Low-temperature Swelling Research Articles

Overcoming cellulose recalcitrance in woody biomass for the lignin-first biorefinery

BackgroundLow-temperature swelling of cotton linter cellulose and subsequent gelatinization in trifluoroacetic acid (TFA) greatly enhance rates of enzymatic digestion or maleic acid–AlCl3 catalyzed conversion to hydroxymethylfurfural (HMF) and levulinic acid (LA). However, lignin inhibits low-temperature swelling of TFA-treated intact wood particles from hybrid poplar (Populus tremula × P. alba) and results in greatly reduced yields of glucose or catalytic conversion compared to lignin-free cellulose. Previous studies have established that wood particles from transgenic lines of hybrid poplar with high syringyl (S) lignin content give greater glucose yields following enzymatic digestion.ResultsLow-temperature (− 20 °C) treatment of S-lignin-rich poplar wood particles in TFA slightly increased yields of glucose from enzymatic digestions and HMF and LA from maleic acid–AlCl3 catalysis. Subsequent gelatinization at 55 °C resulted in over 80% digestion of cellulose in only 3 to 6 h with high-S-lignin wood, compared to 20–60% digestion in the wild-type poplar hybrid and transgenic lines high in guaiacyl lignin or 5-hydroxy-G lignin. Disassembly of lignin in woody particles by Ni/C catalytic systems improved yields of glucose by enzymatic digestion or catalytic conversion to HMF and LA. Although lignin was completely removed by Ni/C-catalyzed delignification (CDL) treatment, recalcitrance to enzymatic digestion of cellulose from the high-S lines was reduced compared to other lignin variants. However, cellulose still exhibited considerable recalcitrance to complete enzymatic digestion or catalytic conversion after complete delignification. Low-temperature swelling of the CDL-treated wood particles in TFA resulted in nearly complete enzymatic hydrolysis, regardless of original lignin composition.ConclusionsGenetic modification of lignin composition can enhance the portfolio of aromatic products obtained from lignocellulosic biomass while promoting disassembly into biofuel and bioproduct substrates. CDL enhances rates of enzymatic digestion and chemical conversion, but cellulose remains intrinsically recalcitrant. Cold TFA is sufficient to overcome this recalcitrance after CDL treatment. Our results inform a ‘no carbon left behind’ strategy to convert total woody biomass into lignin, cellulose, and hemicellulose value streams for the future biorefinery.

Cellulose modification by recyclable swelling solvents

BackgroundThe invention of efficient systems for lignocellulose conversion is essential for economically feasible production of bio-based chemicals and biofuels. One limiting step is highly selective processes to quickly decrystallize the compact cellulose structure for efficient hydrolysis. We evaluated the impact of trifluoroacetic acid (TFA) and phosphorous acid (PA)-induced swelling of crystalline cellulose on enhancement of enzymatic digestion.ResultsIn this study, two swelling agents, TFA and PA, are compared and found to be highly efficient for cellulose decrystallization at low temperatures within 1 h. After treatment, the microfibril structure of swollen celluloses was observed to develop distinct microscopic morphology and subsequent enzymatic hydrolysis resulted over 90% cellulose conversion within 24 h. The crystalline cellulose change was determined by reduction of loss of X-ray diffractability, and loss of resistance to enzymatic hydrolysis. NMR results suggest that both TFA and PA efficiently converted most of the crystalline cellulose regions to amorphous regions through cellulose chain relocation that inhibits recrystallization. It was found that the swelling mechanism is different between TFA and PA. To the best of our knowledge, it is the first time to compare and quantify the cellulose regions transformation by swelling agents.ConclusionThis study shows the low-temperature swelling of different celluloses in TFA and PA reduces recalcitrance of crystalline cellulose to enzymatic hydrolysis. TFA and PA are both ideal candidate swelling agents for a closed system for ease of solvent recovery by either simple distillation or filtration. This study provides potentially useful agents in large-scale deconstruction of biomass.

Porosity evolution study in irradiated UO2 fuel based on fuel matrix swelling

Abstract The volume porosity of irradiated UO2 fuel in the form of a correlation is developed which includes two individual parts as the pore and swelling porosity in terms of the local density and fractional matrix swelling. Based on a low temperature swelling model for UO2 fuel, the matrix swelling terms are calculated and the evolution of porosity up to burn-up levels of 120 MWd/KgU is presented. It is seen that for high burn-up PWR fuel pellet rim, the dominant contribution to total porosity comes from pores generated due to Xe depletion in the ceramic matrix while the nearly constant swelling porosity makes a small contribution to the total porosity. The porosity evolution is also validated by comparing against experimental data and a fairly good agreement was found.

Influence of the structure on the collapse of poly(N-isopropylacrylamide)-based microgels: an insight by quantitative dielectric analysis.

The collapse of poly(N-isopropylacrylamide)/poly(acrylic acid) semi-interpenetrating polymer network (PNIPAM/PAA SIPN) and poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-co-AA)) microgel suspensions is studied by dielectric spectroscopy in a frequency range from 40 Hz to 110 MHz as a function of temperature. Dielectric measurements show that the structure affects the relaxation behavior of microgels: two relaxations (micro-Brownian motion and interfacial polarization at low frequency and counterion polarization at high frequency) are observed in the SIPN microgel whose charges mainly exist in domains and one relaxation (interfacial polarization) is observed in the copolymer microgel whose charges distribute in the whole network. A dielectric model is proposed to describe the collapsed microgel suspensions, from which some parameters, such as the volume fraction and the permittivity of microgels, were calculated using Hanai's equation. The temperature dependencies of these parameters show that the SIPN microgel has better low-temperature swelling properties and thermal responsiveness. This is caused by different polymer-solvent and electrostatic repulsion interactions in different microgels. Compared with pure PNIPAM, the relationship of volume phase transition temperature (VPTT) is VPTTP(NIPAM-co-AA) > VPTTPNIPAM/PAA SIPN > VPTTPNIPAM, and it is explained from the viewpoint of interaction. Besides, the activation energy data prove that the structure influences the electrical properties of microgels, which is consistent with the results obtained from quantitative dielectric analysis.

Microstructure evolution and degradation mechanisms of reactor internal steel irradiated with heavy ions

Structure evolution and degradation mechanisms during irradiation of 18Cr–10Ni–Ti steel (material of VVER-1000 reactor internals are investigated). Using accelerator irradiations with Cr3+ and Ar+ ions allowed studying effects of dose rate, different initial structure state and implanted ions on features of structure evolution and main mechanisms of degradation including low temperature swelling and embrittlement of the 18Cr–10Ni–Ti steel. It is shown that differences in dose rate at most irradiation temperatures mainly exert their influence on the duration of the swelling transient regime. Calculations of possible transmutation products during irradiation of this steel in a VVER-1000 spectrum were performed. It is shown that gaseous atoms (He and H), which are generated simultaneously with radiation defects, stabilize the elements of radiation microstructure and influence the swelling. The nature of deformation under different temperatures of irradiation and of mechanical testing is investigated. It is shown that the temperature sensitivity of swelling behaviour in the investigated steel, with different initial structures can be connected with the dynamic behaviour of point defect sinks.

Water-like solvation thermodynamics in a spherically symmetric solvent model with two characteristic lengths

We examine by molecular dynamics simulation the solubility of small apolar solutes in a solvent whose particles interact via the Jagla potential, a spherically symmetric ramp potential with two characteristic lengths: an impenetrable hard core and a penetrable soft core. The Jagla fluid has been recently shown to possess water-like structural, dynamic, and thermodynamic anomalies. We find that the solubility exhibits a minimum with respect to temperature at fixed pressure and thereby show that the Jagla fluid also displays water-like solvation thermodynamics. We further find low-temperature swelling of a hard-sphere chain dissolved in the Jagla fluid and relate this phenomenon to cold unfolding of globular proteins. Our results are consistent with the possibility that the presence of two characteristic lengths in the Jagla potential is a key feature of water-like solvation thermodynamics. The penetrable core becomes increasingly important at low temperatures, which favors the formation of low-density, open structures in the Jagla solvent.

Degradation Mechanisms of Pressure Vessel Internal Steel (18Cr-10Ni-Ti) Irradiated with Heavy Ions

Mechanisms of degradation of physical-mechanical properties of PVI steels during irradiation are studied. Microstructure evidence of influence of irradiation temperature, dose and dose rate on processes of low-temperature swelling and embritllement of pressure vessel internal materials, 18Cr-10Ni-Ti steel, of reactor WWER 1000 are presented. Micro mechanisms of plastic deformation and steel failure in wide range of temperatures and irradiation doses are described. Analysis of influence of subsequent and simultaneous irradiation with beams of gas and heavy ions is carried out for investigation of influence of gaseous impurities that form through transmutation nuclear reactions on defected structure evolution under irradiation.

Void swelling of AISI 321 analog stainless steel irradiated at low dpa rates in the BN-350 reactor

In several recently published studies conducted on a Soviet analog of AISI 321 stainless steel irradiated in either fast reactors or light water reactors, it was shown that the void swelling phenomenon extended to temperatures as low as ∼300 °C or less, when produced by neutron irradiation at dpa rates in the range 10 −7–10 −8 dpa/s. Other studies yielded similar results for AISI 316 and the Russian analog of AISI 316. In the current study a blanket assembly duct from BN-350, constructed from the Soviet analog of AISI 321, also exhibits swelling at dpa rates on the order of 10 −8 dpa/s, with voids seen as low as 281 °C and only 0.65 dpa. It appears that low-temperature swelling occurs at low dpa rates in 300 series stainless steels in general, and also occurs during irradiations conducted in either fast or in mixed spectrum reactors as shown in other studies.

Microstructural development in cubic silicon carbide during irradiation at elevated temperatures

Microstructural development in chemically vapor-deposited (CVD) high-purity beta-SiC during neutron and self-ion irradiation at elevated temperatures was studied. The CVD SiC samples were examined by transmission electron microscopy following neutron irradiation to 4.5–7.7 × 10 25 n/m 2 ( E > 0.1 MeV) at 300 and 800 °C and 5.1 MeV Si 2+ ion irradiation up to ∼200 dpa at 600–1400 °C. The evolution of various irradiation-produced defects including black spot defects, dislocation loops, network dislocations, and cavities was characterized as a function of irradiation temperature and fluence. It was demonstrated that the black spot defects and small dislocation loops continue to dominate at relatively low temperatures (<∼800 °C), whereas they grow into Frank faulted loops and finally develop into dislocation networks at a higher temperature (1400 °C). Substantial cavity formation on grain boundaries and stacking faults was confirmed after ion irradiation at 1400 °C. These observations were discussed in relation with the known irradiation phenomena in SiC, such as low temperature swelling and cavity swelling.

Radiation synthesis and characterization of poly( N, N-dimethylaminoethyl methacrylate-co- N-vinyl 2-pyrrolidone) hydrogels

In this study, radiation synthesis and characterization of swelling behavior and network structure of poly( N, N-dimethylaminoethyl methacrylate) (PDMAEMA), and poly( N, N-dimethylaminoethyl methacrylate-co- N-vinyl 2-pyrrolidone) (P(DMAEMA-co-VP)), hydrogels were investigated. PDMAEMA and P(DMAEMA-co-VP) hydrogels in the rod forms were prepared by irradiating the ternary mixtures of DMAEMA/VP/cross-linking agent, ethyleneglycol dimethacrylate (EGDMA), by gamma rays at ambient temperature. In composition ranges where the three components were completely miscible, water was also added to the ternary mixture to provide the formation of homogeneous polymerization and gelation. The influence of irradiation dose, comonomer, VP, and cross-linking agent, EGDMA, content on the total percentage gelation and monomer conversion were investigated. The effect of pH and temperature on the swelling behavior of hydrogels have also been examined. Hydrogels showed typical pH response and temperature responses, such as low-pH and low temperature swelling and high-pH and high temperature deswelling. Polymer–solvent interaction parameter ( χ) and enthalpy and entropy changes appearing in the χ parameter for the P(DMAEMA-co-VP)–water system were determined by using Flory–Rehner theory of swelling equilibrium. The negative values for Δ H and Δ S indicate that prepared pure PDMAEMA and P(DMAEMA-co-VP) hydrogels have lower critical solution temperature (LCST) and Flory–Rehner theory of swelling equilibrium provides a satisfactory agreement to the experimental swelling data of the hydrogels.

Properties of low temperature swelling hydrogels prepared with partially saponified PVA and drug release using the hydrogels

AbstractThe hydrogels prepared by the crosslinking of partially saponified poly(vinyl alcohol) (PVA) which has low critical solution temperature (LCST) in water showed characteristics of swelling at low temperature and shrinkage at high temperature. The hydrogels showed repeatable swelling–shrinking behavior. The hydrogels containing release substances such as cyanocobalamin, p‐acetamidophenol, insulin and ovalbumin were prepared by dipping these aqueous solutions and the release substances were studied. Insulin and ovalbumin were not absorbed by the hydrogels when the use of partially PVA with the degrees of polymerization (DPs) of 540 were prepared, but absorbed by the hydrogels with DPs of 1860. The size of the polymer network prepared with a higher DP was suitable for the absorption of insulin and ovalbumin. In accordance with release substances, the release patterns were different. In this way, the polymer network sizes and their swelling behaviors of partially saponified PVAs were estimated. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Radiation synthesis of poly(N‐vinyl‐2‐pyrrolidone‐g‐tartaric acid) hydrogels ­and their swelling behaviors

AbstractPoly(N‐Vinyl 2‐pyrrolidone‐g‐tartaric acid), PVP‐g‐TA hydrogels were prepared by γ‐irradiating ternary mixture of VP/TA/Water. The influence of pH, temperature and ionic strength of swelling media on the equilibrium swelling properties of these hydrogels was investigated. Typical pH and temperature responses were observed by hydrogels such as high pH and low temperature swelling and low pH and high temperature deswelling. A change in the ionic strength of the swelling solution from 0.01 to 0.2 caused a decrease in equilibrium degree of swelling hydrogels. The average molecular weight between cross‐links, M c and polymer ‐ solvent interaction parameter, χ of PVP‐g‐TA hydrogels were determined according to equation recently derived by Şen and Güven for the swelling behavior of charged polymeric network. Copyright © 2002 John Wiley &amp; Sons, Ltd.

Low Temperature Swelling in Beta-SiC Associated with Point Defect Accumulation

An experimental technique to characterize irradiation-induced swelling, or isotropic volume expansion, through a combined utilization of medium-to-high energy accelerators and interferometric surface profilometry, was established. The technique was successfully applied to a characterization of swelling behavior in beta-silicon carbide arising from the accumulation of point defects at relatively low temperatures, i.e., 333–873 K, as a function of fluence level, displacement damage rate and irradiation temperature. Swelling rate and swelling at any given fluence level exhibited a negative dependence on irradiation temperature. The saturated low temperature swelling fell on the lower edge of neutron irradiated swelling data band. The influence of displacement damage rate appeared unremarkable. An additional study on the synergistic effect of atomic displacement damage and helium production revealed an enhancement of low temperature swelling in silicon carbide in the presence of helium.

The effect of external stimuli on the equilibrium swelling properties of poly(N-vinyl 2-pyrrolidone/itaconic acid) poly-electrolyte hydrogels

Hydrogels with varying crosslink densities and ionic moieties were prepared from the ternary systems N-vinyl 2-pyrrolidone/itaconic acid/water by irradiation with γ rays at ambient temperature. The influence of external stimuli such as pH, temperature and ionic strength of the swelling media and the type of buffer on the equilibrium swelling properties were investigated. Hydrogels showed typical pH response and temperature responses, such as high-pH and low-temperature swelling and low-pH and high-temperature deswelling. A change in the ionic strength of the swelling solution from 0.01 to 0.20 caused a decrease in the equilibrium degree of swelling of hydrogels. Oscillatory swelling behaviour was also observed and investigated in response to changes in the pH of the solution.

Effect of Formation and Growth of Dislocation Loops and Cavities on Low-Temperature Swelling of Irradiated Uranium-Molybdenum Alloys

AbstractScanning electron photomicrographs of U–10 wt.% Mo irradiated at low temperature in the Advanced Test Reactor (ATR) to about 40 at.% burnup show the presence of cavities. We have used a rate-theory-based model to investigate the nucleation and growth of cavities during low-temperature irradiation of uranium-molybdenum alloys in the presence of irradiation-induced interstitial-loop formation and growth. Our calculations indicate that the swelling mechanism in the U–10 wt.% Mo alloy at low irradiation temperatures is fission-gas driven. The calculations also indicate that the observed bubbles must be associated with a subgrain structure. Calculated bubble-size-distributions are compared with irradiation data.

Thermo-responsive behavior of a methacryloyl-DL-alanine methyl ester polymer gel prepared by radiation-induced polymerization

Loosely cross-linked poly(methacryloyl- DL-alanine methyl ester, MA- DL-AlaOme) gels, which were prepared by radiation-induced polymerization, exhibited a reversible low-temperature swelling and high-temperature deswelling when cycled in water at different temperatures at 24-h intervals, in the range of 0 and 40°C. The thermo-response strongly depended upon irradiation condition. Increasing the irradiation dose resulted in a formation of lower molecular weight polymer owing to the scission of polymer chain, in which it gave a high swelling ability at low temperature, in contrast to a sluggish shrinkage at high temperature. On the other hand, no irradiation temperature affects the thermo-response of the gel. An important characteristic of the MA- DL-AlaOMe polymer gel is the formation of the membrane barrier at the surface with the rise in temperature, but it disappears in reswelling, to be termed “surface-controlling on-off switch system”. Brilliant blue FCF (BB) as a model compound was corporated into the gel to evaluate the capability as a thermo-responsive carrier for application in drug delivery systems, and it was found that the reversibly surface-controlling on-off switch function responsible to temperature changes plays an important role in a pulsatile release of BB of BB from the gel in vivo.

Dynamics of irradiation-induced grain subdivision and swelling in U 3Si 2 and UO 2 fuels

Observations on low-temperature swelling of irradiated uranium silicide dispersion fuels have shown that the growth of fission-gas bubbles is strongly affected by fission rate. The plot of swelling versus fuel burnup exhibits a distinct “knee” that shifts to higher fission density with increased fission rate. State-of-the-art models of fission-gas behavior do not predict such a dependence. Below the knee, no gas bubbles can be detected by scanning electron microscopy. Just at the knee, gas bubbles are seen to form in a heterogeneous fashion. Above the knee, the bubble population rapidly multiplies and the bubble size increases with fission density. “Subdivision” of the original grains has been observed in high-burnup uranium dioxide. In addition, the peripheral region of LWR fuel pellets reveals an increasingly porous microstructure with burnup. Observations of this “rim effect” show that an extremely fine-grained structure formed by subdivision of the original fuel grains is associated with the porous microstructure. The singular observation that gas-bubble swelling is strongly dependent on fission rate has led us to speculate that a dense network of subgrain boundaries forms in UO 2 and U 3Si 2 at high burnup. Fission-gas bubbles nucleate at the newly formed boundaries and then grow at an accelerated rate relative to that of fission-gas bubbles in the bulk material. A theoretical formulation is presented wherein the stored energy in the material is concentrated on a network of sink-like nuclei that diminish with dose due to interaction with radiation-produced defects. Grain subdivision is induced when the energy per nucleus is high enough that the creation of grain-boundary surfaces is offset by the creation of strain-free volumes, with a resultant net decrease in the free energy of the material. This formulation, applied within the context of a mechanistic treatment of fission-gas-bubble behavior, is shown to provide a plausible interpretation of the observed phenomenon.

Low temperature swelling of Argonne Premium Coal Samples: 2. Micropore wall chemistry during swelling

An electron paramagnetic resonance (e.p.r.) spin probe method was used to study the micropore wall chemistry of coal during swelling at 298 and 333 K with polar and non-polar solvents. Argonne Premium Coal Sample coals were swelled in the presence of small nitroxide molecules with R groups differing in their ability to hydrogen bond to coal. The results showed that unswelled coals contained small, spherical pores which disappeared when coal was swelled in the presence of polar solvents. Nitroxides with polar R groups were retained in the micropore structure due to the ability of the R group to hydrogen bond with the coal. However, probe retention decreased with rank, emphasizing that hydrogen bonding was important primarily in low-rank coals. The presence of polar solvents like nitrobenzene and pyridine decreased polar spin probe retention due to competition for binding sites. Site competition was the greatest in pyridine. Finally, the results indicated the presence of hydrogen bonding sites in coal which vary in reactive strength.

Controlled release of 9-β- D-arabinofuranosyladenine from thermo-responsive devices based on acryloyl- L-proline methyl ester

Loosely cross-linked polymer gels consisting of acryloyl- L-proline methyl ester (A-ProOMe), 2-hydroxyethyl methacrylate (HEMA), and polyethylene glycol dimethacrylate ( nG) were synthesized by radiation-induced polymerization, using γ-rays from a 60Co source. The percent swelling behavior of the gels obtained was examined in water in the range of 0–50°C, showing that gels exhibit a characteristic thermo-response such as low-temperature swelling and high-temperature deswelling, depending strongly upon monomer composition. 9-β- D-Arabinofuranosyladenine was incorporated into this polymer gel to evaluate the pulsatile drug release when cycled at 10 and 37°C, in which the drug release kinetics could be explained by a matrix pumping mechanism.

Low-temperature swelling of metals and ceramics

A theory of low temperature swelling of crystalline materials is proposed, which is based on kinetics of defect accumulation and dislocation microstructure evolution at early stages of irradiation. This effects is of practical importance for refractory materials (e.g., ceramics, or tungsten) which might be used in fission and fusion facilities. The model provides a good qualitative picture of experimental features of the effect (swelling saturation, temperature dependence, etc.) and gives reasonable quantitative predictions.