Article | REF: P1050 V4

Texture of divided materials Specific surface area of powders or nanoporous materials

Authors: Françoise ROUQUEROL, Jean ROUQUEROL, Isabelle BEURROIES, Philip LLEWELLYN, Renaud DENOYEL

Publication date: May 10, 2017, Review date: October 23, 2020

You do not have access to this resource.
Click here to request your free trial access!

Already subscribed? Log in!


Overview

Français

ABSTRACT

This article gives an introduction to the measurement of the specific surface area of powders and porous materials by gas adsorption. After listing the main features and terminology of these materials, it presents Brunauer, Emmett and Teller’s (BET) theory of gas adsorption, and Langmuir’s from which it derives. The experimental aspects of isotherm determination, especially by gas adsorption manometry, are then presented. Lastly the methods most often used for determining the specific surface area are examined in detail: the BET method, de Boer’s t method and Sing’s ?S method. Special attention is paid to the meaning and usefulness of the areas obtained.

Read this article from a comprehensive knowledge base, updated and supplemented with articles reviewed by scientific committees.

Read the article

AUTHORS

  • Françoise ROUQUEROL: Professor Emeritus, Aix-Marseille University - Aix-Marseille Université-CNRS, Laboratoire MADIREL Unité mixte de recherche n° 7246, France

  • Jean ROUQUEROL: Emeritus Research Director, CNRS - Aix-Marseille Université-CNRS, Laboratoire MADIREL Unité mixte de recherche n° 7246, France

  • Isabelle BEURROIES: Senior lecturer at Aix-Marseille University - Aix-Marseille Université-CNRS, Laboratoire MADIREL Unité mixte de recherche n° 7246, France

  • Philip LLEWELLYN: CNRS Research Director - Aix-Marseille Université-CNRS, Laboratoire MADIREL Unité mixte de recherche n° 7246, France

  • Renaud DENOYEL: CNRS Research Director - Aix-Marseille Université-CNRS, Laboratoire MADIREL Unité mixte de recherche n° 7246, France

 INTRODUCTION

The aim of this article is to use gas adsorption to determine one of the main characteristics of porous or powdery materials: the extent of their surface area. The scale considered ranges from 1 nm to 1 mm for particles and from 0.1 to 50 nm for pores.

Divided solids" (either powdery or porous) are ubiquitous in nature and in industrial processes.

In nature, the surface area and porosity of a soil largely determine its capacity to retain not only water, but also fertilizing, weed-killing, phytosanitary or even toxic substances (heavy metals, possibly radioactive). Sand, in its most divided form, is capable of remaining suspended in the air, where it forms an aerosol of dust that can be transported over thousands of kilometers, before being precipitated to the ground by rainfall: this is how pink or yellow dust from the Sahara ends up on cars in the south of France the day after it rains.

In industrial processes, the same phenomenon, once mastered, controlled and, above all, channeled, is today the basis for pneumatic conveying of powders: food flours, cements, sulfur, talcum powder, etc.... Another special feature of very fine powders is their ability to "sinter", i.e. to weld particles together at a temperature well below the material's melting point. This property is the basis of the pottery and ceramics industries, but it also applies to metal powders: this is how the Etruscans made gold statuettes in furnaces that were incapable of reaching the melting temperature of gold (1,063°C), thanks to the mass setting of compacted gold powder.

However, it is the adsorbent properties of porous materials that have given rise to the most diverse applications. Man has long exploited the adsorbent properties of coal or volcanic porous stones for medical purposes (to draw venom from a wound), or the porosity of pottery to enable cooling by evaporation of the water passing through it. Today, we're inventing new adsorbents that can be fine-tuned (in terms of granulometry, pore size and surface chemical functions) to suit the intended applications.

It is easy to understand that the efficiency of these adsorbents is not unrelated to the extent of their surface area, hence the interest in reliable measurement of this characteristic. To this end, this article successively examines the textural complexity of divided materials and the way in which the adsorption of a gas by a solid can provide access to its surface area using the most common methods. The quality and exact significance of the results obtained are also discussed.

You do not have access to this resource.

Exclusive to subscribers. 97% yet to be discovered!

You do not have access to this resource.
Click here to request your free trial access!

Already subscribed? Log in!


The Ultimate Scientific and Technical Reference

A Comprehensive Knowledge Base, with over 1,200 authors and 100 scientific advisors
+ More than 10,000 articles and 1,000 how-to sheets, over 800 new or updated articles every year
From design to prototyping, right through to industrialization, the reference for securing the development of your industrial projects

This article is included in

Functional materials - Bio-based materials

This offer includes:

Knowledge Base

Updated and enriched with articles validated by our scientific committees

Services

A set of exclusive tools to complement the resources

Practical Path

Operational and didactic, to guarantee the acquisition of transversal skills

Doc & Quiz

Interactive articles with quizzes, for constructive reading

Subscribe now!

Ongoing reading
Texture of divided materials