Decrease In Melting Point Research Articles

Multicomponent crystals: Solubility enhancement of simvastatin using arginine and glycine coformers

Context: Simvastatin can be modified by the formation of multicomponent crystals to increase its solubility. Aims: To compare the solubility of multicomponent simvastatin crystals to pure simvastatin. Methods: The in silico study of simvastatin and the coformers arginine and glycine revealed non-covalent interactions, so multicomponent preparations of simvastatin crystals were prepared by solvent evaporation using a mole ratio of 1:1; 1:2 and 2:1. Results: Each simvastatin-arginine and simvastatin-glycine ratio increased the solubility, with the highest increase observed for the 1:2 ratio compared to pure simvastatin. Conclusions: Simvastatin-arginine multicomponent crystals (1:2) showed the best dissolution profile in phosphate buffer medium pH 7.0 with 67.69% dissolution, while simvastatin-glycine multicomponent crystals (1:2) exhibited the best dissolution profile in buffer media pH 1.2 with 16.19% dissolution. Characterization of the multicomponent crystals revealed a shift in the peaks, a decreased melting point, and enthalpy, indicating decreased % crystallinity and the formation of a new solid phase.

A novel cocrystal approach celecoxib with piperine: Simultaneously enhance dissolution rate and compressibility

Celecoxib, a selective COX-2 inhibitor non-steroidal anti-inflammatory drug (NSAID), exhibits analgesic and anti-inflammatory properties similar to piperine, the secondary metabolite of Piper nigrum L. Unfortunately, celecoxib has a low compressibility and low dissolution rate in aqueous medium. This study aimed to prepare a cocrystal of celecoxib and piperine to enhance the dissolution rate and compressibility properties of celecoxib. The cocrystal was synthesized using the seeding method and thoroughly characterized using Powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), infrared spectrophotometry, and single-crystal X-ray diffraction techniques. The complete change in PXRD, decrease in melting point in DSC measurements, and shift in the NH stretching band in the FT-IR spectrum suggested the formation of cocrystals phase. Single-crystal XRD confirmed the formation of an equimolar ratio of cocrystals of celecoxib and piperine. The intrinsic dissolution test was conducted to confirm the impact on the cocrystal to dissolution, and it showed a slight increase compared to intact celecoxib. To assess the physico-mechanical properties, the cocrystal powders were compressed into tablets with varying forces. The results demonstrated a significant improvement in compressibility compared with intact celecoxib owing to the slip plane in the crystal lattice of the cocrystal. In conclusion, our novel celecoxib-piperine cocrystal exhibited distinct physicochemical characteristics compared to intact celecoxib, showing enhanced dissolution rate and compressibility.

Melting point decrease induced by synergistic effect of proton implantation and radiation defects in aluminum

Melting point decrease induced by synergistic effect of proton implantation and radiation defects in aluminum

Sonochemical synthesis and characterization of Fe(II) and Cu(II) nano-sized complexes of sulfamethoxazole

Nanoparticle drug delivery systems are precisely designed technologies that utilize nanoparticles to deliver therapeutic drugs to specific targets and regulate their release. In recent times, nanoparticles have garnered significant interest owing to their potential for efficient drug delivery. This work is aimed at synthesizing Fe(II) and Cu(II) nano-sized complexes of sulfamethoxazole (SMX) using the sonication method. The physical and spectroscopic studies showed a colour change from white to grey, and a decrease in melting points suggested the formation of the metal complexes. The nanometal complexes were insoluble in water. XRD analysis showed that the crystallite sizes of Fe(II) and Cu(II) nanometal complexes were determined to be 76.08 nm and 37.13 nm, respectively, using the Debye-Scherrer equation. The FTIR results of the SMX, Fe(II), and Cu(II) nanometal complexes showed a shift of the amine band from 3243 to 3191 cm^-1 and the sulfone band from 1154 to 1092 cm^-1 in both complexes. The proton NMR showed a shift of the amine proton from 6.100 ppm to 6.035 ppm in the spectra of the Cu(II) complex. The amine chemical shift was absent in the spectra of the Fe(II) complex, showing deprotonation. The carbon-13 NMR spectra showed a similar chemical shift. The spectra studies indicated that SMX coordinated with the metal ions through the amino and sulfone groups. A tetrahedral structure was proposed for the complexes. SMX coordinated as a bidentate ligand to Fe(II) and Cu(II) ions.

High-throughput composition screening of high-entropy rare-earth monosilicates for superior CMAS corrosion resistance up to 1873 K

Superior calcium-magnesium-aluminum-silicate (CMAS) corrosion resistance is the key to the applications of high-entropy rare-earth monosilicates (HEREMs) as environmental barrier coatings (EBCs) for next-generation gas turbine engines. Here, we report a high-throughput composition screening strategy to achieve superior CMAS corrosion resistance in HEREMs for the first time. Specifically, we first fabricate ten kinds of (Ho0.25Yb0.25Lu0.25X0.25)2SiO5 (X = Sc, Tm, Er, Y, Dy, Gd, Eu, Sm, Nd, and La) HEREM samples using a high-throughput pressure-less sintering technique, and subsequently screen their CMAS corrosion resistance at 1673 K via a high-throughput testing apparatus. Among all the as-fabricated samples, the HEREM-Er samples are found to have the best CMAS corrosion resistance, even up to 1873 K, which outperforms the EBC materials that have been reported. Such superior CMAS corrosion resistance of the HEREM-Er samples is primarily attributed to the formation of a dense apatite barrier layer, which results from its decreased melting point, as confirmed by first-principles calculations and molecular dynamic simulations. Our work provides a guide for designing exceptional anti-CMAS corrosion high-entropy rare-earth silicates.

Polymer-derived W-doping (Zr, Hf, Nb, Ta)C high entropy ceramics: Preparation, Properties and DFT calculation

(Zr, Hf, Nb, Ta, W)C high entropy carbides nano-powders (average particle size less than 65 nm) with low oxygen content (0.2–1.4 wt%) were synthesized through pyrolysis of polymer precursors. Bulk ceramics were fabricated through the process of hot-pressing, and their characteristics were studied by both computational and experimental methods. Density functional theory was carried out to analyze the effects of defects and the W element on the melting point, hardness, modulus, and toughness of ceramics. The results showed that W content had limited influence on the melting points and the aforementioned mechanical properties of ceramics, while carbon vacancies lead to a significant decrease in melting point, hardness and modulus, with slight increases in toughness. Experimental results indicated that the grain size, grain boundary strength, and lattice distortion of ceramic bulks increased with the increase of W content, which affected the mechanical properties consequently. Ceramics with W content of 5 mol% exhibited the best experimental comprehensive performances, with the Vickers hardness, fracture toughness and flexural strength of 23.82 ± 0.49 GPa, 5.66 ± 0.22 MPa·m1/2 and 593.95 ± 15.71 MPa, respectively.

Computational discovery of novel U-N-C ternary phases as promising accident-tolerant fuels

Recently, uranium carbonitride solid solution has been recognized as a promising nuclear reactor fuel due to its excellent physicochemical properties. However, due to the complexity of U-N-C ternary system, the research on the structure and properties of uranium carbonitride is still insufficient. In this work, a series of promising accident-tolerant ternary compounds in the U-N-C system were predicted through a combination of first-principles calculations with an evolutionary algorithm. Fifteen dynamically and mechanically stable novel U-N-C ternary compounds with seven chemical compositions, including U-N-C solid solutions and new intermetallic structures, were suggested to be promising for experimental synthesis. For U-N-C solid solutions with rock-salt structures, it was revealed that the lattice expansion and bond length elongation caused by the substitution of carbon atoms for nitrogen atoms can lead to a decrease in elastic moduli and melting point and an increase in toughness. Moreover, two newly identified structures P63/mcm-U3N2C and P2/m-U4NC were considered to be very promising accident-tolerant fuels due to their high mechanical strength, excellent melting point, low thermal expansion coefficient, and high thermal conductivity. The larger atomic number density of P63/mcm-U3N2C enables a higher elastic modulus and a satisfactory melting point than those of rock-salt structures. While for P2/m-U4NC, its unique shorter and stronger U-N/C and U-U bonding leads to its highest mechanical strength and appropriate melting point. Furthermore, the linear thermal expansion coefficients of P2/m-U4NC and P63/mcm-U3N2C are comparable to those of UN and UO2, respectively, and their thermal conductivities increase with temperature, much higher than that of UO2.

The roles played by anionic and cationic species in the curing process of aromatic nitrile resins

Understanding the curing mechanism of aromatic nitrile (AN) resins is crucial for improving their curing efficiency. Blending the Bronsted acid-containing aromatic nitrile monomers (ACN) and Bronsted base-containing aromatic nitrile monomers (BCN) is a novel approach that simultaneously lowers the melting point and rapid curing reaction temperature of AN resins. To investigate the impact of anionic and cationic species on the curing behavior of ACN-BCN blends, a series of ACN-BCN blends were designed and synthesized. DSC and TGA results demonstrated a significant improvement in the curing efficiency when ACN and BCN blended, the curing temperature decreased by more than 50 ℃, accompanied by a decrease in melting point. According to the DMA results, the Tg of the cured substance of the system can reach 405 ℃ at the curing temperature of 325 ℃. The curing behaviors of ACN-BCN blends were studied through thermal analysis and spectroscopic analysis, which indicates that cationic species can polarize the cyano rather than attack the cyano groups, promoting their curing reaction. Moreover, it was determined that while cationic species play a polarizing role on the cyano, active anionic species attack the cyano, serving as the rate-determining step in the curing process of ACN-BCN blends.

Promoting ordering degree of intermetallic fuel cell catalysts by low-melting-point metal doping

Carbon supported intermetallic compound nanoparticles with high activity and stability are promising cathodic catalysts for oxygen reduction reaction in proton-exchange-membrane fuel cells. However, the synthesis of intermetallic catalysts suffers from large diffusion barrier for atom ordering, resulting in low ordering degree and limited performance. We demonstrate a low-melting-point metal doping strategy for the synthesis of highly ordered L10-type M-doped PtCo (M = Ga, Pb, Sb, Cu) intermetallic catalysts. We find that the ordering degree of the M-doped PtCo catalysts increases with the decrease of melting point of M. Theoretic studies reveal that the low-melting-point metal doping can decrease the energy barrier for atom diffusion. The prepared highly ordered Ga-doped PtCo catalyst exhibits a large mass activity of 1.07 A mgPt−1 at 0.9 V in H2-O2 fuel cells and a rated power density of 1.05 W cm−2 in H2-air fuel cells, with a Pt loading of 0.075 mgPt cm−2.

Deep eutectic solvents as sustainable solvents for industrial separation problems: A recent update

Deep eutectic solvents (DESs) are ionic liquid analogues that consist of Lewis or Brønsted acids and bases. These systems are characterized by a substantial decrease in melting points as compared to those of the neat constituents. Activity coefficients at infinite dilution of organic solutes is used as a screening tool for extracting solvents, an approach that is useful for identifying acceptable precursors and assessing separation performance in practical applications. This review assesses the effectiveness of DESs as solvents for chemical separations wherein the data is presented for the activity coefficients at infinite dilution for 33 solutes in different DESs at various temperatures. Additionally, the selectivities and capacities for various solute extraction problems are also appraised from the activity coefficients at infinite dilution at T = 323.15 K; capacity represents the solvent's ability to extract the component.

Research on aggressiveness of CMAS+NaVO3 mixtures towards thermal barrier coatings from the perspective of physical and chemical characteristics

Thermal barrier coatings (TBCs) used in marine condition recently suffer from a new degradation mainly induced by the coupling effect of calcium-magnesium-aluminum-silicate (CMAS) and molten salt. In present study, physical and chemical properties of CMAS+NaVO3 mixture with varying CMAS/NaVO3 ratio were examined to determine its aggressiveness towards TBCs. It was found that the crystallization behavior of CMAS was remarkably changed due to NaVO3 addition. The experimental results also revealed a decreasing melting point and viscosity with increasing NaVO3 content, indicating an enhanced aggressivity even at a relatively low temperature. More specifically, the Log viscosity values of the melts were found linearly dependent on NaVO3 content. In addition, theoretical results implied that thermo-chemical damage aroused by CMAS+NaVO3 mixtures would be potentially mitigated to a certain extent as compared with the case in CMAS corrosion.

Synthesis of a polyester with a liquid crystalline silsesquioxane-contained backbone Chain

A one-pot multistep growth melt procedure utilizing multistep feeding has been developed to enable the synthesis of thermoplastic polymers based on 4-hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid (HNA)with greater numbers of alternating units in their backbone chains. The decreased melting point (Tm) and glass transition temperature (Tg) indicated that the multistep feeding procedure helped to enhance the flexibility of the backbone chain due to the increasing number of alternating blocks, due to a reduction in the stacking between different main-chains, thus enabling the formation of liquid crystalline polyester (LCP) fibers with oriented structures. The covalent incorporation of rigid cage-like silsesquioxane groups led to a significant reduction of the melting point, resulting from the inevitable transformation of the original symmetrical backbone structure to a less ordered structure, due to the steric effect and hybrid feature of silsesquioxane. The presentation of silsesquioxane groups also enhanced the aggregation of ultrafine fibers with well-aligned orientation in the molten state and produce stronger fiber bundles.

INCREASING SOLUTION IN THE DRUG SIMVASTATIN WITH SOLID DISPERSION TECHNIQUE USING POLYMER SOLUPLUS

Objective: Simvastatin is a bioactive compound belonging to the class II Biopharmaceutic Classification System (BSC), which has high permeability but low solubility. The low solubility of Simvastatin showed by low bioavailability so modification is required for its solubility. Methods: There are many techniques to improve the solubility of poorly water-soluble drug; one of them is solid dispersion prepared by the solvent evaporation method. This study aims to determine the solid dispersion formulation of simvastatin using soluplus as a polymer with a ratio of 1:1, 1:2, 1:3, and 1:4 which is employed to increase the solubility and dissolution rate of simvastatin. Furthermore, characterization was carried out using IR spectrophotometry, differential scanning calorimetry (DSC), and powder X-ray diffraction (PXRD). Results: The maximum solubility test yielded a 1:4 solid dispersion, which is up to 20 times more potent than pure simvastatin. Simvastatin's solubility increased from 17.33% to 82.50% for a 1:4 solid dispersion at 60 min, affecting the dissolution rate as well. Conclusion: A solid dispersion was formed in an amorphous state, as evidenced by the fact that the results of characterization using IR spectrophotometry showed no new functional groups were formed in the solid dispersion, the results of characterization using Differential Scanning Calorimetry (DSC) showed a decrease in melting point, and the results of x-ray diffraction characteristics did not show a sharp peak.

Mastering morphology of non-fullerene acceptors towards long-term stable organic solar cells

Despite the rapid progress of organic solar cells based on non-fullerene acceptors, simultaneously achieving high power conversion efficiency and long-term stability for commercialization requires sustainable research effort. Here, we demonstrate stable devices by integrating a wide bandgap electron-donating polymer (namely PTzBI-dF) and two acceptors (namely L8BO and Y6) that feature similar structures yet different thermal and morphological properties. The organic solar cell based on PTzBI-dF:L8BO:Y6 could achieve a promising efficiency of 18.26% in the conventional device structure. In the inverted structure, excellent long-term thermal stability over 1400 h under 85 °C continuous heating is obtained. The improved performance can be ascribed to suppressed charge recombination along with appropriate charge transport. We find that the morphological features in terms of crystalline coherence length of fresh and aged films can be gradually regulated by the weight ratio of L8BO:Y6. Additionally, the occurrence of melting point decrease and reduced enthalpy in PTzBI-dF:L8BO:Y6 films could prohibit the amorphous phase to cluster, and consequently overcome the energetic traps accumulation aroused by thermal stress, which is a critical issue in high efficiency non-fullerene acceptors-based devices. This work provides insight into understanding non-fullerene acceptors-based organic solar cells for improved efficiency and stability.

MICRONIZED EUTECTIC MIXTURE OF FENOFIBRIC ACID-SACCHARIN FORMATION FOR SOLUBILITY AND DISSOLUTION ENHANCEMENT

Objective: This study aims to increase the solubility and dissolution rate of fenofibric acid by forming a micronized eutectic mixture of fenofibric acid-saccharin with spray drying technique.
 Methods: Suspension of the eutectic mixture was prepared in ethanol: distilled water (3:1) followed by a spray drying method to obtain the microparticles. Microparticles characterization was performed by particle size analysis (PSA), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), FT-IR spectroscopy, and scanning electron microscopy (SEM). Solubility test was carried out in CO2-free distilled water, meanwhile the dissolution rate study was conducted in phosphate buffer solution at pH 6.8.
 Results: The results showed the mean of the samples’ particle size was 72.29±7.33 µm. Compared to the intact fenofibric acid, the micronized eutectic mixture sample has a decreased melting point, fusion enthalpy, and crystallinity without any wavenumber shifted in the FT-IR spectra. The solubility of micronized eutectic mixture was 2.2 times higher than intact fenofibric acid, while the amount of micronized eutectic mixture dissolved at 60 min was 11.7 times higher.
 Conclusion: It can be concluded that the spray-dried micronized eutectic mixture of fenofibric acid-saccharin was having the ability to enhance the dissolution of fenofibric acid.

Cyclopropane as an Unsaturation "Effect Isostere": Lowering the Melting Points in Lipid-like Ionic Liquids.

The replacement of unsaturation with a cyclopropane motif as a (bio)isostere is a widespread strategy in bacteria to tune the fluidity of lipid bilayers and protect membranes when exposed to adverse environmental conditions, e.g., high temperature, low pH, etc. Inspired by this phenomenon, we herein address the relative effect of the cyclopropanation, both cis and trans configurations, on melting points, packing efficiency, and order of a series of lipid-like ionic liquids via a combination of thermophysical analysis, X-ray crystallography, and computational modeling. The data indicate there is considerable structural latitude possible when designing highly lipophilic ionic liquids that exhibit low melting points. While cyclopropanation of the lipid-like ionic liquids provides more resistance to aerobic degradation than their olefin analogs, the impact on the melting point decrease is not as pronounced. Our results demonstrate that incorporating one or more cyclopropyl moieties in long aliphatic chains of imidazolium-based ionic liquids is highly effective in lowering the melting points of such materials relative to their counterparts bearing linear, saturated, or thioether side chains. It is shown that the cyclopropane moiety effectively disrupts packing, favoring formation of gauche conformer in the side chains, resulting in enhancement of fluidity. This was irrespective of the configuration of the methylene bridge, although marked differences in the effect of cis- and trans-monocyclopropanated ILs on the melting points were observed.

Effect of CeO2 Content on Melting Performance and Microstructure of CaO-Al2O3-SiO2-MgO Refining Slag

CeO2 can be applied to refining slag to minimize the size of inclusions, speed up the deoxidization process, and adsorb Al2O3 inclusions. The impact through which CeO2 content affects slag’s melting efficiency is still uncertain. The thermal analyzer was used to measure the thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) curves of the slag melting process. According to the study results, with the increase in CeO2 content, the melting temperature of slag decreased first and then increased. The slag’s melting point fell from 1364 °C to 1324 °C and then rose to 1503 °C. XRD and SEM were used to analyze the CaO-Al2O3-SiO2-MgO-CeO2 slag’s microstructure. The mineral-phase structure of CeO2-containing refining slag was primarily composed of Ca2SiO4 and 3CaO·Al2O3, MgO, SiO2, CaO·Al2O3, and Ca8Ce6Al6O26. The proportion of 3CaO·Al2O3, CaO·Al2O3, and Ca2SiO4 decreased as the rare-earth-oxide content increased, while the proportion of Ca8Ce6Al6O26 increased. FactSage was used to estimate the equilibrium-phase compositions of slags with various compositions, and a model for predicting melting points was carried out by a linear regression model. Results were obtained through the analysis of equilibrium-phase composition and crystal structure transformation. The main reasons for the melting point decrease were the change of degree of polymerization and the decrease in contents and complete melting temperature of high-melting-point Ca3Al2O6 and Ca2SiO4 compounds. The latter increase in melting point was due to the number of Ca8Ce6Al6O26 compounds and precipitation temperature increases and the complexity of the structural-network increases.

Optimization of Ball Ratio in Planetary Ballmill in Nimodipine-poloxamer 188 Nanoparticle Formulation Process

Nimodipine is a drug that belongs to the class II biopharmaceutical classification system which has low solubility with high permeability. The ball mill ratio is a factor that affects the results of milling using a planetary ballmill. This study aims to see the optimal ball ratio in the milling process with a planetary ball mill in the physicochemical characterization of nimodipine-poloxamer 188 nanoparticles and their dissolution rate. Milling in a planetary ball mill was carried out using zirconium balls at a ratio of 20%, 25%, and 30% to the volume of the vessel respectively for 1, 2, and 3 nanoparticles. The characterization of nanoparticles includes PSA with the results showing a reduction in particle size, XRD there is a decrease in peak intensity, DSC there is a decrease in melting point, FT-IR doesn’t change the wave number, SEM shows morphologically a change in shape, TLC indicates no chemical interaction, in the assay, the percentage of nimodipine and nanoparticles 1,2,3 was respectively 98.91%, 99.85%, 100.73%, 99.31%. the solubility test of nimodipine and nanoparticles 1,2,3, respectively 0.3390 g/ml, 19.8698 g/ml, 6.0673 g/ml, 8.4405 g/ml, and the dissolution test showed an increase in the 60th minute of nanoparticles 1,2 and 3 respectively 61,5841%, 52,3159%, 56,6027% compared with 23.3978% pure nimodipine. The results of the ANOVA test of solubility and dissolution rate showed that there was a significant difference between nimodipine-poloxamer 188 nanoparticles and pure nimodipine.

Simulation of the Melting Behavior of the UO2-Zircaloy Fuel Cladding System by Laser Heating

The current research focuses on laser melting and successive analysis of laboratory-scale uranium dioxide nuclear fuel samples in direct contact with Zircaloy-4 cladding. The goal was to characterize the melted and refrozen interfaces, in particular, observing local changes of the melting point and interdiffusion of fuel and cladding materials under inert gas (Ar), in the presence of hydrogen (Ar + 6% H2) or in air. Results obtained by laser heating UO2 pellets clad in a Zircaloy ring were interpreted in light of reference tests performed on pellets in which UO2 and zirconium were blended in a series of given compositions. The sample composition was analyzed by scanning electron microscopy to verify the occurrence of diffusion and segregation phenomena during the laser-heating cycles. Laser-melting experiments were performed on pellets of uranium dioxide clad in Zircaloy-4 rings to simulate the configuration of a light water reactor fuel rod. Under inert gas, the material interdiffusion resulted in consistent melting point depression (of up to 200 K below the melting point of pure UO2) at the interface between the fuel and the cladding. Experiments carried out in the presence of H2 displayed a more limited effect on the melting temperature, but they resulted in a remarkable embrittlement of the whole structure, with large fragmentation of the Zircaloy cladding. This was probably due to the formation of brittle and highly volatile Zr hydrides. The observed melting point decrease was even more pronounced (up to over 400 K) under air in uranium-rich samples, due to the change in the stoichiometry of UO2 in UO2+x.

Investigation of thermal and mechanical properties of Sn-Zn and Sn-Zn- Bi near-eutectic solder alloys

In the present work, three near-eutectic lead-free solder melts of Sn-8wt.%Zn; Sn-8wt.%Zn-2wt.%Bi and Sn-8wt.%Zn-4wt.%Bi have swiftly solidified by means of the melt-spinning technique for intermediate –step soldering. The thermal and various mechanical properties of the formed melt-spun ribbons were investigated by dynamic resonance technique, Vickers micro-hardness test under annealing temperatures in the range from 348 K to 448 K. Thermal analysis using differential thermal analysis (DTA) technique revealed a decrease in melting point and solidus point with %Bi. Wettability property was determined by evaluating the contact angle on a different substrate and found to be in the range 31° to 43° on Cu or CuZn30 substrates and in the range from 110° to 115° on Al substrate. The microhardness tests as a function of temperature were performed to determine the stiffness of Sn-Zn solder alloys. Isothermal creep curves for the synthesized samples alloys were determined and plotted under constant applied stresses at a constant temperature of 463 K. Microstructure of the as-cast alloys both, at room temperature and annealed at 348 K were recorded. The creep test on the structure change and properties of Sn–Zn alloys were reported with the effect of the cold work deformation. The Sn-8wt.%Zn-4wt.%Bi is a candidate material for solder which is free of Pb and widely used for packaging of micromechanical systems as a hermetic sealing step.