Research on H500-Type High-Precision Vacuum Blackbody as a Calibration Standard for Infrared Remote Sensing

Based on the calibration requirements of vacuum low background aerospace infrared remote sensing radiance temperature, a high-precision vacuum blackbody (H500 type) is developed for the temperature range from ??93 °C to +?220 °C at the National Institute of Metrology, China. In this paper, the structure and the temperature control system of H500 are introduced, and its performance, such as heating rate and stabilization of temperature control, is tested under the vacuum and low-background condition (liquid-nitrogen-cooled shroud). At room temperature and atmospheric environment, the major technical parameters of this blackbody, such as emissivity and uniformity, are measured. The measurement principle of blackbody emissivity is based on the control of surrounding radiation. Temperature uniformity at the cavity bottom is measured using a standard infrared radiation thermometer. When the heating rate is 1 °C min^?1, the time required for the temperature to stabilize is less than 50 min, and within 10 min, the variation in temperature is less than 0.01 °C. The emissivity value of the blackbody is higher than 0.996. Temperature uniformity at the bottom of the blackbody cavity is less than 0.03 °C. The uncertainty is less than 0.1 °C (k?=?2) over the temperature range from ??93 °C to +?67 °C.     

Effective Debye-Waller parameter and emission intensity of calcium tungstate phosphors

The relation between emission intensity under ultraviolet excitation and Debye-Waller parameter was studied on calcium tungstate phosphors. The samples were prepared by precipitation from aqueous solition of calcium chloride and ammonia-alkaline solution of ammonium paratungstate and by firing at 400°–1000°C in air. The precipitating temperature has a strong influence on the form of precipitated particles, being spherical at 0°C and spindle-shaped at 90°C, and also on the preferred orientation of crystallites in precipitates. The change of emission intensity under ultraviolet excitation with firing temperature shows a correspondence to the change of effective Debye-Waller parameter, B_eff, determined from X-ray diffraction intensity measurements. On the ground samples, of which the original is fired at 900°C and has spherical particles, a linear relation was found between the emission intensity under ultraviolet excitation and the dynamic component B_d in B_eff, which is due to thermal vibration of constituent atoms.     

An improved process for grain refinement of large 2219 Al alloy rings and its influence on mechanical properties

The large 2219 Al alloy rings used to connect propellant tank components of a satellite launch vehicle to each other are conventionally manufactured by radial-axial ring rolling at 460°C with 50% deformation,but often suffer from coarse elongated grain and low ductility. An improved process(hot ring rolling at460°C with 30% deformation, then air cooling to 240°C, followed by ring rolling at 240°C with 20% deformation) was tested for ring manufacturing. The corresponding microstructure evolution and mechanical properties of the produced rings were studied. The results show that the improved process can successfully be applied to manufacture the large 2219 Al alloy rings without formation of macroscopic defects,resulting in a product with fine and uniform grains after heat treatment. The fracture mechanism of both rings was mainly intergranular fracture. With the resulting grain size refinement due to the improved process, more homogeneous slip occured and the crack propagation path became more tortuous during the tensile testing process. Thus, the elongation in all three orthogonal directions was greatly improved,and the axial elongation increased from 3.5% to 10.0%.     

Effect of Environment on Crystallinity and Chemical Stability in Solid-State of Ground Cephalotin Sodium During Storage

Abstract

Effects of environmental conditions on the crystallinity and the decomposition point (Dp) of ground cephalotin sodium during storage were investigated by X-ray diffraction and differential thermal analysis (DTA). The X-ray diffraction peaks of ground products increased after storage at 0% and 75% relative humidity (R.H.), at 35° C. The crystallinity of ground product increased at 75% R.H. and 0% R.H., 35°C, but that of ground product at 0% R.H., -30°C was not changed. The Dp measured by DTA of the ground product increased from 189.5°C to 197°C after 4 days at 75% R.H., but the Dp of the ground product at 0% R.H., -30°C for 4 days was 190.1°C. Relation between the Dp and the crystal Unity of ground cefalotin sodium was a straight suggesting that the thermal stability of cefaiotin sodium in the solid-state depends on the degree of crystallinity.     

相变材料用于可拆卸护臂热防护服的实验研究

针对传统降温服降温效果差、续航时间低、能耗高、噪声大等问题,本文通过应用相变恒温材料Na2SO4·10H2O在高温时发生相变吸收热量的特性,设计了一种应用于夏季高温环境的人体作业可拆卸护臂的热防护服,并在此基础上进行了热水模拟热源实验和真人实验。结果表明：在热水模拟实验中,防护服在30、41、45 ℃的工况下,前胸、侧腹、后背、腹部4测点温度在60 min升至最高,4测点平均温度最终能降至约26 ℃,其中在30 ℃工况下防护服降温性能较好,在45 ℃工况下降温性能较差。在真人实验中,防护服在37.1、39、41 ℃工况下,3 h内4测点平均温度最终能降至约26 ℃;在60 ℃高温极限工况下,3 h内4测点平均温度最终能降至约31 ℃,防护服护臂内外侧平均温度最终均能降至约32 ℃,低于人体的灼痛临界温度45 ℃。因此该防护服有良好的降温效果,能满足夏季户外工作者的热舒适性要求。     

Development of High-Temperature Blackbodies and Furnaces for Radiation Thermometry

Two high-temperature blackbodies were developed and tested. The first one is a graphite blackbody with a maximum temperature of 2000 °C, an opening of 40 mm, and an emissivity of 0.995. It is intended for the routine calibration of pyrometers. The second one is a small version of a pyrolytic graphite (PG) blackbody with a cavity diameter of 15 mm, an opening of 10 mm, and an emissivity of 0.9996. The blackbody has two options with maximum temperatures of 2500 °C and 3000 °C, respectively. With these, the list of high-temperature blackbodies developed at VNIIOFI consists of five PG types and one graphite type, which can be used in radiation thermometry as precision Planckian sources or furnaces for fixed-point applications. The article also describes modifications to the PG furnace, where PG heater rings are replaced partly or totally by graphite elements. Such modifications extend the lifetime of the heater, reduce the cost for some applications and, for some cases, improve the temperature uniformity.     

An apparatus for easy determination of the amount of bound water in cement pastes yielding highly reproducible results

An apparatus designed for the determination of the amount of bound water in cement pastes is described. The drying of the ground paste takes place at 105 °C in a container, the temperature of which is accurately controlled by means of a solid-state proportional temperature regulator. The vapour pressure of water in the container is kept constant independent of the laboratory conditions. This is achieved by letting a small pump force air to bubble through wash-bottles containing distilled water and submerged in a water bath kept at 1°C. The conditioned air stream is heated to 105°C and led into the drying container. The ignition is carried out at 1050°C. The precision of the method and the influence of various testing conditions are discussed. A couple of examples of experimental results are given.     

Backscattering analysis of the successive layer structures of titanium silicides

Solid state reactions of titanium thin films with silicon and with SiO₂ were studied using a backscattering technique. For the Ti-Si system layers of TiSi₂, TiSi and Ti₅Si₃ were detected in the temperature range 500–600°C. For the Ti-SiO₂ system layers of TiO_x and Ti₅Si₃ were formed in the temperature range 700–900°C. At temperatures above 1000°C the oxygen in the film disappeared and silicon was found to reach the film surface. A surface structure of concentric circular rings was observed.     

Impact of climate warming on the ground surface temperature in the sporadic permafrost zone of the Tatra Mountains,Poland and Slovakia

This paper examines the influence of climate change on the temperature of a debris slope surface in the zone of sporadic permafrost occurrence in the Tatra Mountains. This involved applications of linear regression equations which describe statistical dependence of the ground surface temperature (GST) upon the current air temperature in snow-free periods, or upon the previous air temperature and snow depth. These equations are validated using the daily air temperature and snow depth at a reference synoptic station and GST at 5 sites located in different topographic conditions. In order to estimate mean winter half-year, mean summer half-year and mean annual GST at these sites in hydrological years 1955–2010, archival meteorological data were used. The maximum errors in these estimations, determined for two reference years, were 0.5 °C, 0.2 °C and 0.1 °C respectively. The results show that the debris slopes thermal sensitivity to climate warming decreases with the increase of: a) shading, 2) altitude, and 3) depth of seasonal snow cover. In general, the changes of the air temperature influence the changes of mean annual ground surface temperature more in snow-free periods than in snow periods, whereas the degradation of orographically conditioned permafrost patches occurs faster in the places where snow cover is thin during the whole winter. The decrease of the depth of a thick snow cover may be accompanied by the decrease of its bottom temperature, despite the increase of the winter air temperature. We infer that in special orographic-nival conditions, the increase of mean annual air temperature may be accompanied by the decrease of mean annual ground surface temperature.     

Experiences in Calibrating Industrial Platinum Resistance Sensors Between − 196 °C and 80 °C

Recently, a requirement arose to provide sensors for measuring the temperature of a substantial reference blackbody cavity to operate in vacuum over a temperature range from ? 100 °C to 80 °C (~?170 K to ~?350 K), with an additional capability to operate at ~? 170 °C (~?100 K) as a point of near-zero radiance. Several 100 Ω industrial platinum resistance sensors (Pt100) are required for control purposes in order to establish the temperature uniformity of the blackbody structure and its surrounding aluminum-alloy isothermal shield. These sensors should remain stable within the uncertainties of 0.03 °C (k?=?3) ideally for 20 years. This paper discusses the testing and calibration of two types of industrial Pt100 resistors, including checking the interchangeability of sensors from a given batch, and the methods of interpolation over the temperature range. It is concluded that the sensors can meet the requirements provided that they have been individually tested, and that there is a degree of duplication of sensors so that long-term changes can be detected. The calibration data could be fitted by cubic or quartic equations expressing temperature as a function of resistance (or resistance ratio), this being simpler than the ITS-90 formulation and more convenient than using the (technically obsolete) Callendar–Van Dusen equation.     

Structural and wear properties of sputter-deposited laves intermetallic alloy

An adhesive wear-resistant alloy, with a type MgZn₂ close-packed hexagonal Laves intermetallic phase to promote abrasive wear resistance, was d.c. sputter deposited onto steel substrates at temperatures in the range 20–800°C using a hollow cathode sputtering device. Coating thicknesses were in the range 20–60 μm. Coating structures were examined by preparing metallographic cross sections and by X-ray diffraction. The wear properties of coated and uncoated steel rings (hardness, Rc 60), sliding against blocks of cast iron, a soft steel, a tool steel, a cobalt alloy, WC-Co and a cast form of a different Laves phase intermetallic alloy, were compared in both room air and a non-lubricating liquid. Coatings deposited at a substrate temperature of about 800 °C exhibited the Laves phase diffraction profiles. Coatings deposited at lower temperatures exhibited fine-grained (amorphous type) X-ray diffraction patterns. Metallographic cross sections revealed a dense columnar structure. Microhardnesses were about 900 kg mm^-2 (KHN) independent of substrate temperature. In room temperature air with no lubricant, the wear properties of the rings with the sputter-deposited coatings were superior to the uncoated ones when sliding against the tool steel, cobalt alloy and cast Laves phase blocks. No significant improvement was seen for sliding against the cast iron, soft steel and WC-Co blocks. With a poor lubricant and higher normal forces, the coated and uncoated rings performed well against the Laves phase and tool steel blocks; however, the coated rings were generally inferior for the other couples tested.     

Development of freezing–thawing processes of foundation soils surrounding the China–Russia Crude Oil Pipeline in the permafrost areas under a warming climate

The proposed China–Russia Crude Oil Pipeline (CRCOP) will be subjected to strong frost heave and thaw settlement of the surrounding soil as it traverses permafrost and seasonally frozen ground areas in Northeastern China. The freezing–thawing processes, the development of the maximum frozen cylinder in taliks and thawed cylinder in permafrost areas, and the variations in the maximum freezing depths under the pipeline in taliks and thawing depths in different permafrost regions near Mo'he station, the first pumping station in China, were studied in detail using numerical methods in this paper. The inlet oil temperature at Mo'he station was assumed to vary from 10 to − 6 °C in a sine wave form during the preliminary design phase. Research results showed that the freezing–thawing processes of soils surrounding the buried pipeline had distinct differences from those in the undisturbed ground profile in permafrost areas. In summer, there was downward thawing from the ground surface and upward and downward thawing from the pipeline's surface once the temperature of the oil rose above 0 °C. In winter, downward freezing began from the ground surface but upward and downward cooling of the cylinder around the pipeline didn't begin until the temperature of the oil dropped below 0 °C. However, in the undisturbed ground profile, downward thawing from the ground surface occurred in summer and downward freezing from the ground surface and upward freezing from the permafrost table occurred in winter. The maximum thawing depths and thawed cylinder around the pipeline in warm permafrost enlarged with elapsing time and decreasing water content of the soils. In taliks, the maximum freezing depths and frozen cylinder around the pipeline kept shrinking with elapsing time and increasing water content of the soils. The freezing–thawing processes and development of the thawed and frozen cylinders around the pipeline were muted by any insulation layer surrounding the pipeline. Insulation had better thermal moderating on the heat exchange between the pipeline and the surrounding soils during the early operating period. But its role slowly weakened after a long-term operating. Research results will provide the basis for assessment and forecasting of engineering geological conditions, analysis of mechanical stability of the pipeline, foundation design, and pipeline construction and maintenance.     

Use of Salt Baths in the Temperature Range from 175?��C to 540?��C with Uncertainties of Less than 30?m��C

Calibration of thermometers in the temperature range from ?80 °C to 550 °C requires liquid baths; alcohol, water, silicon oil, salt baths and dry block furnaces. In this study, the use of salt baths outside of their usual range of 250 °C to 540 °C for calibrating thermometers in the range between 175 °C and 250 °C is proposed. The calibration range from 150 °C to 250 °C is usually covered by an oil bath, but utilizing a salt bath saves calibration time and resources, improves stability and homogeneity, allows longer term usage of the liquid, and reduces hazardous chemical vapors evaporated at temperatures above 175 °C. This proposal is based on a study of the uncertainty contributions at varying salt bath temperatures in the range from 175 °C to 540 °C which was carried out in this study. Results achieved and analyzed in this study indicate that the implementation of salt baths in this lower temperature range provides opportunities to calibrate reference and/or working thermometers with an uncertainty below 30 m°C, almost the same as the oil-bath uncertainty in the range of 175 °C to 250 °C. The main components of uncertainty contributed by a salt bath over this temperature range are discussed in this study.     

Temperature dependence of the effective permeability of heat treated Sendust alloys

The temperature dependence (-10°C-70°C) of the effective permeability (μeff) of Sendust alloys (Fe-9-10 wt% Si-5-7 wt% Al) quenched at a room temperature from the various temperatures (400°C-700°C) was investigated at every 2°C in the temperature range of -10°C to 70°C. Most of the studied alloys gave a peak of μeffin the studied temperature range. The peak temperature (Tp) giving the peak μeffvaried with different alloy composition. The alloys of Tp = 20°C are supposed to correspond to the alloys of the zero magnetocrystalline anisotropy constant (K1= 0) at 20°C. The deduced K1= 0 lines at various temperatures (-10°C-50°C) were obtained for an Fe-Si-Al ternary system. The values of peak μeffat the same Tp were different, depending on alloy composition, This difference is due to the difference in the polycrystalline magnetostriction constant (λ s) of the alloys. The peak temperatures of the studied alloys vary with the different heat treatments. This variation is due to the variation of K1, induced by the change in microstructures of the alloys. The variation of the values of peak μeffwith heat treatments was small compared to the difference of those in the alloys of different composition. It seems that the variation of the λ s with heat treatments would be small. Both the compositional dependence of μeffat 20°C and the temperature sensitivity (Δμeff/ΔT) were obtained for both the alloys cooled continuously to room temperature and those quenched at room temperature from 400°C.     

Effect of nitrile-functionalization and thermal cross-linking on the dielectric and mechanical properties of PEN/CNTs–CN composites

In this study, a novel series of composite films consisting of nitrile-functionalized carbon nanotubes (CNTs–CN) and poly(arylene ether nitriles) (PEN) were successfully fabricated by the tape-casting method. The –CN groups in PEN chains and the phthalonitrile groups on CNTs–CN formed the thermally stable triazine rings by thermal cross-linking reaction in the presence of diamino diphenyl sulfone, which was characterized by Fourier transform infrared spectroscopy. The result indicated that the chemical cross-linking reaction occurred accompanied by the emergence of a new absorption peak at 1,361 cm^?1. Besides, the effect of cross-linking on the morphology, thermal stability, mechanical and dielectric properties of the PEN/CNTs–CN was investigated. The SEM images showed that the phase interface between surface modified CNTs and PEN matrix was indistinct, and the surface modified CNTs presented a better dispersion behavior in PEN matrix. The mechanical properties of the processed films were improved substantially compared with the unprocessed films. Furthermore, the glass-transition temperature (T _g ) of composite films processed at 320 °C for 4 h (about 245 °C) was higher than that of composite films before thermal treatment (about 205 °C). The 5 % weight loss temperature of the composite films (processed at 320 °C for 4 h) increased by about 110 °C compared with the composite films (unprocessed). More importantly, by thermal cross-linking, the dielectric constant (ε) of composite films with 8 wt% CNTs–CN loading was increased from 31.8 to 33.9, and dielectric loss (tan δ) was decreased from 0.90 to 0.61 at 1 kHz.     

Experimental study on critical breaking stress of float glass under elevated temperature

Cracking and subsequent fallout of glass may significantly affect fire dynamics in compartments. Moreover, the breaking tensile stress of glass, a crucial parameter for breakage occurrence, is the least well known among mechanical properties. In this work, a series of experiments were conducted, through mechanical tensile tests, to directly measure the breaking stress of float glass using Material Testing System 810 apparatus. Clear, ground and coated glass samples with a thickness of 6 mm were measured under ambient conditions, with a room temperature of 25 °C. The breaking stress of smooth glass samples was also measured at 75 °C, 100 °C, 125 °C, 150 °C, 200 °C, 300 °C and 400 °C, respectively. The results show that surface treatment may decrease the critical tensile stress of glass panes. The average breaking stress also fluctuates considerably, from 26.60 to 35.72 MPa with the temperature variations investigated here. At approximately 100 °C, critical stress reached the minimum value at which glass breakage occurs more easily. In addition, the thermal expansion coefficient was established using a thermal dilatometer, to obtain the maximum temperature difference float glass can withstand. It is intended that these results will provide some practical guidelines for fire safety engineers.     

Experimental study of a subcritical heat pump booster for sanitary hot water production using a subcooler in order to enhance the efficiency of the system with a natural refrigerant (R290)

This paper presents the experimental results obtained from a new heat pump prototype for sanitary hot water production, in the application of heat recovery from water sources like sewage water or condensation loops (typical temperature condition between 10 °C and 30 °C). The system configuration is able to produce a high degree of subcooling in order to take advantage from the high water temperature glide (typical value for sanitary hot water production is 10 °C to 60 °C). Subcooling is made by using a separate heat exchanger from the condenser (subcooler). The obtained results have shown a high degree of improvement by making subcooling. COP is 5.61 in nominal conditions, which is about 31% higher than the same cycle working without subcooling (Nominal point: inlet/outlet water temperature at evaporator is 20 °C/15 °C and the water inlet/outlet temperature in the heat sink is 10 °C and 60 °C).     

Influence of solutionising and aging temperatures on microstructure and mechanical properties of cast Al–Si–Cu alloy

Abstract

This paper presents the influence of solution and aging temperatures on the microstructure and mechanical properties of 319 secondary cast aluminium alloy. Experimental alloy was subjected to different heat treatment cycles. Heat treatments were designed with two solutionising temperatures (504 and 545°C) at two solutionising times (4 and 8 h), followed by quenching in water at 60°C and artificial aging. The artificial aging was carried out at two temperatures (200 and 154°C) for 6 h. The improvement in mechanical properties was obtained with low solution temperature (504°C) for 8 h followed by quenching in water to 60°C and aging at low temperature (154°C). The increase in the solutionising temperature from 504 to 545°C was recommendable only for short solutionising time (4 h). Increase in the aging temperature from 154 to 200°C has led to the increase in hardness with the corresponding decrease in ductility. Aging under unfavourable conditions (prolonged aging at high temperature) caused coarsening of spheroidised eutectic silicon crystals and precipitated particles resulted in deleterious effect on the tensile strength.     

Independent control of InAs quantum dot density and size on AlxGa1–xAs surfaces

Decoupling of InAs quantum dot (QD) size and density on Al_xGa_1?xAs surfaces (x = 0, 0.15, 0.30, and 0.45) is achieved by using a low growth rate and careful control of the temperature. The deposition rate of 0.01 μm/h, instead of 0.05 μm/h, allows the QDs to ripen with additional InAs deposition while the substrate temperature (490–520 °C) determines the QD density. On the GaAs surface, an increase of 10 °C results in an order of magnitude lower QD density. The increase of Al in the Al_xGa_1?xAs surfaces results in a higher dot density, lower dot size, and an increased size distribution. All surfaces show reduced QD density with increasing temperature and an identical zero dot density temperature at 523 °C. The GaAs surface shows increasing QD height with temperature while the Al_xGa_1?xAs surfaces show the opposite trend, but the InAs volume fraction in QDs for all surfaces decreases with increasing temperature, implying a more stable wetting layer. Increasing Al content also increases the InAs volume fraction in QDs, implying the wetting layer for all but the 520 °C samples is less than one monolayer. Photoluminescence samples demonstrate ground state QD energies above the GaAs bandedge.