Good Heat Resistance Research Articles

Construction of hierarchical layered double hydroxide/poly(dimethylsiloxane) composite coatings on ramie fabric surfaces for oil/water separation and flame retardancy

Nano/micro composite coating is an important method to fabricate the multifunctional ramie fabrics. Here, layered double hydroxides with different morphologies and poly(dimethylsiloxane) (PDMS) are grown on ramie fabric surfaces to endow ramie fabrics with superhydrophobic and flame retardant abilities. The superhydrophobic and superoleophilic ramie fabric is a very promising material for oil spill cleanup in an environmentally friendly way. The experiment shows that the as-fabricated ramie fabrics with superhydrophobic surface can not only exhibit high separation efficiency in oil/water separation tests, but also present good heat-resistance, mechanical and chemical stabilities in extreme environments. Moreover, to evaluate the environmental adaptability of superhydrophobic and superoleophilic ramie fabrics in a combustion environment, the thermal stability and flame retardant performance were investigated through thermosgravimetric analysis, and vertical burning test (UL-94). Also, the flame retardant mechanism was further studied by char residue analysis with scanning electron microscope and X-ray diffraction. Thus, this work offers a feasible way to design and prepare nano/micro composites coated renewable cellulosic fabric for wearable devices, oily wastewater treatment and flame retardancy.

Lightweight and Robust Carbon Nanotube/Polyimide Foam for Efficient and Heat-Resistant Electromagnetic Interference Shielding and Microwave Absorption.

Excellent electromagnetic interference (EMI) shielding ability, light weight, and good heat resistance are highly required for practical applications of EMI shielding materials, such as in areas of aerospace, aircraft, and automobiles. Herein, a lightweight and robust carbon nanotube (CNT)/polyimide (PI) foam was developed for efficient and heat-resistant EMI shielding. Thanks to poly(vinyl pyrrolidone) (PVP) as a surfactant that not only promotes the uniform dispersion of CNTs to form perfect CNT conductive networks but also can be removed in situ during the polymerization process, the density of resultant CNT/PI foam is only 32.1 mg·cm-3, and the EMI shielding effectiveness (EMI SE) is up to 41.1 dB, which represents one of the highest EMI SE values compared to previously reported polymer-based foams. The CNT/PI foam also achieves the absorption coefficient (A) of up to 82.3%, which is very impressive in CNT/polymer foams at comparable EMI SE levels. The PI matrix endows the foam with excellent heat resistance. The as-prepared CNT/PI foam presents a higher EMI SE than 35 dB even after being subjected to the flame of an alcohol burner. Moreover, the compressive strength and compressive modulus are up to 240.9 and 323.9 kPa. These results indicate its certain application potential in the harsh requirement of aeronautics and aerospace industries as a highly efficient and lightweight EMI shielding material.

Synthesis, characterization and electrical insulation of polyester plasma sprayed by (CaO3Si/CuO) nanoparticles

Textile fabrics possess multitude applications and a wide variety of highly technical uses. Microfiber is one of the most popular synthetic fibers. Its popularity is a result of special properties such as good resiliency, heat resistance, light weight, water proof and durability. In the present work, two woven fabrics were synthesized from polyester microfiber and then coated by calcium silicate/copper oxide-nanoparticles, (CaO3Si/CuO)-NPs, using low temperature plasma (dielectric barrier discharge) technique. The coated textiles were investigated by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX). A broadband dielectric spectroscopy (BDS) was employed to study the treatment conditions on the electrical and dielectric properties over a wide range of frequencies. The results showed that, the resistivity of the textile samples was remarkably enhanced upon coating with the (CaO3Si/CuO)-NPs) accompanied by a reduction of the static charges accumulated on the surface. These results made the plasma sprayed coated textiles promising for electrical applications like cables isolation as well as packing and packaging.

Characterization and Oxidative Stability of Cold-pressed Sesame Oil Microcapsules Prepared by Complex Coacervation.

Although cold-pressed sesame oil (CPSO) possesses high nutritional value, its application in the food industry is limited due to its poor oxidative stability. The aim of this study was to enhance the oxidative stability of CPSO by complex coacervation microcapsule technology with gelatin and gum Arabic as wall materials. The characterization of CPSO microcapsules were evaluated by a particle image analyzer, a laser particle size distribution analyzer, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The encapsulation efficiency (EE) reached 90.25%. The average particle size of the microcapsules was approximately 117.1 μm and many oil droplets were encapsulated by complex coacervation to form a multinuclear spherical microcapsule. The FTIR study confirmed that the process of complex coacervation was formed between gelatin and gum Arabic by electrostatic interactions. The TGA study suggested that the microcapsules had good heat resistance. The fatty acid composition, the content of sesamin, sesamolin and vitamin E in CPSO were determined before and after microencapsulation. It showed that the microencapsulation process had almost no effect on the fatty acid composition, sesamin and sesamolin, only Vitamin E was slightly lost during the microencapsulation process. The accelerated storage test showed that microencapsulation significantly increased the oxidative stability of CPSO.

Prediction of Surface Residual Stress on Titanium Alloy generated by Belt Grinding using Molecular System Dynamics

Abstract With the reason of its high strength, good corrosion resistance and high heat resistance, titanium alloy has been widely used in aeronautical field, especially in aero-engine design. Because of the characteristics of cold state and flexibility, belt grinding is one of the effective titanium alloy finishing. However, the variation of residual stress with grinding parameters in the belt grinding process are not clear, which greatly limits the further application of this method. In this paper, based on the knowledge of molecular system dynamics, a molecular system dynamics model of residual stress on the surface of abrasive belt grinding of titanium alloy is established. Based on the corresponding intermolecular potential function of titanium alloy material, a linear regression equation is established, and the expression of residual stress at molecular level on the surface of belt ground titanium alloy was obtained. The model is simulated with MATLAB, and the results are in good agreement with the intermolecular potential model. Through relevant experiments, the experimental results are compared with the simulation results of titanium alloy molecular system, the error is analyzed and the conclusion is given. When the grinding linear velocity is 8-24 m/s and the feed velocity is 20-60 m/ min, the residual stress of TC17 alloy belt grinding is - 169 to – 254 MPa, and the model prediction error is within 20%.

THE INFLUENCE OF PROCESS CONDITIONS ON GROUND COAL SLAG AND BLAST FURNACE SLAG BASED GEOPOLYMER PROPERTIES

In this study, the material characterization of Vietnamese ground coal slag and ground granulated blast furnace slag (GGBFS), such as particle size distribution, chemical composition, bulk density and particle density are shown. The geopolymer specimens were prepared by mixing an 80 m/m% mass of solid materials (ground coal slag and GGBFS in a different ratio) with 20 m/m % of a 10M NaOH alkaline activator. A systematic experimental series was carried out in order to optimize the preparation process. In that series, the heat curing temperature was 60°C for 6 hours, and then selected specimens were heat treated at a high temperature (1000 °C) for 1 hour. After 7 days of ageing, the physical properties of the geopolymer (compressive strength, specimen density) were measured. Also, after 180 days of ageing, the pH values of water in the geopolymer leaching preparation were determined. The results show that the geopolymer can be used for refractory applications due to its good heat resistance properties. However, geopolymers that were heated at 1000 °C had lower compressive strength, specimen density and pH values of water containing the geopolymer than those that were cured at 60 °C.

Study of wear behaviour of atmospheric plasma spraying composite coating on MS C40

The SiC + ZrO2 + La2O3 composite coating was deposited on the surface of Mild steel C-40 substrate by using air plasma spraying technology, which was done to relieve the wear of substrate during operation. Commercially available Nickel Chromium (Ni-Cr) is selected as bond coat, for top coat a composite of Silicon Carbide (SiC), Zirconium Oxide (ZrO2) and Lanthanum Oxide (La2O3) is selected. Bond coat is done for 75 µm. Top coat thickness is varied between 100 and 300 µm. APS ceramic coating is selected as it gives more importance to obtain the uniform thickness on the substrate. In this work the surface roughness is measured by using Surfcom FLEX 50-A measuring instrument, Morphology of the above TBC system are studied with the help of scanning electron microscope, Coating thickness is done by using image analysis technique, the porosity measured by using image analysis software and the wear test has been performed on Pin-on-disc at, room temperature. From the results and discussion, it can be stated that coating shows good wear and heat resistance.

Synthesis and characterization of novel poly(urethane-urea) elastomers based on 1,3-propanediol bis(4-aminobenzoate) as chain extender

This paper presents the study of new polymer materials based on polycaprolactone diol and hexamethylene diisocyanate, containing urethane and urea groups which are bound both through flexible ether chains as well as through rigid benzene rings belonging to the chain extender structure (1,3-propanediol bis(4-aminobenzoate)). The structure of the chain extender determines the ability of the polymer matrix to perform physical interconnections. A range of cross-linkers with different flexible to rigid structures cross-linkers (propane-1,2,3-triol, castor oil, 1,2,3-benzentriol, 4,5-bis(hydroxymethyl)-2-methylpyridin-3-ol) were used in order to obtain chemical bonds between the polymer chains. The structure and properties of the prepared poly(urethane-urea) were characterized by Fourier transform infrared spectroscopy (FTIR), dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC) and thermogravimetry (TG). FTIR measurements showed a decrease in mobility within the hard segment with the increase in chain extender content. DMA analysis revealed a secondary relaxation towards the rubbery transition. Poly (urethane-urea) elastomers obtained on the basis of 1,3-propanediol bis (4-aminobenzoate) showed good heat resistance at up to 300 °C and excellent mechanical properties with breaking strength of 65 MPa.

Thermal Decomposition Mechanism and Kinetics Study of Plastic Waste Chlorinated Polyvinyl Chloride

Chlorinated polyvinyl chloride (CPVC), as a new type of engineering plastic waste, has been used widely due to its good heat resistance, mechanical properties and corrosion resistance, while it has become an important part of solid waste. The pyrolysis behaviors of CPVC waste were analyzed based on thermogravimetric experiments to explore its reaction mechanism. Compared with polyvinyl chloride (PVC) pyrolysis, CPVC pyrolysis mechanism was divided into two stages and speculated to be dominated by the dehydrochlorination and cyclization/aromatization processes. A common model-free method, Flynn-Wall-Ozawa method, was applied to estimate the activation energy values at different conversion rates. Meanwhile, a typical model-fitting method, Coats-Redfern method, was used to predict the possible reaction model by the comparison of activation energy obtained from model-free method, thereby the first order reaction-order model and fourth order reaction-order model were established corresponding to these two stages. Eventually, based on the initial kinetic parameter values computed by model-free method and reaction model established by model-fitting method, kinetic parameters were optimized by Shuffled Complex Evolution algorithm and further applied to predict the CPVC pyrolysis behaviors during the whole temperature range.

Porous Zr-Based Metal-Organic Frameworks (Zr-MOFs)-Incorporated Thin-Film Nanocomposite Membrane toward Enhanced Desalination Performance.

Four different thin-film nanocomposite (TFN) membranes were prepared by adding different concentrations of porous Zr-metal-organic frameworks (MOFs) (UiO-66 and UiO-66-NH2) to piperazine aqueous solution (aqueous phase) or 1,3,5-benzenetricarbonyl trichloride-n-hexane solution (organic phase) by interfacial polymerization. The main purpose is to study the specific effects of different addition methods and addition amounts of nanoparticles on the structure and performance of the TFN membranes by interfacial polymerization. All four TFN membranes exhibited a higher water permeability while maintaining high salt rejection compared to thin-film composite membrane. On the one hand, the TFN membranes behave differently, which are prepared by adding the same kind of nanoparticles to the aqueous phase or organic phase, respectively. The TFN membrane prepared by adding 0.2 w/v% UiO-66 to the organic phase had a high water flux of 87.86 L m-2 h-1, compared to 46.31 L m-2 h-1 of the membrane prepared by adding 0.3 w/v% UiO-66 in the aqueous phase. This is due to the fact that UiO-66 greatly slows the interfacial polymerization rate when UiO-66 is added to the organic phase, resulting in a thinner and wider-aperture polyamide thin-film layer, reducing the water transmission resistance during filtration. Therefore, it is more economical by adding nanoparticles to organic phase than aqueous phase under the same filtering effect. On the other hand, different nanoparticles can also cause differences in performance and structure of the TFN membranes even in the same preparation manner. TFN membrane with UiO-66-NH2 in the aqueous phase has higher water permeance than the one with UiO-66 in the aqueous phase, owing to the good hydrophilicity of the amino group, which improves the water dispersibility of UiO-66-NH2 so that the TFN membrane is more uniform. In addition, UiO-66-NH2 slows down the process of interface polymerization, making the membrane more porous. The monomers in the aqueous phase and organic phase can be adsorbed in the pores of Zr-MOFs, which makes the interfacial polymerization occur both in the pores and on the surface of the pores. Thus, the compatibility between the polyamide and MOFs was enhanced and less defects were formed in the thin-film layer, resulting in a high salt rejection even when the concentration of Zr-MOFs increased. This is the first time to explain that polyamide membrane has not obvious salt rejection attenuation with increasing porous material content using pore adsorption reaction monomer principle. Also, the Zr-MOFs-based TFN membrane exhibited good heat resistance and antifouling property. This work shows that porous Zr-MOFs nanomaterials have significant advantages in the development of nanofiltration membranes with high water flux and rejection.

Applications and prospects of titanium and its alloys in seawater desalination industry

Seawater desalination (SD) is an effective method to solve the shortage of human water resources. Because of the excellent corrosion resistance of metallic materials in natural waters, as well as the best corrosion resistant, low density, high strength and good heat resistance in seawater, titanium and its alloys are considered the desirable marine material, including in SD equipment. This review introduces material characteristics of titanium and its alloys, and three currently most widely used commercial SD technologies: multiple effect desalination (MED), multi-stage flash (MSF) and reverse osmosis (RO). The applications and prospect of titanium and its alloys in SD industry are overviewed and analysed. This paper can be a reference for the future material selection of SD equipment.

Low‐cost pyrophyllite‐based microfluidic device for the study of enhanced oil recovery

This work proposed a novel method for the fabrication of pyrophyllite-based microfluidic devices for enhanced oil recovery (EOR). Pyrophyllite has good heat resistance, corrosion resistance and similar molecular structure to quartz sandstone, and is suitable for EOR research. A rectangular matrix of the pore structure is designed, representing an idealised porous medium and then fabricated on the surface of pyrophyllite substrate by using the micro-milling method. Finally, a layer of sealing film was applied on the surface of substrate to finish the bonding process. A droplet generator was also fabricated for the demonstration of the proposed technology. A series of displacement experiments with water flooding and surfactant flooding were conducted and the result was carefully analysed and discussed. Compared with the previous study using polymer-based or glass-based microfluidic devices as micromodels for the displacement study in oil recovery process, the surface properties of pyrophyllite are more close to real reservoirs and have compelling advantages as bulk material for microfluidic devices for the EOR study. This work has wide potential applications as the micromodels in EOR research, the proposed fabrication protocols of the pyrophyllite-based microfluidic device are rapid and low-cost, the on-site field test could also be conducted with the proposed technology.

Effects of Chemical Composition of Ca(OH)2 and Precursors on the Properties of Fast-Curing Geopolymers

Geopolymer is an alumina silicate-based ceramic material that has good heat-resistance and fire-resistance; it can be cured at room temperature, and thus its manufacturing process is simple. Geopolymer can be used as a reinforcement or floor finish for high-speed curing applications. In this manuscript, we investigate a high-speed curing geopolymer achieved by adding calcium to augment the curing rate. Metakaolin is used as the main raw material, and aqueous solutions of KOH and K2SiO3 are used as the activators. As a result of optimizing the high bending strength as a target factor for geopolymers with SiO2 / Al2O3 ratio of 4.1 ~ 4.8, the optimum ranges of the active agent are found to be 0.1 ≤ K2O / SiO2 ≤ 0.4 and 10 ≤ H2O / K2O ≤ 32.5, and the optimum range of the curing accelerator is found to be 0.82 ≦ Ca (OH)2 / Al2O3 ≦ 2.87. The maximum flexural strength is found to be 1.35 MPa at Ca (OH)2 / Al2O3 = 2.82, K2O / SiO2 = 0.3, and H2O / K2O = 11.3. The physical and thermal properties are analyzed to validate the applicability of these materials as industrial insulating parts or repairing·finishing materials in construction.

Experimental investigation on the effect of ceramic coating on the wear resistance of Al6061 substrate

In the present research work, various ceramic materials such as Al2O3 - Cr2O3 - SiC, and Al2O3 - ZrO2 - TiO2 were developed for the analysis of wear performance and hardness. The specimens were coated using plasma spray coating technique. A bond coat of 50μm thickness was applied on the substrate using NiCrAlY for good adhesion before laying the top coat. The wear behaviour and hardness of the samples were investigated by wear and hardness tests. The Energy Dispersive X-ray Analysis (EDAX) was performed to analyse the chemical composition of the samples. The Field Emission Scanning Electron Microscope (FE-SEM) was used to analyse the surface and cross-section of the samples. X-ray diffraction (XRD) studies are carried out to understand the structural and crystallographic information. The performances of the coated and uncoated samples were compared and investigated. It was observed that the specimen with Al2O3 (60%) + ZrO2 (20%) + TiO2 (20%) coating produced best results for wear rate (0.03612mm3/Nm) and Coefficient of friction (0.357). The proposed ceramic coating composition could be recommended for automobile components that require good wear and heat resistance to improve the service life.

Preparation, characterization and application of polyether and long-chain alkyl co-modified polydimethylsiloxane

In this paper, by using a self-made hydrogen-containing polymethylhydrogensiloxane having a hydrogen content of 0.20%, a polyether of F-6 and α-olefin having a carbon chain length of even numbers in 6–18 as main raw materials, polyether and long-chain alkyl co-modified polydimethylsiloxane having different molecular structures were successfully prepared via hydrosilylation reactions. 1H-NMR, TGA, DLS, fluorescence spectroscopy and surface tension measurements were used to characterize their structures and properties. The results shows that when the molar ratio of polyether to α-olefin is 5:1, an emulsion type anti-foaming agent with polyether and long-chain alkyl co-modified polydimethylsiloxane as active ingredient was successfully prepared, it basically maintains 90% quality at 300 °C, indicating good heat resistance, and the critical micelle concentration (CMC) of polyether and long-chain alkyl co-modified polydimethylsiloxane is 8.55 mg/L. The surfactant has good dilution stability compared to other small molecule. When the hydrophilic-lipophilic balance (HLB) is equal to 10, the compound emulsifier is made of Span 80 and Tween 80, the emulsification method is a phase inversion method, and the obtained emulsion has the smallest particle size and an average particle diameter of 134.4 nm, the emulsion shows good stability and uniformity, and the particle size distribution is narrow. In summary, the polyether and long-chain alkyl co-modified polydimethylsiloxane synthesized in this work have potential applications in the fields of anti-foaming agent.

Synthesis and characterisation of Φ62 mm polycrystalline diamond compact

To solve the problem of uniform high-quality sintering of large-diameter polycrystalline diamond compact (PDC) cutting tool material on a cubic press, the design of a high-temperature, high-pressure (HTHP) sintering cavity assembly structure of a cubic press is optimised. PDC cutting tool materials with Φ62 mm were successfully sintered at a pressure of 5.5–5.8 GPa and a temperature of 1550–1650 °C. The microstructure and phase composition of PDC samples were detected by scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. The microhardness, flexural strength, interfacial shear strength, wear resistance, and heat resistance of the samples were tested by a Vickers hardness tester, universal testing machine, and an abrasion ratio tester, and their uniformity was analysed. The test results show that the microhardness of Φ62 mm PDC is 86.25 GPa, which is 13.34% higher than that of the conventional PDC cutting tool material on the market; the bending strength is 1398.6 MPa; the interfacial shear strength is 2690.4 MPa; and the wear ratio is 29.8 × 104 with only an 8.09% decrease from the peripheral point to the central point. The wear resistance is basically uniform in the radial direction, indicating that the HTHP sintering process and the structure of the sintering cell assembly are reasonable, and the temperature and pressure field distributions inside the high-pressure sintering cavity are uniform, thereby realising uniform, dense sintering of the Φ62 mm PDC. When the PDC sample was calcined at 750 °C for 2 min, the wear resistance was 29.8 × 104, which is 10.59% lower than the wear resistance at room temperature, and the sample had good heat resistance.

Evaluation of carbon fiber and p-aramid composite for industrial helmet using simple cross-ply for protecting human heads

Using personal protective equipment, such as safety helmets, at industrial sites, is the last method to prevent disasters, and such equipment are widely recognized as consumables. Among them, industrial safety helmets use ABS (acrylonitrile butadiene styrene) or PE (polyethylene) resins as the main material of the shell to absorb shocks, and they also possess a relatively good heat resistance. However, efforts to develop new materials by a simple fabrication method are not actively performed. In this study, to improve the safety performance of industrial helmets, an epoxy resin was used as a matrix to produce a p-aramid/carbon fiber composite as a simple cross-ply, and compared to p-aramid fiber-reinforced composites, carbon fiber-reinforced composites, and ABS plastic. The specimens were prepared by the compression molding method, and their mechanical properties including the impact strength, tensile strength, flexural strength, and inter-laminar shear strength along with heat resistance properties were observed via thermogravimetric analysis.

Algicidal characterization and mechanism of Bacillus licheniformis Sp34 against Microcystis aeruginosa in Dianchi Lake.

Microcystis aeruginosa blooms are a worldwide serious environmental problem and bloom control with bacteria is promising. In this study, a Bacillus licheniformis strain Sp34 with potent algicidal and inhibitory effects on the microcystins synthesis against fast-growing M. aeruginosa was isolated from Dianchi Lake. Sp34 killed the bloom-causing algal strain M. aeruginosa DCM4 of Dianchi Lake with an initial Chlorophyll-a concentration of 2.0 mg/L at a cell density of no less than 1.35 × 105 CFU/ml. It can also efficiently kill some other harmful algal species, such as M. wesenbergii and Phormidium sp. The algicidal activity of Sp34 relied on the release of algicidal substances, which had good heat (-20°C to 121°C) and acid-base (pH 3-11) resistance. In addition, the high algicidal activity depended on the good growth of algae indicated by the significantly positive correlations between algal growth and algicidal ratio (p < .001). The algicidal effect of Sp34 involved causing oxidative stress, lipid peroxidation, and morphological injury of algal cells, along with DNA damage and dysfunction of DNA-repair function, weakening the photosynthesis system, and inhibiting microcystin synthesis. In general, Sp34 can kill fast-growing M. aeruginosa and inhibit algal microcystin synthesis efficiently, so, it is a promising biocontrol agent to mitigate cyanobacterial blooms.

A review on high temperature resistant polyimide films: Heterocyclic structures and nanocomposites

Abstract Polyimide (PI) films are used in a wide spectrum of high-tech fields including photovoltaics , microelectronics, and aerospace engineering thanks to their good heat resistance, large mechanical strength, and low thermal expansion coefficients. Further improving their temperature resistance is expected to expand its applications. However, great challenges still exist in the fabrication of PI film with high thermal stability and good combined properties. This review summaries the design strategies and synthesis route of high thermal stability PI films, and discusses the recent progress on improving the thermal stability of PI films by nanocomposite modification. Especically, reported results by introducing a heterocyclic ring into the polymer chain to improve thermal stability were presented. Inorganic particles such as layered silicate, nitrides or metal oxides , carbon nanotubes (CNTs) and graphene used to make organic/inorganic nanocomposite for PI modification were also discussed.

Preparation of Hollow Glass Microsphere/Organic Silicone Resin Composite Material with Low Dielectric Constant by In-Situ Polymerization

Hollow glass microsphere (HGM) /organic silicon resin composite materials with different quantity of HGM were prepared by in-situ hydrolytic polymerization. The hydrolysis reaction of silicone resin was carried out at the same time with the surface treatment of HGM by the silane coupling agent. It has been found that HGM was treated by silane coupling agent and the silicone resin was hydrolyzed on the surface of HGM. Such in-situ polymerization method solves the poor compatibility between HGM and silicone resin. And then the composite materials were cured by hydrosilylation. The composite material has low dielectric constant (2.40) and good heat resistance. Such new HGM/organic silicone resin composite material is expected to be used for integrated circuit packaging material.