**1. Introduction**

The development of biomaterials has created several significant benefits for the general population over the last few decades, including dental implants, prosthetics, artificial arteries, and contact lenses [1]. These benefits have been either for the purpose of correcting problems or have been esthetic in nature [2].

Various materials have been used as biomaterials. Titanium alloys [3, 4] are among these materials because they have excellent mechanical strength/density ratio, excellent corrosion resistance, and biocompatibility.

The mechanical properties [5], corrosion, and wear resistance [6] of a material are largely dictated by the microstructure. Titanium alloys are favorable because a wide spectrum of microstructures can be obtained, depending on the chemical composition and the processing. This makes titanium alloys advantageous because they allow the desired microstructure to be obtained for specific requirements, as low elastic modulus, for example, [7, 8].

Titanium exists in two allotropic forms. At low temperatures, the so-called alpha phase (with hexagonal compact crystalline structure) is presented, and the beta phase (with body-centered cubic crystalline structure) emerges above 883°C. Some elements called beta stabilizers, such as niobium, molybdenum, iron, vanadium, and nickel, lead to a decrease in beta transus temperature (the transition from alpha to beta phase) when added to the forming titanium alloys and may stabilize this phase at room temperature. These phases determine a classification of titanium alloys: alloys containing only α stabilizers at this phase are known as α alloys, alloys containing 1–2% beta stabilizers and about 5–10% of beta phase are called near-α, alloys containing increased amounts of beta stabilizers resulting in 10–30% of beta phase are called α + β alloys, and alloys containing increased amounts of beta stabilizers where this phase can be retained by quick cooling are known as β metastable phases (these alloys decay into α + β in aging treatments) [9]. Beta transus temperature fulfills a central role in the microstructure's evolution, and so it is of great importance to determine the type of technological processing and heat treatment, which also includes doping with oxygen or nitrogen, whose elements present in the crystalline lattice can significantly affect the properties of the same [10].

In addition to interfering significantly in the structure and microstructure of titanium alloys, substitutional elements interfere in mechanical properties such as elastic modulus and hardness to the extent that they stabilize phases with different properties [11, 12]. The α phase, with a greater packaging factor of atoms, has a greater elastic modulus in relation to phase β, due to greater proximity between the atoms. Regarding toughness, it is usually greater in α phase, which contains fewer plans of slipping in relation to β phase, making the material harder and brittle [13]. However, depending on the alloy and the processing performed, alloys with a β structure have similar hardness [14].

concentration is, the greater the amount of this intermetallic is. By the decay of the β-transus curve, it is concluded that the addition of nickel favors the stabilization of this phase. The eutectoid reaction β ! α + Ti2Ni occurs at 765°C. By the lever rule, in the field β + Ti2Ni, the amount of Ti2Ni is lower in relation to α + Ti2Ni field, in

*Structure, Microstructure, and Some Selected Mechanical Properties of Ti-Ni Alloys*

*DOI: http://dx.doi.org/10.5772/intechopen.86717*

For example, for an alloy with 10 wt% nickel that underwent a homogenization heat treatment at 1000°C, followed by slow cooling, in equilibrium conditions, at this temperature, the alloy presents the β phase of titanium. With cooling, it begins to precipitate the intermetallic phase Ti2Ni. At a temperature just above 765°C, the precipitates of Ti2Ni proeutectoid phase are found in a β matrix of eutectoid composition and just below 765°C and are found in the eutectoid matrix, with a granular microstructure of α and Ti2Ni phases intercalated. From there, the intermetallic

Theoretically, the phases present in these alloys at room temperature are α + Ti2Ni; however, when the eutectoid reaction is suppressed, as in the case where the cooling is not done in perfect equilibrium condition, there is the possibility of β-phase retention at room temperature, the higher the nickel concentration is [24]. According to Ti-Ni binary diagram, a eutectic L ! β + Ti2Ni to 942°C occurs at a concentration of 28.4 wt% of nickel, <700°C in relation to the melting point of pure titanium (1670°C), thus decreasing the melting point and conforming temperature. Therefore, in the case of alloys with 15 and 20 wt% of nickel, at some point during the melting, there is the possibility of developing a microstructure composed of preeutectic precipitates of the β phase in a eutectic matrix, although the melting is not

The Ti-Ni alloys were prepared using commercially pure titanium (Cp-Ti) (99.7% purity, Aldrich Inc., USA) and nickel (99.5% purity, Camacam Industrial, Brazil). The ingots were obtained by arc melting, using a water-cooled copper crucible and an argon-inert atmosphere. The melting was held five times to ensure the homogeneity of the produced ingots. Samples were prepared with 5, 10, 15, and 20 wt% of nickel. Chemical analysis of the samples was performed using an inductively coupled plasma optical emission spectrometry (ICP-OES), Varian, Visa

Ti2Ni composes both precipitates and the eutectoid matrix.

the same concentration.

*Phase diagram of the Ti-Ni system [23].*

**Figure 1.**

done under equilibrium conditions.

**13**

The presence of atoms in interstitial positions of the lattice (e.g., nitrogen and oxygen) strongly influences some properties, such as mechanical resistance and ductility [15]. These elements act as stabilizers in titanium's α and α' phases, increasing the temperature of β-transus [16, 17].

Nickel causes several adverse reactions in the human body, such as carcinogenic, genotoxic, mutagenic, cytotoxic, and allergenic effects [18]. However, when nickel is connected to titanium, these problems are minimized [19]. In a study of corrosion of titanium alloys with varied concentrations of nickel in Ringer's solution, it was found that the potential of disruption occurs from 29 wt% of nickel and decreases rapidly, indicating that alloys below this concentration present promising applications regarding corrosion [20, 21]. A later study on Hank's biocorrosion solution concluded that the daily release of nickel would be hundreds of times smaller than that contained in water intake [22]. In addition, the microhardness of these alloys is similar to enamel (310–390 HVN), which is suitable for use in dental screws [18].

Thus, it is of fundamental importance to understand the role of substitutional nickel in the structure, microstructure, and selected mechanical properties in Ti-Ni system alloys. To this purpose, Ti-Ni alloys containing 5, 10, 15, and 20 wt% of nickel were melted in an arc-melting furnace, mechanically processed by hot rolling, and subjected to heat treatment in a vacuum to cause homogenization and stress relief.

### **2. Materials and methods**

#### **2.1 Ti-Ni alloys**

The phase diagram of the Ti-Ni system is presented in **Figure 1**. This phase diagram shows that alloys considered in this chapter (5, 10, 15, and 20 wt% of nickel) present the phases α and β (both of titanium) and the intermetallic phase Ti2Ni, at high temperatures [23]. By the lever rule, the higher the nickel

*Structure, Microstructure, and Some Selected Mechanical Properties of Ti-Ni Alloys DOI: http://dx.doi.org/10.5772/intechopen.86717*

**Figure 1.** *Phase diagram of the Ti-Ni system [23].*

elements called beta stabilizers, such as niobium, molybdenum, iron, vanadium, and nickel, lead to a decrease in beta transus temperature (the transition from alpha to beta phase) when added to the forming titanium alloys and may stabilize this phase at room temperature. These phases determine a classification of titanium alloys: alloys containing only α stabilizers at this phase are known as α alloys, alloys containing 1–2% beta stabilizers and about 5–10% of beta phase are called near-α, alloys containing increased amounts of beta stabilizers resulting in 10–30% of beta phase are called α + β alloys, and alloys containing increased amounts of beta stabilizers where this phase can be retained by quick cooling are known as β metastable phases (these alloys decay into α + β in aging treatments) [9]. Beta transus temperature fulfills a central role in the microstructure's evolution, and so it is of great importance to determine the type of technological processing and heat treatment, which also includes doping with oxygen or nitrogen, whose elements present in the crystalline lattice can significantly affect the properties of the same [10]. In addition to interfering significantly in the structure and microstructure of titanium alloys, substitutional elements interfere in mechanical properties such as elastic modulus and hardness to the extent that they stabilize phases with different properties [11, 12]. The α phase, with a greater packaging factor of atoms, has a greater elastic modulus in relation to phase β, due to greater proximity between the atoms. Regarding toughness, it is usually greater in α phase, which contains fewer plans of slipping in relation to β phase, making the material harder and brittle [13]. However, depending on the alloy and the processing performed, alloys with a β

*Recent Advancements in the Metallurgical Engineering and Electrodeposition*

The presence of atoms in interstitial positions of the lattice (e.g., nitrogen and oxygen) strongly influences some properties, such as mechanical resistance and ductility [15]. These elements act as stabilizers in titanium's α and α' phases,

Nickel causes several adverse reactions in the human body, such as carcinogenic, genotoxic, mutagenic, cytotoxic, and allergenic effects [18]. However, when nickel is connected to titanium, these problems are minimized [19]. In a study of corrosion of titanium alloys with varied concentrations of nickel in Ringer's solution, it was found that the potential of disruption occurs from 29 wt% of nickel and decreases rapidly, indicating that alloys below this concentration present promising applications regarding corrosion [20, 21]. A later study on Hank's biocorrosion solution concluded that the daily release of nickel would be hundreds of times smaller than that contained in water intake [22]. In addition, the microhardness of these alloys is similar to enamel (310–390 HVN), which is suitable for use in dental screws [18]. Thus, it is of fundamental importance to understand the role of substitutional nickel in the structure, microstructure, and selected mechanical properties in Ti-Ni system alloys. To this purpose, Ti-Ni alloys containing 5, 10, 15, and 20 wt% of nickel were melted in an arc-melting furnace, mechanically processed by hot rolling, and subjected to heat treatment in a vacuum to cause homogenization and

The phase diagram of the Ti-Ni system is presented in **Figure 1**. This phase diagram shows that alloys considered in this chapter (5, 10, 15, and 20 wt% of nickel) present the phases α and β (both of titanium) and the intermetallic phase

Ti2Ni, at high temperatures [23]. By the lever rule, the higher the nickel

structure have similar hardness [14].

stress relief.

**2.1 Ti-Ni alloys**

**12**

**2. Materials and methods**

increasing the temperature of β-transus [16, 17].

concentration is, the greater the amount of this intermetallic is. By the decay of the β-transus curve, it is concluded that the addition of nickel favors the stabilization of this phase. The eutectoid reaction β ! α + Ti2Ni occurs at 765°C. By the lever rule, in the field β + Ti2Ni, the amount of Ti2Ni is lower in relation to α + Ti2Ni field, in the same concentration.

For example, for an alloy with 10 wt% nickel that underwent a homogenization heat treatment at 1000°C, followed by slow cooling, in equilibrium conditions, at this temperature, the alloy presents the β phase of titanium. With cooling, it begins to precipitate the intermetallic phase Ti2Ni. At a temperature just above 765°C, the precipitates of Ti2Ni proeutectoid phase are found in a β matrix of eutectoid composition and just below 765°C and are found in the eutectoid matrix, with a granular microstructure of α and Ti2Ni phases intercalated. From there, the intermetallic Ti2Ni composes both precipitates and the eutectoid matrix.

Theoretically, the phases present in these alloys at room temperature are α + Ti2Ni; however, when the eutectoid reaction is suppressed, as in the case where the cooling is not done in perfect equilibrium condition, there is the possibility of β-phase retention at room temperature, the higher the nickel concentration is [24].

According to Ti-Ni binary diagram, a eutectic L ! β + Ti2Ni to 942°C occurs at a concentration of 28.4 wt% of nickel, <700°C in relation to the melting point of pure titanium (1670°C), thus decreasing the melting point and conforming temperature. Therefore, in the case of alloys with 15 and 20 wt% of nickel, at some point during the melting, there is the possibility of developing a microstructure composed of preeutectic precipitates of the β phase in a eutectic matrix, although the melting is not done under equilibrium conditions.

The Ti-Ni alloys were prepared using commercially pure titanium (Cp-Ti) (99.7% purity, Aldrich Inc., USA) and nickel (99.5% purity, Camacam Industrial, Brazil). The ingots were obtained by arc melting, using a water-cooled copper crucible and an argon-inert atmosphere. The melting was held five times to ensure the homogeneity of the produced ingots. Samples were prepared with 5, 10, 15, and 20 wt% of nickel. Chemical analysis of the samples was performed using an inductively coupled plasma optical emission spectrometry (ICP-OES), Varian, Visa

model, from the sample's dissolution in acid medium. The presence of interstitial elements was carried out using a LECO TC-400 model gas analyzer. **Table 1** shows the chemical analysis of the produced samples.

the samples is important because it allows tests that require symmetrical samples, in addition to causing changes in microstructure and some properties that are of interest in the analysis. The samples were hot rolled as their mechanical processing. After slow cooling, a new heat treatment was performed for strain relief and recrystallization of microstructures as there were internal stresses and deformed microstructures due to an aggressive hot-rolling process. This treatment was

*Structure, Microstructure, and Some Selected Mechanical Properties of Ti-Ni Alloys*

The structural characterization of the samples was carried out by X-ray diffraction (XRD) measurements on a Rigaku diffractometer (D/Max-2100PC model). This included a Cu-Kα radiation of wavelength of 1.544 Å, 20 mA current, and a potential of 40 kV. The fixed mode, with step of 0.02° and time of 1.6 s, in the range of 10–90°, was used. The used method to data acquisition was the powder

For all samples of the Ti-Ni alloys used in this chapter and in all processing conditions, the microstructure was evaluated by both optical and scanning electron microscopy. To obtain the images, an Olympus model BX51M optical microscope with a camera connected to a computer and a SEM Carl Zeiss EVO/LS15 model with

Vickers microhardness tests were performed using a Shimadzu HMV model-2 microdurometer connected to a computer. The load used was 1.941 N for a time of 60 s. Following ASTM standards, almost 20 indentations were made in different regions of the sample [26, 27]. The dynamic elastic modulus was measured using Sonelastic® equipment (ATCP, Brazil). A boost in sample, the frequencies of vibration (through the Sonelastic® software), and damping were calculated and linked with the modulus of elasticity, according to standard ASTM E1876-01 [28].

**Figure 3** shows the X-ray diffractograms of all samples of Ti-Ni alloys after melting. During analysis of the X-ray diffractograms of samples after melting, it was observed that the addition of at least 10% in the weight of nickel caused the appearance of other phases beyond the α phase of titanium. There is the emergence of intermetallic Ti2Ni or Ti4Ni2O phases (which have the same diffraction pattern) [29, 30], and perhaps a small amount of β phase because nickel is a β-stabilizer element. It was also observed that the higher the amount of nickel was, the greater the amount of intermetallic Ti2Ni observed in the increased intensity of the peaks

Cascadan et al. studied casting Ti-5Ni (wt%) [31] and Ti-10Ni (wt%) [17] concerning structural and microstructural characterization. In the case of Ti-5Ni alloy, in the XRD measurements, single α and α'phases were observed, which were corroborated by optical micrographs, showing Widmanstatten-type morphology in the samples that were subjected to quick cooling from above β transus temperature, while larger lamellar structures were observed in samples whose slow-cooling process allowed large-scale diffusion processes. In the case of Ti-10Ni alloy, the structure and microstructure of the produced alloy were analyzed by XRD and SEM, and the results showed that the alloy presents predominantly titanium α phase, with proeutectoid lamellar precipitates in eutectoid matrix of α phase and intermetallic Ti2Ni.

performed at 1143 K for 24 h in a vacuum.

*DOI: http://dx.doi.org/10.5772/intechopen.86717*

**2.2 Sample's characterization**

the SmartSEM software were used.

**3. Results and discussion**

**15**

**3.1 Structural characterization**

and according to the system's phase diagram [23].

method [25].

It can be verified that the obtained ingots show the correct stoichiometry of nickel and a low amount of impurities and interstitial elements, displaying the good quality of prepared alloys.

To check the homogeneity of the produced alloys, the samples were subjected to a mapping of the elements that comprise the alloys using an electron dispersion spectrometry (EDS) technique that used an Oxford Instruments Incax-act model detector coupled to the scanning electron microscope (SEM) Carl Zeiss EVO/LS15 model. **Figure 2** shows the mapping of the elements titanium and nickel obtained by EDS in the produced alloys after melting. In all cases, homogeneous distribution of the elements titanium and nickel can be observed, showing that the melting was complete, without the presence of aggregates or segregates.

After melting, the ingots were submitted to a homogenization heat treatment that consisted of slowly heating the samples up to 1173 K for 24 h in a vacuum of 106 Torr, followed by slow cooling in the furnace. The mechanical processing of

#### **Table 1.**

*Chemical analysis of the Ti-Ni alloys.*

**Figure 2.** *EDS mapping of the elements Ti and Ni that make up the Ti-Ni alloys.*

#### *Structure, Microstructure, and Some Selected Mechanical Properties of Ti-Ni Alloys DOI: http://dx.doi.org/10.5772/intechopen.86717*

the samples is important because it allows tests that require symmetrical samples, in addition to causing changes in microstructure and some properties that are of interest in the analysis. The samples were hot rolled as their mechanical processing.

After slow cooling, a new heat treatment was performed for strain relief and recrystallization of microstructures as there were internal stresses and deformed microstructures due to an aggressive hot-rolling process. This treatment was performed at 1143 K for 24 h in a vacuum.

## **2.2 Sample's characterization**

model, from the sample's dissolution in acid medium. The presence of interstitial elements was carried out using a LECO TC-400 model gas analyzer. **Table 1** shows

*Recent Advancements in the Metallurgical Engineering and Electrodeposition*

It can be verified that the obtained ingots show the correct stoichiometry of nickel and a low amount of impurities and interstitial elements, displaying the good

To check the homogeneity of the produced alloys, the samples were subjected to a mapping of the elements that comprise the alloys using an electron dispersion spectrometry (EDS) technique that used an Oxford Instruments Incax-act model detector coupled to the scanning electron microscope (SEM) Carl Zeiss EVO/LS15 model. **Figure 2** shows the mapping of the elements titanium and nickel obtained by EDS in the produced alloys after melting. In all cases, homogeneous distribution of the elements titanium and nickel can be observed, showing that the melting was

After melting, the ingots were submitted to a homogenization heat treatment that consisted of slowly heating the samples up to 1173 K for 24 h in a vacuum of 106 Torr, followed by slow cooling in the furnace. The mechanical processing of

Ti-5Ni 0.07 0.005 5.36 0.020 0.008 0.001 0.124 0.109 0.012 Ti-10Ni 0.10 0.018 10.03 0.034 <0.001 <0.001 0.380 0.179 0.007 Ti-15Ni 0.12 0.035 15.83 0.052 <0.001 <0.001 0.023 0.290 0.058 Ti-20Ni 0.12 0.028 19.80 0.072 <0.001 <0.001 0.160 0.300 0.076

**Cr (wt%)**

**Cu (wt%)**

**C (wt%)**

**O (wt%)**

**N (wt%)**

**Mn (wt%)**

the chemical analysis of the produced samples.

complete, without the presence of aggregates or segregates.

**Ni (wt%)**

*EDS mapping of the elements Ti and Ni that make up the Ti-Ni alloys.*

quality of prepared alloys.

**Alloy Fe**

**Table 1.**

**Figure 2.**

**14**

**(wt%)**

*Chemical analysis of the Ti-Ni alloys.*

**Al (wt%)**

The structural characterization of the samples was carried out by X-ray diffraction (XRD) measurements on a Rigaku diffractometer (D/Max-2100PC model). This included a Cu-Kα radiation of wavelength of 1.544 Å, 20 mA current, and a potential of 40 kV. The fixed mode, with step of 0.02° and time of 1.6 s, in the range of 10–90°, was used. The used method to data acquisition was the powder method [25].

For all samples of the Ti-Ni alloys used in this chapter and in all processing conditions, the microstructure was evaluated by both optical and scanning electron microscopy. To obtain the images, an Olympus model BX51M optical microscope with a camera connected to a computer and a SEM Carl Zeiss EVO/LS15 model with the SmartSEM software were used.

Vickers microhardness tests were performed using a Shimadzu HMV model-2 microdurometer connected to a computer. The load used was 1.941 N for a time of 60 s. Following ASTM standards, almost 20 indentations were made in different regions of the sample [26, 27]. The dynamic elastic modulus was measured using Sonelastic® equipment (ATCP, Brazil). A boost in sample, the frequencies of vibration (through the Sonelastic® software), and damping were calculated and linked with the modulus of elasticity, according to standard ASTM E1876-01 [28].


Author details

Jing Huang Physics Department, South China University of Technology, Guangzhou, China

\*Address all correspondence to<EMAIL_ADDRESS>
© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


**2. Pathophysiology**

Acute aortic syndromes are a group of disease entities that include penetrating aortic ulcers in addition to aortic dissections and intramural hematomas. Aortic dissections are defined by a tear of the intima that results in passage of blood and separation of the intimal and medial or adventitial layers of the vessel wall (Figure 1) [4]. This typically occurs in patients with cystic medial necrosis or medial degeneration. This creates a false lumen, and propagation of the tear either antegrade or retrograde can result in aortic valve insufficiency, cardiac tamponade, and/ or organ malperfusion [5]. Intramural hematomas are caused by rupture of the vaso vasorum. This leads to hemorrhage within the aortic media, and can subsequently lead to rupture of the aortic wall or inward disruption of the intima with resultant secondary aortic dissection [6,7].

As the name suggests, penetrating aortic ulcers arise from atheromatous plaques that ulcerate, causing disruption of the internal elastic lamina [6]. Erosion into the medial layer can lead to development of an intramural hematoma or dissection, complications that can eventually lead to pseudoaneurysm formation or aortic rupture. Penetrating aortic ulcers tend to occur in patients with advanced atherosclerosis. Furthermore, they can occur in isolation or in multiples

© 2013 Kilic and Kilic; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

In a study of 19 patients with penetrating aortic ulcers, common comorbidities included hypertension (95%), chronic obstructive pulmonary disease (63%), cardiac disease (42%), chronic renal insufficiency (26%), and diabetes mellitus (16%) [14]. This comorbidity pro‐ file was similar to that seen in patients with intramural hematomas. Patients with pene‐ trating aortic ulcers were found to have the highest rate of concomitant abdominal aortic

Penetrating Aortic Ulcers http://dx.doi.org/10.5772/54107 377

A large series of 105 patients with penetrating aortic ulcers demonstrated similar results [15]. Moreover, patients tended to be elderly with an average age of 72 years, and most patients were males (70%) and symptomatic (75%). Common comorbidities included hypertension (92%), smoking (77%), coronary artery disease (46%), chronic obstructive pulmonary disease (24%), and chronic renal insufficiency (21%). Concomitant abdominal aortic aneurysms were

The diagnosis of penetrating aortic ulcers relies first upon a thorough history and physi‐ cal examination. The typical patient is elderly with a history of hypertension. As men‐ tioned previously, these patients can also have a history of coronary artery disease, chronic obstructive pulmonary disease, renal disease, and tobacco use. They typically present with anterior chest or midscapular pain. Similar to aortic dissections, those with anterior chest pain usually have ascending aortic involvement and those with back pain typically have descending aortic involvement. The differential diagnosis with this typical presentation includes acute coronary syndrome, aortic aneurysm, aortic dissection, intra‐

Physical examination should initially include a review of airway, breathing, and circulation to ensure that the patient is stable. Murmurs indicative of aortic insufficiency typically reflect aortic dissection as opposed to isolated penetrating ulcers, which are focal in nature. Similarly, signs of malperfusion such as neurologic deficits, acute renal insufficiency, visceral vessel compromise, or limb pain with pulse deficit usually occur with dissection as opposed to isolated penetrating aortic ulcers. It is important to note, however, that penetrating aortic ulcers and aortic dissections can occur concomitantly, and therefore, the presence of these signs on physical examination does not exclude a diagnosis of penetrating aortic ulcer. Penetrating aortic ulcers may also be discovered incidentally in asymptomatic patients with imaging

Radiological imaging is essential to the diagnosis of penetrating aortic ulcers given its similarities to other acute aortic syndromes with respect to clinical presentation. A plain chest roentgenogram is frequently obtained in patients presenting with these symptoms and may

found in 61% of patients, and 30% had a pleural effusion on presentation.

aneurysms (42%).

**5. Diagnosis**

**5.1. History and physical examination**

mural hematoma, and pulmonary embolism.

performed for other indications.

**5.2. Diagnostic modalities**

**Figure 1.** Acute aortic syndromes include aortic dissections, penetrating aortic ulcers (PAU), and intramural hemato‐ mas (IMH), each with different pathophysiologies. Aortic dissections are defined by a tear in the intima and separation of the intimal and medial or adventitial layers. Penetrating aortic ulcers result from lesions that ulcerate and disrupt the internal elastic lamina. Intramural hematomas can arise from penetrating aortic ulcers, or can occur in isolation after disruption of the vaso vasorum (from Reference 4 – permission granted).

[8]. Most commonly, penetrating aortic ulcers affect the descending thoracic aorta and less commonly the aortic arch, abdominal aorta, or ascending aorta [9].


*Article* **Multiphase Storm Deposits Eroded from Andesite Sea Cli**ff**s on Isla San Luis Gonzaga (Northern Gulf of California, Mexico)**

**Rigoberto Guardado-France 1, Markes E. Johnson 2,\*, Jorge Ledesma-Vázquez 1, Miguel A. Santa Rosa-del Rio 1 and Ángel R. Herrera-Gutiérrez 1**

Received: 25 May 2020; Accepted: 15 July 2020; Published: 16 July 2020

**Abstract:** The 450-m long spit that extends westward from the northwest corner of Isla San Luis Gonzaga is one of the largest and most complex constructions of unconsolidated cobbles and boulders found anywhere in Mexico's Gulf of California. The material source derives from episodic but intense storm erosion along the island's andesitic cliff face with steep northern exposures. A well-defined marine terrace from the late Pleistocene cuts across the same corner of the island and provides a marker for the subsequent development of the spit that post-dates tectonic-eustatic adjustments. A total of 660 individual andesite clasts from seven transects across the spit were measured for analyses of change in shape and size. These data are pertinent to the application of mathematical formulas elaborated after Nott (2003) and subsequent refinements to estimate individual wave heights necessary for lift from parent sea cliffs and subsequent traction. Although the ratio of boulders to clasts diminishes from the proximal to distal end of the structure, relatively large boulders populate all transects and the average wave height required for the release of joint-bound blocks at the rocky shore amounts to 5 m. Based on the region's historical record of hurricanes, such storms tend to decrease in intensity as they migrate northward through the Gulf of California's 1100-km length. However, the size and complexity of the San Luis Gonzaga spit suggests that a multitude of extreme storm events impacted the island in the upper gulf area through the Holocene time, yielding a possible average growth rate between 7 and 8 m/century over the last 10,000 years. In anticipation of future storms, a system to track the movement of sample boulders should be emplaced on the San Luis Gonzaga spit and similar localities with major coastal boulder deposits.

**Keywords:** coastal boulder deposits; storm waves; hydrodynamic equations; Holocene; western North America


**3.2.2 3D MEMS switch**

Telecommunication switches with large port count have been the main driver for the twoaxis scanner in the past few years. With increasing number of wavelengths and bandwidth in dense wavelength-division-multiplexed (DWDM) networks, there is a need for optical crossconnect (OXC) with large port count [86,87,88]. The dual axis analog scanning capability is the key for these applications since each mirror associated with the input fiber array can point to any mirror associated with the output fiber array. Implementation of NxN OXC using two arrays of N analog scanners is illustrated in Figure 3-28. Even though the implementations may vary, we can always conceptually refer to this illustration. This switch is often called a 3D MEMS switch because the optical beams propagate in three-dimensional space. 3D switch is a better choice for larger port-count NxN OXC compared to 2D switch as the number of mirrors for a 2D switch is N2. Since the optical path length is independent of the switch configuration, uniform optical insertion loss (2 to 3 dB) can be achieved. The port count of the 3D MEMS switch is limited by the size and flatness of the micromirrors, as well as their scan angle and fill factor. For a complete discussion of scaling laws for MEMS free space optical switches, see Syms [88]. For large port count (approaching 1000 x 1000), single crystal micromirror scanners are necessary to achieve large mirror size with required flatness.

During the telecom boom, several companies have invested heavily to develop 3D MEMS OXC's. These companies include (but not limited to) Lucent Technologies [86,88,89,90,91,92,93,94], Corning [95,96,97], NTT Corp. [98,99], Fujitsu Laboratories, Ltd. [100,101], Tellium, Inc. [102,103,104], and Calient Networks [105]. They have demonstrated various designs of two-axis scanners, which are the key components of these 3D MEMS switches.

Neuchatel has perfected the mirror etching technology by DRIE [85]. A surface roughness of 36 nm has been achieved. The switch has excellent optical performance: 0.3-0.5 dB optical insertion loss and 500 sec switching time, and very low polarization dependence [84].

Fig. 3.27. Schematic and SEM of 2x2 switch fabricated by SOI MEMS (Picture courtesy of

Telecommunication switches with large port count have been the main driver for the twoaxis scanner in the past few years. With increasing number of wavelengths and bandwidth in dense wavelength-division-multiplexed (DWDM) networks, there is a need for optical crossconnect (OXC) with large port count [86,87,88]. The dual axis analog scanning capability is the key for these applications since each mirror associated with the input fiber array can point to any mirror associated with the output fiber array. Implementation of NxN OXC using two arrays of N analog scanners is illustrated in Figure 3-28. Even though the implementations may vary, we can always conceptually refer to this illustration. This switch is often called a 3D MEMS switch because the optical beams propagate in three-dimensional space. 3D switch is a better choice for larger port-count NxN OXC compared to 2D switch as the number of mirrors for a 2D switch is N2. Since the optical path length is independent of the switch configuration, uniform optical insertion loss (2 to 3 dB) can be achieved. The port count of the 3D MEMS switch is limited by the size and flatness of the micromirrors, as well as their scan angle and fill factor. For a complete discussion of scaling laws for MEMS free space optical switches, see Syms [88]. For large port count (approaching 1000 x 1000), single crystal micromirror scanners are necessary to achieve large mirror size with required

During the telecom boom, several companies have invested heavily to develop 3D MEMS OXC's. These companies include (but not limited to) Lucent Technologies [86,88,89,90,91,92,93,94], Corning [95,96,97], NTT Corp. [98,99], Fujitsu Laboratories, Ltd. [100,101], Tellium, Inc. [102,103,104], and Calient Networks [105]. They have demonstrated various designs of two-axis scanners, which are the key components of these 3D MEMS

Nico de Rooij. Reprinted from [83] with permission).

**3.2.2 3D MEMS switch**

flatness.

switches.

Fig. 3.28. Configuration for 3-D optical switch (NxN) with 2N analog scanning mirrors.

Lucent technologies employed a self-assembly technique which was driven by the residual stress in deposited thin films (Cr/Au on polysilicon) to raise two-axis polysilicon scanners (500 m mirror diameter) to a fixed position 50 m above the substrate [106,107]. The scanning electron micrograph (SEM) is shown in Figure 3-29. Two-axis scanning is achieved

Fig. 3.29. SEM of surface-micromachined 2-axis scanners Lucent Technologies (Courtesy of [109] Lucent Technologies Inc. © 2003 Lucent Technologies Inc. All rights reserved.)

Optical MEMS 323

Fig. 3.31. Comparison of switching under open-loop and closed-loop operation (Picture

Fig. 3.32. DC transfer characteristics of the two-axis scanner of Tellium, Inc., with and without sidewall driving (Picture courtesy of C. Pu. Reprinted from [104] with permission)

In this Chapter, we present the history, common actuators, and fabrications of various Optical MEMS devices for display, imaging, and telecom applications. Each actuation mechanism has its own advantage that can be optimally deployed in each application. For instance, electrostatic actuation requires very low current and achieves short range in motion suiting

Reprinted from [102] with permission)

**4. Conclusion**

by electrostatic force between the mirror and the quadrant electrodes on the substrate. SCS two-axis scanner with long-term stability and high shock resistance has also been developed by Lucent Technologies for 3D MEMS switches [108, 109]. SCS is used to improve the mirror flatness. The long-term stability is achieved by the removal of exposed dielectric to avoid electrostatic charge-up effect (Figure 3-30). The scanning angle is 7 degrees.

Fig. 3.30. Cross section of the SCS two-axis mirror developed by Lucent Technolgies (Picture courtesy of A. Gasparyan. Reprinted from [108] with permission)

NTT Corp. has reported a two-axis micromirror array driven by terraced electrodes. The mirrors and the electrodes are fabricated on separate chips and then bonded together. The use of terraced electrodes reduces the applied voltage by half, compared to regular parallelplate-driven mirrors. The mirror is tilted by 5.4 degree at a maximum of 75 V. The resonant frequency of the fabricated mirror is approximately 1 kHz [98].

The two-axis scanner developed by Fujitsu Laboratories, Ltd. is based on vertical combdrive actuators. SOI with 100-m top and bottom (substrate) silicon layers has been used to fabricate the device [100]. The top silicon is for the moving comb fingers and mirror while the fixed fingers are made of the bottom silicon. V-shape torsion springs are adopted to improve the lateral stability which is a critical issue in comb-drive actuators. Rotation angle of +/- 5 degrees has been achieved with 60-V driving voltage.

Tellium, Inc. has demonstrated an electrostatic parallel-plate actuated two-axis scanner, featuring nonlinear servo closed-loop control [102]. The nonlinear servo closed-loop control enables the mirror to operate beyond the pull-in angle. Figure 3-31 shows the comparison of switching under open-loop and closed-loop operation. The closed-loop angular trajectory can exceed the pull-in (snap-down) angle and shows no overshoot. They have also developed a two-axis micromirror driven by both sidewall and bottom electrodes [104]. The addition of sidewall electrodes improves the linearity of the DC transfer characteristic. The mirror with sidewall electrodes also exhibits a larger scan angle than that driven by merely bottom electrodes (Figure 3-32).

by electrostatic force between the mirror and the quadrant electrodes on the substrate. SCS two-axis scanner with long-term stability and high shock resistance has also been developed by Lucent Technologies for 3D MEMS switches [108, 109]. SCS is used to improve the mirror flatness. The long-term stability is achieved by the removal of exposed dielectric to avoid

Fig. 3.30. Cross section of the SCS two-axis mirror developed by Lucent Technolgies (Picture

NTT Corp. has reported a two-axis micromirror array driven by terraced electrodes. The mirrors and the electrodes are fabricated on separate chips and then bonded together. The use of terraced electrodes reduces the applied voltage by half, compared to regular parallelplate-driven mirrors. The mirror is tilted by 5.4 degree at a maximum of 75 V. The resonant

The two-axis scanner developed by Fujitsu Laboratories, Ltd. is based on vertical combdrive actuators. SOI with 100-m top and bottom (substrate) silicon layers has been used to fabricate the device [100]. The top silicon is for the moving comb fingers and mirror while the fixed fingers are made of the bottom silicon. V-shape torsion springs are adopted to improve the lateral stability which is a critical issue in comb-drive actuators. Rotation angle

Tellium, Inc. has demonstrated an electrostatic parallel-plate actuated two-axis scanner, featuring nonlinear servo closed-loop control [102]. The nonlinear servo closed-loop control enables the mirror to operate beyond the pull-in angle. Figure 3-31 shows the comparison of switching under open-loop and closed-loop operation. The closed-loop angular trajectory can exceed the pull-in (snap-down) angle and shows no overshoot. They have also developed a two-axis micromirror driven by both sidewall and bottom electrodes [104]. The addition of sidewall electrodes improves the linearity of the DC transfer characteristic. The mirror with sidewall electrodes also exhibits a larger scan angle than that driven by merely

courtesy of A. Gasparyan. Reprinted from [108] with permission)

frequency of the fabricated mirror is approximately 1 kHz [98].

of +/- 5 degrees has been achieved with 60-V driving voltage.

bottom electrodes (Figure 3-32).

electrostatic charge-up effect (Figure 3-30). The scanning angle is 7 degrees.

Fig. 3.31. Comparison of switching under open-loop and closed-loop operation (Picture Reprinted from [102] with permission)

Fig. 3.32. DC transfer characteristics of the two-axis scanner of Tellium, Inc., with and without sidewall driving (Picture courtesy of C. Pu. Reprinted from [104] with permission)

### **4. Conclusion**

In this Chapter, we present the history, common actuators, and fabrications of various Optical MEMS devices for display, imaging, and telecom applications. Each actuation mechanism has its own advantage that can be optimally deployed in each application. For instance, electrostatic actuation requires very low current and achieves short range in motion suiting

Optical MEMS 325

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The Optical MEMS technology promises to revolutionize nearly every product category with the ability to directly manipulate light or optical signal. With the integration of microelectronics and microoptical components, it is the possible realization of complete systems on a chip.

#### **5. References**

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**13**

*USA*

**Optical-Thermal Phenomena in Polycrystalline**

Many microelectromechanical systems (MEMS) applications utilize laser irradiation as an integral part of the system functionality, including projection displays, optical switches, adaptive optics (Andrews et al., 2011; Andrews et al., 2008), optical cross-connects (Knoernschild et al., 2009), and laser powered thermal actuators (Serrano & Phinney, 2008; Serrano et al., 2005). When laser irradiation is incident on small-scale systems, such as these MEMS applications, the propensity for exceeding the thermal handling capability of the devices dramatically increases, often leading to overheating, and subsequent deformation and permanent damage to the devices. In most instances, this damage is a direct consequence of the device geometry and the material thermal properties, which hinder the transport of heat out of any locally heated area. Such thermally-driven failures are common in electrically-powered systems (Baker et al., 2004; Plass et al., 2004). However, for laserirradiated MEMS, particularly those fabricated of surface-micromachined polycrystalline silicon (polysilicon), the optical properties can also affect the thermal response of the devices by altering how the laser energy is deposited within the material. Even more concerning in these types of devices is the fact that the thermal, optical, and mechanical response can be intimately coupled such that predicting device performance becomes difficult. In this chapter, we focus on understanding some of the basics of optical interactions in laserirradiated MEMS. We will first look at how the optical properties of the materials affect the laser energy deposition within a device. We will then expand upon this by looking at the coupling that exists between the optical and thermal properties, paying particular attention to the implications that transient temperature changes have in the optical response, ultimately leading to device failure. Finally, we will look at various cases of laser-induced damage in polysilicon MEMS where the device geometry and design and optical-thermal

Understanding the coupling that exists between the thermal and optical behavior in laserirradiated MEMS must begin by looking at the optical properties of the irradiated materials and at how the laser light interacts with each material. The primary factor that affects the magnitude of this interaction is the material's complex refractive index, *n n ik ˆ* . A wave

**1. Introduction**

coupling have led to device failure.

**2. Optical interactions in MEMS**

**Silicon MEMS During Laser Irradiation**

Justin R. Serrano and Leslie M. Phinney

*Albuquerque, New Mexico,*

*Engineering Sciences Center, Sandia National Laboratories*

International Conference on Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS 2003, 8-12 June 2003), vol. 1, pp.360 – 363.


**Developmental Exposure to Environmental Contaminants**

Editors **Kimberly Keil Stietz Tracie Baker Jessica Plavicki**

MDPI ' Basel ' Beijing ' Wuhan ' Barcelona ' Belgrade ' Manchester ' Tokyo ' Cluj ' Tianjin

*Editors* Kimberly Keil Stietz Comparative Biosciences University of Wisconsin-Madison Madison United States

Tracie Baker Aquatic Pathobiology Laboratory Department of Environmental Global Health University of Florida Gainesville United States

Jessica Plavicki Pathology and Laboratory Medicine Brown University Providence United States

*Editorial Office* MDPI St. Alban-Anlage 66 4052 Basel, Switzerland

This is a reprint of articles from the Special Issue published online in the open access journal *Toxics* (ISSN 2305-6304) (available at: www.mdpi.com/journal/toxics/special issues/developmental exposure contaminants).

For citation purposes, cite each article independently as indicated on the article page online and as indicated below:

LastName, A.A.; LastName, B.B.; LastName, C.C. Article Title. *Journal Name* **Year**, *Volume Number*, Page Range.

**ISBN 978-3-0365-5886-8 (Hbk) ISBN 978-3-0365-5885-1 (PDF)**

© 2022 by the authors. Articles in this book are Open Access and distributed under the Creative Commons Attribution (CC BY) license, which allows users to download, copy and build upon published articles, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications.

The book as a whole is distributed by MDPI under the terms and conditions of the Creative Commons license CC BY-NC-ND.


**Modeling, Optimization and Design Method of Metal Manufacturing Processes**

Editors

**Guoqing Zhang Zejia Zhao Wai Sze YIP**

MDPI ' Basel ' Beijing ' Wuhan ' Barcelona ' Belgrade ' Manchester ' Tokyo ' Cluj ' Tianjin

*Editors* Guoqing Zhang College of Mechatronics and Control Engineering Shenzhen University Shen Zhen China

Zejia Zhao College of Mechatronics and Control Engineering Shenzhen University Shen Zhen China

Wai Sze YIP Industrial and Systems Engineering The Hong Kong Polytechnic University Hong Kong

*Editorial Office* MDPI St. Alban-Anlage 66 4052 Basel, Switzerland

This is a reprint of articles from the Special Issue published online in the open access journal *Processes* (ISSN 2227-9717) (available at: www.mdpi.com/journal/processes/special issues/metal manufacturing processes).

For citation purposes, cite each article independently as indicated on the article page online and as indicated below:

LastName, A.A.; LastName, B.B.; LastName, C.C. Article Title. *Journal Name* **Year**, *Volume Number*, Page Range.

**ISBN 978-3-0365-6034-2 (Hbk) ISBN 978-3-0365-6033-5 (PDF)**

© 2022 by the authors. Articles in this book are Open Access and distributed under the Creative Commons Attribution (CC BY) license, which allows users to download, copy and build upon published articles, as long as the author and publisher are properly credited, which ensures maximum dissemination and a wider impact of our publications.

The book as a whole is distributed by MDPI under the terms and conditions of the Creative Commons license CC BY-NC-ND.


*3.1. Proximate Composition*

The approximate analysis of the pig brain is shown in Table 1.  Among the dry matter, fat was the most abundant composition (9.25% fw), followed by protein (7.25% fw), carbohydrate (2.21% fw), and ash (1.33% fw), respectively. Lipids and their intermediates are important parts of the brain's structure and function. Behind adipose tissue, the brain has the second largest lipid content, with lipids accounting for half of the brain's dry weight [20]. Krafft et al. [21] reported that brain tissue is composed of around 70–83% water, 7.5–8.5% protein (fw), and 5–15% lipid (fw). Brain tissue contained high content of lipid, which was mainly divided into three major groups, including neutral lipids, phospholipids, and sphingolipids [21].  The protein content of the pig brain, on the other hand, was lower than that of fresh pork (19.80%, fw) [23] and other pork by-products, particularly viscera portions (8.45–22.05% fw), which have been reported in the literature [19]. The results revealed that the pig brain could be a rich source of nutrients, especially lipid and protein. The total protein and lipid content of the original material are both important factors in deciding how to use and recover by-products [24,25].

**Table 1.** Chemical composition of pig brain.

Values are given as mean ± standard deviation from triplicate determinations.

### *3.2. Total Phospholipids and Cholesterol Contents*

Phospholipids are functional and structural components of cell membranes that are easily absorbed by the body and therefore perform their functions. Phospholipids are a dietary supply of lipoproteins, which play a significant role in lipid metabolism. Dietary phospholipid has been shown, in mammalian studies, to limit lipid deposition in the liver by blocking lipid absorption and oxidation [26,27]. Phospholipid is one of the most abundant lipids in brain tissue [21]. From this study, the phospholipid content of the oil extracted from pig brain was 0.86 g/100 g fw. The phospholipid content of crude lipid from pig brain was similar to that of alternative foods such as sago palm weewil (*Rhynchophorus ferregineus*) larvae (2.6–9.3 g/100 g lipid) [28], but it was lower than that of popular ingredients, such as fish oil (13.7–32.9 g/100 g lipid) [29] and krill oil (32.5 g/100 g lipid) [30]. Phospholipid is a natural surfactant that may be used to prepare emulsions and has high emulsifying characteristics in general [31]. Phospholipids can also act as an antioxidant [32]. Phospholipids can form associations with cholesterol in cell membranes [33]. Cholesterol is also a significant constituent of brain cell membranes [34]. The typical quantity of cholesterol found in an animal is around 2.1 g/kg of body weight [35]. Table 1 shows that the total

cholesterol concentration of the pig brain was 0.30 g/100 g fw, resulting in a phospholipid to cholesterol ratio of around 3:1.  Cholesterol is a lipid produced by the liver of animals and found in all animal-based foodstuffs, including eggs, red meat, and fish [36]. Cholesterol, which is one of the main structural components of cell membranes and is turned into hormones, is essential to good health at a normal level [37]. Hypercholesterolemia, cardiovascular disease, and coronary heart disease are all linked to a high-cholesterol diet [37]. The adult population should consume no more than 300 mg of cholesterol each day [28].  Separating cholesterol from pig brain oil could be an approach for increasing the oil's use as a functional ingredient.

### *3.3.  This was attributed to the presence of a blood vessel in the brain, which is evident in Table 1. Blood vessels, particularly capillaries, form a dynamic and intricate architecture that transports oxygen and nutrients to the brain [38]. As food, the presence of heme protein in form of blood may influence the storage stability, specifically, discoloration, rancidity development, and microbial growth [13,39,40]. Positive *a*\* (5.60) and *b*\* (15.43) values with a redness index of 0.36 indicated that the presence of heme protein caused the pig brain to be reddish brown in color (Table 2). The high moisture content in the pig brain (Table 1) was represented by a high *L*\* (63.88) value (Table 2). The elevated redness levels could be explained by the presence of heme proteins. The amount of moisture, membrane protein, connective tissue, lipid, and heme proteins in pig brain may affect its color. Moisture, membrane protein, and connective tissue can cause lightness; lipid can give yellowness; heme proteins (e.g., hemoglobin) can cause redness; and hemoglobin oxidation/denaturation can cause a yellow-brownish color.

**Table 2.** Color attributes and appearances of pig brain.

Values are given as mean ± standard deviation from triplicate determinations. *L*\* = lightness, *a*\* = redness/greenness, *b*\* = yellowness/blueness.


**2. Innovation in Latin America**

Innovation and entrepreneurship have gained strength in Latin America during the last decade. Technological startups have tripled since 2017 and have multiplied their estimated value from USD 7 billion to USD 221 billion, reaching in 2021 the number of twenty-seven unicorns (private startups valued at more than one billion dollars) [12].

Despite this, the region is still characterized by low levels of public and private investment in research and development (R&D). As can be seen in **Figure 3**, by 2020,

**Figure 3.** *R&D expenditures as a percentage of GDP. Source: Adapted from [1].*

most countries are still far from reaching 0.5% investment in R&D with respect to GDP, a fact that contrasts with the average of 2.3% in OECD countries during the last decade and the notable advances of some Asian countries such as Thailand. On the other hand, in several countries, registered investment comes primarily from public funds, with minimal private funds.

The latter implies that the development of innovation and technological industries continues to be a difficult challenge. Added to this is the fact that in the Latin American context, the markets are not well developed, and there is a deficient business climate, with limited inventiveness [13], lack of resources and scientific and technological infrastructure [14], deficient institutional development [11], and a weak policy [15].