Rheological properties of SiC suspension for direct ink writing
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摘要: 碳化硅（SiC）凭借高强度、轻质性以及耐高温性能等优势已成为时下应用最广泛的陶瓷材料之一。传统的制备方法生产周期长、成本高且难以制造相对复杂结构的陶瓷。本文利用直写成型方法制备三维复杂结构的SiC陶瓷,研究分散剂含量、pH值、固相体积分数和增稠剂等因素对SiC浆料流变性能的影响,制备可打印的SiC浆料并直写成型,获得SiC的三维点阵结构。结果表明：调节分散剂含量能使浆料黏度获得最低值；pH值影响分散剂的解离度进而改变浆料的黏度；固相体积分数越高,打印结构完整性越好；添加甲基纤维素（MC）可增加浆料的黏度和剪切弹性模量,使其可打印。优化的SiC浆料配方为：分散剂聚丙烯酸（PAA）质量分数为0.01%,固相体积分数为63%和MC质量分数为0.04%,pH>10。Abstract: Silicon carbide is one of the most widely used ceramic materials today due to its excellent properties such as high strength, light weight and high temperature resistance. However, the traditional preparation method has long production cycle, high cost and is difficult to manufacture relatively complex structures. In this paper, the SiC slurry used in direct ink writing was studied to fabricate SiC ceramics with 3D complex structure. The effects of dispersant content, pH, solid loading and thickener on the rheological properties of SiC suspension were investigated. Printable SiC suspension was prepared and direct-written into three-dimensional lattice structures of silicon carbide. The results show that the optimum content of dispersant results in the lowest paste viscosity; pH affects the dissociation of the dispersant to change the viscosity of the paste; the higher the solid loading, the stronger the printable structural integrity; and the addition of methyl cellulose (MC) increases the viscosity and shear elastic modulus of the slurry, making it printable. The optimized silicon carbide slurry formulations are: 0.01% polyacrylic acid (PAA)in mass fraction, 63% solid loading and 0.04% MC in mass fraction, pH > 10, respectively.
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Keywords:
- silicon carbide /
- direct-ink writing /
- rheological properties /
- additives /
- solid loading /
- pH value
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0 引言
锂离子电池因其具有比能量高、电池电压高、工作温度范围宽、存储寿命长等优点得到广泛应用.其正极材料LiNi1/3Co1/3Mn1/3O2综合了LiCoO2良好的电化学性能、LiNiO2的高比容量、LiMn2O4的高安全性及低成本等特点, 因此受到众多研究人员的关注[1-2].然而在动力电池和大规模储能电池等大功率锂离子电池应用过程中, 仍需改善其循环性能.研究表明通过掺杂Mg[3]、Al[4]、Ti[5]等可有效改善正极材料的循环性能.通常采用的方法是将前驱体与掺杂氧化物粉末混合均匀后再进行煅烧[6-7].此外, 溶胶-凝胶法也被运用于正极材料的掺杂研究中[8].本文采用氢氧化物共沉淀法对前驱体进行了Mg掺杂, 合成出掺杂型正极材料Li (Ni1/3Co1/3Mn1/3)1-xMgxO2, 并利用扫描电镜、X-射线衍射、电化学测试等手段, 比较研究了掺杂与未掺杂正极材料的形貌、结构和电化学性能.
1 实验
1.1 正极材料合成
(1)对于未掺杂的正极材料, 将NiSO4、CoSO4、MnSO4按产物计量比配成一定浓度的混合溶液.并配制一定浓度的NaOH和氨水的混合溶液.将2种溶液缓慢滴加到温度为40 ℃的一定浓度的氨水溶液中, 搅拌并控制pH值为11[9-10].滴加完成之后继续搅拌陈化12 h.将所得料浆进行过滤、干燥, 得到前驱体粉末.按前驱体与Li2CO3物质的量之比1: 1.05混合并球磨3 h, 之后在空气炉中先在550 ℃预烧6 h, 然后升温至950 ℃煅烧10 h, 冷却至室温, 得到LiNi1/3Co1/3Mn1/3O2未掺杂的正极材料.
(2)对于掺杂的正极材料, 按合成产物计量比, 将NiSO4、CoSO4、MnSO4、MgSO4配制成总离子浓度与(1)相同的混合溶液, 其他条件和步骤与(1)相同, 合成出了Li (Ni1/3Co1/3Mn1/3)1-xMgxO2(x=0.01, 0.02, 0.03, 0.04)掺杂型正极材料.
1.2 正极材料表征
采用日本株式会社的SU1510型扫描电子显微镜(SEM)观察正极材料的形貌、粒径.采用欧美克激光粒度测试仪分析正极材料的粒径及粒径分布.采用X-射线衍射仪(CuKα靶)对正极材料进行X-射线衍射物相分析(XRD), 扫描范围10°~80°, 扫描速度8°/min.
1.3 正极材料充放电性能测试
按质量比86: 2: 6称取一定量的正极材料、石墨、炭黑置于玛瑙研钵中, 加入质量分数为11 %的聚偏氟乙烯(PVDF), 再用N-甲基吡咯烷酮(NMP)调匀成浆.将料浆均匀涂布在长方形铝箔上然后转移至烘箱中, 在105 ℃干燥12 h.用切片机将铝箔机切成圆形小片并压实得到正极片.将得到的正极片, 与负极的金属锂片, 1 mol/L LiPF6/EC-DMC电解液, Clegard2300隔膜, 在氩气气氛的手套箱中装配成2032扣式电池.在武汉蓝电充放电测试仪上进行电化学性能测试.测试电压为2.7~4.2 V, 测试电流为0.2 C.
2 结果与讨论
2.1 掺镁对正极材料结构的影响
图 1为正极材料Li (Ni1/3Co1/3Mn1/3)1-xMgxO2(x=0, 0.01, 0.02, 0.03, 0.04)的XRD谱图, 表 1为其晶胞参数和结构参数.
表 1 LLi（Ni1/3Co1/3Mn1/3）1-xMgxO2的晶胞参数和结构参数
由图 1可知, 各峰峰形尖锐且强度较高, (006)峰和(102)峰, (108)峰和(110)峰发生明显的分离, 说明合成的正极材料均属于六方晶系α-NaFeO2层状结构.掺杂型正极材料与未掺杂的正极材料的XRD图类似, 没有出现掺杂元素镁的氧化物的衍射峰, 这可能是Mg进入了LiNi1/3Co1/3Mn1/3O2晶格的缘故.表 1显示, 与未掺杂正极材料相比, Mg掺杂型正极材料的a和c值随着掺杂量的增加而有所增大, 晶胞体积也随之增大, 这有利于Li+在充放电过程中的脱嵌.c/a值是正极材料层状结构的重要标志[11-12], c/a值越大(大于4.96), 表明正极材料层状结构越趋于完整.通常用(003)峰与(104)峰的衍射峰强度之比I003/I104来表示阳离子混排程度, 当I003/I104>1.2时, 表明阳离子混排程度较低.掺杂型正极材料I003/I104值略高于未掺杂的正极材料, 表明Mg的掺入在一定程度上抑制了正极材料的阳离子混排.
2.2 掺镁对正极材料粒径及形貌的影响
掺杂与未掺杂正极材料的SEM结果如图 2所示.
由图 2可以看出, LiNi1/3Co1/3Mn1/3O2及其掺杂型正极材料均由立方体的一次颗粒聚集形成类球形的大颗粒, 其形貌差别不大, 表明镁的掺入不会改变正极材料的形貌.
粒度测试结果如表 2所示.由表 2可知, 随着掺镁量的增加, 颗粒粒径有所下降.原因可能是在强碱性溶液中, Mg2+与NH3的配位作用较弱, 在金属离子总浓度不变的情况下, 游离的金属离子浓度增加, 溶液过饱和度升高, 成核速率加快, 生长速率有所降低, 颗粒粒径减小[13].
表 2 Li（Ni1/3Co1/3Mn1/3）1-xMgxO2的粒径
2.3 掺镁对正极材料的电化学性能的影响
图 3、图 4分别为掺杂不同量Mg2+的正极材料的充放电曲线和相应的放电比容量-循环曲线图.由图 3可知, 各正极材料的充放电曲线平滑, 充放电电压平台比较平稳, 均在3.75 V左右.图 4显示, 与未掺杂的LiNi1/3Co1/3Mn1/3O2相比, Mg2+掺杂后正极材料的初始容量有所降低, 这与其中参与电化学反应活性物质减少有关, 因为Mg2+在充放电前后价态不变, 不具有电化学活性.此外, 微量镁可能占据Li+位置, 导致Li+的脱嵌量减少[14].然而掺杂少量的Mg2+之后, 正极材料循环性能有所改善, 这是因为进入锂层的Mg2+能有效地抑制阳离子混排程度, 同时Mg2+半径大于Li+半径, 能起到层间支撑的作用[15].
正极材料的放电容量如表 3所示.由表 3可知, 当掺杂量x=0.03时, 循环性能最优, 充放电循环50轮之后正极材料的放电比容量为131.1 mAh/g, 保持率为94.91 %, 高于未掺杂正极材料的119.5 mAh/g和82.21 %.掺杂量进一步增大, 正极材料仍能保持良好的循环性能.
表 3 Li（Ni1/3Co1/3Mn1/3）1-xMgxO2的放电容量
3 结论
(1)采用共沉淀法制备Mg掺杂的前驱体, 并经过混锂、球磨、高温煅烧, 制备出Li (Ni1/3Co1/3Mn1/3)1-xMgxO2正极材料, 掺杂与未掺杂的正极材料都具有单一的α-NaFeO2型层状结构; 无衍射杂峰出现.
(2)掺镁正极材料的首次放电容量均有不同程度的降低, 但具有稳定的充放电平台, 循环性能有明显改善.其中以Mg掺杂量为0.03时, 正极材料Li (Ni1/3Co1/3Mn1/3)1-0.03Mg0.03O2的循环性能最好, 首次放电比容量为138.17 mAh/g, 50次循环后放电比容量为131.14 mAh/g, 容量保持率为94.91 %.
赵中波 -
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图 1 添加剂对SiC浆料的沉降高度和黏度的影响： （a）不同分散剂对SiC浆料的沉降高度的影响；（b） PAA含量对SiC浆料黏度的影响；（c） PAA含量对低剪切速率下（1 s-1）SiC浆料黏度的影响
Fig 1. Effect of additives on the settling height and viscosity of SiC suspension： （a） effect of different dispersants on the settling height of SiC suspension； （b） the effect of PAA content on the viscosity of SiC suspension； （c） the effect of PAA content on the viscosity of SiC suspension at low shear rate （1 s-1）
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图 2 不同pH对SiC浆料黏度的影响
Fig 2. Effect of different pH value on the viscosity of SiC suspension
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图 3 不同固相体积分数对SiC浆料黏度的影响
Fig 3. Effect of different soild loading on the viscosity of SiC suspension
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图 4 MC含量对SiC浆料流变性能的影响：（a）不同MC含量对SiC浆料黏度的影响；（b）在低剪切速率（1 s-1）下,SiC浆料的黏度随MC含量的变化；（c）不同MC含量对SiC浆料剪切弹性模量的影响；（d）不同MC含量对SiC浆料屈服应力的影响
Fig 4. Effect of MC on the rheological properties of SiC suspension： （a） viscosity vs. shear rate； （b） viscosity vs. content of MC under low shear rate （1 s-1）； （c） shear elastic modulus vs. shear stress；（d） yield stress vs. content of MC
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[1] 邹芹, 周鑫, 李艳国, 等. SiC复合材料的研究进展与展望[J]. 中南大学学报(自然科学版), 2020, 51(11): 3220-3232. [2] 向忠宁, 何秦川, 王益群, 等. 中空SiC球形纳米颗粒的合成及吸波性能[J]. 有色金属科学与工程, 2022, 13(1): 83-92. [3] MAYO M J. Processing of nanocrystalline ceramics from ultrafine particles[J]. International Materials Reviews, 1996, 41(3): 85-115.
[4] WU J G, FAN Z, XIAO D Q, et al. Multiferroic bismuth ferrite-based materials for multifunctional applications: Ceramic bulks, thin films and nanostructures[J]. Progress in Materials Science,2016,84：335-402.
[5] RAMADHAS A S, XU H M. Intake air heating strategy to reduce cold-start emissions from diesel engines[J]. Biofuels, 2018, 9(3): 405-414.
[6] HAJIALI F, TAJBAKHSH S, SHOJAEI A. Fabrication and properties of polycaprolactone composites containing calcium phosphate-based ceramics and bioactive glasses in bone tissue engineering: A review[J]. Polymer Reviews, 2018, 58(1): 164-207.
[7] ANTIL P, SINGH S, SINGH S, et al. Metaheuristic approach in machinability evaluation of silicon carbide particle/glass fiber-reinforced polymer matrix composites during electrochemical discharge machining process[J]. Measurement and Control, 2019, 52(7/8): 1167-1176.
[8] MENDES M A A, GOETZE P, TALUKDAR P, et al. Measurement and simplified numerical prediction of effective thermal conductivity of open-cell ceramic foams at high temperature[J]. International Journal of Heat and Mass Transfer, 2016, 102: 396-406.
[9] CAO J J, DONG X F, LI L L, et al. Recycling of waste fly ash for production of porous mullite ceramic membrane supports with increased porosity[J]. Journal of the European Ceramic Society, 2014, 34(13): 3181-3194.
[10] MURPHY S V, ATALA A. 3D bioprinting of tissues and organs[J]. Nature Biotechnology, 2014, 32(8): 773-785.
[11] DONG C J, WANG R C, CHEN Y X, et al. Near-net shaped Al/SiCP composites via vacuum-pressure infiltration combined with gelcasting[J]. Transactions of Nonferrous Metals Society of China, 2020, 30(6): 1452-1462.
[12] LIU J J, YANG H C, REN B, et al. Highly porous ZrO2 cellular ceramics with 3D network architecture[J]. Ceramics International, 2020, 46(6): 7149-7154.
[13] LI W, CUI C C, BAO J X, et al. Properties regulation of SiC ceramics prepared via stereolithography combined with reactive melt infiltration techniques[J]. Ceramics International, 2021, 47(24): 33997-34004.
[14] WANG J C, DOMMATI H, HSIEH S J. Review of additive manufacturing methods for high-performance ceramic materials[J]. The International Journal of Advanced Manufacturing Technology, 2019, 103(5/6/7/8): 2627-2647.
[15] XIE H B, ZHANG J L, LI F L, et al. Selective laser melting of SiCp/Al composites: densification, microstructure, and mechanical and tribological properties[J]. Ceramics International, 2021, 47(21): 30826-30837.
[16] LI S, LI Y F, WANG Q W, et al. Fabrication of 3D-SiC/aluminum alloy interpenetrating composites by DIW and pressureless infiltration[J]. Ceramics International, 2021, 47(17): 24340-24347.
[17] LU Z L, XIA Y L, MIAO K, et al. Microstructure control of highly oriented short carbon fibres in SiC matrix composites fabricated by direct ink writing[J]. Ceramics International, 2019, 45(14): 17262-17267.
[18] HU S J, FENG B, TANG X X, et al. Porous alumina ceramics obtained by particles self-assembly combing freeze drying method[J]. Materials (Basel), 2019, 12(6): 897.
[19] LI Z W, AN S J, LIU Y F, et al. Practical modification of tannic acid polyether demulsifier and its highly efficient demulsification for water-in-aging crude oil emulsions[J]. ACS Omega, 2019, 4(24): 20697-20707.
[20] XIONG H W, ZHAO L Z, CHEN H H, et al. 3D SiC containing uniformly dispersed, aligned SiC whiskers: Printability, microstructure and mechanical properties[J]. Journal of Alloys and Compounds, 2019, 809: 151824.
[21] BAI L, GRECA L G, XIANG W, et al. Adsorption and assembly of cellulosic and lignin colloids at oil/water interfaces[J]. Langmuir：the ACS Journal of Surfaces and Colloids,2019, 35(3): 571-588.
[22] GENSOWSKI K, TEPNER S, SCHWEIGERT S, et al. Conductive highly filled suspensions for an electrochemical dispensing approach to pattern full-area thin metal layers by physical vapour deposition[J]. Scientific Reports, 2020, 10(1): 1-10.
[23] ZHOU L, ZHU J W, ZHAO Y F, et al. A molecular dynamics study on thermal conductivity enhancement mechanism of nanofluids-Effect of nanoparticle aggregation[J]. International Journal of Heat and Mass Transfer, 2022, 183: 122124.
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