High-pressure High-temperature Treatment Research Articles

Reduction of Furan Formation by High-Pressure High-Temperature Treatment of Individual Vegetable Purées

The present study addressed the need for furan mitigation measures at the level of food production, where the effects of extrinsic (process-related) and intrinsic (product-related) properties on furan formation in vegetable-based systems were investigated. For the first time in the literature, the effect of high-pressure high-temperature (HPHT) processing on the formation of furan was demonstrated. HPHT processing was proven to be an interesting alternative for furan reduction in vegetable-based systems, when aiming for sterilization intensities. Following HPHT treatment, the furan concentrations of a wide range of individual vegetable purées dropped to levels close to the analytical limits (1–2 ng/g purée). A higher processing cost might limit the use of HPHT processing to high-value added products, which means that for many other conduction-heated food products, conventional heating would remain the standard technology. As a first step towards control of furan formation in the latter products, a mixed model regression was used to identify the major precursors in vegetable-based systems. Significant correlations were observed for vitamin C and sugars, which were attributed to the efficiency of the conversion and high concentrations, respectively. Next to furan, the HPHT- and thermally treated purées were analyzed for 2- and 3-methylfuran, which are likely to undergo the same metabolic fate as furan. For most of the vegetables tested, the total amount of methylfuran found in the thermally treated purées could not be ignored. Similarly to furan, there was a clear reduction in the concentrations found in the HPHT-treated purées.

Effects of High Pressure/High Temperature Processing on the Recovery and Characteristics of Porcine Placenta Hydrolysates

This study was performed to investigate the effects of high pressure/high temperature (HPHT) treatment on the recovery efficiency and characteristics of porcine placenta hydrolysates. The placenta hydrolysates were characterized by solubility, free amino acid contents, gel electrophoresis, gel permeation chromatography (GPC) and amino acid composition. Placenta was treated at 37.5 MPa of pressure combined with various temperatures (150, 170, and <TEX>$200^{\circ}C$</TEX>) or various holding times (0, 30, and 60 min at <TEX>$170^{\circ}C$</TEX>). Insoluble raw placenta collagen was partially solubilized (> 60% solubility) by the HPHT treatment. Free amino group content of placenta collagen was increased from 0.1 mM/g collagen to > 0.3 mM/g collagen after HPHT treatment, reflecting partial hydrolysis of collagen. The molecular weight (<TEX>$M_w$</TEX>) distribution showed evidence of collagen hydrolysis by shifting of <TEX>$M_w$</TEX> peaks toward low molecular weight when treated temperature or holding time was increased. Alanine (Ala), glycine (Gly), hydroxyproline (Hyp), and proline (Pro) contents increased after the HPHT treatments compared to a decrease in the others. In particular, the increase in Gly was obvious, followed by Hyp and Pro, reflecting that placenta hydrolysates were mainly composed of these amino acids. However, increasing temperature or holding time hardly affected the amino acid compositions. These results indicate that the HPHT treatment is advantageous to hydrolyze collagen derived from animal by-products.

Investigation of New Routes for the Synthesis of Mn4Si7

In this work, we investigated two different ways to synthesize the higher manganese silicide (HMS) Mn4Si7. In the first approach, a bulk material was subjected to a heating treatment at 773 K (500 °C) under high pressure (5 GPa) in a multianvil system, whereas in the second one, thin manganese layers deposited onto silicon substrate (Mn/Si) underwent a rapid thermal annealing at different temperatures under vacuum. The guiding principle of these investigations was to study HMS materials in a constrained environment. The atomic composition of the bulk system we studied was Mn35Si65. At room temperature and atmospheric pressure, the sample was made of two phases, namely Mn27Si47 and pure silicon, the latter one being in small quantity. X-ray diffraction measurements performed on this sample after high-temperature—high-pressure treatment evidenced a complete transformation of Mn27Si47 into Mn4Si7. Rapid thermal annealing performed on Mn/Si systems also led to the formation of Mn4Si7.

A Study of the relationship between brown colour and extended defects in diamond using core-loss electron energy loss spectroscopy

There is strong evidence to support the theory that the vacancy cluster, a by-product of dislocation interaction, is the extended defect responsible for brown colour in natural type IIa diamonds. A characteristic of these open volume structures is the hybridised sp2 bonding of the 3-fold coordinated carbon atoms that line their cage-like surfaces. When present in sufficiently large concentrations the sp2 bonds alter the electronic and optical properties of type IIa diamond dramatically. Similar sp2 bond concentrations are found in dark brown CVD diamond, although the defects in this material appear much larger in size than in the natural diamond. In this study we employ core-loss electron energy loss spectroscopy (EELS) and aberration corrected scanning transmission electron microscopy (AC-STEM) to compare the relative sp2 content of brown coloured natural type IIa diamonds and dark brown CVD diamonds, using 100% sp2 bonded graphite as a reference. The effect of high-pressure high-temperature (HPHT) treatment on sp2 content is also investigated.

Structure and properties of superelastic hard carbon phase created in fullerene-metal composites by high temperature-high pressure treatment

Treatment of a fullerene soot extract and metal (Co) powder mixture under pressure of 5 and 8 GPa at 1000 °C leads to the transformation of fullerites into superelastic hard phase (SHP) and to simultaneous sintering of the powder mixture to nonporous composite material reinforced by the SHP particles. The structure of the SHP particles reveals a topological relation to the initial fullerite crystal morphology. Upon indentation, the SHP particles demonstrate an elastic recovery of up to 96%. The universal microhardness of the SHP particles HU = 26 GPa, and their microhardness HV = 35 GPa. A high ratio between the microhardness and elastic modulus (HV/E = 0.19-0.21) of the SHP particles makes them perspective candidates for design of materials with superior wear resistance and tribological properties.

고온고압법에 의한 Type II, Type I aB 갈색 다이아몬드의 색향상

It is possible to enhance the color of the natural diamond with a high pressure high temperature(HPHT) process. We employed a pyrophyllite tube cell and cubic press apparatus for HPHT treatment on the brown colored Type Ⅱ (5.6 ㎬/ 1700℃/ 52 min), and Type Ⅰ aB(5.6 ㎬/ 1650℃/ 30 min) diamond samples. We investigated the microstructure, Types, fluorescence, properties of the diamonds with an optical microscopy, FT-IR, photoluminescence(PL) spectroscopy, Diamond-View, and micro-Raman spectroscopy. Two tinted brown diamonds changed into colorless just after the HPHT process. Optical microscopy showed that no crack and significant inclusion evolution occurred during the HPHT process except the small graphite spot appeared in Type Ⅰ aB sample. FTIR spectrum confirmed that no Type, amber center, and platelet defect change with the HPHT treatment. Diamond-View could not distinguish the HPHT treated diamonds from the naturals. PL spectroscopy showed that N3 and H3 color centers remained even after HPHT process. Consequently, we successfully changed the color of diamonds into colorless by 5.6 ㎬ HPHT process.

XPS Characterization Onion-Like Carbon from Nanodiamonds and Carbon Structure from Onion-Like Carbon after High-Pressure High-Temperature Treatment

In this work, we report the results of X-ray photoelectron spectroscopy research into the relative concentrations of sp3 and sp2 hybridization type atoms in onion-like carbon (ONC) specimens and in structures synthesized by high pressure and high temperature treatment (HPHT structures). The experimental method was based on the analysis of C1s core line and plasmon loss spectra. ONC specimen graphitization degree was analyzed as a function of treatment temperature for the 1000–1600°C range. Reverse processes, that is, sp3 bond formation, were observed in HPHT structures at 7.7 and 15 GPa and 500–1500°C.

A MWCNT/Polyisoprene Composite Reinforced by an Effective Load Transfer Reflected in the Extent of Polymer Coating

Tensile and microstructural properties of multiwall carbon nanotube (MWCNT)/polyisoprene (PI) composites have been investigated after cross-linking achieved purely by simultaneous high-pressure high-temperature treatment. The method enables gradual increase of the cross-link density without interference of vulcanization chemicals, and the results suggest a link between an interfacial PI layer wrapped/coated on the MWCNTs and reinforcement in carbon nanotube (CNT)/PI composites. The interfacial layer, which is augmented by high-pressure treatment, was detected indirectly in swelling experiments and also reflected in results of atomic force microscopy. The results imply more efficient load transfer and mechanical reinforcement by CNTs with improved interfacial layer and that changes in the layer can be probed by swelling measurements.

FeCO3 Microparticle Synthesis by Fe-EDTA Hydrothermal Decomposition

We developed a new procedure for synthesizing highly crystalline FeCO3 by hydrothermal decomposition of the Fe(III)-EDTA complex in the presence of urea, starting from ferric ammonium sulfate and Na4EDTA as the main precursors. Single phase FeCO3 microcrystals with a size in the range of 50–200 μm have been obtained after high pressure–temperature treatment time between 15 and 26 h at 230 and 250 °C. Without changing the concentrations of the precursors and synthesis temperature, we have investigated the kinetics of phase transitions between 2 and 40 h of high pressure–temperature treatment time. A transition from hematite (in the first 4 h) to magnetite microoctahedrons with superparamagnetic behavior at room temperature, via a single phase of iron carbonate microcrystals, has been recorded.

High pressure–temperature degradation kinetics of polyacetylenes in carrots

The present study assessed the effect of high pressure–temperature (HPT) processing on the levels of three polyacetylenes in carrot disks immediately after processing in comparison to sous-vide processing. The degradation kinetics of these compounds following processing at HPT was also investigated. The highest pressure–temperature combination which gave maximum retention during the time 10–30min, for falcarinol it was 400MPa, at 50 and 60°C for 10min; for falcarindiol it was 400MPa, at 50°C for 10min and for falcarindiol-3-acetate was 400MPa, at 50°C for 10min, respectively. Falcarindiol-3-acetate was found to be most barosensitive and falcarindiol was found to be most thermosensitive of the three polyacetylenes studied. When compared with sous-vide (SV) processed carrot disks, HPT processed samples showed higher retention of polyacetylenes. The changes in the levels of polyacetylenes during HPT treatment were adequately described by Weibull model function.

Characterization of the Materials Synthesized by High Pressure-High Temperature Treatment of a Polymer Derived t-BC₂N Ceramic.

Bulk B-C-N materials were synthesized under static high thermobaric conditions (20 GPa and 2,000 °C) in a multianvil apparatus from a polymer derived t-BC1.97N ceramic. The bulk samples were characterised using X-ray synchrotron radiation and analytical transmission electron microscopy in combination with electron energy loss spectroscopy. Polycrystalline B-C-N materials with a cubic type structure were formed under the applied reaction conditions, but the formation of a ternary cubic diamond-like c-BC2N compound, could not be unambiguously confirmed.

Thermal properties and transition studies of multi-wall carbon nanotube/nylon-6 composites

Transition behavior and thermal properties of a multi-wall carbon nanotube (MWCNT)/nylon-6 composite (P-composite) made by in situ polymerization and subsequently structurally modified by high-pressure–high-temperature treatment have been established. The thermal conductivity ( κ) of nylon-6 improved ∼27% by the addition of 2.1 wt.% MWCNT filler simultaneously as the heat capacity per unit volume decreased ∼22% compared with that of nylon-6 at 1 atm and 298 K. Moreover, the MWCNT filler raises the glass transition temperature ( T g) of nylon-6, but the pressure dependence of T g remains unchanged. A model for κ indicates that the interfacial thermal resistance between the MWCNT filler and the nylon-6 matrix decreases 20% up to 1 GPa and most significantly above 0.8 GPa. P-composite was structurally modified by a sluggish cold-crystallization transition at 1.0 GPa, 530 K, which further increased κ by as much as ∼37% as the crystallinity of nylon-6 improved from 31% to 58% with a preferred crystal orientation and increased crystal size.

Hydrogen formation observed during high pressure treatment of silica glass

Silica glass treated at high pressures and temperatures (1–3 GPa, 1100–1250 °C) in a solid-media pressure apparatus incorporated observable quantities of hydroxyl and hydride. The FTIR absorbance signals for these species appeared only when the glass sample was pressurized in the presence of water together with graphite at a high temperature, and the hydroxyl signal disappeared completely when the glass was heat-treated at 1000 °C in air for 1 h. These results indicate that hydrogen diffused into and reacted with the silica glass during the high pressure–temperature treatment. Reduction of H 2O by graphite at high pressure/temperature conditions is the probable source of hydrogen.

Effect of high pressures and temperatures on carbon nano-onion structures: comparison with C60

The results of investigations of the structure and properties of carbon nano-onions before and after high-pressure high-temperature (HPHT) treatment are presented. The onion structures are retained after HPHT treatment up to 15 GPa and 1450 °C, which was confirmed by X-ray diffraction, electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The HPHT treatment was shown to increase the hardness and the density of these carbon forms due to the formation of sp3-hybridized carbon atoms.

A Study of Difference in Reflow Characteristics Between Electroplated and Sputtered Cu in a Dual-Damascene Fabrication Process for Silicon Semiconductor Devices

The difference in reflow characteristics between electroplated and sputtered Cu films during high-temperature high-pressure treatment was confirmed, and the basis for this difference was analyzed. Using test element groups containing a number of via holes, it was found that electroplated Cu films had much superior embedding characteristics compared with sputtered Cu films. This was confirmed by measurements of the stress–strain curves of these Cu films, which indicated that the strength at high temperature of the electroplated films was lower than that of sputtered films. Identification of lattice defects and analysis of the microstructure of these films were carried out by positron lifetime measurements and transmission electron microscopy, respectively. The results showed that a large quantity of vacancy clusters was present in the electroplated Cu films, and this increased to a maximum after isochronal annealing at 300°C. From the results, it was shown that Cu atoms in electroplated films with a large number of vacancy clusters diffuse rapidly at around 300°C, and this rapid diffusion contributes greatly to softening of the film and a promotion in reflow behavior. This study revealed that the reflow behavior of Cu films strongly depends on the presence of vacancy clusters within it.

Effects of cross-links, pressure and temperature on the thermal properties and glass transition behaviour of polybutadiene

The thermal conductivity κ, heat capacity per unit volume ρc(p) and glass transition behaviour under pressure have been established for medium and high vinyl content polybutadiene PB with molecular weights 2600 and 100,000 and their highly cross-linked (ebonite) states obtained purely by high-pressure high-temperature treatments. Cross-linking eliminates the glass transitions and increases κ by as much as 50% at 295 K and 1 atm, and decreases ρc(p) to a limiting level close to that of the glassy state of PB, which is reached before the ultimate cross-link density is achieved. The pressure and temperature behaviours of κ are strongly changed by cross-links, which increases the effect of temperature but decreases the effect of pressure. We attribute these changes to a cross-linked induced permanent densification and consequential increase of phonon velocity simultaneously as conduction along polymer chains is disrupted. The glass transition temperatures for a time scale of 1 s are described to within 0.5 K by: T(g)(p) = 202.5 (1 + 2.94 p)(0.286) and T(g)(p) = 272.3 (1 + 2.57 p)(0.233) (p in GPa and T in K) up to 1 GPa, for PB2600 and PB100000, respectively, and can be estimated for medium and high vinyl content PBs with molecular weights in between by a constant, pressure independent, shift in temperature.

Study of C60 Peapods After a High-Pressure–High-Temperature Treatment

The present work is devoted to studying the products formed from C60 peapods after treatment at 8 GPa, from 200°C to 1200°C by SEM, TEM, XRD, and Raman techniques. It is confirmed that at temperatures up to 600°C the C60 molecules polymerize in forming the known 1D polymeric crystal with a C60 – C60 distance of 9 Å. In addition, we also find that at 1000°C the peapods begin to transform into different products including nanodiamond particles, amorphous carbon, and graphitic ribbons. At 1200°C only well-formed graphite is observed.

β-Conglycinin and glycinin soybean protein emulsions treated by combined temperature–high-pressure treatment

Most studies on functionality of soybean proteins have been made with total protein isolates, with the drawback to limit the knowledge of phenomena due to the important complexity of protein composition. In this study we have tried to better understand the behavior of soy emulsions by using their two partially purified fractions: β-conglycinin (7S) and glycinin (11S). Furthermore, we have assessed the combined effect of temperature (20–60 °C) and high pressure (0.1–600 MPa) on physicochemical, microstructural and rheological properties of oil-in-water emulsions prepared with 7S or 11S proteins at 7% (w/v). Our results show that 7S and 11S emulsions behaved differently under the combined treatments and that 7S protein was responsible for the global properties of soybean emulsions, whereas 11S proteins exerted a negligible effect. From 400 MPa and at 60 °C, we have noticed for 7S emulsions an increase of flocculation and gelation, largely confirmed by confocal microscopy due to aggregation between adsorbed and aqueous 7S proteins. Globally we have evidenced that temperature reinforces the effect of high pressure and that the threshold to obtain some changes is 400 MPa. The very different behavior of 7S and 11S proteins in emulsions under treatments could help to orientate their commercial use as function of planed treatments.

Investigation on Optical Properties of Natural Brown Diamonds with Various Types by High Pressure and High Temperature Treatment

High Pressure High Temperature (HPHT) treatment can significantly change the color of diamonds. We studied the variation of the optical properties according to the nitrogen arrangement in natural brown diamonds of various types (type IaAB, type IaB, type IaA > B, type IaA < B, IaA = B) after HPHT treatment. The diamonds with different arrangements of nitrogen were annealed at temperatures in the range <TEX>$1700-1800^{\circ}C$</TEX> under a stabilizing pressure of 5 GPa. HPHT treated samples were analyzed using UV-Vis-NIR, FT-IR, and PL spectroscopy. The absorption and luminescence spectra were measured to compare the variations of nitrogen arrangement in the natural brown diamonds before and after HPHT treatment. After HPHT treatment, the brown coloration in all types of diamonds was reduced and a decrease in the peaks related to the A-aggregate of nitrogen was more predominant than the B-aggregate. Furthermore, the peaks related to N3 (415.4 nm), H4 (496.4 nm), and platelet decreased and the peaks related to H3 (503.2 nm) and G-band increased after HPHT treatment. In conclusion, spectroscopic analysis of natural brown diamonds after HPHT treatment showed that a yellow color was produced by absorption in the H3 centers and a green color was generated by interaction between absorptions of the H3 and H2 centers.

High pressure synthesis of new heterodiamond phase

New heterodiamond phase (structure type of cubic boron nitride) with boron and nitrogen atoms partially substituted by carbon has been synthesized by using high pressure-high temperature treatment of the mixture of boron and C 3N 4 carbon nitride powders. This phase consisted of up to 5 micron-sized individual crystals. The composition of new phase was established with the help of microanalysis and structure refinement.