With the rapid development of electronic information and technology, especially the explosive advance of novel electronic devices, ultra-wideband radar detector and satellite communication, the elimination of adverse electromagnetic waves (EWs) effectively is very necessary both for electronic safety and national defense security. As one of the important material basis for controlling adverse EW pollution, compatibility, shielding, and stealth capability of weaponry, microwave absorbing materials has long been an area of intense research activity. Graphene-based materials have attracted great interests for microwave absorption in recent years due to the unique structure and physicochemical properties of graphene, such as high specific surface area, ultrathin thickness, large interface, optical transmittance, and tunable conductive properties, etc. In this paper, the properties and absorption behavior of different kinds of microwave absorbing materials based on graphene were reviewed and discussed in detail. In addition, the perspective of the current challenges and key issues for achieving better microwave absorption performance of the graphene-based materials are provided.

Hydrogenated amorphous carbon (a-C:H) films with a designed buffer layer of amorphous hydrogenated silicon carbide on the substrates were fabricated by plasma enhanced chemical vapor deposition (PECVD). The effect of radio frequency (RF) power on the structural and optical properties of a-C:H films was investigated. The ratios of sp 3 to sp 2 of carbon atoms and hydrogen contents in the RF power range of 75–175 W are determined and a similar trend as a function of power. The increase of sp 3 to sp 2 ratio leads to the increase of transmittance and optical gap of a-C:H films. a-C:H film under an RF power of 175 W possesses high transmissive ability (>80%) in the visible wave length, even the highest transmittance value of about 94.2% is achieved at the wave length 550 nm. These results show the optimal a-C:H films which are promising for the applications in the area of solar cells acting a window layer and antireflection layer.

In this work, the high-performance silicon carbide particle SiCp[carbon nanotube (CNT)] hybrid reinforcement is currently explored to develop the advanced metal matrix composites. 17 wt% SiCp(CNT)/Al composites were fabricated by a powder metallurgy technique, in which SiCp(CNT) hybrid reinforcement with various CNT contents (e.g., 3, 6 and 9 wt%) were applied. Effects of CNT content on the morphology of SiCp(CNT) hybrid reinforcement, the microstructural characteristics, and the tensile mechanical behavior of SiCp(CNT)/Al composites were studied as well. Especially, the SiCp(CNT)/Al composites with 6 wt% CNT in SiCp(CNT) hybrid reinforcement exhibited the most significant enhancing effects in the elastic modulus and tensile strength. Meanwhile, the SiCp(CNT)/Al composites produced a synergistic strengthening effect of SiCp and CNT compared to SiCp/Al composites, while the SiCp(CNT)/Al composites with high CNT content in SiCp(CNT) hybrid reinforcement provided weak improvement in the tensile strength and ductility due to the forming agglomeration of CNT in the matrix.

With increasing output of petroleum coke, the value-added exploitation of petroleum coke has become a tough problem. Preparing porous carbons is a traditional way to the value-added exploitation of petroleum coke. Here, we used a facile and efficient hard-templating strategy to synthesize mesoporous carbon with high surface area from petroleum coke. N2 adsorption analyses show that the BET specific area and pore volume of the carbons can reach up to 864 m2/g and 1.37 cm3/g, respectively. To utilize the abundant mesopores of the carbons, anthraquinone-modified mesoporous carbon was tested as an electrode material for supercapacitor applications. Electrochemical measurements demonstrated that the specific capacitance reached up to 366 F/g at the current density of 1 A/g, indicating a promising prospect of using this carbon in electrochemical energy-storage field. More importantly, the strategy used in this work can be easily modified to prepare other nano-carbon materials from petroleum coke.

The amorphous carbon thin films were deposited by the ion beam sputtering deposition technique on Ni–Cu alloy substrates. The effect of sputtering ion beam energy on wettabillity, surface, and structural properties of thin films was examined. The sputtering ion beam energy was varied over a wide range from 2 to 5 keV. Raman spectra showed that the values of ID/IG ratio and the ‘G’ peak position have a reduction trend by increasing the argon ion beam energy while the surface roughness increased due to the resputtering effect. The wettability and surface energy of a-C carbon films were studied by contact angle measurements in relation to structure and topography. The deposited films showed a relatively high water contact angle (CA) that decreases from 87° to 75°. The X-ray photoelectron spectroscopy showed that the value of sp3/sp2 bond content of a-C thin films deposited with the highest argon ion beam energy of 5 keV was about 0.8. Furthermore, the optical band gap followed similar trends of the structural properties.

A chemomechanical coupling model is presented in the temperature range of 1200–1800 °C based on the microstructure during oxidation of ZrB2–SiC. The model includes the interaction of the oxidation rate and the mechanical stress. The stress is generated due to the constraint from the substrate to the lateral growth. The generated stress results in the shrink of the pores in the oxide. At the outer glassy layer surface, the boundary layer evaporation is adopted to describe the evaporation rate. Using the coupling model, the evolutions of the oxide layer thickness, weight gain, pore radius, and stress in both the oxide and substrate are provided, and the theoretical calculated results agree well with the reported experimental results. The results reveal large stress in the oxide layer during the oxidation process. By comparing the results of ZrB2 with different volume fractions of SiC, it is found that ZrB2 with higher volume fraction of SiC has more excellent oxidation resistance and smaller stress.

The synthesis of aluminum nitride (AlN) powders from aluminum (Al) particles via a thermal nitridation process was carried out at high temperature (>900 °C) with a long reaction time (∼several hours). This study proposes a two-stage plasma-chemical synthesis process to efficiently minimize the agglomeration of Al particles, reduce the reaction time and temperature, and promote the formation of AlN powders. In the first stage, partially nitrided Al powders were produced at temperatures lower than 600 °C in atmospheric-pressure microwave N2 plasma. The particle size of the as-prepared powders was similar to that of the original Al powders. In the second stage, the reaction temperature was increased to 700–800 °C and the reaction time was less than 5 min in N2 plasma. Well-dispersed AlN powders with almost no agglomeration were produced. Moreover, the particle size was lower than that of the original Al.

Sintered zirconium carbide (C/Zr ≈ 0.95) was studied by pulsed electrical heating method with microsecond duration. Thermophysical properties such as Joule energy, heat of melting, the specific heat, and electrical resistance were measured in the temperature range of 2500–5000 K by this method for the first time. The steep increase of the specific heat just before melting may be associated with the formation of nonequilibrium pairs point Frenkel defects at high temperatures under fast heating. It was established that the melting of the carbide occurs in the temperature range: solidus—3450 K and liquidus—3850 K, that is close to the values presented in some equilibrium phase diagrams of the system Zr–C. This means that there is no shift of the phase transition points at the heating rates up to 108 K/s, and makes it possible to use this method for the study of high temperature behavior of the complex substances. The comparison of the data of measured properties with the literature data is provided.

To clarify the effect of bainite in microstructure on hydrogen diffusion and trapping behavior and susceptibility to hydrogen assisted cracking of API grade linepipe steel, three specimens with different fraction of bainite in the microstructure are used. Firstly, hydrogen diffusion and trapping behaviors of the steels are studied by utilizing the electrochemical permeation technique. For fundamental analysis on the experimental data, a variety of diffusion parameters were determined by curve-fitting with a theoretical diffusion equation based on numerical finite difference method (FDM). It indicates that the steel with higher fraction of bainite exhibits much higher sub-surface hydrogen concentration and much lower apparent hydrogen diffusivity. This behavior can be understood by the fact that the steel containing higher fraction of bainite in the microstructure has higher concentration of reversible traps and consequent larger diffusible hydrogen, leading to much slower diffusion kinetics of hydrogen atoms. Consequently, the susceptibility to hydrogen induced cracking (HIC) and sulfide stress cracking (SSC) of the steel with higher fraction of bainite increases significantly.

The hydrogenation behavior of Ti–44Al–6Nb (at.%) alloy was studied at temperature range of 1373–1693 K, and the effect of hydrogen on hot deformability was tested on Gleeble-1500D thermo-simulation machine. It is found that the lnCH increases linearly with 1/T, and hydrogen content increases with increasing of hydrogen time and flow rate logarithmically. The positive heat of solution of hydrogen denotes that hydrogen absorption in TiAl alloys is an endothermic reaction. The results also show that hydrogen promotes the lamellar colony size and lamellar spacing because that hydrogen can promote the diffusion of elements. There is more residual B2 phase in the hydrogenated alloy revealing that hydrogen stabilizes the B2 phase during hydrogenation. The nanohardness and elastic modulus of the alloy are decreased from 4.4 and 213.5 GPa to 4.2 and 199.8 GPa after hydrogenation with 0.033 wt% H. Thermal simulation results show that the peak stress is decreased by 30% after hydrogenation with 0.033 wt% H which corresponds to decreasing the deformation temperature by about 50 K. This is attributed to hydrogen-promoted dynamic recrystallization and dislocation movement.

X-ray diffraction (XRD), transmission Mössbauer spectroscopy, and vibrating sample magnetometry were used to study the influence of precipitates on the magnetic properties of aged Fe–Cr–Mo alloys. XRD patterns and Mössbauer spectra showed that the alloys have body-centered cubic structure similar to that of α-Fe. Small amounts of precipitates were also identified with relative fraction found to be related to Mo content, aging times, and temperatures. Magnetic measurements showed that the increase in the density of precipitates contributes significantly to the increase in the magnetic hardness of the material. This mechanism is related to a process of pinning of magnetic domain walls. It was also found that saturation magnetization is affected by the Mo content in the alloy. The techniques used in this work were shown to be very useful to understand the mechanisms through which the formation of precipitates affects the magnetic properties of the alloys and may be used as complement to the usual microscopy-based techniques for this purpose.

A Cu–0.13Cr–0.074Ag (wt%) alloy has been synthesized by the nonvacuum melting and casting followed by thermal-mechanical treatment, and microstructure and mechanical properties have been tailored to make a trade-off between the strength and the electrical conductivity. Results illuminated that the designed alloy has a tensile strength of 473 MPa, a hardness of 140 HV, a yield strength of 446 MPa, an elongation of 10.5%, and an electrical conductivity of 94.5% IACS. Microstructure observations of the samples aged at 480 °C showed that: an fcc structure Cr-phase with a cube-on-cube orientation relationship with the Cu matrix was formed as aged for 15 min, while an ordered bcc structure Cr phase with B2 structure formed as aged for 2 h. The 3DAP results revealed that the Cr was formed to be precipitates and the Ag was formed as solutes distributing evenly in matrix. The high electrical conductivity was ascribed to the Cr element precipitated from the Cu matrix, Ag dissolved in the Cu matrix had little effect on the scattering of Cu electron.

The surface hardening of Cu is an effective way to keep good electrical conductivity and increase chemical inertness. Here, Cr and Zr are introduced into Cu films to stabilize N and increase the film hardness. CuN-based alloy films are prepared on single-crystal Si(100) substrates using magnetron sputtering. Cu(Cr, N) films are mainly composed of Cu and Cr2N nanocrystals while Cu and Zr2N nanocrystals compose Cu(Zr, N) films. The thermal stability of the ternary films comes from the strong interaction between Cr (or Zr) and N which is contributing to the generation of stable nitrides. In terms of resistivity and hardness, the Cu(Cr, N) and Cu(Zr, N) films prepared at the N2/Ar ratio of 1/10 show preferable properties. Especially, the Cu86.1Zr6.1N7.8 film exhibits the highest hardness (∼4.7 GPa) and lowest resistivity (63.6 μΩ·cm). The chemical inertness of Cu film can also be improved by adding Cr–N and Zr–N. These ternary films are expected to apply for Cu surface nitrogenization.

This study examined the effects of a variety of metallurgical factors on the electrochemical corrosion behavior of superaustenitic stainless steel welds. First, the effects of the sigma (σ)-phase on the corrosion behavior were studied by means of a three-dimensional-atom probe. Cr and Mo depletion areas formed around the σ-phases which are precipitated in the interdendritic area were clearly observed. Second, the effects of oxide inclusion on the pitting corrosion of the steel welds were analyzed. The utilization of high resolution transmission electron microscope clearly demonstrated that the thickness and Cr content of the passive film formed on the steel surface decreased significantly with decreasing distance to the oxide inclusion, resulting in a deterioration of the corrosion resistance. Third, the effects of alloying elements, Cu and Al, were evaluated using an electrochemical polarization technique. This confirmed that Cu has a detrimental effect on the resistance to localized corrosion of the steel. The addition of Al up to 0.25 wt% had no significant effects on corrosion resistance in a chloride environment despite the presence of an Al-based oxide layer (Al2O3) on the outermost surface.

Thermal stability of pulsed laser deposited (PLD) nanocrystalline tantalum was explored through in situ transmission electron microscopy (TEM) annealing over the temperature range of 800–1200 °C. The evolution of the nanostructure was characterized using grain size distributions collectively with electron diffraction analysis and electron energy loss spectroscopy (EELS). Grain growth dynamics were further explored through molecular dynamics (MD) simulations of columnar tantalum nanostructures. The as-deposited grain size of 32 nm increased by only 18% at 1200 °C, i.e., 40% the melting point of tantalum, conflicting with the MD simulations that demonstrated extensive grain coalescence above 1000 °C. Furthermore, the grain size remained stable through the reversible α-to-β phase transition near 800 °C, which is often accompanied by grain growth in nanostructured tantalum. The EELS analysis confirmed the presence of oxygen impurities in the as-deposited films, indicating that impurity stabilization of grain boundaries was responsible for the exceptional thermal stability of PLD nanocrystalline tantalum.

In the present study, the effect of heat treatment on microstructure and mechanical properties of gas tungsten arc (GTA) welded 15CDV6 high strength low alloy steel is discussed. Experiments were carried out based on Taguchi L9 orthogonal array to weld 15CDV6 plate of thickness 3.7 mm. The input parameters considered in this work were current, voltage, and welding speed. Tensile strength, microhardness, and impact strength were measured as performance characteristics. Post weld heat treatment was carried out on the weldments to study its effect on the properties of weldments and microstructures were characterized using optical microscope and the X-ray diffraction analysis revealed the presence of MO2C and VC precipitates in the weld. Post weld heat treatment of the GTA welded samples and base metal successfully produced properties required for aerospace applications.

The metadynamic recrystallization (MDRX) behavior of a medium carbon Cr–Ni–Mo alloyed steel 34CrNiMo was investigated using two-stage hot compression test on a Gleeble thermal-mechanical simulator in the temperature range of 1273–1423 K, strain rate range of 0.1–5.0 s−1, and interval times of 0.5–5 s. The softening of the flow stress at the second stage of compression and microstructure observation confirm the occurrence of MDRX at the elevated temperatures within very short interval time. Then the MDRX softening fraction was calculated based on the flow stress curves. The results indicate that the MDRX softening fraction increased with increasing interval time, deformation temperature, and strain rate. The kinetics of MDRX softening behavior was established using Avrami equation and the apparent activation energy of MDRX for 34CrNiMo steel was evaluated as 93 kJ/mol. The predicted results show good agreements with the experimental ones, indicating the efficiency of proposed kinetics equation.

The constitutive equation was established based on the consideration of strain compensation to describe the hot deformation behavior of low carbon reduced activation ferritic/martensitic (RAFM) steels at the temperatures of 850–1050 °C and the strain rates of 0.01–10 s−1. The result indicates that the flow stress is increased with the increase of strain rate but decreased with increase of deformation temperature. During the hot deformation process, the increase of temperature is beneficial to attain the complete dynamic recrystallization (DRX). However, excessively high temperature leads to grow up of dynamic recrystallized grain. Higher strain rate leads to finer recrystallized grains. The material constants (α, n, A) and deformation activation energy (Q) are calculated by the regression analysis. The increase of strain caused the decrease of Q, indicating the DRX occurred more easily. In addition, the developed constitutive equation could accurately predict the hot deformation behavior of the low carbon RAFM steel.

Modern hydrogen technology requires materials with high capacity storage. Many metals and alloys form cheap metal hydrides that can contain a high volume density of hydrogen. The quaternary alloy Cr–Fe–Ti–Zr with Laves phases is one promising hydrogen storage material. Understanding phase equilibria properties is essential to improve the Laves phases’ hydrogen storage capacity. In this work, the thermodynamic description of two constituent ternary phase materials, Cr–Ti–Zr and Fe–Ti–Zr are investigated using the Calphad method. A set of Gibbs energies was optimized during this work and good agreement between modeling and available experimental information was found. Moreover, a new thermodynamic model for a binary Fe–Zr system was developed based on recent experimental investigation about intermetallic compounds FeZr2 and FeZr3. Obtained in this work results can find application in development of new hydrogen storage materials.

A theoretical model for the Functionally Graded Shape Memory Alloy (FG-SMA) cylinders subjected to internal pressure is investigated. The gradient properties in this work are embodied in the Young’s modulus and Poisson’s ratio gradient through the thickness of the cylinder. The critical transformation stresses and maximum formation strain are all assumed to be constant. Combining the elasticity and exponential function of the Young’s modulus and Poisson’s ratio with the different gradient parameters, the elastic stress distributions and displacement distributions for the FG-SMA cylinder under the internal pressure are obtained, respectively. To get the theoretical solution, the Tresca yield function and the ideal elastic–plastic constitutive model are selected for the shape memory alloy to illustrate the phase transformation. The relationships between the internal pressure and total strain at the internal radius with different gradient parameters are then given, and the results show that the total strains are greatly influenced by the different parameters.