Thermal Strength Research Articles

Assessing the durability of bio-based materials with respect to microbial contamination: Microstructure and macroscopic properties

The aim of this paper was to assess the effect of the microorganism development on the thermal and mechanical properties of building insulation materials (rapeseed straw and lime (RL) and sunflower bark and pith and lime (SL)) and three plant aggregates (rapeseed straw (RS), sunflower bark (SB) and pith (SP)). The samples were exposed to accelerated ageing, in a static environment with a temperature of 30°C and a high humidity of 90 % (±3 %), to favor the proliferation of microorganisms. The paper presents the biological study of the cultivated bacteria and fungi at four ageing times (0, 3, 6, and 12 months) using a counting test. The results showed that these materials were more vulnerable to fungi than to bacteria. Cryo-HRSEM observations were carried out to follow the development of microorganisms at micro scales, at 0 and 6 months of exposure to microbial ageing. The observations showed that the aggregates (RS, SB, and SP) were colonized by microorganisms prior to microbial conditioning for 6 months, but not with the same tendency on the biocomposites (SL and RL) studied which presented weaker development of microorganisms by comparison to the aggregates. The lime has an immediate anti-microbial effect on the aggregates after storage conditions. After ageing, the microorganisms continued to grow on the aggregates, as did the biocomposites, which showed microbial growth of microorganisms of the same type as those found initially on the aggregates. Physical characterization was conducted in order to evaluate the effect of the microbial development. The thermal conductivity was measured with hot wire method for plant aggregates and heat flow meter for the biocomposites. Mechanical characterization was performed by uniaxial compressive test. The studied functional properties (thermal conductivity and compressive strength) of RS, SB, RL, and SL showed a decrease after 3 months, and after 6 months for SP.

Mechanism of thermal compressive strength evolution of carbon-bearing iron ore pellet without binders during reduction process

Mechanism of thermal compressive strength evolution of carbon-bearing iron ore pellet without binders during reduction process

CMC strength and damage prediction considering thermal mechanic coupling effect

Continuous Fiber Reinforced Ceramic Matrix Composites (CMC) confront significant and undeniable elevated thermal gradient. In this study, a periodic RVE geometrical model was simplified based on the XCT scanning images of 2.5D woven CMC, and the model of the thermal structural strength of 2.5D woven CMC under the influence of fine-scale temperature fields was developed. In conjunction with the temperature distribution of the aero-engine turbine working state, ten sets of temperature field conditions were established and the model of thermal structural strength of 2.5D woven CMC under the influence of fine-scale temperature fields was developed. The effects of the overall temperature level, the form of the temperature difference and the size of the temperature difference on the tensile curve, the failure limits, the form of damage evolution, and the distribution of the failure unit at the time of failure of the 2.5D woven CMC were discussed. It was found that the temperature field induced by temperature difference in the thickness direction has a more significant effect on the tensile mechanical properties of the material, which is a key consideration for the structural design process using this material.

Multifunctional Integrated Organic–Inorganic-Metal Hybrid Aerogel for Excellent Thermal Insulation and Electromagnetic Shielding Performance

HighlightsThe homogeneous hybridization of organic–inorganic-metal elements in 3D aerogel was achieved by an expeditious method.The aerogel tightly integrates excellent thermal insulation (49.6 mW m−1 K−1), ablative resistance, mechanical strength, and superhydrophobic properties.The ablated carbon aerogel combines notable electromagnetic interference shielding properties (31.6 dB) and load-carrying properties (272.8 kN·m kg−1).

Nylons with Applications in Energy Generators, 3D Printing and Biomedicine.

Linear polyamides, known as nylons, are a class of synthetic polymers with a wide range of applications due to their outstanding properties, such as chemical and thermal resistance or mechanical strength. These polymers have been used in various fields: from common and domestic applications, such as socks and fishing nets, to industrial gears or water purification membranes. By their durability, flexibility and wear resistance, nylons are now being used in addictive manufacturing technology as a good material choice to produce sophisticated devices with precise and complex geometric shapes. Furthermore, the emergence of triboelectric nanogenerators and the development of biomaterials have highlighted the versatility and utility of these materials. Due to their ability to enhance triboelectric performance and the range of applications, nylons show a potential use as tribo-positive materials. Because of the easy control of their shape, they can be subsequently integrated into nanogenerators. The use of nylons has also extended into the field of biomaterials, where their biocompatibility, mechanical strength and versatility have paved the way for groundbreaking advances in medical devices as dental implants, catheters and non-absorbable surgical sutures. By means of 3D bioprinting, nylons have been used to develop scaffolds, joint implants and drug carriers with tailored properties for various biomedical applications. The present paper aims to collect evidence of these recently specific applications of nylons by reviewing the literature produced in recent decades, with a special focus on the newer technologies in the field of energy harvesting and biomedicine.

Preparation and properties of three-dimensional continuous network reinforced Graphite/SiC ceramic composite insulation materials

Addressing the challenge of existing insulation materials struggling to achieve the synergy of lightweight construction, high strength, and low thermal conductivity, this paper presents a method based on multi-material assembly technology to achieve a controlled composite of a three-dimensional continuous silicon carbide network and graphite matrix. Following an examination of the impact of various forming densities and the addition of expandable graphite on the thermal conductivity and compressive strength of graphite/SiC composites, the study explored the effects of different "enhancement network" topologies on the properties of these composites. The investigation demonstrates that adjusting the forming density and incorporating expandable graphite enable regulation of both the porosity and closed porosity of the composites, thereby controlling their compressive strength and thermal conductivity. Additionally, the construction of a three-dimensional continuous SiC network structure within the graphite matrix significantly enhances the compressive strength of the composites, with only a slight increase in thermal conductivity. A graphite/SiC composite thermal insulation material was ultimately developed, boasting a density of merely 1.1 g/cm³, a low thermal conductivity of 1.847 W/m·K, and an impressive compressive strength reaching 15.627 MPa. Its overall performance surpasses that of water-glass sand, making it a promising candidate for various applications in the foundry industry as a thermal insulation material.

Enhanced polyacrylamide polymer hydrogels using nanomaterials for water shutoff: Morphology, thermal and rheological investigations at high temperatures and salinity

This study focuses on the synthesis, characterization, and performance evaluation of polyacrylamide (PAM)/polyethyleneimine (PEI) hydrogels enhanced with nanomaterials for potential application in conformance control in oil wells. The materials used include PAM with a molar mass of 25,000 Kg mol−1, PEI with an average weight molar mass of 25 Kg mol−1, and synthetic brine (ionic strength 0.6). Nanomaterials such as titanium dioxide (TiO2) nanoparticles, oxidized carbon nanotubes (CNT-ox), and graphene oxide (GO) were incorporated into the hydrogel matrix. A simple method was used for the incorporation of nanomaterials into the polymeric matrix, ensuring their good dispersion in the hydrogels formed. Characterization techniques including thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were employed to analyze the structure, morphology, and thermal stability of the hydrogels. Rheological measurements and gel strength evaluations were conducted to assess the performance of the hydrogels. Results indicate that the incorporation of nanomaterials enhanced the thermal stability, gel strength (Sydansk code), and resistance to syneresis of the hydrogels. Specifically, the addition of TiO2 nanoparticles exhibited the highest improvement in viscosity and thermal stability, attributed to strong interactions between TiO2 and PAM molecules. A notable decrease in syneresis percentages was observed with the inclusion of nanomaterials compared to the PAM reference sample, reaching 70.1 % for the hydrogel modified with GO. These findings suggest that nanomaterial-enhanced hydrogels hold promise for applications in conformance control in oil wells, offering improved stability and performance over extended periods of use.

Investigating the effects of temperature on thermal and mechanical properties of polyurethane/polycaprolactone/graphene oxide nanocomposites: focusing on creating a smart polymer nanocomposite via molecular dynamics method

ABSTRACT Polycaprolactone, a biodegradable polyester renowned for its biocompatibility, controlled degradation capability, and processability, finds application across diverse industrial sectors. Graphene oxide has been utilised to strengthen polymers and rectify any existing issues. This research aims to investigate the effects of temperature on the thermal and mechanical properties of polyurethane/polycaprolactone/graphene oxide nanocomposites, focusing on creating a smart polymer nanocomposite via the molecular dynamic method. The research is innovative as it investigates the nanocomposite's thermal behaviour and strength in detail. Additionally, the use of molecular dynamics methods to achieve the goal of creating a smart polymer nanocomposite represents an innovative approach that contributes to the advancement of nanocomposite materials. The results show that raising the initial temperature to 350 K decreased heat flux and thermal conductivity to 681.85 W/m2 and 0.82 W/m.K, respectively, while increasing the structure volume to 27364 nm3. Additionally, as the Temp increased from 300 to 350 K, the ultimate strength and Young's modulus values decreased from 72.59–68.22 MPa and 6.63–6.36 MPa, respectively. In general, this research provided valuable insights into understanding and evaluating the attributes of polyurethane/polycaprolactone/graphene oxide polymer nanocomposite through molecular dynamic simulations.

Impact of multi‐walled carbon nanotubes on the thermal, mechanical, and electrical properties of guar gum hydrogel

AbstractThis research investigates the transformative impact of incorporating unmodified multi‐walled carbon nanotubes (um‐MWCNTs) on properties of guar gum (GG)‐based hydrogel. The study focuses on the enhancement of thermal stability, mechanical strength, and electrical properties of hydrogel composite. Thermal analysis reveals a significant increase in residual weight remaining at 430°C from 3% to 10% with the addition of 0.2 wt% um‐MWCNTs to GG hydrogel. Viscoelastic properties of hydrogel composite investigated by rheology analysis observed that enhancements in storage modulus from 0.2 to 2.2 MPa indicative of enhanced structural integrity. Moreover, electrical conductivity exhibits a substantial increase with the addition of nanotubes, indicating the potential applicability of the composite in electronic and sensing applications. This research showcases the potential of GG/um‐MWCNT composites for diverse applications in biomedicine, sensors, and advanced materials.Highlights Distribution of um‐MWCNTs into guar‐gum matrix to obtain maximum benefits. Inclusion of um‐MWCNTs improves the rheological properties of GG/um‐MWCNTs composites. Rheological properties can be tuned with um‐MWCNT content. MWCNTs improved thermal stability of the GG hydrogel. MWCNTs improved electrical conductivity of the GG hydrogel.

Achieving high strength and low thermal conductivity: Additive manufacturing of mullite lightweight refractory

Complex geometries of mullite lightweight refractory materials with high strength and low thermal conductivity were successfully achieved through additive manufacturing using the direct ink writing technique and fly ash beads coated with alumina sol. In the refractory preparation process, printing ability of the ink was enhanced by adding additives (dispersant and binder). The adjustment of printing parameters, such as pressure, nozzle size, and printing speed, resulted in an enhancement of the refractory structure's accuracy. Compared to the ink with uncoated fly ash beads, the inks with coated fly ash beads show better stability and shear thinning behavior. The compressive strength of the refractories improved significantly. Meanwhile, the thermal conductivity of the refractories kept in a low level. The use of fly ash beads coated with alumina sol in the preparation of porous refractory resulted in the formation of mullite wishers within the pore walls. This created micron-size pores between the whiskers, greatly enhancing the thermal insulation and strength of the porous refractories. The Ashby-Glicksman model was particularly advantageous in predicting the thermal conductivity of the insulation refractories, especially when dealing with a complex pore structure. Therefore, utilizing the direct ink writing technique to produce lightweight refractory materials shows promise in addressing the challenge of creating intricate lightweight refractory parts.

Structure, mechanical, and neutron radiation shielding characteristics of mechanically milled nanostructured (100-x)Al-xGd2O3 metal composites

Metallic substances are favored for storing and transporting spent nuclear fuels (SNFs) due to their thermal stability, mechanical strength, and corrosion resistance. Adding gadolinium (Gd) significantly enhances neutron shielding, improving efficiency with reduced thickness and dimensions. In this study, Al–Gd2O3 metal nanocomposites were synthesized using powder-processed mechanical milling. The crystal structure features of (100-x)Al-x%Gd2O3 samples with varying percentages of Gd2O3 (5 %, 10 %, and 15 % by weight) were analyzed by X-ray diffraction. Microstructural properties were studied using scanning and transmission electron microscopy (SEM and TEM). The synthesized composites' neutron and γ-radiation shielding characteristics were investigated theoretically using the MCNP6.2 transport code. Analysis of the XRD data revealed prominent peak shifts with increased milling time, indicating reduced particle sizes. Differential scanning calorimetry (DSC) indicated Gd2O3-induced changes in temperature behavior, and the Vickers microhardness tests demonstrated enhanced mechanical strength with increasing gadolinium concentration. Improved neutron radiation shielding was observed with higher Gd2O3 content. Our study highlights the potential of Gd2O3-enriched metal matrix composites for advanced industrial applications.

Exploring the potential of poly (caprolactone) and guar gum biodegradable blend film: an investigation for supercapacitor

A biodegradable polymer electrolyte comprising poly (caprolactone) (PCL) and guar gum (GG) doped with lithium perchlorate (LiClO4) was investigated for its application in supercapacitors. The films’ thermal properties, surface morphology, and tensile strength were determined to understand the interaction between the blend system and the salt. Scanning electron microscopic images showed a network of GG channels across the polymer matrix. A unique combo of THF/water as solvent was used for this study as they bring out relaxation in GG segments and compatibility between GG and PCL. The blend polymer electrolyte (BPE) was characterized using conductivity, dielectric, and biodegradation studies. Supercapacitors were fabricated, and electrochemical studies were performed. The optimized BPE was used to fabricate supercapacitors, producing a specific capacitance of 125 F g−1. The time constant was measured at 0.8 s, and a consistent cyclic pattern was observed during galvanostatic charge/discharge studies with 96% Coulombic efficiency. This novel amalgamation of polymeric films holds immense promise for supercapacitor applications.

Investigation of liquid crystal epoxy resin composites for application in cryogenic environments

AbstractIt is well accepted that the intrinsic thermal conductivity is extremely important in achieving excellent thermal conductivity composite and can be improved via incorporation of mesogens. In this work, an azomethine type liquid crystal epoxy (LCE) with aliphatic ether was designed and synthesized with expected structure, and the liquid crystal epoxy resin (LCER), together with KH‐550‐modified boron nitride (K‐BN)/LCER composites, has been obtained. Results show an increase of 31.6% in the thermal conductivity of the matrix, which could result in an enhancement of 57.7% for the composites when compared with E‐51. Additionally, the coefficient of thermal expansion (CTE), dielectric properties, and shear strength of LCER and K‐BN/LCER composites were assessed across a broad temperature range. Remarkably, the 30 wt% K‐BN/LCER composites showed a maximum decrease of 37.8% in CTE, while maintaining adequate shear strength to fulfill the bonding requirement and high thermal conductivity at both RT and −196°C.

Advancements in precast concrete sandwich panels for load bearing structures

Concrete sandwich panels consist of two concrete layers separated by an insulating foam core, offering thermal insulation, structural strength, and fire resistance. This study investigates sustainable precast concrete sandwich panels made with industrial waste materials like limestone slurry, quarry waste, and basalt fiber as shear connectors. The research evaluates the flexural and axial strength behavior of these panels and explores strategies to improve their structural performance. The panels were fabricated with outer concrete layers, an expanded polystyrene (EPS) insulation core, and basalt fiber connectors. Flexural tests using four-point bending and axial compression tests were conducted on panels with varying concrete layer thicknesses and basalt fiber widths. Findings revealed panels with thicker outer concrete layers (35mm) and wider basalt fiber connectors (11.5mm) exhibited higher cracking loads, load-hardening behavior, and increased ductility compared to thinner layers and narrower connectors. The axial test showed premature failure at the top and bottom quarters. Thicker concrete layers and wider basalt fiber connectors enhanced crack control, load distribution, and ductile behavior under flexural loading. Strengthening measures like additional reinforcement, proper anchorage detailing, and increased shear reinforcement at the end regions are recommended to improve axial load-bearing capacity and prevent premature end failures. The PCSP demonstrated up to 40% cost savings over commercial products while providing better thermal insulation than conventional brick masonry due to the EPS core. Overall, the study promotes developing sustainable, energy-efficient, and cost-effective load-bearing sandwich panel systems.

Capsicum leaf protein-based bionanocomposite films for packaging application: Effect of corn starch content on film properties

The addition of corn starch (CS) enhances the interfacial adhesion of the film-forming liquids (FFLs), weakening the internal relative molecular motion. As a result, the rheological properties and zeta potential values of the FFLs were affected. A tight spatial network structure between capsicum leaf protein (CLP), lignocellulose nanocrystals (LNCs) and CS can be formed through intermolecular entanglement and hydrogen bonding interactions. The crystallinity, thermal degradation temperature, tensile strength and water contact angle of the protein-based bionanocomposite films (PBBFs) increased with increasing CS addition. This is due to the transformation of the secondary space structure of the CLP inside the PBBFs and the increase in cohesion. However, the excessive addition of CS forms aggregated clusters on the surface of PBBFs, which increases the surface roughness of PBBFs and causes more light scattering. Therefore, the brightness and yellowness values of the PBBFs increase, and the transmittance decreases.

Development and application of low-melting-point microencapsulated phase change materials for enhanced thermal stability in cementing natural gas hydrate layers

In the exploration of deep-water oil and gas resources, encountering natural gas hydrate (NGH) layers poses significant challenges, particularly during cementing operations critical for wellbore stabilization. This study proposes a strategy employing cement slurries integrated with micro-encapsulated phase change materials (MPCMs) to address the destabilization of NGH layers, a key obstacle in deep-water cementing. MPCMs containing BaCO3 shell and low-melting binary PCMs in the core were synthesized by the self-assembly method. The structure and thermal properties of MPCMs were thoroughly characterized. MPCMs exhibited a distinct core-shell structure with a hydrophilic and well-sealed shell. Their phase change temperatures were in closely matched the temperatures found in NGH formations, at 3.5 °C and 13.9 °C. A comprehensive evaluation of the fundamental properties of cement slurries containing MPCMs (CSM) was conducted, including thermal stability, setting time, pore structure, and mechanical strength. Additionally, a laboratory device was employed to simulate cementing operations, allowing for intuitive analysis of the impact of hydration heat evolution on NGH stability—a notably underexplored aspect in related literature. The results demonstrated that MPCMs effectively reduced the hydration heat generated by cement slurry within the initial 36 h. Specifically, at a 9% MPCMs dosage, the hydration heat of CSM decreased by 19.0%, resulting in the sustained stability of NGH. In contrast, the control group's cementing process directly led to the complete decomposition of NGH. Even at lower MPCMs concentrations, the decomposed NGH was more likely to recrystallize and return to a stable state due to the slower hydration heat release rate of CSM. This study not only provides evidence of the effectiveness of MPCMs as heat inhibitors in reducing the disruption of hydrate stability during well cementing but also provides theoretical guidance for the design and application of cement slurries for NGH reservoirs. By enhancing the stability of NGH layers, this work supports the safe and efficient exploitation of undersea hydrocarbon resources, contributing to shaping future global energy strategies.

Preparation and microstructure of Cu-Al2O3 composites by a novel supercritical water liquid phase in-situ reaction method

The high solubility, reactivity and solubility of supercritical water provide a new way for the preparation of advanced metal matrix composites. In this paper, Cu-Al2O3 composites are prepared by supercritical water liquid phase in situ reaction (SW-LIR). In this method, the Cu-Al atomized alloy powder are used as raw material, deionized water as reaction medium, H2O2 as liquid phase oxygen source, and the Cu-Al2O3 composite powder are prepared at 380 ℃ and 22.1 MPa for 10 min. The Cu-Al2O3 composite block is prepared by spark plasma sintering (SPS). The results show that Al2O3 has an average size of 41.8 nm and mainly exists in the form of mixed crystals. The interface with the matrix is coherent or semi-coherent. With the increase of Al2O3 content, the mechanical properties of the composites are obviously improved. When the Al2O3 content is 1.12 wt%, the microhardness is as high as 164.52 HV and the tensile strength is 441 MPA, while still maintaining a high electrical conductivity (75 %IACS). At the same time, it shows quite excellent high temperature performance. It can still retain the characteristics of high strength at 1000℃, which solves the shortcomings of high thermal conductivity but low strength of pure copper. Compared with the traditional method, SW-LIR method has the characteristics of low reaction temperature, fast reaction speed and green environmental protection.

Preparation and Properties of Attapulgite/Brucite Fiber-Based Highly Absorbent Polymer Composite.

The ATP-BF-P(HEC-AA-AMPS) composite highly absorbent polymer was copolymerized with acrylic acid (AA) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) using an aqueous solution method with attapulgite (ATP) and attapulgite (ATP) as a matrix. The prepared ATP-BF-P(HEC-AA-AMPS) was characterized in terms of microstructure and tested for its water absorption capacity, water retention properties, and pH dynamic sensing ability. The results showed that the synthesized ATP-BF-P(HEC-AA-AMPS) had a rough and porous surface and a high water absorption capacity and rate, almost reaching the maximum water absorption around 20 min, and demonstrated excellent water retention performance at low and medium temperatures. ATP-BF-P(HEC-AA-AMPS) has a sensitive dynamic sensing ability in different pH solutions, with a high swelling capacity between pH 6.0 and 10.0. When the pH value exceeded 10.0, the swelling rate decreased rapidly. Additionally, the thermal stability and mechanical strength of the highly absorbent polymers were significantly improved after blending with ATP and BF.

Reconfigurable Cellulose Acetate‐Based Thermosets Cross‐Linked with Diboronic Acid

AbstractCellulose acetate (CA) has found broad applications for many years. However, the development of mechanically strengthened CA materials without losing the processibility in solution remains quite difficult. In this work, novel CA thermosets are reported that can be readily constructed by employing alkyl diboronic acid as a crosslinking agent, which has allowed convenient reconfiguration of CA networks without demanding catalysts or harsh processing conditions. Various properties including thermal stability, creeping resistance, rheological and mechanical strength have been successfully improved by using small amounts (1–5 wt%) of diboronic acid. The dynamic cross‐linked network based on boron chemistry has facilitated solution processing during three times of recycling. Control experiments have shown that alkyl diboronic acid can deliver superior mechanical strength to CA as compared to aryl diboronic acid or single‐arm alkyl boronic acid. Based on the importance of CA materials, this work should be attractive to the design of reprocessible CA thermosets with high performance.

A novel organic–inorganic matrix nanofiltration membrane for remediating copper with enhanced thermal stability and mechanical strength

A novel organic–inorganic matrix nanofiltration membrane for remediating copper with enhanced thermal stability and mechanical strength