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Cardioembolic stroke, a subtype of ischemic stroke with the worst prognosis, is quietly threatening public health. We aimed to visualize the development trend and hotspots of research on cardioembolic stroke. A total of 2886 papers about cardioembolic stroke published from 2012 to 2022 were retrieved in the Web of Science Core Collection (WoSCC) database. Further, we performed a bibliometric analysis of these publications, such as generating cooperation maps, co-citation analysis of journals and references, and cluster analysis of keywords. According to the results, cardioembolic stroke research faces many clinical challenges. We obtained the knowledge maps of countries/institutions, authors, journals with high publications and citations, and representative references in this field. Studies about optimal prevention strategies for cardioembolic stroke, identification of cardioembolism in cryptogenic stroke, and prophylactic anticoagulation for patients with embolic stroke of undetermined source (ESUS) or at high risk of left ventricle (LV) thrombus are in the spotlight.

To date, Nao-an capsules are the only Chinese patent medicine primarily prescribed for the primary prevention of stroke.To evaluate the efficacy and safety of Nao-an capsules in the primary prevention of stroke in high-risk patients.A systematic review and meta-analysis of randomized controlled trials.We searched 7 electronic databases and 2 registries from inception to January 13, 2022 for relevant randomized controlled trials. Two independent investigators selected trials, collected data, and judged the risk of bias. We performed a meta-analysis using the Review Manager software.Nine randomized controlled trials involving 14 744 patients at high risk of stroke were included. Nao-an capsules reduced the risk of first stroke compared with no intervention (risk ratio [RR] = 0.49, 95 % confidence interval [CI] 0.29 to 0.82, p = 0.006) or aspirin (RRIn addition to controlling specific risk factors, Nao-an capsules might provide additional preventive effects on first stroke with an acceptable safety profile for populations at high risk of stroke. However, as current evidence is too weak, a firm recommendation depends on further confirmation from more studies with more rigorous methodology.

The disorder trapping induced by supercooling is innovated to promote the formation of chemically disordered solid solution phase in high-entropy alloy (HEA) when the ordered phase is more inclined to form. We design a new MoNbReTaW HEA, consisting of the top five refractory metals with the highest melting points, whose liquidus temperature attains 2788 K. It is featured with a very large negative enthalpy of mixing and a strong mismatch of atomic size. As a result of sluggish atomic diffusion under a sufficient supercooling up to 500 K and consequent disorder trapping at a crystal growth velocity of 15 to 25 m/s, the original single solid solution phase with a conspicuous local chemical ordering transforms into a chemically disordered state. Owing to the decrease of atomic size mismatch, not only the lattice is turned out to be well-aligned but also the dislocation density is reduced. By the supercooling-based rapid solidification approach under electrostatic levitation condition, we successfully achieved the growth of spherical single crystals with 2 to 3.5 mm in diameter and interior misorientation less than 2 angle degrees. The notable suppression of microsegregation helps to enhance the microhardness to 6.8 GPa at the maximum supercooling of 538 K. Disorder trapping contributes to the increase of nanohardness up to 11.2 GPa. The liquid supercooling is capable of strengthening the mechanical property by optimizing the local chemical ordering.

Tungsten oxide (WO3) has received attention as an electrochromic material because of its excellent properties. However, the long switch time and low coloration efficiency of WO3 film limit its use. Herein, a nanocomposite film containing Preyssler-type polyoxometalate (POM) K12.5Na1.5[NaP5W30O110]·15H2O (P5W30) and WO3 nanoparticles has been fabricated by layer-by-layer (LbL) self-assembly methods and characterized by UV-Vis spectra, scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical workstation. Compared to the pure WO3 film, the [P5W30/WO3]20 film has better electrochromic properties. Then, the electrochromic properties of [P5W30/WO3]20 film were studied in different electrolyte. The results indicated that the composite film show high coloration efficiency (191.62 cm2 C− 1), fast switch time (2.58 s, 1.48 s), good CV stability (500 th) in 0.5 M LiClO4/PC electrolyte, and successfully assembled of an electrochromic device. These advantages can make the nanocomposite film become a promising candidate for potential application in electrochromic devices.

Background: Post-stroke cognitive impairment (PSCI) affects more than one-third of stroke patients, and causes much greater harm to long-term function than the initial brain damage. No conventional Western medications have shown convincing clinical effectiveness for treating PSCI. Research shows that Traditional Chinese medicine (TCM) can improve cognitive function in patients. However, the clinical efficacy and safety remain controversial. The aim of this study was to examine the effectiveness and harmful effects of TCMs in the treatment of PSCI.Method: We searched seven databases and two clinical registration websites for randomized controlled trials (RCTs). The revised Cochrane risk of bias tool (RoB 2.0) was used to evaluate the methodological quality and RevMan 5.4 was used for data analysis. This study has been submitted to PROSPERO with registration number is CRD42020149299.Results: We included 34 studies in this review. The results of this study showed that TCM adjuvant therapy improved scores on the MoCA [MD = 2.55, 95% CI (1.56, 3.53), p < 0.00001; MD = 3.07, 95% CI (1.98, 4.17), p < 0.00001 at treatment duration of p < 0.00001; MD = 2.53, 95% CI (1.59, 3.47), p < 0.00001; MD = 2.91, 95% CI (1.26, 4.56), p = 0.0006; MD = 3.11, 95% CI (−0.04, 6.27), p = 0.05 at treatment duration of p < 0.0001; MD = 8.98, 95% CI (4.76, 13.21), p < 0.0001 at treatment duration of p < 0.00001; MD = −2.00, 95% CI (−2.94, −1.06), p < 0.0001 at treatment duration of 3 and 4 months, respectively], NIHSS [MD = −2.48, 95% CI (−4.97, 0.00), p = 0.05; MD = −3.81, 95% CI (−6.21, −1.40), p = 0.002 at treatment duration of p < 0.00001 at a treatment duration of 3 months]. No serious adverse reactions were observed.Conclusion: Despite the significant positive results, the present evidence supports, to a limited extent because of the methodological flaws and herbal heterogeneity, that TCM adjuvant therapy can be used for patients with PSCI. While, further rigorous RCTs are warranted to confirm the efficacy and safety of TCM.Systematic Review Registration:https://www.crd.york.ac.uk/prospero, identifier CRD42020149299.

The rapid solidification mechanism of Ni3Ti intermetallic compound within undercooled Ni75Ti25 and Ni74Ti18Al8 alloys was investigated by electrostatic levitation(ESL) and liquid quenching(LQ) techniques. The dendritic growth velocity of Ni3Ti phase in these two alloys revealed power law relations versus liquid undercooling, whose maximum value was 138.9 mm s−1 for binary Ni75Ti25 alloy at 255 K(0.15TL) undercooling, while it was only 54.7 mm s−1 at 222 K(0.13TL) undercooling for ternary Ni74Ti18Al8 alloy. The crystalline structure of Ni3Ti phase in both alloys was characterized by fine dendrites under LQ state, whereas it displayed faceted growth mode under ESL condition. In addition, the Ni3Ti grains of Ni75Ti25 alloy show a transition from incompletely to completely surrounded by the grain boundaries.

The liquid state property and intermetallic compound growth of Zr2Ni alloy were investigated by electrostatic levitation(ESL) technique. The relation between liquid undercooling and superheating followed a sigmoidal curve, which was probably attributed to the liquid structure transition. This assumption was supported by the density and viscosity measurement of liquid Zr2Ni alloy. Meanwhile, the diffusion-limited growth mechanism of Zr2Ni compound phase was demonstrated by the measured dendritic growth velocity. Within the undercooling range of 70–277 K(0.20 TL), the dendritic growth velocity displayed a parabolic relation versus undercooling, which achieved a maximum value of 27 mm s-1.

Spinel ZnCo2O4 nanorods were synthesized by a simple template-free hydrothermal method in the presence of zinc chloride, cobalt chloride, glucose, and urea. The phase structure, morphology and chemical composition have been characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and the corresponding selected area electron diffraction (SAED). The results showed that the typically porous and poly-crystalline structure was successfully grown on the surface of ZnCo2O4 nanorods. The ZnCo2O4 nanorods were further applied to remove methyl blue (MB), which was used as a model of organic pollutants in aqueous solution. In particular, the maximum equilibrium adsorption capacity of MB in ZnCo2O4 nanorods reaches up to 2400 mg/g, which is higher than that of most adsorbents. The adsorption isotherms and kinetics followed standard Langmuir and pseudo-second-order models, respectively. MB adsorption decreased with increasing solution pH at pH > 7 implying that MB adsorption on ZnCo2O4 nanorods may via chemisorption between negatively charged MB molecular and positively charged adsorption sites on the surface of ZnCo2O4 nanorods. This study provides great promise of using ZnCo2O4 nanorods as adsorbent for removal of pollutant dyes.

The liquid structures of undercooled Zr90Nb10, Zr70Nb30 and Zr50Nb50 alloys were studied by molecular dynamics simulation combined with electrostatic levitation experiments. The densities of three alloys were measured by electrostatic levitation to modify the Zr-Nb potential functions by adjusting parameters in potential functions. In simulation, the atomic packing in Zr-Nb alloys was more ordered at lower temperatures. The Voronoi tessellation analyses indicated Nb-centered clusters were easier to form than Zr-centered clusters although the Nb content was less than 50%. The partial pair distribution functions showed that the interactions among Zr atoms are quite different to that among Nb atoms.

It has been rarely reported that the microwave absorption materials can exhibit excellent low-frequency EM wave absorbing properties. In this paper, we synthesized steady short carbon fibers (SCFs)@TiO2 composites by using simple one-pot hydrothermal process. The conductive short carbon fibers could be separated by TiO2 nanoparticles from each other and reduced the conductivity of composite materials as a whole, meeting the requirements of impedance matching. With the introduction of SCFs content, SCFs@TiO2 composites showed improved tanδE values at low frequencies, implying the enhanced microwave attenuation ability at low and medium frequency. We unexpectedly found that the SCFs@TiO2 composites exhibited very strong absorbing peaks (i.e., −46.3 dB) at low frequencies with relatively thin matching thickness. Interestingly, when the thickness of the SCFs@TiO2 composite was only 1.0 mm, the absorbing bandwidth with a RL value less than −10 dB was over 14.3–16.7 GHz (i.e., absorbing frequency bandwidth is 2.4 GHz).

Hot deformation behavior of a corrosion-resistant nickel-based alloy was studied in temperature range of 1050-1200 °C and strain rate range of 0.001-10 s−1 by employing hot compression tests. An approach of processing map was used to reveal the hot workability and microstructural evolution during the hot deformation. The results show that different stable domains in the processing map associated with the microstructure evolution can be ascribed to different dynamic recrystallization (DRX) mechanisms. The discontinuous dynamic recrystallization (DDRX) grains evolved by the necklace mechanism are finer than those evolved by the ordinary mechanism, respectively, arising from the strong nucleation process and the growth process. If subjected to low temperature and high strain rate, the flow instability domain occurs, due to the continuous dynamic recrystallization (CDRX) based on the evolution of deformation micro-bands within the deformed grains. Based on the processing map, a DRX mechanism map is established, which can provide an idea for designing desired microstructure.

Hot deformation behavior of Nickel-based corrosion-resistant alloy (N08028) was studied in compression tests conducted in the temperature range of 1050-1200 °C and the strain rate range of 0.001-1 s−1. The flow stress behavior and microstructural evolution were observed during the hot deformation process. The results show that the flow stress increases with deformation temperature decreasing and strain rate increasing, and that the deformation activation energy (Q) is not a constant but increases with strain rate increasing at a given strain, which is closely related with dislocation movement. On this basis, a revised strain-dependent hyperbolic sine constitutive model was established, which considered that the “material constants” in the original model vary as functions of the strain and strain rate. The flow curves of N08028 alloy predicted by the proposed model are in good agreement with the experimental results, which indicates that the revised constitutive model can estimate precisely the flow curves of N08028 alloy.

An ultrafast crystal growth velocity of 122 m/s for β–Ti dendrites was achieved at a liquid undercooling of 352 K (0.18Tm) by electrostatic levitation technique. In contrast, most refractory metals attained slower dendrite growth velocities but displayed similar power laws with liquid undercooling. A combined analysis by current dendrite growth theory with molecular dynamics simulation indicates that liquid thermal diffusion rather than solid-liquid (S/L) interface kinetics is still the dominant factor to control dendrite growth. Besides, the atomic-scale thickness of the S/L interface layer may determine the dendrite growth velocity difference for various refractory metals.

HAADF-STEM and HRTEM images of Pt particles. (DOCXÂ 2196Â kb)

Usually, we must use an appropriate support material to keep the metal species stable and finely dispersed as supported metal nanoparticles for industry application. Therefore, the choice of support material is a key factor in determining the dispersion and particle size of the noble metal species. Here, we report the synthesis of a single-atom Pt material in the solution and supported Pt nanoclusters on microporous La2O3 by a one-step acoustic levitation method without any pretreatment/modification of raw oxide. We have strongly contributed to the synthetic methodology of the surface/interfacial heterogeneous catalysts in this study, and this finding could open another door for synthesis of supported metal nanoparticles on porous materials for environmental catalysis. Electronic supplementary material The online version of this article (10.1186/s11671-018-2467-8) contains supplementary material, which is available to authorized users.

Three-dimensional (3D) porous ZnO nanostructures were synthesized via one-pot solvothermal treatment. The structural, morphological and spectral properties were investigated using X-ray diffraction (XRD), N 2 sorption measurement, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Raman spectroscopy, and photoluminescence (PL) spectroscopy. It was found that the minimum reflection loss value of ZnO calcined at 500 °C reached − 5.62 dB at 16.24 GHz with the thickness of 2.5 mm, which had a superior performance of microwave absorption than those uncalcined and calcined at 600 °C. The possible mechanism for the formation of porous ZnO hollow spheres was proposed. The relationship of the ZnO microstructure and the microwave absorption properties was revealed via studying the dielectric loss and interference multi-reflection absorption in this paper as well. In addition, the photoluminescence results show that the uncalcined ZnO and porous hollow ZnO calcined at 500 °C and 600 °C show a narrow and sharp UV emission at 355.8 nm and a relatively broad visible spectra emission at around 423 nm.

Ordered mesoporous carbon (OMC) coated with thorny-like Fe–Ni alloy composites have been successfully synthesized. The electromagnetic (EM) parameters of Fe–Ni alloy/OMC/paraffin wax composites were measured. Interestingly, the μ″ values of Fe–Ni(0.2)/OMC were very negative from ∼7 to 18 GHz and the minimum value was −0.7, which are mainly caused by the eddy current. The reflection loss (RL) values were calculated with the measured EM parameters based on the transmission line theory. Results showed that the effective absorption bandwidth (

The hot deformation behavior of Nickel-based corrosion resistant alloy was studied in the temperature range of 950–1200 °C and the strain rate range of 0.001–10 s −1 by employing hot compression tests. The results show that the peak stress increases with decreasing temperature and increasing strain rate, and the activation energy is about 465 kJ/mol. The processing maps were prepared on the basis of flow stress data. In order to understand the correlation between dynamic recrystallization (DRX) phenomena and efficiencies of hot working domains, the volume fraction of DRX and the grain size in each domain were evaluated. It is observed that the efficiency peaks of the stable domains are associated with DRX nucleation process at high strain rate, with DRX nucleation and growth process at low strain rate and temperature, and with DRX growth process at low strain rate and high temperature. Under the lower temperatures and intermediate strain rates (domain F), the dynamic precipitated sigma phase assists in nucleating DRX and results in the typical “necklace” structure. Finally, the optimum hot working conditions for Nickel-based corrosion resistant alloy are suggested to be based on the processing map.

In this paper, we report a novel strategy for the synthesis of Prussian Blue microcubes via hydrothermal conditions by using K 3 [Fe(CN) 6 ] and glucose for the first time, and then hollow Fe 2 O 3 microboxes have been successfully fabricated by calcination from a Prussian Blue microcube precursors. The phase structures and morphologies were studied using X-ray powder diffraction (XRD), scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and high resolution transmission electron microscopy (HRTEM) with selected area electron diffraction (SAED). The results depict that highly pure and single crystalline monodisperse hollow Fe 2 O 3 microboxes are successfully obtained, which have a diameter ranging from 3 to 5 μm. The optical properties of the Prussian Blue microcubes and hollow Fe 2 O 3 microboxes were observed by photoluminescence spectra.

Amorphous hierarchical NiCo2O4–CoNiO2 hybrids have been successfully fabricated via a facile one-pot hydrothermal route, followed by morphological conversion into urchin-like structured NiCo2O4–CoNiO2 nanorods and irregular-shaped hierarchical NiCo2O4–CoNiO2 polyhedral nanocrystals through air-annealing treatment at 450 °C and 650 °C, respectively. The phase structure, morphology and chemical composition have been characterized in detail. Calcined hierarchical NiCo2O4–CoNiO2 hybrids show improved microwave absorption properties, which are ascribed to the synergistic effect of dielectric CoNiO2 and NiCo2O4 phases. In particular, the calcined hierarchical NiCo2O4–CoNiO2 hybrids at 450 °C exhibit significant enhancement in complex permittivity with respect to others due to their remarkable dipole polarization and interfacial polarization. The maximum reflection loss (RL) of the calcined hierarchical NiCo2O4–CoNiO2 hybrids at 450 °C reaches −42.13 dB at 11.84 GHz with a matching thickness of 1.55 mm, and a relatively broad absorption bandwidth (RL ≤ −10 dB) in the 13.12–17.04 GHz range. Very interestingly, the electromagnetic (EM) wave absorption performance of the hierarchical NiCo2O4–CoNiO2 hybrids shows dependence on the Co2+/Co3+ ratio. The calcined NiCo2O4–CoNiO2 hybrids at 450 °C of the most defect concentration possess the best EM wave absorption ability among all the samples. The results suggest that appropriate interactions between the building blocks in hybrids can guide us to design and fabricate highly efficient EM wave absorption materials.

We reported a facile approach to prepare peculiar porous α-Fe2O3, γ-Fe2O3 and Fe3O4 nanospheres by combining a facile hydrothermal route with a calcination process in Ar or H2 atmosphere. The synthesized monodisperse porous α-Fe2O3 nanospheres with uniform average diameters of ~ 60 nm in fact contained randomly distributed pores. A close view further revealed that there are two types of pores, one is large mesopores (ca. 15–20 nm) in the center, and the other is small mesopores (ca.

The dendritic growth and thermal expansion of isomorphous refractory Nb–5%Zr, Nb–10%Zr, and Nb–15%Zr alloys were studied by electrostatic levitation technique. The obtained maximum undercoolings for the three alloys were 534 (0.2T L), 498 (0.19T L), and 483 K (0.18T L), respectively. Within these undercooling ranges, the dendritic growth velocities of the three alloys all exhibited power laws, and achieved 38.5, 34.0, and 27.1 m s−1 at each maximum undercooling. The microstructures were characterized by coarse dendrites at small undercooling, while they transformed into refined dendrites under large undercooling condition. In addition, the measured thermal expansion coefficients of solid Nb–Zr alloys increased linearly with temperature. The values at liquid state were more than double of those at solid state, which also displayed linear dependence on temperature.

The need for microwave absorbers and radar-absorbing materials is ever growing in military applications as well as in civilian applications. Whatever the application for which the absorber is intended, weight reduction and optimization of the operating bandwidth are two important issues. A composite absorber that uses nanooxide particles in combination with a polymer matrix offers a large flexibility for design and properties control, as the composite can be tuned and optimized via changes in both the nanooxide inclusions (Ni/OMC, γ-Fe2O3@C, C@Ni–NiO, iron oxide, and ZnO) and the embedding matrix (paraffin and epoxy resin). This chapter offers a perspective on the experimental efforts toward the development of microwave absorbers composed of nanooxide inclusions in a polymer matrix. The absorption properties of such composites can be tailored through changes in geometry, composition, morphology, and volume fraction of the filler particles. Polymer composites filled with nanooxide particles provide a versatile system for probing at the nanoscale physical properties of fundamental interest and of relevance to a wide range of potential applications.

We reported the preparation of C@Ni–NiO core–shell hybrid solid spheres or multi-shelled NiO hollow spheres by combining a facile hydrothermal route with a calcination process in H 2 or air atmosphere, respectively. The synthesized C@Ni–NiO core–shell solid spheres with diameters of approximately 2–6 μm were in fact built from dense NiO nanoparticles coated by random two-dimensional metal Ni nanosheets without any visible pores. The multi-shelled NiO hollow spheres were built from particle-like ligaments and there are a lot of pores with size of several nanometers on the surface. Combined Raman spectra with X-ray photoelectron spectra (XPS), it suggested that the defects in the samples play a limited role in the dielectric loss. Compared with the other samples, the permeability of the samples calcined in H 2 and air was increased slightly and the natural resonance frequency shifted to higher frequency (7, 11 and 14 GHz, respectively), leading to an enhancement of microwave absorption property. For the sample calcined in H 2 , an optimal reflection loss less than − 10 was obtained at 7 GHz with a matching thickness of 5.0 mm. Our study demonstrated the potential application of C@Ni–NiO core–shell hybrid solid sphere or multi-shelled NiO hollow sphere as a more efficient electromagnetic (EM) wave absorber.

Various sizes, fractions and morphologies of interdendritic σ phase in the as cast N08028 alloy due to different solidification conditions are characterised. Dissolution behaviours of the secondary phase in both the as cast and the forged alloys are investigated during heat treatment at 1100, 1150 and 1200°C. A recently developed analytical model, subjected to necessary modification, is applied to describe the dissolution process of σ phase in the alloys with and without prior hot deformation. A recipe derived from transformed fraction is applied to evaluate the effective activation energy for dissolution. It has been found that, the prior hot deformation accelerates the dissolution process, which can be attributed to the decreased particle size and the reduced effective activation energy.

Bamboo-like and cubic single-crystalline silicon carbide nanowhiskers (SiCNWs) were synthesized using multiwalled carbon nanotube via a process of calcination in the molten-salt circumstance. The system was heated to 1,250 °C and maintained for 6 h in argon atmosphere, and obtained the sample. The as-prepared sample was characterized by a series of techniques. Especially, the microwave absorption properties of SiCNWs/paraffin composites (30 wt%) were investigated over 2–14 GHz. The result shows the optimal reflection loss can reach −48.1 dB at 13.52 GHz when the thickness of the match is only 1.9 mm. The excellent microwave absorption properties of the SiCNWs/paraffin composites due to the dielectric loss would make it as a promising candidate for the application of absorbing materials. In addition, a possible growth mechanism of SiCNWs was also discussed.

The ordered mesoporous carbon (OMC)/paraffin composites were successfully prepared by a facile physical mixing method and an EMI SE of 21-23 dB was achieved at the OMC loading of 5.69 wt.% in the X band. This indicates that the composites are very suitable for an application as effective and lightweight EMI shielding materials. The EMI shielding of the composite shows an absorption-dominant mechanism, i.e., a contribution shift from reflection to absorption is observed with the increase in OMC loading and frequency. This could be explained by the intrinsic properties (electrical conductivity, complex permittivity and potential large defects) and novel structure of the composites.

Hematite (α-Fe 2 O 3 ), magnetite (Fe 3 O 4 ), and maghemite (γ-Fe 2 O 3 ) micropine dendrites were synthesized by a facile hydrothermal method and oxidation-reduction process. The samples have been thoroughly characterized by various physicochemical techniques. The adsorption ability, quantum efficiency, and the photo-induced charge separation of the electron–hole pair in the samples were demonstrated by the XPS, FTIR, UV–vis, and PL spectroscopy. The α-Fe 2 O 3 showed higher catalytic activity than the other two samples for photocatalytic oxidation of gaseous toluene. This may be attributed to the phase transformation-induced crystal plane effect of the α-Fe 2 O 3 micropine dendrite, which has relatively more reactive crystal planes {0 0 1} and {1 1 0} exposed on the surface of α-Fe 2 O 3 .

Magnetite dendrites/sugar carbon (MDs/SC) nanocomposites, embedding MDs within amorphous SC matrix, were prepared by simple carbonization–reduction method using α-Fe 2 O 3 dendrites (HDs) as precursor of MDs and sucrose as SC source, while still maintain the dendritic shape of the precursor. The morphology, composition, structure and static magnetic properties of the as-prepared MDs/SC nanocomposites were characterized by various techniques thoroughly. Particularly, the electromagnetic and microwave absorption properties of the MDs/SC and MDs paraffin composites (40 wt.%) were compared over 2–14 GHz. The results show that the microwave absorption performance of MDs/SC samples is comparable or even superior to that of MDs case. The absorption band with reflection loss (RL) below −20 dB for one of the MDs/SC samples can cover the whole X-band (8–12 GHz) with thickness of 1.8–2.4 mm when the content of MDs in the MDs/SC nanocomposite is 25.8 wt.%, and the minimum RL can reach −49.9 dB at 12.1 GHz when the layer thickness is only 1.9 mm. The excellent microwave absorption properties of the MDs/SC paraffin composites are attributed to the proper match between the complex permittivity and permeability, and the unique fractal structures of MDs.

Hematite dendrites/polyaniline (HDs/PANI) nanocomposite, i.e. coating HDs with conductive PANI, has been successfully synthesized through a two-step polymerization of aniline monomers on the surface of pre-synthesized HDs for the first time. It is discovered that a lower concentration of HCl (0.02 mol L−1) has only a slight adverse effect on the dendritic structures of the coated HDs, while a higher concentration of HCl (0.04 mol L−1) results in severe damage to the sub-branches of the HDs. The morphology, composition, structure, static magnetic, and spectral properties of the as-prepared pristine HDs and HDs/PANI composites were thoroughly characterized by various physicochemical techniques. Moreover, the electromagnetic and microwave absorbing properties of the HDs and HDs/PANI wax composites were compared in detail. It was found that the frequency of absorption obeys a quarter-wavelength model for both of them, and the HDs/PANI wax composite exhibits far superior microwave absorption properties. This phenomenon can be attributed to the improved dielectric loss abilities and the complementary behaviors resulting from the PANI coatings and fractal-structured HDs.

We propose and demonstrate a new scheme to improve microwave absorption property through polyaniline (PANI)-functionalized Ni-doped ordered mesoporous carbon (OMC) by in situ polymerization method. The polymer-functionalized nanocomposites, embedding polyaniline within ordered mesoporous carbon, exhibit strong and broadband microwave absorption due to its better dielectric loss characteristic. OMC-Ni0.15/PANI exhibits an effective absorption bandwidth (i.e., reflection loss (RL) ≤ −10 dB) of 4.7 GHz and an absorption peak of −51 dB at 9.0 GHz. The absorption peak intensity and position can be tuned by controlling the thickness of the coating.

CeO 2 and Zn-modified CeO 2 microstructures have been synthesized by a facile hydrothermal method and their microwave absorption properties have been investigated in detail. Complex permittivity and permeability of CeO 2 and CeZn paraffin composites have been measured over the range of 2–18 GHz. Excellent microwave absorption properties have been obtained for CeO 2 and CeZn microstructures compared with ZnO nanoparticles. Especially, maximum RL increases with increasing the concentration of CeZn microspheres in the composites and minimal RL value is −35 dB with 70 wt.% CeZn microspheres at 2.0 mm thickness. This phenomenon is attributed to both unique structure properties and geometric effect of CeO 2 and CeZn microstructures.

Electromagnetic and microwave absorbing properties of the ordered mesoporous carbon (OMC) doped by Ni 2 O 3 nanoparticles absorber was investigated for the first time. A minimum reflection loss (RL) value of −39 dB at 10.9 GHz and a broad absorption band with the RL values under −10 dB is obtained in the whole Ku-band and X-band when the thickness is 2.0 mm and 2.8 mm, respectively. It showed far more excellent microwave absorbing properties with respect to undoped Ni 2 O 3 OMC/paraffin composite. This phenomenon could be attributed to the strong cooperative effect between Ni 2 O 3 and OMC.

Microwave absorbing materials composed of ordered mesoporous carbon (OMC) as absorbent and paraffin as matrix were prepared, and their electromagnetic and microwave absorbing properties could be tuned by changing the weight fraction of OMC at 2–18 GHz. The minimum reflection loss (RL) value reached −9.3 dB at 8.0 GHz and the absorption range with RL lower than −5 dB was obtained at 5.8–14.4 GHz for a single-layer absorber filled with 1.98 wt.% OMC at 3.0 mm. If a double-layer structure was adopted, the total thickness of the absorber could be reduced below 2.0 mm and the effective absorption range (RL

Microwave absorbing materials carbonyl iron (CI)-doped Ag/ordered mesoporous carbon (OMC) paraffin wax composites were prepared by colloidal deposition and impregnation methods, and their electromagnetic and microwave absorbing properties were investigated in the frequency ranging from 2 to 18 GHz. The microstructures and chemical compositions of the Ag/OMC and Ag/OMC-CI paraffin wax composites were characterized by TEM, XRD, XPS, SEM and EDS, respectively. The complex permittivity of the paraffin wax composites show dual resonance behavior, resulting from the multi-interfaces among Ag nanoparticles, OMC nanorods, CI and paraffin wax. The magnetic loss was mainly caused by natural resonance and eddy current loss, respectively. The minimum reflection loss (RL) value of Ag/OMC-CI was below −10 dB at 12 GHz, which were superior to those of OMC-CI and Ag/OMC. This phenomenon is attributed to the enhancement of dielectric polarization and magnetic loss.

Electromagnetic (EM) and microwave absorbing properties of highly ordered mesoporous carbon (OMC) supported by ultra-fine gold nanoparticle absorber was investigated for the first time. A minimum reflection loss (RL) value of −32 dB at 9.7 GHz and a broad absorption band with the RL values under −10 dB was obtained in the whole Ku-band and X-band when the thickness was 2.0 mm and 2.8 mm, respectively. Au-doped OMC/paraffin composite showed far more excellent microwave absorbing property with respect to undoped absorber. This could be attributed to the promotion effects of Au nanoparticles on better impedance match between absorber and air.

Gold supported on cobalt oxide has been successfully synthesized through a colloidal precipitation method and tested in toluene and p -xylene total oxidation. It has been demonstrated that the catalytic activity of Au/Co 3 O 4 for toluene and p -xylene oxidation is much higher than that of Au/Al 2 O 3 and Au/MgO in spite of its lower BET surface area and larger gold crystalline size. The enhanced catalytic activity in toluene and p -xylene oxidation has been linked to a high concentration of superficial electrophilic oxygen species and oxygen vacancies, which may be originated from a strong interaction in the colloidal Au–Co 3 O 4 system.