Search results

Sensor Review publishes the results of a major sensor survey.

In this paper, it can be seen from AFM images of the as-deposited ZnO and CZO films, and the particle size and shape are not clear, while by increasing annealing temperature, they become distinguishable. By increasing temperature to 600°C, ZnO and CZO, CAZO and aluminum-doped zinc oxide (AZO) films particles became almost spherical. Due to high content of Cu in CZO target, and of Al in AZO target which was 5% weight ratio, doping plays a great role in the subject. Therefore, the annealing processing strongly affect the size and the shape of nanoparticles.

In this paper, the authors tried to study, in detail, nobel optical characterizations of ZnO films doped by transition metals in different annealing temperature. The authors found that the values of skin depth, optical density, electron–phonon interaction, steepness parameter, band tail width, direct and indirect carriers transitions and the dissipation factor, free carriers density and roughness of films affect the optical properties, especially the optical absorptions of ZnO films doped by transition metals. Also these properties were affected by annealing temperatures. The authors also found that topography characterizations strongly were affected by these parameters.

The CZO films have maximum value of coordination number ß, with considering N_C = 4, Z_a = 2, N_e = 8. The CZO films annealed at 500 °C have maximum value of optical density. The as-deposited CAZO films have maximum value of steepness parameters in about of 0.13 eV. The as-deposited AZO films have maximum value of dispersion energy Ed in about of 5.75 eV. Optical gap and disordering energy plots of films can be fitted by linear relationships E_g = 0.49 + 0.2 EU and E_g = 0.52 + 0.5 EU, respectively.

With considering N_c = 4, Z_a = 2, N_e = 8 for ZnO films, coordination number ß has maximum value of 0.198. CZO nanocomposites films annealed at 500°C have maximum value of optical density. Different linear fitting of ln (α) for films were obtained as y = A_x + B where 5<A < 17 and 5<B < 12. As-deposited CAZO nanocomposites films have minimum value of electron phonon interaction in about of 4.91 eV. Optical gap and disordering energy plots can be fitted by linear relationships E_g = 0.49 + 0.2 EU and E_g = 0.52 + 0.5 EU for as-deposited films and films annealed at 500°C, respectively. Steepness parameters of as-deposited CAZO nanocomposites films have maximum value of 0.13 eV. Dispersion energy Ed for as-deposited AZO nanocomposites films has maximum value of 5.75 eV.

To investigate the influences of environmental stresses on board‐embedded polymeric waveguides.

Optical multimode waveguides were embedded on printed circuit boards using commercial polymers. The optical‐PCBs varying in board structure and in optical build‐up materials were exposed to heat, moisture and ionic‐contaminants in accelerated reliability tests. The influence of stress factors on the structural integrity and functional parameters, namely the refractive index and optical transmissivity, was investigated at the key communication wavelengths.

Isothermal annealing reduced the refractive index to the greatest extent. The optical‐PCB structure with an optical surface build‐up layer was observed to be more vulnerable under temperature shock when compared with the optical‐PCB with optical inner layer. The buffer layer beneath the optical build‐up was found to improve the stability of the optical waveguides significantly. The results indicated of wavelength dependence to the aging factor with a failure mechanism. The factors affecting the performance and reliability of polymer‐based optical waveguides on PCBs were discussed.

More experimental data and investigations of failure mechanisms are required to ultimately obtain sufficient reliability statistics for accurate life‐time prediction models.

Optical interconnects are seen as a promising solution to overcome performance limitations encountered with high‐frequency electrical interconnections. As an emerging technology, only a limited amount of reliability data on optical/electrical packages is available. The paper investigates the influences of environmental stresses on board‐embedded polymeric waveguides.

The majority of methods for the optical monitoring of gases can be divided into two main groups. In the first, the intrinsic optical properties of the gas are exploited to sense it. In the second group, an indicator is used to transduce the gas concentration into a measurable optical parameter. Most gas sensors are usually sensitive to only one parameter of the monitored gas. This paper contains a description of a gas multisensor that is suitable for measuring gas concentration and pressure at the same time. It needs a special sensor construction that can measure the mentioned properties in parallel. The essence of this sensor is the double rle of the diaphragm. This means that the diaphragm itself is for sensing the pressure and suitable layer with an immobilised reagent is applied on top of the diaphragm for sensing the concentration of the gas. The sensing method is a fibre guided incident light beam to the diaphragm's surface. The incident beam passes through the concentration‐sensitive layer twice as the diaphragm's surface reflects it. The properties of the reflected beam contain the required information — pressure and concentration — about the measured gas. At the output of the system the reflected light intensity is proportional to pressure and the spectrum is promotional to concentration of gas. The paper describes the design and results in detail.

The purpose of this paper is to provide a detailed review of radiation dosimetry techniques based on optical fibre dosimeters. It presents a comprehensive bibliography of the current research activities in the area.

A range of published work on optical fibre radiation dosimeters are presented, with the merits and limitations discussed. Each radiation dosimetry technique is discussed in turn, providing examples of dosimeters using such techniques reviewed. The main focus is on gamma radiation although other radiation dosimeters are considered.

This paper provides information on the wide range of research activity into radiation dosimeters. The dose ranges of these dosimeters are presented, along with the advantages and disadvantages of different dosimetry techniques.

A comprehensive review of published research in the area of solid radiation dosimetry is presented in this paper. It provides an individual with a review of the various techniques used and most recent research in that field.

The purpose of this paper is to investigate the structural, electronic and optical properties of pure zinc oxide (ZnO) and transition metal (Tm)-doped ZnO using Tm elements from silver (Ag) and copper (Cu) by a first-principles study based on density functional theory (DFT) as implemented in the pseudo-potential plane wave in CASTEP computer code.

The calculations based on the generalized gradient approximation for Perdew-Burke-Ernzerhof for solids with Hubbard U (GGA-PBEsol+U) were performed by applying Hubbard corrections U_d = 5 eV for Zn 3d state, U_p = 9 eV for O 2p state, U_d = 6 eV for Ag 4d state and U_d = 9.5 eV for Cu 3d state. The crystal structure used in this calculation was hexagonal wurtzite ZnO with a space group of P63mc and supercell 2 × 2 × 2.

The total energy was calculated to determine the best position for Ag and Cu dopants. The band structures and density of states show that Tm-doped ZnO has a lower bandgaps value than pure ZnO because of impurity energy levels from Ag 4d and Cu 3d states. In addition, Ag-doped ZnO exhibits a remarkable enhancement in visible light absorption over pure ZnO and Cu-doped ZnO because of its lower energy region and extended wavelength spectrum.

The results of this paper are important for the basic understanding of the 3d and 4d Tm doping effect ZnO and have a wide range of applications in designing high-efficiency energy harvesting solar cells.

The effects of γ‐radiation on both the optical and the electrical properties of Tellurium dioxide (TeO₂) thin films were investigated. TeO₂ thin films were fabricated using thermal vacuum deposition method. Samples were exposed to a ⁶⁰Co γ‐radiation source with a dose rate of 6 Gy/min. Absorption spectra for TeO₂ thin films were recorded and values of the optical band gap for as‐deposited and γ‐irradiated films were calculated. Sets of measurements based on Hall effect were carried out. From the data received the dependences of sheet resistance, density of charge carriers, mobility and Hall coefficient with radiation dose were determined.

The purpose of this paper is to formulate two component polyurethane coatings based on acrylic polyol, to study the effects of variable nanosilica loadings in these coatings on different morphological, optical, mechanical, corrosion resistance and weather resistance properties and to study the intercalation of acrylic polyol molecules into nanosilica crystals by XRD technique.

Two component polyurethane coatings were synthesised using acrylic polyol and isocyanate HDI. The nanosilica was incorporated in polyurethane formulation at the weight ratios of 1%, 3% and 5% based on total weight of polyol and isocyanate. The performance of nanocoatings was compared for variable loads of nanosilica for different properties such as morphological, optical, mechanical, corrosion resistance, weather resistance and were studied for intercalation of acrylic polyol into nanosilica crystals by XRD technique.

Improvement in the properties of polyurethane coatings is achieved with the incorporation of nanosilica. The improvement is the result of inherently high properties of inorganic nanosilica. Tensile strength, scratch hardness, abrasion resistance, corrosion and weathering resistance show significant improvement in performance with the incorporation of nanosilica. Properties are found to deteriorate beyond a certain loading of nanosilica; hence it is important to optimise loading level. The optimal range for high performance was found to be in the range of 1% to 3%. The improvement was a result of synergistic behaviour and good interfacial interaction between polyurethane and nanosilica at optimal levels.

The method used for incorporation of nanosilica into polyurethane was direct incorporation method. The other method of incorporation, i.e. in situ addition and its effect on properties can also be studied.

With the addition of optimal loading level of nanosilica to polyurethane coatings, properties can be enhanced up to the mark. The addition is relatively easy and cost effective.

The paper proves the significance of incorporation of nanosilica on original properties of polyurethane coatings and widens the area of applications of two component polyurethane coatings from acrylic polyol by strengthening them in their properties. The coatings can be applicable in high performance topcoats especially for automotive topcoats.

Reports on tests in which barium metaborate pigment and its modified form are prepared, identified by chemical and X‐ray diffraction methods, and specified according to standard methods. Evaluates the modified barium metaborate as a new filler for paper making by carrying out two series of experiments. Details the results which showed that the efficiency of the filler retention when using modified barium metaborate was higher than that of the other two conventional fillers. Reveals that at relatively low filler addition (2–5 percentage weight), higher improvement in the strength properties can be obtained when using the modified pigment instead of titanium dioxide and kaolin, but observes the reverse (i.e. a detrimental effect) at relatively high filler addition (8–10 percentage weight). Discovers that the optical properties of the modified pigment‐loaded sheets lie between those of titanium dioxide and kaolin. Shows that blending barium metaborate with kaolin or titanium dioxide has a significant effect on strength properties rather than optical properties. Concludes that modified barium metaborate pigment can be successfully used in paper filling applications and that modified barium metaborate pigment‐kaolin blend (80/20 per cent) can be used instead of titanium dioxide as a paper filler.

This paper aims to study the influence of the Cu-Al₂O₃ film-coated Cu substrate as a thermal interface material (TIM) on the thermal and optical behaviour of the light-emitting diode (LED) package and the annealing effect on the thermal and optical properties of the films.

A layer-stacking technique has been used to deposit the Cu-Al₂O₃ films by means of magnetron sputtering, and the annealing process was conducted on the synthesized films.

In this paper, it was found that the un-annealed Cu-Al₂O₃–coated Cu substrate exhibited low value of thermal resistance compared to the bare Cu substrate and to the results of previous works. Also the annealing effect does not have a significant impact on the changes of properties of the films.

It is deduced that the increase of the Cu layer thickness can further improve the thermal properties of the deposited film, which can reduce the thermal resistance of the package in system-level analysis.

The paper suggested that the Cu-Al₂O₃–coated Cu substrate can be used as alternative TIM for the thermal management of the application of LEDs.

In this paper, the Cu substrate has been used as the substrate for the Cu-Al₂O₃ films, as the Cu substrate has higher thermal conductivity compared to the Al substrate as shown in previous work.