Small, light weight and multifunctional electronic components are attracting much attention because of the rapid growth of the wireless communication systems and microwave products in the consumer electronic market. The component manufacturers are thus forced to search for new advanced integration, packaging and interconnection technologies. One solution is the low temperature cofired ceramic (LTCC) technology enabling fabrication of three-dimensional ceramic modules with low dielectric loss and embedded silver electrodes. During the past 15 years, a large number of new dielectric LTCCs for high frequency applications have been developed. About 1000 papers were published and ∼500 patents were filed in the area of LTCC and related technologies. However, the data of these several very useful materials are scattered. The main purpose of this review is to bring the data and science of these materials together, which will be of immense help to researchers and technologists all over the world. The comme...

Low loss dielectric materials for LTCC applications: a review

Nanomaterials have emerged as an amazing class of materials that consists of a broad spectrum of examples with at least one dimension in the range of 1 to 100 nm. Exceptionally high surface areas can be achieved through the rational design of nanomaterials. Nanomaterials can be produced with outstanding magnetic, electrical, optical, mechanical, and catalytic properties that are substantially different from their bulk counterparts. The nanomaterial properties can be tuned as desired via precisely controlling the size, shape, synthesis conditions, and appropriate functionalization. This review discusses a brief history of nanomaterials and their use throughout history to trigger advances in nanotechnology development. In particular, we describe and define various terms relating to nanomaterials. Various nanomaterial synthesis methods, including top-down and bottom-up approaches, are discussed. The unique features of nanomaterials are highlighted throughout the review. This review describes advances in nanomaterials, specifically fullerenes, carbon nanotubes, graphene, carbon quantum dots, nanodiamonds, carbon nanohorns, nanoporous materials, core–shell nanoparticles, silicene, antimonene, MXenes, 2D MOF nanosheets, boron nitride nanosheets, layered double hydroxides, and metal-based nanomaterials. Finally, we conclude by discussing challenges and future perspectives relating to nanomaterials.

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Nanomaterials: a review of synthesis methods, properties, recent progress, and challenges

With the rapid arising of information technology, microwave absorbing materials (MAMs) are playing an increasingly significant role in electronic reliability, healthcare, and national defense security. Hence, development of high performance MAMs with thin thickness, low density, wide bandwidth, and strong absorption has attracted great interests. Recently, taking graphene as MAMs for high-performance electromagnetic (EM) wave attenuation has grabbed considerable attention, owing to their low density, high specific surface area, strong dielectric loss, and high electronic conductivity. Furthermore, in order to address the interfacial impedance mismatching of the sole graphene materials, incorporation of other lossy materials has been widely studied as the imperative solution to improve its MA performance. In this review, we introduce the theory of microwave absorption and summarize recent advances in the fabrication of graphene-based MAMs, including rational design of the microstructure of pure graphene and tunable chemical integrations with polymers, magnetic metals, ferrites, ceramics, and multicomponents composites. The key point of enhancing MA in graphene-based MAMs is to regulate their EM properties, improve of impedance matching, and create diversified loss mechanisms. Furthermore, the shortcomings, challenges, and prospects of graphene-based MAMs are also put forward, which will be helpful to people working in the related fields.

Graphene-based microwave absorbing composites: A review and prospective

The porous three-dimensional (3-D) flower structures assembled by numerous ultrathin flakes were favor for strengthen electromagnetic absorption capability. However, it still remains a big challenge to fabricate such kind of materials. In this study, an easy and flexible two-step method consisting of hydrothermal and subsequent annealing process have been developed to synthesize the porous 3-D flower-like Co/CoO. Interestingly, we found that the suitable heat treatment temperature played a vital role on the flower-like structure, composition, and electromagnetic absorption properties. In detail, only in the composite treated with 400 °C can we gain the porous 3-D flower structure. If the annealing temperature were heated to 300 °C, the Co element was unable to generate. Moreover, when the annealing temperature increased from 400 to 500 °C, these flower-like structures were unable to be kept because the enlarged porous diameter would wreck the flower frame. Moreover, these 3-D porous flower-like structures...

Porous Three-Dimensional Flower-like Co/CoO and Its Excellent Electromagnetic Absorption Properties

Recent progress in synthesis, properties and potential applications of SiC nanomaterials

The rational design and fabrication of SnO2-based anode materials could offer a powerful way of effectively alleviating their large volume variation and guaranteeing excellent reaction kinetics for electrochemical lithium storage. Herein, we present an ultrarapid, low-cost, and simple microwave-assisted synthesis of ultrathin SnO2 nanosheets at the gram-scale. The two-dimensional (2D) anisotropic growth depends on microwave dielectric irradiation coupled with surfactant structural direction, and is conducted under low-temperature atmospheric conditions. The ultrathin 2D nanostructure holds a great surface tin atom percentage with high activity, where the electrochemical reaction processes could be facilitated that highly dependent on the surface. Compared with 1D SnO2 nanorods, the ultrathin SnO2 nanosheets exhibit remarkably improved electrochemical lithium storage properties with a high reversible capacity of 757.6 mAh g–1 at a current density of 200 mA g–1 up to 40 cycles as well as excellent rate capa...

Microwave-Assisted and Gram-Scale Synthesis of Ultrathin SnO2 Nanosheets with Enhanced Lithium Storage Properties

CoxFe3−xO4 (x = 0–1) spheres are synthesized via a solvothermal reaction using ethylene glycol (EG) as a solvent They are characterized, and the results show that the prepared spheres are mainly 300–500 nm in diameter and constituted by small grains For the EG solution containing stoichiometric ingredients (atomic ratio of Co2+:Fe3+ = 1:2), the obtained spheres are Co09Fe21O4 at 200 °C (sphere A) and Co074Fe226O4 (sphere B) at 300 °C, whose crystallites are 23 nm and 30 nm in size, respectively VSM measurements reveal improved properties with sphere B Variations of complex permittivity and permeability for different composite (75% mass ratio of spheres) have been studied as a function of frequency The calculated reflectivity value indicates that the composite containing sphere A displays better microwave absorption capability The minimum reflection loss reaches −41089 dB at 1208 GHz, with a matching thickness of 2 mm The dielectric loss contributes even more than magnetic loss in the frequency range of 3–14 GHz The synergistic effect of dual losses makes the submicrosphere a promising absorbent in X and Ku bands The composite consisting of sphere B is inferior in dielectric properties owing to ferrous ion migration from octahedral to tetrahedral sites and due to the big crystallites lacking defects After the calcination treatment of the spheres at 700 °C, the dielectric loss turns out to be low due to the disappearing Fe2+ ↔ Fe3+ pairs in adjacent octahedral sites and the loss of defects Variations of the cobalt ratio in spheres can change the resonance frequency and crystallinity of the spheres and ultimately the minimum reflection loss and corresponding frequency band The microwave absorption properties of mixed magnetite and cobalt ferrite spheres are influenced by the cationic stoichiometry and crystalline integrity

Solvothermal synthesis of CoxFe3−xO4 spheres and their microwave absorption properties

Growth and characterization of single-crystal ZnSe nanorods via surfactant soft-template method

In the present work, mesoporous NiCo2O4 hollow nanocubes are synthesized using a "coordinating etching & precipitating" (CEP) route. The hollow nanocubes are characterized using SEM, TEM, XRD, XPS and BET methods. The hollow nanocubes have a uniform morphology of 300-500 nm, a high surface area of 134.52 m(2) g(-1) and a mesoporous structure of 2.4-6 nm. These mesoporous NiCo2O4 hollow nanocubes exhibit the specific capacitance of 795.6 F g(-1) at a constant discharge current density of 1 A g(-1). The high specific capacitance and the stability of the NiCo2O4 hollow nanocube electrode are attributed to its large specific surface area and mesoporous structure. The specific capacity retention is 97.5% at a current density of 1 A g(-1) and 96.1% at a current density of 2 A g(-1) over 2000 charge-discharge cycles. The high specific capacitance and excellent cyclic stability indicate that NiCo2O4 hollow nanocubes are excellent supercapacitor electrode materials.

Hierarchical mesoporous NiCo2O4 hollow nanocubes for supercapacitors

SiC-C coaxial nanocables were synthesized via a one-step and low-temperature (∼250 °C) solvothermal process using SiCl4, C6Cl6 and Na as starting materials. The orientation accumulation of β-SiC tapered crystallite nanowires coated by an amorphous carbon sheath was formed. The mechanism of the growth of SiC nanocables at low temperature is discussed.

Huazhang Zhai

Papers

Microwave-Assisted and Gram-Scale Synthesis of Ultrathin SnO2 Nanosheets with Enhanced Lithium Storage Properties

Solvothermal synthesis of CoxFe3−xO4 spheres and their microwave absorption properties

Growth and characterization of single-crystal ZnSe nanorods via surfactant soft-template method

Hierarchical mesoporous NiCo2O4 hollow nanocubes for supercapacitors

One-step synthesis of orientation accumulation SiC-C coaxial nanocables at low temperature