High Performance Thermal Insulation Research Articles

Foam gel-casting preparation of SiC bonded ZrB2 porous ceramics for high-performance thermal insulation

Lightweight SiC-ZrB2 porous ceramics is of great potential as thermal insulation material used in aerospace, chemical and energy industries. In this work, a series of SiC bonded ZrB2 (SiCb-ZrB2) porous ceramics with porosity high up to 86.9% were prepared by a simple foam gel-casting method. The SiCb-ZrB2 porous ceramic prepared at 1573 K exhibited a low thermal conductivity of 0.280 W/(m∙K) and a reasonable compressive strength of 0.52 MPa. It could maintain the original geometric shape and microstructure after a secondary heat treatment at 1473 K in inert atmosphere. When heating the samples with thickness of 30 mm for 12 min with an alcohol spray lamp (∼1273 K), the temperatures of the cold sides of SiCb-ZrB2 ceramics were all lower than 432 K, demonstrating their exceptional insulation capabilities. The present work provides a simple route to produce robust and thermally-insulating non-oxide porous ceramics for use under high temperature.

Preparation of high-performance thermal insulation composite material from alkali-activated binders, foam, hollow glass microspheres and aerogel

• Physical foaming, hollow glass microspheres and aerogel were used for AAB. • CMC minimized foam and slurry delamination and improved foaming effect. • KH550 treated hollow glass microspheres showed enhanced the interfacial bonding. • PE100-hydrophobic aerogel had extern hydrophilic and internal hydrophobic effect. Herein, a high-performance thermal insulation composite material was prepared by adding physical foaming agent (FA), hollow glass microspheres (HGMs) and aerogel (AG) with alkali-activated binders (AABs) as the matrix. The results of orthogonal experiments revealed that AG has the greatest effect on thermal conductivity, followed by the effect of FA and HGMs. The thermal conductivity value of AABs was reduced from 0.6057 to 0.0870 W/(m·K) at an AG dosage of 4 g (42.48 kg/m 3 ) in the single factor experiments. The effect of compressive strength followed an order of: HGMs < FA < AG. Under the temperature condition of 400–800 °C, the FA exacerbated the linear shrinkage of the sample, HGMs inhibited the linear shrinkage at 400 °C and 600 °C, and exacerbated it at 800 °C, while AG inhibited the linear shrinkage. X-ray diffraction and scanning electron microscopy analyses revealed that the sample maintained stable performance below 800 °C. Orthogonal experiment results concluded that the optimal level combination was 6 g FA, 6 g HGMs and 3 g AG (A6B6C3) and exhibited the minimal thermal conductivity (0.0434 W/(m·K)). The compressive strength of A6B6C3 at 30 °C was 0.38 MPa, which gradually increased with temperature, reaching the maximum of 0.79 MPa at 800 °C. This composite can meet the thermal insulation, mechanical and high temperature resistance properties. In addition, accredited to simple preparation process, short curing period, and low cost, this approach can be deemed of great significance for applications in composite thermal insulation materials in nuclear power plants and other key areas.

Layer-by-layer self-assembly of sodium alginate and zinc ions on the surface of graphene oxide to improve the fire protection ability of intumescent waterborne epoxy coatings

In this study, polyethyleneimine (PEI) was first adsorbed on the GO surface, resulting in a positively charged GO/PEI composite. Afterwards, SA and Zn2+ were loaded on the surface of GO/PEI through a facile route to obtain an organic-inorganic hybrids (GPS@Zn). Among them, the gas phase products of SA delayed the progress of the combustion reaction, while the catalytic carbonization of zinc oxide and the high barrier effect of GO effectively improved the thermal insulation efficiency of the char layer. The fire performance test results showed that the backside temperature of GPS@Zn/EP decreased to 161.2 °C after burning for 60 min. The swelling height and swelling ratio of GPS@Zn based EP remained at the highest value compared to the other samples. In addition, the residual char content of EP loaded GPS@Zn was as high as 31.2 %, which lays the foundation for its high thermal insulation performance. The PHRR, THR, SPR and TSP values of GPS@Zn/EP were 420.2 ± 13 kW/m2, 13.2 ± 0.6 MJ/m2,0.078 ± 0.05 m2/s and 1.87 ± 0.05 m2, respectively, which were significantly lower than the other samples, thus proving its best flame retardant and smoke suppressing properties. The carbon residue analysis confirmed that zinc oxide remained in the char layer, which was beneficial to the improvement of its thermal insulation performance and strength.

Polyethersulfone foam with aligned porous structure from frozen solvent templating for high-performance thermal insulation

Polyethersulfone foam with aligned porous structure from frozen solvent templating for high-performance thermal insulation

Fiber Templated Epitaxially Grown Composite Membranes: From Thermal Insulation to Infrared Stealth.

Thermal insulation materials show a substantial impact on civil and military fields for applications. Fabrication of efficient, flexible, and comfortable composite materials for thermal insulation is thereby of significance. Herein, a "fiber templated epitaxial growth" strategy was adopted to construct PAN@LDH (PAN = polyacrylonitrile; LDH = layered double hydroxides) composite membranes with a three-dimensional (3D) network structure. The PAN@LDH showed an impressive temperature difference of 28.1 °C as a thermal insulation material in the hot stage of 80 °C with a thin layer of 0.6 mm. Moreover, when a human hand was covered with 3 layers of the PAN@LDH-70% composite membrane, it was rendered invisible under infrared radiation. Such excellent performance can be attributed to the following reasons: (1) the hierarchical interfaces of the PAN@LDH composite membrane reduced thermal conduction, (2) the 3D network structure of the PAN@LDH composite membranes restricted thermal convection, and (3) the selective infrared absorption of LDHs decreased thermal radiation. When modified with Dodecyltrimethoxysilane (DTMS), the resulting PAN@LDH@DTMS membrane can be used under high humidity conditions with excellent thermal insulation properties. As such, this work provides a facile strategy for the development of high-performance thermal insulation functional membranes.

Halloysite-based aerogels by bidirectional freezing with mechanical properties, thermal insulation and flame retardancy

Halloysite (Hal) is a natural nanotubular clay mineral with the characteristics of low price and easy availability. The aerogels prepared by Hal are low thermal conductivities, good thermal stabilities and low flammability, which have great application prospects in the field of thermal insulation with flame retardancy. However, they typically suffer from inferior mechanical property and difficulty of mechanically resilient or flexible. Herein, aerogels with anisotropic mechanical properties were prepared by bidirectionally freezing aqueous suspensions of Hal with a small proportion of chitosan (CS). The directionally aligned porous structure gave the aerogels prominent strength in the direction of lamellar orientation, and superelasticity in the vertical direction. The Hal-based aerogels showed good performance in the combination of thermal insulation and flame retardancy. The thermal equilibrium temperatures of Hal/CS aerogels at 50 °C and 100 °C are 27.5 °C and 35.2 °C, respectively. They also remained unscathed after 180 s of burning in a candle flame. The present study provided a versatile method for design and fabrication aerogels for high-performance thermal insulation materials and had significance in the high-value utilization of Hal mineral resources.

Silica–Resorcinol–Melamine–Formaldehyde Composite Aerogels as High-Performance Thermal Insulators

Here, we report the gelation and supercritical drying of ethanol-based silica–resorcinol–melamine–formaldehyde (RMF) composite aerogels with relative concentrations of initial reagents ranging from neat silica to neat RMF alcogels. The as-prepared materials are subsequently supercritically dried with carbon dioxide. Their properties include a thermal conductivity in the 15–20 mW·m–1·K–1 range even with a silica content as low as 20%wt. The possible reasons behind this interesting insulation performance and the mechanisms leading to the underlying gel structure are discussed in depth. A focus is made on the different gelation modes happening between the RMF and silica phases, from a coating of silica surfaces with RMF species to discontinuous RMF particles within a silica backbone and a continuous RMF backbone with isolated silica particles. The implications in terms of mechanical properties and thermal conductivity are elaborated upon. The initial ratio of silica–RMF species in this ethanol-based synthesis affects the micro- and macrostructure of the composites, resulting in materials with drastically different pore structures and thus an interesting array of possibilities for a new class of silica-organic composite aerogels, based on a sol–gel process.

Proton Donor-Regulated Mechanically Robust Aramid Nanofiber Aerogel Membranes for High-Temperature Thermal Insulation

High-performance thermal insulators are urgently desired for energy-saving and thermal protection applications. However, the creation of such materials with synchronously ultralow thermal conductivity, lightweight, and mechanically robust properties still faces enormous challenges. Herein, a proton donor-regulated assembly strategy is presented to construct asymmetric aramid nanofiber (ANF) aerogel membranes with a dense skin layer and a high-porous nanofibrous body part. The asymmetric structure originates from the otherness of the structural restoration of deprotonated ANFs and the resulting ANF assembly due to the diversity of available proton concentrations. Befitting from the synergistic effect of the distinct architectures, the resulting aerogel membranes exhibit excellent overall performance in terms of a low thermal conductivity of 0.031 W·m-1·K-1, a low density of 19.2 mg·cm-3, a high porosity of 99.53%, a high tensile strength of 11.8 MPa (16.5 times enhanced), high heat resistance (>500 °C), and high flame retardancy. Furthermore, a blade-scraping process is further proposed to fabricate the aerogel membrane in a continuous and scalable manner, as it is believed to have potential applications in civil and military fields.

An efficient approach to fabricate lightweight polyimide/aramid sponge with excellent heat insulation and sound absorption performance

Polyimide sponges have bright prospects in the weight reduction, heat insulation, and sound absorption equipment of aerospace, navigation, and other area due to their unique three-dimensional cellular structure and outstanding comprehensive performance. However, most polyimide sponges suffered from long and complex fabrication processes. Herein, an efficient and scalable approach, i.e. water-based foam forming, was proposed to fabricate ultralight and porous polyimide/aramid sponges (PASG). Attributed to the bubble-template nature of foam-forming, PASGs exhibit high porosity (>99%) and ultra-low density (∼10 mg/cm3), and possess excellent thermal and sound insulation performance with an optimum thermal conductivity of 34.89 mW/m·K and noise reduction coefficient of 0.41. Besides, PASGs demonstrate outstanding mechanical properties after 500 compression cycles. This strategy providing more possibilities for developing the next generation of high-performance thermal insulation and noise reduction materials.

Interactive analysis of green building materials promotion with relevance to energy consumption and greenhouse gas emissions from Taiwan’s building sector

Service and residential sectors have become significant sources for reducing greenhouse gas (GHG) emissions relevant to the electricity demand for heating, ventilation & air conditioning (HVAC) in buildings. In Taiwan, the energy efficiency (or energy saving) in buildings is a very important issue because the service and residential sectors in this subtropical/tropical island region are the primary sources of GHG emissions. Therefore, the main purpose of this work was to present an interactive analysis of Taiwan’s energy consumption, GHG emissions from the services and residential sectors, and the certified green building materials (GBM) during the period of 2005–2020 based on the official statistics. Furthermore, the policy for promoting the GBM products with high thermal insulation performance and their compulsory specifications were also addressed. On average, the service and residential sectors accounted for about 15% of total domestic energy consumption during this period. By contrast, the electricity consumption shared around 35% in 2020, and also indicated a decreasing trend from 2005 to 2020 due to the governmental policy for improving energy saving and energy efficiency through the establishments of greenhouse buildings (GB) and GBM. In line with international trend of low-carbon buildings, the Taiwan government has promoted the GBM labeling system under the promulgation of relevant regulations since the early 2000s. A total of 2668 GBM labels have been issued over the years of 2005–2020, showing that the number of approved and issued GBM reached a record high in 2020. In summary, the certified high-performance GBM products indicated significant increases since 2013 under the regulatory promotion. The new and/or retrofitted buildings will adopt the certified GBM with high insulation performance totally by 2030 under the sustainable development goals (SDGs).

Ultra-elastic and super-insulating biomass PEBA nanoporous foams achieved by combining in-situ fibrillation with microcellular foaming

High-performance thermal insulation materials play a critical role in thermal management and saving energy. The current conventional thermal insulation materials cannot meet the increasing requirements of thermal management for thermal insulation performance. The advanced insulating materials represented by silica aerogels have excellent thermal insulation properties, but the brittleness limits their applications. Herein, we reported a flexible and environmentally friendly method to prepare ultra-elastic and super-insulating bio-based nanocellular material by means of microcellular foaming of in-situ fibrillated PA reinforced PEBA nanocomposites with the mixture of CO2 and N2 as blowing agents. Thanks to the significantly reduced air thermal conductivity within nanoscale cells, the nanoporous foam exhibits outstanding thermally insulating properties with a thermal conductivity of as low as 25.6 mW/m K. More importantly, the nanoporous foam also shows excellent compression and stretch resilience and outstanding flexibility. The excellent thermal insulation, ultra-elasticity, biomass and biodegradability, environmental friendliness, and manufacturing scalability make the material attractive for high-performance thermal management applications.

Graphene/MXene Composite Aerogels Reinforced by Polyimide for Pressure Sensing

Here, polyimide (PI) was introduced as a binder and enhancer of graphene oxide (GO) and MXene sheets to prepare robust rGO/MXene/PI (GMP) composite aerogels with good mechanical elasticity, high conductivity, excellent thermal stability, and reliable heat insulation ability. The unique physical and chemical interactions among GO, MXene nanosheets, and the PI precursor enhance the three-dimensional network framework of aerogels. As a sensing material, the GMP aerogel with a layer-strut network structure prepared by directional freezing has a low density (8.97–12.71 mg/cm3), high conductivity (3.08 S/m), significant reversible compression (90%), and excellent fatigue resistance (10,000 cycles). The piezoresistive sensor based on the GMP composite aerogel can quickly detect a tiny strain, which could be further used for pulse beating, breathing, vibration, finger bending, and other human health monitoring. With the assistance of PI, the aerogel also presents high thermal insulation performance (0.022 W/(m·k)) and excellent low-temperature tolerance (−196 °C), showing wide application potential in many fields.

ТЕПЛОІЗОЛЯЦІЙНІ ПОКРИТТЯ НА ОСНОВІ СТИРОЛ-АКРИЛОВОЇ ДИСПЕРСІЇ ТА ПОРОЖНИСТИХ АЛЮМОСИЛІКАТНИХ МІКРОСФЕР

The article contains information about the areas of application of modern thin-layer polymer heat-insulating materials. Technological and operational indicators of the developed coating based on styrene-acrylic dispersion and hollow aluminosilicate microspheres are given. The developed thermal insulation coating has low water absorption, high thermal insulation performance, high adhesive strength to concrete.

Preparation of High-Performance Thermal Insulation Composite Material from Geopolymer, Foam, Hollow Glass Microspheres and Aerogel

Preparation of High-Performance Thermal Insulation Composite Material from Geopolymer, Foam, Hollow Glass Microspheres and Aerogel

Rounded atelectasis after exposure to refractory ceramic fibres (RCF)

BackgroundRefractory Ceramic fibres (RCF) are man-made mineral fibres used in high performance thermal insulation applications. Analogous to asbestos fibres, RCF are respirable, show a pleural drift and can persist in human lung tissue for more than 20 years after exposure. Pleural changes such as localised or diffuse pleural thickening as well as pleural calcification were reported.ResultA 45 years old man worked in high performance thermal insulation applications using refractory ceramic fibres (RCF) for almost 20 years. During a occupational medical prophylaxis to ensure early diagnosis of disorders caused by inhalation of aluminium silicate fibres with X-ray including high-resolution computed tomography (HRCT), bilateral pleural thickening was shown and a pleural calcification next to a rounded atelectasis was detected. Asbestos exposure could be excluded. In pulmonary function test a restrictive lung pattern could be revealed. In work samples scanning electron microscopy (SEM) including energy dispersive X-ray analysis (EDX) classified used fibres as aluminium silicate fibres. X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) showed crystalline as well as amorphous fibres.ConclusionsA comprehensive lung function analysis and in case of restrictive lung disorders additional CT scans are needed in RCF exposed workers in accordance to the guidelines for medical occupational examinations comparable to asbestos exposed workers.

A facile method to prepare high-performance thermal insulation and flame retardant materials from amine-linked porous organic polymers

Developing porous functional materials with good thermal insulation and flame retardant properties is of great importance in modern eco-friendly buildings. Herein, we report the one-step synthesis of imine chain monolithic porous phosphorus-containing organic porous polymers (PPOPs) using Schiff base polycondensation reaction and as an example of efficient thermal insulation and flame retardant. Experimental results show that the PPOPs have low thermal conductivity (0.055 W·m−1·K−1) and excellent flame retardant properties. Measurements by microcalorimetry (MCC) showed a peak heat release rate (pHRR) value was 23.9 W·g−1, which is nearly an order of magnitude lower than that of most currently reported flame retardant materials. Using PPOPs in the epoxy resin (EP) matrix, the prepared EP composites exhibited excellent flame retardant properties. Cone calorimeter (CC) tests showed that the peak heat release rate (pHRR) and peak smoke release rate (pSPR) during combustion of PPOPs/EP composites were reduced by 42.0% and 36.4%, respectively, compared with pure EP. Tensile tests showed that the addition of PPOPs improved the mechanical properties of the composites to some extent. In addition, PPOPs can be designed into different shapes for practical applications compared with those fragile inorganic insulation materials and powders that were usually non-processable. Taking these advantages into account, PPOPs have great potential for modern building applications as monolithic foams or coatings with both excellent flame retardancy and thermal insulation properties.

Engineering a superinsulating wall with a beneficial thermal nonuniformity factor to improve building energy efficiency

To increase the energy efficiency of buildings and lower carbon emissions, heat losses through exterior walls could be considerably decreased by using high-performance thermal insulation materials with superlow thermal conductivities or superhigh heat capacities. A superinsulating layer would result in a highly nonuniform distribution of thermal resistance and capacitance within the exterior wall. An interesting problem concerns how to engineer the nonuniform thermal distribution for given total resistances and capacitances to improve energy efficiency. This paper proposes using a thermal nonuniformity factor to quantitatively characterize the nonuniform distribution of thermal resistance and capacitance in an exterior wall built with superthermal aerogel insulating panels and given total resistance and capacitance values. Various thermal nonuniformity factors for several insulation modes were investigated by calculating the relevant transmission loads through the walls. The effect of the thermal nonuniformity factor on the wall transmission load was explored to improve the energy efficiency of a building. The results indicated that the wall heat flux could be greatly decreased by engineering walls with a high nonuniformity factor. For instance, engineering a wall in a sandwich mode with thermal nonuniformity factor of 0.97 could decrease the wall heat flux by ∼35% compared to a uniform wall. These findings on engineering walls based on thermal nonuniformity factors to decrease the wall heat flux could be a useful reference for superinsulated buildings and for further improving thermal insulating performance and building energy efficiency.

A facile method to prepare superhydrophobic nanocellulose-based aerogel with high thermal insulation performance via a two-step impregnation process

A facile method to prepare superhydrophobic nanocellulose-based aerogel with high thermal insulation performance via a two-step impregnation process

Thermal insulation performances of carbonized sawdust packed bed for energy saving in buildings

Sawdust, a natural and renewable material from wood processing, has become more and more widely reused in biomass-based thermal insulating material preparation. However, there is still a lack of biomass-based thermal insulating material, which should possess a characteristic of easily preparation but high thermal insulation performance. Herein, we developed an eco-friendly thermal insulation material by firstly pre-pressing sawdust powder into packed bed and then carbonizing the sawdust bed into porous carbon bed. The influences of the bed structure, environmental temperatures and humidity on the thermal conductivity of the prepared beds were firstly investigated. Results turn out that the carbonized pine sawdust packed (CPP) bed could have a low thermal conductivity of about 0.062 Wm-1K-1. A high intrinsic porosity of sawdust particle, high porosity of bed, and spherical shape of pores in the CPPs are preferred for reducing the thermal conductivity. Moreover, the prepared CPPs not only possess hydrophobicity but also show excellent reusability and structural stability. The thermal conductivity of CPPs can be fully recovered without obvious structure collapse, if dried again after placed under a relative humidity of 60% for more than 24 h. Importantly, the CPPs has excellent flame-retardant and smoke-free property because of the carbonization treatment in the preparation, and it can self-extinguish within 6 s in the vertical burning test. This work provides a facile and sustainable strategy to manufacture thermal insulation material from recycling waste bioresources, which has potential for future energy saving in buildings.

Analysis of indoor environment and performance of net-zero energy building with vacuum glazed windows

The total energy and indoor thermal environment of an office building, which aims at the net-zero energy building, were measured and analysed. The annual total primary energy consumption of ‘Measurement’ was smaller than the value of ‘Calculation’ at design phase and achieved net-zero. The result of analysis of the thermal environment shows that the comfortable thermal environment was maintained. Also, the insulation performance and heat balance of the vacuum glazed windows in winter was evaluated. The overall heat transfer coefficients calculated by using the monitoring data were almost equal to the rated overall heat transfer coefficient and the high insulation performance of vacuum glazed windows was maintained even in the second year’s operation. In addition, the amount of heat gain due to solar radiation on the window surface was much larger than the amount of heat loss due to transmission. The vacuum glazed windows with high thermal insulation performance on the south side can reduce the heating load and contribute to the achievement of net-zero in the buildings.