Inorganic Dielectrics Research Articles

Improving Building Floor Acoustics with Innovative Inorganic Sound Insulation Coating

Floor impact sound insulation is essential for improving living environments and has become a mandatory requirement for green buildings in Southern China. This study introduces an innovative inorganic sound insulation coating technology for enhancing building floor acoustic performance. Through comprehensive laboratory experiments and field tests, we evaluated inorganic coatings of 3 mm and 5 mm thickness, comparing their performance against traditional methods, including organic coatings and soundproof mortar. Standardized impact sound pressure level measurements, conducted in accordance with the China GB/T 50121 standard, demonstrated significant acoustic improvements. Laboratory testing revealed impact sound reductions of 6–7 dB and 9–10 dB for the 3 mm and 5 mm inorganic coatings, respectively, while field applications of the 3 mm coating achieved an average reduction of 14.3 dB. The inorganic coating exhibited superior performance characteristics compared to both organic coatings and soundproof mortar in terms of sound insulation efficiency, fire resistance, and application feasibility, demonstrating particularly effective attenuation in the mid- to high-frequency range. This investigation presents an innovative, cost-effective, and environmentally sustainable solution for improving floor sound insulation in green buildings.

Regulation of Interface Compatibility and Performance in Soft Magnetic Composites with Inorganic Insulation Layers by FePO4 Intermediate Transition Layer.

In the fabrication of soft magnetic composites, the lattice mismatch between the inorganic insulation layer and the iron matrix often leads to the formation of cracks during the molding process, which significantly impairs the operational performance of the materials. Consequently, it is imperative to develop novel strategies for inorganic insulation coatings that offer high electrical resistivity and thermal stability and are less susceptible to cracking during formation. This paper presents a new structure for soft magnetic composites that incorporates FePO4 as an intermediate transition layer between the iron-based soft magnetic particles and the inorganic ceramic insulation layer. This configuration is designed to provide insulation coatings with superior voltage and thermal resistance, as well as high electrical resistivity. The research details the processes forming the FePO4 intermediate transition layer and the SiO2 insulation layer on the iron powder surface, along with their interaction mechanisms. An analysis comparing the scenarios with and without the FePO4 intermediate transition layer shows its beneficial impact on the magnetic properties and mechanical strength of the soft magnetic composites. Further investigations reveal that at a phosphoric acid concentration of 1 wt.%, the FePO4 layer significantly enhances the interface compatibility between the Fe powder matrix and the SiO2 insulation layer. Under these conditions, the Fe@ FePO4/SiO2 soft magnetic composites demonstrate outstanding overall performance: the saturation magnetization stands at 215.60 emu/g, effective permeability at 83.2, resistivity at 57.42 Ω·m, power loss at 375.0 kW/m3 under 30 mT/100 kHz, and radial compressive strength at 15.95 Kgf. These findings offer novel insights and practical approaches for advancing inorganic insulation coating strategies and provide vital scientific support for further enhancing the magnetic and mechanical properties of soft magnetic composites.

Development and performance evaluation of ultra-lightweight geopolymer foam insulation material

The preparation technology for new ultra-lightweight geopolymer insulation materials (ULGIM) has been developed based on the principle of alkaline activation, and ULGIM for building walls have been obtained. It has improved the problem of traditional inorganic foam insulation material that cannot balance density, insulation performance, mechanical performance and environmental performance. The composition of supplementary cementitious materials, the mass ratio between each component, and water to binder ratio (w/b) were used to analyze the thermal conductivity, dry density, volumetric water absorption, compressive strength, average pore diameter, and porosity of ULGIM. The life cycle assessment (LCA) method was employed to assess the environmental impact of ULGIM production. The test results showed that ULGIM achieved a dry density and thermal conductivity of ULGIM only 181.17 kg/m3 and 0.0427 W/(m·K), respectively, and the optimal compressive strength was 0.72 MPa at 7 d. ULGIM exhibited superior compressive strength, lower thermal conductivity, and smaller environmental impact in comparison to cement-based foamed materials with comparable dry density.

Effect of glass fiber on the mechanical and thermal insulation performances of kaolinite-based thermal insulator

The development of high-performance thermal insulators is essential for achieving building energy efficiency. The mechanical properties of traditional inorganic porous thermal insulators are not ideal enough. Among various inorganic fiber materials, glass fiber is widely recognized as the most cost-effective option and is expected to significantly enhance the mechanical performance of inorganic porous thermal insulators. The present study employed kaolinite and water glass as primary raw materials, with the addition of glass fiber as a reinforcing material. By means of the chemical foaming method, a kaolinite-based thermal insulator was prepared. The impact of glass fiber on the physicochemical properties of insulator was investigated. The results revealed that the samples containing 15 wt% glass fiber exhibited compressive strength of 1.06 MPa and thermal conductivity of 0.075 W/(m·K), while achieving a remarkable strength-to-density ratio of 4.36. After undergoing heat treatment, the samples exhibited enhanced thermal insulation performance with a reduction in thermal conductivity by approximately 34.2 %. However, the compressive strength showed a significant decline. The samples showcased exceptional thermal insulation capabilities in a simulated high-temperature outdoor environment.

A Comprehensive Review and Recent Trends in Thermal Insulation Materials for Energy Conservation in Buildings

In recent years, energy conservation became a strategic goal to preserve the environment, foster sustainability, and preserve valuable natural resources. The building sector is considered one of the largest energy consumers globally. Therefore, insulation plays a vital role in mitigating the energy consumption of the building sector. This study provides an overview of various organic and inorganic insulation materials, recent trends in insulation systems, and their applications, advantages, and disadvantages, particularly those suitable for extreme climates. Moreover, natural and composite materials that can be used as a low-cost, thermally efficient, and sustainable option for thermal insulation are discussed along with their thermal properties-associated problems, and potential solutions that could be adopted to utilize natural and sustainable options. Finally, the paper highlights factors affecting thermal performance and essential considerations for choosing a particular insulation system for a particular region. It is concluded that the most commonly used insulation materials are found to have several associated problems and there is a strong need to utilize sustainable materials along with advanced materials such as aerogels to develop novel composite insulation materials to overcome these deficiencies.

Light-weight high strength porous thermal insulation materials based on dolomite-granite waste

The first choice for the treatment of solid waste is its industrial utilization. Therefore, in the present study, dolomite tailings and granite waste are used as the basic raw materials, along with silicon carbide as a high-temperature foaming agent, to prepare a light-weight, high-closed porosity thermal insulation material. The effects of (i) the chemical compositions of the main raw materials and (ii) the relationship between the sintering process and the properties, microstructure and crystalline phase of the samples are systematically investigated. At the same time, the formation mechanism of high closed porosity of the thermal insulation material is analyzed. The results showed that when sintering temperature, time, and heating rate are 1200 °C, 30 min, and 3 °C/min, respectly, the sample density, compressive strength, true porosity, and closed porosity are 0.7 g/cm3, 6.62 MPa, 74.21%, and 66.36%, respectively. In addition, due to the high closed porosity, relative to traditional inorganic thermal insulation materials, the water absorption and thermal conductivity are significantly reduced to as little as 1.5%, and 0.30 W/(m·K), respectly. This research not only realizes the recovery and utilization of granite waste and dolomite tailings, but also provides a new prospect for energy saving and consumption reduction in the construction industry.

Oil-based drilling cutting pyrolysis residues- phosphogypsum foamed ceramics: Basic properties, microsintering mechanism and heavy metals solidification

Oil-based drilling cutting pyrolysis residues(ODPR) and phosphogypsum(PG) are typical types of industrial solid waste in China, characterized by low utilization rate and high output. The large amount of untreated accumulation will release heavy metals(HMs) and other pollutants, posing risks to the environment. Therefore, there is an urgent need to develop a high value-added building material product that can reduce environmental hazards while improving utilization rate. Based on this background, this study uses ODPR and PG as raw materials to explore their potential applications in the field of foamed ceramics. Research has shown that different sintering processes have a significant impact on the appearance and performance of products. By adjusting the preparation process, foamed ceramic products with excellent performance can be prepared. When the sintering temperature is 925℃, the foaming agent dosage is 3 %, and the raw material ratio ODPR:PG:Borax=35:45:20, a foamed ceramic product with a porosity of 60.95 %, water absorption rate of 3.4 %, compressive strength of 4.8 MPa, thermal conductivity of 0.8016 W/(m·k), and acid and alkali resistance of 98.57 % and 99.44 % can be prepared. The product meets the relevant requirements of “Fired heat preservation brick and block (GB/T 26538)” and “ General Specification for porous ceramic products (GB/T 16533)”. The HMs content test showed that the Ni and Pb contents in the pre-sintered blanks were the highest, at 0.6308 mg/kg and 0.3182 mg/kg, respectively. However, after high-temperature calcination, the solidification rate of HMs could reach up to 98.93 %, and the leaching amount was significantly reduced. The three further evaluation methods indicate that HMs in the pre-sintered blanks and foamed ceramic products do not pose significant ecological risks. The research results provide a green inorganic insulation material in the field of solid waste control and building materials.

Low-voltage organic field-effect transistors by using solution-processable high-κ inorganic-polymer hybrid dielectrics

Organic field-effect transistors (OFETs) incorporating hybrid high-κ inorganic Al2O3 and polymer dielectrics, including polyvinyl alcohol (PVA), polystyrene (PS), or polymethyl methacrylate (PMMA), through solution-processing techniques were fabricated. The analyses revealed that the high surface energy and hydrophilicity property of Al2O3 and PVA, and the relatively hydrophobic property of PS surface, hindered the performance of corresponding OFETs. The Al2O3/PMMA-based OFET achieved the optimized performance, with a threshold voltage of −2.7 V, a hole carrier mobility of 0.056 cm2/Vs, and a current on/off ratio of 1.0 × 104 at a low operating voltage of −5 V. Through analyzing the characteristics of leakage current, capacitance, contact resistance, and trap density of OFETs, we found that the PMMA-engaged films possessed the optimized electrical properties. The introduction of PMMA eliminated the interfacial trapping, thereby lowering the threshold voltage and enhancing the performance of the device. The COMSOL Multiphysics simulation was conducted to confirm the physical mechanism. The strategy of utilizing Al2O3/PMMA hybrid dielectric could simultaneously ensure the low operating voltage and good performance of OFET, while guaranteeing the low leakage current by the thick PMMA.

The time evolution of electrical and thermodynamic characteristics of surface dielectric barrier discharge caused by dielectric degradation

Abstract The degradation of the dielectric layer is a common issue in dielectric barrier discharge (DBD). The performance of DBD devices may suffer from instability due to potential corrosion of the dielectric layer caused by discharge, which could even result in structural failure. To gain a comprehensive understanding of the degradation of DBD devices during discharge, the evolution of the performance of DBD devices with various dielectric materials over time is studied. Periodic patterns are found to form on the dielectric surface along the edge of the high-voltage electrode. The electrical data, emission spectra, and surface morphologies of DBD devices with three different dielectric materials, namely ceramics, glass, and PCB, are obtained during an eight-hour discharge. The electrical and thermodynamic characteristics of DBD devices with the three dielectric materials are found to initially decrease by about 20~40%. Subsequently, they remain stable in devices with ceramics and PCB dielectric layers but increase in devices with glass dielectric layers until the end. Surface morphologies reveal that periodic patterns consisting of metal accumulations, etching pits, and metal depositions form on the surfaces of ceramics, glass, and PCBs, respectively. Some organic compounds vaporize from the surface of PCBs. The deposition, etching, and vaporization could be reasons for changes in the electrical and thermodynamic characteristics. It shows that degradation occurs not only in organic dielectrics like polymers but also in inorganic dielectrics such as ceramics and glass. To enhance stability and prevent potential failures and overestimations, electrical and optical measurements could be utilized as diagnostic methods in applications involving DBD devices.


Effect of microstructure on the physicochemical characteristics of foam glass made by soda lime -CRT glasses and aluminium dross

Foam glass, an inorganic insulation material, is primarily manufactured from recycled glass or sand combined with a foaming agent. During fabrication, gas bubbles are generated in the softened glass, causing it to expand and form a cellular structure. Critical parameters such as cell size, type (closed or open cells), distribution, and uniformity significantly influence the physical and chemical properties of foam glass, ensuring sustained thermal efficiency. This research aims to produce foam glass exclusively from waste materials, thereby promoting the circular economy by utilizing container glass, cathode ray tube (CRT) glass, and aluminium dross. A comprehensive microstructural analysis, employing computer tomography and scanning electron microscopy, elucidated key properties including density, thermal conductivity, and water absorption. The manufactured foam glass exhibited lightweight characteristics, with a density ranging from 0.15 to 0.18 g/cm³. Additionally, the foam glass demonstrated low thermal conductivity (between 0.038 W/m·K and 0.05 W/m·K), which can be attributed to the heterogeneous distribution of cells that effectively reduce heat convection. This property makes foam glass an excellent thermal insulator. Furthermore, both high-absorption (open porosity) and low-absorption (closed porosity) foam glasses were successfully produced.

A Study on the Evaluation of Thermal Insulation Performance of Cellulose-Based Silica Aerogel Composite Building Materials.

Buildings utilize both inorganic and organic insulation materials to conserve energy and prevent heat loss. However, while exhibiting excellent thermal insulation performance, organic insulation materials increase the risk of fire due to the emission of intense heat and toxic smoke in the event of a fire. Conversely, inorganic insulation materials are characterized by a lower thermal insulation performance, leading to an increase in the weight of the building with extensive use. Therefore, the necessity for research into new insulation materials that address the drawbacks of existing ones, including reducing weight, enhancing fire resistance, and improving thermal insulation performance, has been recognized. This study focuses on evaluating the enhancement of the thermal insulation performance using novel building materials compared to conventional ones. The research methodology involved the incorporation of porous aerogel powders into paper-based cellulose insulation to improve its insulating properties. Samples were prepared in standard 100 × 100 mm2 panel forms. Two control groups were utilized: a pure control group, where specimens were fabricated using 100% recycled cardboard for packaging, and a mixed control group, where specimens were produced using a mixture ratio of 30 wt% ceramic binder and 40 wt% expandable graphite. Experimental group specimens were prepared by increasing the aerogel content from 200 to 1000 mL under each condition of the control groups (pure and mixed) after mixing. The thermal insulation performance of the specimens was evaluated in terms of thermal conductivity and thermal diffusivity according to ISO 22007-2 (for solids, paste, and powders). Through this study, it was found that the thermal insulation performances of the pure control and experimental groups improved by 16.66%, while the mixed control and experimental groups demonstrated a 17.06% enhancement in thermal insulation performance with the addition of aerogel.

Preparation and Properties of Lightweight Geopolymer by Bio-Based Foaming Agent.

Lightweight geopolymers have the advantages of a wide source of raw materials, chemical corrosion resistance, high mechanical strength and excellent durability, and are expected to replace traditional building insulation materials. In this paper, a green bio-based foaming agent with a small 1 h settlement distance, high average foaming multiple and low bleeding ratio was obtained by a Cetyltrimethylammonium Bromide/yeast solution. When the amount of Cetyltrimethylammonium Bromide is 0.50 wt%, the foam prepared by the yeast and Cetyltrimethylammonium Bromide solution exhibits the improved 1 h settlement distance, the large average foaming multiple, the small bleeding ratio and uniform foam size. Subsequently, a lightweight geopolymer based on metakaolin and fly ash (or silica fume) was successfully prepared by the bio-based foaming agent, and the effects of different foam content on the properties of the geopolymer, such as dry density, water absorption, thermal conductivity, compressive strength and morphology, were studied. With an increase in foam content, the dry density, thermal conductivity and compressive strength of the geopolymer gradually decrease, the water absorption increases, regardless of whether silica fume or fly ash are added. Herein, it is confirmed that the foaming agent based on yeast can be effectively used to prepare lightweight geopolymers, which can provide vast opportunities to turn into candidates for novel inorganic thermal insulation materials.

Binary-Network structured PI@SiO2 nanofibrous composite aerogels with temperature invariant superelasticity for thermal insulation

The extreme temperatures encountered in aerospace pose formidable challenges to the performance of elastic materials in spacecraft and related apparatus. Traditional organic insulation materials face hindrance due to inadequate fire resistance, while inorganic insulation materials are often brittle. Herein, we designed binary-network composite aerogels with dual-crosslinked PI nanofibers as the scaffold and uniformly distributed silica nanoparticles within the anisotropic aerogel matrix. Owing to the dual-crosslinked PI nanofiber network, the resulting PI@SiO2 aerogel can withstand 1000 cycles of radial fatigue testing under 50 % compressive or buckling strains, maintaining structural stability across a wide angular frequency range of 0.1–100 rad/s. DMA testing shows that PI@SiO2 aerogel can endure 100,000 fatigue cycles from 25 to 300 °C, with storage modulus and loss modulus, and damping ratio, indicating robust long-term performance over a wide temperature spectrum. Even with liquid nitrogen (−196 °C) and butane torch flames (1100 °C), PI@SiO2 aerogel preserves its superelasticity through repeated compressions. Moreover, the composite aerogel exhibits excellent thermal insulation, with low thermal conductivity (27.2 mW m−1 K−1), and reachs the top flame-retardant level (UL94-V0). This work not only establishes a novel pathway for constructing polymer-based materials with temperature-invariant superelasticity but also holds great promise for extensive applications in ongoing and near-future aerospace exploration.

Research Progress in High-Temperature-Resistant Electromagnetic Wire.

Electromagnetic wire is the carrier of energy and signal transmission. With the rapid development in aerospace, atomic energy, and other industrial fields, there is an increasing demand for the high-temperature-resistance of electromagnetic wires. In using traditional electromagnetic wires, it is difficult to meet the current temperature-resistance requirements. Therefore, the development of high-temperature-resistant electromagnetic wire has extremely important application value. In this paper, high-temperature-resistant electromagnetic wires are divided into organic insulated high-temperature-resistant electromagnetic wires, organic-inorganic insulated composite high-temperature-resistant electromagnetic wires, and inorganic insulated high-temperature-resistant electromagnetic wires. The method of improving the temperature-resistance level of organic insulated high-temperature-resistant electromagnetic wire is introduced. The selection principle of organic-inorganic and inorganic insulation high-temperature-resistant electromagnetic-wire conductor materials is analyzed. The current research status of organic-inorganic and inorganic insulated high-temperature-resistant electromagnetic wires is reviewed. The technical routes for preparing inorganic insulated high-temperature-resistant electromagnetic wire are compared. Finally, the challenges faced by the current high-temperature-resistant electromagnetic wire are pointed out, and the future development direction of organic-inorganic-composite insulation and inorganic insulation high-temperature-resistant electromagnetic wire is proposed.

Synergistic effects of organosilicon flame retardant and DOPO-based reactive compatibilizer for high performance PC/PBT composites

PC/PBT alloy is flammable resulting in fire safety hazards in practical applications and the existing flame retardants have a great influence on the mechanical properties, which limits its application range. Therefore, it is an urgent problem to improve the flame retardancy of PC/PBT alloy while taking its mechanical properties into account. Herein, a novel flame retardant and reactive compatibilizer was synthesized by grafting 9,10-dihydro-9-oxa-10-phosphophenanthrene-10-oxide (DOPO) onto ethylene-methyl acrylate-glycidyl methacrylate (EMA-GMA), named as DOPO-EG, to improve the flame retardancy and mechanical properties of PC/PBT alloy simultaneously. Additionally, based on the effective synergistic effect of enhancing the charring and flame retardancy between silicon and phosphorus, the organosilicon flame retardant (RMSi) is introduced and compounded with DOPO-EG to prepare excellent flame retardancy PC/PBT/DOPO-EG/RMSi composites. The results showed that the PC/PBT/DOPO-EG/RMSi composites with 10 wt% DOPO-EG and 8 wt% RMSi (CBE10P10Si8) reached UL-94 V-0 rating and the peak of heat release rate (PHRR) and total heat release rate (THR) of CBE10P10Si8 decreased by 42% and 16% respectively. This is due to the fact that DOPO is cracked into phosphorus radicals to capture and eliminate the active H and OH radicals, inhibiting the chain free radical reaction, and RMSi is enriched on the surface of CBE10P10Si8 to form an inorganic oxygen insulation protective layer during combustion. The impact strength of CBE10P10Si8 increased from 5.8 kJ/m2 to 11.9 kJ/m2. The improvement of impact strength is owing to the existence of DOPO-EG which promotes the formation of the interface layer between PC and PBT phases, resulting in the transfer of stress between the two phases. This work provides a new method for the preparation of PC/PBT alloy with excellent flame retardancy and mechanical properties, and also provides a certain reference value for the research of flame retardancy and toughening modification of polymer composites.

Biocompatible neem gum-modified polyvinyl alcohol composite as dielectric material for flexible energy devices

In our pursuit of a flexible energy storage solution, we have developed biocompatible (bc)-NG/PVA composite polymers by combining neem tree gum (NG) with polyvinyl alcohol (PVA). This innovative bio-inspired approach harnesses NG's unique properties for both the bio-electrolyte and bio-electrode components. The resulting bc-NG/PVA composites exhibit superior dielectric strength and versatility, surpassing traditional inorganic ceramic dielectrics in advanced electronics and pulsed power systems. Our study investigates the dielectric characteristics, conductivities, electric modulus, and impedance parameters of Pure PVA and NG-doped PVA composites. Adding 5 % NG to PVA significantly boosts its conductivity from 10−8 S cm−1 to 10−4 S cm−1, while the dielectric constant of PVA/5 % NG composite jumps to 104.5 compared to pure PVA. These improvements position the composite films of 5 % NG added PVA as promising materials for diverse applications. The heightened performance of these NG-blended PVA composite materials underscores their potential as a valuable resource for flexible energy storage solutions.

Performance of periodic EOM-CCSD for bandgaps of inorganic semiconductors and insulators.

We calculate bandgaps of 12 inorganic semiconductors and insulators composed of atoms from the first three rows of the Periodic Table using periodic equation-of-motion coupled-cluster theory with single and double excitations (EOM-CCSD). Our calculations are performed with atom-centered triple-zeta basis sets and up to 64 k-points in the Brillouin zone. We analyze the convergence behavior with respect to the number of orbitals and number of k-points sampled using composite corrections and extrapolations to produce our final values. When accounting for electron-phonon corrections to experimental bandgaps, we find that EOM-CCSD has a mean signed error of -0.12eV and a mean absolute error of 0.42eV; the largest outliers are C (error of -0.93eV), BP (-1.00eV), and LiH (+0.78eV). Surprisingly, we find that the more affordable partitioned EOM-MP2 theory performs as well as EOM-CCSD.

High throughput synthesis of SiO2 microspheres enhancing dielectric properties of quartz fibers insulation composites for high temperature resistant communication cable

The development of the digital society has led to an urgent demand for high-temperature-resistant, low-dielectric cable insulation materials. In order to meet the stable high temperature service performance, it is necessary to use inorganic materials instead of the traditional organic insulating materials as the cable insulation layer. Silicon dioxide (SiO2) as a widely used inorganic dielectric material has great potential for application, and quartz fiber is another wave-transparent material with good dielectric properties. The combination of SiO2 and quartz fiber can provide a feasible path for pure inorganic composite insulation materials. In this work, the high-throughput (>50 g) synthesis of SiO2 was investigated to explore the factors affecting the dielectric properties. The effects of different quartz fiber composite amounts and sintering temperatures on the dielectric properties of the composites were investigated by testing the dielectric properties of the composite powders after pressing. The composite powders doped with 20 wt% quartz fibers at 600 °C sintering temperature were found to have better dielectric properties with dielectric constant of 2.48 and dielectric loss of 0.0109 at 20 M Hz. Furthermore, the composite powders were filled into the cables and measured for electrical properties by a network analyzer. And dielectric properties of the cables preliminarily meet the performance requirements for the applications of high temperature (900 °C) radio frequency (RF) communication cables with dielectric constant of 1.731 and insertion loss of 2.02 dB at 18 G Hz. Therefore, this inorganic composite material can be used as the insulation layer for RF high-temperature-resistant communication cables for aerospace, nuclear power plants and energy fields.

Hollow glass microspheres embedded in porous network of chitosan aerogel used for thermal insulation and flame retardant materials

In recent years, biopolymer aerogels as thermal insulation materials have received widespread attention due to natural abundance, cost-efficiency, and environment-friendly. However, the flammability and low strength hinder its practical application. Hollow glass microspheres (HGMs) as an inorganic thermal insulation filler have been filled in biopolymer aerogels to improve flame retardancy. However, the structure formed by HGMs embedded porous network of biopolymer aerogel has rarely been investigated, which not only reduce thermal conductivity through high porosity, but also adjust the filling volume of HGMs and achieve uniform distribution through chemical cross-linking. Herein, a biopolymer aerogel composite was assembled by chitosan aerogel (CSA) and different volume of HGMs by chemical cross-linking, freeze-drying, and silylation modification processes. When the filling volume fraction of HGMs reached 40 %, a skeleton structure was initially formed. The composites with HGMs volume of 40 %–60 % exhibited low density, high porosity, low thermal conductivity, good mechanical property, and excellent flame retardancy. According to GB 8624-2012 standard for classification, the composite with 60 % HGMs achieved class A1 non-combustible.

Crack behavior of expanded polystyrene foam-ceramsite composite thermal insulation mortar

To compensate for the deficiencies of thermal insulation, fire and crack resistances of traditional thermal insulation mortars, this paper prepares expanded polystyrene foam (EPSF)-ceramsites composite thermal insulation mortar (ECTIM) with ceramsite and EPSF particles as insulation aggregates. The effects of fiber content (i.e., P = 0.3%, 0.6%, 0.9%), fiber length (i.e., l = 3 mm, 6 mm, 9 mm) and fiber types (i.e., polypropylene fiber (PF), steel fiber (SF), alkali resistant glass fiber (ARGF)) on crack resistance of the ECTIM were analyzed. The test results demonstrated that the incorporation of fibers could significantly improve crack resistance and delay the cracking of mortar. With the increase of fiber content P, the water loss rate and cracking index decreased to 43.70% and 79.17% of the specimen without fiber. As the fiber length l increased from 0 mm to 9 mm, the water loss rate and cracking index decreased by 41.50% and 77.08%, respectively. Comparatively, the PF could obviously improve the crack resistance of the ECTIM. Based on the experimental research, the microscopic stress mechanism of mortar cracking, as well as the early and late anti-cracking mechanism of the ECTIM were revealed. In addition, considering the effects of fiber content and fiber length, a comprehensive influence coefficient ϖ was introduced, and a formula for conveniently calculating the maximum crack width Wmax of the ECTIM was proposed. The predicted results agreed well with the test data. The thermal insulation mortar prepared in this study could considerably overcome the deficiencies of traditional organic and inorganic thermal insulation mortars, and had excellent thermal insulation, fire and crack resistances. The resource utilization of iron tailings and the introduction of ceramsite reduced the materials cost. The prepared thermal insulation mortar could be used for wall substrate, geothermal heat insulation layer, external wall, internal wall and roof insulation.