BJH Adsorption/Desorption Report

The BJH calculation determines the mesopore volume/area distribution, which accounts for both the change in adsorbate layer thickness and the liquid condensed in pore cores. Reports can be generated from both adsorption and desorption data. The fields for both BJH Adsorption Report Options and BJH Desorption Report Options are identical unless otherwise specified.

  An incomplete pore distribution may be generated if a thickness curve selection is not a good match for the sample being analyzed.

 

 

Circled selection is applicable to BJH Adsorption only
BJH Adsorption/Desorption Report
Field or Button Description
Adsorptive [button] Displays the Adsorptive Options window. The recommended adsorptives and their values are shown. Up to eight adsorptive and adsorbate property factor combinations may be specified.

BJH Correction
[group box]

Select the type of correction to apply to calculations. The selected type will display in the report header.

Faas. Good for statistical thickness curves.

Kruk-Jaroniec-Sayari. Good for reference thickness curves.

Standard. Uses original BJH models.

Cumulative Reports
[group box]

Larger. Use to report the total volume found in pores larger than the current pore size.

Smaller. Use to report the total volume found in pores smaller than the current pore size.

Pores [group box]

Enter the minimum and maximum diameter (radius or width) of pores to include in the BJH reports.

Fraction of pores open at both ends. This field is not available for the BJH Desorption Report Options window.

During adsorption calculations, the analysis program assumes that all pores are closed at one end. Occasionally, a percentage of pores may be open at both ends causing disagreement in the adsorption and desorption data or in the values for total volume and total BJH pore volume. Enter the fraction of pores open at both ends to compensate for this error.

Pressures [button]

Use to select a pressure range for report calculations and points for exclusion from calculations.

Calculation pressure range. Enter the minimum and maximum pressures to be used in the pressure table.To exclude a point from the calculations used to generate the report, select Exclude.

Exclude All. Select to exclude all pressure points in the table.

Include All. Select to include all pressure points in the table.

Select Reports
[group box]

Select the report names to include in the report. Highlight the report name, then click Edit to modify report parameters.

Smooth differentials
[check box]

Use to smooth all differential calculations, thus eliminating variations in the differential computation caused by noise in the input data.

Thickness Curve
[group box]

Select the thickness curve, then click Edit to modify the values in the equation for the selected curve. The Frenkel-Halsey-Hill thickness curve can be applied using the Halsey option.

Kruk-Jaroniec-Sayari / Halsey / Harkins and Jura / Broekhoff-de Boer / Carbon Black STSA. Select the thickness curve option, then click Edit. Modify the equation for the selected curve as needed.

Reference. Select Reference, then click Edit to define a t-curve by entering both the relative pressure and thickness values. One predefined curve is shipped with the analysis program and is found in the Reference directory.

To import values from an existing thickness curve (.THK file), click Open, then select the file containing the values. The table to be imported must have a .TXT or .THK file extension and have a two-column format with the relative pressures in the first column and the thickness values in the second column. Columns must be separated by a space or a tab.

  For fields and buttons not listed in this table, see Common Fields and Buttons.

BJH Plot

The fields for all plot options are identical for specifying plotting methods and customizing plots. Highlight any plot option in the Selected Reports list box in the BJH Report Options window, then click Edit.

BJH Plot Report
Field or Button Description
Autoscale [check box] When enabled on the report parameters windows, allows the x- and y‑ axes to be scaled automatically. Autoscale means that the x‑ and y‑ ranges will be set so that all the data is shown. If Autoscale is not selected, the entered range is used.
Plot curve / Plot points [check box]

Select to plot points on the graph.

X-Axis [group box] Use to have the x-axis on a logarithmic or linear scale.
Y-Axis [group box]

Overlay. Select an option to overlay onto the current report.

Variable. Select a variable.

  For fields and buttons not listed in this table, see Common Fields and Buttons.

BJH Tabular Report

Highlight BJH Tabular Report in the Selected Reports list box on the BJH Adsorption Report Options window, then click Edit to specify the method of data reduction.

BJH Tabular Report
Field or Button Description
Collected points
[selection]
Use to include all relative pressure points collected. Refer to the Columns button below.
Columns [button] Select the data types to include in the report. Column [n] indicates the column order and data contents for the report.

Fixed pore size table
[selection]
Use to specify exact pore sizes for volume or area data. Click Table to modify the fixed pore size table. Refer to Table and Columns buttons elsewhere in this table.
Table [button] The fixed pore size table must contain a minimum of two points. The points must be strictly decreasing. Enabled only when Fixed pore size table is selected.
  For fields and buttons not listed in this table, see Common Fields and Buttons.