The chemical functionalization of graphene nanoplatelets through solvent-free reaction

Graphene nanoplatelets (GNPs) were functionalized through 1,3-dipolar cycloaddition of azomethine ylide using a solvent-free approach and under different reaction conditions. The yield and the functionality of the carboxyl-terminated pyrrolidine ring attached on the surface of GNPs could be affected by varying the reaction temperature as well as the reactant to GNP weight ratio. The functionalized GNPs were characterized extensively using a range of spectroscopic and microscopy techniques.

Carboxyl-terminated pyrrolidine functionalized graphene nanoplatelets through a solvent-free reaction.     

Thermal property improvement of polytetrafluoroethylene nanocomposites with graphene nanoplatelets

Thermal properties including the crystallization behavior, thermal stability and thermal conductivity for a series of graphene nanoplatelet (GNP)–polytetrafluoroethylene (PTFE) nanocomposites were studied. The GNP–PTFE nanocomposites were fabricated via solvent-assisted blending followed by cold-pressing and sintering. The results indicated that the GNP–PTFE nanocomposites retained the good thermal stability of the PTFE matrix, and possessed better crystallization and much higher thermal conductivity than pure PTFE. The thermal conductivity of PTFE nanocomposites with a GNP mass fraction of 20% could reach 4.02 W (m K)⁻¹, which was increased by 1300% compared with pure PTFE. Additionally, a theoretical model was proposed to analyze the thermal conductivity of GNP–PTFE nanocomposites. It is demonstrated that adding GNPs into PTFE homogeneously can effectively improve the thermal properties of the nanocomposites.

Adding GNPs into PTFE can significantly improve the thermal properties of nanocomposites.     

Synthesis of styrene maleic anhydride copolymer grafted graphene and its dispersion in aqueous solution

In this study, three simple methods were described to synthesize covalently functionalized graphene nanoplatelets (GNPs) with poly(styrene-co-maleic anhydride) (SMA) via ester linkages. Furthermore, the dispersibility of modified GNPs in aqueous solution was characterized by several techniques. Anchoring of SMA long-chains on GNPs via chemical bonds was confirmed by Fourier transform infrared spectroscopy. Furthermore, field emission scanning electron microscopy analysis indicated that the SMA unevenly covered the surface and edges of the GNPs. Solubility measurements showed that the modified GNPs prepared by the designed method had excellent dispersibility in aqueous solution, and the grafting rate of modified GNPs showed an obvious positive correlation with the concentration in aqueous solution as revealed by ultraviolet absorbency and thermogravimetric analysis results. Markedly, the modified GNPs during ultrasonic treatment exhibited better dispersibility and grafting rate compared to others. Moreover, the experimental results confirmed that GNP concentration reached up to 0.32 mg mL⁻¹ in aqueous solution and the grafting rate was 18.02%. The content of SMA had little effect on grafting rate; however, the ultrasonic duration significantly affected the process.

Three simple and cost-effective method were described to synthesize covalently functionalized graphene nanoplatelets (GNPs) with poly(styrene-co-maleic anhydride) (SMA), which offer the possibility of using graphene for low-value products such as cement-based materials.     

Functionalization of pristine graphene for the synthesis of covalent graphene–polyaniline nanocomposite

Polyaniline (PANI) is one of the most studied conducting polymers owing to its high electrical conductivity, straightforward synthesis and stability. Graphene-supported PANI nanocomposite materials combine the superior physical properties of graphene, synergistically enhancing the performance of PANI as well as giving rise to new properties. Covalent nanocomposites have shown to give higher stability and better performance than their non-covalent counterparts, however, the covalent graphene–PANI nanocomposite are primarily prepared from graphene oxide. We report a new method to synthesize covalent graphene–PANI nanocomposites from pristine graphene. Using few-layer graphene (FLG) flakes as the model system, we first conjugated aniline to FLG via a perfluorophenyl azide (PFPA)-mediated coupling chemistry. A subsequent in situ polymerization of aniline gave polyaniline covalently grafted on the FLG surface. Characterization by FTIR, TEM, SEM, XPS, XRD and electrochemistry confirmed the successful conjugation of PANI to FLG. The grafting density of PANI was estimated by thermal analysis to be ∼26%. As the PFPA-mediated coupling chemistry is applicable to other carbon materials including carbon nanotubes and fullerene, the method developed in this work can be readily adapted to grow PANI on these materials.

Polyaniline was covalently grafted on pristine few-layer graphene via a perfluorophenyl azide-mediated coupling chemistry.     

Boron carbide composites with highly aligned graphene nanoplatelets: light-weight and efficient electromagnetic interference shielding materials at high temperatures

B₄C-based ceramic composites containing 0–2 vol% highly aligned graphene nanoplatelets (GNPs) are fabricated. The electromagnetic interference (EMI) shielding properties of the obtained composites are investigated at X-band (8.2–12.4 GHz) frequency range from room-temperature up to 800 °C. All composites exhibit outstanding EMI shielding properties with satisfactory frequency- and thermal-stability. The shielding effectiveness (SE) of GNP/B₄C composites increases monotonically with increasing GNP loading. Superior room-temperature SE close to 40 dB is achieved with only 2 vol% GNPs and high SE around 35 dB still persists at 800 °C. Considering their relatively low density, GNP/B₄C composites possess a high specific shielding effectiveness (SSE) of 16 dB cm³ g⁻¹ which is among the highest values in reported ceramic-based shielding composites. Especially, the GNP/B₄C composite with 2 vol% GNPs exhibits the highest SSE/t (SSE divided by thickness) values at temperatures above 200 °C for all reported shielding composites, indicating that GNP/B₄C composites belong to the most promising high-temperature shielding composites. The excellent shielding properties of GNP/B₄C composites arise mainly from the high electrical conductivity, high dielectric loss and the multiple reflections by the highly aligned and large-sized GNP layers.

The incorporation of a small amount of highly aligned graphene nanoplatelets into boron carbide leads to light-weight and efficient high-temperature electromagnetic interference shielding composites.     

Anisotropic thermal conductive properties of cigarette filter-templated graphene/epoxy composites

Herein, a cigarette filter-templated graphene/epoxy composite was prepared with enhanced thermal conductive properties. The through-plane thermal conductivity of the epoxy composite was up to 1.2 W mK⁻¹, which was 4 times that of it in the in-plane (0.298 W mK⁻¹) after only 5 filtration cycles. The thermal conductive anisotropy and improvement in the through-plane thermal conductivity of the epoxy composite were attributed to the particular structure of cigarette filter-templated graphene in the epoxy matrix. The unique structure formed effective conductive pathways in the composite to improve the thermal transportation properties. The excellent thermal transportation properties allow the epoxy composite to be used as an efficient heat dissipation material for thermal management applications.

We report a facile method to prepare cigarette filter-templated graphene/epoxy composites with excellent thermal transport performance.     

Electrodeposited nickel–graphene nanocomposite coating: effect of graphene nanoplatelet size on its microstructure and hardness

In this study, the effect of graphene nanoplatelet (GNP) size on the microstructure and hardness of the electrodeposited nickel–graphene nanocomposite coatings were investigated. GNPs with different sizes were prepared by using a high energy ball milling technique. The experimental result revealed the high energy ball milling technique could reduce the size, increase the surface area, and improve the dispersion ability of GNPs. The microstructure, hardness, and components of the nanocomposite coatings were greatly affected by GNP sizes. The highest microhardness was measured to be 273 HV for the nanocomposite coatings containing 5 h-milled GNPs, which is increased up to ∼47% compared to pristine Ni coating. The enhancement in the hardness is attributed to the uniform dispersion of the small GNP sizes inside the Ni matrix and the Ni grain size reduction when using milled GNPs.

The effect of graphene nanoplatelet size on the microstructure and hardness of electrodeposited nickel–graphene nanocomposite coatings was investigated.     

Preparation of self-healing polyurethane/functionalized graphene nanocomposites as electro-conductive one part adhesives

We report the synthesis and investigation of the electrical conductivity and self-healing properties of moisture curable polyurethane (PU) adhesives filled with functionalized graphene nanosheets and isophorone diisocyanate (IPDI) loaded poly(methyl methacrylate) (PMMA) nanocapsules. For this purpose, chemically functionalized graphene was prepared by covalently grafting 4-(4,5-diphenyl-1H-imidazol-2-yl)phenol (DIP) on the surface of graphene oxide and synthesized PMMA nanocapsules were loaded with IPDI. Both nanofillers were then dispersed in a polyurethane matrix and the effects on the adhesion properties of the adhesives in aluminum–aluminum metal joints were studied. The results showed that by surface modification and better exfoliation of graphene nanosheets, the electrical conductivity was increased from 2.2 × 10⁻⁹ S m⁻¹ to 4.1 S m⁻¹ for pure PU and 10 wt% graphene based nanofiller loaded PU, respectively. The thermal stability, electrical conductivity, shear strength and self-healing process of the ECAs were also studied. The results provide evidence that the prepared adhesives have the potential for applications in electronic device packaging.

One part moisture curable adhesives based on polyurethane/functionalized graphene nanocomposites were synthesized and showed good electrical conductivity, thermal stability, shear strength and self-healing properties.     

Aryl fluoride functionalized graphene oxides for excellent room temperature ammonia sensitivity/selectivity

Herein, we report the covalent functionalization of graphene oxide (GO) through ‘‘click’’ reaction and its applications towards ammonia sensing. This inimitable method of covalent functionalization involves linking GO with azide moiety and click coupling of different derivatives of aryl propargyl ether, which enhances the sensitivity towards ammonia. The functionalized GO were characterized using NMR, XRD, SEM, FT-IR, Raman, UV-Vis, TGA and DSC. Compared to pristine GO, the GO functionalized with Ar samples (GO-Ar) exhibit excellent room temperature ammonia sensing properties with good response/recovery characteristics. It has been observed that 2,3-difluoro and 2,3,4-trifluoro substituted aryl propargyl ether functionalized GO (GO-Ar2 and GO-Ar3) shows superior ammonia sensing with response/recovery of 63%/∼90% and 60%/100%, respectively at 20 ppm. The GO-Ar3 exhibits high sensitivity towards ammonia at 20–100 ppm. Computational studies supports the high sensitivity of GO-Ar towards ammonia due to its high adsorption energy.

Covalent functionalization of graphene oxide (GO) through ‘‘click’’ reaction and its applications towards ammonia sensing has been demonstrated.     

Graphene as a nanofiller for enhancing the tribological properties and thermal conductivity of base grease

During mechanical processes, violent friction and wear between the friction contact surfaces not only causes wear to mechanical components, reducing the instrument life, but also causes friction heat, reducing the working efficiency of machines during operation. The addition of graphene-reinforced grease to the mechanical friction surface can effectively reduce the friction coefficient and improve the thermal conductivity. In this work, the tribological properties and thermal conductivity of base grease with graphene were investigated systematically. The tribological results showed that the grease with 2 wt% graphene had the best tribological properties among all these greases. The wear scar diameter and average friction coefficient of graphene grease with 2 wt% graphene reached 0.43 mm and 0.10 (the values for base grease are 0.50 mm and 0.118), respectively. In addition, the average friction coefficient and wear scar diameter increased proportionally with the increasing load and frequency. The thermal conductivity of the grease with 4 wt% graphene reached 0.28 W (m K)⁻¹, an increase of 55.5% in comparison with the base grease. It is proposed that the addition of graphene into the base grease effectively enhanced the tribological properties and thermal conductivity.

The addition of graphene-reinforced grease to the mechanical friction surface can effectively reduce the friction coefficient and accelerate heat transportation.     

Surface modification of carbon nanotubes with copper oxide nanoparticles for heat transfer enhancement of nanofluids

Over the last few years, nanoparticles have been used as thermal enhancement agents in many heat transfer based fluids to improve the thermal conductivity of the fluids. Recently, many experiments have been carried out to prepare different types of nanofluids (NFs) showing a tremendous increase in thermal conductivity of the base fluids with the addition of a small amount of nanoparticles. However, little experimental work has been proposed to calculate the flow behaviour and heat transfer of nanofluids and the exact mechanism for the increase in effective thermal conductivity in heat exchangers. This study mainly focuses on the development of nanomaterial composites by incorporating copper oxide nanoparticles (CuO) onto the surfaces of carbon nanotubes (CNTs). The CNT–CuO nanocomposite was used to prepare water-based heat transfer NFs. The morphological surfaces and loading contents of the CNT–CuO nanocomposite were characterized using field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) while the physical and thermal properties of the water-based nanofluids were characterized using differential scanning calorimetry (DSC), the Mathis TCi system and a viscosity meter for measuring the heat capacity, thermal conductivity and viscosity of the synthesized NFs, respectively. The heat transfer and the pressure drop studies of the NFs were conducted by a horizontal steel tube counter-flow heat exchanger under turbulent flow conditions. The experimental results showed that the developed NFs with different concentrations of modified CNTs (0.01, 0.05 and 0.1 wt%) have yielded a significant increase in specific heat capacity (102% higher than pure water) and thermal conductivity (26% higher than pure water) even at low concentration. The results also revealed that the heat rate of the NF was higher than that of the base liquid (water) and increased with increasing the concentration of nanoparticles. Furthermore, no significant effect of the nanoparticles on the pressure drop of the system was observed.

Over the last few years, nanoparticles have been used as thermal enhancement agents in many heat transfer based fluids to improve the thermal conductivity of the fluids.     

A thermal energy storage composite by incorporating microencapsulated phase change material into wood

Phase change energy storage wood (PCESW) was prepared by using microencapsulated phase change materials (MicroPCM) as thermal energy storage (TES) materials and wood as the matrix. The incorporation of MicroPCM and wood was realized using a vacuum impregnation method. The morphology and microstructure of MicroPCM, delignified wood (DLW) and PCESW were observed by scanning electron microscopy (SEM); the thermal properties including phase change temperature, enthalpy, thermal stability, thermal conductivity of MicroPCM and PCESW were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TG) and laser flash analysis (LFA). The results showed that: (1) delignification improved the porosity of wood and enhanced the impregnation effect, MicroPCM got into the delignified wood successfully and mainly distributed in the vessels; (2) PCESW had excellent energy storage capacity and suitable phase transition temperature for regulating indoor temperature; (3) PCESW had prior thermal stability at room temperature and great durability after 100 heating–cooling cycles; (4) addition of graphene greatly improved the thermal conductivity of PCESW. The TES composite can be used as an indoor temperature regulating material for building energy conservation.

Phase change energy storage wood (PCESW) was prepared by using microencapsulated phase change materials (MicroPCM) as thermal energy storage (TES) materials and wood as the matrix.     

One-pot synthesis of amine-functionalized graphene oxide by microwave-assisted reactions: an outstanding alternative for supporting materials in supercapacitors

A simple and straightforward method using microwave-assisted reactions is presented for the functionalization of graphene oxide with aromatic and non-aromatic amines, notedly dibenzylamine (DBA), p-phenylenediamine (PPD), diisopropylamine (DPA) and piperidine (PA). The as-synthesized amine-functionalized graphene oxide materials (amine-GO) were characterized using spectroscopic techniques including XRD, FTIR, ¹³C NMR, XPS, TEM for imaging and thermogravimetric analysis (TGA). The characterization confirmed the functionalization for all amines, reaching relatively high surface nitrogen atomic concentrations of up to 8.8%. The investigations of electrochemical behavior for the amine-GOs show the significant improvement in GO''s electrochemical properties through amine functionalization, exhibiting long life cycle stability and reaching specific capacitance values of up to 290 F g⁻¹ and 260 F g⁻¹ for GO-PA and GO-DPA samples, respectively, confirming their potential application as alternative supporting materials in supercapacitors.

A simple and straightforward method using microwave-assisted reactions is presented for the functionalization of graphene oxide with aromatic and non-aromatic amines.     

Nanofiller-conjugated percolating conductive network modified polymerization reaction characteristics of aromatic thermosetting copolyester resin

Deliberately controlled interfacial interactions between incorporated nanofiller particles and host polymer backbone chains constitute a critical element in the realm of polymer nanocomposites with tailorable multifunctional properties. We demonstrate the physicochemical effects induced by graphene nanoplatelets (GNP) of different sizes on the condensation polymerization reaction of aromatic thermosetting copolyester (ATSP) through the formation of electrically conductive percolating networks as enabled by interfacial interactions. Carboxylic acid and acetoxy-capped precursor oligomers of ATSP are solid-state mixed with chemically pristine GNP particles at various loading levels. Upon in situ endothermic condensation polymerization reaction, crosslinked backbone of the ATSP foam matrix is formed while the carbonaceous nanofillers are incorporated into the polymer network via covalent conjugation with functional end-groups of the oligomers. The controlled GNP size promotes different electrical percolation thresholds and ultimate electrical conductivities. Microstructural analysis demonstrates GNP distributions in the matrix as well as morphological modifications induced by the formation of conductive percolating GNP networks. Cure characteristics reveal the thermochemical changes prompted in the polymerization processes for GNP content above the requirement for percolation formation. Chemical spectroscopy of the ATSP nanocomposite morphology exhibits the formation of a robust interfacial coupling mechanism between the GNPs and ATSP backbone. The findings here may guide the developmental efforts of nanocomposites through better identifying roles of the morphology and content of nanofillers in polymerization processes.

Physicochemical effects induced by graphene nanoplatelets on the in situ polycondensation reaction of aromatic thermosetting copolyester through the formation of conductive percolating network assembled via interfacial interactions.     

Facile fabrication of polyurethane/epoxy IPNs filled graphene aerogel with improved damping,thermal and mechanical properties

In this article, polyurethane (PU)/epoxy (EP) interpenetrating polymer networks (IPNs) filled graphene aerogel (PEGA) was facilely fabricated by a one-step vacuum-assisted filling process. Effects of PU content on damping performance, thermal stability and mechanical properties of the PEGA composites were studied systematically. Results reveal that addition of graphene aerogel improves damping properties of PU/EP IPNs and increases the thermal decomposition temperature. Mechanical tests show that flexural strength, flexural modulus and Shore D hardness of the PEGA composites also improved by incorporation of graphene aerogel. The enhanced damping, thermal and mechanical properties of PEGA composites can be attributed to the uniform distribution of graphene sheets in the IPN matrix, which benefits from the three-dimensional interconnected porous network structure of the graphene aerogel used and good interfacial adhesion at the nanofiller-matrix interface. It is expected that the PEGA composites can be used as good structural damping materials in future.

PEGA composites were facilely fabricated by a one-step vacuum-assisted filling method, and exhibited improved damping, thermal and mechanical properties.     

Ionic cellulose-stabilized gold nanoparticles and their application in the catalytic reduction of 4-nitrophenol

A novel strategy for the synthesis of highly stable gold nanoparticles (GNPs) was designed by reducing HAuCl₄ with NaBH₄ in an aqueous solution of water-soluble ionic cellulose composed of dimethylimidazolium cations and phosphite-bound cellulose anions. NMR and UV-Vis analysis along with the measurement of the zeta potential suggest that the exceptionally high stability of GNPs originates from the strong interaction of GNPs with the phosphite groups of the ionic cellulose. The thus prepared GNPs exhibit excellent catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol, a model hydrogenation reaction.

Gold nanoparticles (GNP) were highly stabilized by water soluble ionic cellulose by the strong interaction of GNP with the phosphite groups and showed extremely high catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol.     

Flexible PEBAX/graphene electromagnetic shielding composite films with a negative pressure effect of resistance for pressure sensors applications

In the current work, we fabricated flexible poly(ether-block-amide) (PEBAX)/graphene composite films by a combination of facile melt blending and compression molding technique. The graphene content significantly affects the mechanical properties, electrical conductivity and electromagnetic interference (EMI) shielding performance. An electrically conductive percolation threshold of 1.75 vol% graphene was obtained in the PEBAX/graphene composites. With the introduction of 4.45 vol%, and 8.91 vol% graphene content, the average EMI SE of composite films could reach 16.6 and 30.7 dB, respectively. More interestingly, the PEBAX/graphene composite exhibited a nearly-linear negative pressure coefficient (NPC) effect of resistance with increasing outer pressure stimulation, which was attributed to the formation of more conductive pathways caused by the decreased distance between adjacent graphene. In addition, these composites demonstrated good sensing stability, recoverability and reproducibility after stabilization by cyclic pressure loading. The current study provides guidelines for the large-scale preparation of elastomer NPC sensors and smart EMI shielding devices.

Graphene/PEBAX composite films present high-efficiency EMI shielding properties and good sensitivity as well as sensing stability.     

Ultrathin flexible graphene films with high thermal conductivity and excellent EMI shielding performance using large-sized graphene oxide flakes

As the demand for wearable and foldable electronic devices increases rapidly, ultrathin and flexible thermal conducting films with exceptional electromagnetic interference (EMI) shielding effectiveness (SE) are greatly needed. Large-sized graphene oxide flakes and thermal treatment were employed to fabricate lightweight, flexible and highly conductive graphene films. Compared to graphene films made of smaller-sized flakes, the graphene film made of large-sized flakes possesses less defects and more conjugated domains, leading to higher electrical and higher thermal conductivities, as well as higher EMI SE. By compressing four-layer porous graphene films together, a 14 μm-thick graphene film (LG-4) was obtained, possessing EMI SE of 73.7 dB and the specific SE divided by thickness (SSE/t) of 25 680 dB cm² g⁻¹. The ultrahigh EMI shielding property of the LG-4 film originates from the excellent electrical conductivity (6740 S cm⁻¹), as well as multi-layer structure composed of graphene laminates and insulated air pores. Moreover, the LG-4 film shows excellent flexibility and high thermal conductivity (803.1 W m⁻¹ K⁻¹), indicating that the film is a promising candidate for lightweight, flexible thermal conducting film with exceptional EMI shielding performance.

As the demand for wearable and foldable electronic devices increases rapidly, ultrathin and flexible thermal conducting films with exceptional electromagnetic interference (EMI) shielding effectiveness (SE) are greatly needed.     

A facile strategy for the synthesis of graphene/V2O5 nanospheres and graphene/VN nanospheres derived from a single graphene oxide-wrapped VOx nanosphere precursor for hybrid supercapacitors

It remains a challenge to develop a facile approach to prepare positive and negative electrode materials with good electrochemical performance for application in hybrid supercapacitors. In this study, based on a facile strategy, a single graphene oxide-wrapped VO_x nanosphere precursor is transformed into both electrodes through different thermal treatments (i.e., graphene/VN nanospheres negative electrode materials and graphene/V₂O₅ nanospheres positive electrode materials) for hybrid supercapacitors. The conformally wrapped graphene has a significant influence on the electrochemical performance of VN and V₂O₅, deriving from the simultaneous improvements in electronic conductivity, structural stability, and electrolyte transport. Benefitting from these merits, the as-prepared graphene/VN nanospheres and graphene/V₂O₅ nanospheres exhibit excellent electrochemical performance for HSCs with high specific capacitance (83 F g⁻¹) and good long cycle life (90% specific capacitance retained after 7000 cycles). Furthermore, graphene/VN nanospheres//graphene/V₂O₅ nanosphere HSCs can deliver a high energy density of 35.2 W h kg⁻¹ at 0.4 kW kg⁻¹ and maintain about 70% high energy density even at a high power density of 8 kW kg⁻¹. Such impressive results of the hybrid supercapacitors show great potential in vanadium-based electrode materials for promising applications in high performance energy storage systems.

It remains a challenge to develop a facile approach to prepare positive and negative electrode materials with good electrochemical performance for application in hybrid supercapacitors.     

The influence of graphene nanoplatelets (GNPs) on the semi-blunt puncture behavior of woven fabrics impregnated with shear thickening fluid (STF)

Fabrics are widely applied in various fields, such as body armor, aerospace industry and military equipment. This paper reports the semi-blunt puncture behavior of fabrics impregnated with a shear thickening fluid (STF), which is a dispersion system of nano silica/polyethylene glycol (SiO₂/PEG). The rheological properties and microstructure of the STF were tested to evaluate the influence of SiO₂ particle size and additives (graphene nanoplatelets) on the puncture behavior of the final fabrics. The surface characteristics of neat and STF-treated fabrics were separately measured by field emission scanning electron microscopy (FESEM), which helps study the damage morphology and mechanism of the fabric. The surface characteristics of the silica nanoparticles and additives were also measured by transmission electron microscopy (TEM). The results demonstrated that the puncture behavior of the woven fabric was significantly enhanced due to the presence of STF. Moreover, the presence of additive GNPs induced a relatively lower shear thickening phenomenon, while a significant enhancement in the semi-blunt puncture behavior of the woven fabric was observed.

Fabrics are widely applied in various fields, such as body armor, aerospace industry and military equipment.