自呼吸式微型直接甲醇燃料电池的设计与性能分析

为了提高燃料电池的机械强度并降低加工成本,设计了一种基于不锈钢材料的空气自呼吸式微型直接甲醇燃料电池(DMFC).采用高温微型冲压技术制作电池的极板,并在其表面溅射Au和TiN来防止电化学腐蚀和减少接触电阻.在不同运行参数条件下对电池进行性能和稳定性的测试,结果表明阳极流速、甲醇浓度以及工作温度等均对电池性能有较明显的影响.该自呼吸式微型直接甲醇燃料电池在室温(20℃)条件下最高功率密度达到23.38 mW/cm2,并在温度40℃时可稳定地长时间工作,具有一定的应用价值.     

液相进样直接甲醇燃料电池性能研究

采用商品PtRu黑和Pt黑催化剂制备成甲醇阳极和氧阴极,Nafion(R)-117为固体电解质膜,组装成活性面积为6.4516cm2的单电池,研究了单电池的极化与功率特性以及单电池在放电运转过程中各种操作条件,如甲醇进样浓度、阴极氧化剂种类和压力、操作温度、燃料和氧化剂的进样方向等对单电池性能的影响,并考察了单电池的放电性能.结果表明:单电池极化曲线由3个特征区构成,最大功率密度约为15mW/cm2;甲醇浓度对单电池性能的影响与单电池运行温度有关;较之纯氧,以空气作为氧化剂时单电池的性能有所降低,随着空气压力的增加单电池的性能有所提高;随着操作温度的升高单电池性能明显改善;阳极甲醇由下往上进样,同时阴极空气由上往下进样时单电池性能最好;单电池在放电过程中具有性能自恢复特征.     

Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)-Ce_(0.9)Gd_(0.1)O_(2-δ)中低温固体氧化物燃料电池复相阴极的研究

采用溶胶-凝胶法制备Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3–δ)(BSCF)粉体后,使用Ce_(0.9)Gd_(0.1)O_(2–δ)(GDC)溶胶包裹BSCF粉的方法制备疏松多孔的BSCF-x GDC(x=30wt%,40wt%,50wt%)复相阴极。通过X射线衍射仪、场发射扫描电镜和透射电镜对复相阴极的物相组成、单电池断面形貌及GDC对BSCF颗粒的包裹形貌进行表征。利用阻抗谱测试研究了复相阴极材料的电化学性能,讨论了掺入GDC量对阴极性能的影响。结果表明:通过GDC溶胶包裹BSCF粉体的制备方法改善了阴极的电化学性能,在同一温度下,BSCF-40GDC阴极的极化电阻最小,在650℃时阴极极化阻抗约为0.397?·cm~2;以BSCF-40GDC为阴极制备的单电池,以H_2+3%H_2O为燃料气、空气为氧化气体,650℃下电池的最大功率密度为0.514 W/cm~2,欧姆电阻为0.257?·cm~2,两极极化电阻为0.0588?·cm2。     

选择性混合型燃料电池膜电极的制备及性能研究

以Pt-Ru/C和Pt/C分别为阴极、阳极催化剂,以多孔聚丙烯薄膜浸渍Nafion溶液作为CMRFC的固体电解质膜(MEA),自制多孔选择性膜电极,并组装了单电池以及测试系统。以甲醇和氧气共同输送作为混合燃料,研究了阴极PTFE与Nafion含量及其分布对单电池的极化与功率特性以及单电池在放电运转过程中阴极氧化剂种类对单电池性能的影响,并考察了单电池的放电性能。研究表明,气体扩散层中微孔碳层中PTFE的质量含量为40%,催化层PTFE为30%时,在燃料供给条件为18.9mL.min-1,0.5mol.L-1的甲醇溶液+0.21 min-1O2时,MEA的电性能最好,稳定放电时最大功率可达0.55mW.cm-2(0.125V时)。     

低温燃料电池用聚(2,5-苯并咪唑)/磺化海泡石复合质子交换膜的制备与性能EI北大核心CSCD

采用原位法制备了一种适用于低温燃料电池的新型聚(2,5-苯并咪唑)/磺化海泡石(ABPBI/S-Sep)复合质子交换膜。对海泡石酸活化和磺化改性前后的化学结构、亲水性和分散性以及复合膜的形貌、吸水率、磷酸掺杂水平与质子传导率等性能进行了表征和测试。结果显示,所制备的S-Sep粒子在ABPBI聚合物基体中分散均匀,并能促进聚合物分子链的规整排布;与纯ABPBI膜相比,S-Sep粒子的添加显著增强了复合膜对水和磷酸的吸收和保留能力,且在相同或相近磷酸掺杂水平下,ABPBI/S-Sep复合膜的质子传导率显著提高。在40～90℃温度范围内,饱和湿度98%RH时复合膜的质子传导率与Nafion 212相当;在低湿度60%RH时,高磷酸掺杂水平的ABPBI/S-Sep复合膜质子传导率略低于98%RH的结果,但显著优于Nafion 212的质子传导性能。不同温湿度环境下的质子传导率结果表明S-Sep改性ABPBI复合膜具备低温环境使用的特点,可替代Nafion类全氟磺酸膜应用于低温质子交换膜燃料电池。     

低温燃料电池用聚(2,5-苯并咪唑)/磺化海泡石复合质子交换膜的制备与性能

采用原位法制备了一种适用于低温燃料电池的新型聚(2,5-苯并咪唑)/磺化海泡石(ABPBI/S-Sep)复合质子交换膜。对海泡石酸活化和磺化改性前后的化学结构、亲水性和分散性以及复合膜的形貌、吸水率、磷酸掺杂水平与质子传导率等性能进行了表征和测试。结果显示,所制备的S-Sep粒子在ABPBI聚合物基体中分散均匀,并能促进聚合物分子链的规整排布;与纯ABPBI膜相比,S-Sep粒子的添加显著增强了复合膜对水和磷酸的吸收和保留能力,且在相同或相近磷酸掺杂水平下,ABPBI/S-Sep复合膜的质子传导率显著提高。在40～90℃温度范围内,饱和湿度98%RH时复合膜的质子传导率与Nafion 212相当;在低湿度60%RH时,高磷酸掺杂水平的ABPBI/S-Sep复合膜质子传导率略低于98%RH的结果,但显著优于Nafion 212的质子传导性能。不同温湿度环境下的质子传导率结果表明S-Sep改性ABPBI复合膜具备低温环境使用的特点,可替代Nafion类全氟磺酸膜应用于低温质子交换膜燃料电池。     

高温拉伸制备交联聚乙烯微孔膜的探索研究

采用热拉伸-高温退火-冷拉的拉伸工艺制备了交联聚乙烯微孔膜,考察了交联聚乙烯的交联度、拉伸温度、退火温度和冷拉等工艺条件对交联聚乙烯微孔膜成孔性能的影响,并对成孔过程和机理进行了探讨.交联聚乙烯的交联度显著影响成孔性能,随着交联度的增加,成孔性增加.拉伸温度在90～120℃时,膜片基本由纤维状晶构成.拉伸温度升至130℃,并在此温度进行高温退火处理,膜片开始出现细缝状微孔.施加冷拉可以调控细缝状微孔形态演变,进一步被拉伸成圆形或椭圆洞状微孔.本文所用拉伸工艺为制备高性能聚乙烯微孔膜提供了一种新的思路,有助于开发自主知识产权的聚乙烯微孔膜技术,突破锂离子电池隔膜等高端聚乙烯微孔膜的国外技术垄断.     

聚丙烯接枝聚乙二醇改性聚丙烯微孔膜

以聚丙烯接枝聚乙二醇(PP-g-PEG)对聚丙烯共混改性,通过单向拉伸工艺制备亲水性聚丙烯微孔膜。使用压汞仪、扫描电镜、Gurley值和水蒸气透过率表征微孔膜的孔结构和透过性能,研究PP-g-PEG含量、PEG接枝率及链长对微孔膜孔结构、水蒸汽透过率及锂电池性能的影响。结果表明,对于接枝率为0.78%的PP-g-PEG,随着添加剂PP-g-PEG含量增加,微孔膜孔隙率和微孔尺寸下降,反映孔道结构的曲挠度及喉孔比上升;微孔膜孔结构与亲水性的综合作用导致水蒸气透过率在PP-g-PEG含量为2.5%时达到最大值。PP-g-PEG含量为2.5%和5.0%的微孔膜组装的锂电池具有较低的电荷转移电阻和较高的充放电比容量,电池性能优于未改性微孔膜组装的电池。提高PEG接枝率使得改性微孔膜孔结构有所变差,但是水蒸气透过率提高,组装电池的性能也更好。长PEG侧链PP-g-PEG对微孔膜孔结构的破坏程度大于短PEG侧链PP-g-PEG,导致组装电池的性能变差。     

国内温湿度检定箱选用情况分析

一、温湿度检定箱概述目前,我国温湿度检定箱的性能指标主要有降温时间、温度及湿度偏差、均匀度等。具体指标为:温湿度范围为(5～50)℃/(20～90)%RH;温度波动度≤±0.2℃;温度均匀性≤0.3℃;湿度波动度≤±0.8%RH(20℃);湿度均匀性≤1%RH(20℃)。温湿度检定箱选用时,温湿度均匀度和波动度是判定温湿度检定箱性能的重要参数。此外,温湿度检定箱的连续无故障运行时间也是考量温湿度检定箱技术性能和可靠性的重要依据。为确保温湿度检定箱的性能达到需要的指标,用户可以请有资质的第三方验收。第三方验收时,首次验收费用一般由用户承担;第一次验收不合格时厂家要进行再调试或设计变更,验收费用由生产厂家负责。     

低温对海泥发电性能的影响

环境温度对海泥发电(海底微生物燃料电池)具有重要影响。本文进行了4℃环境与常规室温环境(25℃)电池性能对比试验,结果表明:4℃环境下电池阳极启动时间明显慢于室温(25℃),阴极启动几乎无影响。4℃条件电池内阻(1005Ω)高于室温条件(703Ω),室温电池最大输出功率密度比4℃环境升高10mW/m2,电流密度增加46.6 mA/m2。低温环境(4℃)可导致微生物活性降低,物质扩散速度变慢,进而导致其电池性能低于室温环境。此实验对实海环境下海底微生物燃料电池设计提供了指导,具有实际意义。     

Thermal dilation and internal relative humidity of hardened cement paste

The coefficient of thermal dilation (CTD) of hardened cement paste and concrete is a function of the state of internal moisture in the pore system. It has been theorized that changes in the pore fluid pressure induced by temperature change causes additional dilation when the material is partially saturated. Drying shrinkage stresses in early-age concrete also evolve from changes in the pore fluid pressure. The Kelvin-Laplace equation relates changes in the pore fluid pressure to the measured internal relative humidity (RH). This research investigated the role of pore pressure changes on the CTD through internal RH measurements. A maximum change in humidity (ΔRH) due to temperature change (ΔT) was measured when the initial humidity was at an intermediate value. Likewise, the maximum CTD was also measured at an intermediate initial RH. Based on these findings, the additional thermal strain caused by changes in pore fluid pressure was modelled using internal RH measurements as a primary parameter.     

环境试验箱内湿度场及其特性的实验研究

基于环境试验箱内加湿过程的实验,通过干湿球热电偶测量相对湿度的测量方法,分析箱内湿度场及其均匀性。实验结果表明:送风温度、加湿量(入口湿度值)与加湿位置等均是箱内湿度分布的重要影响因素;随着温度的升高,箱内相对湿度随时间变化的波动幅度变小;进风状态为低湿的情况下,高温进风时,测点相对湿度平均值的偏差较小;低温进风时,该偏差较大,反之亦然;进风状态为低湿情况下,测点的相对湿度均匀性较差;而在高湿进风情况时,测点均匀性较好。     

多孔聚氨酯-聚丙烯酸/丙烯酰胺复合恒湿材料的性能研究

制备了多孔聚氨酯-聚丙烯酸/丙烯酰胺(PU-PAA/AM)复合材料,并研究了其恒湿性能.结果表明:在30℃,100％RH环境下预吸湿0.5～6h后,20g多孔PU-PAA/AM复合材料可迅速自动吸湿或放湿,特6L密闭容器内的相对湿度恒定在43％RH～59％RH之间的某个值.在25～53℃高低温交变环境下,40g多孔PU-PAA/AM复合材料可将6L密闭容器内的湿度恒定在50％RH.多孔PU-PAA/AM复合材料还具有优异的拉伸性能和回弹性能,并且具有网状开孔结构,可将防震缓冲和恒湿性能有机结合起来,在武器装备的存储包装防潮领域和其它民用领域具有很大的应用价值.     

Effect of process conditions on dynamics and performance of PEMFC: Comparison with experiments

Three-dimensional numerical computations have been carried out to investigate the dynamics inside proton-exchange membrane fuel cell (PEMFC) and its performance using Star-CD solver, the computational fluid dynamics software. Theoretical results in polarization curves quantitatively corroborate the experimental findings previously reported in Jung et al. [2]. Also, effects of various process conditions such as relative humidity, stoichiometric ratio at anode and cathode channels, and cell configuration on the performance of fuel cell have been further scrutinized. It has been revealed that the moderately high stoichiometric ratio at cathode channel and single serpentine geometry improve the cell performance and also the humidity change at cathode makes the cell voltage variation high, comparing with the humidity change at anode.     

Humidity-independent portable air-hydrogen fuel cells with slotted silicon based gas-distributing plates

We have studied the characteristics of small-scale air-hydrogen fuel cells (FCs) operating in a free-breathing cathode regime. The cells are provided with a new gas-distributing element on the cathode side, which is based on a silicon plate with narrow through slots (slotted Si plate). It is shown that the use of a slotted Si plate significantly weakens the dependence of the FC characteristics on the humidity of environment in a broad temperature range. Indeed, at a fixed temperature, the FC power only changed within 10% when the relative humidity of the ambient air varied between 50 and 98%.     

Physical parameters effect on ozone-initiated formation of indoor secondary organic aerosols with emissions from cleaning products

The effect of air exchange rate (ACH), temperature (T), and relative humidity (RH) on the formation of indoor secondary organic aerosols (SOAs) through ozonolysis of biogenic organic compounds (BVOCs) emitted from floor cleaner was investigated in this study. The total particle count (with D(p) of 6-225 nm) was up to 1.2 × 10(3)#cm(-3) with ACH of 1.08 h(-1), and it became much more significant with ACH of 0.36 h(-1) (1.1 × 10(4)#cm(-3)). This suggests that a higher ventilation rate can effectively dilute indoor BVOCs, resulting in a less ultrafine particle formation. The total particle count increased when temperature changed from 15 to 23 °C but it decreased when the temperature further increased to 30 °C. It could be explained that high temperature restrained the condensation of formed semi-volatile compounds resulting in low yields of SOAs. When the RH was at 50% and 80%, SOA formation (1.1-1.2 × 10(4)#cm(-3)) was the more efficient compared with that at RH of 30% (5.9 × 10(3)#cm(-3)), suggesting higher RH facilitating the initial nucleation processes. Oxidation generated secondary carbonyl compounds were also quantified. Acetone was the most abundant carbonyl compound. The formation mechanisms of formaldehyde and acetone were proposed.     

基于Edlén公式空气折射率测量系统的校准研究

为了检验对激光干涉仪测量精度有很大影响的空气折射率测量系统的测试性能,提出一种可用于基于Edlén公式的空气折射率测量系统的校准方法,并且设计了专门的校准装置,该装置主要由温度、气压以及湿度测量系统组成。实验证明：取包含因子k=2时,温度在(5~40)℃区间,测量不确定度U优于0.02 ℃;气压在(66~105)kPa区间,U=18 Pa;湿度在(10~90)%RH区间,U=2.0%RH,等效于整个系统对应的空气折射率测量的相对不确定度优于1×10^-7     

Pt nanoparticle-reduced graphene oxide nanohybrid for proton exchange membrane fuel cells

A platinum nanoparticle-reduced graphene oxide (Pt-RGO) nanohybrid for proton exchange membrane fuel cell (PEMFC) application was successfully prepared. The Pt nanoparticles (Pt NPs) were deposited onto chemically converted graphene nanosheets via ethylene glycol (EG) reduction. According to the powder X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) analysis, the face-centered cubic Pt NPs (3-5 nm in diameter) were homogeneously dispersed on the RGO nanosheets. The electrochemically active surface area and PEMFC power density of the Pt-RGO nanohybrid were determined to be 33.26 m2/g and 480 mW/cm2 (maximum values), respectively, at 75 degrees C and at a relative humidity (RH) of 100% in a single-cell test experiment.     

面向氢空、无增湿操作条件的高保水性质子交换膜的制备与性能

作为质子交换膜燃料电池(PEMFC)的一个重要应用场景,开发满足无人机用的低温质子交换膜燃料电池(Low Temperature-PEMFC)正受到越来越多的关注。无人机所采用的PEMFC操作条件比较特殊,作为原料的H₂、空气均为无加湿的干气。针对这一特殊操作条件,需开发相应的具有保水能力的质子交换膜。为此,首先合成了一种具有高保水性的高分子树脂(PAAAM),将其加入Nafion溶液中混合均匀,利用溶液浇铸法制膜,探索并优化了PAAAM的加入量;随后,对保水复合膜进行了FTIR、SEM、质子传导率、保水性、溶胀率、拉伸强度、热失重性能等表征,并进行电池输出性能测试;最终结果表明:Nafion系质子交换膜在原料为干空气、干H₂的条件下,最适宜的操作温度区间为50~55℃。当PAAAM加入量为1.0wt%时,Nafion基复合膜(NFPAM1)具有更优的电池性能。当电池温度55℃、干燥H₂、空气流量分别为0.1 L·min?1和0.55 L·min?1时,采用NFPAM1复合膜的PEMFC最高功率密度为691 mW·cm?2。      

电影胶片贮存温度湿度探讨

电影是人类重要的文化遗产之一,然而记录电影的载体电影胶片由于受自身构成材料和保存环境等因素的影响,面临巨大威胁。其中保存环境的温度、湿度是影响电影胶片长期保存的关键因素之一,实践证明低温低湿有利于胶片的长期保存,但温度、湿度过低会导致胶片变脆、变形,降低其机械性能,同时也会增加保存运行成本,增加档案管理工作的复杂性。结合我国的具体国情,我们初步认为电影胶片较为适宜的保存温度范围为-5℃～5℃,相对湿度范围为30％RH-50％RH。