-
石墨烯样品的制备及表征过程中所使用的试剂和仪器如表1、表2所示。
表 1 实验试剂及厂家
Table 1. Experimental reagents and manufacturers
Name of reagent Purity Manufacturer Flake graphite AR Aladdin 98% H2SO4 AR Beijing Chemical Works NaNO3 AR Xiya Reagent KMnO4 AR Beijing Chemical Works 30% H2O2 AR Beijing Chemical Works HCl AR Beijing Chemical Works CH3CH2OH AR Aladdin 表 2 实验仪器及厂家
Table 2. Experimental instruments and manufacturers
Name of instrument Model Manufacturer Analytical balance SI-234 Denver Instrument Electrothermal thermostatic water bath HH-2 Kewei Yongxing Electric thermostaticdrying oven 101-2BS Lichen Bonsi Vacuum tube furnace SK-B08123K Tianjin Zhonghuan Benchtop centrifuge LC-LX-L60D Lichen Bonsi Freeze drier FD-1A-80 BIOCOOL SEM QUANTA FEG450 FEI Company X-Ray diffractometer Bruker D8 Bruker 红外消光性能测试过程中所使用的仪器:黑体辐射源,HFY-206B,提供180 ℃ (± 0.01 ℃)的红外热源,上海福源光电技术有限公司;红外热成像仪,DL700,工作波段8~14 μm,浙江大立科技股份有限公司;傅里叶变换红外光谱仪,WQF-530,北京瑞利分析仪器有限公司。
-
向25 mL 98% H2SO4中加入1 g天然鳞片石墨和1 g NaNO3,冰浴搅拌2 h,再慢慢加入4 g KMnO4,过程中使温度保持在20 ℃以下,搅拌1 h后将烧杯放入35 ℃的水浴中,搅拌2 h至溶液为深褐色。将50 mL的去离子水加入到溶液中,继续升温至95 ℃,在恒温下搅拌15 min,然后停止加热。加入150 mL去离子水和10 mL 30 % H2O2,溶液变为淡黄色,再用5 % HCl洗涤并离心,用去离子水、无水乙醇反复洗涤,使上清液至中性,然后对离心后的沉淀进行冷冻干燥、研磨,得到氧化石墨烯粉末[16]。
将上述氧化石墨烯置于电炉内,在氩气下加热到500 ℃,反应5 min,使氧化石墨烯进一步还原和片层剥离,得到石墨烯粉末。
-
石墨和碳纤维是两种常见的烟幕材料,它们的成本较低廉,在军事中常用于干扰红外。为了更全面地研究石墨烯的红外干扰性能,以石墨、碳纤维这两种传统碳材料为参考材料,采用烟幕箱实验和溴化钾压片法测试石墨、碳纤维和石墨烯三种材料的红外消光性能,在同等测试条件下对这三种碳材料的红外消光性能进行对比分析。
-
实验在内腔体积0.11 m3(长0.58 m×宽0.38 m×高0.48 m)的烟幕箱内进行,光程为0.58 m;并将红外热成像仪DL700和温度设为180 ℃的标准黑体置于烟幕箱的两端。调试好红外热成像仪设备并开启工作,以记录施放烟幕前后的靶标和靶标周围背景的红外图像。把称量好的烟幕材料倒入烟幕箱,同时打开烟幕箱中的风扇搅拌,使材料分布均匀。实验完毕后,存储视频并关闭风扇,收集烟箱中沉降或表面粘附的样品并做称重记录,将烟幕箱内的材料清空,然后进行下一次的实验。
通过红外热成像仪采集三种材料对靶标干扰过程的红外视频,选取最具有代表性的红外图像,根据公式(1)[17]计算出透过率T(%)。
$$ T=\frac{T_{0}^{\prime}{ }^{4}-T_{1}^{\prime}{ }^{4}}{T_{0}{ }^{4}-T_{1}{ }^{4}} \times 100 {\text{%}} $$ (1) 式中:T0、
$T_{0}^{\prime}{ } $ 为烟幕施放前后靶标的温度;T1、$T_{1}^{\prime}{ } $ 为烟幕施放前后背景周围的平均温度,单位为K。再计算烟幕材料质量浓度C(g·m−3),由于烟箱体积较小,无法通过采样装置测量实时浓度,因此在收到中,烟幕的质量浓度C按照公式(1)进行计算。
$$ C=\frac{m_{0}-m}{V} $$ (2) 式中:m0为加入烟箱的样品质量,g;m为烟箱中沉降或表面粘附的样品质量,g;V为烟箱体积,m3。
最后将所得透过率、浓度代入公式(3)[18]计算出用以描述烟幕的消光性能的质量消光系数α(m2/g):
$$ \alpha=\frac{1}{C L} \ln \frac{1}{T} $$ (3) 式中:C为材料质量与烟幕箱体积之比的理论浓度,g·m−3;L为光程,m。
为了更直观地描述三种材料的消光性能,定义一个新的无量纲参数k,用于对任意两种材料的消光性能进行比较,其数值等于这两种材料质量消光系数的比值。
-
将溴化钾粉末于烘箱中烘干24 h后,利用玛瑙研钵对其进行充分研磨,然后称量200 mg研磨后的溴化钾于模具中,使用压片机在15 MPa的压力下,将其压成片状物,测试并存储溴化钾本底光谱。按照样品与溴化钾质量比1∶400,准确称量200 mg左右的混合样品,采用红外光谱仪对样品进行测试,并存储数据,取出压片后测试下一个样品[19]。
-
利用扫描电镜对石墨烯样品进行了观察,图1是不同放大倍率的石墨烯SEM图。可明显看出,所制得的石墨烯样品具有显著的层状结构,其片层直径在几微米至数十微米之间,并且呈现褶皱和弯曲。
-
用X射线衍射仪分析鳞片石墨、氧化石墨烯和石墨烯的结构,结果如图2所示。由图2可知,在26.5°处,天然鳞片石墨有一明显特征峰,是石墨的(002)晶体结构,晶面层间距为0.335 nm;氧化反应后,(002)衍射峰消失,在9.2°处新的衍射峰出现,层间间距也增加至0.969 nm,这是因为石墨被氧化后,形成的多种含氧官能团使得晶面层与层的间距增大,可见氧化性石墨烯的制备是成功的。还原后的石墨烯在9.2°的吸收峰消失,且在26.2°处出现一个宽峰,与石墨(002)的衍射峰相似,但是强度有所下降,这是因为石墨烯为剥离的较薄片层结构,晶体结构完整性低于石墨。可见,石墨烯的制备是成功的,可用于对比测试其红外消光性能。
-
利用红外热成像仪测试石墨、碳纤维和石墨烯烟幕在8~14 μm红外波段的红外图像,图3所示为烟幕材料质量为0.75 g的靶标图像。由图3可知,随着烟幕的释放,热像仪显示的靶标热像图发生变化,在烟幕释放前,图中靶标清晰均可见,如图3(a)所示;石墨和碳纤维烟幕施放后,红外靶标模糊,具有一定的遮蔽效果,如图3(b)、(c)所示;而在石墨烯烟幕遮蔽施放后,红外靶标几乎完全被遮蔽,如图3(d)所示。对比图3(b)、(c)和(d)的靶标图像,可以看出,(d)图中靶标的能见度最低,说明相同质量浓度下,石墨烯烟幕对靶标的遮蔽效果优于石墨和碳纤维。
图 3 (a)原始靶标图像;(b)石墨遮蔽靶标图像;(c)碳纤维遮蔽靶标图像;(d)石墨烯遮蔽靶标图像
Figure 3. (a) Original target image; (b) Graphite masked target image; (c) Carbon fibre masked target image; (d) Graphene masked target image
烟幕箱实验时发现箱底有烟幕材料堆积成团的现象,因此需要收集烟箱中沉降或表面粘附的样品并称重记录,根据公式(2)计算烟幕的实际浓度。烟幕材料的堆积成团不仅使烟幕红外干扰效果减弱,而且对颗粒的悬浮性有一定影响,使烟幕的有效遮蔽时间大大缩短。图4所示为烟幕箱中加入0.75 g烟幕材料的沉降情况。
图 4 (a) 石墨沉降图像;(b) 碳纤维沉降图像;(c) 石墨烯沉降图像
Figure 4. (a) Graphite settling image; (b) Carbon fiber settling image; (c) Graphene settling image
表3为根据公式(1)~(3)计算得到的三种材料在烟幕箱实验中的红外透过率、烟幕实际质量浓度、质量消光系数和无量纲参数k,表中k为石墨烯与石墨、碳纤维的质量消光系数之比。
表 3 材料在8~14 μm的质量消光系数及其比值
Table 3. Mass extinction coefficient and their ratio of materials at 8-14 μm
Materials m0/g m/g C/g·m-3 T α/m2·g-1 k Graphite 0.25 0.14 1.0 59.5% 0.87 2.25 0.40 0.26 1.3 50.6% 0.88 2.17 0.50 0.31 1.8 41.5% 0.85 2.39 0.60 0.35 2.4 30.6% 0.87 2.57 0.75 0.48 2.6 26.8% 0.89 2.22 Carbon fiber 0.25 0.10 1.4 62.3% 0.58 3.33 0.40 0.20 1.8 53.8% 0.58 3.29 0.50 0.26 2.3 48.7% 0.55 3.69 0.60 0.30 2.9 37.0% 0.60 3.72 0.75 0.39 3.4 32.3% 0.58 3.39 Graphene 0.25 0.12 1.3 24.0% 1.95 - 0.40 0.17 2.2 11.0% 1.90 - 0.50 0.21 2.7 4.2% 2.03 - 0.60 0.28 3.0 2.1% 2.23 - 0.75 0.35 3.8 1.4% 1.97 - 由表3可以看出,石墨烯烟幕的红外透过率远低于石墨和碳纤维,与红外热成像仪观察得到的结论相符。观察表3数据还发现,在同种烟幕材料下,随着烟幕浓度的增加,红外透过率不断下降,可见烟幕材料的种类和烟幕浓度都是影响红外干扰效果的关键因素。由表3数据可知,石墨烯的质量消光系数是同等测试条件下石墨的两倍多,是碳纤维的三倍多,可见石墨烯的红外消光性能远远好于石墨和碳纤维。
从理论上讲,对于某种材料其质量消光系数应当是固定的,并不会随着测试条件和浓度等变化。为了更准确地比较三种材料的消光性能,测试不同质量浓度下的红外透过率,进行拟合,计算平均质量消光系数。
对公式(3)进行变换得到:
$$ -\ln T=\alpha \cdot C L $$ (4) 由公式(4)可知,利用平均透过率的自然对数与面密度作图进行线性拟合,所得斜率为烟幕的平均质量消光系数[20]。
图 5 材料在8~14 μm的质量消光系数线性拟合曲线
Figure 5. Linear fitting curves of material mass extinction coefficient at 8-14 μm
由拟合公式得到该实验条件下,石墨、碳纤维和石墨烯的平均质量消光系数分别为0.88、0.59、2.10 m2/g。石墨烯的平均质量消光系数是同等测试条件下石墨的2.39倍,是碳纤维的3.56倍,说明石墨烯的红外消光性能远远好于石墨和碳纤维,是一种消光性能优异的新型碳材料烟幕。
-
利用溴化钾压片法,测试了石墨、碳纤维和石墨烯的静态红外干扰能力,其红外透过光谱如图6、图7所示。
对红外光谱仪测得的数据从3~5 μm、8~14 μm波段分别积分,再除以这个波段的宽度,即为其平均透过率[21],并根据公式(5)计算其红外衰减率(%),结果如表4所示。
$$ \varphi=1-T $$ (5) 由表4数据可知,溴化钾压片测试中,石墨烯对3~5 μm中红外和8~14 μm远红外波段的衰减率分别为98.87 %和98.82 %,衰减效果优于石墨和碳纤维。可见,石墨烯在中远红外波段均具有良好的红外消光能力,优于石墨和碳纤维,这与烟幕箱实验所得结果一致。
表 4 溴化钾压片法测试结果
Table 4. Results of potassium bromide compression test
Materials 3-5 μm 8-14 μm T φ T φ Graphite 6.85% 93.15% 7.16% 92.84% Carbon fiber 25.95% 74.05% 26.06% 73.94% Graphene 1.12% 98.87% 1.17% 98.82%
Test research on far-infrared extinction performance of graphene
-
摘要: 为了研究石墨烯的红外消光性能,采用氧化还原法制备了石墨烯,并通过扫描电镜图像、X射线衍射图谱确认了石墨烯的结构;利用烟幕箱实验和溴化钾压片法,测试了石墨烯的红外消光性能,并在同等条件下与石墨、碳纤维的消光性能进行了比较。结果表明:石墨烯在远红外波段的红外消光性能非常优异,对于8~14 μm远红外波段,其平均质量消光系数约为2.10 m2/g,是同等条件下石墨平均质量消光系数的2.39倍,碳纤维的3.56倍,比传统的碳材料烟幕具有更好的红外干扰能力;溴化钾压片测试也表明,石墨烯在中远红外波段均表现出非常好的红外消光能力,优于传统碳材料烟幕。Abstract: In order to investigate the infrared extinction properties of graphene, graphene was prepared by redox method. The structure of graphene was also confirmed by scanning electron microscope images and X-ray diffraction mapping. The infrared extinction properties of graphene were tested using the smoke box test and potassium bromide compression method, and compared with those of graphite and carbon fibres under the same conditions. The results show that the infrared extinction performance of graphene in the far infrared band is excellent. For the 8-14 μm far infrared band, its average mass extinction coefficient is approximately 2.10 m2/g, which is 2.39 times of that of the the average mass extinction coefficient of graphite and 3.56 times that of carbon fiber under the same conditions, providing better infrared interference than conventional carbon material smoke screens. Potassium bromide press tests also show that graphene exhibits very good infrared extinction in both mid and far infrared bands, outperforming traditional carbon material smoke screens.
-
Key words:
- infrared /
- smoke screen /
- mass extinction coefficient /
- graphene /
- carbon material
-
表 1 实验试剂及厂家
Table 1. Experimental reagents and manufacturers
Name of reagent Purity Manufacturer Flake graphite AR Aladdin 98% H2SO4 AR Beijing Chemical Works NaNO3 AR Xiya Reagent KMnO4 AR Beijing Chemical Works 30% H2O2 AR Beijing Chemical Works HCl AR Beijing Chemical Works CH3CH2OH AR Aladdin 表 2 实验仪器及厂家
Table 2. Experimental instruments and manufacturers
Name of instrument Model Manufacturer Analytical balance SI-234 Denver Instrument Electrothermal thermostatic water bath HH-2 Kewei Yongxing Electric thermostaticdrying oven 101-2BS Lichen Bonsi Vacuum tube furnace SK-B08123K Tianjin Zhonghuan Benchtop centrifuge LC-LX-L60D Lichen Bonsi Freeze drier FD-1A-80 BIOCOOL SEM QUANTA FEG450 FEI Company X-Ray diffractometer Bruker D8 Bruker 表 3 材料在8~14 μm的质量消光系数及其比值
Table 3. Mass extinction coefficient and their ratio of materials at 8-14 μm
Materials m0/g m/g C/g·m-3 T α/m2·g-1 k Graphite 0.25 0.14 1.0 59.5% 0.87 2.25 0.40 0.26 1.3 50.6% 0.88 2.17 0.50 0.31 1.8 41.5% 0.85 2.39 0.60 0.35 2.4 30.6% 0.87 2.57 0.75 0.48 2.6 26.8% 0.89 2.22 Carbon fiber 0.25 0.10 1.4 62.3% 0.58 3.33 0.40 0.20 1.8 53.8% 0.58 3.29 0.50 0.26 2.3 48.7% 0.55 3.69 0.60 0.30 2.9 37.0% 0.60 3.72 0.75 0.39 3.4 32.3% 0.58 3.39 Graphene 0.25 0.12 1.3 24.0% 1.95 - 0.40 0.17 2.2 11.0% 1.90 - 0.50 0.21 2.7 4.2% 2.03 - 0.60 0.28 3.0 2.1% 2.23 - 0.75 0.35 3.8 1.4% 1.97 - 表 4 溴化钾压片法测试结果
Table 4. Results of potassium bromide compression test
Materials 3-5 μm 8-14 μm T φ T φ Graphite 6.85% 93.15% 7.16% 92.84% Carbon fiber 25.95% 74.05% 26.06% 73.94% Graphene 1.12% 98.87% 1.17% 98.82% -
[1] Li Y. Research on test method of infrared smoke shielding effect [D]. Changchun: University of Science and Technology, 2020. (in Chinese) [2] Liu G S, Guan H, Lv H P, et al. Effect of diameter graphite particles on infrared & 10.6 μm laser attenuation performance [J]. Chinese Journal of Energetic Materials, 2009(2): 9-12. (in Chinese) [3] Cai W B, Wang N Y, Song D M, et al. Effect of diameter graphite particles on IR extinction characteristics [J]. Infrared Technology, 2003, 25(5): 68-71. doi: 10.3969/j.issn.1001-8891.2003.05.018 [4] Zhang J Y, Song X P. Research on application of carbon fiber in interferenceand energetic materials [J]. Electro-Optic Technology Application, 2022, 37(1): 40-43, 78. (in Chinese) [5] Appleyard P G. Infrared extinction performance of high aspectratio carbon nanoparticles [J]. Journal of Optics A: Pure and Applied Optics, 2006, 8: 101-113. [6] Wang X Y, Dong W J, Pang M H, et al. Granular characteristics and infrared extinction coefficients of graphite aerosol [J]. Procedia Engineering, 2015, 102: 1238-1244. [7] Sun Y Y, Wang X Y, Dong W J, et al. Study on the influence of carbon fiber’s particle size on infrared/millimeter wave inter-ference performance [J]. Infrared and Laser Engineering, 2022, 51(3): 20210254. (in Chinese) doi: 10.3788/IRLA20210254 [8] Chen N, Pan G P, Gua H. Study on IR extinction performance of graphite micro-powder smoke in vacuum [J]. Initiators and Pyrotechnics, 2007(3): 34-36. (in Chinese) [9] Ning G T, Li P, Cui Y L, et al. Flowability and infrared interference properties of modified graphite flake with hydrophobic nano-silica [J]. Chinese Journal of Energetic Materials, 2015, 23(12): 1217-1220. (in Chinese) [10] Zhang D Z. Research on the composite technology and performance of multi-spectrum interference materials[D]. Nanjing: Nanjing University of Science and Technology, 2012. (in Chinese) [11] Li Y, Qiao X J, Ren Q G, et al. Preparation and microwave absorbing properties NiCo/NiFe coated carbon fibers [J]. Aerospace Materials and Technology, 2012, 42(3): 29-33. (in Chinese) [12] Wang H X, Liu D Z, Song Z B, et al. Study on infrared extinction performance of carbon nanofibers smoke screen [J]. Infrared Technology, 2007, 29(6): 324-327. (in Chinese) [13] Li K, Wang X Y, Gao Y Q, et al. Complex refractive index and extinction performance ofgraphene in infrared bands [J]. Infrared and Laser Engineering, 2021, 50(4): 20200246. (in Chinese) doi: 10.3788/IRLA20200246 [14] Santhanam K S V. Graphene: Preparations, properties, appli-cations, and prospects [J]. MRS Bulletin, 2020, 45(10): 867. doi: https://doi.org/10.1557/mrs.2020.262 [15] ChemT J, Moosa A A, Abed M S. Graphene preparation and graphite exfoliation [J]. Turkish Journal of Chemistry, 2021, 45(3): 493-519. doi: 10.3906/kim-2101-19 [16] Li X D. Preparation of graphene oxide and its application as substrates for SERS [J]. Journal of Chemistry, 2018, 2018: 1-5. doi: 10.1155/2018/8050524 [17] Wang X Y. Testing the infrared extinction characteristics of red phosphorous smoke screen by thermal imaging method [J]. Journal of Anti-Chemistry, 2007(3): 63-65. [18] Zhao X Y, Hu Y H, Gu Y L, et al. A comparison of infrared extinction performances of bioaerosols and traditional smoke materials [J]. Optik, 2019, 181: 293-300. doi: 10.1016/j.ijleo.2018.12.052 [19] Chen H, Gao X B, Xu X C, et al. Middle and far infrared interference properties of CNT/graphene/carbon composites smoke screen [J]. Chinese Journal of Energetic Materials, 2019, 27(3): 249-254. (in Chinese) [20] Liu Q H, Liu H F, Dai X D, et al. Infrared interfering performance of graphene smoke screen [J]. Infrared Technology, 2019, 41(11): 1071-1076. (in Chinese) [21] Chen Z. Study on preparation and extinction properties of composite materials as combustion-type anti-infrared smoking agent [D]. Nanjing: Nanjing University of Science & Tech-nology, 2018. (in Chinese)