滑动弧放电等离子体催化协同技术处理正己烷

采用滑动弧放电低温等离子体催化协同技术研究了催化剂床填充材料、初始浓度、流量等对正己烷降解的影响.研究表明,滑动弧放电催化协同技术可以实现正己烷的有效裂解.对于反应器中不同的填充材料.蜂窝状催化荆优于颗粒状;降解率以蜂窝状Al2O3,填充时最高;单位功耗以填充蜂窝状Al2O3,最小.无论是以Al2O3,填充还是以Pt/Pb催化剂填充,正已烷的降解率均随初始浓度、流量的增加而呈现降低的趋势,但绝对处理量增大.     

微生物燃料电池电极烧结工艺研究

以活性炭颗粒和柔性石墨颗粒为原料,聚四氟乙烯(PTFE)为粘结剂,制作微生物燃料电池电极。在进行压制试验和烧结试验的同时,讨论烧结电极的强度、亲水性、电导率和孔隙率,得出最佳条件:PTFE浓度为30%,PTFE与乙醇质量比为4∶1,烧结温度为380℃,保温4 h,200℃以下时的升温速度为80℃/h,200℃以上时为60℃/h,随炉冷却降温。     

内燃机气缸孔表面微织构设计与摩擦性能模拟试验

为提高内燃机气缸孔的使用寿命,根据气缸孔/活塞摩擦副往复运动的特点,采用0.10、0.30、0.50三种织构密度,设计出气缸孔表面两组不同密度组合形式,采用ZY型电路板制作机,在模拟气缸孔的钢块试样表面上分段织构出不同密度的微凹坑,与模拟活塞的钢销试样组成面对面摩擦副进行往复运动摩擦试验.结果表明:气缸孔两组不同密度组合形式表面摩擦系数均随着试验速度的升高而下降,且大多趋于平稳;中间区域织构密度高,两端区域织构密度低组合形式起增摩作用;中间区域织构密度大,两端区域织构密度低组合形式,低速相对运动时减摩效果不太明显,高速时减摩效果显著增强,0.30 +0.10 +0.30密度组合形式减磨效果较佳,当运动速度分别为0.10m/s、0.20m/s时,气缸孔摩擦系数相对无织构表面分别降低了19.3％和30％.     

相变蓄热式PV/T集热器的试验研究

为冷却光伏组件,用定型相变材料填充管板式PV/T集热器,并以无集热器组件和保温材料填充的集热器为参照组,进行了工质(水)温升及对组件冷却效果的试验。试验结果表明:采用相变材料填充的相变蓄热式集热器能明显降低组件温度,并提高了热能利用率,其冷却效果和工质温升均优于保温材料填充式集热器;在流量为30 L/h的开式水冷条件下,相变材料填充式集热器工质(水)的平均温升为5.6℃,平均获得热能702k J/h,组件温度平均降低了6.8℃,理论光电转换效率提高了3.4%;使用相变蓄热式集热器的组件温度变化约滞后于太阳辐射变化2 h,最低效率时刻避开了辐射值最大时刻,全天效率得到提高。     

辛烷值改进剂和工况对GDI轻型车非常规排放的影响

在底盘测功机上利用MEXA-6000FT等设备对比研究了NEDC/WLTC/FTP75三种循环工况和乙醇/MTBE两种辛烷值改进剂对轻型GDI车辆NO2/SO2/NH3/HCHO/HCOOH/C6H6/C7H8等十种非常规气体排放的影响,试验车辆为国内外不同厂家生产的3辆轻型GDI车辆。研究发现,循环工况对GDI轻型车非常规排放有明显影响,三种循环相比较而言,NEDC循环下HCHO、HCOOH、C6H6、C7H8、CH4、NO排放最高,FTP75循环下最低;相对于NEDC循环下,FTP75循环下HCHO降幅最小约25%,C7H8降幅最大约85%;NEDC循环下NH3排放最低;FTP75循环下NO2、SO2排放最低,WLTC循环下N2O排放最低。研究还发现,相对于普通汽油,乙醇汽油和MTBE汽油可以减少NH3排放40%以上,但HCOOH排放增加6倍以上,N2O排放增加20%以上。     

La掺杂对523型镍钴锰酸锂正极材料电化学性能的影响

文章研究了稀土元素La掺杂对镍钴锰酸锂Li Ni_(0.5-x)La_xCo_(0.2)Mn_(0.3)O_2(x=0,0.05,0.08,0.12)的物相和电化学性能的影响。利用液相共沉淀法+固相煅烧工艺制备了目标产物,并综合利用XRD、恒电流充放电技术及交流阻抗技术对材料物理和电化学性能进行了表征。La掺杂量x=0.05样品的首次放电比容量为152.6 mAh/g,库伦效率为93.6%,在1C电流密度下,经过30次电化学循环后的容量保持率为95.9%;在5C充放电电流密度下,掺杂样品的放电比容量为115.3 mAh/g,达到0.2C下放电比容量的76.4%。La掺杂增加了三元材料沿c轴方向的晶格常数,为锂离子在晶格内部的脱嵌提供了更大的空间,提高了锂离子在晶体中的扩散速度,从而显著增强了材料高倍率充放电性能。     

环境条件对猪粪堆肥卫生无害化效果的影响

为明确环境条件对猪粪堆肥卫生无害化效果的影响,选取不同C/N比和不同供氧方式进行堆肥试验,试验结果表明：C/N比和供氧方式是影响猪粪堆肥卫生无害化效果的重要因素,调节C/N比为25～30、采用强制通风与翻堆相结合的供氧方式能够得到更好的卫生无害化效果。     

气缸套—活塞环摩擦副材料匹配的研究

作者对国产中小型柴油机缸套一活塞环摩擦副常用的典型材料,进行交替配对组成九种摩擦副,在一定的速度及滴油润滑条件下,以法向载荷及摩擦时间为参变量,考察它们的摩擦磨损性能。试验结果表明,合适的材料组配可以大大提高摩擦副的耐磨性能;摩擦系数随载荷而变化;在一定的载荷作用下,由于材料的塑性变形及石墨的润滑作用可使摩擦系数降低;摩擦系数与磨损量之间不能建立对应的函数关系;在合适的金相组织范围内较硬材质有较高耐磨性;活塞环材质硬度比缸套材质硬度较高时(本试验为40HB)摩擦副的磨损量最小;摩损系数也随载荷而变化。     

动物粪便与秸秆成型坯块制备工艺参数试验研究

为探究动物粪便和秸秆混合物料的成型生产工艺,获得较佳的成型工艺参数组合,以成型压力、成型温度、物料含水率和秸秆质量分数为试验因素,以成型坯块抗破坏强度和松弛比为成型质量评价指标,进行四因素二次通用旋转组合试验,并建立各试验因素与试验指标的回归模型,利用Design-Expert 8.0.6响应面分析软件优化成型工艺参数组合。试验结果表明:各试验因素对成型坯块抗破坏强度影响的顺序为物料含水率成型温度成型压力秸秆质量分数;各试验因素对成型坯块松弛比影响的顺序为物料含水率成型压力秸秆质量分数成型温度;在成型压力为125 kN,成型温度为146℃,物料含水率为12%,秸秆质量分数为6%条件下,成型坯块的成型效果最好,成型坯块的抗破坏强度为353.6 N,松弛比为96.68%。     

兆瓦级水平轴风力机叶片铺层设计参数影响分析

为研究主梁材料及铺层角度对风力机叶片结构特性影响,基于三维建模软件NX二次开发建立风力机叶片几何模型,结合铺层设计并通过CFD方法获取叶片表面压力分布,采用有限元方法对叶片进行结构模态、强度及屈曲分析。结果表明:碳纤维主梁叶片质量较玻璃钢减轻约8.08%,主梁材料对模态振型影响较小,主梁铺层角度对挥舞方向运动影响更大;0°铺层主梁叶片共振破坏风险低且应力应变峰值均最小,碳纤维主梁叶片较玻璃钢应力及应变峰值降幅最大约20.57%、26.51%;主梁0°铺层时叶片屈曲因子最大,而60°铺层时最小,碳纤维主梁叶片较玻璃钢临界屈曲载荷增幅最大约17.84%,有效降低屈曲失稳风险;额定工况下,叶片局部屈曲域在近叶尖处尾缘区和近叶根处最大弦长截面前缘区。     

Optimization of GDLs for high-performance PEMFC employing stainless steel bipolar plates

The effects of polytetraflouroethylene (PTFE) content in the gas diffusion layer (GDL) on the performance of PEMFCs with stainless-steel bipolar plates are studied under various operation conditions, including relative humidity, cell temperature, and gas pressure. The optimal PTFE content in the GDL strongly depends on the cell temperature and gas pressure. Under unpressurized conditions, the best cell performance was obtained by the GDL without PTFE, at a cell temperature of 65 °C and relative humidity (RH) of 100%. However, under the conditions of high cell temperature (80 °C), low RH (25%) and no applied gas pressure, which is more desirable for fuel cell vehicle (FCV) applications, the GDL with 30 wt.% PTFE shows the best performance. The GDL with 30 wt.% PTFE impedes the removal of produced water and increases the actual humidity within the membrane electrode assembly (MEA). A gas pressure of 1 bar in the cell using the GDL with 30 wt.% PTFE greatly improves the performance, especially at low RH, resulting in performance that exceeds that of the cell under no gas pressure and high RH of 100%.     

Preparation and characterization of C/Ni-PTFE electrode using Ni-PTFE composite plating for alkaline fuel cells

Graphite particles (80 μm) and PTFE particles (40 μm) were coated with Ni (18-50 wt.%) and PTFE fine particles (0.3 μm; 8 wt.%) via electroless Ni-PTFE composite plating. The conductivity of Ni-PTFE plated graphite (C/Ni-PTFE) and PTFE (PTFE/Ni-PTFE) particles increased with the Ni content. At 35 wt.% Ni content, the conductivity (300 Sm⁻¹) of C/Ni-PTFE particles was about 2 times higher than that of PTFE/Ni-PTFE particles. The particles were pressed into plates under a pressure of 10-500 kg cm⁻² and the plates were then subjected to heat treatment at 350 °C. The surface of C/Ni-PTFE plates contained infinitely many gaps of 0.01-20 μm; these gaps are useful as a pathway for reacting gases. The conductivities in a direction perpendicular and parallel to the C/Ni-PTFE plates were respectively about 3.5 times (510 Sm⁻¹) and 16 times (48 × 10³ Sm⁻¹) higher than those of the PTFE/Ni-PTFE plates. Furthermore, the total pore volume (0.145 cm³ g⁻¹) of C/Ni-PTFE plates was higher than that of PTFE/Ni-PTFE plates, which improved the gas permeability of the former. The current density (84 mA cm⁻² at 0.3 V) of C/Ni-PTFE electrode was about 2 times higher than that of PTFE/Ni-PTFE electrode. This increase in the current density might be attributed to the improvement in the total conductivity and gas permeability of C/Ni-PTFE electrode.     

Liquid water breakthrough pressure through gas diffusion layer of proton exchange membrane fuel cell

The dynamic behavior of liquid water transport through the gas diffusion layer (GDL) of the proton exchange membrane fuel cell is studied with an ex-situ approach. The liquid water breakthrough pressure is measured in the region between the capillary fingering and the stable displacement on the drainage phase diagram. The variables studied are GDL thickness, PTFE/Nafion content within the GDL, GDL compression, the inclusion of a micro-porous layer (MPL), and different water flow rates through the GDL. The liquid water breakthrough pressure is observed to increase with GDL thickness, GDL compression, and inclusion of the MPL. Furthermore, it has been observed that applying some amount of PTFE to an untreated GDL increases the breakthrough pressure but increasing the amount of PTFE content within the GDL shows minimal impact on the breakthrough pressure. For instance, the mean breakthrough pressures that have been measured for TGP-060 and for untreated (0 wt.% PTFE), 10 wt.% PTFE, and 27 wt.% PTFE were 3589 Pa, 5108 Pa, and 5284 Pa, respectively.     

Improved electrochemical performance and thermal compatibility of Fe- and Cu-doped SmBaCo2O5+δ-Ce0.9Gd0.1O1.95 composite cathode for intermediate-temperature solid oxide fuel cells

Fe- and Cu-doped SmBaCo₂O_5+δ (FC-SBCO)-Ce_0.9Gd_0.1O_1.95 (CGO) composites with various CGO contents (0-40 wt.%) are investigated as new cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs) based on a Ce_0.9Gd_0.1O_1.95 electrolyte. The effect of CGO incorporation on the thermal expansion coefficient (TEC), electrochemical properties and thermal stability of the FC-SBCO-CGO composites is investigated. A composite cathode of 30 wt.% CGO-70 wt.% FC-SBCO (CS30-70) coated on a Ce_0.9Gd_0.1O_1.95 electrolyte shows the lowest area specific resistance (ASR), i.e., 0.049 Ω cm² at 700 °C. The TEC of the CS30-70 cathode is 14.1 × 10⁻⁶ °C⁻¹ up to 900 °C, which is a lower value than that of the FC-SBCO (16.6 × 10⁻⁶ °C⁻¹) counterpart. Long-term thermal stability and thermal cycle tests of the CS30-70 cathode are performed. Stable ARS values are observed during both type of test. An electrolyte-supported (300-μm thick) single-cell configuration of CS30-70/CGO/Ni-CGO delivers a maximum power density of 535 mW cm⁻² at 700 °C. The unique composite composition of CS30-70 demonstrates improved electrochemical performance and good thermal stability for IT-SOFCs.     

The influence of anode gas diffusion layer on the performance of low-temperature DMFC

The influence of the anode gas diffusion layers (GDLs) on the performances of low-temperature DMFCs, and the properties of mass transport and CO₂ removal on these anode GDLs were investigated. The membrane electrode assembly (MEA) based on the hydrophilic anode GDL, which consisted of the untreated carbon paper and hydrophilic anode micro-porous layer (comprised carbon black and 10 wt.% Nafion), showed the highest power density of 13.4 mW cm⁻² at 30 °C and ambient pressure. The performances of the MEAs tended to decline with the increase of the PTFE content in the anode GDLs due to the difficulty of methanol transport. The contact angle measurements revealed that the wettabilities of the anode GDLs decreased as the increase of PTFE content. The wettabilities of the GDLs were improved by addition of hydrophilic Nafion ionomer to the GDLs. From the visualizations of CO₂ gas bubbles dynamics on the anodes using a transparent cell, it was observed that uniform CO₂ gas bubbles with smaller size formed on hydrophilic anode GDLs. And bubbles with larger size were not uniform over the hydrophobic anode GDLs. It was believed that adding PTFE to the anode GDL was not helpful for improving the CO₂ gas transport in the anode GDL of the low-temperature DMFC.     

Aluminum agglomeration reduction in a composite propellant using tailored Al/PTFE particles

In solid propellants, aluminum is widely used to improve performance, yet theoretical specific impulse is still not achieved largely because of two-phase flow losses. Losses could be reduced if aluminum particles quickly ignited, more gaseous products were produced and if upon combustion, aluminum particle breakup occurred. To explore this, tailored, fuel-rich, mechanically activated composite particles (aluminum/polytetrafluoroethylene, Al/PTFE 90/10 and 70/30 wt.%) are considered as replacements for reference aluminum powders (spherical, flake, or nanoscale) in a composite solid propellant. The effects on burning rate, pressure dependence, and aluminum ignition, combustion, and agglomeration are quantified. Using microscopic imaging, it is observed that tailored particles promptly ignite at the burning surface and appear to breakup into smaller particles, which can increase the heat feedback to the burning surface. Replacement of spherical aluminum with Al/PTFE 90/10 wt.% does not significantly affect propellant burning rate. However, Al/PTFE 70/30 wt.% increases the pressure exponent from 0.36 to 0.58, which results in a 50% increase in propellant burning rate at 13.8 MPa. This increased pressure sensitivity is consistent with more kinetically controlled combustion that occurs from smaller burning metal particles near the surface. Combustion products were quench collected using a new, liquid-free technique at 2.1 and 6.9 MPa and were measured. Both Al/PTFE 90/10 and 70/30 wt.% composite particles reduce the coarse product fraction and diameter. The most significant reduction occurs from 70/30 wt.% particle use, where average coarse product diameter is 25 μm, which is smaller than the original, average particle size and is also smaller than the 76 μm products collected from reference spherical aluminized propellant. This is a 66% decrease in agglomerate diameter or a 96% decrease in volume compared to agglomerates formed from reference spherical aluminum. Smaller diameter condensed phase products and more gaseous products will likely decrease two-phase flow loss and reduce slag accumulation.     

Effective factors improving catalyst layers of PEM fuel cell

Cathode catalyst layer has an important role on water management across the membrane electrode assembly (MEA). Effect of Pt percentage in commercial catalyst and Pt loading from the viewpoint of activity and water management on performance was investigated. Physical and electrochemical characteristics of conventional and hydrophobic catalyst layers were compared. Performance results revealed that power density of conventional catalyst layers (CLs) increased from 0.28 to 0.64 W/cm² at 0.45 V with the increase in Pt amount in commercial catalyst from 20% to 70% Pt/C for H₂/Air feed. In the case of H₂/O₂ feed, power density of CLs increased from 0.64 to 1.29 W/cm² at 0.45 V for conventional catalyst layers prepared with Tanaka. Increasing Pt load from 0.4 to 1.2 mg/cm², improved kinetic activity at low current density region in both feeding conditions. Scattering electron microscopy (SEM) images revealed that thickness of the catalyst layers (CLs) increases by increasing Pt load. Electrochemical impedance spectroscopy (EIS) results revealed that thinner CLs have lower charge transfer resistance than thicker CLs. Inclusion of 30 wt % Polytetrafluoroethylene (PTFE) nanoparticles in catalyst ink enhanced cell performance for the electrodes manufactured with 20% Pt/C at higher current densities. However, in the case of 70% Pt/C, performance enhancement was not observed. Cyclic voltammetry (CV) results revealed that 20% Pt/C had higher (77 m²/g) electrochemical surface area (ESA) than 70% Pt/C (65 m²/g). In terms of hydrophobic powders, ESA of 30PTFE prepared with 70% Pt/C was higher than 30PTFE prepared with 20 %Pt/C. X-Ray Diffractometer (XRD) results showed that diameter of Pt particles of 20% Pt/C was 2.5 nm, whereas, it was 3.5 nm for 70% Pt/C, which confirms CV results. Nitrogen physisorption results revealed that primary pores of hydrophobic catalyst powder prepared with 70% Pt/C was almost filled (99%) with Nafion and PTFE.     

Regulation of the hydrolysis reaction performance of aluminum composites by PTFE and investigation of the hydrolysis mechanism

Improving the hydrolysis reaction properties of aluminum to prepare renewable and environmentally friendly hydrogen is of great interest for the application of mobile hydrogen sources. Here, a series of poly(tetrafluoroethylene)-based activated aluminum composites were prepared, and their microstructures and hydrogen generation properties were investigated in detail.The results show that PTFE can effectively increase the hydrolysis reaction rate of activated aluminum composites. The sample Al–8Bi-2PTFE exhibits the fastest hydrolysis reaction rate. Through observing the microscopic morphology of the hydrolyzed products of Al–8Bi-2PTFE at different reaction times, the catalytic role of PTFE in the hydrolysis reaction of the composite was proved. PTFE can accelerate the rupture of the particles of Al–8Bi-2PTFE during the hydrolysis reaction, thereby accelerating the hydrolysis reaction rate of aluminum.     

Effect of PTFE content in microporous layer on water management in PEM fuel cells

The effect of hydrophobic agent (PTFE) concentration in the microporous layer on the PEM fuel cell performance was investigated using mercury porosimetry, water permeation experiment, and electrochemical polarization technique. The mercury porosimetry and water permeation experiments indicated that PTFE increases the resistance of the water flow through the GDL due to a decrease of the MPL porosity and an increase of the volume fraction of hydrophobic pores. When air was used as an oxidant, a maximum fuel cell performance was obtained for a PTFE loading of 20 wt.%. The experimental polarization curves were quantitatively analyzed to determine the polarization resistances resulting from different physical and electrochemical processes in the PEM fuel cell. The polarization analysis indicated that the optimized PTFE content results in an effective water management (i.e., a balancing of water saturations in the catalyst layer and the gas diffusion layer), thereby improving the oxygen diffusion kinetics in the membrane-electrode assembly.     

Development of Fe–Ni/YSZ–GDC electrocatalysts for application as SOFC anodes: XRD and TPR characterization and evaluation in the ethanol steam reforming reaction

Electrocatalysts based on Fe–Ni alloys were prepared by means of modified Pechini and physical mixture methods and using on a composite of Yttria Stabilized Zirconia (YSZ) and Gadolinia-Doped Ceria (GDC) as support. The former method was based on the formation a polymeric precursor that was subsequently calcined; the later method was based on the mixture of NiO and the support. The resulting composites had 35 wt.% metal load and 65 wt.% support (70 wt.% YSZ and 30 wt.% GDC mixture) (cermets). The samples were then characterized by Temperature-Programmed Reduction (TPR) and X-Ray Diffraction (XRD) and evaluated in the ethanol steam reforming at 650 °C for 6 h in the temperature range of 300–900 °C. The XRD results showed that the bimetallic sample calcined at 800 °C formed a mixed oxide (NiFe₂O₄) with a spinel structure, which, after reduction in hydrogen, formed Ni–Fe alloys. The presence of Ni was observed to decrease the final reduction temperature of the NiFe₂O₄ species. The addition of iron to the nickel anchored to YSZ–GDC increased the hydrogen production and inhibited carbon deposition. The resulting bimetallic 30Fe5Ni sample reached an ethanol conversion of about 95% and a hydrogen yield up to 48% at 750 °C. In general, ethanol conversion and hydrogen production were independent of the metal content in the electrocatalyst. However, the substitution of nickel for iron significantly reduced carbon deposition on the electrocatalyst: 74, 31, and 9 wt.% in the 35Ni, 20Fe15Ni, and 30Fe5Ni samples, respectively.