Increasing Solution Concentration Research Articles

Investigation of the Metal Bioremediation Ability of Two Populations of Peganum Harmala

The present study aimed to investigate the effects of zinc exposure (0, 1, 5, 15, 30 mg/L zinc) on the biochemical and physiological parameters of Peganum harmala seedlings. Two populations (metallicolous and non-metallicolous) were compared in Zn tolerance, Zn accumulation, photosynthetic pigments, and enzymatic antioxidant activities. Plants were treated with Zn at concentrations of 0, 1, 5, 15, and 30 mg/L for 14 days. The study results showed that the increase of Zn concentration in the nutrient solution reduced shoot length, root length, root dry weight, shoot dry weight, chlorophyll a, chlorophyll b, total chlorophyll, and carotenoid in both populations; however, the accumulation was more pronounced in metallicolous populations (M) than in non-metallicolous (NM) ones. In response, the activities of antioxidant enzymes such as guaiacol peroxidase, lipoxygenase, superoxide dismutase, catalase, and ascorbate peroxidase were enhanced Zn exposure in both populations. Moreover, it was found that the metallicolous population of P. harmala had a greater capacity to adapt to oxidative stress caused by Zn than the non-metallicolous population, and antioxidative defense in the metallicolous population of P. harmala might have played an essential role in Zn tolerance. Therefore, P. harmala seemed to be a suitable candidate for accumulation; however, it was recommended that further investigations be carried out to explore its metal remediation ability. It is concluded that P. harmala can be a potential candidate for bioremediation of Zn contaminated soils.

Experimental Study on Damage Characteristics of Solidified Mud under Coupling Action of Freeze-Thaw Cycle and Chloride Salt

The physical properties of solidified mud will deteriorate under the combined action of freezing-thawing cycle and chlorine salt, which will affect the safety and stability of solidified mud engineering. In order to study the damage characteristics of solidified mud under the action of freeze-thaw cycle and chloride salt, the solidified mud samples were soaked in different concentrations of sodium chloride solution and treated with freeze-thaw cycle. Besides, the unconfined compressive strength test was carried out to study the damage characteristics of the samples caused by different concentrations of sodium chloride solution and freeze-thaw cycles. The test results show the following. (1) Under the action of freeze-thaw cycle and sodium chloride solution, the surface of the sample deteriorated in varying degrees. With the increase in freeze-thaw cycle times and sodium chloride solution concentration, the mass loss of the sample was greater. (2) Under the action of chlorine salt and freeze-thaw cycle, the strength of the sample decreases with the increase in freeze-thaw cycle times. With the increase in the concentration of sodium chloride solution, the strength of the sample decreases and the damage degree increases gradually. (3) Under the action of freeze-thaw cycle, the internal pores of the samples gradually expand and more honeycomb holes appear, and the content of hydration products is higher. As the concentration of sodium chloride solution increases, the particle connection inside the sample gradually weakens, and the sample is more likely to be damaged.

Influence of solution concentration and temperature on the repair effect for electrophoretic deposition of rust-cracked reinforced concrete

Electrophoretic deposition is a new method for the repair of rust-expanded cracked reinforced concrete, which needs high performance epoxy resin repair solution. Selecting an appropriate solution concentration and temperature, clarifying the molecule electrophoretic deposition rule in the repair process, and revealing the influence mechanism of solution concentration and temperature on the repair effect will help maximize the application potential of the proposed method and control repair costs. In this study, four high-performance epoxy resin solutions with different concentration and temperature were prepared. The molecule electrophoretic deposition rule during the repair process was explored via macroscopic observation, mass increment, and resistance tests. The influence mechanism of solution concentration and temperature on the repair effect is discussed using microscopic observations combined with theoretical analysis. The results show that the waterproofing, carbonation resistance, and stray current erosion resistance of repaired specimens improve as the solution concentration increases. With the increase of solution concentration, the number of molecules per unit volume and the current density between electrodes increased, so the repair speed was faster and the repair effect was better under the condition of high concentration. The high temperature reduced the viscosity of the repair solution, which was conducive to the rapid deposition of molecules in the solution on the surface of the specimen at the early stage of the repair, but was not conducive to the film formation of epoxy resin on the surface of the specimen. Therefore, the waterproof and carbonization resistance of the repaired specimen decreased after the temperature increased.

All-Chemical YBCO-Based Architecture Using a Simplified Multilayer Buffer Deposition

Chemical solution deposition (CSD) is a versatile and cheap technique widely used for both buffer layer and YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7−<i>δ</i></sub> (YBCO) epitaxial film growth. One of the main limits hindering the widespread use of the CSD technique in the field of coated conductors is the limited film thickness that can be reached without degradation. Among the different strategies adopted to obtain thicker film by CSD, increase of precursor solution concentration and viscosity can be mentioned. Another interesting approach is the use of multilayer deposition in order to overcome the limits of CSD technique. Multilayer deposition has been so far realized by performing a complete heat treatment - or at least a pyrolysis step - after each deposited layer, resulting in increased processing time and overall cost. In this contribution, we show that an epitaxial multilayer buffer can be easily obtained by means of multiple successive depositions, in which after each layer only a fast drying step of the precursor solution is carried out. In this way, only a single conversion heat treatment can be used. This approach not only allows a significant reduction on the processing time but also it is more suitable for the growth on metallic template. The viability of this approach is shown by using multilayer Zr-doped CeO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> buffer deposition on single crystalline YSZ substrate. It is shown that, up to 8 layers, no significant structural and morphological degradation of the buffer layer occurs. Further, YBCO film grown by CSD was used to test the suitability of multilayer buffer. YBCO film grown on multilayer buffer shows excellent superconducting properties, with zero-resistance critical temperature up to 92 K and a critical current density exceeding 1 MA/cm2 at 77 K in self field.

Composition dependence in glass-forming ability of Cu–Ag binary alloys

Alloys around eutectic points are thought to be good glass formers. However, the glass-forming ability (GFA) as a function of composition from pure metals to the eutectic alloy has not been quantified and the underlying microstructural and dynamical origins are unclear. In this work, the GFA of Cu–Ag alloys at various compositions was thoroughly investigated by using molecular dynamics simulations. According to the results, the critical cooling rate for glass formation Rc (K/s) varies with solute content x′ (at%), following Rc ≈ Aexp(kx′) where A = 4.61 × 1012 and k = -0.25 on the Cu side and A = 4.43 × 1012 and k = -0.19 on the Ag side. The Rc of the eutectic alloy is about 5 orders of magnitude lower than that of the pure metals. Structurally, the number of densely packed icosahedral-like clusters in Cu–Ag metallic glasses increases with increasing solute content, resulting in the most densely packed structure at the eutectic composition. The dynamical properties of Cu–Ag melts are basically independent on composition at high temperatures, but obviously change with composition at low temperature. Besides the largest reduced glass transition temperature, the highest five-fold symmetry (FFS) local structure and more importantly the retarded dynamics of liquid atoms below the liquidus temperature around the eutectic composition impart the eutectic alloy with the best glass-forming ability.

Subcritical growth of a crack interacting with the stress field of mobile solutes in an elastic solid in the presence of image effects: A kinetic Monte Carlo study

It is well known that the presence of foreign solutes could critically affect fracture properties of the solid solutions of critical importance to many technological advances. It has been shown recently that a prevalent continuum theory widely applied to such systems is inconsistent with classical elasticity which predicts that two point defects in an isotropic unbounded solid do not interact, and interact only in a finite solid through image stresses arising due to the presence of the boundaries. Previous studies have shown that the image stresses resulting from an external boundary of a finite solid also generally raise the stress intensity factors (SIFs) induced by the solutes at a crack tip. Here, we examine the possibility that the increase in the SIFs by image stress effects together with variations in the configuration of mobile solutes around a crack tip could from time to time push the crack tip SIFs beyond the critical value required for crack growth, and hence cause subcritical crack growth over time. Incorporating crack growth criterion in kinetic Monte Carlo (KMC) simulations and fully accounting for the image stress effects, we investigate this possibility by examining how temperature, solute concentration, and the difference between the loading-induced SIF and the critical SIF could affect crack growth. In agreement with an analysis based on the central limit theorem presented for the limit of high temperatures, our simulations indicate that the probability of the Griffith-Irwin criterion being met among various solute configurations generally increases with increasing solute concentration. The model shows that, within a certain range of the loading-induced SIF below the critical SIF, the crack growth rate increases with solute concentration, and this effect becomes particularly more evident at larger temperatures.

Chiral emergence in multistep hierarchical assembly of achiral conjugated polymers

Intimately connected to the rule of life, chirality remains a long-time fascination in biology, chemistry, physics and materials science. Chiral structures, e.g., nucleic acid and cholesteric phase developed from chiral molecules are common in nature and synthetic soft materials. While it was recently discovered that achiral but bent-core mesogens can also form chiral helices, the assembly of chiral microstructures from achiral polymers has rarely been explored. Here, we reveal chiral emergence from achiral conjugated polymers, in which hierarchical helical structures are developed through a multistep assembly pathway. Upon increasing concentration beyond a threshold volume fraction, dispersed polymer nanofibers form lyotropic liquid crystalline (LC) mesophases with complex, chiral morphologies. Combining imaging, X-ray and spectroscopy techniques with molecular simulations, we demonstrate that this structural evolution arises from torsional polymer molecules which induce multiscale helical assembly, progressing from nano- to micron scale helical structures as the solution concentration increases. This study unveils a previously unknown complex state of matter for conjugated polymers that can pave way to a field of chiral (opto)electronics. We anticipate that hierarchical chiral helical structures can profoundly impact how conjugated polymers interact with light, transport charges, and transduce signals from biomolecular interactions and even give rise to properties unimagined before.

Effects of functional groups and side chains on assembly of “X”-shaped new aggregation-induced emission molecules

The self-assembly properties of aggregation-induced emission molecules play important roles in electroluminescence devices and fluorescence sensors because noncovalent interactions in self-assembly structures would accelerate the excitation energy consumption. However, there are only few studies to explore their self-assembly properties on the interface and there is still a great need for further understanding self-assembled mechanisms from the viewpoint of molecular design. Here, we presented three X-shaped aggregation-induced emission molecules X1, X2 and X3, which decorated with different functional groups and alkyl side chains. The self-assembly structures were revealed by scanning tunneling microscopy technique in combination with density functional theory. Results showed that X-shaped molecules self-assembled into different structures, depending on their molecular structure, especially the functional groups. Furthermore, self-assembly structures could be regulated by adjusting solution concentration. In more detail, parallel with gradually increasing solution concentration, the molecules approached closer and molecule–molecule interactions were enhanced, finally resulting in new nanostructures. The self-assembly properties of three X-shaped aggregation-induced emission molecules on the liquid/solid interface would give a guidance for further exploring the aggregation state in three-dimensional space. Meanwhile, the two-dimensional nanostructures might show special properties, which could be used in fabricating next generation functional films.

Effect of varying pore water salinity on frost susceptibility behaviour of soils

The susceptibility of soil to frost action is a major distress for engineering infrastructure constructed over it in regions that experience seasonal freezing and thawing. The soil deposits which are not otherwise problematic for use as a subgrade/foundation material can become very problematic under seasonal freeze-thaw. Since presence of dissolved salts in pore water depresses the freezing-point and increases the unfrozen water content, it can be ascertained that pore water salinity can affect soil frost susceptibility due to seasonal temperature variations by reducing the total ice content during freezing. An experimental investigation was carried out to assess the effect of pore water solute content on the behaviour of a frost susceptible soil subjected to freeze-thaw cycles in a laboratory test setup as per ASTM D5918-13. The presence of solute primarily depressed the freezing point of the soil. The heave rate, maximum heave and the frost penetration depth was found to decrease with increasing solute concentration in pore water. The effect on the thaw-CBR value, variation in water migration pattern and micro-structural changes along the depth of the sample was also examined. It was found that the presence of solutes negates the undesirable effects during freezing by controlling ice segregation, frost penetration and heaving of the soil which in turn limit the adverse weakening during thawing. The destruction to soil at micro-structural level was also restricted in the samples containing solute in their pore water.

Evaluation of hydro-mechano-chemical behaviour of bentonite-sand mixtures

Bentonite-sand mixtures are widely used in engineering barrier of deep geological disposal of high-level radioactive nuclear waste and anti-seepage barrier of civil geotechnical engineering. Under the action of groundwater solution infiltration and external stress, the hydro-mechanical (HM) behaviour of bentonite-sand mixtures, i.e. the swelling characteristics and permeability, will change. Once the anti-seepage and filtration effect is weakened or lost, the pollutants will spread to the biosphere. Therefore, it is necessary to study the swelling characteristics and permeability of bentonite-sand mixtures under coupled mechano-chemical (MC) effect and to establish corresponding prediction model. For this reason, swelling tests under salt solution with different concentrations are conducted on pure bentonite and its mixtures with 30%, 70% and 90% sand contents, the compression tests are carried out on saturated samples, and the saturated permeability coefficient k of the sample under each load is calculated by Terzaghi's one-dimensional consolidation theory. The concepts of true effective stress p e , montmorillonite void ratio e m and critical sand content α s are introduced to determine the e m - p e relationship and finally the k - e m relationship of bentonite-sand mixtures. It is found that when the sand content α ≤ α s , the e m - p e relationship of the mixture is linear and independent of the salt solution concentration, and when α > α s , the e m - p e relationship of bentonite-sand mixture is bi-linear with the true effective deviatoric stress p esα as the intersection. In addition, the e m - k relationship also shows the linear trend when α ≤ α s , and the slope of the line increases with the increase of the salt solution concentration. When α > α s , the k - e m relationship will deviate from the linear relationship. Moreover, the larger the sand content is, the farther the deviation is. On the basis of summing the regularity, a model for predicting the HM behaviour of bentonite-sand mixture under the coupled MC effect is proposed. By comparing the swelling and permeability test results with model prediction results of different types of bentonite and its sand mixtures, the predictive model is verified. The study on the HM behaviour of bentonite-sand mixtures under salt solution infiltration and the model establishment can provide experimental and theoretical basis for the design and construction of anti-seepage engineering by bentonite-sand mixtures.

Comparison of different treatment methods on macro-micro characteristics of Yellow River silt solidified by MICP technology

The cementation of Yellow River silt into green and sustainable building materials through microbial induced calcium carbonate precipitation (MICP) is a novel technology with a wide range of applications. The MICP treatment of abandoned Yellow River silt was carried out by multiple-phase injection method and pre-mixing method in this paper. The effects of cementation solution concentration and treatment times on the chemical conversion efficiency were investigated, and the effectiveness of the two treatment methods in improving the mechanical properties of Yellow River silt was evaluated. The results showed that the chemical conversion efficiency of the pre-mixing method was about 5% higher than that of the multiple-phase injection method. With the increase of the cementation solution concentration and the treatment times, the unconfined compressive strength (UCS) of the samples treated by the pre-mixing method increased faster and the distribution of calcium carbonate (CaCO3) was more uniform. After ten treatments, the UCS of the samples treated by pre-mixing method exceeds 5 MPa with a relatively uniform CaCO3 content of 25%.

Abrupt changes in the physical and biological structure of endorheic upland lakes due to 8‐m lake‐level variation during the 20th century

AbstractClimate‐induced variation in lake level can affect physicochemical properties of endorheic lakes, but its consequences for phototrophic production and regime shifts are not well understood. Here, we quantified changes in the abundance and community composition of phototrophs in Kenosee and White Bear lakes, two endorheic basins in the parkland Moose Mountain uplands of southeastern Saskatchewan, Canada, which have experienced &gt; 8 m declines in water level since ~ 1900. We hypothesized that lower water levels and warmer temperatures should manifest as increased abundance of phytoplankton, particularly cyanobacteria, and possibly trigger a regime shift to turbid conditions due to evaporative concentration of nutrients and solutes. High‐resolution analysis of sedimentary pigments revealed an increase in total phototrophic abundance (as β‐carotene) concurrent with lake‐level decline beginning ~ 1930, but demonstrated little directional change in cyanobacteria. Instead, significant increases in obligately anaerobic purple sulfur bacteria (as okenone) occurred in both lakes during ~ 1930–1950, coeval with alterations to light environments and declines in lake level. The presence of okenone suggests that climate‐induced increases in solute concentrations may have favored the formation of novel bacterial habitats where photic and anoxic zones overlapped. Generalized additive models showed that establishment of this unique habitat was likely preceded by increased temporal variance of sulfur bacteria, but not phytoplankton or cyanobacteria, suggesting that this abrupt change to physical lake structure was unique to deep‐water environments. Such climate‐induced shifts may become more frequent in the region due to hydrological stress on lake levels due to warming temperatures across the Northern Great Plains.

Comparative Analysis of Root Na+ Relation under Salinity between Oryza sativa and Oryza coarctata

Na+ toxicity is one of the major physiological constraints imposed by salinity on plant performance. At the same time, Na+ uptake may be beneficial under some circumstances as an easily accessible inorganic ion that can be used for increasing solute concentrations and maintaining cell turgor. Two rice species, Oryza sativa (cultivated rice, salt-sensitive) and Oryza coarctata (wild rice, salt-tolerant), demonstrated different strategies in controlling Na+ uptake. Glasshouse experiments and gene expression analysis suggested that salt-treated wild rice quickly increased xylem Na+ loading for osmotic adjustment but maintained a non-toxic level of stable shoot Na+ concentration by increased activity of a high affinity K+ transporter HKT1;5 (essential for xylem Na+ unloading) and a Na+/H+ exchanger NHX (for sequestering Na+ and K+ into root vacuoles). Cultivated rice prevented Na+ uptake and transport to the shoot at the beginning of salt treatment but failed to maintain it in the long term. While electrophysiological assays revealed greater net Na+ uptake upon salt application in cultivated rice, O. sativa plants showed much stronger activation of the root plasma membrane Na+/H+ Salt Overly Sensitive 1 (SOS1) exchanger. Thus, it appears that wild rice limits passive Na+ entry into root cells while cultivated rice relies heavily on SOS1-mediating Na+ exclusion, with major penalties imposed by the existence of the “futile cycle” at the plasma membrane.

Frustrated Coulombic and Cation Size Effects on Nanoscale Boehmite Aggregation: A Tumbler Small- and Ultra-Small-Angle Neutron Scattering Study

To better understand the effects of solution chemistry on particle aggregation in the complex legacy tank wastes at the Hanford (WA) and Savannah River (SC) sites, we have performed a series of tumbler small- and ultra-small-angle neutron scattering experiments on 20 wt % solid slurries of nanoparticulate aluminum oxyhydroxide (boehmite) with M1+ nitrates of various concentrations and radii. The solutes consisted of H, Li, Na, K, and Rb nitrates at 10–5, 10–3, 10–1, 2, and 4 molal (m) concentrations, as well as in pure H2O. Synthetic boehmite nanoparticles were used with a size range from ∼20 to 30 nm. Tumbler cells were used to keep the solids from settling. Although particles initially form individual rhombohedral platelets, once placed in solution, they quickly form well-bonded stacks, primary aggregates, up to ∼1500 Å long, and a second level of aggregates whose concentration and structure vary as a function of cation type and concentration. Aggregation generally increases with increased solute concentration and with cation radius up to a concentration somewhat above 10–1 m, at which point the trend reverses. Primary aggregates become more rodlike and larger. The Kirkwood-like reversal probably reflects a change from Derjaguin–Landau–Verwey–Overbeek (DLVO)/Debye behavior controlled by surface chemistry to a frustrated Coulombic system controlled by the solution structure. These data suggest that an understanding of the effects of salt concentration and chemistry on nanoparticle aggregate structures provides useful physical insights into the microscopic origin of slurry rheology in the Hanford and Savannah River legacy wastes.

Dynamic precipitation and strengthening in a Mg-Zn-Gd alloy during hot deformation

Dynamic precipitation and microstructural evolution during hot deformation in a Mg-Zn-Gd alloy were investigated through systematic microstructural characterizations. Fast dynamic precipitation of β’-Mg7Gd rods was activated along dislocations during plastic deformation in Mg97Zn1Gd2 samples annealed at 773 K for 10 h. Transformation of Mg3GdZn to 14H long-period stacking ordered (LPSO) phase increased solute concentration in Mg matrix by ~ 50% after annealing, which perhaps play an important role in activating dynamic precipitation during subsequent hot deformation, besides assistance of heterogeneous nucleation along dislocations. However, dislocations in cold deformed samples would dissociate upon subsequent annealing at 573 K, producing stacking faults with Suzuki segregation of both Zn and Gd, instead of activating fast precipitation of β’-Mg7Gd rods. Moving dislocations may attract Gd atoms near their slip planes during hot deformation, which is critical for producing local compositional fluctuation high enough to facilitate dynamic precipitation of β’-Mg7Gd. Both the formation of 14H LPSO and dynamic precipitation of β’-Mg7Gd should play a role in strengthening the Mg97Zn1Gd2 alloy.

Physicochemical Limitations of Capillary Models Applied to High-Concentration Polymer Solutions.

Advances in binder jet printing (BJP) require the development of new binder–powder systems, for example, to increase compatibility with better performance metal alloys or to increase the strength of parts using stronger binders. The dynamics of binder absorption are principally understood through capillary models. However, validation of these models in BJP has focused on variation of powder properties. Using a design-of-experiments approach and an optical observation method to track absorption of droplets, this study tests the influence of fluid properties on absorption time against the predictions of capillary models. Properties specific to polymeric binders, such as molecular weight and entanglement state, are also considered. Capillary models are found to be generally accurate in predicting absorption time in dilute systems; however, these predictions are not accurate for highly concentrated binder solutions. The effect of polymer entanglement becomes prevalent as the solution concentration increases, which can also potentially occur as a result of increased evaporation due to powder bed heating. Specifically, concentrated solutions close to the onset of entanglement will absorb much more slowly than predicted. Future models of BJP systems must account for the possibility of polymer entanglement throughout the absorption process. Improved models will provide a more accurate understanding of the flow and solidification of the binder in the powder, allowing faster development of new binders for improved performance in printing.

Shear strength of bentonite saturated with saline solutions exhibiting variety of cations

Investigation of saline solutions on the shear strength (SS) of compacted bentonite is desideratum to evaluate the safety of engineered barriers in order to safely dispose of the high-level radioactive waste. Undrained shear experiments were carried out on Na-bentonite saturated with CaCl2, KCl, and NaCl solutions. The stress-strain relationship of all the bentonite samples exhibits strain softening behavior, and the peak stress increases with the increase of the saline solution concentration. The SS of samples in saline solutions at 0.1 mol/L (M) follows the order of NaCl< KCl < CaCl2, whereas, in 0.5 M salt solutions it follows the order of NaCl<CaCl2 < KCl, indicating that the cation exchange process has a major impact on the SS of bentonite. The modified effective stress concept p’ was used to express the SS in various salt solutions based on Mohr-Coulomb criterion. The results further revealed that the solution concentration had minimal effect on the angle of internal friction φ’. In addition, the strength envelope remains the same when samples are saturated with different concentrations of NaCl solution, unlike the samples saturated with KCl and CaCl2. At lower salinity concentration (0.1 M), the SS in CaCl2 solution approaches maximum value because of higher osmotic suction. On the contrary, the SS of bentonite saturated with KCl attains the highest value at high concentration (0.5 M), which is attributed with strong K-linkage and low hydration energy of potassium ion.

Experimental Study on Durability and Mechanical Properties of High Ductile Concrete under Long-Term Sulfate Attack

Uniaxial compression on high ductile concrete after erosion by different concentrations of sulfate solutions was conducted. The compressive strength, mass change fraction, corrosion resistance coefficient and other parameters on the basic mechanical properties of high ductile concrete is studied. The erosion form and uniaxial compression failure characteristics of the samples was analyzed. And using scanning electron microscope to observe the microscopic morphology of the samples, it is found that sulfate and age accelerate the damage to high ductile concrete, with its damage mechanism revealed. The test results are as follows: with the increase of age, the compressive strength and quality of high ductile concrete in 5%, 10% and saturated sulfate solution will increase first and then decrease; the mass change fraction of high ductile concrete is greater than that of ordinary concrete, it has the characteristics of self-compacting before the erosion age of 270 days, Then, as the sulfate solution concentration increases, the damage of the high ductile concrete becomes more serious. The comparison test with ordinary concrete shows that high ductile concrete has higher resistance to sulfate attack. This research can provide experimental basis for the application of high ductile concrete in engineering under sulfate corrosion environment.

Synthesize of ZnO Nanorods on Quartz Substrates with Seed Layer via Hydrothermal Method: Influence of Solution Concentration

Vertically oriented ZnO nanorods have been synthesized by hydrothermal method on quartz substrates with a seed layer. The influence of solution concentration on the morphology, structural and optical properties was analyzed. Results indicated that with the increase of solution concentration, the diameter and uniformity of ZnO nanorods increased. And the preferred orientation is obviously which shows better crystal quality. Typically, when the solution concentration is 0.03 mol/L, the nanorods exhibit a stronger UV emission peak located around 380 nm. In the visible region, all synthesized samples demonstrate more than 80% of optical transparency.

A volumetric and intra-diffusion study of solutions of AlCl3 in two ionic liquids - [C2TMEDA][Tf2N] and [C4mpyr][Tf2N

Intra-diffusion coefficients (DSi) have been measured for the ionic liquid constituent ions and aluminium-containing species in aluminium chloride (AlCl3) solutions in the ionic liquids 1-(2-dimethyl-aminoethyl)-dimethylethylammonium bis(trifluoromethylsulfonyl)amide ([C2TMEDA][Tf2N]) and N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([C4mpyr][Tf2N]), to investigate whether spectroscopically detected interactions between the ions and AlCl3 affect these properties. Such electrolyte solutions are of interest for the electrowinning of aluminium. The temperature, composition and molar volume dependences are investigated. Apparent (Vϕ,1) and partial molar (V1) volumes for AlCl3 have been calculated from solution densities. For [C2TMEDA][Tf2N] solutions, Vϕ,1 increases with increasing solute concentration; for [C4mpyr][Tf2N] solutions, it decreases. In pure [C2TMEDA][Tf2N], the cation diffuses more quickly than the anion, but this changes as the AlCl3 concentration increases. In the [C4mpyr][Tf2N] solutions, the intra-diffusion coefficient ratio remains equal to that for the pure ionic liquid and the aluminium species diffuses at approximately the same rate as the anion at each composition. The intra-diffusion coefficients can be fitted to the Ertl-Dullien free volume power law by superposing the iso-concentration curves with concentration dependent, but temperature independent, molar volume offsets. This suggests that they are primarily dependent on the molar volume and secondarily on a colligative thermodynamic factor due to dilution by AlCl3. AlCl3 complexation by [Tf2N]- and [C2TMEDA]+, confirmed by 27Al, 15N and 19F NMR spectroscopy, seems to play a minor role. Our results indicate that the application of free volume theories might be fruitful in the study of the transport properties of ionic liquid solutions and mixtures.