Kulim Kht Washburn Method

Washburn Method
This method is chosen when the solid sample to be tested contains a porous architecture which leads to
absorption of the wetting liquid. The solid is brought into contact with the testing liquid and the mass of
liquid absorbed into the solid is measured as a function of time. The amount absorbed is a function of the
viscosity, density and surface tension of the liquid, the material constant of the solid , and the contact angle
of the interaction. If the viscosity, density and surface tension of the liquid are known the material constant
and contact angle can be solved for. KSV instruments produces two instruments capable of finding contact
angles via the Washburn technique, the Sigma 70 and LPR 902. See Application Note #104 for details.

Utilization of Contact Angle Data:
The primary focus of contact angle studies is in assessing the wetting characteristics of solid/liquid
interactions. Contact angle is commonly used as the most direct measure of wetting. Other experimental
parameters may be derived directly from contact angle and surface tension results. Some examples are:
Work of Adhesion: defined as the work required to separate the liquid
and solid phases, or the negative free energy associated with the
adhesion of the solid and liquid phases. Used to express the strength
of the interaction between the two phases. It is given by the Young
-Dupre equation as:
Wa = (1+ cos )
Work of Cohesion: defined as the work required to separate a liquid into
two parts, it is a measure of the strength of molecular interactions
within the liquid. It is given by;
Wc = 2
Work of Spreading: the negative free energy associated with spreading
liquid over solid surface. Also referred to as Spreading Coefficient
it is given as:
Ws = (cos - 1)
Wetting Tension: a measurement of force/length defined as:
= Fw / P = lv cos

Kulim Kht Semi Auto Tensiometer

Kulim Kht Surface Tension & Contact angle

How come contact angle and surface tension are so important ? Molecules inside (bulk) a liquid/solid are in every direction affected by equal attraction forces, whereas the molecules at the surface lack a neighbor towards the air phase and therefore they have larger attraction forces towards the liquid/solid than air (see figure below). This leads to a situation where the interface has excess free energy. This excess free energy is characteristic for any liquid or solid. For liquids a spontaneous contraction of the surface will take place due to this free energy and the Surface Tension of a liquid is a direct measure of it. In the case of solids a contraction is hardly ever seen, but still this free energy is present at the interface of a solid. However, now it is called Surface Free Energy (instead of Surface Tension as for liquids) and can be accessed by measuring the contact angle of a series known liquids placed on the solid surface. The dimension of Surface Tension and Surface Free Energy is mN/m.

Kulim Kht Conference Booth ICSSST 2012

KHT Booth at 4th. International on
Solid State Science and Technology Dec.2012

Kulim Kht QCMD Fatty Acid

Fatty acid collectors for phosphate flotation and their adsorption behavior
using QCM-D
J. Kou a,b, D. Tao b,⁎, G. Xub
a School of Civil and Environment Engineering, University of Science and Technology Beijing, 30 Xueyuan Road, Haidian District, Beijing, 100083, PR China
b Department of Mining Engineering, University of Kentucky, Lexington, KY 40506, USA
a r t i c l e i n f o a b s t r a c t
Article history:
Received 31 July 2009
Received in revised form 5 March 2010
Accepted 11 March 2010
Available online 25 March 2010
Keywords:
Fatty acid

QCM-D

In this paper the relationship between the flotation performance of phosphate collectors and their adsorption
behavior was evaluated using a variety of techniques including the Crystal Microbalance with Dissipation
technique (QCM-D). The adsorption of the collectors on the surface of hydroxyapatite was primarily
characterized using QCM-D, which is a high sensitivity in-situ surface characterization technique. Additionally,
the collectors were evaluated via zeta potential and FTIR analyses. The flotation performance of the collectors
was evaluated using a laboratory mechanical flotation cell at different process parameters such as pH, collector
dosage, diesel dosage and flotation time. The two collectors evaluated were a commercial plant collector and a
refined tall oil fatty acid. The QCM-D data showed that the refined tall oil fatty acid adsorbed on phosphate
more readily and produced stronger hydrophobicity and better flotation performance than the plant collector.
The chemisorption and surface precipitation mechanisms of the refined tall oil fatty acid on the surface of
hydroxyapatite were demonstrated by means of zeta potential measurements and FTIR analysis.


1. Introduction
In the conventional phosphate flotation (Crago) process, a
significant amount of the silica present in the feed is floated twice,
first by fatty acid, and then by amine (Zhang et al., 1997). The Crago
process is therefore inefficient in terms of collector efficiency. The
phosphate mining industry is faced with higher fatty acid prices, lower
feed grade, and stricter environmental regulations (Sis and Chander,
2003). To meet the market demand for higher effectivity, lower cost
and better selectivity of phosphate flotation collectors, there is a need
to evaluate surface adsorption techniques that may help researchers
develop better collectors by understanding how the adsorption
behavior of materials affects their performance as flotation collectors.
In order to evaluate this relationship, a plant collector of proprietary
composition and a refined tall oil fatty acid were compared. The
refined tall oil fatty acid, referred to as GP193G75, was comprised of
47% oleic and 33% linoleic acids.1 Flotation tests were performed at
varying process parameters such as pH, collector dosage and flotation
time with phosphate ore from CF Industries' phosphate rock mine in
Hardee County, Florida. To better understand the behavior of the
collectors on an apatite surface, their adsorption on the surface of a
hydroxyapatite-coated sensor was studied using the QCM-D technique.
The adsorption and flotation characteristics of the two
collectors were then compared.
Most of the studies about the adsorption mechanism of collectors
on mineral surface were conducted based on ex-situ measurements
such as contact angle, adsorption isotherm, FTIR spectroscopy, and
zeta potential, which unfortunately cannot monitor the real-time
formation process and characteristics of adsorbed layer. QCM-D is the
second generation of QCM, which has been shown by many
investigators to be a sensitive tool for studying the behavior of protein
and surfactant adsorption in aqueous solutions, with sensitivity in the
ng/cm2 (submonolayer) region (Hook et al., 1998). It can simultaneously
determine changes in frequency and energy dissipation of a
quartz crystal at nanoscale in real-time and derives valuable in-situ
information on adsorbed mass as well as the mechanical (viscoelastic)/
structural properties of the adsorbed layer from experimentally
obtained data of energy dissipation in relation to frequency shift (Paul
et al., 2008). The purpose of this study was to investigate in-situ the
adsorption behavior of two collectors on the hydroxyapatite surface by
means of QCM-D technique and to determine whether the differences
observed may lead to differences in flotation performance.

Kulim KHT Wafer Cleanliness

Checking wafer cleanliness by measuring static contact angle.

An optical tensiometer is the instrument of choice to measure the contact angle between a drop of water and a wafer. The wafer is placed on the sample stage and a drop is dispensed from the liquid dispenser onto the wafer. The sessile drop can be observed with a high quality camera. The optical tensiometer software analyzes the drop shape and measures the contact angles.
Typically, when assessing the cleanliness of a wafer, a contact angle of zero is desired: the liquid wets completely the surface. Impurities increase the contact angle which is detected by the optical tensiometer.


Studying surface coating properties by measuring dynamic contact angle
Once your wafer surface has been treated or coated, an optical tensiometer can tell you about Surface Free Energy (SFE), adhesion and heterogeneity to name a few. In that case, a dynamic contact angle is preferred even though a static contact angle can also be used. The production of drops with advanced and receded edges involves one of two strategies. Drops can be made to have advanced edges by addition of liquid. Receded edges may be produced by allowing sufficient evaporation or by withdrawing liquid from the drop. Alternately, both advanced and receded edges are produced when the stage on which the solid is held is tilted to the point of incipient motion. Using an instrument with high speed image capture capabilities shapes of drops in motion may be analyzed.


A video of such an experiment can be seen at http://www.attension.com/contact-angle.aspx together with an explanation of the measurement technique.
The two application examples presented above demonstrate how an optical tensiometer can be used by wafer manufacturer. Optical tensiometers are useful instruments for semiconductor process control, surface modification process development and quality control.

Attension
Attension provides precision tensiometers with outstanding simplicity of use for liquid and solid surface characterization in research and industrial processes. The offering consists of optical, force, bubble and volumetric tensiometers for all needs and budgets, ranging from versatile, fully automated instruments, to more compact, manual systems. We are present in www.attension.com

Kulim KHT Krafft temperature & Cloud Point via CMC

Krafft Point Temperature
The Krafft temperature (also known as Krafft point, or critical micelle temperature) is
the minimum temperature at which surfactants begin to soluble (if the sample
concentration is below the CMC) and in some cases form micelles (if the sample
concentration is above the CMC).
Krafft point can be also regarded as the temperature at which micelles become
soluble (in the case of surfactant concentration is above the CMC value).
Below the Krafft temperature, there is no value for the critical micelle concentration
(CMC), i.e., micelles cannot form.
A surfactant with a low Krafft point is more soluble than a surfactant with a high Krafft
point.
The low Krafft point surfactant became insoluble at a concentration which was only
slightly lower than the CMC. By a slight increase in temperature the surfactant can
be further solubilized until the CMC is reached.
The Krafft temperature is a point of phase change below which the surfactant
remains in crystalline form, even in aqueous solution.
Surfactants in such a crystalline state will only solubilize if another surfactant assists
it in overcoming the forces that keep it crystallized, or if the temperature increases,
thus causing entropy to have a stronger force and encouraging the crystalline
structure to break apart.
Increasing the length of the hydrocarbon chain increases the Krafft temperature
because it improves Van der Waals forces.
Surfactants are effective at temperatures above their Krafft points.
Krafft Point Determination
The Krafft point can be estimated by measuring the temperature at which the
surfactant solution forms a clear solution (applies to all surfactant concentration
sample).
At this temperature the solubility of the surfactant becomes equal to the critical
micelle concentration. It is best determined by locating the abrupt change in slope of
a graph of the logarithm of the solubility against t or 1/T (applies to surfactant
concentration sample above CMC).


Cloud Point Temperature
Definition
• Anionics - is the temperature at which a product becomes turbid when it is
cooled under specified conditions.
• Nonionics - is the temperature at which a product becomes turbid when
heated.
Cloud points are characteristic of nonionic surfactants.
Cloud point may result in phase separation and instability.
Properties
• Anionics - The shorter the hydrophobic chain, the lower the cloud point of the
surfactant.
• Nonionics - The greater the degree of ethoxylation, the higher the cloud point.
Cloud Point Determination
Cloud points are typically measured using 1% aqueous surfactant solutions.
Anionics.
A neat surfactant sample is placed into a tube with a thermometer and then
immersed into an ice bath. The sample is cooled at a specified rate while stirred (to
provide even cooling). When the sample first begins to show slight hazing, the tube
is removed from the bath and inspected regularly. The cloud point is that
temperature at which the thermometer immersed in the sample is no longer visible
when viewed horizontally through the tube and sample.
Nonionics.
A 1% aqueous solution of a nonionic surfactant is heated at a specified rate and
monitored for haziness. The cloud point is the temperature at which the first haze is
observed.