新型线形火灾探测元件研制

从结构、原理模型、相关试验等方面,对新型线形火灾探测元件进行了研究,发现该新型线形火灾探测元件不仅具有良好的电阻NTC热敏特性,而且具有良好的电容PTC热敏特性,而且其时间常数与温度成指数关系变化,提出了用新型线形火灾探测元件进行过热监测和着火报警的新途径.     

MnCoNiCuVO系NTC热敏半导体陶瓷显微结构与电性能研究

本文研究了MnCoNiCuO与MnCoNiO系NTC热敏陶瓷在烧结特性以及在电性能方面的差别;探索了V2O5对MnCoNiCuO系NTC热敏陶瓷显微结构以及电性能的影响.实验结果表明:MnCoNiCuO系半导体陶瓷材料有较低的烧结温度,同时热敏陶瓷的电阻率和材料常数B值显著下降.在MnCoNiCuO中添加V2O5可以明显改善陶瓷的显微结构,提高陶瓷的材料常数(B).MnCoNiCuVO体系有望成为具有较低烧结温度,同时具有合理电性能的NTC热敏电阻基础材料.     

NTC电阻器热敏功能薄膜材料研究进展

过渡金属氧化物NTC热敏材料具有良好的电阻-温度特性,是理想的温度传感材料.特别是薄膜材料,由于晶粒间的不完全接触和空洞的减少,可能从根本上解决目前广泛使用的体材热敏材料存在的稳定性和重复性差的问题.分析对比了几种常用的薄膜制备方法,认为溅射镀膜法更容易得到致密、平整的热敏薄膜;阐述了NTC热敏材料两种主要的电子传导模型:最近邻跳跃(NNH)模型ρ(T)=CT·exp(T0/T)和变程跳跃(VRH)模型ρ(T)=CT2p·exp(T0/T)p;介绍了当前薄膜热敏电阻的研究现状和存在的主要问题.     

电子信息材料

国产NTC热敏元件赶超世界水平 日前,在美的集团召开的传感器采购竞标中,华工科技产业股份有限公司高理电子分公司生产的NTC（负温度系数）热敏电阻器击败多家著名制造商,一举中标,此举打破了国外企业垄断该产品国内市场的局面,同时表明国产NTC热敏元件的技术、质量和产业化水平已达到和超过进口产品。 高精度NTC热敏电阻及温度传感器是利用特殊氧化物半导体的阻温特性而设计生产的一种热敏功能陶瓷产品,广泛应用于现代通信、电子测量、汽车、家电、空调制冷、办公自动化等诸多领域,市场前景广阔。该产品由日本企业最先进行实用化研究和规模化生产,日、韩等企业不仅一度垄断了国内市场,而且主导了产品技术性能及测试标准,设置了较高的技术门槛。     

NTC热敏电阻材料的制备、性能优化及相关机理的研究进展

总结了NTC热敏电阻材料的类型和常用的制备方法.综述了材料基体中主要元素和掺杂元素对材料性能的影响以及降低烧结温度的方法.最后介绍了NTC热敏材料的导电机理和发展前景.     

测量超低温用NTC热敏电阻的制备和性能研究

采用Pechini法制备La掺杂的Fe-Co-Mn-Ni系尖晶石型负温度系数(negative temperature coefficient,NTC)热敏陶瓷,使用X射线衍射仪和扫描电镜表征了复合陶瓷的相组成和微观结构,测量了其电学性能和老化.结果表明,制备的NTC热敏陶瓷20K时电阻值在90～120kΩ之间;在20～45K温度范围内电阻灵敏度在0.5～45kΩ/K之间,测试电流在2～15μA内变化时引起的温度测量误差<0.1K,热敏电阻常数B20K/40K值在180～210K之间,制备的NTC热敏电阻性能稳定.     

MF5602型低温热敏电阻温度计的特性研究

采用新工艺生产的MF5602型NTC热敏电阻温度计在20-50 K之间进行了电学测量,老化实验后研究了其稳定性和磁场强度对温度计测量结果的影响.结果表明:新工艺生产的MF5602型NTC热敏电阻温度计可在20-50 K之间使用,相对电阻灵敏度、稳定性、磁场诱发的温度测量误差等传感器特性均优于美国Lake Shore公司...     

Al_2O_3掺杂对MnCoNi系NTC热敏电阻材料性能的影响研究

掺杂金属氧化物是对NTC热敏电阻的材料性能加以改善的常用手法,其中MnCoNi系的NTC热敏电阻会因为掺杂氧化铝而产生电性能的变化,但目前国内对其具体机理和特点的研究较少。因此本文将通过具体的实验来分析氧化铝掺杂过程中,该类NTC热敏电阻晶体结构、晶粒、材料常数、电阻率、激活能等各项参数的变化关系,希望以此深化NTC热敏电阻的应用研究,促成其进一步推广。     

Mn-Co-Ni-Pb-O系NTC热敏电阻制备及电性能的研究

采用XRD、SEM和电性能测试等手段,研究了Mn1.05-xCo0.92Ni0.03PbxO4系列NTC热敏陶瓷的烧结特性和电性能参数与Pb掺入量的关系。结果表明掺Pb可以降低Mn-Co-Ni-O系NTC热敏电阻的烧结温度和室温电阻率。当Pb掺杂量x=0.12时样品的收缩率最大,样品的老化稳定性最好,该陶瓷样品的最佳烧结温度降至900~950℃之间,烧结温度为950℃时样品的ρ25和B值分别为490Ω.cm和3969K,具有较低的ρ25和较高的B值。     

水热法制备Co-Mn-Ni-Mg-Fe-O系NTC热敏电阻材料

分别用共沉淀法和水热法合成了Co-Mn-Ni-Mg-Fe-O系NTC热敏电阻材料,对两种方法的合成进行了比较,确定用水热法制备NTC热敏电阻材料,可以直接合成尖晶石相纳米粉体材料.实验发现以NaOH为沉淀剂,在250℃的水热合成温度下恒温10h制备的纳米粉体材料效果最佳.测试表明其晶体结构完整,颗粒呈球形,平均粒径为75nm,比表面积为64m2/g, 粒度均匀,分散性好.研究还发现,水热反应时间的延长有利于晶体结构的形成,而粒度变化不大.     

New Methods of Measuring Capacitance and Resistance of Very High Loss Materials at High Frequencies

Two new circuits for the accurate measurement of specimen capacitance and resistive loss are described. The capacitance measurements are unaffected by the specimen resistance when the parallel resistance is greater than 30 ?. The practicality of the circuit is enhanced by its use of coaxial cable to provide both connection to the sample and the inductance required for circuit operation. An important characteristic of the circuit is its ability to measure capacitance and resistance of very high loss specimens accurately.     

Capacitance of High-Voltage Coaxial Cable in Plasma Immersion Ion Implantation

［1］J.R.Conrad, J.I.Radtke, R.A.Dodd, F.J.Worzala and N.C.Tran: J. Appl. Phys., 1987, 62, 4591. ［2］P.K.Chu, S.Qin, C.Chan, N.W.Cheung and L.A.Larson: Mater. Sci. Eng.: Reports, 1996, R17(6-7), 207. ［3］P.K.Chu, B.Y.Tang, Y.C.Cheng and P.K.Ko: Rev.Sci. Instrum, 1997, 68, 1886. ［4］X.B.Tian, B.Y.Tang and P.K.Chu: J. Appl. Phys.,1999, 86, 3567. ［5］M.M.Shamim, J.T.Scheuer, R.P.Fetherston and J.R.Conrad: J. Appl. Phys., 1991, 70, 4756. ［6］M.P.J.Gaudreau, P.E.Jeffrey, M.A.Kempkes, T.J.Hawkey and J.M.Mulvaney: J. Vac. Sci. Technol.,1999, B17, 888. ［7］I.Langmuir and K.Blodgett: Phys. Rev., 1924, 24, 49. ［8］R.A.Stewart and M.A.Lieberman: J. Appl. Phys.,1991, 70, 3481.     

Hydrodynamics and heat transfer for the single-phase flow of a coolant in a porous electric cable

Transfer processes in a cryogenic coaxial electric cable with a porous inner tube are analyzed; the analysis reveals ways of intensifying the outflow of the heat generated when electric power is transmitted along the cable.     

Low Temperature Properties of a Superconducting Niobium Coaxial Cable

Semirigid coaxial cables with seamless metal shields are promising for readout from sensitive devices operating below liquid helium temperature. Low thermal conduction of such cables are also essential to reduce heat penetration into cryogenic temperature. We have developed thin semirigid coaxial cables employing niobium-titanium and niobium in both center and outer conductors, taking advantage of low thermal conductivity and extreme small electrical resistivity of superconductors. We assembled an adiabatic demagnetization refrigerator and measured thermal and electrical characteristics of those superconducting coaxial cables below T _c. Thin niobium coaxial cable with an outer diameter of 0.86 mm showed two-orders lower thermal conduction than expected, which is considered as the effect of impurity of niobium and forming process. Small attenuation was observed up to high frequency above 10 GHz at 3 K.     

炭黑填充聚乙烯PTC效应及其稳定性

可控自发热高分子材料是利用炭黑填充结晶高分子材料的正温度系数特性（PTC效应）制成的具有自动控温性能的功能高分子材料，文中通过对6种炭黑填充聚乙烯体系电性能的研究，分析了产生PTC效应的机理，筛选出了具有较强PTC效应的炭黑填充聚乙烯体系，并通过对该体系PTC稳定性研究得出，较佳的消除高于熔点的负温度系数效应（NTC效应）的方法是辐射交联，本研究为制备出具有实用价值的可控自发热聚乙烯的材料奠定了基础。     

A New Kind of Linear NTC Sensitive Ceramics

［1］National Natural Science Foundation of China: Inorganic Nonmetal Material Science, Science Publishing House, Beijing, 1997, 31. (in Chinese) ［2］Mingtang WU and Xiaohua ZHOU: Inorganic Semiconductor Physics, Xi′an Communication University Publishing House, Xi′an, 1995, 126. (in Chinese) ［3］Shipu LI: Special Ceramics Technology, Wuhan University of Technology Publishing House, Wuhan, 1997,249. (in Chinese)     

同轴式套管换热器应用于家用循环式热泵热水器的特性试验研究

分析以采用普通高效换热管的同轴式套管换热器为冷凝器的热力特性,并针对其运用在家用循环式热泵热水器的特点,试验研究采用该套管换热器的家用循环式热泵热水器的特性,得到在名义制热工况及冷却水进口温度为30℃条件下,不同水流量所对应的冷凝负荷、功率等特性及性能。结果可应用于家用循环式热泵热水器的开发设计。     

A near kind of linear NTC sensitive ceramics

The preparation method of a new kind of SnO2-CdO-WO3 linear NTC (negative temperature coefficient) thermal sensitive ceramics was related in this paper. The electron transfer formula of this N type semiconducting ceramics was given. Factors which affect temperature - resistance characteristic curve, such as the composition of the material, heat treatment condition, the speed of the temperature rising, heat preservation time and sintering atmosphere were thoroughly studied and analyzed.     

Stirling Cryocooler for High-Temperature Super Conductor RF Filters

The High Temperature Super Conducting (HTSC) radio frequency (RF) filters (as used, for example, in ground base stations for cellular phone systems) are passive devices. To operate properly, they must be cooled well below their transition temperature to super conducting stage (usually to 65–80 K). These HTSC RF filters are connected through a coaxial cable to an array of Low Noise Amplifiers (LNA), which are active devices and, therefore, induce a few hundreds mWatts of heat. On the other hand, the LNA array is connected by coaxial cable to a feedthrough of the vacuum chamber. This coaxial cable also contributes a few hundreds mWatts of heat load. The third source of heat load is the thermal radiation from the vacuum jacket wall to the cryogenically cooled surfaces. This portion of heat load is assessed as hundreds of mWatts as well. The signal-to-noise ratio of LNA devices is improved significantly when they are cooled down to a temperature of 90–110 K and their effectiveness reaches 99% at a temperature of 77 K. Traditionally, cooling of the system is achieved by placing both the HTSC RF filters and the LNA array device on the cold tip of a single-stage cryogenic cooler. Hence, both devices are cooled down to a temperature of 60–80 K, which is required by the manufacturers of HTSC RF filters. Because of the high level of heat loads induced by the LNA array, this method requires an extra cooling capacity from a cryogenic cooler. This increases power consumption, weight, and size and decreases its reliability. This paper describes a method of reducing the overall heat load. This method relies on the idea of maintaining the HTSC RF filters and the LNA arrays in different operational temperatures. The objective of this method is to provide a reduction in thermal losses, input power, weight, and size and to increase the reliability of the entire cryogenic cooler. The method allow for better ruggedising of the mechanical support for cooled electronic package of the LNA array plate.