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The potential to use single-crystal sapphire optical fiber as an alternative to silica optical fibers for sensing in high-temperature, high-pressure, and chemically aggressive harsh environments has been recognized for several decades. A key technological barrier to the widespread deployment of harsh environment sensors constructed with sapphire optical fibers has been the lack of an optical cladding that is durable under these conditions. However, researchers have not yet succeeded in incorporating a high-temperature cladding process into the typical fabrication process for single-crystal sapphire fibers, which generally involves seed-initiated fiber growth from the molten oxide state. While a number of advances in fabrication of a cladding after fiber-growth have been made over the last four decades, none have successfully transitioned to a commercial manufacturing process. This paper reviews the various strategies and techniques for fabricating an optically clad sapphire fiber which have been proposed and explored in published research. The limitations of current approaches and future prospects for sapphire fiber cladding are discussed, including fabrication methods and materials. The aim is to provide an understanding of the past research into optical cladding of sapphire fibers and to assess possible material systems for future research on this challenging problem for harsh environment sensors.

We have evaluated controlled decarburization as a method for probing the effect of alloying elements on ferrite growth from austenite. The technique permits the exploration of longer-time ferrite layer growth; it minimizes the effects of interface structure on ferrite growth; and it permits the isolation of the effects of temperature and alloying element concentration on ferrite/austenite interface motion. The study of the decarburization of initially homogeneous Fe-C-Ni alloys was complemented by experiments using specimens with a controlled nickel concentration gradient. Although the decarburization method yields consistent results at longer times, it is found to be less appropriate for the study of initial ferrite growth. Nucleation in the gas/solid interface region, coupled with uncertainties about the precise time of decarburization, leads to large relative errors at the earliest times. For these reasons, the method is considered a valuable complement to studies based on precipitation boundary conditions.

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To relieve the environmental issues of sewage sludge (SS) disposal and greenhouse gas (GHG) emission in China, we proposed an integrated method for the first time to simultaneously deal with these two problems. The hot slags below 920 °C could act as a good heat carrier for sludge gasification and the increasing CO2 concentration in CO2/O2 atmospheres enhanced the production of CO and H2 at 400–800 °C. Three stages of syngas release were clearly identified by Gaussian fittings, i.e., volatile release, char transformation and fixed carbon reaction. Additionally, the effect of sulfur retention of slags and the synergy effect of the stabilization of toxic elements in the solid residuals were discovered in this study. Furthermore, a novel prototype of multiple industrial and urban systems was put forward, in which the produced CO + H2 could be utilized for direct reduced iron (DRI) production and the solid residuals of sludge ash and glassy slags would be applied as cementitious materials. For a steel plant with an annual production of crude steel of 10 million tons in China, the total annual energy saving and GHG emission reduction achieved are 3.31*105 tons of standard coal and 1.74*106 tons of CO2, respectively.

The current work investigates dynamic phenomena at the microstructural level during iron and manganese recovery from the liquid FeO-CaO-SiO 2 -MnO slags using an oxidation method. A hot-stage-equipped confocal scanning laser microscope (CSLM) was used to analyze the kinetic behavior of crystallization in synthetic slags. Based on observed precipitations on cooling in the 1273 K (1000°C) to 1873 K (1600°C) temperature range, a timetemperature-transformation (TTT) diagram has been created. The crystallization studies were conducted in air.