Combined proximal humerus fracture and acromioclavicular joint injury: A case report

Journal Pre-proof Combined proximal humerus fracture and acromioclavicular joint injury: A case report Chaiwat Chuaychoosakoon, Prapakorn Klabklay

PII:

S2210-2612(20)30112-7

DOI:

https://doi.org/10.1016/j.ijscr.2020.02.038

Reference:

IJSCR 4357

To appear in:

International Journal of Surgery Case Reports

Received Date:

18 November 2019

Revised Date:

11 February 2020

Accepted Date:

18 February 2020

Please cite this article as: Chuaychoosakoon C, Klabklay P, Combined proximal humerus fracture and acromioclavicular joint injury: A case report, International Journal of Surgery Case Reports (2020), doi: https://doi.org/10.1016/j.ijscr.2020.02.038

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Research Article

Effect of Ni content on high power laser ablation behavior of coatings sprayed by Ni covering graphite/SiO2 powders

Wenzhi Li1, 2, Lihong Gao1, 2, *, Zhuang Ma1, 2, Yanbo Liu1, 2, Fuchi Wang1, 2, Jiawei Wang3, Lijun Wang3, Hezhang Li1, 2

School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081,

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1

China 2

National Key Laboratory of Science and Technology on Materials under Shock and Impact, Beijing

100081, China

State Key Laboratory of Laser Interaction with Matter, Northwest Institute of Nuclear Technology,

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Xi’an 710024, China

*Corresponding author.

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E-mail address: [email protected] (L.H. Gao).

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[Received 26 June 2019; Received in revised form 11 November 2019; Accepted 23 November 2019]

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Faced with the challenge of high energy ablation problems, especially for laser ablation, effective energy dissipation protective materials fabricate by efficient preparation method

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is a feasible solution. The Ni-graphite/SiO2 coatings with different Ni content were prepared by plasma spraying method with optimized plasma spraying parameters. All coatings are pure without oxidation and dense. Their ablation behaviors were investigated by high power continuous wave laser. The results indicate that the Nigraphite/SiO2 coating with appropriate Ni content could realize the purpose of energy consumption by endothermal reaction of graphite/SiO2 and reflection improvement. High Ni content will block the occurrence of endothermal reaction of graphite/SiO2 and increase the heat diffusion to interior part of coating, which can make the ablation

situation of coating more serious. Key words: Ablation behavior; High power laser; Plasma sprayed coating 1. Introduction In some high-energy ablation application fields, especially high-temperature ablation area, many novel ablative materials based on new reinforcements have been studied in the last couple of years [1-5]. Among these materials, the combination of SiO2 and resin exhibits excellent ablation resistant property and widely research [6, 7]. To date, several important achievements related to high-temperature ablation mechanisms have been obtained. Srikanth et al. [8] introduced the

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ablation resistance of nano SiO2 modified the carbon-phenolic composites. They found that during the high-temperature ablation, the melt of SiO2 could not only consume part of heat energy, but also form a viscous layer acting like binder and holding the whole composite. Besides, the reaction

between carbon and SiO2 can reduce the deposited heat energy and generated SiC can withstand

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aerodynamic shear forces effectively, thereby enhancing the ablation resistance [9]. Ma et al. [10]

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found that the energy-consuming reactions between SiO2 and C provide strong heat consumption capacity. The generated SiC, as an ultra-high temperature ceramic, can further against the

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subsequent incident energy. Therefore, SiO2 is considered as a feasible additive to modify the ablation property of composites [11-13].

In recent years, high power continuous wave laser method has been considered as a new

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emerging tool to evaluate the ablation properties of materials [14]. SiO2 modified resin materials may still have good high-power energy resistant property. However, compared with polymers,

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inorganic composites have higher ablation-resistant temperature and lower mass ablation rates. Hence, inorganic SiO2 and carbon may have more widespread ablation resistant application

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potential, particularly applying on the surfaces of the key components. Although bulk graphite/SiO2 composites have been proved owning good laser resistant properties [15], compared with bulk composite materials, preparing on the surface in form of functional coating is more convenient. Atmospheric plasma spraying, as a thermal spray technique, has been widely used in numerous

many areas such as automotive industry, medicine, aeronautics, and astronautics [16, 17]. Also, it has been proved to be efficient and economical for coating preparation [18, 19]. Combining with the densification and modification strategies of feedstock powders and optimized plasma spraying parameters we achieved in our previous work [20], dense Ni-graphite/SiO2 coating can be obtained.

However, due to the different structures, the laser ablation behavior of coating may totally differ from that of bulk materials. Also, there are rare detailed studies about the laser ablation behavior of novel Ni modified graphite/SiO2 coatings and it may provide a new development in the application of this material into an extreme environment. Therefore, it is worthy to study the laser ablation behaviors of inorganic Ni-graphite/SiO2 coatings. In this work, the laser ablation behaviors of Ni-graphite/SiO2 coatings with different Ni content were evaluated. The phase and microstructure before and after laser irradiation were characterized to evaluate the ablation behaviors of coatings. Combining with optical reaction test and backsurface temperature evolution of samples, the detailed laser energy consumption ability of coating

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was also discussed. 2. Experimental

According to our previous work [20], Ni covering spray-dried and heat-treat densified

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graphite/SiO2 powder was implemented by hydrothermal reduction with pressurized hydrogen. The activator was 0.2 wt.% anthraquinone (AR, Aladdin Industrial Corporation). The commercially available flake graphite (approximately 10 μm, AR, Forsman Scientific Co., Ltd, China),

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amorphous SiO2 powders (approximately 20 μm, AR, Forsman Scientific Co., Ltd, China) and

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aqueous solutions of NiSO4, NH3·H2O (Fanmeiya Materials Co. Ltd., China) were used to fabricate this shell-core structured Ni-graphite/SiO2 powders. Based on the processing parameters confirmed by our previous work, we still chose the same heat treatment and hydrothermal reduction

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parameters as 1400 °C for 2 h and 3 MPa H2 pressure at 800 rpm, respectively. The mass ratio of Ni and raw graphite/SiO2 mixture was designed as approximately 25% and 50%.

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Then the modified Ni covering graphite/SiO2 powers with different Ni content were used to deposite related coatings (for different Ni content, we denoted 25 wt.% and 50 wt.% Ni contained

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coatings as NGS-1 and NGS-2 coatings hereafter). The coatings were prepared by an atmospheric plasma-spraying system (APS, SG100, Praxair, USA), with Ar and He as the primary and secondary gases, respectively. Before spraying, the surface of mild steel substrates was cleaned by acetone and degreased. The substrates were then grit-blasted to roughen their surfaces and thus enhance the bonding strength of the coating. Modified Ni covering graphite/SiO2 powder and commercial NiCoCrAlY powders (CO-210, Praxair, America) were deposited as top layer and bond layer, respectively. The additive of bonding layer contributes to reduce the thermal expansion mismatch between the top coating and substrate. According to the high deposition rates and dense surface

morphology shown in our previous work [20], same modified plasma spraying parameters of top layer and bond layer are chosen, shown in Table 1. All coatings in this work had the same thickness of about 0.3 mm which consisted of a 0.1 mm bonding layer and a 0.2 mm top NGS layer. The thickness of substrate was around 2 mm. The phase composition of the corresponding coatings was characterized by X-ray diffraction (X’Pert PRO MPD, PANalytical Inc., Holland) with Cu Kα radiation, and the XRD patterns were analyzed by the Jade 10.0 software. The surface and cross-section morphologies of each kind of coatings were studied by scanning electron microscopy with secondary electrons (SEM, HITACHI S4800, Japan). All cross-section samples are prepared, cut and polished at atmospheric

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environment. The chemical composition was identified by energy dispersive spectroscopy (EDS, Oxford Instruments Co. Ltd., Oxfordshire, UK). Optical reflectivity was measured by UV/VIS/NIR spectrophotometer (Varian, Cary 5000, USA) with an integrating sphere. The tensile bond strengths

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of all coatings were tested using the Multi-Specimen-Test Machine analysis system (WDW-1000, China).

The samples were irradiated by an infrared commercial Nd:YAG continuous laser with 1070 nm

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wavelength. The spot area is 10 mm ×10 mm. The evolution of ablation behaviors of all coatings was investigated under the laser parameters of 1000 W/cm2, 10s. Meanwhile, the back-surface

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temperature of substrate was detected by K-type ceramic thermocouple and a real-time data

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recording system was used to analyze the obtained temperature data.

3. Results and discussion

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3.1 Phase and microstructure of NGS-1 and NGS-2 coatings The XRD patterns of NGS coatings with different Ni content before laser irradiation are shown in

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Fig. 1. The patterns show that the composition of two NGS coatings purely consists of graphite, SiO2 and Ni. According to the comparison of the main diffraction peak intensity of graphite and Ni, the more Ni contains, the greater the intensity of diffraction peak exhibits, which is in agreement with the Ni content design of raw powder materials. K-value method was used to calculate the composition content of each coating according to the intensity of graphite and Ni peaks. The results shown in Fig. 2 indicate that the less Ni content, the more graphite/SiO2 mass loss of coating happens, which is hard to avoid. Besides, it is noteworthy that the XRD pattern of two coatings shows wider diffraction peaks, especially for Ni component. This phenomenon is caused by repaid

heating and melting in plasma flame, and then fast cooling and solidifying on the substrate of Ni phase, which suggests that Ni exhibits decreased crystallinity. The absence of some strong peaks of NiO phase at 37.248° and 62.878° indicates that no oxidization occurred in metallic component Ni of coatings during plasma spraying deposited by the gas protection and our optimal parameters. The surface and cross-section SEM morphologies of NGS-1 and NGS-2 are shown in Figs. 3 and 4, respectively. Generally, the as-sprayed powders would melt and compact on the substrate as a splat after be heated and sped up by the plasma jet. But for Ni covering graphite/SiO2 powders, during plasma spraying, graphite and SiO2 are expected to contact closely, so Ni is designed to be bonding phase to increase the deposition rate of the coatings. Therefore, it would be difficult to

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form flattened coatings. From Fig. 3(a), it can be seen that the coating is indeed not that flat as general plasma sprayed coating [21]. Also due to the low Ni content (25 wt.%), the as-sprayed

molten state of coating is poor and the shape of raw materials including graphite and SiO2 are easily

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observed. Magnified morphology shown in Fig. 3(b) reveals that the molten Ni drops just deposited sporadically on the coating surface. From the magnified cross-section morphology near surface on

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the top right corner of Fig. 3(b), obvious fluctuations can be observed. Even so, there are no obvious pores or cracks existed and the coating still exhibits dense structure, which contributes to

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reduce the absorption of laser energy by defects. Cross-sectional morphology of NGS-1 coating is presented in Fig. 3(c). It can be found that the NGS-1 coating exhibits considerably low porosity compared with several conventional ceramic coatings [22-25]. Compared with the available

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literature related to Ni-coated graphite-containing coatings [26], the compactness of coating microstructure prepared by modified NGS powders is markedly improved. This compact structure

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of the coating is attributed to the following reasons. Firstly, the particle size of feedstock powders is very small. Together with the impact action of subsequent sprayed powder, there is no large

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overlapping pores appear between the powders. Secondly, surface heating effect caused by the plasma jet provides enough energy to melt the thin Ni coating layer, so the well-melted Ni has a good effect on filling the pores. Besides, Ni maintains a separating distribution state, while graphite and SiO2 shows a continuous state. This materials distribution state has the positive effect to guarantee the occurrence of endothermal reaction between graphite and SiO2 under high power laser irradiation without reducing the bonding strength of the coating (6.39 MPa). With the Ni content of as-sprayed powder increase to 50 wt.%, more flat surface morphology can be observed from Fig. 4(a), which is more obvious from the magnified cross-section morphology

near surface in Fig 4(b). Moreover, continuous molten Ni layer was formed after plasma spraying, which is because the selected optimal plasma spraying parameters can ensure Ni phase to reach a good molten state, allowing the molten Ni to get fully deform and connection. As a result, more molten Ni fills the gaps and asperities among the previously deposited splats and promotes to form a denser cross-sectional structure than that of 25 wt.% Ni contained coating (shown in Fig. 4(c)). However, although NGS-2 coating exhibits less porosity structure, the Ni connects with each other forming continuous Ni layer in both horizontal and vertical directions. Continuous Ni layer may contribute to improve the thermal diffusion of coating and relieve surface heat concentration under laser irradiation. Besides, the increase of Ni content also improves the bonding strength of NGS-2

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coating to 8.76 MPa. However, this kind of distribution of Ni phase block the contact of

graphite/SiO2 mixture phase, which may be harmful to the occurrence of endothermal reaction

between graphite and SiO2, and reduce the energy dissipation by reaction. Moreover, due to the high

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temperature characteristic of plasma jet, a small consumption of graphite and SiO2 cannot be

avoided, so the volume ratio of mixture graphite/SiO2 and Ni in prepared coating may differ from

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that of raw Ni-graphite/SiO2 powder.

3.2 Laser ablation behaviors of NGS-1 and NGS-2 composite

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After all coatings irradiated under 1000 W/cm2 laser for 10 s, the phase structure, macro- and micro-structure are investigated. The laser ablation behaviors of NGS-1 and NGS-2 coatings are totally different and some interesting phenomenon appeared. Fig. 5 shows all phase structure and

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morphological information of NGS-1 coating after laser ablation. It can be seen from the Fig. 5(a) that macro-morphology of NGS-1 coating irradiation area turns to green, which indicates that some

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reactions were taken place during the laser ablation. XRD patterns of ablation area in Fig. 5(b) clearly illuminate the phase composition after laser irradiation. The appearance of SiC (111), (220)

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and (311) crystal planes proves the occurrence of endothermic reaction between graphite and SiO2, and the incident laser provides sufficient kinetic energy to initiate the reaction. Meanwhile, the laser energy also drives the crystallization of Ni, which is equivalent to making a heat treatment to the low crystallized Ni. It can be seen that the diffraction peak of Ni become sharper. Besides, no diffraction peaks of mild steel were detected, which means the coating exhibits the laser resistant and there is no coating penetration behavior happen. In addition, the laser ablated NGS-1 coating exhibits a special ablative morphology, shown in Fig. 5(c), that two different regions were formed apparently. The flat and smooth region corresponds to the area where the molten Ni is enriched,

while the region consists of tiny particles are mainly related to the graphite, SiO2 and generated SiC mixture area. According to the magnified morphology of boundary area (shown in Fig. 5(d)), two different regions can be observed clearly, where are defined as reaction region and molten Ni region. In the reaction region, many fine isometric particles are generated, which are confirmed as SiC by EDS test results shown in Fig.5(d). In molten Ni region, partially covered Ni layer could protect the generated SiC from subsequent laser ablative oxidation and maintain the positive effect of SiC. At the same laser irradiation parameters with increased Ni content, the macro-ablation performances of NGS-2 coating are totally different from that of NGS-1 coating. After laser

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ablation, the macro-morphology of NGS-2 coating presented in Fig. 6(a) shows the characteristic of transpiration cooling materials material [27]. There is no obvious green matter generated, which indicates that the endothermal reaction of graphite/SiO2 may do not happen. Further proof is

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needed. However, many spherical particles can be observed at the surface, which was formed by solidification after Ni melting. The melt of Ni has the positive effect to consume part of incident

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laser energy and relief the serious ablation situation of coating. XRD patterns shown in Fig. 6(b) illuminate the variation of phase during laser irradiation that oxidation of Ni was happened and no

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SiC was detected indeed. Although according to the appearance of NiO (111), (200) and (220) crystal planes, the oxidation of Ni can be confirmed, its low peak intensity comparing with Ni phase peak indicates that the oxidation of Ni is not that severe. Combining the observation of molten Ni

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ball, Ni still dominates the main composition of coating. From Fig. 6(c) the surface morphology, the Ni molten balls are observed. Also, there are many cracks and pores were left, which supposed to be

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the molten Ni diffusion channels under high power laser irradiation. It can be concluded that at high Ni content coating, the enrichment of Ni is more obvious under laser ablation. At the flat area near

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to the Ni molten ball shown in Fig. 6(d), many tiny molten Ni locates on the surface and boundary of graphite and SiO2 particle, which means Ni is still enriched in the flat area. The existence of Ni reduces the connection between graphite and SiO2, and blocks the occurrence of their reaction, which is reason why the reaction between graphite and SiO2 did not happen. 3.3 Effect of Ni content of NGS coating on laser energy consumption Laser, as a kind of light, reflection is an effective way to dissipate the incident laser energy. Therefore, coating surface reflectivity is the most important property to evaluate the laser resistance of coating. Moreover, in order to evaluate the laser energy consumption ability of NGS coating with

different Ni content, the highest back-surface temperature was also used. Before and after laser ablation, the reflectivity of all coatings is presented in Fig. 7. Because the reflectivity of two as-sprayed coatings is almost the same, we just list one reflection curve in Fig. 7. It can be seen that the coating reflectivity before laser irradiation is very low, just around 11%-12%. NGS-1 coating has higher reflectivity than NGS-2 coating, which may be caused by the new phase generation in NGS-1 coating, but they all higher than the reflectivity of as-sprayed coating. This situation indicates that during the laser irradiation, the effect of laser heating increases the surface reflectivity. It should be noted that during laser irradiation, the higher the reflectivity of the coating is, the more incident laser energy could be dissipated. Since NGS-1 coating exhibits the higher

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reflectivity (35%) at 1070 nm, compared with NGS-2 coating (16%), NGS-1 coating may have better laser energy consumption ability.

The back-surface temperature curve of the central point of laser irradiated coating can reveal the evolution of back-surface temperature. The corresponding results are shown in Fig. 8. After

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1000W/cm2, 10 s laser irradiation, the highest back-surface temperature of NGS-2 coating is

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1025 °C, which almost reaches the application temperature threshold of mild steel and obvious high temperature ablation traces were appeared. However, the highest back-surface temperature of NGS-

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1 coating is just 856 °C, which is almost 170 °C lower than that of NGS-2 coating and still in the allowable application temperature. Indeed, NGS-1 coating exhibits better laser energy consumption ability, which was related to three reasons. The occurrence of endothermal reaction between

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graphite and SiO2, and the improvement of reflectivity during laser irradiation in NGS-1 coating together increase the consumption of incident laser energy. What’s more, although the continuous

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Ni structure in NGS-2 coating raises the energy diffusion in horizontal direction, it could also increase the energy diffusion in vertical direction. As a result, the increase of back-surface

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temperature of NGS-2 coating is higher than that of NGS-1 coating. According to the analysis above, the dense graphite/SiO2 mixture with appropriate Ni bonding

phase could not only make the coating maintain a relatively high bonding strength, but also improve the laser energy consumption ability greatly. Faced with the extreme thermal environment exposed to laser, this novel coating with high energy consumption ability may have the potential to prevent the substrate from thermal damage.

4. Conclusions

The NGS coatings with different Ni content were prepared by plasma spraying with optimized plasma spraying parameters. Their ablation behaviors were studied by high power continuous wave laser. The main conclusions obtained are as follows: (1) All as-sprayed coatings are dense and pure without oxidation. Ni phase illuminates separate and continuous distribution states in NGS-1 and NGS-2 coatings, respectively, which plays a significant role in subsequent laser ablation behaviors. (2) After laser ablation, endothermal reaction between graphite and SiO2 happened in Ni separating distributed NGS-1 coating. Meanwhile, the generation of SiC also improves the reflection of coating. These two factors improve the energy consumption ability of NGS-1 coating

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and reduce the highest back surface temperature.

(3) Only melt and oxidation of Ni happened in Ni continuous distributed NGS-2 coating.

Continuous Ni structure not only blocks the reaction of graphite/SiO2, but also promotes the heat

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diffusion in vertical direction of coating. Finally, the ablation situation of NGS-2 coating is more serious. Therefore, the NGS coating with appropriate Ni content has the great potential to apply in

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the field with high energy protection requirements.

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Acknowledgement

This work was financially supported by the National Natural Science Foundation of China (No. 51302013).

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References

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Table list: Table 1 APS parameters of NGS coating. Primary

Secondary

Carrier

Powder

gas

gas

Current gas

feed

Ar

He

(A)

Ar

rate

(L/min)

(L/min)

(L/min)

(g/min)

Bond layer

56.6

4.7

750

4.7

Top layer

42.5

16.5

850

4.7

Spray Layer

Gun

distance speed (mm/s)

2.0

100

500

3.0

75

500

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(mm)

Figure list:

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Fig. 1. XRD patterns of NGS coatings with different Ni content before laser irradiation.

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Fig. 2. Mass ratio of two kinds of plasma sprayed Ni-graphite/SiO2 coatings.

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Fig. 3. SEM morphologies of NGS-1 coating: (a) surface morphology; (b) magnified surface

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morphology; (c) cross-section morphology.

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Fig. 4. SEM morphologies of NGS-2 coating: (a) surface morphology; (b) magnified surface

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morphology; (c) cross-section morphology.

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Fig. 5. Sample information of NGS-1 coating irradiated at 1000 W/cm2 for 10 s：(a) Surface

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macro-morphology; (b) XRD pattern at irradiation area; (c) SEM surface morphology and (d)

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magnified SEM surface morphology & EDS results.

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Fig. 6. Sample information of NGS-2 coating irradiated at 1000 W/cm2 for 10 s.

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and (d) magnified SEM surface morphology.

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(a) Surface macro-morphology; (b) XRD pattern at irradiation area; (c) SEM surface morphology

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Fig. 7. Reflectivity of as-sprayed coating and NGS1, NGS2 coatings after laser ablation.

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Fig. 8. Back-surface temperature of NGS-1 and NGS-2 coatings during laser irradiation.