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To maintain the structural integrity of fuel elements for a high temperature gas-cooled reactor (HTGR) under beyond design conditions, strong and oxidation-resistant fuel elements should be further developed. The HTGR fuel elements employ a hot-pressed silicon carbide (SiC)/carbon (C) mixed matrix to improve the oxidative resistance. Hot-press conditions such as pressure, temperature, and duration would be one of the factors that affect the strength of the HTGR fuel elements. To identify the optimal hot-press conditions for preparing the high-strength fuel elements, modeling their effects on the mechanical-strength properties of the HTGR fuel elements should be evaluated quantitatively. In this study, the response–surface model, which represents the relationship between the hot-press conditions and the mechanical-strength properties, has been constructed by introducing statistical design of experiments approaches. The model estimated the optimal hot-press conditions for producing the high-strength fuel elements. We discuss the model’s validity by comparing its predictions with experimental observations.

The effect of hot-press sintering temperature on density of tungsten heavy alloys is presented in this paper. The experiments were performed for the WNi5Cu3 samples of W-Ni-Cu heavy alloy system. The hot-press sintering temperature was ranged from 1300 to 1440 °c with a constant applied pressure of 40 MPa. Subsequently, the sintered samples were annealed at 1000 °c in acgon atmosphere during 3 h. The results showed that the obtained heavy alloys had maximum density of 17,427 g.cm3 and final particle size around (10 + 15) mm. The obtained results met the requirement for fabrication of small balanced parts for aeronautical industry.

In the study, the bonding strength of phenol-formaldehyde (PF) adhesive on plywood under different hot press temperature and time was evaluated. A mechanical mathematical model was established to a...

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 used to resinify a renewable source-derived linear 1,4-linked β-D-glucan copolymer, i.e., konjac glucomannan (KGM), via the generation of reactive aldehyde groups ...

The microstructures and properties of powder metallurgy Ti-45Al-10Nb (at.%) alloys fabricated by vacuum hot pressing consolidation of milled powder have been investigated. Under the sintering condi...

An aluminophosphate adhesive was used as the binder in plywood. The hot-pressing parameters of aluminophosphate adhesive-based plywood (APPs) including hot-press temperature (A), time (B), and pressure (C) were optimized using response surface methodology. Results indicated that the hot-press temperature was the most dominant factor. The maximum bonding strength of 1.98 MPa was found with an optimal parameter of 171 °C (hot-press temperature), 7.5 min (hot-press time), and 1.0 MPa (hot-press pressure). Additionally, the chemical reaction mechanism between aluminophosphate adhesive and wood fibers was characterized by X-ray photoelectron spectroscopy (XPS). Results showed that good interaction was generated between wood fibers and adhesives through their surface functional groups. In conclusion, the optimized pressing conditions of plywood significantly improved bonding strength of APPs.

This study was conducted to investigate the effect of low-density polyethylene on the microstructural and mechanical properties of 3105 aluminum composites produced by the continuous hot-press method. This production method ensures superior flatness to the composite and excellent peel strength between the composite plies. To this end, the bond between AA3105 and low-density polyethylene was initially characterized using a T-Peel stripping test. Tensile tests were performed on AA3105, low-density polyethylene and 3105 aluminum composites for determining mechanical behavior. A scanning electron microscope was used to characterize the cross-sectional cuts of the 3105 aluminum composite specimens obtained from the tensile tests. The microstructural analysis shows that low-density polyethylene and AA3105 exhibit a good interfacial adhesion bond before the fracture of the first AA3105 sheet. The results of the tensile tests clearly show that the uniform elongation at maximum load (Ag) of the 3105 aluminum composite is higher than that of AA3105. Furthermore, AA3105 exhibits negative strain rate sensitivity due to dynamic strain aging while 3105 aluminum composite exhibits a higher strain-hardening exponent than AA3105. Due to the higher strain rate sensitivity and strain hardening exponent, the 3105 aluminum composite exhibits higher formability than AA3105. This is of crucial importance for the manufacturing process.

The purpose of this study is to develop a control scheme for the hydraulic proportionalsystem using PID function on Mitsubishi PLC Q series, which can rapidly control the pressurein a hydraulic cylinder with very short stroke. The mathematical model of the control system isestablished according to the principle of the electro-hydraulic system. Considering the mentionedcharacteristics, simulation of the system modelling will be established to know the systemresponse. In order to improve the control precision of the hydraulic hot-press system, theMitsubishi PID controller are designed by selecting appropriate tuning parameters. Their controlperformances are analysed in time domain respectively. The variation of PID controllerconfiguration will be conduct to know the better model for this system controller. The validityof the proposed control scheme is confirmed through the experiments to verify the rationality ofthe theoretical model. The results show that the Mitsubishi PID and the ideal PID give the sameresult for the tuning parameter resulted from simulation. And also the experiment give the betterstability in the 3 different pressure set value that conduct by 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.

In this study, a microwave hot press sintering (MHPS) strategy was developed for metal-bonded diamond composites (MBDC). The main focus was on the MHPS process of Fe60Cu40 pre-alloy bonded diamond composites. The temperature rise characteristics of the metal powders were obtained within a microwave field. Further, the composition change law of the composites was determined during the sintering process by analyzing the properties and microstructure of the composites. The successful development of this strategy will provide a reliable reference for the application of microwave sintering in the fabrication of MBDC.

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...

This research investigates the performance of medium density fiberboard (MDF) with respect to hot press parameters. The performance of the board, type of glue, and production efficiency determine the optimum temperature and pressure for hot pressing. The actual temperature of the hot press inside the MDF board determines the properties of the final product. Hence, the optimal hot press parameters for the desired product are experimentally obtained. Moreover, MDF is experimentally investigated in terms of its vertical density profile, bending, and internal bonding under the various input parameters of temperature, pressure, cycle time, and moisture content during the manufacturing process. The experimental study is carried out by varying the temperature, pressure, cycle time, and moisture content in the ranges of 200–220 °C, 145–155 bar, 260–275 s, and 8–10%, respectively. Consequently, the optimum input parameters of a hot-pressing temperature of 220 °C, pressure of 155 bar, cycle time of 256 s, and moisture content of 8% are identified for the required internal bonding (0.64 N/mm2), bending (32 N/mm2), and increase in both the core and peak density of the vertical density profile as per the ASTM standard.

Investigations on ion-transport and materials properties of poly (ethylene oxide) (PEO) based Zn2+ conducting Nano-Composite Polymer Electrolyte (NCPE) membranes: [90 PEO: 10 Zn (CF3SO3)2] + xAl2O3, have been reported. NCPE films have been prepared by a completely dry hot-press cast technique using Solid Polymer Electrolyte (SPE) composition: [90 PEO: 10 Zn (CF3SO3)2] as I phase and Al2O3 nano-filler particles (< 50 nm) as II- Phase dispersoid. In an earlier study, SPE used here as I phase host has been identified as optimum room temperature conducting film exhibiting (srt) ~1.01 x 10-5 S/cm. As a consequence of fractional dispersal of nano-filler particles in SPE, additional srt enhancement of an order of magnitude was obtained. This has been referred as NCPE OCC film. Ion transport behavior in NCPE OCC has been characterized in terms of ionic conductivity (?), total ionic (tion)/cation (t+) transport numbers which have been measured using different ac/dc techniques. Temperature dependent conductivity study has also been carried out to understand the mechanism of ion transport and to compute activation energy (Ea) from ‘log s-1/T’ plot. Materials and thermal properties have been characterized with the help of SEM, XRD, FTIR and DSC / TGA techniques.

The present article focused on the residual strains and deformation of the laminates fabricated by rapid hot press process using prepreg. Strain gauges and laser tracker were utilized to measure th...

As society considers alternatives to energy systems based on fossil fuel combustion, high-temperature proton exchange membrane (HT-PEM) fuel cells may play an important role in our future energy and transportation portfolio. When compared to low-temperature proton exchange membrane (LT-PEM) fuel cells, HT-PEM technology offers enhanced electrode kinetics, simplified water management, and most notably increased tolerance to fuel impurities such as carbon monoxide. However, compared to more conventional LT-PEM systems, less is known about the durability, performance, and fabrication of HT-PEM materials. Comprised of multiple layers, the membrane electrode assembly (MEA) is a fuel cell’s central component. In a fabrication process similar to LT-PEM MEAs, the proton-conducting membrane, electrodes, gas diffusion layers and sub gaskets are usually hot-pressed together. The parameters surrounding the hot-pressing operation can have a significant impact on the ultimate performance of the fuel cell, in addition to influencing process reliability and repeatability. In the current research, measurements of MEA thickness, impedance, and adhesion strength were obtained for samples over a range of conditions to optimize for the most suitable processing parameters. Testing in this study quantified the effects of hot-press time, temperature and pressure, within ranges of 1-10 minutes, 140 – 200oC, and 7.72 – 92.67 MPa (1120 - 13440 psi), respectively. After hot pressing, the MEA samples were tested for resistance with a 1260a Solartron impedance gain phase analyzer in tandem with a Solartron Ametek 12962a sample holder, and with a Scott internal bond tester for adhesion strength. Based on the results of these tests the optimal hot-press parameters were established, four 25 cm2 MEA were built and tested for performance with post-mortem analysis conducted utilizing scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX). These measurements enabled interrogation of potential sources of conductivity loss associated with material layer delamination and/or dehydration of phosphoric acid in the polybenzimidazole (PBI) membrane. In this case, all tests were conducted at 140oC and the resulting material assembly was allowed to cool to room temperature in a nitrogen glove box prior to executing conductivity measurements (i.e., inverse of resistance). Our results have demonstrated that the optimal conditions for MEA hot-pressing for the HT-PEM system are around 170oC and 23.1 MPa for 5 minutes. Each curve in Figure 1 represents the performance of in-house MEAs, prepared using the optimized hot-pressing condition, with variation of platinum-on-carbon content (Pt/C) and total Pt loading. The data presented in Figure 1 demonstrate the effect of varying electrode thickness on MEA performance. Figure 1

Among refractory metals, tantalum has long been the primary material of use in high strain rate applications. Hot pressing (HP) is a technique to produce specimens with high density and homogeneous...

High-strength hot-press-formed (HPF) steels with a fully martensitic microstructure are being widely used in the fabrication of automotive body structure, and 2.0 GPa-strength HPF steel has recently been commercially launched. However, heat-affected zone (HAZ) softening is unavoidable in welding martensitic steel. In this study, the HAZ softening characteristic of 2.0 GPa HPF steel was investigated by applying a high-brightness laser welding process, wherein the heat input was controlled by varying the welding speed. Microstructural evaluation and hardness test results showed that the base metal with a fully martensitic microstructure was changed to the same type of fully martensitic microstructure in the weld metal, while relatively soft microstructures of tempered martensite and ferrite phase were partially formed in the intercritical HAZ (ICHAZ) and subcritical HAZ (SCHAZ) areas. In the tensile test, the joint strength was 10–20% lower than that of the base metal, and the fracture initiation was estimated at the ICHAZ/SCHAZ boundary, where the lowest hardness was confirmed by the nanoindentation technique.

The Fe/FeAl2O4 cermet was prepared with Fe-Fe2O3-Al2O3 powder by a hot press sintering method at 1400 °C. The raw materials for the powder particles were respectively 2 µm (Fe), 0.5 µm (Fe2O3), and 0.5 µm (Al2O3) in diameter, the sintering pressure was 30 MPa, and the holding time was 120 min. The effects of different Fe mass ratios on the microstructure and mechanical properties of Fe/FeAl2O4 cermet were studied. The results showed that a new ceramic phase FeAl2O4 could be formed by an in situ reaction during the hot press sintering. When the Fe mass ratio was increased, the microstructure and mechanical properties of the Fe/FeAl2O4 cermet showed a change law that initially became better and then became worse. The best microstructure and mechanical properties were obtained in the S2 sample, where the mass ratio of Fe-Fe2O3-Al2O3 was 6:1:2. In this Fe mass ratio, the relative density was about 94%, and the Vickers hardness and bending strength were 1.21 GPa and 210.0 MPa, respectively. The reaction mechanism of Fe in the preparation process was the in situ synthesis reaction of FeAl2O4 and the diffusion reaction of Fe to FeAl2O4 grains. The increase of the Fe mass ratio improved the wettability of Fe and FeAl2O4, which increased the diffusion rate of Fe to FeAl2O4 grains, which increased the influence on the structure of FeAl2O4.

The hot-press technique is applied to lower the sintering temperature and shorten the sintering process of Li1.5Al0.5Ge1.5(PO4)3 (LAGP). The hot-press conditions are studied to obtain well sintered LAGP pellet with high Li ion conductivity. The highest Li ion conductivity is obtained at 550 oC for 30 min at 7 MPa and the values are 3.8, 3.4 and 1.8×10-4 S cm-1 in bulk, grain-boundary and total conductivities, respectively. These values are comparable to reported values, however, sintering temperature is more than 250 oC lower and holding time is more than several hours shorter than conventional sintering processes.

Hot-press drying has gained attention due to its excellent drying rate and surface strengthening effect. The moisture state in poplar lumber (Populus tomentosa) with moisture content (MC) above fibre saturation point (FSP) was analyzed during hot-press drying. The effect of heating platens’ temperature on the temperature and pressure inside poplar lumber was investigated. The moisture state changes inside the poplar lumber during hot-press drying were further analysed in accordance with the measured pressure and theoretical pressure calculated with the measured temperature inside poplar lumber. Results were as follow: When the heating platens’ temperature increased from 120 to 140 °C, the maximum values of temperature and pressure also increased by 14.5 and 26.2%, respectively. However, a delay occurred between the maximum values of pressure and temperature. The moisture at the center layer of poplar lumber with MC above FSP was in liquid state, i.e. unsaturated water under overpressure condition in hot-press drying process. Flashing occurred to the unsaturated water in poplar lumber during the opening period of heating platens and resulted in the decrease in MC. This phenomenon is the main moisture transfer mode in wood hot-press drying process with MC above FSP.

Metallic material processing plays a significant role in terms of global environmental impact which contributes to the climate change phenomena that is a serious international environmental concern and the subject of much research and debate. Thus, energy-and resource-efficient strategies in the metal shaping technology domain need to be identified urgently. A frequent theme in the debates that surround waste and resources management is the extent to which the recycling of metallic materials offers genuine benefits to the environment. Solid state recycling techniques allow the manufacture of high density aluminum alloy parts directly from production scrap. In this paper the environmental impacts associated with ‘meltless’ scrap processing routes through hot press forging process with varying parameter has been studied. A comparative analysis has been performed, with different operating temperature and holding time of direct recycling hot press forging process AA6061 aluminum chip. The importance of an environmental performance analysis that included both parameter setting was discussed and highlighted throughout the paper. Finally, the application of the proposed parameter setup has resulted in the setting up of an eco-process. Indeed, LCA study on recycling (solid-state) are recommended as well it gives a noteworthy benefit to the environment and to fill the knowledge gap.

The applications of pure multi-walled carbon nanotubes (MWCNTs) buckypapers are still limited due to their unavoidable micro/nano-sized pores structures. In this work, polyvinyl alcohol (PVA) was added to a uniform MWCNTs suspension to form MWCNT/PVA buckypapers by vacuum infiltration combined with a hot press method. The results showed an improvement in the thermal, electrical, and electromagnetic interference (EMI) shielding properties due to the formation of dense MWCNTs networks. The thermal and electrical properties rose from 1.394 W/m&middot, k to 2.473 W/m&middot, k and 463.5 S/m to 714.3 S/m, respectively. The EMI performance reached 27.08 dB. On the other hand, ABAQUS finite element software was used to simulate the coupled temperature-displacement performance. The electronic component module with buckypapers revealed a homogeneous temperature and thermal stress distribution. In sum, the proposed method looks promising for the easy preparation of multi-functional nanocomposites at low-cost.

The new ternary CM2A8 (CaMg2Al16O27) and C2M2A14 (Ca2Mg2Al28O46) pure and dense ceramics were first prepared by a hot-press sintering technique, and their physical and mechanical properties were investigated. The purity of obtained CM2A8 and C2M2A14 ceramics reaches 98.1 wt% and 97.5 wt%, respectively. Their microstructure is dense with few observable pores, and their grain size is about a few dozen microns. For their physical properties, the average apparent porosity of CM2A8 and C2M2A14 ceramics is 0.18% and 0.13%, and their average bulk density is 3.66 g/cm3 and 3.71 g/cm3, respectively. The relative density of CM2A8 ceramic is 98.12% and that of C2M2A14 ceramic is 98.67%. The thermal expansivity (50–1400 °C) of CM2A8 and C2M2A14 ceramics is 9.24×10–6 K–1 and 8.92×10–6 K–1, respectively. The thermal conductivity of CM2A8 and C2M2A14 ceramic is 21.32 W/(m·K) and 23.25 W/(m·K) at 25 °C and 18.76 W/(m·K) and 19.42 W/(m·K) as temperature rises to 350 °C, respectively. In addition, the mechanical properties are also achieved. For CM2A8 ceramic, the flexural strength is 248 MPa, the fracture toughness is 2.17 MPa·m1/2, and the Vickers hardness is 12.26 GPa. For C2M2A14 ceramic, the flexural strength is 262 MPa, the fracture toughness is 2.23 MPa·m1/2, and the Vickers hardness is 12.95 GPa.

This study proposes of harmonizing the original approach of aluminium alloy recycling through hot press forging. By eradicating the melting phase, most of the waste generation can be significantly reduced. To cope with the technology revolution, the finite element is utilised to predict the material behaviour without practically executing the trial. By employing three-dimensional finite element analysis through DEFORM 3D, the evaluations were demonstrated by simulating the isothermal forging process. The flow stress of the material was modified to adequate with the aluminium-based metal matrix composite used in the actual experiment. To that extent, this study found out that the strain of the workpiece had gradually increased on each step. A reduction of ~10% of the flesh observed in the simulation is roughly the same as existed on the experiment workpiece. Above all, the simulation conducted abides by the standard and follows the actual practice that has been done previously. Through the finite element utilization, this study discussed the performance of the recycled based composite. The result presented here may facilitate improvement in the recycling issue and also conserved the environment for the better future.

Electrospun polyimide (PI) ultrafine non-woven fibrous mats (UFMs) with good heat-fusibility via hot press procedure were successfully fabricated. For this purpose, two organo-soluble PI resins were prepared via a two-step chemical imidization procedure from two isomeric oxydiphthalic dianhydrides, including the asymmetrical ODPA (2,3,3′,4′-oxydiphthalic dianhydride, or aODPA) and symmetrical ODPA (4,4′-oxydiphthalic dianhydride, or ODPA) with an aromatic diamine containing phenolphthalein unit in the main chain, 3,3-bis[4-(4-aminophenoxy)phenyl]phthalide (BAPPT), respectively. The derived PI-1 (aODPA-BAPPT) and PI-2 (ODPA-BAPPT) resins showed high numerical average molecular weights (Mn) over 105 g/mol and were easily soluble in polar aprotic solvents, such as N-methyl-2-pyrrolidinone (NMP) and N, N-dimethylacetamide (DMAc). PI-1 and PI-2 UFMs were successfully prepared from the PI solutions in DMAc via the one-step electrospinning procedure. Different rotating speeds of 500–2500 round per minute (rpm) for the cylindrical collector were set to investigate the effects of the fiber morphologies on the properties of the PI UFMs. The derived PI UFMs showed good thermal stability with the glass transition temperatures (Tg) over 280 °C and 5 % weight loss temperatures (T5%) higher than 510 °C in nitrogen. The PI UFMs could be successfully heat-sealed via the hot-press temperature at 320 °C (about 40 °C higher than Tg) for 60s with the pressure of 0.5 MPa.

ZrO2-5CrMnMo composite samples were prepared by hot press sintering. When NiCoCrAlY powders were used as the bonding layer and the different mixtures of NiCoCrAlY alloy and 3YSZ (3mol% yttria stabilized zirconia) ceramic powders were used as the transition layers, the connection between zirconia ceramic and 5CrMnMo steel were strengthened. Three composite samples with different structures were fabricated by heat spraying and hot press sintering. Shear and thermal shock cycle tests were conducted to characterize connection strength and thermal shock resistance of these samples. The shear strength reached 95.69 MPa, and the heating shock cycles achieved to the maximum value of 27.7 times. Microstructures and connection interfaces were analyzed by scanning electron microscopy. The hardness and wearing resistance of 3YSZ coat and 5CrMnMo substrate were compared, and the heat insulation property of composite samples were also discussed. It is shown that these composite materials fabricated in this research are benefited to be used as squeeze casting dies.

Powder byproduct is inevitably produced during spray-forming of 7055 aluminum alloy, greatly reducing the utilization rate of raw materials and increasing production costs. To make such powder byproduct into valuable products, 7055 alloy was prepared by hot-press sintering of powder byproduct in this work. The characteristics of the powder byproduct were studied comprehensively. The microstructure and properties of the as-sintered 7055 alloy were investigated, and the parameters of the hot-press sintering process were optimized using the Taguchi method. The results indicated that the microstructure of the as-sintered alloy was very compact and the grains typically had equiaxed structure, with the main precipitated phase being MgZn2. The tensile strength of the alloy prepared by hot-press sintering with parameters of sintering temperature of 560°C, holding time of 150 min, and pressure of 12 MPa was 287.29 MPa.

(85-x)WC–15 wt%Al2O3–xTiC (x = 0, 1.5, 2.5, 5, 10, and 20 wt%) composites were prepared by vacuum hot-press sintering. The influence of TiC addition on the corrosion behaviour of WC–Al2O3 composites in 0.1 M NaOH solution was revealed. The results suggest that all the samples containing added TiC had the TiC phase and (W, Ti) C solid-solution phase, while the base composite had neither phase. With increasing added TiC content, the average grain size of WC decreased, and the relative density first increased and then decreased. Furthermore, the results suggest that the addition of TiC could noticeably increase the free corrosion potential and impedance and reduce the corrosion current density. However, the composite containing 20 wt% added TiC showed the opposite trend. Therefore, it can be concluded that the corrosion performance of the composites in an alkaline medium can be improved by adding an appropriate amount of TiC. The change in corrosion properties was caused by changes in the solid-solution phase, relative density, and TiO2 oxide film.

The production of magnesium alloys by the powder metallurgy (P/M) method is difficult and troublesome. An alternative production method with easy usability is therefore required, and the properties of new Mg alloys should be examined after production. A type of P/M method (the hot press method) can be applied to produce new Mg alloys with superior properties. In this study, the effect of Al addition and the use of the hot press method on the microstructure and mechanical properties of magnesium alloy were investigated. TZA series magnesium alloys (Mg5Sn4Zn-xAl) were developed, and these alloys were produced in this way for the first time. The paraffin coating technique was applied to prevent the risk of ignition or oxidation of the Mg powders during the mixing process. The experimental results showed that new non-porous Mg alloys with a relative density above 99% were successfully produced using the hot press method. Intermetallic phases were homogeneously distributed at the grain boundaries due to the use of the hot press process. The amount of Mg17Al12 phase in the microstructure increased with the addition of more Al, and this improved the mechanical properties. TZA544 magnesium alloy exhibits mechanical properties that are superior to those of many magnesium alloys in current use.

The drying kinetics of poplar lumber was experimentally investigated as a function of drying temperature (115, 135, 160, 185 and 205°C) during a periodic hot-press-drying process. Poplar lumber was dried under contact (compression ratio of 10%) and high-press states (compression ratio of 44%). Compared with the contact-state, the high-press-state showed higher drying rate and higher efficiency of removing free water than bound water in wood. Eight mathematical models from the literature were established to analyze the drying behavior. The Weibull model, with an average determination coefficient R2 of 0.9958, fitted well for all applied drying conditions. The scale parameter decreased with increasing drying temperature and was lower for high-press-state drying compared with that for contact-state drying. Moisture diffusivity and activation energy were calculated according to the Weibull model. Diffusivity increased with increasing drying temperature, with the average value of 1.734 × 10−6 and 3.313...

A hot-press tackified preform was used to improve the uniformity of the laminates thickness and the mechanical properties of the obtained laminates were studied using vacuum assisted resin transfer molding (VARTM). Two modified preforms were prepared under 0.1 and 0.6 MPa in an autoclave and then were used to fabricate the laminates via VARTM. Permeability and thickness distribution of the laminates were obtained by using a special device. Moreover, the tensile and compressive strengths of the obtained laminates were studied and compared with the unmodified ones. Results show that the tackified laminates present a maximum and minimum thickness under 0.1 and 0.6 MPa, respectively. The thicknesses and in-plane permeability of the tackified laminates, with better thickness uniformity, are significantly decreased compared with that of the unmodified cases, while the tensile and compressive strengths of the tackified laminates are improved obviously. Results show that the mechanical property of the tackified laminates prepared by hotpressing at 0.1 MPa is better than that processed at 0.6 MPa.

Self-assembly of monodisperse colloidal microspheres is a significant approach to construct structural color materials. However, background light interference and point contact among the microspheres result in poor color visibility and mechanical strength. In this work, self-supporting structural color films with excellent stability and flexibility were fabricated using monodispersed polysulfide (PSF) colloidal microspheres with intrinsic light-absorpting characteristic, simultaneously incorporating the polyacrylate (PA) flexible network through interfacial adhesion. More interestingly, multicolor pattern output on standard cotton can be achieved through continuous hot press. Owing to its satisfactory stability and flexibility, the fabric has high resistance to washing and friction, thus ensuring the normal effect in harsh conditions. This study provides a promising solution for the construction of flexible structural color materials to be applied in packaging, decoration, and colorful coating.

Hot press forming (HPF) steel sheets are austenitized, press-formed, and rapidly cooled to obtain a martensitic microstructure with an ultra-high strength. When they are insufficiently austenitized, their microstructures might contain a small amount of untransformed ferrite, which can deteriorate impact toughness as well as strength, but its causes and relevant fracture mechanisms have not been clearly verified yet. In this study, thus, 1.8-GPa-grade HPF sheets were austenitized at various temperature and time, and their tensile and Charpy impact test results were analyzed in relation with untransformed ferrite and its effect on fracture mechanisms. In the HPF sheets containing the untransformed ferrite, voids were formed mostly at ferrite/martensite interfaces, and were grown and propagated linearly to form a cleavage crack, whereas deformation bands were well developed without voids or cracks in the non-ferrite-containing sheets. The highly localized strains accommodated in the soft ferrite made ferrite/martensite interfaces or ferrite itself work as fracture initiation sites, which led to the brittle fracture and consequently to the deterioration of impact energy. This result can provide an important idea for optimization of austenitization conditions demanded for ultra-high strength and excellent impact toughness in HPF applications.

In present research work, a method has been established through powder metallurgical route to produce β-FeSi 2 thermoelectric material without giving long time mechanical alloying treatment to the elemental powders and long duration heat treatment cycle. The elemental powders of iron (98.9% purity, 200 mesh) and silicon (98.5% purity, 400 mesh) have been mechanically alloyed for 6 h using high-energy Attritor ball-mill and was subjected to Hot Press Sintering (HPS). Effect of HPS parameters on density of compacts was studied. The compacts with higher densities (82–92% relative density) were later on subjected to the thermal cycling treatment. The density as well as the amount of β-FeSi 2 phase formation got enhanced due to thermal cycling treatment.

Joining of TiAl to Ti alloy is a potential requirement for manufacturing the components with dual properties. In this paper, the hot-press bonding of Ti-33Al-3V to TC17 was implemented at different pressures and the temperature of 850 °C for 10 min with post bond heat treatment. The influence of pressure on interfacial microstructure evolution and atomic diffusion was analyzed in detail. The microstructure observation and phase composition analysis on the bond indicate that the metallurgical bonding of Ti-33Al-3V/TC17 is produced at pressures of 23–50 MPa, and an interfacial zone with a certain width forms between base alloys. A new α 2 (Ti 3 Al) phase is generated in the interfacial zone. The influence of pressure on the metallurgical bonding of Ti-33Al-3V/TC17 includes two aspects. One is to promote the void shrinkage in the interfacial zone. The quantitative analysis of voids shows an increase in pressure induces a decrease in amount and size of voids. The highest bonding ratio of 96.3% can be obtained at the pressure of 50 MPa with post bond heat treatment. The second is to promote the atomic diffusion across bond line. The diffusion distances of Ti and Al atoms increase with an increase in pressure and the width of the interfacial zone shows a linear increasing law with the pressure. Moreover, a higher pressure induces a higher increment in atomic diffusion distance and width of the interfacial zone in the post bond heat treatment.

A new process of activating sizing film free (removed sizing) carbon fiber (SFF-CF) mats directly with electron beam irradiation (EBI) under oxygen-rich nitrogen gas prior to lamination assembly and hot-press was found to increase bending strength of CFRTP (CF reinforced thermoplastic polypropylene (PP)) interlayered composite composed of 3 SFF-CF mats between 4 PP sheets, [PP]4[SFF-CF]3. The hot-press fabrication was performed under 4.0 MPa at 473 K for 1 min. Experimental results showed optimal condition of 0.22 MGy-EBI under 2,000 ppm-O2-rich, protective N2 atmosphere improved bending strength, σb at all accumulative probabilities, Pf over that of untreated. This could be explained by maximum number of the strong covalent bonds of CF:C:C:PP and oxygen assisted CF:C:O:C:PP bonds adhering bare SFF-CF surface to PP, instead of the weak intermolecular bonding of CF(H2O, N2, O2)PP of untreated. The optimal concentration of O2 molecules together with the EBI probably purified the SFF-CF surface simultaneously generating dangling bonds, which already naturally exist in SFF-CF as evidenced by the highest intensity ESR peak whose inflection point was at B = 323 mT. This, along with attaching O groups to the SFF-CF surface can explain the increased SFF-CF to PP adhesion sites and bending strength increase. Fracture analysis showed the optimum condition prevented ply delamination and reduced damage area along sample length appearing to increase cohesion between the difficult to adhere thermoplastic PP and SFF-CF plies to take on higher loads. Although bending strength was increased, carefulness is always highly recommended when investigating unsized CF composites.

Relaxor ferroelectric PbMg1/3Nb2/3O3-PbTiO3 (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 (er = 4500), piezoelectricity (d33 = 650 pC/N), and electrostrain (SE = 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.

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.