環(huán)境空氣中的3D打印耐火金屬圖案：面向高溫傳感器

來源： i學(xué)術(shù)i科研

在火力發(fā)電,、油井鉆探和航空航天等極端工業(yè)環(huán)境中,，對關(guān)鍵環(huán)境參數(shù)進(jìn)行實(shí)時監(jiān)測對于提高可靠性和防止故障具有重要意義,。難熔金屬(如鉬和鎢)及其合金具有耐高溫,、耐腐蝕以及對熱應(yīng)力和機(jī)械應(yīng)力具有出色的耐久性,，因此是高溫電子器件的理想候選材料。

最先進(jìn)的增材制造(AM)技術(shù)為難熔金屬的工程化提供了新的可能性,，其中以粉末床基方法(包括激光粉末床熔融和電子束粉末床熔融)的研究最為廣泛,。盡管粉末床基增材制造方法具有高精度和能夠制造復(fù)雜形狀的優(yōu)點(diǎn)，但由于對保護(hù)環(huán)境的嚴(yán)格要求,、對高質(zhì)量粉末床的依賴以及與其他電路制造工藝的兼容性差等限制，該方法并不適合制造電子設(shè)備,。另外,，基于油墨擠壓的3D打印，即首先用含有粘合劑的金屬油黑打印圖案然后進(jìn)行熱處理以減少添加劑并燒結(jié)金屬結(jié)構(gòu),，是一種具有低成本和高靈活性的制造導(dǎo)電金屬圖案的吸引人的選擇,。傳統(tǒng)的熔爐燒結(jié)法加熱時間長,、能耗高，而激光燒結(jié)具有高分辨率和高功率密度的特點(diǎn),，已成為對印刷圖案進(jìn)行原位熱處理的有效方法,，并已用于制造銅、銀和鋅的高導(dǎo)電電路,。然而,，金屬材料通常對從可見光到近紅外波長的光具有較高的反射率，導(dǎo)致激光燒結(jié)過程中能量利用率較低,，加熱溫度有限,。此外，激光輻射的增加可能會導(dǎo)致嚴(yán)重的氧化和過度燒蝕,，而不是更好的燒結(jié)效果,。

研究成果
難熔金屬具有耐高溫、耐腐蝕和機(jī)械強(qiáng)度優(yōu)異等優(yōu)點(diǎn),，可用于高溫電子設(shè)備,，但其熔化溫度高、加工性差,，給制造帶來了挑戰(zhàn),。清華大學(xué)臧浠凝&胡楚雄&汪澤教授團(tuán)隊報告了一種直接墨水書寫和焦油介導(dǎo)激光燒結(jié)(DIW-TMLS)技術(shù)，用于制造高溫應(yīng)用中的3D耐火金屬器件,。利用煤焦油作為粘合劑,，設(shè)計出了具有高粘度和更強(qiáng)光吸收性的金屬油墨。打印出的圖案在環(huán)境中使用低功率(<10 W)激光燒結(jié)成無氧化的多孔金屬結(jié)構(gòu),，只需一個步驟就能快速制造出獨(dú)立的三維結(jié)構(gòu),。本文介紹了幾種應(yīng)用，包括基于分形圖案的應(yīng)變計,、在半球上圖案化的電子小天線(ESA)以及工作溫度高達(dá) 350℃并能承受火焰灼燒的無線溫度傳感器,。DIW-TMLS 技術(shù)為各種金屬材料的快速圖案化鋪平了一條可行的道路，它具有廣泛的適用性,、高靈活性和三維適形性,，拓展了惡劣環(huán)境傳感器的可能性。相關(guān)研究以“Printing Three-Dimensional Refractory Metal Patterns in Ambient Air: Toward High Temperature Sensors”為題發(fā)表在Advanced Science期刊上,。

圖文導(dǎo)讀

Figure 1. a) Schematic illustration of direct ink writing and tar-mediated laser sintering (DIW-TMLS). Photographs showing the b) printing and c) laser sintering processes of a conformal spiral pattern on a ceramic hemisphere. d) Schematic of a wireless sensor based on refractory metal pattern operating in high-temperature environments.

Figure 2. Characterization of the metal-tar inks. a) Comparison of absorption spectrum between metal-tar inks and pure metal powders. b) Apparent viscosity as a function of shear rate showing the shear-thinning behavior. c) Storage modulus (G’) and loss modulus (G’’) as functions of shear stress showing the yield behavior. Scanning electron microscopy (SEM) and optical images of the printed d) Mo-tar and e) Cu-tar filaments shows high printing resolution. Three-dimensional (3D) surface profiles and cross-section views of the printed f) Mo-tar and g) Cu-tar filaments.

Figure 3. Effects of laser scanning parameters on microstructures,， phases， and electrical conductivity of the sintered pattern. a) Scanning electron microscopy (SEM) and optical images of the sintered Cu-tar filaments under different laser powers and scanning rates. Scale bar: 10 μm. b) X-ray diffraction (XRD) patterns of the sintered Cu-tar filaments under different laser parameters. Each curve corresponds to a subgraph in (a). c) Variation of resistivity of the sintered Cu-tar pattern with laser power and scanning rate. d–f) SEM and optical images (Scale bar: 20 μm), X-ray diffraction (XRD)patterns,， and resistivity of sintered Mo-tar filaments under different laser parameters.

Figure 4. Metallic patterns fabricated by direct ink writing and tar-mediated laser sintering (DIW-TMLS) using Cu-tar ink for various applications. a)Photograph of a fractal pattern-based strain gauge printed on an anodized aluminum substrate. b) Schematic of three-point bending test for the strain gauge. c) Resistance change of the strain gauge in response to the cyclic flexural strain. d) Photograph of a conformal spiral antenna printed on a quartz glass hemispherical substrate. e) Simulated and measured reflection coefficient (S11) of the hemispherical antenna. f) Key performance indexes of the hemispherical antenna. g) Schematic of creating self-supported 3D structures by mid-air sintering. h) Photographs showing the printing process of a freestanding helical structure.

Figure 5. Molybdenum pattern-based wireless high-temperature sensor. a) Photograph of the temperature sensor with a split-ring resonator (SRR)pattern printed on ceramic substrate. b) Schematic showing the charge distribution in the metal rings under excitation of polarized electromagnetic waves. c) Schematic of wireless temperature sensing. d) Equivalent circuit of the wireless sensing system. e) Measured reflection coefficient (S11) spectra at different temperatures. f) Variation of the resonant frequency of the sensor with respect to temperature. g) Fire resistance testing of the sensor. The scanning electron microscopy (SEM) images show no significant change in the surface morphology after accumulated 30 s of flame treatment.

總結(jié)與展望
總之,，作者提出了一種DIW-TMLS技術(shù)，用于在環(huán)境大氣中快速制備金屬導(dǎo)電圖案的3D技術(shù)。通過將焦油作為粘結(jié)劑,，開發(fā)了具有增強(qiáng)光吸收和抗氧化性能的粘性金屬油墨,。銅和鉬基油墨都可以用功率小于10 W的紅外激光在環(huán)境空氣中不燒結(jié)，比選擇性激光燒結(jié)所需的低近2個數(shù)量級,。從燒結(jié)機(jī)理的形態(tài),、組成和電學(xué)性能等方面進(jìn)行了研究。在優(yōu)化的激光參數(shù)下,，燒結(jié)鉬型的電阻率達(dá)到與大塊金屬的電阻率相同的數(shù)量級,。演示了一種基于分形模式的應(yīng)變儀和保形半球形天線，驗(yàn)證了DIW-TMLS的高靈活性和廣泛的適用性,。此外,，通過同時實(shí)現(xiàn)打印和激光燒結(jié)，可以創(chuàng)建三維獨(dú)立架構(gòu),。最后,，開發(fā)了一種基于鉬模式的無線溫度傳感器，它能夠在高達(dá)350°C的高溫下運(yùn)行和持久的燃燒環(huán)境下運(yùn)行,。所提出的DIW-TMLS技術(shù)突破了耐火金屬的加工極限,，為高溫傳感器的快速成型提供了一條可行的途徑。

文獻(xiàn)鏈接
Printing Three-Dimensional Refractory Metal Patterns in Ambient Air: Toward High Temperature Sensors
https://doi.org/10.1002/advs.202302479