Calorimetry Measurements Research Articles

Impact of fluorination on membrane-protein stabilization and extraction by lactobionamide detergents.

We report the synthesis of a series of detergents with a lactobionamide polar head group and a tail containing four to seven perfluorinated carbon atoms. Critical micellar concentrations (CMCs) were determined using isothermal titration calorimetry (ITC) and surface tension (SFT) measurements, showing a progressive decrease from 27 mM to about 0.2 mM across the series. While the detergent with the longest fluorinated chain exhibited poor water solubility, the other three derivatives were freely soluble. Dynamic light scattering (DLS) measurements indicated an increase in hydrodynamic diameter with chain length, from 5 nm to 17 nm for the soluble derivatives. We evaluated these detergents for extraction and stabilization of two model membrane proteins, the human adenosine A2A receptor (A2AR) and the Bacillus subtilis multidrug resistance ABC transporter BmrA. The perfluorohexyl derivative demonstrated strong solubilization capacity, while the perfluoropentyl derivative was more effective for stabilization. The lack of a clear correlation between fluoroalkyl chain length and solubilizing or stabilizing efficacy highlights the importance of screening diverse detergents for membrane-protein studies.

Hydration and Biodistribution of Zwitterionic Dendrimers Conjugating a Sulfobetaine Monomer and Polymers.

Zwitterionic polymers exhibit strong hydration, high biocompatibility, and antifouling properties. Dendrimers are regularly branched polymers, which are used in the drug delivery system (DDS). In this study, we synthesized zwitterionic monomer- and polymer-conjugated dendrimers as a biocompatible nanoparticle to investigate the relation between the hydration property and biodistribution. A sulfobetaine monomer (SBM) was conjugated at the termini of the polyamidoamine (PAMAM) dendrimer. Polysulfobetaines (PSBs) were produced by reversible addition-fragmentation chain transfer polymerization and were also conjugated at the termini. Intermediate water, that is, water molecules loosely bound to the material, can be estimated from the melting peaks at less than 0 °C in differential scanning calorimetry (DSC) measurement. Our DSC results showed that the PSB-conjugated dendrimers (PSM-dens) contained more intermediate water than the SBM-conjugated dendrimer (SBM-den). PSB-dens accumulated in the tumor after intravenous administration, but SBM-den did not. These suggested that the amount of intermediate water, that is, the hydration property, was related to the biodistribution of the zwitterionic dendrimers. This relation is a possible design criterion for drug carriers. PSB-dens accumulated in the tumor even after the second injection, possibly overcoming the accelerated blood clearance observed with poly(ethylene glycol)-modified nanoparticles. Thus, this kind of zwitterionic polymer-conjugated dendrimer is useful for the DDS in cancer treatment.

Effect of applying phase change materials (PCM) in building facades on reducing energy consumption

Since fossil fuels are limited and there is an increasing demand for energy consumption, energy conservation and reducing consumption have become significant challenges. Applying phase change materials (PCM) for latent thermal energy storage (TES) systems is an effective method for energy conservation that has been widely considered in recent years. The building facade has the highest capacity for conserving or wasting energy due to its vast exposure to the environment. As a result, a change in attitude toward designing and constructing facades is considered a necessity since it is one of the key elements of building design. One approach to prevent materials from leaching from a structure where PCMs are incorporated is encapsulating and blending them with a suitable polymer. Choosing a PCM with suitable melting temperature, a polymer compatible with this material as a preserver and the best percentage of PCM in the polymer are key components. In this paper, the goal has been investigated through a 2-step process, including experimental and simulation phases. First, the effect of polyethylene glycol (PEG) as the PCM in the mixture with poly methyl methacrylate (PMMA) for heat protection has been studied. Differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) measurement techniques were employed to study and determine the melting points of the samples and the mixed substructures. The results show that the best percentage for PEG in this research is 60%. In the second phase, to study the effect of polymers carrying the PCMs on the building’s energy consumption, a 5-story building with PCMs applied to its facade was simulated in EnergyPlus software. The annual heating and cooling loads of the building in each situation were then calculated. The results of the simulation and modeling shows that applying the PCMs will ultimately lead to a 40% decrease in heating load and 15% decrease in cooling load of the building.

Nanomolar PFOA Concentrations Affect Lipid Membrane Structure: Consequences for Bioconcentration Mechanisms.

Independent methods show that sub-microMolar concentrations of perfluorooctanoic acid (PFOA), a member of the PFAS family of "forever chemicals", change the properties of DPPC vesicle bilayers. Specifically, calorimetry measurements show that PFOA at concentrations as low as 0.1 nM lowers DPPC's gel-liquid crystalline transition enthalpy by several J/g without changing the transition temperature (Tgel-LC), and dynamic light scattering (DLS) data illustrate that PFOA markedly broadens the size distribution of DPPC vesicles. Furthermore, DLS results from PFOA-containing, DPPC vesicle solutions also contain smaller objects having diameters of 30-50 nm. Close inspection of cryo-EM images reveals that DPPC vesicles formed in the presence of PFOA are multilamellar and the smaller objects have a clear bilayer structure similar to niosomes. A consequence of these PFOA-induced changes to DPPC bilayer structure is that the bilayers themselves are more susceptible to secondary solute accumulation. Time resolved emission measurements of Coumarin 152 (C152) report that C152 is 3-fold more likely to partition into the bilayer's acyl chain, hydrophobic interior when PFOA is present, and fluorescence lifetimes from C152 partitioned into the polar region of the lipid bilayer show evidence of PFOA-induced membrane hydration below Tgel-LC.

Effects of Fluorescent Tracer Additives on PET During Material Recycling

ABSTRACTThe material properties and stable chemical structure of PET make it a frequently used polymer, for example, for packaging applications, and allow multiple recycling processes. Fluorescent tracer additives in polymer waste management may enhance the sorting quality of packaging waste streams by using the fluorescent signal of tracer additives introduced into the polymer matrix. Prior to field application of tracer additives, it is necessary to investigate tracer influence on the polymer matrix in general and, more specifically, in multiple recycling cycles. Therefore, PET with mineral tracer concentrations of 0, 10, 100, and 1000 ppm was extruded up to six times. To investigate changes in material properties, differential scanning calorimetry, intrinsic viscosity, spectroscopic analysis, tensile testing, and color measurements were performed. In parallel, the up‐conversion photoluminescence of the tracer was quantified. Polymer degradation is generally induced by mechanical and thermal degradation during multiple processing cycles, leading to chain shortening, reduction of molecular weight, and the formation of new functional groups, as previously published in the literature. The results of the experiments indicate that tracer additives do not further affect the thermal, rheological, chemical, and optical polymer properties. Moreover, photoluminescent tracer properties are not affected by multiple polymer processing cycles.

C–S–H–PCE nanocomposites as hydration accelerator in calcined clay-limestone-blended low carbon cement

Abstract Recently, providing admixtures to improve the performance of the novel low-carbon-blended cement is needed to meet the requirement for environmentally friendly cements. In this study, calcium-silicate-hydrate (C–S–H) nanocomposites which are known as hydration accelerator for Portland cement were employed in such low-carbon cements. The investigation focused on the effect of polycarboxylate ether (PCE) possessing different side-chain lengths on the morphology of C–S–H nanocomposites synthesized from sodium silicate and calcium nitrate via chemical co-precipitation and on their performance (especially early strength enhancement) when applied in a calcined clay-blended cement (OPC substitution rate of 46 wt%). As observed by TEM, addition of PCE effectively controls the size of the C–S–H nanoparticles and delays the transition from C–S–H globules to foils. PCEs with short side-chain (23 EO units) exhibited the highest inhibition effect on the growth of the C–S–H nuclei, which was confirmed by particle size measurements. Additionally, incorporating such C–S–H–PCE nanocomposites into the calcined clay-blended cement (dosage 2.0 % by weight of cement) significantly improved fluidity of the cement pastes. Regarding compressive strength, pristine C–S–H produced only a minor improvement, whereas C–S–H–PCE nanocomposites yielded substantial enhancement, especially after 16 h and 1 day of curing. Remarkably, C–S–H–23PCE pronounced the strongest seeding and strength enhancing effect, owed to its particularly small particle size (d = 21.8 ± 0.3 nm). It also significantly accelerated the hydration of the silicate phases (C3S and C2S) in this blended cement, as was evidenced by isothermal heat flow calorimetry and XRD measurements.

Fumed Silica in Coconut Oil Based Nanofluids for Cooling and Lubrication in Drilling Applications

Virgin coconut oil (VCO) is an edible vegetable oil that is eco-friendly, biodegradable, and sustainable, with high thermal and chemical stability as a phase change material (PCM). In this work, VCO filled with fumed silica A200 nanoparticles was tested as a cutting fluid in drilling processes. Silica concentrations ranging from 1 to 4 vol% were analyzed. Thermal properties were evaluated by differential scanning calorimetry (DSC) and thermal conductivity measurements at different temperatures and concentrations. Thermal conductivity showed an enhancement with the addition of silica powder and reduced with increasing temperature. Based on thermal and flow properties, VCO-3A200 was found to be the optimal concentration. The thermal images of this nanofluid taken after 60 s of drilling exhibited a reduction of 12 °C with respect to the dry process. The friction coefficient versus shear rate was also measured. With 8% VCO, a reduction in the friction coefficient of 8% compared to the dry test was achieved. The addition of 3 vol% of silica to the base oil reduced the friction coefficient by 16% compared to the dry test. The use of fumed silica dispersed in VCO has proven to be a sustainable, recyclable, and environmentally friendly refrigerant and lubricant cutting fluid.

3D‐Printable Polymer Filters for the Selective Complexation of Silver Ions

ABSTRACTThis study presents the fabrication of polymeric filters, which are able to selectively bind silver ions from aqueous solution. Those filters are fabricated within an easy approach via 3D‐digital light processing (DLP)‐printing enabling a tailor‐made design. In first order, an acrylamide containing a benzo‐trithiacrown‐ether (BTCE) functionality is synthesized. This monomer is further 3D‐printed via layer by layer photo‐polymerization together with commercially available comonomers, resulting in polymer networks containing the BTCE‐groups in their side chains as selective binding moiety for silver ions. Within isothermal‐titration calorimetry (ITC) measurements, the complexation abilities of the BTCE to bind the Ag+ ions are determined. Furthermore, the resulting 3D‐printed filters are investigated regarding their complexation behavior, in a detailed fashion applying inductively coupled plasma optical emission spectroscopy (ICP‐OES).

Dissolving alginate-based blend microneedles with enhanced mechanical performance for transdermal delivery of vitamin B12

Transdermal delivery of vitamin B12 (Vit-B12) is challenging due to its high hydrophilicity and molecular weight that limit permeation through the skin. Polymeric microneedles (MNs) have been demonstrated to facilitate enhanced transdermal delivery of various drugs with different properties, by piercing the outermost layer of the skin barrier in a minimally-invasive manner. Although sodium alginate (SA) has been widely investigated and used for pharmaceutical and biomedical applications, MNs made of pure SA, exhibit poor mechanical properties. Therefore, this study investigates the effect of incorporating different excipients into SA MNs, to enhance their insertion ability and mechanical performance, by a modified vacuum deposition micromolding method. Among these, poly(vinylpyrrolidone) (PVP) and polyethylene glycol (PEG)-containing SA MNs at a ratio of 1:8 show improved mechanical strength with minimal height reduction (< 10%) at all tested forces, and higher insertion capabilities into a skin-simulant parafilm model (> 65% in the second layer), compared to control SA MNs. Consequently, Vit-B12 was successfully loaded and concentrated into the MN shafts of the lead formulations, by the addition of hydroxypropyl cellulose to the baseplate. Vit-B12 MNs were characterized by means of fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) measurements, drug loading and dissolution kinetics. The MNs exhibited adequate mechanical properties and a complete drug release within 30 min, while a considerable fraction was released after few minutes. The present study shows promising findings regarding the potential use of SA in the preparation of dissolving MNs with enhanced mechanical performance for transdermal delivery of Vit-B12. However, further preclinical investigations are necessary to comprehensively evaluate their therapeutic efficacy. Additionally, this work suggests that alginate-based blend MNs may have a potential application in the delivery of other hydrophilic and large compounds for improved therapeutic outcomes.

Influence of GeO2/TeO2 ratio on thermal, structure and spectroscopic properties of Dy3+-doped tellurite-germanate glass

Dy2O3-doped tellurite-germanate glasses with an increase of GeO2/TeO2 ratio (TGZ) were synthesized and characterized through X-ray diffraction (XRD), differential scanning calorimetry (DSC), Raman, absorption, and emission spectra measurements. XRD spectra of Dy3+-doped TGZ glass confirmed the amorphous structure. The TGZ glass possess the higher anti-crystallization abilities than that of the pure tellurite glass. Raman spectroscopy showed that the amount of [TeO3] and [TeO3+1] units in the glass network were gradually decreased by increasing the ratio of GeO2 to TeO2. The result was further supported by the optical band gap energy of the TGZ glass. The luminescence intensity of the sample increased with an increase in GeO2 content and reached a maximum value at 10 mol%. The chromaticity coordinates of CIE 1931 were in the warm white light range, and the corresponding color temperature range was 3400 K–3600 K. The results showed that the addition of GeO2 to Dy3+-doped tellurite glass can improve the thermal stability and luminescence performance of the white light-emitting band.

Stereocomplex crystal formation in sheath/core and sea/island Poly(l-lactic acid)/poly(d-lactic acid) fibers prepared through laser-heated melt electrospinning and subsequent annealing processes

Sheath/core (S/C) and sea/island (S/I) bicomponent fibers consisting of poly (l-lactic acid) (PLLA) as the sheath or sea component and poly (d-lactic acid) (PDLA) as the core or island component were fabricated using a bicomponent melt-spinning process. The obtained fibers were then subjected to laser-heated melt electrospinning (LES) using a rotating collector. The molecular orientation of the LES fibers increased as the fiber diameter decreased because of the increase in take-up velocity. Wide-angle X-ray diffraction revealed that the as-spun fibers were in an amorphous state. The differential scanning calorimetry (DSC) measurements showed a cold crystallization peak, followed by melting peaks of the homocrystal (HC) and stereocomplex crystal (SC), with the SC peak being more prominent for the S/I fibers. It is speculated that the distance required for the interdiffusion of PLLA and PDLA molecular chains in the fiber cross section substantially affected the transition from HC to SC during DSC measurements. The S/C and S/I fibers annealed at 120 °C after the LES were composed of HC. However, after annealing at 190 °C, which is above the melting temperature of HC, the S/C fibers fused, whereas the S/I fibers remained intact, resulting in well-separated ultrafine fibers composed of highly oriented SC.

Structural Evolution of Mn-Based Disordered Rock Salt Cathodes

Manganese-based disordered rock salt (DRX) oxides are promising new generation lithium-ion cathode materials due to the low costs and the high theoretical capacities. Recent research has revealed that DRX compounds with high manganese content, denoted as Li1+xMnyM1-x-yO2 (where y>0.5 and M represents hypervalent d0 ions such as Ti4+ and Nb5+), undergo a gradual capacity increase over initial charge-discharge cycles. This phenomenon coincides with the development of localized domains exhibiting a spinel-like cation arrangement within the overall disordered structure, termed the "δ phase."In my presentation, I will detail our effort on systematically investigating the structural changes occurring in manganese-based DRX compounds at various levels of lithium removal through heating. Analysis using synchrotron X-ray, neutron diffraction and 7Li solid state NMR reveals that , during the structural relaxation of delithiated DRX, lithium and manganese/titanium cations selectively migrate to different crystallographic sites within the rock salt structure, driving the observed structural rearrangements. We confirm that the structural evolution is the major factor contributing to the capacity enhancement. Furthermore, our research shows that both manganese-rich and manganese-poor DRX oxides can undergo thermal relaxation into the δ phase at delithiated states. However, the relaxation processes in DRX with different Mn content result in distinct domain structures. Calorimetry measurements and in-situ heating XRD experiments suggest that the structural relaxation exhibits a stronger thermodynamic driving force and lower activation energy for manganese-rich DRX compounds compared to manganese-poor systems. This difference explains why the observed structural evolution occurs predominantly in the former category during battery cycling. Figure 1

Preparation of LaF3-Based Composite Electrolytes for Solid-State Fluoride Shuttle Batteries

Fluoride shuttle battery (FSB)1 is expected as one of the candidates for the post lithium-ion battery. In FSBs, fluoride ions are charge carriers in the electrolyte, and fluorination and defluorination reactions of transition metal compounds are the charging and discharging reactions. Since many transition metals can be multivalent, FSBs are expected to have high theoretical capacities. All-solid-state FSBs have the advantage of high safety due to the non-flammability of the inorganic solid electrolytes. However, inorganic solid electrolytes have problems in that the effective ionic conductivity is lowered because of the poor contact between solid electrolyte particles. Although high-temperature sintering increases the effective ionic conductivity, it is energy-consuming and might transelement the interface between electrode and electrolyte in the case of integral sintering. This becomes an obstacle to constructing all-solid-state batteries.From the view of the practical process, it may be effective to fill the voids between electrolyte particles with a flexible electrolyte, such as a polymer electrolyte, to construct an electrolyte layer without sintering. Research on electrolytes for FSB is limited, not only on composite electrolytes but also on polymer electrolytes.2 In this study, we synthesized a new fluoride-ion conductive polymer electrolyte and prepared composite electrolytes by adding the polymer electrolyte to the lanthanum fluoride (LaF3) as the sintering-free electrolytes.Acetonitrile solutions of a polymer electrolyte using polyethylene oxide (PEO, M w 600,000) and potassium fluoride (KF) were prepared with/without the addition of an oligomer having boroxine rings as a nonvolatile anion acceptor (AA). The polymer solutions were vacuum-dried to obtain a polymer electrolyte membrane. Differential scanning calorimetry (DSC) and ionic conductivity measurements were performed for the polymer electrolytes. Composite electrolyte powder was obtained by mixing the LaF3 powder and polymer solution containing AA, followed by vacuum drying. The composite electrolyte powder was pelletized using a uniaxial press to obtain a composite electrolyte pellet. Ionic conductivity measurements were performed for the composite electrolyte pellet, pellet of LaF3 powder, and dense LaF3 disk.In the case of the polymer solution without adding AA, KF remained undissolved, but by adding AA, it completely dissolved. DSC of the polymer electrolyte showed that the softening point of the polymer electrolyte decreased from 69°C to 57°C with the addition of AA (Fig. 1a). The ionic conductivity of the polymer electrolyte is shown in Fig. 1b. The slope of ionic conductivity with respect to the temperature changed at 50–70°C, corresponding to the softening point. The polymer electrolyte with AA had higher ionic conductivity by three orders of magnitude and lower activation energy in the low-temperature range than without AA. The AA works to increase carrier density by increasing the solubility of KF to the polymer and to activate carrier conduction by plasticizing the polymer electrolyte.Ionic conductivities of the composite electrolyte and LaF3 pellet are shown in Fig. 1c. The behavior of the ionic conductivity of the composite electrolyte changed at 50–60°C. This was influenced by the softening point of the PEO-based polymer electrolyte, indicating that the polymer electrolyte is involved in ion conduction in the composite electrolytes. The main ion conduction path in the composite electrolyte is probably the polymer electrolyte/LaF3 interfacial layer. Although the composite electrolyte increased the ionic conductivity by more than an order of magnitude compared with the LaF3 pellet, it was still an order of magnitude lower than the dense LaF3 disk. Further investigation to form an optimal ionic conduction path is necessary to construct a sintering-free solid electrolyte for all-solid-state FSBs. M. A. Reddy and M. Fichtner, J. Mater. Chem., 21, 17059 (2011). K. Takahashi, A. Yokoo, Y. Kaneko, T. Abe, and S. Seki, Electrochemistry, 88, 310 (2020). This research is based on results obtained from a project, JPNP21006, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Figure 1

Thermal and Electrical Simulations for Thermal Runaway Propagation in Lithium-Ion Battery Modules

In recent years, standards for evaluating thermal runaway (TR) propagation in battery systems have been developed following a series of fire accidents, such as those occurred in electric vehicles. Those standards require the safety of battery modules even if one of the component cells goes to TR. To predict module safety, simulation models for TR propagation have been actively researched. However, limited studies have focused on the short-circuit currents that occur during TR propagation between electrically connected parallel cells.In this study, we investigate the impact of short-circuit currents between parallel-connected cells on TR propagation. For this purpose, we combine an electrochemical cell model and an electric circuit module model to simultaneously calculate the heat generation from chemical reactions and electric currents. The TR reaction in each battery cell is modeled by fitting differential scanning calorimetry (DSC) data obtained from both cathode and anode with theoretical curves. The accuracy of the individual cell model is validated through adiabatic reaction calorimetry (ARC) measurements. The model for 2P12S battery module is constructed by connecting cell models thermally and electrically. The short-circuit current is modeled based on the potential difference between parallel-connected cells, which is caused by the voltage drop in the TR cell. First, we investigate the TR propagation when cells are connected in parallel by busbars, through experiments and simulations. Next, we simulate the TR propagation when busbars are severed and short-circuit currents are absent, to explore how electrical short circuit affects TR propagation. The result revealed that the short-circuit currents between parallel-connected cells accelerate the TR propagation.Figure (a) illustrates the simulation results when a cell located on the side of a 3x8 cell array module is heated. Each line represents the cell temperature, revealing that many cells go to TR following the first trigger cell. The schematics shows the arrangement of cells with colors corresponding to the cell temperature plots, and numbers indicating the order of TR. The result shows TR propagates across the long side of cells, subsequently spreading in the short side direction. This observation highlights the significant influence of thermal resistance between cells on TR propagation. Importantly, the simulation result corresponds to the test conducted on an actual battery module.Figure (b) represents short-circuit currents, with their paths schematically depicted in the right-hand figure. Assuming that each cell shorts above 180°C, these short-circuit currents arise due to the voltage difference between parallel-connected cells when one of them reaches 180°C, and stops when both cells exceed 180°C. As the result demonstrates, short-circuit currents are inevitable as long as cells are connected in parallel, leading to the generation of Joule heat.Figure (c) illustrates the simulation result when short-circuit currents between cells are absent. Notably, the TR does not propagate beyond two cells, emphasizing the critical role of short-circuit currents. In other words, interrupting the short-circuit current can effectively prevent TR propagation. During the session, we will discuss the detailed evaluation focusing on how heat transfer and Joule heat contribute to TR propagation. Figure 1

Development and Application of a Cooling Rate Dependent PVT Model for Injection Molding Simulation of Semi Crystalline Thermoplastics.

This technical paper delves into the creation and application of an enhanced mathematical model for semi crystalline thermoplastics based on the Pressure-Volume-Temperature (PVT) Two Domain Tait Equation. The model is designed to incorporate the impact of the cooling rate on the specific volume of the material. This is achieved by utilizing Flash differential scanning calorimetry (fDSC) measurements, thereby ensuring a direct correlation to the actual behavior of the material in reality. The practical application of the model in the context of injection molding simulation was also considered. This was done by integrating the mathematical model into the Moldflow software via the Solver API. The paper underscores the discontinuity issue inherent in the traditional Tait equation with cooling rates and proposes a solution that guarantees a correct transition from the liquid to the solid phase, even at high cooling rates and pressures. The results demonstrated a realistic PVT curve across a wide range of cooling rates and high pressures. The model was put to the test using a 3D tetrahedron meshed calculation model in the injection molding simulation. This study marks a significant step forward in the simulation of injection molding processes, as it successfully bridges the gap between real material properties and simplified simulation, paving the way for more accurate and efficient simulations in the future.

Thermal behavior of polymers and copolymers based on plant oils with differing saturated and monounsaturated content

AbstractPlant oil‐based acrylic monomers from hydrogenated sunflower (HFM), palm (PMM) and castor (CSM) oils were polymerized to investigate the effect of chemical composition on polymer phase transitions at temperatures relevant to physiological range. While HFM and PMM possess a highly differing content of saturated palmitic and stearic acids combined with unsaturated fatty acids, CSM contains primarily fragments based on monounsaturated ricinoleic hydroxy acid (up to 90%). Differential scanning calorimetry (DSC) measurements indicate that polymers from PMM and HFM are both semicrystalline (with Tm = −6 and −13 °C, respectively), while poly(CSM) appears to be amorphous (Tg = −49 °C). Considering the similarity in polymers' molar mass (Mn = 16 000–20 000 g mol−1), the observed thermal transitions can be explained by the formation of ordered morphological domains due to the presence of saturated palmitic and stearic acid fractions in poly(PMM) and poly(HFM). For copolymers of CSM, PMM and HFM (80 wt% of monomer feed) with styrene, DSC data show two transitions corresponding to the mobility of long alkyl fatty acid side fragments and the macromolecular backbone. For copolymers of PMM and HFM, comparable values (−52.8 and −55.5 °C, respectively) were obtained, while the second transition for poly(CSM‐co‐styrene) appears at 35 °C. We attribute this higher value to the presence of hydroxyl groups in ricinoleic acid fragments of CSM serving as additional chain transfer sites and the formation of macromolecular fractions enriched with polystyrene fragments. We expect that the temperature transitions obtained can be relevant to the future use of these polymers for biomedical applications, including the synthesis of polymer brushes. © 2024 Society of Chemical Industry.

Enhancing yellow-green emission in Eu/Tb co-doped tellurite glasses controlled by Lu2O3

In this research, Lu2O3 was incorporated into Eu3+ and Tb3+ co-doped tellurite glasses to enhance structural stability and modify the yellow-green emission. A series of microstructural analyses, including Differential Scanning Calorimetry (DSC), Raman spectroscopy, and density measurements, confirmed that the addition of Lu2O3 causes the long-chain or cyclic Te–O–Te network structure to break, resulting in the formation of more [TeO3], which in turn leads to an increase in non-bridging oxygens (NBO) and lowers the phonon energy of the matrix material. Fluorescence spectral characterization revealed that both green and yellow luminescence intensities peaked when Lu2O3 concentration reached 15 %. Additionally, the Judd-Ofelt theory supports its superior laser performance. With the addition of Lu2O3,The radiative transition probability (Arad), lifetime (τrad), and branching ratio (β) of the excited states of Tb3+ and Eu3+ have all been enhanced. Under the regulation of 15 % Lu2O3, The maximum absorption cross-section of at 544 nm is 1.88 × 10−20 cm2, and the maximum emission cross-section is 2.14 × 10−20 cm2. At 611 nm, the maximum absorption cross-section is 1.05 × 10−20 cm2, and the maximum emission cross-section is 1.44 × 10−20 cm2. The decay curve indicates a fluorescence lifetime enhancement from 0.6 ms to 1 ms with Lu2O3. These results underscore the potential of Lu2O3 modulated Eu3+/Tb3+ co-doped tellurium glass as an effective yellow-green laser gain medium.

Unified structure–property appraisal of NIR-emitting Yb3+-activated phosphate glasses

Near-infrared (NIR)-emitting Yb3+-containing glasses with 50P2O5-(50 – x)BaO-xYb2O3 (x = 0, 0.5, 1.0, 2.0, 3.0, 4.0 mol %) nominal compositions were made by melting and studied comprehensively through refractive index, density, X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, dilatometry, differential scanning calorimetry, UV–Vis-NIR optical absorption, and photoluminescence spectroscopy measurements. The results obtained from the various techniques were analyzed quantitatively in detail and discussed in the context of the variation in Yb2O3 contents and the impact of high-field strength Yb3+ ions affecting the different properties. Ultimately, concentration correlations with data obtained from densitometry, Raman scattering, dilatometry, calorimetry, and photoluminescence measurements pointed to the occurrence of a critical Yb2O3 concentration at about 1.9 (± 0.3) mol% distinguishing low- and high-concentration effects of Yb3+ ions.

Combined effects of carbon content and heat treatment on the high-temperature tensile performance of modified IN738 alloy processed by laser powder bed fusion

Laser powder bed fusion (LPBF) is an advanced manufacturing technology used in processing nickel-based superalloys, notably for aero-engine components. One such material, the LPBF-fabricated IN738 superalloy, is prone to significant cracking issues. This study found that a change in carbon content (the optimal content of which was also determined) effectively mitigated the cracking. This study has systematically investigated the impact of different heat treatments on microstructural alterations and high-temperature tensile properties. The addition of 0.55 wt% of graphite proved effective in entirely inhibiting cracking in LPBF-fabricated IN738 specimens. Pre-alloyed IN738-M powder with the optimal carbon content was then produced and processed via LPBF to assess its formability. The as-built specimen revealed the presence of continuous carbides along the subgrain boundaries. Heat treatment promoted the transformation of substructured grains into recrystallised grains, accompanied by the precipitations of carbides and the γ′ phase; their morphologies were strongly determined by the solution treatment temperature. Differential scanning calorimetry measurements were employed to elucidate the differing microstructural states following distinct heat-treatment regimens. Under a 900 °C testing condition, stress-relieved (SR) specimens were found to exhibit superior performance, demonstrating an ultimate tensile stress (UTS) value of 843.6 MPa, a yield strength (YS) of 807.3 MPa and an elongation of 8.54 %. Notably, SR specimens also exhibited the highest UTS and YS values at 1000 °C, measuring 380.0 MPa and 346.5 MPa, respectively. This study's findings will furnish valuable insights for researchers who aim to enhance the high-temperature tensile performance of LPBF-fabricated nickel-based superalloys.

Impact of hydrothermal aging on microstructure transformation in Poly(L‐lactide) nonwovens under tension in condition close to a living organism

AbstractThe analysis of mechanical properties and structure of bioresorbable polymer nonwoven materials is an important area of research in the medical industry, the properties and structure of which directly affect the processes of cellular activity. In this work, the processes of reorganization of the fibrous microstructure of poly(l‐lactide) nonwoven materials under uniaxial tension in a water environment were investigated. The study which included volumetric ultrasound imaging, mechanical testing, differential scanning calorimetry, X‐ray diffraction, and melting rate measurements was the first attempt to identify correlations between the mechanical behavior of fibrous meshes and changes in the supramolecular structure of the polymer during 3 months of hydrothermal aging T = 37°C. An increase in crystallinity by 4%, a shift of glass transition temperature by 4°C, and a 2 times increase in melt flow rate under hydrolysis were indicated degradation of the amorphous phase. Local degradation of the amorphous phase of fibers led to the formation of surface cracks, an increase in the number of microcracks during hydrothermal aging resulted in a decrease in the mobility of fibers in the volume of the nonwoven material and a decrease in the elasticity of the entire nonwoven material, which was revealed using the volume ultrasound imaging and optical microphotographs.