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

Cheap and sensitive gamma-ray detectors are desired for defence, medical and research applications. Solid-state gamma-radiation detectors made from solution-grown perovskites have now been demonstrated for multiple practical applications.

Detection of gamma photons using solution-grown single crystals of hybrid lead halide perovskites

Semiconductor-based thermal neutron detectors provide a compact technology for neutron detection and imaging. Such devices can be produced by externally coatingsemiconductor-charg ed-particle detectors with neutron reactive films that convert free neutrons into charged-particle reaction products. Commonly used films for such devices utilize the 10 B(n,a) 7 Li reaction or the 6 Li(n,a) 3 H reaction, which are attractive due to the relatively high energies imparted to the reaction products. Unfortunately, thin film or ‘‘foil’’ type thermal neutron detectors suffer from self-absorption effects that ultimately limit neutron detection efficiency. Design considerations that maximize the efficiency and performance of such devices are discussed. Theoretical and experimental results from front coated, back coated, and ‘‘sandwich’’ designs are presented. r 2002 Elsevier Science B.V. All rights reserved. PACS: 29.40.W

Design considerations for thin film coated semiconductor thermal neutron detectors—I: basics regarding alpha particle emitting neutron reactive films

A possibility of manufacturing plastic scintillators with efficient neutron/gamma pulse shape discrimination (PSD) is demonstrated using a system of a polyvinyltoluene (PVT) polymer matrix loaded with a scintillating dye, 2,5-diphenyloxazole (PPO). Similarities and differences of conditions leading to the rise of PSD in liquid and solid organic scintillators are discussed based on the classical model of excited state interaction and delayed light formation. First characterization results are presented to show that PSD in plastic scintillators can be of the similar magnitude or even higher than in standard commercial liquid scintillators.

Plastic scintillators with efficient neutron/gamma pulse shape discrimination

Due to events of the past two decades, there has been new and increased usage of radiation-detection technologies for applications in homeland security, nonproliferation, and national defense. As a result, there has been renewed realization of the materials limitations of these technologies and greater demand for the development of next-generation radiation-detection materials. This review describes the current state of radiation-detection material science, with particular emphasis on national security needs and the goal of identifying the challenges and opportunities that this area represents for the materials-science community. Radiation-detector materials physics is reviewed, which sets the stage for performance metrics that determine the relative merit of existing and new materials. Semiconductors and scintillators represent the two primary classes of radiation detector materials that are of interest. The state-of-the-art and limitations for each of these materials classes are presented, along with possible avenues of research. Novel materials that could overcome the need for single crystals will also be discussed. Finally, new methods of material discovery and development are put forward, the goal being to provide more predictive guidance and faster screening of candidate materials and thus, ultimately, the faster development of superior radiation-detection materials.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400030016

Radiation Detector Materials: An Overview

Developments in neutron detection technology during the past three years are reviewed with special emphasis on those technologies with known or possible application to safety, security, or industrial development. The technologies discussed include track detectors, image plates, activation detectors, bubble detectors, proton recoil instruments, time-of-flight instruments, moderating detectors, proportional counters, semiconductor detectors, and scintillation detectors. The review concentrates on advances in detection technology rather than on the use of existing methods for applications. For the purposes of this review, neutron spectrometry is considered to be a subset of the general area of neutron detection.

Recent developments in neutron detection

The phenomenology and present theoretical understanding of energy nonlinearity (nonproportionality) in radiation detection materials is reviewed, with emphasis on gamma-ray spectroscopy. Scintillators display varying degrees and patterns of nonlinearity, while semiconductor detectors are extremely linear, and gas detectors show a characteristic form of nonproportionality associated with core levels. The relation between nonlinear response (to both primary particles and secondary electrons) and spectrometer resolution is also discussed. We review the qualitative ideas about the origin of nonlinearity in scintillators that have been proposed to date, with emphasis on transport and recombination of electronic excitations. Recent computational and experimental work on the basic physics of scintillators is leading towards a better understanding of energy nonlinearity and should result in new, more linear scintillator materials in the near future.

Energy nonlinearity in radiation detection materials: Causes and consequences

In the present work, a Monte Carlo (MC) method has been developed to simulate various quantum mechanical processes for the energy loss of photons and fast electrons. The MC model is demonstrated by application to the interaction of photons with silicon over the energy range from 50 eV to 2 MeV and the subsequent electron cascades. The electron cascade process is commonly represented by two macroscopic parameters, the mean energy required to create an electron–hole pair, W , and the Fano factor, F , describing the electron yield and its variance. At energies lower than 5 keV, W generally decreases with increasing photon energy (from 3.96 to 3.58 eV), and it exhibits a sawtooth variation, as observed previously. However, discontinuities at the shell edges follow the photoionization cross-section, in contrast to previous results. The function, F ( E p ), initially increases with increasing photon energy, E p , to a maximum value of 0.187 around 155 eV, and then decreases at higher energies. Above the K shell edge, F has a value of 0.135. These results are consistent with experimental observations. The simulated distribution indicates that the interband transition and plasmon excitation are the most important mechanisms of electron–hole pair creation, while core shell ionization appears to be significant only at high energies.

Monte Carlo method for simulating γ-ray interaction with materials: A case study on Si

The interaction of X-ray and gamma-ray photons with materials is of fundamental interest to many fields. The interaction of these primary photons with atoms results in the creation of fast electrons. Electron-solid interaction can be determined experimentally by measuring physical quantities, such as scattering cross section, but the partitioning of energy loss into different quantum mechanical processes is important to determine the mean energy required to create an electron-hole pair, W, and the intrinsic variance (or Fano factor, F) for radiation detectors. In the present work, a Monte Carlo (MC) method previously developed has been employed to simulate the interaction of photons with Ge over the energy range from 50 eV to ~1 MeV and the subsequent electron cascades. Various quantum mechanical processes for energy loss of fast electrons, which control the broadening of Fano factor, are investigated in detail. At energies lower than 1 keV, W generally decreases with increasing photon energy from 2.95 to 2.75 in Ge, whereas it has a constant value of 2.64 eV for higher energies. Also, the function, F, decreases with increasing photon energy. Above the L shell edge, F has a value of 0.11 that is smaller than that in Si (0.14). However,more » F exhibits a sawtooth variation, and discontinuities at the shell edges follow the photoionization cross section. These results are in good agreement with experimental measurements. The simulated distribution indicates that the interband transition and plasmon excitation are the most important mechanisms of electron-hole pair creation in Ge, while core shell ionization appears to be significant only at high energies.« less

A.J. Peurrung

Papers

Radiation Detector Materials: An Overview

Recent developments in neutron detection

Energy nonlinearity in radiation detection materials: Causes and consequences

Monte Carlo method for simulating γ-ray interaction with materials: A case study on Si

Gamma-ray interaction in Ge: A Monte Carlo simulation