"Drop water does not enter" ultra-hydrophobic paint appears

China Paint network
: back to the south, the floor water, walls "sweating", let people crazy. In some industries, water is even more hostile: water brings bacteria, corrosion and pollution. Bias around us the water is everywhere, "sabotage" can not be prevented. Is there a way to keep water out when it's not welcome? Ultra-hydrophobic materials bear the heavy burden.
in a TED talk, scientists poured a basin of water on a metal plate, which rolled down like steel beads and remained dry. A oar immersed in the water tank, took out did not bring out a drop of water, as if never put in the same; A glass of water poured on a specially treated glass plate, the water firmly in the center of the "do not cross the mine pond half step", that is, the use of hand stirred out a drop or two also immediately run back ...
Because of waterproof and corrosion-resistant and other special effects are widely concerned about the urgent need to move from the laboratory to the actual promotion and application
These contrary to our naked eye "common sense" phenomenon, is the "ultra-hydrophobic materials" troublemaker. The new material, which changes the surface free energy and surface roughness of the material, is inspired by lotus leaves in nature. Because of its waterproof, corrosion-resistant, antibacterial special effects, has become an international hot research field, can be in environmental protection, industry, medical and other fields you can not imagine.
the surface of the material can determine whether the material is hydrophobic or hydrophobic, the lower the free energy, the stronger the hydrophobic; The roughness of the surface microscopic determines the strength of hydrophobic water, the rougher the surface, the stronger the hydrophobicity
a droplet of water on the surface of the material, if it spreads quickly, is the hydrophobic or ultra-hydrophobic surface; If the water beads form a spherical shape, can roll around, is hydrophobic and even ultra-hydrophobic surface.
the surface of some plant leaves in nature has super-hydrophobic properties and self-cleaning function, the most typical is the surface of lotus leaves, forming a "lotus leaf self-cleaning effect", "silt without dyeing".
the nature of super-hydrophobic water formation? To figure this out, the super-hydrophobic phenomenon of nature may be used by humans.
, an expert in ultra-hydrophobic materials at the School of Chemistry and Chemical Engineering of South China University of Technology explained that, according to the laws of thermodynamics, substances with high surface energy cannot spread on surfaces with low surface energy. Water is a surface can be relatively high substances, so the surface can be lower than water, such as some substances containing silicon, fluorine will show hydrophobic, water on such a surface will try to shrink themselves into a spherical.
composition of low surface energy determines whether a substance is hydrophobic, but hydrophobic properties alone are not sufficient. In the 1930s and 1940s, scientists discovered the relationship between surface roughness microstructurs and immersion. In microenculation, liquid droplets on solid surfaces do not completely fill the concave surfaces of rough solid surfaces, and there is air between droplets and solid concave surfaces.
the contact interface between solids and liquids seen at the macro level is actually a hybrid interface consisting of a gas-liquid interface and a solid-liquid interface. The rougher the microseelectration, the more air it locks in, the less contact it has with water, and the more hydrophobic the solids are.
In 1997, researchers such as German biologist Barthlott studied the surfaces of nearly 300 plant leaves and concluded that the self-cleaning properties of plant leaves were created by the lactic protrusions of micron structures on rough surfaces and waxy materials that hydrophobic surfaces.
smooth-looking lotus leaves, but under an electron microscope, the surface is covered with grainy mastostic protrusions that look rough and uneven. Between these mastures and mastides, they are covered by a large number of nanoscale wax crystals. Waterproof waxes and micron-grade mastina make the surface of the lotus leaf ultra-hydrophobic.
the above-mentioned experts, the material surface freedom can determine whether the material is hydrophobic or hydrophobic, the lower the surface free energy, the stronger the hydrophobic; The roughness of the surface microscopy determines the strength of hydrophobic and hydrophobic, and the rougher the surface, the stronger the hydrophobic. Therefore, when the surface is hydrophobic, the roughness of the solid surface can be increased.
In 2002, Jiang Lei's team, a well-known nanomaterials expert in China, found that there were nanostructures on the mastina of the micron structure on the surface of the lotus leaf, with an average diameter of 5-9 microns, with each mastina surface distributed with a diameter of 124±3) nanometers. Nanostructures also exist on the surface between masts. In addition, nanostructures can also be found on the lower surface of the lotus leaf, which effectively prevents the lower layer of the lotus leaf from being moisturized.
, only micron structure, hydrophobicity is not strong enough, microna multi-layer structure is the ultimate mystery of the phenomenon of hydrophobic phenomena in nature.
researchers often use contact angles to express how well a liquid immerses a solid, or hydrophobic. The contact angle is the cut of the gas-liquid interface through the angle between the liquid and the solid-liquid interface. If the water beads are perfect spherical on the surface of the material, it means that the plate is completely hydrophobic, with a contact angle of 180 degrees; If the water is completely tiled on the surface, the material is very hydro-hydro, and the contact angle is 0 degrees.
the contact angle, the lower the immersion. By definition, ultra-hydrophobic surfaces generally refer to surfaces with a contact angle greater than 150 degrees.
planes in reality are often not horizontal, but more sloped. Water droplets may roll or stall on an oblique surface, a manifestation of hydrophobicity, which needs to be expressed in rolling angles. A rolling angle is a critical surface tilt angle at which a droplet begins to roll on a solid surface. The smaller the tilt angle at which the droplets start rolling, the better the super-hydrophobicity of the surface.
the above experts, the water beads roll down, the ability to defilt is stronger than the slip, and the tilted smooth surface water beads are mostly in a sliding state, which explains the self-cleaning characteristics of ultra-hydrophobic surfaces.
People have been inspired by nature to produce materials of the same super-hydrophobic properties, and the study of anthopoly opposites can control which direction and extent the liquid is immersed in solids
According to the above experts, the surface of the wing is composed of a well-arranged nano-pillar structure with a diameter of about 80 nanometers and a spacing of about 180 nanometers. The regular arrangement of nano-protrusions builds a roughness, so that the surface of the wing stabilizes and absorbs a layer of air film, inducing the super-hydrophobic quality, thus ensuring the self-cleaning function.
gecko's toes also have a fascinating hierarchy. Microscopic observations can see that its toes are made up of thousands of silk-like "scales" and hundreds of tiny structures like shovels. Such a structure makes geckos' feet unusually rough and can crawl freely on walls.
water, known as "iron-legged water drift" on rivers and lakes although its own weight is small, but it can float on the surface of the water mainly by the ultra-hydrophobic structure of its legs. Jiang Lei's team carried out a thorough and detailed study of the water legs and found that the surface of the water legs was directed with micron-scale needle-like rigid hair, and there was a spiral-shaped nano-scale groove structure on the hair. The fresh hairs can absorb bubbles in the grooves to form air cushions, allowing the water to glide freely across the water without wetting the legs.
inspired by , many researchers have designed new super buoyant materials. Researchers such as Dr. Pan Qinmin of the Department of Applied Chemistry at Harbin University of Technology base themselves on porous copper mesh and make them into stamp-sized miniature boats, which are then soaked in solutions such as silver nitrate to make the surface of the ship ultra-hydrophobic.
the material also has a micro-nanostructure surface, which can form air cushions on the outside surface of the ship, changing the ship's contact with water and making the surface of the hull less subject to water resistance. The miniature boat can carry 50% more weight than its maximum displacement while floating freely on the surface of the water.
water droplets show an opposite nature when rolling on the leaf surface of some plants, which can simply be interpreted as showing different properties in different directions. Jiang Lei's team observed that water droplets on the surface of rice leaves always rolled in the direction of parallel leaf veins. Originally, the surface of rice leaves has a multi-stage structure similar to the micronnamical combination of lotus leaf surface, but on the surface of rice leaves, the milk protrusions are arranged in a well-organized direction parallel to the edge of the leaves, and the vertical arrangement is very "willy", so the water beads are more likely to roll down in the direction of parallel leaf veins.
2009, Jiang Lei's team also found an anodesic water droplets rolling on the surface of butterfly wings. Butterfly wings are covered by micron-sized scales overlapping, each with a neatly arranged nano-strip structure, and each nano-stripe is made up of a layer of periodically tilted flakes. Global
Coatings Network
that this particular microstructure causes water drops to be anodesic as they roll on the surface of butterfly wings.
these results provide important information for the preparation of a solid surface with controlled immersion. With this in place, one can control not only whether solids and liquids are immersed, but also in which direction and to what extent the liquid is immersed.
application of ultra-hydrophobic materials is quite extensive, covering aerospace military, construction, medical and other aspects. However, due to the current technology and development costs and other constraints, the actual industrialization and commercialization of
ultra-hydrophobic performance applications in what areas? Many researchers have come up with ideas about this.
think about what's relevant to our lives. Ultra-hydrophobic surfaces with antibacterial self-cleaning effect can be applied to household goods, which can reduce the trouble of cleaning; Refrigerators, freezers and other refrigeration equipment on the surface of the inner bile, no longer condensed water, frost, ice phenomenon; Applications such as waterproofing, snow and stain resistance to walls, glass and metal frames in the interior and exterior of buildings can greatly reduce the cleaning and maintenance costs of buildings.
's a little more open-minded. The super-hydrophobic molecular film applied to the inner wall of natural gas and oil pipelines can prevent pipe corrosion and improve the transmission efficiency of oil and gas. It is coated on the bottom of an ocean-going ship, which can be anti-fouling and anti-corrosion.
ultra-hydrophobic materials also perform well in microflow control applications. The researchers suggest that controlling the movement and flow of microdrops and using them to create microdrops to control needles makes it easier to measure liquid droplets during experiments or production.
There are experts believe that if such technology is applied to such technologies as electrostitive spraying field, such as the use of ultra-hydrophobic materials to make spray, etc. , will make the spray droplets more uniform, atomization effect is better, can be used in the spray effect has special requirements for the occasion.
The above-mentioned experts, ultra-hydrophobic materials are currently mainly several preparation methods, including template method, plasma method, chemical vapor deposition method, electrostectonic spinning method, sol-gel method, etc. , are basically on the low surface energy material construction rough surface.
these methods are either too expensive; Either the equipment is demanding, the conditions are harsh, the cycle is long, can only be manufactured in a small number of laboratories; Either the hydrophobic surface strength is not resistant to wear; Either hydrophobic persistence is not strong, easy to be contaminated by oily substances... At present, the researchers are trying to create different structures with different characteristics of hydrophobic materials, such as some hydrophobic and oil-sparing ultra-double dredging material research, on the other hand, they are also racking their brains to get them into practical applications.
, the relevant team of the School of Chemistry and Chemical Engineering of South China University of Technology has made good progress in the preparation of ultra-hydrophobic coating film. After they have prepared the particles of the micro-nano composite structure, and silicone composite into
coating
, spraying this coating can prepare ultra-hydrophobic coating film, has become one of the few practical application value of the technical methods.
For ultra-hydrophobic coatings easy to wear and lead to the problem of insufficient strength, the above-mentioned team also put forward a new idea: on the surface of the object first apply a layer of glue, and then spray hydrophobic coatings, so that hydrophobic coatings and surfaces of the object better bonding, hydrophobic strength is guaranteed.
In the latest issue of science, Lu Yao, a phD student in the Department of Chemistry at University College London, also suggests that spraying ultra-hydrophobic coatings on adhesives can effectively improve the wear-prone weaknesses of ultra-hydrophobic coatings, "and "give weaknesses in the field of super-hydrophobics to more mature adhesive techniques to overcome".