High Isostatic Pressure Research Articles

Improvement of the Water Resistance of a Narrow-Band Red-Emitting SrLiAl3 N4 :Eu(2+) Phosphor Synthesized under High Isostatic Pressure through Coating with an Organosilica Layer.

A SrLiAl3 N4 :Eu(2+) (SLA) red phosphor prepared through a high-pressure solid-state reaction was coated with an organosilica layer with a thickness of 400-600 nm to improve its water resistance. The observed 4f(6) 5d→4f(7) transition bands are thought to result from the existence of Eu(2+) at two different Sr(2+) sites. Luminescence spectra at 10 K revealed two zero-phonon lines at 15377 (for Eu(Sr1)) and 15780 cm(-1) (for Eu(Sr2)). The phosphor exhibited stable red emission under high pressure up to 312 kbar. The configurational coordinate diagram gave a theoretical explanation for the Eu(2+/3+) result. The coated samples showed excellent moisture resistance while retaining an external quantum efficiency (EQE) of 70 % of their initial EQE after aging for 5 days under harsh conditions. White-light-emitting diodes of the SLA red phosphor and a commercial Y3 Al5 O12 :Ce(3+) yellow phosphor on a blue InGaN chip showed high color rendition (CRI=89, R9=69) and a low correlated color temperature of 2406 K.

Improvement of the Water Resistance of a Narrow‐Band Red‐Emitting SrLiAl3N4:Eu2+ Phosphor Synthesized under High Isostatic Pressure through Coating with an Organosilica Layer

AbstractA SrLiAl3N4:Eu2+ (SLA) red phosphor prepared through a high‐pressure solid‐state reaction was coated with an organosilica layer with a thickness of 400–600 nm to improve its water resistance. The observed 4f65d→4f7 transition bands are thought to result from the existence of Eu2+ at two different Sr2+ sites. Luminescence spectra at 10 K revealed two zero‐phonon lines at 15377 (for Eu(Sr1)) and 15780 cm−1 (for Eu(Sr2)). The phosphor exhibited stable red emission under high pressure up to 312 kbar. The configurational coordinate diagram gave a theoretical explanation for the Eu2+/3+ result. The coated samples showed excellent moisture resistance while retaining an external quantum efficiency (EQE) of 70 % of their initial EQE after aging for 5 days under harsh conditions. White‐light‐emitting diodes of the SLA red phosphor and a commercial Y3Al5O12:Ce3+ yellow phosphor on a blue InGaN chip showed high color rendition (CRI=89, R9=69) and a low correlated color temperature of 2406 K.

Point pinning centers in SiC doped MgB2 wires after HIP

In this study we show that dominant point pinning mechanisms in SiC doped MgB2 wires can be obtained by annealing in high isostatic pressure. The results indicate that the point pinning centers increase the critical current density in medium and high magnetic fields, but not at low magnetic fields. In addition, our study shows that dominant pinning mechanism changes from point to surface type with increase of magnetic fields. An MgB2 wire heat treated in a high pressure of 1.4 GPa shows a high critical current density of 100 A mm−2 in 13 T at 4.2 K. Scanning electron microscope studies show that high isostatic pressure increases the density of the MgB2 material, eliminates voids, allows for small Si precipitates and homogeneous distribution of Si precipitates. Transport measurements E - B and E - I show that the MgB2 wires manufactured by Hyper Tech Research did not heat up after transition into a normal state. This is important for applications in coils.

Energy and time saving processing: A combination of hot isostatic pressing and heat treatment

The technique of hot isostatic pressing (HIP) is used to simultaneously heat up and apply high isostatic pressure to a metallic or ceramic entity in order to reach compaction. The integration of heat treatment into the compaction process generates much curiosity in the HIP community. This paper resumes the different methods for accelerated cooling and gives an overview of the research done with integrated heat treatment. Results in the field of steels, lightweight alloys and superalloys are resumed.

Innovative High Gas Pressure Microscopy Chamber Designed for Biological Cell Observation.

An original high-pressure microscopy chamber has been designed for real-time visualization of biological cell growth during high isostatic (gas or liquid) pressure treatments up to 200 MPa. This new system is highly flexible allowing cell visualization under a wide range of pressure levels as the thickness and the material of the observation window can be easily adapted. Moreover, the design of the observation area allows different microscope objectives to be used as close as possible to the observation window. This chamber can also be temperature controlled. In this study, the resistance and optical properties of this new high-pressure chamber have been tested and characterized. The use of this new chamber was illustrated by a real-time study of the growth of two different yeast strains - Saccharomyces cerevisiae and Candida viswanathii - under high isostatic gas pressure (30 or 20 MPa, respectively). Using image analysis software, we determined the evolution of the area of colonies as a function of time, and thus calculated colony expansion rates.

Binomial effects of high isostatic pressure and time on the microbiological, sensory characteristics and lipid composition stability of vacuum packed dry fermented sausages “chouriço”

Abstract The effect of high pressure processing (HPP), at different combinations of pressure and time, on dry fermented sausages (DFS) was evaluated by chemical, microbiological and sensory analyses. Lipid composition and stability were also assessed. HPP (> 400 MPa and longer than 154 s) produced a reduction in spoilage microbiota, without negative effect on fermentative microbiota, that will be able to continue their role. Total fatty acids and lipid stability were not affected. Only a small effect on fatty acid (FA) composition was observed. Nutritional value of the lipid fraction was only affected by the ratio n − 6/n − 3 FA. Treatments at 400 MPa for 154 s or 960 s resulted in DFS being detected as different from control by sensory analysis. Those differences did not depreciate the product; on the contrary it seems to improve the bright aspect of the whole sausage, the cohesion and firmness and the correctly dried aspect of slices. Industrial relevance Dry fermented meat sausages are very popular ready-to-eat meat based products. This study assesses the effects of HPP on this much appreciated traditional products. The results showed that HPP can be successfully applied to these Mediterranean fermented products without losses of sensory and nutritional characteristics. The modelling and optimization of the HPP process applied on dry fermented sausages demonstrated in this study are an advantage to industry efficiency. The utilisation of HPP by the industry can significantly increase dry fermented meat sausage shelf life and safety, providing it an opportunity to reach the global market.

Comparative effects of high isostatic pressure and thermal processing on the inactivation of Rhizomucor miehei protease

This study compared the inactivation of the proteolytic (PA) and milk-clotting (MCA) activities of Rhizomucor miehei protease by high isostatic pressure (HIP) up to 600 MPa/20 min/25 °C and by a thermal process (TP) up to 72.0°C/30 min. Pressures above 300 MPa caused a loss of enzyme activity, MCA being expressively more affected than PA. The inactivation of the protease showed a nonlinear behavior, converging to a two-component system model (stable and labile fractions). The stable fraction represents higher activity for PA and the labile for MCA. The D-values for stable PA (3.35 ± 0.42 min for HIP and 5.58 ± 0.48 min for TP) and labile MCA (0.34 ± 0.04 min for HIP and 0.47 ± 0.04 min for TP) were significantly lower for the HIP processed enzyme, highlighting the effectiveness of the process in inactivating this enzyme. Therefore, the results highlight HIP at 600 MPa as an optional process to inactivate R. miehei protease (without the use of heat), being more effective than the thermal process.

Making Artificial Heart Components – Selected Aspects Of Casting Technology

Abstract This study shown possibilities of Rapid Prototyping techniques (RP) and metal casting simulation software (MCSS), including non inertial reference systems. RP and MCSS have been used in order to design and produce essential elements for artificial heart. Additionally it has been shown possibilities of Fused Deposition Modeling (FDM) technique and DodJet technology using prototyped elements of rotodynamic pump. MAGMASOFT® software allowed to verify the cast kit heart valves model. Optical scanner Atos III enabled size verification of experimental elements supplied by rapid prototyping together with metal casting elements. Due to the selection of ceramic materials and assessment of molten metal – ceramic reactivity at high temperatures together with pattern materials selection model it was possible to design, manufacture a ceramic mould for titanium based alloys. The casting structure modification has been carried out by means of high isostatic pressure technique (HIP). The quality assessment of the casting materials has been performed using X-ray fluorescence (XRF), ARL 4460 Optical Emission Spectrometer, metallographic techniques and X-ray computed tomography.

Ultra high pressure homogenization (UHPH) inactivation of Bacillus amyloliquefaciens spores in phosphate buffered saline (PBS) and milk.

Ultra high pressure homogenization (UHPH) opens up new areas for dynamic high pressure assisted thermal sterilization of liquids. Bacillus amyloliquefaciens spores are resistant to high isostatic pressure and temperature and were suggested as potential surrogate for high pressure thermal sterilization validation. B. amyloliquefaciens spores suspended in PBS buffer (0.01 M, pH 7.0), low fat milk (1.5%, pH 6.7), and whole milk (3.5%, pH 6.7) at initial concentration of ~106 CFU/mL were subjected to UHPH treatments at 200, 300, and 350 MPa with an inlet temperature at ~80°C. Thermal inactivation kinetics of B. amyloliquefaciens spores in PBS and milk were assessed with thin wall glass capillaries and modeled using first-order and Weibull models. The residence time during UHPH treatments was estimated to determine the contribution of temperature to spore inactivation by UHPH. No sublethal injury was detected after UHPH treatments using sodium chloride as selective component in the nutrient agar medium. The inactivation profiles of spores in PBS buffer and milk were compared and fat provided no clear protective effect for spores against treatments. Treatment at 200 MPa with valve temperatures lower than 125°C caused no reduction of spores. A reduction of 3.5 log10CFU/mL of B. amyloliquefaciens spores was achieved by treatment at 350 MPa with a valve temperature higher than 150°C. The modeled thermal inactivation and observed inactivation during UHPH treatments suggest that temperature could be the main lethal effect driving inactivation.

Influence of high isostatic pressure on structural and functional characteristics of potato protein

Potato protein possesses promising nutritional and techno-functional properties, but distinct heat sensitivity. Therefore, the potential of high isostatic pressure as an alternative preservation and modification method was investigated. Pressures of 200, 400 and 600MPa were applied at isothermal conditions of 20 and 40°C to dispersions made of potato protein concentrate and isolated patatin for dwell times of 10min. Process induced changes in solubility, foaming properties and selected structural characteristics were compared to results of pure thermal treatments from 20 to 80°C. Potato protein solubility in neutral solutions made of concentrate was reduced to 21% after heating to 70 and 80°C whereas it only decreased to 74% after pressurization at 600MPa. Processing of isolated patatin at pH6 and pH adjustment from 7 to 6 after processing reduced protein solubility to 12% for heat treatments and to 55 and 89%, respectively, for pressure treatments indicating different denaturation or aggregation mechanisms. Hydrogen bonds and hydrophobic interactions were involved in pressure induced aggregation, whereas aggregates formed during heat treatments were primarily stabilized by hydrophobic interactions. The surface hydrophobicity of soluble protein increased by factor 2.5 to 4.5 after heat treatments and by factor 1.3 at maximum after pressure treatments. High pressure processing provides therefore a good alternative to conventional heat pasteurization as initial potato protein quality may be preserved to a higher extent. Foam stability was increased to 177% by pressure treatments, but this modification was not long-term stable. Applying high pressure with the aim of a functional modification therefore requires further investigations.

High pressure treated Bacillus subtilis spores — Structural analysis by means of synchrotron and laboratory based soft X-ray microscopy

Abstract Measurements were carried out on high pressure treated (HPT) bacterial endospores of the Bacillus subtilis strain PS832 by means of laboratory (LTXM) and synchrotron based transmission soft X-ray microscopy (SynchTXM). Using LTXM at 500 eV HPT spores could be identified by a higher transparency, due to dipicolinic acid (DPA) release from the spore's core, and their shriveled appearance caused by air-drying. Dormant spores were investigated at different photon energies at SynchTXM. Inner structures were visualized and it was shown that at a photon energy of 280 eV the micrographs yielded bigger absorption differences, and thus better contrast between the core/coat and the peptidoglycan-rich cortex. Tilt series of dormant and HPT spores were reconstructed. Virtual sections revealed the dormant spores' core, cortex and coat without the need to physically slice the sample. It was also possible to visualize the inside of the HPT spores, which proved to be void of DPA. Industrial relevance Isostatic high pressure processing (HPP) is often regarded as the major recent technological innovation in food preservation. However, this technology is only applied in large scale for pasteurization and not for sterilization, which is largely due to the unknown inactivation mechanisms of highly resistant bacterial endospores. The structural analysis of high pressure treated endospores by X-ray microscopy could be used to study the progress of spore germination and inactivation under pressure and may add to the information already gathered in previous studies such as (Reineke et al., 2013) to establish the high pressure thermal sterilization at industrial scale. This technology in combination with different extrinsic factors like chemical or thermal preservation may open up new possibilities for a multi-target spore inactivation strategy for food sterilization.

Fabrication and characterization of composite materials based on porous ceramic preform infiltrated by elastomer

Abstract The paper presents the experimental results of fabrication and characterization of ceramic- elastomer composites. They were obtained using pressure infiltration of porous ceramics by elastomer As a result the composites in which two phases are interpenetrating three-dimensionally and topologically throughout the microstructure were obtained. In order to enhance mechanical properties of preforms a high isostatic pressure method was utilized. The obtained ceramic preforms with porosity gradient within the range of 20-40% as well as composites were characterized by X-ray tomography. The effect of volume fraction of pores on residual porosity of composites was examined. These results are in accordance with SEM images which show the microstructure of composites without any delaminations and voids. Such composites exhibit a high initial strength with the ability to sustain large deformations due to combining the ceramic stiffness and rubbery elasticity of elastomer. Static compression tests for the obtained composites were carried out and the energy dissipated during compression was calculated as the area under the stress-strain curve. The dynamic behavior of the composite was investigated using the split Hopkinson pressure bar technique. It was found that ceramic-elastomer composites effectively dissipate the energy. Moreover, a ballistic test was carried out using armor piercing bullets.

Quality changes in high pressure processed ginger paste under refrigerated storage

Abstract This investigation was carried out to evaluate quality changes in ginger paste followed by high hydrostatic pressure and thermal treatment during 6 months of storage at 6±1 °C. Ginger samples were washed in water, peeled manually and pulverized in the form of smooth paste and were mixed with ascorbic (100 mg kg −1 ) and citric (100 mg kg −1 ) acids and subsequently packed in polyethylene pouches (25 μm thickness, 50 g pack size). The pastes were processed in an isostatic high pressure system at a pressure of 200, 400 and 600 MPa at 30 °C for 5 min. The high pressure and thermal treated samples were analyzed for various physico-chemical, enzymatic, sensory and microbiological parameters. The pH and titratable acidity were not significantly ( p E ), showed that there were significant differences ( p

Potential of high isostatic pressure and pulsed electric fields to improve mass transport in pea tissue

The aim of this study was to investigate and evaluate the potential of high isostatic pressure (HP) and pulsed electric fields (PEF) for implementation in innovative legume processing concepts. Whole peas were subjected to HP (400MPa, 40°C, 10min) and PEF (5kVcm−1, 125kJkg−1) treatments. The impact on the pea tissue was assessed by means of microscopic changes, release of protein and oligosaccharides during treatment and rate of subsequent drying and rehydration steps. HP and PEF resulted in altered cell wall structures and improved mass transport in comparison to the control samples (20°C, 10min). Effects on the extent of diffusion depended on the molecular size of the cell compounds. More than 10% of raffinose equivalent sugars were removed during treatments while preserving more than 99.9% of nutritionally valuable protein. Hence, both emerging technologies may be implemented in pea processing for a targeted reduction of flatulence causing oligosaccharides. The drying and rehydration rates of whole peas were increased to a higher extent by HP and PEF than by conventional thermal treatments (80°C, 10min). These innovative pre-treatments may therefore be applied to enhance the efficiency of industrial mass transfer processes or to decrease the preparation time of meals with whole dried peas and thus increase the flexibility for the consumer.

Inactivation of microorganisms by high isostatic pressure processing in complex matrices: A review

The benefits of high pressure processing (HPP) for microbial inactivation in food production include reduced thermal treatment and minimized effects on sensory and nutritional profiles. These benefits have resulted in increasing commercial production of high pressure pasteurized foods. In this review, the current state of the art in terms of vegetative cell and bacterial spore inactivation by HPP in complex food matrices is assessed with an emphasis on mechanisms of inactivation and treatment of products that have low or non-uniform water activity (aw) profiles. Low aw can be the result of a high concentration in solutes, the presence of oils/fats, or the physical removal of water through dehydration. Microbial inactivation in low aw environments remains a particular challenge for HPP and studies on microbial inactivation observed in the different types of low aw food matrices are reviewed in detail. HPP-treated food products with low aw have been on the market since the nineties, but the mechanisms of microbial inactivation at low aw are still not well understood, which hinders the development of new applications in low or inhomogeneous aw food. This review summarizes the state of the art in terms of HPP microbial inactivation mechanisms in model systems and various low aw food environments. Thereby, it identifies existing and potential new applications as well as the current gaps and future research needs.

APLICAÇÃO DE ALTA PRESSÃO ISOSTÁTICA NA PRODUÇÃO DE DERIVADOS LÁCTEOS: UMA REVISÃO

High Isostatic Pressure (HIP) has gained prominence in several food industry sectors, including dairy. This emerging technology is effective to ensure microbiological safety to food similarly to conventional thermal processes (pasteurization), with the advantage of maintaining favorable sensory and nutritional characteristics, providing consumers products similar to the natural. The aim of this study was to put up a literature review on the application and prospects of HIP in food industry, especially regarding the dairy industry.

Peculiarities of boron distribution in as-grown boron-doped diamond

Boron doped diamond (BDD) single crystals have been grown under conditions of high isostatic pressure by the temperature gradient method. Numerous equilateral triangles were found on the fluorescence images of {111}-diamond facets. Structural peculiarities of BDD were investigated by JEM-2010 transmission electron microscope with GIF Quantum attachment for electron energy loss spectroscopy (EELS). High resolution image of diamond lattice revealed some distorted {111}-layers. EELS testifies the presence of boron in distorted regions of diamond lattice. The crystallographic features of BDD and their connection with the superconductivity are discussed.

HP/HT synthesis and characterization of novel multiferroic Bi-based perovskites

Bi-based perovskites (BiM1-xM'xO3, where M e M' are 3d and 4d metal ions) are considered very promising candidates to show multiferroic magnetoelectric character. A multiferroic magnetoelectric is a material in which ferromagnetism and ferroelectricity are not only coexistent but also coupled. Such properties, very rare in natural materials, are suitable for electronics, data storage and spintronics applications. Therefore, the interest in this class of compound showed an increasing trend of scientific publications in the last ten years. Unfortunately most members of this family cannot be synthesized with conventional techniques, due to their highly unstable and distorted crystallographic structure. High isostatic pressures and high temperatures can be exploited to overcome this fundamental drawback. The strategy is to induce ferroelectricity (e.g. polar symmetry) achieving the stereochemical effect of Bi3+ 6s2 lone pair, that polarizes the bonds with the neighboring oxygen anions, and independently to bring magnetism through the introduction of magnetic ions of the third or the fourth period on the octahedral coordinated B-site of the perovskite structure. We have synthesized simple and complex (quadruple [1,2] and double [3]) Bi-based perovskites in wide ranges of pressure (from 3 to 9 GPa) and temperature (from 9000C to 16500C) by means of solid state reactions in a multi-anvil Walker-type Press. We present an accurate study of the structural, magnetic and electric properties. Furthermore, unconventional home-made set-ups are also presented as the tools to probe the coupling between the electric and the magnetic properties through crossed magnetic characterizations (magnetic susceptibility dependence on an applied electric field) and reversely crossed electric characterizations (polarization as a function of an external magnetic field).

Synthesis and TEM Studies of Al2O3-Filled BNC Tubules

BNC tubules have been synthesized in a high isostatic pressure apparatus in Ar at 1650°C and 1.5 MPa. The synthesis of tubules was performed in BN-crucible in the presence of yttrium aluminum garnet. TEM studies were carried out using a JEM-2010 transmission electron microscope with EELS and EDS techniques, and a JSM-7600F scanning electron microscope. It is established that carbon content varies for different tubules in the sample and does not exceed 50%, and boron and nitrogen amounts in each tubule are approximately the same. It is shown that the tubules contain the Al2O3-filling with β-, ϵ- or γ-phase crystal lattice.

Characterization of light output and scintillation emission in CsI(Tl), NaI(Tl), and LaBr3(Ce) under isostatic pressure

The application of high isostatic pressure has been known to affect the electronic band structure of the host lattice and the electronic states of luminescence centers in scintillators. Using pulse-height gamma-ray and photoluminescence spectroscopy, the scintillation light output, decay time, and emission behavior of CsI(Tl), NaI(Tl) and LaBr3(Ce) were studied under high isostatic pressure up to 800 MPa. The light output behavior of CsI(Tl) was found to exhibit a different trend than those observed by NaI(Tl) and LaBr3(Ce), explained by shifts in the photoluminescence wavelengths with increased applied pressure. Scintillation decay times were also observed to shorten with pressure. The observed trends in light output and decay times are explained and compared to estimations by analytical models.