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1

Development of ultrasonic technique using phased array probes in type IV low-pressure tank

Kozera Paulina, Sarniak Łukasz, Dydek Kamil, Wolanin Andrzej, Boczkowska Anna

Composites Theory and Practice

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2025

|

R. 25, nr 4

234--242

EN

The aim of this work is to develop an ultrasonic technique employing phased array probes to detect structural defects in type IV low-pressure tanks used for the storage of hazardous chemicals. Ultrasonic testing was performed by means of an OmniScan MX2 phased-array ultrasonic flaw detector with appropriate probes, and numerical simu lations were conducted utilizing CIVA software. Attenuation coefficients were measured for a composite layer excised from a two-layer low-pressure tank. Based on these results, a centre frequency of 5 MHz was selected as optimal. The determined parameters, such as the attenuation coefficient and the structural noise level, were implemented in the CIVA model. The detection criteria were established and color-coded: defects with a signal-to-noise ratio (SNR) < 0 dB were labelled white (undetectable); those 0-10 dB were labelled yellow (limited detectability); and those > 10 dB were labelled green (optimal detectability). The simulation results were validated by testing the composite samples with polytetrafluoroethylene (PTFE) inserts of varying sizes and depths. The defect detectability determined from the simulations was consistent with that obtained from testing reference samples.

2

The characteristics of motor vehicle technical tests on the example of selected vehicle inspection stations

Janczura Józef

Archiwum Motoryzacji

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2025

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Vol. 107, nr 1

5--26

EN

In recent years, Poland has seen a dynamic increase in the number of vehicles on the road. Vehicles participating in road traffic come from both the domestic market, some registered as new, and are imported from foreign markets. The latter are mainly imported from Western Europe and from the American market. Vehicles imported onto the domestic market are several years old and quite often considerably worn out. On the other hand, vehicles from the American market are relatively new and sometimes damaged as a result of road incidents. The aim of this work is to perform a comparative analysis of the results of vehicle technical tests. Research was conducted at two regional vehicle inspection stations over three consecutive years. As part of this analysis, questions about the number of successful and unsuccessful technical tests were answered by the test type. In addition, the number of vehicles using the services of the various stations was evaluated, and the number of vehicle technical tests was analysed by the energy supply of those vehicles. This was followed by the comparison of the test results with the nationwide data in the Central Register of Vehicles and Drivers. A decrease in the number of unsuccessful vehicle tests was noted. Moreover, a greater number of tests of electric vehicles has been noted recently, which may be advantageous to the environment in the future.

3

Microplasma spraying of coatings from wire of heat-resistant nickel alloy Inconel 82 with laser melting

Korzhyk Volodymyr, Gao Shiyi, Khaskin Vladyslav, Bernatskyi Artemyi, Kislitsya Oleksandr, Voinarovych Sergii, Kuzmych-Yanchuk Yevhenii, Kaluzhnyi Sergyi, Hu Yanchao, Guirong Guirong

Advances in Science and Technology. Research Journal

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2025

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Vol. 19, no. 7

164--178

EN

The work is devoted to studying the technological capabilities of the processes of microplasma spraying of wires from heat-resistant nickel alloy Inconel 82 with further laser melting of the sprayed layers to produce narrow-path coatings during restoration of worn end faces of ribbed parts, used in nuclear engineering, aerospace and textile industry, etc. Numerical modeling by finite element method was applied to select the parameters of the modes of microplasma wire spraying and further laser melting of sprayed layers of Inconel 82 alloy. This made it possible to select the parameters of the modes with an accuracy of up to 20% (current 30-40 A at voltage 40 V, deposition speed 100 mm/min; radiation power 3.0 kW, defocusing spot 3 mm, remelting speed 750 mm/min). The value of the parameter of coating growth rate during microplasma spraying of Inconel 82 alloy wire was determined (it was equal to 1 mm of coating height / 1 cm of narrow path length / 1 min of spraying process duration). The work shows for the first time that the useful area of the microplasma spraying spot is close to the defocused laser radiation spot, ensuring unique possibilities for deposition of narrow paths and their laser remelting without hard phase burnout. This is experimentally confirmed by ~17% (290-350 HV) increase in the hardness of sprayed Inconel 82 layer (200-240 HV) during its remelting by radiation with power density of ~4.3·104 W/cm2. It was also determined that the features of structure formation during laser remelting of Inconel 82 alloy promote an enhancement of its corrosion resistance up to 1.5 times and increase in wear resistance by 20-40%, compared to sprayed coatings.

4

Termomodernizacja ścian zewnętrznych o niedostatecznej izolacyjności termicznej. Wstęp do diagnostyki technicznej

Choromański Stanisław

Izolacje

|

2024

|

T. 29, nr 11/12

116--118, 120--124

PL

Artykuł przedstawia proces wyboru wariantu termomodernizacji ścian zewnętrznych o niedostatecznej izolacyjności termicznej ze szczególnym uwzględnieniem diagnostyki technicznej poprzedzającej inwestycje. Autor podaje wady występujące na elewacjach i kryteria doboru ekspertów od diagnostyki oraz zasady wykonania oględzin, badań technicznych, a także finalnych ocen i rekomendacji z uwzględnieniem norm prawnych i zasad sztuki budowlanej.

EN

The article presents the process of selecting a thermal modernization option for external walls with insufficient thermal insulation, with detailed reference to pre-investment technical diagnostics. The author outlines the existing defects on the facades and the criteria for selecting diagnostic experts, along with the principles of visual inspections, technical tests, final assessments and recommendations in accordance with legal norms and good building practice.

5

Causes of Defects and Damage to Brick Masonry Elements in Historic Buildings

Niedostatkiewicz Maciej, Majewski Tomasz

Civil and Environmental Engineering Reports

|

2024

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Vol. 34, no. 4

423--448

EN

Ceramic brick masonry elements constitute the largest number of structural systems of historic buildings, especially sacral and public utility buildings. In the past, they were also very commonly used as a material for the construction of military facilities. Historic buildings and masonry structures undergo destructive processes over time, the course of which can be very diverse and depends, among other things, on the physicochemical properties of the materials, the type of structure, the age of the building, working conditions and random conditions and events. The paper is an engineering review of the causes of damage to masonry structures and indicates the need for cooperation between representatives of various specialties of science and technology, in particular architectural historians, specialists in the field of conservation of monuments, structural engineers and specialists in the field of geotechnics, geology, hydrogeologists and meliorators in order to ensure the protection of masonry structures in historic buildings.

6

Identyfikacja wad budowlanych w budynkach mieszkalnych

Pochybełko Karol, Hoła Bożena

Przegląd Budowlany

|

2023

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R. 94, nr 1-2

129--134

PL

Powstawanie wad budowlanych jest problemem występującym w każdym procesie inwestycyjnym. Celem przedstawionych w artykule badań jest identyfikacja wad w oddawanych do użytkowania budynkach mieszkalnych oraz ocena stopnia ich istotności. Do oceny stopnia istotności wad zaproponowano analizę Pareto-Lorenza oraz tzw. klasyfikację ABC. Na podstawie przeprowadzonych badań stwierdzono, że istotnymi dla jakości budynku są wady zidentyfikowane w następujących elementach budynku: tynki, okna, posadzki, instalacje elektryczne, części wspólne, instalacje wodno-kanalizacyjne, niewłaściwe oczyszczenie elementów, drzwi i szyby.

EN

The formation of construction defects is a problem that occurs in every investment process. The aim of the research presented in the article is to identify defects in residential buildings handed over for use and to assess their degree of significance. To assess the significance of defects, the Pareto-Lorenz analysis and the called ABC classification. Based on the research, it was found that the defects identified in the following building elements are significant for the quality of the building: plasters, windows, floors, electrical installations, common parts, plumbing, improper cleaning of elements, doors and glass.

7

Imaging methods of detecting defects in photovoltaic solar cells and modules: a survey

Maziuk Maurycy, Jasińska Laura, Domaradzki Jarosław, Chodasewicz Paweł

Metrology and Measurement Systems

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2023

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Vol. 30, nr 3

381--401

EN

In pursuit of increased efficiency and longer operating times of photovoltaic systems, one may encounter numerous difficulties in the form of defects that occur in both individual solar cells and whole modules. The causes of the occurrence range from structural defects to damage during assembly or, finally, wear and tear of the material due to operation. This article provides an overview of modern imaging methods used to detect various types of defects found in photovoltaic cells and panels. The first part reviews typical defects. The second part of the paper reviews imaging methods with examples of the authors’ own test results. The article concludes with recommendations and tables that provide a kind of comprehensive guide to the methods described, depending on the type of defects detected, the range of applicability, etc. The authors also shared their speculations on current trends and the possible path for further development and research in the field of solar cell defect analysis using imaging.

8

Zmiany w odbiorze lokalu mieszkalnego lub domu jednorodzinnego posiadającego wady w świetle nowej ustawy deweloperskiej

Lichota Agnieszka

Budownictwo i Prawo

|

2023

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R. 26, nr 4

14--19

PL

Przedmiotem artykułu jest analiza prawna przepisów dotyczących wad stwierdzonych w trakcie odbioru lokalu mieszkalnego lub domu jednorodzinnego, ale przed przeniesieniem prawa własności na nabywcę, wprowadzonych na mocy ustawy z dnia 20 maja 2021 r. o ochronie praw nabywcy lokalu mieszkalnego lub domu jednorodzinnego oraz Deweloperskim Funduszu Gwarancyjnym (t.j. Dz.U. z 2021 r. poz. 1177). W artykule uwzględniono najnowszą literaturę przedmiotu, a rozważania dopełniają dotychczasowe poglądy doktryny i orzecznictwo.

EN

The subject of the article is a legal analysis of the provisions regarding defects found during the acceptance of a residential premises or a single-family house, but before the transfer of ownership to the buyer, introduced under the Act of May 20, 2021 on the protection of the rights of the buyer of a residential premises or a single-family house and the Developer Guarantee Fund. (consolidated text: Journal of Laws of 2021, item 1177). The article takes into account the latest literature on the subject, and the considerations are complemented by current views of the doctrine and case law.

9

Enhancing heat and mass transfer to suppress void defects in friction stir welding by superimposing ultrasonic vibration

Wang Xue, Zhang Xiankun, Shi Lei, Wu Chuangsong, Chen Gaoqiang

Archives of Civil and Mechanical Engineering

|

2023

|

Vol. 23, no. 4

art. e256, 1--16

EN

Heat and mass transfer in the process of friction stir welding (FSW) determine the weld formation quality. Meanwhile, the formation of voids in FSW limits welding speed improvement and welding efficiency. Although superimposing ultrasonic vibration can be adopted as an effective means to restrain the formation of voids, the potential suppression mechanism was still unrevealed. Herein, a multi-physical model using the shear stress boundary conditions was put forward to quantitatively study the influence of ultrasonic vibration on the heat and mass transfer behaviors and the resulting weld formation which was also validated experimentally. Our results show that ultrasonic vibration in FSW slightly enhances the heat flux at the tool-work piece interfacial contact surface as well as the plastic deformation heat generation near the tool. Therefore, the high-temperature area (higher than 690 K) near the tool pin side increases from 2.11 to 2.29 mm. The slightly higher heat rate and temperature enhance the fluidity of plastic material, resulting in an obvious increase in the flow velocity. As a consequence, the plastic material moves farther to fill the cavity at the rear advancing side, which is conducive to eliminating the void defects. The maximum strain rate on z = 2 mm horizontal plane at the AS is 206.7 s−1 in UVeFSW, while it is 13.5 s−1 in CFSW. The strain rate of the contact interface on AS increases by nearly 5 times, which implies an enhanced plastic material flow and is the main reason for suppressing void defects by superimposing ultrasonic vibration in FSW.

10

Investigation of defective reinforced concrete beams with obtained damage of compressed area of concrete

Blikharskyy Zinoviy, Lobodanov Мaksym, Vegera Pavlo

Production Engineering Archives

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2022

|

Vol. 28, Iss. 3

225--232

EN

In the building industry, it is a frequent cause of damage to elements at different stages: during transportation, operation, installation, etc. Since replacing an element is not always possible due to various circumstances, it entails significant financial losses, logistics, and others. For this reason, the expediency of studying the effect of damage on the bearing capacity of reinforced concrete elements is growing. This effect is dependent on its type and has significant variability. In the case of the combination of the defect and damage in reinforced concrete elements, the complexity of the research of this element increases significantly. In this article is discussed: a review of damaged reinforced concrete elements; researching the influence of the damage and additional factors on the element; developed testing methodology for bending reinforced concrete elements with damage to concrete in a compressed zone with insufficient reinforcement, when performing damage to the action of the load and during the action of the load, is presented; the influence on the deformability and bearing capacity of the variability of damage on the sample with insufficient reinforcement is reflected, taking into account the factor of change in the load at which the damage is performed; a comparison is made of the dependence of the change in the actual height of the compressed zone on the change in the load on the elements; implementation of conclusions on the result of the study.

11

Uszkodzenia i awarie rur GRP

Kuliczkowski Andrzej

Instal

|

2022

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nr 11

64--67

PL

Zestawiono najczęściej popełniane błędy na etapie instalowania rur GRP podając jednocześnie możliwe ich przyczyny oraz sposoby ich unikania. Zamieszczono przykład dotyczący możliwych uszkodzeń tych rur w oparciu o ich badanie techniką CCTV w jednym z polskich miast. Badania te zostały wykonane w dwu okresach, bezpośrednio po odbiorze i 14 miesięcy później. Inwestycja ta obejmowała odcinki przewodu kanalizacyjnego o średnicach 300 i 400 mm. Zamieszczono 7 zdjęć ilustrujących zaobserwowane uszkodzenia. Podano także inne przykłady awarii rur GRP, które stwierdzono zarówno w kraju, jak i za granicą.

EN

The paper presents the most common errors made at the stage of installing pipes, together with possible causes of these errors and the ways of avoiding them. An example of possible damage to GRP pipes, which were examined using the CCTV technique, is provided. Tests were performed in one Polish city and covered two stages, immediately after the pipes were commissioned, and then again 14 months later. The investment covered sections of sewers that had a diameter of 300 mm and 400 mm. The observed damage is shown in 7 photos. Other examples of GRP pipe failures, from both Poland and abroad, are also provided in the paper.

12

Porosity assessment of suspension and saturated composite castings with the use of microscopic examinations

Staude Marek

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2021

|

nr 67 (139)

53--57

EN

Good quality in composite castings can be confirmed primarily by their user. The producer is obliged to create a good product that meets the user’s needs that should undergo quality control. Omission of technological procedures and improper quality control may result in various defects like porosity. This paper presents the characteristics of the casting defect, namely porosity, with a particular focus on porosity in suspension and saturated metal composites. This defect is different, specific to composite castings, making its identification very difficult. The aim of the study is to detect and describe porosity in composites with the use of microscopic and submicroscopic examinations. The assessment of the porosity of the microstructure of composite castings allowed for the formulation of the following conclusions: in addition to the porosity that occurs in castings of classic materials (cast steel, cast iron, and non-ferrous metal alloys), metal composites also distinguish between primary and secondary agglomerates, leaving the reinforcement space not filled, occluded bubbles, and separated gas bubbles.

13

Analysis the Influence of Steel Sheet Production Technology on the Quality Products in Steel Service Polska

Sitko Jacek

Multidisciplinary Aspects of Production Engineering

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2021

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Vol. 4, Iss. 1

301--308

EN

The process of production and processing and preparation for distribution of steel products is associated with the requirements of maintaining appropriate procedures. They allow, in accordance with industry standards to avoid unforeseen problems associated with the preparation, implementation and finalization of activities aimed at achieving the intended purpose, which is a finished product of adequate quality and customer satisfaction. It is not always possible in the production process to meet all the requirements and technological, organizational and human factor recommendations. The analysis of selected problems, which includes the content of the article allows to significantly determine the factors and parameters associated with the preparation and technical implementation affecting the implementation of the intended objectives of the company, i.e. achieving an appropriate level of quality and minimizing the defects in the process of steel sheet preparation. Analysis of selected parameters was made on the basis of data obtained in the company operating on the international market Company Steel Service Poland. At the request of company representatives, the name has been changed due to the production data used in the article, which may be considered as sensitive. The article contains data based on research carried out in Steel Service Poland. Selected problems are the subject of analysis of steel sheets cutting processes with the analysis of causes of customer complaints with reference to the produced steel products. Selected steel grades and factors affecting the efficiency of the technological process are presented. The analysed set of factors translates into the level of product quality and reduction of arising defects.

14

Multiproduct Fabrication-Shipment Decision Making Incorporating an Accelerated Rate and Ensured Product Quality

Chiu Yuan-Shyi Peter, Chiu Victoria, Lin Hong-Dar, Chiu Tiffany

Management and Production Engineering Review

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2021

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Vol. 12, No. 2

33--44

EN

Facing severely competitive global markets, managers of the modern transnational corporations must effectively integrate its intra-supply chain system to meet customers’ multiproduct demands with good quality items, minimum operating expenses, and in a timely delivery matter. Inspired by assisting current transnational firms to achieve the mission, this study builds a mathematical model to explore a multiproduct fabrication-shipment problem incorporating an accelerated rate and ensured product quality. A single machine production scheme under a common cycle policy and with random defects, rework, and an accelerated fabrication rate is considered. The speedy rate option is associated with extra setup and linear variable costs, which aims to cut short the common cycle time. Mathematical derivation is employed to find the long-run average system expense. The optimization method is used to jointly derive the decision for common length and delivery frequency per cycle for the problem. Numerical illustration is offered to confirm the applicability of the results and expose the individual/combined influences of diverse crucial system features on the problem, thus facilitate the intra-supply chain’s fabrication-shipment decision making.

15

Defects of AC lining at Josefův Důl dam and their refurbishment

Říha Jaromír, Špano Miroslav

Gospodarka Wodna

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2021

|

Nr 9

17--22

EN

The Josefův Důl embankment dam is located in the Czech Republic on the river Kamenice, about 15.5 km away from the Czech boundary with Poland. It consists of the main dam with the crown length 360 m and height 44 m above the foundation, and the auxiliary dam with the crown length 360 m and the height of 15 m above the foundation. Both dams are covered upstream with asphalt concrete (AC) lining serving as impervious membrane. As the results of permeability pressure tests did not meet the design requirements, a new asphalt layer was placed on the original AC lining just after the dam commissioning. It was placed on the entire surface of the auxiliary dam and only along a few strips at the main dam. Plastic deformations of the upper, newly added layer have occurred, mainly at the auxiliary dam. The first defects appeared in the years 2007 and 2008, when – following wetting of the mantle at the auxiliary dam – bulges appeared on considerable part of the surface. Since 2014, many significant defects have repeatedly occurred, in particular at the locations of repairs. In 2015, new cracks appeared on another considerable area of the auxiliary dam. The main damage was repaired locally with a COLETANCHE bitumen strip. In the following years, further local repairs were carried out on the damaged surfaces of the additional AC layer. The paper describes and makes an assessment of the AC lining and proposes possible variants of lining repair, listing the expected advantages and disadvantages. For provisional repairs, the authors recommend the extension of the structure’s service life by application of a protective mastic coating at both dams. At the same time, preparations for complete lining renewal should be started.

PL

Zapora ziemna (narzutowa) Josefův Důl na rzece Kamenice jest zlokalizowana w Czeskiej Republice około 15,5 km od granicy z Polską. Składa się z zapory głównej o długości w koronie 360 m i wysokości 44 m powyżej poziomu posadowienia i zapory pomocniczej (bocznej) o długości w koronie 360 m i wysokości 15 m powyżej poziomu posadowienia. Od strony wody górnej obie zapory są wyposażone w okładzinę z asfaltobetonu (AC), która służy jako nieprzepuszczalna membrana. Jako, że testy szczelności nie spełniały wymagań projektowych, nowa warstwa asfaltu została położona na oryginalnej okładzinie asfaltobetonowej zaraz po oddaniu zapory do użytku. Zabieg ten wykonano dla całej powierzchni skarpy odwodnej zapory pomocniczej i tylko dla kilku odcinków zapory głównej. Na zaporze pomocniczej pojawiły się odkształcenia plastyczne górnej, nowo dodanej warstwy. Pierwsze usterki pojawiły się w latach 2007 i 2008, kiedy to po zwilżeniu uszczelnienia zapory pomocniczej powstały wybrzuszenia w znacznym zakresie. Od 2014 roku wielokrotnie pojawiały się poważniejsze usterki, w szczególności w miejscach napraw. W 2015 roku na zaporze pomocniczej pojawił się następny znaczący obszar z nowymi pęknięciami. Główne uszkodzenia naprawiono lokalnie za pomocą taśmy bitumicznej COLETANCHE. W kolejnych latach prowadzono dalsze lokalne naprawy uszkodzonych powierzchniach dodatkowo ułożonej warstwy AC. W artykule opisano i dokonano oceny okładziny AC wraz z propozycją możliwych wariantów naprawy wykładziny z wyszczególnieniem spodziewanych zalet i wad. W celu wykonania naprawy prowizorycznej zalecono wydłużenie żywotności poprzez nałożenie ochronnej powłoki mastyksowej na obu zaporach. Jednocześnie należy przystąpić do przygotowania kompletnej naprawy okładziny.

16

Ultrasonic Assisted Active-Passive Filling Friction Stir Repairing to Eliminate Volume Defects

Wang Tao, Gong Xue, Ji Shude, Xue Gang, Lv Zan

Archives of Metallurgy and Materials

|

2021

|

Vol. 66, iss. 1

217--222

EN

Ultrasonic assisted active-passive filling friction stir repairing (A-PFFSR) was proposed to repair volume defects in the metallic parts. Sound joints without interfacial defects could be achieved. Firstly, the ultrasonic was beneficial to improving material flow and atom diffusion, and then eliminated kissing bond defects compared to conventional A-PFFSR joints. Secondly, the equiaxed grains were refined by ultrasonic vibration. Lastly, the repairing passes were reduced due to the ultrasonic, which decreased softening degree of the repaired joints. The maximum tensile strength of 150 MPa was achieved. Therefore, this strategy to repair the volume defects is feasibility and potential in the remanufacturing fields of aerospace and transportation.

17

Evaluation of the Cause and Consequences of Defects in Cast Metal-Ceramic Composite Foams

Popielarski P., Sika R., Czarnecka-Komorowska D., Szymański P., Rogalewicz M., Gawdzińska K.

Archives of Foundry Engineering

|

2021

|

Vol. 21, iss. 1

81--88

EN

In this research, the quality of manufactured cast metal-ceramic foams (manufactured using blowing gas) was tested. The causes responsible for defect formation in the composite foams and their consequences were analyzed using the FMEA (Failure Mode and Effects Analysis) method, which is a useful tool for minimizing losses caused by low product quality. This method involves analytically determining correlations between the cause and consequences of potential product defects, and it takes into account the criticality factor (risk). The FMEA analysis showed that pore breaks were the most "critical defect" (with the highest number of effects on the product, the Risk Priority Number, affecting the quality of the composite foam). The second most critical defect was discontinuities in the foam frame structure. Destruction or damage to the foam structure (although very rare) deprived the composite foam of its primary function, which is to reinforce the product. The third most critical defect was non-uniform foam pore size.

18

Comparison of selected point estimators of vibration signals for purposes of fault detection in rolling bearings

Krol Adrian, Fidali Marek, Jamrozik Wojciech

Vibrations in Physical Systems

|

2020

|

Vol. 31, nr 2

art. no. 2020212

EN

Most of machine breakdowns relate to bearing failures thus it is very important to diagnose bearing conditions. The main purpose of the study was to classify the condition of bearings and identify defective ones based on visual inspection and the values of classic parameters of the acceleration signal vibration, such as Peak, RMS, Kurtosis. The results were compared to parameters provided by the SPM method. All vibration parameters were estimated for high pass filtered signals where filters had following cut-off frequencies 0.5; 1, 2, 5 and 8 kHz. Bearings were tested on the laboratory test bench being built at the Silesian University of Technology. Based on the signal analysis and visual inspections it can be stated that there is agreement in the assessment of the conditions between the parameters of the SPM method and the Peak and RMS parameters. It was observed that the sensitivity to the existence of low-intensity defects increases when the vibration parameters are determined for signals in the band above 2kHz.

19

Enhancement of electrical performance of ZnSe thin films via Au nanosandwiching

Qasrawi A. F., Taleb Maram F.

Materials Science Poland

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2020

|

Vol. 38, No. 1

174--180

EN

In this work, we report the effect of sandwiching of Au nanosheets on the structural and electrical properties of ZnSe thin films. The ZnSe films which are grown by the thermal evaporation technique onto glass and yttrium thin film substrates exhibit lattice deformation accompanied with lattice constant extension, grain size reduction and increased defect density upon Au nanosandwiching. The temperature dependent direct current conductivity analysis has shown that the 70 nm thick Au layers successfully increased the electrical conductivity by three orders of magnitude without causing degeneracy. On the other hand, the alternating current conductivity studies in the frequency domain of 10 MHz to 1800 MHz have shown that the alternating current conduction in ZnSe is dominated by both of quantum mechanical tunneling and correlated barrier hopping of electrons over the energy barriers formed at the grain boundaries. The Au nanosheets are observed to increase the density of localized states near Fermi level and reduce the average hopping energy by ~5 times. The conductivity, capacitance, impedance and reflection coefficient spectral analyses have shown that the nanosandwiching of Au between two layers of ZnSe makes the zinc selenide more appropriate for electronic applications and for applications which need microwave cavities.

20

Dependence of defect concentration, optical and photocatalytic properties of β-Ni(OH)2/ZnO and NiO/ZnO composite powders on phase transformation

Suwanboon Sumetha, Klubnuan Sarunya, Homkaew Mukdawan, Amornpitoksuk Pongsaton

Materials Science Poland

|

2020

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Vol. 38, No. 2

219--227

EN

β-Ni(OH)2/ZnO composite powders were successfully synthesized by hydrothermal method at 180 °C for 15 h whereas NiO/ZnO composite powders formed after the as-prepared powders were calcined at 800 °C for 1 h in air. The X-ray diffractometer (XRD), scanning electron microscope (SEM), UV-Vis spectrophotometer were used to characterize the phase, particle shape as well as size and optical properties, respectively. In this system, it was found that ZnO is a major phase while β-Ni(OH)2 and NiO are a minor phases. The altered particle shape of ZnO was influenced by addition of Ni(CH3COO)2ˑ6H2O whereas the particle shape of the minor phase was changed due to the calcination process. The optical band gap decreased when the amount of minor phase increased. For photocatalytic study, it was found that 6 mol% β-Ni(OH)2/ZnO composite powders exhibited the best decolorization of methylene blue aqueous solution.