scholarly journals A Bidirectional Knudsen Pump with a 3D-Printed Thermal Management Platform

Micromachines ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 58
Author(s):  
Qisen Cheng ◽  
Yutao Qin ◽  
Yogesh B. Gianchandani
Keyword(s):  
Thermal Management ◽  
Pore Diameter ◽  
Operating Temperature ◽  
Maximum Flow ◽  
Membrane Thickness ◽  
Average Pore ◽  
Management Platform ◽  
3D Printed ◽  
Knudsen Pump ◽  
Total Membrane

This paper reports on a bidirectional Knudsen pump (KP) with a 3D-printed thermal management platform; the pump is intended principally for microscale gas chromatography applications. Knudsen pumps utilize thermal transpiration, where non-viscous flow is created against a temperature gradient; no moving parts are necessary. Here, a specialized design leverages 3D direct metal laser sintering and provides thermal management that minimizes loss from a joule heater located on the outlet side of KP, while maintaining convective cooling on the inlet side. The 3D-KP design is integrative and compact, and is specifically intended to simplify assembly. The 3D-KP pumping area is ≈1.1 cm2; with the integrated heat sink, the structure has a footprint of 64.2 × 64.2 mm2. Using mixed cellulose ester (MCE) membranes with a 25 nm average pore diameter and 525 μm total membrane thickness as the pumping media, the 3D-KP achieves a maximum flow rate of 0.39 sccm and blocking pressure of 818.2 Pa at 2 W input power. The operating temperature is 72.2 °C at ambient room temperature. In addition to MCE membranes, anodic aluminum oxide (AAO) membranes are evaluated as the pumping media; these AAO membranes can accommodate higher operating temperatures than MCE membranes. The 3D-KP with AAO membranes with 0.2 μm average pore diameter and 531 μm total membrane thickness achieves a maximum flow rate of 0.75 sccm and blocking pressure of 496.1 Pa at 9.8 W at an operating temperature of 191.2 °C.

An Innovative Spherical Fuel Element to Inhibit the Infiltration of Liquid Fluoride Salt in Molten Salt Reactor

2017 ◽  
Author(s):  
Yajuan Zhong ◽  
Jun Lin ◽  
Liujun Xu ◽  
Haitao Jiang ◽  
Zhiyong Zhu
Keyword(s):  
Fuel Element ◽  
Molten Salt ◽  
Pore Diameter ◽  
Coefficient Of Thermal Expansion ◽  
Operating Temperature ◽  
Molten Salt Reactor ◽  
Fluoride Salt ◽  
Average Pore ◽  
Innovative Design ◽  
Density Graphite

To inhibit the infiltration of liquid fluoride salt and easy to load and unload, fuel element in molten salt reactor (MSR) was isostatically pressed with an innovative design: A fuel-free low density graphite core of ≤ 30 mm diameter embedded in fuel-zone shell of ≥ 2.5 mm thickness, and then enveloped in a high density graphite shell of ≥ 5 mm thickness. Bulk density of the spherical fuel element can be designed from the range of 1.65–1.80 g/cm3, which is lower than the density of the liquid fluoride salt to make sure the fuel element can float in the MSR to load and unload. Characteristics of mercury infiltration and molten salt infiltration in graphite shell were investigated and compared with A3-3 graphite to identify the infiltration behaviors. The results indicated that the graphite shell has a low porosity about 9%, and an average pore diameter of 100 nm. The fluoride salt occupation of A3-3 was 10 wt% under 6.5 atm, whereas the salt gain did not infiltrate in graphite shell even up to 6.5 atm. It demonstrated that the outside graphite shell could inhibit the infiltration of liquid fluoride salt effectively. At the operating temperature of MSR (700 °C), thermal conductivity of graphite shell was 13.61 W/m K. The coefficient of thermal expansion (CTE) of outside graphite shell lied in 6.01×10−6 K−1 (α⫽) and 6.15×10−6 K−1 (α⊥) at the temperature range of 25–700 °C. The anisotropies factor of graphite shell calculated by CTE maintained below 1.12, which could meet the requirement of the spherical fuel element (below 1.30). The constant isotropic properties of graphite shell are beneficial for the integrity and safety of the spherical fuel element for a MSR.

scholarly journals Preparation and characterization of porous Al2O3 based on nano-Al2O3 powders and PLA template by microwave sintering

2020 ◽  
Vol 14 (2) ◽  
pp. 128-133
Author(s):  
Zhenhua He ◽  
Shifei Zhu ◽  
Canhui Liu
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Pore Diameter ◽  
Microwave Sintering ◽  
Single Crystal Structure ◽  
Sintered Body ◽  
Filling Rate ◽  
Average Pore ◽  
3D Printed

Macroporous and mesoporous Al2O3 body was prepared using mesh screening shaped polylactic acid (PLA) template. The mesh screening shaped PLA template was made from 3D cylindrical model by adjusting the PLA filling rate at 30 vol.%. After 3D printing, the PLA template was filled with Al2O3 nano-powders and microwave sintered at 1673K for 20min. During the sintering, the PLA template was decomposed and left large pores which could promote sintering of Al2O3. The Al2O3 sintered body showed macroporous structure with the pore size of 100 to 300 nm and also mesoporosity with local single crystal structure. The average pore diameter of mesoporous structures in the Al2O3 sintered body was about 7.6 nm. The Vickers hardness of the porous Al2O3 is 1.254 ? 0.039GPa. The obtained results confirmed that 3D-printed PLA template assisted microwave sintering is a promising technical processing for the fabrication of macroporous and mesoporous Al2O3 with local single crystal structure.

Fuels Desulphurisation by Adsorbtion on Fe / Bentonite

2017 ◽  
Vol 68 (3) ◽  
pp. 483-486
Author(s):  
Constantin Sorin Ion ◽  
Mihaela Bombos ◽  
Gabriel Vasilievici ◽  
Dorin Bombos
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Volume ◽  
Pore Diameter ◽  
Adsorption Process ◽  
Continuous System ◽  
Gas Oil ◽  
Average Pore ◽  
Atmospheric Distillation

Desulfurisation of atmospheric distillation gasoline and gas oil was performed by adsorption process on Fe/ bentonite. The adsorbent was characterized by determining the adsorption isotherms, specific surface area, pore volume and average pore diameter. Adsorption experiments of atmospheric distillation gasoline and gas oil were performed in continuous system at 280�320oC, 5 atm and volume hourly space velocities of 1�2 h-1. The efficiency of adsorption on Fe / bentonite was better at desulphurisation of gasoline versus gas oil.

scholarly journals Photocatalytic activity of Pr-modified TiO2 for the degradation of bisphenol A

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Denise S. Cordeiro ◽  
Fernando L. Cassio ◽  
Larissa Ciccotti ◽  
Thiago L. R. Hewer ◽  
Paola Corio ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Bisphenol A ◽  
Pore Diameter ◽  
Sol Gel ◽  
Bandgap Energy ◽  
Photocatalytic Efficiency ◽  
Average Pore ◽  
X Ray ◽  
Vis Spectroscopy ◽  
Adsorption Desorption

AbstractPraseodymium doped TiO2 nanoparticles were successfully prepared by the sol–gel method and characterized by X-ray powder diffraction, N2 adsorption–desorption isotherm, and UV–vis spectroscopy. The effects of the dopant on the crystallite size, specific surface area, average pore diameter, pore volume, and bandgap energy were investigated. The photocatalytic activity of the catalysts was evaluated by bisphenol A degradation and mineralization, which is a representative endocrine disruptor. Furthermore, under visible light irradiation the Pr-modified TiO2 photocatalysts exhibited higher photocatalytic efficiency than unmodified TiO2. When praseodymium was loaded (1.0–5.0%) onto the surface of TiO2, the rates of degradation and mineralization were increased 3–5 times.

Diffusion of Heavy Oil in SiO2 Model Catalyst and FCC Catalyst

2012 ◽  
Vol 550-553 ◽  
pp. 158-163 ◽  
Author(s):  
Zi Yuan Liu ◽  
Sheng Li Chen ◽  
Peng Dong ◽  
Xiu Jun Ge
Keyword(s):  
Diffusion Coefficient ◽  
Pore Size ◽  
Effective Diffusion Coefficient ◽  
Pore Diameter ◽  
Effective Diffusion ◽  
Model Catalyst ◽  
Average Pore ◽  
Diffusion Factor ◽  
Fcc Catalyst ◽  
Fcc Catalysts

Through the measured effective diffusion coefficients of Dagang vacuum residue supercritical fluid extraction and fractionation (SFEF) fractions in FCC catalysts and SiO2model catalysts, the relation between pore size of catalyst and effective diffusion coefficient was researched and the restricted diffusion factor was calculated. The restricted diffusion factor in FCC catalysts is less than 1 and it is 1~2 times larger in catalyst with polystyrene (PS) template than in conventional FCC catalyst without template, indicating that the diffusion of SFEF fractions in the two FCC catalysts is restricted by the pore. When the average molecular diameter is less than 1.8 nm, the diffusion of SFEF fractions in SiO2model catalyst which average pore diameter larger than 5.6 nm is unrestricted. The diffusion is restricted in the catalyst pores of less than 8 nm for SFEF fractions which diameter more than 1.8 nm. The tortuosity factor of SiO2model catalyst is obtained to be 2.87, within the range of empirical value. The effective diffusion coefficient of the SFEF fractions in SiO2model catalyst is two orders of magnitude larger than that in FCC catalyst with the same average pore diameter. This indicate that besides the ratio of molecular diameter to the pore diameter λ, the effective diffusion coefficient is also closely related to the pore structure of catalyst. Because SiO2model catalyst has uniform pore size, the diffusion coefficient can be precisely correlated with pore size of catalyst, so it is a good model material for catalyst internal diffusion investigation.

Pore Structure and Mechanical Properties of ZrC/SiC Multi-Components Modified C/C Composites

2013 ◽  
Vol 833 ◽  
pp. 159-164 ◽  
Author(s):  
Xiu Qian Li ◽  
Hai Peng Qiu ◽  
Jian Jiao
Keyword(s):  
Mechanical Properties ◽  
Pore Diameter ◽  
Testing Machine ◽  
Average Pore Diameter ◽  
Flexural Properties ◽  
Matrix Interface ◽  
Polymeric Precursor ◽  
Average Pore ◽  
Fiber Matrix Interface ◽  
Injection Apparatus

The ZrC/SiC multi-components modified C/C composites were prepared by using a hybrid precursor containning polycarbosilane and organic zirconium-contained polymeric precursor as impregnant and C/C composites of low density as preform. The porosity, microstructure and mechanical properties of samples were characterized with mercury injection apparatus, scanning electron microscopy and universal electron testing machine respectively. The results show that the porosity and average pore diameter decrease firstly and increase subsequently with the increase of organic zirconium content of the precursor. When the content of organic zirconium is 50%, the porosity and average pore diameter reach minimum which were7.27% and 0.0795um respectively. The most probabilistic pore diameter shifted from 10-100um to 1-10um at the same time; Meanwhile, the flexural properties also increases and drops immediately as the content of organic zirconium in the precursor adds. When the content of organic zirconium is 25%, the flexural strength reaches maximum of 245.20MPa.The improved flexural properties is attributed to the proper bonding of fiber-matrix interface and the low porosity of samples.

Hydrothermal Synthesis of Nanorods/Nanoparticles TiO2 for Photocatalytic Activity and Dye-sensitized Solar Cell Applications

2006 ◽  
Vol 951 ◽  
Author(s):  
Sorapong Pavasupree ◽  
Supachai Ngamsinlapasathian ◽  
Yoshikazu Suzuki ◽  
Susumu Yoshikawa
Keyword(s):  
Photocatalytic Activity ◽  
Surface Area ◽  
Pore Diameter ◽  
Mesoporous Structure ◽  
Energy Conversion Efficiency ◽  
Bet Surface Area ◽  
Average Pore ◽  
Dye Sensitized ◽  
Prepared Material ◽  
20 Nm

ABSTRACTNanorods/nanoparticles TiO2 with mesoporous structure were synthesized by hydrothermal method at 150 °C for 20 h. The samples characterized by XRD, SEM, TEM, SAED, HRTEM, and BET surface area. The nanorods had diameter about 10-20 nm and the lengths of 100-200 nm, the nanoparticles had diameter about 5-10 nm. The prepared material had average pore diameter about 7-12 nm. The BET surface area and pore volume of the sample are about 203 m2/g and 0.655 cm3/g, respectively. The nanorods/nanoparticles TiO2 with mesoporous structure showed higher photocatalytic activity (I3− concentration) than the nanorods TiO2, nanofibers TiO2, mesoporous TiO2, and commercial TiO2 (ST-01, P-25, JRC-01, and JRC-03). The solar energy conversion efficiency (η) of the cell using nanorods/nanoparticles TiO2 with mesoporous structure was about 7.12 % with Jsc of 13.97 mA/cm2, Voc of 0.73 V and ff of 0.70; while η of the cell using P-25 reached 5.82 % with Jsc of 12.74 mA/cm2, Voc of 0.704 V and ff of 0.649.

Electrochemistry at single molecule occupancy in nanopore-confined recessed ring-disk electrode arrays

2016 ◽  
Vol 193 ◽  
pp. 51-64 ◽  
Author(s):  
Kaiyu Fu ◽  
Donghoon Han ◽  
Chaoxiong Ma ◽  
Paul W. Bohn
Keyword(s):  
Single Molecule ◽  
Pore Diameter ◽  
High Signal ◽  
Current Response ◽  
Disk Electrode ◽  
Operating Characteristics ◽  
Electrode Arrays ◽  
Average Pore ◽  
Redox Species ◽  
Metal Insulator Metal

Electrochemical reactions at nanoscale structures possess unique characteristics, e.g. fast mass transport, high signal-to-noise ratio at low concentration, and insignificant ohmic losses even at low electrolyte concentrations. These properties motivate the fabrication of high density, laterally ordered arrays of nanopores, embedding vertically stacked metal–insulator–metal electrode structures and exhibiting precisely controlled pore size and interpore spacing for use in redox cycling. These nanoscale recessed ring-disk electrode (RRDE) arrays exhibit current amplification factors, AFRC, as large as 55-fold with Ru(NH3)62/3+, indicative of capture efficiencies at the top and bottom electrodes, Φt,b, exceeding 99%. Finite element simulations performed to investigate the concentration distribution of redox species and to assess operating characteristics are in excellent agreement with experiment. AFRC increases as the pore diameter, at constant pore spacing, increases in the range 200–500 nm and as the pore spacing, at constant pore diameter, decreases in the range 1000–460 nm. Optimized nanoscale RRDE arrays exhibit a linear current response with concentration ranging from 0.1 μM to 10 mM and a small capacitive current with scan rate up to 100 V s−1. At the lowest concentrations, the average pore occupancy is 〈n〉 ∼ 0.13 molecule establishing productive electrochemical signals at occupancies at and below the single molecule level in these nanoscale RRDE arrays.

Templated fabrication of nanostructured Ni brush for hydrogen evolution reaction

2010 ◽  
Vol 25 (10) ◽  
pp. 2001-2007 ◽  
Author(s):  
Sheng-Chieh Lin ◽  
Yu-Fan Chiu ◽  
Pu-Wei Wu ◽  
Yi-Fan Hsieh ◽  
Cheng-Yeou Wu
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Anodic Aluminum Oxide ◽  
Electroless Deposition ◽  
Pore Diameter ◽  
Pore Channel ◽  
Average Pore ◽  
Anodic Aluminum ◽  
Anodization Process ◽  
Pore Opening

We fabricated a nanostructured brush by carrying out Ni deposition on a through-channel anodic aluminum oxide (AAO) template, followed by removal of the AAO skeleton. The AAO was prepared by a two-step anodization process resulting in pore diameter and thickness of 350 nm and 40 μm, respectively. Subsequently, the AAO underwent an electroless deposition involving sensitization, activation, and Ni plating, in conjunction with polyethylene glycol used as the inhibitor to prevent premature closing of pore opening. After deliberate control in relevant parameters, we obtained a conformal Ni overcoat along every pore channel leading to a reduced average pore diameter of 78 nm. Afterward, the sample was immersed in a KOH solution to remove the AAO structure, forming freestanding Ni tubules in a brush configuration. The nanostructured brush revealed considerable enhancement for hydrogen evolution reaction in both current-potential polarization and galvanostatic measurements, which were attributed to the increment in apparent surface area.

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