Elevated Solution Temperatures Research Articles

Effects of solution treatments on the microstructure and mechanical properties of Inconel 625 fabricated by electron beam freeform fabrication

The present study investigated the effects of solution treatments on the microstructure and mechanical properties of Inconel 625 fabricated by electron beam freeform fabrication. The results indicated that the microstructure of the as-deposited specimen exhibited typical dendritic characteristics. Meanwhile, the Laves ((Ni,Fe,Cr)2(Nb,Mo,Ti)) phases and needle-shaped δ phases precipitated. The deposition process led to the development of a preferred orientation feature along the building direction, and the typical {001}<100> plate texture was observed. Solution treatments at 900 °C and 1000 °C resulted in the precipitation of more δ phases, and the volume fraction was approximately 5.29 % and 7.96 %, respectively. The precipitated phases fully dissolved at solution temperatures of 1100 °C and 1200 °C, and equiaxed grains with a twin substructure were formed. The recrystallization weakened the preferred orientation, leading to a decrease in grain size and the formation of {111}<1–10> texture. The as-deposited specimen exhibited an ultimate tensile strength (UTS) of 682 MPa, a yield strength (YS) of 410 MPa, and an elongation of 56.4 %. Solution treatment had minimal impact on the UTS, and the YS was mainly contributed by the solid solution strengthening. However, the elongation was greatly improved at elevated solution temperatures, and the elongation was increased to 72.1 % at most. The primary mode of fracture was toughness fracture, which was attributed to the coalescence of microvoids. The solution treatment at 900 °C led to a fracture pattern that exhibited a combination of toughness and brittleness, and decreased the elongation to 48.5 %.

Experimentally verified thermodynamic framework for corrosion

Utilizing the foundational principles of thermodynamics, this study characterizes material degradation resulting from corrosion, substantiating the outcomes through experimental verification. The proposed methodology establishes a unified corrosion model, effectively correlating entropy generation with measurable parameters, including potential difference, corrosion current, and temperature. The Degradation Entropy Generation (DEG) theorem is applied to establish a linear relationship between entropy generation and the degradation rate through a constant material property known as the degradation coefficient (B). Material degradation, quantified by assessing the material loss, is systematically examined with a focus on low-carbon steel (LCS 1018) and Al6061-T6. Corrosion experiments were conducted using a three-electrode electrochemical corrosion cell immersed in a 3.5 wt% NaCl aqueous solution. The degradation parameter, B, for both materials was assessed through multiple accelerated corrosion tests, where various magnitudes of potentials were applied to specimens with differing exposed areas. The presented results unveil a consistent degradation coefficient of (30±2)×10−9 m3K/J for LCS 1018 and (25±2)×10−9 m3K/J for Al6061-T6. To ascertain the generalizability of these findings under diverse environmental conditions, additional experiments are conducted on LCS 1018, exposing it to varying environmental parameters such as different percentages of NaCl solution, acidic conditions, and elevated solution temperatures. Remarkably, the degradation coefficient remains constant across all tested corrosive environments, attesting to its independence. This study offers a novel approach to understanding material degradation through a thermodynamic lens and demonstrates the applicability of the proposed corrosion model in diverse and challenging operational conditions.

Synthesis and characterization of sulfate precursor based SnS thin films using SILAR technique at elevated solution temperature

In this study, a microprocessor-controlled SILAR technique was used to prepare SnS thin films on glass substrates using equimolar SnSO4 and Na2S precursors. The combination of sulfate precursor and increase in the solution temperature lead to the dilution of phase purity. The effects of these heterogeneous phase blend on the structural, optical, electrical and photo-response properties of the films were studied in detail. The coexistence of the SnS and SnO2 phases was confirmed by XRD and Raman analysis. The energy band structure of the films was significantly affected by the presence of SnO2. The optical band gap of the films shifted from the mid-visible to the UV region of the electromagnetic spectrum as the amount of mixed phases in the films increased. The photoluminescence spectra also showed prominent emission in the blue and green regions arising from the phase coexistence. Marginal increase in the electrical conductivity was observed for higher solution temperature. The rise-time of the photocurrent was found to increase significantly (nearly 80 %) owing to the presence of heterogenous phase blend. This prolonged decay time suggests the possibility of persistent photoconductivity (PPC) in the films. Data availability statementThe data cannot be made available at this point as the results presented here are part of ongoing research work.

ВПЛИВ ВИСОКОТЕМПЕРАТУРНОГО ОКИСЛЕННЯ НА КОРОЗІЙНУ СТІЙКІСТЬ ХРОМОСИЛІЦІЙОВАНОЇ СТАЛІ 45

Purpose. Improving the heat resistance and corrosion resistance of carbon steels can be achieved by applying to their surface coatings based on molybdenum and silicon, niobium and silicon, vanadium and silicon, chromium and silicon, which form on the surface protective films of oxides. In this work properties of chromosilicide diffusion coatings applied to steel 45 obtained by the gas method are investigated. Methodology. Diffusion chromosilicide coatings were applied to steel 45 by the gas method. The process was carried out for 6 hours in a closed reaction medium at the pressure of the active gas phase (106 Pa) and a temperature of 1323K. In the work wad studied phase and chemical compositions of diffusion coatings. The heat resistance of the coatings was studied in a specially designed shaft furnace. Corrosion tests were performed by massometric method .The electrochemical behavior of steel and coated steel was studied by the method of removing polarization curves on the potentiostat PI-50.1.1. Results. X-ray diffraction layer analysis revealed that the diffusion layer on the surface of steel 45 consists of two zones - the outer (10–15) 10-6 m, which contains chromium carbides Cr23C6 and Cr7C3 and inner (60–80) 10-6 m, which consists of a solid solution of silicon and chromium α-Fe. The total thickness of the coatings is 100 μm. Microhardness – 19.5 GPa. It was found that chromosilicide coatings obtained by the gas method have high heat resistance up to 1000 С. It is shown that diffusion chromosilicide coatings oxidized at temperatures of 700–800С have higher corrosion resistance in various aggressive environments and a more stable passive state than non-oxidized ones. The degree of protection reaches 99,92–99,99%. Based on the research, a new method of diffusion coatings on the surface of carbon steels with subsequent oxidation was proposed. Practical value. Chromosilicide coatings can be recommended for the protection of machine parts operating at elevated temperatures in various aggressive solution. References 20, tables 1, figures 3.

Meticulous Doxorubicin Release from pH-Responsive Nanoparticles Entrapped within an Injectable Thermoresponsive Depot.

The dual stimuli-controlled release of doxorubicin from gel-embedded nanoparticles is reported. Non-cytotoxic polymer nanoparticles are formed from poly(ethylene glycol)-b-poly(benzyl glutamate) that, uniquely, contain a central ester link. This connection renders the nanoparticles pH-responsive, enabling extensive doxorubicin release in acidic solutions (pH 6.5), but not in solutions of physiological pH (pH 7.4). Doxorubicin-loaded nanoparticles were found to be stable for at least 31 days and lethal against the three breast cancer cell lines tested. Furthermore, doxorubicin-loaded nanoparticles could be incorporated within a thermoresponsive poly(2-hydroxypropyl methacrylate) gel depot, which forms immediately upon injection of poly(2-hydroxypropyl methacrylate) in dimethyl sulfoxide solution into aqueous solution. The combination of the poly(2-hydroxypropyl methacrylate) gel and poly(ethylene glycol)-b-poly(benzyl glutamate) nanoparticles yields an injectable doxorubicin delivery system that facilities near-complete drug release when maintained at elevated temperatures (37 °C) in acidic solution (pH 6.5). In contrast, negligible payload release occurs when the material is stored at room temperature in non-acidic solution (pH 7.4). The system has great potential as a vehicle for the prolonged, site-specific release of chemotherapeutics.

Removal of vanadium from aquatic environment using phosphoric acid modified rice straw

Vanadium (V) is a toxic metal, which dominantly exists as V5+ in an aquatic environment. Rice straw, which is an abundant agricultural by-product throughout China was used to treat V5+ containing wastewater as an adsorbent after phosphoric acid treatment. The effects of initial V5+ concentration, solution temperature, pH and reaction time on V removal by phosphoric acid modified rice straw (AcM) were systematically assessed. A pH range of 2.0–3.0 was favorable for V removal and the adsorption capacity of V by AcM increased with elevated solution temperature. The maximum adsorption capacity for water containing 500 mg V5+ L−1 was 24.70 mg V g−1 dry matter under the optimum operation (3.33 g L−1 AcM, pH = 2.0, 50 °C, and 200 rpm for 4 h). Adsorption experiment data fitted well to pseudo-second-order kinetic and Langmuir adsorption isotherm models. In the presence of coexisting ions, Na+, Cu2+, NO3− and Cl− had no significant (P > 0.05) effect on V removal. These results indicated that AcM derived from agricultural waste was effective to remove V5+ from aqueous solution.

Effect of Immersion Time on the Structure of Octanethiol Self‐Assembled Monolayers on Au(111) at an Elevated Solution Temperature

STM images showing the phase transition of OT SAMs on Au(111) from the closely packed c(4 × 2) phase to the loosely packed (6 × √3)25° phase.

Abnormal increase of TCP phase during heat treatment in a Ni-based single crystal superalloy

Generally, elevated solution heat treatment temperature decreases the residual dendritic segregation of refractory elements (i.e. Re and W) and suppresses the precipitation of deleterious topologically close-packed (TCP) phases in Ni-based superalloys. However, in the present study, elevated solution temperature resulted in an abnormal increase of TCP phases in a Ni-based single crystal superalloy after long-term thermal exposure at 900 °C. Microstructural analysis suggested that higher supersaturation in γ phase which promoted the formation of TCP phases was induced by the increased γ′ precipitation after heat treated at elevated solution temperature.

High-temperature annealing of ZnO nanoparticles increases the dissolution magnitude and rate in water by altering O vacancy distribution

The effects and mechanism of high-temperature annealing, a frequently-used strategy to modulate the properties of nanoparticles (NPs), on the dissolution of zinc oxide (ZnO) NPs are investigated in this study. The results show that annealing increases the ZnO NPs dissolution magnitude via increasing O vacancy abundance on the surface and in the bulk crystal. The face-dependent distribution of O vacancy is revealed by characterizing ZnO single crystal, and the (000-1) face has a higher abundance than the (10-10) face. Particularly, O vacancy abundance in the bulk (000-1) is about 3 times higher than in the bulk (10-10). Annealing further strengthens the face-dependence of O vacancy distribution, therefore both raw and annealed (000-1) faces contribute dominantly to the dissolution of ZnO NPs. Typical topographies of the surface defect sites on the (000-1) face and their evolutions during dissolution are collected. Annealing promotes the formation of larger and deeper etching pits. Elevated solution temperature and annealing synergize to further accelerate ZnO dissolution. The dissolution behaviors of ZnO NPs with different annealing statuses, surface properties, and solution temperatures investigated in this study have potential implications to the evaluations of environmental fate and risk of metal oxide NPs.

Abnormal Increase of TCP Phase During Heat Treatment in a Ni-Based Single Crystal Superalloy

Generally, elevated solution heat treatment temperature decreases the residual segregation of refractory elements (i.e. Re and W) and suppresses the precipitation of deleterious topologically close-packed (TCP) phases in Ni-based superalloys. However, in the present study, elevated solution temperature resulted in an abnormal increase of TCP phases in a Ni-based single crystal superalloy after long-term thermal exposure at 900 oC. Microstructural analysis suggested that higher supersaturation in γ phase which promoted the formation of TCP phases was induced by the increased γ' precipitation after heat treated at elevated solution temperature.

Substance P in Solution: Trans-to-Cis Configurational Changes of Penultimate Prolines Initiate Non-enzymatic Peptide Bond Cleavages.

We report ion mobility spectrometry and mass spectrometry studies of the non-enzymatic step-by-step degradation of substance P (subP), an 11-residue neuropeptide, with the sequence Arg1-Pro2-Lys3-Pro4-Gln5-Gln6-Phe7-Phe8-Gly9-Leu10-Met11-NH2, in ethanol. At elevated solution temperatures (55 to 75 °C), several reactions are observed, including a protonation event, i.e., [subP+2H]2+ + H+ → [subP+3H]3+, that appears to be regulated by a configurational change and two sequential bond cleavages (the Pro2-Lys3 peptide bond is cleaved to form the smaller nonapeptide Lys3-Met11-NH2 [subP(3-11)], and subsequently, subP(3-11) is cleaved at the Pro4-Gln5 peptide bond to yield the heptapeptide Gln5-Met11-NH2 [subP(5-11)]). Each of the product peptides [subP(3-11) and subP(5-11)] is accompanied by a complementary diketopiperazine (DKP): cyclo-Arg1-Pro2 (cRP) for the first cleavage, and cyclo-Lys3-Pro4 (cKP) for the second. Insight about the mechanism of degradation is obtained by comparing kinetics calculations of trial model mechanisms with experimental data. The best model of our experimental data indicates that the initial cleavage of subP is regulated by a conformational change, likely a trans→cis isomerization of the Arg1-Pro2 peptide bond. The subP(3-11) product has a long lifetime (t1/2 ~ 30h at 55 °C) and appears to transition through several structural intermediates prior to dissociation, suggesting that subP(3-11) is initially formed with a Lys3-trans-Pro4 peptide bond configuration and that slow trans→cis isomerization regulates the second bond cleavage event as well. From these data and our model mechanisms, we obtain transition state thermochemistry ranging from ΔH‡ = 41 to 85kJmol-1 and ΔS‡ = - 43 to -157Jmol-1K-1 for each step in the reaction. Graphical Abstract.

Strong Blue Emission from Sb3+-Doped Super Small CsPbBr3 Nanocrystals.

Colloidal lead halide perovskite nanocrystals (NCs) have high tunability in the visible light region and high photoluminescence quantum yields (PL QYs) for green and red emissions, but bright blue emission is still a challenge. Super small CsPbBr3 perovskite NCs emit blue light around 460 nm with a narrow peak width, and they do not have the problem of phase separation like their Cl-Br counterparts. However, the blue emission from super small CsPbBr3 NCs easily becomes green over time, and their PL QY is still low. The doping of Sb3+ ions successfully reduced the surface energy, improved the lattice energy, passivated the defect states below the band gap, eventually boosted the PL QY of blue emission to 73.8%, and resulted in better spectral stability even at elevated temperatures in solution (40-100 °C). Its CIE coordinates were (0.14, 0.06), which are close to the primary blue color (0.155, 0.070) according to the NTSC TV color standard.

Conformationally Regulated Peptide Bond Cleavage in Bradykinin.

Ion mobility and mass spectrometry techniques are used to investigate the stabilities of different conformations of bradykinin (BK, Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9). At elevated solution temperatures, we observe a slow protonation reaction, i.e., [BK+2H]2++H+ → [BK+3H]3+, that is regulated by trans → cis isomerization of Arg1-Pro2, resulting in the Arg1- cis-Pro2- cis-Pro3-Gly4-Phe5-Ser6- cis-Pro7-Phe8-Arg9 (all- cis) configuration. Once formed, the all- cis [BK+3H]3+ spontaneously cleaves the bond between Pro2-Pro3 with perfect specificity, a bond that is biologically resistant to cleavage by any human enzyme. Temperature-dependent kinetics studies reveal details about the intrinsic peptide processing mechanism. We propose that nonenzymatic cleavage at Pro2-Pro3 occurs through multiple intermediates and is regulated by trans → cis isomerization of Arg1-Pro2. From this mechanism, we can extract transition state thermochemistry: Δ G‡ = 94.8 ± 0.2 kJ·mol-1, Δ H‡ = 79.8 ± 0.2 kJ·mol-1, and Δ S‡ = -50.4 ± 1.7 J·mol-1·K-1 for the trans → cis protonation event; and, Δ G‡ = 94.1 ± 9.2 kJ·mol-1, Δ H‡ = 107.3 ± 9.2 kJ·mol-1, and Δ S‡ = 44.4 ± 5.1 J·mol-1·K-1 for bond cleavage. Biological resistance to the most favored intrinsic processing pathway prevents formation of Pro3-Gly4-Phe5-Ser6- cis-Pro7-Phe8-Arg9 that is approximately an order of magnitude more antigenic than BK.

Electron-Deficient Near-Infrared Pt(II) and Pd(II) Benzoporphyrins with Dual Phosphorescence and Unusually Efficient Thermally Activated Delayed Fluorescence: First Demonstration of Simultaneous Oxygen and Temperature Sensing with a Single Emitter.

We report a family of Pt and Pd benzoporphyrin dyes with versatile photophysical properties and easy access from cheap and abundant chemicals. Attaching 4 or 8 alkylsulfone groups onto a meso-tetraphenyltetrabenzoporphyrin (TPTBP) macrocylcle renders the dyes highly soluble in organic solvents, photostable, and electron-deficient with the redox potential raised up to 0.65 V versus the parent porphyrin. The new dyes intensively absorb in the blue (Soret band, 440-480 nm) and in the red (Q-band, 620-650 nm) parts of the electromagnetic spectrum and show bright phosphorescence at room-temperature in the NIR with quantum yields up to 30% in solution. The small singlet-triplet energy gap yields unusually efficient thermally activated delayed fluorescence (TADF) at elevated temperatures in solution and in polymeric matrices with quantum yields as high as 27% at 120 °C, which is remarkable for benzoporphyrins. Apart from oxygen sensing, these properties enable unprecedented simultaneous, self-referenced oxygen and temperature sensing with a single indicator dye: whereas oxygen can be determined either via the decay time of phosphorescence or TADF, the temperature is accessed via the ratio of the two emissions. Moreover, the dyes are efficient sensitizers for triplet-triplet annihilation (TTA)-based upconversion making possible longer sensitization wavelength than the conventional benzoporphyrin complexes. The Pt-octa-sulfone dye also features interesting semireversible transformation in basic media, which generates new NIR absorbing species.

Hydrodynamic Effects on Particle Deposition in Microchannel Flows at Elevated Temperatures

Particulate fouling and particle deposition at elevated temperature are crucial issues in microchannel heat exchangers. In this work, a microfluidic system was designed to examine the hydrodynamic effects on the deposition of microparticles in a microchannel flow, which simulate particle deposits in microscale heat exchangers. The deposition rates of microparticles were measured in two typical types of flow, a steady flow and a pulsatile flow. Under a given elevated solution temperature and electrolyte concentration of the particle dispersion in the tested flow rate range, the dimensionless particle deposition rate (Sherwood number) was found to decrease with the Reynolds number of the steady flow and reach a plateau for the Reynolds number beyond 0.091. Based on the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, a mass transport model was developed with considering temperature dependence of the particle deposition at elevated temperatures. The modeling results can reasonably capture our experimental observations. Moreover, the experimental results of the pulsatile flow revealed that the particle deposition rate in the microchannel can be mitigated by increasing the frequency of pulsation within a low-frequency region. Our findings are expected to provide a better understanding of thermally driven particulate fouling as well as to provide useful information for design and operation of microchannel heat exchangers.

Melting Proteins: Evidence for Multiple Stable Structures upon Thermal Denaturation of Native Ubiquitin from Ion Mobility Spectrometry-Mass Spectrometry Measurements

Ion mobility and mass spectrometry techniques are coupled with a temperature-controlled electrospray ionization source to follow the structural transitions of ubiquitin in aqueous solution (pH = 3) at elevated solution temperatures (T = 26-96 °C). Changes in the charge state distribution are consistent with a two-state, cooperative unfolding transition having a melting temperature of Tm = 71 ± 2 °C, in agreement with prior measurements [ Wintrode , P. L. ; Makhatadze , G. I. ; Privalov , P. L. Proteins , 1994 , 18 , 246 - 253 ]. However, analysis of ion mobility distributions reveals the two-state transition is a composite of transitions involving at least nine unique species: three native or native-like structures; two that appear to be equilibrium intermediates (i.e., populations of new conformers that form at elevated temperatures but subsequently disappear at higher temperatures); and four products observed at high temperatures, including the well-characterized ubiquitin A state, and two solution species that are differentiated based on a cis- or trans-configured Glu18-Pro19 peptide bond. These nine states vary in abundances by factors as large as ∼103 over the range of solution temperatures. Although experimental melting transitions are conceived as a loss of well-defined structure leading to a random distribution of unstructured, denatured forms, the results provide evidence for new conformers having at least some well-defined structural elements are stabilized as temperature is increased.

Understanding the galvanic interactions between AA2024T3 and mild steel using the scanning vibrating electrode technique

The scanning vibrating electrode technique has been used to characterize the galvanic interactions between AA2024T3 and mild steel at room temperature and elevated solution temperatures up to 60 °C in naturally aerated 3.5% NaCl solution. The work shows that from a solution temperature of 43 °C and above, highly localised anodic activities with high intensities occur on the mild steel, compared with the anodic activities occurring on the AA2024T3 alloy in a couple system of the two alloys. The highly localised activities on the mild steel were not observed at 34±1 °C with the surface showing no distinct corrosion activities and AA2024T3 alloy was completely the bulk anodic material at this solution temperature. At room temperature, AA2024T3 was also the bulk anode, although mild anodic activities were detected on the surface of the mild steel alloy. The local corrosion activities revealed by the scanning vibrating electrode technique were in agreement with the micrographs of the surfaces of the alloys after the immersion tests.

Defluorination from aqueous solution by Ti(IV)-modified granular activated carbon

Fluoride contamination of drinking water and groundwater is a worldwide concerned issue, and technologies are needed for the treatment of aqueous fluoride. In this study, Ti(IV) species-modified granular activated carbon (Ti(IV)-GAC) was prepared and tested for fluoride removal from aqueous solution. Batch experiments were performed to investigate the equilibrium, kinetics, and mechanism of fluoride adsorption onto the prepared Ti(IV)-GAC. The results showed that the spontaneous fluoride adsorption process followed the Langmuir isotherm model and the pseudo-second-order kinetic model. Fluoride adsorption onto the Ti(IV)-GAC was enhanced as the initial fluoride concentration and contact time increased. Alkaline pH and elevated solution temperature did not favor the adsorption of fluoride. Anion exchange between the fluoride ions and the hydroxyl groups of the adsorbents was the major adsorption mechanism. Both batch experiments and flowing column experiments demonstrated that the Ti(IV)-GAC adsorbent can effectively remove the aqueous fluoride with high efficiency, and bring down the fluoride concentration lower than the permissible limit of fluoride in drinking water in China (1.0 mg/L). Experiments also showed that the Ti(IV)-GAC material had favorable regenerability, and can be used as a versatile adsorbent for treating mixed contamination of fluorides and organic pollutants.

Novel Non-Phosphorous Antiscalants for Inhibition of Calcium Phosphate and Calcium Sulfate Precipitation

A copolymer of acrylic acid (AA)/allylpolyethoxy carboxylate (APEC) was synthesized, characterized and examined as a non-phosphorous antiscalant for industrial cooling-water. Its ability to prevent calcium phosphate and sulfate precipitation was compared with inhibitory power of acrylic acid (AA)/allylpolyethoxy sulfate (APES) and polyamino polyether methylenephosphonate (PAPEMP). Results indicate that the presence of these antiscalants does reduce the extend of calcium phosphate and sulfate precepitation and AA/APEC exhibits the best performance with 99.59% calcium-phosphate inhibition when the dosage of AA/APEC was 6 mg/L and 82.88% calcium-sulfate inhibition at the dosage of 3 mg/L AA/APEC. AA/APEC has also been proven to be an effective inhibitor for calcium phosphate and calcium sulfate even at elevated solution temperature, pH and Ca2+concentration.

Cu-S Nanocabbage Films with Tunable Optical Bandgap and Substantially Improved Stability by Pulse Electrodeposition

Cu-S nanocabbage films were synthesized on ITO substrate using pulse electrodeposition at elevated temperatures in aqueous solution. The bandgap of the films showed a dependence on reaction time and was found to increase linearly with reaction time. This increase was attributed to the change in phase and stoichiometry of the Cu-S nanocabbage films. The stability of Cu-S films is found to be improved substantially when deposited at higher temperature because the Cu atoms have sufficient energy to find the minimum energy site in the lattice.