Laser induced breakdown spectroscopy of soils, rocks and ice at subzero temperatures in simulated martian conditions

We applied Laser Induced Breakdown Spectroscopy (LIBS) on moist soil/rock samples in simulated Martian conditions. The signal behavior as a function of the surface temperature in the range from + 25 °C to − 60 °C was studied at pressure of 7 mbar. We observed the strong signal oscillations below 0 °C with different negative peaks, whose position, width and magnitude depend on the surface roughness. In some cases, the signal was reduced for one order of magnitude with consequences for the LIBS analytical capability. We attribute such a signal behavior to the presence of supercooled water inside the surface pores, which freezing point depends on the pore size. On a same rock samples with different grades of the surface polishing, the signal has different temperature dependence. Its decrease was always registered close to 0 °C, corresponding to the freezing/melting of normal disordered ice, which can be present inside larger pores and scratching. An amount of the signal reduction at the phase transition temperatures does not seem to change with the laser energy density in the examined range. Comparative measurements were performed on a frozen water solution. A large depression, for two orders of magnitude, of the LIBS intensity was observed close to − 50 °C. The same negative peak, but with a smaller magnitude, was also registered on some rock/soil samples. Ablation rates and plasma parameters as a function of the sample temperature are also discussed, and their consequences for in-situ analyses.     

Degradation study on the thermally stable nickel phthalocyanine sheet polymer

Poly (nickel phthalocyanine) which has exceptional thermal stability is synthesized. Knowledge of modes of degradation of this polymer is found to be necessary for its high temperature applications. This polymer showed very high thermal stability with maximum polymer decomposition temperatures (PDT_max) of 500 °C in air and 890 °C in N₂, with char yield 93% at 800 °C. Because of its excellent thermal stability, degradation study with MS as well as GC–MS techniques were found to be very difficult. The present publication deals with MS and GC–MS studies of nickel phthalocyanine sheet polymer at high temperatures ranging from 700 to 1000 °C. Tentative mechanisms are proposed for its modes of fragmentations and based on GC–MS studies, the most probable degradation products are identified.     

Microporous poly(vinyl methyl ether) hydrogels prepared by γ-ray irradiation at different heating rates

We prepared thermoresponsive and microporous polymer hydrogels by γ-ray irradiation of aqueous solutions poly(vinyl methyl ether) (PVME) at different heating rates. Under all temperature programs, opaque and heterogeneous PVME gels formed, which swelled at temperatures below the lower critical solution temperature and shrank at temperatures above it. All of the samples contained porous and phase-separated structures. The shape and size of the gel pores varied depending on the temperature programs. Gels having a sponge-like continuous porous structure formed only when the radiation-induced crosslinking was carried out at an optimum heating rate, which we found to be 0.11–0.13°C min⁻¹. For temperature changes between 10°C and 40°C, gels with this structure showed rapid volume transitions on a time scale of about a minute.     

Three-phase extraction study of cyanex 923-n-heptane/H(2)SO(4) system

Phase behavior of the extraction system, Cyanex 923–heptane/H₂SO₄–H₂O has been studied. The third phase appeared at different aqueous H₂SO₄ concentration with varying initial Cyanex 923 concentration and temperature affects its appearance. Almost all of H₂SO₄ and H₂O are extracted into the middle phase. The H₂SO₄ concentration in the third phase increases with the increasing aqueous acid concentration (C_H2SO4,b) while the water content first increases and then reaches a constant value at C_H2SO4,b=11.3 mol l⁻¹. In the region of C_H2SO4,b higher than 5.2 mol l⁻¹, the composition of the middle phase is only related to the equilibrium concentration of H₂SO₄ in the bottom phase. H₂SO₄ and H₂O are transferred into the middle phase mainly by their coordination with Cyanex 923 when C_H2SO4,b is less than 11.3 mol l⁻¹. When C_H2SO4,b is higher than 11.3 mol l⁻¹, excess H₂SO₄ is solubilized into the polar layer of the aggregates. In the region considered, the extracted complex changes from C923 · H₂SO₄ to C923 · H₂SO₄ · H₂O and then to C923 · (H₂SO₄)₂ · H₂O.     

Thermo-oxidative degradation of some elastomers with a high content of 3,4 isoprene units

New elastomers with high content of 3,4 isoprene units have been developed during the last decades in an attempt to ensure superior performances of the final products and the present study is devoted to the investigation of some peculiarities of their ageing behaviour. On thermo-oxidative degradation, 3,4 isoprene units are less affected in comparison to cis-1, 4 and trans-1, 4 isoprene units. The degradation process consists mainly in splitting of the main chains at temperatures of 80–100 °C while at higher temperatures (120–130 °C) branching becomes a significant modification and this reaction is enhanced for the polymers containing preponderantly 3,4 units. Such behaviour leads to the fact that the processability of polymers containing high amounts of 1,2 and 1,3 isoprene units is less affected by thermo-oxidative degradation in comparison with cis-1, 4-polyisoprene, which could be explained by the fact that large amounts of double bonds are not present in the backbone of macromolecules but in the pendent groups.     

Thermogravimetric study of flame-retarding properties on phosphorylated beech sawdust

Beech sawdust (S) and samples containing 1% of H₃PO₄ (SP), (NaPO₃)_n (PS), P₂O₅ (POS), NaOH/P₂O₅ (SPS), NaOH (SS) or Na₂CO₃ (CS) were analysed using dynamic and isothermal thermogravimetry (TG) in nitrogen and oxygen environments. According to the results of dynamic experiments in nitrogen, the thermal resistance at 275 °C decreased in the order: S > SS > CS > SP> SPS > PS > POS, while in oxygen the order was: S > POS > SPS=CS=PS > SP > SS. The difference in residues obtained in nitrogen in comparison to oxygen environment reaches its maximum at temperatures from 300 to 325 °C and according to the decreasing values the following order could be listed: SS (300 °C/27%) > SP (325 °C/25%) > CS (300 °C/24%) > S (325 °C/23%) > SPS (300 °C/19%) > PS (300 °C/11%) > POS (275 °C/4%). This indicates that with a decreasing difference in residues formed in oxidative and inert environments the flame-retardant effect of the sample is increasing. The calculated initial rate constants of residue formation and gasification and the corresponding activation energies of the processes in nitrogen and oxygen from the isothermal experiments gave smaller values of rate constants for SPS than for S. For the SPS sample in comparison with S the activation energy of residue formation in nitrogen decreased while the three remaining values increased. The E_r* of PS in the oxygen is the biggest from all studied samples under the conditions used, while SPS gave the biggest E_g* in the oxygen environment. The phosphorus could be washed out with water from SP and SPS, while it remained in PS and POS. These last two samples also have the best flame-retarding properties according to TG analysis.     

Preconcentration and speciation of chromium in a sequential injection system incorporating dual mini-columns coupled with electrothermal atomic absorption spectrometry

A procedure for chromium preconcentration and speciation with a dual mini-column sequential injection system coupled with electrothermal atomic absorption spectrometry (ETAAS) was developed. At pH 6, the sample solution was firstly aspirated to flow through a Chlorella vulgaris cell mini-column on which the Cr(III) was retained. The effluent was afterwards directed to flow through a 717 anion exchange resin mini-column accompanied by the retention of Cr(VI). Thereafter, Cr(III) and Cr(VI) were eluted by 0.04 mol L^− 1 and 1.0 mol L^− 1 nitric acid, respectively, and the eluates were quantified with ETAAS. Chemical and flow variables governing the performance of the system were investigated. By using a sampling volume of 600 µL, sorption efficiencies of 99.7% for Cr(III) and 99% for Cr(VI) were achieved along with enrichment factors of 10.5 for Cr(III) and 11.6 for Cr(VI), within linear ranges of 0.1–2.5 µg L^− 1 for Cr(III) and 0.12–2.0 µg L^− 1 for Cr(VI). Detection limits of 0.02 µg L^− 1 for Cr(III) and 0.03 µg L^− 1 for Cr(VI) along with RSD values of 1.9% for Cr(III) and 2.5% for Cr(VI) (1.0 µg L^− 1, n = 11) were obtained. The procedure was validated by analyzing a certified reference material of GBW08608 and further demonstrated by chromium speciation in river and tap water samples.     

Positron lifetimes at the initial stage of pore formation in Vycor glass

The formation of narrow pores during leaching of Vycor glass by sulphuric acid was investigated using the positron lifetime technique. During the leaching process the pore diameter remained roughly constant (except for the case of cold leaching). The time of processing changed the total length of capillaries, but not their number; at the temperature 50°C during 20 min of leaching the average leaching depth was 24 μm.     

Hydration and dehydration behavior of <Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide gel particles

Thermal response of N-isopropylacrylamide (NiPAM) gel particles of submicron size was investigated by means of ultrasonic velocity and density focusing on the hydration and dehydration behavior. Hydration number, defined as the number of water molecules bound to one NiPAM monomer unit, was quantitatively evaluated in the course of the volume phase transition. Hydration numbers at low and high temperatures were about 7.5 (20 °C) and 3 (40 °C), respectively. Hydration number decreases markedly near the volume phase transition temperature, and the decrease is responsible to the formation of hydrophobic bonding and dehydration. The hydration number is independent both of the size and the composition of gel particles in the shrunken state, although there exists a composition dependence in the swollen state. It was also found that the self-assemblies formed by hydrophobic interaction are more bulky compared to those in the hydrated state.     

New PVC materials for medical applications—the release profile of PVC/polycaprolactone–polycarbonate aged in aqueous environments

Medical grade PVC plasticised with polycaprolactone–polycarbonate (PCL–PC) was subjected to aqueous environments at different temperatures. The release profile during ageing was determined by solid phase microextraction (SPME) and GC–MS. At the same time changes in the surface composition due to, for example, migration of PCL–PC from the blend were followed by FTIR. Almost no changes in the material or its surface composition were observed during 98 days at 37 °C in water or phosphate buffer. Only trace amount of 6-hydroxyhexanoic acid the final hydrolysis product of PCL–PC was detected in the GC–MS chromatograms and the weight loss was negligible. Even when the ageing temperature was raised to 70 °C only minor increase in the amount of 6-hydroxyhexanoic acid was observed and the weight loss after 98 days was under 1%. Changes in the FTIR spectra indicating migration of PCL–PC towards the surface of the PVC/PCL–PC tubing were observed first after 70 days at 70 °C. Large increase in the hydrolysis rate of PCL–PC and almost complete depletion of PCL–PC from the blend was observed when the ageing temperature was raised to 100 °C.     

Effects of pigments on the volume‐phase‐transition properties of N‐isopropylacrylamide gels as light‐modulation materials

The effects of pigments contained in N‐isopropylacrylamide (NIPAM) gels on their volume‐change properties were investigated. All the NIPAM gel particles, containing various kinds and concentrations of pigments, showed a volume phase transition at 34 °C. No pigment affected the volume‐phase‐transition temperature of the NIPAM gels. As the concentration of the pigment in the NIPAM gels was increased, the amount of the volume change of the NIPAM gels was reduced. The water absorptivity of the NIPAM gels in the swollen state decreased as the pigment concentration increased, whereas the water absorptivity in the shrunken state was almost constant. Reducing the initial monomer concentration of the polymerization of the NIPAM gel increased the water absorptivity in the swollen state. With an increase in the water absorptivity, the volume changes of the NIPAM gels containing pigments were increased. Prototype light modulators in which the NIPAM gel particles containing pigment were dispersed between glass plates were fabricated. The light modulator using the gel particles with improved diameter change (d/d₀ = 2.3, where d and d₀ are the equilibrium diameter and the diameter of the fully shrunken state at 50 °C, respectively) exhibited a larger transmittance change from 8 to 79% than that using the gel particles before the improvement (d/d₀ = 1.7; from 38 to 79%) according to temperature changes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4644–4655, 2006     

Phase behaviour of mixtures of side-chain LC polyoxetanes with E7 and their field response

We prepared and characterized a series of side-chain liquid crystalline (LC) homo- and copolyoxetanes containing varying fractions of the mesogenic 4-decyloxy-4'-cyanobiphenyl pendent and the non-mesogenic propoxy group. The miscibility of homo- and copolyoxetanes (Co-LCPs) with E7 also was studied. The LC properties of the Co-LCP/E7 mixtures were unique in that, although E7 is a nematic mixture, all the Co-LCP/E7 mixtures form layered smectic mesophases. Among the mixtures, the composition of 30 wt % of LCP bearing 16 mol. % of the mesogenic pendant, Co(16)-LCP, and 70 wt % of E7 formed the smectic phase over a broad range of temperature (-70 to 35°C), although the isotropization temperature of Co(16)-LCP itself was below room temperature. A flexible plastic display was constructed utilizing this mixture and its display characteristics were evaluated. For a device with a 10 µm thick active layer, the threshold voltage was about 30 V and exhibited a rising response time of 200 ms. The most remarkable observation made was that the blends revealed excellent memory behaviour.     

Unusual mobility of hypercrosslinked polystyrene networks: Swelling and dilatometric studies

Hypercrosslinked polystyrene samples were prepared by an intensive postcrosslinking of highly swollen styrene–divinylbenzene copolymer beads to extremely high degrees of crosslinking that amounted to 100% or even higher. When in the dry state, the materials obtained represent transparent beads of reduced density. Despite the high degree of crosslinking, the materials manifest large increases in volume on swelling with any liquid media as well as large changes in volume on heating. The factors determining the unusual swelling ability of the hypercrosslinked polymers are briefly discussed. Thermodilatometric tests of the polymers with a moderate degree of crosslinking reveal a certain contraction of the beads at temperatures higher than 100 °C. When crosslinked far beyond 100%, the networks demonstrate unusual expansion in the 100–220 °C range; this is followed by a sharp shrinking at higher temperatures. The former is caused by an increased intensity of the vibration movements of the network and a partial relaxation of strong inner stresses; the latter is due to partial chemical oxidation, degradation of network units, or both. This degradation, however, is not accompanied by any loss in weight of the polymer but only results in a transformation into a more dense conventional nonporous material. The strained, rigid open‐work structure of the homogeneous expanded hypercrosslinked polystyrene networks is responsible for their unusual mobility. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1553–1563, 2000     

Closure characteristics of a thermally responsive single ion-track pore determined by size exclusion method

Cross-linked poly(N-isopropylacrylamide) (NIPAAm) gel was grafted on the wall of a single ion-track pore in poly(ethylene terephthalate) (PET). The opening and closing of the pore is controlled by temperature and observed by electric conductivity. In the shrunken state of the gel, ions and molecules can penetrate the membrane through the free volume of the pore. In the swollen state, the gel clogs the pore. Using mixtures of polyethylene glycol (PEG) of various molecular weights and 0.1 N potassium chloride, it was demonstrated that the responsive pore acts as a thermally controllable valve preventing the passage of PEG molecules larger than 2 nm. The mean value of the hydrogel mesh size is estimated to be (1.3±0.05) nm.     

Synthesis of oligofluorenes by endcapping

An efficient one-step synthesis of 9,9-di(2-ethylhexyl)-2,7-fluorene oligomers via an endcapping reaction is reported. Controlled endcapping demands a full conversion of functional groups and thus the Yamamoto reaction was chosen as the aryl-aryl coupling method. SEC analysis showed that the endcapping is complete. The molecular weights were adjusted in the range from 1300 to 3800 g mol^-1 by different amounts of endcapper. The mixtures exhibit broad mesophases and the transition temperatures strongly increase with molecular weight. In the series of oligomers reported here, clearing temperatures between 57°C and over 360°C could be realized.     

Thermal expansion of water in fine pores

The relative expansion of water in pores about 50 Å in size has been investigated within the temperature range of 0 to 90°C. It has been established that at a temperature higher than 70°C, the runs of curves in pores and the bulk phase coincide. This demonstrates that the structural peculiarities of water disappear at these temperatures. Comparison between the plotted curves enables one to evaluate the density of water in pores, which at room temperature differs from the bulk density by about 2%.     

Small-angle neutron scattering study on microstructure of poly(N-isopropylacrylamide)-block-poly(ethylene glycol) in water

By employing small-angle neutron scattering (SANS), we investigated the microstructures of, poly(N-isopropylacrylamide) (PNIPA)-block-poly(ethylene glycol) (PEG) (NE) in deuterated water D₂O, as related to macroscopic behaviors of fluidity, turbidity and synerisis. SANS revealed following results: (i) microphase separation occurs at around above 17 °C in a temperature range of transparent sol below 30 °C. In the microdomain appeared in the transparent sol state, both block chains of PNIPA and PEG are swollen by water; (ii) for the NE solution of polymer concentration W_p > 3.5% (w/v), corresponding to opaque gel above 30 °C, a percolated structure, i.e., network-like domain is formed by NE as a result of macrophase separation due to dehydration of the PNIPA chains. As the temperature increases toward 40 °C, the network domain is squeezed along a direction parallel to the NE interface, which leads to increase of the interfacial thickness given by swollen PEG chains and to the macroscopic synerisis behavior.     

A simultaneous TG–DTA study of the thermal decomposition of 2-hydroxybenzoic acid, 2-carboxyphenyl ester (salsalate)

Simultaneous thermogravimetry–differential thermal analysis (TG–DTA) and gas and liquid chromatography with mass spectrometry detection have been used to study the kinetics and decomposition of 2-hydroxybenzoic acid, 2-carboxyphenyl ester, commercially known as salsalate. Samples of salsalate were heated in the TG–DTA apparatus in an inert atmosphere (100 ml min⁻¹ nitrogen) in the temperature range 30–500 °C. The data indicated that the decomposition of salsalate is a two-stage process. The first decomposition stage (150–250 °C) had a best fit with second-order kinetics with E_a=191–198 kJ/mol. The second decomposition stage (300–400 °C) is described as a zero-order process with E_a=72–80 kJ/mol. The products of the decomposition were investigated in two ways:

(a)Salsalate was heated in a gas chromatograph at various isothermal temperatures in the range 150–280 °C, and the exit gas stream analyzed by mass spectrometry (GC–MS). This approach suggested that salsalate decomposes with the formation of salicylic acid, phenol, phenyl salicylate, and cyclic oligomers of salicylic acid di- and tri-salicylides.

(b)One gram samples of salsalate were heated in a vessel under nitrogen to 150 °C, and the residues were analyzed by liquid chromatography–mass spectrometry (LC–MS). The major compound detected was a linear tetrameric salicylate ester.

     

Sunna dosimeter: an integrating photoluminescent film and reader system; work in progress

A new radiation dosimeter, consisting of an optically-stimulated polymer film containing a photofluorescent sensor, can serve as a routine dosimeter and radiographic imaging medium for high-dose applications in the absorbed dose range 0.1–100 kGy. The flexible, colorless, opalescent film having a uniform thickness of 0.240 (±0.005) mm or certain other films in the thickness range 0.08–0.60 mm, are available in large batches. They can be read rapidly with a simple table-top spectrofluorimeter, excitation wavelength (λ=450 nm) and emission wavelength (λ=670 nm), giving a type A uncertainty of dose evaluation of <±5% at 95% confidence level. It supplies either single integrated dose readings or two-dimensional radiographic images with relatively high spatial resolution. The present work focuses on the following gamma-ray response characteristics of the system: inter- and intra-batch reproducibility, pre- and post-irradiation stability, and dependence of dose interpretations on absorbed dose rate and irradiation temperature.     

Effect of porosity on sulfonation of macroporous styrene-divinylbenzene beads

Macroporous styrene-divinylbenzene beads having pore volume in the range of 0.1-2.2 ml/g were synthesized by o/w suspension polymerization using petroleum ether and cyclohexanone as porogen. As the pore volume was increased the pore size distribution shifted towards large pore diameter and the mechanical strength of the beads in the dry state decreased. The copolymers were converted into cation-exchange resins by sulfonation under controlled experimental conditions. The derived resins had the highest capacity when the base copolymers had pore volume in the range of 0.3-0.4 ml/g. The results are explained on the basis of the effect of the porogen on the spaces between chains and cross-links in the copolymer phase and the permanent pores in the beads.