堇青石基透波材料的抗热震性能分析

随着微波技术的发展,透波材料成为材料制备领域的研究热点。堇青石具有热膨胀系数低、热导率小、介电常数低、抗热震性能好及化学稳定性好等优点,将其作为微波冶金的承载体材料,满足了微波冶金过程的使用要求和适用条件。采用MgO、Al_2O_3、SiO_2三种原料,同时添加部分纳米SiO_2粉体代替工业SiO_2,在不同的原料配比下微波烧结合成Mg-Al-Si-O系堇青石基透波材料,并测定分析所得样品在未热震前、热震4次及热震8次的测试下,样品的弯曲强度及抗热震性能的变化。     

高温烧结炉用堇青石一莫来石耐火砖结合剂研究

采用反应烧结法制备了高温烧结炉用堇青石一莫来石耐火砖,研究了不同结合剂对耐火砖组织结构和性能的影响.结果发现,与黏土结合剂在烧结过程巾有大量莫来石相生成相比,堇青石质结合剂在烧结过程中有大量新生相堇青石生成,热膨胀系数和抗折强度普遍较低,气孔率和热震稳定性较高,随着堇青石质结合剂含量的增加,热膨胀系数逐渐减小,气孔率和...     

大型循环流化床锅炉的烘炉实践

大型循环流化床 (以下简称CFB)锅炉的烘炉是使耐火耐磨材料烧结成型并使之达到耐火、耐磨、耐压、抗折、热震稳定性、高温耐压性能的关键。通过大型CFB锅炉的烘炉实践 ,提出了保证大型CFB锅炉烘炉的关键措施 ,分析了烘炉中存在的问题 ,认为耐火材料的理化性能、施工和烘炉是三位一体的 ,必须控制各个环节才能最终保证耐火耐磨材料的性能 ,并为今后大型CFB锅炉的烘炉提供借鉴。     

回转窑焚烧炉用刚玉基浇注料的性能比较

危险废物焚烧回转窑用耐火砖在使用中易出现局部损毁,耐火砖采购周期长,不能满足回转窑快速检修需求,利用浇注料代替耐火砖是必然趋势。以刚玉基浇注料为研究对象,分别制备刚玉莫来石质、铬刚玉质、锆刚玉质和刚玉尖晶石浇注料,研究其物理性能和抗侵蚀性能。结果表明：刚玉莫来石和含锆英石的刚玉浇注料抗渣侵蚀性能差,但含锆英石刚玉浇注料的热震稳定性好;刚玉尖晶石浇注料和铬刚玉浇注料具有较强的抗渣侵蚀性能,Cr₂O₃含量越高其抗侵蚀性能越好。     

无心感应熔铝炉干式成型耐火材料

介绍中频无心感应熔铝炉用新型干式成型耐火材料和使用情况。该炉衬材料热震稳定性好、抗渗透性强、施工周期短和使用寿命长。     

科光871高温胶泥在我省的应用情况

科光871系列高温胶泥是江西科光窑炉技术开发公司开发成功的一种新型高温炉料,由于其具有耐高温、抗冲击、耐急冷急热、耐磨损、防渣侵和整体性强等优异特点,在我省的水泥、冶金、化工、陶瓷等行业得到很快的推广应用。 一、科光871高温胶泥的性能特点 科光871高温胶泥是一种经多年研制成功的高分子新型炉料,在砌筑耐火砖后,其固化过程以及加热后物理化学变化是:中低温时产生化学胶结粘附,使胶泥与耐火砖界面产生反应,通过分子间互相渗透,使砖与砖凝固成整体,出现高强度;高温时,则以晶格转变成陶瓷烧结产生高温强度来体现。目前国内大多数工业窑炉砌体所使用的耐火泥,由于性能欠佳,在砖缝内只能起到一种填充物的作用,成为砌体的薄弱环节,不但难以承受高温气流的冲刷、物料的撞击、急冷急热等物理损毁,而且无法经受有害气体、熔渣和熔融金属的化学侵蚀,在物理化学的综合作用下导致炉龄短和频繁返修。使用科光871高温胶泥可以有效提高炉窑的整体机械强度、耐磨性、耐热震性、抗化学腐蚀性;炉窑的体积稳定性大幅度提高,可防止砌体松动,变形或开裂掉砖所致的漏风窜火,减少灰尘外漏,改善操作环境,延长炉龄,节约能源。 二、科光871高温胶泥在我省的应用 科光871高温胶泥自1992年9月起在我省推广应用以来,     

耐高温改性双马来酰亚胺玻璃布层压板的研制

以改性双马来酰亚胺树脂为胶粘剂 ,浸渍制备相应的玻璃布预浸料 ,并采用热压工艺制得耐高温改性双马来酰亚胺玻璃布层压板。用TGA方法研究了基体树脂的热稳定性 ,通过热重点斜法 (TPS)评定了该层压板的耐热等级。实验结果表明 ,该基体树脂溶液粘度低 ,室温下的贮存稳定性好 ,于浸料使用期长 ,制得的层压板具有优良的机械电气性能 ,能在 1 90℃长期使用。     

高温高发射率釉料的研制

本文所述的高温高发射率釉料是一种耐高温、抗渗碳、耐腐蚀的新型红外辐射材料。本文阐述了它的制备工艺,试验了各种因素对其性能的影响。试验表明:高温高发射率釉层抗渗碳、耐腐蚀、抗热震等性能优于一般红外辐射涂层;实际使用表明这类高温高发射率釉料的节能效果显著。     

700℃机组用Waspaloy合金高温叶片与螺栓研制

700℃高参数汽轮机机组的研发需要以综合性能优异的材料为支撑。对高温叶片和螺栓备选材料Waspaloy合金的化学成分、组织、性能以及加工工艺进行了全面研究,并成功试制出Waspaloy合金高温螺栓样件。研究结果表明:Waspaloy合金不仅具有优异的加工工艺性能,而且在700℃还具有良好的高温强度、持久性能、抗松弛性能以及长时时效稳定性,完全可以满足700℃先进超超临界机组高温叶片和螺栓的使用要求,试制出的Waspaloy合金螺栓样件达到工程化应用的要求。研究成果可为700℃先进超超临界机组高温螺栓与叶片的设计与制造提供参考。     

高温材料在发电燃气轮机中的应用和发展

介绍了当前世界四大燃气轮机制造商热端部件使用的各种高温材料和我国燃气轮机用高温材料的现状,通过分析热部件工作环境对材料性能的要求,提出了热部件材料选择的原则。结合国内外燃气轮机用高温合金的发展和应用现状,提出了我国重型燃气轮机高温材料发展的目标和方向。     

含碳浇注料的研究进展

含碳浇注料因具有优异的抗侵蚀、抗渣渗透及抗热震等性能而被人们所广泛关注，但由于石墨的润湿性和分散性很差，以及石墨易被氧化等特点而限制了其应用。从石墨的润湿性改进和抗氧化剂两方面总结了近10年来国内外含碳浇注料的研究进展，同时阐述了各种改进工艺的特点和不足，并从工业应用的角度指出了未来含碳浇注料的研究重点和发展前景。     

Hydrogen generation from hydrolysis of activated Al-Bi,Al-Sn powders prepared by gas atomization method

Highly activated Al-based composite powders with compositions of Al-20Bi and Al-20Sn (wt.%) were prepared by gas atomization method for hydrogen generation. The Al-20Bi powders formed incomplete core–shell structure with Bi aggregating on the powder surface, while the Al-20Sn powders presented eutectic structure with Sn distributed homogeneously on the grain boundaries of Al. The hydrolysis characteristics of these powders were investigated in distilled water. The results showed that the Al-20Bi and Al-20Sn powders exhibited high hydrolysis performance and violently reacted with distilled water at 30 °C. Elevated temperature could significantly shorten the incubation time, as well as improve hydrogen generation rate and conversion yield of the powders. The hydrolysis mechanism and oxidation resistance property of the powders were carefully investigated too. The miscibility gap and the large difference of linear thermal expansion coefficient between Al and Bi are responsible for the activation and high oxidation resistance of the Al-20Bi powders.     

One dimensional thermal analysis of silicon carbide ceramic foam used for solar air receiver

Using air as heat transfer fluid for electricity generation offers some significant advantages for the development of Concentrated Solar Power (CSP): high conversion efficiency, low environmental impact and being used in deserts or other areas scarce of water resources. Silicon carbide ceramic foams have the characteristics of light weight, high strength, large specific surface areas, high porosity and excellent thermal shock resistance performance which make them particularly fit for absorber material in CSP. In this paper, thermal performance of silicon carbide ceramic foam as solar air receiver is investigated analytically based on the one dimensional physical model. The analytical results show that the air flow resistance increases obviously with increasing air outlet temperature, the air flow resistance while the air outlet temperature is equal to 1000 °C is nearly 3 times the one while the air outlet temperature is equal to 20 °C with air velocity range is between one and six meters per second. The results of one dimensional analysis of flow and heat transfer process of ceramic foams suggest that there exists an input solar energy flux limit for the unpressurized system, which will lead to limit the power capacity and the outlet air temperature enhancement.     

结晶器用铜板强化技术的研究进展

铜及铜合金具有优良的导电导热性能,其在钢铁冶炼过程中的连铸结晶器上起着举足轻重的关键作用.然而结晶器所在的恶劣服役条件却限制了其性能的发挥,较常见的损耗形式为结晶器铜板内表面弯月面处的热裂纹及结晶器铜板下部的摩擦磨损,这些损耗形式在一定程度上大大缩短了结晶器的使用寿命,针对此现象综述了国内外不同表面改性强化技术在结晶器铜板上的应用,通过不同表面改性强化处理,可提高结晶器铜板耐磨性、耐热冲击及耐腐蚀性能,从而提高铸坯质量、延长结晶器使用寿命及降低生产成本的目的.     

Performance of solid particles flow thermal storage material made of desert sand

It is a safe and low-cost new heat storage method to realize sensible heat storage at medium and high temperature by using flowing inorganic inert solid particle materials. The cost and performance of granular heat storage medium are very important for this kind of heat storage technology. The yellow sand in southeast of Tenggri Desert in Ningxia is studied. By thermal shock and grinding methods, the tests of thermal shock-resistance and wear resistance were carried out, under laboratory conditions, for the unscreened raw sand and the screened sand samples with three grain sizes (40–60 mesh, 60–80 mesh, and 80–100 mesh). The particle size of the raw sand is 150–300 µm (60–100 meshes) accounts for 60% (wt %) or more and meets the requirement of heat storage material. The density, thermal conductivity, and specific heat of raw sand are higher than those of three kinds of screened sand. Thermal shock and grinding affect the particle size distribution, density, specific heat, and thermal conductivity of the particles. The degree of influence varies with the particle size. The volume ratio heat capacity is used to measure the heat storage performance of the particles. Thermal shock results in a better thermal storage performance of the screened sand than the original sand. After comprehensive analysis of the properties of three kinds of screened sand, it is found that the content of 60–80 mesh-screened sand (31.75%) is the highest in the original sand. After thermal shock and grinding, the screened sand not only has good heat storage performance (average volumetric specific heat capacity 3.232 J· K^?3· K^?1), but also has the smallest change of particle size (breaking rate is less than 24, and agglomeration rate is less than 6), and the thermal shock resistance and wear resistance are outstanding. It is suggested that the screened sand with the particle size range of 200-300µm (60–80 mesh), also the particles with the highest content in the original sand, should be selected as the solid particle flowing heat storage medium.     

Basic properties of ceramic fibres and their effect on insulation performance

This paper reviews the basic properties of ceramic fibres. Individual characteristics such as chemical composition, physical state, temperature stability, chemical stability, fibre diameter and fibre length are discussed. Emphasis is laid on their combined contribution to the properties of the very wide range of product forms commercially available. These properties include thermal conductivity, low weight, heat storage and thermal inertia, resistance to thermal shock, low thermal expansion, resilience and recovery from compression, acoustic performance, resistance to molten metal attack and heat distribution.     

Unified Thermal Shock Resistance of Ultra-High Temperature Ceramics Under Different Thermal Environments

The thermal shock resistance (TSR) of the ultra-high temperature ceramic (UHTC) plate under convective environments is studied. The critical failure temperature difference has a danger temperature range about the thermal shock initial temperature. However, the critical failure dimensionless time decreases as the thermal shock initial temperature increases. The TSR of UHTCs is susceptible to thermal environments. The heat transfer condition shows its advantage in representing the TSR of UHTCs under different thermal environments. Universal conclusions about the TSR of UHTCs under different thermal environments are drawn using heat transfer condition. Three types of critical heat transfer condition that respectively correspond to the first, second, and third type thermal boundary conditions are introduced to characterize the TSR of UHTCs under different thermal environments similar to using various types of strength in representing the fracture-resistance abilities of the materials under different loads. The critical heat transfer condition is applied to the TSR of the UHTC plate under active cooling. The critical heat transfer condition is susceptible to the difference of the thermal shock initial temperature and the coolant temperature.     

Feasibility study of a vapor chamber with a hydrophobic evaporator substrate in high heat flux applications

A novel vapor chamber was fabricated to assess the feasibility of combining hydrophobic and hydrophilic wettabilities in the evaporator to optimize thermal performance. The proposed vapor chamber included a separate layer of hydrophilic sintered copper powder wick that was pressed in intimate contact with a hydrophobic evaporator substrate with a water contact angle around 140°. The contact between the wick layer and the evaporator was provided by sixteen posts implemented on the condenser, which pushed the wick layer toward the evaporator. The thermal performance was evaluated based on the thermal resistance, source temperature, and temperature uniformity across the condenser. Results were compared with those of a baseline vapor chamber that was fabricated by sintering hydrophilic copper particles on a hydrophilic copper evaporator substrate. The wick size and the copper powders used to fabricate the wick structure were the same in both vapor chambers. Overall, the performance of the proposed vapor chamber was lower than that of the baseline vapor chamber, possibly due to microscale gaps between the wick layer and the evaporator substrate. However, the concept of using a hydrophilic wick to force liquid in contact with a hydrophobic evaporating surface could enable a new family of vapor chambers with low thermal resistance, if more efficient techniques for improving the mechanical contact between the wick layer and the evaporator are introduced through further detailed research. If successful, the fabrication cost of vapor chambers would be reduced as well, by using prepared wick structures, which do not require high-temperature sintering processes on evaporators.     

RELATIONSHIP BETWEEN THERMAL SHOCK STRENGTH BY LASER IRRADIATION TECHNIQUE AND FRACTURE TOUGHNESS FOR CERAMICS

The traditional water quenching technique used to evaluate the thermal shock resistance of ceramics is accompanied by an unstable heat transfer coefficient in the quenching process. This leads to an unreliable result of the value of the thermal shock strength of ceramics. Our purpose is to establish a new method using the laser irradiation technique by which the thermal shock strength of ceramics could be evaluated. Defining the laser power density, the so-called critical power density P L at which the ceramic specimen fractures, the method was evaluated both theoretically and experimentally for several structural ceramic materials. Since thermal shock fractures are caused by the induced thermal stress, the thermal shock strength must be correlated to the fracture toughness of ceramics. This study presents a relationship between the thermal shock strength P L , which corresponds to the critical powerdensity, by laser irradiation and the fracture toughness K IC by the indentation fracture technique for ceramics as a means to investigate their fracture mechanism. The thermal shock strength P L can be used as a fracture criterion corresponding to the critical temperature difference in the quenching method. The thermal shock strength for several ceramics was obtained by the irradiations with CO 2 lasers. On the other hand, their fracture toughness was measured by the indentation technique using a micro Vickers hardness tester. It was concluded that these two quantities, the thermal shock strength and the fracture toughness, were closely correlated; a linear relation was shown in a semi-log plane.     

Integrated design of hydrogen production and thermal energy storage functions of Al-Bi-Cu composite powders

In recent years, the hydrolysis of Al-based composite powders to produce hydrogen has become a hot topic in the field of hydrogen energy research. However, the hydrogen generation products of Al-based alloys have not been reasonably utilized. For this purpose, this study proposed a novel research idea to achieve the integrated design of hydrogen production and thermal energy storage functions of Al-based composite powders. Specifically, Al-Bi-Cu composite powders with stable hydrogen production were taken as research objects. The hydrogen was obtained by the reaction of Al-Bi-Cu alloy powders with H₂O for different reaction times, and then the hydrogen generation products were directly sintered at high temperature to obtain Al-Cu alloy based composite phase change thermal energy storage materials. The results indicated that at 50 °C, the hydrogen yield of Al-Bi-Cu alloy powders in 100min, 200min and 400min are 319.9 mL/g, 428.5 mL/g and 665.8 mL/g, respectively. Importantly, the Al-Cu alloy based composite phase change thermal energy storage materials prepared by the hydrogen generation products exhibited an adjustable phase change temperature (577.3 °C ∼ 598.2 °C), high thermal energy storage density (44.1J/g ∼ 153.5J/g), good thermal cycling stability and structural stability.