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Ceramic Armour
Published in Paul J. Hazell, Armour, 2023
Aluminium nitride (AlN) is an interesting material that is becoming widely used in the electronics and semiconductor processing industries. This material can be made using the pressureless sintering route; however, the best quality materials are hot pressed. It is believed that this material undergoes a brittle-to-ductile transition at elevated strain rates.
Ceramic Substrates
Published in Fred W. Kear, Hybrid Assemblies and Multichip Modules, 2020
Two significant properties of aluminum nitride make it appealing for substrate applications. These are its TCE and its thermal conductivity. Its TCE is 4.7, making it a good match for silicon. It metallizes well using the same processes as for alumina or beryllia. This allows it to provide a good base for lead frame attachment where higher TCEs may tend to set up shear stresses. The thermal conductivity of aluminum nitride is 170 W/m°K, which is not as good as beryllia, but which is significantly better than alumina. Since thermal management is often the most important concern of a design, this property alone may dictate the use of aluminum nitride.
Medium-Scale Cooling: Thermoelectric Module Technology
Published in D.M. Rowe, CRC Handbook of Thermoelectrics, 2018
The modules can be connected through their leads, either in series, in parallel, or any combination of both. The objective is to enable the total system to operate under a given voltage. The ceramic plates usually used are of alumina, although in very special circumstances beryllium oxide has been used because of its higher thermal conductivity. Aluminum nitride has also been used as it is a good thermal conductor and an excellent dielectric insulator; however, it is very expensive.
Design and Modeling of Piezoelectric-AlN-based Acoustic Sensor for Sound Pressure Level Measurements
Published in IETE Technical Review, 2023
Piezoelectric-based devices [1–3] have become increasingly popular due to the inherent advantage of requiring no external power for their operation. Several authors have developed piezoelectric-based sensors mainly for audio applications and have fabricated them using several piezoelectric materials such as PZT, ZnO, and AlN. Aluminum nitride (AlN) demonstrates several useful properties which include wide energy gap (6.2 eV), high melting point (3273 K) [4], high electrical resistivity (approx. 1014 Ω.cm), and high dielectric constant (8–10). It also has a high acoustic velocity (approx. 5500 m/s and 11354 m/s for transversal and longitudinal bulk waves, respectively and 5607 m/s for surface waves). It possesses high piezoelectricity, high thermal conductivity (2.85W/cmK at room temperature), and better chemical stability [5–7]. The low piezoelectric coefficient of AlN is alleviated by a reduced dielectric constant (e.g. e31, f = −1.05 C/m2, ϵ33, f = 10.7 for AlN versus e31, f = −9.6 C/m2 and ϵ33, f = 650–1300 for PZT [8]). The piezoelectric coefficient of AlN is 1/10th of that of PZT. However, its dielectric constant is also 1/100th times smaller than that of PZT. This causes the parallel plate capacitance of sensors with AlN thin film to be smaller. This results in an enhancement in the signal-to-noise ratio (SNR) in those sensors [9]. Moreover, the chemical and thermal stability of AlN is better than that of ZnO.
Structural and optical properties of aluminum nitride nano powder prepared from tris (N,N dimethyl-ethylenediamine)AlCl3 precursor
Published in Journal of Coordination Chemistry, 2023
Himanshi Chaurasia, Santosh K. Tripathi, Kamlesh Bilgaiyan, Akhilesh Pandey, N. Eswara Prasad
AlN has received attention due to its interesting properties and high potential in various applications [1, 2]. Aluminum nitride-based devices are compatible in a high-temperature environment with high processing temperature. Aluminum nitride ceramics are globally utilized due to their high thermal conductivity (180 Wm−1K−1) [3] in comparison to other ceramic materials, high chemical and thermal stability (above 2000 °C), low coefficient thermal expansion (4.3 × 10−6 K−1), high intrinsic thermal conductivity (320 Wm−1K−1) and wide band gap (5.8 eV–6.2 eV) [4]. In view of excellent properties and robust nature AlN ceramics are useful for optoelectronic and microelectronic devices [5] such as deep blue-green ultraviolet LEDs, high electron mobility transistors, piezoelectric sensors, mechanical resonators [6], etc.
Influence of design of microchannel heat exchangers and use of nanofluids to improve the heat Transfer and Pressure drop characteristics: A review
Published in International Journal of Ambient Energy, 2022
Gururaj Lalagi, P. B. Nagaraj, Mallikarjuna Veerabhadrappa Bidari, Ramakrishna N. Hegde
Research has been carried out to improve heat dissipation by using efficient, high thermal conductivity microchannels. Aluminium nitride (AIN) is an advanced ceramic material with high thermal conductivity and fabricates different micro heat exchangers. It was found that remarkable heat transfer enhancement of 59%. The effectiveness of the AIN heat exchanger was improved by 26% compared to Al2O3 made heat exchanger (Fattahi et al. 2020). The artificial neural network (ANN) was used to study the complexity of flow patterns in a microchannel heat exchanger. The ANN is trained and tested using experimental data that operates under various situations. The investigation of network optimisation for different data used for network testing demonstrates that as the number of training data increases, so does the training and testing accuracy, with no apparent overfitting (Giannetti et al. 2020). A microchannel heat sink built of ZrB2 ceramic is quantitatively evaluated to check the performance in extreme circumstances. The finite element approach was used to solve the liquid and solid domain governing equations. The results revealed a high heat transmission rate from the heated surface (Vajdi et al. 2020).