The Self-Healing Ability of Cerium Coating (Chromium Substitute)

In recent years, several research efforts are targeted on the utilization of rare earth elements, especially on cerium thin film coatings. Cerium is a soft, ductile and silvery-white metal that tarnishes when exposed to air, and it so soft that can be cut with a knife. Cerium has no biological role and is not very toxic. Many surface treatments, like sol-gel, chemical vapor deposition (CVD) and physical vapor deposition (PVD) technique, based on the use of cerium and cerium compounds have been investigated because of their low toxicity. In other words, consumption or inhalation of those compounds is not considered harmful to health.

Cerium compound physical vapor deposition permits to improve corrosion protection performance of the surface it is deposited on. The composition of the films has an impact on the corrosion properties of the cerium-based layer. In general, the coatings obtained by PVD are composed of Ce compound in trivalent or tetravalent states. The ratio between these 2 oxidization states is strongly depending on the oxidizing ability of the medium. However, no clear correlation between the Ce oxidation state and corrosion properties was found nowadays.

cerium film
cerium film

What’s more, these cerium coatings have an active mechanism similar to that observed for chromate coatings that they both have the amazing self-healing ability when damage occurs. Chromate coatings have the self-healing properties because of the presence of unreacted Cr6+ ions that are able to migrate to the exposed metal (for example a scratch) and can be further reduced to create a Cr3+ based compound that seals the scratch or the defect. However, the chromate compounds are extremely toxic and carcinogenic. Since cerium is not toxic, it is a perfect substitute for chromate. When it comes to cerium, the contact between a CeO2 film and solution induces the formation of Ce(OH)22+ ions. The existence of oxidizable metal would reduce these ions into Ce3+. Then the precipitation of trivalent cerium oxide occurs; it can be enhanced by the local increase of alkalinity. Therefore, this precipitated oxide seals the film and decreases the corrosion rate of metal. Since cerium is not toxic, it is a perfect substitute for chromate.

In conclusion, cerium is good, but some people would concern their price. Is rare earth element—Cerium—very expensive? The answer is not, actually Cerium is one of the least expensive rare earths and is the major component of “mischmetal”. So don’t care too much about the price.

For high purity sputtering targets & evaporation materials inquiry, please visit SAM Sputter Target.

For more news and knowledge about sputtering target, please see SAM Target News.

Related Blog: How was cerium discovered? | History of Cerium

What is the Indium Bonding for Sputtering Target?

The term “indium bonding” in thin film coating industry, simply speaking, refers to bond two (or more) sputtering targets with indium (In), or one (or more) with indium plate together.

Indium

Indium can be uniquely used in lower temperature solders, is one of the softest materials. Indium is preferred for target bonding because of its excellent thermal conductivity of all available bonds. In addition, indium is the most efficient material at drawing heat away from the sputtering target. Most materials can be indium bonded and there are just a few exceptions.

Apart from indium bonding, indium is also popular for a variety of uses and purposes, such as creating alloys, photoconductors, and thermistors.

Indium bond

Sputtering target can be cracked, warped or damaged due to inadequate cooling, low hardness or other reasons. From this point of view, although target bonding does generate a fee, it can well protect your target from damage. It is especially true for those less-strong target materials and precious metal materials.

Elastomer is an alternative bonding method that touts a higher temperature capability over the indium bond. Elastomer bonds are recommended when you are consistently melting indium bonds. We also recommend elastomer bonding for low melting point target materials, as well as, temperature sensitive compounds and targets that have either low density or are especially fragile.

indium target bonding

Indium bonding is preferred in applications where:

Cryogenic stability is needed

Sealing requires high levels of hermeticity

Maximum thermal transfer is required

Bonding to not-metallic surfaces

Flux cannot be used

Backing plates

OFHC Copper Backing Plate is another well-known backing plate. It is frequently used to bond ceramic targets because of its non-magnetism and low coefficient of thermal expansion. This metal has good electrical and thermal characteristics while also being easy to machine, easy to soften, and readily available at a low cost. Copper backing plates can be re-used, with care, 20 or more times.

Molybdenum plate is usually used to substitute copper plate if copper is not appropriate in the application. For instance, the coefficient of expansion for copper is mismatched with some ceramics. And for high-temperature bonding, copper may also oxidize badly or warp. In these conditions, molybdenum is a more suitable material.

SAM Sputter Target

If you are looking for an indium bonding manufacturer, SAM is undoubtedly your best choice. Stanford Advanced Materials is devoted to machining standard backing plates and working together with the Taiwan Bonding Company for providing bonding services. For questions about target bonding materials, methods and services, please see our listing of frequently asked questions (FAQs).

Related blog: When do you need target bonding?

Deposition of silver on glass by e-beam evaporation

The case

I am attempting to use silver evaporation pellets to deposit one-micrometer thick silver layer on the glass substrate. I found that only electron beam evaporation is accessible within the facility. I tried Ag/Ti/glass but silver peels off the Titanium layer. Up to now, only Ag/Au/Ti/glass can partially work, and only 1/2 of my samples were fully coated with silver; the other half turned into blackish-rainbow color. I wonder what is wrong in the process? Should I should some intermediate layers?

deposit silver on glass substrate
deposit silver on the glass substrate

Possible Cause and Solution

The thickness of the Titanium (Ti) layer may be too large. Generally speaking, 5 to 10 nm is enough in this case.

The process is not operated in a good vacuum condition, thus the titanium layer is oxidized. In electron beam evaporation, as well as other vacuum evaporation, the vacuum degree of the evaporator is extremely important, which will greatly influence the quality of the film obtained. Thus, please make sure the vacuum chamber is well sealed before evaporating.

It is hard to avoid that the evaporated silver (as well as gold) only loosely connected to the glass substrate. Cleaning the glass with acetone and then methanol could help. Or you can just replace the glass substrate by using another transparent substrate, such as Al2O3, SiO2, AlN and Diamond. The silver layer can better deposit on those substrates mentioned above.

Other Suggestions

Titanium is an excellent adhesion layer, but it is also true that it may lose some of its adhesiveness if the vacuum is not good enough. As for its alternatives, Chromium (Cr) and Aluminum (Al) are recommended to act as the adhesion promoter.

Rising the temperature up to 100℃ in the vacuum for a few minutes may also improve the adhesion of metals.

Silver (Ag) Evaporation Materials
Silver (Ag) Evaporation Materials

For the explanation of the terminologies of vacuum coating mentioned in this passage, please refer to Terminologies of Vacuum Evaporation.

For high purity silver evaporation materials, please visit Stanford Advanced Materials.

For more news and knowledge about vacuum coating, please see SAM News.

Molybdenum Target Mammography Detection

Breast cancer, one of the major causes of deaths among women, affects about 12% of women around the world. According to research surveys, the smaller the breast cancer is when it is detected, the less the possibility of death. This requires that women should go over the medical body check regularly to decrease the risk of breast cancer. At present, molybdenum target mammography is considered the recommended breast screening examinations for women’s breast cancer.

What is the Breast Cancer?

Breast cancer is caused by the development of malignant cells in the breast. It is a sign of breast cancer when cells in the breast begin to grow out of control, and these cells usually result in forming a tumor.

Breast Cancer
Breast Cancer

 

Breast cancer itself is not a fatal disease because the breast is not an indispensable organ for maintaining human life. However, if the malignant cells spread to other important parts of the human body, such as the heart, the liver, and kidney, breast cancer may lead to death.

Breast cancer occurs almost entirely in women, but men can get breast cancer, too. And it is closely related to age—only 5% of all breast cancers occurring in women under 40 years old.

What is Molybdenum target mammography?

Molybdenum target, or molybdenum sputtering target, is known as the materials in physical vapor deposition for film coating.

Molybdenum target mammography is another important application of Molybdenum target. It is a non-invasive method to test breast diseases such as breast mass and calcification. From the viewpoint of techniques, it is a digital imaging technology that combines traditional radiology technology with modern computer technology that transforms the X-ray image into a digital image that can be quantized. Molybdenum target mammography enables radiologists to find suspicious malignant lesions in mammography easier. Thus, it has been used as a routine examination to reduce the risk of breast cancer.

Molybdenum target mammography
Molybdenum Target Mammography

Why is Molybdenum target mammography beneficial?

Molybdenum target mammography is currently the primary choice for the diagnosis of breast disease. It is an easy and non-invasive method of examination which can accurately reflect the condition of the entire breast. What’s more, it can be used to observe the breast disease caused by various factors and the results are relatively reliable. With the help of Molybdenum inspection, some precancerous lesions can be found and can be followed up for observation. So it is beneficial for women’s health.

Above information is from SAM Sputter Target, a global sputtering targets manufacturer specialized in Molybdenum target.

How was Molybdenum discovered? | History of Molybdenum

The brief history of the discovery of molybdenum

Although molybdenum was discovered in the late 18th century, it was used early before its discovery. For example, in the 14th century, Japan used a molybdenum-containing steel to make a saber. In the 16th century, molybdenite was used as graphite because it was similar to the appearance and properties of lead, galena, and graphite. At that time, Europeans referred to these kinds of molybdenum-containing ore as “molybdenite”.

Bengt Andersson Qvist
Bengt Andersson Qvist

In 1754, the Swedish chemist Bengt Andersson Qvist tested the molybdenite and found that it did not contain lead, so he believed that molybdenite and galena were not the same substance.

In 1778, the Swedish chemist Carl Wilhelm Scheele found that nitric acid did not react with graphite. While nitric acid reacted with molybdenite and produced a white powder, which was boiled together with an alkali solution to crystallize a salt. He believes that this white powder is a kind of metal oxide. After heating with charcoal, no metal is obtained; and when it is heated together with sulfur, the original molybdenite is obtained, so he believes that molybdenite should be an unknown mineral.

Peter-Jacob-Hjelm
Peter Jacob Hjelm

Inspired by Scheler, in 1781, the Swedish chemist Peter Jacob Hjelm used a “carbon reduction method” to separate a new metal from the white powder and named the metal “Molybdenum”.

Molybdenum industry development

Since molybdenum is easily oxidized and has high brittleness, molybdenum smelting and processing are limited. Molybdenum was not able to be machined in the early period, so it is impossible to apply molybdenum to industrial production on a large scale. At that time, only a few molybdenum compounds were used.

In 1891, France’s Schneider Schneider took the lead in the production of molybdenum-containing armor plates using molybdenum as an alloying element. It was found to have superior properties, and the density of molybdenum was only half that of tungsten. Molybdenum gradually replaced tungsten as an alloying element of steel. The application of the molybdenum industry was started.

At the end of the 19th century, it was found that the properties of molybdenum steel were similar to those of tungsten steel of the same composition after the addition of molybdenum in steel. In 1900, the production process of ferromolybdenum was developed. The special properties of molybdenum steel to meet the needs of gun steel materials were also discovered. This made the production of molybdenum steel rapidly developed in 1910. Since then, molybdenum has become an important component of various structural steels that are resistant to heat and corrosion and has also become an important component of non-ferrous metals — nickel and chromium alloys.

This history column aims at introducing the history of different metal elements. If you are a metal lover or history lover, you can follow our website. For previous posts of metal history, you can look them up in the “history” category.

Please visit https://www.sputtertargets.net/ for more information.

How was cerium discovered? | History of Cerium

Cerium is the most abundant rare earth elements. It is a silvery gray active metal, whose powder is easily oxidized in the air and soluble in acid. Cerium has been widely used in the automotive industry as a catalyst to reduce emission, and in glass industry as glass polishing materials. Cerium sputtering target is an important material in optical coating.

Discovery History

In 1803, when the German chemist Martin Heinrich Klaproth analyzed an ore, he determined the existence of a new metal oxide and called it ochra (ocha-colored soil). and the ore ochroite because it appears to be ochre when burning.

In the same year, the Swedish chemist Jöns Jakob Berzelius and the Swedish mineralogist Wilhelm Hisinger also analyzed the same new metal oxide, which is different from yttrium. Yttrium is dissolved in ammonium carbonate solution and appears red when burning on gas flame. However, this metal oxide is insoluble in ammonium carbonate solution and does not exhibit characteristic flame color when burning.

The ore is thus called ceria (bauxite), and the element is named cerium to commemorate the discovery of an asteroid, Ceres.

Discovery of cerium

Three Early Applications of Cerium

Carl F. Auer von Welsbach
Carl Auer von Welsbach

Eighty-three years after the discovery of “cerium”, in 1886, the Austrian Carl Auer von Welsbach found the first application of cerium (also rare earth) as a luminescent enhancer for steam hoods. He found that heating 99% thorium oxide and 1% cerium oxide would give off a strong light, so cerium used in coal gas lamp gauze can greatly increase the brightness of the gas lamp. The gas lamps in Europe, where electric lights were not yet popular, were the main source of lighting and were essential for industrial production, commerce, and life.

After the First World War, electric lights gradually replaced gas lamps, but cerium continued to open up new applications. In 1903, Welsbach once again discovered the second largest use of cerium. He found that cerium iron alloys can generate sparks under mechanical friction and therefore can be used to make flints. This classic use of cerium has been around for 100 years. Everyone who smokes knows that a lighter uses a flintstone, but many people they that it is cerium that brings fire to people.

cerium arc carbon rods
cerium arc carbon rods

In 1910, the third important application of cerium was discovered for arc carbon rods in searchlights and film projectors. Similar to the steam cover, cerium can improve the efficiency of visible light conversion. Searchlights were once an important tool in war air defense. Arc carbon rods have also been an indispensable source of light for filming.

Modern Applications of Cerium

Since the 1930s, cerium oxide has been used as a glass decolorizer, clarifier, colorant, and abrasive polishing agent.

As a chemical decolorizer and clarifier, cerium oxide can replace the highly toxic white magnetic (oxidation) to reduce operational and environmental pollution.

The use of cerium titanium yellow pigment as a glass colorant produces a beautiful bright yellow art glass.

Cerium oxide as a main component to manufacture various specifications of polishing powder has completely replaced iron red polishing powder, greatly improving polishing efficiency and polishing quality.

As a glass additive, cerium can absorb ultraviolet light and infrared rays and thus has been widely used in automotive glass. It not only protects against UV rays but also reduces the temperature inside the car, thus saving air conditioning power.

cerium polishing powder
cerium polishing powder

This history column aims at introducing the history of different metal elements. If you are a metal lover or history lover, you can follow our website. For previous posts of metal history, you can look them up in the “history” category.

Please visit https://www.sputtertargets.net/ for more information.

Application of titanium and titanium alloys in medical field

Titanium is an ideal medical metal material and can be used as an implant for human body. Titanium alloy has been widely used in the medical field and has become the material of choice for medical products such as artificial joints, bone trauma, spinal orthopedic internal fixation systems, dental implants, artificial heart valves, interventional cardiovascular stents, and surgical instruments.

Application of titanium alloy in facial treatment

When the human face is severely damaged, local tissue repair should be treated by surgical implantation. Titanium alloy has good biocompatibility and required strength, so it is an ideal material for facial tissue repair. The skull bracket made of pure titanium mesh has been widely used in the reconstruction of the humerus and has achieved good clinical results.

titanium mesh
titanium mesh

Application of titanium in the pharmaceutical industry

SAM®Titanium is mainly used in the pharmaceutical industry for making containers, reactors, and heaters. Equipment used in the production of pharmaceuticals is often exposed to inorganic acids, organic acids, and salts, such as hydrochloric acid, nitric acid, and sulfuric acid. Therefore, these devices are easily damaged by long-term corrosion. On the other hand, steel equipment will introduce iron ions that affect product quality.

These problems can be solved with titanium equipment. For example, a penicillin esterification kettle, a saccharification tank, a chloramphenicol thin film evaporator, a dimethyl sulfate cooler, a chemical liquid filter, all have precedents for selecting a titanium material.

Application of titanium in medical devices

In the history of the development of surgical instruments, the first generation of surgical instruments was mostly made of carbon steel, which was eliminated because the performance of carbon steel instruments after electroplating did not meet the clinical requirements. The second generation is austenitic, ferritic and martensitic stainless steel surgical instruments. However, due to the toxicity of chromium in the stainless steel composition, the chrome-plated layer has a certain influence on the human body. Therefore, the third generation–titanium surgical instrument appeared.

titanium surgical blades
titanium surgical blades

The lightweight and high strength of titanium make it particularly suitable for microsurgery. Titanium has the advantages of corrosion resistance, good elasticity, and no deformation; even after repeated cleaning and disinfection, the surface quality of titanium is not affected; titanium is non-magnetic and does not pose a threat to tiny, sensitive implanted electronic devices. These advantages make the application of titanium surgical instruments more and more extensive. At present, titanium has been used to make surgical blades, hemostats, scissors, electric drills, tweezers and so on.

Application of titanium and titanium alloys in dentistry

Metals used in dental surgery began with amalgams and metal crowns in the 1920s. In the 1960s, gold, silver, and palladium alloys were mainly used. After the 1970s, stainless steel became the most commonly used material for permanent and detachable instruments for orthodontics. In the 1990s, titanium casting technology was promoted and applied.

titanium dental implant
titanium dental implant

Titanium has the characteristics of high dimensional accuracy, no bubbles, and shrinkage holes. Among the metal materials used for hard tissue repair in the human body, the elastic modulus of titanium is closest to human tissue, which can reduce the mechanical incompatibility between the metal implant and the bone tissue.

Please visit https://www.sputtertargets.net/ for more information.

Quick link to related titanium products:

Titanium (Ti) Sputtering Target

Planar Titanium (Ti) Sputtering Target

Rotatory Titanium (Ti) Sputtering Target

Short introduction to the element: Scandium

SAM®Scandium was first discovered by Lars Nilson in 1879. The origin of the name scandium comes from the Latin word ‘scandia’ meaning Scandinavia. It is a bright, silvery-white metal with active chemical properties that it easily oxidizes in air and reacts strongly with water. It has many of the characteristics of the rare earth elements, particularly yttrium.

In absolute terms, however, scandium is not rare. Scandium is abundant in minerals that it is found in concentrated amounts in the minerals euxenite, gadolinite and thortveitite; however, most of them existed as the form of scandium oxide (Sc2O3); thus due to the difficulties in the preparation of metallic scandium, global trade of the pure metal Scandium is very limited.

Scandium is usually alloyed with aluminum. Aluminum scandium alloys are used in the aerospace industry and other applications such as bicycle frames, fishing rods, golf iron shafts and baseball bats, etc. When used as an alloying element, adding a small amount of scandium to the aluminum alloy can promote grain refinement and increase the recrystallization temperature from 250 ° C to 280 ° C. Scandium is a strong grain refiner and an effective recrystallization inhibitor for aluminum alloys. It has a significant effect on the structure and properties of the alloy, and greatly improves the strength, hardness and corrosion resistance of the alloy.

Aluminum Scandium alloy

In addition to scandium alloys, garnets containing scandium are used as gain media in lasers, including those used in dental surgery, and scandium-stabilized zirconia has been recognized as a high-efficiency electrolyte in solid oxide fuel cells. Finally, scandium oxide is used in metal-halide lamps that are used to produce high-intensity white light that resembles sunlight.

Basic specification of scandium

Symbol: Sc
Atomic Number: 21
Atomic Weight: 44.95591
Color: silvery white
Other Names: Skandium, Skandij, Scandio
Melting Point: 1541 °C, 2806 °F, 1814 K
Boiling Point: 2836 °C, 5136 °F, 3109 K
Density: 2.985 g·cm3
Thermal Conductivity: 15.8 W·m-1·K-1

Please visit https://www.sputtertargets.net/ for more information about Scandium and other rare earth elements.

When do you need target bonding?

This post gives an answer when should require a target bonding service and how to choose different bonding services.

SAM®Sputtering targets are the material that is indispensable during a sputtering process. Sputtering targets are normally comprised of one to three distinct parts, including the backing tube, a bonding layer, and the target material. The figure shown below is an example of rotatory sputtering target. Among them, the former two parts are not unnecessary, depending on the type of materials required for the sputtering process and the manufacturing techniques that are available to produce the target. If the target material is brittle and can be easily broken during the sputtering process, it is necessary to require a target bonding service.

parts of rotatory target
parts of rotatory target

 

In terms of the target material, sputtering target varies from pure metal to ceramics. Many pure metal targets are stronger, thus some of them can be made into single piece or monolithic targets without the backing tube or a bonding layer. In contrast, ceramic targets usually require the three-layer construction technique because they are not strong enough to support their own weight and the pressure inside the tube.

Ceramic targets are usually bonded to a stainless steel backing tube because of its non-magnetism and low coefficient of thermal expansion. The thermal expansion coefficients of the backing tube material and the target can never be ignored, because a great difference between these two coefficients can lead to large stress concentrations in the target material during the sputtering process that can cause the ceramic materials to crack and break off.

In addition to stainless steel backing, indium bonding is used more frequently due to its low melting point, good thermal conductivity, low chemical reactivity, and good adhesion to most materials. Indium has the best thermal conductivity of all available bonds and is the most efficient at drawing heat away from the target. Most materials can be indium bonded but there are a few exceptions, mainly due to the low melting point of indium. Indium has a melting point of 156.6°C so temperatures in excess of 150°C will cause the bond to melt and fail.

Stanford Advanced Materials is devoted to machining standard backing plate. Please visit https://www.sputtertargets.net/ for more information.

Requirements of ITO sputtering targets for LCDs

After a long period of development, the quality of liquid crystal displays (LCDs) continues to increase, and the cost continues to decline. This means that LCDs have higher requirements for ITO sputtering targets. Therefore, in order to keep up with the development of LCD, the future development trend of ITO targets is as follows:

Liquid crystal displays
Liquid crystal displays
Lower resistivity

In recent years, liquid crystal displays have been moving in a more and more refined direction, and with the upgrade of drivers, a transparent conductive film with lower resistivity is required. Therefore, the resistivity of their raw material—ITO target—is also required to be lowered.

Increase target density

When the target density is low, the surface area for effective sputtering is reduced, and the sputtering speed is also lowered. The high-density target has uniform surface, and can obtain low-resistance film. In addition, the density of the target is also related to its service life, and the high density target generally has a longer life. This means that increasing the density of the target not only improves the film quality, but also reduces the cost of the coating, so it must be the direction for the future development of ITO targets.

Larger size

Now that the LCD screen is getting bigger and bigger, correspondingly, the size of the ITO target has to be larger. However, there are still many problems to be solved in large area coating. In the past, people weld small targets together and splice them to achieve large area coating. But the joints were likely to cause a drop in coating quality. In order to solve this problem, the size of ITO sputtering target is required to be larger in the future. This is also a big challenge for the ITO target industry.

Higher use ratio

Planar targets are still one of the most used types of sputtering targets. But one of the deadliest disadvantage of planar targets is the low use ratio. People may develop other types of ITO target, such as rotatory targets and cylindrical planar targets in the future to increase target utilization.

Please visit https://www.sputtertargets.net/ for more information.