free BiFeO 3 -based ceramics towards high dielectric energy storage applications. [ABSTRACT FROM AUTHOR]

Copper/graphite composites are widely used due to their excellent electrical, thermal, and self-lubricating properties. However, their mechanical and anti-wear properties are usually limited by brittle graphite and soft copper matrix. Enhancing the properties of composites by further introducing harder ceramic particles is an effective way. However, these particles are usually poorly wetted to metal and can easily separate from the matrix during friction, causing more severe abrasive wear. Herein, TiC x -reinforced Cu/graphite composites were prepared by rapid hot press sintering of a hybrid powder consisting of Ti 3 AlC 2 , Cu-plated graphite, and Cu powder. Al atoms diffused out of Ti 3 AlC 2 and solid-solved into the Cu matrix during the sintering process, forming TiC x and Cu(Al) alloys. Such in situ formed TiC x particles have good interfacial bonding with the matrix. With the increase of Ti 3 AlC 2 addition from 0 to 15 wt%, the average grain size of the composites decreased, the relative density increased, the hardness became larger, the electrical conductivity decreased, and the average coefficient of friction were all maintained at about 0.14, but the wear rate was reduced from 3.6569 × 10−4 mm3·N−1·m−1 to 9.35013 × 10−6 mm3·N−1·m−1. The in situ Ti 3 AlC 2 -derived TiC x particles improved the deformation resistance and shear resistance of the Cu/graphite composites, thus contributing to the wear resistance. This research may offer fresh perspectives on how to enhance the properties of copper/graphite composites. [ABSTRACT FROM AUTHOR]

BaFe12O19 hexaferrite thick films having high hysteresis loop squareness (Mr/Ms) and low ferromagnetic resonance (FMR) linewidths were processed through the use of a screen printing technique coupled with hot-press sintering. Scanning electron microscopy and x-ray diffraction measurements exhibit strong crystallographic c-axis alignment of crystals perpendicular to the film plane. Static magnetic resonance and FMR measurements were performed to determine the effect of the preparation technique on magnetic hysteresis and microwave properties. Hot pressing during sintering produced dense thick films having high squareness (>0.95) and reduced coercivity (∼1900 Oe). Of greater importance was the measurement of a minimum peak-to-peak FMR linewidth, 320 Oe at the U band, for films ranging in thickness from 100 to 500 μm. Theoretic estimates suggest that such narrow linewidths can be attributed to the reduction in porosity and the improvement in c-axis orientation of crystallites in polycrystalline barium ferrite films. As such, haxaferrite materials prepared using this technique offer opportunities in the next generation of self-biased planar microwave devices. [ABSTRACT FROM AUTHOR]

In this article, Co 1−x Zn x Fe 2 O 4 (x = 0.0 and 0.5) disc-shaped pellets were formed by hot-press sintering of nanoparticles at temperature 925 °C for 10 min in vacuum atmosphere under 30 MPa mechanical pressure. X-ray diffraction study confirmed the formation of spinel cubic ferrite structure of hot-press sintered spinel ferrite Co 1−x Zn x Fe 2 O 4 (x = 0.0 and 0.5) samples. The scanning electron microscopy image indicated that the growth and densification of smaller ferrite nanoparticles were higher than larger ferrite nanoparticles. Magnetic properties of sintered samples were investigated by the superconducting quantum interface device (SQUID) magnetometer at room temperature. The hot press sintered Co 1−x Zn x Fe 2 O 4 (x = 0.0 and 0.5) pellet samples exhibited magnetic properties dependent on the grain size of spinel ferrite particles. The maximum saturation magnetization 82.47 emu/g was obtained for Co 0.5 Zn 0.5 Fe 2 O 4 hot press sintered sample of ball-milled ferrite particles. Further, the impact of grain size and density of sample on hardness, dielectric property and ac conductivity of hot-press sintered samples was investigated. In addition, the longitudinal wave velocity (V l ), transverse wave velocity (V t ), mean elastic wave velocity (V m ), bulk modulus (B), rigidity modulus (G), Young’s modulus (E), Poisson ratio (σ) and Debye temperature (θ D ) were calculated. The elastic moduli of hot press sintered ferrite samples were corrected to zero porosity using Hosselman and Fulrath model. [ABSTRACT FROM AUTHOR]