Abstract Nano-hydroxyapatite (nano-HA) has been widely studied as a promising biomaterial because of its potential mechanical and biological properties. In this article, different synthesis methods for nano-HA were summarized. Key factors the nano-HA, including reactant concentration, effects temperature, PH, additives, aging time, sintering, separately investigated. The performances depend str...

An effort is underway to develop a prototype Proton Exchange Membrane (PEM) Fuel Cell breadboard system for fuhlre space applications. This prototype will be used to develop a comprehensive des ign basis for a space-rated PEM fuel cell powerplant. The prototype system includes reactant pressure regulators, ejector-based reactant pumps, a 4-kW fuel cell stack and cooling system, and a passive, m...

This work develops a one-dimensional model of an alkaline anion-exchange membrane direct glycerol fuel cell (AEM-DGFC) for cogeneration of tartronate and electricity. The model is validated against steady state and dynamic experiments, and shows good agreement. Steady state modeling includes anode and cathode losses and predicts the single cell polarization and power density curves. Coupled mas...

The objective of this study is to use a new style of waved flow channel instead of the plane surface channel in the proton exchange membrane fuel cell (PEMFC). The velocity, concentration, and electrical performance with the waved flow channel in PEMFC are investigated by numerical simulations. The results show that the waved channel arises when the transport benefits through the porous layer a...

Understanding the effect of two-phase flow in the components of proton exchange membrane fuel cells (PEMFCs) is crucial to water management and subsequently to their performance. The local water saturation in the gas diffusion layer (GDL) and reactant channels influences the hydration of the membrane which has a direct effect on the PEMFC performance. Mass transport resistance includes contribu...

Traditional chemical kinetics may be inappropriate to describe chemical reactions in microdomains involving only a small number of substrate and reactant molecules. Starting with the stochastic dynamics of the molecules, we derive a master-diffusion equation for the joint probability density of a mobile reactant and the number of bound substrate in a confined domain. We use the equation to calc...

The BIAcore is an instrument for measuring rate constants in real time by using a surface–volume geometry. Though current models for the resulting reaction include transport effects for the reactant in solution, they do not account for spatial nonuniformities in the reactant attached to the wall. This work accounts for such nonuniformities and establishes that in the limit of small Damköhler nu...

Subtle features of the reaction front formation in the A+B-->0 reaction are reported for the initially random and equal A+B reactant distribution. Three nonclassical parameters (initial linewidth, minimum, and maximum), for each interparticle gap and nearest neighbor distance distributions, are derived, as a function of time, using Monte Carlo simulations. These empirical front measures and the...

The following study deals with the characteristics of the reaction to form BaSO4 and BaCO3 from Na2SO4 and Na2CO3, respectively, using BaS as the other reactant. These reactions would theoretically increase the efficiency of the chemical recovery process in papermaking to near 100% by completely converting Na2SO4 to Na2S and Na2CO3 to NaOH. Kinetic data were collected, and it was determined tha...

Hydrogen sulfide is a toxic and odorous compound present in biogas produced by the anaerobic digestion of biosolids and other organic materials. Reactive absorption of hydrogen sulfide into aqueous ferric sulfate solution is a direct process for H S removal and Sulfur recovery. Apart from sulfur, only H O is 2 2 generated in the process and consequently, no waste treatment facilities are requir...