Synthesis of Scandium Nitride Crystals from Indium–Scandium Melts

The synthesis of scandium nitride (ScN) nanoscale crystals by dissolving N₂ into In‐Sc melts is demonstrated for the first time. The crystallization mechanism of ScN from In‐Sc melts is investigated. In the N₂ pressure of 0.3 MPa, the ScN yield increases with the Sc concentration in flux and the growth temperature within the range 900–1100°C, achieving a maximum value of about 70% at temperatures above 1100°C. Scanning electron microscopy evidences the growth of round‐shaped ScN crystals with increasing average size from 48 to 860 nm in the temperature range of 900–1300°C. This study shows that Sc effectively promotes the dissolution of N₂ in the In‐Sc melt, and In‐Sc is a promising flux for the synthesis of ScN nanocrystals.     

Preparation of high density ZnO ceramics by the Cold Sintering Process

High-density ZnO ceramics were prepared by a Two-Step Cold Sintering Process (TS-CSP) at an ultralow-temperature. The densification process of ZnO ceramics was demonstrated by TS-CSP. And the density, microstructure and electrical properties of the ZnO ceramics were investigated. The results indicate that most of the crystallization of ZnO ceramic can be completed in the first step of sintered at 150 °C/200 MPa for 30 min, with a relative density approaching 97.36%. This relative density was further improved to 99.43% after the second sintering step was deployed at 200 °C/200 MPa for 30 min, which displayed an average grains size of 1.5 μm and resistivity of 0.125 Ω cm. This work demonstrated an effective method to reduce CSP temperature and pressure in the production of high-performance ZnO ceramics.     

Y3Al5O12-α-Al2O3 composites with fine-grained microstructure by hot pressing of Al2O3-Y2O3 glass microspheres

Yttrium aluminate glass microspheres with the eutectic composition 76.8 mol. % Al₂O₃ and 23.2 mol. % Y₂O₃ were prepared by combining the sol-gel Pechini method with flame synthesis. The sol-gel method was applied to achieve the desired composition homogeneity of the prepared glass and hence, improve the microstructure homogeneity and mechanical properties of bulk polycrystalline materials. The latter were prepared by hot pressing, more specifically pressure assisted sintering, at 1050 °C, 1300 °C and 1600 °C using pressures of 30 MPa and 80 MPa and holding times between 0 and 30 min. This also led to the crystallization of the glass. A composite with the Vickers hardness 18.0 ± 0.7 GPa and an indentation fracture toughness 4.9 ± 0.3 MPa.m^1/2 was obtained by sintering at 1600 °C, at the pressure of 80 MPa and with 30 min isothermal heating at the maximum temperature. Improved mechanical properties were observed when increasing the temperature of sintering and the holding time. This can be attributed to the formation of a unique microstructure consisting of α-Al₂O₃ grains in the μm-scale embedded in a YAG (yttrium-aluminium garnet) matrix in the hot-pressed samples.     

Crystalline structure and morphology of poly(L‐lactide) formed under high pressure

The poly(l ‐lactide) (PLLA) samples were prepared by the annealing under 100 MPa at 75–145^°C and 200 MPa at 105–145^°C for 6 h, respectively. The crystalline structures, thermal properties and morphology were investigated using differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), and scanning electron microscopy (SEM). On the basis of the DSC and WAXD results, it can be seen that the α′ form was formed by the annealing under 100 MPa at 85–95°C but not found under 200 MPa at 105–145°C. A phase diagram of PLLA crystal form under high pressure was constructed under the given experimental conditions, which displayed the α′ form was formed at limited temperature and pressure range. Besides, SEM suggested that the PLLA samples annealed under 100 MPa crystallize to form lamellar‐like crystals due to the low growth rate and the confined crystallization behavior under high pressure. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40637.     

In-situ synthesis and densification of boron carbide and boron carbide-graphene nanoplatelet composite by reactive spark plasma sintering

Simultaneous synthesis and densification of boron carbide and boron carbide- graphene nano platelets (GNP) were carried out by reactive spark plasma sintering of amorphous boron and graphene nano platelets at temperature ranging from 1200 to 1600?°C, pressure of 50?MPa and heating rate of 50?°C/min and 100?°C/min. X-ray diffraction and Raman spectroscopy confirmed the formation of required phases. Electron microscopic images revealed the formation of sub-micron and nano sized grains of plate like morphology. Sintered product with high relative density of 96%TD was achieved at a temperature of 1600?°C and heating rate of 50?°C/min for B₄C stoichiometric composition and also exhibited maximum hardness of 21.10?GPa.     

Magnetic properties of magnetite-based nano-glass-ceramics obtained from a Fe-rich scale and borosilicate glass wastes

Magnetite-based glass-ceramic is a special composite material composed by magnetic nanocrystals embedded in a vitreous matrix. In this work, it was developed magnetic glass-ceramics based on borosilicate glass wastes and, for the first time, by using iron-rich scale (a waste from the metallurgical industry). Different compositions were established with increasing scale contents (20, 30, 45?wt%). Raw materials were melted (1550?°C/4?h) and later cast in a preheated steel mold at 400?°C. Then, the obtained samples were heat-treated at 700?°C/ 30?min. The sample with 45?wt% scale also was heated at 800?°C and 900?°C/ 30?min, in order to promote more crystallization. The obtained glass-ceramics properties were investigated using X-ray diffraction (XRD), Raman spectroscopy, vibrating-sample magnetometer (VSM), Mössbauer spectroscopy and transmission electron microscopy (TEM). Magnetite nanocrystals (average size in the 40–64?nm range) in the glass-ceramics were evidenced by TEM images and Mössbauer spectrum. VSM analysis revealed that the obtained ferrimagnetic glass–ceramic with composition of 45?wt% scale annealed at 800?°C/ 30?min, improved the magnetic saturation (Ms), reaching 42?emu/g. Results indicated a great potential of this magnetic-based glass-ceramics for being applied in many applications, such as the biomedical engineering field, in magnetic devices, magnetic resonance imaging contrast agents, hyperthermia, waste sorbent, and microwave devices.     

Continuous synthesis of tetraalkylammonium-Based ethyl sulphate ionic liquid and its kinetic study in microreactors

A tetraalkylammonium-based ionic liquid (IL) was synthesized with diethyl sulphate and triethylamine in a capillary microreactor. Solvent-free conditions coupled with microreactor technology greatly simplified the IL construction process. Optimization of process parameters (e.g., temperature, residence time, and inner diameter of capillary) was performed, and the maximum yield was 94% with the residence time of 300 s at 90°C. Interestingly, the obtained product could exist as a molten salt with low viscosity at a low melting point of 24.1°C. Key dimensionless groups such as Pe, Bo, and DaII numbers were calculated to account for the mass transport phenomena and reaction performance in this IL synthesis or to validate the reliability of the corresponding reaction kinetics study. Based on fast heat and mass transfer rates provided by the microreactor, intrinsic reaction kinetics could be obtained. Moreover, gold (III) extraction was remarkably improved by the application of the synthesized IL. © 2018 American Institute of Chemical Engineers AIChE J, 65: 1245–1255, 2019     

Effects of molding temperature and pressure on properties of soy protein polymers

Because of the worldwide environmental pollution problem with petroleum polymers, soy protein polymers have been considered as alternatives for biodegradable plastics. The objective of this research was to study the curing behavior of soy protein isolates (SPIs) for that application. The molding variables of temperature, pressure, and time and curing quality factors of tensile strength, strain, and water resistance were evaluated. The maximum stress of 42.9 MPa and maximum strain of 4.61% of the specimen were obtained when SPI was molded at 150°C and 20 MPa for 5 min. The water absorption of the specimen decreased as molding temperature and time increased. Glycerol greatly improved the flexibility of the specimen but decreased its strength. For SPI with 25% glycerol added, the maximum stress and strain of about 12 MPa and 140%, respectively, were achieved when the specimen was molded at 140°C for 5 min. Molding temperature, pressure, and time are major parameters influencing the curing quality of soy protein polymers. At fixed pressure, the molding temperature and time had significant interactive effects on curing quality. At high temperature (e.g., at 150°C) it took about 3 min to reach optimum curing quality; however, at low temperature (120°C) it took about 10 min to reach optimum curing quality. The maximum strength and strain of the cured protein polymer occurred at the molding temperature close to its phase transition temperature or about 40°C below its exothermic temperature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2595–2602, 1999     

Aging of polypropylene using high oxygen pressure: Influence of sample thickness and stabilization

Thin films (0.05–0.08 mm thick) of stabilized and unstabilized polypropylene were aged under 4.24 MPa (614 psi) of oxygen at 90°C. The oxidation of these films was monitored using transmission infrared spectroscopy. Previously it was shown that embrittlement for the thin unstabilized polypropylene films occurred 3.6 times faster in 4.24 MPa of oxygen than in air at atmospheric pressure. For thick stabilized polypropylene (3.18 mm thick), the oxidative induction time at 120°C and 4.24 MPa of oxygen was drastically reduced compared with conventional air aging at this temperature. Specifically, sample embrittlement occured in 1 week during the high oxygen pressure aging in stark contrast to 70 weeks for conventional air aging. Consequently, due to the shortening of time to age samples at high oxygen pressures, aging can be conducted at this lower temperature (nearer the service temperature) rather than at this commonly used aging temperature of 150°C.     

Continuous synthesis of palladium nanorods in oxidative segmented flow

Laminar and segmented flow methods are presented for producing Pd rod‐shaped nanostructures from Na₂PdCl₄ in mixtures of water, ethylene glycol, polyvinyl pyrrolidone, and KBr. Synthesis in laminar flow produced an evolution from Pd nanoparticles to short nanorods with residence time. Use of air as the segmentation gas tuned the oxidative environment promoting anisotropic growth of Pd. Moreover, the elevated temperatures (160°C and 190°C) and pressure (0.8 MPa) reduced the synthesis time from hours for most batch systems to 2 min. The ratio of polyol and Pd precursor metal flow streams controlled the anisotropic growth, obtaining nanorods with a diameter approximately 4 nm and an aspect ratio up to 6. Nanorods were single crystal with the {100} lattice spacing of fcc structure, and without any dislocation, stacking fault, or twin defects. The resulting Pd nanorods had high activity at moderate temperature (40ºC) and pressure (0.2 MPa) in the catalytic hydrogenation of styrene. © 2015 American Institute of Chemical Engineers AIChE J, 62: 373–380, 2016     

Supercritical fluid extraction and chromatography of emulsifiers

Selected emulsifiers, which included acetylated monoglycerides, lactylated monoglycerides, hexaglycerol distearate, triglycerol mono/dioleate and decaglycerol decaoleate, were separated with capillary supercritical fluid chromatography on a 25% cyanopropyl stationary phase with a mobile phase of CO₂ at 100–150°C. In general, the density/pressure programs that produced the best separations were those with reduced pressure/density ramp rates, which encompassed the largest possible pressure or density range. Samples of acetylated monoglycerides were placed in a supercritical fluid extraction cell on a glass bead bed and extracted for 15 min at 50°C at 340, 408, 544 and 680 atm with CO₂. At 544 atm, 103.6 ± 1.0% of the emulsifiers was extracted. Acetylated monoglycerides were added during twin-screw extrusion of cornstarch (3% w/w emulsifier/corn starch). The acetylated monoglycerides were extracted from the cornstarch extrudate for 15 and 45 min, at 544 and 646 atm and 50–120°C with 0 and 5% added methanol. The percent acetylated monoglyceride extracted after 45 min at 120°C and 646 atm was 60.0 ± 5.7%, while the amount extracted during a 7.5-h Soxtec extraction ranged from 17.9 to 29.4%, depending upon the solvent used.     

Influence of Film Casting Condition and Thermal Treatment on Order Structure of Polyurethane Block Copolymer

An attempt has been made to investigate the influence of film casting temperature and thermal ageing on order structure formation of segmented polyurethane (SPU) block copolymer. For this purpose films were casted at three different temperature of 60, 80, or 100°C and thermal aged at 100, 120, 130, or 150°C. The structure of films were investigated by Fourier-transform infrared (FT-IR), wide angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). Film casted at slow solvent evaporation has more regular structure than the film casted at rapid solvent evaporation. Crystaline structure decreases with increase in casting temperature due to chain entanglement, which makes crystallization process tougher. The effect of ageing temperature on crystalline structure formation remains unclear. Decrease of ordered structure was observed when the samples were heat treated at 100 or 120°C, however, slight increase of ordered structures were observed for the samples heat treated at 130 or 150°C. Therefore, the influence of thermal ageing has been explained in terms of order-disorder temperature of block copolymer.     

Continuous synthesis of 1-ethoxy-2,3-difluoro-4-iodo-benzene in a microreactor system and the Gaussian and computational fluid dynamics simulations

A microreactor system consisting of membrane-dispersion tube-in-tube microreactors and delay loops was developed for the continuous synthesis of 1-ethoxy-2,3-difluoro-4-iodo-benzene. Because of the high mass and heat transfer in the microreactor system, ortho- and halogen-lithiation could be performed at −40 and −20°C, respectively, which are much higher than the temperature required (−70°C) for the batch reaction. In stirred tanks, the yield of 1-ethoxy-2,3-difluoro-4-iodo-benzene reaches 91.0% in 70 min. Nearly the same yield of 91.3% was achieved within a shorter time of 16 min in the microreactor system. Furthermore, the kinetics of ortho-lithiation calculated by the Gaussian software, were used for the computational fluid dynamics (CFD) simulations of the reaction process in another microreactor system. Thus, a Gaussian-CFD-coupled-method for efficiently predicting reaction kinetics and yield without experiments could be established. The predicted yield reached 88.7% at 1000 s, which is comparable with the experimental yield of 90.1% at 960 s.     

Polymer‐Derived SiC/B4C/C Nanocomposites: Structural Evolution and Crystallization Behavior

Structural evolution and crystallization behavior between 600°C and 1450°C during the preparation of bulk SiC/B₄C/C nanocomposites by the pyrolysis of CB‐PSA preceramic were investigated. The CB‐PSA preceramic converts into carbon‐rich Si–B–C ceramics up to 800°C. Structural evolution and crystallization of Si–B–C materials could be controlled by adjusting the pyrolytic temperature. The Si–B–C ceramics are amorphous between 800°C and 1000°C. Phase separation and crystallization begin at 1100°C. The crystallization of β‐SiC takes place at 1100°C and B₄C nanocrystallites generate at 1300°C. The sizes of β‐SiC and B₄C nanocrystals increase with the pyrolytic temperature rising. In addition, the boron‐doping effect on structural evolution was studied by comparing the crystallization and graphitization behavior of Si–B–C ceramics and the corresponding Si–C materials. Boron is helpful for the growth of β‐SiC nanocrystals and the graphitization, but harmful for the nucleation of β‐SiC crystallites.     

Preparation of Tubular Silicalite Membranes by Hydrothermal Synthesis with Electrophoretic Deposition as a Seeding Technique

Preparation of tubular silicalite membranes by hydrothermal synthesis with electrophoretic deposition (EPD) as a seeding technique was investigated. Two micrometers of small silicalite seeds were produced by an open-system hydrothermal synthesis at 100°C. These seeds were dispersed in 1-propanol and seeded on porous tubular stainless-steel supports by EPD; it had a high productivity and uniformity. The seeded support was then hydrothermally treated, and a tubular silicalite membrane was obtained. The pervaporation performance of this membrane showed a separation factor α of 70 with a total flux of 0.35 kg·(m²·h)⁻¹ for a 5 vol% EtOH aqueous solution at 30°C.     

Crystallinity of isothermally and nonisothermally crystallized poly(ether ether ketone) composites

PEEK/carbon fiber composites were prepared by a modified diaphragm forming machine under vacuum. The study of the degree of crystallinity versus the differential scanning calorimetry (DSC) heating rate indicated that 50°C/min was an optimal heating rate to suppress the reorganization of the specimens crystallized between 315°C and 255°C and to avoid superheating the specimens. A high volume of fibers constrained the spherulitic growth by an impingement mechanism, which depressed the crystallization rate and reduced the crystallinity. Thus the crystallization was still in process even after 240 min annealing at 300°C. The effect of the cooling rate on the degree of crystallinity was simulated and investigated in DSC at a heating rate of 50°C/min. The results indicated that the cooling rates ranging from 1°C/min to 100°C/min could be divided into five regions that were associated with a high volume of fiber and the crystallization regime. A Time-Temperature-Transformation diagram superposed on the Continuous-Cooling-Transformation curves allows us to predict the amount of crystallization in different regimes. The data points for the DSC method deviated from the prediction at the cooling rates above 60°C/min because of the recrystallization during DSC heating scans.     

Effect of pressure on TiO2 crystallization kinetics using in‐situ high‐temperature synchrotron radiation diffraction

The phase transformation behavior of TiO₂ sol‐gel synthesized nanopowder heated in a sealed quartz capillary from room temperature to 800°C was studied using in‐situ synchrotron radiation diffraction (SRD). Sealing of the capillary resulted in an increase in capillary gas pressure with temperature. The pressures inside the sealed capillary were calculated using Gay‐Lussac's Law, and they reached 0.36 MPa at 800°C. The as‐synthesized material was entirely amorphous at room temperature, with crystalline anatase first appearing by 200°C (24 wt% absolute), then increasing rapidly in concentration to 89 wt% by 300°C and then increasing more slowly to 97 wt% by 800°C, with there being no indication of the anatase‐to‐rutile transformation up to 800°C. The best estimate of activation energy for the amorphous‐to‐anatase transformation from the SRD data was 10(2) kJ/mol, which is much lower than that observed when heating the material under atmospheric pressure in a laboratory XRD experiment, 38(5) kJ/mol. For the experiment under atmospheric pressure, the anatase crystallization temperature was delayed by ~200°C, first appearing after heating the sample to 400°C, after which crystalline rutile was first observed after heating to 600°C. The estimated activation energy for the anatase‐to‐rutile transformation was 120(18) kJ/mol, which agrees with estimates for titania nanofibers heated under atmospheric pressure. Thus, heating the nanopowders material under pressure promoted the amorphous‐to‐anatase transformation, but retarded the anatase‐to‐rutile transformation. This behavior is believed to occur in an oxygen‐rich environment and interstitial titanium is also expected to form when the material is heated under high gas pressure. This suggests that atmospheric oxygen appears to accelerate the amorphous‐to‐anatase transformation, whereas interstitial titanium inhibits TiO₂ structure relaxation, which is required for the anatase‐to‐rutile transformation.     

On the effects of LiF on the synthesis and reactive sintering of gahnite (ZnAl2O4)

The effects of LiF on the synthesis and reactive sintering of polycrystalline gahnite (zinc aluminate spinel, ZnAl₂O₄) were studied using XRD, high-temperature simultaneous thermal analysis and a spark plasma sintering (SPS) apparatus. It was demonstrated that the LiF reduces the onset of synthesis by about 200 °C and plays an important role in the densification process. SPS consolidation of a LiF-doped ZnO-Al₂O₃ mixture under an applied pressure of 150 MPa and at a sintering temperature of 1100 °C for 20 min generated fully dense gahnite with adequate transparency and mechanical properties.     

Liquefaction of sawdust for liquid fuel

Pressurized liquefaction of sawdust was carried out in an autoclave in the presence of solvent under cold hydrogen pressure ranging from 2.0 to 5.5 MPa at the temperature range of 150C–450°C. The reaction time varied from 5 to 30 min. Investigations were made on the effects of temperature, reaction time, cold hydrogen pressure and solvent on the liquefaction process. Results indicate that liquefaction of sawdust can start at a temperature of 200°C, much lower than that for coal in a hydrogen-donor solvent, e.g., tetralin which was used in this run of experiment. Oil yield increase with the rise either in temperature and in cold hydrogen pressure or with the longer reaction time.     

Precise measurement of the PVT of polypropylene and polycarbonate up to 330°C and 200 MPa

An apparatus for measuring the pressure—volume—temperature (PVT) properties of polymers using a metal bellows has been developed at temperatures from 313 to 623 K and pressures up to 200 MPa. A calibration of the device was performed by measuring PVT of mercury and water. The experimental uncertainty of specific volumes was estimated to be within ±0.2%, while that of temperatures was within ±0.1 K below 300°C and ±0.3 K above 300°C. The estimated uncertainty of pressures was ±0.1 MPa below 100 MPa and ±0.25 MPa above 100 MPa. The PVT properties of polypropylene and polycarbonate were measured by the apparatus in the temperature ranges from 40 to 300°C and from 40 to 330°C, respectively, and pressures from 10 to 200 MPa. The effects of a sample cup and sample forms were investigated. The use of the sample cup showed a little effect on the measurments of PVT properties for both samples. The shape (pellet and pillar) of the samples caused a small difference in the specific volumes only under high temperatures and low pressures. The PVT properties in a melt state were correlated by the Simha-Somcynsky equation of state, showing a good agreement with measurements. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 141–150, 1997