基于低居里点PTC材料的风机叶片防冰数值模拟及试验验证

叶片覆冰会严重影响风机的安全稳定运行。目前,电热防冰是最高效可靠的风机叶片防冰方法,但存在防冰区域受热不均匀、局部覆冰以及过多分区导致防冰系统过于复杂等问题。为此提出采用正温度系数(positive temperature coefficient,PTC)材料进行风机叶片自适应电加热防冰的创新方法,通过原位聚合法成功制备了一种低居里点PTC材料,其居里温度点为1℃。随后,基于该材料的阻-温特性,建立了风机叶片的电加热防冰模型,并进行数值模拟。研究结果显示,当采用低居里点PTC材料进行风机叶片电加热防冰时,无需进行防冰区域的分区,就能使得防冰区域受热更加均匀。在一定的工作电压下,低居里点PTC材料在不同环境温度和风速下展现出自适应调节加热功率的能力,并且经过100次循环阻-温测试后,材料仍具有极强的自适应调节能力。最后,通过试验验证了材料的这种自适应调节能力。该研究结果为后续基于低居里点PTC材料的风机叶片防冰系统的研究奠定了坚实基础。

Analysis of burnup performance and temperature coefficient for a small modular molten‑salt reactor started with plutonium

In a thorium-based molten salt reactor(TMSR),it is difficult to achieve the pure 232Th–^(233)U fuel cycle without sufficient^(233)U fuel supply.Therefore,the original molten salt reactor was designed to use enriched uranium or plutonium as the starting fuel.By exploiting plutonium as the starting fuel and thorium as the fertile fuel,the high-purity^(233)U produced can be separated from the spent fuel by fluorination volatilization.Therefore,the molten salt reactor started with plutonium can be designed as a^(233)U breeder with the burning plutonium extracted from a pressurized water reactor(PWR).Combining these advantages,the study of the physical properties of plutonium-activated salt reactors is attractive.This study mainly focused on the burnup performance and temperature reactivity coefficient of a small modular molten-salt reactor started with plutonium(SM-MSR-Pu).The neutron spectra,^(233)U production,plutonium incineration,minor actinide(MA)residues,and temperature reactivity coefficients for different fuel salt volume fractions(VF)and hexagon pitch(P)sizes were calculated to analyze the burnup behavior in the SM-SMR-Pu.Based on the comparative analysis results of the burn-up calculation,a lower VF and larger P size are more beneficial for improving the burnup performance.However,from a passive safety perspective,a higher fuel volume fraction and smaller hexagon pitch size are necessary to achieve a deep negative feedback coefficient.Therefore,an excellent burnup performance and a deep negative temperature feedback coefficient are incompatible,and the optimal design range is relatively narrow in the optimized design of an SM-MSR-Pu.In a comprehensive consideration,P=20 cm and VF=20%are considered to be relatively balanced design parameters.Based on the fuel off-line batching scheme,a 250 MWth SM-MSR-Pu can produce approximately 29.83 kg of ^(233)U,incinerate 98.29 kg of plutonium,and accumulate 14.70 kg of MAs per year,and the temperature reactivity coefficient can always be lower than−4.0pcm/K.

Assembly-level analysis on temperature coefficient of reactivity in a graphite-moderated fuel salt reactor fueled with low-enriched uranium

To provide a reliable and comprehensive data reference for core geometry design of graphite-moderated and low-enriched uranium fueled molten salt reactors,the influences of geometric parameters on the temperature coefficient of reactivity(TCR)at an assembly level were characterized.A four-factor formula was introduced to explain how different reactivity coefficients behave in terms of the fuel salt volume fraction and assembly size.The results show that the fuel salt temperature coefficient(FSTC)is always negative owing to a more negative fuel salt density coefficient in the over-moderated region or a more negative Doppler coefficient in the under-moderated region.Depending on the fuel salt channel spacing,the graphite moderator temperature coefficient(MTC)can be negative or positive.Furthermore,an assembly with a smaller fuel salt channel spacing is more likely to exhibit a negative MTC.As the fuel salt volume fraction increases,the negative FSTC first weakens and then increases,owing to the fuel salt density effect gradually weakening from negative to positive feedback and then decreasing.Meanwhile,the MTC weakens as the thermal utilization coefficient caused by the graphite temperature effect deteriorates.Thus,the negative TCR first weakens and then strengthens,mainly because of the change in the fuel salt density coefficient.As the assembly size increases,the magnitude of the FSTC decreases monotonously owing to a monotonously weakened fuel salt Doppler coefficient,whereas the MTC changes from gradually weakened negative feedback to gradually enhanced positive feedback.Then,the negative TCR weakens.Therefore,to achieve a proper negative TCR,particularly a negative MTC,an assembly with a smaller fuel salt channel spacing in the under-moderated region is strongly recommended.

某纯电车型空调PTC不制热故障分析与改进

为分析电动汽车空调系统不制热故障原因,以某车企收到的4S店空调故障案例为例,使用质量管理工程师常用的检测方法和仪器对加热零部件进行分析与诊断,结果表明是由于软件问题导致熔断器开路,造成空调故障,提出对软件控制的临界值进行改进的故障排除建议。

炭黑/十四醇基低居里温度PTC复合材料的热控性能

具有正温度系数(PTC)的导电高分子复合材料组成的自控温热敏电阻,可代替普通电阻用于加热器件,在电子设备主动控温方面具有很大优势。然而,现有PTC复合材料的居里温度(>60℃)普遍较高,在常温段工作电子设备的控温方面应用受到限制。基于此,本文以低相变温度的十四醇为相变基体,炭黑(CB)为导电粒子,乙烯-醋酸乙烯酯共聚物(EVA)为骨架,通过熔融共混和模压成型方法制备了具有低居里温度(35℃)的PTC复合材料,探究了CB质量分数对复合材料电性能和PTC性能的影响。结果显示,当CB质量分数为12%时,复合材料室温电阻率为0.5Ω·m,PTC强度高达7.0,且未出现负温度系数(NTC)效应。通过扫描电子显微镜观察了复合材料微观结构,并将复合材料电性能变化与微观结构相关联,解释了复合材料获得优异PTC性能的内在机理。此外,研究了PTC复合材料的热控行为,发现与普通电阻加热器相比,PTC复合材料作为电阻加热器具有自适应控温能力,无需外部控制系统条件下可将受控器件温度控制在常温段温度范围内并保持平衡。

Fabrication and characterization of NiCr-based films with high resistivity and low temperature coefficient of resistance

As a metal alloy,NiCr films have a relatively high resistivity and low temperature coefficient of resistance (TCR) and are widely used in electronic components and sensors.However,the resistivity of pure NiCr is insufficient for high-resistance and highly stable film resistors.In this study,a quaternary NiCrAlSi target (47:33:10:10,wt.%) was successfully used to prepare resistor films with resistivities ranging from 1000 to 10 000μΩcm and TCR within±100 ppm/K.An oxygen flow was introduced during the sputtering process.The films exhibit hightemperature stability at 450℃.The films were analyzed using Auger electron spectroscopy,x-ray diffraction,time-of-flight secondary-ion mass spectrometry,and x-ray photoelectron spectroscopy.The results show that the difference in the oxide proportion of the films caused the differences in resistivity.The near-zero TCR values were considered to be due to the competition between silicon and other metals.This study provides new insights into the electrical properties of NiCr-based films containing Si,which will drive the manufacturing of resistors with high resistivity and zero TCR.

高分子基PTC复合材料的研究进展

高分子基正温度系数材料(PTC)因温度敏感性而受到广泛关注,但在高功率应用中,电子元件更容易受到高温引起的电阻变化、电流失控和热失效的影响。本文对高分子PTC复合材料的工作机理、原材料组成、电学性能等进行了全面的总结,综述了影响材料电学性能的因素,以期为高分子基PTC材料的相关研究提供参考。

Plutonium utilization in a small modular molten-salt reactor based on a batch fuel reprocessing scheme

A molten salt reactor(MSR)has outstanding features considering the application of thorium fuel,inherent safety,sustainability,and resistance to proliferation.However,fissile material^(233)U is significantly rare at the current stage,thus it is difficult for MSR to achieve a pure thorium-uranium fuel cycle.Therefore,using plutonium or enriched uranium as the initial fuel for MSR is more practical.In this study,we aim to verify the feasibility of a small modular MSR that utilizes plutonium as the starting fuel(SM-MSR-Pu),and highlight its advantages and disadvantages.First,the structural design and fuel management scheme of the SM-MSR-Pu were presented.Second,the neutronic characteristics,such as the graphite-irradiation lifetime,burn-up performance,and coefficient of temperature reactivity were calculated to analyze the physical characteristics of the SM-MSR-Pu.The results indicate that plutonium is a feasible and advantageous starting fuel for a SM-MSR;however,there are certain shortcomings that need to be solved.In a 250 MWth SM-MSR-Pu,approximately 288.64 kg^(233)U of plutonium with a purity of greater than 90% is produced while 978.00 kg is burned every ten years.The temperature reactivity coefficient decreases from -4.0 to -6.5 pcm K^(-1) over the 50-year operating time,which ensures a long-term safe operation.However,the amount of plutonium and accumulation of minor actinides(MAs)would increase as the burn-up time increases,and the annual production and purity of^(233)U will decrease.To achieve an optimal burn-up performance,setting the entire operation time to 30 years is advisable.Regardless,more than 3600 kg of plutonium eventually accumulate in the core.Further research is required to effectively utilize this accumulated plutonium.

Low TCR-MIM氮化钽极板制备及其性能研究

阐述TCR-MIM结构具有更好的稳定性、精度和可调性,适用于高精度、高稳定性的场景。通过研究沉积次数、溅射功率和N2流量对氮化钽(TaN)极板及MIM性能的影响,获得一种Low TCR TaN作为MIM结构底部极板。当沉积2次,保持基准功率,N_(2)流量约为基准流量1.2倍时,MIM结构TCR达到2ppm/℃,MIM结构可靠性测试通过,获得一种优异的低温度漂移系数TaN极板,有利于高性能MIM电容的制备。

高频低温漂TC-SAW滤波器的设计

该文设计了一款温度补偿型声表面波(TC-SAW)滤波器,建立了弹性材料及压电材料温度方程,对滤波器的温度场进行仿真分析。通过在压电材料(128°YX-LiNbO3)上沉积SiO2作为温度补偿层,降低了滤波器的频率温度系数。为了解决在沉积SiO2温度补偿层后,谐振器的反谐振频率处出现杂散响应,通过增加电极厚度,降低了谐振器杂散响应对滤波器性能的影响。采用四阶级联提高滤波器的带外抑制。仿真结果表明,设计的TC-SAW滤波器中心频率为2497 MHz,频率温度系数为-9.89×10^(-6)/℃,-30~85℃工作温度范围内的带内最大插损为1.95 dB,带外抑制大于30 dB,-3 dB损耗带宽大于97 MHz。

Characterization of the BaBiO_3-doped BaTiO_3 positive temperature coefficient of a resistivity ceramic using impedance spectroscopy with T_c=155℃

BaBiO3-doped BaTiO3 （BB-BT） ceramic, as a candidate for lead-free positive temperature coefficient of resistivity （PTCR） materials with a higher Curie temperature, has been synthesized in air by a conventional sintering technique. The temperature dependence of resistivity shows that the phase transition of the PTC thermistor ceramic occurs at the Curie temperature, Tc = 155℃, which is higher than that of BaTiO3 （≤ 130 ℃）. Analysis of ac impedance data using complex impedance spectroscopy gives the alternate current （AC） resistance of the PTCR ceramic. By additional use of the complex electric modulus formalism to analyse the same data, the inhomogeneous nature of the ceramic may be unveiled. The impedance spectra reveal that the grain resistance of the BB-BT sample is slightly influenced by the increase of temperature, indicating that the increase in overall resistivity is entirely due to a grain-boundary effect. Based on the dependence of the extent to which the peaks of the imaginary part of electric modulus and impedance are matched on frequency, the conduction mechanism is also discussed for a BB-BT ceramic system.

Preparation and study on performance of submicron nickel powder for multilayer chip positive temperature coefficient resistance

Base metal nickel is often used as the inner electrode in multilayer chip positive temperature coefficient resistance （PTCR）. The fine grain of ceramic powders and base metal nickel are necessary. This paper uses reducing hydrazine to gain submicron nickel powder whose diameter was 200-300 nm through adjusting the consumption of nucleating agent PVP properly. The submicron nickel powder could disperse well and was fit for co--fired of multilayer chip PTCR. It analyes the submicron nickel powder through x-ray Diffraction （XRD） and calculates the diameter of nickel by PDF cards. Using XRD analyses it obtains several conclusions： If the molar ratio of hydrazine hydrate and nickel sulfate is kept to be a constant, when enlarging the molar ratio of NaOH/Ni^2＋, the diameter of nickel powder would become smaller. When the temperature in the experiment raises to 70-80 ℃, nickel powder becomes smaller too. And if the molar ratio of NaOH/Ni2＋ is 4, when molar ratio of （C2H5O）2/Ni^2＋ increases, the diameter of nickel would reduce. Results from viewing the powders by optical microscope should be the fact that the electrode made by submicron nickel powder has a better formation and compactness. Furthermore, the sheet resistance testing shows that the electrode made by submicron nickel is smaller than that made by micron nickel.

Research on the effect of the heavy nuclei amount on the temperature reactivity coefficient in a small modular molten salt reactor

Small modular thorium-based graphite-moderated molten salt reactors (smTMSRs), which combine the advantages of small modular reactors and molten salt reactors, are regarded as a wise development path to speed deployment time. In a smTMSR, low enriched uranium and thorium fuels are used in once-through mode, which makes a marked difference in their neutronic properties compared with the case when a conventional molten salt breeder reactor is used. This study investigated the temperature reactivity coefficient (TRC) in a smTMSR, which is mainly affected by the molten salt volume fraction (VF) and the heavy nuclei concentration in the fuel salt (HN). The fourfactor formula method and the reaction rate method were used to indicate the reasons for the TRC change, including the fuel density effect, the fuel Doppler effect, and the graphite thermal scattering effect. The results indicate that only the fuel density has a positive effect on the TRC in the undermoderated region. Thermal scattering from both salt and graphite has a significant negative influence on the TRC in the overmoderated region. The maximal effective multiplication factor, which shows the highest fuel utilization, is located at 10% VF and 12 mol% HN and is still located in the negative TRC region. In addition, on increasing the heavy nuclei amount from 2 mol% HN to 12 mol% HN (VF = 10%), the total TRC undergoes an obvious change from - 11 to - 3 pcm/K, which implies that the change in the HN caused by the fuel feed online should be small to avoid potential trouble in the reactivity control scheme.

Investigation on the plastic work-heat conversion coefficient of 7075-T651 aluminum alloy during an impact process based on infrared temperature measurement technology

The plastic work-heat conversion coefficient is one key parameter for studying the work-heat conversion under dynamic deformation of materials. To explore this coefficient of 7075-T651 aluminum alloy under dynamic compression, dynamic compression experiments using the Hopkinson bar under four groups of strain rates were conducted, and the temperature signals were measured by constructing a transient infrared temperature measurement system. According to stress versus strain data as well as the corresponding temperature data obtained through the experiments, the influences of the strain and the strain rate on the coefficient of plastic work converted to heat were analyzed.The experimental results show that the coefficient of plastic work converted to heat of 7075-T651 aluminum alloy is not a constant at the range of 0.85–1 and is closely related to the strain and the strain rate. The change of internal structure of material under high strain rate reduces its energy storage capacity, and makes almost all plastic work convert into heat.

Influence of Temperature and Frequency on Minority Carrier Diffusion Coefficient in a Silicon Solar Cell under Magnetic Field

In this study, the effects of temperature and frequency on minority carrier diffusion coefficient in silicon solar cell under a magnetic field are presented. Using two methods (analytic and graphical), the optimum temperature corresponding to maximum diffusion coefficient is determined versus cyclotronic frequency and magnetic field.

Anisotropic Rock Poroelasticity Evolution in Ultra-low Permeability Sandstones under Pore Pressure,Confining Pressure,and Temperature:Experiments with Biot's Coefficient

This study aimed to show anisotropic poroelasticity evolution in ultra-low permeability reservoirs under pore pressure,confining pressure,and temperature.Several groups of experiments examining Biot's coefficient under different conditions were carried out.Results showed that Biot's coefficient decreased with increased pore pressure,and the variation trend is linear,but the decreasing rate is variable between materials.Biot's coefficient increased with increased confining pressure;the variation trend is linear,but the increasing rate varies by material as well.Generally,Biot's coefficient remains stable with increased temperature.Lithology,clay mineral content,particle arrangement,and pore arrangement showed impacts on Biot's coefficient.For strong hydrophilic clay minerals,expansion in water could result in a strong surface adsorption reaction,which could result in an increased fluid bulk modulus and higher Biot's coefficient.For skeleton minerals with strong lipophilicity,such as quartz and feldspar,increased oil saturation will also result in an adsorption reaction,leading to increased fluid bulk modulus and a higher Biot's coefficient.The study's conclusions provide evidence of poroelasticity evolution of ultra-low permeability and help the enhancing oil recovery(EOR)process.

Temperature coefficient of resistivity of TiAlN films deposited by radio frequency magnetron sputtering

Titanium aluminum nitride （TiAlN） film, as a possible substitute for the conventional tantalum nitride （TAN） or tantalum-aluminum （TaAl） heater resistor in inkjet printheads, was deposited on a Si（100） substrate at 400 ℃ by radio frequency （RF） magnetron co-sputtering using titanium nitride （TIN） and aluminum nitride （AlN） as ceramic targets. The temperature coefficient of resistivity （TCR） and oxidation resistance, which are the most important properties of a heat resistor, were studied depending on the plasma power density applied during sputtering. With the increasing plasma power density, the crystallinity, grain size and surface roughness of the applied film increased, resulting in less grain boundaries with large grains. The Ti, Al and N binding energies obtained from X-ray photoelectron spectroscopy analysis disclosed the nitrogen deficit in the TiAlN stoichiometry that makes the films more electrically resistive. The highest oxidation resistance and the lowest TCR of-765.43×10^-6 K-l were obtained by applying the highest plasma power density.

集成电路用NTC热敏电阻温度计校准方法研究

针对集成电路在21~23℃范围内近mK量级测温精度的需求,研究了负温度系数(negtive temperature coefficient,NTC)热敏电阻温度计的校准方法对集成电路测温系统精度的影响。利用比较法对24支3种不同型号的NTC热敏电阻温度计进行校准,使用最小二乘法进行基本方程、Hoge-1方程、Steinhart-Hart方程的系数计算,分析校准方程的内插残差,评价低阶精准校准方程的可行性,为集成电路制作工艺的高质量中的温度测控提供技术支撑。结果表明:基本方程、Steinhart-Hart方程、Hoge-1方程残差的标准偏差分别为2.29、0.63、0.65 mK;使用2个校准点的基本方程的性能最差,使用3个校准点的校准方程的Hoge-1方程表现出最好的内插性能,在集成电路窄温区温度精确测量方面具有较高的应用价值。

Minority Carrier Diffusion Coefficient <i>D</i>*(<i>B,T</i>): Study in Temperature on a Silicon Solar Cell under Magnetic Field

This work deals with minority carrier diffusion coefficient study in silicon solar cell, under both temperature and applied magnetic field. New expressions of diffusion coefficient are pointed out, which gives attention to thermal behavior of minority carrier that is better understood with Umklapp process. This study allowed to determine an optimum temperature which led to maximum diffusion coefficient value while magnetic field remained constant.

Effect of low temperature thermo-mechanical treatment on microstructures and mechanical properties of TC4 alloy

The effects of low temperature thermo-mechanical treatment （LTTMT） on microstructures and mechanical properties of Ti-6Al-4V （TC4） alloy were studied by optical microscopy （OM）, tensile test, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The experimental results confirm that the strength of TC4 alloy can be improved obviously by LTTMT processing, which combines strain strengthening with aging strengthening. The effect of LTTMT on the alloy depends on the microstructure of the refined and dispersed a＋fl phase on the basis of high dislocation density by pre-deformation below recrystallization temperature. The tensile strength decreases with the increase of pre-deformation reduction. The optimal processing parameters of LTTMT for TC4 alloy are as follows： solution treatment at 900 ℃ for 15 min, pre-deformation in the range of 600-700 ℃ with a reduction of 35%, finally aging at 540 ℃ for 4 h followed by air-cooling.