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1.
在多晶硅太阳能电池的生产过程中, 金刚线切割技术(Diamond wire sawn, DWS)具有切割速度快、精度高、原材料损耗少等优点, 受到了广泛关注。金刚线切割多晶硅表面形成的损伤层较浅, 与传统的酸腐蚀制绒技术无法匹配, 金属催化化学腐蚀法应运而生。金属催化化学腐蚀法制绒具有操作简单、结构可控且易形成高深宽比的绒面等优点, 具有广阔的应用前景。本文总结了不同类型的金属催化剂在制绒过程中的腐蚀机理及其形成的绒面结构, 深入分析和讨论了具有代表性的银、铜的单一及复合催化腐蚀过程及绒面结构和电池片性能。最后对金刚线切割多晶硅片表面的金属催化化学腐蚀法存在的问题进行了分析, 并展望了未来的研究方向。  相似文献   
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董柯静  夏广辉  杨玺  赵煜 《化工进展》2021,40(Z1):204-214
基于质子交换膜燃料电池(PEMFC)的转换效率主要受阴极氧还原反应(ORR)动力学缓慢的限制,设计高效稳定的低铂催化剂,对于降低PEMFC产业化应用的成本和提高催化性能至关重要。目前,研究人员已对此开展广泛研究,并取得了丰硕成果,开发包括具有可调晶面、高指数晶面、Pt-M(M为过渡金属)合金的Pt纳米结构。本文从利用不同添加剂调控Pt基催化剂晶面结构和形貌以促进氧还原电催化性能的角度着手,综述了保护剂、络合剂、封端剂、还原剂、分散剂等常用添加剂对Pt基催化剂正四面体、立方体、八面体以及具有高指数晶面的凹纳米立方体等晶面结构进行调控的研究进展,在湿化学法、电沉积法、合金法、溶剂热法等不同研究方法中添加剂在调控晶面结构和提高催化性能方面发挥的作用,并对Pt基催化剂中Pt晶面调控在未来面临的挑战和发展方向做了简要总结。  相似文献   
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Poor antioxidant and thermal-shock capacities of C/C composites thermal barrier coating (TBC) caused by cracking and shedding of coatings has been a major obstacle blocking the development of C/C composites. Herein, in-situ growth of whisker reinforced silicon carbide transition layer and inter-embedding mechanism of multi-gradient coatings were brought into the design of TBC to enhance the antioxidant and thermal-shock capacities. A three-layer gradient coating SiC-SiCw/ZrB2-SiC/ZrSiO4-aluminosilicate glass (ZAG) from inside to outside, in which ZrB2-SiC/ZAG serve as oxygen barrier layers with self-healing ability and SiC-SiCw provides thermal stress buffering and bonding against cracking and shedding of coatings, is designed. The ZAG mainly forms a dense oxygen blocking frontier with self-healing ability through fluidized glass, while the ZrB2-SiC can react actively with infiltrated oxygen in a way of self-sacrifice, preventing oxygen erosion to C/C matrix and SiC-SiCw transition layer. As a result, the collaborative work among layers endows this coating with excellent high temperature service performance. This work provides a new insight for the design of excellent TBC.  相似文献   
5.
《材料科学技术学报》2019,35(7):1309-1314
Degenerate pattern is a seemingly disordered morphology but it exhibits the inherently ordered crystal connected with tip-splitting and limited stability which makes it difficult to observe in the metallic system. Here we employ (100)[011] orientated planar-front seeds using directional solidification and reveal the fundamental origins of the degenerate pattern growth in an Al-4.5 wt% Cu alloy. We find that the spacing of the tip-splitting (λ) in the degenerate of the alloys followed a power law, λV−0.5, and the frequency (f) of the splitting was related to the growth velocity (V) by ƒ∝V1.5. The dimensionless growth direction (θ/θ0) increased monotonously and approached 0.6 with faster velocity, attributed to its anisotropy in the interface kinetics. Once growth velocity exceeded a threshold, two types of pattern transitions from degenerate to regular dendrites were proposed. One of them exhibited a random and chaotic mode and the other underwent a rotation in growth direction.  相似文献   
6.
本文利用固溶体合金中的‘团簇加连接原子’模型解析了典型高温近α-Ti合金Ti1100的成分,其团簇成分式为[Al-(Ti13.7Zr0.3)](Al0.69Sn0.18Mo0.03Si0.12)。在此基础上,采用相似元素替代原则设计了微量元素Hf、Ta和Nb添加的系列合金成分,即 [Al-(Ti13.7Zr0.15Hf0.15)](Al0.69Sn0.18Si0.1(Mo/Ta/Nb)0.03)。对该系列合金进行950 ℃/1 h固溶+560 ℃/6 h时效处理,然后进行组织结构、硬度、抗高温氧化及电化学腐蚀性能测试。研究结果表明,Zr0.15Hf0.15合金与参比合金具有相同片层β转变组织,而在此基础上Ta和Nb的添加会使合金中产生大量等轴α组织;但组织的改变对系列合金的显微硬度影响不大,介于330-370 HV。650 ℃氧化100 h后系列合金均具有较强的抗氧化能力,氧化增重小于1.0 mg/cm2,而在800 ℃氧化100 h后,添加Hf、Ta、Nb元素的合金氧化增重明显低于Ti1100合金,氧化层厚度为25~27 μm,且氧化层致密,其中[Al-(Ti13.7Zr0.15Hf0.15)](Al0.69Sn0.18Si0.1Ta0.015Nb0.015)合金具有最优的抗高温氧化性能,800 ℃/100 h后的氧化增重仅为2.6 mg/cm2。此外,该系列合金在在3.5 %NaCl溶液中也具有较好的耐蚀性。  相似文献   
7.
Hydrogen addition effectively reduces the fuel consumption of spark ignition engines. We propose a new on-board reformer that produces hydrogen at high concentrations and enables multi-mode operations. For the proposed reformer, we employ a catalytic fuel decomposition reaction via a commercial NiO–CaAl2O4 catalyst. We explore the physical and chemical aspects of the reforming process using a fixed bed micro-reactor operating at temperatures of 550–700 °C. During reduction, methane is decomposed to form hydrogen and carbon. Carbon formation is critical to hydrogen production, and free space for carbon growth is essential at low temperatures (≤600 °C). We define a new accumulated conversion ratio that quantitatively measures highly transient catalytic decomposition. The free space of the coated monolith clearly aided low-temperature decomposition with negligible pressure drop. The coated substrate is therefore suitable for on-board applications considering that our reformer concept also utilizes the catalytic fuel decomposition reaction.  相似文献   
8.
The traditional chemical vapor infiltration (CVI) method still faces massive challenge in improving the densification owing to its unavoidable bottleneck effect. Herein, laser assisted-chemical vapor infiltration (LA-CVI) was introduced to fabricate C/SiC composites with mass transfer channels. As a result, the densities of the C/SiC composites were improved due to the dense band formed during the LA-CVI process. Also, with different spacing of mass transfer channels, C/SiC composites exhibited enhanced degree of densification varying from 2.10 to 2.23 g/cm3. When the spacing of channels was 3 mm, the maximum value of flexural strength reached 528 ± 12 MPa. Additionally, micro-CT and finite element analysis were empolyed to investigate dense band and density gradient in detail. The results show that C/SiC composites prepared via LA-CVI method with suitable spacing of channels had improved density and great flexural strength. The proposed method provides a novel route for the preparation of ceramic matrix composites with high density.  相似文献   
9.
Cr掺杂的类金刚石非晶碳具有良好的导电性和耐腐蚀性,这对于燃料电池金属双极板涂层改性特别重要。使用团簇加连接原子模型对其非晶结构进行了详细解析,在该模型中,良好的玻璃形成材料由覆盖特征性最近邻团簇加上几个下一壳层原子的结构单元来表述。根据文献,在Cr掺杂的类金刚石非晶碳中占优势的团簇是Cr中心和C壳层的[Cr-C4]四面体团簇,然后将该团簇与适当的连接原子匹配,以满足电子轨道饱和原理。由此推导出了两个最优组成式,即[Cr-C4]CrC3(22.2%Cr)和[Cr-C4]Cr3C2(40%Cr),它们显示出良好的非晶态结构稳定性。实验结果显示,所提出的这两组化学组成的涂层材料兼具低电阻率(低至10-4Ω·cm)和优异的耐腐蚀性(腐蚀电流密度~10^-2μA/cm^2)。在sp2键含量和渗流理论的框架内讨论了导电和耐蚀的协同行为。这项工作验证了团簇加连接原子模型在具有高耐腐蚀性和高导电性的涂层材料成分设计中的可行性。  相似文献   
10.
Insufficient corrosion resistance, electrical conductivity and wettability of bipolar plates are some of the important issues affecting the performance of hydrogen fuel cells. To address these issues, an amorphous Al–Cr–Mo–N coating is deposited on type 316L stainless steel using direct current (DC) magnetron sputtering. The electrochemical corrosion behaviour is investigated under simulated fuel cell anode (H2-purging) and cathode (air-purging) environment consisting of 0.5 M H2SO4 + 2 ppm NaF at 70 ± 2 °C. The corrosion current density is reduced to 0.02 μA cm−2 comparable to the commercially used Ta/TaN coatings. The polarization resistance increases by two orders of magnitude and the interfacial contact resistance (ICR) reduces significantly due to the application of the coating. Further, the coating shows better water management due to high hydrophobicity than the bare stainless steel.  相似文献   
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