首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
The feasibility and the effectiveness of using hydroxyapatite (HAP) formed by reacting limestone with a solution of diammonium hydrogen phosphate (DAP) in mild conditions, as a consolidant for carbonate stones were investigated. Firstly, a novel method for predamaging limestone was developed. Then, the effects of DAP solution concentration and reaction duration were evaluated to define the best treatment conditions, and the strengthening effect was evaluated on artificially damaged Indiana Limestone samples. Treated samples exhibit a significant increase in the dynamic elastic modulus and tensile strength, which is attributed to microcrack reduction and pore filling consequent to formation of calcium phosphate phases at grain boundaries, as assessed by SEM/EDS and ESEM/EBSD. Consequent to a slight reduction of coarser pores, as revealed by MIP, the sorptivity of treated samples is only slightly reduced, so that water and water vapor exchanges with the environment are not significantly blocked.  相似文献   

2.
The growing interest in the conservation of historic buildings encourages the development of water-repellent materials and methodologies to consolidate and/or protect stones. Recently, particular attention was devoted to composites of inorganic oxides nanoparticles and hybrid siloxane or silicone polymers. Here we present a study on the water repellence of a thin protective coating obtained through sol-gel process starting from Glymo and Dynasylan 40®, and loading the silicate matrix with nano-sized silica particles (Aeroxide LE1® -Degussa-Evonik). The coatings were applied to limestone, sandstone and granite samples. The silica nanoparticles have been characterized by XRD, the siloxane matrix through micro-Raman spectroscopy, while the surface morphology was examined by SEM. The efficacy of the treatments has been evaluated through static contact angle measurements and capillary water absorption. The optical appearance of the coatings was evaluated by colorimetric measurements. Nanoparticles at suitable concentration gave high values for the static contact angle (up to ∼ 150°), for all stone species even for four months exposure to atmospheric conditions. The coatings, in the water capillary absorption tests, however, behave as expected only for granite even if the long-term water direct contact reduces the hydrophobicity.  相似文献   

3.
This paper presents a complementary analytical approach to characterize vegetable tanning materials in historic leathers. It is described the application of two molecular spectroscopic techniques, ATR-FTIR and UV-Vis, and three specific chemical tests to analyse tannins present in leathers. Acid butanol, nitrous acid and rhodanine colorimetric tests, evaluated both visually and spectrophotometrically, were used to identify condensed tannins, ellagitannins and gallotannins, respectively. Ten samples of commercial, or laboratory prepared, vegetable tannins and seven new vegetable tanned leathers were also analysed and obtained results were used for comparison. The complete analytical procedure was performed, in a semi-micro-destructive scale, using fibres collected from leather. Analysis of ATR-FTIR and UV spectra of commercial and laboratory prepared vegetable tannins allowed the establishment of the characteristic bands of condensed and hydrolysable tannins and, more specifically, gallotannins. These data were used to confirm the type of vegetable tanning agents used in new leather extracts. The same approach was used in cultural heritage leathers, supported by the colorimetric tests, since protein degradation products were co-extracted in aged leathers and interfered in IR spectra.  相似文献   

4.
With the aim of identifying new water dispersed polymers for textile conservation, the structure and properties of three commercial polyacrylates and one commercial polyvinylacetate were analysed. The characteristics of these materials, not previously used in the conservation and restoration fields, were compared with that shown by Primal AC33 and Mowilith DMC2 and SDM5, widely used as consolidating or adhesive agents of ancient textiles. To achieve a thorough characterisation of each polymer, molecular, thermal, structural and mechanical investigation techniques were applied on film samples, obtained from polymer water dispersions through water casting at room temperature and/or compression moulding. The photo-oxidative resistance of these materials was also assessed by artificial weathering of water cast films and by measuring the Yellowing Index (YI) as a function of the exposure time under xenon-arc lamp. Collected data were used to appropriately compare the performances shown by these polymers when applied on artefacts consisting of natural fibres. In particular it was found that, among the products not previously used in the conservation and restoration fields, a high potential for carrying out treatments on textiles is shown by the samples commercialised with the trade names of Acrilem RP6005 and Acrilem 30WA. These products, in fact, exhibit properties that make them suitable as substitutes for Primal AC33 and Mowilith DMC2 and SDM5, respectively, depending upon conservation needs. It was very interesting to note that Acrilem 30WA, also after aging, shows YI values lower than that shown by Mowilith DMC2 and SDM5.  相似文献   

5.
Ceramic samples made with a mixture of 70% ball clay and 30% quartz sand were moulded and then fired at 900 °C in an electric kiln. Samples were then treated with different products and analyses and tests were performed to evaluate the physical changes induced by the application of these products and their effects on the quality of the ceramics. A petrographic study indicated that the ceramics were composed of quartz, small amounts of mullite and sanidine and traces of hematite. Mineral clays (i.e. kaolinite) disappeared during firing. Two consolidating products (Paraloid B72 and Tegovakon V) and one water repellent (Silo 111) were applied to samples by capillarity, and physical changes (colour, water flow, porosity and pore size distribution) were measured. Finally, we carried out salt crystallization tests in order to determine which product improved the quality of the ceramics. Treated samples registered a decrease in porosity and a general increase in pore size. The application of Silo 111 drastically reduced water absorption by immersion and by capillarity. This product was also responsible for a decrease in pore interconnection. Samples treated with Tegovakon V performed better in terms of their overall hydric behaviour. Silo 111 was the only product that did not modify the colour of samples when compared with untreated ones, and after accelerated aging tests, samples treated with this product hindered the absorption of saline solution into ceramic pores and prevented their decay. Paraloid B72 did not improve any of the properties of the ceramics.  相似文献   

6.
Using inductively coupled plasma–atomic emission spectrometry (ICP-AES), atomic absorption spectrometry (AAS) and instrumental neutron activation analysis (INAA) the concentration of Ag, As, Au, Bi, Cu, Fe, Ga, In, Ni, Sb, Sn, and Zn in 53 samples taken from archaeological finds dated to 4th–2nd century BC and found in the territory of ancient Thracia was determined. Additionally using inductively coupled plasma–mass spectrometry (ICP-MS) and MS for determination of the lead isotope ratios in the samples was carried out. On the basis of these analytical results using cluster analysis for grouping the samples on the bases of the similarity in chemical and isotopic content and the available data from the literature for lead ore deposits in the Balkan Peninsula, the geological origin of the investigated archaeological finds was evaluated. That confirms the expectation that sources of lead might be almost all possible deposits of lead ores on the Balkan Peninsula—from Lavrion through Chalkidiki to the Rhodope mountain. The result indicates that the Thrace did not utilize one single lead source continuously but that lead was provided according to availability from different production centers.  相似文献   

7.
The efficiency of a recently described non-aqueous method for paper deacidification using Ca(OH)2 nanoparticles in isopropanol was evaluated by pH and colorimetric measurements and by the analysis of the degree of polymerization (DP). Samples of plain paper and paper with iron gall ink were tested. The results were compared with non treated samples and samples submitted to the traditional treatment with saturated aqueous Ca(OH)2 solution. By comparing the two conservation methods, the aqueous one shows higher neutralization reaction kinetics than the non-aqueous one. The iron gall ink samples maintain their coloration closer to the original after the non-aqueous Ca(OH)2 nanoparticles treatment, in contrary to the aqueous treatment that changes the ink aesthetics considerably. Artificial aging tests revealed a general increase in the aging stability of deacidified paper samples. The Ca(OH)2 nanoparticles treatment can be an alternative for papers who can not be treated by the classical aqueous treatment, e.g. papers with water soluble components.  相似文献   

8.
The protective performances of two new fluorinated acrylic copolymers (based on the monomers 1H,1H,2H,2H-perfluorodecyl methacrylate (XFDM) and 1,1,1,3,3,3-hexafluoroisopropyl methacrylate (HFIM) are evaluated and compared with Paraloid B72, a commercial copolymer ethyl methacrylate/methyl acrylate (EM/MA) and its partially fluorinated homologous 2,2,2-trifluoroethyl methacrylate/MA (TFEM/MA). The polymeric materials have been tested on Candoglia marble, a very low open porosity stone (<1%) used in Italian historical architecture (Milan Cathedral). The copolymers were tested according to UNI-Normal protocol. Measurements of capillary water absorption, static contact angles, colour variation and water vapour permeability were made before and after accelerated photo-ageing. FTIR spectroscopy and size exclusion chromatography (SEC) analyses were carried out on samples aged on inert substrate to assess the photostability of the copolymers themselves. The relationship between the protection efficacy and the fluorine content and distribution has been investigated. The results obtained show that the addition of a partially fluorinated co-monomer to the Paraloid B72 copolymer structure did not result in the expected improvement of the coating properties, while the fluorination of the copolymer side chain gave rise to encouraging performance.  相似文献   

9.
The preservation of historical monuments requires both a detailed understanding of water circulation inside construction materials, and a deep comprehension of the associated physical and chemical effects on building structure. Combining mass and temperature measurements may be a new powerful tool to achieve this purpose, as first results obtained on a wall of the Saint-Gatien cathedral in Tours, France, indicate. The proposed method has been evaluated with dedicated experiments in a climatic chamber, regulated in both temperature and humidity, using three types of stones: Tours tuffeau, Baumberg limy sandstone, and Rüthen sandstone. Climatic chamber data indicate that temperature gradients between rock surface and atmosphere provide a meaningful and practical estimate of the water flow, which controls the heat exchange between rock and atmosphere because of the high enthalpy of vaporisation of water. Continuous measurements of the mass of a sample confirm this assumption and allow the calibration of temperature data with respect to water flow estimations. Temperature gradients between points on the stone surface are also dominated by changes in the water flux, and they provide a sensitive estimate of local variations in the heat and water transport properties of non-saturated stones. Combined mass and temperature measurements therefore appear as a promising method to estimate in situ the global and local water flow between the rock and the atmosphere and thus to diagnose the state of stone degradation, or to estimate quantitatively the efficiency of treatment processes, both in the field and in the laboratory.  相似文献   

10.
Titanium dioxide (TiO2) can be used to realize transparent self-cleaning coatings on stone surfaces as an active and preventive protection system, limiting cleaning and maintenance actions, reducing their costs in Architectural Heritage. This self-cleaning ability is due to photo-induced hydrophilicity on treated surfaces. The aim of this investigation is to analyze this effect, since it could bring to a greater water absorption, a potential source of damage for stone surfaces. Titania sol, obtained by sol-gel and hydrothermal processes, was deposited on travertine by spray coating, in two different ways. Water absorption by capillarity, static contact angle and a specific surface water absorption analysis were assessed before and after the TiO2 treatments. The effects of deposited amount of titania on the characteristics of treated surfaces were evaluated. It was shown that there were no evident changes in the substrate reactivity without ultraviolet (UV) light exposure, while it seems that hydrophilicity due to UV light does not lead to higher water absorption, thus encouraging the use of TiO2 coatings in the field of Architectural Heritage. However, before widely applying this conservative treatment, some further researches are recommended in order to better assess its durability and sustainability.  相似文献   

11.
The influence of chemical treatments based on novel organic products on the consolidation of deteriorated wood by insect attack was evaluated on two hardwoods and one softwood: fir (Abies alba), beech (Fagus sylvatica) and deciduous oak (Quercus sp.). Degraded and intact specimens of the three wood species were impregnated with two different chemical treatments aimed to verify the potential synergic action of the novel products on wood. Then, the specimens were subjected to bending, compression parallel to the grain, impact, hardness and water absorption tests. Untreated specimens of the same botanical species, both degraded and non-degraded, were examined for comparison purposes. The experimental results showed a different effectiveness of the proposed chemical treatments to improve the mechanical and absorption properties of degraded wood. The most effective treatment was the one assuming the concurrent use of the studied novel consolidants. The species more susceptible of the enhancement in mechanical properties were fir and beech. The observed differentiations were most likely caused by the different structure of the botanical species considered, leading to a consequent different product penetration in the wood structure. The dimensional stability in terms of water repellent and antiswelling efficiency, after a three-month immersion in deionized water, was found to improve in all the treated wood specimens. Overall, experimental results showed that the impact of the chemical treatments was higher on degraded samples than on intact ones.  相似文献   

12.
An epoxy coating modified by PDMS hydroxyl terminated is presented in this paper in order to evaluate its potential use as a protective of a stone surface. With a view to its use in restoration sites, visible and long-wavelength photoinitiated cationic polymerization is proposed here. The system investigated is based on a crosslinking mechanism which shows remarkable advantages for stone protection, such as the low toxicity of the products and facility of mixture preparation. Furthermore, the visible light exploitation represents the most important advantage, because it is easy to apply in a restoration site, with or without irradiation instruments. Besides coating characterization through FT-IR, DMTA analyses and contact angle measurement on glass slides, analyses were also carried out on coated plaster samples. These analyses were performed in order to evaluate the effectiveness of the protective, in relationship to hydrophobicity (contact angle measurement, capillary water absorption) and morphology surface changing (SE/SEM observations, colorimetric measurements) before and after polymer application and UV aging test of coated samples. The overall characterization makes it possible to consider it a suitable coating for stone protection.  相似文献   

13.
This paper provides new insights into understanding the causes of deterioration of the Corbii de Piatra rupestrian church and shows the significance of studying the geological environment of historical rock-cut settlements when undertaking preservation and restoration actions. The Corbii de Piatra church is one of the few rupestrian churches remaining in Romania and is an important part of the country's heritage. The church is carved in a stratum of polymictic sandstone of Oligocene age, which is part of the Getic Depression, located in the southern part of the South Carpathians. In the 14th century the interior walls of the church were decorated with mural paintings of a high artistic value. Over the centuries, the church's walls and mural paintings have been negatively affected by a series of physicochemical processes. These processes were studied through field investigations and laboratory analyses carried out between October 2007 and November 2010. The investigations revealed that tectonic fissuring and the structural anisotropy of the rock facilitate the infiltration of meteoric water through the walls into the interior of the church, from north to south, maintaining a high-level of humidity in the northern wall and in the interior of the church. The most harmful effects observed were: (i) the partial hydrolysis of the feldspars through reaction with water from the pores, producing a friable mass of phyllosilicates which led to a superficial disaggregation of the rock and to a diminished cohesion between the rock and the mortar of the fresco, (ii) the reprecipitation of the gypsum as efflorescences on the northern wall and ceiling, covering the mural painting in localized areas, as a result of the transportation of the gypsum by water from the upper strata, (iii) the alteration of the cinnabar pigment, as a result of water penetration by diffusion through the fresco from the wet rock to the pictorial layer (the secondary effect observed being the formation of sulfuric acid, which further reacted with the carbonate from the fresco to form gypsum), (iv) the development of biotic crusts, predominately algal, on the interior wet walls, which, facilitated by the permanent high humidity and the semi-obscurity of the interior of the church, have covered large surfaces of the fresco. Compared to the interior, the exterior vertical walls have been exposed to prolonged daily and seasonal variations of temperature and humidity. These variations have caused repeated variations in the volume of the sandstone, leading to contraction fissuring and peeling of the vertical walls. Any future procedures that might be used to conserve the church should strive to reduce the humidity of the sandstone in the interior walls.  相似文献   

14.
The investigation of capillary water rise mechanisms in old masonries is of great practical interest, as well as the investigation of the electrical effects accompanying such phenomenon. In fact, moisture presence facilitates all the decay processes in porous building materials and strongly threatens the preservation of materials in architectural heritage. Previous papers have shown that performing a correct and accurate measurement of spontaneous electric potential in masonries is very challenging due to several variables influencing these phenomena, such as materials microstructure, soluble salts nature and amount. In this paper, the influence of mortar joints on the capillary water rise and on the related electrokinetic effects was investigated on laboratory assemblies; then, the same measuring procedure was applied on site to a real XVI Cent. masonry building affected by rising damp.  相似文献   

15.
Lasers have served as cleaning tools for historical objects and artworks for about 40 years. In many cases, superior results of laser cleaning were achieved with respect to traditional methods. In this technique, contaminations on the surface of the object are ablated by laser irradiation. In order to apply laser cleaning method to fragile materials such as paper made of cellulose or parchment, heat deposition to the bulk should be minimal, to prevent damage. In this work, it is demonstrated that laser pulses with femtosecond (fs) duration can exhibit non-thermal ablation of contaminants on paper samples. In particular, laser cleaning studies are concentrated on paper samples with sizing. Fs laser cleaning is performed on artificially soiled and aged samples, as well as on historical ones. The laser used in the experiments has pulse duration of 550 fs and 1030 nm center wavelength. The fluence of the laser is varied and the post-cleaning statuses of samples are investigated. The analyses are color changes, fiber integrity, chemical composition changes and mechanical strengths. These results show that fs lasers can be very efficient in cleaning paper samples, yielding minimal discoloration and no damage to fibers distinguishable on microscopic examination. The presence of sizing also provides further protection against possible side effects.  相似文献   

16.
For conservation of the built cultural heritage, the application of conservation products like consolidants or water repellents is often suggested. Their impregnation depth is a key factor for the assessment of the treatment efficiency. It will vary depending on the internal structure of the stone material and the properties of the conservation products. In this study a porous bioclastic limestone from Maastricht (the Netherlands) and a porous sandstone of Bray (Belgium) were selected for treatment with either ethylsilicate-based consolidant products or siloxane-based water repellents. We explore the potential of neutron radiography to visualize the conservation products after polymerization, since previous experiments already proved their detectability before polymerization. Additionally, water absorption by capillarity was monitored inside the samples. The experiments in this study illustrate that the ethylsilicate-based consolidants remained visible for neutrons even after the polymerization process, while the siloxane-based water repellents can only clearly be distinguished in the stone as long as they contain a certain amount of solvent. The study proves that neutron radiography can provide important additional information for the research in the built cultural heritage domain, especially as it allows to successfully visualize the impregnation depth of silicate-based consolidants inside natural building stones.  相似文献   

17.
The performance of five synthetic coatings for the protection of stone monuments of Hellenistic and Byzantine period has been evaluated. The selected coatings included four commercially available siloxane-, siloxane/acrylic- and perfluoroether-based compositions, as well as a new composition based on newly synthesized fluoro-organosilane. The coatings were applied onto petrologically different stone substrates, such as marble, travertine, sandstone and a newly baked brick compatible with Roman period bricks, used for the restoration processes in Galerius Palace, Thessaloniki, Greece. The coatings' protective efficiency was investigated by measurement of water–stone contact angles, water vapor permeability, and water absorption by capillarity. The optical properties of the applied coatings were also investigated and they were also ranked with regard to their optical characteristics.  相似文献   

18.
Nanolime dispersed in 2-propanol was extensively used for the consolidation of wall paintings. The knowledge of the advances of this methodology dealing with all the possible effects associated with the nanolime new material in conservation is fundamental to assess and improve the technique. In this paper, four different dispersions of Ca(OH)2 nanoparticles were characterised by Small Angle X-rays Scattering technique (SAXS) and Transmission Electron Microscopy (TEM) in order to achieve information on size, shape, polydispersity, agglomeration, and crystal structure (by SAED patterns) of the particles. Once characterised, the dispersions were tested in two different case studies, the Carceri dello Steri in Palermo with their graffiti and the 18th century lunettes at the SS. Giuda e Simone Cloister, Corniola (Empoli) with their lime-based mural paintings. The treated samples were characterised in relationship to either their morphology and surface chemical composition by Scanning Electron Microscopy coupled with Energy Dispersive X-rays spectroscopy (SEM-EDX), or their water absorption and mechanical properties (resistance to material abrasion). The results obtained showed that all the dispersions were nanometrically structured and their application succeeded in recovering the mechanical properties of the painting or graffito layers, not altering their permeability to water and keeping perfectly the wall transpiration. However, the dispersions constituted of the nanoparticles obtained via a synthesis able to control size and shape of the Ca(OH)2 particles resulted in a better performance in situ, even if the differences found by SAXS and TEM were slight.  相似文献   

19.
The damage to historical documents and books caused by the acidic character of paper is often manifested as a complete loss of their mechanical properties. Deacidification and restoration of archived paper objects require knowledge of the long-term behaviour of paper before and after repair actions. Our study was focused on the investigation of mechanical properties (tensile strength, stretch, tensile index, zero-span tensile strength, folding endurance) of original papers (one alkaline and three different acidic samples) exposed to five methods of dry-heat and moist-heat accelerated ageing. The degree of paper deterioration upon ageing was significantly influenced by the temperature and relative humidity, along with the intrinsic chemistry of the individual paper samples. The correlation matrix evaluated at a 95% confidence level for tensile strength, stretch, tensile index and zero-span showed linear correlations between these mechanical properties for all the paper samples. However, a linear dependence of folding endurance on zero-span tensile strength was found only for alkaline paper, which revealed the highest resistance to the accelerated ageing tests. In addition, the concentration of paramagnetic semiquinone species in the acidic lignin-containing paper samples was monitored by Electron paramagnetic resonance spectroscopy.  相似文献   

20.
The present work reports a basic investigation aimed at optimizing laser cleaning interventions on pliocene sandstone of Siena. Irradiation trials were performed with a short free running Nd:YAG laser, on quarry samples and on samples from Palazzo Spannocchi presenting black crust. The physical parameterization associated with a detailed petrographic and mineralogic diagnostics of the induced effects, allowed the irradiation thresholds for damage phenomena to be derived and their nature understood. The experimental results reported here allow the definition of the best irradiation conditions and the laser parameter ranges for a safe and controlled black crust removal from pliocene sandstone.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号