scholarly journals Improved Thermal Emitters for Thermophotovoltaic Energy Conversion

2016 ◽  
Author(s):  
Veronika Stelmakh ◽  
Walker R. Chan ◽  
John D. Joannopoulos ◽  
Marin Soljacic ◽  
Ivan Celanovic ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Photonic Crystal ◽  
Energy Conversion ◽  
Temperature Stability ◽  
Square Lattice ◽  
Natural Material ◽  
Efficiency Gain ◽  
High Temperature Stability ◽  
Selective Emitter ◽  
Thermal Emitters

Thermophotovoltaic (TPV) energy conversion enables millimeter scale power generation required for portable microelectronics, robotics, etc. In a TPV system, a heat source heats a selective emitter to incandescence, the radiation from which is incident on a low bandgap TPV cell. The selective emitter tailors the photonic density of states to produce spectrally confined selective emission of light matching the bandgap of the photovoltaic cell, enabling high heat-to-electricity conversion efficiency. The selective emitter requires: thermal stability at high-temperatures for long operational lifetimes, simple and relatively low-cost fabrication, as well as spectrally selective emission over a large uniform area. Generally, the selective emission can either originate from the natural material properties, such as in ytterbia or erbia emitters, or can be engineered through microstructuring. Our approach, the 2D photonic crystal fabricated in refractory metals, offers high spectral selectivity and high-temperature stability while being fabricated by standard semiconductor processes. In this work, we present a brief comparison of TPV system efficiencies using these different emitter technologies. We then focus on the design, fabrication, and characterization of our current 2D photonic crystal, which is a square lattice of cylindrical holes fabricated in a refractory metal substrate. The spectral performance and thermal stability of the fabricated photonic crystal thermal emitters are demonstrated and the efficiency gain of our model TPV system is characterized.

High Temperature Stability of SiC/Ti Interface

2011 ◽  
Vol 685 ◽  
pp. 340-344 ◽  
Author(s):  
Tung Wai Leo Ngai ◽  
Chang Xu Hu ◽  
Wei Zheng ◽  
Heng Xie ◽  
Yuan Yuan Li
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Composite Materials ◽  
Temperature Stability ◽  
Diffusion Path ◽  
Interfacial Stability ◽  
Diffusion Couples ◽  
High Temperature Stability ◽  
High Temperature Structural Material ◽  
Thermal Stability Of

Ti, SiC and their composite materials have been widely used as high temperature structural material. The knowledge of interfacial stability between SiC and Ti is vital in high temperature applications. In this study, SiC/Ti diffusion couples were prepared to investigate the interfacial reactions between SiC and Ti at 1273 K. Phase forming sequence, microstructure and thermal stability of SiC/Ti interface were studied. It was indicated that after annealed at 1273 K for 10 days, 4 reaction layers were formed at the SiC/Ti interface. The diffusion path between SiC and Ti is SiC/Ti3SiC2/Ti5Si3/Ti5Si3+TiC/Ti3Si/Ti. As the annealing time prolong, the thicknesses of these reaction layers increased.

scholarly journals Thermal Stability of Pepper Leaf Extracts

HortScience ◽  
2004 ◽  
Vol 39 (4) ◽  
pp. 855A-855
Author(s):  
Jeff Anderson*
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Tissue Concentration ◽  
Temperature Stability ◽  
High Temperature Stability ◽  
Leaf Extracts ◽  
Acute Heat Stress ◽  
Dependent Change ◽  
Time Dependent Change ◽  
Thermal Stability Of

Acute heat stress can denature and aggregate proteins. The objective of this study was to determine how changes in the chemical and physical environment affected high temperature-induced turbidity and precipitation in pepper (Capsicum annuum L.) leaf extracts. High temperature stability of leaf extracts decreased as the tissue concentration increased. Control extracts exhibited a time-dependent change in resistance to turbidity and precipitate development, but the presence of polyvinylpolypyrrolidone stabilized the extracts. Ethylenediamine-tetraacetic acid had a less marked effect on turbidity and precipitation. Solution thermal stability increased as buffer pH increased from pH 6.0 to 7.0 regardless of whether the pH was adjusted before or after tissue extraction. Mannitol strongly stabilized pepper leaf extracts, but a surfactant lowered the thermal stability.

Thermal stability of TiSi2 films on single crystal and polycrystalline silicon

1991 ◽  
Vol 6 (7) ◽  
pp. 1502-1511 ◽  
Author(s):  
Krishna Shenai
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Single Crystal ◽  
Polycrystalline Silicon ◽  
Temperature Stability ◽  
Process Variations ◽  
Titanium Silicide ◽  
High Temperature Stability ◽  
Crystal Silicon ◽  
Thermal Stability Of

The stability of selectively formed TiSi2 films on single crystal and polycrystalline silicon layers at elevated process temperatures is reported. Extensive electrical and analytical studies were performed to understand the high-temperature stability of TiSi2 films as a function of (i) substrate dopant concentration, (ii) titanium silicide thickness, (iii) silicide formation sequence, and (iv) silicide post-processing steps. It is shown that all four process variations have a profound influence on the thermal stability of TiSi2 films. It is observed that titanium silicide films formed on single crystal silicon are stable at higher processing temperatures compared to those formed on polysilicon substrates under similar conditions. The degradation of high-temperature stability of TiSi2 films on polycrystalline silicon can be related to increased number of defects and grain boundaries. It is shown that TiSi2 films can be successfully used in silicon integrated circuit applications where the post-silicide processing temperatures do not exceed 1000 °C.

Thermal Stability of Nanoscale Multilayered ZrAlN/ZrB2 Coatings

2005 ◽  
Vol 107 ◽  
pp. 137-140 ◽  
Author(s):  
D.J. Li ◽  
J.J. Zhang ◽  
Ming Xia Wang
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Partial Pressure ◽  
Layer Structure ◽  
Temperature Stability ◽  
Substrate Bias ◽  
High Temperature Stability ◽  
Dc Magnetron Sputtering ◽  
Hardness Values ◽  
Thermal Stability Of

Multilayered ZrAlN/ZrB2 coatings were synthesized using a multi-cathode dc magnetron sputtering technique. Effects of substrate bias and N2 gas partial pressure on structural, mechanical properties, as well as thermal stability were investigated. Low bias was beneficial to synthesis of nanolayers with weak internal stress. The nanolayers deposited at lower N2 partial pressure and substrate bias exhibited good high-temperature stability in the crystalline and layer structure, and hardness values were increased significantly after high-temperature annealing.

High Temperature Stability of MGC’s Gas Turbine Components in Combustion Gas Flow Environments

2005 ◽  
Author(s):  
Narihito Nakagawa ◽  
Hideki Ohtsubo ◽  
Kohji Shibata ◽  
Atsuyuki Mitani ◽  
Kazutoshi Shimizu ◽  
...  
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Gas Flow ◽  
Temperature Stability ◽  
High Temperature Strength ◽  
High Temperature Stability ◽  
Exposure Test ◽  
Excellent Thermal Stability ◽  
Combustion Gas ◽  
Flow Environment

Melt growth composites (MGCs) have a unique microstructure, in which continuous networks of single-crystal phases interpenetrate without grain boundaries. Therefore, the MGCs have excellent high-temperature strength characteristics, creep resistance, oxidation resistance and thermal stability in an air atmosphere at very high temperature. In order to investigate the recession behavior of MGCs in combustion gas flow environment, we have just started the exposure tests to evaluate the influence of combustion gas flow environment on MGCs. The MGCs have about 95% of the initial flexural strengths after the exposure test for 10 hours at T = 1500 °C, P = 0.1–0.3 MPa, V = 150–250 m/s, PH2O = 15–45 kPa in the combustion gas flow environment. MGCs have excellent thermal stability and water vapor resistance in comparison with conventional ceramic materials such as Si3N4 and Al2O3 under the high temperature combustion gas flow environment.

Improvement of Thermal Stability of ZrO2-SiO2 Aerogel Modified by Ca(II) Cations

2018 ◽  
Vol 281 ◽  
pp. 105-110 ◽  
Author(s):  
Hang Yuan Zhao ◽  
Xiao Lei Li ◽  
Jian He ◽  
Zhi Peng Hu ◽  
Hui Jun Yu
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Calcium Nitrate ◽  
Temperature Stability ◽  
Secondary Phase ◽  
Ethanol Solution ◽  
Hydroxyl Groups ◽  
High Temperature Stability ◽  
Excellent Thermal Stability ◽  
Surface Hydroxyl

Ca (II) modified ZrO2-SiO2 aerogel (CaZSA) with excellent thermal stability at 1000 °C was prepared by aging the ZrO2-SiO2 wet gel in calcium nitrate (Ca (NO3)2) ethanol solution followed with alcohol supercritical fluid drying method. The reaction between surface hydroxyl groups on the aerogel and Ca (II) ions played an important role in reducing the high temperature activity and inhibiting the particle growth caused by the condensation of hydroxyl groups of aerogel. Moreover, tiny secondary-phase particles, Ca (II) ions, introduced along grain boundaries serve as the pinning particles to inhibit the crystallization of ZrO2-SiO2 aerogel (ZSA). Thus the high-temperature stability of ZSA was significantly improved by surface modification with Ca (II). The specific surface area of CaZSA still maintained 223 m2·g-1 after 1000 °C calcination, which was 52.7% higher than that of ZSA at the same treatment condition.

scholarly journals Efficient Encapsulation of Citral in Fast-Dissolving Polymer-Free Electrospun Nanofibers of Cyclodextrin Inclusion Complexes: High Thermal Stability, Longer Shelf-Life, and Enhanced Water Solubility of Citral

Nanomaterials ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 793 ◽  
Author(s):  
Zeynep Aytac ◽  
Asli Celebioglu ◽  
Zehra Yildiz ◽  
Tamer Uyar
Keyword(s):  
Thermal Stability ◽  
Inclusion Complex ◽  
Shelf Life ◽  
Water Solubility ◽  
Temperature Stability ◽  
Electrospun Nanofibers ◽  
High Temperature Stability ◽  
Fiber Morphology ◽  
Electrospinning Technique ◽  
Beta Cyclodextrin

Here, we report a facile production of citral/cyclodextrin (CD) inclusion complex (IC) nanofibers (NFs) from three types of CDs (hydroxypropyl-beta-cyclodextrin (HPβCD), hydroxypropyl-gamma-cyclodextrin (HPγCD), and methylated-beta-cyclodextrin (MβCD)) by an electrospinning technique without the need of any polymeric carrier matrix. Self-standing nanofibrous webs of citral/CD-IC nanofibers (citral/CD-IC-NF) with uniform fiber morphology have been successfully electrospun from aqueous solutions of citral/CD-IC. Thanks to the inclusion complex formed with CDs, the efficient preservation of citral (up to ~80%) in citral/CD-IC-NFs was observed. In addition, the citral/CD-IC-NFs have shown ~50% preservation of citral for 15 days at room temperature even though citral has a highly volatile nature. The enhanced thermal stability of citral (~100–300°C) in citral/CD-IC-NFs compared to pure citral (~50–165°C) has been observed. Moreover, citral/CD-IC-NFs tended to disintegrate in water very quickly. To summarize, citral was efficiently encapsulated in citral/CD-IC-NFs, and these citral/CD-IC-NFs have been shown to be fast dissolving. In citral/CD-IC-NFs, citral/CD-ICs have enhanced water solubility of citral along with high-temperature stability and a longer shelf-life.

An Experimental Study on Thermal Stability of Age-Hardenable Aluminium Alloys Modified by Scandium Inoculation

2015 ◽  
Vol 830-831 ◽  
pp. 387-390
Author(s):  
P.K. Mandal
Keyword(s):  
Thermal Stability ◽  
Grain Refinement ◽  
Aluminium Alloys ◽  
Early Stage ◽  
Effective Means ◽  
Temperature Stability ◽  
Age Hardening ◽  
Recrystallization Temperature ◽  
High Temperature Stability ◽  
Grain Boundary Pinning

The Al-Zn-Mg system is a familiar age-hardenable 7xxx series of aluminium alloy. Aluminium alloys are gaining wide popularity in aeronautical, automotive, and transportation industries. Scandium (Sc) has the ability to refine grain size of cast aluminium structure. It has been possible to achieve an ideal combination of strength, density, and thermal stability because of the unique age-hardening characteristics of Sc. Moreover, low solid solubility of Sc in aluminium is responsible for the improvement of the microstructure and mechanical properties when added in small amounts (≤0.6 wt.%). Further, inoculation is an effective means of grain refinement in liquid state of as-castaluminium alloys. So, density of GP zones formation and early stage of ageing effects assessment main priority in the present work. However, coherent precipitates like ScAl3are finely dispersed to provide thermal stability by increasing recrystallization temperature. Hence, the improvement in the high temperature stability of aluminium alloys (7xxx series) may be attributed to the grain boundary pinning (e.g. Zenerdrag mechanism) by the fine precipitates.In this paper, the relationship between the mechanical behavior and microstructure characteristics of Al-Zn-Mg-Sc based alloys are investigated to understand the thermal stability mechanism of grain refinement and dispersive precipitation.

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