复配表面活性剂SDS+SDBS强化CO2水合物蓄冷性能研究

本文采用压缩式制冷循环,研究了不同质量浓度(0.4、0.5、0.6 g/L)的表面活性剂十二烷基硫酸钠(SDS)溶液、不同质量浓度(0.2、0.3、0.4 g/L)的表面活性剂十二烷基苯磺酸钠(SDBS)溶液及复配表面活性剂溶液(SDS+SDBS)中,CO₂水合物的蓄冷特性。结果表明：与纯水体系相比,SDS、SDBS及SDS+SDBS对CO₂水合物蓄冷性能均有强化作用,且3种表面活性剂的最佳质量浓度分别为0.5 g/L、0.3 g/L、0.5 g/L(SDS)+0.3 g/L(SDBS)。对比3种最佳质量浓度的表面活性剂发现,采用0.5 g/L(SDS)+0.3 g/L(SDBS)时蓄冷性能最优：预冷时间(21.51 min)和蓄冷时间(27.56 min)最短;潜热蓄冷量(1 308.27 kJ)、总蓄冷量(2 967.35 kJ)、平均蓄冷速率(1.79 kW)和水合物生成质量(2.55 kg)均最大。说明复配表面活性剂对于CO₂水合物蓄冷性能具有最显著的强化效果。     

高分子稳泡剂和SiO2纳米颗粒对二元表面活性剂复配体系泡沫性能影响

利用短链氟碳表面活性剂(FS-50)、阴离子碳氢表面活性剂十二烷基硫酸钠(SDS)、亲水性SiO₂纳米颗粒和水溶性聚合物(羧甲基纤维素钠(NaCMC)和黄原胶(XG))制备了泡沫混合体系,系统研究了纳米颗粒和聚合物对FS-50/SDS复配体系的分子间相互作用和泡沫性能的影响。结果表明,FS-50/SDS/纳米颗粒/聚合物体系存在着强烈的分子间相互作用,导致其表面活性、黏度和电导率出现了复杂的变化。5%的SiO₂纳米颗粒可以提高FS-50/SDS复配体系的泡沫稳定性和起泡性能;0.05%的XG或0.5%的NaCMC在提高FS-50/SDS复配体系的泡沫稳定性的同时会降低其起泡性能。纳米颗粒和聚合物可以协同提高FS-50/SDS复配体系的泡沫稳定性;但是,同时存在纳米颗粒和聚合物会大幅降低FS-50/SDS复配体系的起泡性能。该研究结果可为开发性能优异的泡沫稳定剂提供理论参考。     

TiH2对乳化炸药性能的影响研究

为获得高威力且热稳定性良好的乳化炸药,研制了一种含有TiH₂的乳化炸药,并对该乳化炸药的性能进行测定。爆速、爆热和猛度实验研究发现,加入TiH₂会使乳化炸药爆速微降,同时提升其爆热和猛度。当乳化炸药中TiH₂质量分数为2%、4%时,爆热分别增加了4.21%、5.66%;猛度分别增加了15.29%、17.20%。TG-DTG实验研究发现,加入TiH₂不会影响乳胶基质的热分解过程,但会降低其表观活化能。当乳化炸药中TiH2的质量分数为2%、4%时,乳化基质的表观活化能分别降低了21.04%、12.61%。TiH₂能够在不影响乳化基质热分解过程的同时,提高乳化炸药威力。     

Gemini表面活性剂的合成及在乳化炸药中的应用

以N,N-二甲基十二烷基叔胺和1,3-二溴丙烷为原料,无水乙醇为溶剂合成阳离子型Gemini表面活性剂.反应产物以混合溶剂乙酸乙脂-乙醇重结晶纯化后,用红外光谱及核磁共振进行结构表征,并将其作为晶形改变剂及助乳剂应用于乳胶基质中,使乳化炸药具有小而分布均匀的W/O粒子和较强的稳定性及良好的爆炸性能.     

表面活性剂对TiO2纳米粒子形貌和结晶性的影响

二氧化钛(TiO₂)半导体材料因优异的光电性能在太阳能电池、发光二极管和紫外探测器等光电器件领域得到广泛应用,引入表面活性剂制备的TiO₂纳米粒子具有更好的光电性能。采用低成本的油酸作为表面活性剂,通过溶剂热法在较低的反应温度下得到了具有高结晶性和窄尺寸分布的TiO₂纳米粒子,其粒径分布在10～11nm之间且纳米粒子的形状均一,具有优异的分散性能。热重分析表明500℃时油酸已完全分离,有利于TiO₂纳米粒子在光电器件中的应用。     

CO2制冷压缩机性能检测装置与试验研究

根据CO₂制冷压缩机的运行特点,设计了一套适用于跨临界循环的压缩机性能检测装置,该装置适用于制冷量为14 kW⁷0 kW的冷冻冷藏及热泵系统用CO₂压缩机的测试,试验方法为制冷剂气体流量计法和跨临界气体冷却器法;在此基础上开展了CO₂制冷压缩机的性能测试,结果表明,该压缩机的主侧制冷量、辅侧制冷量及主辅侧平均值的测量结果重复性偏差均在±1%以内。     

非离子型三硅氧烷表面活性剂的合成及其界面性能

1,1,1,3,5,5,5-七甲基三硅氧烷和单烯丙基聚乙二醇甲基醚在氯铂酸催化下经硅氢加成反应合成出了非离子型三硅氧烷表面活性剂(NTS)。通过红外光谱IR确证了NTS的结构,并通过测定NTS水溶液的平衡表面张力研究了其表面活性。结果表明在NTS浓度为6.3×10-4mol.L-1时,可将水的表面张力降低至23.5mN.m-1。0.1%NTS(质量分数)水溶液在塑料薄膜上的瞬间接触角为33.9°,15s时的接触角为17.3°,而空白水在塑料薄膜上的瞬间接触角为69.9°,30s时的接触角为59.3°;0.1%NTS(质量分数)水溶液铺展面积是水的7.2倍。     

S型异质结Bi4O5Br2/CeO2的制备及其光催化CO2还原性能

光催化CO₂还原技术的关键是开发高效光催化剂,而构建具有紧密界面结构的异质结是增强界面电荷转移,实现高效光催化活性的有效途径。本研究采用静电纺丝技术结合水热法,将Bi₄O₅Br₂纳米片镶嵌在CeO₂纳米纤维表面,制得Bi₄O₅Br₂/CeO₂纤维光催化材料(B@C-x,x对应反应物的加入量)。利用不同方法表征其微观结构、形貌和光电性能。结果表明,适当Bi₄O₅Br₂含量的Bi₄O₅Br₂/CeO₂异质结可以显著提高CeO₂纳米纤维的光催化性能。与纯Bi₄O₅Br₂和CeO₂相比,B@C-2在模拟太阳光下表现出最佳光催化活性,不使用任...     

CsPbBr3钙钛矿的光催化CO2还原研究进展

探索绿色发展、解决能源危机已成为近年来商业发展的趋势。金属卤化物钙钛矿因其独特的光催化性能而备受关注。其中,CsPbBr₃钙钛矿具有较高的光催化活性和优异的稳定性,在光催化CO₂还原方面发展迅速。在能源发展趋势下,减少碳排放和催化还原CO₂作为燃料是研究热点和主要途径。然而,纯CsPbBr₃较差的CO₂吸附还原能力、严重的电荷复合和较低的电荷效率严重阻碍了钙钛矿光催化的商业化。为了解决纯CsPbBr₃材料光催化中的一系列问题,对CsPbBr₃钙钛矿进行表面改性或构建多组分复合材料是目前最经济、最有前景的解决方案。本文讨论了CsPbBr₃钙钛矿的光催化反应原理及所面临稳定性和还原能力的阻碍,对CsPbBr₃钙钛矿及其复合物的光催化CO₂还原研究进行了系统的回顾。最后对构建更加稳定、高效及可持续性的CO₂还原光催化剂新的探索方向进行了展望。     

水性聚氨酯膜吸收CO2矿化形成复合膜及其防腐蚀性能

以异佛尔酮二异氰酸酯(IPDI)、聚醚二元醇(PPG)和N,N-二甲基-N’,N’-二(2-羟丙基)-1,3-丙二胺等为主要原料制备了聚氨酯预聚体,并利用乙酸、3-羧基-3-羟基戊二酸和2,2-二羟甲基丙酸(DMPA)为成盐剂与聚氨酯预聚体反应,产物经乳化得到3种阳离子水性聚氨酯胶乳(WPU1,WPU2和WPU3),并将其制膜后浸泡在模拟海水中。研究了3种水性聚氨酯膜吸收CO₂并矿化形成聚氨酯-碳酸钙(PU-CaCO₃)复合膜的过程及防腐蚀性能。红外光谱分析结果表明,成功合成了3种阳离子水性聚氨酯。粒径分析表明,WPU1,WPU2和WPU3胶乳粒径大小分别为19.38 nm,93.08 nm和84.33 nm。X射线衍射、扫描电镜和电化学测试结果表明,WPU2和WPU3膜经模拟海水浸泡后表面出现CaCO₃矿化层,WPU3膜表面形成的矿化层较致密,且具有优良的防腐蚀性能,其腐蚀速率和腐蚀电流密度分别为1.70×10^-3mm/a和1.44×10^-7A/cm²。     

CO2-shielded arc as a high-intensity heat source

The characteristics of a CO₂-shielded arc are studied to evaluate its potential as a novel heat source for material processing, with lower costs and higher productivity than that of the tungsten–inert gas (TIG) arc. A double-gas-shielded system, using both CO₂ and an inert gas, is employed for the arc torch; this minimizes consumption of the tungsten electrode and gives arc stability equivalent to an argon TIG arc for 1800 s operation. The arc voltage of the CO₂-shielded arc is about 19 V for an arc current of 150 A and an arc gap of 3 mm, which is much higher than the 12 V obtained for an argon TIG arc. The CO₂ constricts the arc, resulting in an increase in the maximum heat flux density at the anode surface by a factor of about 10 relative to the TIG arc. The penetration depth of stainless steel melted by the CO₂-shielded arc is much larger than that for the argon TIG arc. It is concluded that the greater heating power of the CO₂-shielded arc, which is due to the greater arc constriction, in turn a consequence of the greater specific heat of CO₂, should lead to a large increase in material processing productivity.     

Solid fraction modelling for CO2 and CO2–THF hydrate slurries used as secondary refrigerants

In the present paper, the suitability of hydrate slurries in secondary refrigeration was investigated by the means of a new hydrate solid-fraction model. Considering the high melting enthalpy of CO₂-containing hydrates, slurries presenting high hydrate solid fractions can carry sufficient latent heat to be useful for a two-phase secondary-refrigerant application. The model presented in this paper allowed to calculate the solid fraction of CO₂ and CO₂–THF hydrate from thermodynamic conditions of pressure and temperature. Contrary to a previous work on single CO₂ hydrates in a closed system, the present model can take into account hydrate mixture and is well adapted to additional CO₂ injections (opened system). By relying on the hydrate-conversion model results, the study of hydrates in suspension in a carrying liquid was also studied in an experimental loop and was based on a formation process by CO₂ injection in a cooled aqueous solution.     

Simulated performance and cofluid dependence of a CO2-cofluid refrigeration cycle with wet compression

Recent experiments demonstrate the viability of a low-pressure CO₂-cofluid compression refrigeration cycle in which CO₂ and a non-volatile cofluid are circulated in tandem and co-compressed in a compliant scroll compressor. This work explores the theoretical performance limitations of such a cycle operating under environmental conditions representative of automotive air conditioning and studies the dependence of this performance on the properties of the CO₂-cofluid mixture. The vapor–liquid equilibrium and thermodynamic properties of the mixture are described using a previously reported activity-coefficient model. A coupled system of physically based equations that allows for consideration of both ideal and real hardware components is used to represent the system hardware and its interaction with the environment. The system efficiency is analyzed in terms of entropy generation rates in the various hardware components; entropy generation in the internal heat exchanger—a component required to achieve sufficiently low cooling temperatures—strongly influences overall system efficiency. The vapor pressure of the CO₂-cofluid mixture and the heat of solution of CO₂ in cofluid have large and somewhat independent contributions to the system performance: lower saturation pressure lowers the optimal operating pressures at fixed CO₂ loading, while increasingly negative heat of solution contributes to higher specific refrigeration capacity and efficiency.

Résumé

Recent experiments demonstrate the viability of a low-pressure CO₂-cofluid compression refrigeration cycle in which CO₂ and a non-volatile cofluid are circulated in tandem and co-compressed in a compliant scroll compressor. This work explores the theoretical performance limitations of such a cycle operating under environmental conditions representative of automotive air conditioning and studies the dependence of this performance on the properties of the CO₂-cofluid mixture. The vapor–liquid equilibrium and thermodynamic properties of the mixture are described using a previously reported activity-coefficient model. A coupled system of physically based equations that allows for consideration of both ideal and real hardware components is used to represent the system hardware and its interaction with the environment. The system efficiency is analyzed in terms of entropy generation rates in the various hardware components; entropy generation in the internal heat exchanger—a component required to achieve sufficiently low cooling temperatures—strongly influences overall system efficiency. The vapor pressure of the CO₂-cofluid mixture and the heat of solution of CO₂ in cofluid have large and somewhat independent contributions to the system performance: lower saturation pressure lowers the optimal operating pressures at fixed CO₂ loading, while increasingly negative heat of solution contributes to higher specific refrigeration capacity and efficiency.     

Synthesis of carbon-doped TiO2 nanoparticles using CO2 decomposition by thermal plasma

This study examined the synthesis of carbon-doped titanium dioxide using TiCl₄ and CO₂ as titanium and carbon sources, respectively, by thermal plasma at atmospheric pressure. The effect of the CO₂ gas flow rate on the preparation of TiO₂ was investigated. The results showed that the decomposition rate of CO₂ was 90% at a CO₂ gas flow rate of 1 L/min. When TiCl₄ was added to produce TiO₂, the decomposition rate of CO₂ reached 95% at a CO₂ gas flow rate of 1 L/min. The resulting powders contained mixed anatase and rutile phases with particle sizes ranging from 20 to 50 nm. The carbon in the CO₂ acted as a dopant to produce the carbon-doped TiO₂. The prepared samples were mainly characterized by X-ray diffraction, X-ray photoelectron spectroscopy, specific surface area measurements and ultraviolet-visible spectroscopy.     

固相法合成氮掺杂碳纳米管及其二氧化碳吸附性能研究

以二乙烯苯(DVB)和1-乙烯基-3-丁基咪唑溴盐([VBIm]Br)共聚物为原料,铁氰化钾为催化剂前驱体,在600~1000℃下固相碳化制备了掺氮纳米碳管(NCNT)块体。利用SEM、TEM、Raman、XPS、物理吸附等对样品进行了表征。采用KOH在600~800℃下对NCNT进行活化,发现处理温度和时间是影响其孔结构的关键因素。CO_2吸附实验表明,单位孔容的微孔吸附量与碳材料表面氮含量之间存在明显的线性关系。     

Supercritical CO2/co-solvent extraction of porogens and surfactant templates to obtain ultralow dielectric constant films

A method of pore generation by supercritical CO₂ (SCCO₂) and co-solvent extraction for the preparation of nanohybrid film and mesoporous organosilicate thin film for ultralow dielectric constant materials is investigated. The films were treated with SCCO₂/methyl ethyl ketone-tetrahydrofuran co-solvent combination and it was found that the treatment produced dielectric constant (k) values of 2.30 for closed-pore and 1.61 for open-pore nanohybrid films; 2.14 for cetyl trimethylammonium bromide-based and 2.50 for polyethylene glycol octadecyl ether-based films. These results suggest that the SCCO₂/co-solvent treatment produces closely comparable results with thermal decomposition in terms of Fourier Transform Infrared spectroscopy data, optical constants obtained from variable angle spectroscopic ellipsometry, and k values.     

Synthesis of polymer/1T-TaS2 layered nanocomposites

Single-phase layered nanocomposites containing 1T-TaS₂ and poly(ethylene oxide) or poly(ethylenimine) have been first synthesized by using the exfoliation-adsorption method. They have been characterized by powder X-ray diffraction. As the products exhibited lattice expansions along the stacking direction, poly(ethylene oxide) and poly(ethylenimine) were intercalated into 1T-TaS₂ galleries. Despite high conductivity of the host material, the resistivities of the polymer/1T-TaS₂ nanocomposites were found to be high in the order of 5.9-13 Ω cm.     

Modelling the performance of a transcritical CO2 heat pump for high temperature heating

A prototype transcritical CO₂ heat pump was constructed for heating water to temperatures greater than 65°C while providing refrigeration at less than 2°C. The heating capacity was 115 kW at an evaporation temperature of +0.3°C and a hot water temperature of 77.5°C, with a heating coefficient of performance (COP) of 3.4. Performance data is presented for each of the compressor, the gas cooler, and the recuperator as well as for the overall heat pump system. Equipment performance data was incorporated into a computer model to enable parametric investigations of heat pump performance. Model predictions showed that the hot water temperature could be increased from 65 to 120°C with a relatively small reduction in heating capacity and heating COP of 33 and 21%, respectively. Model predictions also highlight the potential for significant capacity improvements by eliminating the recuperator in favour of a larger gas cooler.     

Commercial refrigeration system using CO2 as the refrigerant

Various field-test systems using carbon dioxide as the only refrigerant have been installed since December 2001. In this paper we will analyse an ‘all-CO₂’ supermarket, which has been operating in the North of Italy since January 2003.The seasonal COP is calculated, based on prior laboratory measurements, and a comparison is made with a conventional direct expansion system using R404A.The total annual energy consumption of the installed CO₂ system is estimated to be about 10% higher than the direct expansion R404A solution. It is still possible to further improve efficiency and approach the efficiency of present R404A systems. These improvements are identified.The cost of the CO₂ installation is compared to the cost of an equivalent direct expansion R404A installation, the most economic among the various present types of commercial refrigeration systems. Because of the lack of suitable mass-produced components, the CO₂ installation is estimated to be, today, about 20% more expensive.     

超临界CO2流体辅助合成Si-Fe-Fe3O4-C复合材料及储锂性能

硅碳负极是未来锂离子电池材料发展的重点方向之一,本文针对传统球磨法制备硅碳负极复合不均匀、界面融合差等问题,提出了一种超临界二氧化碳(scCO₂)流体介质球磨合成Si-Fe-Fe₃O₄-C复合材料的新方法。研究发现,纳米硅和中间相碳微球(MCMB)在scCO₂介质球磨混合过程中,CO₂和Fe反应先得到均匀分散的Si-FeCO₃-C前驱体,然后FeCO₃原位高温固相分解得到Si-Fe-Fe₃O₄-C复合材料。同时,在scCO₂流体渗透下,MCMB剥离成石墨片,并与纳米硅和Fe-Fe₃O₄实现较好的界面融合,Fe-Fe₃O₄的引入显著提升了硅碳负极的储锂容量、循环稳定性和倍率性能,Si-Fe-Fe₃O₄-C复合材料在0.2 A·g?1下100次循环后可逆容量保持在1065 mA·h·g?1。本方法利用超临界流体渗透性好、扩散能力强等特点,合成工艺简便,容易工业化实施,具有商业化开发潜力。