Increasing seed oil content in Brassica species through breeding and biotechnology

Increasing the seed oil content of Brassica species and other major oilseed crops is of paramount importance in maintaining a future supply of vegetable oil for a growing global population. Currently, commercially‐available Brassica species with enhanced seed oil content have all been developed through plant breeding. Many quantitative trait loci including gene interactions are involved in the control of seed oil content. Despite this complexity, manipulation of specific steps in storage lipid biosynthesis using genetic engineering has resulted in transgenic lines of Brassica napus with increased seed oil content. Recent studies suggest that engineering of seed oil content can be guided using methods in metabolic analysis.     

Integration Concepts for the Fabrication of LTCC Structures

At the Keck Smart Materials Integration Laboratory at Penn State University, low-temperature co-fired ceramic (LTCC) material systems have been used to fabricate a number of devices for a variety of applications. This article presents an overview of the integration of the concepts and materials that we have used to achieve miniaturization and unique device function. Examples of microwave filters, metamaterial antennas, and a dielectrophoretic cell sorter will be presented, with emphasis on device modeling and design, prototype construction methods, and test results.     

Resistance Degradation in Y(Cr,Mn)O3–Y2O3 Composite NTC Ceramics in Hostile Environments

A series of composite, negative temperature coefficient (NTC) ceramics were carefully processed with compositions based on the Y(Cr,Mn)O₃+Y₂O₃ system and these were investigated for resistance stability in hostile environments. This specific system is of interest for high-temperature automobile thermistors, however either through the processing or in use of these, materials can be exposed to reducing atmospheres at temperatures around 900°–1000°C. The thermochemical processes at intermediate temperatures and low     <10⁻¹⁰atm can influence the resistance of the given ceramics. Through an impedance analysis it is determined that the resistance increase is associated primarily with a grain boundary resistance increase. The grain and grain boundary elements are modeled through parallel constant phase element and resistance equivalent circuits connected in series. Possible origins of the defect chemistry being controlled through high-temperature processes at the sintering are partial Schottky reactions that are compensated through a superoxidation reaction on cooling and aging. The reduction process reversed the superoxidation reaction and transited the grain boundary surfaces to ionically compensated B-site vacancies with oxygen vacancies.     

<Emphasis Type=Italic>In Situ</Emphasis> Characterization of Strength and Distortion During Powder Metal Processing

Thermogravimetric analysis and dilatometry are two common in situ measurement techniques used in powder processing to obtain information regarding thermal debinding and sintering. However, these two techniques provide negligible information regarding critical phenomena such as distortion or cracking. This paper discusses newer characterization techniques used to measure in situ strength evolution to help understand defect generation during the thermal debinding process. The information obtained from these in situ measurement techniques assists in intelligent design of optimal thermal cycles and in selection of binders targeted at manufacturing dense sintered components with minimum defects and distortion. The paper discusses examples of applications developed based on the information provided by in situ characterization of strength and distortion.     

The infrared infiltration and joining of advanced material

JOM - Infrared processing is a newly developed technique for materials processing. Key features include rapid processing, simplicity, and low cost. Because of the rapid processing, very little...     

Effect of powders and binders on material properties and molding parameters in iron and stainless steel powder injection molding process

It is essential to study and optimize multiple objective functions such as binder system design, feedstock, part geometry, mold design, and processing conditions in order to develop a successful powder injection molding process. A powder with different combinations of binder systems and a binder system with different combinations of powder systems were investigated with a combined experimental and simulation study. First, an experimental rheological study was performed to evaluate the influence of the powder/binder combinations on the rheological behavior and thermal stability of carbonyl iron and stainless steel powder injection molding (PIM) feedstocks. Second, based on the characterization of the feedstock, the simulation study revealed that the pressure-related parameters such as wall shear stress, injection pressure, and clamping force were mainly dependent on the binder system and not much on the powder characteristics, in the range of particle attributes studied. Third, to the temperature-related parameters such as melt front temperature difference and cooling time, binder selection is more critical than powder selection. Fourth, for the velocity-related parameter, maximum shear rate, the selection of both powder and binder system is critical in control. It is demonstrated that the simulation study is essential in the development stage for successful PIM.     

Structural drivers controlling sulfur solubility in alkali aluminoborosilicate glasses

If the direct feed approach to vitrify the Hanford's tank waste is implemented, the low activity waste (LAW) will comprise higher concentrations of alkali/alkaline-earth sulfates than expected under the previously proposed vitrification scheme. To ensure a minimal impact of higher sulfate concentrations on the downstream operations and overall cost of vitrification, advanced glass formulations with enhanced sulfate loadings (solubility) are needed. While, the current sulfate solubility predictive models have been successful in designing LAW glasses with sulfate loadings <2 wt.%, it will be difficult for them to design glass compositions with enhanced loadings due to our limited understanding of the fundamental science governing these processes. In this pursuit, this article unearths the underlying compositional and structural drivers controlling the sulfate solubility in model LAW glasses. It has been shown that the preferentially removes non-framework cations from the modifier sites in the silicate network, thus, leading to the polymerization in the glass network via the formation of ring-structured borosilicate units. Furthermore, though the sulfate solubility slightly decreases with increasing Li⁺/Na⁺ in the glasses, the prefers to be charge compensated by Na⁺, as it is easier for to break Na–O bonds instead of Li–O bonds.     

IR transmission prediction,processing, and characterization of dense La2Ce2O7

High-throughput computation, based on density functional theory (HT-DFT), is used to predict the bounds for optical transparency, from the ultraviolet to the infrared, for materials in the pyrochlore family. The HT-DFT approach adopted here uses an initial screening from Materials-Project database, with millions of calculated properties. Band gaps and phonon spectra were calculated from selected pyrochlore crystal structures taken from the Materials Project database. Short and long wavelength bounds for optical transparency were calculated for chemistries with stable, cubic structures. The calculations predict that La₂Ce₂O₇ has one of the broadest range of transparency for the pyrochlore family. Based on these calculations, dense polycrystalline samples of La₂Ce₂O₇ were produced by sintering and hot-isostatic pressing. Transparency was characterized by methods that did not require large samples with high optical quality, obtaining 7.15 and 7.5 µm at 95% and 90% normalized transmittance, respectively. Bandgap calculations suggest a lower bound of UV transparency cut-off of 0.3 µm. The infrared wavelength cut-off is higher than that reported for other pyrochlores, and higher than for yttria, zirconia, or other common infrared transparent ceramics. We discuss our prediction and characterization methods as well as the suitability of pyrochlores for mid- and far-infrared optical applications.