Physico-mechanical and micro-chemical changes on the ceramic and metal artifacts surfaces treated with laser

Чишћење је један од најважнијих процеса у конзервацији предмета културне баштине, али такође и један од најосетљивијих процеса са могућношћу оштећивања оригиналних материјала. Микроморфолошке и микрохемијске анализе на површинама артефаката пре и после процеса чишћења указују на ефикасност методе чишћења, а представљају и користан податак о пореклу и степену деградације артефакта. Значај ласерских техника код чишћења предмета културне баштине почива на особинама ове технике као што су висока осетљивост, недеструктивност, селективност, прилагодљивост, применљивост на лицу места и др. Ове технике се данас широко користе у рестаурацији и чишћењу, архитектонских камених површина. Код других предмета културне баштине (слика, вишебојних папирних докумената, керамичких предмета, стакла, метала, текстила итд.) њихова примена се још увек испитује због комплексног процеса деловања ласерског снопа на ове осетљиве материјале. За безбедно и ефикасно чишћење веома је важно одабрати одговарајуће параметаре ласера и оптимизовати методу ласерског чишћења. Због разноликости материјала који се срећу у културној баштини сваки допринос у овој области је изузетно значајан. У овом раду приказани су принципи методе чишћења ласером, као и резултати примене CO2, Nd:YAG и Er:Glass ласера код чишћења предмета културне баштине од керамике, метала и предмета сложеног састава (комбинације метал-текстил). Испитивања су спроведена на савременим и археолошким узорцима мењањем параметара ласера као што су таласна дужина, број импулса и енергија снопа. За дијагностику микроморфолошких промена на површини озрачених узорака коришћене су оптичка и СЕМ микроскопија. EDX, LIBS, XRF и XRD анализе коришћене су за испитивање хемијског саства узорака и промена састава које, услед деловања ласера, настају у саставу материјала на зонама третираним ласером...Cleaning is one of the most important processes for the conservation of cultural heritage artifacts, but also one of the most delicate and potentially damaging to the original materials. Micromorphological and microchemical analyzes of artefacts surfaces material before and after cleaning process indicates on cleaning effectiveness and can also be useful information for determination of artefacts provenience and degradation degree. Importance of laser techniques in cleaning of cultural heritage objects is based on the properties of these techniques, such as high sensitivity, nondestructivity, selectivity, flexibility, applicability on the spot and others. These techniques are now widely used in the restoration and clean, architectural stone surfaces. In other objects of cultural heritage (picture multicolored paper documents, pottery, glass, metal, textiles, etc.). For reliable and efficient cleaning, selection of the appropriate laser parameters and laser cleaning method optimization is of great significance. Due to the diversity of materials that can be found in cultural heritage, each contribution in this area is extremely important. In this dissertation, the principles of the laser cleaning method, as well as the results of applying the CO2, Nd: YAG and Er:Glass lasers in cleaning of cultural heritage objects made of ceramic, metal and complex (metal-textile combination) materials are presented. Laser cleaning investigations are carried out on contemporary and archaeological samples by varying laser parameters such as wavelength, number of pulses and laser beam energies. For the diagnostics of micromorphological changes on the surface of irradiated samples, optical and SEM microscopy were used. EDX, LIBS, XRF and XRD methods were used for the analysis of changes in samples treated zones chemical compositions caused by lasers irradiation. Measurement of micro and nano hardness was carried out to test the change in the microhardness of the sample after laser action on the surface. By profilometry tests the roughness of the irradiated surfaces of samples before and after irradiation are determined. By image analysis the degree of surface cleaning were determined..

Polyaniline thin films in sensors for detection of toxic welding vapors

In this paper the possibilities of applying sensors based on filters with surface acoustic waves (SAW) for the detection of harmful products in welding processes are analyzed. This review discusses the sensing mechanism and configurations of the sensors. The principles of SAW sensors are considered with special emphasis on the application of conducting polyaniline nanocomposites as sensitive thin layers in sensors for the detection of CO, NO2, and COCl2. The literature suggests the use of In2O3 as a dopant for CO and NO2 detection sensors, and ethylenediamine and phenylenediamine in COCl2 sensors. The paper presents original results of modeling of sensors that are designed for detection of CO and NO2 for which there are experimental data in the literature. The results obtained based on this model are in excellent agreement with results from the literature, which shows the validity of modeling. Based on the developed modeling methods, calculations were done for sensors for the detection of these gases in which the structure was the surface of quartz. From these modeling results it can be concluded that the use of the quartz substrate provides better sensitivity. In addition, the quartz sensors are thermally stable.U radu su analizirane mogućnosti primene senzora u čijoj osnovi se nalaze filtri sa površinskim akustičkim talasom (PAT), za detekciju štetnih produkata u procesu zavarivanja. Objašnjeni su principi rada PAT senzora sa posebnim osvrtom na primenu elektroprovodnih polianilinskih nanokompozitnih materijala – polianilin/In2O3 i etilendiamin i fenilendiamin polianilinskih nanokompozita kao osetljivih tankih slojeva za detekciju CO, NO2 i COCl2. Prikazan je deo originalnih rezultata modelovanja PAT senzora koji su namenjeni detekciji pomenutih gasova. Rezultati dobijeni na bazi sopstvenog modela poređeni su sa rezultatima iz literature. Pokazano je da se ovim na činom modelovanja može uspešno odrediti koncentracija štetnih gasova u okruženju

Turbulence recognition in free convective flow by thermal-video post-processing in the case of a thermal power plant mill

This paper presents a study of a free convection flow around the walls of a ventilation mill of the Thermal Power Plant "Kostolac B", Kostolac, Serbia. A combined method consists of thermography and software post-processing, PATS. The PATS is specially developed for recognition of turbulence zones by the custom processing of large input data sets from thermal videos. The calculations determine maximum temperature fluctuation i.e. peak-to-peak fluctuation at every spot during the recording time. Three thermal videos of the walls were analyzed. Maximum temperature fluctuation occurred in the zones close to the obstacles, which are thus recognized as one of the main sources of turbulence. Besides, PATS has recognized fine camera oscillations and mechanical movements of a flexible material near the dozer wall. The detected zones of turbulence correspond to the previous studies and to the theory. The method shows good potential in the field of free convective flow research through the improvement of testing efficiency and cost savings. State-of-the-art thermograph cameras and updated software are recommended

Ispitivanje interakcije rubinskog lasera sa staklom

This paper presents the results of the ruby laser light interaction with glass surface. The investigation was conducted in order to determine the maximum density of laser light energy (λ = 694.3 nm, t = 30ns) that can be safely applied in different laser systems used in nondestructive testing methods (NDT). The process of irradiation took place in atmospheric conditions. The results show that interaction of laser beams with glass materials is a complex phenomenon. It depends on many factors and it is associated with localized formation of plasma, heating of the material that leads to melting and transient stresses causing mechanical damages. The zones of laser light interactions were investigated by scanning electron microscope (SEM) with energy-dispersal unit for the analysis of X-ray (EDX). The results obtained by SEM and EDX analysis show that the maximum allowable energy density is 5 J/cm2 for ruby laser light.У овом раду је приказан део резултата истраживања која се односе на проучавање интеракције светлости рубинског ласера и површине стакла. Циљ испитивања је одређивање максималне густине енергије ласерске светлости (λ = 694.3 nm, t = 30ns), која може безбедно да се користи у различитим ласерским системима за испитивање без разарања (ИБР). Озрачавање стаклених узорака је вршено у атмосферским условима. Резултати показују да је интеракција ласерске светлости са стаклом веома комплексан феномен. Резултати интеракције зависе од више фактора и повезани су са формирањем локалне плазме и грејањем материјала које доводи до топљења и напрезања што причињава механичка оштећења. Зоне интеракције ласерске светлости са површином стакла су испитивани скенирајућим електронским микроскопом (SEM) и енергодисперзивним детектором рендгенских зрака (EDX). Резултати добијени SEM и EDX анализом показују да је DE = 5·J/cm2 максимално дозвољена енергија за безбедан рад оптичких система који користе рубински ласер

Laser cleaning of corrosion, efficient and environmentally friendly method

In recent years, lasers have been used more and more in different areas of human life, science, industry, medicine, military, agriculture, and show business, protection of environmental and culturalheritage objects, in the arts and so on. Laser technology has some advantages in many areas over classical methods. This paper presents the results of laser application for cleaning corrosion of metal objects, cooper and brass. The first sample was oxidised cooper plate and the second ashtray made of brass. Nd: YAG laser was used as a source of radiation to clean surface corrosion deposits. Removal of layers from the surface occurs through the process of laser ablation. Three wavelengths were used with different fluences. The cleaning results, i.e. the morphological and chemical changes were investigated by optical microscopy, XRF analysis and colorimetry. The obtained results show that lasers are efficient corrosion cleaning and environmentally friendly method

Laser cleaning of varnish from bog oak surface

The removal of varnish is a very challenging task in the conservation of wooden artifacts. The results of experiments performed to investigate the suitability of lasers for cleaning aged varnish from bog oak wood (ebony) are presented in this paper. Optimal laser parameters for safe and efficient varnish ablation were determined in order to preserve the integrity of the original wooden substrate during the cleaning process. The ablation threshold for varnish and wood damage threshold was examined using Nd:YAG laser (1064, 532 and 355 nm) emitting pulses of nanosecond (8 ns) duration. Results of induced varnish removal and other morphological alterations to the wood surface were investigated by optical microscopy and colorimetry

One method for ordering turbulence measuring places applied to free-convection flow around thermal plant coal mill

The investigations of the turbulence in the flow are one of the most expensive, thus the improvement of existing ones and the research related to the new methods are in continual development. The multidisciplinary approach led to the application of the infrared thermography in the turbulent boundary layer observations with the endpoint goal of energy and cost savings in its early stages. This work presents the use of the industrial type infrared thermography for identification of the turbulent zones in the free convective flow, so far the less investigated problem related to convection heat transfer. It was shown that the transient spot temperature difference, measured on the complex geometry of the real-scale coal ventilation mill, of the Thermal plant “Kostolac B”, by an infrared camera, is a good parameter for identification of the most influenced positions by turbulence. The defined fields with maximal transient temperature difference are in accordance with theory and values calculated by numerical simulations for clean geometry, confirming the assumptions. The described method is also convenient for use in cases when the other methods are not applicable because of the complex geometry, unapproachable, or for the other similar reasons. The results from this work would support the more precise measurements with the research type infrared camera, the other methods for measurements

Optimizacija laserskog čišćenja metalnih artifakta

Laser techniques have become irreplaceable in solving a wide variety of conservation problems. For the last thirty years, lasers have been used in the diagnostic process, in the process of removing undesirable layers, as well as in repairing damages of cultural heritage objects. Because of the complexity of artifacts, traditional cleaning methods in many cases have partial success. Laser cleaning shows certain advantages such as: high selectivity, precision, efficiency and reliability in application in different types of materials. There are also certain risks for cleaning objects, and the studies of process optimization are the subject of a number researches. This paper presents the methodology and results of the application of infrared thermography for the continuous monitoring of temperature distribution on the surface of metal objects during laser irradiation. A large number of experiments were performed using Nd: YAG laser for cleaning. The obtained results were verified by the results of the numerical simulation of heat propagation in the base material. It has been shown that infrared thermography can eliminate damage to the base material, which is of special importance in the laser cleaning of priceless value artifact.Laserske tehnike su postale nezamenjive u rešavanju najrazličitijih konzervatorskih problema. Zadnjih tridesetak godina koriste se u procesu dijagnostike stanja, u procesu uklanjanja nepoželjnih slojeva, kao i u sanaciji oštećenja na predmetima kulturnog nasleđa. Zbog složenosti artefakata, tradicionalne metode čišćenja, u velikom broju slučajeva, imaju delimičnog uspeha. Lasersko čišćenje pokazuje određene prednosti kao što su: velika selektivnost, preciznost, efikasnost i pouzdanost u primeni kod različitih vrsta materijala. Postoje i određeni rizici po predmete čišćenja, te je optimizacija procesa predmet velikog broja istraživanja. U ovom radu su prikazani metodologija i rezultati primene infracrvene termografije za kontinualni monitoring raspodele temperature na površini metalnih objekta za vreme ozračavanja laserom. Izvršen je veliki broj eksperimenata, u kojima se Nd:YAG laser koristi za čišćenje. Dobijeni rezultati termogarfijom su verifikovani rezultatima numeričke simulacije širenja toplote u osnovnom materijalu. Pokazano je da se primenom infracrvene termografije mogu eliminisati oštećenja na osnovnom materijalu, što je od posebnog značaja kod artefakata neprocenjive vrednosti

Lasersko čišćenje tekstilnih eksponata sa korodiranim metalnim nitima - optimzacije parametara procesa

This paper presents the results of the laser cleaning effects on textile samples with corroded metallic threads. In many museum collections, there are textile exhibits like uniforms, national costumes, flags and home textile, embroidered with metallic threads. Corrosion of metal threads is one of the most common problems that damage embroidered items. In the practice, the application of conventional cleaning methods rarely gives the expected results, and the implementation of laser technology was the next step for corrosion products cleaning. The Nd:YAG laser was used to clean the corrosion of embroidered items from a museum study collection. The effects on the laser irradiated zones were investigated by optical and SEM microscopy and the EDX analysis. The laser irradiation process parameters of the metal threads corrosionU radu su prikazani rezultati čišćenja korozije na tekstilnim eksponatima sa metalnim nitima pomoću lasera. U mnogim muzejskim zbirkama nalaze se eksponati kao što su uniforme, narodne nošnje, zastave i kućni tekstil, ukrašeni vezom metalnim nitima. Korozija metalnih niti je jedan od najvećih problema, koji oštećuje vezene eksponate. U praksi, veoma često, klasične metode ne daju očekivane rezultate i primena lasera je sledeći korak čišćenja korozionih produkata. Nd- YAG laser je korišćen za čišćenje korozije vezenih eksponata iz muzejske, studijske zbirke. Efekti u zonama ozračenim laserom su ispitivani optičkim mikroskopom, SEMom i EDX analizom. Određeni su izabrani parametri za uspešno i bezbedno čišćenje korozije na metalnim nitima.В этой статье приведены результаты очистки коррозии на экспонатах из текстиля с металлическими нитями с помощью лазера. Во многих музейных коллекциях представлены экспонаты, такие как формы, народные костюмы, флаги и домашний текстиль, вышитые металлической нитью. Коррозия металлических нитей является одной из самых больших проблем, которая повреждает вышитые экспонаты. На практике, очень часто, классические методы не дают ожидаемых результатов и применение лазера является следующим шагом очистки следов коррозии. Nd-YAG лазер используется для очистки коррозии вышитых экспонатов из музейных исследовательских коллекций. Эффекты в областях облученных лазером были исследованы с помощью оптического микроскопа, SEM и EDX анализом. Некоторые параметры определяются и выбираются так, чтобы успешно и безопасно очистить металлические нити от коррозии.Dans ce papier on a présenté les résultats du nettoyage de corrosion chez les objets exposés en textile aux fils métalliques réalisé au moyen du laser. Dans plusieurs collections de musée on trouve les objets tels que uniformes, costumes nationaux, drapeaux et textile de maison qui sont ornés de broderie faite en fils de métal. La corrosion des fils en métal est un des plus grands problèmes car elle endommage les objets exposés brodés. En pratique les méthodes classiques ne donnent pas souvent les résultats espérés et l’utilisation du laser est le pas suivant dans le nettoyage des produits de corrosion. Le laser Nd-YAG a été utilisé pour le nettoyage de corrosion sur les objets brodés appartenant à la collection d’étude de musée. Dans les zones irradiées par laser les effets ont été étudiés au moyen du microscope optique et en utilisant les analyses SEM et EDX. On a déterminé les paramètres choisis pour le nettoyage en sécurité et avec succès de la corrosion chez les fils en métal

Corrosion characteristics of laser cleaned brass surfaces

Different types of weapons and military equipment, made of brass, are often exposed to extreme atmospheric conditions, to chemical agents, erosion and wear. It is important to evaluate the corrosion characteristics of brass in different corrosive environments, and especially after laser cleaning of corrosion products, various deposits and other undesirable surface layers. The brass corrosion resistance changes, after surface laser cleaning, were examined in this paper. Nd:YAG laser with lambda=1064 nm was used for laser cleaning process. SEM analysis was applied for investigation of the brass surface micro-morphology before and after laser cleaning. Electrochemical techniques such as linear polarization resistance, electrochemical impedance spectroscopy, linear sweep voltammetry and electrochemical frequency modification were used to study the corrosion characteristics of laser treated and mechanically prepared brass surface. The results of electrochemical tests have shown that the corrosion rate of laser treated brass surface is approximately same as the corrosion rate of brass surface prepared by the standard grinding and degreasing process. This indicates that the brass surface was efficiently cleaned by laser treatment with applied operating parameters without lowering its corrosion resistance. The abilities of different electrochemical methods for determination of corrosion rate were compared