甲醛氣體傳感器外文翻譯

1、1 外文資料翻譯譯文 具有高靈敏度的甲醛氣體傳感器的制備及其氣敏特性相對甲醛混有氧化鉻的氧化銦氣體傳感器特性已經(jīng)研究過了。間接加熱式氣體傳感器是用敏感材料進行制備的。最終的材料的狀態(tài)和傳感層的形態(tài)通過x射線衍射和掃描電子顯微鏡分別在焙燒前后觀察到其特點。操作溫度對傳感器響應的影響氧化鉻和氧化銦傳感器的氣體濃度特性的對比已經(jīng)研究過了。結果表明，在低操作溫度該傳感器對于甲醛具有良好的反應性能，使他們成為甲醛氣體檢測最有希望的候選材料。1介紹作為一個重要的工業(yè)化學品，甲醛被應用于制造業(yè)，建筑板，膠合板和漆這樣的材料。此外，它還是消費產(chǎn)品中一個中間添加物，如洗滌劑和肥皂。由于其殺菌性能也可用于藥理學和

2、藥物中。然而，調查結果表明，因為它是揮發(fā)性有害化合物，所以甲醛會對人體造成許多損害。因此，需要一種有效的方法來監(jiān)測甲醛進而進行氣體環(huán)境測量與控制。制造氣體傳感器被認為是一個理想的監(jiān)測氣體的手段。我們目前的調查主要涉及與甲醛的檢測。雖然半導體金屬氧化物氣體傳感器提供了對有毒氣體或可燃性氣體的安全檢測，但是他們?nèi)匀挥幸欢ǖ木窒扌?，如靈敏度，選擇性，長期穩(wěn)定性等等。為了克服半導體金屬氧化物氣體傳感器的缺點，半導體金屬氧化物的制備與摻雜的研究已經(jīng)做過了。氧化銦是一個有希望的具有寬禁帶的半導體材料（3.70電子伏特），其電子濃度主要取決于計量缺陷的濃度（如氧空位）就像其他金屬氧化物半導體。 就傳感機制來

3、說，顆粒的大小，缺陷，表面與界面的性能和化學計量學直接影響了傳感器表面的氧化物種類的狀態(tài)和數(shù)量，最后影響了金屬氧化物傳感器的性能。因此，為了提高并改善氣體傳感性能（敏感性，選擇性，較好的熱穩(wěn)定性和較低的操作溫度），氧化銦通常用于納米結構形式或摻雜合適的貴金屬和金屬氧化物。作為一個單組分氧化物，由于其良好的靈敏度，氧化銦是一種很有前途的氧化性氣體檢測的候選者。因此，當其他金屬氧化物摻雜氧化銦，對于不同的氣體可調諧的氣體靈敏度也不同。他們已經(jīng)很好的研究了檢測大部分重要氣體的傳感器材料，如乙醇，一氧化碳，二氧化氮，和氫氣。然而，研究很少集中在甲醛傳感器的材料特性。在本次調查中，用固態(tài)合成技術制備氧化

4、鎘和氧化銦的混合物，通過x射線衍射和掃描電鏡圖像來觀察其特點。基于化鎘和氧化銦的混合物的間接加熱的氣體傳感器就被制備好了。甲醛傳感器中混合物的特性也就確定了。2實驗所有的來源于商業(yè)用于實驗的化學試劑需要保證沒有進一步提純。根據(jù)我們的初步實驗，氧化銦或氧化鎘對于甲醛來說不具有良好的傳感特性。氧化銦或氧化鎘粉末是由碳酸鹽和氧化銦制備的。不同階段碳酸鹽氧化銦樣品的成分已經(jīng)研究過了。氧化鎘：氧化銦=1 : 2.5重量比被認為是最有希望的甲醛氣體的傳感特性?；旌险麴s去離子水的碳酸鹽氧化銦樣品仔細研磨至約50-500納米大小的顆粒。然后對樣品分別以500，650，750和850攝氏度在空氣中煅燒1個小時。

5、x射線衍射（x射線衍射, rigaku d/max-3b粉末衍射儀）有著用于鑒定階段目標的銅質物和k輻射（=1.54056a），其中衍射x射線強度被記錄為一個2。該樣本是從10度到70（2）以0.02為一個單位進行掃描。根據(jù)scherrer的公式：rx = 0.9/(b cos ),平均晶粒尺寸（接收）測量從x射線衍射峰以每分鐘2的速度進行掃描，是x射線的波長，是衍射角，b是真正的半個波峰寬度。掃描電子顯微鏡（掃描電鏡）的照片是由荷蘭的xesem-tmp獲得的。該間接加熱傳感器可以根據(jù)文獻13進行制備?；旌喜牧献鳛橐粋€敏感的物質由帶有金屬電極和鉑電線氧化鋁管制備成的。鎳鉻合金線纏繞在氧化鋁管上

6、被用作電阻。這個電阻需要確保有基本的加熱和溫度控制。這些元素在650攝氏度的空氣中燒結1小時。焙燒后，基于氧化銦的敏感物質的厚度大約為0.6 毫米。為了提高其穩(wěn)定性和重復性，氣體傳感器適宜在150攝氏度的空氣中燒1小時。該傳感器電阻通過在電壓為5伏下的串聯(lián)電阻相連接的傳統(tǒng)電路進行測量。氣體反應被定義為在真空和氣體中的電阻比。在650攝氏度煅燒的氧化鉻與氧化銦材料的傳感性能優(yōu)于在500，750，和850攝氏度進行煅燒的傳感性能。在本文中，我們主要討論在650攝氏度焙燒的材料。x射線粉末衍射模式的準備和煅燒材料如圖1所示。氧化銦和氧化鉻峰值可以通過在650攝氏度情況下煅燒1小時的樣品的外形進行觀察

7、。氧化銦和氧化鉻的外形展現(xiàn)了一個很高的結晶度。400攝氏度碳酸鹽分解，氧化鉻形成。相氧化銦的狀態(tài)沒有改變，和其他的狀態(tài)（例如，cdin2o 4）在650度燃燒后并不能看出來。.另一方面，氧化銦的x射線衍射峰的寬度在煅燒前后并不改變，從中我們可以看出氧化鉻能有效地抑制晶粒生長。根據(jù)雪萊的方程計算的晶粒平均尺寸28納米，煅燒后氧化銦30納米，氧化鉻31納米。比較的結果是，掃描電鏡圖片顯示了制備和煅燒樣品中各種大小的粒子。大顆粒由小微晶組成。圖2（a）和（b）分別顯示了制備和焙燒過程中的掃描電鏡圖像。大多數(shù)粒子有不規(guī)則的形態(tài)，顆粒大小的范圍是100500納米。傳感器的導電率取決于氣體種類，同時也取決

8、于暴露在測試性氣體中的傳感材料的操作溫度，這些問題以經(jīng)解決了。圖3描述傳感器的反應和操作溫度之間的關系。操作溫度對反應有重大影響。有趣的是，反應首先逐漸增加，然后隨著操作溫度的提高減少。可以看出，對于甲醛氣體在低溫范圍內(nèi)，基于氧化鉻和氧化銦的傳感器具有優(yōu)異的氣敏特性。在95攝氏度它展出了對甲醛氣體最高的響應。較低的工作溫度在應用中是一個優(yōu)點。如圖4所示，響應的抵押氧化銦基于傳感器的氧化鉻和氧化銦在95度操作時的響應展示了對氣體濃度的良好依賴性。該傳感器對酒精和汽油有著非常小的反應，但對于甲醛氣體有著較大響應。百萬分之十的甲醛氣體的反應超過了百萬之八十的甲醛氣體的響應。本反應是大大高于最近報道氧

9、化鋅和氧化鉛，三氧化鎢和氧化鉛，鎳，和基于甲醛氣體的la0.68pb0.32feo3。這種氣體傳感器展現(xiàn)了對甲醛氣體的較大反應和對酒精與汽油的較高選擇性。這一結果表明，氧化鉻和氧化銦是一個良好的檢測甲醛氣體的氣敏材料，可用于監(jiān)測和控制甲醛氣體。一個良好的反應和快速響應、恢復時間可以用這種傳感器在最佳工作溫度95攝氏度下進行觀察。針對不同甲醛氣體濃度(10100 ppm)的器皿傳感器如圖5所示。作為一個高靈敏度的傳感器，它可以測量非常低濃度，甚至百萬分之一。隨著甲醛氣體濃度的增加輸出電壓的增加呈線性關系并且有較短的響應時間。響應時間和恢復時間（定義為達到最終平衡值90%）為2分鐘，恢復時間為4分

10、鐘。氣敏機理是基于氧化鉻和氧化銦材料的電導的變化。材料的表面對氧的吸收影響了氧化鉻和氧化銦傳感器的導電性。氧的吸附取決于顆粒大小，較大的材料面積，和合適的傳感器操作溫度。隨著空氣中溫度的增加，氧的狀態(tài)被吸附在氧化鉻和氧化銦材料的表面的氧的狀態(tài)在下面的反應中發(fā)生。氧從材料中捕獲電子，導致了空穴濃度的增加和電子濃度的減少。當傳感器接觸甲醛氣體時，被捕獲的電子以吸附狀態(tài)被釋放，導致傳感器電阻減小。因此，氧化鉻和氧化銦傳感器甲醛氣體的減少是敏感的。該傳感器具有良好的穩(wěn)定性（沒有顯示的數(shù)據(jù)）。穩(wěn)定性機制更為復雜和進一步的工作是得到了一一個明確的認識。4總結通過固態(tài)合成技術氧化鉻和氧化銦樣本的制備甲醛探測

11、的傳感材料已被證明是可行的。制作好的傳感器顯示了很大程度的反應，高選擇性，快速反應，和在低操作溫度時良好的恢復性。實驗結果表明了混有氧化鉻的氧化銦氣體傳感器的材料潛力。鳴謝 這項工作得到了中國國家自然科學基金會和中國云南省自然科學基金支持。2 外文譯文the fabrication and gas-sensing characteristics of theformaldehyde gas sensors with high sensitivityabstractgas-sensing characteristics of cdo-mixed in2o3 to formaldehyde wer

12、e investigated. gas sensors of indirect heating type were fabricated by the sensitive materials. the phases in the resulting materials and the morphologies of the sensing layers were characterized by x-ray diffraction (xrd) and scanning electron microscopy (sem), respectively, before and after calci

13、nation. the effects of operating temperature on the sensor response and the response versus gas concentration properties of the cdoin2o3 sensors were investigated. it was shown that the sensors exhibited good response properties to formaldehyde gas at low operating temperature, making them to be pro

14、mising candidates for practical detectors to formaldehyde gas. 1. introduction as an important industrial chemical, formaldehyde is utilized in the manufacturing of building boards, plywood, and lacquer materials 1,2. moreover, it is an intermediate in consumer products, such as detergents and soaps

15、, and also used in pharmacology and medicine because of its sterilization property. however, the investigated results showed that formaldehyde could cause many damages to the human body because it is a volatile and deleterious compound 3,4. therefore, effective methods to monitor formaldehyde have b

16、een demanded for atmospheric environmental measurement and control. the fabrication of gas sensors is thought to be a desirable means for monitoring the gases. our present investigation mainly deals with the detection of formaldehyde. although gas sensors based on semiconductor metal oxides provide

17、the safe detection of toxic or flammable gases, they still have some limitations and challenges such as sensitivity, selectivity, long-term stability, and so on. to overcome the disadvantages of semiconductor metal oxide gas sensors, the research on preparation and doping of semiconductor metal oxid

18、es had been done. indium oxide is a promising semiconductor material with a wide band gap (3.70 ev), whose electron concentration is determined mainly by the concentration of stoichiometric defects (such as oxygen vacancy) like other metal oxide semiconductors. in view of the sensing mechanism, the

19、particle size, defects, the properties of surface and interface, and stoichiometry directly affect the state and amount of oxygen species on the surface of sensors, and consequently the performance of the metal oxide-based sensors. therefore, in order to enhance and improve the gas sensing performan

20、ces (sensitivity, selectivity, good thermal stability, and lower operating temperature), in2o3 is usually prepared in a nanostructured form and/or doped with suitable noble metals and/or metal oxides 511.asa single-component oxide, in2o3 is a promising candidate for the detection of oxidizing gases

21、because of its good sensitivity 12. thus, when other metal oxides were doped into in2o3, the resulting materials have the potential for tunable sensitivity for different gases 6. they have been well studied as the sensor material to detect most of the key gases, such as ethanol 5,co 6,7,no2 7,8, and

22、 h2 9. nevertheless, research has seldom been focused on the formaldehyde sensing properties of the material. in this investigation, the cdo-mixed in2o3 was prepared with solid-state synthesis technology and characterized by x-ray diffraction and sem images. gas sensors for indirect-heating based on

23、 cdo-in2o3 sensing materials were fabricated. the formaldehyde sensing properties of the mixed oxides were determined. 2. experimental all the chemical reagents used in the experiments were obtained from commercial sources as guaranteed-grade reagents and used without further purification. based on

24、our preliminary experiments, in2o3 or cdo does not have good sensing properties to formaldehyde. cdo-in2o3 powders were prepared from cdco3 and in2o3. cdco3in2o3 samples with various phase compositions were studied. the cd:in = 1:2.5 weight ratio was found to be the most promising for the sensing pr

25、operties to formaldehyde gas. cdco3in2o3 samples mixed with distilled deionized water were round carefully to about 50500 nm size, and then the samples were calcined at 500, 650, 750, and 850 .c,respectively, for 1 h in air. x-ray diffraction (xrd, rigaku d/max-3b powder diffractometer) with a coppe

26、r target and k. radiation ( = 1.54056 a) was used for the phase identification, where the diffracted x-ray intensities were recorded as a function of 2. the sample was scanned from 10. to 70. (2) in steps of 0.02. the mean crystallite sizes (rx) were measured from xrd peaks at a scan rate of 2./min

27、based on the scherrers equation: rx = 0.9/(bcos ), where is the wavelength of x-ray, is the diffraction angle, and b is the true half-peak width. scanning electron microscopy (sem) photographs were obtained by xl30esem-tmp, holland. the sensors of indirect heating were fabricated according to the li

28、terature 13. the mixed material used as a sensitive body was fabricated on an alumina tube with au electrodes and platinum wires. a nicr alloy wire crossing the alumina tube was used as a resistor. this resistor ensured both substrate heating and temperature control. the elements were sintered at 65

29、0 .c for 1 h in air. thickness of the sensitive body based on in2o3 was approximately 0.6 mm after calcination. in order to improve their stability and repeatability, the gas sensors were aged at an operating temperature of 150 .c for 150 h in air. the sensor resistance was measured by using a conve

30、ntional circuit in which the element was connected with an external resistor in series at a circuit voltage of 5 v. the gas response was defined as the ratio of the electrical resistance in air (ra)to that in gas(rg). 3. results and discussion sensing properties of cdoin2o3 material calcined at 650

31、.c is better than those at 500, 750, and 850 .c. in this paper, we mainly discuss the material calcined at 650 .c. the x-ray powder diffraction patterns for the as-prepared and calcined materials are shown in fig. 1. the peaks of in2o3 and cdo are observed in the pattern of the sample calcined at 65

32、0 .c for 1 h. the pattern is indexed as in2o3 (jcpds no. 06-0416) and cdo (jcpds no. 65-2908), and shows a high degree of crystallinity. cdco3 will be decomposed and cdo be formed at400 .c 14. the phase of in2o3 is not changed and other new phase (for example, cdin2o4) is not observed after calcinin

33、g at 650 .c. on the other hand, the width of xrd peaks of in2o3 fig. 1. the xrd patterns of as-prepared and calcined materials: (a) cdco3 (jcpds no. 42-1342), (b) in2o3 (jcpds no. 06-0416), and (c) cdo (jcpds no. 65-2908). does not change before and after calcination, revealing that the cdo can effe

34、ctively inhibit the crystalline grain growth 15. the crystallite average sizes calculated according to scherrers equation are about 28 nm for in2o3 before calcination, and about 30 nm for in2o3 and 31 nm for cdo after calcination. comparing with the xrd results, sem images revealed that there were v

35、arious sizes of particles in the as-prepared and calcined samples. the large particles were composed of small crystallites. fig. 2(a) and (b) shows sem images of the as-prepared and calcined materials, respectively. most particles have irregular morphology, and the particle size is in the range of 1

36、00500 nm. it has been addressed that the electrical conductivity of a sensor depends on the gas atmosphere, but also on the operating temperature of the sensing material exposed to the test gas 16. fig. 3 depicts the relation between the response and the operating temperature for the sensor. the ope

37、rating temperature has a great influence on the response. interestingly, the response first increases gradually and then decreases with increasing the operating temperature. it can be seen that the cdoin2o3 based sensor shows excellent gas-sensing characteristics to formaldehyde gas in the low tempe

38、rature range. it exhibited the highest response to formaldehyde gas at 95 .c.the low operating temperature is an advantage in application. as shown in fig. 4, the response of the cdoin2o3 based sensor operated at 95 .c shows good dependence on the gas concentration. the sensor exhibits very small re

39、sponse to alcohol and gasoline, but large response to formaldehyde gas. the response to 10 ppm formaldehyde gas is more than 80. the response is considerably larger than those recently reported for sno2sb2o4,wo3sb2o4, nio, and la0.68pb0.32feo3-based formaldehyde gas sensors 1721. this gas sensor sho

40、wed large response to formaldehyde gas and high selectivity against alcohol and gasoline. this result indicates that the cdoin2o3 specimen is a good gas-sensing material for detecting formaldehyde, which can be applied for monitoring and controlling of the formaldehyde gas. a good response and quick

41、 response/recovery time were observed with this sensor at the optimal operating temperature of 95 .c. the response changes of the gas sensor to different formaldehyde gas concentrations (10100 ppm) are shown in fig. 5. as a highly sensitive sensor, it can measure very low concentrations, even 10 ppm

42、. the output voltage increases in a linear relation to the formaldehyde gas concentration with a short response time. response time and recovery time (defined as the time required to reach 90% of the final equilibrium value) was 2 min and the recovery time was 4 min. the gas-sensing mechanism is bas

43、ed on the changes in conductance of the cdoin2o3 material. the oxygen adsorbed on the surface of the material influences the conductance of the cdoin2o3 sensor. the oxygen adsorption depends on the particle size, large specific area of the material, and the operating temperature of the sensor 22. with the incre