Effect Of Hot-pressing Temperature Research Articles

High-performance CH3NH3PbBr3 Polycrystalline Wafer Prepared by Hot-pressing Method

Considering the drawbacks of the common methods for CH3NH3PbBr3 single crystal growth, such as the complicated and uncontrollable process, a simple hot-pressing (HP) method was introduced to fabricate CH3NH3PbBr3 polycrystalline wafers. The effect of hot-pressing temperature on the crystalline quality and corresponding optical and electrical properties of the CH3NH3PbBr3 polycrystalline wafers was investigated. The hot-pressing temperature for CH3NH3PbBr3 was optimized at 150°C, and the optimized CH3NH3PbBr3 wafer exhibited a low defect density (1.55×1010 cm−3), long carrier lifetime (1734 ns), and high carrier mobility (51.24 cm2V−1s−1) as a photoconductive detector. Furthermore, the detector showed a highly sensitive weak light response under 525 nm LED illumination with an optical power density of 84 nWcm−2, exhibiting a high responsivity of 63 AW−1, EQE of 1.5×104 %, and detectivity of 2.33×1013 Jones, and a fast response speed with a rise time of 17.7 μs and a fall time of 57.4 μs has been achieved.

Effect of hot-pressing temperature on microstructure and the improvement of residual Al on tensile ductility of Ti/Al3Ti heterogeneous structure

Ti/Al3Ti Heterogeneous Structures (HS) with different fractions of residual Al were fabricated at hot-pressing temperatures from 580 °C to 650 °C. The grain boundary distribution and Kernel Average Misorientation (KAM) were characterized by EBSD technique. The varied tensile properties and failure modes were specified, and the local strain evolution was analyzed by DIC. Results show that the distribution of grain boundary, the thickness of individual layers, and mechanical properties were significantly affected by hot-pressing temperature. The elongation of Ti/Al3Ti/Al HS was 64.2%–228.5% higher than that of Ti/Al3Ti HS, which was attributed to stabilized plastic flow and the regulating effect of residual Al. The improvement mechanisms of residual Al on tensile plasticity were found that normal strain was delocalized by promoting strain flow, and shear strain was stabilized by hindering effects. In addition, the tensile strength and work-hardening capability were enhanced by the grain refinement of TC4 layer. The failure mechanism, from HS650 to HS600, is found to transform from brittle fracture determined by normal strain into ductile shearing fracture governed by normal strain and shearing strain. The fracture micromorphology revealed that a mixed model of transgranular and intergranular was presented in the Al3Ti layers. Dimples were distributed in TC4 layers, and tearing ridges were overspread in Al layers. The current views on localized characterizations perhaps provide more complete insights toward the technics-properties design of Ti/Al3Ti HS.

Effect of hot-pressing temperature on characteristics of alkali pretreated reed straw bio-board

We investigated (1) the effects of different hot pressing temperatures on the mechanical properties and dimensional stability of the bio-boards using reed straw as a raw material followed by alkali solution pretreatment and (2) the self-gluing ability of reed fibers using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results showed that the mechanical properties and dimensional stability of the bio-board improved significantly with a rise in hot pressing temperature. The sample with hot pressing temperature of 180 °C has the best performance. After the alkali treatment at hot pressing temperature of 180 °C, the cross section of bio-board became more dense and flat. The IR spectra of the bio-boards showed that the reed fibers generated more functional groups (‒C = O, C‒O‒C, C‒O) following alkali treatments at different hot pressing temperatures. The increase in functional groups (‒C = O, C‒O‒C, C‒O) favored self-gluing of the fibers and improved the performance of the bio-board. Our results demonstrate that bio-boards with high mechanical property and self-gluing ability can be prepared using reed straw at different hot pressing temperatures and alkali solution pretreatment. The hot pressing temperature is an important factor affecting the performance of the bio-board.

Effect of Hot-Pressing Temperature on Characteristics of Straw-Based Binderless Fiberboards with Pulping Effluent.

This study aimed to improve straw-based fiberboard properties without resins by adding pulping effluent as well as to investigate the difference among boards under variable hot-pressing temperatures. The characterization of fiberboards produced from wheat straw under pressing temperatures ranging from 160 to 200 °C was first described. The surface appearance, surface chemistry, thermal transitions, and mechanical performance of the boards were evaluated to investigate the effect of varying hot-pressing temperature. The results indicated that the surface color of boards became darker when the temperature was above 190 °C. Additionally, Fourier transform infrared (FT-IR) measurements showed that more low-molecular constituents and hydrogen bonds were produced under higher pressing temperatures. Furthermore, the physical and mechanical property data were analyzed statistically using one-way analysis of variance (ANOVA) and Tukey’s tests (α = 0.05). The results demonstrated that straw-based fiberboards with effluent under 190 °C exhibited superior strength and water resistance capacities, and showed great potential in commercial decorating and packaging applications.

Effect of hot pressing temperature on dielectric and energy storage properties of Ba0.6Sr0.4TiO3/ poly(vinylidene fluoride) composites

0–3 Ba0.6Sr0.4TiO3 (BST) / poly(vinylidene fluoride) (PVDF) composites were prepared via tape casting and then followed by hot pressing (HP) method. The effect of HP temperature on the microstructure, dielectric properties and energy storage density of the composites were investigated. With the increase of HP temperatures, the dielectric constant increases, whereas the dielectric loss decreases first and then increases. The energy storage density increases first and then decreases. And the composites exhibit a high dielectric tunability (> 85.6 %) and flexibility. Furthermore, the composites display optimal dielectric properties when the HP temperature is 120 °C, the values of dielectric constant and loss are 42.19 and 0.034, respectively. Particularly, compared with the composites formed under HP at room temperature (RT) (1.23 J/cm3) and the pure PVDF matrix (2.8 J/cm3). The values of energy storage density of composites with HP at 120 °C (4.1 J/cm3) has been improved 3.33 times and 1.47 times, respectively. The composites with tunable microstructure and dielectric properties show good potential in supercapacitor and energy storage devices.

Effect of hot-pressing temperature on the properties of aluminum–magnesium spinel optical ceramic

In this paper, we describe the results of research on the effect of the hot-pressing temperature on the spectral properties, density, and microhardness of aluminum–magnesium spinel ceramic. We fabricated experimental samples of a high-density ceramic (density exceeding 99% of the theoretical density) with high transparency over a broad spectral range by using a combination of cold pressing of nanopowders and subsequent hot pressing of the blanks.

Effect of Hot-Pressing Temperature on the Subsequent Enzymatic Saccharification and Fermentation Performance of SPORL Pretreated Forest Biomass

Methods to increase the energy density of biofuel feedstock for shipment are important towards improving supply chain efficiency in upstream processes. Towards this end, densified pretreated lignocellulosic biomass was produced using hot-pressing. The effects of fiber hornification induced by hot-pressing on enzymatic digestibilities of lodgepole pine and poplar NE222 wood chips pretreated by sulfite pretreatment to overcome recalcitrance of lignocelluloses (SPORL) were examined. Pretreated wood chips were pressed at 25, 70, 90, 110, and 177 °C. The cellulose accessibilities of the pressed and unpressed substrates were evaluated using water retention value and direct cellulase adsorption measurements. Hot-pressing below 110 °C produced a degree of hornification (DH) below 0.26 and had limited effect on cellulose accessibility and enzymatic digestibility. Hot-pressing at 177 °C produced a DH of 0.86 that substantially hornified the fibers and resulted near zero saccharification. The saccharification results were consistent with cellulose accessibility data. Ethanol fermentation studies at 18 % solids suggest that a pressing below 110 °C is preferred to reduce its effect on biofuel yield.

Fabrication and mechanical properties of TiB2/ZrO2 functionally graded ceramics

Five layers were considered for the present TiB2/ZrO2 functionally graded ceramics and TiB2/ZrO2 functionally graded ceramics were prepared by hot-pressing. The first layer, marked as L1, was composed of TiB2–15vol%SiC. The L2 layer was composed of TiB2–15vol%SiC–10vol%ZrO2. The L3 layer was composed of TiB2–25vol%ZrO2 without addition of SiC, because 25vol%ZrO2 was enough to densify TiB2. The last two layers, L4 and L5, were composed of TiB2–35vol%ZrO2 and TiB2–45vol%ZrO2, respectively. Denser graded microstructures as well as the stronger interfaces were achieved for TiB2/ZrO2 functionally graded ceramics hot-pressed at 1900°C. Due to the phase transformation of ZrO2, the toughness of TiB2/ZrO2 functionally graded ceramics increased from ~4.3MPam1/2 for the TiB2-rich layer to ~8.9MPam1/2 for the ZrO2-rich layer. The effect of hot-pressing temperature on the toughness of TiB2/ZrO2 functionally graded ceramics was further investigated in detail.

Phase composition and properties of hot-pressed AlN–BN materials

The effect of hot-pressing temperature on the phase composition and properties of AlN–BN materials with addition of Y2O3 or SiC is studied. The composites have higher density and mechanical strength than the hot-pressed AlN–BN material without additions and retain its good insulating properties, thermal and chemical resistance, and adequate machinability.

Microstructure and Magnetic Properties of Hot-Pressed and Hot-Deformed Composite Magnets Produced by Spark Plasma Sintering Method

Bulk isotropic and anisotropic Nd13.5Fe80.4Ga0.5B5.6 and Nd13.5Fe80.4Ga0.5B5.6/Fe magnets were synthesized by applying spark plasma sintering (SPS) technique. The effect of hot-pressing temperature on the magnetic properties of hot-pressed (HP) and hot-deformed (HD) magnets without additive and with 5% Fe addition was investigated. With increasing sintering temperature for HP magnets, the grain grew gradually. For HD magnets, the optimal magnetic properties could be obtained at hot-pressing temperature 680°C due to the development of desired c-axis texture and uniform microstructure, which resulted from the appropriate and uniform grain size in HP magnets. Fe addition could enhance remanence (Br) and magnetic energy products ((BH)m) of HP and HD magnets. However, the maximum magnetic energy product of HD magnets decreased when hot-pressing temperature was higher than 650°C.

Effect of hot-pressing temperature on the phase formation and properties of boron carbonitride composite

The dependence of the phase composition and properties of a boron carbonitride (BCN) composite on hot-pressing temperature is studied. It is established that the composite forms with the synthesis of new reinforcing phases in reaction sintering under pressure. The optimum conditions to obtain the BCN composite are determined. The BCN composite has high thermal strength, oxidation resistance, and electrical insulating properties.

SiCf/SiC composites reinforced by randomly oriented chopped fibers prepared by semi-solid mechanical stirring method and hot pressing

SiC short fibers, with an average diameter of 13 μm, length of 300–1,000 μm and chopped from SiC continuous fibers, were surface modified by the semi-solid mechanical stirring method to produce a discrete coating of aluminum particles. Then the starting mixtures, which consist of SiC short composite fibers, aluminum powder less than 50 μm and α-SiC powder of an average diameter of 0.6 μm, were mechanically mixed in ethanol for about 3 h, dried at 80 °C in air, and hot pressed under 30 MPa pressure at 1,650, 1,750 and 1,850 °C with 1 h holding time to prepare SiCf/SiC composites. Volume fraction of SiC short fibers in the starting powder for SiCf/SiC composites was about 25 vol.%. The composites were characterized in terms of bulk density, phase composition, and mechanical properties at room temperature. In addition, the distribution of SiC short fibers in the matrix and the cracking pattern in the composites were examined by optical microscope. Fracture surface of the composites were performed by a scanning electron microscope (SEM). The effect of hot-pressing temperature on bulk density and mechanical properties was investigated. The results indicated that SiC short fibers were uniformly and randomly distributed in the matrix, bending strength and bulk density of the composites increased with increasing sintering temperature. The composite, hot-pressed at 1,850 °C, exhibited the maximum bulk density and bending strength at room temperature, about 3.01 g/cm3 and 366 MPa, respectively. SEM analyses showed that there were a few of fiber pullout on the fracture surface of samples sintered at 1,650 °C and 1,750 °C, which was mainly attributed to lower densities. But few of fiber pullout was observed on the fracture surface of sample sintered at 1,850 °C, the combined effects of high temperature and a long sintering time were considered as a source of too severe fiber degradation because of the large amount of oxygen in the fibers.

Effect of Hot‐Pressing Temperature on Densification and Mechanical Properties of Titanium Diboride with Silicon Nitride as a Sintering Aid

The effect of hot‐pressing temperature on the densification behavior and mechanical properties of titanium diboride (TiB2) was investigated. TiB2 specimens were hot‐pressed for 1 h at temperatures in the range of 1500°–1800°C, with an addition of 2.5 wt% of silicon nitride (Si3N4) as a sintering aid. The density increased markedly at temperatures in the range of 1500°–1600°C and remained constant thereafter. The formation of a eutectic liquid at 1550°C was attributed to the steep increase in density. The hot‐pressing temperature also improved the mechanical properties, such as the flexural strength, Vickers hardness, and fracture toughness of the specimens. Similar to the density, the mechanical properties improved remarkably at ∼1550°C, so that optimum properties were obtainable at temperatures as low as 1600°C.

Effect of hot-pressing temperature on the optical transmission of zinc sulfide

Two phase mixtures of ZnS consisting of the hexagonal and the cubic phase have been prepared by hot-pressing at different temperatures. The optical properties of these two phase composites were measured in the far infrared. The difference in the index of refraction between the cubic and the hexagonal phases produced scattering that was accentuated at large grain size. The results are correlated with the fourth power dependence of the scattering cross section on the grain size.

The effect of hot-pressing temperature on the tensile strength of B4C coated boron fiber reinforced Al composites.

For the purpose of investigating the effect of interfacial bonding between a fiber and a matrix on the tensile strength of FRM, several B4C coated boron fiber reinforced Al composites were prepared by controlling the hot-pressing temperature. The tensile-test showed that the composites prepared at 550°C exihibited a higher strength than the composites prepared at 500°C and 600°C. The fracture surfaces were changed from a rugged face like a bundle break to a flat face with an increase in the temperature. It was seen from SEM that the interfacial bonding became stronger. So, the transition in the composites' strength was considered as follows ; As the hot-pressing temperature rises, the critical fiber length, a factor determining a fiber's strength in a matrix, becomes gradually shorter, but the stress concentration factor to the adjacent fibers caused by a fiber fracture also becomes larger. Therefore, the higher strength of the composites results in the case that these two factors are properly overlapped. Such a transition of the composites' strength was additionally supported by Batdorf's theory.

ChemInform Abstract: MICROSTRUCTURAL OBSERVATIONS ON HOT‐PRESSED SI3N4

AbstractDie Entwicklung des Gefüges in heißgepreßtem Si3N4 wird an einem typischen Si3N4‐Pulver mit und ohne BeSiN2 als Verdichtungshilfe untersucht.

Effect of Hot-pressing Temperature on Sintering and Graphitization of Coke with B2O3 Addition

Effect of hot-pressing temperature was investigated on some properties of polycrystalline coke compacts made from calcined pitch coke powder with 10% B2O3 addition at various temperatures from 1200 to 2200°C under a pressure of 200kg/cm2.Bulk density was almost constant as 1.6g/cm3 up to 1800°C, and increased rapidly to about 2.0 g/cc above 2000°C.Mechanical strength once decreased at temperature range from 1600 to 1800°C, and it increased again above 2000°C.Graphitization proceeded remarkably above 2000°C.B4C was formed at 1600°C and amount of B4C decreased with increase of temperature.The hot-pressed compacts could be classified into three types.The first is the one made below 1400°C in which coke particles adhered each other with B203 glass phase, the second is the one made between 1600 and 1800°C which consist of the mixture of coke particle and small amount of B4C exist independently, and the last is the one made above 2000°C of which boron is considered to give strong influence for sintering and graphitization of coke by its diffusion into coke structure.