There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Light-emitting diodes (LEDs) are excellent candidates for general lighting because of their rapidly improving efficiency, durability, and reliability, their usability in products of various sizes, and their environmentally friendly constituents. Effective lighting devices can be realized by combining one or more phosphor materials with chips. Accordingly, it is very important that the architecture of phosphors be developed. Although numerous phosphors have been proposed in the past several years, the range of phosphors that are suitable for LEDs is limited. This work describes recent progress in our understanding of the prescription, morphology, structure, spectrum, and packaging of such phosphors. It suggests avenues for further development and the scientific challenges that must be overcome before phosphors can be practically applied in LEDs.

Advances in Phosphors for Light-emitting Diodes.

Carbon (C) is a crucial material for many branches of modern technology. A growing number of demanding applications in electronics and telecommunications rely on the unique properties of C allotropes. The need for microwave absorbers and radar-absorbing materials is ever growing in military applications (reduction of radar signature of aircraft, ships, tanks, and targets) as well as in civilian applications (reduction of electromagnetic interference among components and circuits, reduction of the back-radiation of microstrip radiators). 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 carbonaceous 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 carbonaceous inclusions (C black, C nanotube, C fiber, graphene) and the embedding matrix (rubber, thermoplastic). This paper offers a perspective on the experimental efforts toward the development of microwave absorbers composed of carbonaceous 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. Polymercomposites filled with carbonaceous particles provide a versatile system to probe physical properties at the nanoscale of fundamental interest and of relevance to a wide range of potential applications that span radar absorption, electromagnetic protection from natural phenomena (lightning), shielding for particle accelerators in nuclear physics, nuclear electromagnetic pulse protection, electromagnetic compatibility for electronic devices, high-intensity radiated field protection, anechoic chambers, and human exposure mitigation. Carbonaceous particles are also relevant to future applications that require environmentally benign and mechanically flexible materials.

A review and analysis of microwave absorption in polymer composites filled with carbonaceous particles

The extensive development of electronic systems and telecommunications has lead to major concerns regarding electromagnetic pollution. Motivated by environmental questions and by a wide variety of applications, the quest for materials with high efficiency to mitigate electromagnetic interferences (EMI) pollution has become a mainstream field of research. This paper reviews the state-of-the-art research in the design and characterization of polymer/carbon based composites as EMI shielding materials. After a brief introduction, in Section 1, the electromagnetic theory will be briefly discussed in Section 2 setting the foundations of the strategies to be employed to design efficient EMI shielding materials. These materials will be classified in the next section by the type of carbon fillers, involving carbon black, carbon fiber, carbon nanotubes and graphene. The importance of the dispersion method into the polymer matrix (melt-blending, solution processing, etc.) on the final material properties will be discussed. The combination of carbon fillers with other constituents such as metallic nanoparticles or conductive polymers will be the topic of Section 4. The final section will address advanced complex architectures that are currently studied to improve the performances of EMI materials and, in some cases, to impart additional properties such as thermal management and mechanical resistance. In all these studies, we will discuss the efficiency of the composites/devices to absorb and/or reflect the EMI radiation.

Polymer/carbon based composites as electromagnetic interference (EMI) shielding materials

Solution combustion is an exciting phenomenon, which involves propagation of self-sustained exothermic reactions along an aqueous or sol–gel media. This process allows for the synthesis of a variety of nanoscale materials, including oxides, metals, alloys, and sulfides. This Review focuses on the analysis of new approaches and results in the field of solution combustion synthesis (SCS) obtained during recent years. Thermodynamics and kinetics of reactive solutions used in different chemical routes are considered, and the role of process parameters is discussed, emphasizing the chemical mechanisms that are responsible for rapid self-sustained combustion reactions. The basic principles for controlling the composition, structure, and nanostructure of SCS products, and routes to regulate the size and morphology of the nanoscale materials are also reviewed. Recently developed systems that lead to the formation of novel materials and unique structures (e.g., thin films and two-dimensional crystals) with unusual...

Solution Combustion Synthesis of Nanoscale Materials

Low temperature synthesis of ultrafine α-Al2O3 powder by a simple aqueous sol–gel process

Gradient multilayer structural design of CNTs/SiO2 composites for improving microwave absorbing properties

Effect of Mg2+ co-doping on the scintillation performance of LuAG:Ce ceramics

Fabrication, microstructure and properties of highly transparent Nd:YAG laser ceramics

Yttrium aluminum garnet (YAG) precursor was synthesized via a coprecipitation method with aluminum nitrate and yttrium nitrate as raw materials, using ammonium hydrogen carbonate (AHC) as the precipitant. Fine and low-agglomerated YAG powder was obtained by calcining the precursor at 1200 °C. The primary crystallites were measured to be ∼120 nm in size and weakly agglomerated to a particle size of ∼500 nm, indicating a high degree of sinterability. With 0.5 wt% tetraethyl orthosilicate (TEOS) and 0.1 wt% magnesia as sintering aids, transparent YAG ceramics were fabricated by vacuum sintering at 1730–1790 °C for various hours. The influences of sintering temperature and holding time on the microstructure and transmittance of YAG ceramics were discussed.

Yubai Pan

Papers

Low temperature synthesis of ultrafine α-Al2O3 powder by a simple aqueous sol–gel process

Gradient multilayer structural design of CNTs/SiO2 composites for improving microwave absorbing properties

Effect of Mg2+ co-doping on the scintillation performance of LuAG:Ce ceramics

Fabrication, microstructure and properties of highly transparent Nd:YAG laser ceramics

Co-precipitation synthesis route to yttrium aluminum garnet (YAG) transparent ceramics