Increase In Melting Temperature Research Articles

Effect of MgO on solidification and crystallization properties of ultrahigh-basicity mold flux

The effect of MgO on the solidification and crystallization properties of ultrahigh-basicity mold flux was analyzed (i.e., comprehensive basicity R = 1.75). Results showed that with the increase of MgO content (0–6 wt%), the viscosity, melting temperature and break temperature decreases firstly, and then increases. The change of slag viscosity caused by the change of composition is indistinct, but the variation trend of melting temperature and break temperature is obvious. With the increase of MgO content, the crystallization temperature of ultrahigh-basicity slag decreases gradually, while the crystallization rate decreases firstly, and then increases. When the MgO content reaches 3%, the crystallization rate is the minimum. Research found that Ca4Si2F2O7 is the main precipitated phase in the slag, and as the MgO content continues to increase, the new phases of CaF2 and Ca3MgSi2O8 appear gradually.

Effect of minor La addition on wear behaviour of Mg-10Dy alloy

Magnesium alloys have attracted significant attention as a potential replacement material for aluminium alloys in the automobile industry due to their superior strength-to-weight ratio. The addition of rare earth elements to Mg alloys enhances its strength and tribological properties owing to the solid solution strengthening as well as increased melting temperatures of the second phase. The aim of the current study is to examine the effect of minor La addition on the wear behaviour of as-cast Mg-rare-earth alloy (Mg-10 wt%Dy) in dry sliding conditions at different loads. The addition of rare earth elements to the magnesium alloys improves the wear strength effectively at different loads. The experiments were performed using ball-on-disc tribometer with a steel ball counterface as a function of normal load and at a constant sliding velocity. The wear surfaces were analyzed using a 3D profilometer and a field emission scanning electron microscopy to investigate wear rate and wear mechanisms. It was observed that due to the formation of stable oxide surface layers and improved hardness of La containing alloy, the wear rate is significantly lower than the Mg-10Dy alloy at different applied normal loads. Abrasion, delamination, oxidation, and plastic deformation were established as the governing wear mechanisms.

Genotoxin-responsive DNA capsules for the detection of styrene oxide

Environmental genotoxins cause DNA damage and lead to gene dysfunction and mutation, posing a serious threat to health. In this article, a styrene-7,8-oxide–responsive DNA capsule (SODC) was designed and synthesized to respond to styrene-7,8-oxide (SO) (0–2%) within 10 min. The SODC was constructed by assembling three DNA oligos in a layer-by-layer structure and forming crosslinked hybridized DNA with segmented duplexes in 7–8 bp. The duplexes contained numerous guanine–cytosine pairs that were susceptible to electrophilic attack of SO. The resulting SO–purine adducts caused duplex dehybridization, which led to collapse of the SODC and release of fluorescent cargo. The size, number, zeta potential, and morphology of the SODC were evaluated. The melting curve indicated integrity of the crosslinked hybridization, which was evident from a substantial increase in melting temperature. SO-triggered transformation of the DNA capsules was tracked using a confocal microscope. To maximize the unlocking efficiency of the SODC, the effects of incubation time, temperature, pH, and ionic concentration on the outputted fluorescence were also studied. The response yielded by styrene and toluene (2%) was minimal. The interference caused by a high concentration of K3PO4 (50 mM)—a mimicking condition of intracellular fluid—was negligible. This system presented promising DNA-encoded sensing elements in the surveillance of the effect caused by environmental genotoxins.

A naphthyridine-indole ligand for selective stabilization of G-quadruplexes and conformational conversion of hybrid topology

The development of ligands to stabilize G-quadruplexes (G4s) or induce G4s to transition from metastable topology to stable topology is a potential strategy for inhibiting cancer cell proliferation. In this study, a novel G-quadruplex (G4) ligand based on a naphthyridine scaffold with two indole pendants, L5-DA, is reported to convert hybrid to the parallel topology. Circular dichroism (CD) and fluorescence spectroscopies were used to investigate the interactions between L5-DA and G4s. The CD spectra revealed that the L5-DA induced the conformational conversion from hybrid topologies to parallel topologies with a melting temperature increase of more than 30 °C. According to Förster resonance energy transfer assays, the presence of excess duplex competitor had no effect on the ligand-induced stabilization of the hybrid topology, confirming the L5-DA's selectivity for G4s over ds26. With IC50 values of 4.3 μM, the ligand showed significant cytotoxicity against HeLa cells and effectively induced growth inhibition and apoptosis in HeLa cells. Immunofluorescence microscopy revealed an increase in BG4 foci in the presence of the L5-DA, confirming ligand-induced G4s stabilization in HeLa cells. According to these results, the combination of naphthyridine and indole scaffold was an effective design strategy for G4s stabilization and conformational conversion of metastable G4 topology for inhibiting cancer cell growth.

Thermally improved crystalline phase and intercalated PEO/OMMT nanocomposites for high to ultrahigh radio frequency range low‐permittivity nanodielectrics

AbstractPoly(ethylene oxide) (PEO)/organomodified‐montmorillonite (OMMT) nanoclay based nanocomposites having 1, 3, 5, 10, and 20 wt% OMMT nanofiller were prepared by homogeneous mixing and the melt‐compounding method. These hybrid materials were characterized by employing X‐ray diffractometer, differential scanning calorimeter, and radio frequency impedance analyzer. The experimental results confirmed the formation of OMMT intercalated structures with reduced crystallinity and increased melting temperature of PEO crystallites which are predominantly ruled by the nanofiller amounts in the PEO/OMMT nanocomposites. Dielectric permittivity of these nanocomposites measured at 20°C exhibited a gradual decrease with increasing frequencies of the applied harmonic electric field of high to ultrahigh range (i.e., 1 MHz–1 GHz), but it changed anomalously in the range of 2.6–3.6 with the increase of OMMT amounts in the PEO matrix. The dielectric losses in these composites were found low and their loss spectra exhibited a hydrogen bond dipolar reorientation relaxation process around 1 GHz. The alternating current electrical conductivity of these nanocomposites increased with frequency and also changed with the OMMT concentrations. These PEO/OMMT nanocomposites are classified as low permittivity nanodielectrics which could be potential candidates for advances in flexible and biodegradable radio‐electronic devices.

Investigation of Crystallization Process of Lactose in Milk Serum Permeate

One of the main factors determining physicochemical and structural properties of the dry permeate of spray drying is lactose which is present in permeate as a basic phase. If lactose is in the β-form in a dry powder, the powder easily absorbs moisture from the atmosphere during storage, causing agglutination, clumping, and caking of the product. Prevention of negative consequences associated with increased hygroscopicity, is ensured by the directed crystallization of lactose in a condensed product before spray drying. The purpose of this investigation was to study the crystallization process of lactose in permeate under industrial conditions when using various seed materials. Results of the studies showed that the type of a crystal forming agentdoes not affect the size and shape of lactose crystals and the level of lactose crystallization. Seed material is of critical significance as it will ensure both a high level of crystallization and homogenous crystals which, in general, leads to an increase in melting temperature, due to a decrease in the proportion of amorphous lactose, as well as improves the drying process.

Effect of glasses melting temperature to bubbles size on Sb2O3 doped glasses

The physical and optical properties of the glasses system in compositions (35-x)SiO2 : 30B2O3 : 15Na2O :10CaO :10ZnO : xSb2O3 where x = 0.00, 0.05, 0.10, 0.50, 1.00 and 2.00 mol% were synthesized by using the melt-quenching technique and compared temperatures of 1000, 1100, 1200, 1300 and 1400 ºC. The results show that the density (ρ), molar volume (VM ) and refractive index (n) of glasses were tended to increase with increasing concentration of Sb2O3. On the opposite, when increasing melting temperature the result of the density (ρ), molar volume (VM ) and refractive index (n) of glasses were tended to decrease. The UV-Vis-NIR spectra of glasses were measured at the wavelength of 200-2000 nm. The number of bubbles in glasses tends to decrease with increasing concentration of Sb2O3 and melting temperature also.

The Relationship between the Structure and Thermal Properties of Bi2O3-ZnO-B2O3 Glass System

The influence of Bi2O3 and melting temperature on the thermal and structural properties of xBi2O3-(60-x) ZnO-40B2O3 glasses has been investigated in this study. It is expected that these factors can be used to control the degree of reduction of Bi2O3, and the relationship between these factors and the color change of the process for bismuth glass is discussed. Due to high-temperature melting, the bismuth-doped borate glasses have changed into dark/black from original transparent yellow and the light transmittance will decrease, so it is not used in optical applications. The thermal properties of glass are measured by a thermomechanical analyzer (TMA), and the glass structure is analyzed by FTIR and XPS. The results show that the glass is mainly composed of [BiO6] octahedron, [BiO3] triangle, [BO4] tetrahedron, and triangle [BO3] units, and the network of the glass system is mainly bonded by B-O-B, B-O-Zn, B-O-Bi, and Bi-O-Bi. The glass thermal expansion coefficient (CTE) of this glass system increases with the increase of Bi2O3 content, and the O1s nuclear electron binding energy shifts to the lower energy direction with the increase of Bi2O3 addition. In terms of FTIR, as the melting temperature rises, the B-O-B bonding vibration concentration of [BO4] inside the borate glass decreases, and the density of B-O-B bonding vibration of [BO3] increases, Moreover, the increase in melting temperature increases the probability of reducing Bi ions to Bi0, reduces the bonding of Bi-O-B, and increases the bonding of B-O-B, and the CTE also slightly decreases.

Low concentration of inorganic fullerene tungsten sulfide nanofiller to achieve cost‐effective and significant enhancement on thermal and dynamic mechanical properties of perfluoroalkoxy nanocomposites

AbstractSpecial insulated wires beyond the conventional pure perfluoroalkoxy (PFA) polymers need to be developed to meet the increasing thermal management and mechanical performance requirements. Advanced PFA nanocomposites enhanced by inorganic fullerene tungsten sulfide (IF‐WS2) nanoparticles have been fabricated by melt blending and hot press processes. Benchmarked against the PFA, the presence of IF‐WS2 nanoparticles in the composites resulted in a maximum tensile strength of 21.35 MPa and a maximum elongation at break of 275%, which are 66% and 149% higher than those of pure PFA, respectively. The nanocomposites with 0.5 wt% IF‐WS2 achieved a 17.5% increase in storage modulus, 26.8°C increase in the onset melt temperature, while 1 wt% IF‐WS2 increased the glass transition temperature (Tg) by 3.4°C and the crystallinity (χc) by up to 34.4%. And when the additional amount of IF‐WS2 nanomaterials is 0.25%, the best combination of performance is obtained.

Crystallization and melting behavior of polyvinylidene fluoride in confined space of nanotubes

Homopolymer poly (vinylidene fluoride) (PVDF) thin films were fabricated via high pressure process and then PVDF film was melt into porous anodic aluminum oxide (AAO) templates to form hollow nanotubes and isothermally crystal at a certain temperature. Scanning electron microscopy (SEM) and Transmission Electron Microscope (TEM) is used to observed the microstructure of nanotubes. To explore the influence of nanopores on the crystallization and melting of PVDF, differential scanning calorimetry (DSC) is used. It turns out that crystal phase is restrained in the nanotubes and mainly exists and at high temperature within relatively large nanopores and the bulk. As for phase, the increase of isothermal crystallization temperature results in the increase of melting temperature.

Effect of Si on the Solidification Segregation Behavior of a New Ni–Co‐Based Superalloy

Herein, the effects of Si addition on the microstructure and solidification behavior of a new Ni–Co‐based superalloy are investigated. The microstructure of the as‐cast alloys is mainly composed of γ, γ′, (γ–γ′) eutectics, and MC‐type carbides. The results demonstrate that Si addition significantly decreases the size and volume fraction of (γ–γ′) eutectics, while promoting the formation of Si‐rich phase precipitated in front of the (γ–γ′) eutectics. The formation of a Si‐rich phase is induced by the rejection of Ti and Si into the residual liquid during the γ matrix formation. With the increase in Si content, the size distribution of (γ–γ′) eutectics decreases due to the formation of the Si‐rich phase consuming the forming element of (γ–γ′) eutectics. The solidus and liquidus temperatures of the alloy decrease with the increase in Si. However, the range of melting temperature increases. The Si addition promotes the segregation of alloying elements, and Si tends to segregate in the interdendritic region.

Cross-linked levansucrase aggregates for fructooligosaccharide synthesis in fruit juices

In the present study, the cross-linked enzyme aggregates (CLEAs) of Y246S variant levansucrase from Bacillus licheniformis RN-01, known as oligosaccharide-producing levansucrase (OPL) was prepared for application in levan-type fructooligosaccharide (LFOS) synthesis in sucrose and fruit juices. The OPL-CLEAs with the highest immobilization yield (74.8% ± 8.9%) were prepared using 40 g/100 mL ammonium sulfate, 15 U/mL OPL, and 2 mg/mL bovine serum albumin in a 4 h cross-linking reaction. Compared with those of the free enzyme, the obtained OPL-CLEAs had a broader pH range for catalysis (pH 3–12) and displayed a higher optimum temperature. Moreover, the stability of OPL was significantly improved after immobilization, indicated by an increase in melting temperature and operational duration. Product analysis showed that the OPL-CLEAs could synthesize a similar LFOS profile as free enzymes, with a yield of up to 51%. Additionally, OPL-CLEAs could retain more than 50% of the initial activity after six cycles of reuse. Finally, the potential application of OPL-CLEAs in fruit juices was demonstrated by transforming up to 65%–75% of total sucrose in moderately acidic fruit juices. This study suggests the high potential for application of OPL-CLEAs in food industries.

Structural, magneto-optical and dielectric properties of phosphate tellurite glasses

Phosphate tellurite glasses, with a nominal composition of 40%ZnO+40%P2O5+20%TeO2, have been synthesized by melt quenching procedure. P2O5 can lead to chemically stable phosphate tellurite glasses, compared with those classical synthesized with H3PO4. Magneto-optical measurements have shown a derivative A1 term centered at 532 nm originating from a transition to a degenerated excited state associated with tellurium colloids. The glass densities, measured by the Archimedes method at room temperature, display an increasing value with the melting temperature of the samples. The electrical conductivity shifts toward lower frequencies with the increased melting temperature, being influenced by the mobile charges, which require lower thermal activation energy due to the Teo metallic particles. Together with dielectric constant, the electrical conductivity underlines structural changes, by increasing the melting temperature, associated with the presence of Teo nanoclusters.

Starch-fatty acid complexes improve the gel properties and enhance the fatty acid content of Nemipterus virgatus surimi under high-temperature treatment

The effect of high amylose corn starch (HAS)-fatty acid complexes on the gel properties, protein secondary structure, microstructure, fatty acid content, and sensory properties of surimi under high-temperature treatment were investigated. The formation of HAS-fatty acid complexes increased melting temperature and decreased average particle size of HAS. The addition of HAS-fatty acid complexes significantly improved the breaking force, deformation and whiteness of surimi gels. The water in surimi gels containing HAS or HAS-fatty acid complexes became increasingly immobilized. HAS or HAS-fatty acid complexes promoted protein conformational transition from α-helix structure to other three secondary structure. Surimi gels added with HAS-fatty acid complexes had more compact network structure and higher fatty acid content. Moreover, the better sensory properties were obtained in surimi gels containing HAS-fatty acid complexes. Therefore, starch-fatty acid complexes not only could improve the gel properties of surimi, but also enhance its fatty acid content.

Effect of Na2O on Properties, Structure, and Crystallization of CaO–Al2O3‐Based Mold Fluxes

This article investigates the effect of Na2O on melting properties, viscosity, flux structure, crystallization behavior, and heat transfer of CaO–Al2O3‐based mold fluxes with Na2O concentration varied from 3.5 to 12.1 mass pct. With the increase in Na2O content, both melting temperature and viscosity at a given temperature decrease. The Raman spectroscopy indicates that increasing the Na2O content decreases the degree of polymerization, in line with the decrease in viscosity. Flux crystallization is studied using single hot thermocouple technology (SHTT) and double hot thermocouple technology (DHTT). The results show that flux crystallization tendency is enhanced with the increase in Na2O content. This increase is more significant when the Na2O content changes from 9.1 to 12.1 mass pct. X‐ray diffraction analysis of the fluxes heat treated at different temperatures reveals that the crystal precipitates vary with the flux composition and temperature. Heat transfer measurement using the IR emitter technique (IET) shows that the increase in Na2O concentration impedes the heat transfer, in line with the increased crystallinity of the fluxes.

Mechanistic insights into mitochondrial tRNAAla 3’-end metabolism deficiency

Mitochondrial tRNA 3’-end metabolism is critical for the formation of functional tRNAs. Deficient mitochondrial tRNA 3’-end metabolism is linked to an array of human diseases, including optic neuropathy, but their pathophysiology remains poorly understood. In this report, we investigated the molecular mechanism underlying the Leber’s hereditary optic neuropathy (LHON)-associated tRNAAla 5587A>G mutation, which changes a highly conserved adenosine at position 73 (A73) to guanine (G73) on the 3’-end of the tRNA acceptor stem. The m.5587A>G mutation was identified in three Han Chinese families with suggested maternal inheritance of LHON. We hypothesized that the m.5587A>G mutation altered tRNAAla 3’-end metabolism and mitochondrial function. In vitro processing experiments showed that the m.5587A>G mutation impaired the 3’-end processing of tRNAAla precursors by RNase Z and inhibited the addition of CCA by tRNA nucleotidyltransferase (TRNT1). Northern blot analysis revealed that the m.5587A>G mutation perturbed tRNAAla aminoacylation, as evidenced by decreased efficiency of aminoacylation and faster electrophoretic mobility of mutated tRNAAla in these cells. The impact of m.5587A>G mutation on tRNAAla function was further supported by increased melting temperature, conformational changes, and reduced levels of this tRNA. Failures in tRNAAla metabolism impaired mitochondrial translation, perturbed assembly and activity of oxidative phosphorylation complexes, diminished ATP production and membrane potential, and increased production of reactive oxygen species. These pleiotropic defects elevated apoptotic cell death and promoted mitophagy in cells carrying the m.5587A>G mutation, thereby contributing to visual impairment. Our findings may provide new insights into the pathophysiology of LHON arising from mitochondrial tRNA 3’-end metabolism deficiency.

Study and optimization of effective parameters in the occurrence of Blush defect in the plastic injection molding process by ANOVA

Plastic injection is one of the most important processes in plastic parts production. During this process, many defects can take place that affect products quality. This research focuses on decreasing one of these defects, called Blush. For this purpose, eight parameters with the probability of affecting the occurrence of this defect have been considered to be investigated. To study the effect or lack of effect, the extent, and the manner of effect of these parameters on the Blush defect, a Fractional factorial design of experiment with eight factors and two levels was performed. Then after finite element analysis in MoldFlow software and validation of analysis with experimental tests, the area of defect that occurred in each case was calculated by geometric methods. After ANOVA of the data, it was found that the parameters of runner diameter, holding pressure, flow rate, and melt temperature respectively, have the most significant effects on this defect. Then, for the four factors mentioned, an experimental design of Composite Cube Design was performed and after performing finite element analysis and analysis of variance on the data, it was found that all four parameters have a significant impact. It was also found that by increasing melt temperature, and holding pressure and reducing the runner diameter and flow rate to the optimal level, the area of blush defect will be reduced by 82.2%.

Thermal aging performance of glass fiber/polyphenylene sulfide composites in high temperature

AbstractIn order to use the glass fiber reinforced polyphenylene sulfide composites (GF/PPS) in high temperature environments, thermal aging performance of two kinds of commercial grade PPS composites, reinforced by 40% glass fiber, PPS‐G40 HM and 1140L4, in thermal aging temperature of 250°C was compared by tensile strength, oxidized layer, color, crystallization and melting behavior. The results showed that tensile strength of GF/PPS composites is significantly decreased with increasing of aging time below 200 h and the tensile strength of aged PPS‐G40 HM is higher than that of aged 1140L4. The thickness of dark color area is increased with increasing of aging time. The thickness of oxidized layer of 1140L4 is thinner than that of PPS‐G40 HM. However, the color of oxidized layer of PPS‐G40 HM is lighter than that of 1140L4. The recrystallization in thermal aging results in the formation of crystal with higher melting point and increased melting temperature of GF/PPS composites. It is found that addition of epoxy resin can increase the initial mechanical property and improve the thermal aging performance of GF/PPS composites. A novel modified GF/PPS composite with higher thermal aging properties was obtained.

Enhanced Processing of Regrind as Recycling Material in Single-Screw Extruders

Regrind processing poses challenges for single-screw extruders due to the irregularly shaped particles. For grooved feed zones, the output is lessened by the reduction of bulk density in comparison to virgin material. Simultaneously, the melt temperature increases, reducing the extruder’s process window. Through experimental investigations on a test stand, a novel feed zone geometry (nominal diameter 35 mm) is developed. It aligns the regrind’s specific throughput with that of virgin material. The regrind processing window is essentially increased. As the solids conveying in the novel feed zone cannot be simulated with existing methods, numerical simulations using the discrete element method are performed. Since plastic deformation occurs in the novel feed zone geometry, a new hysteresis contact model is developed. In addition to spheres, the regrind and virgin particles are modeled as superquadrics to better approximate the irregular shape. The new contact model’s simulation results show excellent agreement with experimental compression tests. The throughput of the extruder simulations is considerably underestimated when using spheres to represent the real particles than when using irregularly shaped superquadrics. Corresponding advantages can be seen especially for virgin material.

Effect of MWCNT content on the mechanical and piezoelectric properties of PVDF nanofibers

In this study, the mechanical properties and morphology of aligned and random polyvinylidene fluoride (PVDF) fibers as well as the morphology and mechanical, piezoelectric, and thermal properties of PVDF fibers with different multi-walled carbon nanotubes (MWCNT) contents were analyzed. Although electrospun piezoelectric PVDF-based nanofibers have been extensively studied for application in wearable devices, they do not have sufficient flexibility and strength for practical application. Therefore, in this study, the effects of various experimental parameters, such as MWCNT content and fiber orientation, on the mechanical and piezoelectric properties of PVDF nanofibers were investigated in depth. Scanning electron microscopy analysis revealed that the average diameter of the PVDF nanofibers decreased with an increase in degree of orientation, while transmission electron microscopy analysis revealed the uniform dispersion of MWCNTs in the PVDF nanofibers. The PVDF nanofibers containing 0.008 wt% MWCNTs exhibited an excellent tensile strength. Furthermore, Fourier transform infrared spectroscopy analysis revealed that the β-phase fraction increased with increasing MWCNT content. The thermal stability of the nanofibers increased with an increase in β-phase fraction, as evidenced by the increase in melting and initial decomposition temperatures and decrease in weight loss determined by differential scanning calorimetry and thermogravimetric analysis.