Surface Thermal Properties Research Articles

Thermal Properties of Multi-Junction Cascade Vertical Cavity Surface Emitting Lasers

Thermal Properties of Multi-Junction Cascade Vertical Cavity Surface Emitting Lasers

Enhancing the Interfacial Property Between UHMWPE Fibers and Epoxy Through Polydopamine and SiO2 Surface Modification.

Here, a combination of dopamine self-polymerization and epoxy modified SiO2 (M-SiO2) grafting was proposed, with the purpose of increasing interfacial adhesion of UHMWPE fiber. Inspired by mussel adhesion, polydopamine (PDA) was deposited onto the surface of UHMWPE fiber to form a thin layer with amino and hydroxyl groups. M-SiO2 nanoparticles were then adhered to fiber surface via chemical reactions by a "two-step" or "one-step" technology. In the "two-step" technique, the M-SiO2 nanoparticles were adhered to the surface of PDA modified UHMWPE fiber via reactions between epoxy and amino groups. In the "one-step" method, M-SiO2 and dopamine were added into the UHMWPE/Tris solution at the same time. Surface morphology and thermal properties of various UHMWPE fibers were tested by SEM and TGA, respectively. Surface wettability of different UHMWPE fibers were evaluated by dynamic contact angle. The results proved that PDA and M-SiO2 were successfully adhered to the surface of UHMWPE fibers. The mechanical property of modified UHMWPE/Epoxy composites was investigated, and 43.7 % improvement was obtained, compared with unmodified UHMWPE/Epoxy composite. Additionally, micro-bond test revealed that the interfacial property (IFSS value) of modified UHMWPE fiber via the "one-step" method was 6.08 MPa, significantly higher than that of unmodified UHMWPE fiber (2.47 MPa).

Controllable preparation of hexanitrostilbene (HNS) microspheres with multi-cavity structure to enhance safety and combustion performance

Controlling the structure to meet the demand for high-energy, low-sensitivity energetic materials in modern military and civilian applications is an effective method. In this study, hexanitrostilbene (HNS) microspheres with a multi-cavity structure were prepared using nitrocellulose (NC) and fluororubber (F2604) as binders via microjet droplet technology. The effects of flow rate, receiving liquid temperature, and suspension concentration on the morphology, particle size, and cavity of the HNS microspheres were investigated. Furthermore, the impact of the multi-cavity structure on the microspheres' specific surface area, dispersibility, thermal properties, safety performance, and combustion performance was studied. Results showed that the multi-cavity HNS microspheres retained the raw materials' crystal structure while exhibiting improved dispersibility, higher activation energy, and shorter ignition delay. Moreover, the multi-cavity structure outperformed the solid structure in terms of specific surface area, safety performance, and combustion performance. This study opens up a new direction for the preparation of multi-structured energetic microspheres.

Emerging Roles of Nanozymes in Plant and Environmental Sectors.

The demand for food has increased dramatically as the global population increases, putting more strain on the sustainability of agriculture. To fulfill this requirement, it is imperative to develop brand-new technologies. The application potential of nanozymes in the plant and environmental sectors is progressively becoming apparent as a result of their effective enzymatic catalytic activity and the distinctive characteristics of nanomaterials, including size, specific surface area, optical properties, and thermal properties. Herein, we systematically analyze the catalytic mechanisms of nanozymes with different enzyme-mimetic activities and summarize their applications in improving crop yields by regulating ROS levels and enhancing stress resistance and detecting and removing hazardous pollutants. Finally, we thoroughly analyze the challenges faced by nanozymes regarding size, design, application, economy, and biosafety and look forward to their future development directions to better serve sustainable agriculture.

Integrating geographic knowledge into deep learning for spatiotemporal local climate zone mapping derived thermal environment exploration across Chinese climate zones

The Local Climate Zone (LCZ) scheme representing urban structure and land use pattern is essential for urban heat island (UHI) research. Fine-grained LCZ mapping considering spatial and temporal heterogeneity can provide a more precise characterization of surface thermal properties, thereby enabling a comprehensive analysis and understanding of spatiotemporal trends in climate change research. However, data-driven deep learning-based methods have limitations in coping with the complex urban landscapes of the real-world scenarios, including the spectral similarity of different LCZ and the geospatial heterogeneity of urban LCZ categories. In this study, we constructed a geographic knowledge base for enhanced LCZ characterization with the consideration of prior surface spatial information, including a set of spectral indices and urban morphological parameters (UMPs). Then, we integrated the explicable geographic knowledge base into a learnable deep learning framework in an end-to-end manner for accurate LCZ mapping by fusing multi-source heterogeneous data with a multi-level fusion strategy. The constructed Chinese Climate Zone Time Series LCZ (CClimate-TLCZ) dataset derived from Landsat-8 data with a 30 m spatial resolution, covering 18 representative cities in China, were used to evaluate the proposed framework. The experimental results demonstrate that the proposed framework achieved optimal outcomes across 18 cities, with an average overall accuracy exceeding 94 %, which is more than 20 % higher than that obtained by the standard WUDAPT method. Furthermore, the analysis of LCZ mapping-driven land surface temperature (LST) and surface UHI (SUHI) applications shows that cities within the same climate zone have similar LST distribution patterns, while significant heterogeneity exist between different zones. The annual consistency of LST patterns within each climate zone supports the validity of the LCZ classification scheme and accurate LCZ mapping for urban thermal environment studies. From 2016 to 2022, SUHI intensity initially increases and then decreases, indicating improvements in the urban thermal environment. These findings underscore the critical role of precise LCZ mapping in urban climate resilience and sustainable urban planning.

Biodegradable chitosan hydrogel film incorporated with polyvinyl alcohol, chitooligosaccharides, and gallic acid for potential application in food packaging

The food and beverage industry worldwide is trying to switch to using environment-friendly and bio-degradable materials in food packaging to avoid environmental concerns of using petroleum-derived plastic (synthetic polymers) materials. In this study, chitosan (CH) hydrogel films were fabricated by using its derivative chitooligosaccharides (COS) as an additive, polyvinyl alcohol as a plasticiser, and bioactive gallic acid as a cross-linker. The physical, mechanical, structural, barrier (e.g., moisture, water vapour permeability (WVP), and UV-barrier property), thermal properties, and biodegradation patterns of fabricated films were investigated. The use of bio–composite in CH films exhibited a synergistic effect. A film with a homogenous/smooth surface and excellent mechanical and thermal properties was obtained. Additionally, incorporating COS and gallic acid reduced the moisture content, WVP, and transparency. Moreover, the films exhibited good colour, strong UV-barrier properties, and good biodegradable capacity in soil. The results suggest that eco-friendly CH hydrogel films have promising potential to be used in food packaging.

Aerogels based on Bacterial Nanocellulose and their Applications.

Microbial cellulose stands out for its exceptional characteristics in the form of biofilms formed by highly interlocked fibrils, namely, bacterial nanocellulose (BNC). Concurrently, bio-based aerogels are finding uses in innovative materials owing to their lightweight, high surface area, physical, mechanical, and thermal properties. In particular, bio-based aerogels based on BNC offer significant opportunities as alternatives to synthetic or mineral counterparts. BNC aerogels are proposed for diverse applications, ranging from sensors to medical devices, as well as thermal and electroactive systems. Due to the fibrous nanostructure of BNC and the micro-porosity of BNC aerogels, these materials enable the creation of tailored and specialized designs. Herein, a comprehensive review of BNC-based aerogels, their attributes, hierarchical, and multiscale features are provided. Their potential across various disciplines is highlighted, emphasizing their biocompatibility and suitability for physical and chemical modification. BNC aerogels are shown as feasible options to advance material science and foster sustainable solutions through biotechnology.

Surface modification of polylactide films and their hydrolytic degradation performances in artificial seawater

AbstractBenzophenone (BP) and N‐vinylpyrrolidone (NVP) were used to modify the surface of polylactide (PLA) films by UV grafting method. The effects of light distance, temperature, reaction time, and modifier concentration on the structure and properties of PLA films were investigated by Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy (XPS), nuclear magnetic resonance spectroscopy, differential scanning calorimetry (DSC), and universal testing machine (UTM). With BP and NVP UV grafting, the hydrophilicity of PLA films is improved, but their thermal and mechanical properties are reduced under different surface modification condition. Base on the principle of good surface hydrophilicity, better mechanical and thermal properties, the hydrolytic degradation performance of modified PLA films in artificial seawater at 70°C was studied by scanning electron microscopy, XPS and DSC. The research results show that the degradation of modified PLA films mainly occurs in the amorphous region, and the degradation process conforms to surface hydrolysis mechanism. The grafting modification of NVP is better than BP to accelerate the degradation process of PLA films in artificial seawater. The degradation of modified PLA undergoes water molecule erosion and autocatalytic degradation reaction. The degradation of BP‐PLA obeys the first‐order kinetics in part, while the degradation of NVP‐PLA is more complex. Therefore, surface hydrophilicity modification is an effective technique for improving the degradability of PLA.

Synthesis, structural characterization, Hirshfeld surface analysis and thermal properties of dibutyltin(IV)-based complexes containing thiocyanate and pyridyl ligands

Dibutyltin(IV) complex [SnBu2(NCS)2] (1) has been prepared from the reaction of SnBu2Cl2 and potassium thiocyanate in a molar ratio of Sn:KNCS/1:2 in ethanol. The reaction of [SnBu2(NCS)2] (1) with 4,4ꞌ-di-tert-butyl-2,2ꞌ-bipyridine (bu2bpy) in a molar ratio of Sn:bu2bpy/1:1 resulted in the formation of [SnBu2(NCS)2(bu2bpy)] (2). The products were characterized using elemental analysis, IR, and multinuclear NMR (1H, 13C, 119Sn) spectroscopy. The X-ray crystal structure determination of the complex [SnBu2(NCS)2(bu2bpy)] (2) revealed that the geometry around the Sn(IV) atom is highly distorted octahedral with trans-[SnBu2] configuration. On the other hand, the new single crystals of bu2bpy (3) were characterized by X-ray crystallography from the crystallization of 2 in diethyl ether. The various types of weak interactions in their networks have been assessed using the 3D Hirshfeld surface analysis and 2D fingerprint maps for 2, and 3 which show the major contribution of intermolecular interactions is related to H…H interactions. The thermal properties analysis showed that the complex [SnBu2(NCS)2] (1) is stable up to 153 °C while the complex [SnBu2(NCS)2(bu2bpy)] (2) is stable up to 190 °C.

Deep Eutectic Solvent-Based Polymer Electrolyte Films for an Electrochemical Double Layer Cell

Polymer electrolyte films based on DES were prepared with the solution cast technique. DES(ChCl-glycerol) was prepared with two different glycerols: one purchased from the industry and the other fabricated in the lab from waste vegetable oil. Two polymer electrolyte films were prepared with two different DES (industrial and from oil-based glycerol) were named D1 and D2, respectively. Fabricated polymer film (D1) with DES (prepared with industrial glycerol) shows excellent physical and thermochemical properties. The molecular and structural characteristics of the film were studied via FTIR and XRD. The surface morphology, thermal and electric properties of film were studied with SEM, TGA, and impedance spectroscopy techniques, respectively. The obtained films were flexible, strong, and transparent. Its properties are ascribed to a strong coherent hydrogen bond network with the matrix of the polymer. Polymer electrolyte film D1 exhibited good ionic conductivity of 1.25×10-3 Scm-1. The prepared polymer film was applied as solid electrolytes in symmetric solid-state supercapacitors. The fabricated EDLC cell exhibits specific capacitance of at voltage with scan rate. Moreover, the prepared electrolyte is biocompatible, environment safe and cost-effective that offers a new path for adaptable electronic devices. Keywords: Green electrolytes, Supercapacitor, Deep eutectic solvent, Hydrogen bond network, Choline chloride-glycerol.

Thermal Surface Properties, London Dispersive and Polar Surface Energy of Graphene and Carbon Materials Using Inverse Gas Chromatography at Infinite Dilution.

The determination of these surface properties is carried out using inverse gas chromatography at infinite dilution, which leads to the retention volume of organic solvents adsorbed on solid surfaces. This experimental and fundamental parameter actually reflects the surface thermodynamic interactions between injected probes and solid substrates. The London dispersion equation and the Hamieh thermal model are used to quantify the London dispersive and polar surface energy of graphenes and carbon fibers as well their Lewis acid-base constants by introducing the coupling amphoteric constant of materials. The London dispersive and polar acid-base surface energies, the free energy of adsorption, the polar enthalpy and entropy, and the Lewis acid-base constants of graphenes and carbon materials are determined. It is shown that graphene exhibited the highest values of London dispersive surface energy, polar surface energy, and Lewis acid-base constants. The highest characteristics of graphene justify its great potentiality and uses in many industrial applications.

Incorporation of ground mustard seeds in an active packaging film: structural properties and controlled release of allyl isothiocyanate

SummaryGround mustard seeds can be incorporated into a packaging film material to have a controlled release of allyl isothiocyanates (AITC). However, the properties of film material loaded with ground mustard seeds need to be evaluated, since they might influence the release of AITC from the film materials. This study aimed to assess properties, including surface morphology, spectral analysis, crystallinity, the moisture‐related, thermal and mechanical properties, of the film materials incorporated with the ground seeds and the release of antimicrobial compounds. Furthermore, the effects of relative humidity on AITC release in the headspace were investigated. The results showed that incorporating a larger quantity of ground mustard seeds resulted in the quicker release of AITC due to direct exposure to moisture, as indicated by higher concentrations observed in the headspace. Meanwhile, a smaller quantity of ground seeds added to the film maintained the thermal properties of the materials until 100 °C, resulting in significantly better moisture‐related properties and higher mechanical strength in terms of tensile strength, elastic modulus, and strain at break. However, the smallest ratio (1:5) showed no release of AITC into the packaging headspace at 75% and 100% RH. Furthermore, the relative humidity led to the release of more AITC in the headspace, which is potentially applied for high‐moisture food products. Based on the influence of relative humidity on AITC concentrations, the mechanism of AITC release from the film materials is proposed, describing the AITC diffusion from ground mustard seeds, film, and headspace.

Stereolithography 3D printing of microgroove master moulds for topography-induced nerve guidance conduits

 Patients who have peripheral nerve damage from trauma or disease may suffer lifelong disability. Current interventions such as nerve allografts are inadequate due to limited availability of tissue and donor-site morbidity. Commercial nerve guidance conduits are used to bridge the damaged nerve gap and restore function. Typically, however, they lack cell-instructive guidance cues to promote directed regeneration. Tissue-engineered nerve guidance conduits that utilise micro- and nano-topographical architectures have been demonstrated to direct cell behaviour and contact guidance. This study uses projection micro-stereolithography-based three-dimensional (3D) printing to fabricate microgrooved (10–30 μm) master moulds to produce polydimethylsiloxane (PDMS) moulds and solvent cast polycaprolactone and polylactic acid films. The polymer microgrooves were successfully fabricated and were able to be formed into tubular nerve guidance conduits. The surface morphology, roughness, wettability, and thermal properties of the films were characterised. The microgroove topography improved proliferation and induced alignment of SH-SY5Y cells. This facile 3D printing approach is promising for the fabrication of nerve guidance conduits with topographical guidance cues as it obviates the need for using photolithographic techniques. Thus, this approach provides an alternative that is simpler, faster, cheaper, and offers greater design freedom.

Evaluation of Strain Sensors Based on Poly(acrylonitrile-co-butadiene) and Polypyrrole Synthesized by the Diffusion Method.

In this study, the functionality of an elastomer composite material containing polypyrrole (PPy) as a stress sensor was evaluated. The material was prepared using the swelling method by diffusing the pyrrole monomer into the elastomer before polymerization. To achieve adequate diffusion, organic solvents with affinity for the elastomer were used. The resulting materials were characterized by scanning electron microscopy (SEM), surface electrical resistance, and thermal and mechanical properties for application as a stress sensor. The simultaneous change in electrical resistance and tension stress was measured using a digital multimeter with electrodes connected to the jaws of a universal mechanical testing machine. The influence of stress cycles on the piezoresistivity of the composite materials was investigated. The obtained PPy/NBR composite presented a good combination of electrical conductivity and mechanical properties. The strain at break remained with mild variation after coating with PPy.

Simulation advances with EnviBatE- A case study on urban heat island mitigation in Singapore

Urban morphology and surface thermal properties are two key factors that determine the local-level urban heat island effect. Among different strategies that help in mitigating this effect, applying high reflective cool coating on urban surfaces is one of the most effective ways for changes in both the daytime and night-time urban air temperatures. In this paper, advances in the EnviBatE microclimate model for district-level numerical simulations are presented and the results are compared against full-scale experimental measurements conducted in Singapore. Key aspects of the EnviBatE tool along with their mathematical models are demonstrated. The experimental site consists of two side-by-side street canyons located at an industrial estate in the west of Singapore: one canyon with conventional and the other with cool surfaces for side-by-side comparison. The results suggest that the drop in street-level canyon air temperature varies from 1 to 4 °C with the application of the cool surface coating on roofs, walls and roads in comparison with conventional canyon under various scenarios. By analysing the effects of the three types of built-up surfaces separately, the cool roads scenario appears to have the greatest impact on canyon air temperature (at 3 m above ground), followed by the cool roofs scenario. The cool walls scenario produces negligible cooling impact. The advantages of the cool coating application on urban surfaces in reducing air temperature are statistically analysed and demonstrated. The pedestrian comfort in terms of the Universal Thermal Climate Index (UTCI) is proposed to be integrated with EnviBatE and discussed using the simulation results.

Effects of fatty acid esters on mechanical, thermal, microbial, and moisture barrier properties of carboxymethyl cellulose-based edible films

Fatty acid esters being biodegradable and environment friendly has been a sought-after class of molecule for various food grade applications. This work involves the incorporation of fatty acid esters namely cetyl-caprylate and cetyl-caprate in edible Carboxymethyl cellulose -based films. The esters were enzymatically synthesized by esterification of caprylic acid and capric acid respectively with cetyl alcohol at a molar ratio of 1:1, using Candida antarctica lipase B which was immobilized (10 % w/w) at 65 °C. Carboxymethyl cellulose films were prepared. To it, glycerol and by emulsification, cetyl-caprylate or cetyl-caprate esters were amalgamated. Film characterizations involved analysis of surface morphology, mechanical properties, and thermal properties. It was further characterized by X-Ray diffraction analysis, water vapor permeability, and moisture uptake. Barrier property carboxymethyl cellulose films showed significant improvement due to the incorporation of cetyl-caprylate or cetyl-caprate esters. However, when the film's melting point was measured, it was seen that glycerol influenced the thermal properties more prominently than cetyl-caprylate and cetyl-caprate esters. Thus, the addition of an optimized amount of glycerol and cetyl-caprylate or cetyl-caprate esters to the carboxymethyl cellulose films is required for improved mechanical strength and better thermal properties. Further, an antimicrobial well diffusion assay of both the esters established the antimicrobial property of the same, which thereby recommends the addition of the wax esters even more.

Comparing industrial and analytical kraft lignins as biobased UV-protective additives in coatings

Lignin as the second most abundant biopolymer on Earth has the potential to become the alternative to petroleum-derived materials. It exhibits excellent UV absorption ability due to its aromatic structure and the presence of numerous phenolic, ketone, and intramolecular hydrogen bonds. Due to its complex nature, it is important to investigate its properties which is a very important step towards the valorization of lignin. Revealing its structural complexity allows for a better examination of its influence on the properties of the final lignin-based materials. In our research, we used two different kraft lignins: commercial analytical kraft lignin (AL) and industrial LignoBoost kraft lignin (KL) as UV-protect additives in BPA(Bisphenol A)-free polymer coatings based on diurethane dimethacrylate (DIUR). The maximum addition of KL and AL was 2 wt%. Both lignin samples were characterized in detail (composition analysis, ash content, molar mass and polydispersity, surface morphology, thermal properties, and quantitative measurement of hydroxyl group content). We investigated the influence of lignins on the textural and thermal properties of the coatings. Finally, we studied the application of lignin as a value-added UV-protective component by UV-Vis electronic absorption spectroscopy. KL with a higher purity and lower number of aliphatic OH had a better dispersion in the polymer matrix than AL lignin which had more agglomeration in the polymer matrix. The better dispersion resulted in producing a smoother surface in the coatings made from KL. Finally, a noticeable and significant impact of KL additive on the photoprotective properties of the coating material was demonstrated. These results showed a potential application and opportunity in the valorization of available industrial lignins toward sustainable and value-added products.

Effect of (multi pin) atmospheric cold plasma treatment on curcumin extraction and investigating phytochemicals, antioxidants, physical and morphological properties of turmeric (Curcuma longa L.) powder

This investigation was focused on the impact of cold plasma (CP) on the extraction of curcumin and bioactive compounds of turmeric powder (TP). TP was treated with CP at different applied voltages (10, 20, and 30 kV), with various exposure times (10, 20, and 30 min). The curcumin content was highest at 30 kV for 10 min with a yield of 46.49 mg/g of TP. Total phenols significantly (p < 0.05) enhanced from 163.91 to 360.78 mg GAE/g DW accompanied by a remarkable 16% increment in total flavonoids, paralleled by a 26% increment in antioxidants as of control. Nuclear magnetic resonance spectra justified the extraction of curcuminoids. Moreover, micrographs displayed cell lysis in the treated powder. CP has exhibited a positive effect on surface colour parameters and thermal properties of TP. Overall, CP technology can be tailored for better curcumin extraction and the enhancement of phytochemicals.

Exploring the application of poly(1,2-ethanediol citrate)/polylactide nonwovens in cell culturing.

Biomaterials containing citric acid as a building unit show potential for use as blood vessel and skin tissue substitutes. The success in commercializing implants containing a polymer matrix of poly(1,8-octanediol citrate) provides a rationale for exploring polycitrates based on other diols. Changing the aliphatic chain length of the diol allows functional design strategies to control the implant's mechanical properties, degradation profile and surface energy. In the present work, poly(1,2-ethanediol citrate) was synthesized and used as an additive to polylactide in the electrospinning process. It was established that the content of polycitrate greatly influences the nonwovens' properties: an equal mass ratio of polymers resulted in the best morphology. The obtained nonwovens were characterized by surface hydrophilicity, tensile strength, and thermal properties. L929 cell cultures were carried out on their surface. The materials were found to be non-cytotoxic and the degree of porosity was suitable for cell colonization. On the basis of the most important parameters for assessing the condition of cultured cells (cell density and viability, cell metabolic activity and lactate dehydrogenase activity), the potential of PLLA + PECit nonwovens for application in tissue engineering was established.

Preparation and chemical properties of microencapsulation developed with mulberry anthocyanins and silk fibroin

Anthocyanins, as natural pigments with bright color and non-toxic side effect, are widely used in the agricultural products processing field. In the present research, mulberry anthocyanin microcapsules were prepared with silk fibroin and gum arabic as wall materials for the possible application in cosmetics industry. Anthocyanin microcapsule encapsulation efficiency was up to 95.71% in the condition of silk fibroin: gum arabic at 2:1, wall-core ratio of 7.5:1 and solid content at 15%. Microcapsules improved the thermal stability and pH stability of mulberry anthocyanins with higher retention rates. Besides, scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and fourier transform infrared (FTIR) were applied to analyze the surface morphology, structure, crystallinity and thermal properties of mulberry anthocyanin microcapsules. The results indicated that anthocyanins were embedded in the capsules with crystalline structures, good encapsulation and enhanced thermal stability.