The fluoride ion is crystal chemically very similar to the hydroxyl ion, substituting for hydroxyl in many minerals in which hydrogen bonding is not important. Fluoride substitutions are particularly common in 2:1 layer silicates, such as micas, illites and smectites. The brick and tile industries, which use naturally occurring clays as their primary raw materials, have devoted considerable effort to understanding fluorine evolution during firing of the raw materials due to increasingly stringent fluorine emission regulations. In order to understand fluorine evolution from ceramic raw materials, we have studied a number of phyllosilicate materials used in making bricks. X-ray powder diffraction and fluorine analyses were combined with heating experiments and thermogravimetric analysis to evaluate the chemical and structural changes taking place on heating. Fluorine remained in 2:1 layer silicates to higher temperatures than did hydroxyl, but it behaved identically to hydroxyl in the kaolinite studied. In all cases, fluorine evolution coincided with structural breakdown of the clay host. These results show that fluorine evolution will consistently occur during firing of clay raw materials, and the problems of fluorine emission cannot be readily solved by simple variations of firing temperatures or times.

The Raman spectra of many kaolins are dominated by bands from ancillary anatase. Fired samples of a commercial anatase-bearing kaolin from the Jari River deposit in Brazil showed significant variations of Raman spectra as a function of the firing temperature. The spectra showed the full range of anatase bands up to a firing temperature of 900°C. From 950°C the background increased significantly, leading to an unfavorable signal/noise ratio that allowed observation of only the most intense (Eg) band at ~144 cm−1. X-ray diffraction (XRD), however, confirmed that this band, which persists up to 1200°C, results from anatase. Two factors may be responsible for the high thermal stability of anatase in this sample: its relatively large particle size of ~120 nm and possible reactions with Si and Al that become liberated during kaolinite breakdown. When evaluated with circumspection, Raman and XRD data on anatase can serve as ‘thermometers’ to elucidate the thermal history of fired anatase-bearing kaolins and other anatase-bearing clays.

Additive manufacturing (AM) has made long strides in the recent past and rapidly evolved into a promising alternative in specific applications. The aircraft industry is not an exception to this. The true just-intime production possibility is critical for the aircraft maintenance industries, though the lack of material freedom is a major hurdle. Several fire-retardant materials were investigated for AM in the aerospace context, but mainly for fused deposition modeling (FDM). The material consolidation constraints in FDM led to the expansion to the use of selective laser sintering (SLS) to some extent. Nevertheless, the material options are still limited, proprietary, and lack scientific insights into the material consolidation mechanics. Attempts are made in this paper to fill this gap, evaluating a new fire-retardant material for processing by SLS. Experiments conducted to ascertain the material, process, structure, and consolidation relationships indicated energy density levels 0.062–0.070 J/mm2 with laser power 13 W and scan speed varied slightly around 390 mm/s to give the best laser sintering and mechanical property results in polyetherimide powders.

The Numidian Aquitano-Burdigalian nappe from the Jijel region (northeast Algeria) shows an important clay-rich basal series. In this study, seven representative clay samples were collected from the Djimla and El-Milia areas of this region in order to analyse their mineralogy using X-ray diffraction and Fourier-transform infrared spectroscopy, chemical composition by X-ray fluorescence, particle size, plasticity, morphology by scanning electron microscopy and their ceramic properties. Samples were prepared by pressing the clays and firing them at 800–1100°C, and bulk density, water absorption, linear firing shrinkage, weight loss and bending strength values were determined on the fired samples. The clays are mainly composed of kaolinite and illite, with a small amount of 10–14 Å interstratified clay minerals and chlorite, associated with quartz and feldspars. The main oxides in the samples were SiO2, Al2O3 and Fe2O3. The clays may be classified as moderately plastic according to their Atterberg limits. Ceramic tiles have been produced by dry pressing. At all tested firing temperatures, the clays present the required standard values for linear firing shrinkage, weight loss, bulk density, water absorption and bending strength, and they are defect-free. The main transformations were observed at 1000°C with the appearance of new crystalline phases. The measured technological properties of the investigated deposits confirm that the Numidian clays from the Djimla and El-Milia regions are suitable materials for the production of high-quality structural ceramics.

Illitic clay from the locality of Liepa, Latvia, was investigated using dynamic thermomechanical analysis during the heating and cooling stages of firing. Differential thermal analysis, thermogravimetry, thermodilatometry, X-ray diffraction and porosimetry were also performed to shed light on the processes influencing the elastic properties of clay. The increase in the Young's modulus (YM) at low temperatures was linked to the release of physically bound water. Above 850°C, the bulk density and YM both increased as a consequence of sintering. The YM was more sensitive to the progress of sintering compared to dimension changes. The YM values continued to increase during cooling until the glass-transition temperature was reached. At this temperature, the first microcracks caused by the differences in thermal expansion coefficients of the present phases were expected to appear. The YM showed a sharp V-shaped minimum at the β → α transition of quartz, which was a result of alternation of the mechanical radial stresses around the quartz grains. When the transition of quartz was completed, the YM continued to decrease because microcracks were still being created at the boundaries between the different phases. The decrease of the YM during cooling from the glass-transition temperature down to room temperature was ~50% for all of the firing temperatures and isothermal periods applied.

The physical properties of three montmorillonites before and after heating were studied by reflectance colorimetry, X-ray diffraction (XRD) and infrared (IR) and Mössbauer spectroscopies. Colorimetric data, though not directly relatable to sample mineralogy, provide cheap and rapid information on the temperatures of sample breakdown. X-ray diffraction provides information on sample mineralogy and the transformations that develop during firing and allows the major phases formed in the course of firing to be identified, whereas IR data provide information on water and hydroxyl loss and the final breakdown of the montmorillonite structure. Mössbauer spectroscopy gives information on Fe2+ oxidation (where applicable) and reveals subtle variations in Fe site coordination and Fe mineralogy, including the formation of Fe oxides – that can be quantified in proportions as low as 0.1% – following structural breakdown of the montmorillonites.

Black-glazed tea bowls from the Jian area of Fujian province, China, were analyzed to understand the physical basis of their visual appearance and the special glaze effects of nucleation, crystal growth, control of glaze flow, and hare’s fur and spotted patterns that have frustrated modern and ancient factories that are unable to produce acceptable replicas. The black-glazed Jian bowls are divided into two distinct groups called “Hare’s Fur” and “Oil Spot”. Black glazes and bodies from the Jian kilns are rich in iron and calcium oxides, made from a plentiful local refractory dark red clay, and fired in hill-climbing dragon kilns. Twenty-six sherds were analyzed from the collection made by James Plumer at the kiln site in 1935 [1]. Analyses were conducted using optical microscopy, Xeroradiography, scanning electron microscopy (SEM-EDS) and electron microprobe analysis (WDS), and petrographic thin section analysis to reverse engineer some of the microstructure, composition and thermal history of Jian ware.

This paper presents a theory of the labor market matching process in terms of incentive-based, two-sided search among heterogeneous agents. The matching process is decomposed into its two component stages: the contact stage, in which job searchers make contact with employers, and the selection stage, in which they decide whether to match. We construct a theoretical model explaining two-sided selection through microeconomic incentives. Firms face adjustment costs in responding to heterogeneous variations in the characteristics of workers and jobs. Matches and separations are described through firms' job offer and firing decisions and workers' job acceptance and quit decisions. Our calibrated model for the United States can account for important empirical regularities, such as the large volatilities of labor market variables, that the conventional matching model cannot.

A novel resistive device with a floating electrode (RFED) has been manufactured as a stack of layers Cu/TaOx/Pt/TaOx/Cu in a crossbar array comprising two single resistive switches merged antiserially at the common inert Pt floating electrode. The device exhibits four states HRS/HRS, HRS/LRS, LRS/HRS and LRS/LRS, where HRS and LRS are the high and low resistance states, respectively, with only LRS/LRS being fully conductive. When the voltage on one Cu electrode is increased to a value Vth-on(A), a conductive nanofilament (CF) in switch A is formed, while suppressing CF formation in switch B. When the voltage is then extended to negative bias, a sudden jump in the I-V characteristics is observed at Vth-on(B), when the 2nd CF in switch B is formed rendering the RFED device fully conductive. If the current surge just after the formation of CF in 2nd switch exceeds the reset current of the 1st CF, the 1st CF ruptures shortly thereafter, i.e. the conductive state is destroyed as soon as it has been created. This property proves valuable for applications in neural networks where a generation of a current pulse at a critical threshold is required. The height and the time width of the firing pulse is an inherent property of the device and can be controlled by the parameters of the individual switches and their set/reset operations.

Common igniters such as black powder, benite, and boron potassium nitrate (BKNO3) are routinely employed in all calibers of gun systems. Armament Research Development Engineering Center (ARDEC) has pursued efforts to improve the ignition of gun propellants which has been demonstrated to be the root cause of many tribulations for gun systems. We have developed several extrudable nitrocellulose-BKNO3 based igniter materials that are more energetic, and exhibit smaller ignition delay times than most traditional igniters. We have demonstrated this via static firing. High speed video during static testing has demonstrated significantly more consistent, intense, and rapid flame generation in comparison to Benite leading to improved ignition effectiveness of the propellant bed.

For low-temperature firing of Pb0.94Sr0.06(Ni1/2W1/2)0.02(Mn1/3Nb2/3)0.07(Zr0.51Ti0.49)0.91O3 (PNW–PMN–PZT) system, BiFeO3 is selected as the sintering agent. In this study, the effects of BiFeO3 addition and sintering temperature on the microstructures and piezoelectric properties of the ceramics were investigated in detail. The ceramic with 10 mol% BiFeO3 sintered at 950 °C possesses optimal microstructure and piezoelectric properties. However, with the increase of sintering temperature the lower relative density, abnormal grain growth, and secondary phase accumulated at grain boundaries are observed, which deteriorates the piezoelectric properties. For the ceramics with different BiFeO3 addition sintered at 950 °C, the densification process and the grain growth are improved by suitable BiFeO3, while the morphotropic phase boundary (MPB) moving to the Ti-rich direction and the shrinkage of crystal cell occur. However, extra BiFeO3 inhabits the grain growth and introduces more cavities into the materials. Because of the microstructural changes that accompany the addition of BiFeO3 and the resulting decrease in sintering temperature, the maximum values of the piezoelectric properties are attained. By doping with 10 mol% BiFeO3, the sintering temperature of the PNW–PMN–PZT system can be lowered successfully from 1200 to 950 °C, while the excellent electric properties are kept.

The spectroscopic properties of Ba2Mg(BO3)2:Ce3+ and Ba2Mg(BO3)2:Eu2+ in vacuum-ultraviolet-vis range were investigated. The 5d crystal-field splitting components and the barycenter of Ce3+, the lowest 5d levels, the emission and the Stokes shifts of Eu2+ and Ce3+ in the host lattices, as well as the host-related absorption are identified and discussed in terms of the crystal structure of the host lattice.

Anode-supported planar solid oxide fuel cell (SOFC) was successfully fabricated by a single step co-firing process. The cell comprised of a Ni + yittria-stabilized zirconia (YSZ) anode, a YSZ electrolyte, a Ca-doped LaMnO3 (LCM) + YSZ cathode active layer, and an LCM cathode current collector layer. The fabrication process involved tape casting of the anode, screen printing of the electrolyte and the cathode, and single step co-firing of the green-state cells at 1300°C for 2 hours. The maximum power densities were 1.50W/cm2 at 800°C, and 0.87W/cm2 at 700°C with humidified hydrogen (97% H2-3% H2O) as fuel and air as oxidant. The experimentally measured I-V curves were fitted into a polarization model to obtain cell parameters including the area specific ohmic resistance, exchange current density, effective binary diffusivity of hydrogen and water vapor in the anode, and that of oxygen and nitrogen in the cathode. The cell was also tested at 800°C with various compositions of humidified hydrogen to evaluate the cell performance at high fuel utilization, and the maximum power densities were 1.30W/cm2 with 75.7% H2-24.3% H2O, 0.94W/cm2 with 49.4% H2-50.6% H2O, and 0.49W/cm2 with 27.3% H2-70.7% H2O.

The synthesis of efficient ZnTe powder phosphors is very difficult due to its high moisture sensitivity and chemical instability during processing. In this study, an efficient ZnTe:O powder phosphor for x-ray imaging application was successfully synthesized by vacuum firing ZnTe powder prepared from ZnTe bulk crystals ball-milled in an O2 atmosphere. The phosphors were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, photoluminescence, and cathodoluminescence (CL) measurements and found to exhibit a luminescent efficiency three times that of ZnTe:O prepared by ZnO doping. The ZnTe:O samples exhibited a deep red emission centered at 680 nm and a CL decay time of 1.1μs.

Lutetium nitride (LuN), an end member of a new quaternary system Si3N4–SiO2–Lu2O3–LuN, was synthesized by direct nitridation of a lutetium metal. The nitridation extent of the lutetium ingot (10 × 5 × 2 mm) reached about 97% by heating at 1600 °C for 8 h with an applied N2 pressure of 0.92 MPa; the initial shape of the bulk metal was maintained in the course of nitridation. The resulting nitrided lutetium possessed a moderately low oxygen content (∼0.7 wt%), which enables the preparation of uncharacterized high nitrogen-containing phases in the Lu–Si–O–N system.