Three Kinds of High Temperature Precious Metal Pt-Rh Thermocouples

Platinum rhodium thermocouple, also known as high temperature noble metal thermocouple, is divided into three types: S-type thermocouple (platinum rhodium 10-platinum thermocouple), R-type thermocouple (platinum rhodium 13-platinum thermocouple), B-type thermocouple (platinum rhodium 30-platinum rhodium 6 thermocouple).

It mainly divided into single platinum rhodium and double platinum rhodium, which are suitable for various high temperature situations and widely used in glass, ceramics and industrial salt bath furnaces. And so on in the production process temperature measurement. 

Among them, S-type thermocouple is the most commonly used one in domestic industry. Because the measuring temperature is high, the stainless steel protective pipe can only withstand high temperature up to 1000 degrees, and the stainless steel protective pipe withstanding 1000 degrees or more is expensive. Therefore, corundum ceramic protective pipe with high purity can withstand high temperature up to 1600 degrees, and its shortcoming is fragile.

S-type thermocouple:

Platinum rhodium 10-platinum thermocouple (S-type thermocouple) is a precious metal thermocouple. The diameter of the couple wire is 0.5mm and the allowable deviation is -0.015mm. The nominal chemical composition of the positive electrode (SP) is platinum-rhodium alloy, which contains 10% rhodium and 90% platinum. The negative electrode (SN) is pure platinum, so it is commonly called single platinum-rhodium thermocouple. The maximum long-term service temperature of the thermocouple is 1300 C, and the maximum short-term service temperature is 1600 C.

The S-type thermocouple has the advantages of the highest accuracy, the best stability, the wide temperature measuring range and the long service life in the thermocouple series. It has good physical and chemical properties, thermoelectric stability and oxidation resistance at high temperature. It is suitable for oxidation and inert atmosphere. Since S-type thermocouple has excellent comprehensive performance and meets the international temperature standard, it has long been used as an interpolation instrument of international temperature standard. Although ITS-90 stipulates that it will no longer be used as an internal check instrument of international temperature standard in the future, the International Temperature Advisory Committee (CCT) believes that S-type thermocouple can still be used to approximate International temperature. Mark.

The shortcomings of S-type thermocouple are thermoelectric potential, low thermoelectric potential ratio, low sensitivity reading, low mechanical strength at high temperature, very sensitive to pollution, expensive precious metal materials, and large one-time investment.

R-type thermocouple:

Platinum-rhodium 13-platinum thermocouple (R-type thermocouple) is a precious metal thermocouple wire. The diameter of the couple wire is 0.5mm and the allowable deviation is -0.015mm. The nominal chemical composition of the positive electrode (RP) is platinum-rhodium alloy. The nominal chemical composition of the positive electrode (RP) is platinum-rhodium alloy. The rhodium content is 13%, platinum content is 87%, and the negative electrode (RN) is pure platinum. The maximum service temperature for a long time is 1300 C, and the maximum service temperature for a short time is 1600C.

R-type thermocouple has the advantages of the highest accuracy, the best stability, the wide temperature measuring range and the long service life in the thermocouple series. It has good physical and chemical properties, thermoelectric stability and oxidation resistance at high temperature. It is suitable for oxidation and inert atmosphere. From 1967 to 1971, three major research institutes, NPL, NBS and NRC, carried out a cooperative study. The results show that the stability and reproducibility of R-type thermocouple are better than S-type thermocouple.  

The shortcomings of R-type thermocouple are thermoelectric potential, low thermoelectric potential ratio, low sensitivity reading, low mechanical strength at high temperature, very sensitive to pollution, expensive precious metal materials, and large one-time investment.

Type B thermocouple:

Platinum Rhodium 30-Platinum Rhodium 6 thermocouple (B type thermocouple) is a precious metal thermocouple. The diameter of the couple wire is 0.5mm and the allowable deviation is -0.015mm. The nominal chemical composition of the positive electrode (BP) is platinum-rhodium alloy, which contains 30% rhodium, 70% platinum, and the negative electrode (BN) is platinum-rhodium alloy with 6% rhodium, so it is commonly called Double platinum-rhodium thermocouple wire. The maximum long-term service temperature of the thermocouple is 1600 C, and the maximum short-term service temperature is 1800 C.

Type B thermocouple has the advantages of the highest accuracy, the best stability, the long service life and the high upper limit of temperature measurement in the thermocouple series. It can be used in oxidizing and inert atmosphere or in vacuum for a short time, but not in reducing atmosphere or atmosphere containing metal or non-metal vapor. A distinct advantage of B-type thermocouple is that compensation wire is not needed, because the thermoelectric potential is less than 3_V in the range of 0-50 C.

The shortcomings of B-type thermocouple are thermoelectric potential, low thermoelectric potential ratio, low sensitivity reading, low mechanical strength at high temperature, very sensitive to pollution, expensive precious metal materials, and large one-time investment.

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Zirconia Thin Film VS Hafnium Oxide Thin Film

Thin film is a thin and soft transparent sheet, which is made of plastics, adhesives, rubber or other materials. It is a kind of two-dimensional material which is formed on the surface of the substrate by atoms, molecules or ions.

There are several thin films: optical film, composite film, superconducting film, polyester film, nylon film, plastic film and so on.

Thin films are widely used in electronics, machinery, printing and other industries.

 

Thin film materials refer to thin metal or organic layers with thickness ranging from a single atom to a few millimeters. Electronic semiconductor functional devices and optical coatings are the main applications of thin film technology.

Zirconia (ZrO2) has the characteristics of hardness, compactness and inhomogeneity. The film needs to be dried to remove its absorption.

The purity and importance of the material are not sufficient. The film usually lacks overall compactness. It benefits from the proper use of IAD to increase its refractive index to porosity to overcome its inhomogeneity. The purity reaches 99.99% base.

SAINTY et al. have successfully used ZRO2 as a protective film for aluminum and silver films. The ZRO2 film is obtained by using 700EV argon ion as a plating aid on room temperature substrates. It is generally white columnar or block, and the evaporation molecules are ZRO, O2.

Hafnium oxide (HfO2) is one of the most important high refractive index materials in ultraviolet to near infrared (UV-NIR) band. It has high band gap, high laser damage threshold, corrosion resistance and easy preparation. It is widely used in laser optical thin films, especially in the field of laser thin films with high damage threshold.

The combination of hafnium oxide film and low refractive index silica film can be used to fabricate high reflective film, antireflective film, polarized light splitting film, filter film and other optical thin film components.

The preparation methods of hafnium oxide thin films mainly include electron beam evaporation, ion beam sputtering, magnetron sputtering, atomic layer deposition and other physical vapor deposition techniques.

The hafnium oxide thin films prepared by ion beam sputtering have the advantages of small absorption, amorphous structure, low optical scattering, small defect density and so on, and have become the Important process to prepare hafnium oxide thin films.

Titanium Application in The Pharmaceutical Industry

     Titanium as a new material, developed in the field of the pharmaceutical industry, medical equipment, human implants, etc., but the use of the past two decades. However, it was a great success and has made significant social and economic benefits, shortening the gap between China and the world's advanced countries.

     Another notable feature of titanium is biocompatible, they have been selected as the best human implant material. More than a decade, the world and many of our research department, medical, hospital, also made a lot of basic work and clinical studies confirm that titanium wire is the best material from human implant depth, breadth, all these years with titanium material for the femoral head, artificial wrist, knee, dental Implants, cranioplasty, pacemakers have documented thousands of cases, these years of research, track, compare, titanium is reported so far the best human implant material.

  Medical equipment, surgical instruments is one area of rapid development in recent years, due to the titanium used as a surgical instrument has special advantages, which won the surgery, ophthalmology, cardiothoracic surgeon welcome, but also one of the development of today's surgical instruments.

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Niobium VS Other Refractory Elements in superalloys

Refractory elements are important alloying additions in both nickel-base and ironnickel-base superalloys. They are responsible for the increased high temperature mechanical properties present in current superalloy systems.

These precipitates are formed by the precipitation reaction of Ni with Al and Ti or, in the case of the iron-nickel-base superalloy, Nb and Ti. The refractory elements, Nb and Ta, perform strengthening functions in both the y and the precipitating y’ and y” phases.

 These elements can behave somewhat differently as carbide formers. They are also known to affect corrosion resistance and alloy stability. Both elements are bee metals, and are highly misfitting in the fee Ni lattice; consequently giving rise to their well deserved reputation as potent solid-solution strengthening elements in the y as well as in the precipitating phases. Tantalum and niobium sheet are known to partition into the strengthening phases, and are also MC- type carbide formers.

The detailed roles of refractory elements in superalloys are not well understood. In particular, the science-based technology for substituting one refractory element for another does not exist. For example, it is not known whether Ta and Nb are better strengtheners than other refractory elements W and molybdenum tubing.

Furthermore, to varying degrees these elements increase incipient melting and solidus temperatures. This results in not only a higher and broader temperature range for solutionization and homogenization, but also in segregation problems during the primary vacuum refining and melting process (VIM) and during such secondary structures refining melt processes as VAR and ESR. However, Ta is known to decrease the tendency for freckling during the directional solidification of turbine blades. 

 In addition, it is not known whether the large degree of misfit between the y and precipitating phases, due to refractory element additions, affects such properties as strain strengthening and y and r coarsening kinetics, which is an issue with respect to long term applications.

 In order to design and develop more enhanced superalloys, as well as to conserve on the more expensive and less abundant alloying elements, a better understanding on the role of these refractory elements on the mechanical and microstructural properties in superalloys is necessary.

Carbon Nanotubes May Cheaply Harvest Sunlight

A new alternative energy technology relies on the element most associated with climate change: carbon.

University of Wisconsin-Madison researchers are studying how to create inexpensive, efficient solar cells from carbon nanotubes, which are sheets of carbon rolled into seamless cylinders one nanometer in diameter. Many researchers are studying how to use nanotubes for mechanical and electronics applications, but materials science and engineering assistant professor Michael Arnold is one of the first to apply them to solar energy.

"We are developing new materials and methods to create scalable, inexpensive, stable and efficient photovoltaic solar cell technologies," Arnold says. "Semiconducting carbon nanotubes have remarkable electronic and optical properties that are ideally suited for photovoltaics, so they are an interesting starting point."

Carbon is a promising choice for solar cells because it is an abundant, inexpensive element, and carbon nanotubes have excellent electrical conductivity and strong optical absorptivity. Most current solar cells use silicon, which converts 10 to 30 percent of sunlight absorbed into electricity. This is a good rate, but silicon cells are expensive.

"The cost is upfront for silicon cells, and the cost per kilowatt-hour is five times more than you'd pay for coal over 20 years — that's not very motivating for people," says Arnold. With carbon nanotubes, he hopes to achieve efficiency comparable to silicon solar cells for less cost.

Arnold says solar is a valuable energy source since the sun outputs approximately 1,000 watts per square yard. A solar cell that is only 20 percent efficient would generate about 200 watts per square yard on a sunny day, so coating the roof of an average 40-square yard house with solar cells would make a significant dent in the average energy needs of the household. To have an effect on the national electric grid, Arnold envisions expansive fields of solar cells built in desert regions.

"Solar is a viable technology for producing energy," Arnold says. "It's just too expensive right now."

To create the new carbon nanotube solar cells, Arnold and his students grow nanotube structures and then separate the useful semi-conducting nanotubes from undesirable metallic ones. They also separate the tubes according to diameter, which determines a particular nanotube's bandgap, or wavelength of light the tube can absorb. Certain bandgaps are more suitable than others for absorbing sunlight.

After sorting out the useful nanotubes, the team wraps them in a semi-conducting polymer to make the tubes soluble. They turn the combined nanotubes and polymer into a solution, which can be sprayed in a thin film onto transparent indium-tin-oxide coated glass substrates. The researchers then deposit an electron-accepting semiconductor and a negative electrode on top of the nanotubes to complete the entire cell.

In creating the new solar cells, Arnold, who is funded by the National Science Foundation, is attempting to answer a variety of fundamental science and research questions. He is studying how charge is generated in the nanotubes in response to light and how different electron-accepting materials affect the efficiency and speed of the separation of that charge.

 "The driving question is, can we understand how to both process the tubes to get the morphology we want, and can we also learn how light creates charges in our carbon nanotube materials and how these charges separate?" he says.

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