Ten features of high precision surfacer

First, the high-precision surface surfacing instrument should have the following ten characteristics:

<1> Whether there is a program-controlled wind-heat assisted-desorption system. When the sample is heated and desorbed after the adsorption temperature is saturated at a liquid nitrogen temperature of -195.8°C, the temperature needs to be increased rapidly so that the nitrogen adsorbed on the surface of the powder is rapidly desorbed and entered. Detector; High-speed desorption can concentrate the signal and get sharp and sharp desorption peaks, which is helpful to improve the sensitivity and resolution of the instrument. In addition, the sharp and sharp desorption peak can reduce the influence of background noise and improve the accuracy of instrument testing. The sharp desorption peak is the ideal peak shape sought by chromatographers. In the previous semi-automated instruments, artificially replacing the liquid nitrogen cup with a water cup was generally used, and the temperature of the sample was rapidly raised to room temperature by utilizing the characteristics of water-to-heterogeneous heat; however, in a fully automated apparatus, the auxiliary heating was abandoned if it was automated. Attached to the natural temperature in the air desorption, due to the low thermal conductivity of the glass, the slow temperature rise, will make the desorption peak short and wide, so that increasing the impact of background noise, reduce sensitivity and resolution, loss of test accuracy. Program-controlled wind-heat assist device, automatic program-controlled start-stop, wind-heat time can be set according to the speed of sample desorption, ensure sharp and rapid desorption peaks, shorten the peak time, remove peaks and sharp peaks, reduce background errors .

<2> The nitrogen partial pressure detection control is performed by the flow sensor method or the concentration chromatogram detector method in the BET multipoint method. According to the BET theory, the nitrogen concentration needs to be adjusted from 5% to 30%, and the nitrogen concentration detection is the accuracy of the test result. The key link. In the nitrogen concentration test, the flow sensor method is to measure the flow rate of nitrogen and carrier gas to find the nitrogen concentration. The nominal limit accuracy of the imported Horinville flow sensor used is 0.1 ml/min, and the highest accuracy for the 5 ml/min nitrogen flow rate test is only 2%. Chromatographic concentration sensor test nitrogen concentration, accuracy can reach 0.1% or more, and is not affected by the flow rate range;

<3>Whether there is a program-controlled six-way valve calibration system; whether the quantitative tube volume can be programmed to switch six-way valve is the main calibration device for chromatogram metering, and there are manual six-way valve and electric six-way valve; program-controlled electric six-way valve calibration System, automatic control of calibration process software; optional function of quantitative tube volume programming; for different samples, the specific surface may be thousands of times more than the difference, and the amount of adsorbed nitrogen gas is also very different. It is not possible to calibrate all samples by a single volumetric calibration tube. the amount. So for the calibration system should be connected to different volume of the quantitative tube, can achieve higher accuracy. It is more complicated to manually replace the different volumetric quantification tubes and even open the shells for replacement. Program controlled quantitative switch only need to set the access number in the software, electric switch.

<4>Whether there is a one-piece in-situ purging device in the form of a separate purging furnace, and the sample purging process needs to be installed on a sifter that is separated from the host. After the treatment, the scavengers are disassembled and reinstalled. Test on the instrument host. The integrated purging and processing system has two advantages over the split sifter: first, it is easy to operate and only needs to be installed once; second, the treatment effect is better, and the sample is prevented from contacting the air again when the sample tube is disassembled and disassembled; For organic and biological powder materials, the mass percentage of water content may be relatively large. If it exceeds 1%, it needs to be oven-dried before purging, otherwise it needs to be evacuated and re-weighed;

<5> Whether to have the purge timing function Purge program timing, stop heating at that time, voice prompts, this feature makes the purge processing conditions uniform, also makes the operator more at ease with other tasks, without having to worry about the purge overtime caused by processing Inconsistent conditions;

<6> Whether or not the gas-purifying cold-trap device has a purity of 99.99% to 99.999% of the purity nitrogen and high-purity helium gas used in the surface test, and 0.001%-0.01% of the impurity gas (mainly water and other high boiling points Adsorption gas) will be adsorbed first at low temperature adsorption, thus affecting the amount of adsorbed nitrogen; due to the continuous flow of gas through the sample to be measured in the surface area test, the gas impurities such as water on the surface of the sample will gradually accumulate; The effect is seen in "Impact of moisture on the adsorption process." The cold trap is an effective way to eliminate high-boiling point gas impurities. Generally, this device is equipped in high-demand equipment. The cold trap equipped with the surface meter allows the high-boiling impurities such as moisture absorbed by the sample to be captured by the cold trap in advance. The purified high-purity nitrogen and high-purity helium gas have a moisture content of less than 10-17Pa, which can reach ultra-high purity gas state;

<7> Whether there is a detector constant temperature system Chromatography The surface area meter uses a thermal conductivity cell as a detector; the temperature drift is the main cause of the error in the thermal conductivity cell detector, and generally the detector of the high precision chromatograph has a complicated constant temperature system and The temperature drift suppression and elimination system, but at the same time increase the cost of the instrument; before and after the detector constant temperature device, the zero drift can be reduced from 1% to 0.1%, the device is particularly effective for testing small specific surface area samples (<10m2/g);

<8> Whether there is liquid nitrogen temperature real-time monitoring function than the use of surface nitrogen liquid nitrogen are purchased near the use of units, are generally gas plant oxygen production by-products, the purity instability of a large difference, making the liquid nitrogen temperature has ± Changes around 1°C; nitrogen adsorption is sensitive to changes in liquid nitrogen temperature; in addition, the liquid nitrogen surface inside the Dewar cup has an influence on the amount of adsorption; the liquid nitrogen temperature monitoring sensor can monitor the liquid nitrogen temperature and The amount of liquid nitrogen in the cup is sufficient.

<9> Whether there is an air supply switch indication and protection device Chromatograph generally requires the operator not to turn on the power supply when there is no open air, that is, “open power after opening air first, turn off air after power off first”, otherwise detection may occur. The danger of burnout if the device is energized without ventilation; and the gas source indication and protection device removes this hazard.

<10> Instrument parameters whether hardware and software are simultaneously displayed The main parameters of the specific surface instrument include the main detector voltage, current, concentration detector voltage, current, main detector output voltage signal, concentration detector output signal, signal amplification, liquid nitrogen Temperature and so on. If the instrument has not only detection and display on the software, but also the hardware display function on the LCD screen of the instrument, even if the computer is not turned on or communication is abnormal, the instrument status can be clearly grasped, making the instrument more reliable; The mechanical parts, such as the motor, desorption fan, purge timing, and air supply switch status, have hardware indicators to indicate the working status. The status of each part of the complex equipment is normal or not, and is displayed by the software. The hardware indication is necessary; the gas flow is displayed outside the electronic sensor, and then displayed by the mechanical rotor flow meter, which will make the flow available at a glance, and the size is clear. The modern analysis instrument that is more stable, reliable, and reliable can have only one control button but displays The status indicators of the screen, indicator, etc. cannot be saved.

Second, the purchase of high-precision surface instrument should have the following five key points:

<1>Select the classic manufacturer's product.

Analytical instrument performance evaluation includes accuracy, repeatability, and stability. Accuracy and repeatability The purchaser usually achieves the purpose of inspection by actually sampling and multiple batch or single grouping. The stability is whether the instrument can be operated stably for a long time, adaptability to the environment, etc. The surface surfacing instrument is a comprehensive analytical instrument such as chemistry, mechanics, electronics, and software without long-term practical experience and information feedback from actual customers on site. It is difficult to have a reliable quality stability guarantee, and it is impossible to guarantee the accuracy of the later experimental results and the stability of the instrument. Therefore, one of the selection elements is to select products with long-term R&D production history and classic manufacturers with long-term customers. The 3H-2000 Series Surface Profiler has a 9-year production history and customers in China.

<2> Excellent price/performance ratio.

It's not necessary to spend money on features that don't need it. In the case of guaranteed product quality and basically the same performance, a more favorable price can guarantee the efficiency of the use of capital by a unit or individual. Welcome to the classic manufacturer's economic brand.

<3> Average annual fee.

Including natural loss and maintenance costs. For example: A product purchase price of 80,000 yuan, B product purchase price of 100,000 yuan. If product A has a service life of 5 years, product B has a service life of 10 years. In fact, B products are cheaper than the average annual cost. The above does not include the losses and maintenance costs caused by the interruption of the experiment due to the frequent repair of A products.

<4> The after-sales service of the product avoids quality problems as much as possible. If quality problems occur, classic manufacturers can provide timely and thoughtful services. With fierce market competition, enterprises with viability and basic profits can provide long-term and thoughtful services and technical support.

<5> Humanized design.

The user-friendly design can prevent the instrument from being damaged due to occasional operational errors. At the same time, it guarantees that the user's process is light, comfortable and enjoyable. Such as 3H-2000BET-M type of in-situ purging process, gas source switch indication and automatic gas shut-off protection, various hardware operation instructions, quantitative control program switching, important links sound prompts.

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