Here we report on the spontaneous assembly of Ti
3
C
2
T
x
MXene flakes into monolayer films at the liquid-air interface. According to X-ray reflectivity and grazing incidence X-ray fluorescence both ...the structure of the layers and assembly kinetics depends on the pH value of the solution. At pH > 4 MXene flakes form a single ∼1.5 nm thick layer carrying a negative charge, while in the acidic medium the layer contains coordinated anions with the formation of the Br
aq
−
/Ti
3
C
2
T
x
/subphase interface. The surface layer compression allows the assembling of MXene flakes into a dense monolayer films with the surface coverage of up to 96% and surface pressure exceeding 40 mN m
−1
in the case of the acidic subphase. The films can readily be transferred onto solid substrates by the conventional Langmuir-Blodgett approach or modified by surfactants to form MXene/surfactant composite films.
Here we report on the spontaneous assembly of Ti
3
C
2
T
x
MXene flakes into monolayer films at the liquid-air interface.
X-ray studies revealed the considerable enhancement of metal-binding properties in human hemoglobin under exposure to mild damaging factors (in the presence of 0.09 M urea or upon heating for 30 min ...at 50 °C). Changes in the element composition of the hemoglobin monolayer, formed on the water subphase in the Langmuir trough, have been monitored in real time by the total external reflection X-ray fluorescence measurements. X-ray absorption spectroscopy has been applied to study the local environment of zinc ions bound on hemoglobin molecules. According to these data, each zinc ion is coordinated by four ligands, two of which are cysteine and histidine. The oxidative stress has been found to accelerate extensively the enhancement of metal-binding ability in protein. A two-stage mechanism has been proposed as a possible explanation of the observed phenomenon: First, in the presence of the mild damaging agents, protein molecules can undergo a transition from the native conformation to a more labile intermediate state that increases the accessibility of amino acid residues (in particular cysteine). At the second stage, oxidation of cysteine and the subsequent activation of cysteine SH groups can affect markedly the protein–metal interaction. The presented investigations provide a deeper insight into the pathogenesis of metabolic disorders that excessive concentrations of the endogenic toxicants might trigger in an organism.
Thin graphene oxide (GO) membranes supported on porous anodic aluminum oxide (AAO) substrates prepared by spin-coating and pressure-assisted filtration are tested in gas dehumidification experiments. ...Graphene oxides with different specific nanosheet sizes ranged from 10 × 140 to 3300 nm synthesized by modified Hummer's method were used for membrane preparation. We have shown that 25–60 nm-thick GO membranes exhibit barrier properties towards most of the gases (CH4, N2, O2, C4H10), while revealing high permeance for water and water soluble vapors (CO2). The influence of the GO nanosheet size and the membrane preparation technique on the gas transport characteristics of the composite membranes are investigated. The best membrane performance has been achieved for membranes prepared from medium-flake-sized GO nanosheets providing high enough defect density at the surface to allow water entrance to the interlayer space and large enough nanosheet size to cover AAO nanochannels and create continuous barrier coating towards permanent gases on the surface. Water permeance and H2O/N2 selectivity measured in the relative humidity range of 10–80% shows strong humidity dependence due to the sorption of water vapors in the interlayer space of GO. Maximum H2O/N2 selectivity of 13,000 at water permeance of GO membranes of ~1.4 m3/(m2 h) has been achieved at standard conditions (298 K, 1 bar) and relative humidity of 80%. Water permeance of GO membranes strongly depends on the transmembrane pressure, diminishing an order of magnitude from equi-pressure conditions to 0.1 MPa pressure difference. The effect has been ascribed to a pressure-driven ousting of water molecules from the interlayer spacing of GO. Permeability of the GO membranes towards CO2 in humid mixed gas experiments has been shown to be enhanced strongly due to gas solubility in liquefied water enabling sweetening and dehumidification of natural and technological gases in a single stage.
•Membranes with selective graphene oxide layer were obtained by spin-coating technique.•Graphene oxide with different flake size and chemical properties were used for coating.•Membranes shows barrier properties to most of gases and high permeance of water vapor.•Performance of GO membranes is governed by transmembrane pressure and feed humidity.•Permeance of water soluble and non-soluble gases measured for wet and dry gas stream.
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High-resolution X-ray techniques were applied to examine the effects of gold nanoparticles (size <5 nm) on natural pulmonary surfactant and pure DPPC monolayers preliminarily formed on water subphase ...in a Langmuir trough. Hydrophobic and hydrophilic nanoparticles were delivered from nanoaerosol using electrodeposition method. Grazing incidence diffraction, X-ray reflectivity, and X-ray standing wave measurements allow to monitor the changes in molecular organization of lipid monolayer and to locate the position of gold nanoparticles. X-ray experiments were performed over a period of 9–14 h. The obtained results evidenced that, on a long time scale, the deposition of nanoparticles, even at low doses, can induce pronounced alterations in lipid monolayer. The presented data can help to elucidate the mechanism of pulmonary translocation of inhaled nanoparticles that is of special interest for biomedical investigations of potential risk of nanoaerosols for human health.
The effect of rolling modes and cooling conditions on the structure and mechanical properties medium-carbon manganese low-alloy steels of type 38G2F is investigated. The critical temperatures
Ac
1
...and
Ac
3
are determined. The characteristics of the ferrite, pearlite and bainite structural components (the content and the morphology) and the sizes of the initial austenite grains in pipes with different wall thicknesses are determined. Tensile mechanical tests are performed. It is shown that the high level of mechanical properties (σ
0.2
> 650 MPa, σ
r
> 900 MPa) of the pipes with wall thickness 16.0 mm is a result of the presence of bainitic component in the structure. It is suggested that the temperature of heating of the pipe billet for rolling should be reduced from 1230 – 1260°C to 1170 – 1180°C for manufacturing pipes with a size of ∅93.2 × 13.0 mm and ∅127 × 16.0 mm. The combination of their mechanical properties matches the E strength group.
The design of a roll-type electric baromembrane purifier for separating, concentrating, and purifying industrial solutions is improved; its parameters are calculated. The relative effective area of ...separation is doubled. The volume of the separated solution is increased by 38.2% compared to the prototype purifier.
We report on the specific properties of O- and OH-terminated Ti3C2Tx nanosheets contributing the permeance of MXene membranes with sorption type selectivity. Thin MXene selective layers on porous ...support demonstrated separation factor for NH3/H2 pair over 50 with ammonia permeance up to 5.0 m3(STP)∙m−2∙bar−1∙h−1 facilitated for humid medium and separation factor for H2O/N2 over 1000 with water permeance over 30 m3(STP)∙m−2∙bar−1∙h−1 close to P0(H2O). According to QCM and GIWAXS studies, high permeance and selectivity of membranes towards ammonia and water vapors are attributed both to ultimate sorption capacity for “basic” vapors and condensation-induced expansion of the interlayer space. Sorption capacity of MXene over 0.045 g∙g(MXene)−1 at 0.3P0 for both NH3 and H2O, significantly exceeds the sorption capacity for permanent gases. Calculations of the diffusion coefficient suggest labyrinthine transport of vapors. For permanent gases no variation of diffusion coefficients was observed with feed pressure, indicating Knudsen diffusion mechanism. Diffusion coefficient of strongly absorbed gases significantly increases with pressure. According to GIWAXS the effect was attributed to the increase of the interlayer distance with saturation of membrane with vapors and reduction of activation barriers for hopping diffusion. Demonstrated characteristics of Ti3C2Tx nanosheets makes it a promising candidate for developing of ammonia selective membranes for Haber-Bosch process membrane extractors.
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•Acidic properties of OH groups on MXene surface determine affinity to “basic” gases.•NH3 sorption coefficient attains 52 mmol/(m3·Pa), drastically exceed sorption for other gases.•Membranes with Ti3C2Tx selective layer were obtained by spin-coating technique.•Selectivity for a NH3/H2 exceeds 50 with ammonia permeance up to 3.91 m3 m−2 bar−1∙h−1.•The increase of interlayer distance with MXene saturation with vapors was founded.
The paper reports operando study of ultra-thin (50 nm) graphene oxide membranes by grazing incidence x-ray scattering in air dehumidification experiments. Absorption of water vapors in GO layers ...follows a modified Kelvin equation revealing condensation in an elastic slit, while desorption of water is limited by a few outer GO layers providing bottleneck restrictions to water transport and resulting in classical H2-type isotherms. GO interlayer distances (d) vary in range from 7.2 Å to 11.5 Å depending on partial water pressures in a feed stream and permeate. The permeance of water vapor through GO decreases steadily with decreasing interlayer distance between GO sheets from ~80 000 l/(m2 · atm · h) to ~30 000 l/(m2 · atm · h) falling down to negligible values below d 9.2 Å. Water transport in GO is described by Poiseuille equation and hopping diffusion depending on the number of water layers between GO planes, and was modelled with semi-empirical methods. It is shown the performance of thin GO membranes is strongly governed by the interstitial water quantity as dictated by water partial pressure.
Because tungsten (W) is used in present fusion devices and it is a reference material for ITER divertor and possible plasma-facing material for DEMO, we strive to understand the response of different ...W grades to ion bombardment. In this study, we investigated the behavior of mirrors made of four polycrystalline W grades under long-term ion sputtering. Argon (Ar) and deuterium (D) ions extracted from a plasma were used to investigate the effect of projectile mass on surface modification. Depending on the ion fluence, the reflectance measured at normal incidence was very different for different W grades. The lowest degradation rate of the reflectance was measured for the mirror made of recrystallized W. The highest degradation rate was found for one of the ITER-grade W samples. Pre-irradiation of a mirror with 20-MeV W6+ ions, as simulation of neutron irradiation in ITER, had no noticeable influence on reflectance degradation under sputtering with either Ar or D ions.
•The reflectance of W mirror specimens pre-damaged with W ions to a dose of 0.45 and 1.45 dpa behave just as the undamaged specimens when being subjected to sputtering with ions of Ar or D plasmas.•Behavior of the reflectance depends significantly on the W grade, namely, on the microstructure of W, such as distributions of grains on their size and orientation relative to the surface of the sample.•The dominant factor that defines the reflectance and surface roughness is the difference between the heights of grains with different sputtering rates of faces differently orientated relatively to the sample surface.
The morphology of structural components in hot rolled pipes made of 38G2F steel has been studied by optical metallography. It is shown that the sections elongated along the rolling direction with a ...morphology different from pearlite are sections of upper bainite, the hardness of which is comparable to the hardness of pearlite (~290–300 HV
μ
). Plotting the thermokinetic diagrams (TKD) of the decomposition of supercooled austenite, as well as a joint analysis of the microstructure and hardness, allowed us to determine the minimum velocity
V
cool
~ 0.5°C/s at which the bainite component in the pipe wall is formed. The temperature–time parameters of the decomposition of supercooled austenite with increasing austenitization temperature from 850 to 1000°C have been determined.
