What is Tungsten Disulfide?
By studying the electron distribution in these crystals,
Jamison gave another explanation for the good tribological properties of MoS2
and WS2. In their structure, six nonbonding electrons fill a band and are
confined in the structure. These electrons create a net positive charge on the
surface layer, promoting easy shear through electrostatic repulsion. WS2 is
thermally more stable and oxid-resistant (about 50 to 100°C) than MoS2. The
slow rate of oxidation of WS2 can be explained by the formation of tungsten
trioxide (WO3), which is also known to provide a lower friction coefficient
than molybdenum trioxide (MoO3). In a dry nitrogen environment, the
steady-state friction coefficient of WS2 films grown by pulsed laser deposited
on stainless steel against a steel counterface is about 0.04. A transfer film
made of very thin WS2 sheets is observed on the pin side. Analyzed by SEM, the
sheets are thin enough (60 nm) to be transparent to the electron beam. In this
chapter, we investigated the tribological properties of WS2 or IF-WS2 coatings
in an ultrahigh vacuum and at different temperatures (−130 to 200°C). Friction
experiments were performed in an analytical ultra-high vacuum tribometer. This
tribometer consists of a linear reciprocating pin-on-flat configuration
installed directly inside an ultra-high vacuum chamber. The system uses
traditional surface analysis techniques, X-ray Photoelectron spectroscopy
(XPS), and Auger electron spectroscopy (AES). The pins were made of AISI 52100
steel with a radius of curvature of 4 mm. We used a normal load of 3 N on the
pin leading to a maximum Hertzian contact pressure of 470 MPa. A very low
friction coefficient was obtained with both types of coatings, indicating the
very interesting tribological properties of WS2 coatings.
MoS2 is a single-atom-thick
membrane with hydrophilic sites
MoS2 is a single-atom-thick mem. Vacancies can be easily
introduced into the MoS2 monolayer, which suggests nanoporous MoS2 can be used
in water desalination applications. In one study, it has been found by
molecular dynamic simulations that a nanopore with a single-layer molybdenum
disulfide can effectively reject ions and also increase the permeability of the
membrane. More than 88% of ions were rejected by membranes having pore areas
ranging from 20 to 60 Å2. In that same study, water flux was found to be
increased around 2 to 5 times more than other nanoporous membranes. Another
study reveals that MoS2 nanopores with “open” and “closed” states can be
successfully regulated for water flow and ion filtering. Mechanical stretching
of the filter was used to change the size of the nanopore effectively, and it
has been found that both steric and electrostatic effects contribute to
blocking the passage of ions. Graphene nanopores with functionalized hydroxyl
groups can boost the membrane’s permeability but reduce desalination
efficiencies. The addition of accurate functional groups to the edges of the
nanopores requires complex fabrication.
Inorganic fullerene-like nanoparticles
of WS2 and MoS2
Hollow closed-cage carbon structures, the fullerenes (C60),
and carbon nanotubes have been known for some time. Research into similar
structures from other (inorganic) layered compounds started soon after. Thus,
IF NP and INT of tungsten disulfide (WS2) first and subsequently of molybdenum
disulfide (MoS2) were discovered in 1992 and have elicited considerable
interest in this emerging field. This observation is surprising because the
chemical bond is unstable beyond a few angstroms. Hence, structures with hollow
spaces of a few nanometers and above were initially considered unfavorable. The
formation of such hollow closed cages can be attributed to the inherent
instability of the planar nanostructures of layered compounds. In graphite, the
carbon atoms are bonded in flat sp2 bonds forming a hexagonal network (Figure
13.3A). The graphene sheets are stacked together via weak van der Waals forces.
In the case of MS2, where M stands for a metal atom like
molybdenum or tungsten, the molecular sheet comprises a layer of M atoms
sandwiched between two outer sulfur layers. Each M atom binds to six sulfur
atoms forming a lattice with trigonal biprism (octahedral) coordination. In
analogy to graphite, weak van der Waals forces are responsible for stacking the
S–M–S layers together. Therefore, these compounds are highly anisotropic
concerning their physical and chemical properties. The crystal’s basal (van der
Waals) surfaces, which are perpendicular to the c-axis, consist of sulfur atoms
that form bonds to three underlying W/Mo atoms. These sulfur atoms are
chemically inert. However, rim W (or Mo) and S atoms, that is, atoms on the
edge of the layer, which are abundant in the nanostructure, are only four- and
twofold bonded, respectively, making the planar form unstable and forcing it to
fold and close on itself. Therefore, by folding the molecular sheet and
stitching the rim atoms together, seamless and stable nanotubular
(one-dimensional) and spherical (zero-dimensional fullerene-like) structures
with all W/Mo and S atoms being six- and threefold bonded, respectively, are
produced. Initially, only the transition metal chalcogenides of WS2 and MoS2
were known as closed-cage structures and nanotubes. However, over the years,
this family has been expanded considerably, and it now encompasses a large
number of other compounds like oxides, hydroxides, nitrides, chlorides,
sulfides, selenides, and even pure elements like bismuth, arsine, and
phosphorus.
Price of Tungsten Disulfide
Tungsten Disulfide particle size and purity will affect the
product’s Price, and the purchase volume can also affect the cost of Tungsten
Disulfide. A large amount of large amount will be lower. The Price of Tungsten
Disulfide is on our company’s official website.
Tungsten Disulfide supplier
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material supplier and manufacturer. It has over 12 years of experience
providing ultra-high quality chemicals and nanotechnology materials, including Tungsten
Disulfide, nitride powder, graphite powder, sulfide powder, and 3D printing
powder. If you are looking for high-quality and cost-effective TungstenDisulfide, you are welcome to contact us or inquire any time.
